FIGURE 8. Plan of furnace house at Trollhättan, Sweden.. 9. Plan of furnace at Trollhättan__. 10. Sectional elevation of furnace at Trollhättan__ 11. Sectional elevation of furnace at Trollhättan, showing arrange- 12. Diagram of electrical connnections of furnace at Trollhättan__ 14. Curves showing variation of fuel required and of heat evolved_ 16. Héroult 1,500-kilowatt, three-phase reduction furnace__ 17. Second 1,500-kilowatt, three-phase reduction furnace built at 18. Sectional elevation of 2.5-ton, single-phase Héroult steel fur- 19. Elevation of 1-ton, three-phase Stassano steel furnace, Bonn, 20. Plan of 1-ton, three-phase Stassano steel furnace, Bonn, Ger- 21. Elevation of 1.5-ton, single-phase Kjellin steel furnace, 22. Elevation of 2.5-ton, single-phase Girod steel furnace, showing 23. Elevation of 8-ton, three-phase Keller steel furnace, Unieux, 24. Elevation of 2.5-ton, two-phase Grönwall steel furnace, Shef- 25. Longitudinal elevation of 2.5-ton, two-phase Grönwall steel 26. Elevation of Nathuasius three-phase steel furnace, showing 27. Plan and elevation of 2-ton, single-phase Röchling-Roden- 28. Plan and elevation of 2.5 to 3 ton, single-phase. Girod steel fur- 29. Section of water-cooled steel electrode used in Girod furnace__ 31. Plan and elevation of Hering resistance furnace_ 32. Arrangement of electric-furnace steel plant, Oberhausen, Ger- 110 33. Results of analyses of 19 samples of metal during one heat___ 111 114 35. Specific-energy consumption as function of weight of charge, 114 36. Voltage, output, and power consumption for 2.5-ton, single- 115 ELECTRIC FURNACES FOR MAKING IRON AND STEEL. By DORSEY A. LYON and ROBERT M. KEENEY. THE ELECTRIC FURNACE IN PIG-IRON MANUFACTURE. BY DAVID A. LYON. INTRODUCTION. In the inquiries and investigations that the Bureau of Mines is making with a view to increasing safety, efficiency, and economic development in the metallurgical industries, the application of electricity to various processes, and especially to those in the manufacture of iron and steel, is being given attention. Some results of the work already done are presented in this bulletin, which gives a historical review of the development of electric furnaces for making iron and steel, and discusses the problems that remain to be solved in the use of electric furnaces for the smelting of iron ores and the production of pig iron at a profit on a commercial scale. DEVELOPMENT OF THE ELECTRIC FURNACE FOR SMELTING IRON. In 1898 Capt. Stassano, of Italy, patented an electric furnace for smelting iron ores. In 1900 the production of ferro-alloys in the electric furnace was begun, and at the present time practically all ferro-alloys are made in electrically heated furnaces. INVESTIGATIONS OF THE CANADIAN COMMISSION. INVESTIGATION OF 1904. The work of Stassano and the successful production of ferro-alloys in the electric furnace were brought to the attention of the Canadian Government by Eugene Haanel, Government superintendent of mines. As is well known, Canada is not so favored with abundant high-grade ores and good coking coal as is the United States, and so it seemed to Haanel and his associates that the electric furnace might lead to the solution of their problem in Canada, namely, the treatment of low-grade ores, and of those ores high in phosphorus and sulphur. Ultimately, through the efforts of Haanel, a commission was appointed "to proceed to Europe for the purpose of investigating a Stansfield, A., The electric furnace, 1907, p. 13. and reporting upon the different electrothermic processes employed in the smelting of iron ores and the making of the different classes of steel, then in operation or in process of development, in Italy, France, and Sweden." This commission left Ottawa for England on January 21, 1904. When the commission arrived in England, F. W. Harbord, the wellknown metallurgist, was engaged to act as metallurgist to it. Al f though the commission visited several plants in Europe, yet in none of them was direct smelting being attempted, nor were most of them in any way adapted for making experimental tests of direct smelting. While the commission was at La Praz, France, Dr. Héroult was kind enough to demonstrate that it was possible to produce iron from the ore in an electric furnace. α f ܩܕ EXPERIMENTS WITH KELLER FURNACE, LIVET, FRANCE. At Livet, France, however, the commission found at the works of Keller, Leleux and Co. an electrical installation well suited for smelting tests of iron ores. Figure 1 shows the type of furnace used for making these tests. It consisted of two or more furnaces with vertical electrodes, connected by a central well, the current flowing from each furnace through the vertical electrodes a and b. In the tests made by the commission the iron ore, fluxes, and coke were broken to such a size that all would pass through a 13-inch ring. They were then mixed and "charged into the furnace in the annular space between the electrode and the walls of the furnace." In this connection it should be noted that the report of the commission clearly states that in these experiments the reduction was accomplished by means of solid carbon, as is shown by the following statement: "The heat, generated rapidly, raised the temperature and en FIGURE 1.