钢铁钒钛

Vanadium extraction from hot metal via indirect oxidation using solid oxidizing agents

ZHANG Ningyu, XIE Shaoxian, XIANG Junyi, CHEN Lian, LÜ Xuewei

2026, 47(1): 1-9. doi: 10.7513/j.issn.1004-7638.2026.01.001

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Abstract:
Aiming at solving the problems of temperature control in molten bath, iron loss, and grade reduction of vanadium slag caused by O₂ injection in the traditional process of vanadium extraction from hot metal, a new technology using iron oxides (Fe₂O₃) for vanadium extraction from hot metal was proposed in this study, taking advantage of the characteristics of mild indirect oxidation reaction and controllable process. Thermodynamic calculations identified Fe₂O₃ as the optimal oxidizer with recommended addition ranges of 1.5%–6.0%. A systematic investigation was conducted on the effects of Fe₂O₃ addition ratio, particle size, and bath temperature, revealing the enhancement mechanisms of particle size reduction and temperature elevation on vanadium oxidation. The study further developed a “CaO-Fe₂O₃” oxidizer system that improves reaction efficiency by lowering the melting temperature. Through process parameter optimization, the optimal conditions were determined as: reaction temperature 1350 °C, 4.5% of 0.074–0.5 mm Fe₂O₃ with n(CaO): n(Fe₂O₃) = 0.75. Under these conditions, the reaction reached equilibrium within 2 min, achieving a final V content in the hot metal of 0.016%, oxidation rate of 95.12%, with vanadium slag containing 7.15% V and 1.93% P. This “CaO-Fe₂O₃” system demonstrates efficient vanadium extraction from hot metal and provides new insights for the development of vanadium extraction technologies.

Experimental study of vanadium monoxide synthesis via hydrogen reduction

YU Jie, HUANG Qingyun, ZHONG Dapeng, PEI Guishang, SU Lijia, XU Haiming, XIANG Junyi

2026, 47(1): 10-16, 27. doi: 10.7513/j.issn.1004-7638.2026.01.002

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Abstract:
Vanadium monoxide (VO), recognized as a potential anode material for high-energy and high-power lithium-ion batteries (LIBs), is limited in its application as an electrode material due to its low purity, high cost and complex process in existing synthesis process. The authors propose a novel hydrogen reduction process for VO synthesis using V₂O₃ as the raw material and H₂ as the reducing agent. The key parameters such as reduction temperature, reaction duration, and others were systematically investigated. The preparation of VO is achieved through the V-H-O multiphase reaction, and the resulting VO powder particles have relatively smooth surfaces, presenting an approximating spherical or ellipsoidal shape. The XRD diffraction pattern closely matches with the reference diffraction pattern, with accurate peak positions, sharp profiles, and narrow full widths at half maximum, indicating excellent crystallinity. By optimizing parameters, the optimal reduction conditions were determined. When the reduction temperature is 1500 ℃, the reaction time is 5.5 h, hydrogen flow rate is 0.264 cm/s, the vanadium content is about 78.27%, which is consistent with VO_0.80-VO_1.20.

Effect of cooling temperature-holding time on the crystallization of molten-separated titanium slag

LI Chenhui, DU Peipei, ZHAO Suxing, TIAN Tielei, LI Lanjie, LONG Yue

2026, 47(1): 17-27. doi: 10.7513/j.issn.1004-7638.2026.01.003

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Abstract:
To achieve efficient extraction of titanium components from molten-separated titanium slag, this study took the slag from a steel plant as the research object, and systematically investigated the crystallization behavior of the slag under synergistic control of cooling temperature (1150~1300 ℃) and holding time (0~60 min) through high-temperature melting crystallization experiment and XRD analysis. The results indicated that the optimal crystallization window for anosovite-MgTi₂O₅ is 1250~1300 ℃ with 30~50 min, and the precipitation amount reaches 51.2%~56.2%; the optimal crystallization window for pseudobrookite-Fe₂TiO₅ is 1150~1200 ℃ with 40~60 min, and the precipitation amount is 38%~40%; the optimal crystallization window for rutile-TiO₂ is 1150~1200 ℃ with 0~30 min, and the precipitation amount reaches 25%~35%. The crystallization behaviors of the three phases exhibit an obvious competitive relationship, and the optimal crystallization window of a single phase highly overlaps with the suppression regions of the other two. This provides a precise process optimization window for either directional promotion or targeted suppression of specific titanium-bearing phases, offering a theoretical basis for the directional separation and extraction of titanium components from industrial molten-separated titanium slag.

