低温卷取热轧双相钢的显微组织及疲劳性能

采用扫描电镜、拉-拉疲劳试验机等研究了低温卷取热轧双相钢的显微组织及疲劳性能.结果表明:热轧双相试验钢的疲劳极限约为530 MPa;低温卷取工艺生产的热轧双相试验钢夹杂物平均尺寸多在5 μm以下,晶粒比较细小,马氏体组织较细小且弥散均匀分布,具有良好的综合力学性能.热轧双相试验钢疲劳裂纹源位于样品表面的棱角处,疲劳裂纹...

Microstructure and fatigue properties of low temperature coiling hot-rolled dual phase steel

Microstructure and fatigue properties of low temperature coiling hot-rolled dual phase steel were studied by using SEM and tension-tension fatigue tests. The results show that the fatigue limit of the hot-rolled dual phase steel is approximately 530 MPa. The average size of inclusion of the hot-rolled dual phase steel produced by low temperature coiling is less than 5 μm, with small grain and tiny uniformly distributed martensite, which leads to good comprehensive mechanical propertles. The source of fatigue crack in the hot-rolled dual phase steel is located on the edge of specimen surface. There are plenty of dimples, tearing ridges, fatigue striations and secondary cracks in fatigue crack growth zone. Fatigue final rupture region mainly consists of superficial dimples. Different degree of strain occurred in ferrite and martensite finally results in the born of secondary cracks on the phase interface of ferrite and martensite. The secondary cracks are borned but don't grow. Large number of secondary cracks disperse the stress concentration at the tip of main cracks, which can effectively reduce the driving force of crack growth, slow down the fatigue crack propagation rate, and restrain fatigue crack propagation and finally improve the fatigue properties.