holder is of different type than that used on the older Héroult furnaces. The difficulty with the lining and roof was increased by the necessarily high temperature of the slag and metal. Also the writer believes that less difficulty in this respect would be experienced if the hearth was made more shallow and the lining thinner. This would prevent the "flaming arc," as the electrodes would be farther from the sides. The arc would be more concentrated beneath the electrode and less heat would be directly radiated to the roof.

PRODUCTS.

As previously stated, the product of this furnace is a soft steel containing on an average 0.14 per cent of carbon, the content varying between 0.10 per cent and 0.20 per cent. The manganese and silicon are varied according to the use to which the steel is to be put. Sulphur and phosphorus are kept below 0.03 per cent. The steel produced is equal in all respects to crucible steel maufactured at the same plant.

GIROD STEEL PLANT, UGINE, FRANCE.

The Girod steel plant at Ugine, France, is the first and largest complete steel plant built that uses electric power entirely for furnace purposes. In 1898 Girod began experimental work on the manufacture of ferro-alloys with a small 20-kilowatt furnace. To-day this manufacture has developed into an industry with an annual production valued at about $3,000,000 and using about 22,000 kw. for electric-furnace purposes during periods of high water in the streams. As previously stated, from the electric ferro-alloy furnace was developed the Girod electric furnace. The steel works were erected in 1909, and because of their uniqueness will be described in detail.

LOCATION.

The plant is situated in a place so remote from supplies of coal and raw material that only a product in which one of the chief requisites to commercial success was cheap power could be manufactured profitably there. Ugine is on the line of the Paris, Lyon & Marseilles Railroad between Annecy and Albertville, about 25 miles from Champbery. The plant is about half a mile from the main line, with which it is connected by an electric tramway for freight haulage, which is operated by the Girod company. The buildings are on the north bank of the River Arly.

POWER SUPPLY.

The total capacity of all the Girod power plants is about 28,000 kw., of which about 6,000 kw. is used at the steel plant. There is a possible development of 30,000 kw, more, a total of 58,000 kw. Not all

of this is primary power, however; that is, power 24 hours a day, 365 days a year. The average cost of power from all sources is about $18.66 per kilowatt-year, or 0.2 cent per kilowatt-hour, based on a flat rate. There are three separate power plants, two on the Arly River and one on the Bonnant River. Some power is leased at times of low water. The power is delivered at the steel works at 45,000 volts and is stepped down to the desired voltage.

DESCRIPTION OF PLANT.

All buildings are of stone and cement construction. The stock house at the rear of the furnace house is 58 by 460 feet. It is used for the receipt and storage of steel scrap and furnace materials of all kinds. There are overhead traveling cranes and lifting magnetic cranes, used to unload carloads of scrap iron and steel.

The furnace and casting house is 70 by 550 feet. In it there are two 10 to 12.5 ton 3-phase Girod furnaces (fig. 30) and three 2.5 to 3 ton single-phase furnaces (fig. 28), which have already been described (pp. 77-78). The three small furnaces are operated with 300 kw. supplied by a 25-cycle current at 60 to 65 volts. The larger ones take 1,000 to 1,200 kw., using a 70 to 75 volt, 25-cycle current. The furnaces are placed on a concrete foundation about 6 feet above the ground floor. The working floor of the furnace is concrete, and the furnaces are set at its edge as in an open-hearth plant. The plant is arranged for a production up to 200 tons a day. One of the smaller furnaces is used entirely for small casting work. The other two produce high-priced alloy steels. The two 10 to 12.5 ton furnaces are used for making carbon steels and the more common alloy steels. In front of the furnace platform are casting pits, one end being used entirely for foundry work. The furnace house is provided with two 2-ton traveling electric cranes and two 12-ton traveling electric cranes.

The rolling-mill building is 90 by 250 feet and contains 1 train of three-high rolls capable of rolling ingots 20 inches in diameter and 400 kg. (880 pounds) in weight to rods 5 inches in diameter. Another three-high mill rolls rods 13 inches in diameter to smaller rods of round, square, and other shapes. The trains are driven by a 600-kw. 3-phase motor. This building also contains 2 producer-gas fired furnaces for preheating ingots.

A large forging shop 70 by 250 feet contains 9 hammers operated by compressed air. The largest hammer weighs 5,000 kg. (11,000 pounds) and the others weigh from 1,000 kg. (2,200 pounds) to 100 kg. (220 pounds). A second forging shop contains one 1,000-ton forging press, 1 forging hammer weighing 10 tons, and 3 stamps with falling hammers, weighing, respectively, 3 tons, 2 tons, and

16282°-Bull. 67-14-7

1 ton. In the first shop rough forgings are made, primarily for automobile machinery, shaftings, gears, tool-steel rods and projectiles.

A tempering shop 50 by 200 feet contains furnaces for tempering, annealing, and hardening large forged or cast-steel pieces. An annealing shop 33 by 67 feet contains several furnaces.

The steel foundry contains a carpenter shop for making patterns, a sand-separating plant, molding machines, molding frames, drying and heating ovens, and a sand-blast jet for cleaning finished castings. The foundry is able to produce 10 tons of steel castings daily, but castings weighing 20 tons have been cast.

The power house at the plant, which is 50 by 115 feet, is equipped with 4 electrically driven compressors and 2 rotary converters.

