Mechanism of Formation of Streak-shaped Defects on Ultra-low Carbon IF Steel for Automobile Outer Panels after Press Forming and Influence of Slab Reheating Temperature before Hot Rolling and Sb-addition on Defects

• DOI: 10.2355/tetsutohagane.tetsu-2015-061
• Publication Date: 2016-03-31T00:31:16Z
• Authors: Hiroshi Tsunekawa; Takako Yamashita; Tomohiro Aoyama; Reiko Sugihara
• Keywords: Slab; Streak; Carbon steel; Carbon fibers

Streak-shaped defects were infrequently observed on ultra-low carbon IF cold-rolled steel sheets for automotive outer panels after press-forming. The occurred due to heterogeneous remaining of elongated grains the surface layer. Elongated are hard recrystallize pinning effect small precipitates grain boundaries. These consist mainly Ti(NC), TiS and AlN. In order eliminate streak defect, lower excess Ti, temperature slab reheating Sb-addition efficient. countermeasures result in a drastic reduction defect ratio. This improvement is considered be obtained Ti(CN), AlN