Inclusions, microstructure and properties of flux copper backing submerged arc weld metal

This paper investigates the effect of Ce on inclusions, microstructure and mechanical properties of the weld metal in flux copper backing submerged arc welding. The results show, with the addition of Ce in weld metal, the inclusions are mainly composed of Al2O3, MnO, SiO2, TiO, Ce2S3, CeS and Ce2O2S compound, and the proportion of the inclusions of <1.0 mu m in size increased. In competitive nucleation, acicular ferrite nucleates on the oxysulphides of Ce and inhibits the formation of proentectoid ferrite and ferrite side plate. This led to a high proportion of acicular ferrite, good mechanical properties of weld metal. A small lattice disregistry between CeS, Ce3S4, Ce2O2S and acicular ferrite contributed to low energy for nucleation of acicular ferrite.