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Development of Chinese duplex stainless steel in recent years

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Journal of Iron and Steel Research International 2017年第2期24卷 121-130页

作者： zhi-gang song Han Feng Shao-mei Hu Institute for Special Steels Central Iron and Steel Research Institute Beijing 100081 China

The development in research, production, applications, and national standards of Chinese duplex stainless steel （DSS） in recent years was introduced in light of the worldwide development in the field of DSS. The results showed that the output of Chinese DSS increased greatly, and at the same time its grade gradually evolved into a collaborative developing series including the main grade type 2205 and other DSS types in recent years. Economical DSS and super DSS underwent rapid development, especially after 2010. In re- cent years, the application of Chinese DSS has been expanded further not only in traditional application ar- eas such as the petrochemical industry, but also in diverse new fields such as oil and gas transportation, chemical tanker manufacturing, nuclear power plants, and construction. Moreover, due to the increase in output and improvement in quality, as well as applications in Chinese projects, Chinese DSS has also been exported to the Middle East, Eastern Europe, and other regions.

关键词： Duplex stainless steelNitrogen alloyingHot ductilityPrecipitated phase

Effect of Precipitation on Hot Deformation Behavior and Processing Maps of Nickel-Base UNS N10276 Alloy

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Acta Metallurgica Sinica(English Letters) 2017年第11期30卷 1119-1134页

作者： En-Xiang Pu Wen-Jie Zheng zhi-gang song Han Feng Han Dong School of Materials Science and Engineering Tsinghua University Beijing 100084 China Central Iron and Steel Research Institute Beijing 100081China

The hot deformation characteristics and processing maps of aged nickel-base UNS N10276 alloy were inves- tigated and compared with those of solution-treated UNS N10276 alloy at temperatures of 950-1250 ℃ and strain rates between 0.01 and 10 s-1. The dominant precipitated phase in the aged alloy was identified as topologically close-packed （TCP） # phase enriched in Mo and Ni. The precipitates present in the UNS N10276 alloy could significantly facilitate flow softening after peak stress at temperatures lower than 1150 ℃ and strain rates higher than 0.01 s-1. Processing maps at true strains of 0.1-0.9 were developed using the dynamic materials model and experimental flow stress data. Although aging treatment slightly shrank the suitable hot working window of this alloy, the aged alloy showed higher peak efficiencies of power dissipation and smaller unstable regions in comparison with solution-treated alloy. Furthermore, aging treatment eliminated the instability region of processing maps at true strains of 0.2-0.5. The precipitated phase promoted dynamic recrystallization （DRX） by the particle-stimulated nucleation （PSN） mechanism, which resulted in the larger fraction of DRX as well as finer and more uniform grain structure in the aged alloy specimens compared to the solution-treated alloy.

关键词： UNS N10276 alloy Precipitation Hot deformation Processing map

Constitutive Modeling for Flow Behaviors of Superaustenitic Stainless Steel S32654 during Hot Deformation

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Journal of Iron and Steel Research International 2016年第2期23卷 178-184页

作者： En-xiang PU Han FENG Min LIU Wen-jie ZHENG Han DONG zhi-gang song Central Iron and Steel Research Institute Beijing 100081China School of Materials Science and Engineering Tsinghua UniversityBeijing 100084China

Hot deformation behavior of superaustenitic stainless steel S32654 was investigated with hot compression tests at temperatures of 950-1250 C and strain rates of 0. 001-10 s-1. Above 1150 ℃, with strain rate lower than 0.1 s -1 , the flow curves exhibit nearly steady state behavior, while at higher strain rate, continuous flow softening occurs. To provide a precise prediction of flow behavior for the alloy, the constitutive modeling considering effect of strain was derived on the basis of the obtained experimental data and constitutive relationship which incorporated Ar- rhenius term and hyperbolic sine type equation. The material constants α, n, Q and lnA are found to be functions of the strain and can be fitted employing eighth-order polynomial. The developed constitutive model can be employed to describe the deformation behavior of superaustenitic stainless steel S32654.

关键词： S32654 superaustenitic stainless steel hot deformation constitutive modeling

Grain Growth Behavior of Inconel 625 Superalloy

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Journal of Iron and Steel Research International 2016年第10期23卷 1111-1118页

作者： Min LIU Wen-jie ZHENG Jin-zhong XIANG zhi-gang song En-xiang PU Han FENG School of Physics Science and Technology Yunnan University Kunming 650093 Yunnan China Central Iron and Steel Research Institute Beijing 100081 China School of Materials Science and Engineering Tsinghua University Beijing 100084 China

