Effect of Process Parameters on Angular Distortion of Gas Tungsten ARC Welded 202 Grade Stainless Steel Plates

摘要

Angular distortion is a major problem and most pronounced among different types of distortion in the butt welded plates. In arc welding processes, due to rapid heating and cooling the work piece undergoes an uneven expansion and contraction in all the directions. This leads to distortion in all the directions of the work piece. Restriction of this distortion by restraint may lead to higher residual stresses. This effect can be reduced by providing initial angular distortion in the negative direction, if the magnitude of distortion is predictable. It is difficult to predict angular distortion. Gas Tungsten Arc Welding (GTAW) process is suitable for joining thin and medium thickness materials such as stainless steel sheets and for applications where metallurgical control of the weld is critical. In this research work the effect of process parameters on angular distortion in GTAW of austenite stainless steel grade 202 was studied. A five level five factor central composite rotatable design with 32 experimental runs were used to conduct the experiments. Direct effects and interactive effects of the process parameters were analysed and presented in graphical form. A mathematical model is developed correlating the process parameters and the angular distortion. The developed model is very useful to determine quantitatively the angular distortion in the negative direction. It also helps to select optimum process variables for minimizing distortion in welded structures. It is also possible to optimize the GTAW process and make it a cost effective one by eliminating the weld defects due to angular distortion.