钢铁钒钛

Effects of electroshocking treatment on residual stress and fatigue properties of titanium alloys

SONG Zhengjie, GUO Shuai, ZHANG Jian, WANG Feng, QIAN Dongsheng, LI Kuo, ZHAO Longzhe

2026, 47(2): 1-8. doi: 10.7513/j.issn.1004-7638.2026.02.001

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Abstract:
Regulating residual stress and optimizing stress distribution in metallic materials is crucial for enhancing fatigue performance. This study systematically investigates the effects of electroshocking treatment (EST) on the residual stress regulation and vibration fatigue properties of TC11 titanium alloy. The results demonstrate that EST significantly homogenizes the surface and gradient macroscopic residual stress without significantly altering the phase structure. XRD and EBSD analyses reveal that after EST, the dislocation density is reduced by 9.68%, the standard deviation of the KAM value is decreased by 20%, the microstrain is effectively mitigated, and the stress concentration zones are substantially eliminated. Vibration fatigue tests confirm that the average fatigue life of the specimens is remarkably improved from 4.55×10⁵ cycles to 3.60×10⁶ cycles. Further HRTEM analysis verifies that the energy generated by EST can drive atomic rearrangement in stress concentration regions, thereby reducing dislocation density and alleviating lattice distortion. In summary, EST provides an efficient and novel strategy for precise residual stress regulation and fatigue performance enhancement of TC11 titanium alloy.

Simulation analysis and process optimization of residual stress and machining deformation in the manufacturing of thin-walled titanium alloy rings

WANG Tianle, DENG Jiadong, QIAN Dongsheng, DING Zuojun, LIU Chao

2026, 47(2): 9-17. doi: 10.7513/j.issn.1004-7638.2026.02.002

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Thin-walled titanium alloy rings are critical aerospace components, whose machining deformation severely restricts their dimensional accuracy and service reliability. A full-process finite element model covering rolling, cooling, heating, bulging and heat treatment was established for rectangular thin-walled titanium alloy rings, to systematically investigate residual stress evolution during forming and its effect on machining deformation. The regulation mechanism of bulging on the stress field was revealed by analyzing stress distribution under different bulging parameters, and a theoretical model correlating residual stress and machining deformation was constructed and verified via simulation and experiments. Results show that residual stress mainly originates from the initial cooling stage, and subsequent bulging and heat treatment can significantly reduce stress amplitude and improve distribution uniformity. The optimal residual stress state is achieved at a bulging ratio of 4% and a bulging temperature of 800 °C. Simulation results are in good agreement with theoretical calculations, with a maximum error of 20.37%. The optimized process and model were validated effective for special-shaped rings, providing a theoretical basis and process guidance for residual stress regulation and deformation control of titanium alloy thin-walled rings.

Constitutive modeling and hot processing map of Ti551 alloy in the α+β two-phase region

CHENG Zhicheng, JIANG Huan, WU Jiali, DENG Qinghua, ZHU Xueli, ZHANG Hongling, MA Yingjie

2026, 47(2): 18-28. doi: 10.7513/j.issn.1004-7638.2026.02.003

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Abstract:
As a base material for additive forging processes, a novel titanium alloy Ti551 had been used to conduct hot compression via a Gleeble 3500 thermo-mechanical simulator, and then flow stress curves were obtained over a strain rate range of 0.001～ 10 s⁻¹ and a temperature range of 700～ 900 ℃ in this study. The flow stress curves were fitted using a strain-compensated Arrhenius model and an artificial neural network model, respectively. The strain-stress curves indicate that during deformation in the two-phase region, the flow stress of the Ti551 alloy exhibits a typical post-peak softening behavior under medium-to-low temperatures and high strain rates. Compared with predicated results from the strain-compensated model, the artificial neural network model gives higher prediction accuracy and lower average absolute relative error under low-temperature and high strain-rate conditions, with a correlation coefficient R of 0.9922 and a mean average absolute relative error of 6.3%. Based on the constructed hot processing map of the Ti551 alloy deformed in the two-phase region, the plastic instability domains under different strain conditions were identified. The lower limit of equivalent strain rate during forging in the α+β two-phase region should be no less than 0.01 s⁻¹, corresponding to an actual forging speed of not less than 10 mm/s, and that the final forging temperature should be no lower than 750 ℃. These finds can help design practical forging parameters and numerical simulation of Ti551 alloy in the α+β two-phase region.

