核电用钢SA508Gr.4N两段式本构模型的建立及管板终锻火次模拟

采用新一代核电材料SA508Gr. 4N钢的真应力-真应变数据,建立了该材料基于物象的温度、应变及应变速率的两段式流变应力本构模型,引入了相关系数R及平均相对误差AARE,验证本构模型的预测能力,发现相关系数和平均相对误差分别为0. 9915和5. 06%。采用该本构模型进行二次开发,基于Fortran语言编写子程序嵌入DEFORM软件,结合SA508Gr. 4N钢随温度变化的热导率及比热容等实测热物性参数,对核电关键零件管板大锻件的关键终锻火次,包括平锤头展宽、压平凸台及旋转压实3个子工艺进行了系统模拟,分析了在不同工艺参数下,热锻成形过程中的锻件温度场、应力场、等效应变场及最终成形性能,最后得到了合理的锻造工艺方案。

Establishment of two-stage constitutive model for SA508Gr.4N nuclear power steel and simulation of final forging for tube sheet

Using the real stress-real strain data of the new generation for nuclear power material SA508 Gr. 4 N steel,the two-stage flow stress constitutive model was established based on temperature,strain and strain rate of material. And the related coefficient R and the absolute average relative error AARE were introduced to verify the predictive ability of the constitutive model,which were found to be 0. 9916 and 5. 07%,respectively. Adopting the constitutive model for secondary development,subprograms based on Fortran language were written and embedded in DEFORM software. Combined with measured thermal property parameters such as thermal conductivity and specific heat capacity of SA508 Gr. 4 N steel which changed with temperature,the key final forging of heavy forgings for tube sheet of nuclear power key parts were simulated systematically,including the three sub-processes: the flat hammer head widening,the flattening boss and the rotary compaction. The temperature field,the stress field,the equivalent strain field and the final forming performance of forgings under different process parameters during the hot forging process were analyzed. Finally,a reasonable forging process schem is obtained.