JP2006015399A - Apparatus for improving residual stress of piping - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an improving apparatus of the residual stress of piping which is suitable to improve the residual stress by uniformly heating the wide range of the surface of the piping. <P>SOLUTION: In one viewpoint, this improving apparatus 10 of the residual stress of the piping is provided with a plurality of laser beam heads 6 and a supporting mechanism for supporting the plurality of laser beam heads 6 so as to oppose to the external surface of the piping 4. The laser beams 6a for heating are respectively irradiated to the external surface of the piping with the plurality of laser beam heads 6. The heating of the external surface of the piping 4 by using the plurality of laser beam heads 6 makes the individual control of the intensity of the laser beams 6a for heating in accordance with the shape of the piping 4 possible. Therefore, the uniform heating of the piping 4 having a complicated shape is made possible. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pipe heating apparatus, and more particularly, to a pipe residual stress improving apparatus used for reducing the pipe residual stress.

  When installing large piping used in nuclear power plants and other large plants, the problem is the removal of residual stress in the piping. When welding is performed, residual stress is generated in the pipe, and the residual stress may shorten the life of the pipe. Therefore, it is preferable to remove the residual stress generated by welding.

  Patent document 1 is disclosing the piping heating apparatus for reducing the residual stress of the vicinity of the welding part of piping by heating. The known device includes an arc generating ring located on the outer peripheral side of the pipe, and a ring coil arranged so as to sandwich the ring. When a magnetic field is generated by the ring coil, an arc is generated between the arc generating ring and the pipe, and the pipe is heated. When the pipe is heated, the residual stress of the pipe is reduced.

  Patent document 2 is disclosing the technique which surface-processes the inner surface of piping by irradiating a laser beam to the inner surface of piping. In the known technique, laser light is guided into a pipe by an optical fiber, and the laser light is emitted from the optical fiber and applied to the inner surface of the pipe.

  One of the requirements for a pipe heating device used to remove residual stress is to be able to uniformly heat a wide range of the pipe surface. The ability to heat a wide range of the surface of the pipe is important for improving throughput and ensuring residual stress removal performance. On the other hand, the ability to heat the piping uniformly is important for reducing the residual stress remaining after the heat treatment. Satisfying this requirement is simple when the pipe has a complicated shape, for example, when the pipe is branched or when a wide area needs to be heated particularly for thick-walled pipes. is not.

  From such a background, it is possible to uniformly heat a wide range of the surface of the pipe, and in particular, it is possible to uniformly heat a wide range of the surface of the pipe even if the pipe has a complicated shape. It is desired to provide an apparatus for improving residual stress in piping that can improve stress.

JP 2001-150178 A JP-A-8-19881

  An object of the present invention is to provide a residual stress improving apparatus for piping suitable for uniformly heating a wide range of the surface of the piping and improving the residual stress of the piping.

  In order to achieve the above object, the present invention employs the means described below. In the description of the technical matters included in the means, in order to clarify the correspondence between the description of [Claims] and the description of [Best Mode for Carrying Out the Invention] Number / symbol used in the best mode for doing this is added. However, the added numbers and symbols should not be used for the interpretation of the technical scope of the invention described in [Claims].

  In one aspect, a pipe residual stress improving apparatus (10) according to the present invention supports a plurality of laser heads (6) and a plurality of laser heads (6) so as to face the outer surface of the pipe (4). And a support mechanism (1, 2, 3, 5). Each of the plurality of laser heads (6) irradiates the outer surface of the pipe (4) with a heating laser beam (6a). Heating the outer surface of the pipe (4) using a plurality of laser heads (6) makes it possible to individually control the intensity of the heating laser beam (6a). This makes it possible to individually control the intensity of the heating laser beam (6a) according to the shape of the pipe (4), and is advantageous for uniform heating of the pipe (4) having a complicated shape.

  In order to heat a wide range of the surface of the pipe (4), the support mechanism (1, 2, 3, 5) is a drive mechanism (2 for scanning the plurality of laser heads in the circumferential direction of the pipe (4). It is preferable that the plurality of laser heads (6) are arranged so as to be shifted in the axial direction of the pipe (4).

  In order to heat a wide range of the surface of the pipe (4) with a smaller number of laser oscillators, the support mechanism (1, 2, 3, 5) has a plurality of laser heads (6) connected to the pipe (4). It is preferable to include a drive mechanism (25) that scans in the axial direction.

  In order to uniformly heat the pipe (4), the plurality of laser heads (6) are provided with a heating laser beam so that the spots of the heating laser beam (6a) overlap on the outer surface of the pipe (4). It is preferable to irradiate (6a).

  The pipe residual stress improving device (10) further includes a laser oscillator (7) for generating a first laser beam (7a) and a plurality of second laser beams (7a) by branching the first laser beam (7a). It is preferable that the laser head (6) generates a heating laser beam (6a) from the second laser beam (7a '). Such a configuration makes it possible to heat a wide area of the pipe (4) with a small number of laser oscillators (7).

  In this case, it is preferable that the branch portions (21, 22) include an output adjustment mechanism (22) that individually adjusts the intensities of the plurality of second laser beams (7a ').

