- 百种中国杰出学术期刊
- 中国精品科技期刊
- “中国科技期刊卓越行动计划二期”领军期刊
- 入选“中国精品科技期刊顶尖学术论文(F5000)”
- 入选《科技期刊世界影响力指数(WJCI) 报告》
- EI、CA、JST收录期刊
- 中国金属学会会刊
- 中文核心期刊
- 中国科技核心期刊
- 中国科学引文数据库(CSCD)来源期刊
High-strength steel plates are widely applied in automotive, energy and other fields due to their excellent comprehensive properties. However, the hot strip rolling of high-strength steel faces common problems including excessive transitional materials generated during rapid product specification switching, low plate shape control accuracy and severe rolling mill vibration, which seriously limit the production stability and quality consistency of high-strength steel. This paper reviews the latest research progress of key intelligent stable rolling technologies and full-process intelligent management and control technologies for the hot strip rolling of high-strength steel. Aiming at the low setting accuracy of traditional mechanism and statistical models, the mechanism and data dual-driven modeling method serves as an effective approach to improve the control accuracy of rapid product specification transition and stable rolling process for high-strength steel. Meanwhile, the vibration suppression technology for thin-gauge high-strength steel has evolved from the single mode of equipment supervision and parameter optimization to a systematic management mode from the process genetics perspective covering the full process of heating, descaling and rolling. Combined with the data-driven active disturbance rejection control technology, this technology realizes accurate vibration suppression during the high-strength steel rolling process. To achieve real-time monitoring of complex rolling states, an integrated comprehensive diagnosis and analysis technology incorporating multi-source data diagnosis, single coil/unit intelligent analysis and intelligent product quality scoring is developed. Finally, the construction of collaborative management and control technology for rapid product specification transition and stable rolling realizes the optimal configuration of roll profile, dynamic adjustment of production scheduling and hierarchical optimization of plate shape models. This technology significantly improves the overall regulation capability of the high-strength steel hot strip rolling process and increases the production proportion of high-strength steel. This paper clarifies the technical framework and development trends in this research field, and provides theoretical references for the intelligent and green development of hot strip rolling in the future.
Against the background of the low-carbon transformation of the iron and steel industry and the national dual-carbon goals, exploring low-carbon and clean alternative fuels and reducing carbon emissions from blast furnace ironmaking have become important research topics in the metallurgical field. As a typical carbon-neutral and renewable fuel, biomass exhibits excellent emission reduction benefits in blast furnace injection and acts as a vital technical route for the development of low-carbon metallurgy in the steel industry. However, biomass has the problems of high alkali metal content, poor grindability and low energy density. Combined with imperfect pretreatment processes and poor economic efficiency, the above problems severely limit its large-scale industrial application in blast furnace injection. This paper took biomass for blast furnace injection as the research object, systematically analyzed the core practical challenges and internal action mechanism of biomass injection. It clarified that alkali metals including potassium and sodium in biomass tended to undergo gasification migration and enrichment circulation in the high-temperature blast furnace system, which further destroyed the microstructure of coke and aggravated the deterioration of coke metallurgical properties. Meanwhile, this paper indicated that the dense three-dimensional network structure formed by biomass components was the key cause of its poor grindability. Aiming at the above technical bottlenecks, this paper systematically summarized the process characteristics and application limitations of multiple upgrading methods including ultrasonic cavitation dealkalization, baking pretreatment, steam explosion and hydrothermal carbonization. A novel collaborative treatment technology of dealkalization and grinding aid was proposed. Depending on green and recyclable additives, the technology realized the deep removal of alkali metals and synchronous improvement of grindability in a single step. Experimental results show that the proposed technology can control the total alkali metal content of biomass within the standard range for blast furnace injection and significantly optimize particle size indicators, and has obvious cost advantages compared with traditional processes. The research confirms that single technical optimization or multi-process coupling can make various performance indicators of biomass meet the technical requirements of blast furnace injection. The processed biomass has great application potential for large-scale pulverized coal substitution and can provide effective support for the application of biomass in blast furnaces.
