WO2009096004A1

WO2009096004A1 - Deteriorated portion reproducing method and deteriorated portion reproducing device

Info

Publication number: WO2009096004A1
Application number: PCT/JP2008/051348
Authority: WO
Inventors: Masashi Ozaki; Nobuhiko Nishimura; Fumitoshi Sakata; Masaru Kodama; Masahiro Kobayashi; Akira Shiibashi; Hideshi Tezuka; Ko Takeuchi
Original assignee: Mitsubishi Heavy Industries, Ltd.
Priority date: 2008-01-30
Filing date: 2008-01-30
Publication date: 2009-08-06
Also published as: KR101201659B1; CN101784682B; KR20100049087A; CN101784682A

Abstract

An object is to provide a deteriorated portion reproducing method and a deteriorated portion reproducing device for easily and certainly repairing and reproducing a deteriorated portion generated in a metal member and certainly extending the life of the metal member. A local heating process for locally heating a deteriorated portion (C) using a main heater (25) and allowing the deteriorated portion (C) to be pressure-welded using compression force generated by heat expansion and a periphery heating process for heating the neighborhood of the periphery of a region (HA1) heated in the local heating process using a sub heater (26) are performed. Then, a cooling process for simultaneously cooling the region (HA1) heated by use of the main heater (25) and a region (HA2) heated by use of the sub heater (26) is performed.

Description

Deterioration part reproduction method, degradation part reproduction device

The present invention relates to a regeneration method suitable for, for example, regenerating a deteriorated portion caused by creep or the like generated in a metal member constituting a high-temperature pipe used in a boiler or turbine of a thermal power / nuclear power plant or chemical plant.

In recent years, for example, in high-temperature piping used in boilers and turbines of thermal power / nuclear power plants and chemical plants, as the operation time increases, the equipment deteriorates over time, repeatedly starts and stops, and rapidly changes in load. Maintenance management that fully considers thermal fatigue is becoming increasingly important.
For example, in large-diameter thick-walled pipes that use high-temperature pressure-resistant metal members, nondestructive inspections such as tissue inspection and ultrasonic inspection are regularly performed in order to detect deterioration in the metal members and their welds at an early stage. . Based on the result of the non-destructive inspection, the deteriorated portion is repaired.

Here, as a technique for repairing a metal member, a heat treatment is locally performed on a deteriorated portion where creep voids or cracks are generated using a high-frequency heating coil, and the creep voids or cracks are pressed by the internal pressure of thermal expansion. There is a technique for reproducing (see, for example, Patent Document 1).

JP 2003-253337 A

As shown in FIG. 8A, the reproduction technique described in Patent Document 1 locally heats a region including a deteriorated portion C by a heater 1 made of a high-frequency heating coil. A region where the temperature is increased by this heating is referred to as a heating region 3. At this time, since the temperature around the heating region 3 of the metal member 2 is not increased, compressive stress is generated in the heating region 3 as a result of the thermal expansion being hindered. Therefore, the deteriorated portion C such as a creep void or a crack existing in the heating region 3 disappears by being pressed by this compressive stress. In order to increase the compressive stress of the void pressure welding process, it is effective to raise the temperature of the heating region 3 as much as possible. However, when the temperature of the heating region 3 is increased, the outer surface of the metal member 2 in the vicinity of the heater 1 is melted, so that the heating temperature cannot be increased excessively. Further, as shown in FIG. 8B, the heating region 3 contracts in the process of cooling the region after the heat treatment. At this time, since the periphery of the heating region 3 restrains the shrinkage of the heating region 3, tensile stress is generated in the heating region 3. For this reason, the deteriorated portion C once pressed may open. Further, there is a fear that a tensile residual stress is generated in the heating region 3 after repair, and it is impossible to maintain the repaired state for a long time. Furthermore, although the crystal structure becomes coarse due to the void pressure treatment, the coarse structure is likely to remain only with a thermal cycle in which the temperature is raised and lowered across the transformation point in the subsequent recrystallization heat treatment. It was necessary to perform crystallization.
Therefore, in order to reliably regenerate the deteriorated portion C, the pressure stress during heating is sufficiently large, the residual tensile stress during cooling is reduced, and the coarsened hardened structure is sufficient for a structure equivalent to the base material. It was necessary to recrystallize.

