| 摘要 |
PURPOSE:To prevent bulging of a steel plate in case of forming, and to freely obtain a steel pipe of intermediate size, by installing a control member to upper and lower master dies, when forming an O pipe by installing an insertion die to the inside of said dies, respectively. CONSTITUTION:A lower die 2 is formed by installing insertion dies 2b-2e to the inside of the cavity of a master die 2a. Also, an upper die 2' is formed in the same way. Subsequently, an O pipe swelling control member 1 is installed into a gap between the upper and lower dies 2', 2, and is fixed to the die 2. A steel plate 3 is charged between the upper die 2' and the lower die 2, and is pressed by making the upper die 2' descend. During this pressing, the member 1 is fixed to the die 2, and buckling and bulging of the steel plate 3 in the gap (l) are prevented. |