Study on the effect of TFe on the physicochemical properties of molten vanadium slag

DU Changwu, CHEN Jun, CHEN Lian, FU Xinrui, WANG Lijun

2026, 47(1): 28-35. doi: 10.7513/j.issn.1004-7638.2026.01.004

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Abstract:
The viscosity and melting characteristics of the FeO-SiO₂-V₂O₃-TiO₂- MnO-CaO-MgO system were investigated by rotating column method and hemispherical method, and the influence of total iron content (TFe) on the physicochemical properties of vanadium slag melts was discussed. Combined with X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis, the phase precipitation of vanadium slag at high temperatures and its relationship with viscosity and melting point were investigated. The results showed that with the increase of TFe content, the slag flow temperature decreased while the viscosity increased, and there was an obvious transition point of viscosity when temperature decreased. Above this critical temperature, TFe content had negligible effect on the viscosity of the slag, while below the transition temperature, the viscosity of the vanadium slag increased dramatically with the increase in TFe. At the vanadium extraction temperature of 1350 ℃, the precipitated phase of the slag was mainly a high melting point spinel phase, and the increase in TFe content promoted the precipitation of the spinel phase and the single particle became larger, resulting in a sudden increase in the viscosity of the melt as well as the melting temperature. The present work would provide a theoretical basis to some extent for optimizing the physical and chemical properties of vanadium slag.

Research progress on electron beam melting additive manufacturing of TiAl alloys and heat treatment processes

WANG Shuangzan, GE Gengwu, LU Dong, LIANG Yongfeng, LIN Junpin

2026, 47(1): 36-48. doi: 10.7513/j.issn.1004-7638.2026.01.005

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Abstract:
Electron Beam Melting (EBM) is an ideal forming method for additive manufacturing (AM) of brittle TiAl alloy components, enabling the formation of complex structures and the achievement of superior performance in TiAl alloys. Compared to other additive manufacturing techniques, EBM offers advantages such as high preheating temperatures, resistance to cracking, and low oxygen content, making it widely researched, especially for the Ti-48Al-2Cr-2Nb (4822) alloy. The average grain size of 4822 alloy prepared by EBM is typically less than 20 μm, significantly smaller than that of traditionally cast alloys. The room-temperature strength of 4822 alloy prepared by EBM can reach over 600 MPa, but it exhibits poor ductility and defects. Hot isostatic pressing (HIP) and high-temperature heat treatment (HT) are important post-processing methods to enhance mechanical properties, increasing the room-temperature elongation to 1.3%. However, there are still many issues with the EBM process and HT of TiAl alloys. This paper reviews the recent research progress in EBM additive manufacturing of TiAl alloys and their HT processes, analyzes and summarizes the current problems and countermeasures, and provides an outlook on the future development direction of additive manufacturing of TiAl alloys.

Review on the microstructure and mechanical properties of TiC-NbC synergistically strengthened iron-based alloy wear-resistant coatings

