Patent ID: 8362389

Claim:
A residual-stress improving apparatus for a tubular-body, comprising: at least one optical fiber for transmitting therethrough at least one laser beam from a laser light source; driving means for moving said laser beam around said outer circumference of said tubular-body and about a tubular axis of said tubular-body; and an optical control unit held by said driving means and optically connected to each said optical fiber, wherein said optical control unit includes a hold mechanism for holding said optical fiber, such that said optical fiber is rotatable in a circumferential direction about a tubular axis of said optical fiber, wherein said laser beam irradiates said outer circumferential surface of said tubular body when held by said optical control unit, wherein said optical control unit adjusts an area on said tubular-body irradiated with said laser beam, wherein said laser beam moves along with said driving means to improve residual stress by irradiating on a circumferential surface of a welded portion of said tubular-body.