As a high-carbon emission field, the green low-carbon transformation of the steel industry is of great strategic significance to achieve the goal of "double carbon". The deep integration of hydrogen energy and steel processes, especially hydrogen metallurgy technology, fundamentally reduces the dependence on carbon by replacing "hydrogen" with "carbon" reduction, and has become an important direction of future ironmaking technological innovation. The current mainstream multi-hydrogen metallurgy process technology and its implementation path are systematically described, in-depth analysis is carried out from multiple dimensions such as raw material acquisition and preparation, core reaction mechanism, key equipment application to process flow construction, and is the characteristics, advantages and limitations of each process technology comprehensively evaluated. The coke oven gas zero reforming hydrogen metallurgy demonstration project （HyMEX） of HBIS Group is focused on, and its process technology innovation and operation practice is introduced in detail. The HyMEX project successfully applied the "coke oven gas zero reforming direct reduction technology" engineering for the first time, breaking through the international conventional means of using natural gas to produce reduction process gas, and becoming the direct reduction process of gas-based shaft furnace with the highest proportion of hydrogen in industrial production, setting a benchmark for the industrial application of hydrogen metallurgy technology. Combining with China's industrial policy orientation and the characteristics of resource endowment, the development prospect and sustainable development technology path of shaft furnace hydrogen metallurgy in China is deeply discussed. As the world's largest steel producer, China has rich coke oven gas resources, which provides a unique resource advantage for the large-scale promotion of hydrogen metallurgy technology. In the future, with the continuous improvement of the hydrogen energy industry chain and the reduction of costs, hydrogen metallurgy technology is expected to achieve large-scale commercial application in China, so as to promote the steel industry to accelerate the transformation to the green and low-carbon direction, and provide strong technical support for the realization of the "double carbon" goal.
Under the background of low-carbon transformation of China's iron and steel industry, the high-quality recycling of scrap resources is emphasized, and the development of the electric arc furnace（EAF） process is vigorously promoted as an important way to achieve the goals of "carbon peak" and "carbon neutral" in the iron and steel industry. However, the development of the EAF process is constrained by multiple factors such as resources, energy, and technology. A comparison is made among the resource consumption, energy use, and carbon emission characteristics of the blast furnace-basic oxygen furnace （BF-BOF）, full scrap EAF, and hydrogen-based direct reduced iron （DRI）-EAF processes. It is revealed that the long process, results in high carbon emissions due to substantial fossil fuel consumption, while the full scrap EAF and DRI-EAF processes demonstrate significant advantages in carbon reduction. Furthermore, the challenges faced by EAF processes are explored in terms of resource acquisition, energy supply, and techno-economic feasibility. It finds that the regional distribution of scrap resources in China is highly uneven, with economically developed regions generally having more abundant scrap supplies. However, structural mismatches between resource concentration and efficient utilization present significant challenges. In addition, the development of the domestic DRI industry has been slow, constrained by difficulties in obtaining reductants and iron-bearing raw materials, as well as by economic viability, limiting capacity expansion. Although EAF steelmaking technology is generally mature, there is still room for improvement in equipment scale and automation. Moreover, the production cost of the EAF process is typically higher than that of the traditional BF-BOF route and is more susceptible to fluctuations in scrap prices and electricity costs. Going forward, it is essential to account for regional differences in resource endowment, energy structure, environmental pressure, and policy orientation. Coordinated efforts combining technological advancement and region-specific policy measures are needed to accelerate the low-carbon transition of EAF steelmaking in China.
In view of such problems as high granulation moisture, thick moisture concentration zone, poor air permeability , slow sintering speed, and low productivity when sintering high iron concentrate, a new method called pre-drying process was proposed, which reduced mix moisture ,enhanced air permeability by pre-ignition pre-drying to improve sintering productivity and quality. A systematic laboratory sintering cup test was carried out to explore the influence rule of such factors as ignition temperature, pre-drying time, pre-drying negative pressure, pre-drying temperature, coke dosage on the sintering performance and metallurgical performance of the finished ore. The results show that the sintering indexes are acquired as follows productivity of 1.91 t/（m2·h）, IRD>3.15 mm （reduction disintegration index） of 60.21% under the conditions of 750 mm bed height, 1.65 basicity, mass fraction 4.5% coke powder, 300-500 ℃ pre-drying temperature, 5 kPa pre-drying negative pressure and 2 min pre-drying time, 1.5 min ignition time, 6.0 kPa ignition negative pressure and 1 100 ℃ ignition temperature. Compared with traditional sintering process, sinter productivity increases by 19.4% and IRD>3.15 mm improves by nearly 6 percentage points. The tumble index and fuel consumption are 55.13% and 51.28 kg/t, respectively, which maintain comparable levels to traditional sintering. However, productivity decreases when pre-drying temperature increases 500 ℃. Compared with the traditional sintering process, the pre-drying process improves the reducibility of sinter, which helps reduce the coke ratio in blast furnace smelting. It promotes the formation of SFCA with well-developed crystallization and high crystallinity, tightly bonded with other minerals, thereby enhancing the mechanical properties of the sinter. This provides favorable conditions for the stable operation of the blast furnace.
