JP2005232586A - Method and apparatus for improving residual stress in tubular body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a residual stress improvement method capable of simply, quickly and surely improving a residual stress in a tubular body by reducing the residual stress in a tensile state by heating the tubular body or making the body to a compressing state. <P>SOLUTION: This method comprises: an irradiating process with laser beam Lz to a stress improving range Sr desirable to improve the residual stress in the tubular body Pi; a temperature measuring process for measuring the temperature in the stress improving range Sr; a cooling process for stopping the irradiation with the laser beam and cooling after becoming a prescribed temperature difference to the inner and the outer surfaces of the stress improving region Sr; and a moving process for moving the laser beam Lz in the stress improving region Sr to the non-irradiation portion in a laser beam irradiation part 1 after completing the cooling process. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for improving the residual stress of a tubular body and an improvement apparatus for improving the residual stress.

  In general, an extremely thin corrosion film is formed in advance on a surface of a steel material that is not easily corroded, such as stainless steel, and the corrosion film prevents the progress of new corrosion. In such a material, when the material properties, tensile stress, and corrosion environment all satisfy certain conditions, the material cracks, and the crack propagates with time (Stress Corrosion Cracking: SCC) is known to occur.

  Austenitic stainless steel, which is resistant to corrosion, is often used for piping in plants such as factories and power plants. Austenitic stainless steel is covered with a thin oxide film, and this film protects it, so the progress of the overall corrosion is very slow. As a material most commonly used in austenitic stainless steel and excellent in corrosion resistance, there is a material called SUS316 with a material symbol of JIS. SUS316 is an alloy of iron mixed with about 18% chromium, about 12% nickel, and about 2.5% molybdenum. SUS316 is a stable material in which alloy components are uniformly mixed, but when heated to about 600 ° C., the chromium contained in the material and the carbon contained in the iron combine to precipitate as chromium carbide (chromium carbide). Causes the phenomenon. Furthermore, it has been known from early on that SCC is generated by the action of a large tensile stress.

  In particular, when a stainless steel pipe is welded to form a joint, the vicinity of the welded portion of the stainless steel pipe is heated by welding heat, and the carbon in the stainless steel is combined with chromium, and as a chromium carbide along the grain boundary. Precipitate. Then, a chromium-deficient region is formed in the stainless steel along the vicinity of the crystal grain boundary, and the corrosion resistance is lowered. In a structure with developed chromium-deficient regions, if a large tensile stress is applied, even if the oxygen concentration is high, even in high-temperature pure water (which does not contain corrosive substances), local along the grain boundaries Corrosion occurs and it develops into SCC.

  In addition to the tensile stress directly applied to the pipe, the tensile stress that causes the SCC may include the residual stress in the tensile state accumulated by heating with welding heat in the vicinity of the weld and then rapidly cooling. It has become clear. Further, the residual stress in the tensile state is accumulated not only by welding but also by cold working or mechanical cutting of the material.

  As shown in the above description, the cause of SCC is that the material (decrease in corrosion resistance due to chromium carbide precipitation), environment (corrosive environment), and stress (tensile stress above the yield point) are all constant. It is well known that it is to satisfy. In other words, it is possible to prevent the occurrence of SCC by not satisfying at least one of the SCC generation conditions of these materials, environment, and stress.

First, as a material for improving the material, a method for reducing the content of carbon contained in stainless steel has been studied. When the carbon content in the stainless steel is reduced, generation of chromium carbide can be suppressed, and as a result, it is possible to suppress sensitization.

  It is also possible to prevent SCC by reducing the residual stress in a portion that satisfies the SCC condition of the tube or changing the residual stress from a tensile state to a compressed state. As one of methods for reducing or compressing the residual stress in the tensile state, a high-frequency heating residual stress improvement method (hereinafter referred to as IHSI method) has been proposed. This IHSI method uses a high-frequency induction heating coil from the outer surface side while cooling the inner surface of the tube with flowing water so that a temperature gradient in the thickness direction near the portion satisfying the SCC condition of the tube can be raised by induction heating. After that, the heating is stopped and cooling is continued by flowing water on the inner surface until the thickness direction of the pipe reaches a substantially uniform temperature. As a result, the residual stress in the tensile state near the weld is reduced or compressed. It is. At this time, a certain temperature difference or more is required between the outer peripheral surface of the tube and the inner peripheral surface of the tube at the end of heating.

  As a countermeasure against SCC using laser heating, a method has been proposed in which the surface is heated to a temperature equal to or higher than the melting / solidifying or solution treatment temperature to solidify the carbide precipitated at the grain boundaries. In addition, a method for melting and solidifying a surface opposite to a surface for reducing residual stress and a method for heating to a temperature equal to or higher than the solid solution temperature have been proposed while performing a solid solution treatment (desensitization treatment).

  Further, as a method for improving the residual stress, a shot peening method for improving the residual stress by colliding an infinite number of metal balls with a place where the residual stress is desired to be improved at a high speed has been proposed.

In addition, as a method for improving environmental conditions, a method of removing a corrosive substance contained in a fluid flowing in a pipe or reducing the content of oxygen that causes oxidation is also proposed.
JP-A-57-70095 JP 2001-150178 A Japanese Patent Laid-Open No. 10-272586 Japanese Patent Laid-Open No. 2000-254776 JP 2001-337190 A

  Generation | occurrence | production of a chromium deficiency area | region can be suppressed by reducing the carbon content in the above-mentioned stainless steel piping, and suppressing precipitation of chromium carbide. However, when the carbon content in the stainless steel material decreases, the strength of the stainless steel material decreases. A stainless steel material having a reduced strength can be used depending on the member, but cannot be used in a portion where a large stress is applied. In addition, when it is applied while it is already in use, it is necessary to remove the old pipe and install a new low carbon material pipe. Therefore, it involves a great deal of cost.

  Further, when reducing the residual stress state of the stainless steel pipe using the IHSI method or changing from the tensile state to the compressed state, a high frequency induction coil is disposed outside the portion of the stainless steel pipe that improves the residual stress. The stainless steel pipe is heated from the outside by supplying an electric current to the coil, and water is continuously supplied into the pipe to cool to a predetermined temperature. For this reason, it is easy to implement for a pipe that has already been installed and can be cooled by a water flow, but it is difficult to implement for a pipe body that cannot secure a flowing water state inside the pipe.

  The IHSI method performs high-frequency induction heating in order to create a temperature gradient in the thickness direction of the tube. In the case of heating by the high-frequency induction coil, heat is transmitted depending on the material (dielectric constant) of the tube. The depth and range are different, and it is difficult to limit the heating range when heating with a high frequency induction coil. In addition, the apparatus is large and energy consumption is large. Furthermore, when members having different dielectric constants such as dissimilar material joints are mixed, it is difficult to provide a constant temperature gradient in the thickness direction.

  When heated to the melting / solidification or solution treatment temperature, a new sensitization region may be formed near the melted part, or the temperature may be high and deformation due to thermal shrinkage may occur, preventing the piping function from being satisfied. It is necessary to strictly control the temperature. Moreover, since it cannot heat more than the stress relief annealing of low alloy steel with respect to the dissimilar material joint part containing low alloy steel, application becomes difficult. For example, when a low alloy steel is heated at 750 ° C. or higher, quenching occurs, so that stress relief annealing is required once more. For this reason, heating at 600 ° C. or higher is usually not possible.

  Residual stress reduction associated with solution heat treatment targets the sensitized region and heats only a narrow area in the vicinity of the weld. Therefore, local bending deformation occurs in the axial direction, and a stable residual stress reduction effect is obtained. It is difficult.

  The method for improving the residual stress by shot peening is also very difficult to carry out on the pipes already installed or on the joint inner surface where the pipes are joined.

  Regarding the method for removing the corrosive substance in the fluid, there are some methods that cannot be removed depending on the purpose of use of the fluid flowing in the pipe. In addition, in the case of a plant that has already started operation, it is necessary to install a new device that removes corrosive substances. Takes more than ever.

