Influence of Rare Earth on Microstructure and Carbide of 21-4N Steel

The influence of Ce on microstructure and carbide of austenitic stainless steel 21-4 N both at as-cast and as-forged states were analyzed in this paper.The results show that the dendritic spacing,pearlite-like colony and the primary carbide M₇C₃ of as-cast steel can be refined significantly by adding appropriate rare earth Ce elements.The morphology of as-cast pearlite-like colony is improved and the number of primary carbides M₇C₃ is reduced significantly.Moreover,the grain size of forged austenite is remarkably refined.But the pearlite-like colonies of as-cast steel coarsens and primary carbides increase, therefore as-forged austenite coarsens when Ce content is too high.When Ce content of 21-4 N steel is between 0.011% and 0.015%,as-cast pearlite-like colonies are smaller and spheroidized,primary carbides are refined and increased,and austenite grains are refined.