大钢锭凝固界面换热系数的数值模拟

基于热-黏弹塑性本构方程建立了大钢锭凝固时热-流-力耦合的3D有限元模型,并对8.5t钢锭浇注过程中不同位置处热流密度、气隙宽度和界面换热系数的变化规律进行了模拟分析。结果表明,钢水与钢锭模刚刚接触时的热流密度和换热系数最大,二者随后迅速下降,且角部区域的下降趋势略大于面部。凝固初期时热流密度和换热系数的最大值位置并非位于面部中心,而是在1/4宽度处;由于宽面对钢水静压力的抵抗作用小于窄面,其界面热流密度和换热系数也略大于窄面。凝固中后期时,换热系数的区域差异逐渐趋于不明显。同时,建立了基于凝固时间和界面温度的平均换热系数的反算模型。应用2个模型所求结果计算的钢锭和钢锭模温度变化与实测值及热-流-力耦合模型结果基本一致。进一步研究发现,界面换热系数随温度的变化规律可推广应用到3~30t钢锭的模拟研究中,计算结果与实际更为符合。

Numerical Analysis of Interfacial Heat Transfer Coefficient During Large Steel Ingot Solidification

A 3D FEM solidification model with heat, flow and stress coupled calculation during large steel ingot casting was developed based on viscoelastic-plastic constitutive equations. The heat flux, gap width and interfacial heat transfer coefficient variation as functions of solidification time and location of 8. 5t steel ingot were studied. The results show that the heat flux and heat transfer coefficient decrease dramatically at the very beginning. And those at the corner are the most serious. At the early stage, the heat flux and interfacial heat transfer coefficient on the wide face are both larger than that at the narrow face. However, this difference is observed to be much smaller at the middle and final stage. An inverse calculation model of interfacial heat transfer coefficient against solidification time and temperature has been built up. The simulation temperatures of ingot and mould are very close to the measured and the coupled model′s. The heat transfer coefficient as a function of temperature can be extended to simulate steel ingot solidification with a weight range from 3 to 30t. The solidification time and temperature variation are more coherent with the practical.