China is endowed with abundant collophane resources but poor ore quality, with a high proportion of medium and low-grade ores. The average mass fraction of associated rare earth elements (REEs) in collophane reaches approximately 0.046%, which forms an important rare earth resource. Due to the characteristic of abundant reserves but low grade, a large number of associated REEs are not effectively utilized. Therefore, the efficient recovery of associated REEs from collophane has important strategic significance for improving the comprehensive utilization rate of collophane and ensuring the supply security of rare earth resources in China. This paper reviews the research status and development trend of REEs extraction technologies from collophane from three core links, that is pre-concentration, leaching and separation. Beneficiation and pre-concentration is the key to reduce acid consumption. The flotation method exhibits excellent performance in removing carbonate impurities and synchronously enriching rare earths, while the combined process is an important means for treating fine-grained refractory collophane. In the leaching stage, the advantages and disadvantages of inorganic acid leaching processes such as sulfuric acid, nitric acid, hydrochloric acid and phosphoric acid were analyzed in detail. The results show that the traditional sulfuric acid process has a low REEs leaching rate of only 20%-65% and causes serious phosphogypsum pollution. By contrast, nitric acid, hydrochloric acid and phosphoric acid processes achieve a REEs leaching rate of more than 90%, but they respectively face challenges including difficult impurity removal, severe equipment corrosion and low leachate concentration. In the separation and enrichment stage, solvent extraction remains the mainstream technology for large-scale industrial application, while ion exchange, membrane separation and other technologies present unique advantages in treating low-concentration REEs solutions and improving product purity. Aiming at the current bottlenecks such as poor connection between mineral processing and metallurgical processes and low recovery rate, future research should further develop the integrated leaching-separation process. The development of mixed acid/surfactant/external field-assisted leaching technologies, high-capacity functional resins and acid-resistant selective extractants promotes the collaborative development of technology for associated REEs from collophane toward cleaner, more efficient, lower carbon and collaborative recovery direction.
Iron ore sintering serves as the primary emission source of nitrogen oxides (NOx) in the iron and steel industry. The flue gas generated from this process features low temperature, high humidity and high sulfur content, and contains various toxic substances such as alkali metals and heavy metals, which put forward higher requirements for the working condition adaptability of denitration technologies and the comprehensive performance of catalysts. At present, non-rare earth-based NH3-SCR denitration catalysts generally exhibit poor low-temperature activity, insufficient poisoning resistance and inferior industrial operation stability. These catalysts cannot meet the long-term ultra-low NOx emission standards for sintering flue gas, which becomes a key bottleneck restricting the green and low-carbon development of the iron and steel industry. China is endowed with abundant rare earth resources. With unique 4f electron configurations, rare earth elements possess excellent redox properties and superior surface acidity regulation capability, which provides strong support for the performance optimization of SCR(Selective Catalytic Reduction)denitration catalysts. This paper systematically sorted out the multi-component pollution characteristics of steel sintering flue gas and the current status of industrial denitration treatment, and clarified the deficiencies of traditional denitration technologies in practical industrial application. The laboratory performance and industrial application limitations of various non-rare earth-based catalysts including V-Ti-based, Mn-based, Cu-based and Fe-based catalysts were analyzed. This study emphatically elaborated the technical routes, core advantages and action mechanisms of rare earth modification for different non-rare earth-based catalysts, and summarized the inherent defects of existing rare earth-modified catalysts. Focusing on the industrial application practices of rare earth-based SCR catalysts. This review verified their industrial application values and sorted out the practical operational problems. Finally, this paper analyzes the application prospects of such catalysts by combining practical factors including cost control and large-scale preparation.The research aims to provide theoretical reference and practical guidance for the large-scale engineering application of rare earth-based SCR catalysts applicable to the complex working conditions of sintering flue gas, and promote the realization of ultra-low NOx emissions and the achievement of the "dual carbon" goals in the iron and steel industry.
Rare earth elements serve as indispensable trace additives in the steel industry. By precisely regulating the morphology, size and distribution of inclusions within steel, rare earth treatment can extend the service life of steel, reduce defect rates and enhance environmental friendliness, thus meeting the demands for high performance and sustainable development of high-strength low-alloy steels. To achieve the effective utilisation of rare earth elements and improve the comprehensive properties of steel, researchers carried out extensive research on the modification of inclusions in steel with rare earth elements. Firstly, based on thermodynamic analysis and first-principles calculations, the spontaneous driving force and atomic-scale mechanism of rare earth-modified inclusions were elucidated. The modification mechanisms and evolution patterns of inclusion morphology, size, and distribution under rare earth addition were analyzed from two aspects including single rare earth addition and composite rare earth addition. Furthermore, the differences in treatment effects at the atomic scale between heavy rare earth Y and light rare earths such as La and Ce were analyzed. Rare earth elements can transform coarse and irregular inclusions such as Al2O3 and MnS in steel into fine, dispersed and spherical rare earth oxysulfides such as Ce2O2S and LaAlO3. This transformation significantly improves the strength, toughness and ductility of steel. It also improves the pitting potential of inclusions to make them close to the potential of the steel matrix thus enhancing the local corrosion resistance. Finally, based on the current research status of inclusion modification technology in rare earth-modified steel, the future development trend of inclusion treatment in high-strength low-alloy steels by rare earth elements is prospected. Combining the synergistic advantages of composite addition, an innovative direction for optimizing the ratio and addition sequence of rareearth elementss is proposed. This provides new ideas for the application of rare earth-treated high-strength low-alloy steels in fields such as bridge construction, shipbuilding, oil and gas transmission pipelines and construction engineering, and promotes the high performance and sustainable development of the steel industry.
