- 百种中国杰出学术期刊
- 中国精品科技期刊
- “中国科技期刊卓越行动计划二期”领军期刊
- 入选“中国精品科技期刊顶尖学术论文(F5000)”
- 入选《科技期刊世界影响力指数(WJCI) 报告》
- EI、CA、JST收录期刊
- 中国金属学会会刊
- 中文核心期刊
- 中国科技核心期刊
- 中国科学引文数据库(CSCD)来源期刊
The high-temperature molten metal multiphase flow in a continuous casting mold directly governs the cleanliness, homogeneity, and refinement of the strand, and is therefore one of the core factors determining the final quality of the strand. This system is dominated by highly unsteady turbulence, in which multiple phases including molten steel, gas bubbles, slag, and non-metallic inclusions coexist and interact with each other. It is simultaneously coupled with complex physicochemical processes such as heat transfer, mass transfer, phase transformation, and the electromagnetic fields, forming a typical nonlinear and non-equilibrium multiphysics coupling system that exhibits high complexity and significant uncertainty. Owing to the characteristics inside the mold such as large variations in thermophysical properties of the high-temperature molten metal, complex constitutive relationships, numerous factors affecting the phase interface, and steep gradients of boundary physical quantities, real-time and accurate monitoring of key parameters related to the multiphase flow structures and solidification behavior of the high-temperature molten metal remains extremely challenging. Thus, traditional experimental studies have obvious limitations in the depth of mechanistic analysis and the completeness of parameter acquisition. In this context, computational fluid dynamics (CFD) with its significant advantages in revealing complex flow mechanisms and internal evolution processes has gradually become a key technical method for studying high-temperature molten metal multiphase flow in continuous casting mold. This paper systematically reviews the application progress and research status of CFD in continuous casting mold from the perspectives of multiphase flow models, turbulence models, population balance models, multiphase volume-averaged solidification models, and electromagnetic external field regulation models. It focuses on analyzing the advantages and limitations of different models in describing complex multiphase flow and solidification processes. Finally, combined with the development trend of high-quality continuous casting strand production, the future development directions in terms of refined modeling, multiscale coupling and engineering applicability are prospected.
Converter steelmaking, a mainstream modern process, produces molten steel by blowing oxygen into molten iron to efficiently remove impurities through oxidation reactions. The development of converter automated steelmaking technology is of paramount importance for achieving precise end-point control, enhancing product quality stability, reducing raw material and energy consumption costs, and promoting the intelligent upgrading of steel manufacturing. This paper elaborates on the architecture and control principles of the converter automated steelmaking system, provides an in-depth analysis of the critical role of detection and sensing technologies in automated steelmaking, and discusses the application of key means such as sub-lance, off-gas analysis, and spectral monitoring in real-time process parameter acquisition and dynamic regulation. Furthermore, it systematically sorts out the core status of models and algorithms in automated steelmaking, offering a detailed analysis of the construction principles and application effects of static control models, dynamic control models, as well as end-point carbon and temperature prediction models based on machine learning. The paper emphasizes that the deep integration of mechanism models with data-driven intelligent models is key to improving control accuracy, while also noting that current research still has shortcomings in aspects such as the data silo phenomenon and limited model generalization capability. Converter automated steelmaking is poised to evolve towards a full-process, self-adaptive intelligent control direction underpinned by industrial internet platforms, deeply integrating digital twin and artificial intelligence technologies, ultimately realizing smart steelmaking driven by metallurgical mechanisms and data.
