To simulate the combustion behavior of injected fuels more realistically, the pyrolysis kinetic parameters of bituminous coal (BC), anthracite (AT), and semi-coke (SC) were determined under rapid heating conditions (~ 10⁴ ℃/s) using a drop tube furnace, and the fitted kinetic parameters were incorporated into a numerical model of blast furnace raceway combustion. The results show that differences in volatile release positions and temperature profiles between the three fuels were enlarged after applying the fitted kinetic parameters. BC exhibited the highest burnout rate of 96.23% and the lowest maximum temperature, while SC resulted in the highest maximum temperature and the lowest burnout rate of 84.41%. Rapid volatile release from BC led to the fastest combustion rate and temperature rise at the initial stage. Another factor is that the specific oxygen consumption of BC is the lowest, which resulted in the relatively high oxygen concentration in the middle stage. Due to the lowest higher heating value, the temperature rise of BC condition slowed down at the stage III (fast combustion stage) compared to that of AT. At the final stage (gasification reaction stage), the raceway temperature of SC condition exceeded the two others, benefited by its largest carbon fraction and effective heat value. The final burnout is affected by the oxygen concentration contour and temperature profiles combinedly.

The sticking of iron ore pellets during blast furnace smelting presents a major challenge for high-proportion pellet utilization. The sticking mechanisms and the inhibitory effect of lime slurry spraying were investigated. Results indicate that sticking is primarily caused by the consolidation of low-melting-point compounds that form a liquid phase and the intergrowth of porous metallic iron. An increase in reduction temperature significantly aggravates this process. Experi-ments demonstrate that spraying lime slurry effectively suppresses sticking, with its effectiveness enhancing as the spraying concentration, dosage, and frequency increase. However, this treatment reduces the metallization rate and reduction degree of the pellets. The mechanism involves the formation of a compound layer, primarily consisting of CaSiO₃ and CaFeSi₂O₆, on the pellet surface. This layer mitigates sticking by preventing direct contact between metallic iron particles but simultaneously inhibits the reduction reaction of iron oxides by furnace gas. Therefore, optimizing the spraying parameters is essential in practical applications to balance the suppression of sticking against the loss of reduction performance. Based on experimental results, the recommended parameter range is a lime slurry concentration of 1%-4% and a spray dosage of 1%-3% (single spraying pass), which significantly reduces the sticking index while maintaining a high metallization rate.

To address the limitations of existing rolling force models in temper rolling, characterized by insufficient accuracy and oversimplification, a high-precision iterative rolling force prediction model is proposed. Initially, the rolling deformation zone is meticulously divided into three distinct segments: the entry elastic deformation zone, the central plastic defor-mation zone, and the exit elastic deformation zone. Building upon this refined division, a novel approach is introduced to construct three-segment quadratic equations for precisely fitting the work roll flattening curve, ensuring a smooth transition between these regions. Concurrently, based on the refined segmented deformation zones, rolling force distribution models within each region of the strip are established. The model achieves a synergistic solution of the rolling force model and the roll flattening model through an iterative coupling mechanism between the roll flattening curve and the rolling force distribution in the deformation zone. Validation using 6551 sets of production data from a specific temper rolling mill, covering various steel grades (e.g., DQ-IF, 1180DP, 590DP, 440DQ, 980DP, 780DP), after thorough denoising, demon-strates the model’s superior performance. The RMSE (root mean squared error) of the model is 435 kN, its R² (deter-mination coefficient R-squared) is 0.969, and the MAPE (mean absolute percentage error) is 4.6%. Compared to peer models and conventional models, the proposed model exhibits significant advantages in prediction accuracy and demonstrates excellent robustness across various steel grades. The developed temper rolling force prediction model provides a robust and reliable theoretical basis for precise control and process optimization in temper rolling.

The erosion-corrosion behavior of Ti80 alloy in simulated seawater under varying sand concentrations (3%, 5%, 7%, and 10%) was investigated. A combination of electrochemical techniques and mass loss measurements was employed to quantify the synergistic effects of mechanical erosion and electrochemical corrosion. Electrochemical impedance spec-troscopy and potentiodynamic polarization tests revealed that increasing the sand concentration significantly deteriorated the corrosion resistance of Ti80 alloy, shifting the mechanism from passive film-controlled to charge transfer-dominated. Morphological analysis indicated that edge regions experienced more severe erosion due to the enhanced shear stress. The decoupling analysis of erosion-corrosion components revealed that mechanical erosion was the dominant contributor to the total material loss, while corrosion-accelerated erosion accounted for major part of the synergistic damage, especially at higher sand concentrations. The repassivation capability of Ti80 alloy was effective at low sand contents but was over-whelmed at 10%, resulting in an active surface state and intensified material loss. Cathodic protection showed limited effectiveness at 7% sand concentration but became noticeably more effective at 10%, indicating its increasing benefit under more severe erosive-corrosive conditions.

