Electric furnaces are widely used, not only in the iron industry, but in brass, copper and aluminum works. It is a useful melter of cold metal for making castings. It can be used to convert iron into steel or vice versa. Its most useful sphere, however, is as a refiner of metal, wherein it takes either cold steel or molten steel from open hearth or bessemer furnaces, and gives it the finishing touches. [Illustration: FIG. 5.--"Slagging off" an electric furnace.] [Illustration: FIG. 6.--Pouring the ingots.] As an illustration of the furnace reactions that take place the following schedule is given, showing the various stages in the making of a heat of electric steel. The steel to be made was a high-carbon chrome steel used for balls for ball bearings: 6-TON HEROULT FURNACE 11:50 A.M.--Material charged: Boiler plate 5,980 lb. Stampings 5,991 lb. ----------- 11,971 lb. Limestone 700 lb. 12:29 P.M.--Completed charging (current switched on). 3:20 P.M.--Charge melted down. Preliminary analysis under black slag. Analysis: Carbon Silicon Sulphur Phosphorus Manganese 0.06 0.014 0.032 0.009 0.08 Note the practical elimination of phosphorus. 3:40 P.M.--The oxidizing (black) slag is now poured and skimmed off as clean as possible to prevent rephosphorizing and to permit of adding carburizing materials. For this purpose carbon is added in the form of powdered coke, ground electrodes or other forms of pure carbon. The deoxidizing slag is now formed by additions of lime, coke and fluorspar (and for some analyses ferrosilicon). The slag changes from black to white as the metallic oxides are reduced by these deoxidizing additions and the reduced metals return to the bath. A good finishing slag is creamy white, porous and viscous. After the slag becomes white, some time is necessary for the absorption of the sulphur in the bath by the slag. The white slag disintegrates to a powder when exposed to the atmosphere and has a pronounced odor of acetylene when wet. Further additions of recarburizing material are added as needed to meet the analysis. The further reactions are shown by the following: 3:40 P.M.--Recarburizing material added: 130 lb. ground electrodes. 25 lb. ferromanganese. Analysis: Carbon Silicon Sulphur Phosphorus Manganese 0.76 0.011 0.030 0.008 0.26 To form white slag there was added: 225 lb. lime. 75 lb. powdered coke. 55 lb. fluorspar. 4:50 P.M.-- Analysis: Carbon Silicon Sulphur Phosphorus Manganese 0.75 0.014 0.012 0.008 0.28 Note reduction of the sulphur content. During the white-slag period the following alloying additions were made: 500 lb. pig iron. 80 lb. ferrosilicon. 9 lb. ferromanganese. 146 lb. 6 per cent carbon ferrochrome.