In order to investigate the effect of oxygen-enriched combustion on regenerative ladle baking process. This paper firstly establishes a three-dimensional model of the ladle with the help of SpaceClaim software. Numerical simulation is used to establish a multi-field coupled mathematical model of combustion, flow and heat transfer based on the standard k-ε turbulence model, species transport model, and DO radiation model. Based on the established model, using the finite element ANSYS FLUENT 2024R1 was used to numerically simulate the combustion field of oxygen at volume fractions of 21%, 24%, 27%, 30%, and 99% inside the ladle, and analyze the distribution of flow field, temperature field, lining temperature, and NOx in ladle under different oxygen concentrations. The analysis results show that under the numerical simulation conditions, oxygen enrichment combustion can not only increase the flame temperature of the ladle heating, but also has the characteristics of high combustion efficiency, fast heating speed and saving gas. Therefore, the combination of oxygen-enriched combustion and regenerative baking technology has important theoretical and practical significance for the improvement of ladle baking technology.

The gas-based shaft furnace has the characteristics of high hydrogen enrichment rate of reducing gas, short process and small environmental pollution, which is an important way to reduce carbon emissions of iron and steel metallurgy by "replacing carbon with hydrogen". Especially with the reduction gas source from natural gas to coke oven gas, coal to gas, chemical by-product H2, etc., more gray hydrogen, blue hydrogen, green hydrogen preparation technology has laid the foundation for the global development of gas-based direct reduction. In this paper, based on the current situation of resources in China, the reduction process of iron oxide in hydrogen metallurgy technology of coke oven gas zero reforming shaft furnace is analyzed, and the change of pellet performance in the reduction process of gas-based shaft furnace is summarized in combination with the research status at home and abroad. The operating state of shaft furnace is analyzed, and the characteristics of different reducing gas composition on the reduction thermodynamics, dynamics, reduction performance and operating state of shaft furnace are grasped. Lower gas pressure and higher temperature are beneficial to the reduction of iron oxide under zero reforming process of coke oven gas. Appropriately increasing the H2/CO ratio in the reduction gas is helpful to reduce the reduction expansion of pellets and improve the compression resistance and high temperature thermal bonding performance of pellets during the reduction process. However, the reduction process is affected by many factors, and the reduction rate is not simply proportional to the H2 content in the reduction gas, combined with the influence of the reduction gas composition on the flow distribution, temperature distribution, pressure distribution and other operating states of the shaft furnace. It is found that the temperature system and operating pressure need to be adjusted while regulating the gas composition. Reasonable gas composition not only needs to consider the reduction rate of iron oxides, but also needs to consider the reduction performance of pellets and the operation state of shaft furnace.

The cold rolling of high-grade thin-gauge silicon steel is prone to edge cracking, difficult deformation, and difficult shape control, so it has always been produced by a single-stand 20-high mill in a reversible rolling process, resulting in relatively low production efficiency and benefit. In recent years, both domestic and foreign countries have begun to explore the basic equipment for the cold continuous rolling production process of high-grade thin-gauge silicon steel. China has also taken the lead in rebuilding or newly building the silicon steel-specific cold continuous rolling production line with four stands, five stands, and six stands based on six-high mill. The roll profile, roll diameter, and roll system structure are all different, which brings confusion to the design of new similar projects. In response to this, this paper first sampled 35WD1900 hot-rolled silicon steel plates and obtained the stress-strain curve of the silicon steel through simulated continuous rolling experiments and normal temperature tensile experiments. Then, for the 1500mm UCMW mill, a finite element simulation model of single-stand rolling and simulated continuous rolling with integrated roll system was established based on the ABAQUS platform. Through a large number of working condition simulations and comparisons, it is determined that the optimal roll diameter range of the work rolls of the portal frame of the continuous rolling mill is between 320mm and 360mm; the optimal roll diameter range of the work rolls of the intermediate frame is between 300mm and 340mm; the optimal roll diameter range of the finished frame work rolls is between 300mm and 340mm. At the same time, in the cold continuous rolling process, the five-stand continuous rolling has always been the mainstream choice. This paper deeply compares the influence rules of five-stand, six-stand, and seven-stand continuous rolling on the crown inheritance and evolution of the rolled strip, and comprehensively considers the economic cost, concluding that the six-stand is the better choice. Finally, the roll profiles of the intermediate roll and work roll are optimized for the continuous rolling production of high-grade silicon steel. The research results have reference value for the design of high-grade thin-gauge silicon steel cold continuous rolling mills and provide guidance for the improvement and optimization of silicon steel continuous rolling technology.

Due to the "homomorphic replacement" of aluminum-iron, Al-goethite is formed, and it is difficult to achieve aluminum-iron separation. H2 was used as the reducing agent, and the typical high-iron gibbsite was pretreated by levitation magnetization roasting, and the iron was enriched in red mud by Bayer dissolution and separation, and the effects of roasting conditions on its phase structure, microscopic morphology, specific surface area and dissolution performance were investigated, and its magnetic changes before and after roasting were analyzed. The results show that the roasted ore is loose and porous, the specific surface area is greatly increased, the aluminum mineral is transformed into γ-Al2O3, the dissolution activity is good, the hematite is transformed into magnetite, the Al-goethite is transformed into a porous aluminum replacement magnetite structure, the aluminum element does not migrate, and the separation effect of aluminum and iron is improved, the optimal roasting conditions are as follows: temperature 500 °C, time 10 min, H2 concentration 20%, total gas flow rate 500 mL/min, the relative dissolution rate of alumina reaches 96.47%, and the aluminum content in the dissolved red mud is reduced. The iron content increased, and the TFe content reached 60.56%, which was 11.28% higher than that of the original ore red mud, and the iron mineral still maintained the magnetite structure, and the saturated magnetization was 54.1 A·m2· Kg-1, which can further improve the iron grade through magnetic separation, which is conducive to the reduction of red mud.

