LIBRARY OF CONGRESS^ W- ^'-f^ira UNITED STATES OF AMERICA. ►,1 lA 1 FRONTISPIECE. Fig. I. THE PHENOMENON OF "BARKING," AS MANIFESTED BY IRONS F AND Fx. (See Page 36.) r^.^^^ ■/ Fig. 2. diffkrknce in appearance of fractures produced by impact, of varying degrees (^f ENERG\', I'Ml-: MATERIAL BEING THE SAME. (See Page 35.) Jliliutl/IHS Pr'niliii;! Cii. Iluetan. Bearvslee on Wrought-Iron and Chain-Cables. EXPERIMENTS ON THE STRENaTH OF WROUGHT-IEON AXD OF CHAIN-CABLES. REPORT OF THE COMMITTEES OF THE UNITED STATES BOARD APPOINTED TO TEST IRON, STEEL AND OTHER iMETALS, ON CHAIN-CABLES, MALLEABLE IRON, AND RE-HEATING AND RE-ROLLING WROUGHT-IRON; INCLUDING MISCELLANEOUS INVESTIGATIONS INTO THE PHYSICAL AND CHEMICAL PROPERTIES OF ROLLED WROUGHT-IRON. COMMANDER L^ A. BEARDSLEE, U.S.N., 'C ^ ^ Member of the Board, and Chairman of the Committees. \^^ c BY WILLIAM ^vENT, M.E., Formerly Assistant to the Committee on Allorjs of the United States Board; Associate Editor of the ^^ American Manufacturer and Iron World," Pittsburgh, Penn. NEW YORK: JOHN WILEY AND SONS, 15 AsTOR Place. 1879. 7r COPTRIGHT, 1879, By WILLIAM KENT. PREFACE. The Report of which the following pages are an abridgment was published by the United States Government in 1879, as part of Executive Document No. 98, House of Representatives, Forty-fifth Congress, Second Session. It forms an octavo of two hundred and sixtj'-seven pages, with thirteen hehotype-plates, and several wood-cuts. It is not only by far the most elaborate record of tests of wrought-iron and of chain- cables that has ever been given to the world, but it is the most valuable in results ; in describing newly observed phenomena, in tabulating variations of strength due to differences in methods of manufacture, and reveaUng their causes, in investigation of the effect of impact, in pointing out causes of defects in strength of both bars and cables, and generally in gi\^ng information that is of imme- diate practical value to manufacturers of iron and to engineers. As but a limited number of copies of the report were issued by the Government, and as it contains a large amount of detailed tabular matter, which, while necessary in an official report of this kind, to corroborate the conclusions deduced, is not necessar}^ to a full com- prehension of these conclusions, — it has been thought that an abridgment would be acceptable to many who would be unable to obtain the original work. The undersigned, in preparing the abridgment, has had the full consent of Commander Beardslee, and obtained his approval of " the manuscript prior to iDublication. WM. KENT. Pittsburgh, Pekn"., May, 1879. CONTENTS. SECTION I. Page Introduction 1 The Bar. — Part 1 4 Testing-Machines, and Methods of Testing 5 Notes npon the "Records of Bars tested by Tension" . . . G Strengtli and Elastic Limit of Round Bar-Iron .... 8 The Bar.— Part II 11 Investigation of the Effect of Differences in the Amount of Reduction by the Rolls 11 SECTION II. Part I. — Proper Form and Proportions of Test-Pieces . . 20 Part II. — Comparative Strength of Bars in their Normal Condition, and as Reduced by Turning away the Skin and Adjacent Iron 27 SECTION III. Tests of Bars by Impact; showing Action of Various Types of Iron under Sudden Strains . .31 Method of testing by Impact 32 Barking 36 Crystallization 36 Record of Impact Tests 37 SECTION IV. A Paper describing a Series of Experiments to determine Facts in Regard to the Operation of the Law called the Elevation of the Limit of Stress 40 VI CONTENTS. SECTION y. The Cable 49 Experiments upon Comparative Strength of Studded and Unstud- ded Links 52 Description of Method of testing Cables 54 Weight of Chain-Cables 57 Methods by 'svhieh the Weight of Chain-Cables can be reduced in a greater Ratio than the Strength . . . . . .58 Comparison of Results obtained by Tension upon Sections of Cable-Links, and upon Bars of the Iron from which Links were made 62 < SECTION YL Proof-Straixs for Chain-Cables 08 Effects of the Use of Strains prescribed by the Admiralty Proof- Table G8 Discussion of the Principles upon which Proof-Strains should be based 71 Ratio of Strength of Sections of Links to that of the Bars from which they were made 72 Probable Strength of Round Bars, calculated with an Allowance for Variation in Strength due to Variation in Diameter . . 77 Probable Strength of Cables made from Bars of given Streiigth . 79 Recommended Proof -Table 81 Comparison of the Proof-Strains recommended, and the Strains in Use 81 SECTION VIL Part I. — Notes upon the Irons examined 83 Part II. — Comparison of Chemical and Physical Results . . 92 Analyses of the Irons used in making Chain-Cables ... 93 Relative Values of Iron in Bars, in Tenacity, Reduction of Area, and Elongation, and in Proportion of Chain to Bar ... 95 Summary of the Principal Physical and Chemical Properties of Sixteen Irons 90 Effects of Phosphorus 97 Effects of Silicon 101 Effects of Carbon 102 Effects of Manganese, Copper, Nickel, Cobalt, Sulphur, and Slag, 105 Welding 100 What is learned from Chemical Analyses 113 Conclusions derived from a Comparison of Chemical and Physical Results 117 REPORT OP THE EESULTS or INVESTIGATIONS MADE BY COMMITTEES D, H, AND M, OE THE UNITED-STATES BOAED APPOINTED TO TEST lEON, STEEL, AND OTHEE METALS. SECTION I. INTRODUCTION. The investigations assigned to the three committees desig- nated by the letters D, H, and M were as follows : — To Committee D, " On Chain and Wire Ropes," with instruc- tions " to determine the character of iron best adapted for chain cables, the best form arid proportions of link, and the qualities of metal used in the manufacture of iron and steel wire rope." To Committee H, " On Iron, Malleable," with instructions "to examine and report upon the mechanical and physical proper- ties of wrought-iron." To Committee M, " On Re-heating and Re-rolling," with in- structions " to examine and report upon the effects of re-heat- ing and re-rolling, or otherwise re-working, of hammering as compared with rolling, and of annealing the metals." The work thus assigned to three different committees was of such a -nature, that experiments made by any one of them would necessarily furnish data which would prove of value to 2 WROUGHT-IRON AND CHAIN-CABLES. all ; and as the three committees consisted of but five members of the board, one of whom was chairman of all, it was consid- ered advisable, in order to economize time, labor, and means by the avoidance of duplication of expensive experiments, and of making duplicate and triplicate reports of the same series, to consolidate the committees, and to conduct the investigations in such a manner that a single report would cover the whole ground. In thus concentrating the work, it was necessary that a leading object should be selected, and it was considered that the research required to establish the characteristics of iron best adapted for the manufacture of cables would furnish data which would bear more or less upon the subjects to be investi- gated by Committees H and M ; while it would be quite practi- cable to select from the wide field presented by "wrought- iron," and differences in methods of treating it, any number of lines of research, none of which would prove of much ser- vice in establishing points in regard to chain-iron. Our experiments, therefore, have been all so carried out, that while we have been able to obtain data, both as to the mechan- ical and physical properties of wrought-iron, and as to the effects of different methods of treatment of the raw material, all have been made to contribute their quota toward the estab- lishment of methods by which an iron could be judged cor- rectly as to its adaptability for chain-cable manufacture. Such points well established would prove to possess value, not only to the manufacturers and purchasers of cables and cable-iron, but also to manufacturers of iron bridges and other construc- tions, which, like the cable, depend for their value upon their power of resisting to the utmost destroying forces of various and irregular natures. In submitting this report, we would say that the extent of our investigations has been restricted by narrowness of our means, and the necessity which has arisen that we should sub- mit the results of such work as we have accomplished. They but point the way toward a thorough re-examination of the subjects involved, which, based upon our results, would provide INTRODUCTION. 3 a valuable mass of information, to which this report would occupy the relation of a preface. The cable-link is but a modification of the round rolled bar, and its qualities must depend upon those of the bar from which it is made. Therefore we have selected the eound bar as the foundation of our work ; and our endeavor has been to ascertain what qualities should be inherent in it, and which should re- main without deterioration through various processes incident to the manufacture from it of finished products of other forms. Cables in service are subject to the destroying forces of sud- den strains, alternations of sudden and steady heavy strains, heavy steady strains, abrasion, and corrosion ; and the danger from each takes precedence in the order given. The relative importance of these sources of danger indicates that iron which is best adapted for cables is that which pos- sesses great power to resist both sudden and steady strains, and that neither of these qualities in excess will compensate for a deficiency in the other. The strength of the cable is but that of the weakest link, and the strength of this link but that of the ivealcest part : therefore, in order that a cable shall be strong and reliable, the weakest part of the weakest link must be made as strong as possible. The weakest part of nearly every link is the weld. With certain types of iron the weld is much weaker than with others: hence we consider that the prime elements of value in a cable- iron are power to i^esist sudden strains, and to be welded thor- oughly without loss of strength. By the former we insure against the greatest danger, and by the latter against the frequently repeated ordinary dangers. We Avere not able to obtain any information of value as to the qualities of various American irons in these two respects ; and we therefore resolved upon making a series of experimental investigations, by the results of which we hoped to be able to form a correct judgment. 4 WKOUGHT-IRON AND CHAIN-CABLES. THE BAR. — PART I. Our plan of investigation was to first ascertain, by means of tension tests made upon bars of such irons as we could procure, the amount of strength, elasticity, &c., which would be found to exist in ordinary American bar iron ; next, by tests by im- pact upon the same irons, to ascertain their relative powers to resist sudden strains; and finally, having ascertained these essential points in the material^ to make from each iron a num- ber of cable-links, and by tension to find their strength and uniformity, and the degree of dependence to be placed upon the ivelds. To carry out these investigations, we procured bars of round iron of sizes such as are usually used in the manufacture of cables ; viz., from two-inch diameter to one inch, from the fol- lowing rolling-mills and dealers in iron, viz., Burden & Sons of New York, Bentoni of Pennsylvania, Burgess of Ohio, Cata- sauqua of Pennsylvania, New-Jersey Iron and Steel Company of New Jersey, Niles Iron Company of Ohio, Phoenix of Pennsylvania, Pembroke of Massachusetts, Pencoyd of Penn- sylvania, Tredegar of Virginia, Trego and Thompson of ]Mary- land, Sligo of Pennsylvania, Tamaqua of Pennsylvania, Wyeth Brothers of ^Maryland, and many other bars of unknown origin. The experiments, upon the results of which our report is based, comprise the details of all physical phenomena observed by us while testing to destruction nearly two thousand bar test- pieces by the strain of tension, over fifteen hundred by the strain of percussion, and nearly five hundred cable-links, made in all respects as for service. Tlie tension-tests upon bars were made both upon bars in their normal condition, and upon others from wdiich a portion of the surface had been turned away. Those by impact were made upon portions of the same bars which had been tested by tension, and those upon chain-links from other portions of the same bars. The Navy Department placed at our service THE BAE. 5 the facilities of the Washington Navy Yard, which included the use of forges and of two testing-machines for making tension-tests ; also of such records as we desired, and of a large quantity of contract chain-iron, which it was deemed advisable to examine. A brief description of our testing-machines, and of our methods of testing, with a few physical phenomena we have observed, will enable the terms used in the report to be under- stood. Testing-Machines, and Methods of Testing. In order that we might obtain the tensile strength, elastic limit, ductility, &c., of round bars, our first test was by tension upon full-sized bars, from which the outer portion had not been removed. These tests were made by means of the " chain- proving machine," at the Washington Navy Yard, which in this report is called " testing-machine A." This machine consists of a long trough, in which a fifteen-fathom section of cable can be stretched by means of a hydraulic pump, to which it is con- nected at one end, while the other end is made fast to a holder, which in turn connects with a system of levers, by which the stress is weighed by means of weights placed upon a platform at the extremity of the long lever. The capacity . of the machine is three hundred thousand pounds, and the levers are so adjusted that a weight of one pound upon the platform balances two hundred pounds of stress. The pieces to be tested were sections of the bar at least eight times the diameter in length, and originally fitted with loops of larger-sized iron, welded to the ends. Additional tests by tension were made, upon many of the irons by means of cylindrical test-pieces turned from the bars, and ruptured by the " Rodman Dynamometer," called in this report " testing-machine B." The results obtained by this machine agree very closely, in some cases, with those obtained by testing-machine A, and in 6 T7E0UGHT-IE0X AND CHAIN-CABLES. others differ widely. A portion of these differences is probably due to differences in the accuracy of the two machines and methods, and others to a natural difference in the character of the metal as developed by the entire bar, and by a portion of the core and adjacent iron. This machine holds the specimen to be tested by means of clamps. The capacity of the machine is one hundred thousand pounds, and it will weigh a stress of ten pounds with accuracy. Notes upon the " Records of Baes tested by Tension." Column headed " Diameter.^' — The strength per square inch of a bar, as deduced from the stress at which the entire bar has been torn asunder, cannot be correctly ascertained, except the diameter of the bar be carefully calipered : the nominal size and the exact size seldom coincide ; and at times we have found variations of four-hundredths of an inch, which variation is sufficient to produce important errors. Ai^eas, — The " original area " is that which corresponds to the diameter of the piece before test; the "reduced area" cor- responds with the least diameter after rupture ; the " tensile limit area " corresponds with the least diameter at the highest stress the piece sustains. Length. — The length of the clear cylindrical portion be- tween punch-marks is measured before the stress is applied, and after fracture. In testing with the machine B it is also measured at the " tensile limit." Percentage of Elongation. — This element, as given in many tables, is of little value, the percentage being greatly dependent upon the original length of the specimen. When this is not given, the percentage is of no value. The following experiment will make this clear : From a bar of \%" iron, of very uniform character, three test-pieces were prepared, which were in all respects similar, except in length. The first was 75, the second 20, and the third 10 inches long. THE BAR. 7 They were pulled asunder, and the first was found to have elongated 14 inches, or 18.64 per cent of the original length ; the second had elongated 4.36 inches, or 21.8 per cent ; and the third 2.22 inches, or 22.2 per cent. Our records supply many confirmatory results. First Stretch. — The .bar being fastened to the holders, a pair of large dividers was adjusted to punch-marks, and the stress slowly applied ; at the instant the elongation was suf- ficient to draw one punch-mark clear of the dividers' point, the stress was weighed, and recorded as first stretch. Ultimate stress is the stress which represents the highest which has been withstood by the specimen ; but it was not the amount which finally produced the rupture : this stress pro- duced a weakening, from which, had the specimen been rested, it would have recovered ; by continuing it, the specimen finally parted at much less. ' Original^ Fractured^ and Tensile Limit Areas, — The measure- ments taken at the "tensile limit" introduce a new method by which the comparative values of different irons may be estimated. Ordinarily the tenacity of iron is expressed in the strength per square inch of the sectional area of the test-piece before its form has been changed by stress. Kirkaldy suggested, as a more just method, that the area corresponding to the diameter of the fractured surfaces should be adopted as the limit of measurement. Our experiments lead us to believe that between these extremes of original and fractured areas there is an inter- mediate area which can be used with profit, which is that which corresponds ivith the least diameter of the test-piece at the stress ivhich marks the highest point of resistance to continually/ increasing strains. This point we have termed the " tensile limit. ^^ There are practical difficulties encountered in measuring accurately the diameter of the fractured surfaces. After the test-piece has been pulled asunder, there is a difficulty in joining 8 WROUGHT-IEON AND CHAIX-CABLES. perfectly the two fractured surfaces, and frequently the line of surface is not at right angles with the axis of the cylinder : this necessitates two measurements, — one of the greatest and one of the least diameter, and an interpolation, — and, in making these measurements, there are chances of error, even if the line of fracture is at right angles, which are increased when it is not. The tensile strength per square inch of original area is more liable to be free from errors arising from inaccuracy than is that of the fractured area. But neither of these measure- ments provides us with a standard by which we can judge of the relative amount of change of form that takes place with different irons at the moment when they finally cease to resist an increase of stress ; this deficiency is supplied in the area at the tensile limit, which area corresponds to the diameter of the test-piece, at the instant when affected by the highest stress the material is capable of resistmg, and not by subsequent stress applied to a rapidly-yielding metal. Length of Test-Piece. — Not only the " percentage of elonga- tion " obtained by testing a piece of iron, but the strength, de- pends upon the length of the test-piece. Our experiments show, that, if an iron is judged by a test-piece whose length is less than four diameters, the judgment is wrong. Strength and Elastic Limit of Round Bar-Iron. In the following table the stresses by tension required to rupture many of the bars we have tested are arranged in their relative order, the greatest stress required being given prece- dence upon each size. In the columns in which the stress is reduced to the square inch, the areas corresponding to the actual diameters of the bars have been used. This gives a more correct estimate of the relative order of tenacity than the diameter given in the first column, by using which bars would frequently gain or lose THE BAR. 9 ill precedence on account of excess or lack of material, some being rolled " full," and others " scant." In the column " Standard for Size," the strength which we have found best adapted for cable-iron is placed for com- parison. The elastic limit as given is not from perfectly accurate data : it is simply the amount of stress which produced the first per- ceptible change of form, divided by the bar's area. Strength per Original Area, per Square Inch, and Elastic Limit per Square Inch, of 959 Round Bars. CO Strength. S CO Strength. S a o ^ "h u o f-( •~ "^ 1— 1 ^ £^ a . .a 5 M a t*- u "rt • o ^ u i^ •!> «m u "rt . y ^ 't 'P o e CS S o a S3 S ■11 D CO 3 2 B m a CS S O a 01 a -2 hi. lbs. lbs. lbs. lbs. in. ;6s. lbs. lbs. lbs. \ P 1 2,920 59,885 • • • • n N 2 56,200 56,143 32,267 Fx2 3 55,100 55,927 37,250 1 F 4 5,886 54,090 40,980 E Fx3 1 2 55,142 54,800 53,097 54,644 33,549 34,695 \ C 6 12,311 62,700 .... D 2 54,360 54,687 28,166 C 7 11,699 59,000 .... A 3 53.997 53,900 26,787 c 8 11,388 57,700 .... F 3 53,050 53,850 33,457 c 11 10,881 55,400 .... o 1 50,400 53,035 32,410 F 1 10,359 52,275 39,126 F 2 50,300 50.149 35,493 1 F 5 49,660 52,267 32,019 F 11 16,977 55,450 .... ^ F 4 15,928 52,050 .... K 2 72,960 59,461 36,501 65,914 F 11 17,644 57,660 .... P 2 73,200 56,876 36,868 1 C 1 71,040 57,897 32,469 F 4 22,746 51,546 35,933 D 2 72,300 57,977 31,996 I P 2 70,704 55,782 35,596 F 4 30,850 50,630 33,931 Px 2 70,250 56,334 33,921 1 N 2 69,300 56,478 33,251 K 13 48,480 61,727 .... 