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Ferro Silicon According To Metal Silicon Composition
- Jul 13, 2017 -

Ferro Silicon According to metal silicon composition

The classification of metallic silicon is usually classified according to the content of the main impurities of iron, aluminum and calcium contained in the metallic silicon component. According to the metal silicon iron, aluminum, calcium content, the metal silicon can be divided into 553,441,411,421,3303,3305,2202,2502,1501,1101 and other different grades.

      Industry, metal silicon is usually in the electric furnace by the carbon reduction of silicon dioxide and obtained. Chemical Reaction Equation: SiO2 + 2C → Si + 2CO The silicon purity thus obtained is 97 to 98%, called metal silicon. And then it is melted and then recrystallized, with acid to remove impurities, to obtain the purity of 99.7 ~ 99.8% of the metal silicon.

      The metal silicon component is predominantly silicon and therefore has similar properties to silicon. Silicon has amorphous silicon and crystalline silicon two kinds of allotropes. The amorphous silicon is a grayish black powder and is actually also a microcrystalline. Crystalline silicon has a diamond crystal structure and semiconductor properties, melting point 1410 ℃, boiling point 2355 ℃, density 2.32 ~ 2.34 g / cm 3, Mohs hardness 7, brittle. Amorphous silicon chemical properties of lively, in the oxygen can be intense combustion. It reacts with non-metals such as halogen, nitrogen, and carbon at high temperatures, and also acts with metals such as magnesium, calcium and iron to produce silicides. Amorphous silicon is almost insoluble in all the inorganic and organic acids, including hydrofluoric acid, but can be dissolved in nitric acid and hydrofluoric acid mixed acid. Concentrated sodium hydroxide solution can dissolve amorphous silicon, release hydrogen. Crystalline silicon is relatively lively, even at high temperatures are not combined with oxygen, it is also insoluble in any kind of inorganic and organic acids, but soluble in nitric acid and hydrofluoric acid mixed acid and concentrated sodium hydroxide solution. Ferrosilicon is iron and silicon composed of iron alloy. Ferrosilicon is based on coke, steel scrap, quartz (or silica) as raw materials, made of electric furnace smelting iron-silicon alloy. Since silicon and oxygen are easy to synthesize silica, ferrosilicon is often used as a deoxidizer for steelmaking, and at the same time it is advantageous to increase the temperature of the molten steel while deoxidizing it due to the large amount of heat generated during the formation of SiO2. At the same time, ferrosilicon can also be used as alloying agent, widely used in low-alloy structural steel, spring steel, bearing steel, heat-resistant steel and electrical silicon steel, ferrosilicon in ferroalloy production and chemical industry, commonly used as a reducing agent.

    On this way, the steelmaking industry, the foundry industry and the ferroalloy industry are the largest users of ferrosilicon. They consume about 90% more ferrosilicon. Among the various grades of ferrosilicon, the most widely used is 75% ferrosilicon. In the steel industry, each production of 1t steel consumption of about 3-5kg75% ferrosilicon. Medium, low, micro-carbon ferrochrome generally silicon chromium alloy, chromite and lime as raw materials, with 1500 ~ 6000 kV electric furnace refining desilication, the use of high alkalinity slag operation (CaO / SiO2 1.6 ~ 1.8). Low, micro carbon ferrochrome is also a large-scale use of heat to the law for production. Production with two electric furnace, a furnace smelting silicon chromium alloy, a furnace melting by the chrome ore and lime composed of slag. Refining reaction in two stages in two Sheng barrels: ① slag furnace slag into the first Sheng barrels, the other tank has been the initial desilicon silicon-chromium alloy against the slag due to excess oxidant Large amount of desilicon full, can be obtained less than 0.8% silicon, carbon as low as 0.02% of micro carbon ferrochrome. ② the first Sheng barrels after the reaction of the slag (containing Cr2O3 about 15%) moved to the second Sheng barrels, the silicon-chrome furnace refining silicon chromium alloy (45% silicon) heat into the slag, the reaction After the initial desilicon silicon-chromium alloy (silicon about 25%), into the first Sheng bucket further desilicon, slag containing Cr2O3 less than 2 to 3% can be discarded.

Oxygen refining refining, low-carbon ferrochrome, with liquid carbon ferrochrome as raw materials, blowing to the pool by adding a small amount of lime, fluorite slag, before the iron plus silicon chromium alloy or ferrosilicon to recover the residue chromium. Micro carbon ferrochrome blowing in a certain degree of vacuum is possible.

Vacuum solid decarburization refining, with ground high-carbon ferrochrome as raw material, in which a part of the grinding of high-carbon ferrochrome by oxidation roasting as oxidant, with water glass or other adhesives, pressed into lumps, After drying, in the bottom of the vacuum furnace, the vacuum of 0.5 to 10 mm Hg, the temperature of 1300 to 1400 ° C under heating to restore 35 to 50 hours, can be less than 0.03% or less than 0.01% Ferrochrome.