The addition of rare earth to steel can improve its cleanliness and properties. The research progress of rare earth treatment in Al-killed steel was reviewed. The development and current status of rare earth-containing steel was outlined firstly. Then the effects of adding rare earth to molten steel were summarized on steel cleanliness, inclusion modification, microstructure and mechanical properties, as well as corrosion and oxidation resistance. Among them, the influence of rare earth treatment on inclusions in steel was described in detail including their modification mechanism, evolution, size, density and distribution characteristics, etc. In addition, researches on slag bearing rare earth were introduced including its application in electroslag remelting as well as slag-steel reaction in secondary refining. Finally, a summary and suggestions were provided to offer references for future research and application of rare earth-treated steel.

Through the KR hot metal pre-desulfurization water model test, the main factors affecting the KR hot metal desulfurization kinetics were analyzed and discussed. The research results show that the rotational speed of the agitator, the insertion depth of the agitator, the loading depth of the hot metal tank, and the tank diameter ratio have obvious effects on the kinetics of hot metal desulfurization. The particle dispersion was the best when the rotating speed was 140 r/min, the insertion depth of the agitator was 213 mm, the loading depth of the hot metal tank was 450 mm, and the tank diameter ratio was 0.42. It was found that the optimal range of vortex depth relative to agitator and vortex width relative to agitator was 0.96-1.17 and 0.66-0.72 respectively in the area with the best dispersion of desulfurizer particles.The optimal range of vortex depth relative to agitator depth and vortex width relative to agitator width was 0.88-1.37 and 0.61-1.20 respectively in the area with relatively well dispersion of desulfurizer particles. Based on the results of water model experiments, industrial experiments were carried out to optimize the KR kinetic conditions: compared with the original agitator's 66.8 %, the deep desulfurization ratio of hot metal in the optimized agitator increased by 7.2 percentage points to 74 %.The average mixing time of the new four blade agitator was 630 s, and the mixing cycle was shortened by 18 s. When the stirring period was shortened, the consumption of desulfurizer in the agitator after optimization was reduced by 1.2%, the temperature drop of molten iron decreased by 0.7 ℃,the secondary desulfurization rate reduced by 2.6 percentage points, and the iron loss of slag removal was reduced from 1.71 t to 1.39 t, a decrease of 18.7 %. Industrial tests show that the optimization of KR kinetic conditions has achieved good results under the condition of increasing the proportion of deep desulfurization.

Establishing mathematical models to predict the production status and process parameters of electric arc furnace is of great practical significance to guide production. A dynamic model of electric arc furnace steelmaking was established based on energy efficiency and metallurgical reaction principle, including four moudles: competitive oxidation moudle, energy input moudle, scrap melting and bath heating moudle and temperature solving moudle, to simulate the electric arc furnace steelmaking process. The typical production parameters of an electric arc furnace and the smelting parameters reported in the literatures were substituted into the model for calculation and verification. It was found that the error of simulation temperature and measurement temperature was -7 ℃, the mass fraction error of C, Si ,Mn, and P was 0.017 %、-0.001 %、0.037 %, and -0.000 5 %, respectively. In the meanwhile, the “pick up” of phosphorus could be observed, and the benefits of hot heel on scrap smelting and process performance were demonstrated. The actual production simulation results for multiple heats also showed good prediction results, confirming the good generalizability of the model. The development of this model provides necessary tools to optimize processes and design operational practices to improve the performance and competitiveness of electric arc furnace.

The causes of RH slag oxidation in ultra-low carbon steel and its impact on steel quality, as well as the principles, concrete methods, and implementation effects of the main control process currently dominated by deoxygenation and modification, were summarized. The difficulties and shortcomings of the process control were analyzed. A new control technology with isolation as the main idea and RH vacuum chamber slag-making as the operation method was put forward, its basic principle and theoretical advantages were described, and the preliminary production test and application results were introduced. Both theoretical analysis and practical results indicate that the new control process using RH vacuum chamber slag-making as operation method has the advantages of easy stability control and good effect.And the TFe mass fraction of the bottom layer slag in top slag can be stably controlled to below 4%, which has potential advantages over the current deoxidation and modification process.

In order to improve the cleanliness of silicon-killed steel Q235B and find a suitable refining slag system, thermodynamic calculations and laboratory experiments were carried out to determine the appropriate composition of refining slag and reduce the basicity of the original process slag system.The basicity of the optimized slag system was controlled between 1.70 and 2.0, and the mass fraction of Al₂O₃ was controlled between 7.0% and 10.0%. The optimized slag system were successfully used in industrial tests.The results showed that after optimizing the slag system, the mass fraction of T.O in Q235B silicon killed steel after LF refining in the industrial test furnace could be reduced to 42×10^-6 on average, with a minimum of 26×10^-6.The average mass fraction of  T.O in the slab can be reduced to less than 35×10^-6. The maximum diameter of the inclusions in the tundish can be controlled below 20 μm,the number density of inclusions in the rolled material can be controlled below 15/mm², and the area fraction of inclusions in the rolled material can be controlled below  35×10^-6. The grade of inclusions in steel was significantly reduced and the cleanliness of molten steel was improved.

In the present paper, water modeling was used to study the flow field of a 78 t large double strand symmetrical tundish in a steel plant with different flow control devices.In the 1∶4 scale water model, the particle image velocimetry (PIV), flow field tracer and RTD curve were exploited to study the influence of dam holes, the distance between dam and ladle shroud, the distance between weir and ladle shroud, the height of turbulence inhibitor, the distance between weir and bottom of tundish and the height of dam on the molten steel flow field in tundish from different methods. The results show that with increasing the height of turbulence inhibitor, and decreasing the distance between weir and the bottom of tundish, the average residence times of molten steel in tundish increase obviously, and the volume fractions of dead zone decrease significantly. In addition, the dam without holes can effectively inhibit the development of short-circuit flow, extend the flow distance of molten steel and increase the average residence time. When the distance between the dam and the ladle shroud is increased, the average residence time increases first and then decreases. With increasing the distance between weir and ladle shroud, the short-circuit flow to steel outlet through dam holes is developed, and the average residence time decreases.