China's iron and steel industry is facing major challenges in upgrading its intelligent manufacturing capabilities amid international competition.Among these, intelligent control of the sintering endpoint stands as a key technological link for increasing steel output, optimizing product quality and achieving intelligent manufacturing. It reviewed the progress in sintering endpoint monitoring research both domestically and internationally, encompassing process monitoring, ore quality index monitoring, and process optimization control. It also analyzed the development trends and key issues of sintering endpoints under the framework of multimodal large models. Based on the multimodal large model （DeepSeek） architecture, it integrated heterogeneous parameters such as endpoint position, windbox negative pressure, and tail-end images to construct a high-accuracy and robust soft-sensing model for the sintering endpoint state. Combined with sintering process simulation technology, the model achieved accurate calculation of temperature and pressure data at the bottom of the sintering trolley under complex working conditions, effectively predicting the sintering endpoint status. Addressing the characteristics of sparse labels and time-delayed data in the sintering process, it designed an online monitoring model for sinter quality based on transfer learning and case-based reasoning, enabling real-time prediction and monitoring of key quality indicators such as chemical composition and particle size distribution. Furthermore, a multi-parameter collaborative control model for sintering endpoint optimization was proposed, incorporating an improved adaptive multi-objective genetic algorithm （AMOGA） and rolling horizon optimization strategy to achieve dynamic optimization control of the sintering endpoint under varying working conditions. From the perspective of the metallurgical industry's needs, it provides important theoretical and methodological support for the intelligent and refined control of the sintering process, offering significant scientific value and application prospects for enhancing the intelligent manufacturing level and optimizing production efficiency in the steel industry.
The catalytic purification of carbon monoxide （CO） from sintering flue gas in the steel industry has attracted increasing attention in recent years due to its unique advantages in energy conservation and environmental protection. However, challenges such as catalyst poisoning and barriers to large-scale implementation have so far prevented the realization of practical engineering applications both domestically and internationally. An industrial-scale CO catalytic purification project implemented on a 435 m² sintering machine at Handan Steel was reported, handling the full flue gas volume of 1.6×106 m³/h （standard condition, wet basis）. The project employed noble metal honeycomb catalysts loaded into the spare layer of the original denitrification （DeNOx） tower, achieving CO reduction without the need for additional external equipment. Moreover, the heat released from CO oxidation significantly reduced the consumption of coke oven gas required for flue gas reheating during catalytic denitrification. Results from 4 months of operation show stable overall performance, with CO catalytic conversion efficiency ranging from 76% to 85%, CO emission concentrations between 1 070 and 2 365 mg/m³ （well below the current environmental limit of 2 800 mg/m³）, flue gas temperature increase of 33-55 ℃, and a coke oven gas saving rate of 63% to 100%. Based on continuous monitoring data, it analyzed how flue gas temperature, flow rate, and the presence of other pollutants affect the CO catalytic performance. Special attention was given to system performance during key operational phases, including initial start-up, temporary shutdowns, and switching of flue gas circulation. The findings indicate that the current system is resilient to operational fluctuations and is capable of achieving both compliant CO emissions and complete coke oven gas savings. This translates to an energy consumption reduction of 3.4 kg of standard coal per ton of sintered product. An engineering demonstration system for catalytic purification of CO in sintering flue gas was established, providing an industrial-scale practical paradigm for synergistic multi-pollutant control in the steel industry. Furthermore, it offers a technical foundation for advancing the coordinated optimization of energy conservation, emission reduction, and cleaner production in sintering processes.