As an important strategic resource, tin has irreplaceable applications in various fields due to its excellent physical and chemical properties. The gradual depletion of easily beneficiable tin resources and the low recovery efficiency of refractory tin ores increasingly aggravate the supply pressure of tin resources. Improving the comprehensive recovery and utilization efficiency of tin-bearing secondary resources can not only relieve the supply pressure of tin resources, but also reduce the corresponding environmental impact. This paper focuses on typical tin-bearing secondary resources, including tin middlings and tailings, waste printed circuit boards, tungsten smelting slag, tin alloy waste, and tin anode slime. The global distribution and consumption characteristics of tin resources are analyzed, and the current technical status of tin recovery processes for different tin secondary resources is comprehensively reviewed. Combined with the corresponding reaction mechanisms, the advantages, disadvantages and industrial application status of hydrometallurgy, pyrometallurgy, microbial leaching and combined processes are systematically compared. The development of short-process and high-efficiency tin recovery technologies helps improve the economic benefits of enterprises. On this basis, this study summarizes the major technical bottlenecks restricting the sustainable development of the tin secondary resource utilization industry, including lengthy technical processes and high processing costs in tin smelting, refining and purification. Future development directions of tin secondary resource utilization focus on the preparation of high-value-added products and high-purity products such as sodium stannate and stannous sulfide, so as to improve the utilization benefit of tin waste materials. This research provides a reference for the virtuous cycle and sustainable development of the tin industry.
In the field of iron and steel materials, Nb-Ti composite microalloying technology has become a core method to improve the strength and toughness of steel materials. Nb-Ti-Fe alloy was prepared by aluminothermic reduction of Nb-rich slag with Bayan Obo niobium concentrate as raw material, which can alleviate China's high dependence on imported ferroniobium alloys. Investigating the reduction mechanism and distribution behavior of Nb and Ti during the process is crucial for efficient resource utilization. Exploring the reduction mechanism and distribution behavior of Nb and Ti in the reduction process is an essential prerequisite for efficient resource utilization. In this study, FactSage thermodynamic calculations were combined with experimental investigation to systematically analyze the effects of Al addition amount, reaction temperature, binary basicity w(CaO)/w(SiO2), and SiO2 content in the slag system on alloy composition, microstructure, and mineral phase of the final slag. Thermodynamic optimization and experimental verification show that when the Al addition amount(mass fraction) is 12.39%, the heat released by aluminothermic reduction increases the system temperature by 200-300 ℃, and the reaction can be carried out steadily above 1 800 ℃.When the basicity R is 1.0 with CaF2 addition, the molten slag presents good fluidity and the optimal slag-metal separation effect is achieved. Thermodynamic calculations confirm that reducing the mass fraction of SiO2 in slag to 20% eliminates the pure Si phase (CRSI) in the alloy and increases the contents of Nb and Ti, thus improving the overall quality of the alloy. The final slag mainly consists of CaAl2Si2O8 phase, the high-melting-point Al2O3 phase, and CaTiO3 phase. The increase of slag viscosity is confirmed as the key factor leading to entrainment loss of niobium-titanium alloy particles (MAPs). This research provides a thermodynamic basis and experimental support for the process optimization of preparing Nb-Ti-Fe alloy by aluminothermic reduction of Nb-rich slag.
