Finite Element Analysis of Residual Stresses in Butt Welding of Stainless Steel Plates by GTAW

Abstract

Welding is one of the most commonly used permanent joining processes in the piping and pressure vessel industry. During welding a very complex thermal cycle is applied to the weldment, which in turn causes irreversible elastic-plastic deformation and consequently gives rise to the residual stresses in and around fusion zone and heat affected zone (HAZ). Presence of residual stresses may be beneficial or harmful for the structural components depending on the nature and magnitude of stresses. The beneficial effect of compressive stresses have been widely used in industry as these are believed to increase fatigue strength of the component and reduce stress corrosion cracking and brittle fracture. In large steel fabrication industries such as shipbuilding, marine structures, aero-space industry, high speed train guide ways and pressure vessels and piping in chemical and petrochemical industry the problem of residual stresses and overall distortion has been and continue to be a major issue. It is well established fact that material response of structural components is substantially affected by the residual stresses when subjected to thermal and structural loads. Due to these residual stresses produced in and around the weld zone the strength and life of the component is reduced. As AISI 304 stainless steel has excellent properties like better corrosion resistance, high ductility, excellent drawing, forming and spinning properties, so it is almost used in all types of application like chemical equipment, flatware utensils, coal hopper, kitchen sinks, marine equipment etc. But because of the problems of residual stresses during the time of welding it is very essential to understand the behavior and nature of AISI 304 stainless steel material. So in order to overcome all these problems a 3-dimensional finite element model is developed in a commercially available FEA code by drafting an approximate geometry of the butt welded joint and then the finite element analysis is performed, so that one can understand the complete nature of residual stresses in butt welding of AISI 304 stainless steel plate. In this paper, butt welding simulations were performed on two AISI 304 stainless steel plates by gas tungsten arc welding (GTAW). Analysis of butt welded joint by commercially available finite element analysis code showed that butt weld produced by GTAW resulted in 782.84 MPa of residual stress in plates. In addition, the residual stress is plotted against axial distance to have a clear picture of the magnitude of residual stress in and around weld area.