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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。
The transient distribution of temperature during quenching and cooling of the bending die strip plays an important role in studying the deformation mechanism of 6CrW2Si steel after quenching. Considering the influence of thermophysical parameters, convection heat transfer and other factors on the temperature, the quantitative analysis of latent heat conversion from phase change to equivalent specific heat was deduced and written into the program. The nonlinear transient mathematical model of the three-dimensional temperature field in quenching process was established. The microstructure of 6CrW2Si steel was studied by metallographic observation, XRD phase analysis and microhardness test. The results show that the two factors of surface heat transfer and heat conduction alternately play a leading role in the cooling rate of the parts at different time. The latent heat released by martensite transformation at 65 s causes the cooling rate to decrease significantly. The temperature field of the cross section of the cross section of the strip is gradient distributed from the junction of the two surfaces to the heart; the part only undergoes martensitic transformation and is hardened thoroughly, and the finally obtained microstructure is martensite + residual Austenitic + carbide.