Driven by the urgent demand for the green and low-carbon transformation of the iron and steel industry and the efficient resource utilization of metallurgical solid wastes, iron ore powder cold briquettes, as a new type of iron-bearing burden with low energy consumption and low emissions, can consume secondary iron-bearing resources including sinter return fines and metallurgical dusts. However, there is an obvious research gap in the burden distribution behavior and burden adaptability of cold briquettes in blast furnaces, which restricts their large-scale industrial application. Based on the actual production parameters of a 3 200 m3 bell-less blast furnace of a domestic steel plant, this study established a full-process numerical model of burden distribution covering the weighing pipe, central throat, rotating chute and upper furnace throat by adopting the Discrete Element Method (DEM). The Hertz-Mindlin no-slip contact model was selected to describe the collision, sliding and accumulation interactions between burden particles, and the reliability of the model was verified by comparison with industrial measured data under the same working conditions. On this basis, the effects of cold briquette shape, replaced burden type and addition ratio on the radial segregation and bed pressure drop of burden were systematically compared.Simulation results show that the[1.8, 2.7) m middle diameter area in the upper part of the blast furnace is the main initial landing area for burden distribution. This area presents the highest burden accumulation density and the lowest porosity, forming a high pressure drop zone that limits the overall gas permeability. Under the baseline working condition, the unit pressure drop in this area reaches 15 000 Pa/m. Cold briquettes with different parameters all exhibit the radial segregation characteristic of sparse center and dense edge. As the addition ratio increases from 10% to 20%, the edge enrichment degree gradually decreases, and the radial distribution uniformity reaches the optimum at the addition ratio of 20%. Among the three types of cold briquettes with different shapes, ellipsoidal cold briquettes have the lowest pressure drop and cause the minimum disturbance to the original burden distribution when replacing sinter ore. When the addition ratio exceeds 20%, the pressure drop in the high pressure drop zone increases sharply in a nonlinear manner, and the unit pressure drop surges to 40 000 Pa/m at the addition ratio of 30%, which seriously deteriorates the burden gas permeability.This study clarifies the optimal parameter combination for the application of cold briquettes in blast furnaces, and proposes technical suggestions for industrial production that ellipsoidal cold briquettes are preferentially applied to mainly replace sinter ore with the addition ratio controlled within 20%. The research results can provide data support for the industrial trial production of cold briquettes and the low-carbon adjustment of blast furnace burden structure. Full-process coupling simulation considering the high-temperature metallurgical properties of cold briquettes will be carried out, and industrial addition tests in blast furnaces will be promoted in subsequent research.
The volume of the blast furnace hearth deadman directly restricts the flow channels of slag and hot metal as well as the effective hearth volume, serving as a critical factor for blast furnace stable operation and long-term campaign life. Existing studies have extensively investigated the morphology and behavioral characteristics of the hearth deadman, yet the quantitative characterization of its volume remains insufficient. Based on the macroscopic morphological features of the deadman revealed by the dissection of a blowndown blast furnace, this paper proposes to geometrically equate the hearth deadman to a combined solid consisting of an upright frustum and an inverted frustum, and establishes an equivalent volume calculation model for the hearth deadman determined jointly by design parameters, directly adjustable parameters, hearth state response parameters and boundary equivalent parameters. A 2 580 m3 blast furnace was taken as the research object. This study determined the selection principles of model parameters and calculated the equivalent volume of the deadman. The influence laws of multiple factors including taphole depth, taphole angle, blast velocity, distance from the front end of the raceway to the deadman edge, vertical distance from the deadman corner to the center line of the taphole, and inclination angle of the inverted frustum were analyzed. The results show that the maximum cross-sectional radius at the deadman corner of the blast furnace is 3.826 m, accounting for 74.81% of the hearth radius. The equivalent volume of the deadman is 239.3 m3, occupying 43.50% of the total hearth volume, and the volume of the upper upright frustum accounts for 92.08% of the total deadman volume. Among all the influencing factors, taphole depth exhibits the most significant influence on the deadman volume, followed by the distance from the front end of the raceway to the deadman edge and blast velocity. The vertical distance from the deadman corner to the center line of the taphole increases the deadman volume positively, while the taphole angle and the inclination angle of the inverted frustum have relatively weak effects. The research results confirm that the proposed model can quantitatively characterize the spatial occupation degree of the hearth deadman. It can provide a quantitative reference for hearth state diagnosis, optimization of taphole maintenance systems, adjustment of air supply systems and long-life control of blast furnace hearths.
