Apparatus for improving residual stress in tubular body

A tubular-body residual-stress improving apparatus comprising:

• rotationally driving means that moves circling around an outer circumference of a cylindrical tubular body;
• and
• an optical control unit that is held by the rotationally driving means, the optical control unit making an outer-circumferential surface of a welded portion of the tubular body be irradiated with one or a plurality of laser beams emitted from a laser light source, the optical control unit being capable of adjusting an area irradiated with the one or the plurality of laser beams, the tubular-body residual-stress improving apparatus improving a residual stress of the tubular body by moving, in a circumferential direction of the tubular body, the area irradiated with the one or the plurality of laser beams, wherein
• the optical control unit includes one pair of mirrors which are disposed at final stages of optical systems for the laser beams at both ends and disposed in such a way that the mirrors are placed respectively at both sides, in an axial direction of the tubular body, of final optical paths of the laser beams at both ends to the tubular body, and
• the optical control unit makes the one pair of mirrors reflect inwards a skirting portion, in the axial direction of the tubular body, of the corresponding laser beam so as to irradiate the tubular body with the laser beam thus reflected.

A tubular-body residual-stress improving apparatus comprising:

• rotationally driving means that moves circling around an outer circumference of a cylindrical tubular body;
• and
• an optical control unit that is held by the rotationally driving means, the optical control unit making an outer-circumferential surface of a welded portion of the tubular body be irradiated with one or a plurality of laser beams emitted from a laser light source, the optical control unit being capable of adjusting an area irradiated with the one or the plurality of laser beams, the tubular-body residual-stress improving apparatus improving a residual stress of the tubular body by moving, in a circumferential direction of the tubular body, the area irradiated with the one or the plurality of laser beams, wherein
• the optical control unit includes a trapezoidal prism disposed in an optical system for each laser beam, the trapezoidal prism being placed with its trapezoidal side surfaces facing in an axial direction of the tubular body, and
• the optical control unit makes the trapezoidal prism refract inwards a skirting portion, in the circumferential direction of the tubular body, of the corresponding laser beam so as to irradiate the tubular body with the laser beam thus refracted.

A tubular-body residual-stress improving apparatus comprising:

• rotationally driving means that moves circling around an outer circumference of a cylindrical tubular body;
• and
• an optical control unit that is held by the rotationally driving means, the optical control unit making an outer-circumferential surface of a welded portion of the tubular body be irradiated with one or a plurality of laser beams emitted from a laser light source, the optical control unit being capable of adjusting an area irradiated with the one or the plurality of laser beams, the tubular-body residual-stress improving apparatus improving a residual stress of the tubular body by moving, in a circumferential direction of the tubular body, the area irradiated with the one or the plurality of laser beams, wherein
• the optical control unit includes a different trapezoidal prism disposed in an optical system for the laser beam at least one end, the different trapezoidal prism being placed with its trapezoidal side surfaces facing in the circumferential direction of the tubular body, and
• the optical control unit makes the different trapezoidal prism refract inwards a skirting portion, in an axial direction of the tubular body, of the laser beam at the one end so as to irradiate the tubular body with the laser beam thus refracted.

A tubular-body residual-stress improving apparatus comprising:

• rotationally driving means that moves circling around an outer circumference of a cylindrical tubular body;
• and
• an optical control unit that is held by the rotationally driving means, the optical control unit making an outer-circumferential surface of a welded portion of the tubular body be irradiated with one or a plurality of laser beams emitted from a laser light source, the optical control unit being capable of adjusting an area irradiated with the one or the plurality of laser beams, the tubular-body residual-stress improving apparatus improving a residual stress of the tubular body by moving, in a circumferential direction of the tubular body, the area irradiated with the one or the plurality of laser beams, wherein
• the optical control unit includes a lens in an optical system for the laser beam at least one end, the lens shifting an optical axis of the laser beam, and
• the optical control unit makes the lens shift the optical axis of the laser beam at the one end so as to shift the position of intensity peak of the laser beam at the one end towards an outer side in an axial direction of the tubular body, so that the tubular body is irradiated with the laser beam with the optical axis thus shifted.

A tubular-body residual-stress improving apparatus comprising:

• rotationally driving means that moves circling around and outer circumference of a cylindrical tubular body;
• and
• an optical control unit that is held by the rotationally driving means, the optical control unit making an outer-circumferential surface of a welded portion of the tubular body be irradiated with one or a plurality of laser beams emitted from a laser light source, the optical control unit being capable of adjusting an area irradiated with and the one or the plurality of laser beams, the tubular-body residual-stress improving apparatus improving a residual stress of the tubular body by moving, in a circumferential direction of the tubular body, the area irradiated with the one or the plurality of laser beams, wherein
• the optical control unit includes a light pipe at an early stage of an optical system for each laser beam, the light pipe having a rectangular cross section or a square cross section, and
• the optical control unit makes the light pipe form the laser beam into a rectangular irradiation shape or a square irradiation shape, and irradiates the tubular body with the laser beam thus formed into the shape.