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Effect of Dilution Ratio of the First 309L Cladding Layer on the Microstructure and Mechanical Properties of Weld Joint of Connecting Pipe-Nozzle to Safe-End in Nuclear Power Plant
Zhang Maolong1,2; Lu Yanhong1; Chen Shenghu3; Rong Lijian3; Lu Hao2
Corresponding AuthorRong Lijian(ljrong@imr.ac.cn)
2020-08-11
Source PublicationACTA METALLURGICA SINICA
ISSN0412-1961
Volume56Issue:8Pages:1057-1066
AbstractThe transition joint between austenitic stainless steel pipe and low alloy steel nozzle of the pressure vessel has attracted much attention due to the occurrence of failure during application. Usually, the low alloy steel vessel nozzle should be firstly buttered with several layers of austenitic stainless steel and then welded to the austenitic stainless steel pipe. Cracking phenomenon in the austenitic cladding layer sometimes occurs during fabrication of the transition joint, and the cracking mechanism is not very clear. It is worth noting that microstructure in the first buttering layer is largely dependent on the welding condition, because the variation of the buttering welding parameters would lead to different dilution ratios in the cladding layer. Therefore, it is essential to investigate the effect of dilution ratio of the cladding layer on the mechanical properties of the weld joint. In this work, microstructure of the 309L cladding layer under two kinds of buttering welding parameters was analyzed using OM, SEM, XRD, EPMA and EBSD, and its effects on the mechanical properties of the weld joints were further studied. The results show that duplex microstructure (austenite+martensite) are present in the 309L cladding layers under two kinds of buttering welding parameters, but the dilution ratio could determine the morphology and amount of martensite phase. Microstructure consisting of austenite and lath martensite is found in the 309L cladding layer with a lower dilution ratio. A higher dilution ratio could increase the amount of lath martensite. The formation of needle-like martensite occurs when the dilution ratio exceeds a critical value. The dilution ratio in the 309L cladding layers directly affects the mechanical properties of weld joint. For the weld joint with a lower dilution ratio, no cracking phenomonen is observed during three-point bending test, and the specimens fracture at the weld fusion zone after tensile test. For the weld joint with a higher dilution ratio, cracking phenomenon initiated at the 309L cladding layer is present during three-point bending test, and a significat reduction in the tensile strength and elongation is observed. During deformation, the strain incompatibility between needle-like martensite and austenite is produced, leading to the formation of microcracks at the interfaces. The preferential cracking at the 309L cladding layer with a higher dilution ratio leads to the degradation of mechanical properties of the weld joint.
Keywordbuttering welding dilution ratio microstructure mechanical property cracking mechanism
Funding OrganizationNational Natural Science Foundation of China ; Program of Key Laboratory of Nuclear Materials and Safety Assessment, Chinese Academy of Sciences
DOI10.11900/0412.1961.2019.00449
Indexed BySCI
Language英语
Funding ProjectNational Natural Science Foundation of China[51871218] ; Program of Key Laboratory of Nuclear Materials and Safety Assessment, Chinese Academy of Sciences[2019NMSAKF03]
WOS Research AreaMetallurgy & Metallurgical Engineering
WOS SubjectMetallurgy & Metallurgical Engineering
WOS IDWOS:000550617100001
PublisherSCIENCE PRESS
Citation statistics
Cited Times:3[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Identifierhttp://ir.imr.ac.cn/handle/321006/139852
Collection中国科学院金属研究所
Corresponding AuthorRong Lijian
Affiliation1.Shanghai Elect Nucl Power Equipment Co Ltd, Shanghai 201306, Peoples R China
2.Shanghai Jiao Tong Univ, Sch Mat Sci & Engn, Shanghai 200240, Peoples R China
3.Chinese Acad Sci, Key Lab Nucl Mat & Safety Assessment, Inst Met Res, Shenyang 110016, Peoples R China
Recommended Citation
GB/T 7714
Zhang Maolong,Lu Yanhong,Chen Shenghu,et al. Effect of Dilution Ratio of the First 309L Cladding Layer on the Microstructure and Mechanical Properties of Weld Joint of Connecting Pipe-Nozzle to Safe-End in Nuclear Power Plant[J]. ACTA METALLURGICA SINICA,2020,56(8):1057-1066.
APA Zhang Maolong,Lu Yanhong,Chen Shenghu,Rong Lijian,&Lu Hao.(2020).Effect of Dilution Ratio of the First 309L Cladding Layer on the Microstructure and Mechanical Properties of Weld Joint of Connecting Pipe-Nozzle to Safe-End in Nuclear Power Plant.ACTA METALLURGICA SINICA,56(8),1057-1066.
MLA Zhang Maolong,et al."Effect of Dilution Ratio of the First 309L Cladding Layer on the Microstructure and Mechanical Properties of Weld Joint of Connecting Pipe-Nozzle to Safe-End in Nuclear Power Plant".ACTA METALLURGICA SINICA 56.8(2020):1057-1066.
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