Physical And Numerical Simulation On Twin-Roll Strip Casting System

According to the current situation of research and technique for twin-roll strip,both experimental and numerical studies of φ600 mm×1000 mm twin-roll strip continuous caster were carried out.The effect of delivery system structure and operation parameters on the flow characteristics of molten steel,the fluctuation level of the free surface and the temperature distribution in the molten pool were investigated in order to determine the optimal structure of delivery system and operation parameters for roll casting under the conditions studied.The results are as follows:(1)Under the casting speed of 80 m·min-1,the average wave height decreases by 24%,the variance of residence time distribution increases by 50%with the feeding device of bilateral hole-bottom hole A3 type instead of the feeding device of straight through A1 type.Furthermore,the average wave height decreases by 62%and the variance of residence time distribution increases by 41%with the B6-2 type delivery device instead of the B1 type delivery device.Therefore,the optimal delivery scheme is the combination of the A3 type feeding device and the B6-2 type delivery device under the conditions studied.(2)Increasing the outlet upward angle of the delivery device has significant effect on the fluctuation level of the free surface.However,its impact on the mixing characteristics in the upper area of the molten pool is minor.When the outlet upward angle of delivery device increases from 0° to 15°,the average wave height increases by 0.2 mm,while the variance of residence time distribution only increases by 0.018.However,as the outlet upward angle further increases,both the fluctuation level and the variance of residence time distribution vary slightly.(3)The average wave height increases by 145%and the variance of residence time distribution increases by 257%when the casting speed increases from 40 m·min-1 to 80 m·min-1.When the casting speed further increases to 100 m·min-1,the average wave height is about 2.97 mm while the variance of residence time distribution remains approximately the same.In addition,the average wave height decreases by 50%and the variance of residence time distribution decreases by 20%when the contact angle increases from 45° to 60°.(4)The temperature difference at the free surface decreases by 15 K,when the outlet upward angle of delivery device increases from 0° to 15°.However,the temperature distribution at the free surface changes slightly when the outlet upward angle further increases.The temperature difference at the free surface decreases by 11 K and the temperature distribution of the pool surface is improved when the casting speed increases from 40 m·min-1 to 80 m·min-1.Moreover,the temperature difference at the free surface increases by 20 K with the contact angle of molten pool increasing from 50°to 55°.It is worth to mention that molten steel in some region near the free surface starts to solidify if the contact angle further increases.(5)Increasing the superheat of the molten steel suitably has minor impact on the temperature of molten pool and the center temperature of strip at the outlet.As the heat transfer coefficient of roll surface increases from 8000 W·m-2·K-1 to 10000 W·m-2·K-1,the temperature in the bottom area of the molten pool decreases and the average temperature of the center strip at the outlet gradually decreases by 64 K.(6)The optimal delivery scheme under the conditions studied is the combination of the A3 type feeding device and the B6-2 type delivery device.As for the optimal operating parameters,the outlet upward angle of delivery device is 15°,the casting speed is in the range of 60 m·min-1 to 80 m·min-1,the contact angle is in the range of 50° to 55° and the molten steel superheat is in the range of 20 K to 40 K.