| 摘要 |
PURPOSE:To carry out the excellent hard facing and to prevent the occurrence of a faulty fusion by specifying a nozzle diameter of a torch when the hard facing is carrie out with powder material welded to a spindle end of a valve stem with use of a plasma arc torch. CONSTITUTION:When a hard faced part 58 is formed with a plasma arc torch 10 at a stem end of a stem part 54 in terms of an engine valve material 50 having head part 52 and the stem part 54, the plasma arc torch 10 for satisfying a nozzle diameter of 0.4D2<=D1<=0.95D2 is used with respect to a valve stem diameter D2 of the engine valve material 50. With this constitution a plasma gas is supplied from a piping 22 to generate a plasma arc, while a powder material is supplied to a path 20 from a piping 32 with the aid of a carrie gas to jet out said material from a nozzle 38. Then a shield gas is supplied to a diffuser 48 from a piping 46 to form the had facing part 58 at the stem end of the stem part 54. Thus the occurrence of cavities and blow holes on the heard faced part 58 can be prevented. |
