等温淬火温度对CADI组织及性能的影响

摘要

In this paper, the effects of austempered temperature on the morphology of bainite,contents of retained austenite, mechanical properties and wear resistance of carbide austempered ductile iron (CADI) were researched and the impact fracture mechanism was analyzed. The samples whose as-cast microstructures composed of 75％ pearlite+ferrite+10％ carbide, were .austenited at 920 ℃ for 1.5 h and then austempered at 240 ℃, 280 ℃ and 320 ℃ for 2 h, respectively.The results show that with the increase of austempered temperature the morphology of bainite changes from needle to featheriness; the residual austenite content increases; the impact toughness increases and the hardness and relative wear resistance reduces. After austempering at the optimal temperature 280 ℃, the microstructure is composed of bainite, 22.33％ retained austenite and 10％ carbide. Its hardness is HRC 50.9, impact toughness is 32.72 J/cm2, and the relative wear resistance rises by 11％ than that of the samples austempered at 320 ℃. The fracture morphology of the CADI exhibits a mixed fracture characteristic.%针对含一定碳化物等温淬火球墨铸铁(CADI),研究了等温淬火温度对贝氏体相形貌、残余奥氏体量、力学性能及耐磨性能的影响,分析了冲击断裂机理.结果表明,对于铸态组织为75%珠光体+铁素体+10%碳化物试样,经920℃×1.5 h奥氏体化后,在240℃,280℃及320℃进行等温淬火处理2h,随着等淬温度的提高,贝氏体的形貌由针状变粗至羽毛状,残余奥氏体量增加,硬度减低,冲击韧度提高,相对耐磨性降低.最佳等温淬火温度为280℃,此热处理工艺后组织为贝氏体+22.33%残余奥氏体+10%碳化物,硬度HRC 50.9,冲击韧度32.72 J/c㎡,断口呈混合断裂特征,相对耐磨性比320℃时增加11%.