What Is Ferro Silicon Chrome?
Silicon Chrome, also named Ferro silicon chromium alloy, is mainly composed of silicon, chromium, and iron elements. Generally, Cr>30%， Si>35%， and the balance is iron and a small number of impurities. According to the carbon content, the ferrosilicon chrome can be divided into C0.06max, C0.1max, and C1.0max grades.
Ferro silicon chrome is mainly used as a reducing agent in the low carbon Ferro chrome and micro carbon Ferro chrome smelting with electro-silicothermic process.
In addition, silicon chrome alloy is used as a deoxidizing agent or an alloying agent in steelmaking. With the development of oxygen steelmaking, silicon chrome is widely used as a reducing agent to reduce the chromium element that exists in the slag and increase the chromium content of the molten steel. The average consumption of Si-Cr alloy is about 0.5kg per ton of steel.
The affinity of chromium to silicon is stronger than that of chromium to carbon. The higher the silicon content in the silicon-chromium alloy, the lower the carbon content.
Ferro Chrome Silicon Chemical Composition
Production Methods of Ferro Silicon Chrome
There are two main production methods of si-cr alloy. One is the one-step process (chromium ore smelting method), and the other is the two-step method (slagless process).
The one-step process is to smelt the raw materials ( chromium ore, silica, coke, etc) directly into ferro silicon chrome alloy in a submerged arc furnace. This method occurs a large amount of slag, and the slag contains chromium elements.
MgO, Al2O3, and CaO are partially reduced and volatilized so that the energy consumption of production increases.
The two-step smelting process of si-cr alloy is as below
- The high carbon Ferro chrome is produced in the smelting furnace.
- The high carbon Ferro chrome is broken into a certain particle size. The particle size of carbon Ferro chrome has a great influence on silicon chrome smelting. Production experience shows that when larger pieces of high-carbon ferrochromium are used to smelt ferrosilicon chrome alloy, the carbon content or SiCr alloy can reach 0.13%; and when the particle size is less than 20mm, the carbon content of the SiCr alloy is less than 0.06%. The silicon content of silicon-chromium alloy increases and the carbon content decreases.
- Smelting ferrosilicon alloy with crushed high carbon Ferrochromium, silica, coke, and steel scraps. The process is similar to that of smelting ferrosilicon45%, the difference is that high-carbon ferrochromium particles are used instead of steel scraps. Carbon (carbon of coke and carbide) reduces SiO2 to Si, promoting the conversion of (Cr, Fe)7C3 to CrSi2, FeSi2, and SiC
- Insulation and sedation: Higher temperatures are required for silicon carbide to float from the alloy. Through thermal sedation, the carbon content of the silicon-chromium alloy was significantly reduced, from 0.2% to 0.04%.
- The decarburization process: Produces silicon-chromium alloys with a carbon content of 0.4% to 0.8% in the furnace, which cannot be used to produce micro-carbon ferrochromium. Decarburization treatment is required. Put the molten iron ladle with silicon chromium alloy solution and decarburizer on the shaking rack to make the molten iron ladle move eccentrically. At the rotation speed of 50 ~ 55r/min, the melt in the inclusion produces a “wave-wave” motion. Mixing and stirring are produced by the up-down movement of the particle of the melt, which creates good conditions for the mixing of silicon ferrochrome alloy and decarburizer. SiC is absorbed by decarburizing after precipitation from the alloy. The decarburizing agent is ferrochrome slag or lime and fluorite slag. The dosage is 5% ~ 8% of ferrochrome silicon alloy. Shaking time is 5 ~ 10min. After shaking decarburization treatment, the carbon content of silicon ferrochrome alloy can be reduced to 0.02%.
Slag washing decarburization method: Molten si-cr alloy is directly injected into liquid ferrochrome slag. The slag is dispersed and mixed by the alloy liquid, rising through the liquid alloy, and the slag absorbs most of the silicon carbide. In the cooling process, the alloy continues to precipitate silicon carbide, floating up to the slag and alloy contact surface into the slag. By slag washing, the carbon content in slag can reach 4%, and the carbon content in the alloy can be reduced to 0.02%. Slag washing not only has a high carbon reduction rate but also can recover chromium from micro-carbon ferrochrome slag. The chromium content in slag is reduced to about 0.5%. By slag washing, the phosphorus content of ferrochrome silicon alloy can be reduced by 75% ~ 90%.