| 摘要 |
PURPOSE:To, in a good reproducibility manner, generate uniform stress on the surface of the corrosion factor existence side, by a method wherein the heat treatment for making compressive stress remain on the surface of corrosion factor existence side, said surface is cooled by continuous flow of coolant and the other side surface is heated by induction. CONSTITUTION:The induction heater 2 coconcentrically surrounding the pipe 1 on the periphery of pipe line 1 is installed. Then, coolant 3 is continuously flowed through the pipe 1 and at the same time, the magnetic flux density acting on the pipe 1 is changed by changing the diameter of induction heating coil 4 of heater 2. By thus regulating total heat amount generated on the pipe 1 or the difference of generated heat amount between the outside surface and the inside surface of pipe 1, the periphery of pipe 1 is heated at a temperature lower than transformation temperature and the temperature difference generating thermal stress of yield point and more in different directions is given between said both surfaces. Then, after continuing said cooling and heating for a specified time until the distribution of temperature between said both surfaces is stabilized, the pipe inner surfce of which is strong against corrosion fatigue, stress corrosion cracking, etc., can be obtained by slowly cooling the pipe 1 down to ordinary temperature. |