SHAO Rui, LI Ziyi, FENG Zhongxue, CHEN Min, LIU Xuyang, WENG Liu, ZHANG Xuefeng

2026, 47(1): 49-61. doi: 10.7513/j.issn.1004-7638.2026.01.006

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Abstract:
Under extreme operating conditions such as high temperature, heavy load, and high-speed friction, applying advanced surface engineering technologies to fabricate iron-based wear-resistant coatings on steel substrates is an effective approach to extend the service life of critical components and promote resource recycling. In conventional Fe-Cr-C alloys, coarse primary M₇C₃-type carbides often form; these brittle phases can readily become crack initiation sites under severe service conditions, compromising the coating’s durability. The addition of Nb can lead to the precipitation of fine NbC particles at grain boundaries, thereby suppressing crack initiation and reducing the propensity for cracking. However, excessive Nb addition may cause NbC to agglomerate and form coarse particles, which is detrimental to coating performance. Further introduction of Ti enables in-situ reactions with C to form stable and high-hardness TiC, which can act as heterogeneous nucleation sites for NbC, thus refining and homogenizing the microstructure and effectively enhancing the overall properties of the coating. This review summarizes the nucleation mechanisms involving the synergistic effect of in-situ formed TiC and NbC, and discusses the influence of Nb and Ti additions on the microstructure and mechanical properties of Fe-Cr-C-based alloy coatings, providing theoretical support for the applied research of high-performance wear-resistant iron-based alloy coatings.

Microstructural homogeneity and high-temperature tensile uniformity of TC4 alloy disk forgings

WANG Ying, LI Nan, PENG Wenya, YU Shuai, LIU Jianrong, GUO Hailong, WANG Qingjiang

2026, 47(1): 62-70. doi: 10.7513/j.issn.1004-7638.2026.01.007

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A TC4 titanium alloy disk was fabricated via die forging followed by solution and aging heat treatment. The microstructure and corresponding high temperature tensile properties were systematically investigated across three representative regions. The results reveal significant radial non-uniformity in high temperature tensile properties, the rim region exhibits the highest strength, the 1/2R region appears the lowest, while ductility shows little difference among the three regions. Microstructure, texture and fracture surface analyses indicate that the non-uniformity in high temperature tensile properties originates from variations in the morphology and texture of α phase. The rim and hub regions contain fine secondary α phase with basket-weave morphology, which effectively suppresses dislocation motion and void coalescence, thereby enhancing strength without compromising ductility. In contrast, the 1/2R region contains coarser secondary α phase with a colony-like morphology, promoting localized void growth and early fracture. In addition, due to the high Schmidt factor of the basal slip of the α phase in the 1/2R region, the tensile strength is reduced.

Synergistic regulation of hot drawing and annealing on recrystallization and strength-ductility matching in TB13 titanium alloy

SU Hao, KANG Qin, ZHONG Yong, ZHANG Zeyu

2026, 47(1): 71-79. doi: 10.7513/j.issn.1004-7638.2026.01.008

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The microstructure and texture evolution of TB13 titanium alloy wire were investigated by multi-pass hot drawing (total deformation of 74.4%) combined with different gradient annealing processes (710-740 ℃). The results show that with the increase of hot drawing reduction, the alloy undergoes a transformation from work hardening dominated to dynamic recrystallization softening. Annealing temperature has a gradient regulation effect on the static recrystallization process. Low-temperature annealing (710-720 ℃) is mainly a recovery process, with strength maintained at 810-785 MPa, but the elongation is relatively low, only 22%-24%. Medium-high temperature annealing (730-740 ℃) achieved a good strength-plasticity match of 736-760 MPa in strength and 29%-31% in elongation through recrystallization texture reconstruction and dislocation density reset. Texture analysis shows that hot drawing induces a strong <101> // drawing direction wire texture (orientation density of 4.9), while annealing treatment achieves multi-component weak texture (<212>/<001>/<111> orientation density of 2.28-2.74) through recrystallization texture reconstruction, reducing the anisotropic characteristics.

Preparation of low-cost Ti-4.5Al-xMo-2Fe alloy based on thermite reduction and the effect of Mo content on its properties

CHEN Guangrun, MA Lan, YANG Shaoli, XIAO Jian, ZHANG Yang, ZENG Li

2026, 47(1): 80-88. doi: 10.7513/j.issn.1004-7638.2026.01.009

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Abstract:
Titanium alloys are widely used in aerospace and marine engineering owing to their high specific strength, excellent corrosion resistance, and good high-temperature stability. However, the conventional production routes are energy-intensive and costly, which limits their broader application. In this study, high-titanium slag and titanium dioxide were employed as raw materials, and a Ti–Al-based intermediate alloy was first produced via aluminothermic reduction. After refining and composition adjustment, a Ti-4.5Al-xMo-2Fe near-α titanium alloy was obtained. The effects of Mo content (0, 1.5%, 3%, 4.5%) on the microstructure and properties were systematically investigated. The results show that this short-process method can successfully produce Ti-4.5Al-xMo-2Fe alloys with uniform microstructures. With increasing Mo content, the lamellar α phase becomes significantly refined and β phase precipitation is promoted, leading to increased hardness and density. After hot compression deformation, the alloy containing 3% Mo exhibits the best hot workability at 850 °C, a strain rate of 0.01 s⁻¹, and 50% deformation.