For further optimization of the inclusion plasticization control process of Si-Mn deoxidized steel, the crystallization behavior of CaO-SiO2-Al2O3（-MgO） inclusions during bloom heating process was studied. A series of glassy slags with different MgO contents were prepared in the laboratory to represent the oxide inclusions in the Si-Mn deoxidized steel. The glass-crystallization transition TTT （ time-temperature-transformation） curves of these inclusions were plotted in temperature of 950-1 250 ℃ through isothermal heating experiments. The experimental results show that the low melting point CaO-SiO2-Al2O3 inclusion has weak crystallization ability during the heat treatment and can easily maintain glassy stability. However, with the increase of MgO content, the crystallization ability of inclusions gradually increases. When the mass fraction of MgO is 0, the easy crystallization temperature of synthetic inclusion is 1 150-1 250 ℃. When the mass fraction of MgO exceeds to 4.4%, the easy crystallization temperature of the synthetic inclusion is expanded to 1 100-1 250 ℃. When the mass fraction of MgO exceeds 8.1%, the easy crystallization temperature of the synthetic inclusion is expanded to 950-1 250 ℃. The crystallization mode of these inclusions is primarily surface crystallization, and the crystallization degree of synthetic inclusions increases with higher heat treatment temperature and longer time. The XRD results show that the main crystalline phases precipitate from the synthetic inclusions during heat treatment are Ca2Al2SiO7 and CaSiO3 when the mass fraction of MgO content is 0. With the addition of MgO, the crystalline phases change to Ca2Al2SiO7 and Ca2MgSi2O7. Additionally, a solid-phase reaction occurs between CaO-SiO₂-Al₂O₃-MgO inclusions and the Si-Mn deoxidized steel matrix during heat treatment. As the MgO content in the inclusions increases, the extent of the solid-phase reaction and element diffusion between the inclusions and the steel matrix gradually intensifies. To prevent excessive crystallization of low-melting-point inclusions during heat treatment, it is necessary to strictly control the MgO content in the inclusions and adjust the heat treatment temperature and time appropriately based on the TTT curves.
High scrap steel ratio converter steelmaking represents a carbon emission reduction strategy well-suited to China's national conditions. To ensure proper tapping temperature, scrap preheating is required to supplement thermal energy. As a clean and renewable energy source, biomass pellets offer carbon-neutral characteristics that can effectively replace converter gas in scrap preheating processes, enabling low-carbon metallurgical production. Currently, horizontal tunnel-type preheating furnaces dominate scrap preheating applications but suffer from high energy consumption and low efficiency. To address these limitations, a shaft-type scrap preheating furnace was designed and employed a combined numerical simulation and experimental approach to compare the preheating performance between shaft and horizontal furnaces under various operating conditions. A 3D transient multi-physics coupling model was developed for both preheating scenarios, analyzing the thermal effects on scrap surface and core temperatures using biomass pellet combustion as the heat source across different preheating durations.Results demonstrate that under identical biomass consumption, the shaft furnace achieved significantly higher final scrap temperatures than the horizontal furnace. Both surface and core temperatures increased markedly with preheating time, though the heating rate gradually decreased as scrap temperature rose. At 900 s preheating duration, the shaft furnace reached peak thermal efficiency of 62.5%, with average scrap temperature 124 ℃ higher than the horizontal furnace, delivering 7.1×10⁴ kJ additional heat absorption per ton of steel. The shaft furnace also achieved 51% waste heat recovery efficiency, while the horizontal furnace showed 47.5% thermal efficiency with zero heat recovery. Carbon emissions were reduced by 94.9 kg/t and 111 kg/t at 900 s and 1 200 s preheating durations, respectively. These findings confirm that biomass pellets exhibit substantial potential to replace converter gas in both thermal efficiency and decarbonization performance. The shaft furnace design not only enhances scrap preheating temperatures but also establishes a technical foundation for increasing scrap ratios in converter steelmaking.
