热轧带钢超快速冷却过程的换热分析

采用有限差分数值计算方法,确定了热轧带钢实现超快速冷却的综合对流换热系数范围,对于厚度为3~4 mm的带钢,实现300~400℃/s超快速冷却速率所需的带钢表面对流换热范围约为(4~8)kW/(m2.K).分析了水冷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.温度场的计算分析表明,与层流冷却相比,超快速冷却条件下厚度方向的温度梯度显著增大,有必要在超快速冷却技术的实际应用中考虑厚度方向温度梯度的影响.

Heat Transfer of Hot Strip During Ultra Fast Cooling

Using the finite difference method, the range of average heat transfer coefficient of overall convection during ultra fast cooling (UFC) is given. For the 3-4 mm thick steel strip, the range is around (4-8) kW/(m²·K) if the range of ultra fast cooling rate is 300-400°C/s. The local heat transfer mechanism on the surface of hot strip during water cooling is analysed, and it is deemed that the key to the implementation of ultra fast cooling by the cooling system is to extend the strip surface area where the water jet showers on for heat transfer. Compared with the laminar cooling, the calculation of temperature field shows that the temperature gradient in strip thickness increases so sharply that it should be taken into account in practical application of UFC system.