超大锻件淬火中加热——保温工艺的优化

Discussion of Heating and Holding Process Optimization for Oversized Forgings

针对超大型锻件最终调质热处理中的加热-保温过程建立起轴对称非稳态数值计算模型,用以预测加热-保温过程中锻件温度场的分布规律。将所得模拟结果与实验数据相比较,发现对于截面直径超过一定值的锻件来说,为使锻件心部达到奥氏体化温度而采取的加热及保温措施将会导致锻件表层一定深度范围内的组织因在Ac1温度以上环境中停留过久,造成奥氏体晶粒的过度长大。因此,在制定生产工艺时需要将锻件的热处理要求和锻件材料的奥氏体组织形成动力学曲线结合起来,以便能够制订出较为合理的加热-保温工艺制度。

An axial symmetry unsteady state numerical calculation model is established, which is used for the final quenching and tempering heat treatment of oversized forgings during heating and holding process. Its purpose is to predict temperature field distribution of forgings during heating and holding process. Comparing simulation results and experiment data, we can find that when the section diameter of forgings exceeds a certain value, the holding duration above the Acl temperature is too long for a certain depth of oversized forging in order to assure its core part to reach austenization temperature, which may cause the austenite grain excessive growth. Hence, the heat treatment requirement and forging forming kinetics curve of austenite structure should be combined when prepare production process, so that a reasonable heating-holding process can be established.