High-temperature flue gas is a significant by-product during the rotary hearth furnace (RHF) smelting process. Its acidic components, especially hydrogen chloride (HCl), easily cause pipeline corrosion, thereby seriously endangering the safe and stable operation of the smelting system. Currently, although the studies on the chlorine-induced corrosion of steel under the scenarios of seawater, industrial pollution, and fused salt have been extensively conducted, they have relatively little reference value for understanding the HCl gas corrosion behavior of RHF flue gas, due to its typical characteristics such as large emission volume, high temperature (700-900 ℃), and complex gas and dust compositions. The typical materials of RHF flue gas pipeline (Q245R and 15CrMo) were selected as the objects, and the effects of HCl gas concentration and temperature on the corrosion behavior of the pipeline under simulated RHF flue gas conditions were experimentally studied. Simultaneously, the underlying corrosion mechanisms were clarified. The results showed that the corrosion of both materials is significantly aggravated with increasing temperature and HCl concentration. With the temperature rising from 700 to 900 ℃, the increased weight per unit surface area (IWPSA) of Q245R and 15CrMo under 0.4% HCl is increased from 1.89 and 2.38 to 3.56 and 4.47 mg cm^-2, respectively. Furthermore, at 900 ℃, increasing the HCl concentration from 0.1% to 0.5% leads to an increase in the IWPSA from 2.93 to 4.34 mg cm^-2 for Q245R and from 3.47 to 5.06 mg cm^-2 for 15CrMo. Moreover, compared with 15CrMo, Q245R exhibits better corrosion resistance in the oxygen-deficient environment, since the chromium content, which can facilitate the progress of corrosion reaction, of Q245R is low. Mechanism analysis of the corrosion process reveals that HCl molecules first penetrate the surface oxide layer to reach the interface between the oxide layer and substrate. Subsequently, HCl reacts with the base metal to form FeCl₂, which can be melted and volatilized, destroying the integrity of oxide layer and inducing its severe spallation.

Accurate prediction of mechanical properties in thermo-mechanical control process (TMCP) X80 pipeline steels is essential for process design and quality control. To meet this need, an interpretable multi-target prediction framework is developed for TMCP X80 pipeline steels. The framework simultaneously predicts yield strength (YS), tensile strength (TS), elongation (EL), and drop-weight tear test (DWTT) percent shear area in production settings. A layered stacked ensemble is adopted to learn shared representations, and a dedicated meta-learner is assigned to each mechanical property, thereby separating tasks and enabling selective information sharing. The non-dominated sorting genetic algorithm III (NSGA-III) multi-objective evolutionary algorithm is employed to jointly optimize hyperparameters and to construct a Pareto front that reflects different process trade-offs, while explainable artificial intelligence is used to provide insight at both global and instance levels. The proposed framework is evaluated on real production data, and superior predictive performance over multi-output baseline models is demonstrated. Under the NSGA-III compromise solution, the root-mean-square errors for YS, TS, EL, and DWTT are reduced to 6.69 MPa, 5.17 MPa, 1.31%, and 1.28%, corresponding to relative reductions of about 19.5%, 17.3%, 13.9%, and 18.1%, respectively. Shapley additive explanations based interpretability analysis further clarifies the influence mechanisms of key thermal history and cooling parameters on each mechanical property and enhances the industrial credibility of the framework.

The effects of austempering temperature (above/below martensite start (MS) temperature) and prior ausforming on the transformation kinetics, microstructure, and mechanical properties of a medium-carbon bainitic steel were investigated using a thermal simulation machine, scanning electron microscope, transmission electron microscope, electron backscattering diffraction, and tensile testing. The results show that for above-M_S austempering, prior ausforming accelerated the bainite transformation rate and refined the bainitic ferrite (BF) laths from 518 ± 155 to 454 ± 96 nm. However, an unexpectively increase in the fraction of blocky martensite and martensite/austenite blocks was observed due to the prior ausforming, which led to a reduction in the total elongation. In addition, without ausforming, when the austempering temperature decreased from above M_S (360 ℃) to below M_S (320 ℃), the bainite transformation rate was significantly enhanced and BF laths were further refined to 416 ± 77 nm. Nevertheless, excessive formation of athermal martensite (AM) was induced, resulting in a decreased bainite volume fraction and deteriorated elongation. For below-MS austempered and ausformed specimens, ausforming slightly decreased the bainitic transformation rate due to the sup-pression of AM formation caused by the lower MS temperature. Meanwhile, the volume fraction of bainite was increased and the finest BF laths (377 ± 51 nm in width) were obtained. Consequently, the below-M_S austempered specimens with ausforming exhibited the highest product of strength and elongation of approximately 26.12 GPa %.