In the continuous casting process of titanium-containing microalloyed steel, TiN inclusions with sharp-angled structures are prone to precipitate, and the stress concentration effect induced by them negatively impacts the mechanical properties and service life of the steel. The precipitation of TiN is closely related to the segregation behavior of solute elements Ti and N in steel. By constructing a multi-scale coupling model of microsegregation, macro heat transfer, and TiN precipitation thermodynamics, a continuous casting global solidification model was established based on the three-dimensional slicing method. The influence of solidification behavior and solute redistribution process on TiN precipitation was studied. After solidification, positive segregation of titanium and nitrogen is observed at both the center and the 1/4 thickness position of the casting, whereas negative segregation occurs at the surface layer due to the high cooling rate. Correspondingly, significant TiN precipitation peaks are present in both the central and 1/4 thickness regions, with much less precipitation in the surface layer. Specifically, the mass fraction of TiN at the center of the slab thickness is 0.000 34%, while that at the 1/4 thickness position reaches 0.000 41%-1.2 times higher than the central value. A strong spatial correlation exists between TiN precipitation distribution and the liquid cavities distribution in the slab. The effects of casting speed on solute segregation and TiN precipitation were investigated. The results show that increasing the casting speed will aggravate solute segregation and TiN precipitation behavior. When the casting speed increases from 1.2 m/min to 1.4 m/min, for every 0.1 m/min increase in the casting speed, the average growth rate of the shell thickness is 8.52% and the solidification end point position extends by 1.1 m. The segregation degree of solute N at the center of the slab increases by about 0.91% on average, that of Ti is about 1.15%, and the average increase of TiN mass fraction is 0.35%. The results have theoretical guidence significance for improving the quality of microalloyed steel slab and controlling harmful inclusions.
China's iron and steel industry is facing the severe challenge of carbon emission reduction, and the demand for its low-carbon transformation is extremely urgent. The industry urgently needs to optimize the process through technological innovation in order to cope with the pressure of emission reduction under the national "dual carbon" strategic goal. Therefore, the feasibility of replacing the traditional Ar as the stirring gas by CO2 in ladle bottom blowing and its kinetic behavior were analyzed through numerical simulation system. Based on the theoretical calculation of stirring energy equation, it is found that when CO2 is fully involved in the decarburization reaction, its theoretical maximum stirring energy can be up to twice that of Ar, which can significantly enhance the molten pool fluidity and inclusions removal efficiency, but the effect of reaction efficiency needs to be taken into account in the actual working conditions. By constructing a 180 t ladle multiphase flow model, the effects of parameters such as the angle of the permeable bricks, the center distance and the blowing flow rate on the molten steel flow field, the turbulent kinetic energy distribution and the slag interface behavior were systematically analyzed. The results show that when the angle of double permeable bricks is 135°, the distance from the bottom center is 0.5R, and the bottom blowing flow rate is 550 L/min, the uniformity of the liquid steel flow field is significantly improved, the area of the liquid steel "dead zone" is reduced by 44% compared with the traditional arrangement, the area of the slag eye is reduced by 33.5%, and the risk of slag roll-up is reduced to 1/3 in the Ar system. In addition, the weak oxidizing property of CO2 generates CO bubbles through decarbonization reaction, which promotes the removal of heterogeneous nucleation and uplift of inclusions, and at the same time reduces the refractory erosion rate and gas cost. The result verifies the technical and economic advantages of CO2 in ladle refining, and provides a theoretical basis and process optimization guidance for the transformation of iron and steel industry to low carbonization, which has important valuable in engineering application.
The roll system of a 20-high mill has a complex structure, and the flatness control strategy is flexible and changeable. The reasonable formulation of a flatness control strategy depends on an accurate and stable flatness prediction model. However, due to the model coupling method also existing the inter-roll pressure iteration loop in the inner layer, the calculation speed still has room for further improvement. Therefore, a new type no-iteration model coupling method for flatness prediction of 20-high mills was proposed, which eliminated the inner inter-roll pressure iteration loop and significantly improved the calculation speed at the expense of limited accuracy. A comprehensive comparison of the convergence, calculation time, and calculation accuracy of the three methods （traditional method, model coupling method, and no-iteration model coupling method） was carried out through three examples. The results show that in terms of convergence, the larger the strip width-to-thickness ratio is, the more difficult it is for the traditional method to converge, whereas the model coupling method and no-iteration model coupling method do not have convergence problems. In terms of calculation accuracy, based on the flatness value calculated by the traditional method, the average absolute error （EMA） of the flatness value calculated by the no-iteration model coupling method for the three instances does not exceed 2.51 I, which basically maintains the original calculation accuracy of the traditional method. In terms of calculation time, the traditional method has the longest calculation time, followed by the model coupling method, and the no-iteration model coupling method has the shortest calculation time. The calculation speed of the no-iteration model coupling method is about 7 times that of the model coupling method, and the calculation speed of the no-iteration model coupling method is about 8 627 times that of the traditional method.
