Light railway inside works with turntables, carriages, weighbridge, etc.

Water-supply plant with overhead storage tank and water pipes. to gas scrubber, furnace water jackets and transformers, and pump. with electric motor.

Buildings for furnaces and transformers.

Hoists for ore and lime, storage building for coke, crusher house and hoist.

General stores, offices, and laboratory.

Houses for officials and workmen.

Five electric shaft furnaces for 3,500 estimated horsepower, with foundations, iron constructions, brickwork, and lining.

Electrode holders with water jackets, lifting and regulating arrangements for the electrodes.

Gas blowers with electric motors, gas scrubbers, gas piping.

One tilting open-hearth furnace of 50 tons capacity with rockers and stands, hydraulic tilting cylinder, port ends, chills, gas and air connections and valves.

Working staging.

Iron chimney.

All silica, magnesite, fire, and red brick, silica and fire clay for brick setting, and magnesite.

Three electric steel furnaces, each of 10 tons capacity and 1,500 estimated horsepower, with foundations, iron construction, brickwork and lining, electrode holders with water jackets, automatic regulators, hydraulic tilting cylinders, working stagings, etc.

Two electric cranes of 20 tons carrying capacity.

Transformers for electric shaft and steel furnaces, with oil coolers, regulators, instruments and energy meters, lighting arresters, cables between transformers and furnaces.

Crushing plant with ore and coke crushers and electric motors.
Rails, wagons, weighing machines, tools, and sundries.

Transformers for small motors and for light, including wiring ac

cessories.

Laboratory outfit and office fittings.

Superintendence during construction, drawings, and license.
Contingencies.

The total cost of erection of a plant of this description is estimated at $850,000.

COST OF PRODUCTION.

The estimated cost of producing pig iron and steel in a plant of this description is presented below:

Estimated cost of producing 50,000 tons of electric pig iron a year.

Estimated cost of producing 50,000 tons of electric steel ingots a year.

THE ELECTRIC FURNACE IN STEEL MANUFACTURE.

By ROBERT M. KEENEY.

INTRODUCTION.

The purpose of the second part of this report is to present a brief historical review of the development of the electric-furnace manufacture of steel up to the present time; to describe in detail the types of electric furnaces in commercial operation for the manufacture of steel and, in general, types which have not yet attained wide use; to give a description of the practice of European and American electric-furnace steel plants that were recently visited by the writer; to compare in a general way the different types of furnaces and the more established methods of steel manufacture with the electric-furnace process; and to discuss various problems of the electric-furnace manufacture of steel and the possible future developments of the process.

HISTORY OF THE DEVELOPMENT OF THE ELECTRIC

STEEL FURNACE.

EARLY DEVELOPMENT OF THE ELECTRIC FURNACE.

The process of evolution through which the electric furnace passed before reaching its most highly developed use, which is the manufacture of steel, really began with the furnace of Siemens, the prototype of the modern arc furnace. In 1878 Siemens patented the furnace and operated it in a very small laboratory way. This electric furnace consisted of a crucible of refractory material with a movable vertical electrode, the other electrode being an iron bar passing through the bottom of the crucible. One electrode was connected to the positive pole and the other to the negative pole of a direct-current circuit. The crucible was surrounded by a heat insulator, and the bottom metallic electrode was water cooled.

In 1885 Ferranti devised a furnace the principles of operation of which were the fundamental basis of the modern induction furnace. He used the induced current of a magnetic circuit to heat and melt metals which were arranged like the secondary of a short-circuited transformer.

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Although the electric arc and induced currents were applied to furnace heating by these two pioneers, no attempt was made to operate a commercial electric furnace for the manufacture of steel until 1898. In the meantime, in 1886, the Cowles brothers had devised their arc furnace for the production of aluminum alloys. In 1887 Colby patented an induction furnace for melting metals that was quite similar to the modern Kjellin furnace. In 1892 Willson designed a furnace for the manufacture of calcium carbide that was simply a Siemens crucible reproduced on a commercial scale. In 1893 the radiated heat of the electric arc from two horizontal electrodes was used by Moissan during the course of his extensive experiments on carbides and oxides of metals. From 1893 to 1898 the electric arc furnace was developed rapidly in the manufacture of calcium carbide, although it was still essentially the old Siemens crucible with an upper electrode of carbon and a carbon block in place of the lower metallic electrode.

In 1898, owing to overproduction of calcium carbide and the substantiation of the Bullier patents, many works were compelled to stop the manufacture of carbide, and either turn to the manufacture of other products or shut down, which meant the idleness of many hydroelectric plants capable of developing thousands of horsepower. The experiments of Moissan had shown the possibility of making ferro-alloys in the electric furnace. Ferro-alloys were made in the old carbide furnaces, and with the introduction of these electricfurnace alloys, which were of higher percentage and of greater purity than the blast-furnace product, a steady demand for them arose. As a result, by 1900 a new industry was in operation. In many plants both calcium carbide and ferro-alloys were made, as is the case as present.

EARLY DEVELOPMENT OF THE ELECTRIC STEEL FURNACE.

DEVELOPMENT OF THE HÉROULT STEEL FURNACE.

As the manufacture of ferro-alloys developed and the necessity of producing alloys of low carbon content became apparent the design of the electric furnace was gradually altered so as to make the operation possible without a conducting carbon lining. It was only a step from the Héroult ferrochrome furnace lined with chromite, with a bottom carbon electrode, over which metal was permitted to freeze to prevent carburization, to the nonconducting hearth of the modern Héroult steel furnace, shown in figure 18, as it had been found that this freezing of metal hindered the regular operation of the furnace. The fundamental principles of the modern Héroult steel furnace were patented in 1900.

EXPERIMENTS OF STASSANO.

In the meantime Stassano," of Italy, through an interest in the carbide industry, had attempted to produce steel directly from iron ore in the electric furnace, with charcoal as a reducing agent. The experiments were begun in 1898 and were first conducted in a modified blast furnace, in which electrodes were substituted for tuyères. This furnace being unsuccessful, a new furnace similar to the modern Stassano steel furnace, shown in figures 19 and 20, was built, having horizontal electrodes and arcs heating the charge by radiation, as in

∞

FIGURE 18.-Sectional elevation of 2.5-ton, single-phase Héroult steel furnace, La Praz,

France.

the Moissan furnace. However, it was not well suited to reduction of the ores that were first used.

In these experiments a high-grade hematite ore of low phosphorus and sulphur content was used. The ore was first crushed and then briquetted with charcoal, lime, and tar. The steels produced contained about 0.10 per cent carbon, less than 0.024 per cent phosphorus, and not over 0.073 per cent sulphur. The power consumption aver

a Stassano, E., Treatment of iron and steel in the electric furnace: Electrochem. and Metall. Ind., vol. 6, 1908, p. 315; Catani, R., The application of electricity in the metallurgical industry of Italy: Jour. Iron and Steel Inst., vol. 84, No. 2, 1911, p. 215; Metall. Chem. Eng., vol. 9, 1911, p. 642.