43,665 Fxl 5 68,460 55,253 34,784 D 1 48,000 61,115 33,486 D 1 68,160 55,550 28,166 O 1 46,000 57,363 37,415 E 1 67,200 53,893 32,712 Fxl 5 45,040 55,768 34,729 Fx2 3 66,600 55,132 38,603 P 2 44,500 57,807 39,230 Fx3 2 66,400 53,247 32,520 A 3 44,126 54,690 34,881 A 3 66,112 53,897 27,643 Fx2 3 44,450 56,790 36,885 M 20 65,960 53,752 .... Fx3 2 42,350 53,915 36,336 M 20 65,850 54,090 .... F 2 41,600 51,921 31,300 F 2 64,990 52,970 32,075 D 8 41,547 52,900 .... F 2 64,700 52,729 39,608 F 5 40,660 52,819 32,267 M 20 64,285 53,022 F 4 40,309 51,400 34,600 F 5 62,520 52,620 33.220 H ' 1 61,400 50,040 30,730 K 3 60,096 60,458 37,344 54,261 h\ D 1 58,700 59,582 33,597 P 94 74,427 54,518 35,898 72,133 C 2 57,125 57,470 31,900 If Fxl 5 57,620 56,434 34,682 M 48 86,862 58,926 37,548 78,607 P 2 56,500 57,498 41,311 M 35 87,496 57,649 38,578 10 WROUGHT-IRON AND CHAIN-CABLES. 05 Strength. o CD Strength. o o H .ti'w u c c O fi si; 1— 1 tM ^ a a .5 •"• a S-i h-t %^ .a 85 «2 o N-i O H • S ^ ^ ^ o o V- o "rt . ^2 to • B s o V s 3 5^ 3 02 •i: 3 s ft o « S a £ 1 .5g 3 02 O C3 •J 3 cc O* «0Q 5 i}i. lbs. lbs. lbs. lbs. in. lbs. lbs. lbs. lb8. 1^ D 1 86,800 58,021 32.152 1^ ■^8 Px 2 115,500 54,689 33,427 O K 2 82,248 55,790 31,034 A 2 111,984 54,334 32,163 C 1 81,600 54,949 31,030 D 1 111,360 53,695 30,087 M 28 80,693 54,373 35,820 Fx3 2 111,300 53,339 33,540 N 2 81,200 54,277 33,622 Fxl 5 110,140 53,537 34,335 Fxl 5 80,360 52,968 33.275 D 1 110,500 53,614 30,664 Fx3 2 80,000 52,733 34,606 J 1 109,400 52,748 .... E 1 79,296 52,254 25,930 E 1 109,245 52,675 33,745 A 3 78,994 53,557 33,650 Fx2 3 108,800 53.43S 35,870 P 1 78,624 52,556 30,802 H 1 108,500 52,314 29,364 F 5 78,580 52,537 34,469 E 1 108,384 51,946 27,695 F 2 78,300 52,339 39,103 O 1 108,000 52,401 34,012 M 4 78,150 53,016 35,379 F 2 107,520 52,163 33,907 Fx2 3 76,333 51,487 35,911 G 1 106,200 51,205 33,318 F 2 77,235 51,296 31,992 F 2 105,500 50,529 35,390 O 1 72,400 50,594 34,940 F C 5 1 105,440 101,700 50,970 49,030 33,625 31,099 h\ P 1 89,300 53,345 .... 85,339 m E 1 87,552 53,944 32,542 K 1 130,000 56,595 38,310 114,770 Q 1 86,400 53,238 32,534 B 1 121,150 54,181 .... B 4 84,862 52,287 32,411 J 1 121,000 54,114 .... C 1 84,000 51,756 32,655 B 3 118,273 52,895 33,145 4 1 J 1 81,800 50,400 E G 1 1 116,544 115,800 52,120 57,789 35,549 34,160 li M K 12 2 102,125 101,280 57,052 57,317 38,417 33,412 92,322 If C 1 111,400 49,821 83,184 D 1 101,200 56,505 32,496 K 1 139,200 57,874 .... 122,745 M 25 99,064 55,466 34,780 Px 2 131,900 54,212 33,908 M 26 98,730 55,131 33,771 C 5 130,836 54,410 31,354 P 2 98,300 54,159 33,140 P 2 130,050 52,844 33,842 M 17 98,047 54,540 • • • • Fxl 5 129,500 53,846 36,573 C 4 97,921 55,404 34,770 H 1 129,400 53,800 27,856 E 1 97,920 55,415 32,869 N 2 129,350 55,018 34,283 M 20 97,665 54,816 34,716 D 1 128,600 53,472 31,892 Px 2 97,350 54,354 34,617 J 1 128,100 53,264 M 27 97,095 54,095 35,544 D 1 126,720 52,699 27',8i7 E 1 96,384 54,544 33,027 Fx3 2 126,100 53,154 35,323 P 1 95,904 52,868 29,636 E 1 124,128 51,606 26,541 M 20 95,810 53,512 .... A 2 123,340 51,509 29,404 M 23 94,809 52,941 .... F 1 121,920 50,690 32,229 Fx3 2 94,600 52,819 34,840 G 1 121,200 50,395 36,254 Fxl 5 94,520 53,491 34,307 C 1 121,000 50,312 30,852 M 4 93,500 52,736 34,901 F 2 120,200 50.547 35,954 N 2 93,400 53,555 34,690 Fx2 3 120,1 P7 52,314 35,320 C 1 93,100 52,700 35,880 E 1 119,808 49.816 31,214 H 1 92,700 52,462 29,992 F 5 117,740 49,738 28,907 D 1 92,160 52,155 27,708 O 1 116,500 50,129 32,271 A 2 91,680 51,884 28,794 Ml F 2 91,875 51,994 32,054 K 1 148,800 56,577 .... 130,965 O 1 91,400 50,919 32,312 B 4 138,507 53,655 .... F 5 90,925 51,456 34,591 C 1 131,500 50,969 30,814 Fx2 3 90,967 51,481 34,917 G 1 129,850 50,310 33,565 J 1 90,200 51,047 '. . . . E 1 129,792 50,307 29,767 M 1 87,100 49,292 32,597 J 1 126,300 48,953 If N 2 119,000 56,344 35,889 107,040 n K 2 154,080 55,803 .31,031 139,430 K 4 118,463 57,132 35,026 C 1 150,336 54,447 32,334 M 10 119.800 57,402 35,701 D 1 149,000 53,100 32,074 P 2 117,500 55,634 a3.522 N 1 148,350 54,004 33,610 C 4 116,892 56,227 33,207 Fxl 5 146,780 52,875 35,641 THE BAR. 11 Strength. u o Strength. j3 c p u o H -;-r S-i h-i e^ ^ E^ a <» ^ - ~ =2 s O o S •r «^ 5^ a< X a' 1i a 5 o o s o o 3 3 m OQ in. ^6.S. Ibfs. ». • F 2 140,925 51,039 33,067 ^ Fx2 3 139,000 51,159 33,970 i J*t 1 184,600 50,481 « ■ • • F 2 136,600 49,744 35,615 M 1 186,000 51,225 • • • . F 3 134,500 49,355 32,855 A 1 170,784 48,382 30,459 F 2 132,250 48,670 23,250 2t\ O 129,000 47,478 30,842 M 2 200,000 51,666 .... m M 156,000 51,707 .... 148,137 n M 1 210,400 51,530 M 155,300 51,474 .... M 1 205,800 51.296 .... M 154,000 51,242 .... F 3 195,977 49,290 32,163 2 F 2 195,476 1 49,164 31,966 K 194,880 60,213 31,441 157,080 F 1 192,700 1 48,898 K 188,160 57,567 30,839 F 1 189,600 I 48.812 • ■ • • Px 167,900 52,914 31,198 P 2 184,700 ! 46,866 28,241 M 167,600 52,820 • ■ ■ • j M -'^ 156,000 49,164 .... -h F 2 237,930 48,475 28,932 E 167,712 51,818 27,318 F 3 232,776 i 47,428 ^ 29.941 P Q 165,600 51,684 33,104 F 2 232,400 47,344 29,758 P 161,300 50,834 31,878 1 X 165,400 , 52,127 32,461 2| F 3 275,889 46,446 26,333 N 163,000 51,370 32,460 I Fxl 163,420 i 52,011 34,702 3 F 3 337,603 47,761 26,400 C* 160,704 ' 51,153 29,335 D* 160,700 51.146 28,567 3i F 2 390,019 47,014 24,591 P 159,840 49,872 29,953 rx2 2 155,500 50,000 36,184 ^ F 2 452,191 47,000 24,961 ' Fx3 2 159,500 50,763 33,172 A 9 157,588 50,171 28,983 3f F 2 515,423 46,667 23,636 F 2 152,260 48,596 27,634 4 F 2 151,900 47,812 35,864 F 2 582,100 46,322 23,430 THE BAR.— PART II. Investigation- of the Effect of Differences in the Amount of Reduction by the Rolls. In procuring material upon which to make tests by tension both in the bar and link form, our custom was to purchase from manufacturers at least one bar of each size ordinarily used in chain-cables. Testing these bars in their normal condition by 12 WEOUGHT-IEON AND CHAIX-CABLES. tension, it became evident that the strength of the different sizes was not in j)roportion to their areas ; but that, on the con- trary, there existed a variation in proportional strength which w^as in accord with variations in the diameter of the bars. In general terms it was found, that, as the diameter of the bar became less, the strength per square inch increased; but, in comparing the results obtained from a number of such sets of bars, it became evident that the increase of strength from be- tween the two extremes of, say, 2'' and 1'' was not created by a series of uniform steps upon each successive reduction, but that there was one point in the reduction where a decrease took the place of the usual increase, and that from this point the increase again began, and generally by more rapid steps. Thus the 2'' bar was of less strenglji than the 1|^''; the latter was of less than the If, which was, in turn, less than the 1|'', but the strength of the 1|'' was greater than that of the 1 J'' ; the 1|", 1^\ iy\ and sometimes the V\ being each of increased strength in the order given. We found, that, with a set of bars of the above sizes, the dif- ference in proportional strength between the extremes was from four to six thousand pounds; that the tenacity of the 1|'' ex- ceeded that of the 2'^ from two to three thousand pounds, and that'of the 1^'' from one to three thousand pounds. As we became fully satisfied that these variations did exist in all uniform irons which we examined, we considered ourselves justified in assuming that they would probably occur generally with other irons, and that, so occurring, their existence should be taken into consideration in any attempt to calculate the strength of links or other articles made from bar-iron of various sizes. Exj^eriments at the testing-machine afforded no indications by which we could determine any thing in regard to the causes of these variations. We therefore undertook to watch all the processes connected with the manufacture of a " set of bars," in hopes that while so doing we should be able to detect the hidden reason. THE BAR. 13 At our first visit to a rolling-mill, a set of bars were prepared of carefully selected material, and careful notes were taken dur- ing the process of manufacture, which are herewith reproduced. There were two bars of each size rolled. Notes in Regard to Manufacture of Iron F, Second Lot, Number op 00 Number of n Cu .2S a: -" .5 y o - Fas SES. T "^ o .2 2 si Passes. d o-=s o §=3 £ 5 Square Round = -^ .S'B P c Square Round la Jc c E-'r3^ RoIIl. Rolls. m. CE ft ^^ Rolls. Rolls. h.ni. h.ra. m. 2" 6' X 10" X 26" 2.06 15 9 •09 u 6' X 6" X 26" 1.32 13 8 Oblf 2 6 X 10 X 26 2.15 15 9 08 n 6 x6 x21 1.00 15 8 05 1? 6 xlO x24 2.02 15 9 07 n 6 x6 x21 1.04 15 8 04 ^ 6 X 10 x 24 2.23 15 8 07 ^ 6 X 6 x 14 1.20 15 8 04 n 6 X 10 X 21 1.40 17 9 07 n 6 x6 X 14 1.20 15 8 04 Iff 6 X 10 X 21 1.49 17 9 06 n 6 X 6 X 12 1.10 15 8 04 6 X 10 X 18 1.35 15 9 06 n 6 X 6 X 12 1.10 15 8 04 It 6 X 10 X 18 1.40 15 9 06 1 6 x4 X 14 1.10 15 8 04 ^ 6 X 6 x26 1.26 13 10 05 1 6 x4 xl4 1.10 15 8 04 A study of these notes indicated that if there proved to ex- ist any marked difference in the characteristics of the different bars, it could not be considered as owing to want of care in their preparation. No accident caused delays while passing through the rolls, and the number of passes was quite uniform. By contrasting the areas of these piles with those of the resulting bars, it will be seen that there was a very different amount of reduction produced by the rolls, varying from 5.23 to 2.76 per cent. The tenacity of these bars agreed to some extent with the amount of reduction, but not so closely as had been expected. The experiment was repeated by watching another set of bars rolled by the same mill, of the same material, the set com- prising bars of all sizes, ranging by ^'' from 4^' diameter to |'' diameter. The iron was A^ery carefully heated, and received a nearly uniform number of passes through the rolls. The dimensions of the piles, the proportion borne by the areas of the resultant bars, and the tensile strength and elastic 14 WROUGHT-IRON AND CHAIN-CABLES. limit per square inch of the bars, as found by tests made upon them entire and upon cylinders turned from the cores, are given in the following table. Iron F, Third Lot. Comparisons of the Reductions by the JRolls, ivith the Effects upon Tenacity and Elastic Limit, of Iron Fj Third Lot. Cm < Areaof Bar in percent of area of Pile. Tensile Strength. Elastic Limit. o Entire Bar. Core. Entire Bar. Core. 4 35 31 3^ 3 25 2| f n 1' l| 11 1 3 1 4 Sq. in. 80 80 80 80 80 80 80 72 72 36 36 36 36 36 36 23 25 12^ 9 9 3 Per cent. 15.70 13.80 12.03 10.37 8.83 7.42 6.13 5.52 4.36 7.67 6.68 5.76 4.90 4.12 3.41 3.96 3.14 4.91 3.60 2.50 2.17 3.68 1.60 Pounds. 47*344 48,505 47,872 49,744 50,547 50,529 50,820 52,339 52,729 50,149 51,921 50,716 50,673 52,297 52,275 54,098 57,000 Pounds. 46,322 46,667 47,000 47,014 47,761 46,466 47,428 49,290 48,280 49,370 48,792 49,144 51,838 48,819 49,801 50,530 51,128 50,374 50,276 51,431 52,775 54,108 59,585 Pounds. 29,758 31,267 35,864 35,615 35,954 35,394 35,087 39,103 39,608 35,493 39,066 33,931 33,933 34,450 38,445 38,475 Lost Pounds. 23,430 23,636 24,961 24,591 26,400 26,333 29,941 32.163 31,892 37,042 38,992 34,208 36,467 40,534 37,771 38,596 33,931 35,933 34,545 39,126 40,098 Lost A study of the table shows first that upon the nine succes- sively decreasing sizes, viz., from 4'' to 2'\ there was but one ex- ception to a constant rise in tenacity accomjDanying the increase of reduction by the rolls, and that the elastic limit rose \\])o\\ each successive step with two exceptions, which are very slight, it falling off 350 pounds in one and 67 pounds in another in- stance ; the tenacity of the 2" (4.36 per cent of pile) being over that of the 4'' (15.70 per cent of pile) 1,106 pounds, and the elastic limit 8,462 pounds. From the ly (7.67 per cent of pile) to the 1|'' (3.41 per cent of pile), the iron was somewhat irregular, and there was but a THE BAR. 15 slight rise in tenacity, viz., 431 pounds, but in the elastic limit the rise was 4,993 pounds. The tenacity of the y' (4.91 per cent of pile) was but 104 pounds greater than that of the 1.^' (4.90 per cent of pile), that of the f (2.50 per cent of pile) nearly corresponding with that of the If (4.12 per cent of pile). The effect of reduction was most marked on the smaller sizes, the I'' (2.17 per cent of pile) having nearly 5,000 pounds less tenacity than the \" (1.60 per cent of pile). The notes taken at the mill do not indicate that either bar was under or over heated ; but there are indications that the 1^'^ bar was overheated^ inasmuch as the strength of the core exceeded that of the entire bar. So far as this experiment was expected to account for the usually found greater strength of the 1|^' bar, it proved a fail- ure, for it was weaker than the bars immediately succeeding or preceding ; but we considered that the information gained as to the probable effect of under and over heating was of value. The indications are that if a bar is underheated it will have an unduly high tenacity and elastic limit, and that if overheated the reverse will be the case ; further, if underheated the strength obtained by a cylinder turned from the core will be less than that which would be obtained by testing the entire bar, if the diameter be small, and greater if the cylinder is turned from a large bar. It is possible that the above two points are interdependent, as the large bars are more apt to be irregularly heated than the small ones, and some portions of the pile must be in a state fit to roll before other portions are sufficiently heated ; these over- heated portions we turn off from the bar to produce the cylin- drical test-piece. As in the previous experiment, we believed that the thorough work received by all sizes put them in condition which prevent- ed the effect due to a slight difference in the reduction being plainly manifest. We therefore selected for another experiment the bars of a very slightly worked iron ; viz., iron N. 16 WROUGHT-IRON AXD CHAIN-CABLES. Ieon N. Dimensions of Piles, Areas of Piles, of Bars in percentage of Areas of Piles, Tenacity, Elastic Limit, ^c, of Iron N. Area of Bars Size of Bars. Dimensions of Piles. Area of Piles. in per cent of Area of Piles. Tensile Strength. Elastic Limit. Sq. In. Per cent. Pounds. Pounds. 2 " 6"x4f"x26 " 27 11.63 51,848 32,461 1^ 6 x4f x21 27 10.22 54,034 33,610 If 6 x4f x21 27 8.90 55,018 34.283 If 6 x4| xl6t^ 27 7.68 56,344 35,889 ^ 4 x3| X25*' 15 11.78 53,550 34,690 If 4 x3f x23 15 9.90 54,277 33,622 4 4 x3f xl7 15 8.18 56,478 33,251 4 4 x3| xl6 15 6.62 56,143 32,267 The above results supplied the missmg evidence. With one exception, the tenacity and elastic limit increased upon each successive increase in the amount of reduction by the rolls, as shown more plainly thus, where they are arranged in the order of their reduction: 1^ (6.62 per cent of pile), 56,543; Vi" (7.68 per cent of pile), 56,344; W (8.18 percent of pile), 56,478 ; If" (8.90 per cent of pile), 55,018 ; W (9.90 per cent of pile), 54,277; 11" (10.22 per cent of pile), 54,034; 2" (11.63 per cent of pile), 51,848; W (11.78 per cent of pile), 53,550. The tensile strength of the 2" bar was probably greater than recorded, the iron being so brittle that the head of the test- piece pulled off, and the bar could be broken by sledge-blows, without previous nicking. This iron, under every form of test, showed, by its marked contrast with iron F, the dis- advantages which follow too little work. The evidence submitted is of sufficient value to justify us in asserting that variations in the amount of reduction by tlie rolls of different bars from the same material produce fully as much difference in their physical characteristics as is produced by differences in their chemical constitution. THE BAE. 17 In order to ascertain beyond question if the rule would work- in both directions, and if, by giving to a series of bars a uniform reduction, their tenacity, &c., would prove uniform, the follow- ing experiment was made : — One of the leading manufacturers of the country, having placed both the facilities of his mill and as much material as we wished at onr service, three sets of bars were rolled, which are termed Fx Nos. 1, 2, and 3, all of which were of the same material as iron F, In preparing the piles for the first set, they were so graduated that the percentage of the pile's area borne by the bar should increase slightly upon each reduction in diameter of the bar ; it being believed that the additional work thus given to the smaller sizes would, in a measure, counteract the possible differences which might be due to overheating of the large and underheating of the small bars. The dimensions of piles, &c., are given in the following table, together with the tensile strength, elastic limit, &c., of the resultant bars. FxNo. 1. Dimensions of Piles, of Bars in per cent of Piles, Tenacity and Elastic Limit of Series of Bars, of Fx No. 1. Size Dimen- Area of sions of of Bars. Piles. Piles. In. Inches. Sq.In. 2 8x10 80 1^ 8x 9 72 l| 8x 8 64 l| 6x10 60 4 6x 9 54 If 6x 8 48 H 6x 8 48 4 6x 6 36 1 6x 5 30 Area of Bars in per cent of Area of Piles, Per cent. 3.93 3.83 3.75 3.45 3.27 3.09 2.55 2.76 2.62 Tensile Elastic Strength. Limit. Pounds. Pounds. 52,011 34,702 52,874 35,641 53,846 36,573 53,537 34,235 53,491 34,307 52,968 33,275 55,307 34,784 56,434 34,682 55,770 34,279 Average 53,121 T. S. and 34,700 E. L. Average 55,837 T. S. 34,582 E. L. and 18 TVKOUGHT-IKON AND CHAIN-CABLES. The results show a nearly uniform tenacity for the first six sizes, then an increase, which remains quite uniform for the other three, the elastic limit remaining very uniform tlirough- out. The tenacity of the 2'' bar, rolled by the usual process (iron F, 2''), its area being 5.23 per cent of pile, was 47,569 pounds, showing an increase upon this size, by the experimental pro- cess, of 4,442 pounds ; and the increase of the elastic limit, 5,910 pounds, was still more marked. No explanation, except that they were possibly not enough heated, accounts for the increased tenacity of the IJ'' and the r' bars; and the li^'was, by mistake, rolled from too large a pile. A second attempt to produce a set of bars of uniform tenacity resulted in a complete failure, due, we were assured, to a misunderstanding in regard to heating the piles ; but on a third attempt we were successful, as shown by the following table, in which the usual data are given : — Dimensions and Areas of Piles, Areas of Bars in percentages of Piles, Tensile Strength, Elastic Limit, Sfc, of Nine Bars of Iron Fx No. 3. Area of Bars Size of Dimensions Area of in Tensile Elastic Bars. of Piles. Piles. per cent of Area of Piles. Strength. Limit. Inches. Inches. Sq.In. Per cent. Pounds. Pounds. 2 8x10 80 3.92 50,763 33,258 1^ 8x10 80 3.45 53,361 35,032 If 8x 9 72 3.34 53,154 35,323 n 8x 8 64 3.24 53,329 33,520 u 6x 9 54 3.27 52,819 34,840 If 6x 7 42 3.53 52,733 34,606 11 6x 6 36 3.41 53,248 33,520 H 6x 5 30 3.31 54,648 34,695 1 5x 5 25 3.14 53,915 36,287 The pile for the 2" was necessarily two small, as there were no rolls in the mills which would take a larger pile. The record is, however, of value as a contrast to that of the other THE BAE. 19 eight bars, the average of whose tensile strength, 53,401 pounds, and of the elastic limit, 34,365 pounds, is but slightly varied from by any of the bars. Two practical results of value may be deduced from this investigation of the action of the rolls. The first is, that, as important differences exist in the pro- portionate strength of different-sized bars made of the same material, which are due entirely to differences in the processes by which they are manufactured, and as the elimination or reduction of such differences would necessitate such a great and expensive change in the system by which the bars are pro- duced that it is not probable that it will be often attempted, it is necessary that these differences should be taken into consideration when estimates of the strength of any structure in which rolled wrought-iron, of different sizes, is introduced, are made, and in all tables of strength based upon the strength of such bars. Second, that, where the increased value of the bars will justify the increased expense of their production, those of ^' diameter can be increased in tensile strength over 15,000 pounds ; and it is not improbable that bars of ^' diameter can have the strength increased over 60,000 pounds, with no loss in their power to resist sudden strains. 