PURPOSE: To apply the solution heat treatment, at the same time, to reduce the tensile residual stress and, in this way, to obtain the welded piping, etc. having excellent corrosion resistance and fatigue resistance, by performing the induction heating through ferritic steel, etc. at the quick heating of the surface of the material to be heated, such as austenitic steel, etc.
CONSTITUTION: To the surface of the weld zone 8 of the stainless steel pipe 6 to be welded having large specific resistance/magnetic permeability, the heating elements 1 of ferritic steel, etc. having small specific resistance/magnetic permeability, are sticked losely or jointed. When the primary current of AC is passed through the inductors 2 arranged apart from the heating elements 1, the heating elements 1 and the pipe 6 generate heat, but the greater part of induced current is induced to the heating elements 1 having small specific resistance/magnetic permeability, so that the same temperature gradient as the heating of the most outer surface is obtained to the pipe 6. By quenching the pipe subsequently, the most external layer becomes to be heated rapidly and to the metallurgical properties at the weld zone and its neighborhood on the ineer surface of the pipe at the weld zone 8, the tensile residual stress at the weld zone 8 is reduced and can be converted to compression. Accordingly, the butt welded piping at which the stress corrosion cracking and fatigue crack have been prevented, is obtained.
| WO/2013/030017 | DEVICE FOR HARDENING A SURFACE HAVING RIB-LIKE OR TOOTH-LIKE ELEMENTS |
| WO/2003/086020 | IMPROVEMENTS TO HEATING INDUCTORS, IN PARTICULAR OF METAL STRIPS |
| JP2002351239 | ELECTROPHOTOGRAPHIC DEVICE |
SHIMIZU TASUKU
KOIKE HIROSHI