The frequent occurrence of edge linear cracks with a width of 45~120 mm at the edge of the wide and thick plates during rolling process is a common technical problem in the steel industry. Producing the wide and thick slabs with a concave arc structure on the narrow can effectively prevent the narrow face of the slab turn to the wide side during the rolling process, thus it can significantly reduce the width of edge linear cracks in wide and thick plates. In order to made the wide and thick slabs with narrow concave curved faces, a mold with convex curved structure narrow face copper plates (called a convex lens-shaped mold) was designed in the present work. Based on this, a 3D coupled thermo-mechanical finite element model for the 1/4 slab-mold system was established, and the laws of dynamic deformation of slab shell, the distribution of the heat transfer medium in the gap between slab and copper plate, and the temperature evolution of the solidified slab and the copper plate in the convex lens-shaped mold and a traditional mold were comparatively analyzed. The results show that the maximum interface gap of slab-mold around mold wide face corner is 1.26 mm at the mold exit in the convex lens-shaped mold. As a result, the maximum thickness of the air gap is 0.71 mm, and the thickest slag film in the off-corner area is about 1.13 mm. As to the narrow face, the maximum interface gap forms at the mold corner at the position of 500 mm below meniscus. The maximum thickness is 1.40 mm. Accordingly, the maximum thickness of the air gap is 0.53 mm at the corner, and the thickest slag is 1.35 mm in the off-corner area. Compared with the traditional mold, the maximum interface gap in the wide and narrow corners of convex lens-shaped mold reduce 0.29 mm and 0.33 mm than that of in traditional mold, respectively. Also, the maximum thicknesses of the air gap and slag film reduce by 0.23 mm, 0.18 mm and 0.35 mm and 0.34 mm, respectively. As a result, the distribution ranges of high temperature areas in the wide and narrow off-corner of the slab reduce by 36 mm and 17 mm, respectively, and the maximum temperatures reduces by 35 ℃ and 44 ℃ correspondingly. It improves the uniformity of the slab heat transfer. Moreover, the temperature distribution at position of narrow face around the meniscus becomes more uniform, and the maximum temperature reduces by 15°C since the homogenizing water slit design in convex lens-shaped mold compared to the traditional mold.

Copper is one of the most harmful impurities in steel-making because of its role in causing metallurgical problems during thermo-mechanical processing. It cannot be oxidated from iron-based melt during the conventional refining process but can be sulfurized by sulfur-containing agents according to the strong affinity between S and Cu at high temperature. The decopperization in carbon saturated iron melt using different sulfur-containing agents was studied in this paper, and the results shown that when using Na2S-FeS slag with a ratio of XFeS/XNa2S=6/4, 95.1% of copper can be removed in 15 minutes. Increasing the ratio of Na2S in the slag can limit the increase of sulfur content in iron caused by mass transfer from slag. When XFeS/XNa2S=2/8, the sulfur content in iron after decopperzation can be controlled in 0.032wt%. Adding oxides such as Al2O3 to the sulfide slag can significantly limit sulfur transfer from the slag to iron, but it has a certain impact on the copper removal.

The current hot strip rolling gradually presents the characteristics of variety diversity and process complexity. Due to the consideration of fewer factors, the traditional rolling force prediction models gradually reveal some defects and deficiencies, and cannot meet the requirements of high-precision and high-performance product control accuracy. This article combines a 2250 mm hot rolling finishing mill in China, utilizes data mining technology and intelligent algorithms, and combines with mechanism models to develop an intelligent rolling force model of mechanism model + GBDT model. The model considers all factors, and can obtain plan data in advance, conduct targeted training on the steel grades to be rolled, and improve the prediction accuracy of small samples; it develops self-training and closed-loop control technology, which can be deployed and applied in various environments to achieve automatic closed-loop control. After applying the model on-line, the long genetic prediction accuracy of rolling force is controlled within 5%, and the single calculation time takes less than 10ms. The results show that the model has fast response speed, high calculation accuracy and good calculation stability, which can meet the requirements of rolling force accuracy control under changing steel grades and working conditions, thereby improving the stability of strip rolling and the control accuracy of head thickness, and enhancing product competitiveness.

The yellowing defect on the surface of 16MnCr5 steel plate affects the surface quality of users. The reasons for the formation of yellowing defects on the surface of 16MnCr5 steel were analyzed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), glow discharge spectroscopy (GDS) and other methods.The results indicate that. The yellowing defect is closely related to the state of oxidized iron scale on the surface of hot-rolled steel plates and the control of acid washing process. On the one hand, due to the high Mn and Cr content of 2% in the steel, during the high-temperature coiling process of hot-rolled steel plates, Mn and Cr elements diffuse along the grain boundaries to form intergranular oxidation products, leading to preferential corrosion of the grain boundaries and the formation of pores in the subsequent acid washing process, making it easy for the acid solution to remain in the pores and causing surface oxidation and yellowing. When the rinsing process in the acid washing section is unreasonable, the severity of the yellowing defect is further exacerbated. Corresponding control strategies were proposed, such as reducing the hot rolling coil temperature, increasing the cooling speed after coiling, and improving the rinsing process. After process adjustment, the yellowing defect basically disappeared, achieving the source control of typical genetic defects in hot rolling.

Constrained by energy structure and resource endowment, it is challenging to fundamentally alter the process structure of China’s iron and steel industry, dominated by the traditional blast furnace-converter long process. In this study, a theoretical model integrating gas-solid heat transfer and reaction kinetics is developed for the low-carbon blast furnace technology featuring gas injection as its core. This model considers gas-solid heat transfer effects, ore reduction, coke dissolution loss, burden softening and melting, and slag-iron droplet influence on gas-solid phase interaction. The model is employed to simulate the smelting process of a 2300 m3 blast furnace in China, yielding characteristic parameters consistent with production data, such as gas quantity in the belly and furnace top temperature. Furthermore, the model examines the impact of various injection volumes on gas flow distribution and temperature within a 2300 m3 blast furnace operating under CO-rich gas injection conditions. Results indicate that gas introduction fosters indirect reduction, leading to increased gas and charge temperatures in the upper furnace region with rising injection volumes, while causing a slight drop in pressure.

SPHE steel is produced by the BOF-LF-RH-CSP process in a domestic steel mill. In this paper, the changing law of the type, quantity, and size of inclusions in the refining process of SPHE steel was investigated. The results demonstrated that throughout the entire refining process, the inclusions achieved the following modification process: Al2O3→MgO?Al2O3 spinel with high Al2O3 content→CaS?C12A7?MgO?Al2O3 composite inclusions. The density of the number of inclusions decreased from 97/mm2 when entering the LF station to 12/mm2 when leaving the RH station. Furthermore, the average size was gradually reduced from 5.2 μm to 1.5 μm, and the cleanliness of the steel was significantly improved. Thermodynamic calculations at 1873 K showed that the [Mg] content corresponding to the stabilization interval of the generated MgO?Al2O3 was 0.0000323%~0.0018% for the [Al] content range of 0.0216%~0.0533% in the refining process. Upon entering the RH station, the [Al] content was 0.0533%. The generation of liquid 12CaO?7Al2O3 (C12A7) was favored when the [Ca] content was in the range of 0.00024%~0.00087%. There was a strong tendency to generate MgO?Al2O3 during the refining process, which was the nucleation core of CaS?C12A7?MgO?Al2O3 composite inclusions. The evolution law of inclusions in the refining process under the LF-RH-CSP process was revealed by establishing a schematic of the inclusion evolution mechanism. The research results provide data support for improving the castability of SPHE steel produced by the CSP process.

