Study On Simulation Of Bubble Behavior And Inclusion Removal With Argon Bubbling During Large Steel Ingot Casting

In this study,physical simulation and mathematical simulation were used to investigate the surface porosity of different porous brick,bubble diameter,bubble movement in the mold and the removal of inclusions with different bottom argon bubbling porous plugs during the ingot casting.The study found that the circular plug has the largest pore diameter of 8.2 μm,the porous beam is 5.8 μm,and the annular brick has the smallest pore diameter of 5.6 μm.The porisity per unit area for the annular plug is 161.40 pore/mm2,the one for circlular plug is 73.54 pore/mm2 and the one for the porous beam is 32.27 pore/mm2.Within the gas flowrate range studied,the mean diameter of the bubble produced by the annular plug is the largest,being in the range of 1.68mm～2.72mm,the mean diameter of the bubble produced by the circular plug is 1.05mm～1.58mm and the one of the bubbles produced by the porous beam is 0.42 mm to 0.79 mm.The diameter of bubbles generated by the plugs is related to the surface pore diameter of the plugs and the number of pores per unit area on the plug surface.The diameter of bubbles increases with the increase of the liquid flowrate,bottom gas flowrate,and liquid level.The bubbles from the circular plug are more dispersive in the mold.When the center distance of the plugs,L,is 60 mm,the bubbles are inclined to the inner side at the lower liquid level,then inclined outward near the liquid level,and slopes inward at higher levels.When L=120mm,the bubbles show to be inclined to both sides of the mold at the higher liquid level,and is greatly affected by the flow field in the mold.Increasing the flow rate of liquid and the bottom gas flowrate can increase the degree of dispersion of bubbles in the mold.The bubbles from the annular plug are generally poorly dispersive in the mold and vertically float up to the surface.Increasing the flow rate of water and the bottom gas flowrate at the lower liquid level helps to increase the dispersion of the bubble,but the effect is not large.Increasing the bottom gas flowrate and the liquid flow rate at a higher liquid level can effectively increase the dispersion degree of the bubbles in the mold.When the center distance of the porous beam is L=60mm,the bubbles show a characteristic of first tilting to the inner side at the lower liquid level,and then tilting to the outside near the liquid level.The small bubbles concentrate between the two bubble columns.When the liquid level is high,the bubbles generated by the two porous beams become into a bubble column which disperse to the sides and floate vertically.When L=120mm,the bubbles incline to the inner side,and the small bubbles disperse between the two bubble columns.When the liquid level is high,the bubbles rise almost vertically.When the flow rate and the bottom gas flowrate are increased,the degree of dispersion of the bubbles in the mold is significantly increased,and a large number of small bubbles move with the flow field in the mold.Inclusion removal degree can be significantly increased with bottom gas bubbling.At the lower liquid level,the inclusion removal degree is the highest when the center distance of the circular plug is L=120mm and q=0.055m3/h,being 88.89%.when the liquid level is high,the circular plug L=60mm,q=0.012m3/h have the highest removal degree,too,being 77.78%.The removal degree of inclusions with annular plugs is low.When the bottom gas flowrate exceeds q=0.025m3/h,the removal degree increases little.The inclusion removal degree is the highest when q=0.012m3/h at higher liquid level,being 62.22%.Porous beam have the highest inclusion removal degree at lower liquid level at L=60mm and q=0.055m3/h,being 86.67%,At H=700mm,L=120mm and q=0.055m3/h its removal degree is the highest,being 83.2%and at H=900mm,L=120mm and q=0.025m3/h its removal degree is the highest,being 64.57%.Therefore,increasing the bottom gas flowrate at a lower level,and appropriately reducing the gas flowrate at a higher level can help to remove inclusions.The results from the mathematical simulation are in good agreement with the ones from the physical simulation.Buubles from the double circular porous plugs or beams are drawn by the up-stream and bent to the center at the middle area,but near the liquid level the bubbles flow to the two sides.Finer bubbles from the porous beams are attracted by the center stream at middle and low area and flow up within the center area,while near the liquid level these fine bubbles flow down with the fluid at the tow sides.The bubbles formed from the annular porous plug flow up with the center up-stream and their dispersion degree in the mold is small.The inclusion removal degree during the ingot casting without Ar bubbling is small,being 68.6%at liquid level H=1500 mm and 37.14%at liquid level H=2700 mm,respectively.Bottom Ar bubbling during the ingot casting can improve inclusion removal.At during the ingot casting,increasing bottom Ar flowrate at H=1500 mm can enhance inclusion removal degree,the highest one being 83.06%.At H=2700mm,the inclusion removal degree first increases and then decreases with increase in bottom Ar flowrate,the highest one being 50.4%.