In the wake of the era of big data, the techniques of deep learning have become an essential research direction in the machine learning field and are beginning to be applied in the steel industry. The sintering process is an extremely complex industrial scene. As the main process of the blast furnace ironmaking industry, it has great economic value and environmental protection significance for iron and steel enterprises. It is also one of the fields where deep learning is still in the exploration stage. In order to explore the application prospects of deep learning techniques in iron ore sintering, a comprehensive summary and conclusion of deep learning models for intelligent sintering were presented after reviewing the sintering process and deep learning models in a large number of research literatures. Firstly, the mechanisms and characteristics of parameters in sintering processes were introduced and analysed in detail, and then, the development of iron ore sintering simulation techniques was introduced. Secondly, deep learning techniques were introduced, including commonly used models of deep learning and their applications. Thirdly, the current status of applications of various types of deep learning models in sintering processes was elaborated in detail from the aspects of prediction, controlling, and optimisation of key parameters. Generally speaking, deep learning models that could be more effectively implemented in more situations of the sintering and even steel industry chain will promote the intelligent development of the metallurgical industry.

The correlation between the longitudinal crack occurrence and integrated heat transfer of the mold with data mining methods was investigated. Firstly, three kinds of support vector machine models based on principal component analysis with different input features were established to explore the effect of integrated heat transfer on the accuracy of the prediction model for the longitudinal crack. The results show that the accuracy was improved while features including mean and standard deviation of integrated heat transfer were added. Then, the difference in integrated heat transfer between defect and normal samples under the same process parameters was quantitatively compared. Compared with normal samples, the temperature difference of cooling water for defect samples decreased by 0.65%, and the temperature difference fluctuation increased by 31.1%. Finally, the literature data were used to provide support for the quantitative correlation according to defect formation mechanism. A new criterion for the prediction of longitudinal crack and a discovering method for correlation between product quality and process parameters in the manufacturing industry have been provided.

Super-high bed sintering process is an important development direction of iron ore sintering for its lower emission and higher yield. However, there is a lack of deep understanding of the uneven quality of super-high bed sintering products, and the deterioration of reduction disintegration performance, the thickening of hearth layer and the reduction in energy-saving effect are perplexing enterprises and researchers. To ascertain the problems of super-high bed sintering, ten sintering machines with the areas of 265, 280, 360, 550 and 660 m2 and bed depth above 900 mm were sampled and analyzed. The results showed that problems were mainly shown in the unevenness of chemical composition, macrostructure, mechanical strength and metallurgical performance. The chemical composition exhibits severe segregation in both horizontal and vertical directions, with basicity segregation reaching as high as 0.81. The uneven macrostructure of sinter is reflected in a 10% difference in porosity and mechanical strength increase in 16%–19% along the vertical direction. The reducibility and reduction disintegration performance gradually deteriorate along the bed depth, with a difference of 10.5% in reducibility and 7.3% in RDI_{-0.5 mm} (reduction disintegration index of sinter with size smaller than 0.5 mm).

The unstable fluid flow and severe free surface fluctuations in the wheel and belt caster can affect the quality of the cast bar. The lower level height tends to entrap inclusions in the molten metal. On the other hand, the higher level height makes the production process more dangerous due to the overflow of high temperature fluid from the mold. A computational model of the molten metal pouring process was established. The transient fluid flow and free surface fluctuations behavior were calculated using the three-dimensional large eddy simulation model and the volume of fluid model. The results show that the flow velocity of the main jet gradually decreases under the influence of the low kinetic energy fluid in the mold. There is an obvious oscillation in the tail of the jet, while the flow field is asymmetric in space. The jet is closer to the inside radius side due to the Coanda effect, and there is a recirculation zone on the inside radius and the outside radius respectively, according to the 10 s time-averaged results. Compared with the industrial observation and simulation results, the shape of the free surface is a wave that varies with time. In addition, the free surface height is lowest and the flow velocity is highest in the region near the jet.

A rotating stopper-rod technique was proposed to suppress the formation of free-surface vortex in the tundish. The large eddy simulation model coupled with volume of fluid model was developed to study the steel–slag–gas three-phase flow behavior. The critical slag entrapment height of the free-surface vortex and mass of residual steel were predicted at different rotating speeds (30, 60, 90 and 120 r/min) of the rotating stopper-rod. The numerical model was verified by water model experiment. The results showed that by rotating the stopper-rod in the opposite direction of the vortex above the submerged entry nozzle, the formation of vortex can be effectively disturbed and the critical height of the free-surface vortex can be reduced. Particularly for the 2nd strand, when the rotating speeds are 30, 60, 90 and 120 r/min, the critical height of the free-surface vortex above the 2nd strand is 7.3, 4.7, 6.3 and 7.4 cm, respectively. A reasonable rotating speed should be 60 r/min, which can reduce about 2 tons of residual steel. Other rotating speeds just can reduce about 1.6 tons of residual steel.

