Study On The Fluid Flow, Heat Transfer And Solidification During Extra-thick Slab Continuous Casting

As the raw materials of extra-thick plate rolling, extra-thick slab produced bycontinuous casting is a good alternative of ingot because of some benefits such as lowerenergy consumption, higher production efficiency and rolling yield improvement. Thestudy on the fluid flow, heat transfer and solidification during extra-thick slabcontinuous casting has important guiding significance for the improvement ofextra-thick slab quality.By taking the extra-thick slab continuous caster in Xinyu Iron&Steel Group Co.Ltd. as the research object, the steel behaviors during extra-thick slab continuouscasting have been analyzed by industrial tests and numerical modeling with two steelgrades BT/50and Q355and two types of slab section360×2270mm~2and420×2270mm~2. Based on continuous model, the three-dimensional mathematical modelcoupled with fluid flow, heat transfer and solidification has been established and theboundary conditions have been specified. Meanwhile, the shell thickness and surfacetemperature of the extra-thick slab have been measured by nail-shooting experiment andwith infrared double-wave temperature indicator respectively. Compared with industrialtests results, the mathematical model has been validated and modified. Finally, some analyses, which are about the influence of slab thickness, casting speed and steel gradeon the flow field, temperature field and solidifying shell, have been carried out.Study shows that the results obtained by numerical modeling and industrial tests arequite similar, which means that the mathematical model is reliable. The slabstraightening temperature is proper, which is in favor for prevention of surface crosscracks. The flow field in the extra-thick slab is consisted of several circular flow zones.The liquid core in the section is in the shape of dumbbell due to the impingement offlow jet to the solidifying shell. Compared with the situation in360-milimeter-thick slabat the casting speed of0.7m/min, in the420-milimeter-thick slab at the casting speed of0.55m/min, the flow velocity is totally lower, velocity, turbulent kinetic energy andtemperature on the meniscus are also lower, the central temperature is higher, and theliquid core is a little longer. As the casting speed increases, the impingement of flow jetis aggravated, the meniscus stability goes bad, the slab temperature increases, and theliquid core extends. Compared with the situation of BT/50, when the steel grade isQ355, the kinetic energy decreases more slowly, the area with higher temperature islarger, and the relative temperature of meniscus and central line is higher, the mushyzone is narrower, and the liquid core length is similar.