Apparatus for improving residual stress of piping technical field

A weld zone of T-piping and its neighborhood are efficiently laser-heated to remove residual stress. For this purpose, the weld zone of a T-piping (50) is irradiated and heated with a laser beam emitted from a laser head (10) to remove residual stress. At this time, a rotating travel cart (3) travels along a ring rail (2) to adjust the position of the laser head (10) in a θ-direction, a vertical slide (4) slides to adjust the position of the laser head (10) in a Z-direction, a radial slide (5) slides to adjust the position of the laser head (10) in an L-direction, an arcuate piece slide (7) slides along an arcuate piece to adjust the α-direction of the laser head (10), a laser head support portion (9) turns to adjust the β-direction of the laser head (10), and oscillation adjusts the position of the laser head (10) in a γ-direction.

TECHNICAL FIELD

This invention relates to an apparatus for improving the residual stress of piping and, more particularly, to an apparatus for improving the residual stress of piping which is used to decrease the residual stress of a T-piping having the shape of the letter T.

BACKGROUND ART

When piping is installed in a large plant such as a nuclear power plant, residual stress of tension generated in the inner peripheral surface of the piping poses a problem. When pipings are connected by welding, for example, residual stress occurs in the weld zone of the pipings, and stress-corrosion cracking (SCC) is caused to the piping by the residual stress, potentially shortening the life of the piping. Thus, it is desirable to reduce the residual stress generated in the piping by welding or the like.

Japanese Patent Application Laid-Open No. 2001-150178 (Patent Document 1) discloses an apparatus for improving residual stress of piping, which is designed to reduce residual stress in the vicinity of a weld zone of piping by heating. This apparatus, which is publicly known, is equipped with an arc generating ring located on the outer periphery of piping, and a first ring coil and a second ring coil arranged on the outer periphery of the piping above and below the arc generating coil, respectively. When a magnetic field is generated by the ring coils, an arc occurs between the arc generating ring and the piping to heat the piping. Since the piping is heated, the residual stress of the piping is reduced.

Japanese Patent Application Laid-Open No. 1996-19881 (Patent Document 2) discloses a technique for surface machining the inner surface of piping by irradiating the inner surface of the piping with laser light. According to this technique, which is publicly known, laser light is guided into the piping by an optical fiber, whereafter the laser light is delivered from the optical fiber, and directed at the inner surface of the piping.

A method of stress removal by high frequency heating is widely known. However, the method using high frequency heating has the problems that it involves a large-scale apparatus, supply power for a high frequency wave is very great, and the interior of target piping needs to be cooled.

One of requirements of an apparatus for improving the residual stress of piping, which is used for removing residual stress, is to be able to heat a wide range of the surface of the piping uniformly. The ability to heat a wide range of the surface of the piping is important for increasing a throughput and ensuring residual stress removing performance. The ability to heat the piping uniformly, on the other hand, is important to render residual stress, which remains after heat-treatment, low. Fulfilling this requirement is not easy if the piping has a complicated shape, for example, if the piping is branched, or if a thick-walled pipe is targeted and, particularly, its broad range needs to be heated.

Against such a background, there is a demand for the provision of an apparatus for improving the residual stress of piping, which can uniformly heat a wide range of the surface of piping and, especially, can uniformly heat a wide range of the surface of piping even if the piping has a complicated shape, such as a T-piping.

DISCLOSURE OF THE INVENTION

Problems To Be Solved By The Invention

It is an object of the present invention to provide an apparatus for improving the residual stress of piping, which is preferred for uniformly heating, from the outer surface side, a wide range (a weld zone and its vicinity) of the surface of a T-piping in the shape of the letter T.

Means For Solving The Problems

A feature of the present invention, for solving the above-mentioned problems, is an apparatus for improving residual stress of piping, which irradiates an outer surface of a T-piping with a laser beam emitted from a laser head, the T-piping comprising a first piping having one end welded and connected to a tubular circumferential surface of a second piping, and

characterized by having a circumferential position adjusting structure for moving the laser head along a circumferential direction about a tubular axis of the first piping.

Another feature of the present invention is an apparatus for improving residual stress of piping, which irradiates an outer surface of a T-piping with a laser beam emitted from a laser head, the T-piping comprising a first piping having one end welded and connected to a tubular circumferential surface of a second piping, and

a circumferential-direction position adjusting structure for moving the laser head along a circumferential direction about a tubular axis of the first piping;

a tubular axial-direction position adjusting structure for moving the laser head along a tubular axial direction of the first piping;

a radial-direction position adjusting structure for moving the laser head along a radial direction of the first piping; and

an emission-direction adjusting structure for changing an emission direction of a laser beam in a plane including the tubular axis of the first piping, by changing a direction of the laser head.

