A STUDY OF A CARBON RESISTANCE 
 LABORATORY FURNACE FOR 
 TEMPERATURES OF 1800“ C 
 
 BY 
 
 JAMES EDWIN FRITTS 
 
 THESIS 
 
 FOR THE 
 
 DEGREE OF BACHELOR OF SCIENCE 
 
 IN 
 
 CHEMISTRY 
 
 COLLEGE OF LIBERAL ARTS AND SCIENCES 
 
 UNIVERSITY OF ILLINOIS 
 
 1922 
 

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 'A 
 
Digitized by the Internet Archive 
 in 2015 
 
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 1 
 
 https://archive.org/detaiis/studyofcarbonresOOfrit 
 
Acknowled^ent 
 
 The writer wishes to express his appreciation of the 
 gaidance and help given by Dr. S. Putnam and Prof. 
 
 C. W. Parmelee in the preparation of this thesis. 
 
Table of Contents 
 
 I Introduction. 
 
 II History. 
 
 Ill Specifications. 
 
 IV Construction. 
 
 V Tests. 
 
 VI Conclusion. 
 
 VII Bibliography. 
 
- 0 - 
 
 I 
 
 Introduction . 
 
 The development of the electric furnace and its application in 
 the many chemical and metallurgical processes is making very rapid 
 strides, dreat possibilities have been realized in the past fifty 
 years and ever increasing interest is being shown by the metallurgist 
 and electrochemist, who see in it possibilities, far beyond those al- 
 ready offered. 
 
 Many of the processes now carried on by the aid of the electric 
 furnace would be commercially impossible if the temperatures recuired 
 were to be obtained by the methods available prior to the introduction 
 of electricity as a heating agent. 
 
 The electric current is a pov/erful metallurgical agent and 
 great care must be taken by the designer, inventor, and promotor 
 of the many electrical appliances. 
 
 The object of the investigation was to construct a laboratory 
 furnace capable of not only melting about five pounds of steel 
 but capable of obtaining temperatures of about 1800“ C to study the 
 
 deoxidizing agents 
 
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II 
 
 History of the subject. 
 
 The electric furnace raay be described as a short circuit under 
 control. It may also be described as a metallurgical apparatus for the 
 utilization of the thermal effects of the electric current for an in- 
 dustrial purpose. By means of the electric furnace, the electric ener- 
 gy may be transformed into ’’commercial energy”. 
 
 There could be no practical effect obtained from the electric 
 furnace so long as the power was obtained from some primary electric 
 battery as it was too difficult to obtain sufficient power for such 
 a purpose. Attention was turned to the electric furnace only after 
 3dison, Siemens and others had commercialized the dynamo. This 
 afforded an adecuate source of power upon which the experimenter could 
 rely. 
 
 As early as 1853 a form of the arc furnace was constructed by 
 Pichon. It consisted of a series of arcs, set up between electrodes 
 of large size, and throu{^i the independent h^t zones of which, 
 metallic ores, mixed with carbon, were passed, with the object of re- 
 duction. The actual existence of this furnace is very doubtful as 
 nothing but a few papers have been found of this model. 
 
 Sir Hiimphrey Davy, in 16(?0, saw the possibilities of heat gener- 
 ated by the electric current and built a small arc furnace. Despretz, 
 in 1849, made the first resistance t^/pe furnace. These first fur- 
 naces were used for purely experimental purposes. Pepys improved on 
 the resistance type furnace. His construction consisted of a soft 
 iron rod slotted with a fine saw in the direction of its axis and these 
 

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 fine slots filled with diamond dust. The rod was then wound with 
 wire and heated to a red heat for six minutes hy means of the 
 electric battery. An examination of the iron wire showed that 
 that the diamond dust had dissappeared, and that the iron had changed 
 with the absorption of carbon. In this experiment, iron was for 
 the first time treated by the application of electric heat. 
 
