Mathematical Simulation Of Optimization Of Flow Control Devices In A Slab Continuous Casting Tundish And Argon Blowing In Mold

Due to the unreasonable installment of flow control devices in continuous casting tundish and the fluctuation of molten metal in the slab continuous casting mold,there was a large gap in the control level of the content of N,C,O as compared with advanced foreign standards during continuous casting,since high level automotive steel sheet of series IF put into operation in a certain steelmaking plant.For inclusion reason,the amendment rate of the slab was a bit high.In this paper,taking the two-strand slab continuous casting tundish as the research object,the mathematical model was established to study the effect of flow control devices and flow control parameters on flow field and temperature field.The result of mathematical simulation was verified by water modeling experiment.Besides,Using VOF(Volume of Fluid)method and Lagrange Discrete Phase Model,this paper established the mathematical models about the interfacial behavior between liquid steel and molten slag layer in the slab caster mold during argon blowing.Effects of such process parameters as argon gas flow rate,casting speed and nozzle immersion depth on the steel/slag interfacial behavior in the mold were studied by numerical simulation,which provided the theoretical foundation for selecting reasonable technological parameters of argon blowing.The results showed that:(1)The peak time and the mean residence time were too short in the prototype tundish without dam and weir,the mean residence time was just 307.9s and the volume fraction of dead volume was up to 59.4%.The peak time and the mean residence time were significantly prolonged with setting dam and weir,which could obviously improve flow field and temperature field of molten steel.After comprehensive consideration of various factors,the scheme three(the combination of No.2 dam and No.2 weir)was the most reasonable design.Its mean residence time was 487 s which increased by 179.1s compared with the prototype tundish and the volume fraction of dead zone was 35.8%,which decreased by 23.6%.(2)Case No.7 was ascertained as the optimum scheme of flow field optimization after optimizing the flow control parameters of the scheme three,the best case was that the distance between dam and weir was 870 mm and the distance between weir and the long nozzle was 1150 mm.After optimization,the mean residence time was 590 s,which prolonged 103 s under optimization and prolonged 282.1s compared with the prototype tundish(without dam and weir),the volume fraction of the plug flow was 17.4%,the volume fraction of the dead zone was 22.3%.(3)Argon blowing obviously enlarged the fluctuation range of the steel/slag interface near the nozzle,while this range could be effectively decreased with proper casting speed.At the same time,argon blowing reduced the fluctuation of molten steel near the meniscus area of the mold,which could stabilize the steel/slag interface to some extent.(4)The best process scheme for this mold(230mm×110mm)was selected from sixteen ones by mathematical simulation,and the optimal parameter values of casting speed,argon gas flow rate and nozzle immersion depth were 1.2 m/min,9 L/min and 120 mm,respectively.