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Influences of Alloying Elements on Oxidation Behavior of Steels and Microstructure of Oxide Scales

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Journal of Iron and Steel Research International 2016年第3期23卷 231-237页

作者： Hui-bin WU di WANG Peng-cheng ZHANG Jin-ming LIANG Sheng LIU di tang National Engineering Research Center for Advanced Rolling Technology University of Science and Technology Beijing

In order to figure out the oxidation behavior of steels during heating,five micro-alloyed steels were subjected to continuous and isothermal oxidation using the thermo gravimetric analyzer and the Gleeble-3500thermo-mechanical *** microstructure of oxide scales,especially the thickness fractions of Fe2O3,Fe3O4 and FeO layers,was analyzed using the scanning electron microscope（SEM）,electron probe microanalyzer（EPMA）and electron backscattered diffraction（EBSD）*** micro-alloyed steels containing alloying elements（Si,Cr,Ni and Cu）show a higher oxidation resistance compared with the low carbon *** is found that alloying elements accumulated at scale/substrate interface during high temperature *** elements function in two ways in the oxidation of steels：one is enhancing the scale/substrate interface and consequently suppressing the blister of scales;and the other is impeding the outward diffusion of iron cations from substrate to scales,resulting in the decrease of oxidation *** the diffusion of iron cations is impeded,the thickness fractions of Fe2O3 and Fe3O4of micro-alloyed steels are more than those of low carbon steels.

关键词： micro-alloyed steel high temperature oxidation oxidation kinetics microstructure oxide scale

Texture and Microstructure Evolution During Tensile Testing of TWIP Steels with diverse Stacking Fault Energy

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Acta Metallurgica Sinica(English Letters) 2013年第6期26卷 713-720页

作者： Yanxin WU di tang Haitao JIANG Zhenli MI Haitao JING National Engineering Research Center for Advanced Rolling Technology University of Science and Technology Beijing SAIC Motor Passenger Vehicle Co Shanghai

Texture and microstructure evolution in two kinds of the twinning induced plasticity （TWIP） steels （Fe-Mn- Si-AI and Fe-Mn-C） with diverse stacking fault energies during tensile testing were investigated by interrupted testing. The strain-hardening rate curves of the two steels were quite similar, but the texture characterization curves （maximum of pole density measured by X-ray diffraction） were varied. According to the curvature of max pole density curves, the evolution of the texture and the microstructure can be divided into three stages： low strain stage, medium stage and high stage. In low strain stage the difference of the microstructure came from the intensity of dislocation, which was much smaller in Fe-Mn-Si-AI. The main difference of the microstructure in medium and high strain stages originated from the numbers of activated twin systems. There were more than one twin systems activated in Fe-Mn-C, while only a single twin system activated in Fe-Mn-Si-AI. Texture showed various differences in the whole tensile process because it was affected by their micromechanism, such as concentration of the dislocation and the activation of twin systems. Texture in low strain stage was connected with annealing twin; the evolution ofthe texture was mainly induced by deformation twin generation. More than one activated twin systems in medium and high stages may counteract each other in the view of concentration of the grain orientations.

关键词： Work hardening rate Texture TWIP steel Stacking fault energy

Reverse-transformation austenite structure control with micro/nanometer size

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International Journal of Minerals,Metallurgy and Materials 2017年第5期24卷 530-537页

作者： Hui-bin Wu Gang Niu Feng-juan Wu di tang Collaborative Innovation Center of Steel Technology University of Science and Technology Beijing Beijing Engineering Technology Research Center of Special Steel for Traffic and Energy

To control the reverse-transformation austenite structure through manipulation of the micro/nanometer grain structure, the influences of cold deformation and annealing parameters on the microstructure evolution and mechanical properties of 316L austenitic stainless steel were investigated. The samples were first cold-rolled, and then samples deformed to different extents were annealed at different temperatures. The microstructure evolutions were analyzed by optical microscopy, scanning electron microscopy (SEM), magnetic measurements, and X-ray diffraction (XRD); the mechanical properties are also determined by tensile tests. The results showed that the fraction of stain-induced martensite was approximately 72% in the 90% cold-rolled steel. The micro/nanometric microstructure was obtained after reversion annealing at 820-870A degrees C for 60 s. Nearly 100% reversed austenite was obtained in samples annealed at 850A degrees C, where grains with a diameter ae 500 nm accounted for 30% and those with a diameter > 0.5 mu m accounted for 70%. The micro/nanometer-grain steel exhibited not only a high strength level (approximately 959 MPa) but also a desirable elongation of approximately 45%.

