A detailed review of the strengthening and toughening mechanisms, performance characteristics, and application potential of fully austenitic high-manganese steel in liquid hydrogen storage and transportation under extremely low-temperature environments is provided. It is demonstrated that the synergistic activation of twinning-induced plasticity and transformation-induced plasticity effects can be achieved through stacking fault energy regulation, endowing high-manganese steel with a combination of high strength, high ductility and excellent impact toughness at low temperatures. The addition of alloying elements such as Mn and Al can further increase the stacking fault energy and optimize the microstructure, thereby significantly improving the mechanical properties of the material in ultra-low-temperature environments. High-manganese steel exhibits outstanding cost advantages in the process of liquid hydrogen storage and transportation. Compared with traditional stainless steel, it can effectively reduce manufacturing costs. Meanwhile, abundant manganese resources in China provide a guarantee for its large-scale application. In addition, high-manganese steel possesses excellent diffusion coefficients and is regarded as a highly promising candidate structural material for liquid hydrogen environments. Compared with other similar materials, it can maintain superior mechanical properties under low-temperature conditions. However, many challenges are still faced during the engineering application of high-manganese steel, including continuous casting breakout, welding cracking, Mn vapor volatilization and hydrogen embrittlement sensitivity. Future research should focus on addressing the above challenges to promote the reliable application of high-manganese steel in extreme environments such as liquid hydrogen storage and transportation.

To reduce the cost of pulverized coal injection in blast furnaces and improve fuel utilization efficiency, comparative analysis was conducted on the combustion properties of typical anthracite, high-volatile bituminous coal, low-volatile bituminous coal, semi-coke and their respective blended coals. Based on industrial production data, regression relationships were established between pulverized coal utilization rate and combustion characteristic index, as well as between coal pulverization cost and grindability index. A cost-performance evaluation model was proposed that comprehensively considers effective calorific value, pulverized coal utilization rate and coal pulverization cost. The results indicate that high-volatile bituminous coal exhibits the optimal combustion performance, while anthracite shows relatively high ignition and burnout temperatures. The combustion temperature ranges of semi-coke and Xiangshan coal fall between those of high-volatile bituminous coal and anthracite, with semi-coke having slightly superior combustion properties to Xiangshan coal. Increasing the proportion of semi-coke in blended coals can effectively reduce the ignition temperature and improve combustion performance; however, due to the low effective calorific value of semi-coke, the cost-performance index of blended coals is decreased accordingly. Xiangshan coal has the highest grindability index among the tested coals and its effective calorific value is second only to that of anthracite. Although the combustion performance of blended coals is reduced under certain operating conditions after adding Xiangshan coal, the comprehensive cost-performance index is improved.

In the modern steel production process, the behavior of oxygen jets exerts a significant influence on the converter smelting effect. Taking a 120 t converter in a steel plant as the research object, numerical simulation methods are employed to investigate the effects of nozzle arrangement, inclination angle and flow rate ratio of staggered oxygen lances on jet characteristics. The results show that compared with the nozzle arrangement mode with large nozzles and small inclination angles, the arrangement with large nozzles and large inclination angles can make the radial dynamic pressure distribution of jets more uniform, enhance jet independence, and thus obtain a larger effective impact area. Increasing the inclination angle accelerates the attenuation of jet velocity, increases the jet merging distance, and improves the uniformity of radial dynamic pressure distribution, with the effective impact area reaching the maximum value when the inclination angle is 16°. In addition, with the increase of flow rate ratio, the velocity of large-nozzle jets increases while the merging distance decreases, leading to an expanded difference in radial dynamic pressure peaks between large and small nozzles. The effective impact area increases with the rise of flow rate ratio, so the optimal flow rate ratio is determined as 65%/35%.

To reveal the removal mechanism of impurity elements in molten steel by bottom-blowing stirring in converters, industrial tests were carried out to investigate the effects of bottom-blowing gas stirring on the removal of phosphorus, sulfur and oxygen in molten steel in converter baths, based on numerical simulations and cold-state simulation tests. Numerical simulation results showed that the enhancement of bottom-blowing intensity could significantly optimize the kinetic conditions of molten steel baths. When the bottom-blowing intensity reached 0.107 m³/(t·min), the volume proportion of liquid dead zones decreased by 7.2% and 10.5%, respectively, compared with the operating conditions of 0.089 and 0.053 m³/(t·min). Cold-state simulation tests confirmed that the enhancement of stirring effect could effectively shorten the homogenization time of molten steel baths. The volumetric mass transfer coefficient of molten steel baths reached the peak value when the bottom-blowing intensity was 0.107 m³/(t·min), on the basis of which a correlation model between converter bottom-blowing flow rate and volumetric mass transfer coefficient was established. Further industrial tests on 150 t converters indicated that in the post-stirring stage with no oxygen involvement at the end point, the mass transfer rates of phosphorus, manganese and sulfur in molten steel were significantly higher than those in the stage from temperature measurement, sampling and carbon determination to temperature measurement, sampling and oxygen determination. These results demonstrated that the bottom-blowing post-stirring after lance lifting at the end point played a crucial regulatory role in the mass transfer process of elements in molten steel baths.