  In another aspect, the apparatus for improving residual stress in piping according to the present invention includes a laser head (31) that irradiates an outer surface of a pipe (4) with a heating laser beam (31a), and a laser head (31) that is connected to the pipe ( And 4) a drive mechanism (2) for scanning in the circumferential direction. The laser head (31) includes a scanning mechanism (35 to 37) that scans the heating laser beam (31a) in the axial direction of the pipe (4). In this case, the intensity of the heating laser beam (31a) is preferably controlled according to the position of the spot on the outer surface of the pipe (4) of the heating laser beam (31a). Thereby, the residual stress improvement apparatus of the said piping can heat the wide range of the surface of piping uniformly. Specifically, the scanning mechanism (35 to 37) preferably scans the heating laser beam (31a) in the axial direction using a galvanometer mirror (35) or a polygon mirror (37).

  In still another aspect, the apparatus for improving residual stress in piping according to the present invention includes a laser head (41) and a drive mechanism (2) that scans the laser head (41) in the circumferential direction of the piping (4). Yes. The laser head (41) includes a fly-eye lens (42) into which a laser beam is incident and an expansion optical system (43) that expands the laser beam emitted from the fly-eye lens in the axial direction of the pipe (4). . The intensity of the fly-eye lens (42) and the cylindrical lens (45) is made uniform, and an elliptical laser beam is expanded in the axial direction of the pipe (4) and irradiated onto the pipe (4). The apparatus for improving residual stress of piping according to the invention can uniformly heat a wide range of the surface of the piping.

  In the apparatus for improving residual stress in piping, the heating laser beam is preferably transmitted by an optical fiber. According to this structure, the freedom degree of an apparatus increases and workability | operativity can be improved. Further, even when the irradiation part of the heating laser beam is a remote part or the peripheral space is a narrow part, the laser can be transmitted.

  In the apparatus for improving residual stress in piping, the light source of the heating laser beam is preferably a laser diode or a fiber laser. According to this configuration, since the light source can be reduced in size, it can be installed even in a narrow part, and can be installed close to the irradiation part of the heating laser beam.

  In the apparatus for improving residual stress in piping, the intensity of the heating laser beam is preferably controlled according to the position of a spot on the outer surface of the piping of the heating laser beam. According to this configuration, even when the irradiation part of the heating laser beam has a complicated shape or a different material part, heating with an appropriate temperature distribution can be performed.

  Further, in the apparatus for improving residual stress of piping, the plurality of laser heads are configured such that a plurality of heads arranged in a circumferential direction of the piping are arranged in a plurality of stages in an axial direction, and the support mechanism includes the plurality of laser heads It is preferable to include a head drive mechanism that scans the laser head in the axial direction of the pipe. According to this configuration, a temperature distribution is generated in the pipe thickness direction by heating when the first stage head passes at a position on the pipe surface, and the temperature distribution is inclined with cooling after the head passes. Since the reheating is performed when the second-stage head passes after the gradual decrease, the temperature distribution having a substantially uniform temperature gradient from the inner surface to the outer surface of the pipe can be obtained.

  Further, in the apparatus for improving residual stress of piping, the plurality of laser heads are configured such that a plurality of heads arranged in an axial direction of the piping are arranged in a circumferential direction, and the support mechanism includes the plurality of laser heads. It is preferable to include a head drive mechanism that scans the laser head in the circumferential direction of the pipe. According to this configuration, a temperature distribution is generated in the pipe thickness direction by heating when the first stage head passes at a position on the pipe surface, and the temperature distribution is inclined with cooling after the head passes. Since the reheating is performed when the second-stage head passes after the gradual decrease, the temperature distribution having a substantially uniform temperature gradient from the inner surface to the outer surface of the pipe can be obtained.

  In the apparatus for improving residual stress in piping, the intensity of the heating laser beam is preferably adjustable for each of the plurality of laser heads. According to this configuration, even when the irradiation part of the heating laser beam has a complicated shape or a different material part, heating with an appropriate temperature distribution can be performed.

  In the apparatus for improving residual stress in piping, a high-frequency heating unit may be provided in front of the laser head in the scanning direction.

  Moreover, in the residual stress improving apparatus for piping, the piping may be a stainless steel piping of a nuclear reactor plant. In such nuclear power plant stainless steel piping, there is concern about the occurrence of SCC, and when it is applied to piping that has already been used, it is necessary to remove the old piping and install new piping with a low carbon content. is there. For this reason, not only is there a great cost, but the amount of radioactive waste is newly increased, and new costs such as storage of waste are generated. It also leads to an extension of the regular inspection period, which is disadvantageous in terms of economy. Therefore, by applying the apparatus of the present invention, replacement work is not necessary, and the economical efficiency and reliability of the plant are improved.

  Moreover, in the residual stress improving apparatus for piping, the piping may be a BWR (boiling water nuclear power generation) recirculation piping.

  Further, in the residual stress improvement apparatus for piping, the piping is a dissimilar joint of low alloy steel and austenitic stainless steel connected to any one of a nuclear reactor reactor vessel, a pressurizer, and a steam generator. Also good.

  Further, in the apparatus for improving residual stress in piping, the plurality of laser heads are arranged so as to be shifted in at least one of an axial direction or a circumferential direction of the piping, and a spot of the heating laser beam is formed on the piping. It is preferable to irradiate the heating laser beam so as to overlap on the surface. According to this configuration, it is possible to obtain a heating laser beam having an arbitrary intensity distribution, for example, a uniform intensity distribution over a wide area.

  Moreover, in the residual stress improving apparatus for piping, it is preferable that the plurality of laser heads are further shifted in the distance direction from the piping. According to this structure, it can be set as the laser beam for heating which has arbitrary intensity distribution three-dimensionally, and it can heat appropriately also to piping which has a complicated shape.