20 WROUGHT-IKON AND CHAIN-CABLES. SECTIOISr II. Part I. — A Paper showing, hy many Experiments, the Correct Form and Pro- jjoriion of Test-Pieces to be used in order to procure correctly the Tenacity, Elastic Limit, S^^c, of Various Metals. Part II. — A Comparison of the Strength of Bars in their Normal Condition, ivith the same after the Bars have been reduced hy turning away the Surface. PART L— FORM AXD PROPORTIONS OF TEST-PIECES. In obtaining the results introduced in the tables of records of bars tested by tension, we have used the two testing-ma- chines A and B. By the first, we have tested all the bars of diameter greater than one inch ; and, by the latter, bars in their normal condition of less than one inch diameter, and cylinders turned from tlie larger bars. Our tests made upon these cylinders gave results of tensile strength and elastic limit which were so much lower than the manufacturers of the various irons considered their products equal to, that some dissatisfaction and doubt as to their cor- rectness were expressed. Upon examination, we found that in nearly all cases where our results were supposed to be erroneous,- — on account of a lack of coincidence with results obtained in some cases by the experiments of private testers of iron, and in others by tests made in government navy-yards, by persons presumed to be competent, — the tests whose results cast doubt upon ours had been made upon test-pieces turned from the bars to a reduced diameter, which at one point was reduced by a groove to a much less one, as shown in Fig. 1, p. 25. FORM AND PEOPORTIOXS OF TEST-PIECES. 21 The errors which arise through the use of this erroneously shaped and proportioned test-piece have been frequently pointed out, first by Kirkaldy, and subsequently by C. B. Richards, mem- ber American Society of Civil Engineers ; but it does not ap- pear that even yet the errors which thus arise are fully recog- nized. As a case in point, the following comparisons of the strength of various-sized bars of iron F, as found by our tests, and as furnished to the manufacturers by so-called testers, will fully illustrate. This iron is ahcays of so uniform a strength and quality, that the test of one bar furnishes most valuable evidence as to the probable strength of another. Strength per Square Inch of Iron F, as found hy and as furnished to the Coynmittee. Size. 33 H K C d Strength Found. 02 H 6 Strength Furnished. OS o o C From — To — Average From — To — Average k3 «2 Of 2f 21 l^ 1| If 1^ i| If 3 3 3 9 8 8 8 8 8 Pounds. 46,164 47,558 49,i55 46,862 48,370 48,792 49,144 49,342 48,819 Pounds. 46,702 47,871 49,465 49.700 51,300 50,342 51,300 51,840 50,000 Pounds. 46,446 47,764 49,623 48,i32 49,048 50,325 51,221 51,423 52,396 5 4 8 18 15 15 12 i2 Pounds. 58.434 54,759 50,773 58,111 57,473 59,440 57,999 63,ii6 66,3i2 Pounds. 65,357 60.757 64,099 71,025 64,823 67,471 66,907 75,545 68,255 Pounds. 62.540 57,230 59,048 63,586 63,300 63,350 63,230 65,083 67,062 16,094 9,472 13,963 15,2i8 "With the tabulated statement furnished, the average tensile strength of all sizes combined was given at 63,207 pounds ; and the results from the sizes If and If'' had been consolidated, also those from \^' and \\" . With experimenters developing by accident such a uni- formity in the average tensile strength of the various sizes, it is not to be wondered at that no attention had been drawn to 22 WROUGHT-IEON AND CHAIN-CABLES. the variation in strength accompanying variations in diameter, which is i^lainly indicated in our more correctly-made experi- ments. The broken test-pieces by which the results were procured were shown to us, and they were of the groove-form. We determined to thoroughly investigate the effect upon the results which were due to variations in the proportions of the test-pieces. The stock of contract-chain on hand, all of which had been considered to be of a tensile strength of at least 60,000 pounds per square inch (the standard at that time, as it is, or was, also, of the British navy), furnished material for experiment ; and a number of comparative tests were made by means of grooved test-pieces and short cylinders, with results as follows : — Comparison of Results obtained from Chain-Iron on Jiand, hy means of Grooved Test-Pieces and Short Turned Cylinders. Dimensions of Test-Piece. jSTo. of Tests. Tensile Strength PER Square Incu. Grooves ex- ceed Cylin- ders BY — 9 < ■i CI .S ">> > O O o 3 2 2 2 2 2 1 2 2 2 CO o CO o > O 2 o CO C O o Appearance op Fracture. In. 1 1t\ 'A If If h\ We H 1^ If Square Inch. One-quarter. One-quarter. One-quarter. One-quarter. One-quarter. One-quarter. One-quarter. One-quarter. One-quarter. One-quarter. One-half. One-half. One-half. One-half. One-half. One-half. In. 1.20 1.20 1.20 1.20 1.20 1.20 1.20 1.20 1.20 1.20 1.25 1.25 1.25 1.25 1.25 1.25 3 2 3 2 2 2 2 1 2 2 2 2 2 2 2 Pounds. 57,700 50,000 52,000 48,000 58,900 52,400 54,200 58,400 40,900 55,450 54,300 58,400 51,500 50,900 44,000 48,200 Pounds. 71,530 70,000 05,850 59,000 07,400 02,800 07,200 07,200 54,500 05,400 00,000 09,700 04,900 02,400 58,500 56,900 13,830 14,000 13,190 11,000 8,500 10,400 13,000 8,800 7,600 9,950 11,700 11,300 13,400 11,500 9,500 8,700 23.5 24.5 24.0 25.0 14.6 20.0 24.0 15.0 16.0 18.0 21.0 19.0 26. 22. 19! 18. Fine steely. Fine steely. Fine steely. Fine steely. Coarse granulous. Fibrous. Fibrous. Coarse fibre. Coarse granulous. Gray fibre. Gray fibre. Gray fibre. Coarse granulous. Coarse granulous. Coarse granulous. Coarse granulous. rOEM AND PROPORTIONS OF TEST-PIECES. 23 These results made it evident that the government had not received iron of such great tensile strength as was supposed ; and this was made more certain by the results procured subse- quently by comparative tests upon several of the irons which make up our records. These are here given. One groove-test was made upon each size. Comparison of Results obtained from CijUndrical and from Grooved Test-Pieces. Irons C, B, J, F, L, E. Iron. Dimensions OF Test- Piece. T. W W H o c Ultimate Strength per Square Inch. Grooves ex- ceed Cylin- ders BY — 1 ^ Cm .a s o O 5 c 3 O c o O Pi Remarks. c c c c c B B J J F F L L L L L E E In. ■ 5 if !!• k' If . 1 If 11 In. .804 .804 .504 .504 .504 .800 .800 .800 .040 .800 .504 .800 .504 .070 .800 .504 In. 1.25 1.20 1.30 1.20 1.25 1.30 1.30 1.30 1.40 1.20 1.30 1.35 1.37 1.35 V.30 1.30 2 2 2 2 2 2 2 2 2 2 2 2 2 2 1 2 2 2 Pounds. 54,800 57,700 58,900 58,300 59,100 07,000 05,050 57,300 02,200 01,900 00,520 75,250 74,400 94,400 80',600 59,520 01,000 Pounds. 47,885 48,000 50,000 52,000 45,800 51,900 53,000 50,350 50,300 50,130 50,400 58,390 .59,290 75,233 74,000 00,500 50,080 50,000 6,915 9,100 2,900 6,300 13,300 15,100 12,050 6,950 11,900 11,770 10,120 16,860 15,110 19,167 13,500 9,440 11,060 14.5 10.8 5 12.1 20 29 22.5 14 24 23.5 20 29 25 25 26.5 20 18 21 Strong and tough. Hard and coarse. Hard and coarse. Hard and coarse. Strong and tough. Strong, good stock. Not enough work. Irregular. Irregular. Soft and ductile. Soft and ductile. Steel. Steel. Steel. Steel . Steel. Tough and strong. Tough and strong. It is to be noticed that the difference between the results obtained by the two methods is greater in pure refined iron than it is in coarse material. A single experiment, made with a test-piece of each form upon cast-iron, confirmed this view : tlie difference of results was less than one per cent, and the cylinder proved that much the stronger. 24 WROUGHT-IEOX AND CHAIX-CABLES. A series of experiments was undertaken for the express pur- pose of enabling us to decide upon the correct form and proportions necessary in the test-pieces to insure correct results. The first of this series Avas made upon eighteen test-pieces turned from a 2'' bar of a remarkably pure, refined, and uniform iron (K). No. 1 of this series was 10'' long ; and the length decreased upon each successive number, until, at 18, the groove-form was reached. The diameters were nearly constant, except in two cases where seams encountered made it necessary to turn away more iron. The results are given in the following table : — Iron K. Stress per Number. Original Length. Per Cent of Elongation. Per Cent of Contraction Square Inch when Piece Breaking Stress per Remarks. of Area. began to Square Inch. Stretch. Inches. Pounds. Pounds. 1 10 23.1 38.2 29,678 54,888 Slight seam. 9^ 24 3 36.5 28,011 55,288 3 9 21.5 31.1 29,345 55,355 4 2^ 22 31.2 29,315 55,622 5 6 Ik 25 39.9 30,840 54,890 Slight seam. t 25.8 38.6 30,412 55,488 7 H 22.1 40.0 28,562 51.800 Bad seam. 8 6 22.3 34.7 30,600 55.418 9 52 25.4 39.3 29,475 55,333 10 11 O 4 21.2 25 7 32.2 37.*4 29,278 29,705 55,887 55,532 Slight seam. 12 l^ 26.7 36.6 31,817 55,482 13 3 27 38.3 31,123 56,190 14 15 16 17 9 27 36.2 33,428 56,428 Seamy. 1* 26 37 34.0 34.3 42,249 34,288 57,096 58,933 Seamy. „ 4 30 37.0 57,565 59,388 Seamy. 18 Groove. 20.6 45,442 71,300 Nos. 13 and 18 of the preceding table are reproduced in the following illustration : — Fig. 1 being Xo. 18 of the table, and Fig. 2 No. 13 ; In Fig. 1, the length a h was 3'', the diameter, c c, .976''. In Fig. 2, the length a h was 3", the diameter, c c, .970 Tiff FORM AXD PROPORTIOXS OF TEST-PIECES. 25 The pieces were nearly the same in dimensions; yet the stress at whicli No. 13 broke, reduced to the square inch, was over fifteen thousand pounds less than that required to break No. 18. This difference would be very great in estimating the entire strength of the bar from the results of the two pieces. Were those from No. 18 correct, the bar would be equal to a strain of one hundred tons; while No. 13 shows that less than seventy-nine tons w^ould tear it asunder. By the table, we see that the piece No. 13 gave higher results than those w^hich were long- er; the average tensile strength developed by Nos. 2, 3, 4, 6, 9, 10, 11, and 12 being bb^- 488 pounds per square inch, while No. 13 gives 56,190 pounds, — an ex- cess of 751 pounds, — thus suggesting that the length of this piece, viz., three inches, was not sufficient to insure correct results. No. 12 gives a result much closer to the averages, as do Nos. 11 and 10. Assuming that the proper length should be a certain percent- age of the diameter, we find No. 13, which is less than four diameters in length, is not long enough ; No. 12, of about four diameters, gives correct results. The preceding tests in this investigation having been made upon iron with considerable tensile strength, it was thought advisable to make one more experiment with a bar of xqvj soft and ductile iron. I A two-inch bar was selected, which, although 'of low tensile strength, was very tough and ductile. , fl *^ cc^X2Qt^aCc^Qt;oQD2oD3(/j;3a33 ^ -^ O^ OOrt^CjOoOoOoO© OOOOQOOOO -; •uoijoogoQ Ci o aa put; looga '"' C5 •spunod-ioo^ oil.*::::: W •oo.to^ CO *•••••• • -: •uoijooyo([ ^ w > pui;pot)a ^ •spunod-joo^ o * r r : : : : : SlD.IO^ o CO O C5 •uoijoogoQ 00 o a! puu po^^a 05 O •spunod-;oo^ 'oo.io^ o o 8 8::::::: eo CO •uoijooyo(j Cs O O t- O 1-H 1-? o EH O a put; loo{ja •spunod-ioo^ 'oo.io^ rl r-< 8 8 8:::::: o o o_ 00 e* U5E0 -le< nios -»t -» C^i-(i-iT-(i— (r-lr-(i-(iH •X sajL ^0 aaaiciix; 1 t-iMeO'>*'>«wt-.ooo> QD 3 aJ 0^ 3 fC'x; y OQ •. 3 __ if <; 0^ x . . , 1, ooooooo 3 ^tttttth § "3).3 .S .5 .5 .3 .3 .3 i3rtS3SSSB3 =*; '-" ^ ^ ^ ^ ^ Ji! jiS ^'tS O O O O C O O JJS'-' — — ~ — — — 3o555555o •£=. pa :q 000 • o 000 • o o__o o • o coco CO *cf 0CC0O,'l-^V*r"r* r-INCOfeC^feSCifeft OQ 'OOOOOOOO ,00000000 OOOiff>CC II Pounds. II II „ 1 3 34,800 .03 .11 i .03 70,300 4 Q. W. .50 .62 . . H 3 44,400 .03 .10 .03 81,400 2 T. W. , , .70 .72 H 3 61,100 .03 .14 .05 111,000 2 Q.B. , , 1.00 .70 ^ 3 78,000 .05 .24 .03 1 124,000 3 W. 1.45 .75 H 3 80,000 03 .28 .04 1 153,000 2 Q.W , , 1.15 1.00 1* 3 98,000 .03 .28 .06 168,000 2 Q. W , . 1.85 1.25 If 3 100,000 .03 .26 .04 185,000 2 Q. W. , , 1.20 1.40 4 3 110,000 .03 .22 .03 205.600 3 T. W. 1.60 , , 1.30 o" 3 117,200 .03 .19 .04 240,000* • • 1.50 1.70 1.60 These tests indicate, that with ordinary chain-iron, although the first stretch of the open link is produced by a much lower stress than that which the studded one withstands, yet, upon * Not broken. Five ruptures occurred on link No. 2, one on No. 4 studded, and two on open links, in one of which the weld drew. The elongation produced upon the open links by the stress which broke the studded ones was not sufficient to greatly impair their usefulness: the 1", with original inner diameter of 1.55", being reduced to 1.40"; the I5", original inner diameter 2.8", after stress, 2.50"; and the others in proportion, there being sufficient room for the links to traverse freely. 56 WROUGHT-IROX AND CHAIN-CABLES. the strain becoming more severe, the disproportion in its effects becomes less, and that frequently the open link is still service- able after the studded link has broken. The following abstract shows the extreme variation that ^ve have found in the strength of cable of the same size, made from several irons. We gather from it that a variation of from five to seventeen per cent may be expected in the strength of ordinar}* cables ; and that, if proper care is not exercised in selecting the material, the average variation may rise from twelve to twenty-five per cent of the strength of the strongest. Variation in Strength of Cables. i « a) c c 1—1 t- Strength OF Cable. Variation in Strength. Variatiox in Strength byiinclud- ING OMITTED LiNKS. Size of Ca eg c2 a a a 1^ < M i 1 3B 1— ( 3 /' Pounds. Pounds. 1 6 79,200 67,600 11.600 14. P. 18.800 23.7 H 7 89,280 80.900 8,380 9.4 P. 13.200 14.7 4 7 122.100 101,700 20,400 16.6 K. M. 0. 31,100 25 l>c 1 115.000 109.000 6,000 5 M. 40.000 34.7 If 9 137,200 125.000 12,200 8 M. Fx. 42,200 30.7 Wc 2 155,040 139,400 15,640 10 . , , , . H 9 173,000 147,000 26.000 15 M. K. P. 38,400 22.2 1^ 12 199,000 168,000 31.000 15.5 M. 74,000 37 iH 2 2U,160 194,880 19,280 9 , . . , ^ 8 231,300 191,000 40,300 17 Fx. 45,800 19.7 11 2 231.940 204,400 27,540 12 ^ , . , , . 17 6 252,960 215.000 37,960 11 Fx. 47,360 18.6 2^ 8 283,200 240,000 43,200 15 • • • • Aver age • • • 12.1 • • • 25.1 The excessive variation in case of the If is due to the fact that a portion of a lot of excellent chain-iron, C, was composed of very inferior material, which was very irregular in strength ; the strongest link in the lot breaking at 231,300 pounds, and five out of eleven sections breaking at less than 200,000 pounds ; the minimum being that in the table, 191,000 pounds. THE CABLE. 57 No system of tests made upon cable-bolts alone would liave detected with certainty this inferior iron. Had the iron been furnished in thirty-feet bars, each bar would have produced sixteen bolts, with a remainder of twenty-four inches for test purposes, the test of which would have given valuable evidence of the character of the sixteen links. Weight of Chain-Cables. The chain-cables manufactured by the ordinary systems are very heavy ; and we are led by the results of our investigation to believe that their weight can be reduced advantageously, and as great, if not greater, safety be secured. The weight and dimensions of various portions of cables of different sizes, and of full cables, of the length ordinarily used, are given in the following table : — Nwiiber and Weujlit of Links in 150 FatJioms of Cahle. Number of Links in 150 Fatuoms. o . Finished Links. '^ Z J ^ z < Total Weight of 150 Fathoms Cable. Oj Length. Vidth. Weight. Studded Link. Open Link. if if if 19_ 16 ir 113 1' if 2JL 2,925 2,775 2,700 2,550 2.450 2.325 2,250 2,100 2,025 1,950 1,875 1,800 1.725 1.650 1,650 1.575 1,500 1,500 1.425 1,350 Pounds. .25 .25 .44 .44 .50 .50 .62 .62 .75 .75 1.06 1.06 1.25 1.25 1.50 1.50 2.09 2.09 2.25 2.25 5U" 610 ■;i6 7-5- Q 1 -^ loii 11-s- Q 9 " In r 4 2_ 4 ' 4" 4il "l6 614 "l6 * 16 7t'6 710 ' 16 712 * 16 Pounds. 2.90 3.43 4.22 4.89 5.68 6.50 7.52 8.50 9.70 10.87 12.45 13.81 15.47 17.05 19.00 20.80 23 32 25.38 27.72 30.04 191 18^ 18" 17 16 151 lo 14 IP 1? 11* 11 101 10 10 I' Pounds. 8.665 9,701 11,650 12.726 14.236 15,442 17,326 18,256 20,143 21,697 2.3.996 25.510 27.480 28.933 32.334 33.744 36,125 39.215 40.811 41,864 Pounds, 7.934 9,008 10.462 11,604 13.020 14.279 15,931 16,954 18.624 20,234 22.008 23.602 25,330 26.870 29.859 31.382 32.990 36.080 37,605 38,827 58 aykought-irox and chain-cables. Methods by ^vhich the Weight of Cables can be se- duced IN A GREATER RaTIO THAN THE STRENGTH. Two methods of reducing the weight of chain-cables, without impairing their strength, present themselves as results of our experiments ; the first founded upon our investigation of the action of the rolls and our impact tests combined, and the second upon comparative experiments of the strength of studded and open links. I. We have found, that, when made from the same material, the large bars possess less strength, in proportion to their areas, than the small ones, as opposed to steady strain, and generally much less absolute power to resist sudden strains. The strength per square inch of a l§''-bar being 54,000 pounds, that of the ^' would be 50,000 pounds, and the entire strength of the \%'\ 112,000 pounds; which is 71 per cent of that of the 2'', viz., 157,000 pounds. If the two bars, 2^' and \%'\ were equally valuable in every respect for cable, and both in link form developed the same percentage of the bar's strength, say ^1 63 per cent, the strength of the li" cable would be 182,600 pounds, which is 71 per cent of that of the 2'', viz., 256,000 pounds; while its weight, 23,996 pounds, would be but 66.4 per cent of that of the 2^', viz., 36,125 pounds. If it be considered that the loss in actual power to resist steady tension is not counterbalanced by the gain in reduced weight, the comparative powers to resist sudden strains should be considered. It is more than probable that the greater work given to the \%" will have so increased its ductility that its power to resist sudden strains will prove greater than that of the 2'' cable. These views are borne out by many of our experiments, from which we will select the bars of iron N for comparison. This iron was sent to us by a prominent manufacturer, in answer to an order for "samples of best cable-iron." The 2''-bar had tenacity 51,748 pounds, and, when broken by THE CABLE. 59 tension, had a very slight reduction of area and elongation : broken by impact, it proved very brittle, and, while in no ways nicked or injured, would break like a pipe-stem by moderate blows. Tested as cable, the links developed but 141 per cent of the bar's strength ; viz., 232,000 pounds. The If'^-bar, with tenacity 56,344 pounds, when tested by tension, reduced in area to 60 per cent of the original, and elongated 23 per cent. Tested by impact, it proved fairly tough, deflecting to over 60° before breaking, and, when circled with a score, resisted to a greater extent than did the 2'' in its normal condition. Tested as cable, the links developed 164 per cent of the bar's strength, breaking at 195,500 pounds, or at 84 per cent of the strength of the 2''. In this case, there can be no doubt but that the smaller and lighter cable would have proved the most reliable. Irregularity in strength is a great fault in cable-iron : this is more apt to occur in large than in small bars ; one reason for which is, that irregularity in heating the piles produces irregu- larity in strength, and to this the large bars are more greatly exposed than the small ones. The pile and resultant bar of 2'' weighs four or five hundred pounds, and, while passing through the roll, is, of course, much more difficult to handle than a lighter pile or bar; there are greater liabilities of "buckling" and " bending;" and, while the workmen are mauling the bar to straighten it, tlie next bar to be rolled is being delayed in the furnace, and the effects of variation in the heat are not pro- vided against by regulating the latter. It seems but natural, that, if the pile for a small bar is heated enough for rolling in one hour, portions of the large pile are, in the same time, equally ready, and that by longer delay in the furnace they become overheated. The effect of overheating is to lower both the elastic limit and the strength. Irregularity in the workmanship by which the links are 60 WROUGHT-IEON AXD CHAIN-CAELES. manufactured produces irregular strength in the cable. To this the larger bars are exposed to a greater extent than the smaller ones : the lueld is less apt to be perfect. A small bar is, when at the right heat, welded by a few quick blows ; and the time of the operation is not great enough to allow the iron to become cool. With a large bar it is different. It requires more and harder blows, and more time ; and, if at the right heat when the operation is begun, it may be too cool before it is ended, or, in order that it shall not be, it may be heated a little too much on the start ; the surface of the weld is greater, and is more exposed to the danger of interposition of ashes, dust, or scoria, either of which will prevent a perfect weld. Finally, if the cable be finished without any accidental defect, the proof of the 2!' so far exceeds that of the If', in proportion to its strength, that it is possible that the strength it may have had will be lowered by it. For the reasons assigned, we are of the opinion that the margin of safety secured by the use of a cable of If" iron, weighing twelve tons, is equally great as by the use of the 2'', weighing eighteen tons. II. The second method of reducing the weight of cables con- sists in the substitution of open for studded links. There exists a strong prejudice against the use of cables made from links without studs. This prejudice is based upon the opinion which is very generally entertained, that, first, the open link is not as strong as the studded one ; second, that, owing to the want of the support given to the sides by the stud when used, the open link will collapse at a much lower strain than the studded one will, and that this collapse will be so great that the links will nip each other, and become rigid ; and, third, that the liability of the relative position of the links to become misplaced is greater with the open than with the stud- ded links, from which cause jams may occur in the hawse-pipe when the cable is running out, or, after having remained some time with a slack cable, a sudden squall, tautening it, might produce the same effect. THE CABLE. 