Effects of Composition and Heat Treatment on CaS Formation in Ferritic Stainless Steel

Abstract

The formation of CaS around CaO–Al₂O₃ in ferritic stainless steel was investigated. CaS was observed in the samples after heat treatment, although it was not detected in cast ingots. Al and S contents affect the precipitation of CaS because of the following reaction: 2[Al]+3[S]+3CaO=Al₂O₃+3CaS. The formation of CaS cannot be predicted by thermodynamic calculation. The growth of CaS during heat treatment is thought to be mainly controlled by S diffusion in steel. The factors for reducing CaS precipitation are discussed in this work.