  In the apparatus for improving residual stress in piping, it is preferable that the intensity of the heating laser beam can be individually adjusted. According to this configuration, even when the irradiation part of the heating laser beam has a complicated shape or a different material part, heating with an appropriate temperature distribution can be performed.

  In the apparatus for improving residual stress in piping, the laser head includes a spherical lens on which a laser beam is incident, and a magnifying optical system that expands the laser beam emitted from the spherical lens in one direction on the surface of the piping. Are preferably included. According to this configuration, the laser beam can be a beam having an elliptical spot shape, and the spot system can be irradiated in an enlarged form in an arbitrary direction.

  In the apparatus for improving residual stress in piping, the magnifying optical system can be composed of a cylindrical lens.

  In the apparatus for improving residual stress in piping, the laser head preferably includes at least one of a condensing system, a zoom system, and a collimating system for processing a laser beam. According to this configuration, even when the irradiation part of the heating laser beam has a complicated shape or a different material part, heating with an appropriate temperature distribution can be performed.

  In the apparatus for improving residual stress in piping, the laser beam emitted from the laser head is preferably irradiated on the surface of the piping through one or more reflecting means. According to this configuration, since the optical path of the laser beam can be bent by reflection, for example, a laser head can be installed even in a narrow part near the plant piping, or a long optical path length in a small space. Therefore, for example, the beam spot diameter can be enlarged even in a narrow portion.

  In the apparatus for improving residual stress of piping, at least one of the optical fiber, the spherical lens, the magnifying optical system, the cylindrical lens, the condensing system, the zoom system, the collimating system, or the reflecting means is provided. It is preferable to scan the heating laser beam on the surface of the pipe by driving. According to this configuration, it is possible to scan the laser beam without largely moving the laser head itself or without moving it at all.

  In the apparatus for improving residual stress in piping, the laser head adjusts at least one of an interval between adjacent laser heads, a distance from the surface of the piping, or a rotation angle with the laser beam as a central axis. It is preferable to contain. According to this configuration, alignment between a plurality of laser heads can be performed precisely.

  In the apparatus for improving residual stress in piping, the temperature at which the laser beam is irradiated and heated is not higher than the solution temperature. By heating below the solid solution temperature, the deformation of the object is reduced and the risk of sensitization is eliminated. Further, it can be applied to a dissimilar material joint such as a low alloy steel.

  In the residual stress improving apparatus for piping, the region to be irradiated with the laser beam and heated may be 2.5√rt or more. By uniformly heating the welded portion at 2.5√rt (r: the average radius of the tube, t: the plate thickness of the tube) or more, the residual stress at that portion can be reduced.

  According to the apparatus for improving residual stress in piping of the present invention, it is easy to uniformly heat a wide range of the surface of the piping (formation of a soaking zone).

First Embodiment First Embodiment Overall Configuration FIG. 1 shows a configuration of a piping residual stress improving apparatus 10 according to a first embodiment of the present invention. The piping residual stress improving apparatus 10 includes a ring rail 1, a rotating traveling carriage 2, and a heating optical system 3. The ring rail 1 is provided so as to surround the pipe 4 to be heated, and is used as a track for moving the rotary traveling carriage 2 along the circumferential direction (θ direction) of the pipe 4. The rotary traveling carriage 2 supports the heating optical system 3 by means of an arm 5 provided on it.

  In the heating optical system 3, a plurality of laser heads 6 for irradiating and heating the outer surface of the pipe 4 with a laser beam 6 a are arranged in the axial direction (z direction) of the pipe 4. . When the laser head 6 is accommodated, heating is uniformly performed at 2.5√ (rt) (r: average radius of the tube, t: plate thickness of the tube) or more, preferably 3√ (rt) or more, centering on the weld 4a. It is arranged and accommodated. The heating temperature at this time is preferably less than the solution temperature. Unlike the case where the surface treatment of the inner surface of the pipe 4 is performed, when the residual stress is reduced, the laser beam is irradiated on the outer surface of the pipe 4 so that the apparatus configuration of the pipe residual stress improving apparatus 10 is improved. This is advantageous for simplicity.

  Referring to FIG. 2, heating the pipe 4 using a plurality of laser heads 6 is suitable for uniformly heating a wide range of the surface of the pipe 4. The use of a plurality of laser heads 6 is effective for increasing the irradiation area of the laser beam 6a, and facilitates uniform heating of the pipe 4 regardless of the shape of the pipe 4. The use of multiple laser heads 6 makes it possible to individually adjust the intensity of the laser beam 6a emitted therefrom. This is advantageous for heating the pipe 4 having a complicated shape more uniformly. For example, referring to FIG. 1, the spot size on the surface of the pipe 4 of the laser beam 6 a may be different for each laser head 6 at a portion where the pipe 4 is bent. In this case, it is possible to uniformly heat the pipe 4 by reducing the intensity of the laser beam 6a having a small spot and increasing the intensity of the laser beam 6a having a large spot. Thus, the use of the plurality of laser heads 6 makes it possible to individually adjust the intensity of the laser beam 6 a according to the shape of the pipe 4.

  As shown in FIG. 2, each of the plurality of laser heads 6 is connected to a laser oscillator 7 via an optical fiber 8. Each laser oscillator 7 generates a laser beam 7 a and supplies the laser beam 7 a to the laser head 6 via the optical fiber 8. The laser oscillator 7 has a function of adjusting the intensity of the laser beam 7a generated by each. Each of the laser heads 6 expands the laser beam 7 a supplied from the laser oscillator 7 to generate a laser beam 6 a and irradiates the outer surface of the pipe 4. By irradiating the laser beam 6a, a desired portion of the pipe 4, for example, the periphery of the welded portion 4a of the pipe 4 is heated.

