ELECTRIC MELTING OF COPPER AND BRASS C. A. HANSEN _s cC) A paper to be presented at the Annual : Meeting of the American Institute of 1 | Metals, September 24th to 27th, 1912, Buffalo, N. Y. (Advance Copy. Not to be published before the date of the meeting. Discussion Invited.) o i: ELECTRIC MELTING OF COPPER AND BRASS. C. A. Hansen. Dr. W. R. Whitney has turned over to me a request from the American Institute of Metals for a paper on the above subject, one that I hesitate to write upon since I have had but very little experience with copper and its alloys in any type of furnace. Mr. W. G. Rothwell, Superintendent of our Schenectady Works Brass Foundry, who yearly turns out from 3,000,000 to 4,000,000 lbs. of castings, and Mr. L. G. Cooper, our Fuel Engineer, have, however, supplied me with considerable information concerning the more commonly used melting methods, the publication of which will undoubtedly interest many. The general purpose of this paper, then, will be to summarize theoretical requirements, results obtained under ordinary and extraordinary conditions in furnaces of the Rockwell, Charlier and Schwartz types; results obtained in a few experiments with an electric furnace; and a comparison and discussion of the results. In this discussion I shall try to confine myself to the few things I feel more or less competent to discuss. THERMAL DATA. Specific heats—Calories per gram per degree Centigrade. Grvheriuatee. cick 0°C 0.0939 Richards’ BE) Pet ete et at este, 2 os 300°C 0.09846 Naccari DOPREr Sti au ty ees: 900°C 0.1259 Richards’ Popper sirom. e...- 0FCto -3008C09) 104 LeVerrier” ORY, Wag NE tee ee 20°C to 1300°C 0.110 Assumed Zine from.......--. 300°C to 500°C 0.122 — LeVerrier’ Pew dk LOI cs ks rans GA COeh LOS Goaes1 30 Assumed 7 36678 Melting Points. Goppeia ae) 2 eee ce eens 1084°C LICR RANT | ORO oe ee cea ee 419°C Brasses— 90. CopperelO: Zines. = ave ee ete er 1040°C SU LC OpDeracU sine. ee ea eee 1000°C JUS OD eres 0 SAincke mete ee eee. 940°C 60. Copper vO Fin Gra. fens eee eo DU “COPper soU SAI Gute we neon reat ee 860°C Heats of Fusion—Calories per gram. 06 6 010 @ £2 © © © 0 © © 0 6 ae « © (© © 6 © © «16 @ 6 © © © Zine Shepherd* Shepherd*® Shepherd Shepherd® Shepherd’ Richards’ Persons Heat of Solution—Zine in copper—Calories per gram alloy. 32% copper—68% zine D2. Baker* eoseeere ee eeeeweeeve @ Baker found that the above ratio—CuZnz—evolved more heat than any other combination and found a possible sub- maximum corresponding to CuZn. I shall assume that all of the zine in the brass melted combines with copper in the ratio CuZnz. Vapor Pressures. COP Dereater a 1700°C— 0.002 atmospheres Greenwood’ CoOpnperaiin eas 1900°C— 0.009 atmospheres Greenwood’ Coppercatacw. 2h 2100°C— 0.022 atmospheres Greenwood’ ANIC RO Lee ae 900°C— 0.732 atmospheres Barus PAW ACE IN a el ere, Erte 1000°C— 2.5 atmospheres Greenwood PAAUCW At Rete am 1100°C— 6 atmospheres Greenwood JAN GRR ee asets 1200°C—12 atmospheres Greenwood Brass— 76 copper—24 zine 1000°C+15°—0.29 atmospheres Hansen*® 76 copper—24 zine 1084°C+15°—0.66 atmospheres Hansen* 76 copper—24 zine 1150°C+15°—1.18 atmospheres Hansen’ 55 copper—45 zine 900°C+15°—0.24 atmospheres Hansen*® 55 copper—45 zine 950°C+15°—0.44 atmospheres Hansen*® 55 copper—45 zine 1000°C+15°—0.72 atmospheres Hansen’ 55 copper—45 zine 1100°C+15°—1.55 atmospheres Hansen’ TLandoldt und Bornstein—Physikalische Tabellen. 2Chemiker Kalender, 1905. ®’Jour. Phys. Chem., 8-421-1904—Approximated from Shepherd’s curve. 4Proc. Royal Soc., 68-9-1901. 