Prediction of intermediate crack risk in billet continuous casting process with solidification end reduction

During the solidification end-reduction process of the billet continuous casting process, intermediate cracks are easily caused by excessive deformation. In this study, a three-dimensional thermal-mechanical coupling model of a 160-mm square continuous casting billet for 0.87wt% carbon steel was established, considering the effect of thermal contraction of the billet. Based on hot tensile tests, the temperature range of the intermediate crack sensitivity zone for 0.87wt% carbon steel was determined, and a critical strain criterion for intermediate cracks under different temperatures and strain rates was derived. By combining the critical strain criterion and the thermomechanical coupling model, the initiation of intermediate cracks was predicted using different reduction schemes. The results show that the theoretical maximum reduction amount of 160 mm square 0.87wt% carbon steel billets is 2.5 mm for the billet centerline solid fraction (f_s) no more than 0.537, 3.5 mm for that of 0.604, 4.8 mm for that of 0.719, and 6.7 mm for that of 0.812. After complete solidification (f_s = 1.0), the billet centerline temperature was outside the crack-sensitive temperature range, and a large reduction did not cause the intermediate crack.