HARDLY HYDRATING EXPANDABLE OR HARDLY POWDERING SLAG AND TREATMENT OF SLAG REMOVAL THEREOF

摘要

PROBLEM TO BE SOLVED: To prevent the hydrating expansion and the powdering of slag after removing the slag by adjusting the slag composition in the specific range according to a target, at the time of removing the slag produced in melting or refining of the chromium-containing steel. SOLUTION: At the time of separating and removing the slag produced in the melting process or the refining process of the chromium-containing steel, the slag composition is adjusted so that one side or both of a slag expansion index M and slag powdering index D defined in equations (1), (2) and (3) satisfy zero or lower. Each oxide and T.Fe in equations (1) to (3) show each concn. (mass%) and X shows CaO/SiO2 . The M and the D values are obtd. by executing the analysis of the slag composition. In the case only the M value exceeds zero, one side or both of Al2 O3 source and SiO2 source are added in the slag. In the case only the D value or both values of the M and the D exceed zero, SiO2 source is added in the slag. The slag, in which the M value and D value become zero or lower, is separated from the molten metal surface.