Laser-CMT (cold metal transfer) hybrid welding was performed on S30408 stainless steel. The effect of laser power on weld morphology, microstructure, and mechanical properties of the hybrid weld joint was studied. An optimal laser power of 2.5 kW for single-pass hybrid welding of 5 mm thick steel plates was recognized within series laser powers. As to dual-pass welding of 10 mm thick plates, increasing the laser power from 2.5 to 4.5 kW significantly improved penetration depth and expanded the hybrid-fusion zone. Dual-pass weld joints at both laser parameters achieved more than 93% tensile strength of the base metal. However, the impact energy at -196 ℃ of the weld zone notably increased from 91.8 J (2.5 kW) to 154.5 J (4.5 kW), which was attributed to the homogeneous microstructure. Microhardness mapping revealed a hardened zone in the heat-affected zone with a maximum hardness of 241 HV₁, regardless of laser power. These results demonstrate that optimizing laser power in dual-pass hybrid welding could effectively enhance the weld joint integrity and cryogenic toughness of stainless steel.

The effect of Hf on formation, residual stress, and adhesion of the pre-oxidation film on the surface of Fe-45Ni-25Cr-4Al-1Nb-0.3Si-0.45C-xHf (x = 0, 0.05, 0.25 wt.%) austenitic stainless steel was studied using a two-step process under low oxygen pressure. In comparison with Hf-free alloy, Hf segregated at columnar Al₂O₃ grain boundaries, effectively sup-pressing both outward Al³⁺ and inward O^2- diffusion, which led to a reduction in film thickness. The thinner film resulted in lower growth stress, inhibiting wrinkling, and minimized elastic strain energy accumulation during cooling. Further-more, Hf addition hindered interfacial pore formation and promoted internal oxides near the surface. However, with only 0.05 wt.% Hf, spallation was not completely inhibited. When Hf content was raised to 0.25 wt.%, the columnar grains were refined, thereby improving the film elasticity. Simultaneously, the internal Hf-rich oxide pegs formed at the film/matrix interface, along with the enriched HfO₂ pinning phases located between the columnar grains adjacent to the substrate, collectively improving the adhesion of Al₂O₃ film and significantly enhancing its resistance to cracking and spallation.

An optimized cold rolling-annealing route was developed to regulate the microstructure and texture of micro-carbon (0.037 wt.% in carbon content) steel sheets with the purpose of improving their formability. A systematic investigation was carried out on the evolution of microstructural features and crystallographic texture during processing, highlighting their intrinsic correlation with mechanical performance. The results demonstrate that applying a 75% cold rolling reduction followed by annealing at 630 ℃ yields better formability, where the average plastic strain ratio ($\overline{r}$) increases markedly from 0.86 to 1.48. Under these conditions, the microstructure is mainly composed of equiaxed ferrite with a minor amount of granular pearlite, and the ferrite grains have an average size of about 15.3 lm, displaying fine-grain bands and a bimodal size distribution along the rolling direction. Heavy cold rolling strongly promotes the development of the beneficial c-fiber texture {111}//ND (normal direction), while suppressing the unfavorable a-fiber texture <110> //RD (rolling direction). Grains with {111} orientation store higher strain energy, which provides preferential sites for nucleation and recrystal-lization during annealing, leading to a strengthened c-fiber texture and enhanced formability. In addition, high-strain regions adjacent to carbides activate the particle-stimulated nucleation mechanism, which further reinforces the c-fiber texture and contributes positively to the improvement of sheet formability.

Traditional oxygen lance nozzles for electric arc furnace (EAF) employ conventional conical designs, which severely constrain particle acceleration and focusing during supersonic gas–solid jet (SGSJ) operations, ultimately resulting in a weak gas–solid jet. To address these limitations and enhance the impact force of EAF oxygen lances, three nozzle profile designs for the Raoult nozzle are investigated. The objective is to optimize the phosphorus removal kinetics in the molten pool by modifying the oxygen jet morphology and lime powder injection method. Through numerical simulation, an SGSJ model was established for three distinct nozzle profiles (Conical Line, Vitosinski curve, and Bicubic curve). This revealed the interaction mechanisms between gas and solid phases within the supersonic jet under different nozzle geometries, yielding the following results: (1) The double-cubic-curve nozzle (Nozzle 1) formed a stable jet core region, exhibiting superior gas acceleration performance and flow stability compared to the other two nozzles; (2) The smooth streamlined design optimized energy exchange between the gas and solid phases. Nozzle 1 achieved the highest average particle velocity at the outlet, indicating superior momentum transfer efficiency and particle acceleration capability; (3) Nozzle 1 exhibits stronger vorticity and shear effects within the flow channel, with significant velocity slip between gas and solid phases. In contrast, the conical nozzle (Nozzle 3) experiences energy loss and premature particle velocity decay due to abrupt geometric changes; (4) Nozzle 1 delivers superior initial acceleration, core flow stability, and overall jet quality, though particle velocity decay at the jet’s trailing edge occurs faster than in Nozzle 3. Overall, the double-quadratic nozzle outperforms other designs in achieving efficient gas acceleration, maximizing initial particle kinetic energy, and ensuring core flow stability.

