Class TS , Book ._£Ll CjDRfRIGRT DEPOSIT. TOOL STEELS DATA AND TABLES APPERTAINING TO ELECTRIC TOOL STEELS MANUFACTURED BY CARNEGIE STEEL COMPANY PITTSBURGH, PA. G1250MM518 Copyright, 1918, by CARNEGIE STEEL COMPANY Pittsburgh, Pa. ©CI.A5()6960 First Edition, July 1, 1918. 0tC2il9l8 Steel is a complex mixture of iron with other ingredients. Some of these ingredients are impurities, the kinds and amounts of which depend on process of manufacture and raw materials used. Other ingredients impart useful properties to metal and are added to or allowed to remain in the steel to produce or intensify these properties. The aim of the steel maker is to reduce the proportion of impurities to the minimum and to add to the iron just that percentage of useful ingredients which will give, those chemical and physical properties most suitable for the uses to which the particular grade of steel is to be put. CLASSIFICATION OF STEEL. Various grades of steel are classified by uses, processes of manufacture or chemical composition. 1. Uses. Structural Steel is that grade in general use in the fabrication of bridges, buildings, cars and ships. Spring Steel goes into the manufacture of car and carriage springs, etc. Tool Steel is peculiarly adapted to be hardened and tempered for the manufacture of machine and hand tools of all kinds, etc. 2. Processes of Manufacture. The terms, Crucible Steel, Bessemer Steel, Acid Open-Hearth Steel, Basic Open-Hearth Steel and Electric Steel, refer to different methods of manufacture and are somewhat indicative of quality for the reason that a particular grade of steel is best made by one or the other of these processes. 3. Chemical Composition. On the basis of chemical composi- tion there are three main kinds of steel. a. Carbon Steel. In addition to phosphorus and sulphur which are present only in such small quantities as it is impossible to remove in the process of manufacture, carbon or plain steels contain iron, carbon CARNEGIE STEEL. COMPANY and manganese, though the percentage of carbon and manganese may be very small. Differences in these steels as to hardness, tensile strength, temperability, etc., are due in the main to the different percentages of carbon which they contain. b. Alloy Steel. In addition to iron, carbon and manganese, alloy steels contain some element or elements which may have been added or allowed to remain, to modify and improve mechanical properties so as to make them more suitable for particular uses. These are often named from the element or elements which impart the dis- tinctive properties; nickel steel, chrome-nickel steel and tungsten steel are examples. c. Alloy-Treated Steels. AUoy-treated steel is carbon steel with the addition of an alloy in small quantities for curative purposes. While the percentage of alloy is not sufficient to impart markedly distinctive properties, its addition serves to improve the natural properties of the carbon steel. Such steels are not properly classed as alloy steels. FACTORS AFFECTING QUALITIES OF STEEL. Chemical composition, method of manufacture, mechanical treatment in shaping and heat treatment before use, are all factors of importance in developing maximum serviceability in steel. Service failures may be due either to improper nianufacture or to improper treatment after manufacture. Since the chemical composition, the method of manu- facture and much of the mechanical treatment are factors that rest with the steel maker, it is obvious that to produce the best steel for any particular use requires adequate and proper facilities and skill in manufacture. On the basis of experience Carnegie Steel Company recommends for tools its carbon steels made in the electric furnace with those percentages of carbon indicated by experience as best suited for the particular use to which such tools are to be put, in the confidence that, when the steel has been properly made and properly treated, carbon steel may be made to serve the requirements of the tool maker for most purposes as well as the more expensive alloy steels. Service failures will likely be due to use of the improper grade or to defects in heat treatment. QUALITIES OF STEEL Ready to Charge Hot Metal Charging Hot Metal from Open-Hearth Furnace Fig. 1. Electric Furnace — Duquesne Steel Works CARNEGIE STEEL COMPANY At Commencement of Heat Ready to Cast Steel into Ladles Fig. 2. Electric Furnace— Duquesne Steel Works HEAT TREATMENT TESTS HEAT TREATMENT. Dependent upon the arrangement of the particles of carbon and iron, steels of the same chemical composition ma}^ be soft or hard. The purpose of heat treatment is to further refine the grain structure of well-made steel and to retain a desired arrangement of the particles of carbon and iron. By proper heat treatment it is possible with steels of the same chemical composition to obtain the structures characteristic of hardened steels or that of annealed steel, structures in which a given steel is in its hardest condition or where maximum ductility is combined with the greatest strength or, again, where it is the softest. Metcalf test pieces, Fig. 3, show clearly the effect of temperature on grain size. A piece of tool steel of con- venient size is lightly nicked across, hot, at intervals of about one inch or an inch and a half. One end is then placed in a fire and gradually heated until it is actually burnt or melted as shown by the shower of sparks when it is taken out. The heat travels back from the heated end so that the temperature varies along the bar from a melting heat, where it was in the fire, to a black heat or almost cold at the other end. As soon as the bar has been heated, it is quenched in water (to make it easier to break), dried carefully (so no water will reach the fractures and rust them) and broken at the nicks. Based on the appearance of the fractures, the bar may be divided into three portions : 1. Where the grains are unchanged, having the same size as in the bar before it was heated. This is the portion of the bar away from the fire where the temperature has been below the hardening point. 