There is an inevitable static crossing after the rolling mill roll is tied to the machine,and the rolling process will produce the dynamic crossing of the roll oscillation,which greatly affects the stability of the rolling mill system and the product quality during the rolling process,so the research on the crossing state of the roll system and industrial control are the key to improve the accuracy of the rolling mill equipment. Based on the Hertz theory,the stiffness variation law on both sides of the roll system when crossing at small angles was calculated,the influence error of the bearing seat assembly and measurement method on the calculation of the axial position of roll was analyzed,and the calibration and leveling data were analyzed in combination with the geometric relationship of the static crossing of roll axis,and the vibration experiment was carried out by adjusting the state of the roll housing on the upper machine to verify the theoretical model. It is found that the contact area between finite long rolls based on Hertz contact theory is an incomplete ellipse,and by calculating its flattening and deflection states,it is concluded that adjusting the intersection angle of roll axis in the range of 100-1 000 μrad is the most beneficial to improve the stiffness. At the same time,combined with the flattening and deflection deformation of rolls under the crossover state between rolls,the crossover state between rolls is obtained and analyzed in real time during the calibration and leveling process,and the stiffness state of the roll system controlled under hydraulic pressure in the condition of parallel roll system is the most stable,on the contrary,the stiffness difference of the roll system on both sides of the rolling mill is large. Finally,experiments were carried out on the influence of stiffness difference between the two sides of roll system on the vibration of roll system caused by the crossing state between the rolls. It is found that the goal of reducing the stiffness difference between the two sides of the rolling mill and improving the constraint limit of the dynamic roll system position fluctuation can be achieved by reducing the static crossing degree of the roll system,which can effectively suppress the roll vibration.
By introducing a gradient structure, the mechanical properties of duplex stainless steel can be enhanced. However, its highly heterogeneous structure results in more complex and variable stress-strain distribution behavior. To investigate the effect of the gradient structure on the deformation behavior of duplex stainless steel, gradient-structured duplex stainless steel was prepared using ultrasonic surface rolling processing （USRP） and the crystal plasticity finite element method was employed to examine the stress distribution between austenite and ferrite phases as well as the interphase deformation coordination mechanism. The results indicate that after USRP, the grain size in the surface layer is significantly refined, and the proportion of low-angle grain boundaries increases. Dislocation walls and dislocation cell structures form within ferrite grains, while stacking faults and twins develop within austenite grains. Moreover, the pronounced heterogeneous deformation-induced （HDI） hardening effect in the gradient duplex structure increases the yield strength from 581.34 MPa to 690.98 MPa, demonstrating an excellent strength-ductility combination. Simulation results reveal that significant stress concentration occurs at phase boundaries and grain boundaries in the gradient duplex structure, while the HDI hardening effect in the fine-grained region effectively reduces the strain mismatch between ferrite and austenite, alleviating local stress concentration. Furthermore, under the same grain size conditions, austenite and ferrite exhibit different deformation sequence characteristics. During tensile deformation, regions with smaller grain sizes exhibit lower microstructural heterogeneity, and high-density geometrically necessary dislocations gradually propagate from the surface to the core, reducing the microstructural heterogeneity. The strain-coordination evolution mechanism of gradient duplex stainless steel during deformation is elucidated, providing theoretical insights and experimental support for optimizing material design and enhancing the comprehensive properties of duplex stainless steel.
