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通过对曲轴进行宏观形貌、化学成分、拉伸力学性能、冲击性能和断口形貌等进行观察和检测,研究了汽车曲轴发生断裂的原因。结果表明,断裂曲轴的化学成分符合TYPE416材料的规定要求,拉伸力学性能和冲击性能符合ASTM A582/A582M-12标准的要求;汽车曲轴纵剖面上密集分布着细小的点状、条状和串状硫化物类夹杂,断口附近和基材的组织都为索氏体+少量铁素体,源区附近没有发现气孔或者机械加工缺陷存在;汽车曲轴根部存在局部应力集中,条状夹杂物降低了材料的横向性能,使得汽车曲轴在外加应力作用下发生层状纵向开裂。
By analyzing the macroscopic morphology, chemical composition, tensile mechanical properties, impact properties and fracture morphology of the crankshaft, the reasons for the crankshaft rupture were studied. The results show that the chemical composition of fracture crankshaft meet the requirements of TYPE416 material, tensile mechanical properties and impact properties meet the requirements of ASTM A582 / A582M-12 standards. The longitudinal distribution of automobile crankshaft is densely distributed with small dots, stripes and strings Like sulfide inclusions, near the fracture and the substrate are sorbite + a small amount of ferrite, there is no stomata near the source area or machining defects exist; there is localized stress concentration in the root of the automobile crankshaft, strip inclusions decreased Transverse performance of the material, making the car crankshaft in the application of stress under the layer longitudinal cracking.