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Effects of Si on the stability of retained austenite and temper embrittlement of ultrahigh strength steels

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International Journal of Minerals,Metallurgy and Materials 2011年第5期18卷 543-550页

作者： li-jun Wang Qing-wu cai hui-bin wu Wei Yu National Engineering Research Center for Advanced Rolling Technology University of Science and Technology Beijing Beijing 100083 China

Effects of silicon （Si） content on the stability of retained austenite and temper embrittlement of ultrahigh strength steels were investigated using X-ray diffraction （XRD）,transmission electron microscopy （TEM）,and other experimental *** results show that Si can suppress temper embrittlement,improve temper resistance,and hinder the decomposition of retained *** austenite appears gradually with the increase of Si content during *** has a significant effect on enhancing carbon （C） partitioning and improving the stability of retained *** and C atoms are mutually exclusive in lath bainite,while they attract each other in austenite.ε-carbides are found in 1.8wt% Si steel tempered at 250℃,and they get coarsened obviously when tempered at 400℃,leading to temper *** ε-carbides but acicular or lath carbides lead to temper embrittlement in 0.4wt% Si steel,which can be inferred as cementites and composite *** embrittlement is closely related to the decomposition of retained austenite and the formation of reversed austenite.

关键词： silicon ultrahigh strength steel retained austenite temper embrittlement reversed austenite

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

Influence of Mo on Growth and Coarsening of Nanometer-sized Carbides in Low-alloy Ferritic Steels Containing Ti

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Journal of Iron and Steel Research International 2014年第9期21卷 878-885页

作者： bin-hao HU Qing-wu cai hui-bin wu Engineering Research Institute University of Science and Technology Beijing

By optical microscopy, transmission electron microscopy and energy dispersive spectroscopy, the changes with aging time in size, composition and distribution of nanometer-sized （Ti, Mo）C precipitated in Ti-Mo low-alloy ferritc steel have been studied in comparison with that of nanometer-sized TiC precipitated in Ti low-alloy ferritc steel. It was found that the growth rate of （Ti,Mo）C in Ti-Mo steel was less than that of TiC in Ti steel. Nanometer- sized carbides formed at 650 ~C （or 550 ~C） for 55 h were at transitional stage from growth to coarsening. When aging time reaches 55 h, the coarsening rates of nanometer-sized carbides in Ti and Ti-Mo steel tend to be the same and in- variable. The influence of Mo on growth and coarsening of nanometer-sized carbides tends to decrease with increasing aging time, and Mo contents in nanometer-sized carbides with the same size at different aging time were different.

关键词： Ti-Mo low alloy ferritic steel nanometer-sized carbide precipitation strengthening Ostwald coarsening

Kinetics of Precipitation Behavior of Second Phase Particles in Ferritic Ti-Mo Microalloyed Steel

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Journal of Iron and Steel Research International 2013年第7期20卷 69-77页

作者： HU bin-hao cai Qing-wu wu hui-bin Engineering Research Institute University of Science and Technology Beijing

Two types of stress relaxation tests were carried out to investigate the incubation time for incipient precipi-tation of Ti（C,N） in deformed austenite and （Ti,Mo）C in ferrite of ferritic Ti-Mo microalloyed steel The size dis-tribution, amount and chemical composition of precipitates were obtained by using physicochemical phase analysis, and calculated according to thermodynamics and kinetics. The experimental results demonstrated that the incubation time was reduced with increasing Ti content, and prolonged with the addition of Mo. After 30 % deformation at 850 ℃, the nucleation of strain-induced Ti（C,N） was a relatively slow process. On the other hand, the temperature where the nucleation rate of （Ti, Mo）C in ferrite was the highest descended first and then ascended with increasing Ti content, and so did the temperature where the incubation time was the shortest. The key point is that the tempera-ture of steel containing about 0.09 % Ti is the lowest. The mass fraction of MC-type particles with size smaller than 10 nm in steel containing 0.09% Ti and 0.2% Mo reached 73.7%. The size distributions of precipitates in steel containing 0.09% Ti were relatively concentrated compared with that in steel containing 0.07% Ti.

关键词： ferritic Ti-Mo microalloyed steel precipitation behavior second phase particle stress relaxation parti-cle size distribution

Bacterial communities fluctuate in abundance and diversity under simulated oil-contaminated seawater conditions

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Journal of Oceanology and limnology 2019年第2期37卷 615-627页

作者： li Xiaohong YOU cai QU liang zhou bin TANG Xuexi XIAO hui College of Marine life Sciences Ocean University of China Qingdao 266003 China Laboratory for Marine Ecology and Environmental Science Qingdao National Laboratory for Marine Science and Technology Qingdao 266071 China Institute of Oceanology Chinese Academy of Sciences Qingdao 266071 China CNOOC limited Tianjin Branch Tianjin 300459 China

Marine bacteria have recently been identified as a potent solution for petroleum hydrocarbon degradation in response to hazardous oceanic oil spills. In this study, a mesocosm experiment simulating a petroleum spill event was performed to investigate changes in the abundance, structure, and productivity of bacterial communities in response to oil pollution. Cultured heterotrophic bacteria and total bacteria showed a consistent trend involving an immediate decrease in abundance, followed by a slight increase, and a steady low-level thereafter. However, the changing trend of bacterial productivity based on bacterial biomass and bacterial volume showed the opposite trend. In addition, the density of oil-degrading bacteria increased initially, then subsequently declined. The change in the bacterial community structure at day 0 and day 28 were also analyzed by amplified ribosomal DNA restriction analysis (ARDRA), which indicated that the species diversity of the bacterial community changed greatly after oil pollution. Alphaproteobacteria (40.98%) replaced Epsilonproteobacteria (51.10%) as the most abundant class, and Gammaproteobacteria (38.80%) became the second most dominant class in the whole bacterial community. The bacterial communities in oil-contaminated seawater (32 genera) became much more complex than those found in the natural seawater sample (16 genera). The proportion of petroleum-degrading bacteria in the oil-contaminated seawater also increased. In this study, culture-dependent and culture-independent approaches were combined to elucidate changes in both bacterial productivity and community structure. These findings will contribute to a better understanding of the role that bacteria play in material cycling and degradation in response to oil pollution.

