| 摘要 |
<p>The outer surface of a core pipe 31 is pressed so as to form projections 313 on the inner surface of the core pipe 31, and a winding pipe 32 is helically wound around the outer circumference of the core pipe 31. Subsequently, the core pipe 31 and the winding pipe 32 are bent together, and brazing is performed. As a result, the outer surface of the winding pipe 32 is in contact with the outer surface of the core pipe 31 without any gap therebetween at a bending center portion (D), and the outer surface of the winding pipe (32) is bonded to the outer surface of the core pipe (31) by a brazing material (33) at the bending center portion (D) of the bent part C-C.</p> |