  In view of such a problem, the present invention is a method for heating a tubular body to reduce the residual stress in the tensile state or to make it compressed, and to improve the residual stress of the tubular body simply, quickly and reliably. It is an object of the present invention to provide a method for improving residual stress that can be improved.

  In addition, the present invention is a method for heating a tubular body to reduce the residual stress in the tensile state or compressing the tubular body, so that the residual stress of the tubular body can be easily and quickly reduced without preparing a large-scale device and a large energy source. Another object of the present invention is to provide a method for improving residual stress that can be reliably improved.

  In order to achieve the above object, the present invention is a residual stress improving method for improving the residual stress on the inner surface of a tubular body, and is disposed outside the tubular body in a stress improving region where the residual stress of the tubular body is desired to be improved. The present invention provides a method for improving residual stress in a tubular body, which comprises irradiating the outer surface of the tubular body with laser light from a laser light irradiating section.

  According to this configuration, the residual stress of the portion irradiated with the laser beam is improved by irradiating the outer surface of the tube with the laser beam. The laser beam has high energy density and rapidly heats the surface of the tube. be able to. As a result, the inside of the tube body can be brought into a state having a predetermined temperature difference between the inner surface side and the outer surface side of the tube body, and the residual stress can be easily improved accordingly. it can.

  In addition, the heating with the laser beam can heat the vicinity of the portion irradiated with the laser beam, so that the residual stress can be improved uniformly and efficiently without the heat escaping to an unnecessary portion. Is possible.

  In the above configuration, the laser beam irradiation may be capable of adjusting the output of the laser beam to be irradiated according to the material of the tube.

  According to this configuration, by appropriately setting the output of the laser light according to the material of the tube body, the surface can be heated before heat penetrates in the thickness direction of the tube body. Since the temperature difference between the inner surface side and the outer surface side can be formed before heat propagates to the tube, the residual stress can be improved regardless of the thickness and material of the tube.

  In the above-described configuration, the residual stress in the stress improvement region of the tubular body may be improved by moving the laser light irradiation unit continuously or intermittently to a portion where the laser beam in the stress improvement region is not irradiated.

  Since the vicinity of the portion irradiated with the laser light can be heated, the heated portion and the unheated portion can be easily determined. From this, it is not necessary to heat the entire area where residual stress is to be improved at once, and it is possible to apply the residual stress improvement process in multiple times for each part. It is possible to improve the residual stress regardless of the material.

  In the above configuration, the laser beam irradiation has a predetermined width in the axial direction of the stress improvement region of the tubular body, and the laser beam is irradiated substantially uniformly and simultaneously in the circumferential direction. The irradiation unit may be moved in the axial direction of the tubular body.

  According to this configuration, it is possible to heat the outer surface of the tube uniformly and simultaneously in the entire circumference, and since the movement is only in the axial direction, the residual stress can be improved regardless of the length of the tube. It is possible to improve the residual stress of the tubular body over a wide range in a short time.

  In the above-described configuration, the laser beam irradiation irradiates a rectangular laser beam having a length equal to or substantially the same as the axial length of the stress improvement region of the tubular body and having a predetermined width in the circumferential direction. May move the laser beam irradiation section along the stress improvement region in the circumferential direction of the tubular body.

  According to this configuration, the stress improvement region can be simultaneously heated to the axial width length, and since the movement is only in the circumferential direction, the residual stress can be improved regardless of the diameter of the tube. .

  Further, at this time, a plurality of laser beam irradiation units may be detachable, or a number of laser beam irradiation units that can be driven by the number corresponding to the stress improvement region may be used.

  In the above-described configuration, the laser beam irradiation is to irradiate the stress improvement region of the tube with a rectangular laser beam, and the movement moves the laser beam irradiation unit in the circumferential direction of the tube, and the laser beam The irradiation unit may be moved in the axial direction.

  According to this configuration, since the movement moves in the circumferential direction and the axial direction, the size of the laser beam irradiation portion can be reduced, and the residual stress can be obtained regardless of the circumferential size and the axial length of the tubular body. The improvement process can be easily performed.

  In order to achieve the above object, the present invention provides a residual stress improving method for improving the residual stress on the inner surface of a tubular body, wherein the entire stress improving region in which the residual stress of the tubular body is desired to be improved is placed inside the tubular body. A laser light irradiation step of irradiating the inner surface of the tube with laser light from the arranged laser light irradiation portion, and cooling water in the stress-improving region from the cooling water jetting portion that has stopped laser light irradiation and is inserted inside the tube. A method for improving the residual stress of a tubular body, comprising: a cooling step of performing rapid cooling by ejecting water.

  According to this configuration, the laser beam irradiation part is inserted into the inner surface, the laser beam is irradiated onto the inner surface of the tube body, and then rapid cooling is performed, so that a temperature difference between the outer surface side and the inner surface side of the tube body is forcibly created. The residual stress can be improved.

  Moreover, since the laser beam irradiation part is inserted into the tube body and heated from the inside, the residual stress can be improved even if the size in the diameter direction of the tube changes compared to the one heated from the outside. it can.

  Furthermore, in order to achieve the above object, the present invention provides a residual stress improving method for improving a residual stress on an inner surface of a tubular body, the first region adjacent to a stress improving region where the residual stress of the tubular body is desired to be improved, and At least one of the second regions is irradiated with a laser beam from a laser beam irradiation unit provided outside the tube, and the laser beam is irradiated in the stress improvement region and the laser beam irradiation step. A temperature measuring step for measuring the temperature of the irradiated region, and a cooling step for stopping and cooling the laser beam irradiation after the stress improving region and the laser beam irradiation region have reached a predetermined temperature difference; There is provided a method for improving a residual stress of a tubular body characterized by comprising:

  According to this configuration, since the residual stress is improved by utilizing the temperature difference in the axial direction of the tubular body, compared to the method of improving the residual stress by utilizing the temperature difference in the thickness direction of the tubular body. It is easy to measure the temperature difference, and it is possible to improve the residual stress reliably.

  Further, since the temperature difference in the axial direction of the tubular body is utilized, it is possible to perform a residual stress improvement process regardless of the thickness and size of the tubular body.

  In the above configuration, the laser beam irradiation, the temperature measuring step, and the cooling step may be performed simultaneously on the first region and the second region.

  According to this configuration, since the residual stress improvement process uses the temperature difference in the axial direction and is heated at the same time, the size of the portion irradiated with the laser beam can be reduced and the process can be completed in a short time. Can do.

  In the above configuration, the method for improving residual stress of a tubular body includes a moving step of moving the laser beam irradiation unit between the first region and the second region, After performing the laser beam irradiation step, the temperature measurement step, and the cooling step, the laser irradiation unit is moved in the moving step, and the laser beam irradiation step, the temperature measurement step, and the second region are moved. The cooling process may be performed.

  According to this configuration, the laser light irradiation step, the temperature measurement step, and the cooling step can be performed on the first region and the second region with one laser light irradiation unit.

  The stress improvement region may be in the vicinity of a dissimilar material joint in which pipes of different materials are joined and welded.

  Since the output of the laser beam can be changed, it is possible to improve the residual stress of the dissimilar material joint obtained by joining the dissimilar material pipes.

  Furthermore, in order to achieve the above object, the present invention is an apparatus for improving residual stress for improving the residual stress on the inner surface of a tubular body, and irradiates the outer surface of the tubular body with laser light so that the residual stress improving region is substantially uniform. Residual stress of a tubular body, characterized by comprising laser light irradiation means having one or a plurality of laser light irradiation portions heated to heat, and control means for controlling the operation of the laser light irradiation means Provide an improvement device.

  According to this configuration, since heating is performed by irradiating laser light, it is not necessary to heat a useless area, and energy consumption can be reduced accordingly.

  In the above configuration, the laser beam irradiation means may be capable of adjusting the output of the laser beam to be irradiated according to the material of the tube.

  The said structure WHEREIN: You may have a moving means to move the said laser beam irradiation means along the said stress improvement area | region.

  According to this configuration, since the laser light irradiation means moves to heat a wide range, the area to be irradiated with the laser light at the same time may be small, the laser light output only needs to be heated in a small area, and the apparatus itself is compact. It can be configured at low cost.

