检索结果-南通市图书馆

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

在线全文

学校读者我要写书评

暂无评论

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 b.c.use 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

calculation of Phase Transformation Kinetics from Dilatation curves

在线全文

学校读者我要写书评

暂无评论

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

Field topologies in ideal and near-ideal magnetohydrodynamics and vortex dynamics

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2015年第1期58卷 12-31页

作者： LOW b.c. High Altitude Observatory National Center for Atmospheric Research

Magnetic field topology frozen in ideal magnetohydrodynamics （MHD） and its breakage in near-ideal MHD are reviewed in two parts, clarifying and expanding basic concepts. The first part gives a physically complete description of the frozen field topology derived from magnetic flux conservation as the fundamental property, treating four conceptually related topics： Eulerian and La- grangian descriptions of three dimensional （3D） MHD, chandrasekhar-Kendall and Euler-potential field representations, magnetic helicity, and inviscid vortex dynamics as a fluid system in physical contrast to ideal MHD. A corollary of these developments clar- ifies the challenge of achieving a high degree of the frozen-in condition in numerical MHD. The second part treats field-topology breakage centered around the Parker Magnetostatic Theorem on a general incompatibility of a continuous magnetic field with the dual demand of force-free equilibrium and an arbitrarily prescribed, 3D field topology. Preserving field topology as a global con- straint readily results in formation of tangential magnetic discontinuities, or, equivalently, electric current-sheets of zero thickness. A similar incompatibility is present in the steady force-thermal balance of a heated radiating fluid subject to an anisotropic thermal flux conducted strictly along its frozen-in magnetic field in the low-fl limit. In a weakly resistive fluid the thinning of current sheets by these general incompatibilities inevitably results field notwithstanding the small resistivity. Strong Faraday in sheet dissipation, resistive heating and topological changes in the induction drives but also macroscopically limits this mode of energy dissipation, trapping or storing free energy in self-organized ideal-MHD structures. This property of MHD turbulence captured by the Taylor hypothesis is reviewed in relation to the Sun＇s corona, calling for a basic quantitative description of the breakdown of flux conservation in the low-resistivity li

关键词： magnetic topology magnetic reconnection current sheets magnetic helicity thermal conduction solar corona magnetohy-drodynamics interstellar clouds

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

在线全文

学校读者我要写书评

暂无评论

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

在线全文

学校读者我要写书评

暂无评论

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, b.c.use 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

Preparation, characterization, and catalysis of mecro-catalysts

在线全文

学校读者我要写书评

暂无评论

Science china chemistry 1996年第4期39卷 347-353页

作者：肖丰收 b.c. Gates State Key Laboratory for catalysis Dalian Institute of Chemical Physics Chinese Academy of Sciences Dalian 116023 China department of chemistry Jilin University Changchun 130023 China department of chemical Engineering and Materials Science University of California Davis CA95616 USA

b.c.use catalysis by metals is a surface phenomenon, many technological catalysts contain small (typically nanometre-sired) supported metal particles with a large fraction of the atoms exposed. Many reactions, such as hydrocarbon hydrogenations, are structure-insensitive, proceeding at approximately the same rates on metal particles of various sizes provided that they are larger than 1 nm and show bulk-like metallic behavior. but the catalytic properties are not known when metal particles b.c.me so small that their sizes are indium clusters consisting of several indium atoms. Here the catalytic behavior of precisely defined clusters of just four and six indium atoms on solid supports is shown. It is found that the Ir4 and Ir6 clusters differ in catalytic activity both from each other and from metallic Ir particles.

关键词： metal clusters catalysis preparation characterization toluene hydrogenation EXAFS analysis chemisorption.

Thermal Stability of Retained Austenite in TRIP Steel After Different Treatments

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2008年第1期15卷 61-64页

作者： SHI Wen LI Lin bruno c de cooman Patrick Wollants YANG chun-xia department of Material Science and Engineering Shanghai University Shanghai 200072 China Laboratory for Iron and Steel Making Department of Material Science and Engineering Technologiepark 903 BE-9052 Ghent Belgium department MTM KU Leuven Heverlee B-3001 Belgium

Thermal decomposition of retained austenite in TRIP steel was investigated by means of differential scanning calorimetry（DSc）.The decomposition curve was abnormal,and the decomposition temperature and the activation energy were measured by the Kissinger method,which were all higher than those in quenched *** thermal decomposition data of samples soaked in liquid nitrogen after TRIP treatment were all similar to those without additional low temperature *** indicated that there is a high thermal stability in retained austenite of the TRIP steel at low temperature,which was also proved by XRD analysis.

关键词： TRIP steel retained austenite thermal stability differential scanning calorimetry