The Gleeble-1500D thermal simulator was used for the isothermal compression test of 21-4N heat-resistant steel under the T range of 1273–1453 K and $\dot{\epsilon }$ of 0.01–10s^-1. Using the obtained stress - strain data, various parameters of the Fields–Backofen (F-B), the modified F–B (m–F–B) equations and the modified Zerilli–Armstrong (m–Z–A) equations were calculated respectively. The constitutive equations of 21-4N heat-resistant steel based on the F–B, the m–F–B and the m–Z–A were established. Second, the predictive ability of the three constitutive equations were evaluated using the correlation coefficient (R), average absolute relative error (AARE) and the relative error (r). Third, the established model was imported into Deform-3D to simulate the valve forging process of 21-4N heat-resistant steel, and the distribution rules of the effective stress, effective strain, temperature and damage condition of the forging were analyzed. Finally, a hot forging experiment was performed on a 160t hot die forging press. Results show that the flow stress of 21-4N heat resistant steel is affected by temperature, strain rate and strain. The m–F–B and m–Z–A models can describe the rheological behavior of 21-4N heat-resistant steel, while the original F–B model has a high predictive ability, but only under low temperature, low strain rate and small deformation. The simulation process can be completed successfully, indicating that the established models can be used for the simulation study of the thermal deformation of 21-4N heat-resistant steel and all models are correct. The results can provide some important basic data for the simulation of 21-4N heat resistant steel in the plastic deformation process.

Gleeble-1500D热仿真器用于在1273–1453 K和T范围内的21-4N耐热钢进行等温压缩试验。 $\dot{\epsilon }$的0.01–10s ^-1。使用获得的应力-应变数据，分别计算了Fields-Backofen（FB），修正的F-B（m-F-B）方程和修正的Zerilli-Armstrong（m-Z-A）方程的各种参数。建立了基于F–B，m–F–B和m–Z–A的21-4N耐热钢的本构方程。其次，使用相关系数（R），平均绝对相对误差（AARE）和相对误差（r）评估了三个本构方程的预测能力。第三，将建立的模型导入Deform-3D中，以模拟21-4N耐热钢的气门锻造过程，分析了锻件的有效应力，有效应变，温度和破坏条件的分布规律。最后，在160吨热模锻压机上进行了热锻实验。结果表明，21-4N耐热钢的流动应力受温度，应变速率和应变的影响。m–F–B和m–Z–A模型可以描述21-4N耐热钢的流变行为，而原始的F–B模型具有较高的预测能力，但仅在低温，低应变率和变形小。仿真过程可以成功完成，表明所建立的模型可用于21-4N耐热钢热变形的仿真研究，所有模型都是正确的。研究结果可为模拟21-4N耐热钢塑性变形过程提供重要的基础数据。m–F–B和m–Z–A模型可以描述21-4N耐热钢的流变行为，而原始的F–B模型具有较高的预测能力，但仅在低温，低应变率和变形小。仿真过程可以成功完成，表明所建立的模型可用于21-4N耐热钢热变形的仿真研究，所有模型都是正确的。研究结果可为模拟21-4N耐热钢塑性变形过程提供重要的基础数据。m–F–B和m–Z–A模型可以描述21-4N耐热钢的流变行为，而原始的F–B模型具有较高的预测能力，但仅在低温，低应变率和变形小。仿真过程可以成功完成，表明所建立的模型可用于21-4N耐热钢热变形的仿真研究，所有模型都是正确的。研究结果可为模拟21-4N耐热钢塑性变形过程提供重要的基础数据。表明所建立的模型可以用于21-4N耐热钢热变形的仿真研究，所有模型都是正确的。研究结果可为模拟21-4N耐热钢塑性变形过程提供重要的基础数据。表明所建立的模型可以用于21-4N耐热钢热变形的仿真研究，所有模型都是正确的。研究结果可为模拟21-4N耐热钢塑性变形过程提供重要的基础数据。