| Project/Area Number |
59850123
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| Research Category |
Grant-in-Aid for Developmental Scientific Research
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| Allocation Type | Single-year Grants |
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| Research Field |
溶接工学
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| Research Institution | Osaka University |
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Principal Investigator |
ARAKI Takao 大阪大学, 工, 助教授 (70029312)
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| Project Period (FY) |
1984 – 1985
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| Project Status |
Completed (Fiscal Year 1985)
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| Budget Amount *help |
¥5,700,000 (Direct Cost: ¥5,700,000)
Fiscal Year 1985: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1984: ¥4,300,000 (Direct Cost: ¥4,300,000)
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| Keywords | Liquid metal embrittlement / Commercial weldable structure steel / Sustained load test / Time dependence fracture / 表面エネルギー / 粒界破壊 / 破壊時間の推定法 / 液体金属の硬さ依存性 |
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| Research Abstract |
The effect of hardness and grain size of steels and their welds on fracture stress and sensitivity of Liquid Metal Embrittlement Cracking in molten Zinc (L MEC) was investigated. The experiment was conducted using commercial weldable structual steels and Sustained Load Test (SLT) was conducted in molten Zinc with heating range of 430゜C-470゜C.
The liquid metal embrittlement cracking of heat affected zone (HAZ) of steel in hot dip galvanizing was investigated. The experiment was conducted using synthetic HAZ of JIS G 3444 STK55 and Sustained Load Test at 370゜C-470゜C heating range in liquid (molten) and solid Zinc.
The LMEC behavior of steels and welds in molten Zinc is of thermal activated process, and fractures are intergranular (IG) type witch corresponds to actual LMEC in hot dip galvanising. Estimation of fracture stress of steels and welds in molten Zinc is obtained by measuring Vicker's hardness and grain size, and these estimation values are correspond with test results. The sensitivity of LMEC is affected by hardness of steels and welds.
LMEC behavior is of thermal activated process and LMEC sensitivity is affected by hardness of HAZ. The coarse grain region in HAZ showned the highest LMEC sensitivity. The interfacial enegy of steel is redused by the exsistence of Zinc. The reaction rate process of LMEC of steel is controlled by grain boundery diffusion of Zinc. The nucleation and the propagation of LMEC in steel are likely to have a close relation to the reduction of interfacial energy due to the grain boundery diffusion of Zinc.
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