| 摘要 |
PROBLEM TO BE SOLVED: To provide a hydroforming method of a metal tube enabling HF- forming of the metal tube with the strength at which the corner shaping is impossible with the maximum internal pressure of the specification even without remodeling any pressure system in an existing HF-forming device. SOLUTION: By using an axially-pressing punch 3 of double structure having an inner 5 which can be inserted in the metal tube 1 having a liquid filling hole 5a and an outer 6 abutted on a tube end face of the metal tube 1 provided on the outer circumference of the inner 5 in the axial direction in a relatively movable manner, a tip face of the outer 6 is abutted on the tube end face of the metal tube 1 set to a die 2, the metal tube 1 is axially pressed by integrally moving the inner 5 with the outer 6, the liquid is filled in the metal tube 1 through the filling hole 5a, the inner 5 is moved and inserted in the metal tube 1 to increase the forming pressure while the outer 6 is fixed to the position at which the metal tube 1 is axially pressed by the predetermined quantity, and the metal tube 1 is hydroformed in a desired shape.
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