As a typical representative of the third-generation advanced high-strength steel, medium manganese steel has the heterogeneous structure design as a key approach to break through the strength-plasticity inversion contradiction. Based on 0.2C-5Mn-1Al-0.5Si（mass fraction,%） medium manganese steel, a cross-scale gradient heterogeneous structure was successfully constructed in 0.2C-5Mn steel through a combined process of carburizing at 950 ℃ for 14 h and re-austenitizing in salt bath at 790 ℃ for 25 s. The surface layer is a FCC （face-centered cubic）/BCC （body-centered cubic） nanolamellar duplex structure, while the core is a martensitic matrix. The mechanical properties are coupled through a continuous carbon mass fraction gradient from 0.8% at the surface to 0.2% at the core. By combining DICTRA phase transformation thermodynamic simulation, TEM-EDS interface characterization and microhardness mapping, the regulation laws of carburizing temperature ranging from 950 ℃ to 1 050 ℃ and re-austenitizing temperature ranging from 750 ℃ to 790 ℃ on the characteristics of the duplex interface and the kinetics of element diffusion were revealed. The research results show that the carburizing process makes the carbon mass fraction gradient at the surface, inducing the formation of a pearlite layer with a thickness of 615 μm to 1 000 μm, which provides an initial carbon potential field for the subsequent austenite reconstruction. During the short-time re-austenitizing process at 750 ℃ to 810 ℃ for 25 s, the short-range diffusion of Mn elements leads to the interface composition segregation of the FCC phase rich in Mn （mass fraction of 14%） and the BCC phase poor in Mn （mass fraction of 2% to 5%）. By reducing the stacking fault energy and locally stabilizing austenite （TRIP effect）, the strength and plasticity are synergistically enhanced （surface hardness of 500HV, core hardness of 400HV）. The results provide a theoretical basis for the design and performance optimization of gradient heterogeneous structures based on diffusion control.
Press hardening steel（PHS） has become an important material for automobile manufacture with the purpose of lightweighting, energy conservation and emission reduction due to its ultra-high strength. However, the potential hydrogen induced delayed fracture of PHS parts with strength above 1 000 MPa is one of the most concerned problems for automobile manufacturers. Hydrogen ingress inevitably occurs during both manufacturing processes and actual service conditions, resulting in delayed fracture behavior of high-strength PHS. The hydrogen embrittlement of 1 800 MPa tensile strength PHS was investigated through electrochemical hydrogen pre-charging to simulate hydrogen ingress under practical service conditions. Based on hydrogen content measurement, slow strain rate tensile（SSRT） testing, and fracture morphology analysis, the correlation between hydrogen content, hydrogen-induced mechanical properties, and fracture mechanisms of the high-strength PHS was systematically revealed. Under specific hydrogen-charging current density condition, the hydrogen concentration in specimens initially increases and subsequently decreases with prolong in charging time. SSRT results demonstrate that compared with uncharged specimens, all hydrogen-charged specimens exhibit significant hydrogen-induced strength degradation, characterized by sudden fractures during the elastic stage of tensile, meaning that this steel exhibit high hydrogen embrittlement susceptibility. Both fracture strength and elongation decrease remarkably with increasing hydrogen content. Fractographic observations reveal that uncharged specimens display typical dimple fracture characteristics, while hydrogen-charged specimens show the transition fracture mode from ductile fracture to a mixed quasi-cleavage fracture, intergranular cracking and dimpled fracture. With increasing hydrogen content, the proportion of intergranular fracture areas expands while shear lips narrow. According to the hydrogen-enhanced decohesion （HEDE） mechanism, hydrogen atoms preferentially accumulate at prior austenite grain boundaries, reducing local cohesive energy and making hydrogen-induced intergranular fracture become the dominant failure mode. The result elucidates the core mechanism of hydrogen-induced delayed cracking in 1 800 MPa grade hot-stamped steel and its resulting severe degradation of mechanical properties. These findings provide critical theoretical support for enhancing hydrogen embrittlement resistance and service safety in ultra-high-strength hot-stamped steels.
Based on the Hall-Petch relationship, grain size directly influences the mechanical properties, corrosion resistance, and magnetic characteristics of pure iron materials, making its standardized and accurate measurement critical for material performance evaluation. To address the limitations of traditional manual methods,such as inefficiency and operator dependency, and the shortcomings of existing image processing and machine learning algorithms in repairing fractured grain boundaries and suppressing artifacts, a cascaded dual-stage grain boundary analysis framework was proposed. By constructing dataset of 960 pure iron metallographic images, "recognition-reconstruction" collaborative mechanism was established. In the first stage, enhanced U-Net （U-shaped convolutional network） architecture with weighted loss functions was employed to achieve grain boundary localization, addressing the class imbalance between grain boundaries and grains while maintaining 97.3% of recognition accuracy. The second stage utilized a defect-augmented dataset to train reconstruction network, effectively repairing fractured boundaries and improving grain boundary integrity to 92.7%. Experimental results demonstrate that the framework outperforms existing methods in key metrics, Dice coefficient of 0.621 for boundary recognition, 98.5% closed-loop rate for reconstructed boundaries, and processing time of 0.28 s per image. For grain size measurement, 57.5% of test samples exhibit relative errors below 5%, with a mean absolute percentage error （EMAP） of 4.78%, achieving high consistency with manual measurements while enhancing efficiency and objectivity. Ablation studies confirm that the synergy between boundary reconstruction and twin crystal merging reduces the mean absolute error （EMA） of grain size measurement by 69.7%, while the dynamic weighted loss function improves the Intersection-over-Union （IoU） by 9.7%. This approach achieves co-optimization of topological integrity and measurement accuracy within a deep learning framework. By eliminating operator dependency, the measurement repeatability has been enhanced, providing a standardized and interpretable automated solution for industrial metallographic analysis, which is conducive to promoting the development of quantitative characterization techniques for material microstructure.