Under the "double carbon" targets in the new era, China's iron and steel industry has entered a critical stage of green development. The high-proportion pellet technology, which uses basic pellets to replace sintered ore, is one of the important technical directions for low-carbon blast furnace smelting in China. However, basic pellets have a major problem of abnormal swelling during the reduction process, which can cause major production accidents such as abnormal furnace conditions. To address this issue, this study conducted reduction swelling rate tests on pellets with natural basicity and basicity ranging from 0.2 to 1.2. Results show that the swelling rate of pellets increases with the increase of basicity, reaches the maximum value when the basicity is 0.8, and decreases significantly as the basicity further increases. X-ray diffraction (XRD) analysis and optical microscopy were used to analyze the mineral phase changes of pellets with basicity of 0.8 and 1.2 during the reduction process. Results indicate that the main binding phase of pellets with basicity of 0.8 is calcium iron silicate minerals, which have poor reducibility and a lower reduction rate than hematite. The inconsistent internal stress generated between the two during reduction leads to abnormal swelling of the pellets. In contrast, the main binding phase of pellets with basicity of 1.2 is calcium ferrite (SFCA), whose reduction rate is basically consistent with that of hematite. The internal stress generated between the two during reduction is basically uniform, thus avoiding abnormal swelling. Therefore, it is recommended that pellets with a basicity of more than 1.0 be produced in industrial production to reduce the swelling rate of pellets.
Consteel electric arc furnace (EAF) is a high-efficiency, green and low-carbon steelmaking equipment widely used in China, and its molten pool stirring process has an important influence on smelting. Most of them are equipped with side-blowing technology, while a few feature bottom-blowing systems. The side-blowing oxygen lances (or burners) play a key role in improving the uniformity of the molten pool in addition to cutting scrap steel and eliminating cold spots. To enhance the flow and mixing efficiency of molten steel, this paper simulates the impact of the side-blowing process on the flow field within the molten pool based on gas-liquid-solid three-phase flow. A hydraulic model with a similarity ratio of 1∶8 was made based on a 150 t Consteel EAF and its side-blowing oxygen lances. Referring to fluid mechanics theory, a side-blowing arrangement with non-uniform gas flow was proposed. Simulated tests were then conducted to study the movement behavior of gas-liquid-solid three-phase flow and the melting phenomenon of scrap simulants under different side-blowing conditions. The average mixing time, flow field movement and melting of scrap simulants were used as criteria to obtain the preferred non-uniform gas volume arrangement scheme. The results show that a 10° horizontal deflection of the simulated side-blowing oxygen lances is the optimal angle in this study. At a horizontal deflection of 10°, increasing the side-blowing gas volume is more conducive to mixing. However, when the gas volume is large, the reduction in average mixing time caused by increasing the same gas volume is significantly reduced, and the gas energy utilization rate decreases. Under a certain side-blowing intensity, when increasing the total side-blowing gas volume, concentrating the gas volume increase on one specific side-blowing lance is more conducive to mixing than uniformly increasing the gas volume of each lance. Under the S4 condition of this study, the No.4 side-blowing lance is located at the junction of two cold zones, the feeding zone and the eccentric bottom tapping(EBT) zone. Under the same gas volume, this configuration achieves the shortest average mixing time and increases the gas utilization rate by 15%. At this time, the liquid phase mixing and scrap simulant movement speed are faster. Meanwhile, the amount of scrap entering the cold zones decreases, and the accumulation and bonding phenomena are significantly alleviated. Overall, this is the preferred non-uniform arrangement. The results of this experimental study provide reference and guidance for the position adjustment and process parameter optimization of actual side-blowing oxygen lances in EAFs.
To systematically investigate the thermodynamic behavior of key elements in molten steel during the bottom-blown CO2 process for refining SWRH72A cord steel, clarify the control mechanism of CO2 injection on elemental content, and thereby optimize the refining process for precise composition control, this study takes Aosent Special Steel's SWRH72A steel as the test subject. Through a series of high-temperature hot tests, the reaction behavior of key elements under different CO2 injection parameters was systematically compared. Experimental results indicate that pure CO2 injection exhibits the most pronounced effect on carbon removal. Under continuous pure CO2 injection for 120 min, the carbon mass fraction decreases from 0.57% to 0.30%. Mixed injection tests further demonstrate that a mixture ratio of 30%CO2 (volume fraction) + 70%Ar (volume fraction) can stably control carbon content within the process internal control requirements. At a flow rate of 20 mL/min for 120 min, the Si mass fraction decreases from 0.105% to 0.042%. The oxidation rate of Si showed a positive correlation with CO2 flow rate and its proportion in the mixed gas, with the greatest Si removal occurring under pure CO2 conditions. Mn removal efficiency increases with higher CO2 injection flow rates. Under pure CO2 at 20 mL/min for 120 min, Mn mass fraction decreases from 0.37% to 0.19%. To meet stringent internal control requirements for Mn content in cord steel, an optimized process using a lower injection flow rate of 10 mL/min is recommended. Furthermore, the reaction between Al and CO2 is extremely rapid. Due to its low initial content, Al is completely removed within 10 min after injection initiation, with its mass fraction dropping to 0. The 120 min injection test further confirmed that the Al mass fraction decreases to 0, achieving deep removal. Through systematic high-temperature hot-state experiments, this study elucidates the thermodynamic reaction mechanisms of bottom-blown CO2 with four key elements(C, Si, Mn, and Al)during the refining process of SWRH72A cord steel. The findings provide theoretical support for applying CO2 in precise control of molten steel composition during refining, offering significant reference value for enhancing the quality of high-end cord steel products and developing new green smelting technologies.
