基于材料计算下淬火配分钢的贝氏体设计

Bainite design in quenching and partitioning steel based on numerical calculation

将材料热、动力学与中试试验相结合,针对商用淬火配分(Q&P,Quenching and Partitioning)钢的贝氏体进行优化设计。基于试验膨胀数据建立Bohemen切变模型,充分考虑淬火配分工艺下过时效等温阶段的组织演变复杂性,特别是回火阶段马氏体中碳化物析出特性以及对膨胀结果的影响,通过合理化数据对Bohemen模型进行修订,建立等温贝氏体相变动力学模型,实现贝氏体相变的精准预测。结合修订的Bohemen模型计算结果分析淬火配分钢中贝氏体/马氏体交互作用对残余奥氏体保留及稳定性的影响。结果显示,低淬火温度下马氏体板条间的残余奥氏体含量高,占据变形过程中的主导地位;反之,高淬火温度下贝氏体中的残余奥氏体含量高。由此形成基于材料计算下淬火配分钢的贝氏体优化设计。

In this study,an optimum design of bainite phase in the commercial quenching and partitioning(Q&P)steel was achieved through the combined results from thermodynamics,kinetics analysis and the pilot experiments.Considering the complex microstructure evolution during partitioning stage of the Q&P treatment,especially the precipitation characteristics of carbides in martensite and their influence on the expansion result,the Boheman model was established and further revised based on the result of expansion experiment.A kinetic model of isothermal bainitic transformation was also set up to simulate this transformation accurately.According to the predicated result from the revised Bohemen model,the effect of the interaction between bainite and martensite on volume fraction and stability of retained austenite was analyzed.The results show that at a low quenching temperature,retained austenite between martensitic laths has a higher volume fraction and plays a dominant role during the deformation.On the contrary,under high temperature quenching condition the volume fraction of retained austenite in bainite is high.