| 摘要 |
A flat plate is molded in such a manner that a pair of semidivided cylindrical portions are arranged in parallel to each other with an arc-shaped connecting portion between them. Tube insertion holes are formed in one of the pair of semidivided cylindrical portions. Then, the connecting portion is projected from the inside thereof to thereby dispose the pair of semidivided cylindrical portions in such a manner that they are opposed to each other. The mutually opposed semidivided cylindrical portions are butted against each other, thereby manufacturing a cylindrically-shaped header pipe. The tube insertion holes are formed only in one of the pair of semidivided cylindrical portions in such a manner that the tube insertion holes are not allowed to extend up to the connecting portion.
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