GB670011A - Production of stainless steel in an arc electric furnace - Google Patents

Abstract

A method of making casting steel comprises the following combination of steps. An electric arc furnace is charged with 1,300 parts of steel scrap having not over 0.07 per cent carbon, 8-10 per cent nickel and 18-22 per cent chromium; 1,600 parts of steel scrap having not over 0.10 per cent carbon content; and 250 parts of manganese iron ore. Heat is applied to melt the charge, preferably with an arc of 1 1/4 inch and 125-150 volts on the electrodes, 150 parts of dry pebble lime is added for slag which is then removed to clean the molten metal, further lime then being added to form a crust. 850 parts of ferro-chromium having not over 0.10 per cent carbon are placed on the crust, after which the temperature may be raised to 2800 DEG F, 30-50 parts of 85 per cent ferro-silicon are added in shots at about 5-minute intervals, finishing lime is added to form a finishing slag, the furnace is tapped and about 4 parts of calcium-silicon alloy are added to the molten metal in the ladle. The resulting steel contains not more than 0.07 per cent carbon, 10-35 per cent chromium and 7-30 per cent nickel and may contain also selenium, molybdenum, tungsten, titanium and/or columbium. Molybdenum and columbium, if used, are added to the initial charge, further nickel may be added with the steel scrap and manganese ore. Titanium is added after the first slag removal, tungsten just prior to tapping the furnace and selenium in the ladle after tapping. All such additions are preferably in the form of ferro-alloys.