大型轴类锻件典型锻造工艺微观组织模拟

Microstructure simulation of typical forging process for large shaft forgings

大型锻件自由锻过程的道次多、流程长,无法通过实验验证锻造过程中再结晶程度及晶粒尺寸的变化。建立了40Mn钢动态再结晶模型,并通过Gleeble热压缩实验进行了验证,然后,采用该动态再结晶模型对典型锻造工艺的镦粗和拔长进行模拟。结果表明:第2道次拔长后,锻坯大部分区域发生了完全动态再结晶,继续变形,则动态再结晶循环进行。变形后,锻坯中心区域的平均晶粒尺寸为117μm左右;从中心向外,平均晶粒尺寸逐渐减小,表层平均晶粒尺寸为50μm左右。靠近钳口位置的平均晶粒尺寸急剧变化,容易出现混晶现象;锻坯水口方向靠近表面,温度低,晶粒来不及长大,即开始进行下一轮动态再结晶,平均晶粒尺寸为33μm左右。

The free forging process of large forgings has many passes and long production process, and it is impossible to verify the changes in the degree of recrystallization and grain sizes during the forging process through experiments. The 40 Mn steel dynamic recrystallization model was established and verified by Gleeble thermal compression experiment. Then, the dynamic recrystallization model was used to simulate the upsetting and stretching of the typical forging process. The results show that after the second pass during stretching, most areas of forging billet occurred complete dynamic recrystallization, and the dynamic recrystallization cycle proceeds as the deformation continuous. After deformation, the average grain size in the center area of forging billet is about 117 μm, and the average grain size gradually decreases from the center to the outside. The average grain size of surface layer is about 50 μm. The average grain size changes sharply near the jaws, and the phenomenon of mixed crystal is easy to appear. The temperature near the surface of forging billet is low along the direction of nozzle, so the next round of dynamic recrystallization begins before the grains have time to grow up, so the average grain size is about 33 μm.