5Trans, Faraday Soc., 1911. ‘Boiling points in Arsem Vacuum Furnace in Hydrogen atmosphere (not pub- lished.) From these boiling points, the calculated heat of solution of a gram equivalent of zinc in copper is (a) 5400 ealories for 24% Zn alloy. (b) 2500 calories for 45% Zn alloy. Baker’s value for 68% alloy was 5040 ealories. Heating Materials Used in This Paper. Texas crude oil—7.25 lbs. per gallon. Heat value—19,000 B. T. U. per lb. Heat value—34,700,000 calories per gallon. 1 kilowatt hour—850,000 calories. Thermal Calculations. Heat required to bring 100 lbs. copper to 1300°C pouring temperature. PPLE OM rece ie ts acs PLS | 6,290,000 calories Ve PGI gre ee ak ee os 3 1,950,000 calories POG a tem crt td wise a Acs, 8,240,000 calories Heat required to bring 100 lbs., 80 copper, 20 zine brass to pouring temperature of 1100°C. Lentil ges GOP Dele ssa... > 4. 4,310,000 calories WeltinenGoppenan si. 1,560,000 calories laksa niion WANG eae ote nee 1,270,000 calories eee iC eee eie 4. 255,000 calories 7,395,000 calories Less heat of solution of Zn 476,000 calories OLE Me enier ita. oT tdotte, 8 evs 6,919,000 calories Theoretical Requirements. To bring 100 lbs. copper to 1300°C........ 0.237 gallons oil To bring 100 Ibs. copper to 1300°C......... 9.70 Kw. hours To bring 100 lbs. 80:20 brass to 1100°C.... 0.199 gallons oil To bring 100 Ibs. 80:25 brass to 1100°C.... 8.13 Kw. hours Oil Fired Furnaces. Strictly comparative tests were made on Schwartz, Rock- well and Charlier furnaces in which particular care was taken to get the best results out of each furnace as regards metal recovery and fuel consumption. Typical Mixture Melted. 200 Ibs. Copper scrap. 200 Ibs. Copper turnings 200 lbs. Brass turnings 300 lbs. Brass gates 8 lbs. Tin 12 lbs. Lead 80 lbs. Zine 1000 lbs. Total. Typical Analysis of Metal Poured. COppeine 4 tare ee 80.7 % AN Cri aia th etae pe ore 16.4% LUCE TGR oe Soar ra eee ae 1.2% A a bores Sa aio atta Tear oe Lt% UO Tiger cae ee crea, trace Results Obtained Under Strict Test Conditions of Operation. Furnace A Bes C Number -Oteneats. POUreC esata teres D 8 Average weight charge, lbs............ 1000 700 Average time per heat minutes........ 113 64 Totala Metal chareereel bs = cows metder rere 5000 5650 Total Metal recovered? lbs:2. se esac r= 4886 5d40 Total svietalsloss "Liss eee ar. eee eee 114 110 Perycent.c Meta la1Ose ren at. ae ee eee 2.28 1.81 'TOLa bE bss Pele 01) Siig ec sme ence yee ates 765 760 Gallons-oN persGalpse metal meer een 2.02 dee: Similar results not obtained under strictly test conditions but under conditions of ordinary practice were as follows: Furnace A B C Numbersot heats spoured 5. eee ee 1 6 6 Average weight charge.:..:;:.......3> 1000 750 750 Average time per heat minutes........ 88 71 85 otaleMetal teharcved saps. weee see oe 17009 4487 4500 Total Metal recovered, Ibs......:3..... 16020 4371 4364 Potalaetal alosss. Hes uwi te. fom ae., aimee 989 116 136 Rerécents, Wietale loss: so. ieee eee 0.82 2.0 3.02 otal Eosmfuel soul sused.ss nwt: Ree 4216 682 696 Gallons soil perjOrlbs* metab... meee 3.46 nes 2.00 “uotIoI jo esinor) ul soeuin J AW AJe1OYY $ JRA ch me) hf Concerning B Furnace—the cost of lining is about $14.00, of which $10.00 is labor. Special Munroe fire brick shapes are used and the life of a lining averages slightly more than 1000 heats, making this item about 2/10 cents per 100 lbs. metal melted. One man looks after each furnace and, beyond a few minutes spent each morning punching tuyeres and claying up pitts in the lining, his attention is given wholly to the metal he is melting. All of the copper alloys are poured into heated graphite