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State of the art in the control of inclusions by slag in steelmaking process of ultra-low carbon IF steel Steelmaking    2024, 40 (2): 1-22.   Abstract （36）      PDF（pc） （19824KB）（51）       Knowledge map    Save Ultra-low carbon IF steel sheet is mainly used in ultra-deep drawing parts such as automotive exposed panel, etc., which is faced with main surface quality problems caused by the steelmaking defects of inclusions, mold flux entrapment and bubbles. Therefore, the slag properties used in the whole steelmaking process play an important role in controlling inclusions in steel. In the present paper, the effects of slag on inclusion control were summarized from two aspects of the slag physicochemical properties and the slag characteristics in different steelmaking stages. It was found that the adsorption and dissolution of inclusions by slag was related to the physicochemical properties of slag and the sizes of inclusions. The main control objectives of RH refining slag were low oxidation and appropriate w(CaO)/w(Al2O3). The TFe mass fraction was generally controlled in 2.0 %–8.0 %, and the w(CaO)/w(Al2O3) was controlled in 1.2–1.8. In addition, the basicity of refining slag was generally controlled in 4–10. The tundish flux and mold flux should first prevent the carbon increase in the molten steel, and secondly prevent the secondary oxidation of the molten steel caused by SiO2 in the slag. At the same time, they should also be capable of adsorbing inclusions. The high basicity tundish flux for ultra-low carbon IF steel generally had the basicity of 2.9–11.5, the w(CaO)/w(Al2O3) was controlled in 1.0–2.5, and the (FeO +MnO) mass fraction was controlled in 1.9 %–4.0%. The basicity of the mold flux for ultralow carbon IF steel was generally controlled in 0.85–1.0, the w(CaO)/w(Al2O3)  was controlled in 5.0–8.5, and the (FeO+MnO) mass fraction was less than 1 %. Related Articles | Metrics

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Practice of automatic steelmaking in converter without sublance and off-gas analysis Steelmaking    2024, 40 (2): 39-43.   Abstract （25）      PDF（pc） （4486KB）（33）       Knowledge map    Save Based on the intelligent metallurgical model system with slag electronic thermodynamic function theory as the core, under the conditions of without sublance and off-gas analysis in the converter, automated steelmaking of an 80 t converter has been achieved through smelting scheme construction, problem analysis and optimization. Compared with before the automatic steelmaking system was put into use，the hit rate of converter steelmaking at first turning down increased by 6.5 percentage points，the smelting cycle of converter was shortened by 0.2 min，and the steel material consumption was 5 kg/t lower than that of manual steelmaking during the same period. The auxiliary material consumption reduced by 2.89 kg/t，and the technical and economic indicators of converter were significantly improved. Related Articles | Metrics

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Investigation on the crust mechanism of tundish cover powder during continuous casting of ultra-low carbon steel Steelmaking    2023, 39 (2): 36-41.   Abstract （78）      PDF（pc） （5489KB）（101）       Knowledge map    Save The industrial trials and thermodynamic calculation were carried out to investigate the composition evolution, crystallization phase, and crust mechanism of tundish cover powder (TCP) during continuous casting of ultra-low carbon steel. The results showed that the ladle slag had a relatively strong oxidation capacity at RH departure and the w(CaO)/w(Al2O3) in the slag was low. The top slag of RH refining needs to be modified. Due to the slag carryover, mix of ladle filler sands and TCP, the composition of TCP during continuous casting has been significantly changed. Furthermore, the MgO·Al2O3 spinel in liquid phase was first formed and it promoted the nucleation and growth of 2CaO·Al2O3·SiO2 and CaO·TiO2 phases, resulting in the crust of TCP. To avoid the crust of TCP during continuous casting, the ladle carryover at cast end should be strictly controlled, and the  mass fraction of SiO2 and MgO in the original TCP are reduced to (10±2.5) % and 5.0 %～7.5 % respectively, which will inhibit the precipitation of 2CaO·Al2O3·SiO2  and MgO·Al2O3 spinel phases. Related Articles | Metrics