A study on the melting process of novel Ti551 titanium alloy using VAR numerical simulation

LUO Kun, ZHENG Youping, GENG Naitao, YOU Yanjun, LI Jingmao

2026, 47(2): 29-36. doi: 10.7513/j.issn.1004-7638.2026.02.004

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Abstract:
To meet the demand for pressure-resistant materials in deep-sea equipment, this study investigated the melting process of a novel α+β titanium alloy Ti551 based on Vacuum Arc Remelting (VAR) numerical simulation. By optimizing parameters through numerical simulation, the melting process was directly scaled up from a 150 kg model to produce 3-ton industrial-scale ingots via VAR. The results demonstrate the successful production of high-purity, highly homogeneous 3-ton Ti551 industrial ingots. The study focused on the effects of melting current and arc-stabilizing current on compositional homogeneity and pool profile, identifying reduced melting current as the optimal parameter. Through comparative experiments of five different melting processes, it was concluded that the optimized process conditions—a melting current of 21~24 kA, an arc-stabilizing current of 15 A, and an AC arc stabilization time of 30 s—yielded the best results. Based on this optimized process, the produced 3-ton industrial ingots exhibited a smooth surface free from defects such as cold shuts, subsurface porosity, and slag inclusions. The ingots demonstrated good compositional uniformity, with the range of key elements including Cr, Fe, Sn, V, and Zr all within 0.03, indicating no significant macrosegregation. The overall properties meet the stringent requirements for raw materials used in deep-sea equipment.

Study on melting simulation of Ti551 alloy ingots with spatial coordinate transformation based on MeltFlow-VAR

ZHU Zhenze, ZHOU Siyuan, ZHANG Yifan, YANG Guoqing, ZHANG Hongling, MA Yingjie

2026, 47(2): 37-45. doi: 10.7513/j.issn.1004-7638.2026.02.005

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Abstract:
Vacuum arc remelting (VAR) is the key technology for the preparation of titanium alloy ingots. However, traditional processes struggle to precisely control the coupling effect of multi-physical fields, which easily leads to compositional segregation of ingots. In this paper, melting simulation research was carried out on Ti551 alloy with a target composition of Ti-5.3Al-1.5Mo-1.0V-1.0Sn-1.0Zr-1.0Cr-0.1O-0.15Fe. The MeltFlow-VAR software was adopted to simulate the solidification segregation of Ti551 titanium alloy, and four melting cases with spatial coordinate transformation were designed for Ti551 alloy ingots. By simulating the melting processes of primary and secondary ingots, the distribution characteristics of alloying elements such as Al, Mo and V under different cases were analyzed. The results show that obvious elemental segregation exists in the primary Ti551 ingot. Al, Mo and O exhibit negative segregation, while V, Sn, Zr and other elements present positive segregation, and the segregation is mainly concentrated in the riser of the ingot head and the ingot tail. Among the four cases, the cutting and welding cases have the optimal effect on improving the compositional uniformity in the middle of the ingot. Case 2 enables the elemental content in the middle region to be closer to the standard values, and case 4 effectively weakens the element concentration fluctuation of large-size long ingots. The traditional head-to-tail inversion method cannot fundamentally eliminate segregation defects, whereas the restructured melting based on spatial coordinate transformation can break the original segregation distribution pattern. In addition, Mo features a high melting point and high density with prominent negative segregation during VAR processing. The reconstruction methods including cutting and welding can regulate the transport and redistribution mechanism of Mo in the molten pool, which effectively optimizes the compositional uniformity in the middle of ingots. This study provides a technical reference for the segregation control of high-melting-point elements and the improvement of finished product rate of titanium alloy ingots.

