| 摘要 |
To provide a pipe member composed of a small-diameter metal pipe and a large-diameter metal pipe integrated via a double pipe structure part. A diameter expanding punch 12 is press-fitted into a small-diameter pipe 3 through a large-diameter pipe 2, thereby integrally expanding the diameter of the small-diameter pipe 3 and the large-diameter pipe 2. As the diameter of the small-diameter pipe 3 is expanded, the longitudinal dimension of an expanded part 3b is shortened, and the tip end of the expanded part 3b of the small-diameter pipe 3 is spaced apart from a step part 2c of the large-diameter pipe 2. In this state, the large-diameter pipe 2 and the small-diameter pipe 3 are displaced with respect to each other in the longitudinal direction. To avoid this, during molding of an expanded part 2b and the expanded part 3b, a part of the expanded part 2b of the large-diameter pipe 2 is radially inwardly deformed by a pin 11 to form a retaining part 5 that is engaged in the expanded part 3b of the small-diameter pipe 3.
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