大锻件用25Cr2Ni4MoV钢镦粗与拔长工艺分析

Analysis on upsetting and stretching process of 25Cr2Ni4MoV steel for heavy forgings

以25Cr2Ni4MoV钢大锻件的镦粗与拔长过程为研究对象,采用圆柱体单轴压缩试验得到了材料的真实应力-真实应变曲线,构建了材料的高温流变应力模型和加工图,并基于弹塑性有限元法建立了用于镦粗与拔长过程分析的有限元模型。通过对镦粗和拔长过程的数值仿真分析,获取了不同工艺条件下锻件内部典型节点的温度、应变和应变速率的工艺参数变化,确定了典型节点在加工图中的工艺参数位置,分析了镦粗和拔长过程的工艺稳定性,确定了合理的开坯锻造工艺。结果表明,镦粗过程采用1200℃的初始温度、50 mm·s^(-1)的压下速率,拔长过程采用方案2(3道次拔长+摔圆)有利于改善工件变形后的温度和变形均匀性,获得更大的耗散值,进而改善锻件组织,使材料表现出较好的塑性加工能力。

The upsetting and stretching processes of 25Cr2Ni4MoV steel for heavy forgings were taken as the research object,and the true stress-true strain curves of the material were obtained by cylindrical uniaxial compression tests.The flow stress model at high temperature and the processing map(PM)of the material were established,and the finite element models for upsetting and stretching processes analysis were established based on the elastic-plastic finite element method(FEM).Through the numerical simulation analysis of upsetting and stretching process,the variations of temperature,strain and strain rate of the inner typical nodes of forgings under different process conditions were obtained,the positions associated with the process parameters of the typical nodes in the PM were determined,the process stability during upsetting and stretching processes was analyzed and the reasonable cogging forging process was determined.The results show that the initial temperature of 1200℃,compression rate of 50 mm·s^(-1) in the upsetting process,and the scheme 2(three stretching+rolling)in the stretching process are good for improving the temperature and deformation uniformity of the workpiece after deformation and getting a higher dissipative value to improve microstructure of forging,which makes the material show better plastic processing performance.