Aluminum ash (AA) was attempted to replace Al₂O₃ in LF refining slag, and the melting temperature of refining slag was optimized by adjusting slag system composition to realize resource utilization of aluminum ash and reduce environmental pollution caused by solid waste discharge. Based on the CaO-SiO₂-Al₂O₃ ternary phase diagram, the ratio of basic slag system was designed. When the mass fractions of CaO and Al₂O₃ were controlled within the range of 30%-70% and the mass fraction of SiO₂ was not higher than 15%, the low-melting-point phase 12CaO·7Al₂O₃ was easily formed in the slag. This region belonged to the low-melting-point zone, where the liquidus temperature ranged from 1 350 to 1 450 ℃. Meanwhile, the basicity of the slag system was moderate to meet the requirements of refining. Within this region, six groups of basic slag systems with different basicity were selected. The effects of different aluminum ash addition amounts and basicityon the melting temperature of the slag system were investigated by means of FactSage software and the hemisphere method, and the phase composition was characterized by XRD. Results indicated that the melting temperature of the slag system showed an overall upward trend as the mass fraction of aluminum ash increased from 0 to 20%. In the low-basicity system (C/S<8), the formation of high-melting-point phases was limited when aluminum ash was added in an appropriate amount (AA≤10%, mass fraction same hereinafter). However, excessive addition (AA>10%) might break the original equilibrium, leading to the massive formation of high-melting-point phases (MgAl₂O₄) in the slag and thus an increase in melting temperature. In the high-basicity system (C/S≥8), the introduction of a small amount of aluminum ash (AA≤5%) might promote the formation of more eutectic structures by generating low-melting-point compounds, thereby reducing the melting temperature. On the contrary, excessive addition (AA>5%) would break the optimal eutectic ratio between CaO and Al₂O₃ due to the introduction of excessive Al₂O₃, resulting in a sharp increase in melting temperature. When the aluminum ash addition amount was fixed, the melting temperature of the slag system exhibited a“V”-shaped variation(decreasing first and then increasing) with the basicity increasing from 4 to 11. This variation was related to the formation of the low-melting-point phase 12CaO·7Al₂O₃ and the high-melting-point phase Ca₂SiO₄ in the slag.

Calcium treatment can convert Al₂O₃ into liquid calcium aluminate, effectively mitigating nozzle clogging risks and improving steel quality. The effect of Ca content on inclusions was investigated. Results show that in untreated steel, inclusions are primarily solid Al₂O₃. At 0.000 8 wt.% Ca, small Al₂O₃ inclusions are partially modified into calcium aluminate, while large Al₂O₃ inclusions exhibit only partial surface modification, forming layered composite inclusions of Al₂O₃ and calcium aluminate. At 0.001 5 wt.% Ca, the inner Al₂O₃ layer in composite inclusions decreases and is converted into an outer layer ofcalcium aluminate indusions. At 0.002 4 wt.% Ca, inclusions are fully modified into calcium aluminate. At 0.003 9 wt.% Ca, CaS begins to attach to the calcium aluminate surface, forming CaO-Al₂O₃-CaS composite inclusions. At 0.005 1 wt.% Ca, the CaS content in CaO-Al₂O₃-CaS inclusions increases significantly. With increasing Ca content, the inclusion composition shifts from Al₂O₃-rich to calcium aluminate; the average diameter first decreases, then increases, and then decreases slightly, while sphericity first increases and then decreases. At 0.001 5 wt.% Ca, inclusions achieve the smallest average diameter and the highest sphericity. Inclusions in the steel with 0.001 5 wt.% Ca still undergo significant changes during cooling and solidification. From 1 600 to 1 480 ℃, the inclusion composition remains primarily calcium aluminate, but the size increases notably. Between 1 350 and 1 200 ℃, CaS begins to precipitate on the calcium aluminate surface, with the amount of precipitation increasing as the temperature decreases, forming core-shell CaO-Al₂O₃-CaS composite inclusions. From 1 600 to 1 200 ℃, the average inclusion diameter first increases and then decreases, while the number density first decreases and then increases. At 1 350 ℃, the average diameter reaches its maximum and the number density reaches its minimum.

