Grain-oriented electrical steel (GOES) is a crucial soft magnetic material for high-efficiency transformers. However, its slabs suffer from severe oxidation loss and decarburization during high-temperature reheating, significantly impairing final product quality and production efficiency. Consequently, high-temperature oxidation inhibition coating technology has become a core strategy for ensuring GOES production and performance. Focusing on protective coating technology, this paper systematically reviews the latest research progress in oxidation inhibition coatings for GOES slabs of high-temperature reheating. Initially, it elaborates on the unique high-temperature oxidation behavior of GOES and its specific requirements for protective coatings (e.g., high-temperature stability, resistance to molten slag erosion and excellent descaling ability). Subsequently, it deeply analyzes the core components (high-melting-point ceramics, low-melting-point glass phases, functional additives), and protective mechanisms of various coatings, with a focus on the multi-layer structural evolution and physicochemical synergistic protection of coatings at high temperatures. Finally, future development directions for high-performance, eco-friendly, and intelligent protective coatings for GOES are prospected, including the exploration of new material systems, green preparation processes, and multi-functional integration, aiming to provide theoretical reference and technical support for enhancing the sustainable development of the GOES industry.
With the acceleration of the construction of intelligent steel rolling plant, a number of intelligent production lines with demonstration and leading functions, represented by Masteel and Nangang, have emerged, marking a new stage of transformation of China's steel rolling manufacturing from traditional automation to digital and intelligent deep integration. However, compared with the hot and cold strip rolling production line with high connectivity of information flow and data flow, the hot rolled seamless steel pipe production line has the dual characteristics of process manufacturing and discrete manufacturing. It faces higher complexity and technical challenges in material tracking, fine quality control and multi process collaborative optimization, and has become the most difficult key field in the construction of steel rolling intelligent factory. Combined with typical technical modules and engineering application cases, the technical realization path and value embodiment of digital quality control of hot rolled seamless steel pipe in the intelligent factory scene are systematically discussed. First of all, the hot-rolled seamless steel pipe tracking technology and equipment and the construction of digital twin driven intelligent steel rolling plant were introduced, and the key technology foundation of realizing accurate identification and data mapping of the whole process of steel pipe under complex working conditions was mainly displayed. Secondly, the matching holographic quality intelligent detection equipment, including internal and external surface defect detection and size and shape holographic detection system, is described, which provides technical support for the realization of efficient intensive and intelligent unmanned control. Furthermore, a digital quality control technology system for high-precision manufacturing is proposed, which covers core technologies such as dynamic optimization of piercing process parameters, online closed-loop of continuous rolling process size, intelligent optimization of steel pipe head and tail sawing amount, and online detection and control of grain structure, significantly enhancing the stability and consistency of quality control of hot-rolled seamless steel pipe. Finally, the intelligent control technology of process quality covering the whole life cycle of products is introduced, and the closed-loop control system from data acquisition, analysis and decision-making to process optimization is constructed to help the hot-rolled seamless steel pipe manufacturing continue to move towards digitization, intelligence and high quality.
In order to deeply investigate the mechanism of gas-solid reaction in the hydrogen-based shaft furnace and optimize the actual operating parameters of the hydrogen-based shaft furnace process, the interaction mechanisms between H2/CO and Fe3O4(111) surface in hydrogen-based shaft furnace were analyzed based on density functional theory(DFT) calculations. The results revealed that H2 molecules preferentially adsorbed onto Fetet1-terminated surface, exhibiting optimal adsorption energy of -1.36 eV. H atoms bonding with Oa (0.978 Å)(1 Å=0.1 nm) and Ob (0.971 Å) were generated by the dissociative adsorption, forming two hydroxyl groups. Bader charge analysis indicated values of 0.69e and 0.68e for the respective H atoms. In contrast, Feoct2-terminated surface demonstrated stronger CO binding affinity, achieving a maximum adsorption energy of -1.56 eV. This process generated a CO2 molecule precursor, where the C atom exhibited electron loss, increasing its Bader charge to 2.06e and promoting CO2 formation. Lower activation energies for both H2 (0.83 eV) and CO (2.23 eV) were displayed on Fetet1-terminated surface, suggesting superior kinetic favorability for H2. Consequently, minerals enriched with Fetet1 surface should be preferred in hydrogen-based shaft furnace. However, H2O generation via H2 reaction required 1.03 eV energy input, necessitating elevated temperature in industrial application.