61 The first of these objections, viz., that the open link is weaker than the studded one, our experiments show to be without foun- dation. The contrary is the case under all circumstances. We are led, by the results of our tests, to doubt that the second objection exists to the extent generally supposed. We find, that, in all cases, the open links begin to change form at a lower stress than the studded ones ; but the sides having straightened somewhat, the stress is soon resisted by the tena- city of the material itself, and unless the iron is very soft and ductile (much more so than is usually the case with chain- iron), the closure does not continue to be rapid ; and at an extreme stress, sufficient to rupture the studded link, if there be one in the section under test, the closure has not been so great as to unfit the open links for service. With irons F and O, both extremely ductile, some of the open links were too much closed for service, but others were not, after having resisted the stress which broke the studded links. Such iron, however, will not often be made into cables ; and we have, to a certain extent, a resource by which this early closure of the sides may be delayed with all irons. A cable made of bolts of | of an inch greater diameter, without studs, will possess fully twenty per cent more strength than the smaller studded cable, and will weigh but a trifle more. For instance, the total weight of 150 fathoms or ten sections of \l" studded cable would be 20,143 pouuds ; and that of 150 fathoms or ten sections of li'' open cable would be 22,008 pounds. Thus the difference in weight would be but 1,865 pounds. The probable strength of the 1^'' studded cable would be, at greatest, 157,000 pounds; that of the U^ if studded, 182,000 pounds, and if unstudded considerably more ; the minimum difference of 25,000 pounds being nearly sixteen per cent of the entire strength of the 1^'' cable. And, as the action of the studs tends to pry open such welds as may not be perfect, the chances for regularity in strength are much increased by its omission. And it is more than probable that the extreme stress 62 WROUGHT-IROX AND CHAIN-CABLES. at which the li'' would break would not close the links of 1|" to such extent as to render them unserviceable. The third objection to the use of open-link cables is that it is presumed that they are more liable to become fouled and kinked than the studded-link cable, while being stowed in the chain-locker, or when slack, and the vessel changes her position without tautening the cable. There are reasons based upon facts which actually exist, connected with the process of manufacture, which justify us in the assumption that the danger from this cause is not so great with open-link as with studded-link cables. [These reasons are given at length in the original report.] CoMPARisox OF Results obtained by Tension upon Sec- tions OF Cable-Links, and upon Baes of the Iron FPvOM which Links were made. It was considered that if there existed, as seemed probable, a relationship between the strength and other properties of the round bar, and those of the links made from it, it would be a valuable result to determine such relationship, and to find to how great an extent it could be depended upon, and within what margins it existed ; inasmuch as the simple and inexpen- sive test of tension upon a portion of a bar would provide data b}^ which the probable strength of a cable made from it could be judged. The following tables have been prepared for the purpose of developing this relationship, and finding its margins. We find that with iron of moderate tenacity, and witli good welding properties, the percentage of the bar's strength, which is carried with great uniformity into the link, is from 160 to 175 per cent ; that, with irons of unsuitable qualities, this per- centage is frequently low and frequently high, it being very irregular, and averages of less than 155 per cent, made up of very irregular factors, are common ; and that Avith the best chain-iron, although there may be links which develop over 175 per cent, such cases are rare. THE CABLE. 63 Comparison of Strength of Cable-Links and Round Bars. Iron A. Cable Links. Round Bars. Ratios of Links & Bars. rs Stress in Pounds. c Stress in Pounds. jo 2 • 1 6 jq • i o '6 O o "a 1s| '6 St O o O 1) 2 > s s ^ ^ rt o j; £ o . 1:3 O IP c"'Sfc to rt A > o o Sb.2 1* C ^ =3 P 1^ a .^11 1^ i o 10 o . 2 J3 11 o5 O 'T ^ ii c; .2 s ft ^ s Ph aa — < m ^ f-^ ^ Ch 25 ^j 25 *n 4 43,700 87,650 84,360 49.9 34,848 55,152 53,097 63.1 1 62.9 158.9 *n 4 44,625 113,650 91,138 1 39.3 28,320 67,200 53,893 42.1 59.2 169.1 *n 4 54,500 134,900 88,925 i 40.4 39,360 79,296 52,254 49.6 58.8 170.2 *n 2 68,650 160,650 90,916 i 42.7 50,080 97,920 55,415 59.3 61. 164. *it 2 72,250 189,800 90,991 [ 38.1 57,792 108,384 51,940 53.3 57.1 175.1 *ij 1 91,000 221,500 92,099 1 41. 63,840 124,128 51,606 51.4 56. 178.4 *i| 2 93,800 233,600 82,858 1 40.2 2 76,608 142,991 50,880 53.5 61.3 163.2 Iron F. First Lot. n n n n 2 28,500 50,000 51,000 60,540 71,000 76,400 83,500 105,000 86,400 101,700 119,000 155,500 174,700 203,500 230,900 268,750 87,698 33. .60 3 82,855 : 49.1 .... 2 79,545 42.9 .90 2 88,002 38.9 1.00 2 84,764 40.6 1.00 2 84,615 37.5 1.90 2 83,177 i 36.1 2.4 2 86,414 i 39.1 .... 2 32,993 39,360 48,190 56,640 69,890 77,520 91,295 85,950 53,053 64,990 77,235 91,875 107,520 121,920 140,925 152,260 53,850 52,970 51,296 51,994 52,163 50,690 51,039 48,956 62.1 1 61.4 ! 60.5 63.9 ' 62.3 64.9 61.6 59. 64.9 61.5 63.5 ; 59.9 64.7 I 60.6 56.4 ! 56.6 162.8 156.4 154. 169.2 162.5 166.9 163.8 176.5 Iron F. Third Lot. 35,600 67,600 84,372 52.6 2 31,300 41,600 51,921 75.2 61.5 162.4 n 47,600 85,000 84,745 56. 2 35,600 50,300 50,149 70.7 59.1 168.8 1 1 55,000 107,600 87,693 51.1 2 48,600 64,700 52,729 75.1 60.1 166. i| 65,600 128,600 85,962 51. 2 58,500 78,300 52,339 74.7 60.8 164.2 I5 70,600 150,500 85,172 47. 2 62.000 89,800 50,820 69. 59.6 167.6 ii .. .... 2 72,000 103,500 50,529 69.5 .... ii 90,000 1*97,600 83,095 45.5 2 85,500 120,200 50.547 71.2 60.8 164.6 ii 90,000 215,600 78,514 41.7 2 97,800 136,600 49,744 71.7 63.3 15^.8 2 100,600 233,600 73,621 43. 2 113,800 151,900 47,872 74.8 65. 148.8 1 3 1,533 3,775 76,003 40.7 1 2,919 59,585 .... 77.6 129.3 § 4 3,875 8,916 80,647 43.7 4 4,410 5,949 54,090 74.1 67.1 149.9 1 3 6,600 16,933 «6,100 39.1 1 7,680 10,343 52,772 74.3 61.2 163.7 1 2 5,800 25,400 85,519 20.9 3 10,834 15,924 52,051 67.9 62.7 159.5 3 2 10,000 34,700 74,460 29. 3 16,748 23,024 50,764 72.8 66.9 150.6 1 2 15,805 46,400 74,999 3 21,097 31,317 50,716 67.4 67.7 148.1 Iron Fx. First Lot. 34,800 70,300 86,036 49.5 1.12 5 27,680 45,040 55,770 61.5 64. 156.8 V, 44,400 81,400 79,725 54.5 1.42 5 35,500 57,620 56,434 61.5 70.8 141.2 61,100 111,000 90,464 55. 1.70 5 43,100 68,460 55,253 63. 61.7 162. 78,000 124,000 82,887 62.9 2.25 5 50,480 80,360 52,968 64.8 62.8 154.2 ^5 80,000 153,000 88,593 52.3 2.15 5 60,620 94,520 53,491 64.1 61.8 161.8 If 98,000 168,000 81,513 58.3 3.11 5 70,560 110,140 53,537 64. 65.6 152.4 IS 100,000 185,000 76,923 54. 2.60 5 87,960 129,500 53,846 67.9 70. 142.8 1| 110,800 205,600 74,063 53.9 2.90 5 98,920 146,780 52,875 67.3 71.4 140. 2 1 117,200 240,000 76,384 Not br'k'n 4.8 5 108,980 163,420 52,011 66.6 .... .... * The tests marked * were upon single links, the others upon sections of cable. THE CABLE. 6b Iron Fx. Third Lot. Cable Links. Round Bars. Ratios of Links&Baes. ■3 Stress in Pounds. tc 6 c c Stress in Pou nds. i-% cS ■£ an o O d A 2 3 o . to O «S 9 2:3 an •^ CD .2 rt cS'-' Cm o o n o o ■^ 1 O — ? o o rt ^ o rO II o a |3 34,500 69,600 88,617 49.6 2 28,500 42,350 53,915 67.3 ' 60.8 164.4 n 39,600 86,000 85,724 46. 2 34,800 54,300 54,644 63.5 63.7 157. ji 49,000 105,000 84,202 46.7 2 41,800 66,400 53,247 62.9 63.2 158. ii 60,000 126,800 83,586 47.3 2 52,500 80,000 52,733 65.6 63. 158.6 li 70,600 152,800 85,315 46.2 2 62,400 94,600 52.819 65.9 61.9 161.6 ig 83,000 179,000 85,769 46.4 2 70,000 111,300 53,329 62.9 63.1 160.8 ^T 100,000 190,600 80,237 .52.5 2 81,000 126,100 53,154 64,8 66.2 151.2 1| 109,000 229,000 83,394 47.6 2 96,200 146,500 53,361 65.7 64. 156.4 2 118,000 238,600 75,938 49.5 2 104,500 159,500 50,763 65.5 66.8 149.6 Iron G. 160,100 195,200 215,200 P0,605 94,118 89,480 1 62,600 91,800 51,958 1 68.1 1 69,100 106,200 51,205 65.6 1 87,200 121,200 50,.395 71.9 57.3 I 174.4 54.4 183.2 56.3 I 177.6 Iron II. *ii *1J 1 1 1 170,000 204,100 225,200 96,208 97,409 93,638 .... .... 1 1 1 53,000 60,900 67,000 92,700 108,500 129,400 52,462 57.1 52,314 56.1 53,800 51.7 1 54.5 53.2 57.5 183.4 188. 174. Iron J. 1 1 1 157,600 120,000 222,700 89,190 57,859 92,600 .... .... 1 1 1 90,200 109,400 128,100 51,047 52,748 53,264 .... 57.2 91.2 57.5 174.6 109.6 173.8 Iron K. n 1 39,400 84,500 85,001 46.6 1.70 3 37,120 60,096 60,458 61.7 71.1 140.6 i\ 1 47,000 96,000 78,240 49. .50 2 44,640 72,960 59,461 61.1 76. 131.4 li 1 58,000 125,800 84,714 42.2 .47 2 46,080 82,848 55,790 55.6 65.8 150.6 1^ 1 57,600 143,000 80,925 31.2 .87 2 59,040 101,280 57,317 58.2 70.8 141.2 Iff 2 72,900 177,450 85,559 41. .86 4 72,640 118,463 ! 57,132 63.1 66.8 149.7 4 1 72,500 172,800 71,850 42. .65 1 79,680 139,200 57,874 57.2 80.5 124.1 1? 1 97,000 246,800 89,387 39. 1.00 2 85,680 154,080 55,803 55.6 62.4 J60. 2 1 104,000 258,900 82,400 40. 1.00 2 101,280 191,520 58,890 52.8 74. 135.2 Iron L. *ii 193,200 163,600 254,600 109,337 78,881 105,862 50,500 92,200 87,200 123,300 139,200 145,000 69,779 67,116 60,291 41. 66. 60. 63.8 85. 56.9 156.6 116.2 175.6 Iron M. n 6 53,700 117,716 98,905 45.7 .... 20 ••••»• 65,960 53,752 « • • • 57.3 178.4 n 22 59,390 116,628 78,341 51.4 .... 115 54,789 83,300 55,991 65.8 72.0 140.5 ih 6 71,700 152,467 86,270 47.2 162 61,808 97,250 54,480 62.9 63.8 159.3 Is 2 (80,000 (79,000 125,000 180,000 60,270 86,788 64. 1 43.7 i .... 10 74,510 119,750 57,402 61.7 .... * The tests marked * were uijon single links, the others upon sections of cable. 66 WEOUGHT-IEON AND CHAIN-CABLES. Iron M. Second Lot. Cable Links. w 13 Stress in Pounds. it) ij '^3 "cS a 01 M = « o ■ji — o O «5- . O 00 Q) . v« m ^ ~ « r; " a . .a<1 o ti 2^ iOs !^ S fe M it? Round Bars. Stress in Pounds. £^ ^ CS c >-• ■z< " c 3.- to 0) u ^ ^ D cs O cS Ratios of Links&Baks. 4'iJ 1?C5 o a 13 1-5- If iJ^i -^16 ll3 92,000 to 114,000 77,000 to 117,000 113,100 to 133,000 155,000 to 169,000 187,000 207,000 212,000 to 225,600 210,000 to 228,000 255,000 to 278,000 75,244 to 92,909 57,650 to 86,474 76,094 to 89,562 88,058 to 95,642 90,175 92,576 88,149 to 93,804 81,395 to 88,605 81,158 to 91,661 72,700 59,248 .... 76,800 56,761 .... 84,300 56,777 .... 99,429 56,270 .... 113,760 127,700 54,851 57,115 137,092 57,003 .... 142,367 55,181 .... 171,490 54,580 .... 63.8126.6) to to J 79.0,156.8) 65.6100.3) to I to J 99.7152.3) 63.4|l34. ) to to } 74.6ll57.7) 58.8:156.4] to I to j 63.9|169.9] 60.8,164.4 61. 7 1 162.1 60.8154.7] to 64,7 61.4 to to 164.5] 147.6) to } 67.8167.6) 61.7 148.6) to I to 5 67.3162.1 Iron iV. n 45,000 85,000 84,915 53. 1.76 2 32,300 56,200 56,143 57.5 66.1 151.2 n 58,000 105,000 85,574 53.8 2.06 2 40,800 69,300 56,478 58.1 66. 151.4 n 70,100 126,400 84,492 55.4 2.52 2 50,300 81,200 54,277 62. 64.2 155.4 H 80,000 152,200 87,270 52.5 2.77 2 60,500 93,400 53,555 64.7 61.4 162.8 Is 96,200 195,500 92,566 49.2 3.60 2 75,800 119,000 56,344 63.6 60.9 164.2 n 110,300 201,100 85,538 54.8 1.75 2 80,600 129,350 55,018 62.3 64.3 161.8 ^ 116,200 223,700 81,463 51.9 3.40 2 92,300 140,150 51,037 66.1 62.6 159.6 2 118,000 232,000 73,116 50.8 2.60 2 103,000 164,200 51,748 62.6 70.8 141.2 Iron O. 31,400 68,000 84,872 46.2 30,000 46,000 57,363 65.2 67.6 n 35,000 80,900 85,131 43.3 30,800 50,400 53,035 61.1 62.3 H 45,800 95,500 77,832 48. 36,900 61,400 50,040 60.1 64.3 51,200 125,400 87,631 40.8 50,000 72,400 50,594 69. 57.7 i| 1 60,000 155,500 86,823 38.6 58,000 91,400 50,919 63.4 58.8 74,500 180,000 87,336 41.4 70,100 108,000 52,401 64.9 60. n 90,000 207,000 89,070 43.5 75,000 116,500 50,129 64.3 56.3 n 102,000 237,000 87,288 43. 83,800 129,000 47,478 65. 54,4 2 119,800 238,000 75,747 50.8 98,700 151,600 48,249 65.1 63.7 148. 160.6 155.6 173.2 170. 166.6 177.6 183.8 156. THE CABLE. 67 Iron P. n 1-5- n n 2 Cable Links. Round Bars. Ratios of Links&Baus. 1 s 'to O O J?; Stress in Pounds. llatio between first Stretch and Frac- ture. a o p o . 00 Stress in Pounds. ItiUio between Stress- es of first Stretch and Frai^ture. 00 1— < a n o ;-l ai a CS First Stretch was observed. J4 o o £ • Borne by end per square inch sectional at Area. O o pS :3 c _ 52,800 6| 61,800 l' 125,000 112,320 110,000 134,592 141,000 134,592 256,320 88,612 .... 2 91,317 47.6 94 89,968 .... 1 86,876 43.8 2 74,196 .... 1 80,000 48.8 1 45,124 48,550 46,080 53,760 96,000 70,704 55,782 61.4 74,427 54,518 65.3 .... 78,624 52,556 58.6 58.4 89,300 53,345 .... .... 95,904 52,868 56.1 71.2 59,840 49,872 63. 62.4 157.9 i6o!4 Iron P, Second Lot. 1 IS n n n n n n 2 38,000 45,200 50,400 60,000 73,600 86,000 106,000 115,000 129,000 60,400 76,000 122,100 118,400 156,000 199,000 212,000 233,000 242,000 78,461 77,141 94,871 76,933 85,950 94,270 86,143 83,933 Not bro 62.9 2 59.5 2 43.1 2 50.7 2 47.2 2 43.2 2 50. 2 49.4 2 ken 2 30,200 40,700 47,450 53,500 60,650 70,800 82,400 89,700 101,150 44,500 56,500 73,200 85,000 98,300 117,500 130,050 145,200 161,300 57,807 67.9 73.7 57,289 72. • • • • 56,876 64.8 60. 55,230 62.9 71.6 54,159 61.7 ! 63. 55,634 60.2 75.3 52,844 63.4 ' 61.3 52,305 61.8 1 62.3 50,834 62.7 1 .... 135.8 im.s 139.6 158.6 169.4 163. 160.4 Iron Px. n 53,000 116,000 93,023 45.7 .... 2 42,300 70,250 56,334 59.5 60.6 165.2 1^ 71,400 156,000 87,102 45.8 .... 2 62,000 97,350 54.354 64. 62.4 160.2 1^ 84,600 196,200 91,003 43.1 .... 2 70,600 115,500 54,689 61.1 58.8 169.9 1^ 98,000 209,800 86,231 46.7 .... 2 82,500 131,900 54,212 62.5 63.1 158.4 n 108,200 236,000 85,943 45.8 .... 2 88,600 142,000 51,762 62.2 60. 166.2 2 120,000 242,000 Not bro ken .... 1 98,600 168,800 53,198 58.4 .... .... 68 WKOUGHT-IEOX AXD CHAIN-CABLES. SECTION YI. PROOF STRAINS FOR CHAIN-CABLES. Effects produced by the Use of the Strains pre- scribed BY the Admiralty Proof Table. — Discussion OF THE Principles upon which "Proof Strains" SHOULD BE based. — PrOOF TaBLE CALCULATED UPON SUCH Principles. A finished cable has 3'et a final ordeal to undergo before it is issued for service, — one which may prove disastrous to its value, even if it has escaped every danger that has accompanied its manufacture. It is to be '' proved ; " which means that each of the fifteen-fathom '' sections " of which it is composed is to be subjected to a tensional strain sufficient to make it probable that the presence of any defective links will be made manifest, that they may be removed, and replaced by others. As tension in excess will probably injure the cable, it becomes a matter of importance to fix upon a strain for each size, wiiich, while sufficient to insure the detection of unduly weak links, ivill not produce them. Most American manufacturers of cable use for each size a stress which is prescribed by the standard proof table of the British Admiralty ; and their cables are sold with a guaranty that they have been so proved. Our experiments lead us to doubt the wisdom of thus apply- ing this English standard to measure American material. We consider, that, as applied to cables made of American bar-iron, this standard is faulty in two important respects : — Firsts The stress prescribed by it for every size of cable is too great. Second^ The stresses for the different sizes are unequal in their proportion to the strength of the links. PEOOF STEAINS FOR CHAIN-CABLES. 69 And we assign the following reasons for these opinions : — First, The stress for all sizes is based upon the assumption that the cable bolts of all diameters possess a strength equal to sixty thousand pounds per square inch. Few bars of Ameri- can iron have this strength, and, when they have, their cost pre- cludes their use as cable-iron ; and, as has been shown in the investigations by tension, although this strength may be found in the small bars, it is not found in the large sizes of the same iron. Secondly, If the bars of all sizes did possess this strength, the "proof" is still too great; for it probably exceeds by a considerable amount the elastic limit of the links. The table as furnished to the committee by two prominent manufacturers, viz., Messrs. J. B. Carr & Co. of Troy, and Mr. H. L. Fearing of Boston, is herewith given, that the discussion which follows may be clearly understood. Size. Column 1. Stress in Column 2. Stress in Column 3. Stress in Tons. Pounds. Tons. Pounds. Tons. Pounds. 1 " 1-3- 1-5- li 1 5 ll' 113 O 3 "16 2^ "4 18 20 23 26 28 30 34 37 41 44 48 52 -60 64 (jS 72 80 88 40,320 44,800 51,520 58,200 62,720 67,200 76,160 82,880 91,800 98,500 107,520 116,480 125,440 134,400 143,360 152,320 161,280 179,200 197,120 18 20 23 25 29 31 34 37 41 43 48 51 56 59 64 68 72 76 81.3 91.1 40,320 44,800 51,520 55,960 64.960 61>,440 76,160 82,880 91,800 ' 96,320 107,520 114,240 125,440 132.160 143.360 152,320 161,280 171,360 181,120 204,064 18 20.32 22.78 25.38 28.12 31.01 34.03 37.22 40.50 43.94 47.53 51.25 55.12 59.05 63.38 67.57 72 76.59 81.28 86.13 91.11 40,320 45,517 51,030 56.857 63,000 69.457 76.230 83.317 90,720 98,437 106,470 114.817 123,480 132.275 141.750 151,357 161.280 171,517 182.070 192.937 204,120 70 WROUGHT-IRON AND CHAIN-CABLES. The formula upon which column 3 is calculated is one embodied as a rule as follows : — " For proof of each size, square the number of eighths of an inch in the diameter of the bar, and multiply the result by 630," the result being the stress in pounds. Thus : V\ 8 eighths, squared = 64, and 64 X 630 =: 40,320 pounds." Our experiments show that the elastic limit of the large bars is generally lower than that of the small ones of the same iron. Hence the irregular effect of the proof strains becomes a danger- ous one. The practical and actual results which we have found to occur through the use of this table, and which have doubtless occurred with many cables proved by it, but which have not been founds are that the stress is so great that it always exceeds the elastic limit of the links, and frequently cracks them. A few such results will be given. Six sections, each five fath- oms in length, were made up from good chain-iron ; three were of 1|'', and three of 1|'': all were "proved " by the Admiralty Table, and after proof inspected in the shop ; all were "passed " as sound ; but upon examination by aid of a magnifying-glass fourteen of the 387 links were found to be cracked. In the following table the strength of the strongest and weakest links made from several of the best of the chain-irons we have examined is given, with the ratio borne to such strength by the Admiralty proof strains for the sizes : — Iron. Strength of Large Links. Admiralty Proof, percentage OF Strength of Small Links. Admiralty Proof, percentage OF s 1 5 o 1 to C s t-5 O 1 o o m o ■ 1 01 A C D F N O P 2" n n ii n n Pounds. 283,000 231,300 215,000 215,600 225,700 237,000 233,000 Pounds. 248,000 191,000 57 53 66 66 63.3 60 60.8 65 64 1 " n Pounds. 72,670 96,960 79,200 67,600 85,600 68,000 122,100 Pounds. 69,600 74,488 55.5 52.5 51.3 59.6 60 59.3 51.2 58 65 Average. . .... 61. 64.5 .... 55.6 61.6 PROOF STEAIXS FOR CHAIN-CABLES. 71 Convinced by the evidence which has been given, that prov- ing American cables by this standard was a fruitful source of weakened cables, we were also aware, that, in recommending that it should be no longer used, we should, if the advice were followed, deprive manufacturers of good cables of a safeguard against competition by those who might unchecked use inferior iron. We have therefore considered it essential that we should provide a substitute which would, in our judgment, prescribe strains which would fully ^:>ror^ cables, and not be liable to injure them. We submit such a table, which is based upon the two principles, that a j^roof strain should not greatly exceed the elastic limit, and that the strength of a cable is equal only to that of its weakest link. In the preparation of this table it was first necessary for us to establish within reasonable limits the probable maximum and minimum strength of cables of various sizes, and the elastic limit of the links. Neither of these factors can be fixed definitely : there are many causes which tend to produce great differences, both in the strength and elastic limit of links made from the same bar. The most important of these causes is the liability of the welds, wliich at the best are the weak spots of all links, to lack uniformity ; and no rules can be given which will insure uniform work from a number of chain-welders. We were therefore compelled to base our table upon data which, at the best, could be considered as but indicating probabilities. Assuming as a standard of perfection the characteristics of a bar, which when made into a link should develop twice the origi- nal strength of the bar, we considered that the iron which ap- proached most closely and with uniformity this standard was that which should be considered as the most suitable for cables. We have the records of the strains at which a large number of bars in their normal condition were ruptured by tension, and of many sections of cable made from them, which are incorporated in the "Tables of Comparative Action of Bars and Links." From these tables we have made the following abstracts which enable us to arrive at conclusions as to the probable strength of cables made from irons varying in characteristics : — WROUGHT-IROX AND CHAIN-CABLES. ft ^ N o S • 2 ^ ^ , , CJ . . . CI Oi . rH . . . . . OS ^ • • »o • ; o cs ! CO • • CO ' o . «o o o CO >— < 1-H 1— ( tH 1-H 00 LO CO . CO . CO Ttl . . rtt . lO ? lO '*! CO '. Ci ! 