| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of manufacturing an eccentrically expanded pipe, in which reduction in thickness of the peripheral surface of a highly expanded pipe on which cracking and necking are apt to occur is suppressed. SOLUTION: In the state where the end part 11 of a pipe stock part 1 is projected in the range of the concentric inner surface 311 of a concentric die 31 having a concentric inner surface 311 having a radius De which is larger than the orthogonal distance Ds from the axial center Oo of the pipe stock part 1 to the peripheral surface 21 of a low expansion pipe of an expanded part 2 and the concentric inner surface 311 having a radius De which is smaller than the orthogonal distance Db from the axial center Oo of the pipe stock part 1 to the peripheral surface 22 of the highly expanded pipe 22 of the expanded part 2, by force-fitting the concentric punch 32 into the end part 11 of the pipe stock part 1, the end part 11 is expanded concentrically. In the state where the end part 11 of the pipe stock part 1 which is concentrically expanded is projected in the range of the eccentric inner surface 411 of the eccentric die 41 having the eccentric inner surface 411 equal to the outer shape of the expanded part 2 and the end part 11 is inclined toward the peripheral surface 22 of the highly expanded pipe of the end part 11 by applying the peripheral surface 21 of the lowly expanded pipe of the end part 11 to the eccentric inner surface 411, the eccentric punch 42 is force-fitted into the end part 11 and the end part 11 is eccentrically expanded. COPYRIGHT: (C)2009,JPO&INPIT
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