As one of the implementation methods of heavy pressing technology, single roll heavy reduction is different from only using heavy pressing technology as a supplement or optimization of soft reduction technology. Instead, it is studied and applied as an independent pressing technology different from soft reduction. It is necessary to verify the effectiveness of its process, and even systematically explain it based on practice. This article is based on the practical results of single roll heavy reduction of 82B steel grade with 180mm x 180mm square billets. On the basis of reliable evaluation of center shrinkage and center segregation methods, the improvement effect of center shrinkage and center segregation after single roll heavy reduction at different pressing positions is analyzed to verify the effectiveness of single roll heavy pressing technology in independently improving the quality of casting billets. Combined with practice, the mechanism, method, and guiding principles of single roll heavy pressing process control are proposed. Finally, the advantages of single roll heavy pressing technology in simplifying equipment schemes are presented. Through the practice and research analysis of single roll heavy reduction in this article, the following conclusions can be drawn: The optimal pressing position for improving center shrinkage under continuous casting heavy pressing is before the filling and shrinking channels are closed and the shrinkage holes are formed, rather than welding after the shrinkage holes are formed;The optimal location for improving center segregation under heavy reduction is also before the filling and shrinking channels are closed and shrinkage holes are formed; The formation of central porosity, shrinkage, and central segregation is interrelated in mechanism. By applying single roll heavy reduction in suitable areas where the feeding and shrinking channels are not closed and shrinkage cavities are not formed, both central shrinkage and central segregation can be effectively controlled simultaneously, achieving the effect of improving the quality of the casting billet; As the amount of single roller reduction increases, there is a tendency for loose and shrinkage defects to aggregate towards the center, while the accompanying center segregation does not show an increasing trend; The critical position for the end of the filling and contraction channel of 82B steel grade is around 0.73 in the center solid phase ratio; The single roll heavy pressing process will simplify the equipment for pressing square billets, greatly reducing the cost of pressing square billets.

Blast furnace as the key link of steel production, its stable operation is very important for production efficiency and product quality. Therefore, it is necessary to monitor and evaluate the operation condition of blast furnace in a timely and comprehensive manner. According to the historical production data of blast furnace, based on the methods of Factor Analysis, K-Means cluster analysis and statistical process control (SPC), a software system which can comprehensively evaluate and monitor the running state of blast furnace is developed by using computer technology, information technology and database technology. In this paper, firstly, the problems of missing values and outliers in historical data are solved by filling and deleting method and boxplot method, and the data normalization process is completed to ensure the integrity and accuracy of the data. Then, according to the experience of experts and the characteristics of blast furnace operation, 29 key parameters are selected to construct the evaluation model. Secondly, factor analysis and K-Means cluster analysis are used to establish a BF state evaluation model, and a comprehensive BF operating state evaluation system is established by extracting key indicators that can fully reflect the BF operating state, and K-Means cluster analysis is applied to classify and judge the BF operating state. The accuracy and reliability of the model are verified by actual production data. Then, the SPC control chart is used to monitor the operation status and evaluation indicators of the blast furnace, and trace the cause of the abnormal operation, so as to help the operator adjust the production strategy in time and ensure the continuous and stable operation of the blast furnace. Finally, based on the above model, the blast furnace evaluation and monitoring system is developed to realize the visualization of the operating state of the blast furnace, which greatly assists the operators in monitoring and managing the efficiency of the stable operation of the blast furnace, and helps to achieve the goals of high quality, low energy consumption, high output, high efficiency and long life of the blast furnace production.

The cold rolling flatness control is a complex system engineering, involving rolling process, control theory, applied mathematics, computer communications, as well as artificial intelligence and other subject areas. The cold rolling flatness control technology is one of the core technologies of the iron and steel industry, it is a key technological component to realize the stable production of high-quality steel strip, and represents one of the highest levels of a country in the field of iron and steel technology, and its related technology has always been the difficulty and hot spot in the field of cold rolling technology research. This paper provides an overview of the research progress in flatness characterization and measurement technology, flatness presetting control technology, flatness feed-forward control technology, flatness closed-loop control technology and core flatness control model, and analyses the current status and characteristics of various control technologies. Based on this foundation, combined with the research results accumulated by the author's team in the field of cold rolling flatness control for many years, the research route and development direction with digital twin and cyber-physical systems (CPS) as the technical architecture are proposed. By continuously focusing on the key technical problems in the field of cold rolling flatness control, combining data processing technology, artificial intelligence and other cutting edge knowledge, integrating the rolling mechanism and optimization control theory, and proposing a digital research methodology for cold rolling flatness control technology, enhancing the technical level of thin strip cold rolling production and product quality, promoting the rolling industry from process technology to product quality, and facilitating the iron and steel industry to move towards the direction of green and low carbon development.

To study the impact of Y and Zr on inclusions, microstructure, and mechanical properties of non-modulated steel, three experimental steel variants were produced using a vacuum induction furnace in the laboratory, followed by forging. Inclusions in both as-cast and as-forged samples were quantified and analyzed via scanning electron microscopy. Microstructural examination of the forged steel was conducted using a metallographic microscope. The mechanical properties of the experimental steel were assessed using a universal material testing machine and an impact testing machine. Results indicate that the addition of Y and Zr led to predominantly class III and class I MnS inclusions in A2 and A3 as-cast steels, with average diameters of 2.9 μm and 1.8 μm, respectively. The oxygen content is not the primary determinant of MnS morphology and distribution in the steel. YAlO3 and Y4Zr3O12 formed within the steel exhibit a slight Lattice disregistries with MnS, facilitating heterogeneous nucleation and precipitation with oxide as the core during solidification. MnS with oxide as the core demonstrates enhanced deformation resistance during forging. Following Y and Zr alloying, the experimental steel experiences reduced grain size, heightened intragranular ferrite proportion, with average grain sizes decreasing from 36.5 μm (B1) to 22.8 μm (B2) and 11.4 μm (B3). Intragranular ferrite proportion increased from 2.4% (B1) to 6.2% (B2) and 11.1% (B3). Steel B3, exhibiting the smallest grain size, highest intragranular ferrite proportion, and smallest MnS size, demonstrates superior mechanical properties, with a yield strength of 825 MPa and room temperature impact energy of 52 J.

For the control of oxidizable elements Hf, Al, and Ti in the process of electroslag remelting of K4002 alloy, this study is based on the six-member slag system CaF2-CaO-Al2O3-MgO-TiO2-HfO2 and combines theoretical and experimental research to investigate the effect of components of slag change on components activity and oxidizable element content by using the thermodynamic model established by molecular and ion coexistence theory(IMCT). At the same time, the validity of the model is verified by slag-metal equilibrium experiments. The results of the study show that the variation of components in the slag has no significant effect on the Ti content, and has a large effect on Hf and Al. Adding HfO2 to the slag can inhibit the oxidative burnout of Hf, but also exacerbate the oxidative burnout of Al. Increasing the temperature can inhibit the burnout of Hf, and decreasing the temperature can inhibit the burnout of Al. The components of slag are in the order of HfO2>SiO2>TiO2>MgO in the ability to inhibit Hf oxidative burnout, and Al2O3>CaO>CaF2 in the order of enhancing Hf burnout; the order of the ability to enhance the loss of Al content is HfO2>SiO2>TiO2>MgO, and the order of inhibiting the loss of Al content is Al2O3>CaO>CaF2. The optimal ratio of the main components that can effectively reduce the oxidation and burning loss of Hf, Al, and Ti elements during the electroslag remelting process of K4002 alloy is 10%~12% HfO2, 20%~25% Al2O3, and 10%~15% CaO. In addition, the S content in the alloy is reduced from 22 ppm to less than 7 ppm, indicating that the designed slag system has a strong S removal capability.