Aiming at the application bottleneck of the third generation of advanced high strength and high plasticity medium manganese automobile steel in cold stamping forming, 0.1C-5.5Mn（mass fraction,%） medium manganese automobile steel was taken as the research object, systematically explored the effect of austenite reverse phase transformation annealing process on the microstructure and mechanical properties of medium manganese steel, and analyzed its feasibility in the stamping forming of A-pillar inner plate of new energy vehicle based on numerical simulation. The experimental steel was prepared by vacuum melting, hot rolling, cold rolling and austenite reverse phase transformation annealing process. Combined with scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD） and tensile test, the synergistic effect of annealing temperature and holding time on microstructure evolution and properties was revealed. The results show that under the optimized conditions of holding at 650 ℃ for 15 min, the carbide is fully dissolved, the C and Mn elements are evenly distributed, and the ferrite is equiaxed, which significantly improves the deformation coordination. The tensile strength of the experimental steel reaches 1 148 MPa, the yield strength is 907 MPa, the elongation is 32.54%, and the peak value of the product of strength and plasticity reaches 36.51 GPa·%, which is attributed to the synergistic strengthening of the phase transformation induced plasticity effect and the optimization of grain boundary characteristics. Further, the stamping forming law of A-pillar inner plate is analyzed by numerical simulation. It is found that when the blank holder force increases from 200 kN to 300 kN, the material flow resistance increases, and the maximum thickness reduction rate decreases from 29.18% to 28.79%, which effectively inhibits the disorderly accumulation in the flange area. When the stamping speed increases from 200 mm/s to 800 mm/s, the thinning rate shows a nonlinear response of increasing first and then decreasing. The forming limit diagram shows that the strain points in the main area of the part are located in the safe area, which confirms that the basic process parameters are feasible. It provides a reference for the application of medium manganese steel in stamping of automotive parts.
Stone crystal composites（SCC） are prone to damage from temperature and oxygen during long-term use, leading to changes in the material's structure and a significant reduction in service life. Therefore, improving heat and oxygen aging resistance is an important prerequisite for the widespread application of the product. Steel slag micro-powder （SS） was surface-modified using a composite solution of polyethylene glycol （PEG）, methyl methacrylate （MMA）, and dicumyl peroxide （DCP） to produce modified steel slag micro-powder （MSSP）. MSSP was then used to replace talcum powder and combined with molten blending and hot pressing to prepare steel slag-based stone crystal composites （MSSP/SCC）. The flexural strength and color changes of MSSP/SCC before and after heat-oxygen aging were tested. Scanning electron microscopy （SEM）, X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FTIR）, and X-ray photoelectron spectroscopy （XPS） were employed to analyze the mechanism of MSSP in the SCC system. The experimental results show that when MSSP replaces talcum powder at a ratio of 50%（mass fraction）, the flexural strength of MSSP/SCC after 16 days of heat-oxygen aging reaches 27.1 MPa, with a flexural strength retention rate of 89.7%. Compared to ordinary stone crystal composites, these values represent increases of 53.9% and 25.3%, respectively. Meanwhile, the total color difference ∆E change is minimal at 0.51. MSSP forms a fibrous network within the MSSP/SCC system. MSSP can act as a crosslinking point, and its surface hydroxyl groups form physico-chemical crosslinking interactions with the SCC system, which is beneficial for resistance to heat and oxygen aging. During heat-oxygen exposure, the fiber network structure formed by MSSP in the SCC system helps improve flexural properties. When the substitution ratio of MSSP for talcum powder is 50%（mass fraction）, the interfacial compatibility between MSSP and the SCC system is good. MSSP and wood flour can be well encapsulated by high-density polyethylene resin（HDPE）, resulting in a tighter surface structure that inhibits the transfer of heat and oxygen. The hydroxyl groups formed on the surface of MSSP combine with the free radicals generated by the SCC system after thermal-oxidative aging, terminating the chain reactions and thereby enhancing the thermal-oxidative aging resistance.
