| 摘要 |
PROBLEM TO BE SOLVED: To provide a method and mold for hydraulic molding and mold for polygonal cross-section component to be used in a fabrication like this. This method and mold make a specific side among polygons more thicker than the initial thickness, and also make a mechanical strength of a formed product improved by a work hardening due to fabrication and an increased board thickness when a hollowed component with polygonal cross-sections is fabricated by a hydraulic molding. SOLUTION: At least two sides among each sides constituting of a polygonal cross section, are formed by a male mold 2 equipped with a protruding portion 2a in a contact face with a material tube T, and also a sectional peripheral length of the part to be formed by a male mold 2, is made shorter than a material length immediately before contacting a male mold 2. In this time, it is favorable for a rang of an angle theta to belong to 135-165 degree, which is made between a contacting face 3b, in which a female type cavity 3 contacts with a male type 2, and a fabricated face 2b in a protruding part 2a.
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