MINIMIZING THE RESIDUAL SHRINKAGES AND STRESSES OF THICK PIPE WELDS USING NARROW GAP WELDING

Abstract

The acceptability of weld joint is primarily governed by required fusion of base metal, minimum undesirable heat affected zone (HAZ) and residual stresses. Generally process used for thick pipe welding is SMA and GMA, where they influence severity of weld thermal cycle in different manner depending upon amount of weld deposition, welding parameters and shielding environment. The severity of thermal and mechanical effects of welding can be considerably minimized by reducing the amount of weld metal in a joint by using narrow gap welding technique. A 333 grade3 is seamless steel pipe widely used in industries. A333 grade3 thick steel Pipes are welded to study the effect of different welding process and groove design. Various experiments like tensile testing, hardness measurement and residual stress measurement have been done according to their standards. Microstructures have been seen at different location of weld for GMA and P-GMA weld joints for revealing the dendritic structures for welds at different heat input. Results are compared for GMA and P-GMA welds for conventional and narrow grooves.