To investigate the effect of CaO-SiO2-Al2O3-MgO-CaF2 refining slag on the composition of non-metallic inclusions, experimental and theoretical analyses were conducted to clarify the influence of Al2O3 content in this refining slag system on the composition of non-metallic inclusions in U71Mn heavy rail steel. The thermodynamic calculation software FactSage was used to determine that the binary basicity is 1.8, and the optimal mass fractions of MgO and CaF2 are 7% and 10%, respectively, for the optimal desulfurization performance of this refining slag system, On this basis, refining slags with mass fractions of Al2O3 of 3%, 10%, 15% and 20% were prepared using a silicon-molybdenum resistance furnace and a muffle furnace. Subsequently, slag-steel reaction experiments were performed at 1 873 K using U71Mn heavy rail steel samples from a domestic steel mill. After the experiments, a scanning electron microscope (SEM) and an automatic inclusion scanning system were used to analyze the type, composition and size of non-metallic inclusions. The results show that without adding refining slag, the inclusions in the steel are mainly MnO-SiO2-Al2O3 type. After the addition of refining slag, the inclusion types transformed into two categories, namely Al2O3-SiO2-MnO and Al2O3-SiO2-CaO. As the mass fraction of Al2O3 in the refining slag increases from 3% to 20%, the mass fraction of Al2O3 in the inclusions rises from 70% to 93%, while the mass fraction of SiO2 decreases from 25% to 4%, and the contents of CaO and MnO remain basically stable. To explain the mechanism by which the increase in Al2O3 content in the refining slag leads to the rise in Al2O3 content in the inclusions, this study proposes a coupled interaction mechanism of the three-phase system involving refining slag, molten steel and inclusions. Theoretical analyses show that the mass fraction of Al2O3 in the inclusions is positively correlated with the Al2O3 and SiO2 activity ratio in the refining slag, and an approximately linear relationship is observed when the Al2O3 content in the refining slag is less than 30%. The increase in Al2O3 content in the refining slag enhances its own activity and reduces the activities of CaO and MgO, thereby regulating the evolution of inclusion composition.
