JP2003253337A - Process and apparatus for regenerating creep deteriorated part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To extend the life of boilers, turbines, etc., by easily regenerating the parts deteriorated by creep damages. <P>SOLUTION: While restraining the swelling in a high-temperature, pressure- resistant weldment 3 by cramping which has been subjected to creep deterioration in a piping 2, the weldment 3 is heated with a high-frequency heating coil 10 to perform regenerative heat treatment. Alternatively, after repair welding, the repaired weldment 30 can also be heated to reduce the mismatch in strength between the repaired weldment and the deteriorated part which could not be repair welded. Since deterioration is most likely to progress at swollen parts at the bases of nozzle stubs of a header or in the outer periphery of a curved part of a pipe, these deteriorated parts can be heated through the same process. By heating them at a temperature equal to ore above transformation temperature, the hardened structure at the deteriorated weldment is made identical to a base material, while the deteriorated part in the base material is made identical to an unused material to realize further life extension. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a portion deteriorated by creep damage, particularly a welded portion and a base material, for example, a high temperature pressure welded portion of a boiler or a turbine and high temperature pipes and pipes in a thermal power / nuclear power plant or a chemical plant. The present invention relates to a method and an apparatus for regenerating a creep-deteriorated portion of a base material such as a headstock and a nozzle.

[0002]

2. Description of the Related Art In recent years, for example, in a thermal power plant, due to long operating hours, deterioration of equipment due to long-term use, thermal fatigue due to frequent start-stop and rapid load changes, etc. have been fully taken into consideration. Maintenance management is becoming more and more important. For example, in a large-diameter thick-walled pipe in which a high-temperature pressure-resistant metal member is used, scratches such as cracks often occur inside the welded portion. In order to detect this scratch early, non-destructive inspection such as tissue inspection and ultrasonic inspection is regularly performed.

[0003]

As a result of such a periodic inspection, the remaining life of the creep deteriorated portion of the welded portion and the base material which have been creep-deteriorated due to long-term use is determined by the next periodical inspection (usually 2 years, cycle). If it is judged that there is no extension until 4 years), the following measures will be taken.

(1) In the case of thick-walled large-diameter pipe weld a. Replacement in principle: It takes a long time (for example, several months) to arrange materials, so replacement within a regular inspection period is difficult. Therefore, the following emergency measures will be taken. b. Reinforcement plate installation: If replacement is not possible, install a reinforcement plate in the creep deterioration area. However, a thick member such as the main steam pipe has a problem that the reinforcing plate has to be thick. Further, since the reinforcing plate is attached by welding, annealing after welding is necessary. c. Repair welding: When repair welding a creep-degraded part, repair welding is performed after deleting some of the creep damage, but damage such as creep voids at that part cannot be completely removed. Damage such as creep voids that could not be removed due to stress or the like may be accelerated, resulting in a problem of poor practicality. That is, repair welding is generally performed with 0.2 of the base plate thickness t.
Since only the depth of t can be applied, damage such as creep voids in deeper parts cannot be completely removed. Then, this repair welded part (strong in strength) and the deteriorated part that could not be repaired welded (weak in strength)
Due to the difference in strength (which is called "mismatch") between them, cracks are generated at their boundaries, and these cracks are accelerated by thermal stress, which is not practical. d. Monitoring the progress of cracks: An electrode is attached to the creep-degraded part and the progress of cracks is regularly monitored by the electrical resistance method. In this case, the life can be extended to the limit, but the life cannot be extended.

(2) In the case of a base material, a member that is severely damaged, for example, a pipe head of a heading is replaced, but it is necessary to interrupt the operation of the equipment for the replacement, and when it is replaced, a construction period and a great cost are required. Takes. However, when the number of replacements is large and there is no stock of materials, some of the members that have no life until the next periodic inspection remain. In this case, refreshing (after removing cracks, overlay welding, R finishing, and annealing) is performed. Then, it is necessary to perform life monitoring by life inspection by inspection at an appropriate time before the next regular inspection.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a method and an apparatus for regenerating a creep deteriorated portion which can easily extend the life.

[0007]

According to a first aspect of the present invention, there is provided a method for regenerating a creep-deteriorated portion, wherein the creep-deteriorated portion is heated while the expansion of the creep-deteriorated portion is restrained. It is characterized by doing.

According to this means, the creep void / crack is pressed and repaired by utilizing the internal pressure of the thermal expansion generated by heating the creep-deteriorated portion while restraining the expansion of the creep-degraded portion. Life can be extended.
A jig may be used to restrain the expansion of the creep-deteriorated portion, but if the member itself that has undergone creep-deterioration is large, the expansion of the heated portion is restrained by the unheated portion. It can be unnecessary.

