Microstructure and mechanical properties of a gas-tungsten-arc-welded Fe-24Mn-3.5Cr-0.4C high manganese steel pipe using a Fe-22Mn-2.34Ni-0.38C welding wire

Abstract

In this study, Fe-24.34Mn-3.53Cr-0.42C high manganese steel sheets were joined using a gas-tungsten arc welding (GTAW) and a plasma arc welding (PAW) using a newly-developed Fe-22.2Mn-2.34Cr-1.95Ni welding wire. Microstructure analysis revealed that Mn-depleted zone appeared in the weld zone due to Mn segregation during solidification. With plastic deformation, a small amount of epsilon-martensite was found in the Mn-depleted zone i.e., dendritic region, of the weld zone. Mechanical properties of the weld zone were found to be lower than in the base metal. On the other hand, due to recrystallization and grain growth induced by heat treatment at 1050 degrees C, the mechanical property differences between the base metal and the weld zone were reduced. Strain rate sensitivity test showed negative strain rate sensitivity in the base metal and heat-treated weld zone possibly due to the reduced work hardening caused by the reduction of twinning nucleation. On the contrary, the as -welded zone exhibited positive strain rate sensitivity due to the reduction in twinning stress caused by coarse grains.