Exothermic acid slag-forming mixt. for refining tapped steel - contg. perlite or fluorspar to increase combustion

摘要

An exothermic slag-forming mixt. contains (by wt.) 0.1-15% Al powder, 24-40 NaNO3, 5-15% CaO, 0.1-20% Si-coating component, 5-15% expanded perlite as fluorspar with the balance being a SiO2-contg. component. Suitably the Si-contg. component is 0.1-6% of powdered Si, the other components then being 9-15% Al powder, 28-30% Na2NO3, 5-15% CaO, 5-15% expanded perlite or fluorspar and balance silica-contg. component. The compsn. produces a molten acid slag for refining tapped steel from a high-prodn. basic open hearth furnace or converter. It is esp. useful for ball-bearing or stainless steels. The presence of perlite or fluorspar in the mixt. increases the combustion rate and thereby facilitates melting without the considerable cost increase involved in achieving the same result by increasing Al content.