Another feature of the present invention is an apparatus for improving residual stress of piping, which irradiates an outer surface of a T-piping with a laser beam emitted from a laser head, the T-piping comprising a first piping having one end welded and connected to a tubular circumferential surface of a second piping, and

a circumferential-direction position adjusting structure for moving the laser head along a circumferential direction about a tubular axis of the first piping;

a tubular axial-direction position adjusting structure for moving the laser head along a tubular axial direction of the first piping;

a radial-direction position adjusting structure for moving the laser head along a radial direction of the first piping;

a first emission-direction adjusting structure for changing an emission direction of a laser beam in a plane including the tubular axis of the first piping, by changing a direction of the laser head; and

a second emission-direction adjusting structure for changing an emission direction of a laser beam in a plane intersecting the plane including the tubular axis of the first piping, by changing a direction of the laser head.

Another feature of the present invention is characterized in that

the laser head is provided in a laser head support portion so as to be moved in an oscillatory manner, or a plurality of the laser head are provided in the laser head support portion.

Effects of the Invention

According to the present invention, a laser beam can be directed toward the weld zone of the T-piping, namely, a zone where the first piping and the second piping are welded and connected together. Thus, residual stress generated in the T-piping owing to welding can be effectively removed.

DESCRIPTION OF THE NUMERALS

1Apparatus for improving residual stress of piping

3Rotating travel cart

7Arcuate piece slide

9Laser head support portion

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinbelow, embodiments of the present invention will be described in detail based on Examples.

FIGS. 1 and 2show an apparatus for improving the residual stress of piping according to Example 1of the present invention.FIGS. 1 and 2are displaced by 90 degrees in terms of the direction of drawing, and are also different in the slide position of an arcuate piece slide7and in the position of oscillatory movement of a laser head10.

The apparatus1for improving the residual stress of piping is designed to heat a T-piping50. The T-piping50is a T-shaped piping produced by welding and connecting one end of a first piping51to the tubular circumferential surface of a second piping52. The apparatus1for improving the residual stress of piping heats the weld zone of the T-piping50and its neighborhood (a shaded area inFIG. 1) to reduce residual stress.

A ring rail2of the apparatus1for improving the residual stress of piping is mounted on the first piping51so as to surround the periphery of this piping51. The ring rail2is composed of, for example, two semi-arcuate rail members. The ring-shaped ring rail2is mounted on the piping51by coupling the semi-arcuate rail members together, with the piping51being sandwiched therebetween.

A rotating travel cart3travels along the circumferential surface of the ring rail2. That is, the rotating travel cart3travels on the ring rail2as a track, while engaging the ring rail2. Thus, the rotating travel cart3travels and moves along a circumferential direction (θ direction) about the tubular axis51aof the piping51. The travel of the rotating travel cart3is carried out by driving a drive device, such as a motor, provided in the rotating travel cart3. Moreover, the driving and stoppage of this drive device are controlled by a controller (not shown).

The ring rail2and the rotating travel cart3mentioned above constitute a circumferential-direction position adjusting structure which moves the laser head10along the circumferential direction about the tubular axis51a.

A vertical slide4can slidingly move along a vertical direction (the direction of the tubular axis51aof the piping51, namely, a Z-direction) while being supported by an outer peripheral portion of the rotating travel cart3. The sliding movement of the vertical slide4is made by driving a drive device, such as a motor, provided in the vertical slide4. Moreover, the driving and stoppage of this drive device are controlled by a controller (not shown).

The vertical slide4serves as a tubular axial-direction position adjusting structure which moves the laser head10along the direction of the tubular axis51a.

A radial slide5can slidingly move along a direction, in which it approaches and leaves the piping51(the radial direction of the piping51, namely, an L-direction), while being supported by a lower end portion of the vertical slide4(an end portion beside the piping52). A portion of the radial slide5, which faces the piping51, is provided with a front end guide roller5amaking rolling contact with the circumferential surface of the piping51. A support portion5bsupporting the front end guide roller5ais fixed to the vertical slide4, and the radial slide5can slidingly move in the L-direction with respect to the support portion5b. The sliding movement of the radial slide5is made by driving a drive device, such as a motor, provided in the radial slide5. Moreover, the driving and stoppage of this drive device are controlled by a controller (not shown).

The radial slide5serves as a radial-direction position adjusting structure which moves the laser head10along the radial direction of the piping51.

An arcuate piece6of an arcuate shape is fixed to the radial slide5, and an arcuate piece slide7can slidingly move along this arcuate piece6in an arcuate manner (an α-direction). A laser head support portion9is mounted on the arcuate piece slide7via a coupling material8. Thus, the arcuate piece slide7, the coupling material8, and the laser head support portion9can integrally move along the arcuate piece6in the α-direction. The sliding movement of the arcuate piece slide7is made by driving a drive device, such as a motor, provided in the arcuate piece slide7. Moreover, the driving and stoppage of this drive device are controlled by a controller (not shown).

The arcuate piece6and the arcuate piece slide7mentioned above constitute a first emission-direction adjusting structure which changes the emission direction of a laser beam emitted from the laser head10.

