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Effect of Dissolved and Precipitated Niobium in Microalloyed Steel on Deformation Induced Ferrite Transformation(DIFT)

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Journal of Iron and Steel Research International 2009年第4期16卷 67-71页

作者： LIU qing-you DENG Su-huai SUN Xin-jun DONG Han weng yu-qing Central Iron and Steel Research Institute Beijing 100081 China Chinese Society for Metal Beijing 100711 China

Hot deformation processing was designed to study the effects of niobium （Nb） on DIFT. A prestrain of 0.51 at 880 ℃ for different isothermal time was used for adjusting the deformed austenite constitution and Nb existing state, followed by a secondary heavy deformation at 780 ℃ for inducing the ferrite transformation. The volume fraction and grain size of deformation induced ferrite （DIF） obtained at different isothermal time between double hits were investigated. It was found that Nb dissolved in austenite is adverse to DIFT; however, the precipitation of Nb is beneficial to DIFT. As Nb plays the role in the conventional TMCP, Nb retards the recrystallization of deformed austenite and enhances the deformation stored energy in the multipass deformation, and in result, Nb promotes DIFT.

关键词： niobium precipitation recrystallization deformation induced ferrite transformation

Effect of Boron on Delayed Fracture Resistance of Medium-Carbon High Strength Spring Steel

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Journal of Iron and Steel Research International 2007年第6期14卷 53-57,67页

作者： NIE Yi-hong HUI Wei-jun FU Wan-tang weng yu-qing State Key Lab of Metastable Material Science and Technology Yanshan University Qinhuangdao 066004 Hebei China Institute for Structural Material Central Iron and Steel Research Institute Beijing 100081 China Chinese Society for Metals Beijing 100711 China

The delayed fracture behavior of medium carbon high strength spring steel containing different amounts of boron （0. 000 5%, 0. 001 6 %） was studied using sustained load delayed fracture test. The results show that delayed fracture resistance of boron containing steels is higher than that of conventional steel 60Si2MnA at the same strength level and it increases with the increase of boron eontent from 0. 000 5% to 0. 001 6%. The delayed fracture mode is mainly intergranular in the boron containing steels tempered at 350℃, which indicates that the addition of boron does not change the fracture character. However, the increase of boron content enlarges the size of the crack initia tion area. Further study of phase analysis indicates that most boron is in solid solution, and only a very small quantity of boron is in the M3 （C, B） phase.

关键词： borons delayed fracture resistances medium-carbon high strength spring steel

Hot Working of High Nitrogen Austenitic Stainless Steel

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Journal of Iron and Steel Research International 2010年第10期17卷 45-49,67页

作者： LANG yu-ping ZHOU Yong RONG Fan CHEN Hai-tao weng yu-qing SU Jie Institute for Structural Materials Central Iron and Steel Research Institute Beijing 100081 China School of Materials Science and Engineering Beihang University Beijing 100191 China Chinese Society for Metals Beijing 100711 China

With hot rolling in laboratory and Gleeble thermal simulator, the hot working of a high nitrogen austenitic stainless steel （HNASS） was researched. The results showed that dynamic recovery （DRV） and dynamic recrystalli- zation （DRX） in HNASS occurred during hot working, and both of them had well-defined stress peaks in flow curves under different conditions. During hot rolling experiment at temperature from 950 to 1 050 ℃, recrystallization phe- nomenon does not take place in test material until the deformation ratio is up to 40%. Recrystallization influences remarkably the strength and ductility of material, and the test HNASS possesses better combination of strength with ductility. According to the curve of θ--α （strain hardening rate-steady state stress）, the DRX critical strain of test material was determined. Also, the activation energy of hot working was calculated to be 746.5 kJ/mol and the equation of hot working was obtained.

关键词： HNASS hot working DRX: DRX critical strain

Hot Deformation Behavior of a New 9%Cr Heat Resistant Steel G115

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Journal of Iron and Steel Research International 2013年第9期20卷 73-79页

作者： YAN Peng LIU Zheng-dong LIU Wei BAO Han-sheng weng yu-qing Key Laboratory of Advanced Material of Ministry of Eclucation of China School of Materials Science and EngineeringTsinghua University Institute for Special Steels China Iron and Steel Research Institute

The hot deformation behavior of a new heat resistant steel Gl15 designed for 650 ℃ ultra-supercritical （USC） power plants was experimentally studied. Hot compression test was carried out in the temperature range of 900-1 200 ℃ and the strain rate range of 0.1-20 s i by using Gleeble 3800 thermal-mechanical simulator, and the corresponding flow curves were obtained. Experimental results show that the flow stress increases with the decrease of deformation temperature and the increase of strain rate. The hot deformation activation energy of G115 steel was determined to be 494 kJ/mol and the constitutive equation was also obtained. For convenience of the practical applica-tion, a good approximate equation was obtained for calculating the peak stress values of Gl15 steel under different deformation conditions. At the strain value of 0.9, natural logarithm of the critical Zener Hollomon parameter Zc of Gl15 steel was determined to be in the scope of 49.67 and 50.65, above which there will be no dynamic recrystalliza-tion （DRX）. And natural logarithm of the critical Zener-Hollomon parameter Zc of Gl15 steel was determined to be in the scopes of 45.58 and 46.27, below which full DRX may occur. Then, the status diagram of dynamic micro structures of G115 steel was established. In addition, the strain rate sensitivity of Gl15 steel is not constant during the test temperature range and it increases linearly from 900 to 1 200 ℃. Therefore, hot deformation at higher tem- peratures would obtain better workability.