To investigate the formation mechanism of large-size CaO–Al2O3–SiO2 inclusions in high-speed railway wheel steel, the characteristics of inclusions are analyzed by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). Additionally, the formation process is calculated using FactSage thermodynamic software. The results reveal that the inclusions in the continuous casting billet of wheel steel mainly comprise CaO–Al2O3–SiO2, categorized into two different types. The first type is the small-size solid and semi-solid inclusion formed during the cooling and solidification process of liquid steel. The second type is the large-size liquid inclusion originating from the refining process. Notably, among these liquid inclusions, up to 43% exceed 10 μm in size and can be traced back to the calcium treatment stage during the refining process. Following calcium treatment, the liquid steel undergoes a reaction leading to the formation of liquid CaO–Al2O3–SiO2 inclusion. Due to their low contact angle with the liquid steel, these inclusions are difficult to remove and consequently persist in continuous casting billet. The formation of liquid CaO–Al2O3–SiO2 inclusions remains unaffected by controlling the Al content in the steel during calcium treatment. Only precise control of the Ca content can prevent the formation of such inclusions. When the Ca content is maintained at 0.0007%, the inclusions with a liquid phase ratio of 20% can be formed. Unlike the liquid CaO–Al2O3–SiO2 inclusions, these inclusions do not affect the continuous casting of liquid steel and can be easily removed. Achieving such accurate Ca content necessitates precise calcium treatment, as well as appropriate Al content and refining slag composition.

With the deepening of energy conservation work, the energy conservation work of iron and steel industry is more difficultly. As the energy conversion unit of iron and steel industry, coke-making process is an important link in the process of iron and steel production. Therefore, the comprehensive analysis of the influencing factors of the coke-making process and the deep exploration of the energy saving limit of the coking process are of great significance to the energy saving and emission reduction work of iron and steel industry. Based on the analysis method of input-output and heat balance, this paper comprehensively analyzes the influence of energy conversion difference and coking heat on energy consumption. Based on the heat balance, the coking heat is further divided into four factors: coal volatiles, moisture, coke oven heat loss and gas consumption ratio, and the influence of these factors on coke oven energy consumption is discussed. In addition, based on the reaction mechanism of the coke-making process, the corresponding production process is assumed by thermodynamic method, and the theoretical limit energy consumption of the coke-making process is calculated based on the actual raw materials, fuel parameters and reaction conditions, which provides a theoretical basis for accurately judging the energy saving limit of the coke-making process. Combined with the energy consumption characteristics of the current coke-making process, the application status of technology and the implementation path of extreme energy efficiency work, the energy saving ways and energy saving potential of the coke-making process are analyzed. To sum up, by exploring the influencing factors of energy consumption in the coking process and analyzing the theoretical limit energy consumption of the coke-making process, the paper aims to provide a theoretical basis for the ultimate energy efficiency of the iron and steel production process and help the iron and steel industry achieve the goal of reaching carbon peak and carbon neutrality.

In order to improve the cleanliness of Q690 steel and seek suitable refining slag system, thermodynamic calculations and laboratory experiments were carried out to determine the most suitable components of Q690 steel refining slag system. The calcium aluminum ratio of the original process slag system was reduced, and the optimized slag system CaO/Al2O3 was controlled between 1.8-2.0, and the alkalinity was controlled between 5.0-7.0. And the optimized slag system components were successfully used in industrial experiments, and the results showed that after slag system optimization, Q690 steel had T The content of [0] can be reduced to below 7ppm, and the maximum diameter of inclusions in the research stage is 40-60 μm decreases to 10-20 μm; The area fraction, number density, and maximum diameter of inclusions detected in steel significantly decrease. The number density of inclusions in cast steel samples can be reduced to below 1/mm2, the area fraction of inclusions can be reduced to below 16ppm, and the maximum diameter can be reduced to 17 μm. The inclusion levels of Class D and Ds in the rolled plate are both less than 1.0, meeting the requirements of high-grade and high-quality steel.

In order to solve the surface cracking problem of 10CrNi9MoV large-scale electroslag remelting slab, the characteristics and formation mechanism of surface cracks on electroslag slab were investigated by using the analytical methods of residual stress, macrostructure, crack morphology, microstructure and hardness analysis. The results show that most of the surface cracks on electroslag slab cracked along the coarse columnar crystal grain boundaries, which exhibit the typical feature of intergranular fracture. And there is obvious oxidation phenomenon at the cracks, indicating that the cracks were mainly generated in the solidification and cooling stage of electroslag slab. The formation mechanism of surface crack on electroslag slab was analyzed, the intergranular bonding force of coarse martensite columnar crystals which formed under a rather large cooling intensity by crystallizer was weak, which caused cracks along grain boundaries under the instantaneous tensile stress produced by martensitic transformation, and that is the main reason for surface intergranular cracks on the experimental electroslag slab. Based on the formation mechanism of surface cracks, the process optimization measure of reducing the crystallizer cooling water flow rate from 130 m3·h-1 to 80 m3·h-1 was proposed and industrially verified. It was verified that the microstructure of the electroslag slab is mainly composed of mixed martensite and bainite, whose average hardness is reduced by about 40 HV10 compared with the pre-optimization electroslag slab. And no crack was found on the surface, which indicated that the adopted optimization measure for the cooling rate of the crystallizer is reasonable and effective.

The RTD curve obtained by physical or numerical simulation is an important method for optimizing the structure of tundish through analyzing the residence time and flow field region. Dimensionless quantities are converted by filtering, organizing and summarizing the data of single or two strand tundishes through literature research. The effects of structural parameters such as the width, liquid level height, inlet-outlet spacing, sidewall inclination angle of tundish, the height and cross-sectional area of the turbulence inhibitor, as well as the position and height of the weir and dam on the residence time and flow field are summarized. The optimal ratios of different structural parameters for tundish and flow control devices are also summarized. The ratio of the width to the length of the tundish should be between 0.15 and 0.3; the ratio of the liquid level height to the tundish length should be between 0.15 and 0.3; the ratio of the inlet-outlet spacing to the tundish length should be between 0.8 and 0.9; and the inclination angle of the tundish sidewall should be between 10-15o. For turbulence inhibitors, the ratio of the height of the turbulence inhibitor to the height of the liquid level should be in the range of 0.1 and 0.2 and the ratio of the cross-sectional area to the cross-sectional area of the tundish bottom should be close to 0.15. The ratio of the distance between weir and shround to the length of tundish should be close to 0.2; the ratio of the height to the liquid level should be close to 0.4 or 0.7; the ratio of the distance between the weir and the dam to the length of tundish should be between 0.05 and 0.1; and the ratio of the dam height to the liquid level should be around 0.3.

