| 摘要 |
PURPOSE:To attain to prevent the cavitation caused by a fluid pressure and the deterioration of fatigue strength according to fluid pressure change and machine vibration by a method wherein an inner wall surface of a steel pipe with a thick wall and a small diameter for a fuel supply pipe or the like of a diesel engine is coated by a hardened layer comprising a metal compound of FeSn system diffused to the steel side. CONSTITUTION:For example, on an inner surface 2 of a steel pipe 1 with relatively thick wall and a small diameter of which a pipe diameter is 6-30mm and wall thickness is about 2.2-12mm, an Sn material 3 is preliminarily placed or coated. Subsequently, this steel pipe is heated in a furnace and is formed a hardened layer 4 comprising a intermetallic compound of FeSn or FeSn2 or coexisted material thereof diffused into a steel side. That is, this hardened layer 4 is obtained by placing a Sn material 3 on an inside wall surface 2' of a pipe body 1' or applying a coating of an Sn material and heating the said Sn material to diffuse it into a steel side. By this method, the fatigue strength of the pipe body is increased and the mechanical property against crack or breakage is enhanced. |
