Model Study on Behavior of Niobium in High Carbon Rare Earth Steel Original Research Article

A coupling thermodynamic model which quantificationally described elements segregation and inclusions precipitation during solidification process of high carbon RE steel was proposed. According to the SEM and energy spectrum analysis, the model could completely consist with experiment results. Effects of mass fraction of niobium on the state of rare earth and niobium and constituents of inclusions during the solidification process of high carbon rare earth steel were studied. The results as follows:(1) Niobium carbide is gradually precipitated during solidification process. The content of solid niobium solution is rapidly increased at the late stage of solidification. With increasing mass fraction of carbon, concentration distribution of solid niobium solution is decreased at first and then increased.(2) With increasing mass fraction of niobium, both the temperature and content of niobium carbide precipitation are increased; the average precipitation content of solid niobium solution is gradually increased.(3) With increasing mass fraction of niobium, the content of solid RE solution. RE oxysulfide and nitride are increased, and the content of RES inclusion and RE aluminate are decreased.