Effects of welding parameters on hard zone formation at dissimilar metal welds

TLDR: In this article, an experimental study was conducted to determine effects of welding parameters and to optimize those parameters that have the most influence on eliminating or reducing the extent of hard zone formation at dissimilar metal welds (DMWs).

Abstract: An experimental study was conducted to determine effects of welding parameters and to optimize those parameters that have the most influence on eliminating or reducing the extent of hard zone formation at dissimilar metal welds (DMWs). Preheat, base metal thickness and welding electrode composition were found to have the most influence. Maintaining an optimum preheat for a given base metal thickness and controlling the maximum interpass temperature throughout welding resulted in drastic reduction and often complete elimination of hard zones at DMWs fabricated with ENiCrFe-3 electrodes, but not those welds fabricated with E309 stainless steel electrodes. This finding indicates that depending on the cooling rate and composition of the welding electrode, hard zones in DMWs can be eliminated. The cooling rate must be slow enough to avert formation of hard allotropic structures (i.e., martensite) and fast enough to avoid precipitation of hard intermetallic phases. The optimum welding electrode composition is one that will retard formation and precipitation of intermetallic phases during welding while the preheat needed to prevent the formation of allotropics is being maintained. Unfortunately, this unique characteristic is not available in most, if not all, austenitic stainless steel electrodes; nickel-based welding electrodes have been demonstrated to be more receptive.