| Project/Area Number |
07650773
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Physical properties of metals
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| Research Institution | Waseda University, School of Science and Engineering |
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Principal Investigator |
MAGUMO Michihiko Waseda University, School of Science and Engineering Professor, 理工学部, 教授 (40208062)
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| Project Period (FY) |
1995 – 1996
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| Project Status |
Completed (Fiscal Year 1996)
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| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1996: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1995: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Keywords | High Strength Steel / Hydrogen Embrittlement / Delayd Fracture / PC Ban / Hydrogen Analysis / Environmental Degradation / 水素昇温分析 / 鉄鋼 / 水素分析 |
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| Research Abstract |
The enhanced reduction of delayd fracture life by the environmental variations has been revealed with Prestressed Concrete steel bars. Applied load and external hydrogen potential were employed as the environmental parameters to be varied. Maximum load or potential were kept constant for the variations, and the degradation was evaluated by means of slow elongation rate tensile test and constant stress tests. The environmental variations dis not affect the amount or rate of hydrogen absorption, in contradictory to the former concepts that the load variation destroys the protective surface layr. The variation of hydrogen potential did not altered the diffusion constant of hydrogen which was evaluated from the absorption and desorption rates.
In order to examine the origin of the environmental variation effects, hydrogen thermal desorption spectroscopy was conducted. Two types of hydrogen exist in the weekly trapped hydrogen which desorbs at about 1000ﾟC,one is the hydrogen the amount of which increases with plastic deformation and the other is trapped a the intrinsic microstructures such as precipitates. From hydrogen thermal desorption spectroscopy of specimens subjected to plastic deformation and successive annealing at low temperatures as low as 200ﾟC,it was revealed that the trapping sites of hydrogen which increase with plastic deformation was point defects. Thermal desorption of hydrogen at 200ﾟC is the consequence of annealing out of point defects during heating. The effect of the environmental variations is likely to result in the increase of the defect density which is annealed out during heating. A new theory has been proposed that the hydrogen embrittlement of steels is induced by the defects which are introduced by plastic deformation and stabilized by hydrogen. The variance of environment enhances this effect.
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