Effect of annealing temperature on the microstructure and mechanical properties of Ti551 alloy forgings

LI Jiaqiao, WANG Yunfeng, GUO Yifeng, JIA Zhen, XU Bin, MA Yingjie, SUN Mingyue

2026, 47(2): 46-54. doi: 10.7513/j.issn.1004-7638.2026.02.006

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Abstract:
To clarify how annealing temperature regulates the microstructure–texture–property anisotropy in hot-forged titanium alloys, a near-α titanium alloy forged at 920 °C was selected as the research object and annealed in the range of 910~950 °C. Texture evolution was characterized by electron backscatter diffraction(EBSD) combined with α/β pole figures, and room-temperature tensile and impact properties were evaluated along the longitudinal direction(LD) and normal (thickness) direction (ND). The results show that the microstructure at 910~920 ℃ is dominated by primary α (α_p) with a relatively low fraction of secondary α (α_s). With increasing annealing temperature to 930~950 ℃, the microstructure gradually transforms into a bimodal structure, and orientation-consistent blocky regions of α_s become more pronounced. As the annealing temperature increases, the intensity of the {0001} pole figure of α phase increases progressively, while the {110} pole figure of β phase also exhibits a trend toward stronger orientation concentration. In terms of mechanical properties, the ultimate tensile strengths along LD and ND remain close with minor fluctuations, whereas the directional differences in yield strength and ductility are more sensitive. Anisotropy is more pronounced in the equiaxed regime but is effectively improved in the bimodal regime. The as-forged condition shows relatively large anisotropy, which is alleviated after annealing. The absorbed impact energy is generally higher along LD than along ND; however, the LD–ND difference converges markedly with increasing annealing temperature. A favorable strength–toughness balance with reduced anisotropy can be achieved at 950 ℃. These trends are attributed to enhanced transformation-variant selection and basal-texture strengthening caused by α_p dissolution and β-grain growth during sub-β-transus (T_β) to near-T_β annealing, as well as the combined constraint effects of multiscale interfaces/grain boundaries in the bimodal microstructure on deformation accommodation and crack propagation paths.

Effect of double annealing on microstructure and mechanical properties of near-α titanium alloys

YANG Ruize, LUAN Chao, HE Wenxuan, LI Xuqing, GUO Yifeng, XU Bin, SUN Mingyue

2026, 47(2): 55-62, 131. doi: 10.7513/j.issn.1004-7638.2026.02.007

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Ti6321 alloy, a near-α titanium alloy independently developed in China, has become a key structural material for marine engineering because of its high strength, high toughness and outstanding seawater-corrosion resistance. Nevertheless, under conventional heat treatment its strength and ductility are difficult to balance, restricting its use in deep-sea extreme environments. In this work, ship-grade Ti6321 alloy was subjected to single annealing (970, 980, 990, 1000 ℃ for 2 h, air cooled) and duplex annealing (980 ℃ for 2 h, air cooled, then 550 ℃ or 600 ℃ for 2 h, air cooled). The effects of these annealing routes on microstructure and mechanical properties were systematically investigated by optical microscopy (OM), scanning electron microscopy (SEM) and mechanical testing. The results revealed that single annealing produced the typical α+β two-phase microstructural evolution, with the best strength–toughness combination obtained at 980 ℃. Duplex annealing refined the microstructure by precipitating secondary α phases within and along the boundaries of the β-transformed structure, annealing treatment at 980 ℃ + 550 ℃ markedly increased both strength and toughness. This study provides a theoretical basis for optimizing the heat treatment process of Ti6321 alloy for marine engineering applications.

The influence of hot rolling deformation on recrystallization and texture evolution of Ti551 alloy

WANG yunfeng, LUO jinru, GUO yifeng, WANG yueqian, YUE junying, WU jinhao

2026, 47(2): 63-70. doi: 10.7513/j.issn.1004-7638.2026.02.008

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As a representative thermomechanical processing step, hot rolling can generate texture evolution that is critical to the strength–ductility synergy of titanium alloys. Ti551 is a newly developed medium-strength, high-toughness alloy designed for deep-sea service; however, its texture-evolution behavior during rolling remains unclear. In this work, Ti551 as-forged billets were hot rolled at near β-transus temperature region (T_β, 950 ℃) with reductions from 5% to 50%. Electron backscatter diffraction (EBSD) was used to quantitatively analyze the fractions of low-angle grain boundaries (LAGBs), grain orientation spread (GOS) and the evolution of α {0001} texture. The results show that, taking the annealed condition (0 reduction) as the reference, when the cumulative reduction increases from 0 to 30%, the area fraction of recrystallized/strain-relieved regions decreases from ~55% to ~36%, and remains nearly unchanged as the reduction is further increased to 50%. In addition, hot rolling develops a basal texture, but its overall intensity decreases with increasing reduction (i.e., the peak intensity drops and the texture becomes more diffuse). These finds indicate that under near T_β condition, when the rolling direction is perpendicular to the dominant texture direction of the forged billet, a higher cumulative reduction is more effective in weakening the basal texture and dispersing the orientation peaks. This can help select the final-pass reduction to obtain a basketweave microstructure with smaller orientation-cluster length scales and improved microstructural uniformity.