  In the above-described configuration, the laser beam irradiation means has the laser beam irradiation portions arranged at equal central angular intervals outside the tube, and the laser beam is uniformly and simultaneously spread over the entire circumference with a predetermined axial width on the outer surface of the tube. The moving means may irradiate light, and the moving means may move the laser light irradiating means in the axial direction along the tubular body.

  According to this structure, since it can heat uniformly in the circumferential direction of the outer surface of a tubular body, it is possible to improve a residual stress uniformly. In addition, since it moves only in the axial direction, the structure is simple, and it can be manufactured at a lower cost.

  In the above-described configuration, the laser light irradiation means has the laser light irradiation portion in which the laser light irradiation region has a predetermined length in the circumferential direction on the outer surface of the tubular body and is the same as or substantially the axial length of the stress improvement region in the axial direction. The moving means may rotate the laser light irradiation means in the circumferential direction of the tube body.

  According to this structure, since it can heat uniformly in the axial direction of the outer surface of a tubular body, it is possible to improve a residual stress uniformly. Moreover, since it moves only in the circumferential direction, the structure is simple, and it can be manufactured at a low cost.

  According to this configuration, the stress improvement region can be simultaneously heated to the axial length of the stress improvement region, and the moving means moves only in the circumferential direction. Therefore, the residual stress can be improved regardless of the diameter of the tube. Is possible.

  Further, at this time, a plurality of laser beam irradiation units may be detachable, or a number of laser beam irradiation units that can be driven by the number corresponding to the stress improvement region may be used.

  In the above-described configuration, the laser light irradiation means is arranged such that the laser light irradiation part has a predetermined length in the axial direction and the circumferential direction on the outer surface of the tubular body, and the moving means is the laser beam. The light irradiating means may be rotated in the circumferential direction of the tubular body and moved in the axial direction every time it makes a round around the tubular body.

  According to this configuration, since the moving means moves the laser light irradiation means in the circumferential direction and the axial direction, the size of the laser light irradiation portion can be reduced, and the circumferential size and the axial length of the tube body can be reduced. Regardless, it is possible to apply.

  Furthermore, in order to achieve the above object, the present invention is an apparatus for improving residual stress for improving the residual stress on the inner surface of a tubular body, wherein one or a plurality of laser light irradiation sections for irradiating the inner surface of the tubular body with laser light Laser beam irradiation means, temperature measurement means for measuring the temperature of the tubular body irradiated with the laser light, cooling water injection means for jetting cooling water onto the inner surface irradiated with the laser light, and the laser A control unit for controlling operations of the light irradiation unit, the temperature measurement unit, and the cooling water injection unit, and the laser beam irradiation unit outputs an output of the laser beam to be irradiated according to the material of the tube body. A device for improving residual stress of a tubular body characterized by being adjustable.

  According to this configuration, the laser beam irradiation part is inserted into the inner surface, the laser beam is irradiated onto the inner surface of the tube body, and then rapid cooling is performed, so that a temperature difference between the outer surface side and the inner surface side of the tube body is forcibly created. Can do.

  Further, since the laser beam irradiation unit is inserted into the tube body and heated from the inside, the present invention can be applied even if the size in the diameter direction of the tube body is changed as compared with that heated from the outside.

  The laser light irradiation means includes a laser light source, and a laser diode or a fiber laser may be employed as the laser light source.

  According to this configuration, the laser beam irradiation means can be easily formed and the power plant can be made smaller as compared with the case where other laser light sources are used, so that the operation efficiency is high and the manufacturing and operation costs are reduced. It is possible to provide a cheap residual stress improving device for a tubular body.

  In the method for improving the residual stress of the tubular body, it is preferable that the laser light is transmitted through an optical fiber. According to this structure, the freedom degree of an apparatus increases and workability | operativity can be improved. Further, even when the residual stress improving part is a remote part or the peripheral space is a narrow part, the laser can be transmitted.

  In the method for improving the residual stress of the tubular body, the laser light source 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 portion, and can be installed in the vicinity of the residual stress improving portion.

  In the method for improving residual stress of a tubular body, the laser beam irradiation may be performed according to an energy density of a laser beam irradiation position or a laser beam irradiation position defined by a laser irradiation angle, an irradiation distance, or the like. It is preferable that the output can be adjusted. According to this configuration, even when the residual stress improvement site has a complex shape, the irradiation angle or the irradiation area changes, the heat input energy density changes, or even when the heat transfer characteristics differ between different materials, Distribution heating can be performed.

  In the method for improving residual stress of a tubular body, an absorbent is preferably applied to the surface of the tubular body irradiated with the laser light. According to this configuration, it is possible to improve the absorptance of the laser beam and to suppress a change in the absorptance due to the surface state, and it is possible to stably improve the residual stress.

  Moreover, it is preferable that the said absorber contains carbon. According to this configuration, an absorbent that is stable at high temperatures and easily absorbs laser light can be obtained.

  The absorbent preferably contains mica. According to this structure, stability at high temperature can be imparted to the absorbent.

  Further, it is preferable that the absorbent does not contain a halogen element. According to this structure, generation | occurrence | production of SCC resulting from the residue of an absorber can be suppressed or eliminated (halogen element may cause SCC generation | occurrence | production), and the soundness of a plant improves.

  In the method for improving residual stress of a tubular body, the laser light irradiation is preferably performed while the inner surface of the tubular body is cooled with water or air. According to this configuration, the temperature distribution in the tube thickness direction can be a temperature distribution having a substantially uniform temperature gradient from the inner surface to the outer surface.

  In the method for improving the residual stress of the tubular body, the laser light irradiation is preferably performed on the outer surface of the tubular body while water-cooling or air-cooling the forward direction or the backward direction of the moving direction of the laser light irradiation unit. . According to this configuration, it is possible to improve the temperature distribution in the tube thickness direction, and to suppress an unnecessarily high temperature rise on the tube surface.

  In the method for improving residual stress of a tubular body, it is preferable that the laser beam irradiation is performed intermittently with the laser beam irradiation. According to this configuration, it is possible to improve the temperature distribution in the tube thickness direction, and to suppress an unnecessarily high temperature rise on the tube surface.

  Further, in the method for improving residual stress of a tubular body, the movement is performed by moving the laser light irradiation unit one or more times along the circumferential direction of the tubular body so that the initial stage and the final stage of movement overlap each other. The laser light irradiation preferably suppresses laser output at the initial stage of movement and at the end of movement. According to this configuration, it is possible to suppress the non-uniformity of the tube temperature that is likely to occur at the beginning and end of movement, and to make the temperature distribution in the tube thickness direction uniform over the entire circumference of the tube. it can.

  Further, in the method for improving residual stress of a tubular body, the movement may be performed by causing the laser beam irradiation unit to return to the original position after making the circumferential direction of the tubular body substantially half a circumference along the stress improving region, and It is preferable to return to the original position after approximately half the circumference in the direction opposite to the moving direction. According to this configuration, it is possible to simplify the handling while maintaining the effect of improving the residual stress over the entire circumference of the tubular body, while preventing the construction device such as the cable from being entangled with the tubular body.

  In the method for improving residual stress of a tubular body, the tubular body may be a stainless steel pipe of a nuclear reactor plant. There is concern about the occurrence of SCC in stainless steel pipes in nuclear power plants. When applied to steel pipes that have already been used, it is necessary to remove the old piping and install new low-carbon material piping. 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, when applied to stainless steel piping in a nuclear power plant, replacement work is not necessary, and the economics and reliability of the plant are improved.

  In the method for improving residual stress of a tubular body, the tubular body may be a recirculation pipe of BWR (boiling water nuclear power generation).

  Further, in the method for improving residual stress of a tubular body, the tubular body includes a low alloy steel and austenite connected to any one of a nuclear reactor reactor, a pressurizer, and a steam generator in which generation of SCC is concerned. It may be a dissimilar joint of stainless steel, for example, a safe end weld.

