Theoretical argon flow rate analysis of ladle shroud in continuous casting process
In the continuous casting process,air can enter the nozzle through the gap between ladle shroud and col-lector nozzle and cause the molten steel to re-oxidize.Argon injection is used at the shroud to prevent air suction,but improper control of the argon flow rate will lead to defects in the billet.The air suction is due to the internal pressure of nozzle being lower than atmospheric pressure.At present,the control of nozzle argon flow rate is not re-lated to the adjustment of process parameters.A mathematical and physical model of mass-energy conservation from ladle to tundish was established.The model was based on the continuity equation and the Bernoulli equation.The pressure distribution in the nozzles during the flow of molten steel in ladle shroud and the fluid distribution in the la-dle shroud under different outlet conditions and argon flow rates were summarized.The effects of teeming time,casting speed,the diameter of slide gate and ladle shroud,immersion depth of ladle shroud,and the effect of argon flow rate on pressure distribution in the nozzles were investigated,and the theoretical argon flow rate under different conditions was calculated.The results show that increasing the casting speed,the immersion depth of the ladle shroud or the argon flow rate,and reducing the diameter of the slide gate or ladle shroud are beneficial to reduce the negative pressure in the nozzle.When increasing the casting speed,the immersion depth of the ladle shroud and the diameter of the nozzle,the argon flow rate should be increased.The use of trumpet ladle nozzle can decrease the outlet rate of molten steel,which has smaller pressure than the conventional ladle shroud,and more slowly increases the outlet rate of molten steel than that of the conventional ladle shroud in argon injection.The research results pro-vide theoretical basis for determining the argon flow rate in the ladle nozzle.
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