00 05 I CO '. O • • CO H-l CO CO o CO . ^^ CO . '^ • CO LO r-( »— 1 1—1 1— ( f—t tH 1—1 l—^ . GO Ol C5 ■^ . . , . P^ • • CO 05 tH t- o • • • ' • • lO lO ■^ !>. lO -ti o r-H I— 1 1— ( 1— 1 I— 1 1-H o o . Ol . o . CO . r/:> . t^ d CO o o '. « ! o CO ! t^ '. ^ CO ! »0 -t^ o o . t- . t- o . 1- . 00 ^ o r— 1 >— 1 T— 1 r-\ I— I iH j—i iH ^ tH . Ol rH . (M . CO CI . CO . CO Cl . CO ^ • rH 1— ( ! "^ ! c^i -^ ■ 1— ( ! cJ i-H * lO lo o . o . '^ o • o ! '-'^ ■^ o ""^ I— I rH y—^ 1— ( r-t rH 1-H iH . . -*l . ' CJ CO . . . t^ S • • CO : o ! 1^ r- • • * * o I^ . "^ . »^ CI uO rH 1— ( tH tH j-i . o -* . CO . CI t^ . 1— t . CI . o w o T-H : o , 1— t C5 ! "^ : CO LO '. 1-H ^ CO . ^^ . "^ ■rfi . i^« . o CO tl r— ( 1— ( rH rH 1— 1 1— ( rH 1-H rH ^ . CO . CO CO • CI • r^l CO lO >< "-t" »^ CO ! CO ' iH. o * 1— ( ! CO 05 ; t-1 Ph o LO lO . ^^ o o . ^ . "O ■^ o 1— 1 1— ( 1— ( tH T-t. rH 1— t 1-H 1—t 1-H CO (M . CJ . CO TjH . CO . Tfl V, o »— ( Ol ; ^ * 1— ( CI ! o\ : o 1-H ' f^ irt! ■^ o . LO • o o . ^ . "^ o T— 1 T— 1 1—1 »— ( T-^ 1-H 1— ( r^ rH Tt^ CO . CI . o CO . CO . GO . ICO ^ OI O) o ! -H ! t^ '-H '. l>^ '. CO • • CI o o CO . <^ . <^ CO . ^^ . "^ CO »— ( »-H T— ( rH 1— t tH r-\ »-H iH . CO Tfl . . CI o . CS . O) iO ^ CI o ; -^ ; o CI ! '^ : CO CO ; -M CO o . ^^ . «^ o . CO . CO t^ CO t— ( rH 1-H rH rH 1—1 1— ( rH 1-H CO . . CO GO . CO . CI . CO ft lO o o ! CO '. o -tl ! CO ! '^ * 00 o -^^ o o . t^ CO . '-'^ . '^ o 1-^ T— t T— ( 1-H lH tH 1-H rH tH . . . , . C5 o . . . CO d • • • • . 1-H lO : CO • • • CO . "^ lO ; «o o 1— ( lH 1— ( 1-H . . . -^ . t^ . t^ . . CI w • • • • CO I • CO ; 1-H * • CO t^ CO o o 1—1 1-H 1-H ^ o o o . CO . lO CO . . CO C5 T-H -^ 1— t -M CO : CO : t^ o ! CO \ CO O CO 00 CO CO 1-H rH iH rH 1-H l^ CO o rH « u . . • • • • • . • • . . ' • a • • • "'l* wloo J** * • r-lto • tn\t£, • • < -^1« r-lrr ^|r- H« »o|ao rHlr- eol-f r«r- t-lOO m »— ( 1-( rH T— 1 r-\. rH tH rH rH r-t rH 1-H CJ PEOOF STRAINS FOR CHAIX-CABLES. 73 '^^ V- •2 i^^ s ^ ^ "cS • tH • IC CO CO r-H OJ Ol »C) t^ lO T+( CO -^ ^ 1 o I ^ r-l f— 1 CM •rjl CO Cl 1—1 1—1 1— ( Cl >< , ^ . ^ . . • CI CO • • ■ • lO Ph • . . • • • • tH • . . Cl S 1 ] ^^ 1 ! 1 1 Q • ■ • • • ♦ T-l r-{ CO 1-t 1 CO 1 u 1 H ^ < ft w T-i O . CO • CI T— 1 ; C5 ij O o •A • r-i 1—1 ^ CO o *>< 1-1 (M , CI tH Cl 1 =o P^ • 1 . 1— ( 1—1 CO ^ . 1 *^ P^ • • • • . . »-( T— 1 "^ c y-i j 05 ^ • • Q T-t 1—1 '. CO Cl • 1—1 1 ^ 1 d »— ( 1— ( Oi CO "nH CO '. '. ! 1—1 M ! : 1-i r-i CO •o Cl •^ iCt Cl t- TtH CO < '. '. '. '. ! ca Cl 1— CO 3D Tt^ i O 1 '^J ' • • • • • • . -fJ -u •i^ -1^ •4^ -^3 -+J -4J -tJ -fcJ -tJ C S G c s ^ 0^1 <1> c z O O O O O o o O o « o a o o o o H ;h ^H ^H ^ ^ u :-> ^ ^ ;^ ^ ;h •j in Jh ^4 o Qj a; (D o) a (D OJ a a; 0) OJ CL' Q) QJ 0) a ;::lh ^L, c^ Cli p H CU &( P^ & p-( -1 P-( P-( Ch P- ■t o o O o o O »!0 o o o O o >0 O )0 o fH O '-H (M CO CO 1— I T— ( 1-^ rH rH 1—1 tH o r— ( r— t o o 1— ( t^ t^ CO CO o fe o o o o O O O o o o o o o o o Q -M -4J -*-S HJ -M -4^ -U -U ■4^ -tJ -^ -tJ -t-J -tJ ■+J -^ o o o o o o »o o lO o lo O lO o o ■ w o r— 1 I— 1 Ol 1—1 CO I—I CO 1—1 T— 1 4(0 1— ( r-t o 1—1 o 1—1 1—1 1-^ CO I— ( 'JD 1—1 74 TTROUGHT-IRON" AND CHAIN-CABLES. We have the comparative records of 210 sections of cables broken by tension, which were made of fifteen different irons. Assuming that the utmost strength which can be found in a link is equal to 200 per cent of that of the bar from which it was made, we have a standard by which to compare the irons, and establish their relative value. Examining the abstracts by this standard, we find that 36 sections developed over 170 per cent of the bar's strength, 22 of them exceeded 175 per cent, 9 exceeded 180 per cent, and only one exceeded 185 per cent. On the other hand, 67 sections developed less than 155 per cent, leaving 107, or over 50 per cent of the series, which developed between 155 and 170 per cent of the bar's strength ; and of these the average development was 163 per cent. The 210 sections of various irons can be reduced to 143 sec- tions of iron which may be considered as more or less suitable for cable, by eliminating the records of the 67 sections, which were broken at less than 155 per cent of the bar's strength, and at once deciding that they have no claim to be considered as having been made from suitable chain-iron. This we can do in many cases, and assign good reasons : 24 sections were made from an iron (M) in which analysis demon- strated that phosphorus, copper, nickel, and in some cases chromium, occurred, and possibly reduced their welding values, as all the " low breaks " of this iron occurred " through the weld ; " eight were made from iron K, in which carbon was high, and ten from irons Fx and P, which w^ere known to have been overworked, leaving but 22 such percentages to be assigned to the chapter of accidents. From which data we conclude that bars of fairly good chain-iron will produce links whose strength wdll not be less than 155 per cent, and not over 170 per cent ; and that by a series of tests an average of not less than 163 per cent, made up of fairly uniform factors, should be expected. We have therefore adopted for our standard of strength and welding qualities combined, 170 per cent of the strength of the bar for a maximum, 163 per cent for an average, and 155 per cent for a minimum. Iron which in the link form develops the PEOOF STRAINS FOR CHAIN-CABLES. 75 average, by results which do not vary greatly, we consider to be suitable ; that which falls below the average, or produces it by very irregular factors, we consider as unsuitable. It remains to decide upon the strength of bar, which will most probably produce links which will develop the largest and most uniform percentages. Our records again supply the re- quired data. We find the irons A, B, O, and F, which were low in tensile strength, sustained the process of manufacture into links with less loss of strength than did other irons which exceeded in this respect ; and with all of the series excess of tensile strength was accompanied by deficiency in strength and uniformity as cable. , We have therefore decided upon adopting a low tensile strength as a probable indication of a high iveldiyig value, and as shown by the relative order as judged by the power of resisting sud- den strains, of great resilience. In selecting the low tensile strength, we did not decide arbi- trarily in favor of the precedence which should be given to the ^percentage of bar's strength developed by the links. We find that in many cases the actual strength of the links made from the bars of low tensile strength equals and exceeds that of others from much stronger bars. For example, iron K 2'' bar, tensile strength 58,900 pounds per square inch ; strength of link, 258,900 pounds. Iron A, tensile strength 2^' bar, 50,171 pounds ; strength of link, 265,000 pounds. Iron D, tensile strength 2" bar, 51,152 pounds ; strength of link, 276,500 pounds. Iron F, tensile strength 2"' bar, 48,956 pounds ; strength of link, 268,750 pounds. In recommending for cable-manufacture iron of this character, we are aware that in so doing we will come in contact with a widely-spread and deeply-rooted prejudice in favor of the strong bar as best adapted to make strong links. It undoubtedly would be so, were it not that great strength in the direction of the fibre is not found often to exist except through the effect of T6 WROUGHT-IRON AND CHAIN-CABLES. a great amount of work, which will cause the iron to be too expensive for cable-iron, or through the presence of various chemicals which increase tenacity at the expense of welding properties, thus unfitting it for use as cable-iron. We consider that our experiments justify us in recommend- ing as a suitable strength for a 2'' bar of chain-iron a mean between the margins found to exist in those bars whose record both in bar and link form has been just given ; and as the links of iron D, with tensile strength 51,152 pounds, and of iron F with 48,956 pounds, were equally good and strong, we adopt their mean of 50,000 pounds. And we find that iron A, which possesses nearly the medium strength as a bar (50,171 pounds), produces cable which is remarkably strong and uniform. Considering, then, that an iron is suitable, which, as a 2^' bar, has strength of 50,000 pounds per square inch, and that other irons whose variation from this strength does not exceed five per cent above or three per cent below are equally suitable, we have, in determining the strength for the other sizes, to avail ourselves of the information procured in the investigation of the action oL the rolls ; which is, in brief, that the proportional strength of the bars of the same material increases as the diameter decreases, and that the aggregate of the increase for the sixteen sizes (meas- uring by sixteenths of an inch between 2'' and 1'') is from four to six thousand pounds, produced b}^ steps which are made more or less irregular by irregularities in heating the piles. Using the mean of the aggregate of increase of our best and most uniform irons, we find that the strength per square inch of a bar of V^ diameter is about 5,600 pounds greater than that of the 2'\ and that, if the 2'' bar is equal to 50,000 pounds, it is probable the V^ will be equal to 55,600 pounds. It was necessary to connect these strengths assigned to the extremes by a series of successivel}^ increasing factors, the aggre' gate of which should equal 5,600 pounds. It was evident that a uniform co-efficient of increase for each of the sixteen reduc- tions could not be used, as the difference in strength produced by variations in reductions changed much less rapidly than did that PEOOF STRAINS FOR CHAIN-CABLES. 77 in the entire strength of the various-sized bars produced by variations in diameter. We therefore calculated a ratio which produced a constantly increasing co-efficient to be applied as the diameters decreased, with the results given in the table below ; each of which results is the correction to be added to the strength per square inch of any size in order to obtain that of the size ^'' less in diameter. Starting with 50,000 pounds as the strength of the 2", and adding the increasing co-efficient, we arrive at a strength per square inch for each size which agrees closely with that found in the best and most uniform chain-irons. The latter, however, being exposed to constant chances of irregularities from many causes, cannot be expected to coincide in strength very closely with any calculated table. Using the above factors of correction, we obtain the following table : — Probable Strength of Round Bars, calculated with an Alloivance for Variation in Strength due to Variation in Diameter. Strength of Bar. Size of Strength op Bar. Size of Bar. Per Square Coefficient nf Of Entire Bar. Per Square Coefficient of Increase. Of Entire Inch. Increase. Bar. Inch. Bar. Pounds. Pounds. Pounds. Pounds. Pounds. Pounds. 2 " 50,000 245 157,080 h\ 52,584 357 85,339 HI 245 253 148,137 If 941 376 78,607 n 498 262 139,430 h\ 53,317 398 72,133 lit 760 273 130,966 H 715 423 65,914 If 51,033 284 122,745 l>fi 54,138 451 59,958 IH 317 296 114,770 4 589 484 54,261 15 613 309 107,040 IV 55,073 523 48,800 h% 922 323 99,560 1 596 , , 43,665 li 52,245 339 92,322 Accepting this rate of increase of strength as one which ap- proximates to the actual increase of tenacity of iron bars of decreasing diameter, we have used it in the calculation of our proof-table. A few examples will be given, which show conclusively that, 78 WKOUGHT-mON AND CHAIN-CABLES. by means of the corrections for variation in diameter given in the table, the strength of a bar of, say, 2'', can be closely esti- mated from the data fnrnished by the test of V bar. Selecting irons A, F, O, and P, which were qnite uniform, the strength of the 2'' bars was : — Actual strength A, 157,630 lbs.; F, 150,413 11)8.; O, 151,597 lbs.; P, 159,720 lbs. Calculated with correction A, 154,190 lbs. ; F, 151,346 lbs. ; O, 148,989 lbs. ; V, 163,800 lbs. Calculated without correction A, 181,836 lbs.; F, 163,136 lbs. ; O, 166,635 lbs. ; P, 181,600 lbs. The latter process involving an over-estimate of from 12,700 to 24,200 pounds ; which error is reduced in two cases by the use of the corrections to an over-estimate of 4,080 and 933 pounds, and in others to an under-estimate of 3,448 and 2,608 pounds. The following table has been prepared, in which the aver- age strength of such bars as have produced good cables is placed in contrast with the strength called for by the calcu- lated table : — Comparison of Calculated loitli Actual Strength of Bars. Strength. Irons represented in Averages. Size Differ- of Bar. Calcu- lated. By actual Tests. ence. No. of Irons. No. of Tests. Name of Irons. Pounds. Pounds. Pounds. 2 " 157,080 157,580 500 9 35 A, C, D, E, F, Fx, M, 0, P. m 148,137 .... .... .. .. H 139,430 141,120 1,690 9 26 Same as 2". Hf 130,966 131,975 1,009 5 8 B, C, E, G, H. if 122,745 124,580 1,835 13 33 A, C, D, E, F, G, H, J, Fx, 0, N, P, M. m 114,770 115,690 920 4 7 B, C,E, G. 1 5 107,040 108,800 1,760 10 25 A, C, D, E, F, Fx, G, H, J, 0. h\ 99,560 .... .... .. .. H 92,322 93,358 1,036 13 34 Same as 1|". 1^ 85,339 85,000 339 6 12 B, C, E, G, II, P. If 78,607 79,311 704 9 27 A, C, D, E, F, Fx, N, 0, P. h\ 72,133 74,505 2,372 1 94 P. H 65,914 66,724 810 '9 106 Same as 1|". h\ 59,958 .... .. ' ^ 54,261 54,570 309 9 29 Same as 1§". iiV 48,800 .... .... .. 1 43,665 44,126 461 6 26 A, D, F, Fx, O, P. PEOOF STEAINS FOE CHAIN-CABLES. 79 Having thus fixed upon a suitable strength for each sized bar, we deduce the probable strength of cables made from them by the aid of the percentages of the bar's strength which we have found will probably be developed by the links, as indicated by those found in such irons as we have examined. In this table of strength of links it is considered that no iron should be expected to possess in link form over 170 per cent of the bar's strength, and that no suitable chain-iron should possess less than 155 per cent of the same ; and that the average strength of a number of tested sections should not be less than 163 per cent, such average to be made from fairly uniform factors. Probable Strejir/th of Cables made from Bars with Strength corresponding to that gicen in Table. Size of Bar. Strength of Entire Maximum, Average, Minimum, Bar. 170 per cent of Bar. 163 per cent of Bar. 155 per cent of Bar. Pounds. Pounds. Pounds. Pounds. 2" . . . 157,080 267,036 256,040 243,474 m 148,137 251,833 241,463 229,612 n 139,430 237,031 227,271 216,116 m 130,966 222,642 213,475 202,997 If 122,745 208,666 200,074 190,255 iH 114,770 195.109 187.075 177,894 If 107,040 181,968 174,475 165,912 lA 99.560 169,250 162,283 154,318 H 92,322 156,947 150,485 143,099 ItV 85,339 145,076 139,103 132,275 If 78,607 133,632 128,129 121,841 ii% 72,133 122,626 117,577 111,806 H 65,914 112,054 107,440 102,167 1^ 59,958 101,929 97,731 92,935 n 54,261 92,244 88.445 84,105 iiV 48.800 82,960 79,544 75,640 1. 43,665 74.230 71,172 67,681 We have concluded that we cannot adopt a safer proof-strain than one which approximates to the elastic limit of the link ; and the link whose elastic limit we should adopt is the weakest one which will, after proof, remain in the cable. We have found by a great number of tests of bars in their 80 WROTJGHT-IEON AND CHAIN-CABLES. normal condition, that the elastic limit of good cable-iron is about 57 per cent of its ultimate strength. The process by which the links are manufactured undoubt- edly changes both the strength and elastic limit of the portion upon which the welds are made : the extent of this change we have no means of knowing ; and so irregular are the processes of manufacture, that, if accurately ascertained in regard to a tested link, the data would be of no value in estimating its extent in the case of another. We are therefore again reduced to probabilities. Generally the elastic limit of material is coincident with the first percep- tible permanent change of form produced b}^ stress. With a chain-link this cannot be accepted as correct, as, through vari- ous causes, the form of the link may change at a stress not great* enough to produce change in the atomic relations of the material. Still, this first change of form indicates an approach to this limit ; and we have carefully observed it in the test of many links, and find that with such irons as A, B, C, F, Px, and others considered suitable for cable, the percentage of the stress which will break the cable, at which the elongation can be observed and measured, is about 44 per cent, and that this percentage exists with considerable regularity, so much so that we feel justified in assuming it as the nearest approximation to the elastic limit of the link that can be deduced from our ex- periments. But we believe, for several reasons, that in most cases it is too low a percentage : first of which is, that, tlirough badly fitting studs, many links during the beginning of an in- creasing stress may be considered as open or unstudded ones, and the " first stretch " is produced by a slight closure of the sides upon the stud ; and open links begin to stretch at a much lower stress than studded ones. It is probable that a mean be- tween the ratios of the ultimate strength at which the material in bar form begins to stretch, viz., 57 per cent, and that at which the links first elongate, viz., 44 per cent, will give as nearly the probable elastic limit of the link as can be obtained by any other process. No exact limit can be fixed upon. PROOF STRAINS FOR CHAIN-CABLES. 81 We have, therefore, in calculating the proof-strains, assumed that it is not safe to use fibove 50 per cent of the strength of the weakest part of the cable. The proving strains calculated upon the principles indicated are as follows : — Recommended Proof- Table: being equal to 45.57 per cent of the Strength of the Strongest, and to 50 per cent of that of the Wealcest, Links. Size. Inches. Ill n m If 111 Proving Strain. Pounds. 121,737 114,806 108,058 101,499 95,128 88,947 82,956 77,159 71,550 Tons. •^^•2 24 ^^224 AQ 530 ^C>2 24 ^"^2 24 ^^ 2 2 4 QQ \A3J- ^^2 24 Q7 7 6 " * 2 2 4 q_J 999 "*2 24 012110 ^^2Tro Size. Inches. 1^ H H iiV Proving Strain. Pounds. 66,138 60,920 55,903 51,084 46,468 42,053 37,820 33,840 Tons, oniill •"^2 24 07 44 - * 2 2 4 04 2148 -'■*2 24 00 1 8 4 '"'2240 Or> 1 t) ti 8 *''^2 24 1 Q 1 7 3 3 1^22T0 1 f> 19 J_0 -'^224 0" 1 r: 2 4 ■^'^2240 Comparison of the Proving Stra ins recommended, and Strains in Use. Probable Percent- Probable Percent- age of Strength age of Strength Size of Cable. Recommended OF — Admiralty OF — Proving Strain. Proving Strain. Strongest Weakest Strongest Weakest Link. Link, Link. Link. Inches. Pounds. Pounds. 2 . . . 121,737 45.5 50 161.280 60.3 66.2 lit" 114,806 45.5 50 151,-357 60.1 65.9 n ■ 108,058 45.5 50 141,750 59.8 65.5 111- 101,499 45.5 50 132,4.57 59.4 65.2 If 95,128 45.5 50 123,480 59.1 64.9 lU- 88,947 45.5 50 114,817 58.8 64.5 ^ 82,956 45.5 50 106,470 58.5 64.1 1-1% 77,159 45.5 50 98.437 58.2 63.7 H 71,550 45.5 50 90,720 57.8 63.3 IV 66,138 45.5 50 83,317 57.4 62.9 1 3 60,920 45.5 50 76,230 57.0 62.5 i\ 55,903 45.5 50 69,457 56.6 62 1 4 51,084 45.5 50 63,000 56.2 61.6 i\ 46,468 45.5 50 56,857 55.7 61.1 il 42,053 45.5 50 51,030 55.3 60.6 iiV 37,820 45.5 50 45,517 54.8 60.1 1 33,840 45.5 50 40,320 54.3 59.5 82 WEOUGHT-IEON AND CHAIN-CABLES. The important points of difference between the recommended table and the one in use are : — First, In the former, the proof stress is, for every size, uni- form in its proportion to the probable strength of the links ; in the latter, it varies with every change of size. Second, Unless the elastic limit of the link is a greater pro- portion of its ultimate strength than that of the bar was of its strength, the strains of the table in use exceed this limit greatly, upon all sizes, while those of the former do not. Third, The recommended table recognizes the probability of there being introduced into cables links made from bars which, although of equally good iron as the rest, are, through fault in rolling, more or less scanty and, in consequence, possess less strength than bars rolled true ; which deficiency will be carried into the links. Should there, by accident, be a few links of 1||'' in a 2'' cable, the Admiralty proof would strain the strongest of such links to over 62 per cent, and the weakest to over 70 per cent, of the actual strength. For these reasons we recommend that this table, based upon actual strength of American iron, be used in place of that of the Admiralty. NOTES UPON THE IRONS EXAMINED. 