Promoting the use of biomass fuels and hydrogen in rotary-kiln pelletizing is an effective pathway to low-carbon and cleaner pellet production. A custom-built combustion test platform was employed to compare flame characteristics, flue gas composition, and heating performance for biochar (BC) versus pulverized coal (PC), for hydrogen versus natural gas/coke oven gas, and for the co-combustion of BC with these hydrogen-containing gases (HCGs). It was found that compared with PC, BC produced a more concentrated flame and a higher peak flame temperature, attributed to its porous microstructure and catalytically active ash; its lower nitrogen and sulfur contents also yielded reduced NO_x and SO₂. Under equal thermal input and oxidant conditions, higher hydrogen content in HCG enlarged flame size, improved temperature uniformity, and enhanced heating efficiency to the furnace, but NO_x emissions increased. In BC-HCG co-combustion, higher hydrogen fractions in HCG strengthened coupled reactions and further improved heating efficiency. Although NO_x from BC-hydrogen exceeded that from BC-natural gas, it was similar to BC-coke oven gas and remained lower than that from BC alone, due to biochar gasification. These results provide some theoretical guidance for the application of biomass and hydrogen in ferrous metallurgy.

Ilmenite is mainly utilized as a resource through reduction smelting processes, and the presence of impurity elements, especially magnesium, has a great influence on the reduction of ilmenite. The influence mechanism of magnesium element in the reduction process of ilmenite is analyzed at the crystal structure level. The results show that the bond length of the Mg-O bond is smaller than that of the Fe-O bond, so the crystal structure of MgTiO₃ is more compact and difficult to reduce. The doping of Mg²⁺ will replace the Fe²⁺ in the FeTiO₃ lattice, resulting in the crystal structure of FeTiO₃ in ilmenite becoming dense and the reducibility becoming worse. During the reduction process, Mg²⁺ will dissolve Ti⁴⁺ and Fe²⁺, which share O^2-, to form a solid solution that is difficult to reduce, resulting in poor reducibility. Therefore, the influence of magnesium works through the whole process of ilmenite reduction smelting.

The evolution of non-metallic inclusions in various steel grades, along with reoxidation phenomena induced by gas absorption during casting, is examined. Gas absorption leads to a two-stage reoxidation process. In the first stage, a sharp drop in oxygen partial pressure occurs at the melt surface. This is followed by a second stage, characterized by a more gradual decrease in oxygen partial pressure due to the formation of an oxide layer that inhibits further oxygen uptake. Although alloying elements significantly influence gas absorption rates, the thermodynamic and kinetic aspects of their interaction with oxygen remain inadequately understood. The development of a novel CaO-Al₂O₃-SiO₂-based single-layer flux has helped mitigate reoxidation caused by excess SiO₂ content in rice husk ash. However, slag carryover from the ladle can increase the oxidizing potential of the flux in the tundish and enhance the permeability of atmospheric oxygen through the slag layer, raising the risk of reoxidation of liquid steel during a stable teeming process. Furthermore, reoxidation can also result from oxidizing gases produced by carbothermal reactions in refractory materials. Both theoretical and exper-imental studies confirm that, under high-temperature conditions in the tundish, carbon monoxide (CO) is the main oxidizing gas produced by these reactions. Dissolved CO increases localized oxygen content in the molten steel, leading to reoxidation and nozzle clogging. The composition of non-metallic inclusions formed during reoxidation is steel grade-specific. In Al-killed steels, they evolve into aggregates rich in Al₂O₃. For Ca-treated steels, however, their transformation is primarily governed by the concentrations of calcium and sulfur in the melt. At lower CaS content, reoxidation produces solid inclusions. Higher CaS content allows more dissolved oxygen to be absorbed, reducing the formation of solid inclusions. In ultra-low-carbon Ti-containing Al-killed steel, the reoxidation caused by gas absorption produces Al₂O₃ and Al₂O₃-TiO_x composite inclusions. This steel type is also susceptible to oxidation by CO, forming liquid Fe_tO-Al₂O₃-TiO_x phases at the interior surface of the nozzle. These inclusions, along with Al₂O₃ and solidified steel, can contribute to nozzle clogging as Al in the steel reduces the Fe_tO-Al₂O₃-TiO_x phases. For Al-killed and Ce-treated steels, molten steel reoxidation transforms spherical Ce₂O₂S inclusions into clustered Al₂O₃-CeAlO₃ inclusions. Large clusters of Al₂O₃-CeAlO₃ can clog nozzles and create defects in continuous casting billets. In Si-killed stainless steel, reoxidation results in the simultaneous oxidation of Al, Ca, Mn, and Si by atmospheric oxygen, increasing the MnO and SiO₂ contents in inclusions. As the casting stabilizes, MnO is progressively reduced by Al and Ca in the steel, causing MnO-rich inclusions to disappear over time.

