| 摘要 |
PROBLEM TO BE SOLVED: To provide a production method of a vehicle body frame capable of preventing a difference in level from forming in an external appearance at a low cost and preferably providing the regions having partially different rigidity. SOLUTION: Part of a first hollow shape material is reduced in diameter along its outer circumference by electromagnetic forming. The first hollow shape material is cut in a reduced region to obtain a hollow shape material 1a. Successively, the hollow shape material 1a is fitted into in a second hollow shape material 2, the outside face shape of the one end of which is coincided to the outside face shape at the boundary between the reduced region of the hollow shape material 1a and the region not reduced and having a thickness equal to a reduced quantity. The boundary of the hollow shape material 1a and the end part of the second hollow shape material 2 are joined, the reinforcement formed by this joining is removed.
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