HARDENING METHOD OF INSIDE SURFACE OF STEEL PIPE BY PLASMA JET

摘要

PURPOSE:To harden the inside surface of a steel pipe while making up the part thinned by remelting with the molten metal of a wire by positioning a plasma jet torch so as to face the inside of the steel pipe, rotating the steel pipe at a low speed and supplying the wire while moving the torch back and forth. CONSTITUTION:A plasma jet torch 2 is positioned to face the inside surface at one end of a steel pipe 1, and a shielding gas is injected from the torch 2. A wire 9 is fed to the torch 2 while the pipe 1 is kept rotated at a low speed by operating an automatic corrector 7 for vertical positions and a weaving device 6. The molten metal of the wire 9 is injected to the inside surface of the pipe 1 while the inside surface of the pipe 1 and the wire 9 are simultaneously melted. The height of the torch 2 is maintained always at a specified distance from the position of the pipe 1 where the plasma jet falls by the corrector 7. The corrector 7. The corrector 7, the device 6 and a wire feeder 92 are stopped when the pipe 1 makes one turn. The shielding gas is kept injected for a short while after the rotation of the pipe 1 is stopped, then the injection is completed.