关键词： austenitic stainless steel structure control martensite reverse transformation grain refinement

Improvement of the matrix and the interface quality of a Cu/Al composite by the MARB process

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Rare Metals 2007年第3期26卷 230-235页

作者： XU Rongchang tang di REN Xueping WANG Xiaohong WEN Yonghong National Engineering Research Center for Advanced Rolling Technology University of Science and Technology Beijing Beijing 100083 China

The matrix accumulative roll bonding technology （MARB） can improve the matrix performance of metal composite and strengthen the bonding quality of the interface./n this research, for the fwst time, the technology of MARB was proposed. A sound Cu/AI bonding composite was obtained using the MARB process and the bonding characteristic of the interface was studied using scanning electricity microscope （SEM） and energy-dispersive spectroscopy （EDS）. The result indicated that accumulation cycles and diffusion annealing temperature were the most important factors for fabricating a Cu/AI composite material. The substrate aluminum was strengthened by MARB, and a high quality Cu/AI composite with sound interface was obtained as well.

关键词： matrix accumulative roll bonding Cu/Al composite material interface bonding diffusion annealing

Carbide dissolution during Intercritical Austenitization in Bearing Steel

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Journal of Wuhan University of Technology(Materials Science) 2014年第6期29卷 1242-1245页

作者：李辉米振莉 ZHANG Xiaolei tang di WANG Yide Engineering Research Institute University of Science and Technology Beijing

In order to investigate the carbide dissolution mechanism of high carbon-chromium bearing steel during the intercritical austenitization, the database of TCFE7 of Thermo-calc and MOBFE of diCTRA software were used to calculate the elements diffusion kinetic and the evolution law of volume fraction of carbide. diL805 A dilatometer was used to simulate the intercritical heat treatment. The microstructure was observed by scanning electron microscopy（SEM）, and the micro-hardness was tested. The experimental results indicate that the dissolution of carbide is composed of two stages： initial austenite growth governed by carbon diffusion which sharply moves up the micro-hardness of quenched martensite, and subsequent growth controlled by diffusion of Cr elements in M3 C. The volume fraction of M3 C decreases with the increasing holding time, and the metallographic analysis shows a great agreement with values calculated by software.

关键词： intercritical austenitization carbide dissolution bearing steel diffusion mechanism

Effect of roller shapes on strip buckling in a continuous annealing furnace

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International Journal of Minerals,Metallurgy and Materials 2011年第3期18卷 297-302页

作者： Jing Yang di tang Lan Su Hai-tao Jiang Quan Yang National Engineering Research Center of Advanced Rolling University of Science and Technology Beijing Beijing 100083 China

The effect of roller shapes on strip buckling in a continuous annealing furnace was focused on. The tensile stress distribution, the transverse compressive stress, and the critical buckling stress of the strip were studied by the finite element method （FEM） when the flat roller, crown roller, single taper roller, and double taper roller were used, respectively. Simulation results show that strip buckling is most likely to occur with the crown roller, then the double taper roller, and finally the single taper roller. Also, strip buckling can not occur when the flat roller is used. Considering strip snaking, the single taper roller and double taper roller are suggested in the continuous annealing fur-nace. The double taper roller with a better strip snaking-prevention ability should be applied in the sections with high strip temperature, and the single taper roller with a better buckling-prevention ability should be used in the sections with low strip temperature.

