A contribution to hot tearing in the continuous casting process

The main objective of the project is the development of hot tearing criteria for the continuous casting process. Many hot tearing criteria of different materials and based on different approaches can be found in the literature. The present paper briefly summarizes the outcome of the relevant literature considering not only the phenomenon with respect to continuous casting of steel, but also hot tearing in the field of aluminium alloys. Four different hot tearing criteria based on different approaches are described in detail. Furthermore, results of the hot tearing susceptibility determined from a rigorous laboratory experiment are presented. These results served as a benchmark for a comparison of the different models and their relevance for the continuous casting process. The results of the measured HCS in the carbon range between 0.05 wt % and 0.30 wt % C are as expected. The steels with a carbon content of 0.50 wt % and 0.70 wt % show a decreasing tendency to susceptibility to hot tearing. This behavior is in contrast with the general findings from literature, which assume an increasing hot tearing formation with increasing carbon content. Although the applied models are very different, their results show a similar characteristic. Basically, the four criteria describe the hot tearing susceptibility up to a carbon content of 0.30 wt %. However, the decreasing hot tearing susceptibility above 0.30 wt % C can not be reproduced by the criteria. Therefore, the results must be improved, especially for the high C high Mn steels. Apparently, all criteria describe relevant parameters, but only the critical stress and strain criteria fulfil the demands defining a deformation limit. The latter are more easily implemented into common mechanical strand models. Finally, assuming the critical strain criterion as a basic model, the present paper points out the necessary extensions to improve the quality of the hot tearing criterion and the significance for the continuous casting process. The theory of an accumulated strain was illustrated with respect to the continuous casting process. In addition, the necessity of applying the principle of the accumulated strain to the SSCT test was demonstrated when determining critical values of hot tearing. Moreover, results for critical strain determined using the SSCT test were illustrated. These results represent a very important basis in order to improve the quality of the strain-based hot tearing criterion.