  Moreover, in the residual stress improvement method for a tubular body, the laser light irradiation step is performed before, during, and after the irradiation of the laser light along the moving direction of the laser light irradiation portion on the outer surface of the tubular body. It is preferable to perform this while monitoring the temperature change. According to this configuration, the temperature distribution in the tube thickness direction can be appropriately controlled and managed.

  In the method for improving the residual stress of the tubular body, the temperature change may be measured by a radiation thermometer, a thermocouple, a temperature choke, or a contact thermometer installed in a laser light irradiation portion of the tubular body.

  Further, in the residual stress improvement method for a tubular body, after simulating an optimal residual stress improvement method for a flat model of the same material as the tubular body or a pseudo model of the same material and the same shape, Based on this, it is preferable to improve the residual stress of the tubular body. According to this configuration, when improving the pipe that is the actual residual stress improvement target, using the results obtained in advance, the temperature distribution in the pipe thickness direction is improved and controlled appropriately. Can be processed. Particularly, the inner surface of the tube body and the tube body in the narrow portion are useful means because temperature management is difficult.

  Further, in the tubular body residual stress improving apparatus, the laser light is preferably transmitted by an optical fiber.

  In the residual stress improving apparatus for a tubular body, the laser light source is preferably a fiber laser or a laser diode.

  Moreover, in the residual stress improving apparatus for a tubular body, it is preferable that the laser beam irradiation unit can adjust the output of the laser beam according to the irradiation position of the laser beam.

  Moreover, it is preferable that the apparatus for improving residual stress of a tubular body includes a cooling unit that cools or air-cools the inner surface of the tubular body when the laser beam is irradiated.

  Further, in the apparatus for improving residual stress of a tubular body, when irradiating the laser beam, a cooling unit that cools or air-cools the front direction or the rear direction of the moving direction of the laser beam irradiating unit on the outer surface of the tubular body. It is preferable to have.

  Moreover, in the said residual stress improvement apparatus of a tubular body, it is preferable that the said laser beam irradiation means can irradiate the said laser beam intermittently.

  In the tubular body residual stress improving apparatus, the moving means moves the laser light irradiation means one or more times along the stress improving region in the circumferential direction of the tubular body so that the initial stage and the final stage of movement overlap each other. It is preferable that the laser beam irradiation unit suppresses laser output at the initial stage of movement and at the end of movement.

  Further, in the tubular body residual stress improving apparatus, the moving unit may return the laser beam irradiating unit to the original position after making the laser beam irradiating unit substantially circulate along the stress improving region in the circumferential direction of the tube. It is preferable to have a function of returning to the original position after substantially making a half turn in the direction opposite to the moving direction.

  Moreover, in the said residual stress improvement method of a tubular body, it is preferable that the temperature which irradiates and heats the said laser beam is below 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 method for improving the residual stress of the tubular body, it is preferable that a region irradiated with the laser beam and heated is 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.

Furthermore, in order to achieve the above object, the present invention provides a residual stress improving method for improving the residual stress on the inner surface of a tubular body,
A laser beam irradiation step of irradiating the outer surface of the tube body with a laser beam from a laser beam irradiation section disposed outside the tube body in a stress improvement region where the residual stress of the tube body is desired to be improved;
A temperature measuring step for measuring the temperature of the stress improvement region of the tubular body;
And a cooling step of stopping and cooling the laser beam irradiation after the outer surface side and the inner surface side of the stress improvement region reach a predetermined temperature difference.

Furthermore, in order to achieve the above object, the present invention provides a residual stress improving method for improving the residual stress on the inner surface of a tubular body,
A laser beam irradiation step of irradiating the entire inner surface of the tube body with laser light from a laser beam irradiation portion disposed inside the tube body over the entire stress improvement region where the residual stress of the tube body is desired to be improved;
A temperature measuring step for measuring the temperature of the stress improvement region of the tubular body;
After a predetermined temperature difference between the outer surface side and the inner surface side of the stress improvement region, laser light irradiation is stopped, and cooling water is jetted from the cooling water jetting portion inserted into the tube body to the stress improvement region to perform rapid cooling. And a cooling step to be performed.

  According to the present invention, there is provided a method and apparatus for heating a tubular body to reduce or compress the residual stress in a tensile state, and the residual stress of the tubular body can be improved easily, quickly and reliably. It is possible to provide an improved method and apparatus.

  Also, according to the present invention, there is a method and apparatus for heating a tubular body to reduce the residual stress in a tensile state or bringing it into a compressed state, and without preparing a large-scale apparatus and a large energy source, the residual stress of the tubular body is prepared. It is possible to provide a method and an apparatus for improving a residual stress that can be improved easily, quickly and reliably.

  The best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a schematic explanatory diagram of the residual stress improvement method.

  It is well known that stress corrosion cracking on the inner surface of the tubular body can be prevented by improving the residual stress generated on the inner surface of the tubular body Pi from a tensile state to a compressed state. Heating is performed so that a predetermined temperature difference is generated between the outer surface S2 and the inner surface S1 of the residual stress improvement region Sr of the tubular body (see FIG. 1A). At this time, the outer surface S2 is in a compressive stress state, the inner surface S1 is in a tensile stress state, and further, the inner surface S1 is in a tensile yield state (see FIG. 1B). Then, the inner surface S1 and the outer surface S2 of the stress improvement region Sr are cooled. By cooling (see FIG. 1C), the outer surface S2 becomes a tensile stress state, the inner surface S1 becomes a compressive stress state, and the residual stress of the inner surface S1 can be improved from the tensile stress state to the compressive stress state. (See FIG. 1D).

  FIG. 2 shows a schematic layout of the tubular residual stress reducing apparatus according to the present invention. A tubular body residual stress improving apparatus A shown in FIG. 2 is a laser beam irradiating unit 1 that irradiates a laser beam Lz to a stress improving region Sr that should improve the residual stress of the tube Pi, and the laser beam irradiating unit 1 is stress improved. A moving means 2 for moving in the region Sr, a temperature measuring means 3 for measuring the temperature of the portion irradiated with the laser light Lz in the stress improving region Sr, and a control means Cont for controlling the residual stress improving apparatus A; It has.

  The laser light irradiation means 1 includes a laser light source 11 that outputs laser light, and a laser light irradiation unit 12 that irradiates the stress improvement region Sr with the laser light Lz output from the laser light source 11. The laser light Lz output from the laser light source 11 is sent to the laser light irradiation unit 12 via the optical fiber cable 13. Here, a laser diode is used as the laser light source 11. Further, the laser light source 11 is not limited to a laser diode, and a laser light source that can output laser light that can heat the pipe Pi can be widely used.

(First embodiment)
3A and 3B are a front view and a side view showing a residual stress improvement by an example of the method for improving a residual stress of a tubular body according to the present invention. FIG. 3C to FIG. 3E show a procedure of an example of a method for improving the residual stress of a tubular body according to the present invention. FIG. 4 shows a flowchart of a residual stress improving process using the tubular residual stress improving method according to the present invention. Further, the residual stress improving apparatus A1 has substantially the same configuration as that of the residual stress improving apparatus A shown in FIG.

  In the residual stress improving apparatus A1 used in the residual stress improving method shown in FIGS. 3A and 3B, a laser light irradiation unit 12a is provided in the laser light irradiation means 1a provided outside the pipe Pi. Eight are provided at equal central angular intervals (but not limited to 45 ° here).

  The laser beam irradiation unit 12a irradiates with an irradiation width t in the axial direction. By simultaneously irradiating eight laser beams, the stress improvement region Sr of the tubular body Pi is uniformly irradiated over the entire circumference in the circumferential direction. (See FIG. 3B). At this time, the laser beam irradiation region by the laser beam irradiation unit 12a is a ring-shaped R having an axial width t.

