| 摘要 |
PROBLEM TO BE SOLVED: To provide a metallic pipe without possibility of crack due to work hardening, lighter in weight compared to a thick wall pipe. SOLUTION: This double structure metallic pipe 10 has a structure of an inner pipe 11 and an outer pipe 12 closely contacting with each other. The inner pipe 11 is an imperforated pipe, while the outer pipe 12 is a perforated pipe with multiple punched holes 13. The outer pipe 12 is thicker than the inner pipe 11, and has no punched hole near both ends thereof (fixing part 14) to be secured to other members including an exhaust manifold and a muffler of an automobile while the punched holes are evenly provided in a region 15 other than the fixing part 14. The double structure metallic pipe 10 is lightened by a part of weight of punched holes of the perforated pipe compared to conventional metallic pipes with a thickness of the sum of he thickness of the inner pipe 11 to that of the outer pipe 12. Since a process for changing wall thickness is not required, the possibility of the crack due to the work hardening is not generated.
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