  As shown in FIG. 3, the laser heads 6 are arranged so that the spots 6 b of the laser beams 6 a emitted from each of the laser heads 6 overlap on the outer surface of the pipe 4 so as to maximize the intensity uniform region. This is because the intensity decreases as the spot 6b of the laser beam 6a goes from the central part to the outer periphery, and therefore, overlapping the region of 10 to 90% of the peak output increases the uniformity of heating of the pipe 4 over a wide range. It is effective for. The laser beam 6 a emitted from the laser head 6 can be scanned in the circumferential direction of the pipe 4 by moving the rotary traveling carriage 2 along the ring rail 1. The pipe residual stress improving apparatus 10 according to the present embodiment can heat the entire pipe 4 by scanning the laser beam 6 a in the circumferential direction of the pipe 4.

2. FIG. 4 shows a preferred embodiment of the optical system inside the laser head 6. In the embodiment of FIG. 4, the laser head 6 is provided with a connector 11 connected to the optical fiber 8 and spherical lenses 12 and 13. The spherical lenses 12 and 13 adjust the divergence angle of the laser beam emitted from the connector 11 to a desired angle, and generate the laser beam 6a irradiated to the pipe 4. In the embodiment of FIG. 4, the laser beam 6a is a non-parallel beam having a circular cross section. The use of a non-parallel beam as the laser beam 6a irradiated to the pipe 4 is preferable in that the laser beam 6a can be irradiated over a wide range.

  As the laser beam 6a, a non-parallel elliptical beam whose major axis is parallel to the axial direction (z-axis direction) of the pipe 4 can be used. In this case, as shown in FIG. 5, the collimating lens 14 and the cylindrical lens 15 are used in place of the spherical lenses 12 and 13, respectively. The collimating lens 14 collimates the laser beam emitted from the connector 11. The cylindrical lens 15 transforms the beam emitted from the collimating lens 14 into an elliptical beam by condensing it in only one direction, and generates a laser beam 6 a that is irradiated to the pipe 4. As shown in FIG. 6A, the laser head 6 has the major axis of the spot 6b of each laser beam 6a parallel to the axial direction of the pipe 4, and the spot of each laser beam 6a is the outer surface of the pipe 4. It arrange | positions so that it may overlap in the upper part. In this way, the irradiation drive speed in the axial direction of the laser beam can be increased, which is suitable for heating a wide range. Further, as shown in FIG. 6B, the laser head 6 has the major axis of the spot 6b of each laser beam 6a perpendicular to the axial direction of the pipe 4, and the spot 6b of each laser beam 6a is piped. 4 can be arranged to overlap on the outer surface. In this way, the driving speed in the axial direction is slower than in the case of FIG. 6A, but the irradiation width in the circumferential direction can be widened. The configuration of the laser head 6 in FIG. 5 is suitable for ensuring the energy density in the range irradiated with the laser beam 6a while allowing the laser beam 6a to be irradiated in a wide range in the axial direction of the pipe 4. Yes, it is possible to provide a heating state suitable for the object by adjusting the dimensions of the long and short axes.

  A parallel beam can also be used as the laser beam 6a. In order to generate a parallel and circular laser beam 6a, collimating lenses 16, 17 are used instead of spherical lenses 12, 13, as shown in FIG. 7A. On the other hand, in order to generate a parallel and elliptical laser beam 6a, a collimating lens 16 and cylindrical lenses 18 and 19 are used in place of the spherical lenses 12 and 13, as shown in FIG. 7B. The In addition, even when a circular beam or an elliptical beam is used as the laser beam 6a, the arrangement of the laser head 6 is changed as shown in FIGS. 8A and 8B. Specifically, as shown in FIG. 8A, the laser heads 6 are arranged in two rows in the axial direction of the pipe 4, and the positions of the laser heads 6 are shifted in the axial direction for each row. The direction of the optical axis of the laser beam 6 a emitted from each laser head 6 is directed obliquely with respect to the radial direction (r direction) of the pipe 4. Thereby, the spots 6 b of the laser beam 6 a are overlapped with each other on the surface of the pipe 4.

  As shown in FIG. 9, a laser beam 7 a generated by one laser oscillator 7 can be branched and supplied to a plurality of laser heads 6. In this case, preferably, the branching mirror 21 and the output adjustment mechanism 22 are provided in the optical system of the piping residual stress improving apparatus 10. The branch mirror 21 and the laser oscillator 7 are connected by an optical fiber 23, and the laser beam 7 a generated by the laser oscillator 7 is supplied to the branch mirror 21 through the optical fiber 23. The branching mirror 21 splits the laser beam 7 a to generate a plurality of laser beams, and supplies them to the output adjustment mechanism 22. The output adjusting mechanism 22 individually adjusts the intensity of the plurality of laser beams supplied thereto to generate a laser beam 7a ′, and supplies the generated laser beam 7a ′ to the laser head 6 via the optical fiber 24. To do. The laser head 6 generates a laser beam 6a irradiated to the pipe 4 from the laser beam 7a '. The configuration of FIG. 9 is preferable in that a laser beam 6 a irradiated onto the pipe 4 can be generated with a small number of laser oscillators 7. In addition, the configuration of FIG. 9 makes it possible to individually adjust the laser beam 6a emitted from each laser head 6 by the output adjustment mechanism 22 and to heat the pipe 4 more uniformly.

