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, the intermediate cracks were easily caused by excessive deformation. In this work, a three-dimensional thermal-mechanical coupling model of 160 mm square continuous casting billet for 0.87% carbon steel was established, which also considered the effect of thermal contraction of the billet. Based on hot tensile tests, the temperature range of intermediate crack sensitivity zone for 0.87% carbon steel was determined, and a critical strain criterion of the intermediate cracks under different temperatures and strain rates was derived. Combining the critical strain criterion and the thermo-mechanical coupling model, the initiation of intermediate cracks was predicted with different reduction schemes. The results show that the theoretical maximum reduction amount of 160mm square 0.87% carbon steel billets is 2.5 mm for the billet centerline solid fraction (fs) 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 (fs=1.0), the billet centerline temperature is outside the crack sensitive temperature range, and the intermediate crack would not be caused with large reduction amount.