带钢超快速冷却条件下的换热过程

 分析了轧后加速冷却过程中带钢表面的局部换热机理，认为冷却系统实现超快速冷却的关键在于扩大带钢表面射流冲击换热区的面积。确定了薄带钢实现超快速冷却所需的对流换热系数，并采用有限元分析工具ANSYS模拟得到了超快速冷却条件下不同厚度带钢的温度场。温度场的分布表明薄带钢在超快速冷却过程中具有较好的温度一致性。同时还表明随着带钢厚度增加，超快速冷却条件下厚度方向的温度梯度显著增大，对于带钢内部组织的均匀性将产生不利的影响。带钢厚度范围应是超快速冷却技术实际应用过程中的重要考虑因素。

Heat Transfer Process of Hot Strip Under Ultra-Fast Cooling Condition

The local heat transfer mechanism of the hot strip during accelerated cooling after rolling was analysed. The key to the ultra fast cooling system is to expand the water jet impingement zone of the hot strip surfaces. The surface convective heat transfer coefficient which allows the cooling rate to increase up to 300 ℃/s on thin hot strip surface was given by modeling the water cooling, and the temperature field under ultra fast cooling (UFC) condition was simulated by ANSYS FEM software. From the temperature field, the thin strip under UFC condition has the better cooling uniformity compared with the thicker strip. With increasing the thickness, the temperature gradient in thickness direction is larger for the same cooling intensity, which would affect the uniformity of the microstructure in strip. So, the strip thickness would be a great important factor for the application of the UFC.