| 摘要 |
PURPOSE:To form a metallic plate in an arc shape while securing sufficient strength in lengthwise direction by rolling the metallic plate nearly in lengthwise direction, and by regularly varying the extent of the rolling from one end side to the other end side at right angles in said lengthwise direction. CONSTITUTION:A beltlike metallic plate 6, e.g. steel is rolled at more than one part 7 in lengthwise direction. The rolled parts 7 have the regularly varying extents of rolling from one end side (a) to the other end side (b) nearly at right angles in the lengthwise direction of the metallic plate 6. As a result, the extents of the elongation of the metallic plate 6 which correspond to said extents of rolling are varied regularly and the metallic plate 6 has the arc-shaped parts 8 with a radius of curvature centering on a point O. Thus, the metallic plare 6 has the arc-shaped parts 8 succeeding in a doughnut shape or arranged at adequate intervals in a rectangular shape. |
