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Volume-averaged modeling of multiphase solidification with equiaxed crystal sedimentation in a steel ingot

China Foundry 2024年第3期21卷 229-238页

作者： Xiao-lei Zhu Shuang Cao Rui Guan Ji Yang Zhe Ning Xin-gang Ai Sheng-li Li Xin-cheng Miao The key laboratory of material Forming and Structure Property Control Anshan 114051LiaoningChina State Key Laboratory of Metal Material for Marine Equipment and Application Anshan 114009LiaoningChina School of materials and metallurgy University of Science and Technology LiaoningAnshan 114051LiaoningChina

Macrosegregation is a critical factor that limits the mechanical properties of materials.The impact of equiaxed crystal sedimentation on macrosegregation has been extensively studied,as it plays a significant role in determining the distribution of alloying elements and impurities within a material.To improve macrosegregation in steel connecting shafts,a multiphase solidification model that couples melt flow,heat transfer,microstructure evolution,and solute transport was established based on the volume-averaged Eulerian-Eulerian approach.In this model,the effects of liquid phase,equiaxed crystals,columnar dendrites,and columnar-to-equiaxed transition(CET)during solidification and evolution of microstructure can be considered simultaneously.The sedimentation of equiaxed crystals contributes to negative macrosegregation,where regions between columnar dendrites and equiaxed crystals undergo significant A-type positive macrosegregation due to the CET.Additionally,noticeable positive macrosegregation occurs in the area of final solidification in the ingot.The improvement in macrosegregation is beneficial for enhancing the mechanical properties of connecting shafts.To mitigate the thermal convection of molten steel resulting from excessive superheating,reducing the superheating during casting without employing external fields or altering the design of the ingot mold is indeed an effective approach to control macrosegregation.

关键词： ingot casting multiphase solidification model equiaxed crystal sedimentation microstructure macrosegregation

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Inclusions modification by rare earth in steel and the resulting properties: A review

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Journal of Rare Earths 2024年第3期42卷 431-445,I0001页

作者： Xiaoqiang Wang Zhiwei Wu Bing Li Wenxiong Chen Jun Zhang Jian Mao College of materials Science and Engineering Sichuan UniversityChengdu610065China Chengdu Advanced metal materials Industry Technology Research Institute Co. Ltd.Chengdu610303China State Key Laboratory of Metal Material for Marine Equipment and Application Anshan114009China

Rare earth(RE) elements are excellent modifiers for non-metallic inclusions that inevitably appear in steel and affect steel properties. This paper reviews the research status of inclusions modification by RE elements and the changes it cause on steel properties. First, the inclusion changes caused by RE modification are described. Generally, after adding pure RE, the main evolution of inclusions occurs as M →M + RE-Al-O → RE-Al-O + RE_(2)O_(2)S → RE_(2)O_(2)S + RE—S/RE_(2)O_(2)S + RE-O with an increase in the RE content(M represents the inclusions before RE addition). The type of final inclusion obtained after RE modification is related to the relative contents of S and O in the steel. Moreover, fine, regular, and uniformly distributed inclusions can be obtained with appropriate RE addition. However, the effectiveness of inclusions modification by adding both RE and non-RE elements is closely related to the order of their addition. Second, the applications and advantages of thermodynamic calculations in the study of RE-modified inclusions are introduced. Third, the changes in the corrosion resistance, impact properties,and other properties of steel caused by the modification of inclusions by RE are reviewed. Finally, the perspectives and trends of inclusions modified by RE elements in the steel industry are presented.

关键词： Rare earths Inclusions Modification Thermodynamic calculation Properties change

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Multi-physical fields distribution in billet during helical electromagnetic stirring:A numerical simulation research

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China Foundry 2024年第1期21卷 51-59页

作者： Dong Pan Qing-tao Guo Kai-lun Zhang Fu-zhi Yu Yu-ying Li Yu-bao Xiao state key laboratory of metal materials for marine equipment and application Anshan 114009LiaoningChina Ansteel Beijing Research Institute Co. Ltd.Beijing 102200China

