Formation Mechanism and Control Strategy of Transverse Corner Cracks in Continuous Casting of 55SiCr Spring Steel

Abstract

An experimental study is conducted to reveal the formation mechanism of transverse corner cracks by analyzing the metallurgical structure, crack morphology, and hot ductility. The results reveal that the corner temperature of the billet tends to be lower during mold solidification, leading to the formation of grain boundary low‐plasticity ferrite. Additionally, during the straightening process, the corner temperature of the billet falls into the serious low‐temperature brittle zone with temperature lower than 850 °C. These two factors contribute to the formation and propagation of cracks along the grain boundary ferrite under straightening forces. Therefore, after the verification of mold simulation test and industrial trial, the temperature at billet (section size 150 × 150 mm2) corner is improved by increasing the mold chamfer radius from 6 to 12 mm. This adjustment ensures that the straightening temperature at billet corner elevated from 830 to 880 °C, remaining outside the serious low‐temperature brittle zone, and the maximum depth of corner cracks decreases from 741.49 to 344.89 μm.