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Multiphase flow behavior and reaction kinetics in hot metal ladle with submerged injection Steelmaking    2024, 40 (2): 23-30.   Abstract （11）      PDF（pc） （17047KB）（22）       Knowledge map    Save To improve the desulfurization efficiency of hot metal predesulfurization process with injection method, a CFD-DSM(Computational Fluid Dynamics-Desulfurization Model) coupled model was established based on 180 t hot metal ladle. The gas-solid-liquid multiphase flow behavior and reaction kinetics during hot metal pre-desulfurization process were systematically studied, and the contribution of dissolved magnesium desulfurization, magnesium bubble desulfurization, calcium oxide desulfurization, and slag layer desulfurization to the desulfurization reaction was revealed. The effects of carrier gas and magnesium powder flow rates on the desulfurization reaction were clarified. The results are shown as follows: the bubbly plume has a smaller penetration depth, but it does not float up attached to the wall of lance. With the continuous injection of calcium oxide powder, powder floats along the wall of lance. In the desulfurization process, the desulfurization by dissolved magnesium is the main desulfurization mechanism, followed by magnesium bubble desulfurization, calcium oxide desulfurization and slag layer desulfurization, and the desulfurization rate of each reaction mechanism first increases and then decreases. The carrier gas flow rate has little effect on desulfurization reaction. However, the magnesium powder flow rate has the greatest impact on the desulfurization reaction. For the hot metal with an initial sulfur mass fraction of 470×10-6, when the sulfur mass fraction reaches 100×10-6, the injection time is shortened by about 43 s for every 1 kg/min increase in magnesium powder flow rate. Related Articles | Metrics

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Research on intelligent casting process model of continuous casting Steelmaking    2024, 40 (2): 72-79.   Abstract （14）      PDF（pc） （5576KB）（16）       Knowledge map    Save Intelligent casting technology has been promoted and applied in continuous casting production.In order to reduce production accidents, stabilize the quality of casting billet, and realize safe production far away from the casting site, an intelligent casting process model was developed and optimized for the unsteady casting process by combining operation experience. In this paper, some intelligent management and control models were studied and applied for continuous casting production, focusing on some key technologies such as the tundish automatic casting model, SEN one-key quick replacement model, and casting anomaly automatic disposal model. The principles, application and effects of the three models were introduced.Through the research and practice of the above models, the success rate of automatic casting reaches more than 95 %, the success rate of automatic SEN replacement is as high as 100 %, the degradation rate of abnormal casting billet defects of SEN change is reduced by 52 %, the personnel on-site duty time is reduced by 50 % after the automatic disposal of casting anomalies, and efficiency of personnel is increased by about 10 %.The intelligent production process and stable casting quality are promoted. Related Articles | Metrics

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Effect of Ca and S on inclusion removal during vacuum degassing refining process Steelmaking    2024, 40 (2): 51-56.   Abstract （10）      PDF（pc） （6704KB）（16）       Knowledge map    Save The effect of Ca and S on inclusion removal during vacuum degassing refining process was investigated. The Ca content had a significant effect on inclusion removal. When the S mass fraction was in the range of 0.012 %－0.014 %, low Ca content was beneficial for inclusion removal. When the Ca mass fraction was 1×10-6 in steel, the inclusion removal rate was 74.30 %. When the Ca mass fraction was 8×10-6 in steel, however, the inclusion removal rate decreased drastically to 33.95 %. The reason was that the Ca element transferred the solid deoxidation product Al2O3-MgO inclusions to liquid calcium aluminate inclusions which were not easy to float and remove. When the Ca mass fraction was (7-8)×10-6 in steel, high S content was beneficial for inclusion removal. When the S mass fraction was 135×10-6 and 11×10-6  in steel, the corresponding inclusion removal ratios were 33.95 % and 23.71 %, respectively. The reason was that high S content increased the CaS content in the inclusions, which made the melting point of inclusions increased. The sources of Ca and S elements were discussed, and measures were proposed to improve the inclusion removal ratio during vacuum degassing refining process. Related Articles | Metrics

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Application of magnesia spinel bricks in RH vacuum treatment and its effect on chromium increase in molten steel Steelmaking    2024, 40 (1): 47-51.   Abstract （20）      PDF（pc） （976KB）（23）       Knowledge map    Save Related Articles | Metrics