Electromagnetic stirring is one of the widely applied techniques to modify the quality of casting billets.Different from conventional rotate stirring,the helical stirring is more professional in assisting multi-dimensional flow of molten metal and eliminating solidification defects.In this study,the single-winding helical stirring(SWHS)was introduced,offering advantages such as smaller volume and lower electromagnetic shielding compared to traditional helical stirring methods.Following a comprehensive numerical simulation,the stirring parameters of SWHS were adjusted to yoke inclination angle of 43°and frequency of 12 Hz.The higher electromagnetic force and flow velocity in drawing direction,as well as the lower temperature gradient induced by the SWHS,are positive factors for homogeneous solidification of billet.The experimental results on Al-8%Si alloy and 0.4%C-1.1%Mn steel demonstrate that compared to rotate stirring,the SWHS process can induce better billet quality and is more effective in accelerating the equiaxed expansion and reducing element segregation.The SWHS process can enhance the equiaxed ratio of the billet by 58.3%and reduce segregation degree of carbon element by 10.97%.Consequently,SWHS holds great promise as a potential approach for improving the quality of continuous casting billets.

关键词： billet electromagnetic stirring helical solidification element segregation numerical simulation

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Recent research progress in the mechanism and suppression of fusion welding-induced liquation cracking of nickel based superalloys

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International Journal of Minerals,metallurgy and materials 2024年第5期31卷 1072-1088页

作者： Zongli Yi Jiguo Shan Yue Zhao Zhenlin Zhang Aiping Wu Department of Mechanical Engineering Tsinghua UniversityBeijing 100084China College of Engineering China Agricultural UniversityBeijing 100091China state key laboratory of Clean and Efficient Turbomachinery Power equipment Department of Mechanical EngineeringTsinghua UniversityBeijing 100084China key laboratory for Advanced materials Processing Technology Ministry of EducationBeijing 100084China School of material Science and Engineering Southwest Jiaotong UniversityChengdu 610031China

Nickel-based superalloys are extensively used in the crucial hot-section components of industrial gas turbines,aeronautics,and astronautics because of their excellent mechanical properties and corrosion resistance at high temperatures.Fusion welding serves as an effective means for joining and repairing these alloys;however,fusion welding-induced liquation cracking has been a challenging issue.This paper comprehensively reviewed recent liquation cracking,discussing the formation mechanisms,cracking criteria,and remedies.In recent investigations,regulating material composition,changing the preweld heat treatment of the base metal,optimizing the welding process parameters,and applying auxiliary control methods are effective strategies for mitigating cracks.To promote the application of nickel-based superalloys,further research on the combination impact of multiple elements on cracking prevention and specific quantitative criteria for liquation cracking is necessary.

关键词： nickel-based superalloy fusion welding liquation cracking cracking mechanism cracking suppression

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Precipitation behavior of P550 steel for non-magnetic drill collars during isothermal aging at 650–900℃

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Journal of Iron and Steel Research(International) 2022年第4期29卷 636-646页

作者： Li-wei Xu Huai-bei Zheng Hua-bing Li Zhou-hua Jiang Shu-cai Zhang Jiang-tao Yu Hao Feng Yue Lin School of metallurgy Northeastern UniversityShenyang 110819LiaoningChina State Key Laboratory of Metal Material for Marine Equipment and Application Anshan 114002LiaoningChina

Precipitation behavior of P550 steel for non-magnetic drill collars was investigated by microstructure characterization as well as thermodynamic calculation.The results demonstrate that the main precipitate formed at 650–900℃was cellular Cr_(2)N,and its precipitation depended heavily on the aging temperature.The most sensitive precipitation temperature of cellular Cr_(2)N was 750℃.At 750℃,the cellular Cr_(2)N exhibited fast-slow precipitation kinetics with the aging time prolonging.The initial precipitation of cellular Cr_(2)N was governed by the short-range intergranular diffusion of Cr.During long-term aging,its growth was controlled by the long-range bulk diffusion of Cr.In addition,cellular Cr_(2)N induced the precipitation of r phase ahead of the cell after long period of aging.Increasing the nitrogen content resulted in the increment of both the nucleation site and the driving force for the cellular Cr_(2)N,which jointly promoted its precipitation.