The grain growth（GG）behavior of Inconel 625 superalloy was studied in the temperature range of 900-1 250 ℃and holding time range of 10-80 *** of the alloy were characterized by optical metallography,scanning electron microscopy（SEM）and transmission electron microscopy（TEM）.Grains grew obviously with either increasing temperature or extending holding time at temperatures above 1 050℃.However,at temperatures lower than 1 050 ℃,the GG was sluggish due to the pinning effect of carbide particles on grain boundary（GB）.Threshold temperature for transition from mixed grain structure to uniform one was considered to be around 1 100℃.Once the temperatures surpassed 1 200℃,an instant increase in the grain size occurred showing no dependence on holding *** analysis showed that the dominant second phase formed heterogeneously on the GB was M6 C,which significantly impeded grain *** the basis of experimental data,the mathematical model of GG was established,which can describe GG behavior of Inconel 625 alloy during solution treatment（ST）at 1 100-1 250 ℃.The activation energy for GG of Inconel 625 alloy was 207.3kJ,which suggested that the GG of Inconel 625 alloy was controlled by the process of GB diffusion.

关键词： Inconel 625 alloy growth kinetics solution treatment precipitation

Optimization of Hot Workability in Superaustenitic Stainless Steel 654SMO

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Journal of Iron and Steel Research International 2014年第10期21卷 975-982页

作者： En-xiang PU Wen-jie ZHENG zhi-gang song Jin-zhong XIANG Xian-ping WEI School of Physics Science and Technology Yunnan University Central Iron and Steel Research Institute

Hot compression tests were conducted on a Gleeble-3800 machine in a temperature range of 950 to 1200 ℃ and a strain rate range of 0. 001 to 10 s-1 in order to study the hot deformation behaviour of superaustenitic stainless steel 654SMO. The results show that peak stress increases with decreasing temperature and increasing strain rate, and the apparent activation energy of this alloy was determined to be about 494 kJ/mol. The constitutive equation which can be used to relate the peak stress to the absolute temperature and strain rate was obtained. The processing maps for hot working developed on the basis of flow stress data and the dynamic materials model were adopted to op- timize the hot workability. It is found that the features of the maps obtained in the strain range of 0.2 to 1.0 are fun- damentally similar, indicating that the strain does not have a substantial influence on processing map. The combina- tion of processing map and mierostructural observations indicates that the favorable hot deformation conditions are located in two domains of processing map. The first domain occurs in the temperature range of 980 to 1035 ℃ and strain rate range of 0. 001 to 0.01 s-1 with a peak efficiency of 55%. The second domain appears in the temperature range of 1 120 to 1 180 ℃ and strain rate range of 0.3 to 3 s-1 with peak efficiency of 35%. Compared to other stable domains, the specimens deformed in these two domains exhibit full dynamic recrystallization grains with finer and more uniform sizes. An instability domain occurs at temperatures below 1 100 ℃ and strain rate above 0.1 s-1 , and flow instability is manifested in the form of flow localization.

关键词： 654SMO steel superaustenitic stainless steell processing mapl hot deformationl dynamic recrystallization

Tissue elasticity displayed by elastography and its correlation with the characteristics of collagen type I and type III in prostatic stroma

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Asian Journal of Andrology 2014年第2期16卷 305-308,I0011,I0012页

作者： Jie Tang Yan Zhang Ming-Bo Zhang Yan-Mi Li Xiang Fei zhi-gang song Department of Ultrasound Department of Pathology Chinese People's Liberation Army General Hospital Beijing China

We investigated the prostate elasticity displayed by elastography and its correlation with the content and distribution of collagen type I （Col1） and type III （Col3）. A total of 62 patients underwent transrectal real-time tissue elastography （TRTE） examinations, Targeted biopsies were performed after 12-core systematic biopsy, The tissues corresponding to the elastograms were stained with picric acid-sirius red. The distribution of Col I and type Col3 was observed, and the collagen volume fraction （CVF） of these two types of collagen fibers was calculated, The CVFs of Coll in the stiff and soft groups were 0.05 ± 0.02 and 0.02 ± 0.01 {P= 0.002）, respectively. The CVFs of Col3 in the stiff and soft groups were 0.05 ± 0.04 and 0.07 ± 0,03 （P= 0,13）, respectively, The circular analysis results showed that collagen fibers were disorganized both in the soft and stiff groups, Coll and Col3 were mainly cross-linked, and some parallelization was observed in the sections. The distributions of Coll and Col3 were different between the stiff and soft groups （P = 0,03）, In conclusion, the texture of the prostate is due to the content of Coll and its relative correlation with Col3.