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Simulation on influence of gas curtain in induction heating tundish Steelmaking    2024, 40 (2): 65-71.   Abstract （8）      PDF（pc） （10903KB）（12）       Knowledge map    Save In order to study the influence of gas curtain on the transfer behavior in the induction heating tundish, based on an actual one-strand channel-type induction heating tundish, a threedimensional unsteady mathematical model was established by numerical simulation to study the influence of gas curtain on flow, heat transfer and inclusion transfer behavior in the induction heating tundish. The results show that with the use of gas curtain, the molten steel flow in the discasting chamber of induction heating tundish is more reasonable, and the composition of the liquid steel is more uniform. This phenomenon is more beneficial to inclusion removal. The temperature field in the discasting zone is more evenly distributed, the temperature difference does not exceed 1 K, and the low temperature regions decrease further. The inclusion removal rate of induction heating tundish with gas curtain is much higher than that without air curtain, which has improved by about 41 %. Related Articles | Metrics

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Effect of slag washing process on cleanliness and properties of low carbon titanium microalloy steel Steelmaking    2023, 39 (6): 47-52.   Abstract （34）      PDF（pc） （4897KB）（40）       Knowledge map    Save Due to the high inclusion content and low elongation after cold rolling,the DL350 low carbon titanium microalloy cold-rolled structural steel produced by a certain plant cannot meet the customer′s requirements.In order to reduce the production cost and improve the elongation after fracture of cold rolled products,a reasonable slag washing process was developed, and the influence of slag washing process on the cleanliness and performance of steel was analyzed.The results show that the inclusions in steel are mainly MnS, TiN, MnS-TiN and a small amount of Al2O3 inclusions, and the content of oxygen and nitrogen in molten steel decreased significantly with slag washing.After slag washing, the average content of micro-inclusions in the billet decreased from 21.3 to 15.7 per mm2.At the same time, the grade of Class A inclusion was reduced from 2.0-2.5 to 1.0-1.5, and Class B inclusion was reduced from 1.5-2.0 to 0.5-1.0, indicating that the slag washing process significantly improved the cleanliness of the billet. Through the performance test of hot-rolled and cold-rolled products, it can be found that the elongation after hot-rolled fracture of slag-washing process samples has been increased from 26 %-28 % to 29 %-31 %, and the elongation after cold-rolled fracture has been increased from 15 %-16 % to 18 %-20 %, the overall strength changes little, which meets the customer′s requirements. Related Articles | Metrics

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Research on the mechanism of dephosphorization by small particle limestone and liming slag Steelmaking    2024, 40 (2): 44-50.   Abstract （10）      PDF（pc） （6744KB）（12）       Knowledge map    Save In order to investigate the feasibility of converter blown small particle limestone for steel making, based on the basic experiment of slag dephosphorization, the effect of small particle limestone and lime for slagging and dephosphorization under the same conditions was compared, and in-depth analysis was conducted from the mechanism of slag dephosphorization.The study shows that the small particle limestone decomposes in the molten pool to form highly active lime, which can simultaneously achieve dephosphorization reaction inside and at the interface of the molten pool. The dephosphorization effect is equivalent to that of lime, and the dephosphorization rate of the endpoint molten iron can reach over 85 %. Small particle limestone has a faster rate of pre-phosphorus removal than lime, and can remove most of the phosphorus elements in a shorter time. Both small particle limestone and lime can achieve uniform slagging, limestone slagging slag layer is higher, foam slag is more obvious. The distribution of elements in slag is uniform, and phosphorus elements are mainly enriched in Ca3(PO4)2 solid solution phase. Related Articles | Metrics

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Plasticity control of oxide inclusions in low spattering gas shielded welding wire steel ER70S-6 Steelmaking    Accepted: 01 January 1900

