6CrW2Si钢制镶条淬火过程温度场数值模拟及试验

FEM simulation of temperature field and experimentation of 6CrW2Si steel inlaid strip during quenching process

折弯模镶条淬火冷却时温度的瞬态分布特性对于研究6CrW2Si钢淬后变形机理有重要作用。考虑热物性参数、对流换热等因素随温度变化的影响,推导相变潜热转换为等效比热的定量解析并写入程序,建立了淬火过程三维温度场的非线性瞬态数学模型。通过金相观察、XRD物相分析和显微硬度测试方法对6CrW2Si钢镶条组织成分进行了试验研究。结果表明:表面换热边界条件和热传导两因素在不同时刻对零件的冷却速度交替起主导作用;65 s左右时马氏体转变所释放的潜热使得冷却速度有较大幅度降低,心部较表面所受影响大;冷却过程中镶条横截面的温度场由两表面交接处至心部呈梯度分布;零件只发生马氏体转变,且被淬透,最终得到的组织为马氏体+残留奥氏体+碳化物。

In order to study the distortion mechanism of a 6CrW2Si steel part of inlaid strip after quenching process, it is imperative to master the transient temperature distribution of the inlaid strip during quenching. The quantitative relationship between transformation latent heat and equivalent specific heat was deduced, and a nonlinear transient mathematical model of three-dimensional temperature field was established. Micro structure and phases of the 6CrW2Si steel inlaid strip were studied by means of metallographie observation, XRD phase analysis and micro-hardness testing. The results show that boundary conditions of the surface heat transfer and thermal conductivity are dominant alternately in the cooling rate of the part in different time. Latent heat releasing in the process of martensitic transformation makes the cooling rate a significant reduction, and the center is influenced more seriously than the surface. The temperature field of cross- section of the part presents gradient distribution. Only martensite transformation occurs and the part is fully hardened during quenching. The final microstructure of the quenched 6CrW2Si steel inlaid strip is composed of martensite, retained austenite and carbide.