The conventional melting methods were used to obtain in situ TiC particle-reinforced dual-phase steel, followed by hot rolling and heat treatment processes. The aim was to investigate the effect of TiC particles on the fracture behavior of dualphase steel at different annealing temperatures, by analyzing the microstructure and tensile behavior of the multiscale TiC particle-reinforced dual-phase steel. The results showed that TiC particles precipitated in the as-cast microstructure of dualphase steel were distributed along the grain boundaries. During hot rolling, the grain boundary-like morphology of the micron-sized TiC particles was disrupted, and the particles became more refined and evenly distributed in the matrix. The tensile tests revealed that the strength of the TiC particle-reinforced dual-phase steel increased with increasing martensite content, while the elongation decreased. These results were similar to those of conventional steel. The addition of 1 vol.% multiscale TiC particles improved the strength of the dual-phase steel but did not affect elongation of the steel. Cracks and holes were primarily concentrated around the TiC particles rather than at the interface of martensite and ferrite. The main causes of crack sprouting were TiC particle interface cracking and TiC particle internal fragmentation. Overall, the study demonstrated the potential of multiscale TiC particle-reinforced dual-phase steel as a strong and tough material. The refined distribution of TiC particles in the matrix improved the strength of the material without compromising its elongation. The results also highlighted the importance of careful selection of reinforcement particles to avoid detrimental effects on the fracture behavior of the material.

The iron and steel industry, standing as a quintessential manufacture example with high consumption, pollution and emissions, faces significant environmental and sustainable development challenges. Electric arc furnace (EAF) steelmaking process mainly uses scrap as raw material and is characterized by environmentally friendly and recyclable process. However, the further development of EAF route in China is limited by the reserve, supply, availability and quality of scrap resource. Direct reduced iron (DRI) is one of typical low-carbon and clean charges, which can effectively make up for the adverse effects caused by the lack of scrap. The physical and chemical properties, classifications, and production technologies of DRI are firstly reviewed. In particular, the reducing gas types, reduction temperature, and reduction mechanism of the DRI production with gas-based shaft furnace (SF) technology are detailed. Considering the crucial role played by DRI application in EAF, the influences of DRI addition on EAF smelting rules and operations including the blending and charging process, heat transfer and melting in molten bath, slag formation operation, refractory corrosion, and slag system evolution are then further discussed. Finally, the comparative analysis and assessment of the consumption level of material and energy as well as the cleaner production both covering the clean chemical composition of molten steel and the clean environment impact in EAF steelmaking with DRI charged are conducted. From perspectives of metallurgical process engineering, a suitable route of hydrogen generation and application (from coke oven gas, methanol, and clean energy power), CO₂ capture and utilization integrated with SF-EAF process is proposed. In view of the difficulties in large-scale DRI application in EAF, the follow-up work should focus on the investigation of DRI charging and melting, slag system evolution and molten pool reaction rules, as well as the developments of the DRI standardized use technology and intelligent batching and control models.

Two silicon resins with excellent thermal stability, JH1123 and JH7102, are used as the insulated agents and binders for the gas-atomized FeSiAl powder, and corresponding magnetic powder cores (MPCs) are fabricated. The insulation capability and application prospects of the two silicon resins are evaluated by comparing the magnetic properties of the coated powder and MPCs. The scanning electron microscopy, energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy results show that uniform insulation layers are both formed on the powder surfaces. JH1123 has stronger binding ability, and the JH1123-coated powder exhibits severe agglomeration, with d₅₀ (average particle size) approximately twice that of the JH7102-coated powder. Both as-prepared MPCs exhibit outstanding soft magnetic properties. Wherein, the permeability of FeSiAl@JH1123 is up to 74.0, which is 35.5% higher than that of FeSiAl@JH7102 because JH1123 can further improve the density of the MPCs. As for FeSiAl@JH7102, it has better direct current bias and lower core loss of 716.9 mW cm^-3 at 20 mT and 1000 kHz due to its lower coercivity and greater antimagnetic saturation ability. A comprehensive comparison shows that FeSiAl@JH1123 is suitable for medium and high frequency applications, while FeSiAl@JH7102 is more suitable for high frequency applications. This indicates that the use of JH1123 and JH7102 silicon resins for binding and insulated coating not only simplifies the preparation process of MPCs, but also enables the controlled production of MPCs for different applications.

Submerged entry nozzle (SEN) clogging is a major problem affecting the production quality of rare earth steel, and finding a suitable refractory outlet can significantly reduce production costs. To explore the relationship between refractory composition and interface interaction, unprotected coated Al₂O₃–MgO refractories and SiO₂-coated Al₂O₃–MgO refractories were added to rare earth high-carbon heavy rail steel under laboratory conditions, and the Al₂O₃–MgO refractory was found to be more suitable. The results show that, from the epoxy resin side to the refractory side, the contour of the refractory interface reaction layer can be divided into two main layers: an iron-rich reaction layer and an iron-poor reaction layer. Calculations based on the spherical model suggest that the adhesion force is proportional to the size of the refractory particles and inclusions, and the same result applies to the surface tension. Controlling the inclusions at a smaller size has a specific effect on alleviating the erosion of refractories. Combined with the erosion mechanism of Al₂O₃–MgO refractories, the interface reaction mechanism between Al₂O₃–MgO refractories and molten steel was proposed, which provides ideas for solving SEN clogging.

