核电主管道锻件锻造成形均匀性模拟研究

Simulation on Forming Uniformity of Nuclear Main Pipe Forging

核电主管道是核电站关键部件之一。AP1000主管道用钢316LN无法通过热处理细化晶粒,锻造不均匀性导致的混晶最终无法消除,需要在锻造过程中保证锻件变形的均匀性。基于上平下V砧拔长时应变分布规律,通过理论分析,定量给出翻转角度与V砧角度、压下率的关系;改进'双压法'翻转工艺,并在此基础上提出'三压法'翻转工艺。数值模拟结果表明,上平下V砧翻转新工艺显著提高了锻件截面周向变形的均匀性,且越靠近外表面变形不均性的改善越明显。普通砧形翻转新工艺锻件内部存在小变形区,可以通过大圆角V砧翻转新工艺进行改善。研究结果可为主管道锻造工艺方案制定及优化提供理论参考。

Nuclear main pipe is one of key components of pressurized water reactor. The grain refinement of 316LN steel used in nuclear main pipes of AP 1000 could not be completed by heat treatment and the mixed grain caused by forging nonuniformity could not be eliminated finally. Consequently, the forging process will be the key way to solve this problem. Based on the strain distribution of upper flat and lower V-shaped anvil in the stretching process, the relationship between rotation angle, V-shaped anvil angle and reduction rate is given quantificationally after theoretical analysis. The rotation processes of＂double-press process＂ is improved and ＂three-press process＂ is brought. Numerical simulation results show that the new rotation process of upper fiat and lower V-shaped anvil improve the circumferential deformation uniformity of forgings and the effect is better while it is closer to surface. Big fillet V-shaped anvil can be used instead of general V-shaped anvil to improve the hard deformation area at the center of the forging during rotation processing. The results have theoretical referenced value to make and optimize forging process of nuclear main pipes.