To simultaneously enhance remanence (B_r) and coercivity (H_cj) of NdFeB magnets, a powder-state regulation based on the characteristic columnar grain structure is developed. By matching the average powder particle size with the short-axis dimension of the columnar grains, the powder can be transformed from sharp-edged fragments into quasi-spherical particles with well-defined morphology during jet milling. The improved magnetic field alignment behavior originates from the synergistic optimization of particle size distribution and particle morphology. In addition, the quasi-spherical particles retain complete coverage of the rare-earth-rich (RE-rich) phase, which transforms into a uniform and continuous liquid phase during the heating stage of sintering. This effectively inhibits abnormal grain growth caused by direct contact between main-phase grains and weakens the intergranular magnetic exchange coupling. As a result, the B_r increases from 1.462 to 1.481 T, while the H_cj is markedly improved from 823.86 to 1073.8 kA/m. The results demonstrate that tailoring powder characteristics based on the columnar crystal structure enables the formation of quasi-spherical particles uniformly coated with RE-rich phase, thereby optimizing the microstructure of NdFeB magnets and enhancing the magnetic properties.

The meltdown behaviors and mutual interactions among multiple direct reduced iron (DRI) pellets immersed in a molten steel bath were investigated, with the aim of improving melting efficiency and reducing energy consumption. A 3D transient model was developed by coupling the volume of fluid approach with the enthalpy-porosity method to resolve heat transfer and solid-liquid phase change of DRI after immersion. Model credibility was assessed using the predicted complete melting time of the solid phase. The results showed that increasing inter-particle spacing and preheating tem-perature noticeably shortens the melting time: When the spacing increases from 2 to 10 mm, the complete melting time decreases by 19.83%, and raising the preheating temperature from 300 to 1100 K reduces it by 43.00%. Decreasing particle size and increasing voidage in multi-particle DRI system further accelerate melting. Empirical correlations were estab-lished between the complete melting time and four key parameters, i.e., inter-particle spacing, preheating temperature, particle size, and voidage. The melting time exhibits strong negative correlations with spacing and preheating temperature and an exponential positive correlation with particle size; when the voidage exceeds 0.5, its influence becomes negligible. These relationships provide practical guidance for selecting DRI parameters in industrial electric arc furnace operations to enhance melting efficiency and lower energy demand.

The use of biochar can reduce fossil CO₂ emissions from direct reduced iron (DRI)-based electric arc furnace (EAF) steelmaking. The effect of slag B2 basicity and FeO concentration on the interaction between pinebark-based biochar and TiO₂-and V₂O₅-bearing DRI-based EAF slag was examined. For this, a carbonaceous material slag module (CSM) was prepared by placing a slag briquette on a biochar substrate, and the CSM underwent optical dilatometry (OD) at 1773 K in an argon atmosphere to assess the slag swelling index. It revealed that the slags with a B2 basicity of 1.5 and an FeO concentration of 40 wt.% exhibited a higher slag swelling index than the others in their respective categories. The swelling index was observed to decline from B2 basicity of 1.5 to 2.5 and prospers as FeO concentration from 20 to 40 wt.%. A similar trend was confirmed with anthracite-based CSMs. Scanning electron microscopy and energy-dispersive spec-troscopy analyses on the reacted slag from biochar-based CSMs revealed a significant reduction in slag FeO concentration and formation of iron solid solution with vanadium in all samples. The thermogravimetry studies showed that the biochar-slag modules exhibited mass loss correlated with the shape changes of the slag in the OD, confirming the characteristics of interaction between the biochar and the slag.

