Effect of ‘genetic’ rare earth on alloy dissolution behavior in micro-alloyed steel

The solid solubility of alloying elements and microstructures of insoluble second-phase particles of micro-alloyed steel containing genetic and additional rare earth were respectively investigated. Experimental results indicate that adding a rare earth can change the inclusion morphology and promote the formation of a core of composite inclusions with Al, Ca, Mg, S, and a small amount of Ti. The extremely small quantities of genetic rare earth in steel can promote the formation of a solid solution of Nb and Ti. Therefore, although the content of genetic rare earth in steel is negligible, the promotion effect on solid solubility is significant. The addition of a rare earth has no effect on the types of the insoluble second-phase particles; however, it has a distinct dissolution effect on the large particles in steel.