  In order to irradiate the laser beam 6a over a wide range of the pipe 4 with a small number of laser oscillators 7, a head driving mechanism 25 that scans the laser head 6 in the axial direction of the pipe 4 as shown in FIG. Is preferably provided in the heating optical system 3. As the structure of the laser head 6, any of the structures shown in FIGS. 4, 5, 7A, and 7B can be employed. By scanning the laser head 6, it is possible to irradiate a wider area with the laser beam 6 a using a small number of laser oscillators 7. In order to further reduce the number of laser oscillators 7, it is preferable that the laser beam 7 a generated by the laser oscillator 7 is branched and supplied to the laser head 6 as in the optical system of FIG. 9. Also in this case, it is preferable that an output adjustment mechanism is provided and the laser beam 6a emitted from the laser head 6 is individually adjusted.

3. Summary As described above, the piping residual stress improving apparatus 10 according to the present embodiment has a configuration suitable for uniformly heating a wide range of the surface of the piping 4. Heating the pipes 4 using a plurality of laser heads 6 makes it possible to individually adjust the intensity of the laser beam 6 a emitted from each laser head 6 according to the shape of the pipes 4. It is effective for heating a wide range of more uniformly.

  Further, by adopting a configuration in which the laser beam 7a generated by one laser oscillator 7 is branched and supplied to the plurality of laser heads 6, the pipe residual stress improving apparatus 10 of the present embodiment has a small number of laser oscillators. 7 can be used to irradiate a wider area with the laser beam 6a.

  In addition, by adopting the configuration in which the heating optical system 3 is provided with a head drive mechanism 25 that scans the laser head 6 in the axial direction, the residual stress improving apparatus 10 for piping according to the present embodiment uses a small number of laser oscillators 7. This is suitable for irradiating a wide area with the laser beam 6a.

Second Embodiment Referring to FIG. 11, in the second embodiment, instead of a plurality of laser heads 6, one laser head 31 having an optical mechanism for scanning a laser beam in the axial direction is heated. It is mounted on the optical system 3.

  The laser head 31 includes a scanner 36 that drives a galvano mirror 35 by combining a beam expander 32, a condenser lens 33, a fixed mirror 34, and a galvano mirror 35. The beam expander 32 is connected to a laser oscillator (not shown) via an optical fiber 38. The beam expander 32 receives the laser beam generated by the laser oscillator via the optical fiber 38, expands the laser beam, and enters the fixed mirror 34. The incident laser beam is incident on the galvanometer mirror 35 by the fixed mirror 34. The incident laser beam is reflected in the direction of the outer surface of the pipe 4, collected by the condenser lens 33, and irradiated on the outer surface of the pipe 4. In FIG. 11, the laser beam applied to the pipe 4 is indicated by reference numeral 31a.

  The angle of the galvanometer mirror 35 can be changed by the scanner 36, and the laser beam 31 a irradiated on the outer surface of the pipe 4 is scanned in the axial direction (z direction) of the pipe 4 by changing the angle of the galvanometer mirror 35. Is done. Thereby, the laser beam 31a can be irradiated and heated to the wide range of the outer surface of the piping 4. FIG.

  In order to realize uniform heating of the pipe 4, the intensity of the laser beam 31 a irradiated to the pipe 4 is controlled according to the position of the spot on the outer surface of the pipe 4 of the laser beam 31 a. Specifically, such control is realized by controlling the intensity of the laser beam 31 a irradiated to the pipe 4 in synchronization with the angle of the galvanometer mirror 35. When the galvano mirror 35 is at an angle such that the spot on the outer surface of the pipe 4 of the laser beam 31a is small, that is, at an angle such that the distance between the pipe 4 and the laser head 31 is small, the intensity of the laser beam 31a. Is weakened. Conversely, when the galvanometer mirror 35 is at an angle such that the spot on the outer surface of the pipe 4 of the laser beam 31a is large, the intensity of the laser beam 31a is increased. Thereby, the piping 4 can be heated uniformly.

  Instead of the fixed mirror 34, a galvanometer mirror may be used. Such a configuration is suitable for further increasing the scanning range of the laser beam 31a.

  As shown in FIG. 12, a polygon mirror 37 can be used instead of the galvanometer mirror 35. By rotating the polygon mirror 37, the laser beam 31 a is scanned in the axial direction (z direction) of the pipe 4. Also in this case, the intensity of the laser beam 31a irradiated to the pipe 4 is controlled in synchronization with the angle of the polygon mirror 37, and thereby uniform heating of the pipe 4 is realized.

Third Embodiment In the third embodiment, as shown in FIG. 13, instead of the plurality of laser heads 6, a laser head 41 on which a fly-eye lens 42 and a cylindrical lens 45 are mounted, and a beam The magnifying optical system 43 is mounted on the heating optical system 3. The laser head 41 is connected to a laser oscillator (not shown) via an optical fiber 48. The beam expanding optical system 43 is configured by a mirror 44.

  The laser head 41 equalizes the intensity of the laser beam incident from the optical fiber 48 by using the fly-eye lens 42, and reduces the elliptical beam in the end axis direction by the cylindrical lens 45 of the laser beam having the uniform intensity. Then exit. The laser beam emitted from the laser head 41 is incident on the mirror 44 of the beam expanding optical system 43.