The incomplete opening of the slide plate is prone to inducing biased flow in the mold and non-uniform growth of the solidified shell, which critically affects slab quality. Electromagnetic stirring (EMS) is an effective method for regulating the mold flow field, yet further research is needed to quantitatively evaluate its improvement effect on asymmetric flow and solidification behavior under slide-gate control conditions. This study aims to reveal the mechanism of biased flow and investigate the regulation laws of EMS on the asymmetric flow field and solidification behavior. Focusing on a slab mold in a steel plant, a three-dimensional large eddy simulation (LES) model coupling electromagnetic, flow, and thermal fields was established. A "symmetry index" was introduced as a quantitative indicator to systematically investigate the effects of stirring current and slide gate opening rate on the flow field structure and shell uniformity. The results indicate that the asymmetry of the flow field inside the submerged entry nozzle (SEN) is the root cause of the biased flow in the mold. Without EMS, the jet deflects toward the inner radius (IR) side, leading to severe remelting of the IR shell. The application of EMS generates a horizontal recirculating flow that effectively reduces the velocity difference between the two sides of the nozzle, significantly improving flow field symmetry. As the stirring current increases, the average symmetry index rises from 0.62 to 0.71, and the remelting of the IR shell is alleviated; however, excessive current intensifies the scouring of the narrow face shell. The standard deviation of shell thickness decreases first and then increases with rising current, reaching a minimum of 0.215 mm at 600 A where shell growth is most uniform. Furthermore, increasing the slide gate opening rate helps enhance flow field symmetry; as the linear opening rate increases from 50% to 100%, the average symmetry index rises from 0.64 to 0.75, and the standard deviation of shell uniformity decreases to 0.202 mm. In conclusion, EMS can effectively mitigate asymmetric flow caused by slide-gate control, but the stirring intensity must be optimized to balance flow symmetry and shell scouring. Considering both flow field symmetry and shell quality, the optimal stirring current is determined to be 600 A under a 60% slide gate opening condition. These findings provide theoretical guidance for optimizing EMS process parameters and improving slab quality in industrial slab continuous casting applications.
To investigate the effects of sulfur content variation on the morphology, size, and other characteristics of MnS inclusions in 20CrMnTi gear steel, this study conducted high-temperature experiments on 20CrMnTi gear steel using a high-temperature tube resistance furnace. The characteristics of MnS inclusions with sulfur mass fractions of 0.018 1% and 0.091 1% were analyzed by means of metallographic method and non-destructive electrolytic extraction method. Results show that when the sulfur mass fraction in 20CrMnTi gear steel is 0.018 1%, the MnS inclusions are small in size, with morphologies mainly presenting as spherical, sub-spherical, or spindle-shaped. When the sulfur mass fraction in the steel increases to 0.091 1%, the MnS inclusions grow larger, distribute more densely, and their morphologies are mainly blocky, clustered or irregular. Calculations on the nucleation kinetics of MnS inclusions reveal that the nucleation of MnS inclusions is dominated by grain boundary nucleation. When the temperature is lower than 1 728 K, some MnS inclusions precipitate through homogeneous nucleation, but the majority still precipitate predominantly via grain boundary nucleation. Thermodynamic calculations of MnS inclusion precipitation indicate that an increase in sulfur content advances the solid fraction of MnS inclusion precipitation from 0.986 to 0.831 under furnace cooling conditions, and to 0.822 under water cooling conditions. Kinetics calculations of MnS inclusion growth demonstrate that an increase in sulfur content leads to an increase in the size of MnS inclusions, while an increase in cooling rate reduces the size of MnS inclusions. The FactSage thermodynamic software was used to calculate the variation in the precipitated mass fraction of MnS inclusions during the cooling process. At 1 700 K, the mass fraction of MnS inclusions increases from 0.005 1% (at a sulfur mass fraction of 0.018 1%) to 0.172 7% (at a sulfur mass fraction of 0.091 1%). The research results can provide certain theoretical guidance for the study on the formation mechanism of MnS inclusions in 20CrMnTi gear steel, and also offer appropriate reference value for its practical application in industrial production.
This study focuses on continuous casting slab of 45 steel, aiming to explore the influence mechanism of gaseous elements in molten steel on the formation of surface pinhole defects. The influence of gaseous elements on pinhole defect formation was systematically studied by analyzing the characteristics of surface pinholes in continuous casting billets, the relationship between gas content in tundish molten steel and pinhole quantity and depth, and combining with calculations based on gas partial pressure theory. The results indicate that pinholes are unevenly distributed on the cast slab surface and exhibit various morphologies in the depth direction, including channel type, subcutaneous cavity type, subcutaneous chain type, and isolated distribution type. The number of pinholes and their maximum depth are positively correlated with oxygen content. When the mass fraction of total oxygen is no less than 0.003%, the number of pinholes exceeds 100, with depths ranging from 1.5 mm to 4.5 mm. At the mass fraction of hydrogen of 0.000 3%, the number of pinholes reaches 280, showing an upward trend with the increase of hydrogen content but no correlation with the maximum depth. Nitrogen content has no significant correlation with pinhole parameters. Theoretical calculations show that under the conditions of ignoring changes in solubility and setting the bubble escape temperature as the liquidus temperature, the partial pressure reaches 101 325.00 Pa when the volume fraction of active oxygen is 0.004%, 17 225.25 Pa when the volume fraction of hydrogen is 0.001% and 4 053 Pa when the volume fraction of nitrogen is 0.009%. The degree of influence of gaseous elements on bubble formation follows the order of oxygen > hydrogen > nitrogen. After considering segregation, the active oxygen content required to reach a partial pressure of 101 325.00 Pa decreases as segregation proceeds. The research demonstrates that in addition to the original gas content, the segregation and solubility changes of gaseous and carbon elements during the solidification process are also key factors affecting bubble formation.