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Effect of oxygen content on liquid steel cleanliness after RH decarburization of IF steel Steelmaking    2023, 39 (2): 24-27.   Abstract （62）      PDF（pc） （5408KB）（126）       Knowledge map    Save Taking IF steel as the research object, combined with the production practice of 300 t RH furnace of Shougang Jingtang company, the oxygen content at the end of RH decarburization and the size and quantity of inclusions after deoxidation in the smelting process of IF steel were studied by means of production intensive sampling, data statistics, inclusion scanning electron microscope and other analysis methods. It was found that when the oxygen mass fraction after  RH decarburization was controlled at (290-310)×10-6, the Al2O3 inclusions produced in molten steel were the least. Based on this, the control method of oxygen content at the end of RH decarburization was studied. It was found that the hit rate of oxygen content at the end of decarburization in the forced decarburization mode was high and controllable, and the oxidation of top slag in the forced decarburization mode was weaker than that in the natural decarburization mode, which could reduce the formation of Al2O3 inclusions caused by secondary oxidation. The oxygen blowing calculation model was studied and established to ensure accurate control the oxygen content at the end of decarburization, which could improve the cleanliness of molten steel. Related Articles | Metrics

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Vortex image information enhancement method based on hot metal stirring Steelmaking    2024, 40 (2): 31-38.   Abstract （12）      PDF（pc） （5384KB）（11）       Knowledge map    Save The performance of the existing hot metal vortex image recognition system depends largely on the quality of the image. However, due to the interference of steel slag, light change and desulfurizer fog, the camera system faces some difficulties in obtaining the feature information of the vortex image, resulting in a large area of low quality in the image. In order to solve this problem, this paper proposed a method to identify and enhance vortex information in two-dimensional images based on the characteristics of hot metal and vortex. The method adopted an improved Gabor wavelet algorithm to extract the features and crack line information of vortex images. The image was processed by the feature processing unit to reduce the existence of false features and the quantization parameters of vortices were obtained by the vortex diameter recognition method. The experimental results show that, compared with the existing methods, this method reduces the pseudo-feature rate of vortex image information by 43.4 %, improves the accuracy of vortex diameter recognition by 3.6 percentage points, and realizes the enhancement and accurate recognition of vortex feature information on the free surface. Related Articles | Metrics

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Study on improving cleanliness of molten steel in X70 pipeline steel produced by LF+VD process Steelmaking    2024, 40 (2): 57-64.   Abstract （7）      PDF（pc） （9559KB）（11）       Knowledge map    Save In order to study the evolution mechanism of inclusions in the production of X70 pipeline steel by "LF＋VD" process，intensive sampling and analysis were carried out，and the VD furnace deep vacuum process and  calcium treatment process were optimized. The results show that in the deep vacuum process of VD furnace，strong argon stirring for 13 min in the early stage and weak argon stirring for  5 min in the later stage can promote the full floating of large particle inclusions. At the same time，the calcium treatment after the VD furnace broken can control the calcium mass fraction at 0.001 0 %-0.001 4 %，which can promote the full denaturation of inclusions to reach the purpose of low melting point area，so that the qualified rate of inclusions less than or equal to 2.0 in the first inspection of steel plate can be increased from 96.3 % to more than 98.7 %，and the cleanliness of molten steel is improved. Related Articles | Metrics

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Optimization of corner cooling structure of narrow copper plate in small chamfered mold Steelmaking    2024, 40 (2): 80-88.   Abstract （11）      PDF（pc） （5450KB）（13）       Knowledge map    Save In order to solve the problem of increasing the proportion of longitudinal cracks in the corner of the slab during the high-speed production of small chamfered mold in a steel plant, based on the existing chamfer furcal cooling structure water slot, a one-hole one-slot scheme with different round hole diameters and round hole positions was proposed. A three-dimensional heat transfer coupling model of the narrow side copper plate and cooling water was established. Industrial measured thermocouple temperatures and cooling water inlet/outlet temperature difference were used for validation. The temperature and velocity fields of the narrow side copper plate and cooling water were calculated for different one-hole-one-slot cooling structure schemes with different circular hole diameters and positions. The results show that the proposed one-hole-one-slot cooling structure with a circular hole diameter of 8 mm and a circular hole position of 26 mm results in a maximum temperature reduction of 14.4-17.6 K on the chamfered hot surface of bent copper plate and a maximum temperature reduction of 10.9-12.3 K on the chamfered hot surface of bolt cross-sectional copper plate, compared to the furcal water slots cooling structure. The cooling water flow in the circular hole reaches 8.4 m/s, effectively cooling the chamfered surface and vertex of the copper plate. Additionally, the cooling water flow rates on both sides of the bolt's water tank reach 10.0 m/s, enhancing the cooling uniformity of the plate around the bolt.  Related Articles | Metrics