The damage evolution mechanism and its key influencing factors of high-carbon pearlite steel wire during multi-pass drawing process were investigated. By combining the GTN (Gurson-Tvergaard-Needleman) damage model with finite element numerical simulation, the damage distribution inside the steel wire was systematically analyzed. The parameters of the GTN model were calibrated through an inverse method combining uniaxial tensile test and finite element simulation. The effects of key process parameters, including half cone angle, sizing belt length, friction coefficient and drawing pass, on internal damage evolution were quantitatively analyzed. The results show that damage exhibits a distribution characteristic of “higher in the core and lower at the surface”, with the maximum void volume fraction concentrated in the axis region of the steel wire. Parameter analysis indicates that the half cone angle has the most significant effect on damage accumulation, with a contribution rate of 41.67%, followed by drawing pass (12.18%).

High-chromium cast iron has been widely applied in mining, metallurgy, building materials and other industries due to its eutectic carbides of the (Cr, Fe)₇C₃ type with high hardness in the microstructure. To regulate the morphology of eutectic carbides and improve the wear resistance of high-chromium cast iron, the master alloy method was adopted, Al₂O₃ particles were introduced into hypoeutectic high-chromium cast iron, and rare earth elements were added externally. The effects of these two additives on the microstructure and wear resistance of high-chromium cast iron were systematically compared. The results showed that after the introduction of Al₂O₃ particles, a small number of particles were distributed in the dendrite trunks, while most adhered to the surfaces of eutectic M₇C₃ carbides between dendrites. By virtue of the heterogeneous nucleation effect of Al₂O₃ particles, the secondary dendrite arm spacing of the high-chromium cast iron containing Al₂O₃ was reduced by 24% compared with that of the non-added sample, and the area fraction of eutectic M₇C₃ was increased by 3%. The carbide morphology was presented as short and fine plate-like, strip-like and rose petal-like shapes, and the secondary carbides were also significantly refined. In high-chromium cast iron containing rare earth elements, the secondary dendrite arm spacing and secondary carbide size showed little difference from those of the sample containing Al₂O₃, but the proportion of fine rose petal-like eutectics was as high as 12%. Wear resistance tests indicated that the friction coefficient of high-chromium cast iron with externally added Al₂O₃ during the wear process was 0.27, and the wear scar depth was (5.34±0.05) μm. The friction coefficient and wear scar depth were reduced by 61% and 70%, respectively, compared with those of conventional high-chromium cast iron. Its wear mechanism was transformed from fatigue wear to abrasive wear and adhesive wear.After the addition of rare earth elements, the friction coefficient of high-chromium cast iron was further reduced to 0.26, and the wear scar depth was decreased to (1.84±0.17) μm. This excellent performance was closely related to the high proportion of rose petal-like eutectic M₇C₃ in the material.

In response to the domestic demand for developing 960 MPa grade explosion-proof steel and evaluating its blast resistance and mechanism, the mechanical properties, microstructure, and blast resistance of a newly developed high-strength-toughness 960 MPa grade explosion-proof steel (BR900) were investigated. The yield strength of BR900 steel is 1 002 MPa, and its impact energy at -40 ℃ exceeds 200 J. The excellent combination of strength and toughness is mainly attributed to the fine-grain and multiphase microstructure. Dynamic mechanical behavior at high strain rates was analyzed through high-strain-rate tensile tests and constitutive model fitting. The blast deformation behavior of 4 mm thick test plates under a 60 g TNT air blast load was studied using small-scale explosion tests. The results indicate that BR900 steel exhibits excellent blast resistance due to its favorable strength-toughness match and strain hardening capability.