Sintering with a high-iron concentrate proportion serves as a vital way to improve the utilization efficiency of domestic self-produced iron concentrate resources. The Anshan-Benxi area in Liaoning Province hosts the largest iron ore deposits in China. Ansteel intends to carry out sintering production with a high-iron concentrate proportion of over 70%, whereas systematic theoretical researches on high-iron concentrate proportion sintering are still insufficient. Based on the actual raw materials applied in the sintering plant of Ansteel, the thermodynamic software FactSage 8.1 was adopted to systematically investigate the liquid phase behavior and phase evolution mechanism of the sintering system with the mass fraction of iron concentrate ranging from 50% to 100%. The results show that when the iron concentrate proportion increases from 50% to 100%, the initial liquid phase formation temperature rises from 1 150 ℃ to 1 200 ℃, and the liquid phase content in the low-temperature zone presents a gradually decreasing trend. The liquid phase viscosity of the system drops significantly with the increase of temperature, and reaches the maximum value of 0.06-0.10 Pa·s in the low-temperature zone of 1 100-1 200 ℃. With the increase of iron concentrate proportion, the liquid phase viscosity in the low-temperature zone decreases due to the increased FeO content and the reduced polymerization degree of silicate networks. The area of the liquid phase region expands first and then contracts with the rising iron concentrate proportion. The sintering system presents the optimal thermodynamic conditions for liquid phase formation at the iron concentrate proportion of 80%, with the largest liquid phase region area and the lowest initial liquid phase formation temperature. When the mass fraction of iron concentrate exceeds 80%, the liquid phase region shrinks obviously and the spinel phase region expands, which restricts the formation of calcium ferrite liquid phase and sinter mineralization. It is necessary to regulate the liquid phase composition and bonding behavior of sintering by adjusting raw material structure and sintering process parameters. Further analysis of the isothermal sectional phase diagram verifies that the liquid phase region expands remarkably at 1 300 ℃ under the 80% iron concentrate proportion condition. The calcium ferrite phase melts and decomposes, while the dicalcium silicate phase exists stably and provides skeletal support for sinter ores. This study clarifies the thermodynamic essence of mineral phase transformation during high-iron concentrate proportion sintering, and provides a significant theoretical basis for optimizing the process parameters of high-iron concentrate proportion sintering.
Under the background of carbon peaking, carbon neutrality and circular economy goals, the efficient and green resource utilization of copper slag has important practical significance for promoting the sustainable development of copper industry and other metallurgical industries. Aiming at the deficiencies of current copper slag treatment technologies, including high energy consumption, high carbon emission and long process flow, this study adopted a hydrogen reduction-melting separation process to realize the resource utilization of copper slag. Based on the proposed process, the effects of binary basicity on the strength and hydrogen reduction behavior of copper slag pellets were investigated, and the evolution laws of phase composition and microstructure of copper slag pellets during oxidation and reduction processes were analyzed. The results show that increasing basicity improves the quality of green pellets and roasted pellets of copper slag. With the increase of binary basicity, the strengths of green pellets and roasted pellets both increase first and then decrease. The green pellets present relatively high shatter strength (0.5 m) and compressive strength at the binary basicity of 0.79, which are 37.0 times and 29.6 N, respectively, while the roasted pellets achieve superior strength when the binary basicity ranges from 0.28 to 0.45. In addition, the increase of basicity promotes the oxidation and crystal connection of iron-bearing minerals in copper slag, which is beneficial to improving the reducibility of copper slag pellets. Under the conditions of reduction temperature of 1 000 ℃ and reduction time of 138 min, the metallization rates of copper slag pellets with binary basicity of 0.11, 0.45 and 0.79 reach 29.33%, 53.79% and 83.67%, respectively. Meanwhile, Fe-Cu alloy phase forms in the reduction products, realizing the collaborative reduction of iron and copper elements in copper slag. Considering the strength of green pellets and roasted pellets as well as the reduction effect comprehensively, the optimal binary basicity for copper slag pellets is determined to be 0.79. This study provides new ideas and theoretical support for the low-carbon and green resource utilization of copper slag.