The investigation of Mo alloying on the electrochemical behaviour of pure Ti

GAO Qiang, TENG Aijun, KANG Qiang, WANG Peng, WANG Jibing

2026, 47(1): 89-93. doi: 10.7513/j.issn.1004-7638.2026.01.010

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The effect of pure Ti alloyed with different Mo content on the microstructure and electrochemical behaviour was studied for the need of further improvement in corrosion resistance and conductivity of titanium bipolar plates in proton exchange membrane water electrolysis environments. Results indicated that the volume fraction of β phase increased, the grain size of α phase decreased, and the corrosion resistance was improved with the increase of Mo content. The warburg impedance appeared in the low frequency region of impedance spectroscopy obtained at open circuit potential (OCP). When the Mo content was below 1.0%, there were many corrosion pits on the surface after electrochemical corrosionthe. Passivation film formed by polarizing at 1.0 V vs Ref for 4 hours exhibited n-type semiconductor behavior, and the conductivity increasesd with Mo content greater than 1.0%.

Effect of straw charcoal as a “Carbon Neutral” carbon source on the melting behavior of mold flux

SHANGGUAN Duanyan, XU Yuhong, GUO Zhipeng, HAO Ziyi, LI Tao, TAN Min, GU Shaopeng

2026, 47(1): 94-101. doi: 10.7513/j.issn.1004-7638.2026.01.011

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Carbonaceous materials are one of the essential components in mold flux, mainly serving to regulate its melting behavior. Under the background of the “dual carbon” strategy, conventional carbon materials exhibit high contents of fixed carbon, nitrogen, and sulfur, resulting in excessive emissions of CO₂, NO_x, and SO₂, which pose serious environmental concerns. Moreover, their non-renewability and high cost further limit their sustainable application. Therefore, it is urgent to explore the renewable and environmentally friendly alternatives. The research proposed a “carbon-neutral”, renewable and abundant solid waste, straw charcoal, as a new type of carbon source for protective slag. The respective basic physical properties of carbon black C611 and straw charcoal were investigated, and the influence of carbon types and contents on the melting behavior of mold fluxes were systematically analyzed. The results indicate that straw charcoal possesses a higher specific surface area and larger average particle size than carbon black C611, though its fixed carbon content is relatively lower. With increasing straw charcoal content, the softening temperature, melting temperature, and flowing temperature of mold flux increase noticeably, with the melting temperature being the most affected. As the carbon content of straw increases, the melting rate of the mold flux decreases. When the carbon content is 8%, the control effect of straw charcoal on the melting rate of the protective residue is the same as that of carbon black C611.

Research on the effect of refined steel slag waste on the electrical properties of conductive asphalt mixtures