Research on the flue gas circulation system of a 196-square-meter sintering machine in a steel company, a three-dimensional physical model was established as the entire calculation domain for simulation. Focus on improving the structure of the flue gas circulation hood, introducing the concept of immersed nozzle, and organically combining it with the sintered flue gas circulation hood to achieve the goals of flue gas diversion and uniform distribution. The results show that: compared with the original flue gas circulation hood structure, after improving the air inlet structure, the deflection of the central flow is reduced by 85%, and the maximum flow velocity entering the sintered material layer is 3.1381 m/s. The horizontal section of the sintered material layer The speed variance is 0.36, which is 84.1% lower than the original structure, eliminating the problems of flue gas deflection and excessive material surface speed. The flue gas is evenly distributed in the flue gas circulation hood. The improved air inlet structure is consistent with the sintering The synergistic effect of the flue gas circulation cover allows the flue gas and material layer to interact more effectively, thereby achieving higher sintering efficiency and lower exhaust emissions.

To address the frequent occurrence of ultrasonic flaw detection of wind power gear steel, this paper investigated the causes of these defects. Through defect observation and refining process sampling analysis, the types of defects and their formation stages were identified. Then, combining thermodynamic calculations to determine the formation causes of defect inclusions and propose process improvement measures. The results showed that these ultrasonic flaw detections were large-sized inclusions formed by the aggregation of solid magnesium aluminum spinel and liquid CaO-MgO-Al2O3-SiO2 inclusions, with a small amount of CaS attached to the periphery. The size of these defect inclusions ranged from 30 μm to 100 μm. Analysis founded that the low [Al] content in the VD process steel was the root cause of the formation of high SiO2 content CaO-MgO-Al2O3-SiO2 inclusions. Due to the low [Al] content, the [Si] in the steel liquid reduced the Al2O3 in the inclusions, forming high SiO2 content CaO-MgO-Al2O3-SiO2 inclusions. As the [Al] content in the steel liquid rised again, the SiO2 in the inclusions was partially reduced, but some high SiO2 content CaO-MgO-Al2O3-SiO2 inclusions still remained. Increasing the [Al] content in the VD process steel to above 0.010% is a reasonable measure to reduce the occurrence of high SiO2 content CaO-MgO-Al2O3-SiO2 inclusions.

高炉软熔带是保证煤气流合理分布，实现低碳冶炼的关键性因素之一，其位置和形状主要受到含铁炉料的冶金性能及高温交互作用影响。综述了烧结矿、球团矿以及块矿等不同含铁炉料之间的高温交互作用机理、影响因素以及高温交互作用对炉料软熔性能与渣相形成的影响。指出适当调整炉料化学成分和混匀度、优化炉料结构以及改善炉料的还原条件等均能优化含铁炉料间的交互作用，改善炉料的软熔滴落性能和透气性。未来可加强冷压球团、金属化球团和熔剂型球团等优质球团与其他含铁炉料的交互作用机理研究，加深炉料交互作用过程中物相演变及不同含铁炉料的扩散动力学行为的相关性研究，从而对炉料的软化熔滴性能和透气性优化提供参考。

The basic feature of fractal is self-similarity, which means that the local and the whole are similar in some way. Large clusters in steel were formed by collision and aggregation of fine and uniformly distributed solid inclusions, which have irregular fractal characteristics. Therefore, the fractal dimension can be used to quantitatively describe the morphology of inclusions. The surface roughness of inclusions can be characterized by the one-dimensional fractal dimension (D1). The smaller the D1, the smoother the inclusion boundary and the smaller the impact on the material properties. The two-dimensional (D2) and three-dimensional (D3) fractal dimension characterized the density of area and volume, respectively. A three-dimensional fractal dimension less than 2 means that the cluster structure was so sparse that the three-dimensional structure projected onto the two-dimensional plane was not overlap on the two-dimensional plane. Firstly, the definition and different calculation methods of the fractal dimension, the measurement method of three-dimensional fractal dimension, and the models for the transformation between the three-dimensional and two-dimensional fractal dimensions were summarized. Secondly, the main factors affecting the fractal dimension of inclusions were analyzed, including the composition of inclusions and the calculation error. The fractal dimension of large clusters was about 1.7-1.8. In the process of box-counting dimension calculation, the calculation error came from the selection of the maximum size of the covering box. When 0.25≤ε/dmax≤1, the calculation error of inclusion fractal dimension was avoided. Finally, the application of fractal dimension in the study of inclusions was summarized. The theoretical floating velocity of irregular clusters in molten steel can be calculated by fractal dimension. The floating velocity of inclusions increased with the increase of fractal dimension. The fractal dimension can be used to study the morphology of aggregates formed by inclusions after collision and aggregation. During the collision of inclusions, the aggregation between solid inclusions reduced the fractal dimension of clusters, while the aggregation between liquid inclusions and solid inclusions increased the fractal dimension of clusters. Based on the development of fractal theory, the diffusion-limited aggregation model (DLA model) was proposed to simulate the aggregation of inclusions in steel. As the distance between the release point of particles and seeds decreased, the particle size increased, and the seed size increased, the aggregation degree of inclusion increased. The stopper or nozzle can be considered as large seeds, and inclusions were easy to gather on its surface, which caused the nozzle clogging. The stopper or nozzle clogging can be reduced by improving the wettability between the stopper and inclusions. The aggregated clusters inclusions were in a chain or more dispersed branched structure with the increase of aggregation ratio between the basic particles.

In order to study the effect of CaO/Al2O3 on the removal of non-metallic inclusions in aluminum deoxidized high-strength steel in LF refining process, the industrial test of different CaO/Al2O3 refining slag was carried out with Q690 high-strength steel as the research object, and the quantitative analysis was carried out by thermodynamic calculation. The CaO/Al2O3 of the three furnaces were 1.58, 1.77 and 2.22, respectively, and the refining slag with CaO/Al2O3 of 2.22 had the best effect on the removal of inclusions. In the LF refining stage, the number density of inclusions decreased from 13.89 #/mm2 to 6.56 #/mm2 with a change rate of 53%, the area fraction decreased from 0.0122% to 0.0034%, the change rate was 72%, and the average diameter decreased from 4.82 μm to 3.44 μm with a change rate of 29%. By introducing the inclusion capacity Zh of the refining slag and applying it to the thermodynamic calculation of the refining slag with a certain solid phase composition, the Zh numbers of the refining slag in the three furnaces were 0.00194, 0.000307 and 0.000320, respectively, because the CaO/Al2O3 2.22 refining slag has the largest Zh number. So it has the best effect on the removal of inclusions. According to the prediction diagram of inclusion capacity, the Zh number reached the maximum in the liquid phase of the slag with CaO content greater than 55%. In order to ensure the removal effect of inclusions, when the SiO2 content in the refining slag is 15%, the CaO/Al2O3 in the refining slag is 2.04~3.05, when the SiO2 content in the refining slag is 10%, the CaO/Al2O3 in the refining slag is 1.73~2.22, and when the SiO2 content in the refining slag is 5%, the CaO/Al2O3 in the refining slag is 1.51~1.55. With the decrease of SiO2 content in the refining slag, the suitable refining slag CaO/Al2O3 gradually decreases and the range becomes smaller.

