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Static Strain Aging in Fe-Mn-N Steel

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Static Strain Aging in Fe-Mn-N Steel

Investigation on Precipitation Transition in cGHAZ for TRIP Steels containing Vanadium and Titanium

Asia Steel International conference 2012(Asia Steel 2012)

作者： Jaehyuk JUNG Seongho HAN bruno c de cooman Graduate Institute of Ferrous Technology Pohang University of Science and TechnologyPohang 790-784Korea POScO Technical Research Laboratories Gwangyang545-090South Korea

＜正＞Interstitial solutes and dislocations gives rise to three characteristic peaks in the internal friction spectrum of steel: the dislocation-enhanced Snoek peak,the y-peak and the Snoek-Ke-Koster *** internal friction peaks were used to study in detail the N-aging in a Fe-Mn-N bake-hardenable Nb-alloyed hot rolled *** relative amplitude of the y-peak and the Snoek-Ke-Koster peak is related to the degree of dislocation pinning by atmosphere *** low contents of solute N,an increased amount of strain will result in a transition from an internal friction spectrum with a dominant Snoek-Ke-Koster peak to a spectrum with a dominant y-peak.

关键词： Internal friction Static strain aging Dislocation-interstitials interactions

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Journal of Iron and Steel Research International 2011年第S1期18卷 154-158页

作者： cooman de B c Graduate Institute for Ferrous Technology Pohang University of Science and TechnologyPohangSouth Korea

Two kinds of low-carbon low-silicon TRIP (Transformation Induced Plasticity) steels containing vanadium are designed using Thermocalc software in the light of both thermodynamics and *** heat treatment process of different steels is determined according to the calculation results *** HAZ (Heat-Affected Zone) simulation tests indicate the weldability of TRIP steels is crucially sensitive to cE (carban equivelent) of the *** the impact toughness of cGHAZ (coarse Grain Heat-Affected Zone) does not decrease drastically for TRIP steels microalloyed with Ti+*** steel containing both of vanadium and titanium shows smaller grain size compared with that containing vanadium *** is because the precipitation of Ti/V carbonitride slows down the grain boundary motion speed and then retards the grain size coalescence in cGHAZ.

关键词： TRIP steel precipitation transition heat-affected zone cGHAZ simulation

computer-Aided design of Some Advanced Steels and cemented carbides

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Journal of Iron and Steel Research International 2005年第6期12卷 42-48页

作者： LI Lin ZHANG Mei HE Yan-lin de cooman bruno Wollants Patrick Shanghai University Shanghai 200072 China Katholieke Universiteit Leuven Leuven 13-3001 Belgium Universiteit Gent Zwijnaarde 13-9052 Belgium

Thermodynamic and kinetic study on TRIP （transformation induced plasticity） steels, cemented carbides and mold steel for plastics were carried out in order to design modern advanced materials. With the sublattice model, equilibrium compositions of ferrite and austenite phases in TRIP steels, as well as volume fraction of austenite at inter-critical temperatures for different time were calculated. concentration profiles of carbon, manganese, aluminum and silicon in the steels were also estimated in the lattice fixed frame of reference. The effect of Si and Mn on TRIP was discussed according to thermodynamic and kinetic analyses. In order to understand and produce the graded nanophase structure of cemented carbides, miscellaneous phases in the M-co-c （M= Ti, Ta, Nh） systems and co-V-c system were modeled. Solution parameters and thermodynamic： properties were listed in detail. The improvement of machining behavior of prehardened mould steel for plastics was obtained by computer-aided composition design. The results showed that the matrix composition of large-section prehardened mould steel for plastic markedly influences the precipitation of non-metallic inclusion and the composition control by the aid of Thermo-calc software package minimizes the amount of detrimental oxide inclusion. In addition, the modification of calcium was optimized in composition design.