LUAN Liqiang, SHI Yunsheng, CHEN Yaopeng, LI Xiaolong

2026, 47(1): 102-111. doi: 10.7513/j.issn.1004-7638.2026.01.012

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To address the issue of insufficient resistivity stability in conductive asphalt mixtures under temperature variations, loading, and microcrack damage, which affects snow/ice melting efficiency, conductive refined waste steel slag was introduced. Carbon fiber-reinforced conductive asphalt mixtures with varying replacement ratios of fine steel slag were prepared to investigate the changes in electrical properties under thermosensitive and pressure sensitive effect as well as microcrack damage. The conductive mechanism was analyzed at the microscopic level. The results indicate: ①Fine steel slag effectively suppresses the rapid resistivity increase caused by the Positive Temperature Coefficient（PTC）effect in subzero environments, with a maximum suppression level of 54%. ②Under 10 cycles of standard axle loading, the number of resistivity spike fluctuations gradually decreases to zero as the replacement ratio of fine steel slag increases. When the replacement ratio of steel slag aggregate reaches 75%, a stable composite conductive network forms in synergy with 0.3% carbon fiber. The uniform distribution of steel slag significantly stabilizes and mitigates abnormal resistivity spikes in conductive asphalt mixtures. ③Under three types of prefabricated microcracks （1 mm microcracks, 2 mm macrocracks, and damage-induced cracks）, the replacement ratio of fine steel slag exhibits a negative correlation with resistivity growth rate and a positive correlation with healing-induced resistivity recovery rate. At the 100% steel slag replacement ratio under damage-induced cracking, the resistivity growth rate before crack healing was 42.6%, while the post-healing recovery rate reached 96.2%. Compared to the control group, it represents an effective reduction of 0.19 in resistivity growth rate and an improvement of 0.177 in recovery rate. Damage-induced cracks demonstrated the highest resistivity growth amplitude and the most optimal recovery capability compared with the other two crack conditions.

Resource recovery from vanadium-extracted wastewater and high-magnesium desulfurization wastewater via synergistic magnesium ammonium phosphate precipitation

ZHOU Suying, GAO Hui, SUN Xiaohui, CHEN Xiangsheng, DONG Mengge, XUE Xiangxin

2026, 47(1): 112-120. doi: 10.7513/j.issn.1004-7638.2026.01.013

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Vanadium production generates significant quantities of “triple-high” complex vanadium-extracted wastewater (high in ammonia-nitrogen, hexavalent chromium, and salt) from sodic roasting vanadium extraction, alongside magnesium-rich desulfurization effluent from flue gas desulfurization. These effluents pose significant resource and environmental challenges. Traditional separate treatment methods for these wastewater face challenges of large land occupation and high maintenance costs. This study proposes a struvite-driven co-treatment strategy aimed at the preliminary treatment process, where vanadium-extracted wastewater serves as the nitrogen source and desulfurization wastewater provides magnesium for struvite precipitation. Under optimal conditions (pH = 9.5, n(Mg):n(N) = 1.8, n(P):n(N) = 1.5, reaction time = 15 min) with in-progress precipitation pH adjustment mode. The process enabled recovery of NH₄⁺–N (97.72%) and Mg²⁺ (86.62%), and precipitated Cr-free struvite (73.24%) and hazenite (23.75%), highlighting its dual-resource recycling capability. Additionally, the process reduced chemical usage by 22%-60% and minimized land occupation, thereby reducing the treatment load of subsequent high-salt wastewater. This research provides a new and efficient strategy for the resource utilization of wastewater generated by vanadium plants.

Research on the preparation and hydration mechanism of the high-titanium blast furnace slag based cementitious material with low carbon emission

YANG Tingting, ZOU Ruiqi, YANG Zhiyuan, AO Jinqing, SHI Enze, YANG Yuanyi

2026, 47(1): 121-129. doi: 10.7513/j.issn.1004-7638.2026.01.014

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To achieve a lower carbon footprint for cementitious materials in concrete and promote the further efficient and high-value utilization of high-titanium blast furnace slag (HTBFS), a novel low-carbon HTBFS-based cementitious material was developed by using a composite mineral admixture of HTBFS powder (HTBFSP), lithium slag powder (LSP), and silica fume (SF) as a partial replacement for cement. Effects of mix proportions, along with mechanical and chemical activation methods on the physical and mechanical properties of this low-carbon HTBFS-based cementitious material were investigated, and its hydration mechanism was analyzed. The results showed that both mechanical activation and chemical excitation could increase the early and later-age strength of the low-carbon HTBFS-based cementitious material. At a mix proportion of 70% cement, 21% HTBFSP, 6% LSP, 3% SF, and 2% Ca(OH)₂, the compressive strength ratios reached 82.01% at 7 days and 97.21% at 28 days. The hydration reactivity of LSP was enhanced through the mechanical activation, a process that converted mechanical energy into surface energy. Meanwhile, a synergistic effect was achieved between the alkaline activation from Ca(OH)₂ and the sulfate activation from the LSP, which further stimulated the secondary hydration reaction of the composite mineral admixture.

