Calcium is alkaline earth metal, atomic weight is 40.08, outer layer electron structure is 4S2, density (20 DEG C) 1.55g/cm3, melting point 839, 2 DEG C, boiling point is 1484 DEG C. The relation between the vapor pressure and temperature of calcium is
In the formula, pCa is the vapor pressure of calcium, Pa; T is temperature, K. Silicon and calcium produce 3 compounds, namely CaSi, Ca2Si and CaSi2. CaSi (41.2%Si) is stable at high temperature. Ca2Si (29.5%Si) is a peritectic compound formed between Ca and CaSi at less than 910 degrees C. CaSi2 (58.36%Si) is a peritectic compound formed between CaSi and Si at less than 1020 degrees C. The phase groups of industrial production of Si Ca alloy become CaSi2, about 77%, CaSi 5% ~ 15%, Si free <20%, SiC<8%. The density of calcium silicate alloy containing Ca 30% ~ 33% and Fe about 5% is about 2.2g/cm3, and the melting temperature range is 980~1200 centigrade.
Because calcium has a strong affinity with oxygen, sulfur, hydrogen, nitrogen and carbon in molten steel, calcium silicate alloy is mainly used for deoxidation, degassing and sulfur fixation of molten steel. When silicon calcium is added into molten steel, it has a strong exothermic effect. Calcium in molten steel into calcium vapor, steel liquid stirring effect on non-metallic inclusions floating favorable. When the Si Ca alloy is deoxidized, the non-metallic inclusions with large particles and easy floating are produced, and the shapes and properties of non-metallic inclusions are also changed. Therefore, silicon calcium alloy is used in the production of clean steel, oxygen and sulfur content of low quality steel, as well as oxygen and sulfur content is very low special performance steel. Add calcium alloy can be eliminated by using aluminum as final deoxidizer in steel ladle nozzle clogging problem, tundish nozzle clogging and continuous casting | iron etc.. In the process of steel refining, deoxidation and desulfurization with silicon calcium powder or core line can reduce the content of oxygen and sulfur in the steel. It can also control the form of sulfide in steel and increase the utilization rate of calcium. In the production of cast iron, calcium alloy except deoxidizing and purifying effect, but also the breeding effect, contribute to the formation of fine and spheroidal graphite graphite; the uniform distribution of gray cast iron, and can reduce the chilling tendency; increasing silicon, desulfurization, improve the quality of cast iron.