Analysis of Thermal and Mechanical Behavior of Copper Molds during Continuous Casting of Steel Slabs

Three-dimensional finite-element thermal-stress models are applied to predict temperature, distortion and residual stress in a continuous casting mold for steel slabs. The model predictions of temperature, distortion during operation, and residual distorted mold shape match plant observations. During operation, the copper faces bend towards the steel, with a maximum outward distortion on the order of 1mm, found just above the center of the wide faces. Distortion during operation increases with increasing mold temperature, increasing strand width, and decreasing water jacket rigidity. Mold clamping forces, bolt prestress, friction, and ferrostatic pressure have little effect on this behavior. Constraint generated by the temperature gradients and the sides of the bolt holes in the steel water jackets generate stresses and creep in the copper hot face during operation. This leads to permanent distortion and residual stress after cooling to ambient. Residual stress and distortion increase with repeated thermal cycling over a campaign, higher temperatures, smaller water-jacket bolt holes, non-uniform water slot depth, and higher clamping forces. Increased residual distortion requires increased remachining, which reduces mold life. Increased residual stress increases the probability of a catastrophic crack failure. 1