Extraction Method Of Ferrochromium

Medium, low and micro carbon ferrochrome is generally made of silicochromium alloy, chromite and lime, refined and desilicated by 1500~6000 KVA electric furnace, and operated by high basicity slag (CaO/SiO2 is 1.6~1.8). Low and low-carbon ferrochromium is also produced on a large scale using the hot blending method. During production, two electric furnaces are used, one for smelting silicon chromium alloy and the other for melting slag composed of chromium ore and lime. The refining reaction is carried out in two stages in two drums: ① After the slag from the slag furnace is injected into the first drum, the silicon chromium alloy that has been preliminarily desilicified in the other drum is mixed in. Due to the large excess of slag oxidant, the desilication is sufficient, and low-carbon ferrochromium with silicon content below 0.8% and carbon content up to 0.02% can be obtained. ② The molten slag (containing about 15% Cr2O3) after reaction in the first drum is moved to the second drum, and the silicon chromium alloy (containing 45% silicon) refined by the silicon chromium electric furnace is hot mixed into the slag. After reaction, the silicon chromium alloy (containing about 25% silicon) with preliminary desilication is obtained, and further desilication is carried out in the first drum. The slag containing less than 2-3% Cr2O3 can be discarded.

The oxygen blowing method is used to refine medium and low carbon ferrochromium, using liquid carbon ferrochromium as raw material. During blowing, a small amount of lime and fluorite are added to the molten pool to form slag. Before tapping, silicon chromium alloy or silicon iron are added to recover chromium from the slag. The blowing of low-carbon ferrochromium is only possible under a certain vacuum degree.
Refining by vacuum solid decarbonization method uses ground high carbon ferrochrome as raw material, in which a part of ground high carbon ferrochrome is oxidized and roasted as oxidant, added with water glass or other adhesives, pressed into lumps, dried at low temperature, heated and reduced for 35 to 50 hours in a car bottom Vacuum furnace at a vacuum of 0.5 to 10 mm Hg and a temperature of 1300 to 1400 ℃, to obtain low-carbon ferrochrome with carbon content less than 0.03% or even less than 0.01%.