crucibles and the 70-lb. pots used last from 60 to 79 pours at 200 lbs. metal each pour. Blast is furnished to seven furnaces of an aggregate capa- city of 6,000 lbs. metal by means of a positive pressure blower having a displacement of 19.6 cu. ft. per revolution, and driven by a 35 H.P. motor at an average speed of 140 R. P. M. The displacement is therefore 2740 cu. ft. of air per minute at atmospheric pressure and the blast pressure is limited to 16 oz. per sq. in. by suitable valves and by-pass. Theoretically, a 750 lb. heat melted with 2.00 gallons of oil per 100 lbs. metal requires 1240 Ibs. air if the carbon in the oil is burned to carbon monoxide and about half again as much if burned to carbon dioxide. The former condition is probably the one which interests us, since too strenuous en- deavors to economize oil would only lead to the substitution of zine for oil as fuel, and zine is still the more expensive. It requires energy to compress this air to the average value used of 14 oz. pressure and this energy is just as much a part of the fuel bill as the oil. Theoretically it amounts to 0.825 Kw. hrs. per 750 Ibs. heat, or more correctly 0.055 Kw. hrs. per gallon of oil burned. Practically, since the blower is run con- stantly and the air is by-passed when the furnaces cease taking it, some 15 Kw. is expended during 10 hrs. each day for the melting of some 20,000 lbs. of metal, 1.e., for the burning of some 450 gallons of oil and, instead of the theoretical 0.055, we have 0.33 Kw. hrs. per gallon of oil. Summarizing the results and comparing them with the theoretical requirements for the 80:20 brass, which we assume is the equivalent of the alloy made, we get that much abused and generally useless term—thermal efficiency. r Oil Fired Furnaces Melting 80% Copper-Brass. Test Conditions Ordinary Practice Furnace A B Ea as B C Sateoiumer C lbs. metal....2.02 1.78. .... 346 .. 1.97 2.00 Kw. hrs. blast per C lbs. LN, gag ose SEG (ear ay. cr), 24 Oe COG Oil equiv. of blast Kw. Lk EE ROR ern a 0.016 .014 .... 0.028 0.016 0.016 Total oil or equivalent. .2.036 1.794 .... 3.488 1.986 2.016 Theoretical requirements. Gallons oil per C lbs.....0.199 0.199 .... 0.199 0.199 0.199 Thermal efficiency %..... GeTiteiee Le Ueto a eh ee LL Ue Oaca Furnace A was lined with a clay bonded carborun- dum which at least partially explains the decided dif- ference from the others in thermal efficiency. In the above the blast power required is converted to oil equivalent on the basis of 40.7 Kw. hrs. per gallon of oil, i. e., on the basis of perfect interchangeability of theoretical heat values and not on the basis of the actual amount of electrical energy that can be obtained from a gallon of oil with any known engine sys- tem. With the modern oil engine 12.75 Kw. hrs, per gallon of similar oil represents excellent practice. The electric furnace experiments were conducted on copper, and for the sake of comparison the following oil furnace results are approximated by using the comparative theoretical re- quirements. for brass and copper and by assuming the same furnace efficiency. The latter assumption favors the furnace since the higher temperatures used in melting copper will most certainly entail decreased thermal efficiency, Oil Fired Furnaces Melting Pure Copper. Test Conditions Ordinary Practice Furnace A B Cie es) B C POG CTONG YC Ure ee ee ase 6 3 O77. 11.0852... 070° 10-00-3987 10 Week's Rotary Arc Furnace. Theoretical requirements. Gals. oil per 100 lbs. ecop- TES | ok ORS er D3 fen] ee 2 eo la ot Actual gals. oil per 100 PIECE DOD TIC? © o5r.s