An experimental study on adding biochar fuels during the sintering process was conducted in order to reduce the consumption of coke powder and the emission of harmful gases during the sintering process of iron ore fines. The effects of adding biochar at proportions of 0%, 20%, 40%, and 60% on the sintering process were studied by analyzing the changes in sintering technical indicators （sinter yield, tumble index, productivity, and vertical sintering speed）, the temperature of the material layer, and the emissions of harmful gases. The influence of adding biochar on the quality of the sinter was discussed combined with the porosity of sinter, the phase composition, degree of reduction, low-temperature reduction degradation index （IRD>6.3 mm, IRD>3.15 mm and IRD<0.5 mm）, and the evolution of the microstructure. The results show that as the proportion of biochar added increases from 0% to 60%, the sinter yield, tumble index, and sintering utilization coefficient decrease, vertical sintering speed increases, and the time to reach the peak temperature is advanced. Among them, when the proportion of biochar added is 60%, the sinter yield and tumble index decrease particularly significantly. As the biochar addition amount increases, the volume fractions of CO₂, NOₓ and SO₂ decrease. Compared with using only coke powder, when the proportions of biochar are 20%, 40%, and 60%, the CO₂ emission reduction is 1.050%, 1.770%, and 2.660% respectively, the NOₓ emission reduction is 11.71%, 22.80%, and 38.70% respectively, and the SO₂ emission reduction is 16.129%, 32.258%, and 51.610% respectively. The addition of biochar changes the chemical composition and phase content of the sinter and increases the porosity of the sinter. As the proportion of biochar added increases from 0% to 60%, the degree of reduction gradually increases. When the proportion of biochar adds from 0% to 40%, the IRD>6.3 mm and IRD>3.15 mm increases, and IRD<0.5 mm decreases first. When the proportion is further increased to 60%, IRD>6.3 mm and IRD>3.15 mm showes a downward trend, and IRD<0.5 mm increases. Compared with using only coke powder in the sintering process, when different proportions of biochar are added, the phase compositions such as Fe₂O₃, Fe₃O₄, and Ca₂Fe₂O₅ have relative differences, and iron oxides and the bonding phase are interwoven and distributed inside the sinter in different organizational structures.
The life-cycle carbon footprint of ordinary asphalt pavement and steel slag asphalt pavement was evaluated to quantify the differences in carbon emissions between the two materials. This evaluation provides a scientific basis for the selection of low-carbon materials in highway construction under the "dual-carbon" target and supports improved utilization of steel slag asphalt. The entire life cycle, including raw material preparation, paving, and maintenance to demolition and recycling, was assessed using the life cycle assessment （LCA） methodology. An environmental impact assessment model was developed, and energy consumption data for each stage were collected. In accordance with ISO LCA standards,the functional unit was defined as a 1 km long, 3.75 m wide, and 4 cm thick pavement section. Primary data collection and external LCI databases（including the Ecoinvent database and literature-derived data）were utilized. The key materials and energy sources examined included aggregates （stone, steel slag）, explosives, electricity, and diesel. A process-based inventory model was established using the mass allocation method to account for co-products, and the carbon footprints of both pavement types were calculated. The results show that steel slag asphalt pavement has 69.6% lower life-cycle carbon emissions than ordinary asphalt pavement, with the most significant differences occurring in the raw material preparation, pavement construction, and maintenance phases. Due to its extended service life and reduced maintenance needs, steel slag asphalt pavement significantly decreases emissions during the maintenance stage. Furthermore, the carbon emission distribution across various life-cycle stages was analyzed, along with the relative contributions of key materials and energy sources. Future research directions were proposed, including further optimization of pavement engineering technologies, reduction of environmental impacts, and the promotion of low-carbon construction practices. New insights into mitigating the environmental effects of road construction are provided, and theoretical and technical support for carbon reduction in the highway construction industry is offered.
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