2022 Fiscal Year Final Research Report
Evaluation of Local Creep Properties in Weld Joints of Ferritic Heat-Resistant Steels and Control of Creep Strength by Microstructural Modification
| Project/Area Number |
20H02466
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Review Section |
Basic Section 26040:Structural materials and functional materials-related
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| Research Institution | Kyushu University |
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Principal Investigator |
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| Project Period (FY) |
2020-04-01 – 2023-03-31
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| Keywords | 高Crフェライト系耐熱鋼 / 溶接継手 / 溶接熱影響部 / クリープ変形 / ラスマルテンサイト / 電子顕微鏡 / 結晶方位解析 / デジタル画像相関法 |
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| Outline of Final Research Achievements |
In this study, the microstructure of HAZ was clearly captured by a multi-dimensional microstructural analysis method, and the local creep deformation behavior in HAZ was directly evaluated by combining Digital Image Correlation and high temperature creep test methods. A quantitative classification method for microstructures in HAZ was developed by quantitatively evaluating the martensitic microstructure, which is the matrix phase, and precipitates dispersed in the microstructure. By applying this quantitative classification method to specimens after creep deformation, the locations of concentrated voids were identified, which were found to be closely related to the precipitation density of carbides. In addition, the creep test method developed in this study succeeded in specifically identifying the locations where creep strain was concentrated within the welded joint.
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| Free Research Field |
材料工学
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| Academic Significance and Societal Importance of the Research Achievements |
高温用構造材料の多くは、構造物の中に組み込まれる際に溶接を必要とする。溶接継手の高温での寿命は、溶接時に形成する溶接熱影響部によって支配され、強度が半分ほどに激減することもある。したがって、溶接継手の高温変形機構とその破壊機構を理解し制御することは、安全安心に長時間にわたって材料を使用する観点から極めて重要である。本研究で確立した組織区分法と局所変形挙動解析手法は、溶接継手の変形と破壊の学理を議論する上で貴重なデータを創出できる有用な実験手法であり、学術的意義・社会的意義が高い。
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