Trace amounts of rare earth elements Ce (0.0035 wt.%) and La (0.0033 wt.%) were separately added to non-oriented silicon steels to prepare three test steels without rare earth, with Ce, and with La, respectively, and the influences of rare earth on inclusions, magnetic domains, and texture were investigated. The results showed that after rare earth addition, Al₂O₃ and MnS were modified into rare earth aluminates and rare earth oxysulfides. The total pinning force of inclusions in the samples increased from 62.20 (with no rare earth addition) to 69.99 (with Ce addition) and 66.40 Pa (with La addition), and the average grain size decreased from 50.3 (with no rare earth addition) to 34.3 (with Ce addition) and 39.6 lm (with La addition). The magnetic force microscopy results demonstrated that the phase peak values at grain boundaries of the three samples with no rare earth addition, Ce addition, and La addition were 750, 400, and 250 mdeg, respectively, and that the phase amplitudes around the Al₂O₃, CeAlO₃, and LaAlO₃ inclusions were 700, 700, and 500 mdeg, respectively. The steel with La addition had the crossover energy barrier for the lowest magnetization domain wall, facilitating the movement of magnetic domain walls and resulting in the lowest iron loss. From the texture characterization results, the favorable {001}//ND texture intensity increased from 2.28 for the sample with no rare earth addition to 5.66 (with Ce addition) and 5.7 (with La addition), respectively, and the c-fiber texture intensity decreased from 15.97 to 13.21 and 11.41, respectively. The steel with La addition had higher initial permeability and higher saturation permeability than the other two steels and was more likely to reach saturation. The iron loss and magnetic flux density of the steel with the addition of an appropriate amount of La could be simultaneously improved.

To address the challenges in predicting ductile fracture of 3Cr13MoV martensitic stainless steel under complex loading conditions, the fracture mechanisms were systematically investigated through mechanically testing under multi-axial stress states and microscopic damage evolution analysis. Based on the evolutionary processes of voids, a novel uncoupled ductile fracture prediction model was proposed. This model introduced maximum shear stress and maximum principal stress as damage evolution correction factors and quantitatively revealed the induction mechanism of maximum principal stress on void coalescence under stress triaxiality control. Finite element simulations and experimental validation showed that the model accurately predicts behavior across various stress levels.

Aluminum dross is a waste of the aluminum industry, and its improper disposal can pose negative environmental impacts. The metallurgical effects of utilizing nitrided aluminum dross in the smelting process of rebar steel are systematically investigated. Firstly, resistance furnace experiments were performed to evaluate the effects of nitrided aluminum dross addition on the oxygen content, aluminum content, and nitrogen content in steel, as well as the corresponding aluminum yield and nitrogen yield. Secondly, an analysis was conducted on the characteristics of inclusions resulting from the addition of nitrided aluminum dross to steel. Finally, based on the laboratory experimental parameters, industrial trials were conducted in steel plant. The laboratory results showed that as nitrided aluminum dross addition increased from 0.5 to 2.0 g per kilogram of molten steel, w[O] (reduction in oxygen content) increased from 0.0017 to 0.0028 wt.%, and w[Al] (increase in dissolved aluminum content) rose from 0.0064 to 0.0272 wt.%. Compared to metallic aluminum with similar theoretical aluminum input, nitrided aluminum dross achieves comparable w[O] and w[Al], with an aluminum yield of about 60%. The increase in nitrided aluminum dross addition raised w[N] (increase in nitrogen content) from 0.0013 to 0.0038 wt.%, thereby enhancing the precipitation of VN. It was found that nitrided aluminum dross addition leads to a slight increase in inclusion size and number density compared to metallic aluminum. Nevertheless, the resulting steel cleanliness meets all specifications for rebar steel. Industrial practice also proved that nitrided aluminum dross can be effectively utilized as a pre-deoxidizing agent and nitrogen source.

Al-free-ODS and 4Al-ODS steels were fabricated to investigate the influence of Al addition on the microstructure, tensile and impact properties. The morphology, crystal structures and interface coherency with matrix of nano-oxide particles were characterized. The results show that the number density of nano-oxide particles in 4Al-ODS steel increased from 1.1×10²³ to 1.3×10²³ m^-3, while the average size slightly increased from 8.2 ± 1.6 to 9.3 ± 1.6 nm compared to those in Al-free-ODS steel. Y₂(Zr_0.6Ti_0.4)₂O₇ and additional YAlO₃ nano-oxide particles were found in 4Al-ODS steel with better coherent relationship with the matrix. At room temperature to 1273 K, all tensile test results showed that the strength of 4Al-ODS steel consistently increased without a significant reduction of elongation. The total elongation tested at 973 K was about 49%, which was significantly higher than most of ODS steels in the literature. Although the addition of Al slightly elevated the ductile-to-brittle transition temperature, the upper shelf energy was almost unaffected and remained as about 97.5 J, which is still superior to most of ODS steels as reported.