 The first verticle type of an arc furnace was exhibited to 
 the Royal Society of London in 1878 by Sir W. Siemens. I t was 
 very similar in design to the present Heroult Steel furnace. The 
 first design consisted of a crucible surrounded by a metallic case, 
 throu^t the bottom of which projected one pole of the electric 
 circuit. That part of the electrode in direct touch with the charge was 
 provided with a point of platinum or other substance capable of resistan- 
 ce of great heat, in order to avoid contaminating the charge. The se- 
 cond electrode, 7/hich was connected with the other pole of the cir- 
 cuit, entered throu^ the cover of the furnace and was cooled with 
 water. The design of this furnace was later changed, making the 
 electrode, which entered at the top, of carbon, while the lower me- 
 tallic electrode was cooled wi th water. A covering of a very high 
 resisting material was used for the protection of the entire fur- 
 nace. 
 
 Siemens finally used a form of furnace very similar to that 
 of Pichon. Two carbon electrodes were inserted in the sides of a 
 crucible in such a position that they remained on top of the charge, 
 and the arc formed between them did not come into contact with the 
 material to be melted. Ths furnace is the prototype of the rever- 
 

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 beratory arc furnace such as used by Stassano for refining or melting 
 steel, by the late G. P* De Laval for smelting zinc ores and by ’^eeks 
 for distilling crude zinc. 
 
 P. H. and A. F. Cowles were the first to build an electric 
 furnace to be brought into commercial operation. This furnace was 
 installed at Milton, Staffordshire, in 1886. It was for the product- 
 ion of zinc from ores obtained from mines in Mexico. The furnaces were 
 rectangular in shape, constructed of fire clay, and provided at either 
 end wi th an inclined cast iron pipe throu^ which the electrode was 
 introduced. These electrodes consisted of a bundle of several car- 
 bon rods adjusted by means of a screw mechanism. 
 
 The charge consisted of a mixture of corundum, metal, and char- 
 coal. A current of 5000 amps, at 60 volts was passed through the 
 furnace and one and one half hours were required for the complete 
 reduction of each charge. 
 
 In 1892, a series of very important experiments were performed 
 by Henri Moissan, a professor at Sorbonne, Paris. He used about 
 a two hundred horse power current and concentrated the energy of 
 the arc in about one cubic foot of space inside a limestone block, 
 the intense heat of the arc melted the lime above and soon formed a 
 small dome which reflected the heat down on the chaise below. The 
 electrodes were movable and could be adjusted as the interior of the 
 crucible attained a higher temperature. The electrodes used were 
 of retort carbon treated with acids to remove any mineral matter, 
 washed, calcined, and then mixed with pitch. The main reactions 
 investigated were the reduction of the oxides, by carbon, of 
 

 
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chromium, tungsten, molybdenum, uranium and titanium. Also, the 
 formation of the carbides and the allotropic changes of carbon were 
 studied, ^ith a current of 400 amperes at 80 volts, the experiment 
 was completed in about five minutes. 
 
 The electric furnace has now extended its use to a great extent 
 throughout the entire field of chemical and metallurgical processes. 
 There is but very few cases where the supplying of a large amount 
 heat is required that the electric furnace has not been applied. 
 
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5 
 
 Conclusions 
 
 The reasons why the electric furnace produces a superior pro- 
 duct with proper handling for tlie most severe specificationsare* 
 First ; The chemical composition of the consecutive heats can be 
 held more closely to a standard than with any other process. This 
 is most noticeable when handling very easily oxidizable products. 
 Second ; Less of the easily oxidizable metals will have to be 
 added to insure a given final minimum. There will be less oxides 
 formed in the charge. 
 
 Third ; Since the composition can be more accurately controlled, the 
 more certain are likely to be the results of subsecuent heat treat- 
 ment. 
 
 Fourth ; Sulphur compounds are more easily removed. 
 
 Fifth ; It has been found that electric steel is less easily in- 
 jured by overheating than is the case with other steel. 
 
 Sixth ; Alloy additions may be made in the furnace rather than in 
 
 the ladle, which increases the chance of thorou^ diffusion and 
 homogenity. 
 
 Seventh ; The electric steels are freer from slags and non-metallic 
 inclusions than are Bessemer and open hearth steels, 
 
 Ei^th ; All of the above characteristics make for quality, and 
 
 quality is the primary consideration 
 
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 III 
 
 Specifications. 
 