The laser head support portion9is mounted on the coupling material8so as to be capable of turning about an axis9aas the center of rotation (i.e., rotating in a β-direction). The rotation of the laser head support portion9in the β-direction is made by driving a drive device, such as a motor, provided in the laser head support portion9. Moreover, the driving and stoppage of this drive device are controlled by a controller (not shown).

Since the laser head support portion9is adapted to be capable of rotation in the β-direction, a second emission-direction adjusting structure, which changes the emission direction of the laser beam emitted from the laser head10, is constituted.

The laser head support portion9is equipped with the laser head10. The laser head10is adapted to make an oscillatory movement (reciprocating movement) along the direction of the axis9aof the laser head support portion9(i.e., a γ-direction). That is, an oscillating device composed of a linear motor or the like is installed in the laser head support portion9, and the laser head10is moved in an oscillatory manner in the γ-direction by driving the oscillating device. The driving and stoppage of the oscillating device are controlled by a controller (not shown).

A laser beam is supplied from a laser oscillator to the laser head10via optical fibers. This laser beam is applied from the laser head10toward the outer surface of the T-piping50. By adjusting the position of application as will be described later, therefore, the laser beam is applied to the weld zone of the T-piping50and its neighboring area to heat them, thereby enabling residual stress to be reduced.

The position of the laser head10, accordingly, the position of application of the laser beam to the T-piping50is adjusted in the following manner under control of the controller:

By allowing the rotating travel cart3to travel on the ring rail2as the track, the position of the laser head10in the circumferential direction (the position in the θ-direction) can be changed and adjusted.

By moving the vertical slide4slidingly, the position of the laser head10in the vertical direction (the position in the Z-direction) can be changed and adjusted.

By moving the radial slide5slidingly, the position of the laser head10in the radial direction (the position in the L-direction) can be changed and adjusted.

By moving the arcuate piece slide7slidingly along the arcuate piece6, the direction of the laser head10with respect to the α-direction can be changed and adjusted. In other words, the direction of emission of the laser beam emitted from the laser head10can be changed and adjusted in a plane including the tubular axis51aof the piping51and the axis9aof the laser head support portion9.

By rotating the laser head support portion9in the β-direction, the direction of the laser head10with respect to the β-direction can be changed and adjusted. In other words, the direction of emission of the laser beam emitted from the laser head10can be changed and adjusted in a plane orthogonal to the plane including the tubular axis51aof the piping51and the axis9aof the laser head support portion9.

After all, the direction of emission of the laser beam can be changed and adjusted to an arbitrary direction by adjusting the direction of the laser head10with respect to the α-direction and the direction of the laser head10with respect to the β-direction which is the direction orthogonal to the α-direction.

In the present Example, the α-direction and the β-direction are orthogonal to each other, but this is not limitative. Generally speaking, there may be provided the first emission-direction adjusting structure for changing and adjusting the emission direction of the laser beam in the plane including the tubular axis51a, and the second emission-direction adjusting structure for changing and adjusting the emission direction of the laser beam in the plane intersecting (optionally, perpendicularly intersecting) the plane including the tubular axis51a. By providing such first and second emission-direction adjusting structures, the direction of emission of the laser beam can be changed and adjusted to an arbitrary direction.

By moving the laser head10in an oscillatory manner in the γ-direction, the laser beam can be scanned in the γ-direction.

By adjusting the positions of θ, Z, L and the directions of α, β, γ, as described above, the laser beam emitted from the laser head10can be effectively applied to the weld position and its neighborhood. That is, by adjusting the positions of θ, Z, L and the directions of α, β, γ, the laser beam can be applied to the weld position of the T-piping50and all regions in its neighborhood. Also, the laser beam can be rendered incident on the position of application at right angles or at an angle close to a right angle. Thus, effective heating can be performed. Furthermore, the output of the laser oscillator may be controlled such that the intensity of the laser beam emitted from the laser head10is varied according to the position of application.

In Example 1, the laser head10which moves in an oscillatory manner is provided in the laser head support portion9. In Example 2, a multiple-type laser head as shown inFIGS. 3(a),3(b) is used. With the multiple-type laser head, a plurality of the laser heads10are movably mounted on a slide member9aof the laser head support portion9. The spacing between the plural laser heads10can be adjusted in such a manner as to be wide as shown inFIG. 3(a), or narrow as shown inFIG. 3(b). InFIG. 3(a), optical fibers11are shown, but inFIG. 3(b), the optical fibers are not shown.

The features of other portions are the same as those in Example 1.

In Example 1 mentioned above, the position adjusting structures for adjusting the positions of θ, Z, L and the directions of α, β, γ are adopted. In Example 2 above, the position adjusting structures for adjusting the positions of θ, Z, L and the directions of α, β are adopted. However, it is possible to adopt position adjusting structures for adjusting only the position of θ, position adjusting structures for adjusting only the positions of θ, Z, L, or position adjusting structures for adjusting the positions of θ, Z, L and the direction of α.

INDUSTRIAL APPLICABILITY

The present invention can be used for reducing residual stress generated in a large T-piping used in a large plant.