Evaluation of Residual Stresses in Bimetallic Welds

Abstract

Dissimilar metal joints between plates of mild steel and austenitic steel are widely used in various fields like nuclear power plant. failure analysis carried out on dissimilar joints and literature review have shown that a significant number of failure have occurred in the heat affected zone of the dissimilar welded joints residual stresses present in the welded joints are one of the main factors which cause failure in dissimilar welded joints. In the present study mild steel and austenitic stainless steel AISI 304 were joined by the gas tungsten arc weld process using an austenitic stainless steel AISI 309 filler metal. A buttering layer of ER309 was laid on mild steel side to prevent carbon migration from mild steel to weld metal . Temperature measurement were determined by using the nickel and nickel & chrome thermocouples at various points on the dissimilar weld and obtained a profile w.r.t time . Residual stresses were determined in the dissimilar welded joints using stain gauge hole drilling method . Investigation was carried out to asses’ residual stresses in different zones in weld coupons. Tensile test, impact test , chemical composition test were also performed to check the ultimate tensile strength ,yield strength, impact strength, change in composition of weld metal . Micro hardness, microstructure were carried out at different zones of the specimen with different parameters .different zones were heat affected zones ,base metals, fusion line weld centre and buttering layer.