| Title |
Effects of Coiling Temperature and Carbides Behavior on Stretch-flangeability for 980MPa Hot-rolled Steels |
| Authors |
천은준(Eun Joon Chun); 이주승(Ju Seung Lee); 도형협(Hyeong Hyeop Do); 김성주(Seong Ju Kim); 최윤석(Yoon Suk Choi); 박용호(Yong Ho Park); 강남현(Nam Hyun Kang) |
| DOI |
https://doi.org/10.3365/KJMM.2012.50.7.487 |
| ISSN |
1738-8228(ISSN), 2288-8241(eISSN) |
| Keywords |
metals; rolling; precipitation; hardness test; stretch-flangeability |
| Abstract |
To analyze the factors on stretch-flangeability for 980 MPa-grade hot-rolled steels, two types of steels (Fe-Cr and Fe-Mo) were manufactured by hot-rolling. Manufactured steels at the low coiling temperature, such as 400 and 500℃, had poor stretch-flangeability due to un-uniformly distributed carbides and a large deviation of interphase hardness. However, when the coiling temperature was set at 650℃ with Fe-Cr steel, 998 MPa of ultimate tensile strength, 19% of total elongation and 65% of the hole expanding ratio were achieved by microstructural constituents of polygonal ferrite (PF) and granular ferrite (GF) dispersed with fine carbides (<50 nm). Therefore, the material to attain 980 MPa with superior formability was the Fe- Cr steel that was precipitation-hardened in polygonal ferrite and granular ferrite at the coiling temperature 650℃. |