This study investigated the effect of post-weld processes including annealing and drawing on the microstructure and mechanical properties of high-Mn steel pipes welded by gas tungsten arc welding. The weld metal showed a solidified microstructure having coarse and elongated grains due to coalescence of columnar dendrite into welding heat direction. After post-annealing, the solidified microstructure changed into equiaxed grains due to recrystallization and grain growth. Mn segregation occurred during welding solidification and caused lower stacking fault energy (SFE) in the Mn-depleted region. Although ε-martensite formation in the as-welded state and during deformation was expected due to decreased SFE of the Mn-depleted zone, all regions showed a fully austenitic phase. The annealing process decreased strength due to grain coarsening but increased ductility. The drawing process increased strength of weld metal through work hardening. All pipes showed decreasing strain rate sensitivity (SRS) with deformation and negative SRS after certain strain levels. It was confirmed that negative SRS is related to less formation of mechanical twinning at a higher strain rate. This work provides fundamental insights into manufacturing a high-Mn steel pipe and manipulating its properties with annealing and drawing processes.

中文翻译：

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热处理和拉拔对钨极氩弧焊高锰钢管的影响

本研究研究了包括退火和拉拔在内的焊后工艺对气体钨极电弧焊焊接的高锰钢管的组织和力学性能的影响。由于柱状枝晶向焊接热方向的聚结，焊接金属显示出具有粗糙和细长晶粒的凝固的显微组织。后退火后，由于重结晶和晶粒长大，凝固的显微组织变为等轴晶粒。Mn偏析发生在焊接凝固过程中，并导致Mn耗尽区的堆垛层错能（SFE）降低。尽管由于Mn耗尽区的SFE降低，预计在焊接状态和变形过程中会形成ε马氏体，但所有区域均显示出完全的奥氏体相。退火过程由于晶粒粗化而使强度降低，但延展性增加。拉伸过程通过加工硬化提高了焊接金属的强度。在某些应变水平后，所有管道的变形率均降低，应变率灵敏度（SRS）降低，而SRS为负。已证实负SRS与较高应变速率下较少的机械孪晶形成有关。这项工作为制造高锰钢钢管以及通过退火和拉拔工艺控制其性能提供了基本见识。已证实负SRS与较高应变速率下较少的机械孪晶形成有关。这项工作为制造高锰钢钢管以及通过退火和拉拔工艺控制其性能提供了基本见识。已证实负SRS与较高应变速率下较少的机械孪晶形成有关。这项工作为制造高锰钢钢管以及通过退火和拉拔工艺控制其性能提供了基本见识。