| The tundish is the last metallurgical reaction vessel in the steelmaking process,and it plays a key role in removing non-metallic inclusions and the final quality of the cast slab.Aiming at the problem of large macroscopic inclusions formed by the aggregation of small inclusions in the tundish in a steel mill’s bearing steel casting slab,this paper adopts a research method combining numerical simulation and physical simulation.Based on the evaluation and analysis of the current working conditions,The reason for the formation of micro-inclusions in the tundish,the optimization of the tundish flow control device and the related process parameters of the shroud protection casting,the research results have been industrially applied,and the effective control of large macro-inclusions has been achieved.The research results are summarized as follows:The evaluation results of the current process of the tundish show that the structure of the current control device of the tundish under the current process is complex,the amount of refractory material is large,and the probability of the refractory material being washed and corroded increases;the maximum temperature difference between the near flow and the far flow is 6.4K,which does not meet the requirements of<5K Control target;the flow pattern is unreasonable,there is a short-circuit flow and the volume fraction of the dead zone is more than 30%;the floating rate of inclusions is only 67%.The optimization of the tundish flow control device by mathematical simulation simulation results shows that the increase of the inclination angle of the retaining wall and the decrease of the diameter of the retaining wall will increase the throwing distance of the molten steel out of the retaining wall hole,so as to eliminate the short-circuit flow of the short flow and extend the molten steel in the tundish.The retention time in the interior is to promote the floating of inclusions.Increasing the inclination of the retaining wall hole is more effective than reducing the hole diameter;the optimized flow control device reduces the amount of refractory material,and the erosion rate of molten steel on the refractory material is reduced by 13.8%compared with the original working condition;the maximum temperature difference between the tundish flows is3.9K,which meets the target of≤5K;the liquid level in the impact zone is more stable,and the maximum turbulent kinetic energy of the liquid level is reduced by 32%;the average residence time of molten steel is increased by 25.8%compared with the original working condition,and inclusions The floating rate reached 93%,an increase of 38.8%.The results of physical simulation of argon blowing protection casting in the shroud show that:1)Prevent air from entering the shroud,the argon blowing flow rate for the pressure in the shroud from negative pressure to positive pressure is 50L/min;when the argon blowing flow rate at the shroud>55L/min When the oxygen concentration in the long nozzle is less than 0.4%,the oxygen and nitrogen increase in the molten steel can be controlled to a level of less than 1 PPm,and the covering agent in the impact area of the tundish is not exposed.The argon blowing flow value is determined to achieve the protection Horizontal critical argon blowing flow;2)Increase the insertion depth of the shroud,and the fluctuation of the liquid level in the impact zone first decreases and then increases.The pulling speed is 0.62m/min and 0.72m/min,and the corresponding optimal insertion depths of the shroud are respectively It is280mm and 300mm.The production application of the optimization results shows that the temperature difference between the near-flow and the far-flow in the tundish is less than 3K,which meets the target of≤5K;the ability to remove inclusions is strong,and the erosion effect of molten steel on the refractory material is weakened;The water immersion ultrasonic high-frequency flaw detection of the rolling stock meets the requirements of high-end varieties of macro inclusions≤5mm/Nm~3. |
PDF Full Text Request