METHOD OF MANUFACTURING BENT ARTICLE WITH EXCELLENT FATIGUE PROPERTY, AND BENT ARTICLE

摘要

PROBLEM TO BE SOLVED: To improve the fatigue property of a bent part by reducing residual stress without depending on a special residual stress reducing process such as return and heating even when performing a bending work of a steel plate in which the ratio of curvature radius R to sheet thickness t is >=2. SOLUTION: By performing the almost L-shaped bending of the steel plate having the thickness t of 7-10 mm and the tensile strength of >=490 MPa, to >=70 deg. using a die and a punch the radius R of curvature in a sholder part of which is >=2 times the thickness t, the bent article is manufactured. The clearance c between the die and the punch is wider than the thickness t and narrower than 1.02×thickness t. In the bent article manufactured in this manner, the peak of the residual stress in the bending ending region (B) is not more than the maximum value of the residual stress in the bending begining region (A).