关键词： P550 steel Non-magnetic drill collar Precipitation behavior Cellular Cr_(2)N r Phase Nitrogen

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Influence of pH on the Formation, Composition and Protectiveness of Fluoride Conversion Film Deposited on AZ31 Magnesium Alloy in KF Solution

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金属学报:英文版 2023年第9期36卷 1397-1408页

作者： Liping Wu Chen Liu Jie Wei Junhua Dong Lin Zhao Chao Li Wei Ke Yiqing Chen Changgang Wang Shenyang National laboratory for materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang110016China State Key Laboratory of Metal Material for Marine Equipment and Application Anshan114009China

In deaerated 0.1 M KF solution at pH 5, pH 7.5 and pH 9, fluoride films were deposited on AZ31 magnesium (Mg) alloy at − 1.4 V vs saturated calomel electrode (SCE). The morphology, phase composition, elemental and compositional depth distribution of different fluoride films and their influences on the corrosion resistance of AZ31 Mg alloy were explored in detail. The results indicated that the films deposited at weak acidic and nearly neutral pH consisted of two layers with amorphous Mg(OH)_(2) and MgF_(2) as the inner layer, and Mg(OH)_(2), MgF_(2) and KMgF_(3) crystals the outer layer. The film deposited at alkaline pH was a monolayer structure consisting of amorphous Mg(OH)_(2) as the major constitute and MgF_(2) as the minor constitute. The protectiveness of fluoride film was intimately related to its composition and structure. The content and crystal regularity of KMgF_(3) were the two main factors influencing the protectiveness of fluoride film. The fluoride film deposited at pH 7.5 offered the best protection to AZ31 Mg alloy.

关键词： Magnesium alloy Potentiostatic deposition Fluoride film KF solution

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Effect of hollow insulation riser on shrinkage porosity and solidification structure of ingot

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Journal of Iron and Steel Research(International) 2022年第12期29卷 1951-1960页

作者： Ying-jie Liu Chun-lin Peng Wan-ming Li Xiao-lei Zhu Ming-gang Shen Xiang-wei Liao Kun Liu Chong-yi Wei Yusuf Abba Yusuf Ji Yang Chang-you Cai School of materials and metallurgy University of Science and Technology LiaoningAnshan 114051LiaoningChina State Key Laboratory of Metal Material for Marine Equipment and Application Anshan 114000LiaoningChina

The thermal insulation performance of riser is very important to the shrinkage porosity and solidification structure of ingot,but it is difficult to significantly improve due to the limit of thermal conductivity of riser material.A new type of hollow insulation riser was proposed based on the low thermal conductivity of air,which aims to improve the thermal insulation performance of riser.A 14.5-t steel ingot was prepared using the hollow insulation riser,and the casting temperature was 1500°C.The temperature evolution of the external surface of mold during solidification was measured using an infrared temperature instrument.A numerical model was established to simulate the porosity and solidification structure of ingot.The reliability of numerical simulation was verified by comparing simulation and experimental results.Results show that the insulation performance of the riser can be significantly improved through application of the hollow insulation sleeve.Compared with solid insulation sleeve,the shrinkage cavity depth was decreased and the position of porosity was raised when hollow insulation riser was applied.

关键词： Hollow insulation riser Solidification Heat transfer Porosity Thermal conductivity

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Measurement of two-phase velocities in bubble flows using laser Doppler velocimetry

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Journal of Hydrodynamics 2022年第6期34卷 1134-1144页

作者： Ling-xin Zhang Xin-sheng Cheng Han Tu Qi Gao Xue-ming Shao Xiang-Wei Liao Liang Zhao Department of Engineering Mechanics Zhejiang UniversityHangzhou310027China Iron and Steel Research Institutes of Ansteel Group Corporation Anshan114009China State Key Laboratory of Metal Material for Marine Equipment and Application Anshan114009China

The measurement of two-phase velocities in bubble flows using laser Doppler velocimetry(LDV)is studied.The key to the problem is to differentiate the LDV signals from bubbles and tracers,based on which the two-phase velocities can be characterized.In this study,two experiments are carried out.Firstly,the bubble-chain experiment is performed to investigate the optical response of bubble surface and the corresponding LDV signal.The optical response shows that the light received by the LDV detector is dominated by the reflection component,which is similar to specular reflection to some extent.There are three typical patterns of signals of large bubbles passing through the measurement volume,all of which are with high amplitude and saturated.Then,the upward-flow experiment is conducted to study the statistical characteristics of large bubbles as well as micro tracers and micro bubbles.The results show that the amplitude of signal of millimeter bubbles is about an order of magnitude larger than that of tracers or micro bubbles.Based on this significant difference of the amplitude,we propose a phase discrimination method to distinguish two-phase signals.The capability of the proposed method is tested in a complex bubble flow,and its reliability is verified by bubble tracking velocimetry(BTV)technology.