关键词： computer-aided composition design TRIP steel cemented carbide prehardened mould steel concentration profile thermodynamic kinetic equilibrium composition

calculation of Phase Transformation Kinetics from Dilatation curves

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厦门大学学报（自然科学版） 2002年第S1期41卷 15-16页

作者： Mesplont c de cooman B c Laboratory for Iron and Steelmaking Ghent UniversityLaboratory for Iron and Steelmaking Ghent University BelgiumBelgium

The structure of a steel changes with temperature due to phase transformations. This phase change is generally companied by a variation in the specific volume which is exhibited as a departure from the behaviour of the thermal expansion or contraction, at the temperature at which the change occurs. This behaviour can be detected as a change in the dimensions of a suitable test piece, and forms the operating principle of dilatometry. The dilatometric technique may be applicable to the investigation of the phase transformation kinetics if the relation between the fractions of phases, the temperature, the compositions of phases and the dilatation can be built up. Efforts have been made to analyze the dilatation during an isothermal transformation or to calculate the dilatation during the heating of plain carbon steels using the thermodynamic function. The existing models are, however, not directly applicable to the determination of the phase transformation kinetics from a dilatation curve. A detailed analysis has been made of the length change of a hypoeutectoid steel during a continuous cooling. A model has been developed in which the transient dilatation is calculated based on the fraction of the phases present. The model takes into account the redistribution of carbon and is applicable to the determination of the phase transformation kinetics from the dilatation data during a cooling of a hypo-eutectoid steel. The model was validated by comparing the model results with the experimental results of an interstitial free steel. Experiments have been done with an interstitial-free steel and a c-Mn steel. The model has been applied to the calculation of the transformation kinetics indicated by the dilatation curves. Excellent agreements between the model and the experiments have been obtained.

关键词： steels dilatation modelling multistep phase transformation kinetics

Effect of Temperature and Strain Rate on Dynamic Properties of Low Silicon TRIP Steel

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Journal of Iron and Steel Research International 2006年第3期13卷 51-56页

作者： TIAN Rong LI Lin B c de cooman WEI Xi-chen SUN Peng department of Materials Science and Engineering Shanghai UniversityShanghai 200072China Laboratory for Iron and Steel Making Ghent UniversityGhent B-9052Belgium

The dynamic tensile test of 0.11c-0.62Si-1.65Mn TRIP steel was carried out at different strain rates and test temperatures. The results show that both temperature and strain rate affect the retained austenite transformation. At high strain rates, the uniform elongation decreases, whereas the total elongation and energy absorption increase. The tensile strength is less strain rate sensitive. With raising test temperature, the tensile strength is reduced and the mechanical properties generally deteriorate, especially at 110℃,However, excellent mechanical properties were obtained at 50℃ and 75℃.

关键词： TRIP retained austenite dynamic tensile test strain rate tensile strength

design of TRIP Steel With High Welding and Galvanizing Performance in Light of Thermodynamics and Kinetics

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Journal of Iron and Steel Research International 2007年第6期14卷 37-41页

作者： LI Lin de cooman B c LIU Ren-dong VLEUGELS j ZHANG Mei SHI Wen School of Materials Shanghai University Shanghai 200072 China Postech Graduate School of Ferrous Technology Pohang University of Science and Technology Pohang 790784 South Korea Technique center of Ansteel Ansteel Company Anshan 114001 Liaoning China department of MTM Katholieke Universiteit Leuven Kasteelpark Arenberg 44 B-3001 Belgium

A new type of transformation induced plasticity （TRIP） steel with not only high strength and high ductility but also superior welding and galvanizing properties was designed and developed recently. Low carbon and low silicon content were preliminarily selected with the aim of meeting the requirements of superior quality in both welding and galvanizing. Phosphorus was chosen as one of the alloying elements, because it could reduce carbon activity in cementite and increase the stability of austenite. In addition, the possibility of phosphorus segregating at grain boundary was also discussed by thermodynamics as well as kinetics. Phase diagram was estimated at high temperature and the composition of the steel was then selected in the hyperperitectic range to avoid problems, which might occur in sheet steel continuous casting. Phase diagram in the *** temperature was estimated for the steel to obtain the starting temperature of fast cooling. For understanding the minimum rate of fast cooling, pearlite growth kinetics was calculated with self-developed diffusion coefficients of elements in grain boundary. Overaging temperature was determined through the calculation of To temperature by both equilibrium and para-equilibrium assumptions, which was different from the current determination, which is only based on an equilibrium estimation.