The key role of oxide inclusions on the microstructure and mechanical property of a high-strength low-alloy steel was investigated. The field emission scanning electron microscope equipped with energy-dispersive spectrometry was used to characterize MnS precipitates. Oxide inclusions play an important role in the shape control of MnS precipitates. More oxides fovored to decrease the size and the aspect ratio of MnS precipitates. With less oxide inclusions in the steel, approximately over 16.7% MnS precipitates were with aspect ratio a>5 and pure MnS precipitates accounted for 75.9% in number. However, with more oxide inclusions in the steel, only 7.4% MnS precipitates were with a>5 and pure MnS precipitates accounted for 60.1% in number. Refinement of MnS by oxide inclusions improved the strength and inhibited the anisotropy. More oxide inclusions in the steel increased the yield strength and tensile strength of the steel in both longitudinal and transverse directions, and lowered the anisotropy of the mechanical property.

Accumulative roll bonding (ARB) is a severe plastic deformation method to prepare the metallic composite material by physical method at room to elevate temperature, without the generation of additional waste solid or gas. With the physical characteristicsmulti-material and hybrid structure, the mechanical and function properties of the ARB composite material, like Al/steel, Al/Mg, Al/Cu, etc., shall have the “1+1>2” effect on the mechanical and functional properties, including the remarkable properties that include lightweight, high strength, thermal/electrical conductivity, electromagnetic shielding, and other functions. To deeply investigate the preparation method and microstructural evolution of various metal laminates by ARB, as well as the mechanical and functional properties of the laminate, an overview of the history of ARB technique, the breakthrough of ARB sheet properties, as well as the relative products in industries is provided. Additionally, the future development of ARB technology and the utilization of composite materials in different areas will be discussed.

The basic high-temperature properties of iron ore play a crucial role in optimizing sintering and ore blending, but the testing process for these properties is complex and has significant lag time, which cannot meet the actual needs of ore blending. A prediction model for the basic high-temperature properties of iron ore fines was thus proposed based on a combination of machine learning algorithms and genetic algorithms. First, the prediction accuracy of different machine learning models for the basic high-temperature properties of iron ore fines was compared. Then, a random forest model optimized by genetic algorithms was built, further improving the prediction accuracy of the model. The test results show that the random forest model optimized by genetic algorithms has the highest prediction accuracy for the lowest assimilation temperature and liquid phase fluidity of iron ore, with a determination coefficient of 0.903 for the lowest assimilation temperature and 0.927 for the liquid phase fluidity after optimization. The trained model meets the fluctuation requirements of on-site testing and has been successfully applied to actual production on site.

Refill friction stir spot welding (RFSSW) provides a novel method to join similar and/or dissimilar metallic materials without a key-hole in the center of the joint. Having the key-hole free characterization, the similar/dissimilar RFSSW joint exhibits remarkable and endurable characteristics, including high shear strength, long fatigue life, and strong corrosion resistance. In the meanwhile, as the key-hole free joint has different microstructures compared with conventional friction stir spot welding, thus the RFSSW joint shall possess different shear and fatigue fracture mechanisms, which needs further investigation. To explore the underlying failure mechanism, the similar/dissimilar metallic material joining parameters and pre-treatment, mechanical properties, as well as fracture mechanisms under this novel technology will be discussed. In details, the welding tool design, welding parameters setting, and the influence of processing on the lap shear and fatigue properties, as well as the corrosion resistance will be mainly discussed. Moreover, the roadmap of RFFSW is also discussed.

Steels are widely used as structural materials, making them essential for supporting our lives and industries. However, further improving the comprehensive properties of steel through traditional trial-and-error methods becomes challenging due to the continuous development and numerous processing parameters involved in steel production. To address this challenge, the application of machine learning methods becomes crucial in establishing complex relationships between manufacturing processes and steel performance. This review begins with a general overview of machine learning methods and subsequently introduces various performance predictions in steel materials. The classification of performance prediction was used to assess the current application of machine learning model-assisted design. Several important issues, such as data source and characteristics, intermediate features, algorithm optimization, key feature analysis, and the role of environmental factors, were summarized and analyzed. These insights will be beneficial and enlightening to future research endeavors in this field.

Enhancing the ductility and toughness of advanced high-strength steels is essential for the wide range of promising applications. The retained austenite (RA) is a key phase due to the austenite-to-martensite transformation and its transformation-induced plasticity effect. It is commonly accepted that slow RA-to-martensite transformation is beneficial to ductility; therefore, the RA fraction and stability should be carefully controlled. The RA stability is related to its morphology, size, carbon content, neighboring phase and orientation. Importantly, these factors are cross-influenced. It is noteworthy that the influence of RA on ductility and fracture toughness is not consistent because of their difference in stress state. There is no clear relationship between fracture toughness and tensile properties. Thus, it is important to understand the role of RA in toughness. The toughness is enhanced during the RA-to-martensite transformation, while the fracture toughness is decreased due to the formation of fresh and brittle martensite. As a result, the findings regarding to the effect of RA on fracture toughness are conflicting. Further investigations should be conducted in order to fully understand the effects of RA on ductility and fracture toughness, which can optimize the combination of ductility and toughness in AHSSs.

