Waveshape effect on alloying and arc stability of A-C tungsten inert-arc welding

ALUMINUM-CLAD aluminum-silicon-alloy bonded nuclear fuel elements are fusion-welded over the exposed brazed joint to assure a watertight closure. As is common with some brazed joints, there are porosities and pipes in the braze which may provide a path for the cooling water to attack the uranium metal. Work with the fusion welds has disclosed that the braze metal was not alloying with the cladding into a homogeneous weld alloy. In many instances the braze metal was continuous from the parent braze metal to the surface of the weld. Within limits of normal welding speeds but a very small change in alloying occurred with changing welding speed. Current programming was desirable to improve weld quality. This controlled the weld width as the weld progressed and raised the temperature of the metal to be melted. The welding power supply in use had a manually operated mechanical current control which could not be readily converted to current programming.