  The residual stress improvement method is performed by the following procedure. First, the laser beam irradiation means 1a is arranged at the end of the stress improvement region Sr of the tubular body Pi so that the laser beam Lz can be irradiated in a ring shape having a width t (step St1). Then, the laser beam Lz is simultaneously irradiated from the eight laser beam irradiation units 12a provided in the laser beam irradiation unit 1a (step St2). And temperature is measured by the temperature measurement means 3 arrange | positioned outside the pipe Pi (step St3). It is determined whether or not the measured temperature is a predetermined temperature (step St4). When the temperature is not the predetermined temperature (NO in step St4), the temperature measurement is repeated by returning to step St3. When the temperature reaches a predetermined temperature (YES in step St4), the output of the laser light source 11, the heating time, and the temperature of the outer surface of the tube are measured, and the thermal conductivity of the tube is taken into account, thereby stress of the tube The temperature difference between the inner surface and the outer surface of the improvement region Sr can be set to a predetermined temperature.

  When the temperature difference between the inner and outer surfaces of the stress improvement region Sr reaches a predetermined temperature (YES in step St4), the laser beam irradiation from the laser beam irradiation means 1a is stopped (step St5). At this time, the stress state of the heated portion of the stress improvement region Sr is the outer surface S2 in the compressed state and the inner surface S1 in the tensile state (tensile yield state) as described above. After cooling (step St6), when the temperature difference between the inner and outer surfaces disappears, the inner surface S1 becomes a compressive stress state, and the residual stress of the inner surface S1 is improved. Thereafter, the moving means 2 is operated to move the laser light irradiation means 1a in the axial direction (step St7) (see FIG. 2). It is determined whether the moved portion is the stress improvement region Sr (step St8).

  When the movement destination of the laser beam irradiation means 1a is the stress improvement region (YES in Step St8), the process returns to Step St2 to improve the residual stress. When the movement destination of the laser beam irradiation means 1a is not the stress improvement region Sr (NO in step St8), the improvement of the residual stress is finished.

  In the above-described embodiment, the laser beam irradiation means 1a is provided with eight laser beam irradiation sections 12a. However, the present invention is not limited to this, and the laser is simultaneously and uniformly distributed over the entire circumference of the tube body. The number that can be irradiated with light can be employed. In addition, by attaching to a plurality of rows in the axial direction, it is possible to irradiate the laser beam widely in the axial direction simultaneously. It is also possible to continuously move the laser beam in the axial direction.

(Second Embodiment)
5A and 5B are a front view and a side view showing residual stress improvement by an example of the method for improving residual stress of a tubular body according to the present invention. 5 (C) to 5 (E) show a procedure of an example of a method for improving the residual stress of a tubular body according to the present invention. Further, the residual stress improving apparatus shown in FIG. 5 has substantially the same configuration as the residual stress improving apparatus A shown in FIG. 2 except for the laser beam irradiation means, and the same reference numerals are given to substantially the same parts.

  In the residual stress improving apparatus A2 shown in FIGS. 5 (A) and 5 (B), it is arranged simultaneously with the laser beam irradiation unit 12b arranged in a rectangle having the axial length of the stress improving region Sr (six in this embodiment). The laser beam Lz is irradiated uniformly on the stress improvement region Sr. After the temperature is measured by the temperature measuring means at the portion of the stress improvement region Sr irradiated with the laser beam Lz, the temperature reaches a predetermined temperature (the temperature difference between the inner and outer surfaces of the stress improvement region reaches the predetermined temperature). By cooling, the residual stress on the inner surface of the tubular body can be improved from the tensile stress state to the compressive stress state. The mechanism by which the residual stress is improved from the tensile stress state to the compressive stress state is the same as that shown in FIG.

  Thereafter, the laser beam irradiation unit 1b is moved in the circumferential direction of the pipe Pi by the moving unit, and is stopped at a position where the portion of the stress improvement region Sr where the residual stress improvement process is not performed can be irradiated with the laser beam Lz. Residual stress improvement processing is performed (see FIG. 5C). By performing the above operation so that the laser beam irradiation means 1b makes one round in the circumferential direction (see FIG. 5D), the residual stress on the inner surface of the stress improvement region Sr can be improved from the tensile state to the compressed state. (See FIG. 5E). In this step, the laser beam can also move continuously.

  The laser beam irradiation means 1b of the apparatus A2 for improving the residual stress of the tubular body shown in the present embodiment is an example in which six laser beam irradiation sections 12b are arranged in the axial direction, but is not limited thereto. The number according to the stress improvement area | region Sr is employable. Further, the number of the laser beam irradiation units 12b can be arbitrarily changed, or the laser beam Lz is irradiated only from the arbitrary laser beam irradiation unit 12b among the plural laser beam irradiation units 12b. May be.

  By using this method, there is less restriction due to the diameter of the tube compared to the method for improving residual stress shown in FIG. 3, and the method for improving residual stress according to the present invention is applied to more tubes. Can do.

(Third embodiment)
FIGS. 6A and 6B are a front view and a side view showing residual stress improvement by an example of a method for improving residual stress of a tubular body according to the present invention. FIG. 6C to FIG. 6F show the procedure of another example of the method for improving the residual stress of a tubular body according to the present invention. Further, the remaining stress improving apparatus shown in FIG. 6 has substantially the same configuration as the residual stress improving apparatus A shown in FIG. 2 except for the laser beam irradiation means, and the same reference numerals are given to the substantially same parts.

  In the residual stress improving apparatus A3 shown in FIGS. 6A and 6B, the laser light irradiation means 1c has one laser light irradiation section 12c. Laser light is irradiated to an arbitrary place (P1 portion in FIG. 6C) at the end of the stress improvement region Sr. The temperature is measured by the temperature measuring means at the portion of the stress improvement region Sr irradiated with the laser beam, and cooled after the temperature reaches a predetermined temperature (the temperature difference between the inner and outer surfaces of the stress improvement region reaches the predetermined temperature). By doing so, the residual stress on the inner surface of the tubular body can be improved from the tensile stress state to the compressive stress state. The mechanism by which the residual stress is improved from the tensile stress state to the compressive stress state is the same as that shown in FIG.

  Thereafter, the moving means 2 moves the laser light irradiation means 1c in the circumferential direction of the pipe Pi, and stops at a position where the portion of the stress improvement region Sr where the residual stress improvement processing is not performed can be irradiated with the laser light, Residual stress improvement processing is performed (see FIG. 6D). The above operation is performed so that the laser beam irradiation means 1c makes one round in the circumferential direction (see FIG. 6E).

  After the laser light irradiation means 1c makes a round around the tube, the moving means can move the laser light irradiation means 1c in the axial direction and irradiate the portion of the stress improvement region Sr where the residual stress improvement processing is not performed. Stop at the position and perform the above-described stress improvement processing (see FIG. 6F). The laser light irradiation means 1c moves in the axial direction around the tube in the axial direction to perform stress improvement processing, whereby the residual stress in the entire stress improvement region Sr can be improved.

(Fourth embodiment)
7A to 7F are schematic views of a method for improving the residual stress of a tubular body according to the present invention. 7 is a laser beam irradiation means which is inserted into the inner surface of the pipe Pi and simultaneously heats the circumferential direction of the inner surface of the pipe Pi with a predetermined axial width. 1d and the cooling water injection means 4 which cools by injecting cooling water to the heated part irradiated with the laser beam Lz by the laser light irradiation means 1d.

  The laser beam irradiating means 1d transmits the laser beam through the optical fiber cable 13d, and irradiates the laser beam in a ring shape from the laser beam irradiation unit 12d provided at the tip of the optical fiber cable 13d.

  As shown in FIG. 7A, first, the laser beam irradiation means 1d is inserted into the pipe body Pi, and the laser beam Lz is irradiated to the stress improvement region Sr for improving the residual stress. By irradiating the laser beam Lz, the tube body is heated from the room temperature RT by a predetermined temperature ΔT1. FIG. 7D shows the relationship between the thickness of the pipe Pi at this time, the temperature, and the stress. As shown in FIG. 7D, the temperature of the inner surface of the tubular body is higher than that of the outer surface. Moreover, the stress by the thermal expansion which generate | occur | produces by heating the tubular body Pi has produced | generated the small compressive stress on the inner surface side, and the small tensile stress on the outer surface side.