Optimization of heat treatment process for Ti551 titanium alloy based on phase transformation regulation

WANG Yongfeng, SHEN Yubo, ZHANG Hongling, LUAN Baifeng, ZHOU Siyuan, MA Yingjie

2026, 47(2): 71-77. doi: 10.7513/j.issn.1004-7638.2026.02.009

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The effects of heat treatment parameters including solution temperature, aging temperature and cooling rate on the microstructure and mechanical properties of a new medium-strength and high-toughness Ti551 alloy were investigated by means of optical microscopy, scanning electron microscopy and universal tensile testing machine. With the same solid solution temperature at 900 ℃, no obvious changes were observed in the content and size of primary α phase of alloy, while the lamellar thickness of secondary α phase increased from 0.26 μm to 0.42 μm with the aging temperature increasing from 550 ℃ to 650 ℃. With the same aging temperature of 550 ℃, the content of the primary α phase decreased from 45% to 15% as the solution temperature increased from 900 ℃ to 950 ℃, along with continuous refinement of grains and morphological transformation from short rod-like to equiaxed. The lamellar thickness of the secondary α phase increased accordingly, reaching up to 0.72 μm after alloy subject to solid solution treatment at 950 ℃. The morphological feature and size of the microstructure are decisively influenced by the cooling rate: an almost single fully equiaxed primary α phase microstructure is obtained by furnace cooling, whereas the primary α phase is refined and the precipitation of coarse lamellar secondary α phase is promoted by moderate cooling. The results show that optimal strength-toughness combination of the Ti551 alloy is achieved under the composite heat treatment of 900 ℃×2 h+ air cooling, then followed by 550 ℃×6 h aging, which is closely associated with the regulatory role of cooling rate. Acicular secondary α phase can be induced in the transformed β microstructure by higher cooling rate, and the alloy’s strength-plasticity matching effect is further enhanced by the subsequent aging treatment.

Study on the hot-deformation behavior and hot processing map of Ti551 alloy

SHEN Ziyang, DENG Jiadong, QIAN Dongsheng, DING Zuojun, LIU Chao

2026, 47(2): 78-87. doi: 10.7513/j.issn.1004-7638.2026.02.010

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To investigate the hot deformation behavior of Ti551 titanium alloy, isothermal compression tests were conducted at temperatures ranging from 800 ℃ to 950 ℃ and strain rates between 0.01–1 s⁻¹. Based on the true stress–true strain data, the hot deformation characteristics of Ti551 titanium alloy were systematically analyzed. The results indicate that the flow stress of the Ti551 titanium alloy is highly sensitive to variations in temperature and strain rate. An Arrhenius-type constitutive model incorporating strain compensation was established to describe the hot deformation behavior of the alloy, and the predictive capability of the model was evaluated. Furthermore, processing maps were constructed using the Prasad instability criterion, revealing the distribution characteristics of power dissipation efficiency and instability domains as functions of temperature and strain rate. The optimal hot processing window for the Ti551 titanium alloy was identified as the high-temperature and low-to-medium strain rate region, while potential flow instability regions were located in the low-temperature and high strain rate domain. In addition, the evolution of primary α-phase morphology and the variation in the α/β phase fraction under different deformation conditions were investigated. These results provide a theoretical basis for the design of hot working process parameters and the microstructure–property optimization of Ti551 titanium alloy.

