2025 Chamfered Mold Slab Corner Cracks

Transverse corner cracks on the slab surface occur most frequently, especially in hypo-peritectic steel cast by vertical-bending casters, leading to increased machining costs and reheating furnace adjustments. To address this issue, POSCO developed a chamfered mold that effectively reduces transverse corner cracks at casting speeds below 1.0 m/min. However, at higher speeds, adverse side effects such as longitudinal cracks emerged on the chamfered faces. This study utilizes a multiphysics model to investigate the causes of these longitudinal cracks, revealing that they result from uneven solidification associated with excessive gap formation due to insufficient taper at the corner of the mold's top region. Consequently, a revised chamfered mold design was developed, optimizing taper on both face orientations and subsequently decreasing gap size and related defect occurrences. The new mold design is currently being implemented in specific high-speed casters that have exhibited increased cracking rates, and preliminary results demonstrate its effectiveness in mitigating transverse corner cracks without introducing longitudinal cracking or excessive mold wear.