600MPa级热轧双相钢汽车车轮裂纹分析.pdfVIP

1600MPa 级热轧双相钢汽车车轮裂纹分析 张 丹 刘雅政 周乐育 张大伟 刘玉娜 （北京科技大学材料科学与工程学院，北京 100083 ） 摘 要 使用600MPa 级热轧铁素体马氏体双相钢生产汽车车轮，并对车轮进行动态弯曲疲劳试验。在车轮通风孔 处出现疲劳裂纹。利用光学电镜和扫描电镜观察了疲劳裂纹的扩展过程，并分析了显微组织和夹杂物对于裂纹扩展 的影响。实验结果表明，夹杂物处于临界尺寸之下，没有影响裂纹的萌生和扩展。经过机加工冲孔之后，通风孔次 表面处出现大量的显微孔洞，并且显微组织发生强烈的疲劳变形；外表面观察到毛刺，并且观察到由毛刺根部引起 的微裂纹。实验钢有较强的缺口敏感性，导致外表面毛刺根部出现微裂纹，次表面显微孔洞为微裂纹扩展提供便利 通道，经过次表面显微孔洞向内部扩展。 关键词 热轧双相钢 车轮裂纹 弯曲疲劳试验 夹杂物尺寸 Research on Wheel Crack of 600MPa Grade Hot-rolling Dual-Phase Steel Zhang Dan Liu Yazheng Zhou Leyu Zhang Dawei Liu Yuna (Materials Science and Engineering School , University of Science and Technology Beijing , Beijing, 100083) Abstract A kind of 600MPa grade hot-rolling martensite dual phase steel was developed for wheel product. While in the bending fatigue test, fatigue crack appeared on the vent of the wheel. By using of optical microscopy and scanning electron microscope, the fatigue crack propagation process was observed, and the effect of the microstructure and inclusion to crack propagation was observed. The results showed that the inclusions in the test material are under the critical inclusion size, so the inclusions do not induce the happening and propagation of the fatigue crack. After machine processing, a large numbers of micro voids appeared in the subsurface of vent and the microstructure was strongly deformed; a micro crack was appeared from the root of the burr. This shows that the notch sensitivity is bad, so the micro crack must began from the root of the burr and the micro voids were the good ways while the crack propagated to the inner place. Key words hot-rolling dual phase steel, wheel crack, bending fatigue test, inclusion size