奥氏体组织对低碳中锰钢冷弯性能的影响

摘要：采用冷弯直径0～60mm，弯曲角度180°，研究了20mm厚度低碳中锰钢的冷弯性能，冷弯后外表均无可见裂纹，判定合格。利用光学显微镜、扫描电镜、透射电镜、电子背散射衍射（EBSD）、X射线衍射仪等手段分析了显微组织，尤其是奥氏体组织在冷弯过程中对冷弯性能的影响。结果表明，冷弯前显微组织由板条马氏体和奥氏体组成，其中原始奥氏体晶界明显；冷弯直径为0mm变形后，样品弧顶部分奥氏体的体积分数由12.3%降至1.1%，维氏硬度由295HV1增至364HV1，晶粒尺寸由4.07μm增至4.30μm。主要原因是在冷弯过程在中奥氏体组织发生塑性变形，奥氏体晶界变形消失，沿冷弯方向呈拉伸带状组织形貌，冷弯形变时奥氏体发生TRIP效应显著。

Effect of austenite structure on cold bending properties of low carbon medium manganese steel

The cold bending diameter was set to 0-60mm and the bending angle was 180°, the cold bending performance of low carbon medium manganese steel with a thickness of 20mm was studied. There were no visible cracks on the surface after cold bending, and it was judged as qualified. Using optical microscope, scanning electron microscope, transmission electron microscope, electron backscatter diffraction (EBSD), X ray diffractometer and other means to analyze the microstructure, especially the influence of austenite structure on the cold bending performance during the cold bending process. The results show that the microstructure before cold bending is composed of lath martensite and austenite, in which the prior austenite grain boundaries are obvious, after the cold bending deformation diameter becomes 0mm, the volume fraction of austenite at the top of the sample arc is determined from 12.3% to 1.1%, the Vickers hardness is increased from 295HV1 to 364HV1, and the grain size is increased from 4.07μm to 4.30μm. The main reason is that the austenite structure undergoes plastic deformation during the cold bending process. Austenite grain boundaries are blurred due to deformation, along the cold bending direction, it has a tensile band like structure, and the TRIP effect of austenite is significant during cold bending deformation.