The corrosion behavior of high-strength low-alloy 921A steel in a simulated marine atmospheric environment was studied using a high-throughput experimental method. The corrosion behavior, corrosion morphology, and corrosion products of 921A steels were analyzed using various techniques, including corrosion mass loss method, polarization curve, white-light interferometry, scanning electron microscopy, energy-dispersive spectrometry, microbeam X-ray fluorescence spectrometry, X-ray diffraction technique, and X-ray photoelectron spectroscopy. The test results indicated that 921A steel exhibits better corrosion resistance than Q450NQR1 steel in simulated harsh atmospheric environments, as evidenced by a lower corrosion mass loss rate throughout the corrosion tests. The corrosion products of both steels consisted of α-FeOOH, Fe₃O₄, and γ-FeOOH, with α-FeOOH being more prevalent in the rust layer of 921A steel than in Q450NQR1 steel. The inner rust layer of 921A steel also exhibited an appositional enrichment region of Cr, Ni, Mo, and V, leading to its superior corrosion resistance compared to that of Q450NQR1 steel. The efficacy of high-throughput accelerated corrosion experimental methods was highlighted for evaluating the corrosion resistance of steel materials in harsh environmental conditions. The findings suggest that 921A steel exhibits better corrosion resistance compared to Q450NQR1 steel and has the potential to be more suitable in harsh marine atmospheric environments. The characterization of the rust layer structures and composition reveals the parallel enrichment of certain elements in the inner rust layer of 921A steel, which enhances its corrosion resistance.

Hot air sintering technology is used to improve the quality and production efficiency of sintered ore. However, the current thick layer condition highlights the disadvantage of the low oxygen potential of the hot air sintering layer. Therefore, it is considered to use oxygen enrichment sintering to improve the environment of hot air sintering. Traditional sintering, hot air sintering, and oxygen-rich hot air sintering were compared through sintering cup experiments, and the influence of hot air and oxygen-rich hot air on sintering indexes was clarified. Hot air reduced the vertical sintering velocity, while improved the yield and tumbler index. Oxygen-rich hot air sintering contributed to improving the vertical sintering velocity while ensuring the quality of sintered ore, thus comprehensively improving production efficiency. Under the action of hot air, the highest temperature of the sintering layer increased and the high-temperature holding time was prolonged. After oxygen enrichment, the combustion efficiency of fuels in the upper layer of materials was promoted, which optimized heat distribution in the middle and lower layers of materials and increased the content of calcium ferrite in the sintered ore, thus strengthening the sintering process.

The solidification methods of electromagnetic stirring (EMS) and non-electromagnetic stirring were employed to prepare Mg–6Gd–3Y–xZn–0.6Zr (x = 1, 1.5, 2, 3) alloys. The evolution of alloy microstructures and the changes in properties were analyzed for different Zn contents. It has been observed that in alloys without electromagnetic stirring, as the Zn content increases, the alloy structure gradually refines. The primary second phase transitions from Mg5RE phase to long-period stacking ordered (LPSO) phase, resulting in improved hardness and elongation. In alloys subjected to electromagnetic stirring, there is a relatively higher content of the second phase, primarily consisting of LPSO phase. After applying electromagnetic stirring, the quantity and the type of LPSO phase in the alloy change. The alloy structure becomes more uniform with electromagnetic stirring, resulting in increased hardness and reduced hardness gradients within the grains. The mechanical properties of alloys with electromagnetic stirring are superior to those without electromagnetic stirring.

Energy-saving in China’s iron and steel industry still relies on the development and improvement of short-term energy saving technologies. Therefore, a special converter smelting technology incorporating energy saving was proposed. To evaluate the energy-saving potential of the CO₂–O₂ mixed injection (COMI) technology, collected production data were used to develop an improved techno-economic model. Calculations reveal that the technology can save energy through auxiliary material consumption, sensible heat of solid by-product, iron loss reduction, and energy recovery. The application of COMI technology in an enterprise is cost effective, involving the energy saving potential of 0.206 GJ/t, the cost of conserved energy of - 48.83 yuan/GJ, and a simple payback period of 0.35 year for a 60-million-yuan investment. Sensitivity analysis shows that the investment cost and discount rate primarily influence the cost of conserved energy of the technology. As the discount rate increased, the cost of conserved energy also gradually increased. Overall, the COMI technology is an energy-saving technology with good development prospects.

