Modeling of Linear Gas Tungsten Arc Welding of Stainless Steel
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GAS tungsten arc (GTA) welding of austenitic stainless steel has found wide application in aeronautical, marine, and nuclear power engineering in order to produce welded joints of sound quality. Variations in the heat input during GTA welding of stainless steel have significant effects on the weld bead geometry, microstructure, and hardness in the weld metal and heat-affected zone. Apart from melting of the metal, thermal gradients cause liquid motion in the molten pool, which, in turn, affects the bead shape and size. Buoyancy, electromagnetic induction, and surface tension variation are the major factors that drive weld pool convection. In 1941, Rosenthal[1] first developed an analytical model to study heat transfer in welding. In subsequent years, heat conduction models were developed by many authors. Pavelic et al.[2] computed the temperature distribution in GTA welding of thin low-carbon steel plates, using a two-dimensional (2-D), finite-difference model. Paley and Hibbert[3] developed a computational model to evaluate the temperature distribution in lowcarbon steel plates during single-pass and multipass welding processes. Heat and fluid flow models have been developed by many authors,[4–6] assuming laminar flow and a flat free surface at the top of the weld pool. Weld pool convection and top surface deformation were studied by Zacharia et al.[7,8] for nonautogenous and autogenous GTA welding of aluminum alloy 6061 plates, using the transient multidimensional simulation tool, WELDER. Temperature and velocity fields were calculated for both stationary and linear welding. A comparison between the calculated and experimental results for spot and linear GTA welding of stainless steel P. MARAN, Lecturer, and T. SORNAKUMAR, Professor, are with the Department of Mechanical Engineering, Thiagarajar College of Engineering, Madurai 625 015, India. Contact e-mail: sornakumar2000@ yahoo.com T. SUNDARARAJAN, Professor, is with the Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600 036, India. Manuscript submitted December 10, 2007. Article published online August 15, 2008. METALLURGICAL AND MATERIALS TRANSACTIONS B
was made by Zacharia et al.[9–11] Fan et al.[12] predicted the temperature, velocity, and free surface deformation for a partially or fully penetrated weld pool in stationary GTA welding, using an axisymmetric heat and fluid flow model. Choo et al.[13–15] studied the effect of deformed free surface on weld pool convection. It was observed that melt circulation is markedly affected by the free surface shape, and also significant surface depression in excess of 1 mm is found for currents larger than 240 A. Lu et al.[16] developed an integral 2-D model of the GTA welding arc and weld pool, using the finite element software ANSYS. Kim and Na[17] studied the effect of arc pressure on weld pool deformation and found that the effect of arc pressure on penetration is very little at 100 A, because the free surface deformation is less than 0.02 mm, and it is relatively high at 200 A. The effect
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