Kg.

Kg. Kg.

1,725 0.845 0.27

0.31

0.019 0.013

900

FOUNDRY OF MÖNKEMÖLLER & CO., BONN, GERMANY.

At the foundry of Mönkemöller & Co., Bonn, Germany, three Stassano furnaces (figs. 19, 20) are producing low-carbon steel for high-grade steel castings and one additional Stassano furnace of 2-ton capacity is being built. The Stassano furnace in small units is better adapted to this use than to any other.

DESCRIPTION OF PLANT.

There are two 1-ton furnaces, each requiring 200 kw., supplied by a current at 110 volts with a frequency of 25 cycles, and one 2-ton furnace taking 400 kw. at 120 volts; the frequency is 25 cycles. The two small furnaces are of essentially the same construction as shown in figures 19 and 20, having the rotating mechanism. The larger one differs only in that it is set on rollers for tilting. The details of construction are as given in the description of the Stassano furnace.

FOUNDRY PRACTICE.

Scrap steel of various sizes and grades is used as a raw material. This is charged to a point directly beneath the three arcs. The desulphurizing and dephosphorizing operations are in general about the same as at other plants.

It takes about three to four hours to melt the charge and from four to five hours for complete melting and refining. The loss of heat in the water cooling of the electrodes is about 14 per cent. The electrodes consumption is very high, owing to failure to use up stumps. The repair cost is also high. The magnesite brick roof lasts from 80 to 100 heats; the whole furnace must then be relined. The power consumption is about 800 to 1,000 kilowatt-hours per ton. A power factor of from 0.85 to 0.90 is maintained. Power is supplied by a public-service corporation at a cost of about 1 cent per kilowatt-hour. The electrodes are regulated hydraulically, but not automatically, as a man watches the meter for changes all the time.

The metal is poured from the furnace into a 1 or 2 ton ladle, from which it is poured into small shanks for casting. All three furnaces are on the main casting floor of the foundry. Most of the castings made are of small size. The steel has an average content of 0.8 to 0.18 per cent carbon, 0.03 per cent sulphur, and 0.06 per cent phosphorus. Occasionally tool steels, with or without the addition of alloys, are made. The process is said to be much cheaper than the crucible method and gives a better product.

SHEFFIELD ANNEALING WORKS, SHEFFIELD, ENGLAND.

At the Sheffield Annealing Works, Sheffield, England, a 2 to 21 ton Grönwall furnace is in use for the production of steel from scrap.

The chief product is alloy steel, which is cast into ingots and further treated at another works. The scrap steel used consists for the greater part of small pieces of tool scrap and other alloy scrap.

DESCRIPTION OF PLANT.

The furnace (figs. 24, 25) has been described. At some future time the cables to the electrodes are to be replaced by bus bars. The furnace foundation is set level with the ground, with a pit in front for teeming. The building is not well arranged for electric furnace. work; the ventilation is very poor. Two annealing furnaces are adjacent to the casting pit.

The two-phase current is received from the main line of the municipal power system at 2,000 volts, with a frequency of 25 cycles, the cost being about 1 cent per kilowatt-hour. An integrating wattmeter, from which the power is charged to the furnace and from which power figures are taken, is placed on the primary side of the circuit where the line enters the building. The meter is followed in the circuit by choke coils to the two transformers. These transformers can be adjusted to give 50, 60, 70, or 80 volts on the secondary circuit. The usual voltage is 75 volts. The neutral point is connected to the bottom of the furnace and a phase is connected to each electrode. The secondary switchboard has a power-factor meter, which can be thrown into any leg, as well as a voltmeter, with the same adjustment. On the switchboard there is also one ammeter set in the neutral. On the back of the furnace there are two ammeters, one to each phase, by means of which two men regulate the electrodes.

PLANT PRACTICE.

The furnace is operated only 12 hours a day, so that more than two charges are never run in one day; also, in the wintertime, it is necessary not to draw too heavily on the power system late in the afternoon when the load on the city lines begins to get heavy. Such operation, of course, is not economical with respect to power consumption, as the furnace cools overnight. Constant change of temperature in the furnace also increases the wear on the lining and the electrodes.

At the time the furnace was inspected it was charged with steel scrap containing 0.40 per cent carbon, 1 to 2 per cent tungsten, and about 1 to 2 per cent chromium. The object of the run was melting with some refining and the casting of ingots. The charge melted in 2 hours and 15 minutes, during which period 560 kilowatt-hours per ton were expended, and was poured in 4 hours and 5 minutes, with a total expenditure of energy of 902 kilowatt-hours per ton. Thus 62 per cent of the energy consumed was used for melting. During the melting stage the amperage was held at 4,000 amperes, or about