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Practice of precise and specialized production for ultra-low carbon IF steel Steelmaking    Accepted: 01 January 1900

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Density evolution of solid films of mold fluxes for peritectic steel continuous casting Steelmaking    Accepted: 01 January 1900

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Study and practice of BOF less-slag steelmaking technology with high-titanium hot metal Steelmaking    2022, 38 (4): 28-35.   Abstract （173）      PDF（pc） （1638KB）（37）       Knowledge map    Save The consumption quantity of slagging materials is one of key economic and technical indicators of BOF steelmaking and represents the technical level of steelmaking, but it is inconsistent with the requirements of dephosphorization and furnace-lining protection. In an iron and steel enterprise, the contents of titanium and phosphorus in hot metal are high due to titanium-bearing iron ore used for ironmaking in blast furnace, so the consumption quantity of slagging materials is high in order to meet requirements of dephosphorization and furnace-lining protection. Therefore, based on the characters of high-titanium hot metal and the characteristics of slagging in BOF, the rules about oxygen supply and slagging were improved, a method called as “magnesium fixing titanium” (TiO2 becomes inactive due to its combining with MgO) was taken as a technique to suppress the disadvantage influence of high TiO2 slag on dephosphorization and furnace-lining protection to enhance the advantage efficiency of slag. By the continuous improvement of the above processes, a BOF less-slag steelmaking technology with high-titanium hot metal was developed. The consumption quantity of slagging materials was reduced from 55.67 kg/t to 47.86 kg/t. Good economic benefit was achieved, and a foundation for the development of high efficient steelmaking technology was laid. Related Articles | Metrics

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Numerical simulation of the effect of blade structure on mixing efficiency in KR method Steelmaking    2023, 39 (6): 8-14.   Abstract （46）      PDF（pc） （6075KB）（28）       Knowledge map    Save KR (Kanbara Reactor) method is the mainstream desulfurization method in hot metal pretreatment. The mixing efficiency of three kinds of blades, namely, the regular four-blade propeller, the spiral three-blade propeller and the double-layer regular four-blade propeller, was studied by numerical simulation method. The results showed that the mixing time of the double-layer regular four-blade propeller was 7.3 % shorter than that of the regular four-blade propeller, and 37.9 % shorter than that of the spiral three-blade propeller. Through the analysis of the axial velocity and turbulent kinetic energy distribution in the molten iron, it was found that the axial velocity of the molten iron in the double-layer regular four-blade propeller agitator was larger, and the turbulent kinetic energy in the molten iron was widely diffused. The average turbulent kinetic energy of double-layer regular four-blade propeller was 28 % greater than that of regular four-blade propeller and 1.8 % greater than that of spiral three-blade propeller. Related Articles | Metrics

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Thermodynamics and industrial practice of the formation of non-metallic inclusions during deoxidization of heavy rail steel Steelmaking    2020, 36 (4): 12-18.   Abstract （132）            Knowledge map    Save In order to study the thermodynamics on deoxidization and the inclusion control of heavy rail steel,FactSage thermodynamic software was used,combining with the actual production,to analyze the complex deoxidization of U75V heavy rail steel and the formation of inclusions under corresponding conditions.The results show that in the production process of heavy rail steel,the dissolved oxygen content in steel decreased continuously with the deoxidization reaction and the movement of deoxidization equilibrium,and the composition of inclusions transformed from SiO2-MnO to SiO2-MnO-Al2O3 and CaO-SiO2-Al2O3-MgO constantly,the final inclusion was composed of CaO-SiO2-Al2O3-MgO.It was unreasonable to guide the actual production using the thermodynamics of pure iron since there was a large deviation between pure iron and commercial steel on the deoxidization thermodynamics,moreover,the deoxidization thermodynamics for actual molten steel was not yet systematic,and further research was needed.Inclusion controlling should also be considered during the deoxidization process,and it was necessary to ensure the deoxidization effect without affecting the removal efficiency of inclusions and preventing the formation of large size inclusions. Related Articles | Metrics