柴油机球墨铸铁曲轴的早期断裂机制研究

Study on early fracture mechanisms of spheroidal graphite cast iron crankshaft of diesel engine

采用化学成分分析、金相检测、宏观与微观断口形貌分析等方法,对柴油机QT600-3球墨铸铁曲轴的早期断裂机制进行了分析研究.结果表明,轴颈圆角处的表面氧化皮及显微裂纹是引起疲劳开裂的主要原因,淬火组织缺陷诱发裂纹源的形成,对曲轴早期断裂也有一定的影响,断裂机制为解理与准解理断裂,具有典型的脆性断裂特征.

The early fracture mechanisms of QT600-3 spheroidal graphite cast iron crankshaft of diesel engine were analyzed by the chemical composition analysis, metallographical examination, macroscopical and microcosmic fracture morphology analysis, etc. The results show that the surface oxidated layer and microcracks at the round comer of the neck of the crankshaft are the main reasons, the formation of the crack source induced by the quench microstructure defect has certain influence too on the early fracture mechanisms of the crankshaft. The fracture mechanisms are cleavage fracture and quasi-cleavage fracture, with typical characteristics of brittle fracture.