 The furnace was designed for the use in the laboratory for ob- 
 taining temeratures of 1800 C. It was to be of the carbon resis- 
 tance type with the current entering at the base and leaving at the 
 top of the first box. The current passes through a resi stor of 
 200 mesh powdered carbon which completely surrounds the crucible. 
 
 The capacity required was that a melt of about 5 pounds of steel 
 could be had from a single heat. The current was taken frcsn a 440 
 volt circuit throu^ a transformer by which the voltage and amperage 
 could be changed. 
 
 The body of the furnace was made of a veiry hi^ refractory in- 
 sulating material consisting of three parts, the base, the body and 
 the cover. The base is a round piece of fire clay 20 inches in 
 diameter and 6 inches thick. The body is 20 inches in diameter and 
 8 inches thick with a tapering hole throu^ the center as the first 
 box. The cover is the same dimension as the base with a three inch 
 hole directly over the center of the fire box, which is 8 inches 
 in diameter at the top and 6§- inches at the bottom. The furnace is 
 20 inches hi^ and 20 inches in diameter. There is a 5/8 inch hole 
 throu^ one side of the body at the top and another throu^ the 
 opposite side at the bottom for the passage of the electwnGbes. A- 
 romd the outside of the fire box, there is a 3/4 inch ring of hi^ 
 
 refractory material for insulating purposes. 
 
 The electrodes used were of Acheson graphite cut and fitted to 
 
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 the proper size. The inner electrodes were cut from two graphite rods 
 seven and nine inches in diameter. The connection from the inner 
 electrodes to the copper terminals were 5/8 inch graphite rods. 
 

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IV 
 
 Construction 
 The Body of the Furnace. 
 
 The body and the insulating ring were made by the Ceramics 
 department of the University. 
 
 The top and plug were made of 55^ of calcined flint clay, 8- 
 30 mesh, 35^ of Georgia Kaolin, and 10^ of Tennessee ball clay. 
 
 This mixture was mixed with water and allowed to stand for a short 
 time, then cast into molds and placed in a damp closet and allowed 
 to age. It was then dried in air and fired for 48 hours at a temper- 
 ature of 1410*^ C. 
 
 The body was made of 50^ coarse grog — all on 10 mesh — , 10^ 
 coarse grog — all throu^ 10 mesh, and 40^ of Hickory Saggar Clay, 
 
 This was mixed with water and allowed to '*wedge'». It was then 
 molded in iron rings and a central core used when necessary. After 
 standing in a damp closet and ageing, it was then fired at 1410‘’C for 
 48 hours. 
 
 The inside ring or insulator was made of 70^ of calcined 
 Bauxite, 20^ ASnid Mississippi Bond clay, and 10^ of Georgia Kaolin, 
 This was finely ground and treated similar to the top and body. After 
 the firing process, the forms were cooled very slowly and the phy- 
 sical constants taken. 
 
 It was found that the total shrinkage of the body was 6^ and 
 the cover 7,14^. The water plasticity of the cover was 28^ and for 
 the body 30^. The water plasticity of the ring was 27.5^ and the 
 

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 Cons traction (continued) 
 
 The Electrodes, 
 
 Anthracite coal and a distillate of pitch were used in the 
 manufacture of one set of electrodes. The coal was of a hi^ grade 
 anthracite coal with about 80^ fixed carbon and less than ash. 
 
 This was ground to 80 mesh and calcined in a gas furnace at a temper- 
 ature of 750 C for four hoors. This reduced the volatile matter 
 to less than !%• By this treatment of the raw material, the shrink- 
 age and tendency of mud cracking was greatly reduced. 
 
 The binder used was obtained from a hi^ grade coal tar pitch 
 with a fixed carbon content of over 40^. This was placed in an iron 
 pot still and slowly distilled. The distillate was a heavy jelly 
 like tar with a melting point at about 100*G. The distillate was 
 redistilled and the melting point of the distillate lowered to 80° C. 
 
 The carbonaceous residue was then heated to a temperature of about 
 1100° C for three hours. This completelj^ es 5 )elled the volatile matter 
 and reduced the per cent of impurities. The residua was ground to 
 80 mesh and used as the body of smother set of the inner electrodes. 
 