83 SECTIOISr YII. Part I. — Notes upon the Various Irons examined^ icitJi Experiments slioiuing Effects produced hy reworking Material of Different Characteristics. Part 11. — Chemical Analyses of the Irons, loith Comparison of the Chemical and Physical Results. PART L — NOTES UPON THE IRONS EXAMINED. A COMPARISON of the results obtained by steady and sudden strains upon bars, and by steady strains upon the links made from the bars, indicates there are two classes of iron, which, although possessing considerable tensile strength in the form of straight bars, are equally unsuitable for cable-iron, through defective resilience, or inferior welding qualities. The first class includes the greater portion of the ordinary cheap iron found in the market, which is cheap because it has not received enough work which is expensive, to greatly change its characteristics from those which it possessed as crude iron. When tested by tension, iron of this class shows slight change of form at rupture ; and when broken by impact it proves brit- tle and unreliable. After fracture the appearance of the broken surface is de- scribed as " coarse granulous," and generally is bright and glistening. Such iron w^ill, when subjected to impact, break with but little deflection, and sometimes by blows of less force than it had previously withstood without sign of injury. The second class includes many excellent irons with high tenacity, which is due either to very thorough work, or to in- 84 WItOUGHT-IRON AND CHAIN-CABLES. greclients in its composition wliich tend to increase tenacity, frequently at the expense of welding qualities. A few notes in regard to the irons we have examined will illustrate these points. Contract Chain-Iron. The general character of this iron was that of class first, coarse, brittle, and slightly worked. As a result of the tests the entire stock on hand was con- demned ; but much of it having been found to be susceptible of great improvement by re-working, it was so treated with good results. Hammered Iron. The process by which this iron was manufactured was as follows : — Such of the contract chain-iron as our experiments had shown to be most benefited by increased work was selected, heated to a very high heat, and thoroughly hammered by the steam-ham- mer, each link or bolt by itself, until it was flattened to a slab. During the process great quantities of dross and scoria were expelled. Old condemned boilers were cut up, and the better portions cut into slabs, which were heated to a red heat, and the rust beaten off. ^hese slabs of the two irons were then piled in the following manner : — Boiler-iron. Twice -hammered chain -iron. Once- hammered chain- iron. Crown-sheet boiler-iron. Once- hammered chain- iron. Twice -hammered chain- ■iron. Boiler-iron. NOTES UPON THE lEONS EXAMINED. 85 These piles were about W by 10'', and were heated and ham- mered into octagonal irons. The advantages which it was hoped would be secured by the above method of piling were, that the soft and comparatively plastic centre would permit extreme flexure ; that the coarse, once-heated chain-iron Avould, being supported by this yielding centre, sustain flexure to a much greater extent than if not so supported ; and that the thoroughly re-heated and re-worked layers of chain-iron next to the outer layers would impart strength and toughness to the mass, and would absorb any blows or sudden strains, which received upon the outer surface would encounter first a cushion, and then a tough iron ; and that the resultant iron would possess great power to resist both sudden and steady strains, would bend double without breaking, and, the parts not being perfectly homogeneous, the rupture of a portion of a bar would not render valueless the remainder. That we secured all these advantages, our tests show plainly. Tested by tension, the iron showed fair tensile strength (average 53,000 pounds), uniformity, and ductility ; tested by impact, bars of all sizes in their normal condition would sustain heavy blows with slight deflection, and finally double till the sides were close together, without injury. Extreme tests were made by impact : one hundred and ninety-seven bars of 2'' diam- eter were swaged from the blooms, each of which was circled with a score -^ of an inch deep in the centre. These bars were struck upon this score by the wedge-shaped hammer of the impact testing machine, dropped from a height of thirty feet, the hammer weighing one hundred pounds. Each blow was considered to be equal to 3,000 foot-pounds. 2, or 1 per cent, resisted 7 blows. 5, or 2.54 per cent, resisted G blows. 27, or 13.6 per cent, resisted 5 blows. G8, or 34.5 per cent, resisted 4 blows. 71, or 36 per cent, resisted 3 blows. 21, or 10 per cent, resisted 2 blows. 3 broke at first blow. 86 WEOUGHT-IEON AND CHAIN-CABLES. The three which broke at single blow were found to have been made partially of boiler-steel. Ieon a. From these hammered blooms, those which had resisted at least three blows were re-heated and rolled in the copper-mill into iron A. All the bars showed great ductility and change of form under tension, having a rather Ioav elastic limit, which was due, no doubt, to the fact that the softer and more ductile portions stretched first. Tested by impact, all sizes up to 21'^ bent com- pletely double by heavy blows (3,000 foot-pounds) delivered upon the centre of the test-pieces, bending them to the face of the w^edge, when the steam-hammer completed the closure. No iron which we have examined has proved suj^erior to this for cable-iron ; and there is no reason why any manu- facturer should not be able to produce similar material, by suitable mixtures in the piles, and by giving such amount of work as is found to be best adapted to develop good welding properties. Even though it should be considered as impractical to arrange every pile with due attention to a balancing of opposite char- acteristics, the quality of ordinary chain-iron can be vastly improved by subjecting the coarse material of which it is gen- erally composed to much more thorough Avorking than is ordi- narily the custom. Ieon B. Three bars of this iron, viz., lyf ^ ^ii'^ ^^^ -^iV' "^^re fur- nished as sample bars to compete for an order for chain-iron, with bars of irons C, E, G, H, I, J, K, and L, all of which are referred to as the " nine irons." By the result of the tests, this iron was accepted for the three sizes, the contractor having sub- stituted sam2~>les of iron B at the hist moment for those of iron L previously furnished, which proved red-short and worthless. This iron showed plainly the effect upon quality of increased reduction by the rolls, the smaller sizes being the most ductile and welded most firmly. NOTES UPOX THE IRONS EXAMINED. 87 Iron C. Three bars of this iron, viz., If', If', and li'', were furnished to compete with the " nine irons ; " and upon the results of the tests this iron was received in the above sizes. The tests by tension and impact of the sample bars showed great ductility, low tensile strength, and remarkable toughness, with great power to resist impact. As cable the welding value was high, and the single links developed from 178 per cent to 199 per cent of the bar's strength, averaging 187 per cent. The iron delivered differed greatly from the samples : the tensile strength was higher ; and, although generally tough and strong, the characteristics of the iron delivered showed that it had received much less work than the samples, if of the same material. As cable links the IJ'' developed an average of 162 per cent, the If 155 per cent, and the If 153 per cent, of the bar's strength, made up of very irregular factors, ranging from 134 to 177 per cent. The If was brittle under impact, the If less so, and the If generally very tough. Iron D. Two lots of this iron, each consisting of nine bars from ^' to V\ were purchased for testing. Differences in the amount of reduction in the rolls produced with this iron very marked differences in strength, — the smaller bars having much greater tenacity than the larger ones. All sizes possessed great power to resist impact, except the 2'' bars, which were generally very brittle. It seems probable that the second lot, having been prepared expressly for test, received a great deal more work than the first. This overwork manifested itself both in increased tena- city and in decreased welding value ; the single links of the first lot developing an average of 178 per cent, and the sections of the second 158 per cent of the bar's strength. The 2'' bar of both lots differed greatly from all the smaller 88 WROUGHT-IRON AND CHAIN-CABLES. bars, — so greatly that it was difficult to believe that they were of the same iron. Both were very brittle under impact, and when tested by tension, broke with almost imperceptible change of form, showing bright granulous surface of fracture. Iron E. The iron was all of good quality, moderate tensile strength tough under impact, and made good cable. This set of bars presented one peculiarity: the 1^'', instead of being of less tensile strength than the If, as is generally the case, was of greater ; and, on inquiry at the mill for the cause, we found that at this mill the pile used for the li'^ was of the same sectional area as that of the If, while at most mills it is less. Iron F. None of the bars furnished can be considered as chain-iron, for which purpose the manufacturers made a harder and stronger iron. We, however, tested many of them in the form of cables, considering that, in the records of such cables, we would find what could be expected of iron of very low tensile strength. F proved uniform under every form of test, the tensile strength, elongation, reduction of area, strength of links, and percentage of bar's strength developed by links, resistance to impact, and welding qualities, of any one lot, furnishing valuable evidence as to what might be expected of another. Iron Fx. The bars of this iron were rolled from piles made up of the same combination of crude irons as was used in the manufac- ture of iron F, but which piles were made to differ from those of F in sectional area. The proprietors of the rolling-mill furnished, without charge, all the facilities and material necessary to assist the committee in an investigation into the effects of the rolls ; the object of the experiments being the i)roduction of a set of bars, of various sizes, the tensile strength per square inch of which should be uniform. NOTES UPON THE IRONS EXAMINED. 89 This result was accomplished, on the third trial, by so grad- uating the sectional areas of the various piles, that the areas of the bars rolled from them bore uniform ratios to those of the piles. (See the record of this experiment, page 18.) The resulting bars had received much more work than iron F; they had higher tenacity, equal if not superior resilience, but inferior welding qualities. Ikons G, H, I, and J. These bars were furnished to compete with the nine irons for a contract, but few tests were made upon them. G and H both proved of good fibrous material, sufficiently worked, and the few links made from them were strong ; G, as single links, being equal to 174 per cent, and H to 182 per cent, of the bar's strength. Iron I was thoroughly red-short ; and it was impossible to make links from it, they breaking while being bent. Six bars of iron J were furnished, which proved to be of a kind called in the shop "rotten." When tested by impact, with a sledge-hammer, the bars would split under the blows, showing smooth, black faces, resembling charcoal. Iron K. All the bars of this iron were of the same character, which was that of a fine-grained, thoroughlj^-worked, refined bar, of great tensile strength and uniformity, showing, when broken by any form of force, fine bright silvery fractures. The bars were so uniform in strength tliat they were selected as the material from which to make experiments which de- pended upon uniformity in character of material for their value. Under impact-tests, iron K gave peculiar results: if the skin was intact, a bar of ^' diameter could be doubled, cold, by heavy blows, without showing injury ; but if a slight score, or nick, was made in it, this power was entirely lost. The welding properties were not good, that is, by the ordi- 90 WROUGHT-IRON AND CHAIN-CABLES. nary process. With some of the links, that were probably welded at suitable heat, the welds were firm, and they pos- sessed great strength ; but others, made from the same bars, broke at very low strains. The character of the material was so opposite to that of charcoal-bloom boiler-iron, each possessing valuable qualities which were lacking in the other, that it was resolved to make some experiments by mixing the two; and the results show plainly, that, by such admixture, iron superior for chain-cables to either of the constituents could be produced, and that ex- cellent chain-iron can be made by mills whose ordinary prod- ucts cannot be considered as suitable. Iron L. Five bars were furnished to compete with the nine irons. All forms of test indicated that the material was steel ; which analyses subsequently confirmed. The tensile strength was great ; reduction of area abrupt ; power of resistance to impact very slight when scored, but fair when not scored; welding- value low ; strength of links very irregular. Iron M. A great number of tests were made upon this iron, both by physical and chemical processes. It was delivered as chain- iron at a number of different times and lots. The bars of these lots varied greatly among themselves ; and the lots differed in many respects. As cable, the iron proved very defective and irregular. The trouble with it seemed to be, that, if not welded at exactly the right heat (a very low one), the part of the link upon which the weld was made lost its strength by the process, and in many cases, when tested, the links would- break through the weld at very low strains, showing little or no change of form, and the fractured ends remaining unreduced in diameter. NOTES UPON THE IRONS EXA]MINED. 91 Iron N. The bars of this iron (eight in number) were furnished to the committee by a leading manufacturer as samples of " first- class chain-iron : " and they were probably a fair sample of the ordinary character of such chain-iron : tested by tension, the strength was generally high, change of form slight. Under impact, the large bars were very brittle, the 2" breaking by blows, Avhen unscored, which the If resisted after being scored. As cable, the If was superior to the 2''. The fault with this iron was too little work, the large bars receiving much less than the small ones. Iron O. This iron is in no sense of the word a chain-iron ; and its merits should not be- judged by its action in the form of cable. The material was soft charcoal-bloom, and of high price. It proved of value in our experiments upon the effect of the rolls, and as furnishing us with data as to the extreme of change of form which would occur to a link of very soft iron under stress. Although too ductile and soft for chain-iron, some of the larger sizes produced good links, while the smaller sizes were overworked for the purpose, and did not. Irons P and Px. These irons were made at the same rolling-mill, and when the physical tests were made upon Px it was considered to be of the same material as P; and the differences in their character- istics were attributed to variations in the mechanical processes by which they were produced, P having received one course of heating and hammering which was omitted with Px. Sub- sequently chemical analyses showed marked differences in the nature of the two irons. The results of the analyses were con- firmed by a letter from the manufacturer, in which he states that he jiterceives that the weak point of previous lots (iron P) was the lack of transverse strength when scored, and that he 92 WEOUGHT-IEON AND CHALS^-CABLES. has in this lot (Px) overcome the difficulty, without essen- tially lowering the tensile strength. This w^as effected by, first, the selection and rigid puddling of pig-iron as free from phos- phorus as possible ; secondly, using a physic, which tended to eliminate the silicon and sulphur; and finally, the omission of the hammering. The result of these experiments by the manufacturer, to correct the defects found at the testing- machine, was the production of a superior chain-iron, which resisted impact well, and welded firmly. PART II. — COMPAKISON OF CHEMICAL AND PHYSICAL RESULTS. Variations in the physical qualities of iron may be due to different composition, or to different treatment in manufacture, or to both of these complex causes. In order to determine the specific causes of variation, one class of altering conditions should be made to vary largely, while the other class should be kept uniform. Then another class should be varied, and so on until the value of each is ascertained. As all the irons under consideration were intended to have that purity and refinement which was deemed indispensable in chain-cables, their chemical analyses are, perhaps, more important in proving that physical variations result chiefly from variations in treat- ment, than in pointing out the specific effects of certain in- gredients. While the subject of treatment — especially the increase of strength by greater reduction in rolling -;— may be the more important one, it can best be appreciated after we have familiarized ourselves wdth the general chemical and physical characters of the irons. The typical facts are given in the following tables : — COMPAEISOX OF CHE^nCAL AND PHYSICAL RESULTS. 93 O a S < O I-) o m 3 ^ o o o w e4 o >H t^ ►J o < < fa •[osiij) apixo 'njn(iuo.in3 (•lOH •na "I "log) lunuuoaqf) •uo.li JO apixQpuTjSB[g o O (-> -t O o -t< o (M (M e-4 t— r^ o C~» t~ o •^ I-H i-ii— lOi-HT-iOOOOOO •pn^jx oooooooooooooooocooooooo ooooooodooo'oo'ooooooooooo •licqoo _ o o o o o o oooooooooo CO o c3 CO o o o c o CI o CO o CO o o 1—1 o O o ® H o o o o o o [h o o O ;: i I-H T— 1 00 CO § s '.todcIoQ IM CO o o n X) 00 t— to -f I-- 1-1 O I— ' i-l o o o o o o oooooooooo fSoooooo ooooooooooo oooooi^ooooo •osoaBSuBj^ .— ^H CO .-I o o . - IM CI -f CO -^ CO ooooooooooooo oooooooooo •uoq.iKQ pouiquio^ o' d d d d d d d d d d d d u d d d d d d d d d d o. CO -f OOOOr-OOOOOOOOOOOO o o o o o o OOOOOOOOOOO rt c: rt ^ H H IM — _o _o — ^ "' -ic« -i«< ^ . i -let i - =■" LI o - o '^ C^ r-i T-T T— I It-i 0-3 1— Ir-I c*tr -fr< rK? „i "1 ;c d" -^ fi C a ft w' fa" fa fa fa i-r hT --J »-s »^" W Ji! ti! t-f h-f l4" Moqiunx X.!0|c.ioqi:i OIM'^-tOi-IC5Ot-C1C0C0'»J o # . . . o • • d * d ' o o o o o o o o o fH d * * ' • • * d O CO O to <0 CO C» l-H 00 c^ -^ O t^ 00 00 (M -^ 'ti n< I— o o OS CO O O O rH i-H i-l O o o o o « O O O O oo c: -^ I— o «o 00 3 O O O rH O O 00 O O 00 -^ o oi i-i t- a> CI o o o o o o <:i d o 1^ ^ d ddd d d n3 o o S s ■^ •[osui) opixo lunimojqj o o o o ('lOH •11(3 m -log) umiuio.uQ o o o o o o © o •UO.TI JO ox to 00GCtO-*-*-^00-*<00etc3 ^ic : i ; t i-'to ; ; ; '"to j ^ -'^ rica rw rHf ^h rra »e« r»* r-'rn i ^.jg ^ ^ p.^ v ^ l-H h-H 1-5 S S ,i« ^ <^ ..^ ^ ;^ ;^ SS^^cc;h.>re©i— COl— 0C©©rHCO IM rH©Tjl if) ©©©CO'^tlrHC^ CO CO^IPAEISON OF CHEMICAL Ai?D PHYSICAL EESULTS. 95 ^ •S •2 o 5~ p c^ K a -^ c ^ ^ goo c a> O Si O O O :C! CO O O i-O IC O iC O rtn a o pq <3l O Ph Ph Pi Ph O Jz^ Ph P^ ^ lii^ o o O u o Ot^CMl^-CMOOOOOOOIOlOOC^^'^icOCOCO O t^ CO OJ (M OJ 1— t 1—1 T— ( O O GO 00 t^ t^ O O (M GO CM CM C^l CI — lOOOC^ocDlOlOocooc6G6G6occoo OTtlrtl-^rtlTj^TtHr^l'^'^rtlTtlCOOtlCOCOCOCOCM o a H « OD 1-9 OS COO?C»^(MOC5W.— f'Mt^-+fCirT>'-H^CC''rt<0 U^^ O^ O^ O^ C;^ t^ CO^ M^ O^ Ol^ rH 1>^ O^ ir^ -^^ t- 1-1^ r-i^ 1>^ cT x" o" icT o" -TtT -riT -rfT t^" cc" co cf cf cf of i-T r-T r-T cT O lO O O O O O lO O ir:; O O O lO o o o o o o ^ CO ^ W p o g pH;25PiHfiJpPHp<-wwH5p=^o6 w >-9 -< > O o rH(MCOT^OOt>GOOOT-l(MJOTt* nuoo joj 1- I- ■* t O CO CO I-- o o q q o c o o ^ ^^ C> <0 C> • d ^ <6o d <6'd ' ■*OCO-*'*COOOtO fl O O r-l '<£> r-l T-H • •^uao J3J iC to CO I-- CO Ol C-1 -^ r-- r-; q q q q q o d d d d d d d d 1--5 CO O CC O: O CO -* Pi Ci eOiH-^t- nuoQ aaj 0(MtOOOC-»(Mr-l q q q q q q q 0-] d d d d d d d r-K »■- CO C« O OO o M ir^iMcoeoiM r-l r-l r-l r-( •1U90 aaj O'^tO'CINrH'^uO r^r^qqq qCTjH dddddddd 5 O -5 MO .1^ '-S cS C I, -M t. i ?■ Sh as _C 2 C C _2 3 • o . • c. or ^ :h i- ^ ^ . o c o sj o a) 'B.5§||::e- ,o^^^^ s s s sa 3 3 3 3 3 ^ ^;2if^;2; ^ 02 c;. OIS s. ^ QC 1 >, »1 o o o "3 o ^ a t— 1 TS a) c o e3^ rs !>n -3 c a cS cS ^ ^ o ^ ^3 ,^ o -a o ^ «3 a o ss Is 2h5 O cS 3 ^ ^ S- H i. o c ii> '3 COMPARISON OF CHEMICAL AND PHYSICAL RESULTS. 