Modeling of the Effects of Oxygen Content on Flow Patterns in A-Tig Welding
A-TIG焊中氧含量对熔池流动方式影响的数值模拟

A 3D mathematical model was developed to calculate the temperature and velocity distributions in a moving A-TIG weld pool with different oxygen concentrations. It is shown that the oxygen element, which changes the temperature dependence of surface tension coefficient from a negative value to a positive value, can cause significant changes in the weld penetration and depth/width ratio (D/W) of the weld pool. When the oxygen content increases, the weld bead penetration and $ D/W increases sharply while the weld metal width decreases. When oxygen content exceeds 150 10-6, the surface temperature decreases and then remains a constant. When the oxygen content increased beyond 200 10-6, the increase in oxygen content did not effect the weld pool size and shape. As the oxygen content is less than 300 10-6, negative and positive exist at the same time in the weld pool. The increase of oxygen content and the decrease of surface temperature can extend the region of positive surface tension coefficient and increase the depth of the pool. As the oxygen content exceed 300 10-6 the temperature at the maximum surface tension increases beyond the simulated maximum surface temperature, andis positive. Depending upon the oxygen concentrations, three, one, or two vortexes with different positions, strengths, and directions may be found in the weld pool. The contrary vortexes can efficiently transfer the thermal energy from the arc, creating a deep weld pool.