The present invention has been made in view of the above circumstances, and can easily and reliably repair and regenerate a deteriorated portion generated in a metal member, and maintain the repaired state for a long period of time, thereby extending the life of the metal member. An object of the present invention is to provide a method for reproducing a deteriorated part. Another object of the present invention is to provide a reproduction device for a deteriorated part that can implement the method for reproducing the deteriorated part.

In order to achieve the above object, a method for regenerating a deteriorated portion according to the present invention is a method for regenerating a deteriorated portion generated in a metal member, wherein a local region including the deteriorated portion is heated to form a first heating region. A first heating step in which the deteriorated portion is pressed by compressive stress to the first heating region due to a surrounding constraint on the thermal expansion of the first heating region, and the first heating region is being heated while the first heating region is being heated. And a second heating step of forming a second heating region by heating the periphery of the first heating region after a predetermined time has elapsed since the start of heating in the heating step of To do.

According to this invention, while the deteriorated part is locally heated by the first heating step, the periphery of the first heating region is heated by heating the periphery of the first heating region by the second heating step. The pressure due to the thermal expansion force of the portion acts on the first heating region, and the compressive stress acting on the deteriorated portion increases. In addition, the first heating region and the second heating region are simultaneously heated by performing the second heating step after the first heating step is preceded and the compressive stress of the first heating region is sufficiently relaxed by creep. Compared to the case, the compressive stress applied to the deteriorated portion increases, and the deteriorated portion is surely pressed. That is, in the present invention, there is an effect that a compressive stress is further applied to the first heating region by the thermal expansion of the second heating region.

In the present invention, it is desirable to continue the first heating step and the second heating step for a predetermined time. This is because the heat applied from the outside by heating is sufficiently raised to the inside of the thickness of the metal member by heat conduction, and the deteriorated part is surely pressed.

The metal member targeted by the present invention usually includes a base material and a weld metal that connects the base material, and the deteriorated portion exists in a heat-affected portion of the base material generated by welding. In many cases, the base material portion excluding the heat affected zone is not deteriorated as much as the heat affected zone. In that case, the first heating region is formed including the heat affected zone. And it is desirable for the 2nd heating field to be formed in the base material part near the heat affected zone. The base material portion excluding the heat-affected zone is less deteriorated than the heat-affected zone, and usually has a sufficient life even when the residual tensile stress due to the regeneration treatment is applied. In addition, since there is a possibility that voids are generated due to creep damage in the weld metal, there is a risk that if this region is heated, tensile stress acts during cooling to accelerate the damage. Therefore, it is preferable to avoid making the weld metal portion the target of the first heating region and the second heating region.

In the present invention, it is desirable to include a cooling step in which the cooling of the first heating region and the cooling of the second heating region are performed in synchronization. By doing in this way, the tensile stress which generate | occur | produces at the time of cooling is received in the area | region which combined the 1st heating area | region and the 2nd heating area | region. And, compared with the case of FIG. 8 where only the first heating region was subjected to tensile stress, when receiving the tensile stress in the region combining the first heating region and the second heating region as in the present invention, This is because the absolute tensile stress is lowered. Therefore, the possibility that the deteriorated portion once pressed is reopened is reduced, and further, the tensile residual stress acting on the deteriorated reproducing portion during operation of the unit after the regeneration can be reduced.

After completion of the cooling step, it is desirable to perform a recrystallization heat treatment on the reclaimed portion where the first and second heat treatments have been performed on the metal member. The recrystallization heat treatment is a process in which a process of heating a metal member to a temperature above its transformation point and cooling to a temperature below the transformation point is repeated a plurality of times. By applying this treatment, voids, precipitates, or grain boundary segregation existing along the grain boundaries of the structure are confined in the grains, the crack propagation speed is reduced, and the damage propagation speed can be reduced. Furthermore, by performing isothermal eutectoid transformation treatment in this heating and cooling process, the coarse hardened structure produced by the regeneration treatment can be eliminated. Therefore, the factor which impairs fracture ductility is suppressed and the good ductility is obtained at the location where the regeneration treatment is performed.

