Abstract: The magnesium lance with an evaporation chamber is widely used in the pretreatment process of hot metal desulfurization and graphite spheroidization of cast iron, but the bubble generation mode during the blowing process and its effect on magnesium utilization remain unclear. In this paper, the blowing condition of a certain company was taken as the research condition, and the theoretical calculations showed that the time to reach pressure equilibrium between the inner and outer sides at the outlet of the evaporation chamber during the blowing process was very short (0.005 4 s), and it was considered that bubble generation started at the bottom exit inner diameter of the evaporation chamber. A two-stage bubble generation mode of expansiondetachment for the lance with an evaporation chamber was put forward, with the end of the detachment stage occurring in two scenarios due to instability of the bubble or obstruction on the outer side of the evaporation chamber outlet. On this basis, a mathematical model of bubble generation was established, the effect of bubble refinement on magnesium utilization enhancement was analyzed, and the optimization scheme of opening a curved slot along the bottom of the evaporation chamber was proposed. Field experiments showed that reducing the size of the gas outlet could increase the specific surface area of the bubbles in the melt pool, which effectively improved the utilization rate of magnesium and the life of the lance.

Key words: magnesium lance, evaporation chamber, bubble generation, desulphurization, magnesium utilization