The transient behaviours of free surface in a fully penetrated weld pool in gas tungsten arc welding

Abstract

In order to study the phenomenon of the weld pool free surface evolution from partial to full penetration in gas tungsten arc welding (GTAW), the measurement method based on the lattice laser reflection on the weld pool surface was designed. Lattice lasers information and the concavity-convexity in the weld pool free surface were analyzed. Based on the volume of fluid method and the basic principle of fluid mechanics, temperature field and the flow field model which considered the free surface in a fully penetrated weld pool in GTAW were established. Fluid flow including the factor of buoyancy force, electromagnetic force and surface tension gradient was numerically analyzed for a fully penetrated weld pool in stationary GTAW. The result shows that: thermal expansion of metals is the main reason for the convex surface of weld pool at partial penetration. When fully penetrated, the concave surface of the lower surface is greater than that of the upper surface.