  Thereafter, the inner surface of the tube is not limited to this, but here, the laser beam is irradiated from the laser beam irradiation means 1d until the temperature is raised to about 500 ° C., and the laser beam irradiation is terminated. Thereafter, as shown in FIG. 7B, the cooling water injection means 4 is inserted into the pipe Pi, and the cooling water Wr is injected into the pipe to rapidly cool the inner surface of the pipe. The state of temperature and stress at this time is shown in FIG. As shown in FIG. 7E, rapid cooling is performed until the temperature of the outer surface does not decrease and the temperature of the inner surface decreases by ΔT2.

  At this time, since the inner surface is rapidly cooled, a large tensile stress is generated in the stress state, and a tensile yield state is obtained. Further, the outer surface is in a state where compressive stress is generated reciprocally due to a large tensile stress generated on the inner surface.

  Thereafter, as shown in FIG. 7C, the coolant injection means 4 is taken out from the pipe Pi to cool the whole pipe Pi. In addition, FIG. 7F shows the state of temperature and stress at this time. The inner surface of the pipe Pi remains in a compressed state by rapidly cooling only the inner surface and cooling the entire tube until it reaches room temperature RT with the stress state of the inner surface in a tensile state and the stress state of the outer surface in a compressed state. Stress can be formed.

  Since the laser beam irradiation means 1d is provided with the laser beam irradiation part 12d at the tip of the optical fiber cable 13d, when the residual stress in the stress improvement region of the tube Pi is improved by this method, the tube with a small inner diameter is used. Can also be applied.

(Fifth embodiment)
FIG. 8 shows a schematic diagram of a method for improving the residual stress of a tubular body according to the present invention. FIG. 8A is a diagram showing a stress state before the residual stress improvement of the tubular body according to the present invention, and FIG. 8B is a stress distribution when a region adjacent to one of the stress improvement regions is heated. 8C shows the stress distribution after cooling, FIG. 8D shows the stress distribution when a region adjacent to the other of the stress improvement regions is heated, and FIG. 8E shows the stress distribution after cooling. Distribution.

  The method for improving the residual stress of the tubular body shown in the first to fourth embodiments is to improve the residual stress on the inner surface from a tensile state to a compressed state by a temperature difference in the thickness direction of the tubular body Pi. However, the method for improving the residual stress of the tubular body shown in FIG. 8 is to improve the residual stress in the region where the residual stress is desired to be improved (stress improving region Sr) due to the temperature difference in the axial direction.

  As shown in FIG. 8A, the residual stress of the tubular body is in the tensile state in the stress improvement region Sr, and the portions N1 and N2 adjacent to both sides thereof are in the compressed state. First, the laser beam irradiation means 1e is arranged in a portion N1 adjacent to one stress improvement region Sr (hereinafter referred to as the first region N1), and the laser beam Lz is irradiated. After the laser beam Lz is irradiated until the temperature of the first region N1 measured by the temperature measuring means reaches a predetermined temperature, the laser beam irradiation is terminated. At this time, a predetermined temperature difference is generated between the first region N1 and the stress improvement region Sr. In this state, the stress distribution of the tubular body is as shown by the solid line in FIG. That is, a tensile stress is generated in the heating portion (here, the first region N1), and a compressive stress is generated in the adjacent stress improvement region Sr.

  Then, the portion that has been expanded by heating is contracted by cooling, and the residual stress distribution is generated in the first region N1 and the stress improvement region Sr as shown by the solid line in FIG. 8C. In the second region N2, residual stress in a compressed state is generated.

  Thereafter, the laser beam irradiation means 1e is moved to the second region N2, and the laser beam Lz is irradiated. Until the temperature of the second region N2 reaches a predetermined temperature, in other words, until the predetermined temperature difference is generated between the second region N2 and the stress improvement region Sr, the laser light irradiation is performed. Exit.

  At this time, the stress distribution of the pipe Pi is as shown by the solid line in FIG. That is, a tensile stress is generated in the heating part (here, the second region N2), and a compressive stress is generated in the adjacent stress improvement region Sr.

  After cooling, the portion that was expanded by heating contracts, and the distribution of residual stress is as shown by the solid line in FIG. 8E. The first region N1 and the second region N2 are in a tensile state. Residual stress is generated, and compressive residual stress is generated in the stress improvement region Sr.

  The residual stress in the stress improvement region Sr is improved to a compressed state, and the residual stress in the first region N1 and the second region N2 is in a tensile state but is suppressed to a small stress. In addition, stress corrosion cracking, which is the purpose of improving residual stress, occurs when the conditions of the material, stress, and environment are satisfied, but the material conditions are not satisfied in the first region N1 and the second region N2. Even if a slightly large residual stress is generated, it does not cause stress corrosion cracking.

  In this embodiment, the residual stress can be improved by using any of the stress improving apparatuses shown in the first to third embodiments. Further, since the temperature difference is taken in the axial direction instead of the thickness direction of the tubular body, it is possible to perform the residual stress improving process on the thin tubular body using the residual stress improving method. .

  Although the improvement area | region of the residual stress of the pipe body shown to the above each embodiment is not limited to it, a pipe welded joint can be illustrated. Moreover, the area | region which improves the residual stress of tubular bodies, such as a rolling part and a cutting part, can be employ | adopted widely.

<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. 9, the laser optical system 50 is mounted on the robot arm as shown in FIG. 9, and is reciprocated in the axial direction at a scanning speed of about 500 mm / s (30 m / min) to obtain about 80 mm (scanning distance) in the axial direction. 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. 10 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. 11 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.

  Note that the heating region is uniformly heated by 2.5√ (rt) (r: average radius of the tube, t: thickness of the tube) or more, preferably 3√ (rt) or more, centering on the welded portion. You can do it. Further, the heating temperature at this time is preferably less than the solution temperature.

  In the above embodiment, the laser light source 11 is preferably a laser diode or a fiber laser. In addition, it is preferable that the intensity of the laser beam Lz from the laser beam irradiation units 12, 12a, 12b, and 12c can be adjusted depending on the irradiation position, so that the residual stress improvement site has a complicated shape or a different material site. Even if there is, it can respond appropriately. Further, the pipe Pi for which the residual stress is to be improved is 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 reactor vessel, a pressurizer, and a steam generator. And a dissimilar joint between low alloy steel and austenitic stainless steel, such as a safe-end weld (particularly nickel-base alloy).

  Moreover, it is preferable to apply an absorbent, particularly an absorbent containing carbon or mica, to the surface of the tubular body Pi irradiated with the laser light Lz. Moreover, about the application | coating thickness of an absorber, since there exists a possibility that the temperature rise of a pipe body may be prevented when it is too thick, it is preferable to manage to appropriate thickness. In order to suppress the occurrence of SCC, it is preferable that the absorbent does not contain a halogen element.

  Further, as shown in FIG. 4, the example in which the laser beam irradiation is stopped (step st5) and then cooled (step st6) has been described, but the laser beam irradiation process may be performed while the inner surface of the pipe Pi is cooled with water or air. In addition, it is preferable to perform the laser light irradiation step while water-cooling or air-cooling the forward direction or the backward direction of the moving direction of the laser light irradiation units 12, 12a, 12b, 12c on the outer surface of the pipe Pi. Further, when irradiating the outer surface or the inner surface of the pipe Pi with the laser beam, the laser beam Lz may be irradiated intermittently.

  Moreover, as shown in FIGS. 5 and 6, as an example of the driving mode of the laser light irradiation means 1 b and 1 c, an example of making a round in the circumferential direction of the pipe Pi has been shown. It is preferable to move one or more rounds so that the end of movement overlaps, and to suppress the laser output at the beginning and end of movement. Further, the laser beam irradiation means 1b, 1c are made to make a half turn in the circumferential direction of the pipe Pi along the stress improvement region, and then returned to the original position, and further made a half turn in the direction opposite to the half-turned movement direction. After that, it may be returned to the original position. Note that the movement is not limited to substantially a half circumference, and the circumferential direction of the pipe Pi may be divided into a plurality of pieces and moved.

