Study of the Possibility of Obtaining Non-Decomposing Slag During Low-Carbon Ferrochrome Production

Abstract

Methods are analyzed for stabilizing self-disintegrating slags in melting low-carbon ferrochrome, and the main reasons for breakdown are considered. Four methods are shown for stabilizing oxide melts of which a promising method for preventing breakdown under contemporary production conditions for chromium ferroalloys by mixing melts is a reduction in the content of dicalcium silicate with a reduction in the CaO/SiO2 ratio in oxide melt to a value of less than 1.4. However a reduction in CaO/SiO2 slag basicity to 1.33 is demonstrated by experiment (during melting low-carbon ferrochrome containing not less than 5% Si). However, according to the specifications of GOST 4757–91 and the international standard ISO 5448-81 the silicon content in low-carbon ferrochrome should not exceed 1.5%, in view of which the silicothermal process for process for preparing ferrochrome by a mixing method should be separated into two stages. The first stage is preparation of siliceous semiproduct (low-carbon ferrochrome containing Si ≈ 5%) and non-disintegrating slag with reduced basicity (CaO/SiO2 = 1.3–1.4). The second stage is refining the semiproduct with respect to silicon with preparation of highly basic slag (CaO/SiO2 = 1.8–1.9) and ferrochrome with the required silicon content (less than 1.5%). The possibility of obtaining a non-disintegrating slag during melting low-carbon ferrochrome with subsequent processing into building rubble will make it possible to improve the ecological situation in the vicinity of ferroalloy enterprises, to reduce slag dump and adjacent territory contamination and dust content, and also to reduce the amount of slag, loss of chromium, and to increase productivity of the process with a reduction in specific consumption of lime and electrical energy.