Numerical analysis of deformation in multi-pass circumferential TIG welding with narrow gap

As one of the practical issues for narrow gap tungsten inert gas welding, the mechanism of gap width shrinkage in multi-pass circumferential butt welding of thick-walled pipes was examined experimentally and numerically. The experimental result using 600-mm outer diameter pipes with 200-mm wall thickness revealed that the shrinkage of gap at the beginning of the welding process of 174 pass welding for 73 layers would be independent of the groove shape. Also, from the results of the thermal elastic–plastic finite element analyses, it was found that a 2D axisymmetric model was inadequate in predicting the initial shrinkage of gap width. Moreover, the computational results indicate that the shrinkage of gap width could be estimated quantitatively using a 3D model of whole pipe and defining the appropriate heat input area, while the results of the 3D partial model of pipe with small degree was insufficient to predict the initial shrinkage precisely.