  Further, the laser light irradiation process is performed while monitoring the temperature change before, during and after the laser light irradiation along the moving direction of the laser light irradiation means 1, 1a to 1e on the outer surface of the pipe Pi. Is preferred. Thus, in order to appropriately improve the residual stress, it is preferable to appropriately control and manage the temperature distribution in the thickness direction of the pipe Pi. The temperature can be measured with a radiation thermometer, a thermocouple, a temperature choke, or a contact thermometer installed in the laser beam irradiation portion of the tube.

  In addition, a flat plate of the same material as the pipe Pi for improving the residual stress, or a pseudo model of the same material and the same shape is prepared in advance, and an optimal residual stress improving method is simulated for the model, and then the result is obtained. Based on the above, it is preferable to improve the residual stress of the actual pipe Pi.

Figures (A) to (D) are schematic views of the mechanism for improving the residual stress of the tubular body. 1 is a schematic layout diagram of a tubular body residual stress improving apparatus according to the present invention. FIGS. 2A and 2B are a front view and a side view of an example of a tubular body residual stress improving apparatus according to the present invention, and FIGS. 3C to 1E are residual stresses of the tubular body according to the present invention. It is a schematic perspective view which shows the improvement method. It is a flowchart which shows the residual stress improvement procedure by the residual stress improvement method of the tubular body shown in FIG. Drawing (A) and (B) are the front views and side views of other examples of the residual stress improvement device of the tubular body concerning the present invention, and Drawing (C)-Drawing (E) are the tubular bodies concerning the present invention. It is a schematic perspective view which shows the residual stress improvement method. FIGS. (A) and (B) are a front view and a side view of still another example of a tubular body residual stress improving apparatus according to the present invention, and FIGS. (C) to (E) are tubular bodies according to the present invention. It is a schematic perspective view which shows the residual stress improvement method. FIGS. 1A to 1C are schematic perspective views showing a residual stress improving apparatus for a tubular body and a residual stress improving method using the same according to the present invention, and FIGS. It is a figure which shows the temperature difference and stress of an outer surface. FIG. (A) is a diagram showing a stress state before the residual stress improvement of the tubular body according to the present invention, and FIG. (B) is a stress distribution when a region adjacent to one of the stress improvement regions is heated. (C) is a stress distribution after cooling, FIG. (D) is a stress distribution when a region adjacent to the other of the stress improvement regions is heated, and FIG. (E) is a stress distribution after cooling. 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

A, A1, A2, A3, A4 Tubular residual stress improvement device 1, 1a, 1b, 1c, 1d, 1e Laser light irradiation means 11 Laser light source 12, 12a, 12b, 12c Laser light irradiation unit 13, 13d Optical fiber Cable 2 Moving means 3 Temperature measuring means 4 Cooling water injection means Pi tube Sr Stress improvement region 50: Laser optical system 51: Shutter 52: Pipe

Claims (49)

