Research On Fluid Flow Control In Slab Mold For Continuous Casting

With the continues development for efficient continuous casting technology and the improvement of the market requirements for quality steel, more and more people pay attention to the mold metallurgy. As the last link of purifying steel in continuous casting process, molten steel flow in slab molds has a great influence on inclusion removal, slag entrainment, formation of solidified shell and microscopic solidification structure of the slab. The structural improvement of submerged nozzle structure has important significance for improving continuous casting productivity and slab quality. The reasonable flow field makes steel surface becoming stable and prevents slag entrapment, which plays a very important role in improving the purity of the liquid steel and avoiding the slab surface defects and internal defects.Taking a250mm-thick slab mold in continuous casting as the research object, the influence of nozzle export shape, area ratio of the outlet, the outlet angle, immersion depth of dipped nozzles on liquid surface fluctuation in the slab mold has been investigated in physical modeling. Additionally, the method of numerical simulation was applied to analyze the temperature field and the flow field, and based on this to determine the optimal parameters of the nozzles.In the physical simulation experiment, the modeling experiments were conducted in a1:2.1mold model under the conditions of119mm×1000mm and119mmx809mm molds, argon gas flow rate of0.16m3/h, casting speed of1.1m/s and0.9m/s. Through the method of physical simulation, it is known that the optimal SEN is5#and suitable immersed depth is57mm to67mm(the prototypes is120mm-140mm). When the immersed depth of submerged nozzle is57mm (the prototypes is120mm), the averagely different values of peak-valley comes up to0.37cm and the1/3of averagely difference values of peak-valley comes up to0.71cm with the former SEN, whose fluctuations are very severe in meniscus. After using the optimum SEN, the averagely difference values of peak-valley comes down to0.30cm and the1/3of the averagely different values of peak-valley comes down to0.40cm at the same immersion depth. The liquid surface fluctuations are effectively controlled and the free liquid surface tends to be stable.In the mathematical simulation, the impact depth of7#SEN (0=18°) is20mm bigger than that of1#SEN (0=15°). It conforms to the conclusion of physical simulation. Additionally, I analysis the temperature filed of5#SEN (the optimum scheme) in250mmx2100mm mold. From the temperature filed of wide face says face, we can get that the temperature of steel around the outlet is1807.37K; the temperature of steel in the narrow side wall is1794K and the temperature of vortex heart of the backflow is1782.11K. As immersed depth of nozzle increases, the vortex heart of the mold moves down. From the temperature filed of narrow face says face, the temperature of steel in the narrow side wall is1794.74K.