文摘
A numerical model of a three-dimensional transient weld pool was conducted to analyze the hump formation mechanism in high-speed single-wire gas metal arc welding (GMAW) and the hump suppression in triple-wire GMAW. The effect of heat convection, radiation, and vaporization on temperature field and the impact of arc pressure, surface tension, Lorentz force, buoyancy force, and droplet impinging force on the fluid flow field were considered during simulations. In good agreement with the experimental beads and images recorded by high-speed camera, the simulated results are shown: during the hump formation in single-wire GMAW, the liquid channel was formed, elongated, pinched, and solidified due to the strong backward molten metal flow and the normal surface tension. However, in the same line energy, humps were suppressed in triple-wire GMAW. The “pull-push” flow in the triple-wire GMAW weld pool could dramatically slow down the backward trend, which reduced the solidification rate. Consequently, the liquid channel disappears and the humps could not be formed any more.