Surface ultrasonic rolling treatment (SURT) was applied to ER8 wheel steel to create a ~ 250 lm gradient nanostructured (GNS) surface layer. SURT induced severe plastic deformation, grain refinement, increased dislocation density, and continuous dynamic recrystallization. The GNS layer enhanced surface hardness to 728 HV (~ 2.4 × substrate) and improved yield and tensile strength to 680 and 1015 MPa, respectively, while maintaining satisfactory ductility. Under dry sliding, wear rates decreased by 79%–88% compared to coarse-grained samples, with lower friction coefficients and improved wear resistance in deionized water and NaCl solution. High-cycle fatigue tests showed a fatigue strength of 350 MPa at 1 × 10⁷ cycles, with residual compressive stress delaying crack initiation and shifting crack sites inward. These performance enhancements are primarily attributed to the formation of a gradient nanostructured surface layer with refined grains, high dislocation density, and abundant high-angle grain boundaries, together with deep residual compressive stress, which jointly suppress plastic deformation and delay crack initiation. These findings demonstrate that SURT effectively strengthens wheel steel surfaces, improving mechanical, tribological, and fatigue performance, and offers significant potential for extending the service life of high-speed railway wheels.

The cold rolling process entails coupled elastoplastic deformation of the strip and elastic flattening of the work rolls. The complexity from nonlinear strain gradients and inhomogeneous contact conditions poses significant challenges to eluci-dating interfacial behaviors within the deformation zone. With the development of cold-rolled strip toward higher strength and thinner gauge, conventional analytical models based on simplified assumptions fail to adequately capture the intricate physical mechanism. In order to display the characteristics and behaviors within the deformation zone and enable fun-damental exploration of deformation mechanism for the high-strength thin strip, a theoretical modeling framework is constructed: (1) Based on the elastoplastic deformation characteristics of the strip, the deformation zone is partitioned into entry elastic zone, plastic zone and exit elastic zone; (2) considering the slip or stick friction contact behaviors between the rolled strip and the work rolls, the plastic deformation zone is further subdivided into backward slip zone, stick zone and forward slip zone; (3) not using the traditional circular elastic flattening approach, the noncircular flattening curve is analytically expressed by combining the rolling stress distribution with the elastic half-space theory. Subsequently, a numerical iteration method driven by mechanism-data fusion is proposed to decouple the nonlinear roll-strip interactions and determine the key process parameters, which can characterize the distinct deformation zones, including rolling normal stress, friction tangential stress, roll flattening curve, contact arc length, total rolling force, and forward slip. Furthermore, an elastoplastic finite element method model for rolling process is established to verify the presented approach via rolling stress distribution and roll flattening curve, and the calculated parameters of rolling force and forward slip are validated by the actual process data. In addition, the influence of process parameters on interfacial behavior evolution is discussed, and the presented approach is effectively applied to investigate the industrial dynamic rolling process. The proposed approach enables accurate calculation and mechanistic explanation of negative forward slip phenomena, offering theoretical support for practical process optimization.

The erosion-corrosion behavior of three low-alloy martensitic steels with varying carbon contents under two typical flow conditions encountered by dredging metal components of high-velocity normal sand impingement and low-velocity low-angle sand impingement was investigated. The synergistic contributions of corrosion-enhanced erosion and erosion-enhanced corrosion were quantitatively distinguished using electrochemical and gravimetric measurements. The local damage mechanism was further elucidated through surface and cross sectional morphology characterization. Results revealed that the increased hardness and strength associated with higher carbon content significantly enhance the erosion resistance of these steels under both conditions. However, the resistance to erosion-corrosion displayed varying patterns depending on the carbon content. In high-velocity normal sand impingement conditions, total erosion-corrosion loss of the steels stemmed primarily from erosion. The elevated carbon content markedly reduces the fracture of extruded lips on the steel surface, thereby mitigating erosion damage and ultimately improving erosion-corrosion resistance. Conversely, under low-velocity low-angle sand impingement conditions, the synergistic interaction between corrosion and erosion dominated the mass loss mechanism. The formation of erosion-corrosion pits altered the local erosion mechanism from micro-cutting to detachment of the cliff-like substrate at the pit edges. Increasing carbon content shifted the detachment mode at pit edges from ductile fracture to brittle fracture, leading to more severe erosion. Consequently, the erosion-corrosion resistance decreased with the increasing carbon content. Based on these findings, a material selection strategy for low-alloy martensitic steels applicable to different dredging conditions was proposed.

As the core technology of the wire rod controlled cooling process, the Stelmor cooling process (SCP) plays a decisive role in regulating the final microstructure and properties of the products. However, this process is subjected to strong multi-parameter coupling, which frequently leads to non-uniform temperature field distributions and difficulties in precisely controlling phase transformation. These issues severely limit the quality stability and high-value-added manufacturing potential of premium wire rod products. Therefore, the technological evolution of the SCP is reviewed, focusing on the research progress related to modeling of temperature fields, phase transformation kinetics, and control strategies. On this basis, the development of a multi-scale digital materials engineering platform and a digital twin system that integrates mechanistic and data-driven models is envisioned as a promising direction. By employing model order reduction to balance high-fidelity simulation with real-time computational demands, such a framework could lay the foundation for future intelligent, high-precision closed-loop control of the SCP.

