Numerical Simulation Of Inclusions Motion Behavior In Swirling Flow Tundish

The cleanliness of molten steel has a significant influence on the quality of steel,high content of non-metallic inclusions in molten steel will lead to the reduction of mechanical properties of solidified slab,and even the quality defects of the slab.Tundish has a special position in the continuous casting process and has obvious advantages in improving the cleanliness of molten steel.Metallurgists mainly study flow condition control and inclusions motion behavior of molten steel in tundish.Combination use flow control devices can significantly improve flow characteristics,promote the floating removal of inclusions in molten steel.Because of large-size inclusions are fast,optimization of flow field is very effective for the removal of large-size inclusions,when inclusion size less than 50 ?m has good fluidity,the removal effect is unconspicuous.In this paper,inclusions motion behavior in a swirling tundish is studied.Firstly,based on the Euler Lagrangian model,the effect of various forces on inclusions is considered,when diameter of the swirling chamber is 600 mm,change ratio of height to diameter of the swirling chamber on the removal rate of inclusions is considered and the optimum parameter of the swirling chamber is obtained,under the optimum swirling chamber parameters,the influence of the change of flow speed on trajectory of motion and removal rate of inclusions with different sizes was studied.Then,based on the CFD-PBM coupled model,compared and calculated the collision aggregation of inclusions in traditional and swirling tundish under turbulence collision mechanism,obtain changes of total volume fraction,average diameter,number density of inclusions in different size groups.The main conclusions as follows:(1)The simulation of the flow in the swirling tundish is in well agreement with previous water model experiments,rotating flow in tundish after flow control prolong motion path of the molten steel,and the flow is more reasonable.(2)It is concluded from inclusion trajectory that rotating flow of molten steel drives inclusions rotating,which makes the inclusions to collide and aggregate easier,improve the removal rate of inclusions.(3)When the diameter of swirling chamber is 600 mm,change ratio of height to diameter of the swirling chamber to calculate the removal rate of inclusions,when the height to diameter of swirling chamber is 0.75 can ensure the high removal rate of inclusions and the small fluctuation of the surface,which is the optimum parameter of swirling chamber.(4)The results show that removal rate of small inclusions is about 25%under 10?m,with the increase of inclusions size,the removal rate is gradually increased,when the inclusion size is greater than 100 ?m,the removal rate of inclusions is about 95%.(5)The calculation results of the CFD-PBM coupling model show that small-sized inclusions collide and aggregate to generate large-sized inclusions,the collision growth behavior of the inclusions and the molten steel turbulent flow occur simultaneously,however the average residence time of molten steel in the tundish about 689 s,the inclusions reached stability at t=3000 s,this mean that the collision and removal of tundish inclusions is an unsteady process.(6)The results at outlet show that,for traditional tundish,total volume fraction of inclusions is reduced by 16.3%,average diameter of inclusions is increased by 8.12%,for swirling tundish total volume fraction of inclusions is reduced by 20.7%,average diameter of inclusions is increased by 10.68%.(7)The removal rate of inclusions is considered collision,it can be concluded that,collision has a great influence on the removal rate of small-size inclusions,with the increase of inclusion size,for the first six groups of inclusions,collision removal rate of inclusions decreased from 25%to 15%;when the inclusion size is larger than 63 ?m,although the collision removal rate is low,the floating removal rate of inclusions is very high,and the number density of inclusions with inclusion size larger than 63 ?m in molten steel is very small.