  The beam expanding optical system 43 expands the laser beam incident from the laser head 41 in a direction parallel to the axial direction of the pipe 4 and irradiates the pipe 4 with the expanded laser beam. The laser beam applied to the pipe 4 is indicated by reference numeral 41a in FIG.

  The apparatus for improving residual stress in piping according to the present embodiment uses a fly-eye lens 42 to equalize the intensity of a laser beam, and expand the laser beam with the uniform intensity in the axial direction of the pipe 4. Irradiate the outer surface. Thereby, the residual stress improving apparatus for piping according to the present embodiment can uniformly heat a wide range of the surface of the piping 4.

<Other embodiments>
In the present embodiment, a long heating width is provided in the axial direction of the pipe, and the pipe is continuously rotated in the circumferential direction. The apparatus configuration for heating is as shown in FIG. Hereinafter, the heating procedure will be described.

  (1) A heating test was performed in advance while measuring the temperature of the outer surface and the inner surface of a specimen having an equivalent pipe shape. As shown in FIG. 14, the laser optical system 50 is mounted on the robot arm, and heating is reciprocated in the axial direction at a scanning speed of about 500 mm / s (30 m / min), so that about 80 mm (scanning distance) in the axial direction is obtained. Heated. Since the speed becomes 0 and the heat input becomes large at the turn-back point of the reciprocating motion, a water-cooled copper plate shutter 51 was installed, and a heating test was performed using only a constant speed region (shutter distance).

  As the laser oscillator, a 4 kWYAG laser was used, and laser light was transmitted from the oscillator to the optical system 50 through an optical fiber. The pipe 52 was mounted on a rotary positioner and rotated at a constant speed. During heating, an absorbent containing graphite as a main component was applied to the outer surface of the pipe 52. The following heating conditions (laser output and rotational speed of the pipe 52) were determined so that the inner and outer surfaces had a predetermined temperature.

Pipe shape: Diameter φ114.3mm, thickness t13.5mm
Pipe material: SUS304 (Solution temperature is 1050 ° C)
Laser output: 4kW (YAG laser)
Rotation speed: 1.4mm / sec (peripheral speed)
Temperature difference between inside and outside: about 400 ° C
External heating temperature: about 450 ° C
Heating area: about 80 mm in the axial direction (3√rt: r = 57.15 mm, t = 13.5 mm)
Approximately 15mm in the circumferential direction (heating width when there is no circumferential scan)

  FIG. 15 is a temperature distribution diagram in the axial direction. As shown in the figure, about 80 mm in the axial direction could be heated to about 450 ° C. in a substantially uniform manner.

  (2) Thermocouples were installed at two locations on the surface of the pipe 52 for temperature measurement. The thermocouples installed at two places were installed at diagonal positions (positions of 0 ° and 180 °) on the surface of the pipe 52.

  (3) The circumference of the pipe 52 was heated by irradiating laser light under the determined heating conditions. The inner and outer surfaces other than the portion heated by the laser beam were allowed to cool. Moreover, in order to confirm the temperature history at the time of heating, the temperature history obtained from the said thermocouple was recorded on the recorder.

  (4) The pipe was heated in the circumferential direction over the entire circumference. After heating, the pipe 52 was cooled to room temperature by cooling. FIG. 16 is a diagram showing the residual stress distribution in the axial direction of the pipe inner surface after cooling. The figure also shows the residual stress distribution as welded (before heating). From the figure, it can be seen that the residual stress on the inner surface of the pipe is reduced by laser heating.

  In the above embodiment, the laser oscillator 7 is preferably a laser diode or a fiber laser. In addition, the piping to be heated is connected to any one of a stainless steel pipe of a nuclear reactor plant, a recirculation pipe of a BWR (boiling water nuclear power generation), a nuclear reactor vessel, a pressurizer, and a steam generator. Examples include a dissimilar joint between low alloy steel and austenitic stainless steel, such as a safe end weld (particularly a nickel base alloy).

  The laser head 6 is preferably capable of adjusting the interval between adjacent laser heads 6, adjusting the distance from the surface of the pipe 4, and adjusting the rotation angle with the laser beam as the central axis.

  As for the arrangement method of the laser heads 6, an example in which one stage is arranged in the axial direction of the pipe 4 is shown in FIGS. 2 and 3, but the laser head 6 is arranged while being shifted in the circumferential direction of the pipe 4. A plurality of rows are arranged in the axial direction so that the head group is scanned in the axial direction of the pipe 4, or the laser head 6 is arranged shifted in the axial direction of the pipe 4, and this head row is arranged in the circumferential direction. A plurality of stages may be installed, and the head group may be scanned in the circumferential direction of the pipe 4.

  In this case, the laser beams emitted from one head row and an adjacent head row may overlap (see FIG. 8A), but by providing an interval between the head rows without overlapping, At a position on the pipe surface, a temperature distribution is generated in the pipe thickness direction due to heating when the first stage head row passes, and the gradient of the temperature distribution becomes gentle with cooling after passing through the head row. After that, since reheating is performed when the second stage head row passes, the temperature distribution having a substantially uniform temperature gradient from the inner surface to the outer surface of the pipe can be obtained. be able to. At this time, the front row may be heated by a high-frequency heating means.

  As for the arrangement method of the laser heads 6, FIG. 8A shows an example in which the pipes 4 are arranged in two rows in the axial direction and the positions of the laser heads 6 are shifted in the axial direction for each row. It is not restricted to an example, What is necessary is just to shift and arrange | position at least one of the axial direction of pipe 4 or the circumferential direction. Furthermore, it is good to arrange also in the distance direction with the pipe 4.

