Study On The Argon Blowing Process With Four Plugs Installed Around Tapping Hole In Teeming Ladle

In the continuous casting production process,teeming ladle is an important starting link to realize the cleanliness of molten steel in continuous casting(CC)process,and it is of great significance to control the cleanliness of molten steel downstream.In the ladle teeming process,slag caused by the vortex and drain sink will cause pollution to molten steel.At the same time,there are still exist a certain number of inclusions after ladle refining,which are not conducive to the cleanliness of molten steel in CC process.To improve the cleanliness of the molten steel in the teeming ladle,our research group proposed a new argon blowing process with argon injected into ladle around the tapping hole,which can realize the functions of slag carryover controlling and inclusion removal in the teeming process,and do not take up extra processing time.Taking into account the difficulties in processing and on-site implementation of the original annular argon blowing element,this paper takes a 130 t ladle in a steel plant as prototype,combined with physical and numerical simulation,studies on slag carryover controlling and inclusion removal by argon blowing with four plugs installed around tapping hole are carried out.The mechanism of slag control and inclusion removal is revealed,the influence of different process parameters was discussed,and the relationship between shortening soft blowing time and teeming height also was investigated.Finally,industrial test verification was carried out,which provided important theoretical guidance and practical experience for the development of processes suitable for industrial production.The main conclusions of this paper were obtained as follows:(1)The physical simulation results of controlling slag carryover by argon blowing process with four plugs installed around tapping hole in teeming ladle indicate that this process can significantly reduce the critical height of slag carryover.The appearance of foaming slag is related to the initial blowing height and flow rate.The reasonable initial blowing height of slag without foaming is h mm and the flow rate is 0.36 NL/min.With the increase of the number of plugs,the effect of controlling slag carryover is enhanced,and the results of three and two plugs are similar.(2)Numerical Analysis results of controlling slag carryover by argon blowing process with four plugs installed around tapping hole in teeming ladle show that with the increase of eccentricity,the maximum tangential velocity decreases at different teeming heights,and the critical height of vortex decreases accordingly.The tangential velocity of the molten steel above the nozzle and the radial velocity of the molten steel flowing to the nozzle are decreased,and the critical height of the vortex and discharge sink is reduced after argon is blown into ladle via four plugs.With the increase of argon flow rates,the critical height of controlling slag carryover was reduced.The optimal argon flow rate for controlling slag carry-over was 30 NL/min.When different plugs are used,the change about bubble aggregation behavior makes the effect of reducing critical height argon blowing via four plugs better than that of three and two,and the reduction of critical height by two and three plugs is similar.(3)The physical simulation results of inclusion removal by argon blowing process with four plugs installed around tapping hole in teeming ladle indicate that there is an optimal gas flow rate in the range of large and small gas flow rates,and the removal rate of inclusion at small gas flow rate of 0.24 NL/min is higher than that at gas flow rate of 0.84 NL/min.Meanwhile,the reasonable height of residual steel to remove inclusion is 222.2 mm.With the increase of the number of plugs,the inclusion removal rate increases gradually.The removal rate increases obviously at gas flow rate of 0.24 NL/min,but there is little difference in the removal rate between argon blowing via two and three plugs at gas flow rate of 0.84 NL/min.(4)Numerical Analysis results of inclusion removal by argon blowing process with four plugs installed around tapping hole in teeming ladle show that the removal rates of inclusions at 20 NL/min of small gas flow rate and 70 NL/min of gas flow rate are at the peak,and the former is larger.The change rule of slag adsorption removal rate and total removal rate corresponding to different residual liquid steel height is similar.When four plugs are used for argon blowing,the behavior of bubble aggregation is helpful for the removal of inclusions.Due to the decrease of bubble flow strands when three or two plugs are used for argon blowing,the overall slag adsorption removal rate is not high.(5)The industrial test shows that the total oxygen T[O]and[N]of testing furnace 1 and 2 show a decreasing trend after using this process,but the change rule is different with different furnace numbers.Metallochemical statistics of 20 min show that the number and density of inclusions decrease by 23.47%and 17.86%,respectively.(6)The results of automatic inclusion analysis Azec steel show that the total number density of inclusions decreases after argon blowing for 20 min,and the number of inclusions with 0～1 μm,1～2 μm and 2～5 μm decreases gradually,and the decrease of the number density of inclusions with 1～2 μm is significantly greater than that of inclusions with 0～1 μm and 2～5μm inclusions.In addition,when argon blows 20 min,the composite oxide inclusion area per unit area is the largest,and the average area of sulfide inclusion,spinel(Al2O3-MgO)and calcium aluminate(Al2O3-CaO)decreases.