基于多尺度建模与响应面法的55NiCrMoV7模具钢调质热处理工艺优化

Optimization of Quenching and Tempering Heat Treatment Process for 55NiCrMoV7 Die Steel Based on Multi-Scale Modeling and Response Surface Methodology

目的探究大型55NiCrMoV7模具钢锻件(Φ1000 mm×1700 mm)调质热处理的最优工艺方案。方法建立大型55NiCrMoV7模具钢锻件的宏微观耦合的多尺度有限元模型,基于现场实验测试不同位置温度场和组织场的演化规律验证该模型。模拟研究此锻件在不同淬火与回火工艺下的应力分布、HRC硬度和屈服强度变化。以残余应力均方差、硬度和屈服强度为目标函数,建立淬、回火工艺参数与力学性能之间的回归模型。结合所建立的响应面模型分析与遗传算法,对该模型进行参量约束条件下的多目标优化。结果通过响应面模型分析得出最优工艺范围为:淬火温度为850~910℃,回火温度为400~550℃。多目标优化后得到Pareto最优解集:淬火907.4℃+回火443.1℃、淬火907.4℃+回火411.5℃、淬火903.4℃+回火485.1℃、淬火895.2℃+回火535.8℃和淬火892.1℃+回火507.1℃。结论建立的淬、回火温度对应力均方差、HRC硬度和屈服强度的回归模型,为大型55NiCrMoV7模具钢锻件调质热处理工艺优化提供了理论依据。

The work aims to investigate the optimal process scheme of quenching and tempering heat treatment of large 55NiCrMoV7 die steel forgings(Φ1000 mm × 1700 mm). A multi-scale finite element model of macro-micro coupling for 55NiCrMoV7 die steel forgings was established to test the temperature field and microstructure field evolution at different locations based on field experiments and then the model was verified. The stress distribution, HRC hardness and yield strength of the forgings were simulated under different quenching and tempering processes. The regression model between the parameters of quenching and tempering and mechanical properties was established with the mean square error of residual stress, hardness and yield strength as the objective function. Combined with the response surface model analysis and genetic algorithm, the multi-objective optimization of the model under parameter constraints was carried out. According to the analysis of response surface model, the optimal process range was as follows: quenching temperature of 850~910 ℃, tempering temperature of 400~550 ℃. After multi-objective optimization, the optimal solution set of Pareto was obtained: quenching of 907.4 ℃ + tempering of 443.1 ℃, quenching of 907.4 ℃ + tempering of 411.5 ℃, quenching of 903.4 ℃ + tempering of 485.1 ℃, quenching of 895.2 ℃ + tempering of 535.8 ℃ and quenching of 892.1 ℃ + tempering of 507.1 ℃. The established regression model of quenching and tempering temperature on stress mean square error, HRC hardness and yield strength provides a theoretical basis for the optimization of quenching and tempering heat treatment process for large 55NiCrMoV7 die steel forgings.