Effects of rare earth ferrosilicon additions on microstructure and mechanical properties of 45^# steel large ingots

MAN Ning, LI Xin, WANG Jiayi, FAN Jianglei, WEI Shizhong

2026, 47(1): 130-139. doi: 10.7513/j.issn.1004-7638.2026.01.015

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Two 45^# carbon steel ingots with dimensions of 300 mm × 300 mm × 400 mm were prepared by the lost foam casting method, with rare earth ferrosilicon additions of 0.15% and 0.35% respectively. A quarter section of each ingot was sampled along the Y-axis from the center to the bottom. SEM observations shows the microstructure of ingots consist primarily of ferrite and pearlite. From the core to the bottom, the ferrite volume gradually increases while the pearlite decreases, accompanied by a progressive reduction in ferrite size. Additionally, when the rare earth ferrosilicon additions is increased from 0.15% to 0.35%, the overall solute element (Mn,Si) content in the ingots increases, which significantly increases ferrite volume and improves pronounced structural refinement. Mechanical property test results indicates a gradual decrease in both properties from the center to the bottom in both ingots, demonstrating a positive correlation between hardness/tensile properties and pearlite content. Further analysis reveals that compared to the 0.15% addition, the 0.35% rare earth ferrosilicon addition enhances the hardness and tensile properties of the ingot while increasing the solute element content. Consequently, the increase in solute element content resulting from the higher rare earth ferrosilicon addition exerts an important influence on hardness and tensile properties.

Study on improving the performance of vanadium-titanium magnetite oxidized pellets with limonite

LING Xinke, HU Peng, LIN Wenkang, XIE Hongen, PU Shuiqiang, ZHU Fengxiang, HU Meng

2026, 47(1): 140-148. doi: 10.7513/j.issn.1004-7638.2026.01.016

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To improve the compressive strength of vanadium-titanium magnetite oxidized pellets, this study systematically investigated the effects of limonite addition on the quality of green pellets, compressive strength of fired pellets, metallurgical properties, and bentonite dosage ratio through comprehensive pelletizing experiments. The underlying mechanism of limonite in strengthening the compressive strength of vanadium-titanium magnetite oxidized pellets was elucidated through analysis of volume changes and phase composition during the roasting process. Experimental results demonstrate that limonite significantly enhances both green pellet and fired pellet quality. With increasing limonite content, the compressive strength of green pellets, drop resistance frequency, and compressive strength of fired pellets exhibited a progressive improvement. Notably, when the limonite addition reached 9%, the fired pellets achieved a compressive strength of 3514 N/pellet. The study further revealed that increasing limonite content reduced T₁₀, T₄₀, and softening temperature range while expanding the melting temperature range, with the Reduction Swelling Index (RSI) remaining relatively stable. When substituting bentonite with limonite, green pellet quality showed a gradual decline, and the compressive strength of fired pellets initially increased before decreasing, though remaining consistently higher than baseline values. Appropriate limonite addition was found to enhance low-melting-point phases and porosity in pellets, promote faster and more uniform magnetite oxidation rate, optimize pore distribution with reduced cracks, and ultimately improve fired pellet strength. These findings provide critical insights for optimizing vanadium-titanium magnetite pellet production through strategic limonite utilization.

Study on crystallization and heat transfer performance of solid slag film in mold flux for titanium-bearing microalloyed steel

LIU Guoqi, XU Ziqian, SI Xulin, KONG Qichang, HUANG Weili, WANG Xingjuan

2026, 47(1): 149-156. doi: 10.7513/j.issn.1004-7638.2026.01.017

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The solid slag film of mold flux is a key medium between the mold and the continuous casting slab. Based on the solid slag film of mold flux for Ti-containing microalloyed steel prepared by a slag film heat flux simulator, the physical properties of the slag film, such as thickness, porosity, and roughness, were analyzed. XRD, scanning electron microscopy (SEM), and mineral phase microscopy were used to analyze the crystallization performance of the slag film. In addition, the heat transfer properties of the slag film, including thermal resistance and heat flux density, were studied. The results show that the surface roughness of the slag film is formed at the initial stage of solidification of the solid slag film and is significantly affected by the temperature of the liquid slag. The solid slag film has a two-layer structure: glassy and crystalline, with perovskite as the main mineral phase. At the initial stage when the copper probe is immersed in the liquid slag, the heat flux density increases rapidly. When the water-cooled copper probe is immersed in the liquid slag for 13 seconds, the heat flux densities of the mold flux reach their maximum values, which are 0.988 MW·m⁻², 1.208 MW·m⁻², and 1.355 MW·m⁻² respectively. With the increase of the immersion time of the copper probe, the solid slag film gradually thickens, the thermal resistance increases, and the heat flux density decreases gradually.