关键词： steel strips buckling heat treating furnaces annealing rollers finite element method

Precipitation and stability of reversed austenite in 9Ni steel

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International Journal of Minerals,Metallurgy and Materials 2010年第5期17卷 587-595页

作者： Yue-hui Yang Qing-wu Cai di tang Hui-bin Wu Research Institute of Metallurgical Engineering University of Science and Technology Beijing Beijing 100083 China

A new method was used to analyze the factors affecting the precipitation of reversed austenite during tempering. The samples were kept at various tempering temperatures for 10 min and their length changes were recorded. Then, the precipitation of reversed austenite which led to the length reduction was shown by thermal expansion curves. The results show that the effects of process parameters on the precipitation of reversed austenite can be determined more accurately by this method than by X-ray diffraction. When the quenching and tempering process is adopted, both the lower quenching temperature and higher tempering temperature can promote the precipitation of reversed austenite during tempering; and when the quenching, lamellarizing, and tempering process is used, intercritical quenching is considered beneficial to the precipitation of reversed austenite in the subsequent tempering because of Ni segregation during holding at the intercritical temperature.

关键词： cryogenic equipment low carbon steel reversed austenite precipitation stability thermal expansion measurement

A CFD/CSD model for aeroelastic calculations of large-scale wind turbines

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Science China(Technological Sciences) 2013年第1期56卷 205-211页

作者： GUO TongQing LU ZhiLiang tang di WANG TongGuang DONG Lu Department of Aerodynamics Nanjing University of Aeronautics and Astronautics College of Science PLA University of Science and Technology

In this paper,a CFD/CSD model coupling N-S equations and structural equations of motion in the time domain is described for aeroelastic analysis of large wind *** structural modes of blades are analyzed with one-dimensional beam *** combining point matched sliding grid for wind turbine rotation and deforming grid for structural vibrations,a hybrid dynamic grid strategy is designed for the multi-block structured grid system of a wind *** dual time-stepping approach and finite volume scheme are applied to the three-dimensional unsteady preconditioned N-S equations,and DES approach is employed to simulate the unsteady massively separated flows.A modal approach is adopted to calculate the structural response,and a predictor-corrector scheme is used to solve the structural equations of *** and CSD solvers are tightly coupled via successive iterations within each physical time *** a result,a time-domain CFD/CSD model for aeroelastic analysis of a large wind turbine is *** presented method is applied to the NH1500 large wind turbine under the rated condition,and the calculated aeroelastic characteristics agree well with those of the prescribed vortex wake method.

关键词： Large wind turbine aeroelastics time-domain method multi-block grid N-S equations structural equations of motion

Corrosion behavior of high-strength spring steel for high-speed railway

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International Journal of Minerals,Metallurgy and Materials 2018年第5期25卷 527-535页

作者： Gang Niu Yin-li Chen Hui-bin Wu Xuan Wang di tang Collaborative Innovation Center of Steel Technology University of Science and Technology Beijing Beijing Engineering Technology Research Center of Special Steel for Traffic and Energy

The corrosion resistance and evolution of corrosion products in medium-carbon high-strength spring steels were investigated in a neutral salt spray(5 wt% Na Cl solution). A formation model of γ-Fe OOH and a transformation model describing the conversion of γ-Fe OOH to α-Fe OOH were constructed. The results indicated that, at the initial corrosion stage, the corrosion resistance was gradually improved with the addition of Cr; however, with the addition of alloying element V, the corrosion resistance decreased. These results were attributed mainly to the initial corrosion stage being closely related to the matrix microstructure parameters such as grain-boundary character and dislocation density. After the rust layer was formed at a later corrosion stage, the corrosion resistance was reinforced with the addition of Cr and V because Cr strongly influenced the composition, structure, and morphology of the corrosion products. The results presented herein show that Cr was conducive to the transformation of γ-Fe OOH into α-Fe OOH. Moreover, V and Cr exhibited obvious synergy and were enriched in the inner layer of the corrosion products.

关键词： high-strength spring steel corrosion resistance alloying elements rust layers evolution model