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为提高曲轴铸件的综合力学性能,通过连续步进式加热方式对铸态球铁曲轴进行部分奥氏体化正火处理,在球铁基体内获得以珠光体为基体、石墨球周边呈分散状破碎铁素体的组织。研究了正火处理工艺参数对基体中铁素体的形貌、含量及铸件力学性能的影响,发现正火温度对铁素体的含量和破碎状态有显著影响,随铁素体含量的增加,试样的抗拉强度下降,韧性、塑性提高,而且铁素体含量对铸件显微组织形貌有明显影响。实验结果表明,该球铁曲轴的优化热处理工艺为:820℃正火保温65min。在此工艺条件下可以得到破碎铁素体球铁组织,该组织具有较好的综合力学性能。
In order to improve the mechanical properties of crankshaft castings, the as-cast ductile iron crankshafts were partially austenitized and normalized by continuous stepwise heating. The pearlite matrix was obtained in the ductile iron matrix, Crushed ferrite organization. The effect of normalizing treatment parameters on the morphology and content of ferrite in the matrix and the mechanical properties of the casting were studied. It was found that the normalizing temperature had a significant effect on the ferrite content and the fracture state. With the increase of ferrite content, Decreased tensile strength, toughness, plasticity increased, and the ferrite content on the microstructure of castings have a significant effect. The experimental results show that the optimized heat treatment process of the ductile iron crankshaft is: normalizing at 820 ℃ for 65min. In this process conditions can be crushed ferrite ductile iron, the organization has good mechanical properties.