METHOD ACHIEVING COOLING UNIFORMITY AND OPTIMAL PLATE-CURVATURE DURING ULTRA-FAST COOLING IN A HSM

Abstract

The flow field in the top and bottom surface of the hot rolled strip is different during cooling process with effect of gravity. Then it can affect the strip cooling uniformity of the top and bottom surface, and the plate curvature problems may be appeared. The finite element method was taken to study the plate curvature affecting law and a conclusion was obtained: the uniformity of the heat transfer coefficient in the top and bottom surface was the key to keep plate curvature well after rolling. The finite volume method was taken to calculate the heat transfer coefficient during run-out table laminar cooling (LC) and ultra-fast cooling (UFC) with different top nozzle fluxes and water flux ratios. The heat transfer coefficient and its distribution with different cooling methods and process parameters were obtained, and some conclusions were obtained by analysis: the bottom and top surface heat transfer coefficient can be kept nearly the same by adjusting water flux ratio between the bottom nozzle and top nozzle. The optimal water flux ratios of laminar cooling were 1.20 and 1.15 when top nozzle fluxes were 100m3/h and 120m3/h respectively. The optimal water flux ratios of ultra fast cooling were 1.08, 1.10, 1.15, 1.20 and 1.20 when top nozzle fluxes were 80m3/h, 100m3/h, 120m3/h, 140m3/h and 160m3/h respectively. The obtained results and water flux ratio calculating model were used in several strip cooling lines of the hot strip mill lines and obtained favorable effect.