The microstructural characteristics including optical texture, porosity and pore structure and chemical structure of stampcharged coke (SCC) and gravity-charged coke (GCC) with similar conventional macro-indicators were investigated, and the properties including micro-strength, reactivity of coke matrix and that after alkali enrichment were comparatively studied by various characterization methods. The anisotropic structure of SCC is composed of high content of fine mosaic texture, while the content of medium mosaic texture, coarse texture and fibrous texture is low. The statistical average shows that the fine mosaic average of SCC (24.89%) is 3.78 times the GCC average (6.58%), and the coarse mosaic average (1.24%) is only about 1/3 of the GCC average (3.43%). The porosity of SCC is lower than that of GCC, but tamping process does not lead to the fact that the number of closed pores of SCC is significantly lower than that of GCC. Although the structure of SCC is compact, its pore number is large and the pore wall is thin. Pores of coke with diameter less than 150 nm seem unaffected by tamping process. The aromatic structure of SCC was less ordered than that of GCC, which was speculated to be related to the addition of more low metamorphic coal in coking. The microscopic strength and structural strength of SCC are lower than those of GCC. The reactivity of coke matrix is affected by the specific surface area, but it is not the determining factor of its macro-reactivity. The improvement in dissolution reactivity of coke after potassium enrichment is independent of coke type.

To investigate the evolutionary behavior of the MnO–SiO₂–Al₂O₃–MgO inclusions during heat treatment, water quenched samples were isothermally held at 1100 C for 120 min in Ar and air atmosphere, and the obtaining samples were analyzed by X-ray diffraction, scanning electron microscopy and energy dispersive spectrometer. It showed that 3MnO Al₂O₃ 3SiO₂ and MnO SiO₂ were detected in the 5 wt.% MgO system after isothermal holding in Ar atmosphere, while MgO ・Al₂O₃, MnO・SiO₂ and Mn₇O₈・SiO₄ were detected in air atmosphere. The evolutionary behavior of the 10, 15 and 20 wt.% MgO systems after isothermal holding in different atmosphere were consistent. Oxygen affected the solid phase transformation of the low MgO content systems. The calculation results of FactSage 8.1 showed that MgO・Al₂O₃ was formed in the 5 wt.% MgO system with air atmosphere. The solid phase transformation was accompanied by grain coarsening during the isothermal holding process. The differences in the solid phase transformation in different atmosphere of the 5 wt.% MgO system indicated that it was a gas-phase transport grain coarsening mechanism. The enrichment of Al element in the liquid phase region at the grain edges, the homogeneous distribution of Mg element and the disappearance of the liquid phase within the crystal revealed that other MgO content systems were liquid–solid transport grain coarsening mechanism.

H13 tool steel was successfully prepared by selective laser melting (SLM) technology. The effects of heat treatment on the microstructure, mechanical properties, and tribological properties of SLMed H13 steel were investigated. The heat treatment process involved a solution treatment and a double aging treatment of the deposited H13 tool steel prepared bySLM.The aim is to optimize the microstructure and mechanical properties of SLMed H13 steel. Due to the rapid heating and cooling effects of SLM, carbide precipitation in the deposited H13 steel was not uniform and residual stresses were present. The purpose of the solution treatment is to dissolve the solution at a high temperature to eliminate the residual stresses and defects introduced by the SLM-forming structure. The solution treatment and first aging treatment produced the precipitation of small carbides at the grain boundaries and inside the crystals, which increased the hardness of SLMed H13 steel. The hardness increased from 538 ± 4.0 HV of the as-deposited sample to 548 ± 5.8 HV of samples after the first aging treatment. Accordingly, the ultimate tensile strength and the elongation at break decreased from 1882 MPa and 11.5% in the as-deposited sample to 1697 MPa and 7.9% in those after the first aging treatment, respectively. Furthermore, the friction coefficient and wear rate in the as-deposited sample decreased from 0.5160 and 2.36 × 10^–6 mm^-3 N^-1 m^-1 to 0.4244 and 1.04 × 10–6 mm^-3 N^-1 m^-1, respectively. However, the distribution of carbides inside the crystals was not uniform. The second aging treatment adjusted the morphology of carbide precipitation and made it more uniform, but the precipitation of carbides grew and settled at the bottom of the grain boundaries. The hardness decreased to 533 ± 6.7 HV compared with that with the first aging treatment, but the ultimate tensile strength and plasticity reached a balance (1807 MPa, 14.05%). Accordingly, the friction coefficient and wear rate also showed a stable and decreasing trend (0.4407, 0.98 9 10–6 mm-3 N-1 m-1).

The rapid development of iron and steel metallurgy technology has promoted the continuous innovation and iteration of carbon-containing refractories for clean steel smelting. To meet the high-quality requirements for clean steel production and full exploit the performance advantages of carbon-containing refractories in dynamic smelting environment, it is necessary to explore the role of graphite and modified graphite in carbon-containing refractories. Based on this, graphite surface modification methods, including surfactants, surface oxidation, and surface coating, and their applications in carbon-containing refractories are reviewed. The advantages and disadvantages of each method are analyzed for practical use. Furthermore, combined with the existing problems, the application prospect of improved graphite in carbon-containing refractories is discussed.

