原位观察MnS对非调质钢拉伸性能各向异性的影响

利用激光共聚焦扫描显微镜原位观察S质量分数为0.065%的非调质钢纵向与横向拉伸过程中MnS的行为,研究MnS形貌与分布对非调质钢各向异性的影响.原位观察表明锻后钢中存在大量长条形MnS,横向与纵向拉伸过程中MnS长度方向与拉力方向取向不同.横向拉伸过程中MnS更易与基体分离产生裂纹,裂纹随MnS长度方向扩展长大,最终导致基体的断裂.MnS在纵向拉伸时不易与基体分离,因此对纵向拉伸性能影响较小.钢中群聚分布的MnS有利于裂纹的聚合长大,会促进基体的断裂. 

In-situ observation of MnS effect on the tensile strength anisotropy of non-quenched and tempered steel

In-situ observation of the behavior of MnS inclusions in non-quenched and tempered steel with a sulfur mass fraction of 0.065% was performed during tensile tests by using a laser confocal scanning microscope (LCSM) to investigate the effects of the morphology and distribution of MnS inclusions on the tensile property anisotropy of the steel. The result shows that there exist a large number of rod-like MnS inclusions in the forged steel, which have different orientations with the load during transverse and longitudinal tensile tests. The rod-like MnS inclusions separate much easier from the steel base during transverse tensile tests to form initial cracks, and then the cracks spread along the MnS inclusions. In this way, the cracks grow up and lead to the fracture of the steel. In contrast, the MnS inclusions have little effects on the longitudinal tensile properties because the length direction of MnS is parallel to the tensile force. MnS inclusion aggregation promotes the assembling and growth of single cracks, thus accelerating the fracture of the steel during tensile tests.