The SEM and XRD were used to analyze the mineral compositions and crystallization ratio of the original mold flux after melting and cooling down and its agglomerates during continuous casting process in Xiangtan Iron and Steel Group Co., Ltd.. The results indicate that the three types of mold flux samples have high sphericity and smooth surfaces. The main crystalline phases of mold flux A are cuspidine, nepheline, and wollastonite. Those of mold flux B are cuspidine, wollastonite, and iron sodium potassium silicate. Those of mold flux C is cuspidine. The formation and growth of mold slag bars and agglomerates is due to the large amount of bonding in the sintered phase. In order to reduce the possibility of agglomerates, the Al₂O₃ content in the mold flux should be reduced, and the carbon content should be appropriately increased, so that the mold flux are capable of precipitating cuspidine well during the continuous casting process. Therefore, the heat transfer between the casting slab and mold becomes uniform and stable, thereby reducing the possibility of the destruction of dynamic equilibrium of the liquid slag layer due to slag bar sticking. The occurrence of mold slag agglomeration can be reduced.

The effect ofw(CaO)/w(Al₂O₃) on the physical and chemical properties of the refining slag was investigated through the Factsage thermodynamic software, and the slag composition was determined which had low FeO activity, high CaO activity and low Al₂O₃ activity. The semi-killed tapping technology was developed, after industrial application, the temperature drop of converter tapping was abled to lower about 7.7 ℃, and the deoxidation products were large scaled-clustered Al₂O₃ inclusions which were easily removed from molten steel. Though the synergistic effect of the converter semi-killed tapping process and two slag upgrading processes after steelmaking and RH vacuum break, the TFe mass fraction of slag can be controlled to 4%–6%, and the quantity density of the large scaled inclusions (more than 20 μm) in tinplate has significantly decreased, from 2.2 per 100 mm² before to less than 1 per 100 mm².

In order to improve the castability and cleanliness of ultra-low carbon IF steel in continuous casting, the optimization of converter bottom blowing process, carbon and oxygen contents control at the endpoint, top slag modification, efficient vacuum deeper decarburization technology and enhancing protection of casting process were carried out. The results showed that using the annular-tubes type bottom nozzle instead of the original capillary type gas permeable brick bottom blowing, the single tube bottom blowing intensity 0.086 m³/(t·min), and the stirring energy 0.40 W/t, which could significantly improve the stirring capacity in the later stage of blowing. The average carbon and oxygen product of the molten steel at the endpoint of the converter reached 0.002 09. The vacuum was rapidly pumped to the limit vacuum degree, and the vacuum decarburization efficiency was the highest at 3-5 min forced oxygen blowing stage and holding 8-12 min under limit vacuum degree. Reducing the residual oxygen content after vacuum decarburization and optimizing the top slag composition of ladle could significantly reduce the Al₂O₃ inclusion formation and promote the adsorption and dissolution of inclusions by top slag. With the protection of continuous casting,the control level of oxide inclusion and pouring ability of molten steel has been significantly improved.

High speed production of rolled steel strip on continue casting direct rolling is prone to porosity defects during rolling. The main influencing processes and causes were analyzed through methods such as scanning electron microscopy, energy spectrum analysis, and process data statistics. The results show that the main cause of steel strip holes is the detachment of flocs from the stopper bowl mouth and SEN inner wall during non steady state casting due to changes in static pressure and flow rate of molten steel, which are not floating in the mould and adsorbed by protective slag. Finally, large particle inclusions are formed in the billet, and the main type is high melting point composite inclusions of CaO·2Al₂O₃＋CaO·5Al₂O₃. The sum of residual oxygen content and molten steel sulfur content after RH decarburization directly determines the primary inclusion content of molten steel in LF process. Although deep calcium treatment in LF process leads to an increase in the number of inclusions, it reduces the precipitation and enrichment of high melting point inclusions in the turbulent flow of molten steel from ladle to tundish to mould, which can reduce the generation of pore defects. With the same amount of steel flow, the cleanliness control of steel in continuous casting with large cross-section and low drawing speed is better than that with small cross-section and high drawing speed. 

By comparing new energy vehicles with traditional vehicles, the application and advantages of new energy vehicles in metallurgical engineering projects were discussed. The application effect and economic benefits of new energy vehicles were conformed through the introduction of application cases on new construction projects and existing renovation projects. Practical applications showed that new energy vehicles operate flexibly and can achieve equipment and personal safety. After adopting new energy vehicles in the steelmaking workshop, the operating time of casting cranes decreased by about 50 %, the maintenance workload decreased by about 50%, and the mutual interference during crane operation was reduced.The number of hot turnover ladles reduced by 1, the lifes of ladles increased by 7%-20%, and the consumption of refractory materials was reduced. The LF refining time shortened by 0.5-2 min, and the refining power consumption reduced by 5-9 kWh/t, the energy consumption was reduced. The equipment investment was saved, due to the implementation of off-peak power consumption, the cost of electricity consumption reduced by 30%-40%. The production cost of steelmaking reduced by 3.43-6.65 yuan/t, and the carbon emissions per ton of steel reduced by 3.7-7.2 kg. It is also convenient to transform traditional vehicles into new energy vehicles, which has certain demonstration significance for metallurgical engineering projects to adopt new energy vehicles instead of traditional vehicles.