Experimental Studies and Mathematical Modelling of Penetration in TIG and A-TIG Stationary Arc Welding of Stainless Steel

Abstract

Experimental investigations of the kinetics of penetration of stainless steel in TIG and A-TIG welding, and theoretical analysis of thermal, electromagnetic and hydrodynamic processes occurring in the weld pool metal were conducted. The stationary arc welding process was chosen as the focus of investigation, in order to study physical-metallurgical peculiarities of metal penetration in TIG and A-TIG welding. This makes it possible to describe processes occurring in the weld pool within the framework of axisymmetric approximation. The conjugate model of heat exchange in the base metal and hydrodynamics of the weld pool, with the melt affected by the electromagnetic (Lorentz force), buoyancy (Archimedean force) and thermal-capillary (Marangoni effect) forces, was formulated. Comparative analysis of the impact of the electric characteristics of the arc (current, voltage, anode spot diameter) and different force factors causing motion of liquid metal on hydrodynamics of the weld pool and shape of penetration of stainless steel in TIG and A-TIG welding was carried out by the method of mathematical modelling. The relationship between the deformation of the free surface of the molten metal (due to changes in its density depending on the temperature) and energy characteristics of the arc was analysed. It is shown that in contraction of the anode region of the arc (with decrease in diameter of the anode spot, which is characteristic of A-TIG welding), the magnetic-hydrodynamic processes become the dominating factor, determining the penetration depth and formation of the weld as a whole.