| Project/Area Number |
12555193
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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 | 展開研究 |
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| Research Field |
Material processing/treatments
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| Research Institution | Tohoku University |
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Principal Investigator |
KOKAWA Hiroyuki GRADUATE SCHOOL 0F ENGINEERING, PROFESSOR, 大学院・工学研究科, 教授 (10133050)
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| Co-Investigator(Kenkyū-buntansha) |
SATO Susumu KAWASAKI STEELCORPORATION, SENIOR RESEARCHER, 技術研究所, 部門長(研究職)
SATO S. Yutaka GRADUATE SCHOOL OF ENGINEERING,RESEARCH ASSOCIATE, 大学院・工学研究科, 助手 (00292243)
WATANABE Tadao GRADUATE SCHOOL OF ENGINEERING, PROFESSOR, 大学院・工学研究科, 教授 (40005327)
YASUDA Koichi KAWASAKI STEEL CORPORATION, SENIOR RSEARCHER, 技術研究所, 主任部員(研究職)
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| Project Period (FY) |
2000 – 2002
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| Project Status |
Completed (Fiscal Year 2002)
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| Budget Amount *help |
¥13,600,000 (Direct Cost: ¥13,600,000)
Fiscal Year 2002: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2001: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2000: ¥11,500,000 (Direct Cost: ¥11,500,000)
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| Keywords | grain boundary engineering / grain boundary structure / stainless steel / sensitization / intergranular corrosion / intergranular precipitation / thermomechanical treatment / annealing twin / オーステナイト / クロム炭化物 / クロム欠乏 |
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| Research Abstract |
Sensitization by chromium depletion due to chromium carbide precipitation at grain boundaries in austenitic stainless steels can not be prevented perfectly only by previous conventional techniques, such as reduction of carbon content, stabilization-treatment, local solution-heat-treatment, etc. Recent studies on grain boundary structure have revealed that the sensitization depends strongly on grain boundary character and atomic structure, and that low energy grain boundaries such as coincidence-site-lattice(CSL) boundaries have strong resistance to intergranular corrosion. The concept of "grain boundary design and control" has been developed as grain boundary engineering (GBE). GBEed materials are characterized by high frequencies of CSL boundaries which are resistant to intergranular deterioration of materials, such as intergranular corrosion. A thermomechanical treatment was hid to improve the resistance to the sensitization by GBE. A type 304 austenitic stainless steel was cold-roll
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ed and solution-heat-treated, and then sensitization-heat-treated. The grain boundary character distribution was examined by orientation imaging microscopy (OIM). The intergranular corrosion resistance was evaluated by electrochemical potentiokinetic reactivation (EPR) and ferric sulfate-sulfuric acid tests. The sensitivity to intergranular corrosion was reduced by the thermomechanical treatment and indicated a minimum at a small roll-reduction. The frequency of CSL boundaries indicated a maximum at the small reduction. The ferric sulfate-sulfuric acid test showed much smaller corrosion rate in the thermomechanical-treated specimen than in the base material. A high density of annealing twins were observed in the thermomechanical -treated specimen. The results suggest that the thermomechanical treatment can introduce low energy segments in the grain boundary network by annealing twins and can arrest the percolation of intergranular corrosion from the surface. The effects of carbon content and other minor elements on optimization in grain boundary character distribution (GBCD) and thermomechanical parameters wore also examined during GBE. Less
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