Formability of Bimodal Steel Strips Subjected to Heavy-reduction Controlled-rolling Process

• Published in: Tetsu-to-Hagane Vol. 105; no. 2; pp. 190 - 196
• Main Authors: Park, Hyung-Won, Shimojima, Kei, Sugiyama, Sumio, Yanagimoto, Jun
• Format: Journal Article
• Language: English; Japanese
• Published: The Iron and Steel Institute of Japan 2019
• Subjects: anisotropy; bimodal structure; controlled rolling process; formability; low carbon steel
• ISSN: 0021-1575; 1883-2954
• DOI: 10.2355/tetsutohagane.TETSU-2018-074

Erichsen and deep drawing tests were performed to examine the formability of 0.2% carbon steel sheets containing the bimodal microstructure fabricated by 70-75% heavy-reduction controlled rolling process with a range of heating temperatures from 700-1000°C. The formability of steel sheets was analyzed and discussed in terms of the microstructure, the crystallographic texture, the strain-hardening exponent, and the anisotropy coefficient, which are obtained from the tensile test. In Erichsen test, Erichsen Index (EI) of 900- and 1000°C-heated specimens with a bimodal structure of submicron-sized grains (< 1 μm) and micron-sized grains (2-5 μm) is similar to that of as-received specimen with an average grain size of 41 μm, meaning superior formability. In deep drawing test, failure took place in all 700°C-heated specimens, while others could be drawn with a drawing ratio of 2.0. 900- and 1000°C-heated specimens were uniformly deformed without ears.