关键词： TRIP steel design thermodynamics kinetics weldability galvanization property

computer-aided designing and manufacturing of advanced steels

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Rare Metals 2006年第5期25卷 407-411页

作者： LI Lin HE Yanlin B.c. de cooman P. Wollants S. G. Huang J. Vleugels department of Materials Science and Engineering Shanghai University Shanghai 200072 China Laboratory for Iron and Steelmaking Universiteit Gent Zwijnaarde B-9052 Belgium dept. MTM Katholieke Universiteit Leuven Leuven B-3001 Belgium

Suitable optimization and simulation were performed using a powerful software package with a mature database as well as modem measurement facilities, which led to the successful designing and manufacturing of advanced steels. In the course of designing, the composition of a large section of prehardened mold steel for plastics was estimated so as to lower the quantities of oxide inclusions to change the type of carbides and to raise the machinability. The composition and process were adjusted to obtain satisfactory surface quality for the prevailing galvanization in transformation-induced plasticity （TRIP） steel. The refuting process of low-carbon steel was simulated in the light of both Thermo-calc and Factsage. Thermodynamic and kinetic analyses were always conducted during the test and the procedure.

关键词： material science advanced steel computer-aided design refining thermodynamics kinetics

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低碳钢应变时效过程模拟

金属学报 2002年第1期38卷 27-30页

作者：赵九洲 B. c. de cooman 中国科学院金属研究所沈阳110016 Laboratory for Iron and Steelmaking

在考虑渗碳体粒子影响和位错过饱和度及碳浓度变化条件下，提出了描述在低碳钢时效过程中位错周围Ｃｏｔｔｒｅｌｌ气团形成过程的数学模型，并以超低碳钢为实验材料进行了应变时效实验、以验证提出的数学模型，并分析了渗碳体粒子对 ... 详细信息

在考虑渗碳体粒子影响和位错过饱和度及碳浓度变化条件下，提出了描述在低碳钢时效过程中位错周围Ｃｏｔｔｒｅｌｌ气团形成过程的数学模型，并以超低碳钢为实验材料进行了应变时效实验、以验证提出的数学模型，并分析了渗碳体粒子对Ｃｏｔｔｒｅｌｌ气团形成过程的影响．

关键词：低碳钢位错应变时效渗碳体粒子数值模拟

Prevalence,genotypes and factors associated with HcV infection among prisoners in Northeastern Brazil

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World Journal of Gastroenterology 2011年第25期17卷 3027-3034页

作者： bruno Fernandes de Oliveira Santos Nathalie Oliveira de Santana Alex Vianey callado Franca department of Medicine Federal University of SergipeAracajuSergipe 49060-100Brazil

AIM： To determine hepatitis c virus （HcV） seropreva- lence and its genotypes, and to identify the factors associated with HcV infection. METHODS： This cross-sectional study, conducted in two prisons （one male and one female） in the State of Ser- gipe, Brazil, comprised 422 subjects. All of the prisoners underwent a rapid test for the detection of HcV antibod- ies. Patient~ with a positive result were tested for anti- HcV by enzyme linked immunosorbent assay and for HcV RNA by qualitative polymerase chain reaction （PcR）. The virus genotype was defined in every serum sample that presented positive for PcR-HcV. In order to determine the factors independently associated with positive serol- ogy for HcV, multivariate logistic regression was used. RESULTS： HcV seroprevalence was 3.1%. Of the 13 subjects with positive anti-HcV, 11 had viremia confirmed by PcR. Of these, 90.9% had genotype 1. A total of 43 （10.2%） were injecting drug users, and HcV seroprevalence in this subgroup was 20.6%. The variable most strongly associated with positive serology for HcV was use of injecting drugs [odds ratio （OR）, 23.3; 95% confidence interval （cI）, 6.0-90.8]. Age over 30 years （OR, 5.5; 95%cI, 1.1-29.2）, history of syphilis （OR, 9.8; 95%cI, 1.7-55.2） and history of household contact with HcV positive individual （OR, 14.1; 95%cI, 2.3-85.4） were also independently associated with HcV infection. cONcLUSION： Most of the HcV transmissions result from parenteral exposure. However, there is evidence to suggest a role for sex and household contact with an infected subject in virus transmission.

关键词： Hepatitis c Prisoners Drug abusers crosssectional analysis Brazil