铁路车辆用车轴经锻造及机械加工后,在其表面常发现纵向裂纹,造成车轴报废.采用光学显微镜、扫描电子显微镜、能谱仪、维氏硬度计等分析手段,对LZ50钢车轴表面裂纹形成的机理进行了研究.发现车轴微裂纹的形成可有两种机理：一是车轴钢坯中的显微缩松在锻造时被轧扁但未完全弥合所致;二是由车轴钢坯中的氧化铝类夹杂物在锻造时形成裂纹源,导致车轴微观组织脆性穿晶断裂.

The longitudinal cracks were often found on the surface of axles for railway vehicles after forging and machining, resulting in axle scrap.The optical microscope, scanning electron microscope, energy dispersive X-ray spectroscopy as well as Vickers hardness tester were employed to investigate the formation mechanism of cracks on the surface of LZ50 steel axle.It was found that the formation mechanism of microcracks on the axle surface could be classed into two types: one was that micro shrinkage porosity in axle billet was not completely healed during forging of flattening;the other was that alumina inclusions in axle billet formed source of crack and resulted in brittle trans-granular fracture of axle microstructure during forging.