Transport of heat and material properties in continuous casting of steel

Abstract

Liquid steel solidifies within a containment of a continuous casting machine and moves in axial direction as the solidified shell is withdrawn towards the end of the machine. A mechanical model for computing the deformation of the solidifying steel in the roll containment is developed based on the beam theory and on a ferro-static pressure load. The material properties of the steel at high temperatures result from high temperature constitutive equations including creep for the solidified shell between the rolls. The temperature distribution within the solidified shell is computed based on the thermal boundary conditions as in the secondary cooling zone water is spread onto the surface of the steel shell and heat is removed. The solidified steel shell thickness increases along the machine containment up to the point of total solidification. A suitable discretization of the region by the finite beam elements is used to get a suitable mechanical model. The ferro-static pressure acts inside of the solidified shell and causes some bulging of the shell between the roll containment. As there is a slow axial motion of the solidifying shell the numerical modeling of the transport e.g. of heat and of the creep strain, which is computed in each time step, has to be as accurate as possible as a lot of time steps are necessary. Different numerical strategies have been analysed with respect to the accuracy of the computation results.