| 摘要 |
<p>PROBLEM TO BE SOLVED: To inexpensively produce the port fitting for hose made by a brazing process having a high hardness cylindrical small tube so that a cylindrical small tube is not collapsed in caulking a hose insert part. SOLUTION: A cap 20 made of high carbon steel covers a cylindrical inner tube 12 made of low carbon steel, this assembly is subjected to brazing in a furnace, a hardness of the cylindrical inner tube 12 is increased by penetrating carbon into the cylindrical inner tube. Further, an outer diameter dimension of the cylindrical inner tube 12 is made larger or an inner diameter thereof is made smaller, this assembly is integrated by furnace brazing and then subjected to drawing so as to cause flow of the material constituting the cylindrical inner tube 12, thus, a hardness of the cylindrical inner tube 12 is increased.</p> |