The present invention is an apparatus for regenerating a deteriorated portion generated in a metal member so as to perform the above-described regenerating method, the first heater being disposed at a position facing the deteriorated portion and locally heating the deteriorated portion And a second heater for heating the periphery of the heating area by the first heater.
In this apparatus, the heating by the first heater is preceded by the heating by the second heater, so that the deteriorated portion generated in the metal member and its surroundings are heated and cooled while appropriately controlling the temperature. Optimal heat treatment can be easily performed.

The present invention performs isothermal eutectoid transformation processing in a heating and cooling process in which a metal member is heated to a temperature above the transformation point and cooled to below the transformation point, heating and cooling treatment is repeated a plurality of times, and the temperature is raised and lowered across the transformation point. The recrystallization heat treatment method characterized by the above can be carried out independently.

As a result, the portion regenerated by the heat treatment is made into a highly ductile structure by the heating / cooling process after the heat treatment, and voids, precipitates or grain boundary segregation that existed along the grain boundaries of the structure are intragranular. The crack propagation rate is slowed down and the damage propagation rate is lowered, and the coarse hardened structure disappears by the isothermal eutectoid transformation process, the inhibition of fracture ductility is suppressed, and further good ductility is obtained.

According to the method for regenerating a deteriorated part of the present invention, since the periphery of the deteriorated part is heated after the heating of the deteriorated part, a large compressive stress can be applied to the deteriorated part. Further, since the deteriorated portion and its surroundings are cooled in synchronization, the tensile stress generated in the deteriorated portion during cooling can be dispersed over a wide range, and the influence of the tensile stress on the regenerated location can be suppressed as much as possible.
Thereby, the residual stress of the tension | tensile_strength in a reproduction | regeneration location can also be reduced, and the life extension of a metal member can be aimed at.
In addition to the heating / cooling step of transforming the regeneration treatment site multiple times, an isothermal eutectoid transformation step of maintaining the regeneration treatment site at a predetermined temperature for a predetermined time and continuing transformation is also performed. Voids, precipitates or grain boundary segregation existing along the grain boundaries can be confined within the grains. In addition, it is possible to obtain a good ductility by eliminating the coarse hardened structure and suppressing the break ductility. As a result, the crack propagation rate can be slowed down and the damage propagation rate can be lowered.

In addition, according to the deteriorated part regeneration apparatus of the present invention, the first heater and the second heater are provided. Therefore, the temperature of the first heater and the second heater is controlled, so that the deterioration occurs in the metal member. It is possible to easily perform heat treatment optimal for regenerating the deteriorated part by heating and cooling the deteriorated part and its surroundings while appropriately controlling the temperature.

It is a perspective view which shows the reproducing | regenerating apparatus which concerns on embodiment of this invention. It is a figure which shows the positional relationship of the heater at the time of reproduction | regeneration with a reproducing | regenerating apparatus. It is sectional drawing which shows the arrangement | positioning state of the heater with respect to the reproduction | regeneration location. It is a graph which shows the temperature change at the time of reproduction | regeneration. It is a figure explaining the reproduction | regeneration method of a degradation part, (a) is sectional drawing which shows the state currently heated with the main heater, (b) is sectional drawing which shows the state currently heated with the main heater and a sub heater. is there. It is a graph which shows the temperature change at the time of the recrystallization heat processing in the reproduction | regenerating method which concerns on this embodiment, and the change of a metal structure. It is a microscope picture of the HAZ part 15, (a) is a microscope picture before regenerative heat processing, (b) is a micrograph after regenerative heat treatment. It is a figure explaining the conventional reproduction | regeneration method, (a) is sectional drawing which shows the state which is heating, (b) is sectional drawing which shows the state of a cooling process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Reproduction | regeneration apparatus, 14 ... High temperature pressure-resistant welding part (metal member), 15 ... HAZ part (heat influence part), 25 ... Main heater (1st heater), 26 ... Sub heater (2nd heater), C ... Deterioration Part, HA1... Heating region (first heating region), HA2... Heating region (second heating region)