The corrosion resistance effect of rare earth (RE) in the development of weathering steel has become increasingly evident, particularly in weathering steels containing high levels of copper, phosphorus, and other alloying elements. However, there is limited reporting on the corrosion resistance effect of rare earth in low-alloy steels such as No.10 steel. To explore the development of low-cost common corrosion-resistant steel, this study systematically analyzed the effect of composite RE on the atmospheric corrosion resistance of aluminum-containing carbon No.10 steel using cyclic immersion corrosion tests, X-ray diffraction(XRD) rust layer analysis, electrochemical testing, and inclusion detection. The cyclic immersion corrosion test results showed that adding La-Ce composite RE, even at a RE mass fraction below 0.003 0%, significantly reduced the corrosion rate of the steel. By the final stage of corrosion, the average corrosion rate of RE-containing steel decreased by 8.11%, and the corrosion rate exhibited a clear correlation with the RE content, indicating a significant relationship between the corrosion resistance of the steel and its RE content. Rust layer analysis and electrochemical test results revealed that the presence of RE accelerated the formation and increased the proportion of α-FeOOH in the rust layer, resulting in a denser inner rust layer. Consequently, the rust layer resistance and charge transfer resistance increased, while the self-corrosion current density decreased and the self-corrosion potential rose. Inclusion detection indicated that the main inclusions in the steel transformed into composite inclusions consisting of REAlO3, RE2O2S, RE2S3, and incompletely modified Al2O3 and CaS. The number of inclusions increased by 69.0%, while their average size decreased by 30.9%, with inclusions smaller than 2 μm showing the most significant increase. Based on these findings and combined with metal corrosion theory, the atmospheric corrosion process of carbon steel and the mechanism of RE influence were discussed. The corrosion process was proposed to be divided into four stages, corrosion incubation period, initial corrosion period, accelerated corrosion period, and stable corrosion period. During corrosion, the composite RE primarily enhanced the corrosion resistance of the steel by inhibiting pitting corrosion, altering the composition of the rust layer, and improving the compactness of the rust layer. These experimental results provide a reference for the development of low-cost RE corrosion-resistant steel.
Cr12MoV cold-work die steel is a high-carbon, high-chromium ledeburitic steel known for its high wear resistance, hardenability, quenching hardness, dimensional stability, as well as good thermal stability and comprehensive mechanical properties. It is widely used across multiple critical industries in China. As the demand for domestically produced high-quality die steels in advanced manufacturing sectors continues to grow, the need for high-quality Cr12MoV die steel is also gradually increasing. However, controlling the behavior of inclusions in this steel remains a significant challenge. To address this, this experiment utilized a laboratory MoSi2 resistance furnace to conduct trace calcium treatment and cerium treatment on Cr12MoV die steel. Three test groups were designed, a blank group without calcium or cerium addition, a control group with only cerium addition, and an experimental group with both calcium and cerium addition. The effects of calcium and cerium addition on deoxidation and the evolution and mechanism of inclusion behavior in Cr12MoV die steel were analyzed using methods such as FactSage computational software, nitrogenoxygen analyzers, and scanning electron microscopy. The results show that as the amounts of calcium and cerium increase, the cleanliness of the steel gradually improves, and inclusions are progressively refined. The synergistic addition of calcium and cerium reduces the total oxygen (T[O]) mass fraction in the steel from 0.002 8% to 0.001 8%. In the steel without calcium or cerium addition, inclusions are primarily Al2O3 and magnesiumaluminum spinel. After adding 0.03% cerium, the inclusions transforms to mainly Ce-O-S type inclusions. With the addition of 0.001% calcium, the inclusions are modified to Ca-Al-O-S type inclusions. Subsequent cerium addition further transforms the inclusions into mainly Ca-Ce-O-S type inclusions, along with a small amount of aluminumcontaining inclusions. Thermodynamic calculation results indicates that a certain amount of cerium can reduce the size and area proportion of inclusions. When the mass fraction of calcium and cerium is 0.001% and 0.020%, respectively, the modification effect of inclusions in steel is the best. The above findings can provide a reference for controlling inclusion behavior during the production process of Cr12MoV die steel.
