| 摘要 |
PROBLEM TO BE SOLVED: To restrain the occurrence of bending wrinkles, improve bending accuracy, and lengthen the service life of a part while keeping quality of a product at a constant level by applying ceramic, particularly a silicon nitride sintered body excellent in a mechanical characteristic to a bending roller. SOLUTION: The whole ceramic bending roll 1 is formed of ceramic, and among various ceramics, a silicon nitride sintered body excellent in mechanical strength and tenacity and excellent in abrasion resistance is suitably used. The occurrence of bending wrinkles is restrained by using a silicon nitride. An elastic modulus of the silicon nitride is desirably not less than 250 GPa, and bending accuracy is improved thereby. Hardness of the silicon nitride is desirably not less than Hv 1400 from the viewpoint of lengthening the service life of the bending roller. The edge part 3 of a forming pipe groove 2 prevents a defect by contact with a pipe at machining work, and roundness having a radius of curvature not less than 1.5 mm is desirably arranged to lengthen the service life of a part. |
