Korean Journal of Materials Research (한국재료학회지)
- Volume 9 Issue 12
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- Pages.1252-1262
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- 1999
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- 1225-0562(pISSN)
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- 2287-7258(eISSN)
A Study on the Stretch-flangeability of Hot-Rolled High Strength Steel with Ferrite-Bainite Duplex Microstructure
페라이트-베이나이트 복합조직 고강도 열연강판의 신장플랜지 특성에 관한 연구
- Cho, Yeol-Rae (Technical Research Laboratories, Pohang Iron & Steel Co.) ;
- Chung, Jin-Hwan (Technical Research Laboratories, Pohang Iron & Steel Co.) ;
- Koo, Hwang-Hoe (Kwangyang Steel Works, Pohang Iron & Steel Co.) ;
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Kim, In-Bae
(Dept. of Metallurgical Engineering, Pusan National University)
- Published : 1999.12.01
Abstract
The effect of microstructures on the strength-flangeability of Nb bearing hot-rolled high strength steel was investigated in order to improve the strength-flangeability of conventional TS 580MPa grades HSLA steel for the automotive wheel disc. The low temperature coiling method using 3-step controlled cooling pattern after hot rolling was effective to produce the Nb-bearing high strength steel with the polygonal ferrite and bainite duplex microstructures. It was suggested that the suppressed precipitation of grain boundary cementites and the decreased hardness difference between ferrite matrix and bainite cause the excellent stretch-flangeability of ferrite-bainite duplex microstructure steel. Therefore, the formation and propagation of microcracks were suppressed relative to the conventional HSLA steel with ferrite and pearlite microstructure. In addition, the elongation was improved as compared with that of hot-rolled steel sheets using conventional early cooling pattern because the volume fraction of polygonal ferrite was increased.
자동차 휠, 멤버 등의 소재로 사용되는 인장강도 580MPa급 열연강판의 버링성형성을 향상시키기 위하여 강판의 신장 플랜지성(stretch-flangeability)에 대한 미세조직 및 열간압연후 냉각인자의 영향에 대하여 검토하였다. 열간압연후 3단 냉각제어 및 권취온도의 극저온화에 의하여 신장플랜지성이 우수한 페라이트-베이나이트 복합조직강의 제조가 가능하며, 3단 제어냉각에서 강판의 온도를
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