Real flatness images are the bases for flatness detection based on machine vision of cold rolled strip. The characteristics of a real flatness image are analyzed, and a lightweight strip location detection (SLD) model with deep semantic segmentation networks is established. The interference areas in the real flatness image can be eliminated by the SLD model, and valid information can be retained. On this basis, the concept of image flatness is proposed for the first time. An image flatness representation (IFAR) model is established on the basis of an autoencoder with a new structure. The optimal structure of the bottleneck layer is 16 × 16 × 4, and the IFAR model exhibits a good representation effect. Moreover, interpretability analysis of the representation factors is carried out, and the difference and physical meaning of the representation factors for image flatness with different categories are analyzed. Image flatness with new defect morphologies (bilateral quarter waves and large middle waves) that are not present in the original dataset are generated by modifying the representation factors of the no wave image. Lastly, the SLD and IFAR models are used to detect and represent all the real flatness images on the test set. The average processing time for a single image is 11.42 ms, which is suitable for industrial applications. The research results provide effective methods and ideas for intelligent flatness detection technology based on machine vision.

The effect of stress-relief annealing at different stages of thermal fatigue tests on crack growth was investigated using a self-built thermal cycle setup. The results showed that annealing could limit crack expansion effectively. It reduced dislocation density and released the accumulation of residual stress. In addition, the strain accumulation in carbides was reduced by this process. It was also found that double annealing was even more effective at inhibiting crack expansion compared to single stress-relief annealing. After 1000 cycles, the maximum crack length was reduced by 31.1% and 45.2% for the samples after using the optimal single and double annealing processes, respectively. For single stress-relief annealing, earlier annealing provides more benefit in delaying crack expansion. However, effective double stress-relief annealing requires a suitable time interval between the annealing steps. Besides, after 800 cycles, surface hardness decreased significantly accompanied by an increase in the size and number of carbides, and cracks expanded predominantly along grain boundaries.

The effect of lanthanum on the characteristics of inclusions in the slab of non-oriented electrical steels was investigated through industrial trials and thermodynamic analysis. The number, size, and chemical composition of inclusions in the surface, one-quarter of thickness and the center of slabs with and without lanthanum addition were statistically analyzed using an automatic inclusion analysis system. In the lanthanum-free slab, inclusions were predominately MgO[1]Al2O3, MgO, and AlN as well as a small number of Al2O3–MgO–CaO and MgS. The number densities of oxide inclusions and AlN decreased from the surface to the center of the slab, which was ascribed to the difference in cooling intensity during the continuous casting. In the steel with lanthanum addition, inclusions were modified into LaAlO3 and La2O2S and gradually transformed into dual-phase MgO–La2S3 with an increasing distance from the slab surface due to the reaction between the lanthanum-containing inclusion and the steel matrix. The uneven distribution of oxide inclusions along the thickness of the slab was eliminated in the lanthanum-bearing slab because the dissolved oxygen was remarkably decreased by lanthanum. Lanthanum-bearing inclusions were more likely to agglomerate AlN by inducing the heterogeneous nucleation of AlN on their surface, while small-size MgO-Al2O3 inclusions hardly showed a coarsening effect on the size of AlN.

MgO participates in all stages of sintering, pelletizing, and blast furnace ironmaking, and synergistically optimizing the distribution of MgO in ferrous burden can effectively enhance the interaction within the ferrous burdens and optimize the softening–melting properties of the mixed burden. Magnesium-containing pellets mixed with low-MgO sinter or mixed with high-MgO sinter in the blast furnace ferrous burden structure have opposite softening–melting performance laws. When the structure of the ferrous burden is magnesium-containing pellets mixed with low-MgO sinter, the magnesiumcontaining pellets can enhance the interaction of the ferrous burden in the process of softening–melting, which can optimize the composition of the slag phase and improve the slag liquidity. When the structure of the ferrous burden is magnesium-containing pellets mixed with high-MgO sinter, the magnesium-containing pellets weaken the interaction of the ferrous burden in the process of softening–melting, increase the content of the high melting point solid-phase particles in the slag, lead to an increase in the viscosity of the slag and difficult separation of the slag and iron, and decrease the permeability of the charge layer. Therefore, to ensure good permeability of the mixed burden, the following measures are suggested: optimizing the MgO distribution of the ferrous burden, reducing the MgO content of the sinter to 1.96 wt.%, increasing the MgO content of the pellets to 1.03–1.30 wt.%, controlling the MgO/Al2O3 ratio of the mixed burden within 1.15–1.32, narrowing the position of the cohesive zone, and maintaining an S value (permeability index) of approximately 150 kPa °C.

The iron oxide (FeO) content had a significant impact on both the metallurgical properties of sintered ores and the economic indicators of the sintering process. Precisely predicting FeO content possessed substantial potential for enhancing the quality of sintered ore and optimizing the sintering process. A multi-model integrated prediction framework for FeO content during the iron ore sintering process was presented. By applying the affinity propagation clustering algorithm, different working conditions were efficiently classified and the support vector machine algorithm was utilized to identify these conditions. Comparison of several models under different working conditions was carried out. The regression prediction model characterized by high precision and robust stability was selected. The model was integrated into the comprehensive multi-model framework. The precision, reliability and credibility of the model were validated through actual production data, yielding an impressive accuracy of 94.57% and a minimal absolute error of 0.13 in FeO content prediction. The real-time prediction of FeO content provided excellent guidance for on-site sinter production.