A method for improving residual stress that improves residual stress on the inner surface of a tubular body,
A method for improving residual stress of a tubular body, comprising: irradiating a laser beam to an outer surface of the tubular body from a laser light radiating portion disposed outside the tubular body in a stress improvement region where the residual stress of the tubular body is desired to be improved .   The method for improving residual stress of a tubular body according to claim 1, wherein the laser light irradiation can adjust the output of the laser light to be irradiated according to the material of the tubular body. The laser beam irradiation part continuously or intermittently moves to the part where the laser beam of the stress improvement region is not irradiated,
The residual stress improvement method for a tubular body according to claim 1 or 2, wherein the residual stress in the stress improvement region of the tubular body is improved. The laser beam irradiation has a predetermined width in the axial direction of the stress improvement region of the tubular body, and is irradiated with the laser beam substantially uniformly and simultaneously in the circumferential direction,
4. The method for improving residual stress of a tubular body according to claim 3, wherein the movement is performed by moving the laser beam irradiation section in an axial direction of the tubular body. The laser beam irradiation is to irradiate a rectangular laser beam having a length equal to or substantially the same as the axial length of the stress improvement region of the tubular body and having a predetermined width in the circumferential direction,
4. The method for improving residual stress in a tubular body according to claim 3, wherein the movement is performed by moving the laser beam irradiation section in the circumferential direction of the tubular body along the stress improving region. The laser beam irradiation is to irradiate a rectangular laser beam to the stress improvement region of the tubular body,
4. The method for improving residual stress of a tubular body according to claim 3, wherein the movement is performed by moving the laser light irradiation section in the circumferential direction of the tubular body and moving the laser light irradiation section in the axial direction. A method for improving residual stress that improves residual stress on the inner surface of a tubular body,
A laser beam irradiation step of irradiating the entire inner surface of the tube body with laser light from a laser beam irradiation portion disposed inside the tube body over the entire stress improvement region where the residual stress of the tube body is desired to be improved;
And a cooling step for rapidly cooling by stopping cooling with laser light and jetting cooling water from the cooling water jetting portion inserted into the pipe into the stress-improving region. Stress improvement method. A method for improving residual stress that improves residual stress on the inner surface of a tubular body,
At least one of the first region and the second region adjacent to the stress improvement region in which the residual stress of the tubular body is to be improved is irradiated with a laser beam from a laser light irradiation unit provided outside the tubular body. A laser beam irradiation process;
A temperature measuring step of measuring a temperature of the stress improving region and a region irradiated with laser light in the laser light irradiation step;
A residual stress of the tubular body, comprising: a cooling step of stopping and cooling the laser beam irradiation after the stress improvement region and the laser beam irradiation region have reached a predetermined temperature difference How to improve.   9. The method for improving residual stress of a tubular body according to claim 8, wherein the laser beam irradiation step, the temperature measurement step, and the cooling step are simultaneously applied to the first region and the second region. . The method for improving residual stress of the tubular body includes a moving step of moving the laser beam irradiation unit between the first region and the second region,
After performing the laser beam irradiation step, the temperature measurement step, and the cooling step on the first region, the laser irradiation unit is moved in the moving step, and the laser beam is moved on the second region. The method for improving residual stress of a tubular body according to claim 8, wherein an irradiation step, the temperature measurement step, and the cooling step are performed.   The method for improving residual stress of a tubular body according to any one of claims 1 to 9, wherein the stress improving region is in the vicinity of a dissimilar joint obtained by joining and welding tubular bodies of different materials. An apparatus for improving residual stress for improving residual stress on the inner surface of a tubular body,
A laser beam irradiation means having one or a plurality of laser beam irradiation sections for irradiating the outer surface of the tubular body with a laser beam and heating the residual stress improvement region to a substantially uniform temperature;
And a control means for controlling the operation of the laser beam irradiation means.   13. The tubular body residual stress improving apparatus according to claim 12, wherein the laser beam irradiation means can adjust the output of the laser beam to be irradiated in accordance with the material of the tube body. 14. The tubular body residual stress improvement apparatus according to claim 12 or 13, further comprising a moving means for moving the laser beam irradiation means along the stress improvement region. The laser light irradiating means has the laser light irradiating portions arranged at equal central angular intervals outside the tubular body, and uniformly and simultaneously irradiates the outer surface of the tubular body over the entire circumference with a predetermined axial width. Is what
15. The apparatus for improving residual stress in a tubular body according to claim 14, wherein the moving means moves the laser light irradiating means in the axial direction along the tubular body. The laser light irradiation means includes a laser light irradiation unit having a laser light irradiation region having a predetermined length in the circumferential direction on the outer surface of the tubular body and the axial direction of the stress improvement region being the same as or substantially the same as the axial length. Arranged so that
15. The apparatus for improving residual stress in a tubular body according to claim 14, wherein the moving means rotates the laser beam irradiating means in a circumferential direction of the tubular body. The laser light irradiation means arranges the laser light irradiation part so that a laser light irradiation region has a predetermined length in the axial direction and the circumferential direction on the outer surface of the tubular body,
15. The residual pipe body according to claim 14, wherein the moving means rotates the laser light irradiation means in a circumferential direction of the tubular body and moves in the axial direction every time the circumference of the tubular body is made. Stress improvement device. An apparatus for improving residual stress for improving residual stress on the inner surface of a tubular body,
A laser light irradiation means having one or a plurality of laser light irradiation parts for irradiating the inner surface of the tube with laser light;
Temperature measuring means for measuring the temperature of the tubular body irradiated with the laser beam;
Cooling water jetting means for jetting cooling water on the inner surface irradiated with the laser beam;
A control unit for controlling operations of the laser beam irradiation unit, the temperature measurement unit, and the cooling water injection unit;
The apparatus for improving residual stress of a tubular body, wherein the laser light irradiating means can adjust the output of the laser light to be irradiated according to the material of the tubular body. The laser light irradiation means includes a laser light source,
19. The tubular body residual stress improving apparatus according to claim 12, wherein a laser diode or a fiber laser is employed as the laser light source. In the residual stress improvement method of the tubular body according to any one of claims 1 to 11,
The method for improving residual stress of a tubular body, wherein the laser light is transmitted through an optical fiber. In the residual stress improvement method of the tubular body according to any one of claims 1 to 11,
The method for improving residual stress of a tubular body, wherein a light source of the laser light is a laser diode or a fiber laser. In the residual stress improvement method of the tubular body according to any one of claims 1 to 11,
The method of improving residual stress of a tubular body, wherein the laser beam irradiation can adjust the output of the laser beam depending on the irradiation position of the laser beam. In the residual stress improvement method of the tubular body according to any one of claims 1 to 11,
A method for improving residual stress of a tubular body, wherein an absorbent is applied to a surface of the tubular body irradiated with the laser light. In the method for improving residual stress of a tubular body according to claim 23,
The said absorbent contains carbon, The residual-stress improvement method of the tubular body characterized by the above-mentioned. In the method for improving residual stress of a tubular body according to claim 23,
The method of improving residual stress of a tubular body, wherein the absorbent contains mica. In the method for improving residual stress of a tubular body according to claim 23,
The method for improving residual stress of a tubular body, wherein the absorbent does not contain a halogen element. In the method for improving residual stress of a tubular body according to claim 1 or 8,
The method for improving residual stress of a tubular body, wherein the laser light irradiation is performed while water-cooling or air-cooling the inner surface of the tubular body. In the method for improving residual stress of a tubular body according to claim 3,
The method of improving a residual stress of a tubular body, wherein the laser light irradiation is performed on the outer surface of the tubular body while water-cooling or air-cooling a forward direction or a backward direction of a moving direction of the laser light irradiation unit. In the method for improving residual stress of a tubular body according to any one of claims 1, 7 and 8,
The said laser beam irradiation irradiates the said laser beam intermittently, The residual stress improvement method of the tubular body characterized by the above-mentioned. In the method for improving residual stress of a tubular body according to claim 3,
The movement is performed by moving the laser beam irradiation unit one or more times in the circumferential direction of the tubular body along the stress improvement region so that the movement initial stage and the final stage overlap.
The method of improving residual stress of a tubular body, wherein the laser light irradiation suppresses laser output at the initial stage of movement and at the end of movement. In the method for improving residual stress of a tubular body according to claim 3,
The movement is performed by making the laser beam irradiation part substantially half a circumference along the stress improvement region in the circumferential direction of the tubular body and then returning to the original position, and further making a half circumference in the direction opposite to the movement direction. A method for improving the residual stress of a tubular body characterized by returning to the position of the tube. In the residual stress improvement method of the tubular body according to any one of claims 1 to 11,
The method for improving residual stress of a tubular body, wherein the tubular body is a stainless steel pipe of a nuclear reactor plant. In the residual stress improvement method of the tubular body according to any one of claims 1 to 11,
The method of improving residual stress of a tubular body, wherein the tubular body is a recirculation piping of BWR (boiling water nuclear power generation). In the residual stress improvement method of the tubular body according to any one of claims 1 to 11,
The tubular body is a dissimilar material 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. Method. In the method for improving residual stress of a tubular body according to claim 3,
The laser beam irradiation is performed while monitoring temperature changes before, during and after the laser beam irradiation along the moving direction of the laser beam irradiation unit on the outer surface of the tube body. Body residual stress improvement method. The method for improving residual stress in a tubular body according to claim 35,
The temperature change is measured by a radiation thermometer, a thermocouple, a temperature choke, or a contact thermometer installed in a laser beam irradiation portion of the tube body. In the method for improving residual stress of a tubular body according to any one of claims 1, 7 and 8,
After simulating the optimal residual stress improvement method in advance for a flat plate of the same material as the tube, or a pseudo model of the same material, the same shape,
A method for improving the residual stress of a tubular body, wherein the residual stress of the tubular body is improved based on the result. In the residual stress improvement apparatus of the tubular body according to any one of claims 12 to 18,
The apparatus for improving residual stress of a tubular body, wherein the laser beam is transmitted through an optical fiber. In the residual stress improvement apparatus of the tubular body according to any one of claims 12 to 18,
An apparatus for improving residual stress in a tubular body, wherein the laser light source is a fiber laser or a laser diode. In the residual stress improvement apparatus of the tubular body according to any one of claims 12 to 18,
The apparatus for improving residual stress of a tubular body, wherein the laser beam irradiation means can adjust the output of the laser beam according to the irradiation position of the laser beam. In the apparatus for improving residual stress of a tubular body according to claim 12,
An apparatus for improving a residual stress of a tubular body, comprising: cooling means for cooling the inner surface of the tubular body with water or air when irradiating the laser beam. In the residual stress improvement apparatus of the tubular body according to claim 14,
Residual stress of a tubular body characterized by having a cooling means for water cooling or air cooling the front direction or the backward direction of the moving direction of the laser light irradiation means on the outer surface of the tubular body when irradiating the laser light Improvement device. In the residual stress improvement apparatus of the tubular body according to claim 12 or 18,
The apparatus for improving residual stress of a tubular body, wherein the laser beam irradiation means can intermittently irradiate the laser beam. In the residual stress improvement apparatus of the tubular body according to claim 14,
The moving means has a function of moving the laser light irradiating means one or more times in the circumferential direction of the tubular body along the stress improvement region so that the initial stage and the final stage of movement overlap.
The apparatus for improving residual stress in a tubular body, wherein the laser light irradiation means suppresses laser output at the initial stage of movement and at the end of movement. In the residual stress improvement apparatus of the tubular body according to claim 14,
The moving means returns the original laser beam irradiation means to the original position after making the laser beam irradiation means in the circumferential direction of the tubular body along the stress improvement region, and then making the laser beam irradiation means substantially half-turn in the direction opposite to the moving direction. A device for improving residual stress of a tubular body, which has a function of returning to an original position. In the method for improving residual stress of a tubular body according to any one of claims 1 to 11, 20 to 37,
The method for improving the residual stress of a tubular body, wherein a temperature at which the laser beam is irradiated and heated is equal to or lower than a solution temperature. The method for improving residual stress of a tubular body according to any one of claims 1 to 11, 20 to 37, 46,
The method for improving the residual stress of a tubular body, wherein a region to be irradiated with the laser beam and heated is 2.5√rt or more. A method for improving residual stress that improves residual stress on the inner surface of a tubular body,
A laser beam irradiation step of irradiating the outer surface of the tube body with a laser beam from a laser beam irradiation section disposed outside the tube body in a stress improvement region where the residual stress of the tube body is desired to be improved;
A temperature measuring step for measuring the temperature of the stress improvement region of the tubular body;
A method for improving the residual stress of a tubular body, comprising: a cooling step in which laser light irradiation is stopped and cooled after an outer surface side and an inner surface side of the stress improvement region reach a predetermined temperature difference. A method for improving residual stress that improves residual stress on the inner surface of a tubular body,
A laser beam irradiation step of irradiating the entire inner surface of the tube body with laser light from a laser beam irradiation portion disposed inside the tube body over the entire stress improvement region where the residual stress of the tube body is desired to be improved;
A temperature measuring step for measuring the temperature of the stress improvement region of the tubular body;
After a predetermined temperature difference between the outer surface side and the inner surface side of the stress improvement region, laser light irradiation is stopped, and cooling water is jetted from the cooling water jetting portion inserted into the tube body to the stress improvement region to perform rapid cooling. And a cooling step for performing a residual stress improvement method for a tubular body.

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