Heat transfer behavior and homogenous solidification control for high-speed continuous casting slab mold

High-speed continuous casting is the theme for developing a new generation of high-efficiency continuous casting technology as well as a high-efficiency and green steelmaking production line. Presently, the actual casting speed for slabs in China is no more than 1.8 m·min⁻¹, and it is in the range of 1.2–1.4 m·min⁻¹ for continuous casting of peritectic steel. With the increase in the casting speed, the negative factors affecting the solidification in continuous casting mold become more evident, and the lubrication between mold copper plate and solidifying shell deteriorates. The friction force increases due to the increase of heat flux and decrease of mold flux consumption. Hence, the thickness of solidifying shell reduces and becomes nonuniform, decreasing its ability to resist all types of stress and strain during casting. Thus, the occurrence of breakout and cracks with high frequency greatly influences production. The technical issue of high-speed casting and the key to making it a reality should be resolved to ensure homogeneous growth. In this paper, the behavior of heat transfer and solidification in slab mold with high-speed casting for peritectic steel was analyzed. The effect of casting speed on the interfacial heat transfer resistance and the distribution of temperature and stress for solidifying shells in mold were investigated. It was found that the interfacial heat resistance increased evidently as the casting speed was greater than 1.6 m·min⁻¹. The thickness of solidified shell at the exit of the mold was reduced by approximately 10%, as the casting speed increased from 1.4 m·min⁻¹ to 1.6 m·min⁻¹ and 1.8 m·min⁻¹, making it more dangerous for breakout. The relative technologies such as the shape, flux, oscillation, and surface fluctuation for mold with homogenous solidification were presented and discussed. The optimization of mold inner cavity fitting for the growth of solidifying shell should be considered first for the uniformity control of peritectic steel solidification in a high-speed continuous casting mold. It is critical to design mold flux that adjusts to the solidification characteristics of peritectic steel. Moreover, the control of strand bulging is the key to stabilizing the mold surface.