In order to optimize the hot deformation process of DP1180 steel, the high temperature compression test of DP1180 steel was carried out by Gleeble-3800 thermal simulation testing machine under the conditions of deformation temperature of 850 ~ 1100 °C and strain rate of 0.1~10 s-1. The true stress-strain curve of the steel was obtained, and the influence of temperature and strain rate(ε ?) was analyzed. The deformation resistance model was established and modified by the existing model, and the hot processing map of the steel under different strain was drawn according to the true stress-strain curve. Experiments show that the increase of T and the decrease of ε ? will make the flow stress smaller, that is, dynamic recrystallization are more likely to occur. The deformation resistance model established by Origin software, the fitting curve is basically consistent with the measured value, and the accuracy of the error analysis model is high,but its scope of application still has some limitations. By drawing the hot processing map, it is found that there are almost few rheological instability zones in the hot processing map under the experimental conditions. The best theoretical thermal processing area is the strain rate of 1~10 s-1, and the deformation temperature is controlled at 1050~1100 °C.

Reducing the content of alkali metal in pellet is beneficial to reduce the alkali load of blast furnace. Therefore, the application of two kinds of low alkali metal bentonite in pellet production was studied. The results show that under the same ratio, the number of green pellet using two kinds of low alkali metal bentonite increased from 5.0 times / 0.5 m to 5.2 times / 0.5 m and 8.8 times / 0.5 m, respectively. The alkali metal content decreased from 0.203 % to 0.142 % and 0.146 %, respectively. The reduction expansion rate decreased from 13.8 % to 11.9 % and 12.7 %, respectively. The RDI + 6.3, RDI + 3.15 and RDI + 0.5 have a good trend. One of the low alkali metal bentonites was carried out in the pellet production of a steel plant. The results show that the alkali metal content of pellet with low alkali metal bentonite decreased by 0.055 % while the compressive strength changed little, and the reduction expansion rate had a decreasing trend.

At present, the lithium extraction by oxalic acid leaching of clay-type lithium ores has only studied the influencing factors in the leaching stage, and lacks a systematic study on the subsequent lithium extraction from the leach solution. The leachate was treated through methods including light to precipitate iron, excess lime method, and calcium removal by the sodium carbonate to precipitate lithium in this study. The effects of light time, calcium oxide dosage, sodium carbonate dosage, reaction temperature and reaction time on the precipitation separation of impurity ions were investigated. The experimental results indicate that under the conditions of 7 hours of light exposure, 2.5 hours of reaction at 75°C with 4 grams of calcium oxide (per 30 mL of solution after light exposure), and 20 minutes of reaction at 75°C with 40 milligrams of sodium carbonate (per 30 mL of solution after excess quicklime method), the precipitation rate of aluminum reached 99.91%, while that of iron, magnesium, and calcium reached 99.99%..Sodium carbonate calcium removal solution is concentrated and precipitated at high temperatures to obtain the lithium carbonate. Mechanistic analysis showed that iron was mainly precipitated as FeC2O4 after light exposure. The excess quicklime method makes aluminum and magnesium precipitate in the form of hydroxide, which effectively reduces the adsorption of lithium by amorphous aluminum hydroxide. Sodium carbonate, on the other hand, causes calcium to precipitate as the calcium carbonate and lithium to precipitate to give crude lithium carbonate. A method for preparing crude lithium carbonate from roasting-oxalic acid leach solution of clay-type lithium ores was obtained by this experimental study.

As China's steel production continues to increase, the steel industry is facing severe resource and environmental challenges, particularly in the treatment and utilization of steel slag. Currently, a significant amount of thermal energy from steel slag is wasted, and the process of recovering metallic iron is highly energy-intensive. Additionally, the comprehensive utilization rate of tail slag is low, with most steel slag being landfilled or stockpiled. In the context of the carbon peaking and carbon neutrality goals, the development of low-carbon, green technologies for steel slag treatment and utilization is imperative. This paper introduces the current mainstream processes for steel slag treatment and discusses the advantages and disadvantages of different methods. It summarizes the main pathways for resource utilization of steel slag and analyzes the technologies for comprehensive utilization of steel slag in recent years. Considering the current state of steel slag treatment and utilization, this paper discusses and anticipates the future directions in this field. Under thecarbon peaking and carbon neutrality targets, it is essential to effectively utilize the thermal energy of molten steel slag, develop technologies for waste heat recovery and hot steel slag iron extraction, and use steel slag carbonation techniques to produce high-value-added products, achieving full-scale recovery of heat, iron, and tail slag resources.

Refining slag has a very significant effect on the cleanliness of molten steel. It mainly plays the role of deoxidization, desulfurization and adsorption of inclusions. MnS is a common non-metallic inclusion in heavy rail steel. Large-sized long strip MnS has great harm to the performance of steel. Based on the idea of promoting the heterogeneous nucleation of MnS on the surface of oxides to reduce the harm of class A inclusions, this study discussed the influence of the proportion of alumina in slag on the composition, size and distribution of inclusions in combination with industrial experiments and thermodynamics. It was found that when the mass fraction of alumina in slag decreased from 13.72% to 7.23%, the total aluminum content in steel decreased from 24 ppm to 20 ppm, the Al2O3 content in rail inclusions decreased from 83.35% to 75.07%, and the number density of oxide inclusions increased from 2.90 #/mm2 to 5.69 #/mm2. It is beneficial to promote the non-uniform nucleation of MnS on the oxide surface. The results show that with the decrease of the proportion of alumina in the slag, the coarse grade of MnS rating of A method decreases from 2.0 to 1.0, and the fine grade decreases from 1.0 to 0.5. The coarse grade of MnS rating of B method decreases from 0.744 to 0.621, and the fine grade remains at 0.5. The thermodynamic calculation results show that the proportion of alumina in the slag affects the content of [Al] in the molten steel by affecting the activity of Al2O3 in the slag, thus affecting the content of Al2O3 in the inclusions.

