1992 Fiscal Year Final Research Report Summary
Improvement of Formability by Moderate Temperature Forming and Thermo-mechanical Process and Examination of Fatigue Properties of TRIP-aided Dual-phase Steel Sheets.
| Project/Area Number |
03805060
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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 |
金属加工(含鋳造)
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| Research Institution | Faculty of Textile Science and Technology, Sinshu University |
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Principal Investigator |
SUGIMOTO Koh-ichi Faculty of Textile Science and Technology, Sinshu University. Functional Machinery and Mechanics. Associate Professor, 繊維学部, 助教授 (50094272)
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| Co-Investigator(Kenkyū-buntansha) |
KOBAYASHI Mitsuyuki Faculty of Engineering, Shinshu University. Mechanical Systems. Professor, 工学部, 教授 (80021020)
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| Project Period (FY) |
1991 – 1992
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| Keywords | Dual-phase steel / High strength steel / Retained austenite / TRIP / Stretch forming / Stretch flanging / Moderate temperature / Thermomechanical process / Low cycle fatigue |
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| Research Abstract |
TRIP-aided dual-phase steels (TDP steels) have been developed to improve safety and fuel efficiency by reducing vehicle weight. The purpose of the present investigation is to improve stretch-formability and stretch-flange-ability and to examine fatigue strength of TDP steels.
The stretch-formability and stretch-flangeability of TDP steels were improved by moderate temperature forming at 20ﾟC to 200ﾟC. The lower Ms temperature of the retained austenite, the greater these formability and the lower the optimum forming temperature. Thermo-mechanical process in alpha+gamma region gave a significant amount of retained austenite and fine microstructure, but increased the retained austenite Ms temperature, particularly for low manganese and low sili-con steels.
Great fatigue hardening appeared for TDP steels owing to strain induced transformation of the retained austenite and internal stress resulting from a difference of strength between matrix and second phase. The fatigue hardening decreased with increasing testing temperature. Higher fatigue limit compared to that of a conventional dual-phase steel was obtained at 100 to 200ﾟC. The reason is under investigation.
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