2. Where the grains are extremely fine and dull with the appear- ance of broken porcelain. This is the portion of the bar heated only just above the hardening temperature, and the fine grain size shows the refinement due to quenching at the proper temperature. CARNEGIE STEEL COMPANY 5. Greatly Overheated and Quenched 4. Heated just above Hardenino; Point and Quenched 3. Ilr;it(Ml \n il;ir.!(Miin- 1' (,)U(MM'Ii(m1 1. Normal Steel as Rolled Fig. 3.— Metcalf Test Pieces Carnegie Electric Tool Steel No. 1 *,fe.'W HEAT TREATMENT TESTS 4. Overheated Fig. 4. Full Size Test Piece Fractures Carnegrie Electric Tool Steel No. 1 CARNEQIE STEEL CpMPANY 3. Where the grains are very coarse and bright. These are progressively larger towards the melted end of the bar and show the growth in grain size which takes place when steels are heated above the hardening point. Maximum hardness occurs with minimum grain size. To insure this condition steels must be heated above the hardening point. The temperature should be held just above this point to insure uniform heating throughout the bar, but beyond this point steel should not be heated more than absolutely necessary. HARDENING POINT. The hardening temperature for tool steels (the point of minimum grain size) varies with the chemical composition. In carbonless iron it occurs at about 1697° F.;in steels of .90 carbon or over, at 1382° F. It is also affected by the presence of alloys. The line of minimum grain size for carbon steels of different composition is shown on the chart, Fig. 6. Com- panion, Fig. 5, shows the heat colors which are indicative of the different temperatures reached by continuous application of heat. The estimation of temperature by color is liable to the objection that difference in color dis- tinction is bound to exist among different operators and that distinction of color is also affected by different light conditions. More constant results are obtained by the use of pyrometers which should be frequently standardized. METHODS OF HEAT TREATMENT. While explicit direc- tions for working each grade of Carnegie Electric Tool Steel will be given later, some general remarks in regard to the three processes of annealing, hardening and tempering may be of value. 1. Heating. The heating of steel is either for the purpose of forging or otherwise working, or else as a special treatment for annealing, hardening or tempering. In 10 HEAT TREATMENT METHODS heating for forging, the piece is heated uniformly through- out to the temperature desired but is not held in the fire after right heat is reached. The piece is then forged rapidly with as few reheats as possible. Too high a temperature should be avoided, as otherwise the steel may be burnt or become coarse-grained and brittle. The higher the carbon, the lower must be the heat. 2. Annealing. After forging, it is usually advisable to anneal, to relieve any strains which may have arisen and also to make the steel as soft as possible in cases where machining operations are necessary for the proper shaping of tools such as milling cutters. Annealing consists in reheating the steel (after it has become cold) to a temper- ature slightly above the hardening point but not so high as is permissible for forging. When the steel shows uniform heat, it is allowed to cool slowly in the furnace or in lime or ashes until it is black. This slow cooling may be continued until the piece is quite cold or it may be cooled the rest of the way in water, for it is now cooled below the hardening point and will not be affected by quenching. 3. Hardening. When tool steel is to be hardened, it is reheated evenly on a rising temperature to just above the hardening point or, if grade is not known, to the lowest heat at which the steel will properly harden, quenched in water or oil dependent on carbon content, section and degree of hardness required. Steel will not be hardened if heated below the hardening point even though quenched in water. Heating beyond the lowest required temperature will not increase the hardness but makes the grain coarse and increases the brittleness. If steel is overheated, cool to a black color and reheat before hardening. 4. Tempering. Tempering or drawing consists in reheating hardened steel to a low temperature for the purpose of removing the excessive brittleness which it has CARNEGIE STEEL COMPANY TABLE I.— HEAT COLORS Temperature Centigrade Fahrenheit Color Name of Color 1204 2200 1079 996 941 843 746 677 635 566 482 1975 1825 1725 1650 1550 1375 1250 1175 1050 900 White. Light Yellow. Lemon. Orange. Salmon. Bright Red. Light Cherry Red. Medium Cheny. Dark Cherry. Blood Red. Dark Red. HEAT TREATMENT TEMPERATURES m O PQ O