In the converter steelmaking process, blockage of bottom-blowing elements significantly impacts molten bath dynamics and smelting efficiency. The effects of partial blockage of bottom-blowing elements on molten bath stirring and mixing behavior were investigated in a 100-ton combined top and bottom blowing converter equipped with six bottom-blowing elements, utilizing hydraulic experiments and numerical simulations. The results demonstrate strong agreement between the mixing times obtained from hydraulic experiments and numerical simulations, with an average error of 11.3%. A critical range for the influence of bottom-blowing flow rate on mixing time is identified at 0.48-0.60 m3/h. Excessive bottom-blowing flow rates induce violent bath agitation. As the gas flow rate increases from 0.48 m3/h to 0.72 m3/h and 0.84 m3/h, the maximum instantaneous liquid surface fluctuation rises from 34.1 mm to 54.6 mm and 92.1 mm, respectively. This intensifies energy dissipation from gas collisions, thereby reducing bath mixing efficiency. To quantitatively characterize tracer diffusion and evaluate mixing efficiency, the tracer mixing index (Itracer) was proposed. Analysis of turbulent kinetic energy, turbulent energy dissipation rate, velocity vector fields, and three-dimensional streamline diagrams reveals that partial blockage of bottom-blowing elements enhances horizontal circulation patterns in the molten bath. This disrupts barriers between relatively isolated stirring subzones and improves overall mixing homogeneity. Furthermore, blockage alters erosion distribution on the furnace bottom and lining. Severe erosion on the furnace bottom is concentrated between bottom-blowing elements and the lining. For symmetric layouts, critical lining erosion occurs near unobstructed bottom-blowing elements, while for asymmetric layouts, severe erosion shifts to regions adjacent to blocked elements. This study provides a theoretical reference value for the control of actual converter bottom blowing process and the maintenance of refractory lining.
In order to optimize the deoxidation alloying process of Q235B(Ti) steel and avoid low alloy yield and the detrimental effects of inclusions to steel properties, the effects of alloy combination, type, and addition sequence were systematically analyzed through FactSage thermodynamic calculation and high-temperature experimentation. The results show that aluminum has significantly better deoxidation ability than silicon and manganese. Using Al-Si, Al-Mn, or Al-Si-Mn alloys can meet the target molten steel composition, and the total alloy demand decreases as the proportion of aluminum increases. Compared with aluminum wire or electrolytic manganese, aluminum particles, ferromanganese, and silicon-manganese alloy exhibit superior deoxidation effects, reducing the oxygen content of the molten steel to a lower level and improving the yields of silicon, manganese, and titanium. Trace amounts of aluminum or silicon in ferromanganese further enhance the deoxidation effect. Research on the alloy addition sequence indicates that adding aluminum first followed by silicon, manganese, and titanium is the preferred approach, resulting in lower oxygen content, higher alloy yields, and smaller inclusion sizes (predominantly round or oval) with more uniform distribution. Additionally, the end-point inclusions form a composite structure with an Al2O3 core and an MnS shell, which effectively mitigates the adverse effects of single Al2O3 on steel properties. This study provides theoretical support for the optimization of deoxidation alloying process in clean steel production and offers guidance for reducing smelting costs and improving steel quality.
