Effect of cerium on the cleanliness of spring steel used in fastener of high-speed railway

Abstract

The effects of Ce addition on the quantity, size, distribution of inclusions and the content of oxygen, sulfur and other hazardous residual elements in spring steel used as fastener in high speed railway were investigated by metallographic examination, SEM-EDS and composition analysis. The results indicated that the contents of oxygen decreased with the addition of Ce ([Ce]<0.1%) and the content of sulfur continually decreased with increasing content of Ce ([Ce]<1.2%). However, with the further increase of Ce element addition, the content of [O] and T[O] began to increase. The content of Ce Corresponding to the lowest [O] and T[O] lied in the range of 0.10%–0.13% and 0.045%–0.065%, respectively. The addition of Ce in spring steel resulted in the formation of rare earth oxides/oxysulfides and decreased the size of inclusions to less than 3 μm in globular or spheroid shape. Moreover, the residual harmful elements (As, P, Pb and Sn) were found to exist in the Ce-containing inclusions, which had proved that the Ce addition could capture the residual elements and suppress their precipitation behaviors in the grain boundary.