 The finely ground carbon was thoroughly mixed with the binder 
 to form a pasty mass. Both of the constituents were heated to about 
 100° C before mixing to insure a homogeneous mass. The paste was 
 then firmly pressed or ’’rammed" into the circular molds for the 
 inner electrodes. The upper electrode mold was &§• inches in out- 
 side diameter and 6 inches in inside diameter and 1-|- inches thick. 
 
 The bottom mold was 7 inches outside diameter c-,nd 4-^ inches in in- 
 
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 side diameter and 1-| inches thick. 
 
 After the mass was firmly pressed and allaved to cool, the raw 
 electrode was transferred to a fire clay pan and completely covered 
 with coarsely ground calcined anthracity coal to prevent oxidiation 
 and to permit the escape of gasses during the calcining period. The 
 pas was than placed into an oil muffle and heated very slowly up to 
 a temperature of 400® C for four hours. The temperature was slowly 
 raised to about 850'' C and held at this temperature for from six to 
 ei^t hours. The fumace was then shut down and the electrode allowed 
 to remain in the fumace over ni^t inorder tiB t it be cooled very 
 slowly. 
 
 The carbon from the coal and the pitch were treated by the 
 above process in the making of the electrodes, but owing to insuff- 
 icient pressure in the ramming process, the finished produce was 
 somewhat porous and easily crumbled. 
 
 In order to get a more solid aid. compact form of carbon for the 
 inner electrodes, two pieces of Acheson graphite rods, seven and 
 nine inches in diameter, were obtained from the International Acheson 
 Graphite Company, Uiagtira Falls. These rods were cut into discs 
 l-^ inches in thiixkness and turned down to the proper size. 
 
 The connection between the copper terminals and the inner elec- 
 trodes was made by a 5/8 inch graphite rod 20 inches long. One end 
 of this rod was ground down and fitted into a hold in the inner 
 electrode and the other w.s clamped to the leads from the switch 
 board by means of a thin copper sheet bent around the rod and bolted 
 

 
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 to the terminal. The electrode and terminal were cooled by water 
 system throng a thin walled copper tube wound around the electrode. 
 The resistor used was 200 mesh Acheson carbon. This ccmpletely 
 filled the space between the top and bottom electrodes and around 
 the crucible. 
 
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12 
 
 V 
 
 Tests 
 
 The flirance was connected to a 40 volt circuit of 13 and one 
 third K. W. At the end of 45 minutes, a temperature of 1200®C was 
 obtained with a current of 45 amperes. In one hour and twenty- five 
 minutes, a No. 24 Segar cone was melted which m^nt a temperature 
 of 1510*0 of over. This took a current of 50 amperes. A fire clay 
 lined graphite crucible was used and did not break down to any 
 appreciable extent. Owing to the large exposed area of the gra- 
 phite rods to the air, they became white hot and burned. 
 
 The current was then changed 30 volts and 20 W!» At the end 
 of one and one-half hours, a temperature of 1500^0 was obtained and the 
 current again changed to 40 volts and 13 and one-thire K17. The tem- 
 perature rise was 130** 0 in. 15 minutes. 
 
 The carbon rods were shortened and refitted so that the cooling 
 coils were as close as possible to the outside of the furnace. The 
 rods were packed in alundum cement to prevent the oxidizing power 
 of the air. The cooling system and terminals were insulated with 
 sheets of asbestos. The graphite cracible was replaced by a 
 zirconium silicate crucible with a melting point of about 1800^*0. 
 
 A current of 30 volts and 20 K7/ was used and a temperature of 
 1500® C was obtained at the end of one and one half hours. At the 
 end of two hours, a No. 24 Segar cone, which has a melting point 
 
 of 1610* C, was melted. At the end of two and one half hours, the 
 temperature was at the melting point of a No, 29 Segar cone or 
 
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above as the cone melted and the crucible fused. This would re- 
 quire a temperature of from 1750“ to 1800^0. The temperatures 
 up to 1700“ C were confirmed by means of a radiation Pyrometer. 
 
 Some difficulty was encountered in the use of the radiation 
 pyrometer as a small carbon monoxide flame burned at the hole 
 throu^ the cover. 
 
 Th© furnace was taken apart and carefully insi^ected. The 
 body and the inner electrodes showed no ill effect of the pre- 
 vious heats. The insulating ring was cracked but still fit for 
 use. 
 