In the electric arc furnace (EAF) steelmaking process, precise oxygen supply control is critical for optimizing molten steel composition, reducing material consumption, and lowering production costs. This study developed a mechanistic model to calculate theoretical oxygen demand and established a data-driven prediction framework through preprocessing and dimensionality reduction of industrial operational data. Comparative analysis of XGBoost, CatBoost, and ResNet algorithms revealed that a hybrid residual neural network, integrating t-Distributed Stochastic Neighbor Embedding(tSNE), Bayesian Optimization(BO), and reinforced loss function with threshold-exceeding error penalty(RSQL) to achieve superior performance. A browser-server(BS) architecture-based intelligent guidance system was subsequently implemented to operationalize the hybrid data-mechanism model. Experimental results demonstrated hit rates of 90.1% and 99.6% for oxygen supply predictions within ±5% and ±10% error margins, respectively, confirming the model's industrial applicability in enhancing EAF process control.
Based on the mass balance and energy balance models of the Direct Reduction Iron(DRI) electric arc furnace steelmaking process, this study investigated the relationships between the steelmaking cost per ton of steel and DRI carbon content, DRI price increase per unit of TFe (hereinafter referred to as DRI price increment), as well as the price difference between scrap steel and DRI (calculated as scrap steel unit price minus DRI unit price) under different target carbon contents in steel grades, DRI carbon contents, and raw material ratios of DRI to scrap steel. The results indicate that, when the target carbon content in steel is fixed, as the DRI carbon content increases, the electricity consumption per ton of steel decreases while DRI consumption per ton increases, leading to an overall increase in steelmaking cost. With fixed DRI carbon content, the steelmaking cost per ton of steel decreases as the target carbon content in steel increases. When the target carbon mass fraction is 0.2%, within the range where DRI price increment is less than 3.5 RMB/ton, the steelmaking cost increases with carbon content; conversely, it decreases as carbon content increases. For target carbon mass fraction of 0.6% and 1.0%, the critical value of price increment per unit carbon content becomes 1.5 RMB/ton. Under fixed DRI prices, the steelmaking cost of scrap-containing raw materials increases with the price difference between scrap steel and DRI, a trend that remains consistent regardless of variations in target steel carbon content and DRI carbon content. The research results can provide theoretical reference for the formulation of short process production process of DRI electric arc furnace.
To enhance the cooling efficiency of continuous casting molds, researchers have proposed various optimized water-cooling structural designs and heat transfer enhancement techniques. Focusing on the heat transfer enhancement challenges in water-channel molds, a novel design scheme that incorporates turbulator rods into the water channels was presented. Through a combination of heat transfer experiments and numerical simulations, the convective heat transfer coefficient on the water channel walls was quantitatively characterized, while the comprehensive heat transfer performance of the modified mold copper plate was evaluated. The results show that under the conditions of a uniform heating heat flux of 1 MW/m2 on the hot surface of the mold copper plate and a cooling water flow rate of 20-40 m3/h, the improved method of adding turbulator rods increases the convective heat transfer coefficient of the water-channel wall surface by an average of 4.33 kW/(m2·K), and the heat transfer efficiency of the mold copper plate is improved by 11.26%, effectively improving the heat transfer performance. The increased flow resistance caused by turbulator rods results in a comprehensive heat transfer performance evaluation criterion below 1. It provides critical insights for enhancing heat transfer performance by intensifying turbulent flow in mold channels.
Efficient heat transfer on the surface of the casting billet in the secondary cooling zone of continuous casting plays a crucial role in increasing casting speed and improving casting billet quality. Accurately characterizing of the heat transfer behavior of high temperature casting billet surfaces is therefore of great significance. Cold-state experiments were conducted using a TPU9520 pure water nozzle as the spray source to measure the water flux density in the indirect jet zone of the casting billet surface in the foot roller section. A heat transfer experimental platform for casting billet cooling was established to obtain the cooling curves of surface temperature over time in the indirect jet zone, as well as the variations in heat flux density and heat transfer coefficient with surface temperature. Functional relationships among water flux density, surface temperature, heat flux density, and heat transfer coefficient were fitted. The RESULTS show that stable film boiling occurs on the casting billet surface in the indirect JET zone of the foot roller section during secondary cooling. When the nozzle flow rate increased from 0.5 m3/h to 0.7 m3/h, the average heat flux density RISES from 235.2 kW/m2 to 291.2 kW/m2, and the average heat transfer coefficient increased from 272.2 W/(m2·K) to 336.7 W/(m2·K). Similarly, when the surface water flux density increased from 0.70 kg/(m2·s) to 1.23 kg/(m2·s), the average heat flux density grew from 215.8 kW/m2 to 319.9 kW/m2, and the average heat transfer coefficient increased from 250.2 W/(m2·K) to 369.3 W/(m2·K). The fitted mathematical relationships among water flux density, surface temperature, heat flux density, and heat transfer coefficient provide reliable data support for establishing thermal boundary conditions in the secondary cooling process of continuous casting.
