Analysis of internal crack in a six ton

Internal cracks in ingots can result in significant production losses, particularly in high-tensile steel such as P91, which is utilized extensively in power plant piping. This study aims to investigate the occurrence and characteristics of cracks in a six-ton P91 ingot. Utilizing X-ray high energy industrial CT and advanced 3D reconstruction software, we thoroughly examined the morphology of crack-like defects within the longitudinal section of the ingot. Our findings revealed five significant defects exceeding 200 mm³ in volume, of which four were interconnected. These defects were identified to initiate from the continuous liquid film present during casting, subsequently torn apart by excessive tensile stresses induced within the brittle temperature range (BTR). Moreover, we conducted a three-dimensional finite element method (FEM) analysis to simulate the thermo-mechanical phenomena associated with hot tearing. The implications of these results highlight the critical need for improved casting techniques to minimize defect formation, thereby enhancing the quality and yield of P91 steel ingots in industrial applications.