Effect of thermal deformation behavior on manganese sulfide inclusions in hot-rolled 20MnCr5 gear steel bars

WANG Xuhui, YANG Jian, ZHANG Qingsong, LI Wenhao, YIN Qing, WANG Weikun, ZHANG Mei

2026, 47(1): 157-164. doi: 10.7513/j.issn.1004-7638.2026.01.018

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The control of MnS inclusions is the key to the development of high-quality gear steel. In this paper, a Gleeble-3500 thermomechanical simulator was used to carry out single-pass hot compression experiments to investigate the hot deformation behavior of MnS inclusions in 20MnCr5 gear steel hot-rolled bars with a strain rate of 1.0 s^-1, deformation strains of 15%~50%, and deformation temperatures of 900~1100 ℃. At the same time, the effects of deformation ratio and deformation temperature on the size, aspect ratio morphology and relative plasticity of MnS and its composite inclusions were systematically studied. The results showed that the fragmentation degree of MnS inclusion changes periodically with deformation ratio and temperature. At 30% deformation ratio, with rising temperature, the relative plasticity of MnS inclusion first decreases from 2.31 to 2.01 and then increases to 3.55. At 950 ℃, with the increase in deformation, the relative plasticity continuously decreases from 2.98 to 2.01, and then to 0.94. Combined with the change in aspect ratio, size, and relative plasticity of MnS inclusions, the optimal deformation temperature of 20MnCr5 gear steel is 900 ℃ at 30% strain, and the optimal deformation ratio is 50% at 950 ℃.

Comparative analysis of forming performance of 800 MPa grade galvanized dual-phase steels with different components

ZHANG Xi, TONG Lianjie, LIU Lixue, WANG Jiawei, WANG Hailong

2026, 47(1): 165-170. doi: 10.7513/j.issn.1004-7638.2026.01.019

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This study comparatively investigated the forming performance of two 800 MPa grade galvanized dual-phase steel systems, using metallographic analysis, uniaxial tensile testing, forming limit diagrams (FLDs), hole expansion tests, and local/global formability assessment diagrams. The study found that both dual-phase steels exhibited a ferrite-martensite dual-phase microstructure with a similar martensite fraction of ～50%. The high-carbon series dual-phase steel demonstrated a lower yield ratio (0.563), higher uniform elongation (15.65%), and a higher FLD₀ (0.236), but a lower hole expansion ratio (19.62%), making it suitable for complex structural components and parts demanding high drawability, such as B-pillars and longitudinal beam connecting plates. In contrast, the low-carbon series dual-phase steel, achieved through the addition of alloying elements such as Cr and Mo, resulting in a uniform, fine, and dispersed distribution of martensite islands, with a slightly higher yield ratio (0.58), lower uniform elongation (11.72%), and a lower FLD₀ (0.184), but a significantly higher hole expansion ratio (25.68%), making it more suitable for components requiring high local formability, such as flanging and hole expansion applications, including door sills, side rails, and seat side panels. This research provides a theoretical foundation and practical guidance for the material selection and application of 800 MPa grade galvanized dual-phase steel.

