Production technology of silicon calcium alloy
The main components of the silicon calcium alloy are silicon and calcium, but also contain different amounts of iron, aluminum, carbon, sulfur and phosphorus and other impurities. Iron and steel industry used as calcium additive, deoxidizer, desulfurizer and denaturant of non-metallic inclusions. Used as inoculant and denaturant in the cast iron industry. Calcium silicon alloy according to the calcium, silicon content is divided into different grades.
It is generally believed that the chemical reaction of smelting silicon - calcium alloy is expressed as
CaO+SiO2+3C→CaSi+3CO↑
But at high temperature, lime and silica first form calcium silicate slag with lower melting point, which makes carbon reduction difficult to proceed. Calcium has a low boiling point and is volatile enough to produce calcium vapour. And SiO2 is reduced to SiO(gas), so the gas discharged from the furnace is CO, Ca(gas) and SiO(gas). The loss of calcium and silicon in furnace gas is about 10% each. When SiO(gas) and Ca(gas) pass through the material layer, they react with carbon, and most of them are converted to CaC2 and SiC, so the reactivity of carbonaceous reducer is very important for smelting Si-Ca alloy. Calcium oxide and silica with carbon at high temperature to form CaC2 and SiC, is the production of silicon calcium alloy intermediate products. Finally, some of it remains in the slag, so the production of silicon calcium alloy is slag smelting. In fact, the method of industrial production of silicon calcium alloy is realized with CaC2 as the transition product. The density of Si-Ca alloy is slightly smaller than that of slag, and the Si-Ca alloy is basically concentrated in the upper part of molten pool during smelting, which is the characteristic of Si-Ca alloy smelting. Special measures must be taken to separate it from the slag when it is released. According to the above analysis, there are three smelting processes of silica-calcium alloy by electrocarbothermal (reduction) method, that is, mixed feeding method, layered feeding method and calcium carbide method. Electrothermal silicon (reduction) method is also one of the methods to produce silicon calcium alloy.
