| 摘要 |
<p>A brazing material 315 in a paste form is applied in advance to dented portions 314 formed on the outer surface of a core pipe 31, and then a pipe 32 is disposed on the pipe 31, and brazing is carried out in a furnace. In this way, the brazing material 315 that was melted by the heat will be reliably poured into the dented portions 314 and bonded thereto after being cooled down. Thus, the dented portions 314 formed on the outer surface of the core pipe 31 can be reliably filled with the brazing material 33, which consequently eliminates a poor contact between the core pipe 31 and the winding pipe 32. In addition, even if the wall thickness of portions in which projections 313 are formed are made thinner in the process of forming the projections, the dented portions 314 formed on the outer surface are filled with the brazing material 33, so that the core pipe thickness can be reinforced, and the reduction in strength of the portions with the projections 313 can be prevented.</p> |