To investigate the effect of heat treatment on the bonding strength of stainless steel clad plates, the clad plates underwent rolling, normalizing, and post-weld heat treatment (PWHT). The microstructural and mechanical properties of 304/Q345R composite plate were analyzed by metallographic metallography (OM), scanning electron microscopy (SEM), Vickers hardness testing, nano-indentation and shear testing. The results show that the clad plate fractures at the stainless steel matrix in the as-rolled state, while after normalizing and die welding heat treatment, the clad plate fractures at the interface and decarburized layer. The shear strength is the highest in the as-rolled state, reaching 425 MPa, and the lowest in the normalized state, at 363 MPa. After four die welding processes, the shear strength fluctuates between 375 MPa and 397 MPa. The widths of the high-alloy structural band and the chromium-depleted zone are hardly affected by heat treatment, while the interface hardness and the width of the decarburized layer are significantly influenced. The shear strength is negatively correlated with the interface hardness and the width of the decarburized layer. With the increase in the number of PWHT, the shear strength, interface hardness and the width of the decarburized layer change in a wavy pattern. The experimental results provide a guidance for the heat treatment production of clad steel plates.
The demand for lightweighting and safety in the automotive industry has driven the application of high-strength dual-phase steels. However, the coordinated deformation behavior between ferrite and martensite of high-strength dual-phase steels during tensile deformation still lacks in-depth investigation. In this regard, a DP980 was investigated in this study to investigate the geometrically necessary dislocation density, stress-strain concentration, micro-texture, crack formation, and propagation under various true strains by separating ferrite and martensite. The results demonstrated that owing to the uncoordinated deformation of ferrite and martensite, dislocations in ferrite first accumulate at grain boundaries, and then extend into the grain. The rate of increase of geometrically necessary dislocation density decreases with increasing true strain for both ferrite and martensite. A much higher rate of increase in geometrically necessary dislocation density for ferrite than martensite during the predeformation stage. However, the difference in increasing rate of geometrically necessary dislocation density between the two phases decreases continuously with increasing deformation. During the deformation process, ferrite and martensite exhibit similar micro-texture evolution, and both are finally transformed into α-fiber+γ-fiber textures. The stress-strain concentration resulting from the uncoordinated deformation of the two phases first induces the interface decohesion generation. Moreover, in the later stages of deformation, martensitic fracture also occurs as the martensite continues to take on more strain and the inherent brittleness of high-carbon martensite. This study contributes to further understanding of the deformation behavior and fracture mechanism of high-strength dual-phase steels.
The effect of austenitization time on the microstructural evolution of Al-10%Si coating on 22MnB5 steel was investigated. The microstructure and phase composition of the coating after austenitization at 930 ℃ for 4-10 minutes were systematically characterized using scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and electron backscatter diffraction (EBSD). Before austenitization, the coating mainly consists of a ternary eutectic phase (Al+Si+FeSiAl4), with a thin interlayer composed of Fe2Al5 and FeAl3 phases between the Fe2SiAl7 alloy layer and the steel substrate. As austenitization time increases, the primary phases in the intermetallic layer shift from Fe3Si2Al5 to Fe2SiAl3 and Fe2SiAl2. Both the intermetallic and diffusion layers thicken, and the thickening rates of the coating and diffusion layer are consistent. Non-equilibrium diffusion of Al atoms and excess vacancies in the diffusion layer lead to the formation of Kirkendall voids. As austenitization time increases from 4 to 10 minutes, the number of voids increases and voids merge with each other. Additionally, the number of microcracks perpendicular to the coating surface grows, and at 10 minutes, some cracks extend into the adjacent steel substrate. The surface color of the Al-10%Si coating shifts from gray to blue and tan, indicating increased oxidation, which is attributed to the transformation of Fe oxides from black FeO to blue Fe3O4 and red Fe2O3.
