| Based on the prototype of a single-strand thin slab tundish in a steel plant,a new type tundish structure for removing inclusions less than 10 ?m was explored by employing two kinds of flow control devices,which are Multi-Hole-Double-Baffles and turbulence inhibitor respectively in this paper.The effects of new type tundishes with different structures on the flow field of molten steel and the removal efficiency of microscale inclusions(less than 10 ?m)have been studied by combining numerical simulation with physical simulation.Based on the discrete phase model and turbulence model,the local area of Multi-Hole-Double-Baffles is modeled by mathematical simulation method,and the internal flow field and the movement law of small particle inclusions are explored.The whole tundish with multi-stage flow control device is simulated and optimized.The 1:2.5 water model of tundish is established by physical simulation method,and the flow field visualization experiment,RTD curve measurement and micro-scale inclusion removal simulation were completed and used to validate and compare the mathematical models.The main conclusions are as follows:The results of inclusion simulation show that: the motion trajectories of small inclusions is basically the same as that of molten steel,which indicates that the movement of small particle inclusions is significantly affected by the flow field.The precise adjustment ability of the flow control devices for tundish flow field provides a feasible method to effectively improve the removal of inclusions(? 10 ?m).The simulation results of Multi-Hole-Double-Baffles partial model show that: the overall removal rate of small inclusions by Multi-Hole-Double-Baffles with refractory filler is significantly higher than that of Multi-Hole-Double-Baffles without filler because of the high capture and filter ability of the filler layer to small inclusions.The highest removing rate is 88.64%,which is 2 times higher than the lowest removal rate of non-filler Multi-Hole-Double-Baffles.RTD curve analysis shows that the fractions of plug flow volume in the new tundishes are higher than that in the prototype tundish,and the maximum increase is more than 68%.At the same time,the fractions of dead volume in most design plans of tundishes are also lower than that in the prototype tundish,and the mixing effect of molten steel is better.The simulation results of flow field show that: Multi-Hole-Double-Baffles can play an effective role in controlling the flow in tundish.The hole array mode of double baffles and the design of guide-holes with an inclined upward angle of 30°,can directly change the flow field of molten steel,reduce the occurrence of short-circuit flow,enhance the extended distance of the top surface flow of molten steel in the downstream of tundish,thus significantly improving the removal effect of small inclusions less than 10 ?m.The crescent-shaped turbulence inhibitor can form a strong upward swirling flow in the pouring area,which is conducive to the homogenization and centralization of molten steel,and promotes the collision growth of inclusions,and depresses slag entrapment and molten steel exposed.The pulling effect of guide-holes leads to obvious high-speed flow area outside guide-holes.Once molten steel or inclusions enter this area,they can appear the phenomenon of velocity mutation and are difficult to break away again.In this process,the velocity increases exponentially.The research indicates that the position of velocity mutation is within 30~100 mm from the baffle,and the crescent-shaped turbulence inhibitor can weaken this effect by forming a strong swirling flow toward the center.The results of numerical simulation and physical simulation are basically consistent.The better plan for removing microscale inclusions(? 10 ?m)is the new type tundish with "crescent-shaped turbulence inhibitor + X-shaped double baffles + 47.5 mm filler ball".The removal rate is about 87.84%,which exceeds the removal rate of the prototype tundish by 18.35%. |
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