ZHANG Jie
,
CAI Qing-wu
,
WU Hui-bin
,
ZHANG Kun
,
WU Bo
钢铁研究学报(英文版)
A new kind of Mn-Mo-Nb-Cu-B bainite steel which satisfied mechanical demands of E690 offshore plate steel was designed. The effect of two processes——thermomechanical control process (TMCP)+tempering (T) and thermomechanical control process (TMCP)+reheating and quenching (RQ)+tempering (T)——on microstructure and mechanical properties were studied by means of scan electron microscope (SEM), transmission electron microscope (TEM) and electron back scatter diffraction (EBSD). The results showed that optimal mechanical properties were available when tempering at 550 ℃ for both processes. The microstructure of the TMCP+T treated sample tempering in the range of 450 to 550 ℃ for 1 h did not change dramatically yet the lath in the TMCP+RQ+T treated sample merged together and transformed into polygonal ferrite. At the same time, the sub-structure of grain bainite transformed from lath to cell-shape to refine grains with tempering temperature mounting. Lots of sub-grain boundaries were located within bainite and adjacent bainite grain boundaries were high angle.
关键词:
offshore plate
,
low carbon bainitic steel
,
tempering
,
toughness
,
EBSD
JIAO Duo-tian
,
CAI Qing-wu
,
WU Hui-bin
,
et al
钢铁研究学报(英文版)
By analysing the stepped test pieces with optical microscope, the influence of the Technological parameters including rolling temperature and reduction amount on the Austenitic recrystallization fraction of Nb content of 0.08％ steel deformed in high temperature processing was studied, and the deformed austenite recrystallization figures of the test steel were obtained. The result indicates when the reduction amount is 60%, the critical temperature of complete recrystallization is 1070℃ and the borderline temperature of non recrystallization is 900℃. In contrast with general HSLA steel, the recrystallization and non recrystallization temperatures are respectively 120℃ and 100℃ higher so the steel contenting high Nb has better hot processing performance because Nb has great function of holding back recrystallization.
关键词:
Austenicic Recrystallization;Technological Parameter;high content Nb
YU Wei
,
QIAN Ya-jun
,
WU Hui-bin
,
YANG Yue-hui
钢铁研究学报(英文版)
Two types of steel, C-Mn-Cr-Mo-B microalloyed steel and C-Mn-Mo-Nb-Cu-B microalloyed steel, are designed to develop 1000 MPa ultra-high strength steel. Two kinds of processes, thermomechanical controlled process (TMCP) combined with traditional off-line quenching and tempering (QT) process versus controlled rolling process (CR) combined with direct quenching and tempering (DQ+T) process, are applied. The effect of heat treatment processing mode on the microstructure and mechanical properties is studied. The relationship between microstructure and mechanical properties is investigated by SEM and TEM. After tempering at 450 to 550 ℃ for 1 h, the steel produced by TMCP+QT process shows combination of excellent strength and low temperature toughness. The yield strength is above 1000 MPa, elongation above 15% and impact energy at -40 ℃ more than 30 J. After tempering at 450 ℃, a large number of ε-Cu particles precipitated in C-Mn-Mo-Nb-Cu-B steel produced by CR+DQ+T process lead to a significant increase in yield strength. And after tempering at 500 to 600 ℃, the yield strength of the steel is further improved to 1030 MPa because of precipitates, such as nitride or carbide of niobium, carbide of molybedenum and vanadium. When the tempering temperature is increased above 620 ℃, the yield strength is still higher than 1000 MPa and elongation is above 20% and impact energy at -40 ℃ is more than 35 J. After tempering at above 500 ℃, the toughness of the steel treated by TMCP+QT process is superior to that of steel by CR+DQ+T process.
关键词:
Heat treatment, High strength steel, Microtructures, Mechanical properties
ZHANG Kun
,
TANG Di
,
WU Hui-bin
钢铁研究学报(英文版)
The alloy was reheated to 580 ℃ for tempering at rates of 2, 5, 10, 20, and 40 ℃/s, respectively, after quenching. The amount, distribution, and stability of reversed austenite were investigated by X-ray diffraction (XRD) and electron back scatter diffraction (EBSD). The microstructure and cryogenic impact energy were studied by scanning electron microscope (SEM), transmission electron microscope (TEM) and Charpy V-notch (CVN) tests. The results showed that when the sample was heated at 10 ℃/s, the volume fraction of reversed austenite exhibited maximum of 8%; the reversed austenite was uniform along all kinds of boundaries; the reversed austenite contained higher concentration of carbon which enabled it to be more stable. The cryogenic toughness of the alloy was greatly improved when heated at 10 ℃/s, as the fracture surface observation showed that it mainly fractured in ductile rupture mode, which was consistent with the results of cryogenic impact energy.
关键词:
9Ni steel
,
heating rate
,
reversed austenite
,
cryogenic toughness
ZHANG Kun
,
WU Hui-bin
,
TANG Di
钢铁研究学报(英文版)
The high temperature deformation behavior of the 9Ni steel has been studied by the Gleeble-3500 tester. The relationship between deformation resistance and deformation degree, deformation temperature and deformation rate was revealed. The results show that when the deformation degree is less than 02, the deformation resistance increases by about 70 to 200 MPa, while the deformation degree varied between 02 and 04, the deformation resistance increases by about 30-40 MPa, when the deformation degree is larger than 04, the deformation resistance increases slowly, some become stable gradually. The influence of deformation temperature on deformation resistance is larger, and deformation resistance at higher temperature is about 160 MPa smaller than at lower temperature. Higher deformation rate leads to larger deformation resistance. The deformation resistance increases about 70 to 110 MPa with the increase of the deformation rate. A new and highly accurate mathematical model of the steel was established to describe the deformation behavior during rolling.
关键词:
9Ni steel
,
high temperature deformation resistance
,
mathematical model
