为了确定加速冷却或直接淬火时实现预期的冷却速率所需的对流换热系数,利用MSC.MARC有限元分析软件对Q345B中厚钢板冷却过程中温度场进行了数值模拟计算.确定了实现直接淬火条件下不同厚度（〉20 mm）钢板的理论极限冷却速率所需的对流换热系数为15 000 W/（m2·℃）,并分析了冷却速率与对流换热系数、钢板厚度之间关系.研究表明,对于同一厚度、材质中厚钢板,其冷却速率随对流换热系数的增加而增大.超快速冷却或直接淬火时,带钢冷却速率随对流换热系数增加而显著增加;对流换热系数大于15 000 W/（m2·℃）时,厚度（〉30 mm）钢板的冷却速率基本不变,达到其物理极限冷却速率;换热系数增加,厚度方向上温度梯度增加.
To confirm the heat transfer coefficient corresponding to cooling rates during accelerated cooling or direct quenching,the temperature field of Q345B steel plate during cooling process was simulated by MSC.MARC.When the plate thicknesses 20 mm,the heat transfer coefficient is 15 000 W/（m2·℃）,which realizes the theoretical limit cooling rate.The relationship of cooling rate,plate thickness and convection heat transfer coefficient was also analyzed.The results show that the cooling rate of the steel plate increases with the increasing of convection heat transfer coefficient for the same plate thickness.For a 3~6 mm steel strip,the cooling rate increases drastically faster with the increasing of convection heat transfer coefficient during accelerated cooling or direct quenching.Beyond the convection heat transfer coefficient of 15 000 W/（m2·℃）,the cooling rate of the steel plates（30 mm） changes slightly,which substantially equals to the physical limit cooling rate.With the increasing of convection heat transfer coefficient,the temperature gradient along the thickness direction is increased.
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