Chinese name: calcium silicide
English name: CALCIUM SILICIDE
Molecular formula: CaSi2
Molecular weight: 96.251
EINECS No. 234-588-7
Melting point: 1020 º C
Density: 2.5 g/cm3
Properties: An inorganic compound, which is a white or dark gray to black solid substance. It is insoluble in water, but may decompose into hydrogen and calcium hydroxide when encountering water. It will decompose in hot water. Flammable, self igniting in air. Industrial calcium silicide mainly contains iron and aluminum as well as a small amount of carbon and sulfur.
1. Calcium silicide with high purity can be prepared by directly melting silicon and calcium. However, the operation must be carried out in two steps. Step 1: Mix the pure calcium chips and pure silicon powder evenly, place them in the hard ceramic boat, quickly put the ceramic boat into the quartz reaction tube, and inject CO2 into the tube. The ceramic boat has been heated to 1000 ℃. In a few seconds, the mixture will melt, and the reaction will be intense. Take out the porcelain boat, and the product CaSi will immediately coagulate and crush it. CaSi is a porous block, which is lead gray and has metallic luster.
Step 2: Mix CaSi and calculated amount of Si powder evenly, place them in a nickel boat, and heat them at 1000 ℃ in H2 gas flow. Because the final stage of the reaction is slow, it needs to be heated for 15h.
2. CaSi2 can be prepared by mixing pure CaO and silicon with appropriate fluxes CaF2 and CaCl2, and melting at 1400 ℃. In this way, CaSi2 is mixed with a large amount of silicon.
Main applications: calcium silicide is used to make special metal alloys, deoxidize steel, add additives to special steel, remove phosphorus or as deoxidizer. As calcium has strong affinity with oxygen, sulfur, hydrogen, nitrogen and carbon in molten steel, calcium silicide is mainly used for deoxidization, degassing and sulfur fixation of molten steel. The exothermic effect of calcium silicate added to molten steel is strong. Calcium turns into calcium vapor in the molten steel, which has stirring effect on the molten steel and is beneficial to the floating of non-metallic inclusions. After deoxidation of silicon calcium alloy, non-metallic inclusions with large particles and easy to float will be produced, and the shape and properties of non-metallic inclusions will also be changed. Therefore, silicon calcium alloy is used to produce clean steel, high-quality steel with low oxygen and sulfur content, and special performance steel with extremely low oxygen and sulfur content. The addition of silicon calcium alloy can eliminate the problems such as the nodulation of steel with aluminum as final deoxidizer in ladle nozzle, and the clogging of tundish nozzle for continuous casting steel. In the secondary refining technology of steel, calcium silicate powder or core wire is used for deoxidation and desulfurization to reduce the content of oxygen and sulfur in steel to a very low level; It can also control the form of sulfide in steel and improve the utilization rate of calcium. In the production of cast iron, the silicon calcium alloy not only has the functions of deoxidation and purification, but also plays the role of inoculation, helping to form fine or spherical graphite; The graphite in gray cast iron is evenly distributed and the tendency of white cast iron is reduced; It can also increase silicon, desulfurize and improve the quality of cast iron. In the production of fireworks, it is used as fuel to add special mixtures.
Storage conditions: sealed in a cool and dry place.
Stability: It will not decompose if used and stored according to specifications.