| 摘要 |
PURPOSE:To prevent seizure accident or the like by applying a copper plating film on one surface of a steel sheet and chemical conversion film on the other surface. CONSTITUTION:A copper plating film 2 (for example 2-5mu) is formed on one surface of a steel sheet 1 (for example, 0.3-1.0mm.) and a chemical conversion film 3 (for example 2-8mu) composed of phosphate, iron oxalate or tri-iron tetroxide is formed on the other surface. Parallel tapered faces 11, 12 are worked at edge parts on both broadside ends and with the copper plating film 2 side being made outside circumferential face, the sheet is pressure-joined in double winding in the width direction. Parallel with this pressure-joining, the parallel tapered faces 11, 12 of both edge parts are butted by central offset part 4. This is heated in an atmosphere controlled furnace to braze the mutual overlapped circumferential surfaces and at the same time, the chemical conversion film 3 of the inside circumferential face 5 is erased by the heating. Thereby, the seizure on the inside circumferential surface owing to the friction heat during work is prevented and the problems owing to chemical reaction with internal fluid in use as piping etc. are solved. |