Electroplated chromium sludge (ECS) is a hazardous waste containing high levels of Cr(VI). Its complex composition presents significant challenges for global disposal. Although reduction smelting is an effective way to treat ECS, the absence of a suitable smelting slag system has hindered efficient ferrochromium alloy production from ECS. Leveraging the natural high-Ca/low-Mg–Al characteristics of ECS, a customized regulation model for the CaO–SiO₂–Al₂O₃–MgO– Cr₂O₃ quinary slag system was constructed. The effects of various parameters such as Al2O3 and Cr2O3 contents, basicity, and other parameters on the properties of smelting slag were systematically investigated. Under the optimized slag regime (Al₂O₃ 10–15 wt.%, Cr₂O₃ <1 wt.%, binary basicity 0.95–1.20, MgO/Al₂O₃ 0.46–0.57), the smelting temperature was reduced to 1600 ℃, representing a 100 ℃ decrease compared to conventional chromite smelting processes. Notably, over 98 wt.% of the chromium in ECS was recovered into a ferrochromium alloy conforming to the FeCr55C6.0(II) standard. A key finding was that 10–15 wt.% Al₂O₃ significantly improved slag fluidity at high temperatures, thereby effectively promoting slag–metal separation.

The underlying causes of strength deterioration for 9%Cr martensitic heat-resistant steels during high-temperature thermal aging are still debated. The mechanisms of microstructure-driven strength deterioration in 2.6W-G115 steel during thermal aging at 650 ℃ within 11,000 h were systematically investigated by combining ex situ synchrotron radiation X-ray diffraction and chemical phase analysis. The degradation of solid solution strengthening is dominated by C element and W element. The maximum peak of precipitation strengthening occurs at 500 h aging, and M₂₃C₆ carbides exhibit more pronounced pinning effect on martensitic subgrain boundaries. The strength deterioration is most concentrated during aging between 100 and 5000 h, though the microstructural degradation mechanisms vary considerably at different aging stages. During 100-500 h aging, the nucleation and growth of precipitates and the recovery of unstable dislocations predominate. The Hall-Petch strengthening undergoes significant degradation due to the broadening of martensitic laths during 500-1000 h aging. In the later stages of thermal aging (1-5000 h), the degradation of microstructure is governed by solid solution strengthening, precipitation strengthening, and Hall-Petch strengthening. A yield strength prediction model was successfully established based on microstructure degradation by coupling different strengthening mechanisms, which matches well with the experimental data.

In the cold rolling process, owing to the absence of effective process monitoring methods, it is challenging to detect and optimize the degradation of controller performance promptly, often resulting in a reactive approach to anomaly remedi-ation and negatively impacting production efficiency. To address this issue, a novel mechanism-guided maintenance strategy was proposed for thickness and tension control in tandem cold rolling. Specifically, a forward-looking index was introduced, and the mechanism-guided Hurst (MH) index was developed by incorporating domain knowledge, enabling real-time monitoring of the production process. When controller performance falls below expectations, the MH index guides the whale optimization algorithm (WOA) to achieve multi-controller coordinated optimization and overcome the global optimization challenges arising from the nonlinear, multivariable, and strongly coupled nature of cold rolling. Simulation results demonstrate that this approach effectively monitors and enhances the performance of multiple con-trollers in cold rolling. Furthermore, the method was successfully implemented in an industrial setting, enabling real-time monitoring, with enhanced control accuracy post-optimization, providing valuable insights for industrial applications.

The cavitation erosion (CE) behaviour of X65 pipeline steel subjected to electrochemical hydrogen-charging was inves-tigated in both deionized water and a 3.5 wt.% NaCl solution. The findings reveal that hydrogen embrittlement signifi-cantly impacts CE behaviour of the steel. While electrochemical hydrogen-charging slightly improves its corrosion resistance, it notably reduces the steel’s resistance to CE. Additionally, the mass loss due to CE shows a positive correlation with hydrogen-charging current density. For pipeline steel under any hydrogen-charging current density, the combined effects of CE and electrochemical corrosion account for nearly half of the total mass loss attributed to CE damage. Additionally, the role of corrosion in exacerbating CE, regardless of hydrogen-charging, is a critical factor that warrants the attention. Electrochemical hydrogen-charging plays a pivotal role in the degradation of CE resistance in pipeline steel.