Effect of Small Amount of Rare Earth Element Ce on the Mechanical Properties of Medium Carbon Microalloyed Steel

Abstract

With the development of rare earth streated steel, the application and theory research of rare earth element in microalloyed steels are becoming more deeply and widely. So far, many investigations have been made on the effect of rare earth element on low carbon microalloyed steel. However, the effect of rare earth element on medium carbon microalloyed steel have not been clarified yet. In this work，the effect of small amount of rare earth element Ce on mechanical properties of medium carbon microalloyed steel were investigated by SEM, EDS and EBSD. The results show that the addition of rare earth elements can improve the comprehensive mechanical properties of medium carbon microalloyed steel, the strength-ductility balance increases from 23.57GPa% to 27.49 GPa%. In particular, the plasticity and toughness are improved obviously. The elongation rate and the impact toughness are increased by 14.8% and 19.5%, respectively. The rare earth elements did not markedly refine grain size and change matrix structure. However, the addition of rare earths increased the proportion of high-angle grain boundary from 33.2% to 40.2%. In addition, the fracture analysis with scanning electron microscopethe show that rare earth can make the inclusions denatured and hence spherical grain with small size can be obtained. The EDS result shows that rare earth and harmful elements P and O can cause inclusion, which purifies the molten steel and hinders the formation of microalloy element inclusions.