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a method and an apparatus for reproducing a deteriorated portion according to the present invention will be described below with reference to the drawings.
FIG. 1 is a perspective view showing a playback apparatus according to an embodiment of the present invention. FIG. 2 is a diagram illustrating the positional relationship of the heaters when the regeneration method is performed by the regeneration device. FIG. 3 is a cross-sectional view showing an arrangement state of the heater with respect to the regenerated portion.
As shown in FIG. 1, the regenerator 11 is attached to a pipe 12 made of, for example, a low alloy steel pipe.

Here, as shown in FIGS. 2 and 3, in a high-temperature pressure-resistant welded part (metal member) 14 in which the pipes 12 are welded together with the weld metal 13, the weld metal is formed at the boundary between the weld metal 13 and each pipe 12. The HAZ part (heat-affected zone: Heat Affected Zone) 15 is generated due to the thermal effect when welding 13. In the high-temperature pressure-resistant welded portion 14, many deteriorated portions C such as creep voids and cracks may occur in the HAZ portion 15 due to long-term use. For this reason, the strength of the HAZ portion 15 is particularly lowered, which causes a breakage or the like in the high-temperature pressure-resistant welded portion 14.
Here, the material of the pipe 12 is, for example, a low alloy steel (STPA22, STPA23, STPA24) having a Cr content of 3% or less (excluding 0) and a Mo content of 2% or less (excluding 0). ) Further, as the material of the weld metal 13, for example, the Cr content of the material of the pipe 12 and the common metal is 3% or less (however, 0 is not included), and the Mo content is 2% or less (however, 0 is not included). . Of course, the present invention is not limited to the materials mentioned above, but can be applied to various other materials.
Therefore, in the present embodiment, a case will be described as an example where the regenerator 11 is attached to the pipe 12 and the high-temperature pressure-resistant welded part 14 in which the degraded part C is generated in the HAZ part 15 is regenerated.

In the reproducing apparatus 11, a main heater (first heater) 25 and a sub-heater (second heater) 26 each made of a high-frequency heating coil are arranged in parallel at an interval. The main heater 25 and the sub-heater 26 have a flat plate shape and are arranged along the outer peripheral surface of the pipe 12 in a state where the regeneration device 11 is mounted on the pipe 12.
The main heater 25 is disposed at a position facing the boundary portion between the pipe 12 and the weld metal 13 (a position facing the deteriorated portion C) in a state where the regeneration device 11 is disposed along the outer peripheral surface of the pipe 12. Further, the sub-heater 26 is disposed so as to face the pipe 12 at a position deviated from the boundary between the pipe 12 and the weld metal 13. That is, the sub-heater 26 is disposed so as to face a portion outside the boundary between the pipe 12 and the weld metal 13 around the heating area by the main heater 25. Thereby, the reproducing | regenerating apparatus 11 can heat the high temperature pressure-resistant welding part 14 including the heating area | region HA1 (FIG. 5) by the main heater 25, and its circumference | surroundings. The main heater 25 and the sub heater 26 are not limited to a flat plate shape, and may be an annular shape or an arc shape over the entire circumference of the pipe 12.
Further, the regenerator 11 includes a water cooling tube 27 and a power cable 29 for coil cooling. The main heater 25 and the sub heater 26 are controlled so that the member surface temperature detected by the thermocouple attached to the member surface immediately below each heater becomes a predetermined temperature.

Next, a procedure for regenerating the high-temperature pressure-resistant welded portion 14 of the pipe 12 using the regenerator 11 will be described.
In the present embodiment, the regeneration apparatus 11 performs regeneration heat treatment and recrystallization heat treatment.

(Regenerative heat treatment)
First, regenerative heat treatment will be described. FIG. 4 is a graph showing temperature changes during regenerative heat treatment, and FIG. 5 is a cross-sectional view illustrating a method for regenerating a deteriorated portion.

