Modelling of Nitrogen Dissolution During the GTA Welding of Iron and Steels

Nitrogen dissolution during the arc welding of steels is a long-standing issue in the welding research community. Unfortunately, the complexity of the arc welding process has made it impossible to accurately predict these nitrogen concentrations using conventional thermo­dynamics. An attempt to fundamentally understand this complex process is pursued here using mathematical modelling techniques. In this model, plasma phase calculations are combined with those for nitrogen absorption on the surface and those for convection and diffusion of nitrogen in the weld pool to determine the resulting nitrogen distribution in the weldment. This methodology, unlike previous models, is based solely on fundamental principles and can take into account the effects of changes in welding parameters on the resulting nitrogen concentration. A superior correlation is thus observed between the nitrogen concentrations observed in controlled GTA welding experiments and those calculated by this model.