球墨铸铁曲轴部分奥氏体化工艺

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65 min.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.

Incomplete austenitizing treatment of crankshaft made of ductile iron

In order to improve comprehensive mechanical properties of crankshaft made of ductile iron,as-cast crankshaft made of ductile iron was treated by incomplete austenitizing normalizing with steping normalizing fur-nace.After the treatment,there were pearlite in the matrix of ductile iron and dispersed broken ferrite near graph-ite nodule.Effects of normalizing parameters on content and morphology of broken ferrite and mechanical proper-ties of casting were researched,and the results show that normalizing temperature has a significant influence on the content and broken state of ferrite,and with the increase of ferrite content,the strength of the sample increa-ses but the toughness and plasticity decrease.And ferrite content has obvious effect on morphology of microstruc-ture of casting.The experimental results show that the crankshaft which is heated at 820 ℃ for 65 min has micro-structure of broken ferrite which has the best comprehensive mechanical properties.