Influence of Rare Earth Ce Additions on Microstructure and Mechanical Properties of Experimental Pipeline Steels

Herein, the effect of Ce additions ranging from 57 to 263 ppm is evaluated for an experimental pipeline steel. Compared to the Ce-free steel, progressive Ce additions result in a slightly refined microstructure, significantly improve transverse impact properties, and slightly increase strength. All these observations can be attributed to the gradual transformation of Mn sulfide and Mn-Si-Al oxide inclusions to Ce-containing oxide/sulfides. In particular, the inclusions consist exclusively of sub-5 mu m spherical Ce2O2S particles upon near-stoichiometric additions of Ce, considering the oxygen and sulfur impurity level of the steel. The results suggest that Ce is a potentially promising alloying addition for next-generation pipeline steels by replacing overtly deleterious inclusions with potentially beneficial ones. Minor additions of rare earth element Ce can significantly improve the impact toughness and further tune the properties of high-strength pipeline steels. The benefits stem from the transformation of overtly detrimental Mn-sulfide and Mn/Si/Al-oxide inclusions to small, spherical Ce-oxysulfide particles. Complete transformation is achieved upon stoichiometric additions of Ce, considering the sulfur and oxygen impurity levels in the steel.image (c) 2024 WILEY-VCH GmbH