(1) Pretreatment process First, the oxide film of the high temperature pressure-resistant welding part 14 which is a repair object part is removed as needed.
Next, the main heater 25 is disposed at a position facing the boundary between the pipe 12 and the weld metal 13. If it does in this way, the sub-heater 26 will be arrange | positioned so that the piping 12 may be faced in the position remove | deviated from the boundary part of the piping 12 and the weld metal 13. FIG.

(2) Local heating process (first heating process)
In this state, first, the surface of the boundary member between the pipe 12 and the weld metal 13 of the high-temperature pressure-resistant welded portion 14 is rapidly heated by the main heater 25 to the temperature T1 as indicated by a solid line in FIG. Heat to 1050-1250 ° C., preferably 1200 ° C. for minutes). The temperature T1 is preferably higher than the transformation point of the material (for example, the A3 transformation point which is a transformation point between α-Fe and γ-Fe).
Thereby, in the heating area | region (1st heating area | region) HA1 by the main heater 25 in the high temperature pressure-proof welding part 14, the thermal expansion of a heating part arises. At this time, since the periphery of the heating area HA1 is not thermally expanded, a restraining force is exerted against the thermal expansion of the heating area HA1. Therefore, compressive stress acts on the heating area HA1 due to its own thermal expansion and surrounding constraints. Due to this compressive stress, the deteriorated portion C made of creep voids or the like is pressed. The compressive stress acting on the heating area HA1 is indicated by an arrow in FIG.

(3) Ambient heating process (second heating process)
After the heating by the main heater 25 is started and a predetermined time elapses, the heating by the sub heater 26 is started while the heating by the main heater 25 is continued, and the vicinity of the heating area HA1 by the main heater 25 is observed. 4 is heated to a temperature T1 with a profile as indicated by a broken line in FIG. The heating by the sub heater 26 is started, for example, 300 seconds after the surface of the member just below the main heater 25 reaches the target temperature (temperature T1).
If it does in this way, thermal expansion will arise in the heating area | region (2nd heating area | region) HA2 of the piping 12 heated by the subheater 26. FIG. And the heating part of heating area | region HA2 is restrained because the base material part on the opposite side (right side in FIG. 5) to the side adjacent to heating area | region HA1 does not thermally expand. Thereby, the pressure by the thermal expansion force of the heating part of this heating area HA2 acts as a compressive stress on the heating area HA1 softened by the heating by the main heater 25. Therefore, the pressure contact effect of the deteriorated portion C can be enhanced. In order to obtain this effect, it is necessary to continue the local heating process and the ambient heating process for a predetermined time. The compressive stress acting on the heating area HA1 is indicated by an arrow in FIG.
In addition, by performing the heating by the sub-heater 26, the high-temperature pressure-resistant welded portion 14 including the heating area HA <b> 1 at the repair location by the main heater 25 and a wide area around it are heated by a synergistic effect with the heating by the main heater 25. . By extending the heating range in this way, the tensile stress in the subsequent cooling process is reduced.

(4) Cooling step As described above, after the local heating of the heating area HA1 by the main heater 25 and the heating of the surrounding heating area HA2 by the sub heater 26 are continued for a predetermined time, as shown in FIG. The heating temperature by the main heater 25 and the sub heater 26 is lowered synchronously. The cooling rate is preferably about 50 ° C./hr, for example. If it does in this way, the wide range including the reproduction | regeneration location of the high temperature pressure-resistant welding part 14 will be cooled slowly.

Thereby, since the tensile stress generated at the time of cooling is dispersed in a wide range of the high-temperature pressure-resistant welded portion 14, that is, the region including at least the heating region HA1 and the heating region HA2, the absolute value thereof is when only the heating region HA1 exists. Lower than Therefore, the influence of the tensile stress due to the heat shrinkage in the cooling process on the regenerated location is suppressed as much as possible.
Therefore, there is no problem that the welded deteriorated portion C opens or a tensile residual stress is generated in the high-temperature pressure-resistant welded portion 14, and the repaired state of the high-temperature pressure-resistant welded portion 14 is maintained over a long period of time, thereby extending the life of the pipe 12. It becomes possible to plan.

