Development and application of mold flux for high-speed continuous casting of high-carbon steel billets

High-carbon steel billets (> 0.6% C) face challenges in achieving high production efficiency due to the limitations imposed by low casting speeds compared to low- and medium-carbon steels. To address this issue and enable high-speed continuous casting (3.0-3.5 m/min) of high-carbon steel billets with dimensions of 160 mm x 160 mm, an integrated research approach focusing on the development and application of mold flux was undertaken. A theoretical analysis of the solidification characteristics of high-carbon steel was proposed, identifying the specific property requirements for mold flux at elevated casting speeds. Following this, a machine learning algorithm-based prediction software, ((c))IMoldFlux, was developed to predict viscosity and melting temperature of mold flux. This software was used in conjunction with the single high-temperature thermocouple technique for crystallization test to facilitate the chemical design of the mold flux. Concurrently, the effects of various carbonaceous materials and their blend ratios on the melting rate and sintering performance of the mold flux were examined to achieve optimal carbon matching. Ultimately, the developed mold flux was successfully applied in the continuous casting of high-carbon steel billets (similar to 0.7% C) with dimensions of 160 mm x 160 mm at a speed of 3.2 m/min. This application resulted in the elimination of deep and irregular oscillation marks as well as longitudinal cracks, leading to a significant improvement in surface quality of high-carbon steel billets.