Study On The Inverse Calculation Of Heat-Transfer Coefficients Of Secondary Cooling Zone During Heavy Plate Continuous Casting Process

The heat transfer coefficients of secondary cooling is the one of most important parameter in slab continuous casting process, and it effect on the accuracy of solidification calculation of slab significantly. In this paper, based on the specific equipment parameters of 220mm×1800mm wide and thick slab continuous casting machine, a heat transfer model was developed to inversely calculate the heat transfer coefficients of secondary cooling in slab continuous casting process, and in order to improve the accuracy of model results, the boundary conditions were derived from the real measured water flux distributions. The effects of casting speed, super heat and water flow rate on the heat transfer coefficients were investigated, and the major conclusions are summarized as follows:(1) A nozzle characteristic test in secondary cooling zone is established to optimize the nozzles arrangement and the parameters of the water flux distribution and spray angle were measured and compared. The heat transfer boundary conditions of secondary cooling zones were derived from the water flux distribution on the slab broad surface.(2) A two-dimensional heat transfer model and an inverse calculation model of heat transfer coefficients of the secondary cooling were developed. A solidification and heat transfer model, which calculates the temperature distribution of the whole strand, was constructed by the methods of tracking element on the basis of the finite element software ANSYS. Based on the solidification and heat transfer model and the measured surface temperature, an inverse calculation model which gives the heat transfer coefficients of different secondary cooling zones was established as well.(3) The effect of casting speed, super heat and water flow rate on the heat transfer coefficients in the secondary cooling process was analyzed. The heat transfer coefficients decrease gradually with the increasing surface temperature of the slab. Compared with the effect of casting speed and super heat, the effect of water flow rate on the heat transfer coefficients is more significant. The heat transfer coefficients increase dramatically as the spray water density increases. The following fitting expressions are obtained between the heat transfer coefficients h (W/m2·℃) and the water flow rate w (L/m2·min).ZONE2:h= 300.976W1.000777 (R=0.99997)zONE3:h= 271.135w1.00049(R=0.99968)ZONE4:h= 223.385W1.000476 (R=0.99977)ZONE5:h= 221.295w1.00636 (R=0.99966)ZONE6:h= 172.319W1.01799 (R=0.99965)ZONE7:h= 94.183w1.08156 (R=0.99946)(4) The inverse calculation model was verified through the pin-shooting experiments. It proved the inverse calculation model has a high accuracy.