-Sectional plan and elevation of Keller furnace. Used by the Canadian commission in making tests at Livet, France. abled the carbon mixed with the ore to reduce it to the metallic state, and as the temperature rose the metal fused and collected on the sole of the furnace." Later reference to this point is made. The gases resulting from the operation were allowed to escape and burn at the top of the furnace. At Livet the commission made two separate experiments, the first lasting 55 hours and the second 48 hours. In conducting these experiments the materials were weighed and the weights checked. Especial attention was also given to such other points as were necesto obtain accurate data in regard to the following matter: sary The output of pig iron for a given consumption of electric energy. The quantity of coke required as a reducing agent. The quality of pig iron obtained, with especial reference to its suitability for (a) steel manufacture by (1) Bessemer or Siemen's acid process or (2) Bessemer or Siemen's basic process; and (b) foundry purposes. The tests, performed on March 19, 20, and 21, 1904, marked the real beginning of the present practice of the reduction of iron ores in an electric furnace, for although, as will be seen later, the furnaces in use for this purpose at present differ considerably in construction from the Keller furnace, the principle employed is the same namely, the ore, flux, and reducing agent are fed around the electrodes, and the heat generated by the current passing through the charge raises the temperature of the ore and fluxes to their melting point, and thus enables the carbon to reduce the ore with which it is mixed. PROBLEMS NOT SOLVED BY COMMISSION OF 1904. a After the report of the commission had been carefully studied it was evident that further data would have to be obtained in order to establish with some degree of exactitude the quantity of electric energy required per ton of product and the consumption of electrode. Also, the following important questions referring to Canadian conditions were either not taken up or were left in doubt by the Livet experiments: Could magnetite, which is Canada's chief ore and is to some extent a conductor of electricity, be successfully and economically smelted by the electrothermic process? Could iron ores with comparatively high sulphur content, but not containing manganese, be made into pig iron of marketable composition? The experiments made at Livet with charcoal as a reducing agent in substitution for coke having failed, could the process be so modified that charcoal could be substituted for coke? a Haanel, E., Report of the commission appointed to investigate the different electrothermic processes for the smelting of iron ores and the making of steel in operation in Europe: Mines Branch, Department of Interior, Canada, 1904. The last problem was especially important, as charcoal and possibly peat coke would constitute Canada's home products, whereas coal coke for metallurgical processes has to be imported into several of the Provinces. EXPERIMENTS AT SAULT STE. MARIE, ONTARIO, 1906. A sum of $15,000 was placed at the disposal of the Canadian commission for prosecuting experiments at Sault Ste. Marie, Ontario, in 1906. Owing to the advantages offered, the experimental furnace a was erected at the plant of the Lake Superior Corporation at Sault Ste. Marie, Ontario, under the direction of Erik Nystrom, a member of the staff of the mines branch of the interior department, who was later prominently connected with the work at Trollhättan, Sweden. The furnace is shown in section in figure 2. The experiments at Sault Ste. Marie were continued for several weeks. The report made to the Canadian Government by the superin a Haanel, Eugene, Report on the experiments made at Sault Ste. Marie, Ontario, under Government auspices, on smelting of Canadian iron ores by the electrothermic process: Mines Branch, Department of Interior, Canada, 1907, p. 2. |