97 Table I. Analyses of the irons. Table II. Relative values of irons in bars, in tenacity, reduc- tion of area, and elongation, and in proportion of chain to bar. Table III. Summary of principal physical and chemical char- acteristics of sixteen irons. Under the head of phosphorus, the leading chemical and physical facts about each iron likely to be affected by this element are compared, and then the group of irons is con- sidered, and a conclusion is reached ; under the head of silicon, the irons are again gone over in a similar manner ; and so on with carbon and other ingredients. A description of a few irons, in which composition should have the greatest influence on strength, will suffice to introduce these conclusions. Effects of Phosphorus. Iron O: P., 0.07; Si., 0.07; C, 0.04; slag, medium. Chemical impurities all very low. The iron had been thoroughly worked. Tenacity as bar and as link very low. Ductility as bar and as link very high. Welds very good. Low phosphorus does not alone account for these qualities. Iron F, with P. 0.20, Si. 0.16, and C. 0.03, has about the same tenacity and welding power, and approaches the same ductility. Iron P, with P. 0.25, Si. 0.18, and C. 0.033, has about equal ductility, but inferior welding qualities. Seeing that the thorough working of the small bars decreased welding power, as compared with that of the less compressed large bars, it is probable that method of manufacture is an important factor in all physical results. The effects of low phosphorus are not conspicuous. Iron P : P., 0.25 ; Si., 0.18 ; C, 0.03 ; slag, very low. P., rather high ; C, medium ; other impurities, low. Tenacity high as bar, irregular as link. Ductility high when not nicked, low when nicked. Welding value medium, through overwork, and possibly high P. 98 WEOUGHT-IRON AND CHAIN-CABLES. Iron Px; P., 0.09; Si., 0.028; C, 0.066. This iron had the highest average of good qualities of the commercial bars examined, and was the best for general con- struction purposes. The characteristic effects of phosphorus might, previous to our investigation into the effects of reduc- tion, have been considered as shown by the behavior of two specimens, one of iron P, and one of Px, made in the same way, except that one course of piling and hammering was omitted from Px ; viz., — V^ bar-iron P : phosphorus, 0.25 ; tenacity, 57,807 pounds ; elongation, 19 per cent. If" bar-iron, Px : phosphorus, 0.09 ; tenacity, 54,212 pounds ; elongation, 24 per cent. But this increased tenacity and decreased ductility of the smaller bar are not due to P. alone : it had Si. 0.18 against Si. 0.03, and it had more reduction in the rolls. The difference in the tenacity of the bars of the same sizes of iron P, which may be considered as probably of similar composition, was nearly 5,000 pounds ; while between the bars in question, P and Px, it was but 3,600 pounds. Phosphorus may have affected the welding qualities and the ductility ; as iron Px, with much less of this element, welded much better, and had greater powers of resisting sudden strains, than iron P. Iron D: P., 0.18 (0.12 to 0.24); Si., 0.15; C, 0.03- slag, low. Carbon low, other impurities medium. Different bars very differently worked. Tenacity high as bar and link. Ductility medium as bar and link. Welds very good. There are various proofs that low phosphorus, even with low silicon, does not cause high ductility, and that the amount of reduction is the more important factor. For instance : — r' bar, P. 0.24, Si. 0.17, has tenacity per square inch, 61,000 pounds ; elongation, 26 per cent. COMPAEISOX OF CHEMICAL AND PHYSICAL RESULTS. 99 IV^ bar, P. 0.16, Si. 0.11, has tenacity per square inch, 56,000 pounds ; elongation, 23 per cent. 2'' bar, P. 0.21, Si. 0.16, has tenacity per square inch, 49,148 pounds ; elongation, 0.07 per cent. The welds of the medium-sized and worked bars are the best, but all were good. No harmful effects of phosphorus can be traced in this iron. Iron B welded best, and had P. 0.23, and C. 0.015. Iron F; P., 0.20 ; Si., 0.16; C, 0.03: slag, low. Carbon low, other impurities medium. Iron suitabl}^ worked for welding, and very uniform. Tenacity as bar and as link very low. Ductility high. Welding power good. The remarkable uniformity of this iron proves it to have been made with great care, from selected materials. Why its tenacity is so low, it is difficult to say, on chemical grounds. The same iron, Fx, more worked, gives a medium tenacity, with substantially the same analysis. Iron A, with less P., Si., and C, is stronger. Iron E has lower P., the same Si., and only 0.02 C, and yet a higher tenacity. Iron Fx (F more worked): P., 0.19; Si., 0.17; C, 0.03. Ingredients substantially the same as in F. Iron much more worked than F. Tenacity medium in link and bar. Ductility good. Welding power below medium. Iron B : P., 0.23 ; Si., 0.16 ; C, 0.015. P. rather high. Si. medium, and C. very low. Iron not sufficiently worked for strength. Tenacity rather low. Ductility quite low. Welds very good. Notwithstanding the extremely low C, the iron was not duc- tile. P. may well account for this, but not for low tenacity, as some of iron P had more P., and much higher tenacity. Low 100 WEOUGHT-IEON AND CHAIX-CABLES. C. may partly account for low tenacity and good welds, but small reduction seems to be an equal cause. High P. did not prevent excellent welding. Iron M: P., 0.25 (0.21 to 0.32) ; Si., 0.18 (0.16 to 0.26) ; C, 0.04; Ni., 0.18 (0.03 to 0.34) ; Cu., 0.34 (0.13 to 0.43); slag, various. P. rather high, Si. above medium, copper and nickel high, C. rather low. The amount of work the iron received can only be inferred from the sizes of the bars. Tenacity considerably above average. Ductility average. Welds weak. The character of this iron is so complex, and its physical character varies so much in the same-sized bars, that no satis- factory analysis of the data can be made. It seems certain from a comparison of the tables, that neither copper, nickel, cobalt, nor slag materially affected strength. The effects of these ingredients on welding will be considered under another head.* Conclusions about Pliospliorus. — The best of these irons average P. 0.09 to 0.20. The extreme limits are 0.065 and 0.317. A soft boiler-plate steel might have the former amount ; the latter would give high tenacity and brittleness to even a low carbon steel. The investigations have been made so diffi- cult by the chemical similarity and general purity of most of the irons, and by their various degrees of reduction in roll- ing, that the effects of phosphorus cannot be independently traced. The phosphorus (average in each iron) runs very irregularly as follows, beginning with the highest of the following physi- * Chromium occurs only in iron M, four analyses of which show, Cr. 0.061 to 0.089. As this element is known to increase the tenacity of steel, it may have brought iron M up to a good standard of tenacity without helping its other stuctural qualities. These experiments give no absolute evidence as to the eft'ects of chromium; but it may be said that when mere tenacity is made the criterion of fitness, an iron like M may be found which will meet that requirement, and still prove untrustworthy for cables. COMPAKISON OF CHEMICAL AND PHYSICAL EESULTS. 101 cal values : Tenacity, 0.72, 0.15, 0.20, 0.17, 0.22, 0.25, 0.19, 0.19, 0.09, 0.15, 0.19, 0.23, 0.18, 0.20, 0.20, 0.07. Reduction of Area, 0.07, 0.18, 0.09, 0.20, 0.15, 0.25, 0.19, 0.19, 0.20, 0.22, 0.17, 0.15, 0.23, 0.19, 0.07, 0.20. Elongation, 0.09, 0.25, 0.07, 0.18, 0.19, 0.20, 0.19, 0.22, 0.20, 0.19, 0.15, 0.17, 0.15, 0.23, 0.20, 0.07. It may be generally stated that pliosphorus 0.10, with carbon about 0.03, and silicon under 0.15, gave the best chain-cable irons of this group. One of the best irons, however, had P. 0.23, although low tenacity and high ductility are the chief requirements of such irons. The effects of the different constituents on welding will be considered under that head. Effects of Silicon. See foregoing description, of irons O, P, F, and M. In iron F, which is among the highest in silicon, did this ele- ment cause the very low tenacity despite the fair amount of P. (0.20) ? If so. Si. must affect tenacity more than it affects duc- tility. But this is not the fact. In iron J, ductility as well as tenacity is made very low by high Si. (0.27). Iron J: Si., 0.27 (0.18 to 0.32); P., 0.20; C, 0.035; slag, average. Silicon high, other impurities medium. Iron not overworked. Tenacity very low in bar and link. Ductility very low in bar and link. Weld rather bad. There was no apparent chemical or physical cause for this low strength, except excessive silicon. Under sledge-blows the bars split as often as they broke off; and the faces of the fracture were like layers of charcoal, although both carbon and slag were medium. Conclusions about Silicon. — No ingredient of steel is less understood than this one. The technical managers of the Terrenoire Works in France, who have been notably successful in their steel manufactures founded on chemical induction, 102 WROUGHT-IRON AND CHAIN-CABLES. especially in the manufacture of sound steel castings which contain a large amount of Si., believe that this ingredient, up to the amount contained in most of the irons we are con- sidering, does not decrease the tenacity or ductility of steel. And it is true that good steels are made by various processes with as much as 0.20 Si. It is believed by the Terrenoire managers that silica is the cause of the bad effects usually attributed to silicon. The table of analyses will show that in this case the ore has not been mistaken for the metal. The slag, which contains the silica, has been separately determined. Why wrought-iron should differ from steel in respect of the effects of Si., we have not so far been able to determine, if, indeed, it does so differ. It can only be said, with reference to this series of experiments, that there is an apparent decrease of strength due to an excess of this element, while the effects of medium amounts of it are overshadowed by larger causes. The extremes of Si. were 0.028 and 0.321. In the best irons it averaged about 0.15. It ran as follows, with a regularly decreasing order of value : In Tenacity^ Si., 0.09, 0.15, 0.15, 0.15, 0.18, 0.18, 0.17, 0.16, 0.03, 0.16, 0.16, 0.16, 0.14, 0.27, 0.16, 0.07. Reduction of Area, Si., 0.07, 0.14, 0.03, 0.16, 0.16, 0.18, 0.16, 0.16, 0.15, 0.18, 0.15, 0.15, 0.16, 0.17, 0.09, 0.27. Elongation, Si., 0.03, 0.18, 0.07, 0.14, 0.16, 0.16, 0.16, 0.18, 0.15, 0.17 0.16, 0.15, 0.15, 0.16, 0.27, 0.09. Effects of Caebon. See foregoing remarks on iron B, in which C. is extremely low. Iron L: C, average 0.35, highest 0.51; P., 0.10; Si., 0.10; slag, low. Carbon very high, other impurities quite low. Tenacity as bar highest. Ductility as bar and link lowest. Welding power most imperfect, decreasing as C increases. The following table,* from a paper by William Hackney, * Read before the Institution of Civil Engineers, London, April, 1S75. COMPARISON OF CHEMICAL AND PHYSICAL RESULTS. 103 Esq., is valuable in this connection, as showing the amounts of C. in various well-known brands of wrought iron and steel. Percentages of Carbon in some Varieties of Iron and Steel. Sekies of the Irons. Description. Soft puddled iron Armor plates Iron rail Lowraoor boiler-plate .... Staftbrdshire boiler-plate . . Russian bar-iron Swedish iron bar Steely puddled iron .... Iron made by Catalan process direct from the ore .... Soft puddled steel Puddled steel rail Hard puddled steel .... Percentage of Carbon. Trace.* 0.016 t 0.033 t 0.044 t 0.091 0.10 J 0.19 t 0.272 t 0.340 t 0.054 t 0.087 t 0.386 t 0.30 to 0.40 1 \ traces. f ( 0.420 t 0.501 1 0.55 I 1.380 t Series of the Steels. Description. Extra soft Fagersta Bessemer steel Extra soft Dowlais Bessemer steel Crewe boiler-plate steel, Bes semer process .... Locomotive crank-axles, Sera ing Bessemer steel ... Locomotive crank-axle, by Vickers, Shetiield . . . Rails and tires Bessemer spring steel . . Crucible steel : For masons' tools , . , For chipping chisels . . Crank-axle (by Krupp) , Gun (by Krupp) . . , For flat files Forged Indian wootz . . . Percentage of Carbon. j 0.085 § [ 0.135 II 0.22 to 0.2411 0.31 1 0.49 I {0.46* 0.30 to 0.50 0.45 to 0.55 X 0.6* 0.75* 1.05 t 1.18 t 1.20* 1.645 1 Iron L is, therefore, a so-called puddled steel, or more prop- erly a weld-steel. Since its impurities, other than C, are so small, it is impossible to avoid the conclusion that C. is the cause of its marked physical character. This is more plainly shown by the following : — 1^ in. bar, C. 0.45, has nearly 70,000 pounds tenacity per square inch, and 6.5 per cent elongation. 1| in. bar, C. 51, has 67,000 pounds tenacity per square inch, and 6.5 per cent elongation. 11^ and lif in. bar, C. 0.21 to 0.25, have average 58,000 pounds tenacity per square inch, and 13 per cent elongation. IronK: C, 0.07 ; P., C.15 ; Si., 0.15; slag, low. C. slightly high, other impurities medium. Iron well worked and very uniform. Tenacity as bar and link very high. * A. Willie. § D. Forbes. t J. Percy. II Snelus. X A. Greiner. IT F. W. Webb. 104 WEOUGHT-IEOX AND CHAIN-CABLES. Ductility below medium. Welding power quite low. The ductility was very fair when the bar was not nicked. The fracture was fine and silvery, like that of low steel. These facts, and the medium amounts of other impurities, point to C. as the hardening element. Irons having similar amounts of P. and Si., and low carbon, like irons A and C, have lower tenacity and higher ductility. Iron E: C, 0.018; P., 0.18; Si., 0.16. C. very low, other imj^urities medium. Tenacitv below avera^^e. Ductilitv hio'h. Welding power pretty good. These phenomena seem to be connected with low carbon. Conclusions about Carbon. — So much is known concerning the influence of C. on both wrought-iron and steel, that there is little danger of falling into error about it. The irons under consideration have C. almost exclusively low and pretty uni- form : the exceptional cases give very marked physical results, especially iron L, which is the only one really high in C. The other irons ranged between 0.015 and 0.07. Carbon ran with the following decreasing order of value in Tenacity : C. 0.35, 0.068, 0.032, 0.042, 0.044, 0.033, 0.055, 0.032, 0.066, 0.032, 0.032, 0.015, 0.02, 0.036, 0.026, 0.043. Reduction of Area, 0.043, 0.02, 0.066, 0.026, 0.032, 0.033, 0.032, 0.032, 0.032, 0.044, 0.042, 0.068, 0.015, 0.055, 0.35, 0.036. Elongation, 0.066, 0.033, 0.043, 0.02, 0.032, 0.026, 0.032, 0.044, 0.032, 0.055, 0.032, 0.042, 0.068, 0.015, 0.036, 0.35. It seems thus easy to vary the physical qualities of pud- dled iron by carbon ; but whether or not it is easy to uniformly vary the carbon in puddled iron, the checkered history of the " puddle d-sfe el " process will show. As we shall observe far- ther on, for uses in which the value of an iron depends on the strength of the particular kind of weld given to these links, C. must be under 0.04. But for uses in which the strength of the bar is the measure of fitness, C. may run up to 0.50 or more. COMPARISON OF CHEMICAl, AND PHYSICAL RESULTS. 105 Blangmiese is so very low in all these irons, that its effects cannot be traced. It is highest in one lot of iron D, viz., 0.097 ; but even this could have little effect, in view of the fact that Mn. is often three times as high in very soft steels, and some- times runs above one per cent in low structural steels. Mn. seems to toughen steel, and to make it cast sound : its harden- ing effect up to Mn. 0.20 to 0.30 is slight. Copper is very low in all the irons, except M (Cu. 0.31 to 0.43), which has about the average tenacity and ductility. Cu. is next highest (Cu. 0.17) in iron A, which has rather low tenacity, but very high ductility, on account of its low carbon (C. 0.02). These experiments furnish no evidence that copper affects strength. Its effect on welding will be further con- sidered. JSichel was only high (Ni. 0.34) in some of tlie bars of iron M, but did not appear to affect their strength. That it may have helped their welding capacity, is further re- ferred to. Cobalt was so low (Co. 0.11 maximum) that its effects on strength could not be traced. Possibly copper may have been neutralized by Ni. and Co. in its effect on strength, but these data are not evidence one Avay or the other. Sulphur was extremely low in all the irons, S. 0.046 being the highest percentage in one lot of iron M. So little S. did not affect welding power, as we shall observe farther on ; and it could hardly impair strength, when irons red-short from much S. are usually strong. Slag. — This averages about one per cent. It is lowest in iron L (slag 0.38), and highest in the 2'' bar of iron N (slag 2.26). This bar had 51,700 pounds tenacity, and 8.7 per cent elongation; while the 1^'' bar of iron N, with 1.258 slag, had 56,000 pounds tenacity, and 21.7 per cent elongation. Was this the result of too little work on the larger bar, or of tlie slag per se? Is the presence of much slag merely an indi- cation of too little work, — of a loose structure resulting from too little condensation of the fibres? Or does the slag, as slag. 106 WKOUGHT-IROX AXD CHAIN-CABLES. or clirt, exert an independent weakening influence ? Referring to the table of analyses we find : — Iron. Size. Slag. Iron. Size. Slag. L. . . *" 0.668 . . H" 1.096 L. &." 0.388 o . . 13" 0.974 L. 17" 16 0.192 p . . 1" 0.848 L. 11" 0.326 p . . 13" 1.214 L. 15" 8 0.308 D . . 1" 0.570 L. 111" 16 0.452 D . . 2" 0.546 L. 113" ■^16 0.376 It appears that the smallest and most worked iron often has the most slag. It is hence reasonable to conclude that an iron may be dirty and yet thoroughly condensed ; and it therefore seems probable that the 1^ bar of iron N was 4,300 pounds stronger than the 2'' bar, partly because it had one per cent less slag. The V^ bar of iron P had nearly 58,000 pounds tena- city; while the 1|'' bar of Px, with 0.40 more slag, had a little less than 53,000 pounds tenacity. It is, however, impossible to establish any close conclusions from these small variations of slag. The investigation requires analyses of irons equally worked, some of the specimens being purposely made very dirty. Welding. Before comparing the irons under this head, it may be well to briefly consider the heretofore ascertained facts, and the specu- lations which grow out of them. The generally received theory of welding is, that it is merely pressing the molecules of metal into contact, or rather into such proximity as they have in the other parts of the bar. Up to this point there can hardly be any difference of opinion, but here uncertainty begins. What impairs or prevents welding ? Is it merely the inter- position of foreign substances between the molecules of iron and any other substance which will enter into molecular rela- tions or vibrations with iron? Is it merely the mechanical COMPARISON OF CHEMICAL AND PHYSICAL RESULTS. 107 preventing of contact between molecules, by the interposition of such substances ? This theory is based on such facts as the following : — 1. Not only iron, but steel, has been so perfectly united that the seam could not be discovered, and that the strength was as great as it was at any point, by accurately planing and thoroughly smoothing and cleaning the surfaces, binding the two pieces together, subjecting them to a welding heat, and pressing them together by a very few hammer-blows. But when a thin film of oxide of irOn was placed between similar smooth surfaces, a weld could not be effected. 2. Heterogeneous steel-scrap, having a much larger variation in composition than these irons have, when placed in a box composed of wrought-iron side and end pieces laid together, is (on a commercial scale) heated to the high temperature which the wrought-iron w411 stand, and then rolled into bars which are more homogeneous than ordinary wrought-iron. The wrought-iron box so settles together as the heat increases, that it nearly excludes the oxidizing atmosphere of the furnace, and no film of oxide of iron is interposed between the surfaces. At the same time the enclosed and more fusible steel is partially melted ; so that the impurities are partly forced out, and partly diffused throughout the mass, by the rolling. The other theory is, that the molecular motions of the iron are changed by the presence of certain impurities, such as cop- per and carbon, in such a manner that welding cannot occur or is greatly impaired. In favor of this theory it may be claimed that, say, two per cent of copper will almost prevent a weld ; while, if the interposition theory were true, this copper could only weaken the weld two per cent, as it could only cover two per cent of the surfaces of the molecules to be united. It is also stated that one per cent of carbon greatly impairs welding power, while the mere interposition of carbon should only reduce it one per cent. On the other hand, it may be claimed that in the perfect welding due to the fusion of cast-iron, the interposition of ten 108 WKOUGHT-IRON AND CHAIN-CABLES. or even twenty per cent of impurities, such as carbon, silicon, and copper, does not affect the strength of the mass as much as one or two per cent of carbon or copper affects the strength of a weld made at a plastic instead of a fluid heat. It is also true that high tool steel, containing one and a half per cent of car- bon, is much stronger throughout its mass, all of which has been welded by fusion, than it would be if it had less carbon. Hence copper and carbon cannot impair the welding power of iron in any greater degree than by their interposition, provided the welding has the benefit of that perfect mohility which is due to fusion. The similar effect of partial fusion of steel in a wrought-iron box has already been mentioned. The inference is, that imperfect welding is not the result of a change in molecu- lar motions, due to impurities, but of imperfect mobility of the mass, — of not giving the molecules a chance to get together. Should it be suggested that the temperature of fusion, as compared with that of plasticity, may so change chemical affini- ties as to account for the different degrees of welding power, it may be answered that the temperature of fusion in one kind of iron is lower than that of plasticity in another, and that, as the welding and melting points of iron are largely due to the carbon they contain, such an impurity as copper, for instance, ought, on this theory, to impair welding in some cases, and not to affect it in others. This will be further referred to. The next inference would be, that by increasing temperature we chiefly improve the quality of welding. If temperature is increased to fusion, welding is practically perfect; if to plas- ticity and mobility of surfaces, welding should be nearly perfect. Then, how does it sometimes occur, that, the more, irons are heated, the worse they weld ? 