In order to address the strip breakage issue occurring at crescent-shaped notches behind laser welds in electrical steel coils, this study combines experimental analysis with finite element simulation to investigate the mechanical mechanisms of shear-induced fracture and optimize shearing parameters. With the continuous improvement of welding techniques, breakage failures have shifted downstream to the crescent notch area. Residual stress tests and SEM analysis reveal that stress concentration and insufficient shear band thickness are the primary causes of fracture. A dynamic shearing model built in ABAQUS identifies high-stress regions at the crescent tip. Response surface methodology is used to evaluate the influence of shear gap and strip thickness. The results show that when the shear gap is 0.17 mm, the strip thickness is 2.3 mm, combined with a bite depth of 8 mm and a shear speed of 862 mm/s, the shear quality is significantly improved. The results provide a theoretical and practical foundation for stable production of high-grade electrical steel.
Utilizing the pelletizing process to produce spent catalyst-containing pellets is an effective way for steel enterprises to achieve in-plant disposal of denitrification solid waste. However, the roasting strength index of pellets restricts the addition amount of spent catalysts. B2O3 was added to the raw materials for pelletizing, and its effects on the improvement of the roasting strength of spent catalyst-containing pellets and the comprehensive properties of green pellets were investigated. Furthermore, methods such as X-ray diffractometer (XRD), ore microscope, scanning electron microscope-energy dispersive spectrometer (SEM-EDS), and binary phase diagram were used to conduct research on the mechanism of B2O3 in enhancing the roasting strength of pellets. The experimental results demonstrated that when 10% waste catalyst by mass fraction was added to the pellets reduced their roasting strength from 3 088 to 2 103 N/pellet. When B2O3 with a mass fraction of 1%-5% was subsequently added to the waste catalyst pellets with a mass fraction of 10%, the roasting strength exhibited an initial increase followed by a decreasing trend. When the addition amount of B2O3 mass fraction reached 2%, the maximum roasting strength of 4 186 N/pellet. Under this optimal condition, the bursting temperature exceeded 500 ℃, the dry pellet compressive strength reached 160.0 N/pellet, while the green pellet drop number(0.5 m) and green pellet compressive strength were measured as 11.6 times and 19.4 N/pellet, respectively. During the roasting process of pellets, part of TiO2 in the spent catalyst reacts with Fe2O3 to form Fe2TiO5 with a fabric structure, which is distributed around Fe2O3 grains and inhibits the recrystallization and growth of Fe2O3 grains. In addition, part of TiO2 transforms from anatase phase to rutile phase during the roasting process of pellets, resulting in volume shrinkage and forming pores with surrounding minerals. B2O3 forms a low-melting liquid phase with SiO2, providing a liquid phase environment for the reaction between TiO2 and Fe2O3, eliminating the influence of Fe2TiO5 on the recrystallization process, and simultaneously filling the pores generated by the phase transformation shrinkage of TiO2 in the pellets. This study provides theoretical guidance and practical basis for improving the roasting strength of spent catalyst-containing pellets, and is of great significance for steel enterprises to reduce the disposal cost of spent catalysts and achieve in-plant resource utilization.