According to a second aspect of the present invention, in the method according to the first aspect, the creep-degraded portion to be regenerated is a high-temperature pressure-resistant welded portion.

According to this means, in particular, the internal pressure of thermal expansion generated by heating the high-temperature pressure-resistant welded part where creep deterioration has progressed most is utilized, and creep voids / cracks are pressed and repaired to prolong life. Can be achieved.

According to a third aspect of the present invention, in the method according to the first aspect, the creep-deteriorated portion to be regenerated is a root bulge portion of the header.

According to this means, in particular, like the high temperature pressure-resistant welded portion, the internal pressure of thermal expansion generated by heating the root bulging portion of the headstock nozzle where creep deterioration has progressed most is utilized. It is possible to extend the life by pressing and repairing creep voids and cracks.

According to a fourth aspect of the present invention, in the method according to the first aspect, the creep deterioration portion to be regenerated is the outer peripheral portion of the bent portion of the pipe.

According to this means, in particular, similar to the high temperature pressure-resistant welded portion and the root bulging portion of the header, the thermal expansion generated by heating the outer peripheral portion of the pipe bent portion where creep deterioration has progressed most. Using the internal pressure of the, it is possible to extend the life by pressing and repairing the creep voids and cracks.

According to a fifth aspect of the present invention, in the method according to the second aspect, after repair welding of a high temperature pressure resistant welded portion which is a creep deterioration portion to be regenerated, the repaired welded portion is heated. It is characterized by

According to this means, the welded portion which is the creep deteriorated portion to be regenerated is combined with the repair welding and the regenerated heat treatment by heating so that the creep voids which cannot be removed by the repair welding can be pressed and the repair welding can be performed. It is possible to reduce the strength difference (mismatch) between the portion (strong in strength) and the deteriorated portion (weak in strength) that could not be repair-welded to further prolong the life.

The present invention according to claim 6 provides the invention according to any one of claims 1 to 5.
In the method described in any one of 1 above, the heating is high frequency heating.

According to this means, it is possible to heat locally and rapidly by using a high frequency. The rapid heating can prevent the diffusion of heat, and the local heating can concentrate the thermal expansion force in the heating portion.

The present invention according to claim 7 is characterized in that the creep deteriorated portion to be regenerated is pickled and then heated.

According to this means, the cracks that have been oxidized cannot be pressed, but the cracks can be pressed by pre-pickling the cracks.

The present invention according to claim 8 provides the invention according to any one of claims 1 to 7.
The method according to any one of (1) to (4) above, wherein the creep-deteriorated portion to be regenerated is heated to a temperature not lower than the transformation point of the material.

According to this means, it is possible to more effectively press and repair the creep voids / cracks by heating above the transformation point. That is, when the creep deterioration part is a high temperature pressure resistant weld part, the HAZ part (weldheat affec
In the hardened structure such as the ted zone: weld heat affected zone, the structure becomes equivalent to that of the base metal, and the rate of damage propagation becomes slow. further,
At that time, the newly formed grain boundaries confine precipitates and impurity segregates in the new grain boundaries, which slows the crack propagation rate and damage propagation rate. On the other hand, if the creep deterioration part is the outer peripheral part of the root swelling part of the heading nozzle and the bent part of the pipe, heating the deteriorated base material to an appropriate temperature above the transformation point It is possible to extend the life by making the structure of No. 1 into a structure equivalent to that of the unused material.

According to a ninth aspect of the present invention, in the method according to the eighth aspect, the creep-degraded portion to be regenerated is heated to room temperature three times or more repeatedly and then returned to room temperature. And

According to this means, by repeating the heat treatment in the vicinity of the transformation point, it is possible to more effectively confine the precipitate and the impurity segregate in the new grain boundary.

The present invention according to claim 10 is the method according to claim 8 or 9, characterized in that the creep deteriorated portion to be regenerated is annealed after being heated and then returned to room temperature.

According to this means, if the material is rapidly cooled after heating, it becomes martensite, and residual stress is locally generated to cause creep void damage to develop. The same organization as the material,
Further, generation of residual stress can be prevented.

The present invention according to claim 11 is the method according to claim 8 or 9, characterized in that the creep-deteriorated portion to be regenerated is heated and then gradually cooled to room temperature.

According to this means, when rapidly cooled after heating, it becomes martensite, and residual stress is locally generated to cause creep void damage to develop. However, cooling is gradually performed after heating. The structure is the same as that of the base metal and the generation of residual stress can be prevented.