关键词： elastography extracellular matrix lesion prostate ultrasound

Effects of Carbon Content on Mechanical Properties of Inconel 718 Alloy

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Journal of Iron and Steel Research International 2015年第1期22卷 78-83页

作者： Wen-jie ZHENG Xian-ping WEI zhi-gang song Qi-long YONG Han FENG Qing-cheng XIE Central Iron and Steel Research Institute Materials Research Center Dong Fang Steam Turbine Works No.704 Institute of China Shipbuilding Industry Corporation

For improving the service performance of Inconel 718 alloy, especially used as a corrosion-resistant alloy for special environment, the microstructure and mechanical property of different carbon-containing Inconel 718 alloys were investigated by the Thermo-Calc software and experiments. The experimental results indicated that the mor- phology, distribution and types of carbides mainly existing in the form of MC＇were hardly influenced by solution treatment at 1050 ℃ for 1 h. The precipitation amount and particle size of carbides decreased with the decrease of carbon content, which was the main reason resulting in the increase of ductility and toughness. In addition, moving dislocation could be restrained by the precipitation of carbides. Therefore, the strength could benefit from the precip- itation strengthening of carbides when the precipitation of γ′/γ″ phase was not influenced by the precipitation of carbides.

关键词： Inconel 718 alloy microstructure carbide mechanical property precipitation strengthening

Strain-induced Precipitation Behavior ofδPhase in Inconel 718 Alloy

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Journal of Iron and Steel Research International 2014年第3期21卷 375-381页

作者： Xian-ping WEI Wen-jie ZHENG zhi-gang song Ting LEI Qi-long YONG Qing-cheng XIE Faculty of Metallurgical and Energy Engineering Kunming University of Science and Technology Central Iron and Steel Research Institute No.704 Institute of China Shipbuilding Industry Corporation

To study the precipitation dynamics of 3 phase in Inconel 718 alloy, two-stage interrupted compression method was used in the region of cold deformation temperatures and the temperatures range from 875 to 975 ℃. The precipitation-time-temperature （PTT） curve of 3 phase was obtained by analyzing the softening kinetics curves. For verifying the type of the precipitates and confirming the validity of the test, the transmission electron microscopy （TEM）, scanning transmission electron microscopy （STEM） and energy dispersion spectrum （EDS） were em- ployed. Experimental results indicated that the PTT curve for 3 precipitation exhibited a typical ＂C＂ shape and the nose points of start and finish precipitation were about 5 s at 920 ℃ and 2 815 s at 940 ℃, respectively. In addition, the nucleation of δ was heterogeneous. The nucleation sites varied with temperatures, including dislocation, grain boundary and stacking fault within γ″ phase. And 3 particles grew quickly at higher temperature with lower density. Moreover, the driving force of nucleation was mainly including chemical free energy, interracial energy and disloca- tion distorted energy. And the dislocation distorted energy could decide the density of nucleation in the strain-induced process.

关键词： Inconel 718 alloy strain-induced precipitation cold deformation nucleation site

Morphologies of secondary austenite in 2507 duplex stainless steel after heat treatment

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Journal of Iron and Steel Research International 2022年第6期29卷 994-1003页

作者： Xiao-han Wu zhi-gang song Bao-shun Wang Ming-hua Wu Qi-liang Nai Liang Yao Han Feng Wen-jie Zheng School of Material Science and Engineering University of Science and Technology BeijingBeijing 100083China Special Steel Institute Central Iron&Steel Research InstituteBeijing 100081China Engineering Research Center of High-Performance Nuclear Power Pipe Forming of Zhejiang Province Huzhou 313028ZhejiangChina Yongxing Special Stainless-Steel Co. Ltd.Huzhou 313005ZhejiangChina Zhejiang Jiuli Hi-Tech Metals Co. Ltd.Huzhou 313028ZhejiangChina

The microstructure evolution of secondary austenite in 2507 duplex stainless steel was investigated by means of optical metallography,scanning electron microscopy and confocal scanning laser *** types of secondary austenite(γ2)morphologies including partially transformed austenite,grain boundary austenite,Widmannstätten austenite(WA)and intragranular austenite could be formed during cooling after solution *** was concluded that secondary austenite morphology was mainly dependent on cooling *** mechanisms of WA formation were *** nucleated at grain boundary of ferrite or at the formed phase *** electron microscopy(TEM)analysis displayed that WA grew in parallel to the *** effects of Cr_(2)N on secondary austenite precipitation were discussed in *** Cr_(2)N was involved,a mechanism was proposed that secondary austenite formed by element diffusion,leading to the migration of the austenite–ferrite ***_(2)N acted as the nucleation sites forγ2 and provided the nitrogen for the transformation;meanwhile,the precipitation of Cr_(2)N during the rapid cooling was captured by TEM.A process of nucleation followed by diffusion was concluded to be the formation of secondary austenite with no Cr_(2)N *** decomposition of secondary austenite was also studied,which was found to be a diffusion mechanism followed by displacement in connection with the element distribution.

关键词： Secondary austenite Duplex stainless steel Heat treatment Cooling rate Element diffusion