Silicon-calcium alloy is composed of elemental silicon, calcium and iron composed of composite alloy, from about 1907 began to use silicon thermal production.
Calcium and silicon have strong affinity for oxygen. In particular, calcium, not only with the oxygen has a strong affinity, but also with sulfur, nitrogen has a strong affinity, so Calcium Silicon Alloy is an ideal compound deoxidizer, desulfurization agent. Silicon-calcium alloy is not only deoxidized, deoxidized products are easy to float, easy to discharge, but also to improve the performance of steel, improve the plasticity of steel, impact toughness and mobility.
Silica-calcium alloy can be used in the production of high-quality steel, special steel and special alloys, such as steel, steel, low carbon steel, stainless steel and other nickel-based alloys, titanium-based alloys and other special alloys. Silicon-calcium alloy is also suitable for converter steelmaking plant with the warming agent, but also for the cast iron inoculation agent and ductile iron production additives.
Calcium Silicon Alloy is in the reduction furnace with carbon reductant, reduced silica and calcium oxide prepared. There are two kinds of smelting methods, namely: one-step, two-step method.
One step is to weigh and mix evenly lime, silica, carbon reductant together into the electric furnace, using the appropriate process operation, refining Calcium Silicon Alloy. One-step production of silicon-calcium alloy, there are two kinds of domestic feeding method, one is mixed feeding method, one is layered feeding method.
1, mixed feeding method
The operation of the mixed feed method is similar to that of the 75% ferrosilicon production of the small electric furnace, but the Calcium Silicon Alloy charge is not all in the state of mixing into the furnace, but partly in the form of partial feed, -1/3 of the silica is added separately to the electrode after the collapse of the material, the wood is also added alone, the rest of the silica and lime, coke, bituminous coal mixed into the furnace.
2, layered feeding method
The stratified feed method is a mixture of lime and the corresponding amount of coke (according to the production of low-grade calcium carbide required) mixed into the furnace after the concentration, until its clear, the silica and the remaining reducing agent mixed and then added. The operation of the stratified feed method can be divided into three stages:
The first stage is the warming phase. After the iron, the furnace temperature is reduced, so must be warmer. The operation is: the iron after the discharge electrode, pound furnace, the lump out, finishing the material surface, Zhaotou breathable, to strengthen the material surface maintenance, to full load, deep insert the electrode, this stage is generally 1 hour and 20 minutes.
The second stage is the CaC2 generation phase. When the furnace temperature increases, Pa net electrode around the floating material, pick the sticky material, quickly add lime and the corresponding reductant mix, all directly added to the orange around the electrode. To accelerate the formation of CaC2, should try to full load, for the early cover material. This time is generally 30-40 minutes, not too short or too long. Time is too short, CaC2 formation is not sufficient, a large number of non-involved in the reaction of CaO and after the addition of SiO2 salt reaction; too long, calcium element evaporation and heat loss increases, alloy containing Ca lower unit power consumption increased.
The third stage is the use of silica to destroy CaC2 to form the CaSi alloy stage. When CaC2 is formed, add the mixture, the use of SiO2 in the mixture destroyed CaC2, CaSi alloy. Plus finished, the Jiong burning, until the baked.
The third stage of the operation should be added evenly, carefully maintain the furnace conditions, increase the material surface permeability, to ensure that the electrode deep and stable into the charge, to prevent the collapse of fire to reduce the volatilization of Ca and heat loss. This time the melting time is generally 2.5-3 hours.
The time of this stage should not be too long or too short. Too long, Ca volatilization and loss of heat increased, the alloy containing low Ca, the unit power consumption increased; too short, a large number of CaC2 and SiO2 did not fully react, slag increased, low calcium in the alloy, The
Iron and alloy casting, the normal situation every 4-5 hours out of a furnace. When the iron out of the bar with a round bar or burner to open the iron mouth, molten iron and slag at the same time into the tundish. As the slag density is greater than the alloy density, the alloy in the slag to be sedimentary 2-4 minutes, until the alloy is completely floating, the alloy slowly poured into the ingot mold. When the alloy surface is found white, shiny, immediately stop casting, so as not to alloy slag. Alloy condensate, stripping, finishing into the library.
Two-step production of silicon-calcium alloy, first in an electric furnace, CaO> 85% of high-quality lime and carbon reductant prepared CaC2, and then the cooling of CaC2 broken, and then with silica and carbon reductant, In another electric furnace production of Calcium Silicon Alloy. Two-step production of silicon-calcium alloy required equipment conditions and methods of operation, basically the same with ferrosilicon production.
Although this method can achieve a longer furnace age and higher product grade rate, but the need for two electric furnace, integrated power consumption is high, the operation requirements are high, the process is difficult to control, the raw materials in the water requirements, and therefore only in the degree of automation High, good management conditions, mechanized feeding, silo sealed good electric furnace used.