To address the issue of red rust defects in GPa-grade automotive steel alloyed with Si and Mn during industrial production, the oxidation behavior of 0.2C-1.5Si-2.3Mn automotive steel was systematically investigated. Samples were obtained from actual slabs produced on a MCCR line and analyzed under high-temperature conditions ranging from 900 ℃ to 1 250 ℃. This study primarily aimed to explore the mechanisms by which Si and Mn influence the structure, interfacial morphology, and elemental migration of the oxide scale. The results reveal that the oxidation behavior is significantly dependent on temperature. Below 1 000 ℃, the oxide scale predominantly consists of Fe3O4 and Fe2O3, while a layer enriched with SiO2 and Fe2SiO4 forms at the interface between the oxide layer and the substrate, exhibiting lower oxidation levels within the matrix. As the temperature increases to 1 150 ℃, partial liquefaction of the interfacial Fe2SiO4 occurs, leading to the emergence of dispersed SiO2-MnO composite oxides within the inner oxide layer. At temperatures exceeding 1 200 ℃, the manganese element diffuses significantly outward, resulting in the formation of a dense and brittle (Fe, Mn)3O4 spinel solid solution. Concurrently, the olivine phase at the interface transforms into (Fe, Mn)2SiO4, creating a network eutectic structure with SiO2. This eutectic phase intrudes along the grain boundaries of FeO within the oxide scale, anchoring tightly to the steel matrix. Together with the brittle spinel phase, it exacerbates the risk of descaling residue and rolling fractures. Measures such as increasing the casting speed of continuous casting billets, optimizing the exit temperature of tunnel furnaces, and enhancing the design of descaling nozzles effectively suppressed the formation of harmful oxide phases, significantly reducing the incidence of red rust defects. This study provides a theoretical framework for improving surface quality control in short-process high-silicon, high-manganese steel production.
With the increasingly stringent quality requirements for cold-rolled strips in high-end manufacturing sectors such as aerospace and new energy vehicles, the precise control of transverse thickness difference in cold rolling has become a critical technical bottleneck restricting the improvement of product precision. Based on roll profile electromagnetic control technology (RPECT), this study proposes a novel high-efficiency electromagnetic stick featuring a multi-zone induction heating zone structure. Compared with traditional segmented electromagnetic sticks, this design offers more abundant heat transfer paths, a more rapid thermal response, and a more uniform temperature rise in the contact zone. It aims to address the issues of insufficient edge drop control capability and limited work roll profile adjustability in single-stand and tandem rolling mills during the production of thin-gauge strips. Drawing on theories of heat transfer and electromagnetism, a numerical simulation model for electromagnetic-thermal-force multi-physics coupling was established to investigate the roll profile control laws of the new electromagnetic stick versus the traditional segmented one at various limit control positions. The results indicate that the new structure can improve the temperature distribution and heat transfer paths of the induction heating zone, thereby enhancing the average temperature rise and temperature uniformity in the contact zone. It can achieve roll profile control capability equivalent to that of the traditional structure even with reduced magnetic parameter settings, thereby verifying its high-efficiency control advantages. As the electromagnetic stick is positioned closer to the roll center, its maximum thermal bulging capability exhibits a slight attenuation trend, but the attenuation amplitude remains within 3 μm. Furthermore, the asymmetry of the edge roll profile gradually decreases as the installation position moves further away from the roll end. This study validates the feasibility of the multi-zone induction heating structure, providing theoretical support and a design basis for multi-physics actuators for edge drop control in modern strip rolling mills.
