| 摘要 |
PURPOSE:To prevent the occurrence of stress-corrosion cracking, etc., by imposing a compressive residual stress on the inner surface of a piping by a method in which a temperature difference is produced between the outer and inner surfaces of a piping whose surface has a tensile residual stress, a tensile load is imposed to the piping by a loader, and then the piping is heat-treated. CONSTITUTION:A tensile load is imposed on the piping 2 in its axial direction by holding it by a loader 5 to cause a 10kg/mm.<2> tensile stress to produce in the piping 2, and then the outer surface of the piping 2 is heated at approx. 400 deg.C for a short time by the heating coil 3 while flowing the cooling water 4 in the piping 2. And, when the whole of the piping 2 is cooled until an even temperture is reached, the axial force of the loader 5 is removed. The residual stress in this state remains a high compressive residual sress of -25kg/mm.<2> in the inner surface of the piping, and therefore the piping 2 comes to have a high resistance to stress-corrosion cracking, etc. |
