The present status and actual trends of the technological developments in the application of IF steels in Korea is discussed. The auto industry is the biggest market of IF (interstitial-free) steels. This is due to superior formability of IF steels compared with conventional low carbon steels. Strips with superior formability reduce the failure ratio during stamping and enable one-piece stamping of auto parts, enabling cost reduction and weight saving. Several different mild steel grades are available: CQ, DQ, DDQ, etc. The most recent IF steel grade is hyper-EDDQ. The deep drawability of this steel is greater than 2.7. Careful control of impurity, cleanliness and cold rolling and continuous annealing parameters should be carried out to produce this steel. As regulations for environmental protection and safety become stricter, the use of high strength IF steels will increase further. The tensile strength limit of IF steels is considered to be about 500 MPa. Since IF steels with up to this strength level have already been developed, the future development will be focused on formability and surface quality improvement of coated products. The major strengthening mechanism employed to increase the tensile strength of ultra-low carbon steels is solution hardening and the typical elements used are P, Mn, Si, Cr and Cu. IF steels are also manufactured in the bake hardening grade. Springback is the common problem in stamping of high strength IF steels. Optimization is required in controlling the blank holder force and the friction. IF steels are also manufactured in galvanized condition. The Al content in the Zn bath is an important parameter determining the galvannealing behavior. Improvement of the internal and surface quality is always the challenging job. This paper summarizes the present production and application status of IF steels for automotives.
Interstitial-free steels for automotive applications in Korea
IF-Stähle zur Anwendung im Fahrzeugbau in Korea
2003
8 Seiten, 9 Bilder, 2 Tabellen, 23 Quellen
Aufsatz (Konferenz)
Englisch
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