| 摘要 |
PROBLEM TO BE SOLVED: To make cross-sectional peripheral length, plate thickness and a raw material different depending on longitudinal positions, while restraining cost increase, in a tubular vehicle body frame member and its manufacturing method using hydroforming molding. SOLUTION: A rear frame 3 is manufactured by applying the hydroforming molding by including a double tube structure part 3a in a work W, by forming the work W having partially the double tube structure 3a by inserting the other steel pipe 11 into one steel pipe 12, by using the steel pipes 11 and 12 of the different size being substantially the same in one outer peripheral shape and the other inner peripheral shape. The rear frame 3 has the double tube structure part 3a high in relative strength rigidity and a single tube structure part 3b low in relative strength rigidity at different longitudinal parts, respectively. COPYRIGHT: (C)2009,JPO&INPIT
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