[Correction 21.02.2008 based on Rule 91]
(Recrystallization heat treatment)
Next, the recrystallization heat treatment will be described. FIG. 6 is a graph showing temperature changes and metallographic changes during the recrystallization heat treatment in the regeneration method according to the present embodiment.
The metal structure of the regenerated portion that has been gently cooled by the regenerative heat treatment described above is a bainite structure that partially includes ferrite, as indicated by reference numeral a1 in FIG.

[Correction 21.02.2008 based on Rule 91]
(1) Heating step In the recrystallization heat treatment, first, the regenerated portion is heated by the main heater 25 to a temperature T3 (for example, 900 to 950 ° C., preferably about 930 ° C.) exceeding the A3 transformation point, and predetermined. Hold for a time (eg, 30-120 minutes, preferably 60 minutes). In this heat treatment, the metal structure of the regenerated portion is changed to an austenite structure as indicated by reference numeral a2 in FIG. At this time, a coarse hardened structure formed at the time of the regeneration heat treatment partially remains in the metal structure. And this coarse hardened structure may hinder fracture ductility.

[Correction 21.02.2008 based on Rule 91]
(2) Isothermal eutectoid transformation step Next, the temperature of the main heater 25 is controlled, and the regeneration portion is cooled to a temperature T4 lower than the A3 transformation point (for example, 680 to 730 ° C., preferably about 700 ° C.). Isothermal eutectoid transformation treatment is performed at T4 for a certain time (for example, 180 to 600 minutes, preferably 300 minutes). This heat treatment causes eutectoid transformation of the austenite structure. Therefore, as indicated by reference numeral a3 in FIG. 6, the metal structure of the reproduction portion becomes a ferrite pearlite structure in which ferrite and pearlite are co-deposited, and the coarse hardened structure disappears.
Here, if the holding temperature of the isothermal eutectoid transformation is lower than the nose of the isothermal eutectoid transformation, it takes a long time for the isothermal eutectoid transformation at the reproduction site. Transformation becomes difficult. Therefore, the temperature T4 that is maintained in the isothermal eutectoid transformation step is preferably a temperature at which the metal structure at the reproduction site can be smoothly isothermal eutectoid transformed.
Moreover, as time to hold | maintain to temperature T4 in an isothermal eutectoid transformation process, if the area | region where the crystal grain coarsened in the said 1st heating process and 2nd heating process is the time which completes isothermal eutectoid transformation good.

[Correction 21.02.2008 based on Rule 91]
(3) Heating step The regenerated portion is heated again to the temperature T3 exceeding the A3 transformation point by the main heater 25, and held for a predetermined time (for example, 30 to 120 minutes, preferably 60 minutes). In this heat treatment, the metal structure of the regenerated portion is changed to an austenite structure again as indicated by reference numeral a4 in FIG. At this time, since the coarse hardened structure has disappeared in the previous isothermal eutectoid transformation step, the metal structure becomes an austenitic structure without the coarse hardened structure.

[Correction 21.02.2008 based on Rule 91]
(4) Cooling step Next, the regeneration portion is cooled to a temperature T5 (for example, 550 to 650 ° C., preferably about 500 ° C.) sufficiently lower than the A3 transformation point. By this heat treatment, the reclaimed portion is made into a metal structure in which ferrite and pearlite are co-deposited in a part of the austenite structure as indicated by reference numeral a5 in FIG.

[Correction 21.02.2008 based on Rule 91]
(5) Heating step The reproduction part is heated again to the temperature T3 exceeding the A3 transformation point by the main heater 25, and held for a predetermined time (for example, 30 to 120 minutes, preferably 60 minutes). In this heat treatment, the metal structure of the regenerated portion is changed to an austenite structure again as indicated by reference numeral a6 in FIG.

