| In this paper,the behavior of liquid steel in tundish and mould for ultra-thin beam blank with single nozzle was studied by combining physical simulation with numerical simulation.For the tundish,the water simulation experiment was carried out by establishing a physical model of 1:2,the effects of flow control device on the response time of each nozzle,the consistency of tundish diversion and the proportion of dead zone volume ratio in tundish were studied.A 1:1 mathematical model was established to carry out numerical simulation calculation,and the results were compared with those of water simulation experiments.The three-dimensional flow,heat transfer and solidification of liquid steel in a straight channel nozzle mould were studied by establishing a 1:1 mathematical model.The water simulation experiments were carried out by establishing a physical model of 0.7:1 to study the effects of different submerged nozzle structures and different air-blowing quantity on the mould flow field.The main conclusions are as follows:(1)The response time of the prototype tundish 2 nozzle is only 18 seconds.When molten steel enters the tundish,it flows directly into the 2 nozzle,resulting in obvious "short-circuit flow",and the dispersion of the response time of each nozzle is very poor.Its dispersion reaches 37.32,and the dead zone volume ratio of the prototype tundish reaches 31.67%,which greatly reduces the effective volume of the tundish.(2)The response time of the tundish nozzle 2 is 63 seconds after the optimization of the flow control device,which provides favorable conditions for the inclusion floating and improves the cleanliness of steel liquid.The consistency of the tundish diversion has also been greatly improved,the dispersion has been reduced to 5.10,and the dead zone volume ratio of the tundish has been reduced to 13.15%,which greatly improves the utilization ratio of tundish.(3)The experimental results of tundish unsteady-state ladle-changing process show that during the ladle-changing process,intense stirring and emulsification occur in the impingement zone,and slag entrapment occurs above the 2 nozzle;after optimization,the slag entrapment in the ladle-changing process is solved under the action of retaining wall and diversion bottom outlet.(4)The numerical simulation results of single nozzle casting with straight channel nozzle show that the flow field distribution in the single nozzle casting mould of ultra-thin beam blank is extremely asymmetric,and the impact depth in the mould is deeper(0.6-0.7 m),which results in a series of quality problems,such as uneven temperature distribution on the slab surface and uneven thickness distribution of solidified shell.(5)The results of water simulation experiments show that the optimum scheme for the mold without blowing is scheme 6,submerged nozzle with bottom hole diameter of 19 mm.The optimum scheme for the mold blowing submerged nozzle with bottom hole diameter of 17 mm and blowing volume of 3 L/min.Under the two experimental conditions,the mould level fluctuation is within ±3 mm,and the mould slag entrapment is avoided while the activity of the mould liquid level is guaranteed.Under the two experimental conditions,the response time of the mould outlet is 16 s and 18 s respectively,which can reduce the erosion of molten steel on the solidified shell at the mould outlet,and is conducive to the formation of good shell.Under the two experimental conditions,the response time of the above and flange positions of the mould nozzle is identical and the response time is short.On the one hand,it can solve the problem that the liquid surface temperature is too low and the cold steel and mould powder are not easy to melt due to the long response time of the above and flange positions of the mould nozzle.On the other hand,it can improve the homogeneity of the composition and temperature of the liquid steel in the mould,and it provides guarantee for forming good quality slab. |
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