Simulation of Heat Affected Zone Cracking Tendency during Tungsten Inert Gas Welding of Mild Steel Plates

TIG welding has been the most widely accepted welding processes so far in the industry due to its availability and versatility of welding equipment, low-cost equipment and excellent quality. Metallurgical changes, residual stress and distortions near the weld bead due to localized heating by the welding process and subsequent rapid cooling are the major problems to be addressed during welding. Defects may be on the surface or inside the weld metal. Certain defects like cracks are never tolerated but other defects may be acceptable within permissible limits. The 3D numerical simulation ANSYS code is used to predict cracking tendency in the mild steel plate. The thermo-mechanical effect of welding is simulated to study the residual stress distribution and the cracking tendency. As fusion zone of weld comprise of semi-solid phase, considering only the thermo-mechanical effect of welding is not desirable to predict the cracking tendency in the fusion zone as other factors like weld pool flow characteristics, the metallurgy of the zone depends. Thus cracking tendency in the heat-affected zone is only considered for the study. Firstly the thermal distribution developed during welding of mild steel plate was modelled by three-dimensional thermal model. Secondly, the stress distributions arising during the welding of mild steel plate was simulated based on simulated thermal distributions. The structural analysis gives residual stress and critical strain distribution which is further analysed and studied to determine the cracking tendency in the heat-affected zone.