  Moreover, although the example which controls individually the intensity | strength of the several laser beam 6a was shown as a countermeasure when the irradiation part in the piping 4 is a complicated shape or a dissimilar material part, in addition to this, laser The head 6 may be provided with at least one of a condensing system, a zoom system, and a collimating system for processing the laser beam 6a, and these may be controlled.

  Further, for example, when the laser head 6 is relatively large and there is a problem in driving with the head driving mechanism 25 as shown in FIG. 10, as shown in an example in FIGS. Change the position of fiber 8,23,24,38,48, spherical lens 12,13, cylindrical lens 15,18,19,45 (magnifying optical system), condensing system / zoom system (reference numerals 32,33, 42), the collimating lenses 14, 16, 17 or the reflecting means 34, 35, 37, 44, etc. are driven to scan the laser beam 6a on the surface of the pipe 4.

FIG. 1 is a diagram showing a configuration of a piping residual stress improving apparatus according to a first embodiment of the present invention. FIG. 2 is a diagram illustrating a configuration of an optical system of the residual stress improving apparatus for piping according to the first embodiment. FIG. 3 is a plan view showing the shape and arrangement of the spot of the laser beam emitted from the laser head. FIG. 4 is a diagram showing a configuration of an optical system inside the laser head. FIG. 5 is a diagram showing another configuration of the optical system inside the laser head. FIG. 6A is a plan view showing another shape and arrangement of the spot of the laser beam emitted from the laser head. FIG. 6B is a plan view showing still another shape and arrangement of the spot of the laser beam emitted from the laser head. FIG. 7A is a diagram showing still another configuration of the optical system inside the laser head. FIG. 7B is a diagram showing still another configuration of the optical system inside the laser head. FIG. 8A is a top view showing a preferred arrangement of the laser head inside the oscillator. FIG. 8B is a side view showing a preferred arrangement of the laser head inside the oscillator. FIG. 9 is a diagram showing a preferable configuration of the optical system of the residual stress improving apparatus for piping according to the first embodiment. FIG. 10 is a diagram showing another preferred configuration of the optical system of the residual stress improving apparatus for piping according to the first embodiment. FIG. 11 is a diagram showing the configuration of the optical system of the laser head of the apparatus for improving residual stress in piping according to the second embodiment. FIG. 12 is a diagram showing another configuration of the optical system of the laser head of the apparatus for improving residual stress in piping according to the second embodiment. FIG. 13 is a top view showing the configuration of the optical system inside the oscillator of the apparatus for improving residual stress in piping according to the third embodiment. It is a figure which shows the apparatus structure which heats which concerns on other embodiment. It is a figure which shows the temperature distribution figure of an axial direction. It is a figure which shows the residual stress distribution of the axial direction of the pipe inner surface after cooling.

Explanation of symbols

1: Ring rail 2: Rotating traveling carriage 3: Heating optical system 4: Piping 5: Arm 6: Laser head 6a: Laser beam 6b: Spot 7: Laser oscillator 7a: Laser beam 8: Optical fiber 10: Improvement of residual stress in piping Device 11: Connector 12, 13: Spherical lens 14: Collimate lens 15: Cylindrical lens 16, 17: Collimate lens 18, 19: Cylindrical lens 21: Branch mirror 22: Output adjustment mechanism 23, 24: Optical fiber 25: Head drive mechanism 31: Laser head 31a: Laser beam 32: Beam expander 33: Condensing lens 34: Fixed mirror 35: Galvano mirror 36: Scanner 37: Polygon mirror 38: Optical fiber 41: Laser head 42: Fly eye lens 43: Beam expansion Optics 44: Mirror 45: cylindrical lens 48: optical fiber 50: a laser optical system 51: Shutter 52: Pipe

Claims (32)