Existing research conclusions on the correlation between asynchronous rolling process parameters and plate bending behavior are contradictory, and the underlying bending mechanism remains unclear. Taking 08Al steel plate as the research object, this paper systematically investigates the influence law and mechanism of rolling parameters on the bending behavior of steel plates during asynchronous rolling by combining finite element simulation and rolling experiments. A rolling model was established based on ABAQUS software, and the formation mechanisms of plate bending and bending reversal were revealed by analyzing stress evolution and the distribution characteristics of strain rate bands. The results show that X-shaped equivalent plastic strain rate bands distribute in the deformation zone. The number of strain rate bands is positively correlated with the reduction rate and negatively correlated with the initial plate thickness. Asynchronous rolling drives the migration of neutral points on the upper and lower surfaces of the plate and forms a cross shear zone. To balance the moment generated by the cross shear zone, the staggered distribution of rolling pressure on the upper and lower surfaces produces a reverse moment to stabilize the rolling process, which causes an asymmetric distribution of strain rate bands at the roll exit and further induces plate bending. The bending direction is closely related to the number of strain rate bands in the forward slip zone. When only one X-shaped strain rate band exists in the forward slip zone, the steel plate bends toward the fast roll dominated by the asynchronous effect. At a small speed ratio, the number of strain rate bands in the forward slip zone increases with the rise of reduction rate or the decrease of initial plate thickness. In this case, the asynchronous effect is weakened and only affects the distribution of strain rate bands near the neutral point. The newly added strain rate bands before the exit undergo dynamic adjustment, making the steel plate bend toward the slow roll. With the continuous increase of speed ratio, the asynchronous effect is enhanced, and the bending direction of the steel plate reverses toward the fast roll. This study provides a theoretical basis and practical guidance for the plate shape control in asynchronous rolling.
To investigate the microstructural evolution of GCr18Mo high-carbon chromium bearing steel during hot processing and to optimize its hot deformation parameters, single-pass hot compression experiments were performed using a Gleeble-3800 thermomechanical simulator to obtain the corresponding true stress-true strain curves. Under a 60% deformation reduction, the dynamic recrystallization (DRX) behavior was systematically investigated at strain rates ranging from 0.01 s-1 to 10 s-1 and deformation temperatures between 800 ℃ and 1 100 ℃. The empirical models for peak strain (εp) and critical strain (εc) associated with DRX are established, revealing a linear relationship of εc=0.55εp with correlation coefficients (R2) of 0.97 and 0.98, respectively. The apparent activation energy for DRX is calculated to be 53.85 kJ/mol. Analysis indicates that the solute drag effect caused by the addition of Mo is the primary reason for the increased recrystallization resistance. Based on the modified Avrami equation, the material constants are determined as βd=0.63 and kd=3.51, and a kinetic model describing the evolution of the DRX volume fraction is established. Furthermore, the established DRX kinetic model was integrated into the DEFORM-3D finite element software to simulate and validate the extent of DRX during the hot deformation process. A comparison of the results shows that complete DRX (100% volume fraction) occurs at the core of the specimen at 1 100 ℃ and 1 s-1, whereas no DRX occurs at 900 ℃ and 10 s-1. Under a typical partial DRX condition (1 000 ℃ and 1 s-1), the experimentally measured volume fraction of DRX is 42%, while the simulated value is 38%. The overall deviations between the predicted and experimental values are controlled within 5%. Through the comparison of extensive specific data, the accuracy of the model is fully validated, which provides a reliable theoretical basis for predicting DRX behavior and controlling microstructural evolution under complex multi-stage hot working conditions.
To explore the effect of Ni content on the microstructure and mechanical properties of Fe-Mn-Al-C-Ni alloys after solution treatment and aging treatment, two types of austenitic low-density steels with Ni mass fractions of 5% and 10% (denoted as 5Ni and 10Ni) were selected. The precipitation behavior of B2 phase and mechanical properties of the alloys were systematically investigated via scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), room-temperature tensile tests, and phase diagram calculations. The results show that the solution-treated alloys are composed of an austenite matrix and micron-scale B2 phase distributed along grain boundaries. With the increase of Ni content, the volume fraction of B2 phase along grain-boundary increases from 5% to 22%, which strengthens the pinning effect on austenite grain boundaries and refines the matrix grain size from 11.5 μm to 4.3 μm. After aging treatment, nanoscale needle-like B2 phases precipitate within the austenite matrix of both two alloys. The increase in Ni content significantly improves the nucleation rate of B2 phase, achieving a more uniform distribution and finer grain size of the precipitated phase. The plastic deformation mechanism of both alloys is dominated by planar slip. Due to the non-shearable characteristic of B2 precipitates, the Orowan bypass mechanism is activated to interact with dislocations, which endows the aged alloys with excellent work hardening performance. Although the increase of Ni content refines grains and promotes the precipitation of needle-like B2 phases, a larger number of coarse grain-boundary B2 phases in the 10Ni alloy significantly deteriorate its plasticity. Accordingly, the 5Ni alloy presents the optimal strength-ductility matching, with a tensile strength of approximately 1 220 MPa and a uniform elongation of around 36%. This study provides a theoretical basis for regulating the microstructure and properties of austenitic low-density steels through alloy composition design.