1. Not by reason of mere temperature ; for a heat almost to dissociation will fuse wrought-iron into a homogeneous mass. 2. Probably by reason of oxidation, which, in a smith's fire especially, necessarily increases as the temperature increases. Even in a gas-furnace, a very hot flame is usually an oxidizing flame. The oxide of iron forms a dividing film between the COMPAEISOX OF CHEMICAL AND PHYSICAL RESULTS. 109 surfaces to be joined ; while the slight interposition of the same oxide, when diffused throughout the mass by fusion or partial fusion, hardly affects welding. It is true that the contained slag, or the artificial flux, becomes " more fluid as the tempera- ture rises, and thus tends to wash away the oxide from the sur- faces ; but inasmuch as any iron, with any welding flux, can be oxidized till it scintillates, the value of a high heat in liquefy- ing the slag is more than balanced by its damage in burning the iron. 3. But it still remains to be explained, why some irons weld at a higher temperature than others ; notably, why irons high in carbon, or in some other impurities, can only be welded soundly by ordinary processes at low heats. It can only be said that these impurities, as far as we are aware, increase the fusibility of iron, and that in an oxidizing flame oxidation be- comes more excessive as the point of fusion approaches. Weld- ing demands a certain condition of plasticity of surface : if this condition is not reached, welding fails for want of contact due to mobility ; if it is exceeded, welding fails for want of contact due to excessive oxidation. The temperature of this certain condition of plasticity varies with all the different composi- tions of irons. Hence, while it may be true that heterogeneous irons, which have different welding-points, cannot be soundly welded to one another in an oxidizing flame, it is not yet proved, nor is it probable, that homogeneous irons cannot be welded together, whatever their composition, even in an oxi- dizing flame. A collateral proof of this is, that one smith can weld irons and steels which another smith cannot weld at all, by means of a skilful selection of fluxes and a nice variation of temperatures. To recapitulate : It is certain that perfect welds are made by means of perfect contact due to fusion, and that nearly perfect welds are made by means of such contact as may be got by par- tial fusion in a non-oxidizing atmosphere or by the mechanical fitting of surfaces, whatever the composition of the iron may be v/ithin all known limits. While high temperature is thus the 110 WROUGHT-IEOX AND CHAIN-CABLES. first cause of that mobility which promotes welding, it is also the cause, in an oxidizing atmosphere, of that " burning " which injures both the weld and the iron. Hence, welding in an oxi- dizing atmosphere must be done at a heat which gives a com- promise between imperfect contact due to want of mobility on the one hand, and imperfect contact due to oxidation on the other hand. This heat varies with each different composition of irons. It varies because these compositions change the fusing-points of irons, and hence their points of excessive oxi- dation. Hence, while ingredients such as carbon, jDhosphorus, copper, &c., positively do not prevent welding under fusion, or in a non-oxidizing atmosphere, it is probable that they impair it in an oxidizing atmosphere, not directly, but only by changing the susceptibility of the iron to oxidation. The obvious conclusions are : 1st, That any wrought-iron, of whatever ordinary composition, may be welded to itself in an oxidizing atmosphere at a certain temperature, which may differ very largely from that one which is vaguely known as "a welding heat." 2d, That in a non-oxidizing atmosphere, heterogeneous irons, however impure, may be soundly welded at indefinitely high temperatures. These speculations may throw little light on the subject of welding. They are introduced for the purpose of indicating the direction of further inquiry and experiment, and of im- pressing the necessity of caution in arriving at conclusions about these irons from the limited data afforded by these experiments. In reviewing the experiments with reference to welding, and under the precaution mentioned, let us observe ; — 1st, All the irons were so very low in sulphur, that this ingredient could not have materially affected welding power. 2d, As we shall see in detail, farther on, the irregular dif- ferences in the working and reduction of the bars, which affected all other ph3^sical properties, affected this one also. Let us first take the singularly impure iron M. Ite surfaces were pretty well united by welding, but the iron about the COMPAEISON OF CHEMICAL AND PHYSICAL RESULTS. Ill weld was weakened, especially at a high heat. Of 124 rup- tures of links made of this iron, 79 were through the weld, and the iron was little distorted. Of 311 ruptures of links made of other irons, but 37 were through the weld. The li' bar of iron M presents an exception: it stands high on the list in welding capacity, and contains copper 0.31 (average Cu. in iron M, 0.34). Its ]3hosphorus, slag, and silicon are about average. But the bar is also remarkable in containing nickel 0.35, and cobalt 0.11. Did these ingredients neutralize the copper under this special treatment ? No other irons contain any notable amount of them, except iron A, which has Co. 0.07, and Ni. 0.08; but it also has Cu. 0.17.* The welds of this iron were very strong, the links breaking oftener at the butt than at the Aveld. Two links made from iron M were analyzed from specimens taken at the weld end and at the butt end. The weld end had been re-heated and hammered twice ; the butt end had not been hammered, and had received second heat only by conduction from the other end. The analj'ses show that silicon and slag only were materially affected by twice heating and hammering, as follows : — Silicon. Slag. Iron M, 1^ in. bar, weld end " Ig^ in. bar, butt end " If in. bar, weld end " If in. bar, butt end 0.182 0.203 0.177 0.261 0.998 1.074 1.388 1.732 In oxidizing to silica, the Si. diffused a small amount of flux, which should have helped welding by preventing oxidation, or by carrying off oxide of iron, or both ; but the amount was so very small in this case that its effect cannot be traced. Nor does iron J, in which Si. was highest (0.18 to 0.32), confirm * This iron may have received the copper while being rolled in a train ordinarily used for copper, at the Xavy Yard, Washington, D.C., where it was manufactured. 112 WEOUGHT-IRON AND CHAIN-CABLES. this theory. Although the other impurities were not high, and the iron was not overworked, it welded rather badly. The value of short chains is as follows : Best, Si. 0.16, 0.14, 0.07, 0.03, 0.16, 0.15, 0.17, 0.15, 0.17, 0.18, 0.16, 0.18, 0.15, and, including J, 0.27. Phosphorus, up to the limit of i per cent, had not a notable effect on welding. It was lowest in iron O, which welded soundly ; but all impurities were low, and welding power was traced to the reduction of the bar by direct experiment. The same is true of iron P. Omitting one course of piling and hammering largely helped its welding power. Iron P Avelded badly, not necessarily on account of its P. 0.25 ; for iron B, with P. 0.23, and iron D, with P. 0.18, welded soundly. Iron ^M had the high P. 0.23 (0.21 to 0.32). While its surfaces stuck together pretty well, the links broke through the weld when they were made at a high heat, which may be accounted for by the fact that phosphorus increases fluidity, and hence capacity for oxidation. The value of short chains is in the following order : Best, P. 0.23, 0.18, 0.07, 0.09, 0.20, 0.20, 0.19, 0.17, 0.19, 0.25, 0.19, 0.22, 0.15. Carbon notably affected welding. It ran as follows in con- nection with regularly decreasing welding power : Best, C. 0.015, 0.02, 0.043, 0.066, 0.026, 0.032, 0.032, 0.042, 0.055, 0.033, 0.032, 0.044, 0.068, and including L, 0.351. The weld steel, or steely iron, L (C. 0.35), when treated by the uniform method usually adopted for chain-cable irons, made the worst welds. Iron K, with carbon so low as 0.07, made bad welds, although it was otherwise a good average chain- iron, with a medium amount of impurity. Carbon, in a greater degree than phosphorus, promotes fluidity : hence the iron is " burned " at the ordinary welding temperatures of low-carbon irons. Slag was highest (2.26 per cent) in the two-inch bar of iron N, which welded less soundly than any other bar of the same iron, and below average as compared with the other irons. Slag should theoretically improve welding, like any flux. COMPARISON OF CHEMICAL AND PHYSICAL RESULTS. 113 but its effects in these experiments could not be definitely traced. What is learned from Chemical Analyses. So far, it may appear that little of use to the makers or the users of wrought-iron has been learned. But it should be remembered that all these irons were intended to be as nearly as possible alike, and to be adapted to the peculiar use of chain- cable. The makers generally understood the necessary condi- tions, and every effort was made to reach this special standard of excellence. Had it been reached, the irons would have all been exactly alike in physical character, and presumably similar, although not necessarily alike, in chemical character, for certain ingredients may replace others within limits which are perhaps narrow. Certainly the attempt to make all the irons conform to a well-known standard of quality was the worst possible way to ascertain the distinctive effects of the various altering ingredients. In order to make this latter determination, one series of irons should have been made as uniform as possible in all ingredients except one, for instance, phosphorus, and that one should have been varied as much as possible. Another series should have been alike except in silicon ; and so on, through the list of altering ingredients. The series of tests which the Board has undertaken on steels was devised upon this principle. It was, however, thought best, after the phj'si- cal tests of these irons were completed, to subject them to analysis, in the hope that some good result would follow. This hope has been realized in an unexpected and somewhat sur- prising manner. 1st, The want of uniformity in the chemical composition of the same brand of iron is a conspicuous defect which is readily accounted for. In iron M, silicon varied from 0.16 to 0.26 ; in iron J, it varied from 0.18 to 0.32. In iron D, phosphorus varied from 0.12 to 0.24 ; and in iron J, from 0.11 to 0.29. Starting with a uniform pig-iron, the puddling process may or may not remove a large amount of silicon, phosphorus, and 114 WEOUGHT-IRON AND CHAIN-CABLES. carbon, according to the temperature and agitation of the bath, the " fix " used in the furnace, and from many causes under the puddler's control, and dependent on his knowledge and skill. Such variations would be entirely inadmissible in the most common grades of steel : in fact, they could not occur in the cheap steel processes, when using a uniform pig-iron, except by a special effort. In the Bessemer process, the completion of the oxidation of silicon and carbon is obvious to the inexpert observer; in the open-hearth process, unmistakable tests are taken during the operation. The character of steel can be surely predicated on the analysis of its materials; that of wrought-iron is altered by subtle and unobserved causes. Should it be urged in favor of wrought-iron, that P. can be largely removed during its manufacture, while in the steel- manufacture it cannot be, it may be answered that there is an abundance of pig-irons which do not contain much P. ; and it is better to be sure of a definite amount of a deleterious ingre- dient than to run the risk of a variable amount. We are not prepared to show the exact effect of varying reduction on steel. Ingots of the same grade of steel, from six inches square to fourteen inches square, are emploj'cd for the same-sized bars ; the larger ones are preferred, notwithstanding the greater cost of working them, not because small ingots will not make good bars : but because they make too much scrap. Steel depends comparatively slightly on condensation for its density, but very greatly on its being cast from a fluid state. It is a crystalline mass in both large and small ingots, and not a bundle of fibres of iron more or less compacted. 2d, This matter of varying strength due to varying reduction — the most important developed by the series of experiments — is made all the more certain and useful by the analyses ; for, without a knowledge of the composition of the bars and of the specific effects of different ingredients, a part of the variation now traced to reduction might have been attributed to com- position. It may be stated in general terms, that, notwithstanding this COMPAETSON OF CHEMICAL AND PHYSICAL EESULTS. 115 attempt at uniformity, the differences in reduction in the roll- ing-mill from pile to bar caused as much variation in the physical qualities of these irons as did the differences in the chemical composition of the whole series of irons, excepting the steely iron L. The highest difference in tenacity, due apparently to varying reductions, is 11,969 pounds per square inch. The highest difference between the average tensional resistances of all the irons (excepting the steely iron L), due to all causes, is but 7,109 pounds. The following illustrations are more in detail : — Iron P. Tenacity of 1 in. bar (1.74 per cent of pile) above 2 in. (6.98 per cent of pile) . Elastic limit " " " " " " Iron F. Second Lot. Tenacity of IJ in. bar (2.76 per cent of pile) over 2 in. (5.23 per cent of pile) Elastic limit " '♦ " " '« " Iron F. Third Lot. Tenacity of I in. bar (1.60 per cent of pile) o%'er 2\ in. (6.13 per cent of pile) " g in. bar (3.68 per cent of pile) over 4 in. (15.70 per cent of pile) Elasticlimitof g in.bar " " " «« " Tenacity of 1 in. bar (3.14 per cent of pile) " •' " Iron N". Tenacity of 1^ in. bar (6.62 per cent of pile) above 2 in. (11.36 per cent of pile) . . 4,395 lbs. Iron A. Tenacity of 1 in. bar (3.14 per cent of pile) over 2 in. (8.72 per cent of pile) . . 4,519 lbs. Iro7i D. Difference in phosphorus in 1 in. and 2 in. bars, 0.026; other ingredients about alike. Tenacity of 1 in. bar over 2 in. bar 11,969 lbs. The following are apparently results of composition : — Comparative Tenacity. Of iron highest in average qualities over the one lowest in impurities .... 3,136 lbs. Of most tenacious steely iron (carbon 0.35) over least tenacious (carbon 0.04) . . 15,464 lbs. 3d, The variation of welding power by reduction, in a greater degree than by composition, has already been shown in detail. Chemical analyses were necessary to establish this fact. 4th, To the steel maker and user it will appear somewhat remarkable, that phosphorus may run up to nearly a quarter of one per cent in good chain-cable irons, when it is considered Per Sq. In. 6,973 lbs. 7,352 lbs. 4,698 lbs. 3,227 lbs. 9,656 lbs. 7,786 lbs. 15,045 lbs. 4,806 lbs. 116 WEOUGHT-IRON AST) CHAIX-CABLES. that low tenacity and high ductility are the essential features of such irons, and that the effect of this ingredient is to pro- duce exactly opposite results. Suitable working probably counterbalanced its effects. 5th, The comparison of chemical and physical results sug- gests a number of experiments which would go far to settle vexed questions, and improve the practice, especially with regard to welding. (1) Regarding slag, it has been shown that a larger amount is sometimes found in a well-worked than in a less-reduced iron, and that its effects are uncertain. Experiments should be arranged to show what composition of slags will readily come out of the pile in rolling ; whether two-high or three-high trains will best remove them, and how much and what kind of slaof affects strength and welding. A stable oxide of iron, which would probably do the most harm, could be formed b}- blowing superheated steam upon red-hot bars before piling. It might be proved that very fusible slags, or fluxes, should be placed in the pile to protect surfaces from oxidation, and to wash away less fusible impurities. (2) It has already been suggested that special irons, having respectively a certain ingredient in excess and the others low and uniform, should be made, in order to ascertain, in a con- spicuous manner, the physical effects of the various ingredients. (3) Referring to a previous recapitulation of remarks on welding : The effects of very different temperatures on irons varying in composition, as compared with that uniformly high temperature, usually known as a " welding heat," should be much more carefully ascertained. And the effects, and more especially the means of welding in a non-oxidizing flame, where mobility of surfaces can be got without '' burning," should be made the subject of elaborate experiments. The excellent welding of a heterogeneous mass of steel and iron, protected from oxidation by being placed in an iron box which will stand a high heat, has been referred to. The system of gas-welding by which Mr. Bertram welded boilers at Woolwich twenty COMPAEISOX OF CHEMICAL AXD PHYSICAL RESULTS. 117 years ago has since been in regular use by the Butterly Com- pany, in England, for joining the members of wrought-iron beams of large section. It should seem within the power of modern engineering and chemistry to provide means for the perfection in a non-oxidizing atmosphere, of welds, like those of ships' cables and bridge-links, upon which hang so many lives and so much treasure. Conclusions DERrvT:D from a Co:mpartsox of Chemical AND Physical Results. I. Although most of the irons under consideration are much alike in composition, the hardening effects of phosphorus and silicon can be traced, and that of carbon is very obvious. Phos- phorus up to 0.10 per cent does not harm, and probably im- proves, irons containing silicon not above 0.15, and carbon not above 0.03. Kone of the ingredients except carbon in the pro- portions present seem to very notably affect welding by ordi- nary methods. II. The strength of wrought-iron and its welding power by ordinary methods are varied more by the amount of its reduc- tion in rolling than by its ordinary differences in composition. Uniform strength may be promoted by uniform reduction, but only at such increased cost of manufacture that the practice is not likely to obtain. Therefore the reduced strength of large bars made by ordinary methods should be considered in design- ing machinery and structures. III. In accordance with these facts the United-States Test Board has shown, by trial, the unsafety of the Admiralty proof- tables for chain-cable,. and has prepared new ones, and also new tables of the strength of different-sized bars. The Board has demonstrated that the tenacity of two-inch bar for chain-cable should be between 48,000 and 52,000 pounds per square inch, and of one-inch bar between 53,000 and 57,000 pounds ; and that stronger irons than these make worse cables, because they have low ductility and welding power. IV. Chemical analyses, made in connection with physical 118 • WROUGHT-mOM AND CHAIN-CABLES. tests, are indispensable to conclusions about either the charac- ter or treatment of iron. In this series of experiments the demonstration that strength is dependent on reduction is made more definite and useful by the anal3"ses. Y. Analyses also prove that the same brand of wrought-iron may be heterogeneous in composition ; and they empliasize the previously known fact that wrought-iron making processes, as compared with the cheap steel processes, necessarily give an uncertain character to the former material, while to the latter the desired quality may be imparted with certainty and uni- formity. VI. The ordinary practice of welding is capable of radical improvement : the fact has been fully demonstrated; the means should be made the subject of complete experiments. The per- fection of means for welding in a non-oxidizing atmosphere would seem to be the promising direction of improvement. In submitting the foregoing history of their experiments, and deductions therefrom, the committees recognize the fact that much still remains to be done before either of the investigations can be considered complete. But, having exhausted the time and means at their disposal, they are compelled to submit the results as far as accomplished. L. A. BEARDSLEE, Commander U.S.N., Chairman of Committees D, H, and M. Q. A. GILLMORE, Lieut.-CoL, Corps of Engineers, Brev. Major-Gen., U.S.A., Chair- man of Committee B, Member of Committee D. A. L. HOLLEY, C.E., LL.D., Chairman of Committee C, Member of Committee H. WM. SOOY SMITH, C.E., Chairman of Committees E and K, Member of Committees H and M. DAVID SMITH, Chief Enr/ineer U.S.N., Chairman of Committee 0, Member of Committees D and M. NOTE BY THE ABEIDGER. 119 [Note by the ABEn)GER.] The committees referred to in the signatures above were charged with the following divis- ions of the general work of the Board : — D. On chains and wire rope. \ H. On iron, malleable. >• The committees making this report. M. On re-heating and re-rolling. ) B. On armor-plate. "] C. On chemical research. • The reports of these committees E. On corrosion of metals. T have not yet been published. K. On orthogonal simultaneous strains. J