Characteristic and Formation Mechanism of Inclusions in 2205 Duplex Stainless Steel Containing Rare Earth Elements

Abstract

RE2O3, RE2O2S, Cr2O3-RE2O3 and (Ca,Mg,Cr,RE)xOy inclusions are mainly identified in 2205 duplex stainless steel containing 0.041wt% rare earth elements. According to thermodynamic analysis, rare earth inclusions could be produced by rare earth elements combining with oxygen, sulfur, pre-existing Cr2O3 or (Ca,Mg,Cr)xOy. Most spherical or spindle rare earth inclusions may be deformed slightly during the rolling process. Large rare earth inclusions are distributed mainly at the edge and at a quarter of the diameter of the 2205 duplex stainless steel round billet. Prolonging soft blowing time after adding rare earth elements, increasing inclusions floating time and controlling sulfur content to suppress segregation may contribute to reduce the quantity of large rare earth inclusions.