关键词： heat resistant steel G115 hot deformation dynamic recrystallization constitutive equation Zener Hol-lomon parameter

1300 MPa High Strength Steel for Bolt with Superior Delayed Fracture Resistance

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Journal of Iron and Steel Research International 2002年第1期9卷 40-45页

作者： HUI Wei-jun DONG Han weng yu-qing CHEN Si-lian WANG Mao-qiu Central Iron & Steel Research Institute Chinese Society for Metals

By the increase in Mo content,the addition of microalloying elements V and Nb and by reducing the contents of Mn,P and S based on the composition of steel 42 CrMo,we have developed a 1 300 MPa-grade high strength steel(ADF1)for *** sustained load bending test,sustained load tensile test and stress corrosion cracking test have been carried out to evaluate the delayed fracture resistance of steel ADFl and commercial steel 42 *** results showed that steel ADF1 has superior delayed fracture resistance to that of 42 CrMo ***'s concluded that the superior delayed fracture resistance of ADF1 is mainly due to the increase of tempering temperature,fine homogeneously distributed MC carbide and fine prior austenite grain size.

关键词： high strength steel bolt steel delayed fracture hydrogen embrittlement stress corrosion

Effect of Heat Treatment on Delayed Fracture Resistance of High Strength Steel 30CrMnSi2NiNb

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Journal of Iron and Steel Research International 2003年第1期10卷 44-48页

作者： WANG Mao-qiu DONG Han HUI Wei-jun CHEN Si-lian weng yu-qing Central Iron and Steel Research Institute Chinese Society for Metals

The steel specimens of nominal composition 0.3C-1.0Cr-1.0Mn-2.0Si-1.0Ni-0.04 Nb were quenched and tempered or isothermally quenched from various *** is found that the steel quenched and tempered with a tensile strength of 1 500-1 600 MPa has a KISCC（critical stress intensity factor） value below 15.0 MPa · m1/*** steel isothermally quenched with a tensile strength of 1 350-1 750 MPa has a KISCC value about 20.0 MPa·m1/*** addition,with increase of isothermal quenching temperature,the tensile strength decreases greatly and KISCC value does not pronouncedly *** microstructure of isothermally quenched specimens is composed of bainite and retained *** delayed fracture resistance is dependent on the stability of austenite,which is in turn related to the retained austenite volume fraction and carbon content in austenite.

关键词： high strength steel heat treatment mixed microstructure delayed fracture

Microstructure of Ni-Based Self-Fluxing Alloy Coating(PartⅠ)

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Journal of Iron and Steel Research International 2005年第1期12卷 50-53页

作者： HUI Wei-jun DONG Han weng yu-qing WANG Mao-qiu CHEN Si-lian SHI Jie Central Iron and Steel Research Institute Chinese Society for Metals

The delayed fracture behaviors of CrMo-type high strength steels containing different amount of titanium(0to 0.10%)were *** steels were quenched at 880℃ and tempered from 400℃ to 650℃,and a wide range of tensile strength was *** sustained load tensile test was carried out by using notched tensile specimens in Walpole *** experimental results showed that with higher strength,the Ti-microalloyed steels show higher resistance to delayed fracture compared with non-microalloyed steel due to titanium beneficial role and microstructure *** undissolved TiC is uniformly distributed as strong hydrogen traps,retarding or preventing the diffusion and accumulation of hydrogen to lower-interaction energy sites,such as prior austenite and martensite lath boundaries in stress concentration ***,the grain refining effect of titanium is also an important factor to improve the delayed fracture resistance of Ti-microalloyed *** characteristics of delayed fracture remain nearly the same with titanium addition.

关键词： titanium delayed fracture high strength steel CrMo steel

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超细晶钢理论及技术进展

钢铁 2005年第3期40卷 1-8页

作者：翁宇庆中国金属学会北京100711

叙述了由国家973项目:“新一代钢铁材料的重大基础研究”所开展的超细晶钢理论及技术进展。形变相变耦合、纳米析出相引起超细晶以及机械制造用钢的超细晶热处理是3 个主要手段。相应的组织性能预报、细晶钢的焊接及化学冶金高洁净、凝... 详细信息

叙述了由国家973项目:“新一代钢铁材料的重大基础研究”所开展的超细晶钢理论及技术进展。形变相变耦合、纳米析出相引起超细晶以及机械制造用钢的超细晶热处理是3 个主要手段。相应的组织性能预报、细晶钢的焊接及化学冶金高洁净、凝固均质化及细化是制造和应用的关键技术。

关键词：钢超细晶技术

Threshold Stress Intensity of Hydrogen-Induced Cracking and Stress Corrosion Cracking of High Strength Steel

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Journal of Iron and Steel Research International 2001年第2期8卷 42-46页

作者： LI Hui-lu GAO Ke-wei QIAO Li-jie WANG Yan-bing CHU Wu-yang HUI Wei-jun DONG Han weng yu-qing University of Science and Technology Beijing Central Iron & Steel Research Institute

The threshold stress intensity of stress corrosion cracking(SCC) for 40 CrMo steel in 3.5%NaCl solution decreased exponentially with the increase of yield *** threshold stress intensity of hydrogen-induced cracking during dynamical charging for 40 CrMo steel decreased linearly with the logarithm of the concentration of diffusible *** equation was also applicable to SCC of high strength steel in aqueous *** critical hydrogen enrichment concentration necessary for SCC of high strength steel in water decreased exponentially with the increase of yield *** on the results,the relationship between K_(ISCC) and σ_(ys) could be deduced.

关键词： high strength steel stress corrosion hydrogen-induced cracking