等温热处理温度对超级贝氏体组织与性能的影响

Effect of isothermal heat treatment temperature on microstructure and mechanical properties of super bainite

研究了70Si2Mn2CrMo钢经不同温度等温热处理后,产生超级贝氏体组织转变的同时,碳化物析出的情况以及对其力学性能的影响。通过对试样的显微组织和力学性能的检测分析,确定了碳化物析出的温度及类型;同时表明,由于碳化物析出减少了过冷奥氏体中C含量,致使其稳定性下降,超级贝氏体中残余奥氏体质量分数减少。与220℃等温热处理没有碳化物析出的样品相比较,245℃等温热处理样品的抗拉强度降低11%,强塑积降低16%,疲劳循环断裂次数降低55%。

In order to study the super-bainite structure transformation of 70Si2Mn2CrMo steel after isothermal heat treatment at different temperatures, the precipitation of carbide and its mechanical properties were studied. The temperature and type of carbide precipitation were determined by the analysis of the microstructure and mechanical properties of the sample. It is shown that the precipitation of carbide reduces the carbon content in the overcooling austenite,resulting in low stability of the steel and the volume fraction of retained austenite in super-bainite is reduced. Compared with the sample of no carbide precipitation at 220 ℃ isothermal heat treatment,the tensile strength of the sample steel decreased by 11%,the strong plastic product decreased by 16%,and the fatigue cycle fracture times decreased by 55%,at 245 ℃ isothermal heat treatment.