Numerical simulation for dynamic behavior of weld pool and fusion hole in TIG welding with gap

The dynamic behaviors of weld pool and fusion hole are mutually coupled in tungsten inert gas (TIG) welding with reserved gap. This simulation has important significance for revealing the effect of fusion hole on weld pool and in enriching the knowledge of TIG welding process with gap. A combined heat distribution model that is adaptive to the free surface deformation of weld pool was established in the article. The interface of the fusion hole was tracked by using volume of fluid (VOF) method. The heat and fluid flow fields of weld pool and the dynamic evolution of fusion hole were simulated numerically. Simulated results show that the appearance of fusion hole intensifies the internal flow, which facilitates the downward flow of liquid metal and promotes penetration. Under the 1.5-mm gap, the fusion hole reaches the critical unstable state with 2.78-mm width after undergoing the growth stage. The overall fluid flow trends on the top surface of the weld pool are consistent under three different gaps. The fluid on the top surface flows most intensely with the gap of 1.3 mm after the formation of fusion hole. And the initial formation time of fusion hole is advanced with the increase of gap width. The computed results agree well with experimental data.