Ferroferro-silicon alloy, primarily composed of silicon, chromium, and iron. Also known as ferro-silicon alloy. It is mainly used as an intermediate alloy in the electrosilicon thermal process for producing medium, low, and micro-carbon iron. In steelmaking, it is used as a deoxidizer (replacing ferrosilicon) and a chromium additive. It generally contains >30% Cr and >35% Si, with the balance being iron and small amounts of impurities. It is classified according to carbon content, such as ≤0.06%, ≤0.10%, ≤1.0%, etc.
Furthermore, an alloy of iron, chromium, and silicon with a chromium content of not less than 30.0% and a silicon content of not less than 35.0%. Its production processes are divided into two types: one-step process (commonly called the "slag process" or "ore process") and two-step process (commonly called the "slag-free process"). The raw materials used in the one-step process are silica, chromium ore, and coke. The raw materials used in the two-step process are silica, carbon ferrochrome, and steel scrap. Both smelting methods use coke as a reducing agent.
The silicon in the alloy primarily comes from SiO2 in silica, while the chromium comes from chromite and carbon ferrochrome, respectively. Both are produced through smelting in a ferroalloy submerged arc furnace. It is mainly used as a reducing agent in the production of medium- and low-carbon ferrochrome and micro-carbon ferrochrome, and as an intermediate alloying agent in steelmaking. Silicon-chromium alloys can be classified into various grades based on their Si, Cr, and C content. The alloying phases are as follows: Si > 50% consists of (Fe·Cr)Si2; Si > 40% consists of (Fe·Cr)Si2 and (Fe·Cr)Si; Si > 30% consists of (Fe·Cr)Si and (Fe·Cr)Si; and when Si < 19%, (Fe·Cr)3C and (Fe·Cr)23C6 are the most prevalent.
Because the phase composition of the silicon-chromium alloy determines the furnace carbon reduction effect, in industrial production, the Si content in the silicon-chromium alloy is generally controlled to be greater than 40%. The carbon content of freshly produced silicon-chromium alloys is generally between 0.2% and 0.8%, making them difficult to use directly. They must undergo an external carbon reduction treatment to lower the carbon content to below 0.02%. Different grades of silicon-chromium alloys can be produced according to user requirements. In addition, silicon-chromium alloys can also be produced by adding ferrosilicon to liquid high-carbon ferrochrome.