Study on the high-temperature oxidation behavior of high strength steels for photovoltaic applications

LIU Yujia, RAN Changrong, GUO Taixiong, JIN Yongqing, LI Qinglong, YU Hengxiang, CAO Guangming

2026, 47(1): 171-179. doi: 10.7513/j.issn.1004-7638.2026.01.020

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The high temperature oxidation behavior of high-strength steels S350GD and S420GD for photovoltaic applications was systematically studied by a high-temperature thermal gravimetric analyzer (TGA) under dry and humid atmospheres. X-ray diffraction (XRD) and electron probe microanalysis (EPMA) were used to characterize the phase composition, cross-sectional morphologies and element distribution of the oxide scales. The results show that the oxidation weight gain curves of both S350GD and S420GD follow a parabolic law. Compared to S350GD, the oxide scale formed on S420GD is thinner and exhibits a higher fraction of high-valence iron oxides. A silicon-enriched interfacial layer was detected at the oxide/metal substrate interface in S420GD, where SiO₂ and Fe₂SiO₄ phases synergistically reduce the diffusion coefficient of Fe²⁺ ions. When comparing oxidation under dry and humid atmospheres, both steels show similar oxides growth mechanisms; however, the oxide scales are thicker and the content of low-valence iron oxides is increased in humid environments. Moreover, the oxide scales formed under humid conditions contain a significant density of pores and microcracks, which act as fast diffusion pathways for ionic species, thereby accelerating the oxidation process.

Effect of intercritical annealing holding time on microstructure and properties of medium manganese steel in I&Q&P process

LAN Guinian, XIE Jiaxuan, YAN Bowei, LIU mingbo, LI Hongbin, YANG Yinye, ZHOU Chaogang

2026, 47(1): 180-188. doi: 10.7513/j.issn.1004-7638.2026.01.021

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Abstract:
The microstructural evolution and mechanical properties of hot-rolled 6Mn medium manganese steel subjected to a critical intercritical annealing–quenching–partitioning (I&Q&P) process were investigated using SEM, XRD, tensile testing, and Thermo-Calc software with the DICTRA module. Annealing durations of 10, 30, and 60 minutes were employed to elucidate the effect of annealing time on phase transformation behavior and mechanical performance of the studied steel. The results show that as annealing time prolongs, the microstructure gradually transforms from initial blocky ferrite and martensite to lath martensite with finely dispersed retained austenite. The volume fraction of retained austenite increases from 17.6% with 10-minutes holding time to 21.1% with 60 minutes holding time, while its carbon content rises from 0.78% to 1.31%. DICTRA simulations reveal that as the annealing time extends, the γ/α phase interface broadens continuously, and Mn partitioning into austenite forms a concentration gradient, significantly enhancing austenite stability. After annealing for 60 minutes, the specimen exhibits optimal mechanical properties, with an ultimate tensile strength of 1121 MPa, total elongation of 29.1%, and a product of strength and elongation (PSE) of 32.6 GPa·%.

Study on submerged arc welding process and weld microstructure and properties of bimetallic composite pipes

YANG Jun, BI Zongyue, ZHU Lei, WAN Renyuan, WANG Xueyi

2026, 47(1): 189-196. doi: 10.7513/j.issn.1004-7638.2026.01.022

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Abstract:
The microstructures of the composite interface of the hot-rolled coil and the weld joint of the composite pipe were observed using an optical microscope (OM) and a scanning electron microscope (SEM). The line distribution curve of the element content change at the interface was determined by energy dispersive spectrometer (EDS) line scanning test, and the distribution of elements in different micro-regions of the fusion zone of the composite pipe weld joint was measured by EDS mapping analysis. Meanwhile, tensile test, Charpy impact test, bending test, microhardness test and corrosion test were carried out on the weld joint of the composite pipe. The results indicate that the submerged arc welding (SAW) process can be successfully used for the commercial production of 304/Q235B Ø610 mm×(6+1) mm composite pipes. The microstructure of the cladding weld of the composite pipe is a duplex structure consisting of acicular austenite + banded or worm-like ferrite, while the base weld exhibits a duplex structure of reduced proeutectoid ferrite + acicular ferrite. All mechanical properties including weld strength, low-temperature toughness, microhardness, and plastic deformation, as well as intergranular corrosion resistance, fully meet the requirements specified in the national standard GB/T 31940-2015 bimetallic composite corrosion-resistant steel pipes for fluid transport. Therefore, this research results can be used as a theoretical reference and technical support for the commercial production of high-quality bimetallic composite pipes.

Current Issue 2026 Vol. 47, No. 1

Current Issue
2026 Vol. 47, No. 1