500 kw. was on the furnace, while during the refining period this was reduced to 2,500 to 3,000 amperes and about 200 to 300 kw. Often only about 1,500 amperes are on toward the end, but at the very end the temperature is raised to keep the slag fluid. This is said to protect the roof, which seems to be more attacked during the last half hour than any other time. During the melting period a mixture composed of 100 pounds of lime, 30 pounds fluorspar, and 20 pounds of silica was added in two parts. None was added after the melting period, but as soon as the alloy was hot anthracite coal dust was used for deoxidation. In 1 hours the slag became white. At the end of 3 hours and 50 minutes samples of metal and slag were taken. The slag was white. Analysis of the steel showed a carbon content of 0.39 per cent. While the analysis was being made more coal was shoveled in to prevent reoxidation of the slag. Another sample of slag was taken and the charge poured into a 2.5-ton ladle that had been preheated. From the ladle it was teemed by topcasting into ingots. About 20 pounds of 50 per cent ferrosilicon were placed in the spout before pouring, and 20 to 30 pounds of 80 per cent ferromanganese were added to the charge in the furnace. The weight of metal tapped was 2.1 tons. Some aluminum was added to the tops of the ingot molds.

The electrode consumption is about 20 pounds per ton, at a cost of about 4 cents a pound. Under the poor operating conditions the silica roof lasts about 20 heats. The conducting bottom had been in 60 heats at the time of inspection and was still in good condition. The furnace force consists of a superintendent, a chemist, a melter, two assistant melters, a ladle man, and one general laborer.

PLANT OF CRUCIBLE STEEL CASTING CO., LANSDOWNE, PA.

At Lansdowne, Pa., the Crucible" Steel Casting Co. has recently built the first Röchling-Rodenhauser steel furnace to be used commercially in the United States. It is used for producing steel for castings from cold scrap.

The current used is single-phase and the furnace is of 2 tons capacity, similar to the furnace shown in figure 27. It is situated 200 feet from the generator, on an operating platform. The lining is a mixture of magnesite and tar and is tamped by hand. The roof is magnesite brick. A motor-driven blower supplies the air for cooling the transformer coils for the furnace.

A 300-kilowatt generator supplies a 25-cycle single-phase current at 480 volts, and is directly driven by a 2-cylinder oil engine. The power cost is estimated at 0.7 cents per kilowatt-hour.

a Von Bauer, C. H., The Röchling-Rodenhauser furnace of the Crucible Steel Casting Co., Lansdowne, Pa.: Iron Trade Rev., vol. 53, 1913, p. 153.

The furnace is charged while hot with cold scrap, some molten steel from the previous run being left in the furnace. At present it is operated only 12 hours a day, making two melts in that period. The general refining process is the same as in other electric steel furnaces. The length of run varies from four to six hours and the power consumption from 800 to 900 kilowatt-hours per ton. Steel has been produced of the following composition-0.30 per cent carbon, 0.30 per cent silicon, 0.49 per cent manganese, 0.03 per cent phosphorus, and 0.03 per cent sulphur.

SUPERREFINING OF MOLTEN STEEL IN THE ELECTRIC FURNACE.

PLANT OF ILLINOIS STEEL CO., SOUTH CHICAGO, ILL.

The 15-ton 3-phase Héroult furnace at the South Chicago works of the Illinois Steel Co. until recently was one of the two largest electric furnaces in operation for the manufacture of steel. A wide variety of products was made in an attempt to learn what could be done with the electric furnace. The furnace was primarily intended for the refining of molten Bessemer steel, but some cold scrap has been treated.

DESCRIPTION OF PLANT.

The Héroult furnace at South Chicago has already been described. The steel operating platform of the furnace is about 9 feet above the ground level. Around the furnace on this platform, at convenient points, bins are placed for the materials used in furnace operation. The front part of the furnace platform opens to allow a ladle to be hung in position when steel is poured.

Power for the furnace is supplied by the central plant of the works. Dynamos are driven by reciprocating gas engines, reciprocating steam engines, and high-pressure and low-pressure turbines. Blast-furnace gas is used in the gas engines and under boilers. The power cost is about 0.5 cent per kilowatt-hour. The 25-cycle 3-phase current is stepped down at the furnace from 2,200 volts by three 750-kilowatt transformers. These transformers are arranged so that the number of turns in the primary may be altered to give a secondary voltage of 80, 90, 100, or 110 volts. The usual voltage is 90 volts. The pouring platform, 30 feet long, enables eight molds to be placed in position for pouring. The furnace is served by a 50-ton

crane.

PLANT PRACTICE.

Bessemer pig iron is full blown, in a 15-ton Bessemer converter, in 8 to 12 minutes. The analysis of the Bessemer metal shows 0.05 to

"Osborne, G. C., The 15-ton Héroult furnace at the South Chicago works of the Illinois Steel Co.: Trans. Am. Electrochem. Soc., vol. 19, 1911, p. 205; The South Chicago electric furnace plant of the U. S. Steel Corp.: Met. and Chem. Eng., vol. 8, 1910, p. 179.