ZHU Na-qiong
,
LU Li
,
HE Yan-lin
,
LI Lin
,
LU Xiao-gang
钢铁研究学报(英文版)
Coarsening of M23C6 precipitates in an Fe-12.4Cr-0.13C ternary alloy has been investigated ageing at 780 ℃ up to 200 h. Evolution of M23C6 carbides at different ageing times was determined experimentally using transmission electron microscopy. Particle size distribution was obtained with different measuring methods. Simulations of coarsening of M23C6 precipitates were carried out using computational thermodynamics and kinetics. Results showed low coarsening rates for M23C6 precipitates in the Fe-Cr-C ternary alloy. Interfacial energy of M23C6/ferrite interface is between 0.1 and 0.3 J·m-2 for the coarsening of M23C6 ageing at 780 ℃.
关键词:
M23C6
,
coarsening
,
PSD
,
interfacial energy
LI Lin
,
DE COOMAN B C
,
LIU Rendong
,
VLEUGELS J
,
ZHANG Mei
,
SHI Wen
钢铁研究学报(英文版)
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 intercritical 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 selfdeveloped diffusion coefficients of elements in grain boundary. Overaging temperature was determined through the calculation of T0 temperature by both equilibrium and paraequilibrium 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
LI Lin
,
TANG Guangsheng
,
HE Zhiyong
,
et al
钢铁研究学报(英文版)
Carbon black-phenolic resin composite binders with various amounts of nanometer carbon black were prepared through adding KH-550 coupling agent and high-speed mixer. The effects of nanometer carbon black amount added on viscosity of the composite binders were studied. Low carbon MgO-C specimens were fabricated with these composite binders. Effects of nanoscale carbon black contents (0, 2.5%, 5%, 10%, and 15% of phenolic resin in mass) on mechanical properties of low carbon MgO-C specimens were investigated. The results revealed that the viscosity of the composite binder increased rapidly with increase of nanometer carbon black content. Moreover, it indicated that CMOR, HMOR and CCS of the specimens rose gradually with increase of nanometer carbon black content as well.
关键词:
Black carbon;performancr;Mgo-C composite
XIONG Ronggang
,
FU Renyu
,
SU Yu
,
LI Qian
,
WEI Xicheng
,
LI Lin
钢铁研究学报(英文版)
Tensile tests of TWIP steels of two compositions are performed in the strain rate range of 10-5-103 s-1. Results indicate that steel 1# does not exhibit TWIP effect but deformationinduced martensitic transformation appears only. There exists TWIP effect in steel 3#. Tensile properties at room temperature are sensitive to strain rate in the studied strain rate ranges. Analysis on the relationship between strainhardening exponent and strain rates shows that straininduced martensitic transformation and formation of twins during deformation have significant influence on their strainhardening behavior.
关键词:
twininduced plasticity;strain rate;strainhardening;deformation twin
ZHAO Jin-long
,
XI Yan
,
SHI Wen
,
LI Lin
钢铁研究学报(英文版)
Abstract： Microstructure evolution and mechanical properties of newly designed 01C-6Mn-05Si-1Al TRIP-aided steels under different annealing conditions and the effects of matrix microstructure before intercritical annealing on the final microstructure were studied by means of X-ray diffraction (XRD), scanning electron microcopy (SEM), dilatometric simulation, optical microstructure (OM) and tensile testing in this work. The experimental results indicate that the TRIP steel with Mn of 6% could form a considerable amount of retained austenite with good TRIP effect after a simple intercritical annealing treatment, and the matrix microstructure before intercritical annealing treatment can greatly affect the final microstructure. The original microstructure of the ferritic matrix steel was eliminated, while annealed martensite was remained from the martensite matrix steel under the same intercritical annealing conditions.
关键词:
Key words: high manganese TRIP steel
,
intercritical annealing
,
microstructure
,
mechanical properties
WANG Hua
,
SHI Wen
,
HE Yan-lin
,
LU Xiao-gang
,
LI Lin
钢铁研究学报(英文版)
Specimens of two different kinds of bake hardening steels (BH-Mn and BH-P) were prepared and treated with different annealing processes (water quenching and overaging). A novel technique of three dimensional atom probe was used to investigate solute distributions in these steels. The results indicate that C concentration decreases, whereas V increases during overaging in both bake hardening steels. The conclusion that no vanadium carbides precipitate during the overaging is therefore originally obtained by microanalysis in bake hardening steels. Moreover, bake hardening values of all the specimens were tested by tensile experiments with 2% pre-deformation. However, those of overaged specimens were further measured with higher levels of pre-deformation because no bake hardening phenomenon was present at 2% pre-deformation. As the pre-deformation increases from 2% to 6% and 8%, both overaged steels show bake hardening values, and the value data are almost the same.
关键词:
ultra-low carbon
,
bake hardening steel
,
three dimensional atom probe
,
solute C
,
water quenching
,
overaging
,
bake hardening phenomenon
ZHANG Mei
,
LI Lin
,
FU Renyu
,
ZHANG Jicheng
,
WAN Zi
钢铁研究学报(英文版)
Transformation induced plasticity (TRIP) steel exhibited high or rather high carbon equivalent (CE) because of its chemical composition, which was a particularly detrimental factor affecting weldability of steels. Thus the weldability of a TRIP steel (grade 600) containing (in mass percent, %) 011C119Si167Mn was extensively studied. The mechanical properties and impact toughness of butt joint, the welding crack susceptibility of weld and heat affected zone (HAZ) for tee joint, control thermal severity (CTS) of the welded joint, and Y shape 60° butt joint were measured after the gas metal arc welding (GMAW) test. The tensile strength of the weld was higher than 700 MPa. Both in the fusion zone (FZ) and HAZ for butt joint, the impact toughness was much higher than 27 J, either at room temperature or at -20 ℃, indicating good low temperature impact ductility of the weld of TRIP 600 steel. In addition, welding crack susceptibility tests revealed that weldments were free of surface crack and other imperfection. All experimental results of this steel showed fairly good weldability. For application, the crossmember in automobile made of this steel exhibited excellent weldability, and fatigue and durability tests were also accomplished for crossmember assembly.
关键词:
TRIP steel;weldability;welding crack susceptibility;mechanical property;impact toughness
SHI Wen
,
LI Lin
,
Bruno C De Cooman
,
Patrick Wollants
,
YANG Chunxia
钢铁研究学报(英文版)
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 steel. The thermal decomposition data of samples soaked in liquid nitrogen after TRIP treatment were all similar to those without additional low temperature treatment. It 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
