公开(公告)号：US20250033105A1

公开(公告)日：2025-01-30

申请号：US18715661

申请日：2022-12-28

Applicant: NIPPON STEEL CORPORATION

Inventor： Shohei TAMURA ,  Minoru KANEMARU ,  Rikuo KITAYAMA ,  Akira SHIRAI

IPC: B21D9/08 ,  B21D9/12

Abstract: A method is disclosed for forming a curved portion with a small curvature radius in an original tube while suppressing wrinkles and buckling. The method includes placing the original tube between a first die and a second die, and pressing one or more times on the original tube by bringing the first die and the second die closer together and pressing the first die and second die against the original tube, wherein the original tube has a circular cross-sectional shape in at least a portion thereof, the first die has a first curved surface, the second die has a second curved surface, in one of the pressing, cross-sectioning and bending are simultaneously performed on at least the portion of the original tube by pressing the first die and second die against at least the portion of the original tube; in the cross-sectioning, the circular cross-sectional shape of the original tube is reduced in diameter, and a diameter reduction rate in one time of the pressing is more than 0% and less than 10%.