0.10 per cent carbon, 0.005 to 0.015 per cent silicon, 0.05 to 0.10 per cent manganese, 0.035 to 0.07 per cent sulphur, and about 0.095 per cent phosphorus. It is then poured directly from the converter to a transfer ladle and drawn to the electric furnace building, about onefourth of a mile away. As a precaution against the possible formation of a skull in the ladle, the Bessemer charge is blown hotter than in ordinary Bessemer practice.

When the ladle is received at the electric furnace it is lifted by a crane and tilted; the silicious slag is removed by hand rabbling. The metal is then poured into the electric furnace through a spout. The cleaning of the slag and the charging take 5 to 10 minutes. As the metal pours into the furnace the helper shovels iron oxide and lime through the furnace doors to produce a basic oxidizing slag for the removal of phosphorus. In about 30 minutes the furnace is tilted forward and the slag removed in 5 to 10 minutes by hand rabbling. The quantities of carbon, silicon, manganese, and phosphorus have been reduced to a low point in this period.

In the second or deoxidizing stage which now begins sulphur is eliminated as much as possible. The recarburizing agent is added, followed by lime and fluorspar to keep the mass fluid. In about 15 minutes this second slag is fluid, and finely divided coke dust, the deoxidizer, is thrown on top of the slag, forming a reducing atmosphere, as shown by the formation of calcium carbide beneath the electrodes. Thereafter there is a dead melting in a reducing atmosphere. The slag is basic and fluid and contains considerable calcium carbide. It will be seen that the refining practice with molten metal is quite similar to that with cold scrap.

Tests are taken to show the condition of the steel. A small cylindrical test piece is poured and then flattened under a steam hammer at the furnace. If the forged sample appears to be satisfactory, the bath is tapped. The furnace electrodes are raised, and the charge is poured into a ladle, from which it is teemed into ingots.

The quantity of material used in a typical charge is given in the following charge sheet:

Charge sheet of 15-ton Héroult furnace, South Chicago, Ill.

The time consumed in the different operations is divided as follows:

The temperature of the Bessemer metal poured into the electric furnace is almost 1,500° C., whereas that of the steel poured from the furnace is about 1,495° C. At the close of a run the furnace temperature drops from about 1,500° C. to 1,300° C. during the 15 minutes necessary to patch the lining for the next run.

On an average 12 heats are made daily. During a series of experiments in which both dephosphorization and desulphurization took place, the average power consumption was 198 kilowatt-hours per long ton. When desulphurization alone was carried on, the average power consumption was 105.9 kilowatt-hours per long ton. The power factor of the furnace varies from 0.80 to 0.90.

The hearth is fettled after each run with dolomite, from 10 to 30 pounds of dolomite being used per ton of steel. The hearth proper consists of 4 parts dead-burned, ground magnesite mixed with 1 part basic open-hearth slag. To this mixture tar enough is added to make the mass plastic for tamping. After being tamped, the furnace is heated with a wood fire for 48 hours; it is then filled with coke, the current turned on, and the bottom fluxed into place. This bottom and the side walls last a long time. A silica-brick roof withstands about a week's use and is repaired or replaced during the regular weekly shutdown. The roof has then been subjected to about 72 heats, although some roofs have stood 129 heats. A new roof is always kept in reserve.

Extensive tests have been made with various kinds of electrodes. The average consumption of either amorphous carbon or graphite electrodes is given as about 6 pounds per ton of steel. As in coldscrap refining processes, the electrodes are regulated by hand during the first few minutes of a run.

PRODUCTS.

This furnace has produced a greater variety of steel than any electric furnace in operation, the product including high-grade alloy steel, high-grade carbon steel, and ordinary carbon steel. From the ordinary carbon steel produced, rails of a dozen different sections,

billets of all sizes and grades, plates of all sizes and grades, structural shapes, castings, both small and large, and high and low carbon, and forgings of all sizes have been manufactured. Among the alloy steels made are nickel, nickel-chrome, chrome, manganese, and-silicon steels. Some steel has been made from cold scrap.

The main characteristics of the steels produced in the furnace are a comparative freedom from oxidation and from segregation and a higher tensile strength and slightly higher ductility than that of open-hearth or Bessemer steel of the same chemical composition up to 0.4 per cent carbon, where the difference becomes less apparent.

PLANT OF AMERICAN STEEL & WIRE CO., WORCESTER, MASS.

