硫化物形貌对非调质钢力学性能各向异性的影响

为了明确硫化物变性处理前后材料力学性能各向异性的变化规律，利用金相显微镜、SEM、拉伸及冲击试验机研究了工业生产的具有不同硫化物形貌特征(硫化物变性与未变性处理)的35MnVS非调质钢锻态力学性能的各向异性。结果表明，经变性处理后硫化物由未经变性处理的细长条状向短棒状或纺锤状转变，硫化物长宽比在1～8范围内的个数比例由未经变性处理的不到40%提高到变性处理后的90%以上，且分布更加均匀，组织有所细化。硫化物变性处理能够明显地降低试验钢塑性和韧性的各向异性，断面收缩率和冲击功的各向异性分别减小了约10%和34%，横向断口形貌由脆性的朽木分层状向韧窝韧性断裂转变。

Effect of sulfide morphology on anisotropic mechanical properties#br# of microalloyed forging steel#br#

The present study was attempted to investigate the effect of sulfide morphology on anisotropic mechanical properties of as-forged microalloyed forging steel by using optical microscopy, scanning electron microscopy (SEM), tensile and impact tests. Two heats of commercial ferritic-pearlitic microalloyed forging steel 35MnVS with different sulfide morphologies (sulfide modified and non-modified) were tested. The results show that the sulfide shape changed from highly elongated to rod-like and slightly elongated, and the ratio of sulfides with aspect ratio (the ratio of length to width of sulfide) in the range of 1 to 8 increased from lower than 40% for the sulfide non-modified heat to higher than 90% for the sulfide modified heat. Moreover, the distribution of the modified sulfides was more uniform and the microstructure was refined for the latter. The modification of sulfide could significantly alleviate the anisotropy of both ductility and toughness by relative decrease of ~10% and ~34%, respectively. The facture mechanism changed from mainly brittle fracture with many elongated sulfides promoted quasi-cleavage strips to ductile dimple fracture after sulfide modification.