The calcium treatment technology was widely in the production of pipeline steel. The effect of calcium contents on the modification of non-metallic inclusions in the liquid steel and continuous casting slab was studied. It was indicated that as the mass fraction of T.Ca in the molten steel increased from 5 ppm to 20 ppm, the average composition of non-metallic inclusions in the steel initially approached the liquid phase region and then away from it. Moreover, the mass fraction of Al2O3 inclusions in the steel decreased from 68.14 % to 48.89 %, while the mass fraction of CaO inclusions increased from 21.8% to 27.8%. The average size of non-metallic inclusions in the continuous casting slab decreased from 4.02 μm to 3.83 μm, and the number density of non-metallic inclusions reached a minimum value of 6.61 #/mm2 when the mass fraction of T.Ca in the molten steel was 20 ppm. Thermochemical calculations were performed to investigate the transformation of inclusions during the solidification process. It was shown that the mass fraction of MnS in the continuous casting slab of pipeline steel decreased from 10.65 % to 4.84 % as the calcium content in the steel melt increased. Additionally, the precipitation temperature of MnS inclusions decreased from 1340 oC to 1220 oC. The results obtained from thermochemical calculations were consistent with those from industrial experiments.

Non-metallic inclusions in an ultraclean GCr15(100Cr6) bearing steel produced in China were carefully examined by both the automatic scanning electron microscope, ASPEX, and rotatating bending fatigue tests, the latter can locate and reveal the inclusion that has induced the faigue cracking on the frature. Four types of inclusions, including oxide, oxide-sulfide, sulfide and TiN have been characterized by ASPEX and statistically analyzed using the methods of Statistical Extreme Value (SEV) and the Generalized Pareto Distribution (GPD) to predict the maximum characteristics size for each type of inclusions. The following conclusions can be drawn by comparing the two types of derived results. (i) The most frequent fatigue failure is caused by oxide-sulfide inclusions, and the maximum size of this type of inclusions measured on the faigue fracture is closer to that predicted by the GPD method. (ii) Although there are the largest number of sulfide with the coarset size in the ultraclean bearing steel, they do not induce the fatigue fracture at all, indicating that they are the least harmful to fatigue failure. (iii) There are very few large TiN inclusions in the steel, but TiN-induced fatigue crack was indeed observed, indicating that TiN inclusions are detrimental to faigue properties even though they are few. (iv) No oxide inclusions were found on the fatigue fracture and the measured oxide inclusions have the largest size of 10.7?m and the predicted maximum size by GPD is 12.4?m, suggesting that the critical size of the oxide inclusion not to induce fatigue cracking is probably between 10.7 μm and 12.4 μm.

Cr12MoV steel is the most widely used cold work die steel, which belongs to high chromium and high carbon lesteritic steel, and the form, quantity, size and distribution of carbides in the steel have an important impact on the properties of Cr12MoV steel. In this paper, metallographic microscope, scanning electron microscope, three-dimensional corrosion engraving device for inclusions, X-ray diffractometer and energy dispersive analyzer were used to analyze the type, morphology and distribution of carbides in Cr12MoV die casting billets in a factory, and the phase transition and carbide precipitation behavior of Cr12MoV cold work die steel were calculated by using Thermo-Calc 2020b. The results show that the carbide types of Cr12MoV cold work die steel are chromium-rich and iron-rich M7C3 carbides and M23C6 carbides, the main elements of M7C3 carbides are chromium, iron, carbon and molybdenum, and the main elements of M23C6 carbides are iron, chromium, molybdenum and carbon. The carbide morphology in the casting billet can be mainly divided into four categories: granular carbide, massive carbide, rod carbide, and reticulated carbide. The size of granular carbide is 2~5μm, the size of bulk carbide is between 10~15μm, the size of rod carbide is about 30~40μm, and the reticulated carbide is formed by the aggregation of granular, massive and rod carbides, and its size is up to 80μm. The evolution of carbide morphology from the edge to the core is as follows: granular→ blocky→ rod-like → reticulated, the heterogeneity of carbide from the edge to the core is gradually enhanced, and the carbide at the edge is distributed in a granular manner, the carbides at 1/4 were long rod-shaped, and the carbides in the core were segregated into a network. From the edge to the core, the average equivalent diameter of carbide increased from 5.7μm at the edge to 8.5μm at the core, the proportion of carbide area increased from 8.2% to 9.5% from the core, and the density of carbide decreased from 2961/mm2 at the edge to 1189/mm2 at the core.

The fracture behavior and mechanical properties of oxide scale are the key factors affecting the setting of the technological parameters of acid-free descaling. In this paper, molecular dynamics software Lammps was used to simulate the effects of different scratch rates on interface separation. The effects of different scratch rates on the separation of FeO/Fe interface were analyzed from the perspectives of load-displacement relationship, CSP, atomic accumulation, dislocation, temperature, atomic displacement vector and radial distribution function, and verified by scratch test on 430 stainless steel oxide. The simulation results show that: As the scratch rate increases from 100m/s to 200m/s, the normal and tangential loads gradually increase, the degree of disorder at the FeO/Fe interface gradually increases, and the temperature gradually increases, which makes the FeO and Fe layers gradually soften, and the dislocation density, number and atomic bonding strength gradually decrease, promoting the separation of the FeO/Fe interface. The test results show that: With the increase of scratch rate from 0.5mm/min to 2mm/min, the breaking point of 430 stainless steel oxide is advanced, and the binding strength decreases gradually, which corresponds to the simulation results. This study provides theoretical support for understanding the fracture mechanism of the oxide, and provides important guidance for improving the accuracy of parameter setting for acid-free descaling.

Under the background of "carbon peaking and carbon neutrality", high-end equipment and major projects require special steel wire rod to continuously break through the performance limit, and the cutting-edge special steel wire rod represented by ultra-high strength steel needs to be solved urgently in its core technologies such as process, equipment and products. Online isothermal heat treatment (QM) of special steel wire refers to a new type of online isothermal heat treatment technology that uses the residual heat from rolling to directly immerse the wire into a constant temperature salt bath to control cooling after wire drawing. This article introduces the QM process flow, technical principles, and the latest research and development progress of related products. QM technology, utilizing its fast cooling rate and wide temperature range, can be used for special steel wire products such as ultra-high strength and high carbon pearlite steel, medium carbon bainitic non quenched and tempered steel, and non annealed low-carbon alloy steel. The tensile strength of high-carbon pearlitic steel wire rod can reach 1620MPa, and the reduction of section area rate is 30.4%, which is used to manufacture galvanized aluminum steel wire for bridge cable to achieve tensile strength of 2130MPa and number of torsions more than 18. The new bainite non-quenched and tempered steel obtains the full bainite structure through the controlled cooling process without adding precious alloying elements, which meets the strength requirements of standard parts in strength classes 8.8, and can achieve 1/6 cold top forging without cracking. After QM treatment, the reduction of section area rate of the wire of the high strength welding wire steel is significantly higher than that of the traditional slow cooling process, and the deformation capacity is higher, which can realize annealing-free drawing processing. QM technology eliminates the user's secondary heat treatment and realizes the reduction of alloying elements, which has broad market prospects under the background of carbon peaking and carbon neutrality.