关键词： petroleum pollution bacterial community bacterial growth amplified ribosomal DNA restriction analysis (ARDRA)

Effect of Nb on Austenite Recrystallization in High Temperature Deformation Process

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Journal of Iron and Steel Research International 2010年第8期17卷 39-44页

作者： JIAO Duo-tian cai Qing-wu wu hui-bin REN Yi National Engineering Research Center for Advanced Rolling Technology University of Science and Technology BeijingBeijing 100083China Angang Technology Center Anshan 114001LiaoningChina

By analyzing the stepped test pieces with optical microscope,the influence of the technological parameters including rolling temperature and reduction on the austenite recrystallization fraction of steel with Nb content of 0.08% deformed at high temperature processing was studied,and the deformed austenite recrystallization figures of the test steel were *** result indicates that when the reduction 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 than those of ordinary HSLA,so the steel with high content of Nb has better hot processing performance because Nb has great function of holding back recrystallization.

关键词： austenite recrystallization technological parameter niobium

Influence of Microstructural Evolution on the Hot Deformation Behavior of an Fe–Mn–Al Duplex lightweight Steel

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Acta Metallurgica Sinica(English Letters) 2018年第4期31卷 389-400页

作者： li-Xiong Xu hui-bin wu Xin-Tian Wang Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing100083China National Engineering Research Center of Advanced Rolling University of Science and Technology Beijing Beijing100083China

The hot deformation behavior of Fe-26Mn-6.2A1-0.05C steel was studied by experimental hot compression tests in the temperature range of 800-1050℃ and strain rate range of 0.01-30 s-1 on a Gleeble-3500 thermal simulation *** microstructural evolution during the corresponding thermal process was observed in situ by confocal laser scanning *** backscattered diffraction and transmission electron microscopy analyses were carried out to observe the microstructural morphology before and after the hot ***,interrupted compression tests were conducted to correlate the microstructural characteristics and softening mechanisms at different deformation *** results showed that hot compression tests of this steel were all carried out on a duplex matrix composed of austenite and *** the deformation temperature increased from 800 to 1050℃,the volume fraction of austenite decreased from 70.9% to 44.0%,while that of 6-ferrite increased from 29.1% to 56.0%.Due to the different stress exponents（n）and apparent activation energies（Q）,the generated strain was mostly accommodated by δ-ferrite at the commencement of deformation,and then both dynamic recovery and dynamic recrystallization occurred earlier in δ-ferrite than in *** interaction of strain partitioning and unsynchronized softening behavior caused an abnormal hot deformation behavior profile in the Fe-Mn-A1 duplex steel,such as yield-like behavior,peculiar work-hardening behavior,and dynamic softening behavior,which are influenced by not only temperature and strain rate but also by microstructural evolution.

关键词： Microstructural evolution Dual-phase steel lightweight component Hot deformation Dynamic recrystallization

Microstructure and mechanical performances of CGHAZ for oil tank steel during high heat input welding

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Rare Metals 2013年第2期32卷 129-133页

作者： Guo-li liang Shan-wu Yang hui-bin wu Xue-li liu Department of Material Physics and Chemistry University of Science Technology of BeijingBeijing 100083China National Engineering Research Center for Advanced Rolling Technology University of Science Technology of Beijing Department of Electro-Mechanical Engineering Tangshan College

Microstructure and mechanical performances of the coarse grain heat-affected-zone （CGHAZ） for oil tank steel with different Ti content were investigated through Gleeble-3500, scanning electron microscopy, transmission electron microscopy, and energy dispersive spectrometer. The results show that the strength and low- temperature toughness of base material are significantly improved for the high titanium content steel, but the impact toughness of CGHAZ is seriously deteriorated after the high heat input welding and declined sharply with the heat input increasing, while the effects of heat input on impact toughness are very weak for the low titanium content steel, impact toughness of which is gradually larger than that of high titanium content steel with the welding heat input increasing because of the granular bainite increasing, TiN particle coarsening, and （Ti, Nb） N composition evolution during the high input welding for high titanium content steel.

关键词： Ti-steel CGHAZ Impact toughness TiN particle

On the Mechanism of Condensation between 5-Amino-4, 6-dichloro- 2-methylpyrimidine and 1-Acetyl-2-imidazolin-2-one

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Chinese Chemical Letters 2002年第3期13卷 207-210页

作者： bin SU hui li Meng Shen cai Zhong Jun li Department of Chemical Biology School of Pharmaceutical sciencePeking UniversityBeijing 100083

The condensation reaction between 5-amino-4, 6-dichloro-2-methylpyrimidine and 1-acetyl-2-imidazolin-2-one using POCl3 as solvent gave 4, 6-dichloro-2-methyl-5-(1-acetyl-tetra- hydro-imidazo-2-ylidene)-aminopyrimidine predominantly and 4, 6-dichloro-2-methyl-5-{1-[1-(2- oxo-tetrahydro-imidazolyl)]-acetyene}-aminopyrimidine as by-product. No 4, 6-dichloro-2- methyl-5-(1-acetyl-2-imidazolin-2-yl)-aminopyrimidine was found. The result indicated an esterifi- cation-addition-elimination mechanism.

关键词： Moxonidine X-ray single crystal diffraction GHMBC.