Effect of cooling methods on the microstructure and mechanical properties of marine engineering titanium alloy ring components

HE Wenxuan, LUAN Chao, LI Kuo, GUO Yifeng, XU Bin, SUN Mingyue

2026, 47(2): 88-96. doi: 10.7513/j.issn.1004-7638.2026.02.011

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This study systematically investigates the influence of three cooling methods—oil cooling (OC), wind cooling (WC), and sand cooling (SC)—on the microstructure and mechanical properties in large-scale ring-rolled near-α titanium alloy components. Experimental results demonstrate that the strength of specimens heat-treated at 980 ℃ shows no significant variation across different cooling methods. This is primarily attributed to the low volume fraction of the β phase at this temperature, which minimizes the effect of cooling on the formation of the secondary α phase (α_s). Furthermore, the experiments revealed a marked decrease in impact energy following OC heat treatment, which is associated with the rapid cooling rate promoting the precipitation of the brittle martensite phase (α'). An optimal balance between tensile strength and impact toughness is achieved after WC heat treatment at 990 ℃. This phenomenon is mainly attributed to the low volume fraction of the primary α phase (α_p), the absence of brittle α' precipitation from the prior β phase, and the moderate width of the α_s laths. Additionally, SC heat treatment exhibits a faster cooling rate during the high-temperature stage and a slower rate during the low-temperature stage. Since the microstructural morphological features such as phase volume fraction and lath width in titanium alloys are mainly governed by the cooling rate at high temperature, the mechanical properties of SC-treated specimens lie between those of OC and WC.

Effects of build direction on mechanical properties and fatigue behavior of additively manufactured TC4 titanium alloy

WANG Yuxin, MA Tianhao, YANG Qiaofa, ZHOU Changyu

2026, 47(2): 97-106. doi: 10.7513/j.issn.1004-7638.2026.02.012

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This paper systematically investigates the tensile and uniaxial fatigue behaviors of TC4 titanium alloy, by laser powder bed fusion (L-PBF), with three building directions (0°, 12°, 16°) under room temperature. Tensile test results indicate that specimens built along 16° direction exhibit the best ductility at high strain rates. Small building direction variations significantly influence the mechanical properties of L-PBF TC4. A modified Hollomon model is proposed, to effectively integrate the effects of different building directions and strain rates on tensile behavior. This model demonstrates superior predictive capability compared to the Johnson-Cook (JC) model, accurately characterizing the tensile mechanical response of L-PBF TC4. Fatigue test results reveal that under higher applied strain amplitudes (0.8%, 1.0%), the specimens experience transient initial cyclic hardening followed by typical softening characteristics. In contrast, under lower applied strain amplitudes (0.4%, 0.6%), the initial hardening stage is absent, and the specimens directly enter a stable cyclic stage before rapid failure. Finally, a hybrid physics and data-driven VAE-ANN model is developed. All fatigue life predictions fall within the 2 times error band, accurately predicting the fatigue life of L-PBF TC4 under different building directions.

Experimental study of inclusions in CP-Ti EB ingot by electrolytic extraction

LI Yang, LIU Rui, BAI Yuliang, GUI Tianhao, SUN Yanhui

2026, 47(2): 107-115. doi: 10.7513/j.issn.1004-7638.2026.02.013

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The TA2 rolled and pickled coils produced by electron beam cold hearth melting (EBCHM) often exhibits surface peeling defects. To address this issue, this study extracted inclusions from TA2 ingots via electrolytic extraction and investigated their three-dimensional morphology, type, and size distribution using SEM-EDS, while their origins were also analyzed. A dissolution model for titanium oxides inclusion was developed using C code, and the removal mechanism and influencing factors were analyzed. Titanium oxides accounts for 86.84% of the inclusions in the ingots, followed by smaller quantities of Al₂O₃, composite inclusions, and high-density inclusions. The inclusion sizes predominantly range from 80 μm to 300 μm. During dissolution, the surface layer of titanium oxides undergoes phase transformation, forming a thin Ti₃O₅ layer. At 1720 ℃, complete dissolution of a 500 μm TiO₂ particle requires 466.67 s. The content of inclusions in the ingot is inversely proportional to the rolling surface quality. Increasing the melting temperature and reducing the melting rate are beneficial to improving the purity of the ingot and the rolling surface quality.

