Development of self-shielded flux cored wire for X100 pipeline steel and performance analysis of welded joints

The alloy systems of weld metal of X100 pipeline steel were determined with the principle of composition match and structure match. Combined with the principle of weld metal alloying, the types and content of alloy elements which need to transit in the weld can be quantitatively calculated, based on which the flux-cored wire match to X100 pipeline steel was designed and made. The appropriate welding process parameters for welding and the according joint performance were also analyzed. The results showed that the flux-cored wire has excellent mechanical properties with the tensile strength up to 795 MPa, yield strength up to 615 MPa and impact energy value to 47.7J(-40℃). The microstructure of the weld metal consists of lath bainite, granular bainite, and little acicular ferrite, which can match well with base material.