The MgNdGdZnZr bisemiconductor rare-earth heat-resistant magnesium alloy exhibits both high specific strength and excellent casting properties, making it a key material for lightweight aerospace components. However, casting defects can readily lead to fatigue failure, limiting its engineering applications. To compare the fatigue performance of laser beam welding (LBW) and friction stir welding (FSW) in repairing defects in MgNdGdZnZr dual-rare-earth magnesium alloy, cast-state MgNdGdZnZr was used as the test material. Four-point bending fatigue tests were conducted, and fatigue life and S-N curves were obtained using both the staircase method and the group test method. Microstructural features and fatigue fracture morphologies were characterized by means of OM, EBSD, SEM, and TEM. The results reveal that the FSW weld features fine, uniform equiaxed crystals, resulting in significant plastic deformation of the material, the grains in the heat-affected zone are elongated, while the second phase is dispersed without notable segregation, whereas the LBW heat-affected zone exhibits pronounced grain coarsening and segregation of rare-earth phases. The fatigue limit of the FSW joint is 148 MPa, slightly lower than that of the LBW joint (157.5 MPa), yet the coefficient of variation for FSW (4.8%) is higher than that for LBW (2.3%). At high stress amplitudes, fatigue behavior is governed by crack initiation. FSW is prone to introduce sharp geometric discontinuities that accelerate crack nucleation. At low stress amplitudes, fatigue is dominated by crack propagation, during which the fine-grained structure characteristic of FSW effectively impedes crack growth. The LBW fracture surface is generally rough and uneven, with scattered secondary phase particles, oxide inclusions, and micropores on its surface. The FSW fracture exhibits typical fatigue fracture characteristics, its cross-section consists of multiple parallel fatigue extension platforms separated by distinct tearing ridges and crack steps, presenting a relatively smooth overall morphology with numerous directionally arranged fatigue striations distributed across the surface.Based on the classical Hall-Petch relationship, the effects of precipitate strengthening and grain boundary segregation weakening are incorporated.Through multivariate linear combination and dimensionless processing, and by accounting for variations in microstructure, welding defect characteristics, and crack initiation/propagation mechanisms, a quantitative fatigue limit model is constructed and refined. The resulting multi-mechanism coupled fatigue limit model achieves a goodness-of-fit R2>0.98 with a prediction error of less than 0.5%. This investigation provides data support for optimizing welding repair strategies for rare-earth magnesium alloy components in aerospace applications.
As a key procedure of iron and steel metallurgy, the sintering process has long depended on expert experience and is confronted with challenges including strong multivariable coupling and dynamic response lag. The existing data-driven methods have deficiencies in the full utilization of textual knowledge and interpretability. Oriented to the intelligent transformation of the sintering process, this study aims to construct an intelligent question-answering system that deeply integrates domain knowledge and data models. The system can realize accurate reliable and interpretable automatic answers to professional questions and provide support for process optimization and personnel training. This study proposes a solution for large language models that integrates efficient low-rank adaptation(LoRA) fine-tuning and retrieval-augmented generation(RAG). The system takes the DeepSeek-R1-Distill-Qwen-7B model as the base framework. A sintering domain dataset containing 35 019 high-quality question and answer pairs was adopted for LoRA fine-tuning. The method significantly improved the model's semantic understanding of professional terminologies and process logic at a low cost. An RAG module was integrated simultaneously. The module provides accurate external knowledge for model generation through real-time retrieval of a local process knowledge base, which restricts model output and alleviates model hallucinations. Experimental results show that the joint training framework greatly improves the model's performance in answering professional sintering questions. The logic of model answers increases from 1.2 to 2.8 with a full score of 3.0. The correctness of model answers rises substantially from 0.7 to 6.5 with a full score of 7.0. Factual errors of model output are effectively reduced. This study verifies that the joint strategy combining domain fine-tuning and retrieval augmentation effectively improves the practicability and reliability of large language models in vertical domains. The research provides a feasible technical path and practical paradigm for the intelligentization of complex industrial processes based on large language models. Further research can be conducted on multimodal information fusion and real-time decision-making in the future.
