Refining method of ferrochrome
Medium, low and micro-carbon ferrochrome is generally made of silicochrome alloy, chromite and lime as raw materials, refined and desilicated by 1500 ~ 6000 kVA electric furnace, and operated by high alkalinity slag (CaO/SiO2 is 1.6 ~ 1.8). Low - and micro-carbon ferrochrome is also produced by thermal blending on a large scale. In production, two electric furnaces are used, one smelting silicon chromium alloy, the other melting slag composed of chromium ore and lime. The refining reaction is carried out in two stages in two buckets: ① After the slag of the slag furnace is injected into the first bucket, the silicon chromium alloy that has been preliminarily desiliconized in the other bucket is added. Due to the large excess amount of oxidizer in the slag and sufficient desiliconization, the micro-carbon ferrochrome with silicon content less than 0.8% and carbon content as low as 0.02% can be obtained. ② The molten slag (containing about 15% Cr2O3) after the reaction in the first ladle is moved to the second ladle, the silicochrome alloy (containing 45% silicon) made by the silicochrome electric furnace is heated into the slag, and the initial desiliconized silicochrome alloy (containing about 25% silicon) is obtained after the reaction, and further desiliconized is added into the first ladle, and the slag containing less than 2 ~ 3% Cr2O3 can be abandoned.
Oxygen blowing refining medium and low carbon ferrochrome, using liquid carbon ferrochrome as raw material, adding a small amount of lime and fluorite to the molten pool to make slag, adding silicon chromium alloy or ferrosilicon before iron extraction to recover the chromium in the slag. The blowing of micro-carbon ferrochrome is possible under a certain vacuum degree.
Vacuum solid state decarburization refining, using finely ground high-carbon ferrochrome as raw material, in which a part of the finely ground high-carbon ferrochrome is oxidized and calcined as an oxidizing agent, with water glass or other binder, pressed into a mass, after low temperature drying, heated and reduced in a car-bottom vacuum furnace at a vacuum degree of 0.5 ~ 10 mm Hg and a temperature of 1300 ~ 1400℃ for 35 ~ 50 hours. The microcarbon ferrochrome containing carbon less than 0.03% or even less than 0.01% can be obtained.
