Thermo-mechanical analysis of a copper mould for continuous casting of steel

This work deals with the thermo-mechanical analysis of a copper mould, which is a component that controls initial solidification in continuous steel casting. Large temperature gradients, caused by a huge thermal flux imposed by steel, are responsible for high stresses and plastic strains. Plant switch-off also induces residual stresses which may increase with repeated thermal cycling over a casting sequence. Furthermore, oscillations of the melt metal level determine a fluctuation of the temperature peak on the surface of the mould. As a result, thermal fatigue cracks tend to develop on the mould inner surface, especially for increased productivity rates characterized by higher casting speed and thermal flux. This work aims to study the mechanical behaviour of the mould and to propose a simplified approach to relate stress-strain cycles to the component fatigue life. A thermo-mechanical analysis is performed by a finite element elasto-plastic model, supported by simplified analytical models useful to interpret results. Experimental static strength data are used to calibrate the elasto-plastic material model in FE simulations, as well as to estimate the strain based fatigue curve with the so-called Universal Slopes Equation. The component service life is finally estimated as the number of either fatigue cycles or casting sequences.