Research progress on advanced cutting technologies and cutting behavior of titanium alloys

HE Tongzheng, WU Jingxi, LI Zhixing, LUO Guojun, SHEN Xuanjin, TANG Liying, CHEN Yuyong

2026, 47(2): 116-131. doi: 10.7513/j.issn.1004-7638.2026.02.014

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As demand rises for high-performance titanium alloy components in the aerospace sector, cutting technologies encounter major hurdles in delivering high precision and quality. This paper presents a systematic review of the latest advances in titanium alloy cutting technology, along with an in-depth analysis of research methodologies in cutting and chip characteristics. Specifically, it focuses on elucidating how cutting parameters affect cutting performance and tool wear. It also summarizes tool wear modes alongside corresponding improvement strategies. Given the limitations of present study, this paper proposes future development directions for titanium alloy cutting technologies, aiming to provide guidance for enhancing the cutting efficiency and surface integrity of titanium alloy components and to lay a theoretical foundation for subsequent relevant research.

Distribution of inclusions with different compositions in the unsteady ladel exchange slabs of automotive outer panel

GAO Jinqiao, YANG Zhishun, ZHANG Yinhui, YANG Jian, GONG Jian, HUANG Fuxiang, PEI Xingwei

2026, 47(2): 132-142. doi: 10.7513/j.issn.1004-7638.2026.02.015

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In the present work, a statistical analysis of micro-inclusions and large-size inclusions was conducted in 31-meter-long unsteady ladel exchange slabs of two heats (A and B) of IF steel for automotive outer panels, combined with thermodynamic calculation of inclusion precipitation during the solidification process of continuous casting slabs using FactSage 8.1. Analytical results demonstrate that the main micro-inclusions larger than 5 μm are identified as Al₂O₃ inclusions, TiN inclusions and Al₂O₃+TiN composite inclusions, respectively. Typical large-size inclusions above 30 μm extracted in the ladel exchange slabs extracted by the large-sample electrolysis mainly include blocky and clustered Al₂O₃ inclusions of 100-200 μm, entrapped irregular mold flux particles of approximately 800 μm, SiO₂+Al₂O₃ inclusions with the sizes of 100-300 μm, and spherical calcium aluminate inclusions with the sizes of 30-100 μm. During the pouring of B furnace, there is a significant increase in the contents of four types of large inclusions in the transition slabs at 3 m before and 14 m after the start of pouring, and the contents of inclusions in larger size ranges increase more significantly. The average contents of SiO₂+Al₂O₃ inclusions, Al₂O₃ inclusions, entrapped mold flux and CaO+Al₂O₃ inclusions in the transition slabs are 13, 3, 3.5 and 7 times those in the normal slabs, respectively.

Constitutive modeling of high-temperature flow behavior of Fe-27Mn-10Al-1.0C lightweight steel based on the fields-backofen model

JIA Haishen, LIU Limei, GUO Wenjing, ZHANG Jilin, YI Xiangbin, LUO Wencui

2026, 47(2): 143-152, 163. doi: 10.7513/j.issn.1004-7638.2026.02.016

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To characterize the high-temperature flow behavior of Fe-27Mn-10Al-1.0C lightweight steel, high-temperature compression tests were performed using a Gleeble-3800 thermal simulation testing system under experimental conditions of 850-1050 ℃ and 0.01-10 s⁻¹. Based on the Fields-Backofen (FB) model, a constitutive modeling study was conducted using the experimental data. By introducing a temperature softening term and accounting for the strain effects as well as the coupling effects of strain, strain rate, and temperature on model parameters, a modified M-FB model was successfully established. The prediction accuracy of the M-FB model was validated using statistical parameters, including the correlation coefficient (R), average absolute relative error (AARE), and relative error (RE). The research results indicate that Fe-27Mn-10Al-1.0C lightweight steel is significantly sensitive to strain, strain rate, and deformation temperature. The predicted data of the M-FB model are highly consistent with the experimental data, and it can be reliably applied to predict its high-temperature flow behavior.

