Homopolar Pulse Welding of Martensitic Stainless Steel Linepipe
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Homopolar pulse welding (HPW) of low-C martensitic stainless steel seamless pipe was examined as a girth welding method. Weld mechanical properties and microstructures were investigated. The effects of welding parameters on mechanical properties were also surveyed. The HPW welds provided acceptable mechanical properties; including tensile strength and, low temperature impact toughness. The values were comparable with those of its base metal in both the as-welded and tempered conditions. The heat-affected zones were narrow with a fine-grained microstructure. While flash welding generally produces a depression of chemical compositions at the weld interface, there is little of that effect in the case of homopolar welds, and no discernible localized softening zone was observed. The fine-grained microstructui·e of HPW welds is thought to be an effect of the combination of its characteristic rapid thermal excursion and deformation while upsetting. From these results, it has become clear that HPW is considered to have a potential for high productivity girth welding of martensitic stainless linepipe.