[Correction 21.02.2008 based on Rule 91]
(6) Cooling step Thereafter, the temperature of the main heater 25 is controlled, and the regenerated portion is cooled at a predetermined cooling rate (for example, about 50 ° C./hr).
And by cooling in this way, as shown by the symbol a7 in FIG. 6, the austenite structure undergoes continuous cooling transformation, and the ferrite pearlite containing bainite is transformed as shown by the symbol a8 in FIG. Become an organization.

In the recrystallization heat treatment, the regeneration portion is heated and cooled by the temperature control of the main heater 25 and the transformation treatment is repeated a plurality of times, so that the regeneration portion has a ductility equivalent to that of the pipe 12 as the base material. Ferrite pearlite structure. In addition, the recrystallization heat treatment confines voids, precipitates, or grain boundary segregation existing along the grain boundaries during welding, thereby slowing the crack propagation rate and reducing the damage growth rate. In addition, since the coarse hardened structure is eliminated by the isothermal eutectoid transformation process performed in the course of the recrystallization heat treatment, inhibition of fracture ductility is suppressed, and good ductility is obtained.

As described above, according to the method for regenerating a deteriorated portion according to the present embodiment, the pressure due to the thermal expansion force of the heated portion composed of the heated region HA2 around the deteriorated portion C is applied to the heated region HA1 of the deteriorated portion C. Can act. As a result, the deteriorated portion C can be reliably pressed by a high compressive force and can be reproduced well over the entire thickness of the heating area HA1 of the deteriorated portion C, and the reproduction quality can be improved.

Further, since the deteriorated portion C and its surroundings are cooled at the same time, the tensile stress generated in the deteriorated portion C during cooling can be dispersed over a wide range, and the influence of the tensile stress on the regenerated location can be suppressed as much as possible. Further, there is no inconvenience that a tensile residual stress is generated at the regenerated location, the repaired state of the high-temperature pressure-resistant welded portion 14 can be maintained for a long time, and the life of the pipe 12 can be extended. In the present embodiment, the first heating and the second heating are shown twice. However, the number of times of heating is not limited to two as long as it is plural.

Further, by performing a heating / cooling process in which the regeneration part is transformed a plurality of times and an isothermal eutectoid transformation process in which the regeneration part is maintained at a predetermined temperature for a certain period of time and the transformation is continued, the regeneration part is connected to the pipe 12. It can be made into the structure | tissue rich in ductility equivalent to the base material which consists of. In addition, voids, precipitates, or grain boundary segregation existing along the grain boundaries of the structure are confined in the grains, so that the crack propagation rate is slowed and the damage propagation rate can be lowered. In addition, by eliminating the coarse hardened structure, inhibition of fracture ductility can be suppressed and good ductility can be obtained.

In addition, according to the regeneration device 11 for the deteriorated portion C according to the present embodiment, the main heater 25 and the sub heater 26 are provided. Therefore, by controlling the temperature of the main heater 25 and the sub heater 26, The generated deteriorated part C and its surroundings can be heated and cooled while appropriately controlling the temperature, and the optimum heat treatment in the deteriorated part C can be easily performed.

Furthermore, the number of repetitions of transformation of the regenerated portion by the heating / cooling step in the recrystallization heat treatment is preferably 3 to 5 times.
In the present embodiment, an apparatus including two heaters, that is, the main heater 25 and the sub heater 26 is described as an example. However, the number of heaters is not limited to two as long as the number of heaters is plural.
The main heater 25 and the sub heater 26 are not limited to the high-frequency heating coil, and various heaters capable of temperature control can be used.