 The electrode rods were replaced and neiv connections were 
 made between the rods and the inner electrodes. The bottom 
 electrode was made air tight with alundum cement and the carbon 
 rods packed in stlra.mite to prevent oxidiation. A new zircon cru- 
 cible was used. A layer of selmanita was placed in the crucible 
 to prevent the segar cones from forming a slag with the crucible. 
 Numbers 32, 33, 34, 35, and 36 segar cones, with melting points 
 respectively 1770“ G, 1790"C, ISIO^C, 1830“C, and 1850“C, were 
 placed in the crucible. A current of 30 volts and 20 EV was 
 con lected with the furnace for one and one-half hours. Tnis 
 current was then changed to 40 volts and thirteen and one- third 
 K?; for 20 minutes. The crucible collapsed, causing the re- 
 sistor to fall and break the circuit, and ended the test. 
 
 The furnace was then cooled and the contents of the crucible 
 noted. It was found that the crucible melted and fused with the 
 
 silmanite to form a clinker like mass. The fused mass and the 
 
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 carbon resistor was carefully examined for traces of the segar cones. 
 No unmelted cone was found but small pieces which resembled parts 
 of the cones were found in the clinlcer. 
 

VI 
 
 Conclusion. 
 
 15 
 
 It was found that by means of the carbon resistance type of 
 furnace tonperatures of 1800° G and over could be obtained. These 
 temperatures were confirmed by the melting of segar cones wi th 
 melting points of from 1800°C to 1850' 0. 
 
 The current could best be conducted from the copper leads to 
 the inner electrodes by carbon rods about one inch in diameter. A 
 rod 5/8 inches in diameter easily becomes heated and considerable 
 care must be taken in cooling, A water jacketed, copper electrode 
 may be used to good advantage, 
 
 A zirconium silicate crucible cannot be used for temperatures 
 of 1800® C. 
 
 In a crucible c pable of withstanding the hi^er temperatures, 
 steel could be melted in small amounts, if a current of 40 volts 
 and 13 l/3 in, were used. 
 
 Owing to the fact that there was considerable delay in the 
 making of the body and insulating ring, the tests of the furnace 
 >and electrodes were not complete. 
 

16 
 
 VII 
 
 Bibliography 
 
 Furnace Electrodes practically considered, 
 
 R. Trjmhull. 
 
 Transactions of the American Electrochemical Society. 
 
 21 - 397 - 1912 . 
 
 Electrode construction for furnaces. 
 
 Chemical and Iletallurgical Engineering. 
 
 9 - 67 - 1911 . 
 
 Furnace Electrodes. 
 
 Chemical and Metallurgical Engineering. 
 
 8 - 391 - 1910 . 
 
 Standard Electrodes for Electric Furnaces, 
 
 Iron Age. 
 
 98 - 1369 - 1916 . 
 
 Graphite Electrodes in Electrometallurgical Process. 
 
 C. L. Collins. 
 
 Transactions of the American Electrochemical Society. 
 
 1 - 53 - 1902 . 
 
 Electrode Efficiency of Furnaces. 
 
 Carl Hering 
 
 Metallurgical and Chemical Engineering. 
 
 7 - 473 - 1909 . 
 
 Electric Steel. 
 Metallurgical and Chemical 
 
 John Mathews. 
 Engixieering 
 16 - 10 - 5 / 15 / 1917 . 
 
 The Electric Furnace. 
 
 J, TT. Pring. 
 
 Electric Furnaces in the Iron ;3ind Steel Industry 
 
 Rodenhauser and Schoenawa. 
 
 Electric Furnaces and their Industrial Application 
 
 J. Vright. 
 
 Discussion of the Electric Vacuum Furnace. 
 
 Collens 
 
 Transactions of the American Electrochemical Society 
 
 9 - 1906 . 
 
 The use of carbon in the study of temperatures in the electric furnace. 
 Transactions of the American Electrochemical society. 
 
 6 - 1904 . 
 
 Manufacture of Carbon Electrodes for Electric Furnace purposes. 
 Chemical and Metallurgical Engineering. 
 
 22 - 741 - 1920 .