MODEL OPTIMIZATION OF CONTINUOUS-CASTING STEEL SECONDARY COOLING

An implicit enthalpy mathematical solidification model has been developed to calculate three dimensional and stationary temperature field in the strand during C.C. The heat transfer coefficient in the mould and secondary cooling zone have been deduced from experimental data. Experimental results obtained when casting high carbon bearing steel grade show that central segregation decrease as cooling intensity increases up to a given point. Beyond that point higher intensities produce a worsening of the central quality. Two parameters have been defined in order to interpret these results by using the solidification model: the time that takes the billet center to pass from liquidus to solidus, and the solid fraction when thermal stresses develop at the billet center. High cooling decreases the time interval but increases the thermal stresses. In agreement with experimental results, beyond a given intensity the latter parameter has a higher influence than the former and a central quality worsening is predicted. With the aid of the model a secondary cooling is designed in order to optimize both parameters.