The method described above was confirmed.
The pipe 12 was made of STAP24 material (2.25% Cr-1% Mo steel), having a pipe diameter of 355 mm and a wall thickness of 77 mm. The weld metal 13 was also made of the same material as the pipe 12.
FIG. 7A is a photomicrograph of the HAZ part 15 before the regenerative heat treatment, and the number density of voids (deteriorated part C) is 930 / mm ² .
The main heater 25 was disposed 10 mm away from the surface of the pipe 12 in the radial direction at a position facing the boundary between the pipe 12 and the weld metal 13. The sub-heater 26 was disposed at a position 50 mm away from the boundary between the pipe 12 and the weld metal 13 in the circumferential direction of the

pipe

12 and 10 mm in the radial direction.
Then, the surface of the boundary member between the pipe 12 and the weld metal 13 of the high-temperature pressure-resistant welded portion 14 was rapidly heated by the main heater 25 to a temperature T1 = 1200 ° C.
Heating by the main heater 25 is continued 300 seconds after the surface of the boundary member between the pipe 12 and the weld metal 13 of the high-temperature pressure-resistant welded portion 14 reaches the temperature T1 = 1200 ° C. due to the heating by the main heater 25. In the meantime, heating by the sub-heater 26 was started, and the vicinity of the heating area HA1 by the main heater 25 was heated to a temperature T1 = 1200 ° C.
After the heating of the surrounding heating area HA2 by the sub heater 26 was continued for 1200 seconds, the heating temperature by the main heater 25 and the sub heater 26 was lowered synchronously at a cooling rate of 50 ° C./hr.
Thereafter, the regenerated portion was heated to 930 ° C. by the main heater 25 and held for 60 minutes.
Next, the temperature of the main heater 25 was controlled, and the regenerated portion was cooled to 700 ° C. and held for 300 minutes to perform isothermal eutectoid transformation treatment.
Subsequently, the regenerated portion was heated to 930 ° C. by the main heater 25 and held for 60 minutes, and then the regenerated portion was cooled to 500 ° C.
Further, the regenerated portion was heated to 930 ° C. by the main heater 25 and held for 60 minutes, and then the regenerated portion was cooled at about 50 ° C./hr.
FIG. 7B is a micrograph of the HAZ part 15 after the regenerative heat treatment. The number density of voids (deteriorated part C) is 140 / mm ^2, and the void number density is higher than that before the regenerative heat treatment. Was reduced by 85%. Further, it was confirmed that the voids were located at the grain boundaries before the regenerative heat treatment, but were confined in the grains after the regenerative heat treatment.

Claims

A method for regenerating a deteriorated part generated in a metal member,
A local region including the deteriorated portion is heated to form a first heated region, and the deteriorated portion is caused by a compressive stress applied to the first heated region due to a surrounding constraint on thermal expansion of the first heated region. A first heating step for pressure welding,
During the heating of the first heating region, a second heating region is formed by heating the periphery of the first heating region after elapse of a predetermined time from the start of heating in the first heating step. Heating process;
A method for reproducing a deteriorated portion, comprising:
The method for regenerating a deteriorated part according to claim 1, wherein the first heating step and the second heating step are continued for a predetermined time.
The metal member includes a base material and a weld metal that connects the base material,
The deteriorated portion exists in a heat affected zone of the base material generated by welding,
The method for regenerating a deteriorated part according to claim 1, wherein the first heating region includes the heat affected part.
The method for regenerating a deteriorated part according to claim 3, wherein the second heating region is formed in the base material adjacent to the heat affected part.
The method for regenerating a deteriorated part according to claim 1, further comprising a cooling step in which the cooling of the first heating region and the cooling of the second heating region are performed in synchronization.
6. The method for regenerating a deteriorated portion according to claim 5, wherein after the cooling step, recrystallization heat treatment is performed on the first and second heating regions.
The method for regenerating a deteriorated part according to claim 6, wherein in the recrystallization heat treatment, the metal member is heated to a temperature above its transformation point and cooled to a temperature below the transformation point a plurality of times.
The method for regenerating a deteriorated part according to claim 6, wherein an isothermal eutectoid transformation treatment is performed in the course of performing the recrystallization heat treatment.
An apparatus for regenerating a deteriorated part generated in a metal member,
A first heater which is disposed at a position facing the deteriorated portion and locally heats the deteriorated portion;
A second heater for heating the periphery of the heating area by the first heater;
An apparatus for reproducing a deteriorated part, comprising:
The regeneration device for a deteriorated part according to claim 9, wherein the heating by the first heater precedes the heating by the second heater.