Ultra-high-strength medium-thick plates is widely used in the field of construction machinery and industrial protection due to its ultra-high strength, good plastic toughness and weldability. In this paper, the microstructure evolution, hardness and geometrically necessary dislocation density of the test steel during the continuous cooling of austenite were studied by thermal simulation experiments, and the CCT curve was drawn. The hardenability of the test steel was determined by the end hardening test. And the trial production of test steel was carried out according to the above test results. The results show that with the increase of cooling rate, the experimental steel gradually changes from ferrite + granular bainite + martensitic - austenite structure to bainite + martensitic structure, and the hardness and geometric dislocation density are increasing, the phase transition temperature (Bs, Bf, Ms and Mf) decreased continuously. When the cooling rate is greater than 5 ℃?s-1, the whole martensitic structure can be obtained, and the hardness and geometrically necessary dislocation density tend to be stable, and the cooling speed should be controlled at 5~10 ℃?s-1 during quenching. When the cooling rate is slow, the M-A components are distributed in blocks at the grain boundaries and in the bands in the grains, the size of the grain boundaries and the M-A components in the grains decreases continuously after the cooling rate increases, and the large M-A components disappear when the experimental steel is an all-martensitic structure. The depth of the hardened layer of the test steel is about 30mm, and the hardenability is excellent, which can meet the hardenability requirements of medium-thick plates of 30mm and below. After quenching and tempering treatment at 850 °C + 180 °C, the test steel is tempered martensitic structure, its yield strength is 1328 MPa, tensile strength is 1684 MPa, elongation is 13.4%, and -40 °C KV2 is 24.3J.

The technology of blast furnace slag reinforced crushing is to use high-speed gas to mix the strengthened medium to break the slag into slag beads, so as to ensure the kinetic energy of crushing during granulation process, improve the crushing effect of slag, accelerate slag beads cooling rate, and optimize the amorphous content of granulation blast furnace slag beads, which to improve the utilization value of blast furnace slag. In this paper, the solid powder slag is used as intensive cooling medium to the condensation and heat exchange process of granulation slag beads. A two-dimensional model of single-particle slag bead intensive cooling is established by fluid mechanics calculation method, comparing and exploring the difference in temperature field, velocity field, and pressure fields of slag beads with and without cold nucleus. The effects of different airflow, slag bead diameters and cold nucleus diameters on the complete solidification time, cooling rate are studied. The results show that the gas quenched blast furnace slag droplets is cooled and solidified under the joint action of cold nucleus and external air flow, and the addition of the reinforced cooling medium increases the cooling speed. The solidification time of slag beads is 0.65s shorter than that without cold nucleus under the condition of 2.0mm diameter, relative speed of 20 m?s-1 and with a diameter of 0.5mm cold nucleus. The complete solidification time decreases with the increase of airflow velocity, the decrease of slag bead diameter and the increase of cold nucleus diameter; The cooling rate increases with the increase of airflow velocity, the decrease of slag bead diameter and the increase of cold nucleus diameter.

Abstract: This study focuses on the control of sulfide morphology in crankshaft steel 49MnVS3. The morphology, size, distribution, and quantity of sulfides in ingots with different Ce contents were statistically analyzed using OLYMPUS metallographic microscope, ZElSS scanning electron microscope, and OTS steel inclusion automatic analysis system. Observing the three-dimensional morphology of sulfides through electrolytic erosion and evaluating the deformation ability of different types of sulfides through thermal compression experiments. The research results indicate that large-sized elongated MnS inclusions gradually transform into dispersed small-sized spherical (Ce, Mn) S composite inclusions with the increase of Ce content in steel,. The aspect ratio and density of sulfide inclusions in steel have undergone significant changes, with the size of inclusions in steel increasing from 4.6 μm dropped to 2.3 μm. The aspect ratio decreased from 2.9 to 1.8, and the number of inclusions per unit area increased from 32/mm2 to 65/mm2. The spheroidization rate of inclusions in the ingot significantly increased. After hot compression, the size of MnS inclusions in the experimental steel without Ce addition is around 20 μm, it presents a long linear shape in the vertical compression direction, while the sample containing Ce inclusions in Ce added did not undergo significant deformation and maintained good dispersion distribution characteristics.

As people put forward higher strength, toughness, wear resistance and corrosion resistance requirements for high manganese steel materials, high nitrogen high manganese steel came into being. At present, it was mainly produced by high pressure solidification, and the cost was high. In this paper, a method of controlling nitrogen content and reducing nitrogen emission by rapid condensation was proposed. The high nitrogen and high manganese steel with nitrogen content of 0.218 % was melted in a high temperature vertical melting furnace and then air-cooled and water-cooled respectively. The nitrogen content of the samples after air-cooled and water-cooled was detected. The microstructure analysis, primary dendrite ranging and the calculation model of primary dendrite arm spacing were established. The results show that the nitrogen content of the air-cooled sample was 0.181 wt %, and the nitrogen escape rate in the steel was 17 %, while the nitrogen content of the water-cooled sample was 0.206 wt %, and the nitrogen escape rate in the steel was only 5 %. The average primary dendrite spacing of the air-cooled sample was 63.34 μm, and the average primary dendrite spacing of the water-cooled sample was 41.67 μm. The solidification micro-region of the water-cooled sample was small. The local nitrogen-containing micro-pores of the air-cooled sample were larger, and the distribution was more concentrated, showing a loose state. The size of the nitrogen-containing micro-gas in the water-cooled sample was small, below 20μm, and the number of micro-pores was small. The kinetic model of nucleation and growth of microbubbles during solidification of molten steel shows that the higher the ambient pressure is, the greater the external direct inhibition force is, the more difficult it is for microbubbles to form, and the smaller the L of the solidification microzone is. The calculation model of primary dendrite arm spacing showed that with the increase of interface growth rate and temperature gradient, the dendrite arm spacing decreased gradually, up to less than 50μm, and the solidification micro-region in steel also decreased, which was beneficial to inhibit the escape of nitrogen. Therefore, rapid condensation of high nitrogen high manganese steel and reducing the escape of nitrogen during solidification were effective methods to increase the nitrogen content in high manganese steel.

In view of the problem of developed flux ring in stainless steel production site, the composition and performance of imported powdered ultra-low-carbon mold flux were analyzed by using automatic melting point melting velocity meter, D8-Advance X-ray diffractometer and S4800 scanning electron microscope, and the melting speed of raw flux was 58.4s and the sintering rate was 85.81%. The ultra-low-carbon mold flux SRH was obtained by analyzing the composition of the carbonaceous material of the original flux, and the melting speed and sintering rate of the mold flux SRH were verified by experiments, and the properties of the mold flux SRH were the same as those of the original flux. According to the SRH composition and performance of the mold flux, the ultra-low carbon mold flux SRL was optimized, and its performance analysis showed that the melting speed of 58.6s was close to that of the original flux of 58.4s, the sintering rate was 55.44%, which was greatly reduced compared with the original flux, the carbon black content increased from 1.435% to 2.296%, the specific surface area of the carbonaceous material increased, the particle size decreased, the production temperature of the gun spar increased significantly, and the solid-phase reaction temperature of the mold flux was increased, thereby reducing the sintering performance of the mold flux. It effectively inhibits the growth of the flux ring.