Temperature Fields and Thermal Stress in the Solidification of Cylindrical Continuous-Cast Steel Billet

Abstract

Abstract—The influence of nonuniform boundary conditions on the cooling rate of stainless steel in continuous casting of cylindrical billet is investigated. Nonuniformity of the boundary conditions over the billet perimeter is assumed. The longitudinal cooling rate is assumed constant within the cooled sector of the billet. The presence of heat fluxes between cooling sectors is assumed. The gradients of the temperature and the thermal stress that develop in the solidifying billet are compared at different cooling rates in the secondary-cooling zone. The thermal stress is compared with the permissible value for each grade of steel, so as to determine cooling conditions corresponding to permissible thermal stress. The results indicate that the cooling rate affects the appearance of external and internal defects in the continuous-cast cylindrical billet. It is also found that the nonuniformity of the boundary conditions affects the temperature fields in the solidifying continuous-cast cylindrical billet. The results are presented in graphical form and analyzed in detail. A mathematical model is developed to calculate the temperature fields in the solidifying billet, on the basis of the nonsteady heat-conduction equation. The thermal stress is calculated by familiar methods that permit the determination of the stress that appears between cooling zones in the solidifying billet. The results may be used to develop cooling conditions that correspond to permissible thermal stress. By that means, the frequency of internal and external defects in the solidifying continuous-cast cylindrical billet may be decreased.