Multiple laser heads,
A support mechanism for supporting the plurality of laser heads so as to face the outer surface of the pipe,
Each of the plurality of laser heads irradiates the outer surface of the pipe with a heating laser beam and forms a soaking zone by the plurality of laser heads. It is the residual stress improvement apparatus of piping of Claim 1, Comprising:
The intensity of the heating laser beam can be individually adjusted. It is the residual stress improvement apparatus of piping of Claim 1, Comprising:
The support mechanism includes a drive mechanism that scans the plurality of laser heads in a circumferential direction of the pipe,
The plurality of laser heads are arranged to be shifted in the axial direction of the pipe. The apparatus for improving residual stress of piping according to claim 3,
The support mechanism includes a head drive mechanism that scans the plurality of laser heads in the axial direction of the pipe. The apparatus for improving residual stress of piping according to claim 3,
The plurality of laser heads irradiate the heating laser beam so that spots of the heating laser beam overlap on a surface of the pipe. It is the residual stress improvement apparatus of piping of Claim 1, Comprising:
Furthermore,
A laser oscillator for generating a first laser beam;
A branching device for branching the first laser beam to generate a plurality of second laser beams;
The laser head generates the heating laser beam from the plurality of second laser beams. It is the residual stress improvement apparatus of piping of Claim 6, Comprising:
The branching unit includes an output adjusting mechanism for individually adjusting the intensity of the plurality of second laser beams. A laser head that irradiates the outer surface of the pipe with a laser beam for heating;
A drive mechanism for scanning the laser head in the circumferential direction of the pipe,
The laser head includes a scanning mechanism that scans the heating laser beam in an axial direction of the pipe. It is a residual stress improvement apparatus of piping of Claim 8, Comprising:
The intensity of the heating laser beam is controlled according to the position of the spot on the outer surface of the piping of the heating laser beam. It is a residual stress improvement apparatus of piping of Claim 8, Comprising:
The said scanning mechanism scans the said laser beam for a heating in the said axial direction using a galvanometer mirror or a polygon mirror, The residual stress improvement apparatus of piping. A laser head,
A drive mechanism for scanning the laser head in the circumferential direction of the pipe,
The laser head is
A fly-eye lens into which the laser beam is incident;
An apparatus for improving residual stress in a pipe, comprising: a magnifying optical system that expands a laser beam emitted from the fly-eye lens in an axial direction of the pipe. In the piping residual stress improvement apparatus in any one of Claims 1 thru | or 11,
The apparatus for improving residual stress in piping, wherein the heating laser beam is transmitted by an optical fiber. In the piping residual stress improvement apparatus in any one of Claims 1 thru | or 11,
The apparatus for improving residual stress in piping, wherein a light source of the heating laser beam is a laser diode or a fiber laser. In the residual stress improvement apparatus of piping described in Claim 1 or 11,
The apparatus for improving residual stress in piping, wherein the intensity of the heating laser beam is controlled in accordance with a spot position on an outer surface of the piping of the heating laser beam. In the residual stress improving apparatus for piping according to claim 1,
The plurality of laser heads are arranged in a plurality of stages in the axial direction, with heads arranged to be shifted in the circumferential direction of the pipe,
The apparatus for improving residual stress in piping, wherein the support mechanism includes a head driving mechanism that scans the plurality of laser heads in an axial direction of the piping. In the residual stress improving apparatus for piping according to claim 1,
The plurality of laser heads are arranged in a plurality of stages in the circumferential direction, the heads arranged to be shifted in the axial direction of the pipe,
The apparatus for improving residual stress in piping, wherein the support mechanism includes a head driving mechanism that scans the plurality of laser heads in a circumferential direction of the piping. In the residual stress improvement apparatus of piping described in Claim 15 or 16,
The apparatus for improving residual stress in piping, wherein the intensity of the heating laser beam is adjustable for each of the plurality of laser heads. The residual stress improving apparatus for piping according to any one of claims 15 to 17,
An apparatus for improving residual stress in piping, wherein high-frequency heating means is provided in front of the laser head in the scanning direction. In the piping residual stress improvement apparatus in any one of Claims 1 thru | or 18,
The apparatus for improving residual stress of piping, wherein the piping is stainless steel piping of a nuclear reactor plant. In the piping residual stress improvement apparatus in any one of Claims 1 thru | or 18,
The pipe is a recirculation pipe of BWR (boiling water nuclear power generation). In the piping residual stress improvement apparatus in any one of Claims 1 thru | or 18,
The apparatus for improving residual stress in piping, wherein the piping is a dissimilar material joint of low alloy steel and austenitic stainless steel connected to any of a nuclear reactor reactor vessel, a pressurizer, and a steam generator. In the residual stress improving apparatus for piping according to claim 1,
The plurality of laser heads are arranged shifted in at least one of the axial direction or the circumferential direction of the pipe,
The apparatus for improving residual stress of piping, wherein the heating laser beam is irradiated so that spots of the heating laser beam overlap on a surface of the piping. In the residual stress improvement apparatus of piping described in Claim 22,
The apparatus for improving residual stress in piping, wherein the plurality of laser heads are further displaced in the distance direction from the piping. In the residual stress improvement apparatus of the piping according to claim 22 or 23,
The apparatus for improving residual stress in piping, wherein the intensity of the heating laser beam can be individually adjusted. In the residual stress improving apparatus for piping according to claim 1,
The laser head includes a spherical lens to which a laser beam is incident, and an expansion optical system that expands the laser beam emitted from the spherical lens in one direction on the surface of the pipe. Stress improvement device. In the piping residual stress improving apparatus according to claim 25,
The apparatus for improving residual stress of piping, wherein the magnifying optical system includes a cylindrical lens. In the residual stress improving apparatus for piping according to claim 1,
The apparatus for improving residual stress in piping, wherein the laser head includes at least one of a condensing system, a zoom system, and a collimating system for processing a laser beam. In the residual stress improving apparatus for piping according to claim 1,
The apparatus for improving residual stress in piping, wherein the laser beam emitted from the laser head is irradiated onto the surface of the piping through one or a plurality of reflecting means. In the residual stress improvement apparatus for piping according to any one of claims 12, 25 to 28,
By driving at least one of the optical fiber, the spherical lens, the magnifying optical system, the cylindrical lens, the condensing system, the zoom system, the collimating system, or the reflecting means, the heating laser beam is changed. An apparatus for improving residual stress in piping, wherein scanning is performed on a surface of the piping. In the residual stress improving apparatus for piping according to claim 1,
The laser head includes a mechanism for adjusting at least one of an interval between adjacent laser heads, a distance from a surface of the pipe, and a rotation angle with the laser beam as a central axis. Improvement device. In the residual stress improvement apparatus of the piping in any one of Claims 1 thru | or 30,
The apparatus for improving residual stress in piping, wherein a temperature at which the laser beam is irradiated and heated is equal to or lower than a solution temperature. In the residual stress improvement apparatus of the piping in any one of Claims 1 thru | or 31,
An apparatus for improving residual stress of piping, wherein a region to be irradiated with the laser beam and heated is 2.5√rt or more.

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