Microstructure and Chemical Composition of Submerged Arc Weld Metal for High Strength Low Alloy Steel

Taking the submerged arc weld metal of X80 pipeline steel as example,the heterogeneity of chemical composition and microstructure of high strength low alloy steel weld were analyzed.The results show that the segregation of Mn,Ni elements in the weld is faintish,but the segregation of Ce,Ti,Al elements which can promote the forming acicular ferrite nucleation is serious in the center of the weld.The microstructure evolving from fusion zone to center of the weld is columnar pro-eutectoid ferrite and granular bainite → bulk bainite → refined banite → minor acicular ferrite → acicular ferrite.Therefore,it is difficult to obtain acicular ferrite for fusion zone,but the whole tenacious properties of high strength low alloy steel weld increase by promoting the formation of granular bainite and restricting the formation of pro-eutectoid ferrite.