A 1 800 mm compact strip plant (CSP) rolling mill is prone to edge waves or broken edge waves during the rolling process. However, edge wave control via roll bending tends to induce edge-center composite waves or high-order waves, which seriously affects strip quality and production stability. The roll contour directly influences the roll gap shape; superimposing a local reshaping curve on the basic roll contour enables modification of the local roll shape, thereby achieving the adjustment of the local strip profile. To address local edge profile issues, this study modified the edge regions of the continuous variable crown (CVC) roll contours of the downstream F5-F7 stands, realizing local adjustment and compensation of the strip edge profile without affecting the profile control of the strip middle section. A universal edge reshaping (ER) curve design method based on piecewise quartic polynomials symmetric about the roll surface midpoint was proposed for local edge profile problems. Further, a fitted edge reshaping (FER) curve in the form of a sixth-order polynomial was obtained through fitting. A novel roll contour design method was established, which involves superimposing the FER curve on the CVC roll contour to obtain the mixed continuously variable crown (MCVC) roll contour. The designed FER curve was used to reshape the roll contour within the 500 mm edge range of the work rolls. The optimized MCVC roll contour retains the crown control range of the original CVC roll contour, and its quadratic crown varies approximately linearly with roll shifting, achieving a local quadratic crown adjustment ranging from -3 μm to -43 μm for nominal roll gap at rolling widths of 1 000-1 600 mm. Without affecting the crown control characteristics of the strip middle section, the MCVC roll contour reduces the edge reduction within the rolling width range; moreover, the compensation effect on the roll gap shape at the strip edge increases with the increase of strip width. In practical applications of the MCVC roll contour in the downstream F5-F7 stands, the generation of edge waves and complex waves during online profile adjustment is significantly alleviated.
Numerical simulations were conducted using Ansys Fluent software to model the preparation process of Al0.5CrFeNi2.5Six (x=0, 0.25, 0.50) high-entropy alloy powders via vacuum induction melting and inert gas atomization (VIGA method).The effects of different atomization pressures at the same silicon content and different silicon contents under the same atomization pressure on the powder particle size distribution were studied. The VOF multiphase flow model coupled with the standard k-epsilon turbulence model, the VOF multiphase flow model coupled with the LES (large eddy simulation) model, and the DPM (discrete phase model) coupled with the TAB (Taylor analogue breakup) model were employed to simulate the single-phase flow field, primary atomization, and secondary atomization processes during gas atomization, respectively. These simulation results were validated by actual experimental methods. The simulation results indicate that in the single-phase gas flow field, an increase atomization pressure causes the expansion wave area to gradually expand, which in turn shifts the Mach disk position continuously downward. As the atomization pressure gradually increases from 4 MPa to 6 MPa, the gas flow velocity continues to increase, with maximum speeds of 693, 704 and 711 m/s respectively. During primary atomization, under different atomization pressure conditions(4, 5, 6 MPa), the disturbance intensity of the gas flow on the liquid film is significantly enhanced and the fragmentation frequency of the liquid film increases remarkably with the increase of atomization pressure, leading to a gradual shortening of the liquid column length of the Al0.5CrFeNi2.5Si0.25 high-entropy alloy melt. When the atomization pressure is maintained at 5 MPa, the liquid film becomes more prone to detachment from the liquid column as the Si content gradually increases, resulting in more significant primary atomization fragmentation, and the liquid column length of the Al0.5CrFeNi2.5Six(x=0, 0.25, 0.50) melt also gradually shortens. During secondary atomization, the median particle size D50 of the metal powder decreases from 35.30 μm to 32.54 μm with the increase of atomization gas pressure while the umbrella-shaped range of particle descent shows no significant change. Under the same atomization pressure condition, the median particle size D50of Al0.5CrFeNi2.5Six(x=0, 0.25, 0.50) alloy powder decreases from 34.96 μm to 31.77 μm as the Si content increases, and the umbrella-shaped range of particle descent changes slightly. When the Si content increases from x=0.25 to x=0.50, the decrease in median particle size D50 is more significant. Numerical simulations can effectively reproduce the gas-atomized powder preparation process with a small deviation from the actual results, thus providing theoretical support for the optimization of metal powder preparation technology.
