The continuous casting process of steels is mainly influenced by the infiltration of mould slag into thegap between the strand and the mould and the temperaturedependent solidification behaviour ofthe slag. Thus, measurements of the temperaturedependent viscosity and the determination of the break temperature, TBr, which is related to the formation of the first solids in the liquid slag, based on the recorded viscosity data are essential to characterizing mould slags. To enable automatic, person-independent data analysis method, a procedure must be developed that calculates TBr based on the log η versus 1/T representation. This aim was achieved by detecting the maximum absolute value of the second derivative of log η after regression and relating the associated
temperature to TBr; comparisons between these values and the manually determined values showed good agreement. Furthermore, the error was assessed by statistical analysis and the effect of sampling frequency was analysed.