To optimize the comprehensive utilization of vanadium titanomagnetite by direct reduction-smelting processes, it is essential to acquire titanium slag with a higher TiO2 content of 45-60 wt.%. A thermodynamic model was developed based on the ion and molecule coexistence theory, specifically targeting the CaO-SiO₂-Al₂O₃-MgO-TiO_2-V₂O₃-FeO slag system. The impact of slag composition on the smelting of vanadium titanomagnetite was assessed, and the thermodynamic model was utilized to identify the optimal high-titanium slag. The results revealed that increasing the basicity, MgO content, and FeO content within the slag effectively suppressed the reduction of titanium and silicon oxides. Furthermore, the calculated activity coefficient of TiO2 decreased with higher basicity, MgO, and FeO levels. While an increase in basicity significantly enhanced the reduction of vanadium oxides, the effects of MgO and FeO contents on vanadium oxide reduction were comparatively less significant. Notably, higher basicity and FeO content promoted the formation of calcium titanates, whereas an elevated MgO content favored the formation of magnesium titanates. The smelting results indicated that a lower V₂O₃ content and higher TiO₂ activity corresponded to a smaller titanium mass fraction in the iron alloy, while the opposite trend was observed for vanadium.

Segregation of solute atoms in the center of thick plates of the tempered steel can cause an inhomogeneous structural transformation and generate micron-sized inclusions, which leads to lamellar tearing of thick plate and decreases the plasticity and toughness. The formation and fragmentation mechanisms of micron-sized inclusions, like MnS and (Nb, Ti)C, in the center of thick plates were investigated by using thermodynamic calculations, finite element simulations, and electron backscatter diffraction characterization techniques. The results show that micron-sized inclusions nucleate and grow in the liquid phase, and under tensile loading, they exhibit three fragmentation mechanisms. The local stress during the fragmentation of inclusions is lower than the critical fracture stress of adjacent grains, and phase boundaries can effectively impede crack propagation into the matrix. The existence of a low proportion of high-angle grain boundaries (58.1%) and high Kernel average misorientation value (0.534° ) in the segregation band promotes inclusions fragmentation and crack propagation. The difference in crack initiation and propagation direction caused by the morphology of inclusions and physical properties, as well as different matrix arrest abilities, is the main reasons for the diversity of inclusion fragmentation.

Slag corrosion is one of the main factors of the damage of refractory, and its primary manifestations involve the melting of refractory in slag and the slag penetration into refractory, both of which are highly related to the wetting behavior between slag and refractory. The high-temperature wettability could be characterized by parameters including the surface tension, adhesion work, and spreading coefficient of the slag on refractory surface, and it could be suppressed by altering the slag/refractory interface, thus resulting in an improved anti-corrosion performance. From this, the key knowledges of the slag corrosion, theory of wetting behavior and test of high-temperature contact angle were firstly summarized. Then, the major factors influencing the high-temperature slag wetting behavior were discussed based on the aspects of slag composition, refractory composition, and surface microstructure. Finally, the future research direction was proposed in this field.

Horizontal segregation has been a constraint to the development and application of super-high bed sintering. To eliminate the horizontal segregation of super-high bed sintering, several typical sintering machines were sampled and analyzed, and theoretical calculation was made to compare the bed depth and their differences in different areas within the mixture bin. Then, solutions were proposed and applied to a 265 m2 sintering machine. The results showed that the horizontal segregation of the 265 m2 sintering machine was dominated by particles larger than 8 mm with horizontal segregation degree of 0.48, while 360 and 550 m2 sintering machines were affected by 5–8 mm and 1–3 mm particles with horizontal segregation degree of 0.27 and 0.31, respectively. Causes analysis indicated the different segregation distribution results from the matching of the bed depth of each area within the mixture bin. Finally, the horizontal segregation degree not larger than 0.06 was achieved by optimizing the time parameters and the division of three zones on the 265 m2 sintering machine.

Proportioning is an important part of sintering, as it affects the cost of sintering and the quality of sintered ore. To address the problems posed by the complex raw material information and numerous constraints in the sintering process, a multiobjective optimisation model for sintering proportioning was established, which takes the proportioning cost and TFe as the optimisation objectives. Additionally, an improved multi-objective beluga whale optimisation (IMOBWO) algorithm was proposed to solve the nonlinear, multi-constrained multi-objective optimisation problems. The algorithm uses the constrained non-dominance criterion to deal with the constraint problem in the model. Moreover, the algorithm employs an opposite learning strategy and a population guidance mechanism based on angular competition and two-population competition strategy to enhance convergence and population diversity. The actual proportioning of a steel plant indicates that the IMOBWO algorithm applied to the ore proportioning process has good convergence and obtains the uniformly distributed Pareto front. Meanwhile, compared with the actual proportioning scheme, the proportioning cost is reduced by 4.3361 ￥/t, and the TFe content in the mixture is increased by 0.0367% in the optimal compromise solution. Therefore, the proposed method effectively balances the cost and total iron, facilitating the comprehensive utilisation of sintered iron ore resources while ensuring quality assurance.

