| 摘要 |
In this method that is for producing a welded steel pipe by means of a press bending method and that produces a steel pipe by causing a starting-material steel plate to be three-point bend press-molded into an open pipe by means of a pair of dies, which are disposed at a predetermined distance in the direction of steel plate transfer, and a punch, which presses the steel plate between the pair of dies, and then welding the open pipe, after performing a plurality of repetitions of first-half press molding from one end in the widthwise direction of the steel plate towards the center in the widthwise direction (but excepting the center in the widthwise direction), performing a plurality of repetitions of second-half press molding from the other end in the widthwise direction towards the center in the widthwise direction (but excepting the center in the widthwise direction), and when finally performing final press molding in the center in the widthwise direction to result in an open pipe, causing the portion of the steel plate supported at the dies at the center side in the widthwise direction of the steel plate at the final pass of the second-half press molding to be an unmolded portion, thus producing an open pipe having a small amount of irregularity in the welded portion. |
