Microstructure and mechanical property of the thick-walled dissimilar steel joint of FSS/ASS with the combined "TIG cold welding + UNGW"

A combined welding technology of "TIG cold welding + UNGW" in this paper was proposed, in order to effectively solve the problem of welding heat affected zone(HAZ) grain coarsening in ferritic stainless steel, and the problem of forming vermicular δ ferrite in the part of fusion zone of the welded joint and near welding HAZ for welding of austenitic stainless steel, which significantly reduces corrosion resistance in this areas. Welding between 1Cr17/1Cr18Ni9Ti thick wall dissimilar stainless steels was conducted, meanwhile the microstructure, mechanical properties and corrosion resistance of the welded joint were tested and analyzed. The result shows that the HAZ grains of 1Cr17 base metal of combined welded joint are not coarsened, moreover, there is no vermicular δ ferrite in the part of fusion zone and near heat affected zone of 1Cr18Ni9Ti base metal. The tensile strength of combined welded joint is better than that of 1Cr17 base metal, and the impact absorption energy of HAZ of 1Cr17 base metal is equivalent to that of the 1Cr17 base metal. It shows a downward trend of corrosion resistance from the cladding layer of combined welded joint, the 1Cr18Ni9Ti base metal, 1Cr17 base metal, UNGW weld zone to the welded joint.