Distribution of inclusions along the width direction of continuous casting slab of ultra-low carbon automobile exposed panel

ZHANG Xuejiao, YANG Zhishun, YANG Jian, ZHANG Yinhui, ZHI Jianjun, WANG Ruizhi, FAN Zhengjie

2026, 47(2): 153-163. doi: 10.7513/j.issn.1004-7638.2026.02.017

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Ultra-low carbon steel is widely used for automobile exposed panels due to its excellent deep-drawing properties, but inclusions in continuous casting slabs can easily evolve into surface defects. In this study, two-strand continuous casting slabs for two heats with low Al and O contents and high Al and O contents are selected for ultra-low carbon steel of automobile exposed panel. Samples are taken at the 1/4 thickness, and at the positions of 2 cm from the edge, 1/4 width, and 1/2 width of the slab. The morphology, quantity, size, and spatial distribution of inclusions along different width positions are compared and analyzed using the Inclusion Automatic Analysis System (IAAS), to clarify the distribution law of inclusions along the width direction of continuous casting slab of ultra-low carbon steel automotive exposed panel. The results show that the inclusions in the slabs are mainly cluster-like, independent particles, or dispersed Al₂O₃, regular square TiN, and core-shell structure Al₂O₃-TiN composite inclusions. In terms of number density, small-sized TiN inclusions are enriched at the position 2 cm from the edge; large-sized Al₂O₃-TiN inclusions are enriched in the 1/4 width region; and the number density of large-sized inclusions in the heat with high Al and O contents is significantly higher. In terms of size distribution, Al₂O₃ has the largest average size; the high Al and O contents promote the formation and aggregation of Al₂O₃-TiN composite inclusions; TiN tends to be enriched at the edge of 2 cm position in small sizes. The spatial distribution shows that TiN inclusions have the highest number density and are mainly enriched at the edge; the composite inclusions reach their peak number density in the 1/4 width region; the number density of all types of inclusions in the 1/2 width position is generally reduced. Meanwhile, the number density of Al₂O₃ inclusions in the heat with high Al and O contents is higher than that in the heat with low Al and O contents.

Effect of replacing Australian low-alumina iron ore fines with specific high-alumina iron ore fines on high-temperature sintering properties

LIU Yongjun, XING Yapu, LUO Yaosheng, LIU Huayang, KOU Mingyin, WU Shengli, ZHOU Heng

2026, 47(2): 164-171. doi: 10.7513/j.issn.1004-7638.2026.02.018

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A type of high-quality low-aluminum iron ore fines（OE）from Australia has been served as one of the core raw materials in the production of domestic iron and steel enterprises. However, its reserves are gradually being depleted. OA iron ore fines have emerged as one of the potential alternatives to OE due to their favorable price advantage and abundant reserves. Nevertheless, OA iron ore fines exhibit a relatively high Al₂O₃ content. Therefore, how to efficiently utilize OA iron ore fines as a substitute for the low-aluminum OE has become a key research focus in the iron and steel industry. In this study, the mini-sintering method was employed to systematically investigate the variation patterns of the liquid phase fluidity index, intrinsic strength of bonding phase, and formation characteristics of calcium ferrite and high-alumina brittle phases in sintered blended ore after partial or complete replacement of OE with OA. Compared with OE iron ore fines, OA iron ore fines exhibit a higher assimilation temperature and better liquid phase fluidity, whereas their bonding phase strengths are relatively similar. As the OA replacement ratio for OE increases, the liquid phase fluidity index and intrinsic strength of bonding phase of the blended ore increase progressively, whereas the calcium ferrite content decreases correspondingly. X-ray diffraction (XRD) mineral phase analysis reveals that an increase in the OA replacement ratio results in a reduction in calcium ferrite content but an increase in high-alumina brittle phases. Given the high Al₂O₃ content of OA iron ore fines, excessive incorporation of OA tends to inhibit calcium ferrite formation and promote the formation of high-alumina brittle phases. Therefore, in practical production, precise control of the OA replacement ratio is essential to improve the sintering performance of high-aluminum blended ore and enhance the stability of subsequent blast furnace smelting.

Evolution of inclusions in Ce-containing particle-strengthened wear-resistant steel during the RH process

