Numerical Simulation Of Fluid Flow, Heat Transfer And Solidification Shrinkage In Continuous Casting Slab Mold

In continuous casting process, the solidification of high temperature molten steel inmold is always associated with fluid flow, heat transfer, inclusion floating, soluteredistribution, shrinkage of solidified shell and other metallurgical behavior, which havedifferent impact on the surface and internal quality of slab and production efficiency.Mastering the characteristic and rules of the behavior of molten steel can improve slabquality; it can also optimize the process and bring economic benefits.Based on fluid dynamics software FLUENT and finite element software ANSYS,the turbulent flow, heat transfer and shrinkage of solidified shell of the molten steel in1580mm×220mm×950mm mold were simulated. First of all, the three-dimensionalmold model was created with1:1ratio. The fluid flow, fluctuation of free surface andtemperature distribution of molten steel in mold were calculated and analyzed with thestandard k-ε turbulent model, multiphase flow VOF model and Solidification&Meltingmodel of the FLUENT software. Moreover, the results affected by casting speed, depthof submerged entry nozzle and angle of nozzle port were compared. Followed, thetemperature data which calculated from FLUENT software was put into the finiteelement software ANSYS and employed as boundary condition of thermomechanicalindirect coupled analysis. Also the effect of different casting speed on results wascompared.The results of FLUENT software show that:(1) Molten steel which enters into themold from nozzle impacts the narrow side of mold and occurs two swirl areas. Thefluctuation of free surface, inclusion floating, temperature distribution and solidifiedshell morphology are all affected by the flow characteristic of swirl.(2) The increasement of casting speed will intensify the fluctuation of free surface, lead to theslab temperature at the outlet of mold higher and solidified shell thinner.(3) Theincreasement of depth of nozzle and angle of nozzle port will result in molten steelimpacts deeper, at the same time, the swirl areas offset download, which although canhelp reduce intensity of surface fluctuation, the high temperature areas will offsetdownload. This goes against growth of the solidified shell and will increase the risk ofbreakout.The results of ANSYS software show that along the casting direction, surfacestress and solidification shrinkage of slab are tending to increase. The greatest stress andshrinkage are formed at the corner of slab due to the fastest heat transfer rate. With theincreasement of casting speed, surface stress and shrinkage of slab are decreased.Finally, the nozzle structure was optimized. A center-pore was added at the bottomof nozzle based on the original double-pore structure nozzle, and the fluid flow field andtemperature field of molten steel were analyzed with three-pore structure nozzle. Theresults show that the casting speed can increase obviously with three-pore nozzle.