| Project/Area Number |
03650577
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
金属材料(含表面処理・腐食防食)
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| Research Institution | TOTTORI UNIVERSITY |
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Principal Investigator |
OKA Muneo TOTTORI UNIV., FACULTY OF ENGINEERING. PROFESSOR, 工学部, 教授 (60029866)
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| Co-Investigator(Kenkyū-buntansha) |
HAYAKAWA Motozo TOTTORI UNIV., FACULTY OF ENGINEERING. ASSOC, PROFESSOR, 工学部, 助教授 (60093621)
OKAMOTO Hisaki TOTTORI UNIV., FACULTY OF ENGINEERING. RES. ASSOCIATE, 工学部, 助手 (30029889)
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| Project Period (FY) |
1991 – 1992
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| Project Status |
Completed (Fiscal Year 1992)
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| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1992: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1991: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Keywords | Plain Carbon Steel / Bainite Transformation / Structure / Morphology / Formation Mechanism |
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| Research Abstract |
Formation temperature ranges of upper and lower bainites in plain carbon steels (0.04-1.80%C) were studied metallographically. Kinetics and crystallography were also studied by means of dilatomety and transmission electron microscopy. The results obtained in this experiment are summarized as follows :
1. The bainitic ferrite can be considered to nucleate and grow displacively when the Ms temperature of a small region rised up to the isothermal transformation bath temperature by the thermal fluctuation of carbon concentration in austenite matrix.
2. The essential difference between upper and lower bainites was their morphology of ferrite. As the reason why the lath shaped upper bainite was formed above 350ﾟC, it was considered that upper bainite nucleates and grows at the carbon concentration (less than 0.55%) of Ms of the lath martensite, the plate-like lower bainite below 350ﾟC was considered to be formed at the carbon concentration (more than 0.55%) of Ms of the plate martensite.
3. Carbides in the upper and lower bainites precipitated directly from austenite after and simultaneously with the bainitic ferrite formation, respectively.
The proposed mechanism explained satisfactorily that, (1) the Bs temperature was a constant of 600ﾟC, morphological change among the BI, BII, and BIII type upper bainites with descending temperature, and (3) the transition temperature from upper to lower bainites was a constant of 350ﾟC. We are now preparing four papers based on the present results.
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