V-bendability of Ultrahigh Strength Low Alloy TRIP-aided Steel Sheets with Bainitic Ferrite Matrix

Effect of retained austenite characteristics on V-bending in ultrahigh strength TRIP-aided steel sheets with bainitic ferrite matrix (TBF steel) was investigated for automotive applications. V-bending test was performed on a hydraulic testing machine using a rectangular specimen (50 mm in length, 5 mm in width, 1.2 mm in thickness) and 88-degree top angle punch (2.0 mm in punch top radius) and 88-degree groove angle die (12 mm in die groove width, 0.8 mm in die shoulder radius) in a processing speed of 1 mm/min. The main results are as follows.