4Cr5MoSiV1热作模具钢锻造加热工艺的改进

Improvement for Forging and Heating Process of Hot Working Die Steel 4Cr5MoSiV1

攀长钢生产的4Cr5MoSiV1热作模具钢锻材存在超声波探伤合格率较低的问题。分析认为主要原因是沿用较低的锻前加热温度，钢锭加热程度不足造成锻造时大锻材中心没有充分锻透。笔者对4Cr5MoSiV1钢锻造加热工艺进行了递进式改进，逐步调整钢锭加热制度从1180℃最终提高到1270℃．1290℃，同时相应调整退火工艺制度，基本解决了上述问题，探伤废品大幅降低，锻造火次也明显减少，并避免高温加热引起的粗晶降低钢材使用性能，取得了显著的工艺改进效果。另外，采用高温加热也使钢中的显微偏析明显减轻，获得了部分的均匀化扩散退火的效果：一次碳化物减少，尺寸变小，没有尖锐的棱角，冲击韧性比工艺改进前有明显提高。

There is the problem of lower qualification rating in the UT of the hot working die steel 4Cr5MoSiVI forgings produced in this company. Based on the analyzing, the author of this paper considered it was the main reason that the previous lower heating temperature before the forging was used, thus the insufficient heating of the ingot caused the non - through forging in the center of large size blanks in the process. The forging and the heating processes for 4Cr5MoSiVI steel was modified incrementally, with adjusting the heating system of the ingot step by step through increasing temperature from 1180℃ to 1270℃ - 1290℃, and ad- justing correspondingly the annealing process system concurrently, in the end, the said problem was solved basically, and the notqualified products judged by UT method was decreased greatly, forgings passes was decreased obviously also, it was avoMable that the product＇ s properties would be weakened due to the coarse grain grown in the steel caused by heating at elevated temperature, the obvious improvements was obtained. In addition, the results of micro- segregation in steel weakened obviously by heating at elevated temperature, and the partly effect of homogenization diffusion annealing was obtained： primary carbides decreased, whoese size became small without sharp edge angle, therefore, the impact toughness was higher obviously than that of the previous process.