A 15-ton, three-phase Héroult furnace similar to the South Chicago furnace was in operation until recently at Worcester, Mass., for the production of steel for wire from basic open-hearth steel. Owing, presumably, to difficulty in drawing the comparatively highcarbon steel into wire the furnace is not operated regularly at present. The furnace is similar in construction to the furnace at South Chicago. A current of 12,000 volts is received and is transformed to about 110 volts or less at the plant, according to the voltage desired for the furnace. There are three 750-kilowatt transformers, and the furnace is connected to the transformers by bus bars. Electrode regulators similar to those at South Chicago are used. The cost of power is 0.6 to 0.8 cents per kilowatt-hour.

The process is desulphurizing only and hence requires less time than at that at South Chicago. The procedure of one run was as is stated below. The charge of molten basic open-hearth steel contained 0.18 per cent carbon, 0.22 per cent manganese, 0.02 per cent silicon, 0.02 per cent phosphorus, and 0.027 per cent sulphur. As the 12 to 15 ton charge was poured into the electric furnace about 280 pounds of electrode dust were added. Charging took about 5 minutes. When the furnace was charged a mixture made of 700 pounds lime, 350 pounds fluorspar, and 50 pounds of coke was added. In about 30 or 35 minutes 120 pounds of fluorspar were rabbled in. This was followed in 10 minutes by 30 pounds more of fluorspar. About an hour after the charging was completed a sample was taken. One of these contained 0.50 per cent carbon, 0.12 per cent manganese, and 0.019 per cent sulphur. Ferromanganese and pig iron were then added. About 10 minutes after the first sample had been collected another was taken, which contained 0.45 per cent carbon, 0.45 per cent manganese, and 0.02 per cent sulphur. The slag at this time was tested for calcium carbide, then ferrosilicon, sand, and lime were added. The current was then turned off and the charge poured into a ladle and cast into ingots. The finished product contained

0.54 per cent carbon, 0.47 per cent manganese, 0.157 per cent silicon, 0.022 per cent of phosphorus, and 0.015 per cent of sulphur.

The average current strength for a run was 12,310 amperes; the power factor was 0.696; the voltage was 76.2, 97.7, and 73.3 volts; and the power 396, 451, and 404 kw. to the respective phases. The sum of the kilowatts on the three phases was 1,253 kw. and the average length of a run was 1.41 hours, making the total power consumption 1,746 kilowatt-hours. The average power consumption per ton of metal poured is about 152 kilowatt-hours.

The temperature of the steel when charged is about 1,454° C. The temperature of the slag is 1,524° C. The steel is tapped at a lower temperature than it is charged.

The total losses in bus bars, electrodes, and transformers is 6.53 per cent of the current measured at the switchboard. About 2 per cent of this loss is in the transformers. The loss by conduction through the walls is 5.57 per cent of the total power supplied the furnace.

GUTEHOFFNUNGSHÜTTE WORKS, OBERHAUSEN, GERMANY.

a

An extensive test has been conducted at Oberhausen, Germany, on the Girod electric furnace (fig. 32) for the refining of steel from molten basic open-hearth metal.

DESCRIPTION OF PLANT.

The Girod furnace installed here is from 2.5 to 3 ton capacity (fig. 22) and is similar to the usual type of Girod furnace.

The single-phase current is supplied by a motor-generator set consisting of a 3,000-volt, 95-ampere, 575-kilowatt, three-phase induction. motor driving a single-phase 75-volt, 6,700-ampere, 25-cycle, 500-kilowatt generator. The power factor is 0.8. These machines, as well as all conductors carrying high-tension currents, are placed in a room adjoining the furnace. The loss in transforming from three-phase to singe-phase current is about 14 per cent. On the furnace switchboard there are ammeters and voltmeters in the low-tension circuit, with a wattmeter in the primary circuit. The excitation-current regulator for the furnace voltage, the manual and automatic regulator for the electrodes, and the device for tilting the furnace are all controlled from the switchboard.

REFINING PRACTICE.

In continuous operation it is possible at this plant to run 8 heats in 24 hours, a total of 25 tons of steel. The basic open-hearth furnaces

a Mueller, A., The manufacture of steel in the Girod electric furnace: Metall. Chem. Eng., vol. 9, 1911, p. 581.

launder has been removed from the furnace the flux of ore and lime for oxidizing is shoveled into the furnace. The usual practice is followed for oxidation and deoxidation. The results of tests to determine oxidation and deoxidation of impurities is given below.

are tapped only every four hours, so that the electric furnace can not be operated continually. The furnace is charged by means of a 23-foot launder extending from the open hearth. During the charging process the current is 4,000 to 6,000 amperes. After the charging

FIGURE 32.-Arrangement of electric-furnace steel plant, Oberhausen, Germany.