The effect of Mn alloying on hydrogen embrittlement (HE) in Al-0.1Cu-(0.5, 0.9 and 1.4) Mn (mass%) alloys was investigated. Optical microscopy and X-ray diffraction revealed that all three Mn-alloyed samples exhibited a fully face-centered cubic structure with similar grain sizes. After hydrogen charging and tensile testing, the sample containing0.9 mass% Mn showed the poorest resistance to HE. Plastic strain distribution observed by digital image correlation indicated more severe strain localization during tensile deformation in the hydrogen-charged 0.9Mn alloy. Furthermore, a higher number of precipitates was observed in the 0.9Mn alloy, which accelerated HE. Fractography by scanning electron microscopy revealed secondary cracks in the hydrogen-charged 0.9Mn alloy, further confirming its inferior resistance to HE. Thus, Mn alloying can effectively control HE in Al-Cu-Fe-Mn alloys, but the Mn content should avoid0.9 mass% to prevent severe HE.

Conventional characterization methods often fall short in accurately capturing the micro-regional heterogeneity of X80 pipeline steel girth welded joints. Multi-scale high-throughput characterization techniques, including micro-beam X-ray fluorescence spectroscopy, high-throughput scanning electron microscopy, electron backscatter diffraction, micro-Vickers hardness and nanoindentation, were employed to systematically investigate the composition, microstructure, hardness distribution and their correlations across different characteristic zones of the joint. Higher concentrations of Mn, Cu, Nb, Mo and Cr were observed in the heat-affected zone, while Ni, V and Ti were more abundant in the weld metal. Elements such as Mn and Nb promoted the formation of bainite, whereas Ni and Ti facilitated the formation of finely dispersed M-A constituents and acicular ferrite, respectively. The intercritical region exhibited the highest hardness, attributed to the presence of abundant granular bainite, elongated chain-like M-A constituents at grain boundaries (area fraction of 15.2%), and a high dislocation density. In contrast, the fine-grained region showed the lowest hardness, due to a higher content of the soft polygonal ferrite phase and a lower dislocation density.

To enhance the automation accuracy and efficiency of cylindrical roller surface defect recognition, a lightweight multi-view feature-driven classification model termed MFDANet is proposed. The model integrates a multi-view feature augmentation module to fuse raw texture, edge structure, and enhanced information for hierarchical feature extraction of subtle defects. A Haar wavelet downsampling strategy is adopted to reduce computational cost while preserving critical details. Moreover, an efficient channel-spatial attention mechanism is designed to adaptively emphasize defect-related features, and a dilated multi-scale feature extraction module is introduced to achieve collaborative modeling of local and global representations. Experimental results demonstrate that MFDANet achieves an accuracy of 87.70% and a macro-averaged F1-score of 87.33% on the cylindrical roller surface defect classification task. With only 4.41 MB of parameters and 0.026 GFlops of computation, the proposed model significantly reduces complexity while outperforming traditional classifiers, lightweight networks and recent advanced approaches, thereby verifying its efficiency and practicality.

To drive the deep decarbonization of the entire steel industry chain, carbon reduction efforts in the upstream supply chain play a decisive role. Life cycle assessment (LCA) is applied to calculate the carbon emissions of galvanized steel products, with a focus on analyzing the carbon emission proportion of raw fuels and materials. Results show that upstream carbon emissions of the steel industry account for 55.53% of the total carbon emissions of the entire industrial chain. The emission composition ratios of various raw fuels and energy sources are as follows: coke 16.88%, coal 14.79%, iron ore 14.85%, ferroalloy 9.92%, flux 6.01%, industrial gas 9.06%, carbon products 0.20% and electricity 18.50%. Further analysis reveals that the main factors affecting carbon emissions from raw fuels and materials include energy structure and carbon intensity, production processes and technical equipment levels, resource endowments and raw material quality, as well as management standards and production modes. Measured data are obtained through field investigations, and product carbon footprint values of typical raw fuels and materials are calculated via LCA modeling. Among these values, coal reaches 89.42 kg/t, coke 1.36×10³ kg/t, iron ore 119.02 kg/t, ferroalloy 4.78×10³ kg/t, lime 1.21×10³ kg/t and graphite electrodes 8.84×10³ kg/t. On this basis, carbon emission characteristics and carbon reduction measures of each type of raw fuel and material are analyzed in depth. A simulation scenario themed “impacts of upstream raw fuel carbon reduction on steel products” is established based on the above research. A series of carbon reduction measures are implemented comprehensively, namely, adoption of green electricity in coal and graphite electrode production processes, co-combustion of 20% biomass fuel in coke production, low-carbon transformation in iron ore and ferroalloy transportation links, and application of hydrogen calcination technology in lime production processes. Implementation of these measures can reduce carbon emissions in the upstream raw fuel and material sector by 20%-40% and drive a carbon footprint reduction of approximately 8% for galvanized steel products.