Effect of the rolling speed on the flow field and solidification welding line of the roll casting for AZ31 magnesium alloy

Based on the actual working conditions of the ∅880 × 400 horizontal twin-roll caster, the influence of the rolling speed on the flow field and solidification welding line of AZ31 magnesium alloy in the roll casting area is analyzed by finite element simulation. The results show that the molten metal’s convective heat transfer efficiency is improved by two vortexes (upper and lower) in the roll casting area. When the rolling speed increases, the solidification welding line gradually approaches the outlet. And the flow velocity difference between the middle and the edge of the roll casting area gradually increases, resulting in the continuous increase of the position difference L of the characteristic solidification welding points K and K ″ in the rolling direction, which increases the probability of edge cracking of the roll casting strip of magnesium alloy. In order to improve the production efficiency of the roll casting strip of magnesium alloy, it is suggested that the rolling speed should be controlled within the range of 3 ~ 4.2 m/min.