Formation Mechanism and Main Control Methods of Bright-Band Defects in Strip Casting Based on Numerical Simulation

Abstract

Bright-band defects frequently occur on as-cast strips in the twin-roll strip-casting process, particularly at low-casting speeds, with intervals of ≈200 mm. Additionally, the cast-rolling force also exhibits minor fluctuations. With increasing casting speeds, the spacing between bright-band defects widens, and the severity of these defects diminishes. When the casting speed reaches a certain threshold, defects almost entirely disappear. Detailed analysis of the underlying causes of this phenomenon is essential for effectively preventing defect formation. In this study, the numerical simulation method is employed to analyze casting rolls’ thermal deformation and the melt pool's solidification behavior, based on the production site equipment and process conditions. The causes of defects in as-cast strips are thoroughly analyzed based on simulation results, in conjunction with variations in the cast-rolling force. In this study, it is demonstrated that the thermal deformation of casting rolls and the position of the solidification endpoints collectively contribute to the fluctuations in cast-rolling force and are the primary causes of bright-band defects. Fundamental principles for preventing defects are provided based on actual on-site production. Furthermore, simulation results contribute to establishing a theoretical basis for selecting process parameters and controlling cast-rolling force during production.