Fusion welding of steel powder metallurgical preforms to wrought copper

The present paper reports the feasibility studies on joining low density steel powder metallurgical (PM) preforms with wrought copper. In joining of these materials by tungsten inert gas (TIG) welding, the welding current, pulse frequency and the density of the PM preforms were found to have a strong influence in controlling the weld strength. When welded with lower welding currents (continuous current), copper infiltrated into the PM steel and with higher currents, thermal effects dominated in controlling the weld strength. Through the application of a pulsed current, grains became more equiaxed due to dendrite fragmentation. Microstructural refinement was found to be at a maximum at an optimum pulse frequency, which resulted in maximum tensile strength. ? 2004 Institute of Materials, Minerals and Mining.