ZHANG Ke, LIU Zuoyu, WU Huajie, ZHANG Pengcheng, WU Huibin

2026, 47(2): 172-179. doi: 10.7513/j.issn.1004-7638.2026.02.019

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Oxygen and nitrogen content analysis, chemical composition detection, and inclusion scanning were performed on sample taken during the RH refining process to investigate the evolution of inclusions in the steel. The results show that inclusions in steel can be categorized into four types: oxides, sulfides, Ce-containing oxides ang oxysulfides, and Ti(C_xN_y) along with its complex inclusions. Ti(C_xN_y) and its complex inclusions can be further divided into Ti(C_xN_y) and complex inclusions consisting of Ti(C_xN_y) with oxides, sulfides, or rare earth Ce inclusions. The size of inclusions in the samples is primarily in the range of 1 to 2 μm. The RH refining process has little effect on the number density and size distribution of various Ti-containing inclusions. However, it significantly removes oxide inclusions, reducing their number density from 73 particles/mm² before RH treatment to 8 particles/mm² after soft blowing. The precipitation of sulfides is low, and their number density remains basically unchanged. After Ce addition, Ce oxides, Ce oxysulfides, and Ti-Ce complex inclusions appear. Ce-containing inclusions act as dispersed nucleation sites for inclusions tend to form smaller complex inclusions. Ce also modifies the inclusions in steel, lowering the content of high-melting-point oxide inclusions.

Cellular automaton simulation of austenite microstructure evolution in offshore steel during the heating process

GAO Xinliang, ZHANG Zhuangzhuang, LI Wenlong, WANG Chenyang, ZHAO Cong, YANG Zhinan

2026, 47(2): 180-188. doi: 10.7513/j.issn.1004-7638.2026.02.020

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Abstract:
To investigate the evolution law of austenite microstructure in offshore steel during the heating process, this study established a cellular automaton (CA) model for austenitic grain growth in offshore steel during heating based on the mechanisms of thermal activation energy, curvature-driven growth, and grain boundary energy dissipation. The effects of heating temperature and holding time on austenitic grain growth were analyzed. The results indicate that increasing the heating temperature provides a greater driving force for grain boundary migration, promoting grain boundary migration and grain coalescence, leading to an increase in austenite grain size. As heating time increases, the grains continue to grow, and the grain boundaries tend to become smoother. A prediction model for austenite grain growth of offshore steel was established, yielding a grain growth index of 0.45, and the correspondence between real time and simulation time was determined. The findings will provide theoretical support for the precise control of microstructure in offshore steel.

Influence of Mn/S ratio on inclusions and electrical conductivity of ultra-low carbon steel

YIN Haohui, LIU Man, GAN Xiaolong, XU Guang

2026, 47(2): 189-196. doi: 10.7513/j.issn.1004-7638.2026.02.021

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Abstract:
Ultra-low carbon steel is widely used in electrical engineering, automotive industry and other related fields, requiring excellent mechanical properties and electrical conductivity. In steel, FeS can induce the phenomenon of "hot brittleness," and the manganese-to-sulfur(Mn/S) ratio directly affects the FeS content in ultra-low carbon steel, thereby influencing its processability. Meanwhile, the regulation of the manganese-sulfur ratio also impacts the element content and inclusion characteristics in steel, which in turn affects the electrical conductivity of ultra-low carbon steel. To optimize the Mn/S ratio regulation of ultra-low carbon steel and enhance its comprehensive performances, ultra-low carbon steel samples with different Mn/S ratios were smelted using a vacuum induction furnace. The inclusion characteristics and conductivity evolution of ultra-low carbon steel with varying Mn/S ratios were investigated by means of optical microscopy, EBSD, EDS and conductivity testing. The results indicate that the inclusions formed in the steel are primarily near-spherical and long strip-shaped, with the near-spherical inclusions accounting for the vast majority and the long strip-shaped ones for a small proportion. For some inclusions, MnO-SiO₂ binary oxide inclusions serve as the core, around which FeS and MnS or (Mn, Fe)S inclusions are formed. Additionally, some inclusions directly form oxide-sulfide composite inclusions. With the increase of Mn/S ratio, the number of inclusions first increases and then decreases, while the size of inclusions first decreases and then increases. When the Mn/S ratio is 6.4 or higher, there are essentially no FeS inclusions present in the steel. Furthermore, as the Mn/S ratio increases, the electrical conductivity of the ultra-low carbon steel exhibits a monotonic increasing trend. At Mn/S =9.0, owing to the largest inclusion sizes and relatively high number of inclusions, the contents of Mn and S elements dissolved in the steel matrix are significantly reduced. Consequently, the electrical resistivity of the steel decreases, allowing it to achieve the highest electrical conductivity.

Current Articles 2026, Volume 47, Issue 2

Current Articles
2026, Volume 47, Issue 2