大口径阀门阀体多向模锻成形的模具优化设计

Optimal design of a multi-ram forging mold for large-diameter valve bodies

多向模锻是现阶段大口径阀门阀体生产工艺。多向模锻冲头存在过早断裂以及表面压溃变形等问题,冲头使用寿命较短。锻件金属流动的不均匀性是导致冲头受力偏载发生断裂的首要原因,冲头材料热强性较低导致表面发生压溃变形。该文通过优化模具设计改善锻件金属流动趋势,改变冲头与压机的连接方式以减少冲头根部应力集中,采用FGH96高温合金作为锻压冲头材料,提高冲头的高温变形抗力。工艺分析及实验表明:优化模具圆角,水平冲头表面采用光滑化设计,可有效降低冲头连接部位应力集中水平,防止冲头在生产中发生断裂;采用FGH96材料制造的水平冲头在连续生产时,冲头应力水平低于屈服强度,冲头未发生压溃现象。所设计的锻压3吋(7.62cm)旋塞阀用压机水平冲头,经现场实验,其冲压次数达到100件,未发生断裂及表面压溃,冲头的使用寿命有较大幅度延长。

Multi-ram forging is the main production process for large-diameter valves.However,premature cracking at the root of the punch and plastic deformation at the top of the punch are the main problems in the forging process with the punches often having short service lives. This study analyzes the forging process,especially the irregular metal flow that creates offset loading forces on the punch,which leads to punch failures.The low thermal resistance causes the plastic deformation at the top of the punch.This analysis optimizes the metal flow during the forging through die optimization to reduce the stress concentrations at the punch root by changing the joint between the punch and the press.The FGH96 super alloy is used to improve the deformation resistance at high temperatures.Optimization of the fillet radius in the mold and smoothing of the punch surface reduce the stress concentration at the joint to effectively reduce cracking.The stresses at the top of the punch are below the yield strength with the FGH96 super alloy so plastic deformation does not occur at the top of the punch.A horizontal punch made to forge a 3inch（7.62cm）valve body works very well with no cracks or deformation at the punch top for 100 cycles.The punch service life is then much longer.