The warehouse for finished products is 50 by 325 feet, and is made especially large because of the variety of products, and also because it is necessary to carry common shapes over in stock during lowwater periods.

In addition to the buildings mentioned there are a furnace-transformer house, a sand-storage house, a drying-oven house, an assembly shop, a machine shop, a storage house for the rolling mills, a pattern warehouse, general stores, a well-equipped physical and chemical laboratory, and an office building.

REFINING PRACTICE.

a

The refining of cold scrap at the Ugine plant is typical of electric-furnace practice in work of this nature, and is here described in detail. Almost any grade of scrap steel or scrap wrought iron is charged into the Ugine furnaces, the mean proportions of carbon, silicon, manganese, sulphur, and phosphorus in the charge being as follows:

Average proportions of carbon, silicon, manganese, sulphur, and phosphorus in

The refining operation can be divided into two periods, the oxidation period, in which phosphorus is removed from the metal, and the deoxidation period, with the elimination of sulphur.

After the furnace has been charged with cold scrap, an oxidizing flux of lime and iron ore is added. The proportions vary with the charge and product desired, but a mixture commonly used is 80 kg.

a

Girod, P., Studies in the electrometallurgy of ferro-alloys and steels: Trans. Faraday Soc., vol. 6, 1911, p. 172; The electric steel furnace in foundry practice: Metall. Chem. Eng., vol. 10, 1912, p. 663; Borchers, W., Electric smelting with the Girod furnace : Trans. Am. Inst. Min. Eng., vol. 41, 1910, p. 120.

(176 pounds) of lime and from 220 to 250 kg. (485 to 550 pounds) of iron ore. Oxidation of the impurities in the metal begins as soon as the scrap becomes pasty, so that by the time the charge is completely melted the carbon, silicon, manganese, and phosphorus contents of the metal are usually reduced to less than 0.1 per cent each. If this is not the case, the slag is withdrawn by tilting the furnace backwards and another flux of the same composition is added. To cleanse the bath of the last traces of the phosphorous-bearing slag and any phosphorus in the metal, lime is added and the resulting slag removed. This is repeated as often as may be necessary. In this first period the temperature is gradually increased, but the oxidation takes place largely at a low temperature.

When the oxidizing and cleansing slag has been removed, the first deoxidation of the bath is effected by adding reducing agents such as ferrosilicon or ferromanganese, but these alloys are added in such a proportion as not to remain in the bath, serving merely as deoxidizing agents. If a high-carbon steel is to be made, recarburization takes place at this point.

The bath is then covered with a flux consisting of about 5 parts lime, 1 part silica sand, 1 part fluorspar, and a little petroleum coke. In this period the furnace must be tightly closed. For proper deoxidation and desulphurization of the bath all iron oxide in the slag must be reduced. This is done with petroleum coke and deoxidizing alloys such as ferrosilicon, silicomanganese, ferrosilico-manganesealuminum, or even silicon-aluminum. These alloys act energetically and form fluid slags which rise to the surface.

When the slag is completely deoxidized, which is shown by its being white and disintegrating to a powder in air, any desulphurization not completed in the first period is finished by the passage of the sulphur to the slag as calcium sulphide, the chemistry of the process will be described later (p. 124). Carburizing materials are added for finishing the metal, as well as other alloys to bring the steel to the desired composition. If any of the slag from the first period has been left in the furnace, the phosphorus in it will be reduced in the second period, passing into the steel. The average analysis of the final white slag is as follows:

The power consumption recorded at the terminals of the furnace, including melting, refining, and finishing a charge of cold scrap is estimated by Girod at about 850 kilowatt-hours per ton of metal tapped for a 2.5 to 3 ton furnace; at 750 kilowatt-hours per ton of metal tapped for a 10 to 12 ton furnace. The power consumption varies with the charge and product required. A power factor of 0.80 to 0.88 is maintained.

The electrode consumption is stated to be 8 to 9 kg. (17.6 to 19.8 pounds) for a 2.5 to 3 ton furnace, and 8 to 10 kg. (17.6 to 22 pounds) for a 10 to 12 ton furnace. These figures are based on the use of electrodes made at the Girod plant, not designed for continuous feeding, so that this item might be considerably reduced.

Dolomite-and-tar hearths are used. The life of a lining is 90 to 100 heats for a furnace of 10 to 12 tons and about 120 heats for the 2.5 to 3 ton furnace. At the end of that time the side walls are repaired. All burned or oxidized parts of the walls are scraped. About 4 to 6 inches of the bottom is taken up and retamped with a new layer of dolomite. Care is taken to leave the bottom electrodes clear. The roof of the furnace is made of silica brick and stands on an average 50 heats for the 10 to 12 ton furnace and 70 heats for the 2.5 to 3 ton furnace.

The output of metal is 90 to 96 per cent of the charge, depending upon the nature of the metal charged.

A 2.5 to 3 ton furnace requires for operation 1 melter, 1 assistant, and 1 boy; the 10 to 12 ton furnace 1 melter, 2 assistants, and 1 boy. This does not include foremen, cranemen, ladle men, and other laborers.

PRODUCTS OF THE FURNACE.

An idea of the charges, power consumption, and wide variety of products made at Ugine may be obtained from the following record of the operation of this furnace:

a Girod, P., op. cit., and Borchers, W., op. cit.