Under the backdrop of the "dual carbon" strategic goals, China's ferroalloy industry is confronted with increasingly severe carbon emission constraints and structural transformation pressures. Most existing studies focus on macro policy interpretation or single-technology analysis, lacking exploration of systematic transformation pathways at the enterprise level. From a techno-economic perspective, this paper systematically analyzes the industry's transformation pressures in terms of supply-demand structure, regional distribution, and policy regulation, and clarifies the market-driven factors and development trends of ferroalloy low-carbon transformation. The study shows that driven by policy regulations, downstream green supply chains, and high-quality demand from emerging sectors, the industry's competitive mode is shifting from sole cost-based competition to comprehensive capability competition centered on low-carbon technologies, intelligent control, and resource recycling, and the core competitiveness of enterprises is transitioning from external policy compliance to an endogenous driver based on low-carbon technologies. Based on this, the paper proposes a low-carbon transformation pathway comprising industrial collaboration, equipment upgrading, energy structure optimization, and technological innovation, and discusses its intrinsic logic and synergistic mechanisms, aiming to provide a theoretical basis and decision-making support for ferroalloy enterprises in formulating low-carbon development strategies.
The width of strip steel after continuous annealing and leveling directly affects production costs. To understand the variation in strip width after continuous annealing and leveling, a prediction model based on a convolutional neural network combined with a bidirectional gated recurrent unit (CNN+BiGRU) neural network was developed. First, the mechanism of width variation during the continuous annealing and leveling process was analyzed. During continuous annealing, the strip width is primarily influenced by factors such as temperature, tension, and speed, whereas during leveling, it is mainly affected by parameters such as rolling pressure and front/back tension. Subsequently, data feature selection and preprocessing were conducted. Based on the necking prediction model for the continuous annealing process and the Zaretsky formula, 17 parameters, including temperatures and tensions in different process sections of the furnace as well as process parameters in the leveling section, were selected as input features for the model. To ensure prediction accuracy, Min-Max normalization was applied to standardize the data, followed by data denoising using Tukey's fences method. Next, a CNN and BiGRU combined neural network structure was constructed, comprising two convolutional layers and two gated recurrent unit (GRU) layers. The ReLU activation function was used in the convolutional process, with each of the two GRU layers containing four gated units and connected in series for output. The model was then trained and validated. By comparing the performance of standalone CNN, standalone GRU, CNN+GRU, Random Forest, and LightGBM models, the CNN+BiGRU structure was found to outperform the others in overall performance. During training, the CNN+BiGRU model achieved a coefficient of determination R2 of 0.983 9, with mean absolute error (EMA) of 3.492 66, root mean square error (ERMS) of 11.616 7, and mean absolute percentage error (EMAP) of 0.29%. After training, the Shapley additive explanations (SHAP) values of each feature parameter were calculated. It was found that rolling pressure is the most important feature influencing width, with a SHAP value close to 7, significantly higher than other parameters. The tensions in the soaking section and within the furnace ranked second and third in importance, respectively. This finding provides a width adjustment strategy where leveling control serves as the coarse adjustment, and the continuous annealing process is used for fine-tuning. Finally, the trained model was applied in a real production environment, and a self-learning function was developed to enable periodic model updates. By collecting the prediction accuracy of different steel grades, it is found that the predicted value can be controlled within ±3 mm. Comparing width variations across different steel grades revealed that for higher-strength steel grades, the continuous annealing process should be the primary means of width adjustment, whereas for lower-strength steel grades, leveling adjustments should take precedence. The research results realize the accurate prediction of strip width after continuous annealing and leveling, which provides an effective scheme for width adjustment and has good application value.
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