不同温度正火处理对ZG20CrMnSiNi2Mo组织和性能的影响

Effects of Different Temperature Normalizing on the Microstructure and Properties of ZG20CrMnSiNi2Mo

控制臂是汽车悬架系统中传力和导向的重要机构,其制造材料的机械性能直接影响着悬架性能.根据某特种车辆的悬架控制臂的性能设计要求和实际工况分析,研制了一种新型低合金铸钢ZG20CrMnSiNi2Mo.通过金相分析、XRD物相分析、扫描电镜分析和力学性能检测研究了不同温度正火热处理对ZG20CrMnSiNi2Mo组织和性能的影响,分析了不同温度正火热处理后,ZG20CrMnSiNi2Mo组织和性能变化的原因.结果表明:不同温度正火处理后ZG20CrMnSiNi2Mo的组织均为粒状贝氏体组织,960℃以下正火热处理后的组织主要是块型粒状贝氏体组织,960℃处理后的组织是块型+条型粒状贝氏体组织,正火温度超过960℃,组织主要呈条型粒状贝氏体组织;随着正火温度升高,组织中的M-A岛由以块型居多逐步转变为以条状居多,M-A岛尺寸变细小,分布更加均匀.ZG20CrMnSiNi2Mo的硬度值随正火温度的提高先增加后减小,920℃时达到最大值42.0 HRC,冲击韧度随正火温度的升高而增大,超过920℃,冲击韧度随正火温度的增加快速增大,1040℃正火处理后的冲击韧度为49 J.延伸率随着正火温度的升高呈增大的趋势,变化范围为10.5%~13.7%.960~1 000℃正火处理后,实验材料的各项性能满足某型号特种车辆悬架控制臂的性能设计要求.

Control arms are an important mechanism for force transfer and guidance in the automobile suspension system. The mechanical properties of the materials for control arms directly affect the suspension performance. A new type of low alloy cast steel ZG20CrMnSiNi2Mo was developed according to the design requirements and the actual working conditions of a special vehicle suspension control arm. The effects of normalizing at different temperatures on the microstructure and properties of ZG20CrMnSiNi2Mo were studied through metallographic analysis,XRD phase analysis,SEM analysis and mechanical property test. The results are as follows. The microstructure of ZG20CrMnSiNi2Mo is granular bainite after normalization at different temperatures. The microstructure is mainly block granular bainite after normalization at below 960 ℃,is block and strip granular bainite at 960 ℃,and is mainly strip granular bainite at above 960 ℃. With the normalizing temperature increasing,the M-A islands in the microstructure change gradually from block type to strip type,become smaller and distribute more uniformly. With the normalizing temperature increasing,the hardness of ZG20CrMnSiNi2Mo increases first and then decreases,and finally reaches the maximum of 42 HRC at 920 ℃.The impact toughness increases as the normalizing temperature increases,increases quickly when it exceeds 920℃,and reaches the maximum value of 49 J at 1040 ℃. The elongation rate increases with the normalizing temperature,ranging from 10. 5% to 13. 7%. The properties of ZG20CrMnSiNi2Mo meet the design requirements of the special vehicle＇s suspension control arms after normalization at from 960 ℃ to 1000 ℃. And finally the reasons for the changes of microstructure and properties were analyzed.