To investigate low-carbon pathways for the synergistic utilization of ferroalloy solid wastes in glass-ceramic preparation and clarify the mechanism of sintering impact on performance, the technological characteristics of the Petrurgic melting method and one-step sintering method were systematically compared using silicomanganese slag (SMS) and ferrochromium slag (FCS) as raw materials, with a focus on unraveling the "composition-process-performance" correlation. By adjusting the SMS/FCS mass ratios (8∶2, 6∶4, 4∶6) and employing multi-scale characterization techniques including X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), and mechanical tests. It is found that both processes achieve optimal crystallization at 950 ℃. However, significant performance discrepancies arise due to differences in raw material properties and crystallization mechanisms. In the melting method, Cr2O3 in FCS acts as an effective nucleating agent, lowering the crystallization temperature during the cooling and crystallization process of the mixed molten slag and promoting the precipitation of augite and forsterite. The three-dimensional elongated forsterite is embedded in uniformly distributed fine augite grains (5-20 μm), which enhances the mechanical properties, leading to a bending strength of 101 MPa (water absorption 0.37%) for the sample with 60% FCS. In contrast, in the sintering method, interfacial cracks are generated due to the thermal contraction mismatch between forsterite and the glass matrix. To address this, 80% SMS is added to increase the liquid phase content, achieving a bending strength of 28.7 MPa (water absorption 10.4%). The study demonstrates that the melting method, leveraging the nucleation effect, is suitable for direct casting of FCS-dominated molten slag to prepare glass-ceramics, while the sintering method is suitable for utilizing stockpiled SMS as the main raw material. These two methods establish optimized pathways for the high-value utilization of solid wastes.
In order to explore the process route for carbon emission reduction, sulfur reduction, and pollution reduction in the direct reduction process of rotary hearth furnace(RHF), a calculation model for sulfur emission and carbon emission in the direct reduction process of RHF was constructed based on the production conditions of a steel plant. The influence of hydrogen-rich operation and application of biomass carbon-containing pellets on sulfur emission and carbon emission of RHF was studied by means of a mathematical model. Hydrogen enrichment refers to the additional increase in the volume fraction of hydrogen in the gas as a result of the increase in the proportion of coke oven gas in the gas mixture fed into the RHF, which produces metallized pellets (DRI). The results show that the influence of hydrogen enrichment rate on sulfur dioxide emission is negligible, and the use of biomass to replace coke powder can effectively reduce sulfur dioxide emission. Under the synergistic effect of hydrogen-rich operation and the application of biomass carbon-containing pellets, compared with the baseline conditions of the rotary hearth furnace, when the hydrogen content in the mixed gas is 2% and the applied carbon-oxygen ratio is 0.6, the average carbon emissions of the eucalyptus pellets, straw pellets, and giant king oyster mushroom grass pellets process are reduced by 253.49, 269.84, and 249.86 kg/t(DRI), respectively. On this basis, for every 2% increase in the hydrogen content, the average carbon emissions are reduced by 30.8 kg/t(DRI). The synergistic carbon reduction effect of the two is more significant.
With the continuous development of intelligent manufacturing, surface defect detection of rolled steel balls has become a key link to ensure production quality. To address the problems of inaccurate recognition and low detection efficiency in surface defect detection of rolled steel balls, a YOLO11-DSAM defect detection algorithm for rolled steel balls was proposed. Firstly, a DySample dynamic upsampling module was introduced into the neck network to efficiently capture the advantages of target features through a dynamic sampling strategy, enhancing the model's perception ability for various defect features. Secondly, a small target detection head was added, and the Concat operation was used to fuse multi-level features, improving the model's detection accuracy for small targets. Thirdly, depthwise separable convolution and SEAM attention mechanism were integrated into the detection head, which not only reduced the computational complexity of the model but also enabled the model to focus on key features, thereby enhancing the overall detection performance. Finally, a new loss function MCIoU was proposed to guide model training with more accurate loss measurement, achieving rapid and high-precision convergence. Experimental results show that the proposed algorithm improves the average precision by 3.1% on the rolled steel ball dataset compared to the original algorithm, reduces the number of parameters by 12.4%, and lowers GFLOPs (1 billion floating-point operations per second) by 3.17%, achieving high detection accuracy and low computational complexity. At the same time, the algorithm's good generalization performance is verified on the NEU-DET dataset. The defect detection algorithm for rolled steel balls proposed in this study provides technical support for efficient surface defect recognition and the upgrade of industrial quality inspection systems.
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