Parametric Studies on Effect of Trailing Liquid Nitrogen Heat Sink on TIG Welding of Steels

Abstract

Welding is an efficient material joining process. But the localised temperature rise up to the melting point in the vicinity of arc causes non uniform expansion and contraction resulting in residual stress and distortions. Post weld, Pre weld and in-process methods have been studied to reduce these unwanted effects of welding. A trailing heat sink is one such method. This consists of a cooling agent traversing at a constant distance behind the weld arc. Introduction of a cooling agent is reported to reduce the distortion. A liquid nitrogen jet is used as the cooling agent in the present study. A finite element model developed using Sysweld is used to study the effect of liquid nitrogen heat sink on weld distortions and residual stresses. The finite element model developed is used to make a parametric study on the effect of cooling jet radius, cooling strength and the distance between the jet and weld arc on out of plane distortions and stresses. Comparative study of the effect of cooling jet is made for mild steel (MS) and stainless steel (SS). It is observed that the out of plane distortions reduce with increasing cooling strength, jet radius. Reduction in distance between the jet and weld arc also causes a reduction in distortions.