关键词： laser Doppler velocimetry(LDV) bubbly flow phase discrimination bubble tracking velocimetry(BTV)

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Effect of heat treatment on corrosion resistance and antibacterial ability of 0Cr15Ni5Cu3Mo carbon steel

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Journal of Iron and Steel Research(International) 2023年第12期30卷 2505-2516页

作者： Yun-sheng Xue Jia-ji Wang Ying-xue Teng Kui-jun Fu Yin Lei Jin Liu Da-zheng Zhang Shu-wen Chen School of materials and metallurgy University of Science and Technology LiaoningAnshan114000LiaoningChina state key laboratory of metal materials for marine equipment and application Anshan114000LiaoningChina

Before and after heat treatment,0Cr15Ni5Cu3MoN stainless steel(SS)samples were immersed in sulfate-reducing bacteria(SRB)environment to study the effect of heat treatment on the antimicrobial properties of Cu-containing stainless steel.The effect of heat treatment on the corrosion resistance and antibacterial ability of 0Cr15Ni5Cu3MoN SS was studied by scanning electron microscopy,transmission electron microscopy,laser scanning confocal microscopy,and electrochemistry.The results show that 0Cr15Cu3 SS has better antibacterial properties with fewer bacteria adsorbed on the surface after heat treatment,and its corrosion resistance is significantly improved.Interestingly,on the 7th day of immersion,the corrosion resistance of the heat-treated stainless steel was lower than that of the rolled stainless steel.This was due to the fact that the rolled samples were protected by biofilm at this time,while the surface bacteria on the heat-treated samples died,resulting in the exposure of the substrate surface and thus reducing the corrosion resistance of the heat-treated samples.Thus,because of the strong bactericidal properties of the heat-treated Cu-containing stainless steel,the corrosion resistance of the samples suddenly decreases in the middle stage of corrosion,and this discovery provides a new view to study the corrosion process of Cu-containing stainless steel in the SRB environment.

关键词： Antibacterial property Carbon steel-Corrosion resistance Cu-rich phase Biofilm

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Influence of band microstructure on carbide precipitation behavior and toughness of 1 GPa-grade ultra-heavy gauge low-alloy steel

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International Journal of Minerals,metallurgy and materials 2023年第7期30卷 1329-1337页

作者： Peng Han Zhipeng Liu Zhenjia Xie Hua Wang Yaohui Jin Xuelin Wang Chengjia Shang Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing 100083China State Key Laboratory of Metal Material for Marine Equipment and Application Anshan 114000China Yangjiang Branch Guangdong Laboratory for Materials Science and Technology(Yangjiang Advanced Alloys Laboratory)Yangjiang 529500China

This study investigated the influence of band microstructure induced by centerline segregation on carbide precipitation behavior and toughness in an 80 mm-thick 1 GPa low-carbon low-alloy steel plate.The quarter-thickness(1/4t)and half-thickness(1/2t)regions of the plate exhibited similar ductility and toughness after quenching.After tempering,the 1/4t region exhibited~50%and~25%enhancements in both the total elongation and low-temperature toughness at-40°C,respectively,without a decrease in yield strength,whereas the toughness of the 1/2t region decreased by~46%.After quenching,both the 1/4t and 1/2t regions exhibited lower bainite and lath martensite concentrations,but only the 1/2t region exhibited microstructure bands.Moreover,the tempered 1/4t region featured uniformly dispersed short rod-like M_(23)C_(6)carbides,and spherical MC precipitates with diameters of~20–100 nm and<20 nm,respectively.The uniformly dispersed nanosized M_(23)C_(6)carbides and MC precipitates contributed to the balance of high strength and high toughness.The band microstructure of the tempered 1/2t region featured a high density of large needle-like M3C carbides.The length and width of the large M3C carbides were~200–500 nm and~20–50 nm,respectively.Fractography analysis revealed that the high density of large carbides led to delamination cleavage fracture,which significantly deteriorated toughness.

关键词： band microstructure carbides toughness heavy gauge steel centerline segregation

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