Brazing, an important welding and joining technology, can achieve precision joining of materials in advanced manufacturing. And the first principle calculation is a new material simulation method in high-throughput computing. It can calculate the interfacial structure, band structure, electronic structure, and other properties between dissimilar materials, predicting various properties. It plays an important role in assisting practical research and guiding experimental designs by predicting material properties. It can largely improve the quality of welded components and joining efficiency. The relevant theoretical foundation is reviewed, including the first principle and density functional theory. Exchange-correlation functional and pseudopotential plane wave approach was also introduced. Then, the latest research progress of the first principle in brazing was also summarized. The application of first principle calculation mainly includes formation energy, adsorption energy, surface energy, adhesion work, interfacial energy, interfacial contact angle, charge density differences, density of states, and mulliken population. The energy, mechanical, and electronic properties were discussed. Finally, the limitations and shortcomings of the research in the first principle calculation of brazed interface were pointed out. Future developmental directions were presented to provide reference and theoretical basis for realizing high-throughput calculations of brazed joint interfaces.

To comprehensively utilize the low-iron high-vanadium–titanium magnetite, a new method of vortex smelting reduction of vanadium–titanium magnetite was proposed, and the enrichment and reconstitution regularity of Ti-bearing phases in the slag was investigated through X-ray fluorescence spectrometry, X-ray photoelectron spectroscopy, X-ray diffraction analysis, and optical microscopy. The phase diagram revealed that the preferential crystallization of MgTi2O5 can be achieved by adjusting the CaO, MgO, and TiO2 contents of slag. The predominant Ti-bearing phases in the slag obtained from the reduction process are MgxTi3-xO5 (0 B x B 1) and CaTiO3. FeTiO3 is present at carbon–iron ratio (CR) = 1.3, while MgTi2O4 and TiC are formed at CR = 1.3. The enrichment of TiO2 in the slag increases first and then decreases as the CR increases, and at CR = 1.1, the enrichment of TiO2 in the slag reaches 51.3 wt.%. Additionally, the concentrations of MgxTi3-xO5 (0 B x B 1) and CaTiO3 in the slag, along with the grain width of MgxTi3-xO5 (0 B x B 1), decrease with the increase in CR.

The metastable retained austenite (RA) plays a significant role in the excellent mechanical performance of quenching and partitioning (Q&P) steels, while the volume fraction of RA (V_RA) is challengeable to directly predict due to the complicated relationships between the chemical composition and process (like quenching temperature (QT)). A Gaussian process regression model in machine learning was developed to predict V_RA, and the model accuracy was further improved by introducing a metallurgical parameter of martensite fraction ðfa0 Þ to accurately predict V_RA in Q&P steels. The developed machine learning model combined with Bayesian global optimization can serve as another selection strategy for the quenching temperature, and this strategy is very efficient as it found the ‘‘optimum’’ QT with the maximum V_RA using only seven consecutive iterations. The benchmark experiment also reveals that the developed machine learning model predicts V_RA more accurately than the popular constrained carbon equilibrium thermodynamic model, even better than a thermokinetic quenching–partitioning–tempering–local equilibrium model.

Diamond tools have been widely used in national defense military, automobile manufacturing, resource exploitation and other fields. Laser brazing diamond technology is often applied to the preparation of diamond tools. However, the formation and expansion of cracks in the process of laser brazing diamond seriously affect the mechanical properties of diamond tools. In order to solve the crack problem of laser brazing diamond, many scholars are committed to the research on improving the solder, optimizing the laser process parameters, improving the laser brazing equipment, optimizing the design of joint form, and developing ultrasonic-assisted laser brazing technology, etc. These studies have achieved certain results. Aiming at the research status of laser brazing diamond crack problem, the crack characteristics of brazing diamond are firstly introduced, and the formation reasons of laser brazing diamond crack are elaborated. Then, the elemental characteristics of brazing filler metals used in brazing diamond are introduced. The influences of Ni-Cr and Ag-Cu-Ti alloy solder and laser process parameters on the crack problem are viewed. Finally, the solutions to the crack problem by scholars at home and abroad in recent years are summarized, and the future research directions to solve crack problem are prospected.

High-temperature confocal laser scanning microscopy (HT-CLSM) is considered as a powerful tool for in situ observation of the phase transformation of steels at elevated temperatures. It breaks the limitation that conventional approaches on this aspect can only post-mortem the microstructure at room temperature. The working principle and major functions of HTCLSM in initial are introduced and the utilization in details with HT-CLSM is summarized, including the behaviors of melting-solidifying, austenite reversion, as well as the austenite decomposition (formation of Widmanstätten, pearlite, acicular ferrite, bainite and martensite) in steels. Moreover, a serie of HT-CLSM images are used to explore the growth kinetic of phase at elevated temperatures with additional theoretical calculation models. Finally, the in situ HT-CLSM observations of phase transformation, combined with post-mortem electron backscatter diffraction analysis, is also summarized to elucidate the crystallographic evolution.