To address the control challenges of nonlinearity, large time lag and strong coupling of molteniron temperature in blast furnace ironmaking, as well as the industrial limitations of traditional methods including separated prediction and regulation processes, highly subjective rule design, and insufficient model interpretability, this paper investigates an intelligent and explainable regulation method for molten iron temperature. The purpose is to construct an integrated closed-loop architecture of high-precision prediction and scientific regulation, improve the stability and target hit rate of molten iron temperature control, and provide technical support for intelligent and stable production of blast furnaces. Twenty two process parameters collected from the continuous production of a blast furnace from August 2024 to February 2025 were selected as research objects. DBSCAN+LOF two-level outlier detection and random forest missing value imputation were adopted for data preprocessing. Ten core features with both temporal correlation and process coupling characteristics were determined via Spearman correlation analysis and multi-method fusion feature selection. A TSMixer time series prediction model was constructed, and its time mixing layer and feature mixing layer captured the long-term time lag characteristics and parameter coupling relationships of production data, respectively. SHAP (SHapley Additive exPlanations) interpretable analysis was applied to quantify feature contributions, and four online adjustable core variables including oxygen-enriched flow rate, fuel ratio, hot blast temperature and blast kinetic energy were screened out. A data-driven fuzzy controller was designed with molten iron temperature deviation and its change rate as inputs. The controller outputted the incremental values of the four control variables, and process execution constraints were imposed to form executable regulation instructions for field application. Experimental results show that the goodness-of-fit R2 of the TSMixer model reaches 88%, and the single-step inference time is only 12 ms, which delivers superior performance in both prediction accuracy and real-time capability. The proposed regulation architecture increases the target hit rate of molten iron temperature control to 92%, and narrows the temperature fluctuation range from -15 ℃ to 15 ℃ to within -5 ℃ to 5 ℃, exhibiting significantly better regulation stability than PID (Proportional-Integral-Derivative)and MPC (Model Predictive Control) strategies. The innovation contribution of this paper lies in the establishment of a complete prediction-analysis-regulation closed-loop chain. The adoption of SHAP interpretable analysis instead of traditional empirical rules effectively reduces the subjectivity of fuzzy control and improves the engineering adaptability and interpretability of regulation strategies.The innovation of this study is the establishment of a prediction-analysis-regulation. The proposed method can serve as a generalized scheme for the intelligent regulation of blast furnace molten iron temperature. Future research will combine reinforcement learning to realize the dynamic iteration of regulation rules and promote the extended application of the method in multi-blast furnace and cross-working-condition scenarios.
To accurately predict the PLC effect and its spatiotemporal evolution behavior of Ti-15Mo alloy, and solve the problems of numerous parameters, low calibration accuracy and poor efficiency of the traditional calibration methods for the McCormick (MC) constitutive model, this paper proposed a three-dimensional finite element modeling method integrating the particle swarm optimization back propagation (PSO-BP) neural network intelligent optimization algorithm and the MC constitutive model. First, the MC constitutive model was embedded into ABAQUS software via the UMAT user subroutine, and a uniaxial tensile finite element model of Ti-15Mo alloy was established. Second, the PSO-BP hybrid intelligent optimization algorithm was adopted to efficiently calibrate seven key parameters of the finite element model. With the coefficient of determination(R2), root mean square error (RMSE) and mean absolute percentage error (MAPE) as evaluation indices, the effectiveness and reliability of the PSO-BP algorithm in predicting the stress level(σs), average stress drop amplitude (Δσa) and stress drop number (Nd) were verified. Finally, the calibrated finite element model was validated by experimental data obtained from a Gleeble 3500 testing machine, and the spatiotemporal evolution law of the PLC effect in Ti-15Mo alloy was systematically analyzed. The results show that the PSO-BP algorithm converges after 43 iterations. The predicted values of σs、Δσa and Nd are highly consistent with the true values, with all R2 values higher than 0.901 6, all MAPE values lower than 10%, and the minimum RMSE of 0.7. Both the simulated and experimental stress-strain curves exhibit typical serrated fluctuations, and the relative errors of the three characteristic quantities are all less than 9.67%. As the true strain increases from 0.01 to 0.04, Δσa rises from 9.63 MPa to 11.46 MPa, and the stress drop period increases from 0.76 s to 0.854 s. This phenomenon is mainly attributed to the enhanced pinning effect of precipitated phases on mobile dislocations in the process of strain accumulation. In addition, the propagation of PLC bands presents a mixed continuous and hopping mode, and the band inclination angle stabilizes at approximately 60°.
XML
Related Articles
File
