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用化学成分分析、金相检测、力学性能试验等方法对发生早期脆断的QT600-3曲轴进行分析。结果表明,脆断的原因主要是球铁的含磷量过高,使基体中磷共晶数量增加且沿晶界呈网状分布,造成曲轴伸长率和韧性的下降。对高磷球铁曲轴采用快速不平衡正火工艺,可获得含有破碎铁素体的金相组织,并能够减少磷共晶数量,促进伸长率和韧性的提高,最终较好地解决高磷球铁曲轴的脆断问题。
The chemical composition analysis, metallographic examination and mechanical property test were used to analyze the early brittle fracture QT600-3 crankshaft. The results show that the main reason of brittle fracture is that the content of phosphorus in the ductile iron is too high, which increases the amount of phosphorus eutectic in the matrix and distributes along the grain boundaries, resulting in the decrease of the elongation and toughness of the crankshaft. The high-phosphorus ductile iron crankshaft with a rapid unbalanced normalizing process can be obtained with crushed ferrite microstructure, and can reduce the amount of phosphorus eutectic and promote the elongation and toughness to improve, and ultimately solve the problem of high phosphorus Ductile iron crankshaft brittle fracture problem.