According to a twelfth aspect of the present invention, in a device for regenerating a creep deteriorated portion, a clamp for restraining expansion of the creep deteriorated portion to be regenerated and a heating means for heating the creep deteriorated portion are provided. It is characterized by being

According to this means, the expansion of the creep deteriorated portion to be regenerated is restrained by the clamp,
By utilizing the internal pressure of thermal expansion generated by heating the creep-deteriorated portion, creep voids / cracks can be pressed and repaired to prolong the life.

The present invention according to claim 13 provides the invention according to claim 12.
In the apparatus described in the paragraph 1, the heating means is a high frequency heating coil.

According to this means, it is possible to heat locally and rapidly by using a high frequency. Then, by rapidly heating, the diffusion of heat can be prevented, and by locally heating, the expansion tension can be concentrated on the heated portion.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which a regenerating apparatus 1 is detachably attached to a pipe 2 having a high temperature pressure resistant welded portion which is a creep deteriorated portion to be regenerated. The pipe 2 is a high temperature pipe made of low alloy steel pipe,
A weld is formed in a portion covered by the high frequency heating coil 10. Figure 2 shows the cross section of this pipe weld,
Reference numeral 3 is a high temperature pressure-resistant welded portion, and reference numeral 4 is a HAZ portion.

The reproducing apparatus 1 is provided with clamps 5 and 6 on the left and right. The restraint pressure by these clamps 5 and 6 can be adjusted by the pressurizing force adjusting unit 7, and a pressurizing force measuring device 8 for measuring the pressure is provided.
It is not always necessary to pressurize, and it may be simply gripped. A high frequency heating coil 10 is provided between the clamps 5 and 6. This high frequency heating coil 10
It is located so as to face the welded portion 3 of the pipe 2. The high-frequency heating coil 10 has an annular shape surrounding the pipe 2, but when the pipe 2 has a large diameter, a plurality of arc-shaped coils may be used.
Further, a water cooling pipe 11 for cooling the coil, a thermometer 12 for detecting the pipe temperature, and a power cable 13 are provided.

Next, an example of a procedure for regenerating the high temperature pressure resistant welded portion 3 of the pipe 2 using the regenerating apparatus 1 will be described.

(1) Reduction of Creep Void First, it is preferable to pickle the pipe weld 3 in advance so that the crack can be pressed. As a result, the oxide film can be surely removed and the crack can be pressed.

Next, the pipe 2 is restrained by the clamps 5 and 6, and the high-frequency heating coil 10 heats the welded portion 3. At this time, the high frequency heating coil 10 heats only the local portion (welding portion 3) of the pipe 2. Pipe 2 is clamp 5,6
Since the high frequency heating coil 10 heats only the local portion (welding portion 3) of the pipe 2, the pressure due to the thermal expansion force of the heating portion concentrates on the heating portion itself. . As a result, creep voids and cracks are pressed against each other, and repairs can be performed in a shorter period of time than emergency measures such as welding. Further, since the heating can be performed rapidly, the diffusion of heat can be prevented and the thermal expansion force can effectively act on the heating portion.

The heating temperature is the transformation point of the material, for example A
It is preferably higher than 3 transformation points (transformation points of α iron and γ iron). A photograph of the structure is shown in FIG. (A) shows the case where the heating temperature is A3 transformation point or higher, and (b) shows the case where the heating temperature is A3 transformation point or lower. It can be seen that all of them can reduce the creep void, but the heating temperature is set to A3.
The effect of reducing creep voids is higher when the temperature is higher than the transformation point.

Since creep voids and cracks can be reduced in this way, the life of the pipe 2 can be extended. Thus, for example, by extending the life until the next regular inspection, the materials may be arranged by that time and the pipe 2 may be replaced at the next regular inspection.

(2) Recrystallization of HAZ part Further, by controlling the heating temperature as shown in FIG. 4, it is possible to particularly reduce the rate of damage development of the HAZ part 4. That is, the welding portion 3 of the pipe 2 is heated by the high-frequency heating coil 10 in the same manner as above, but first, A
Heat above 3 transformation points, then lower than A3 transformation point,
It is heated again above the A3 transformation point. The heating is repeated in this manner, preferably 3 to 5 times, above the A3 transformation point. After that, the temperature is lowered to some extent and annealing is performed. Alternatively, instead of annealing, it may be gradually cooled.

By doing so, the HAZ portion 4 having a martensite structure can have a ferrite pearlite structure equivalent to that of the base material. Therefore, the ductility is provided, and the damage growth rate can be reduced. Further, as shown in FIG. 5, the precipitate 21 and the grain boundary segregation 22 generated along the as-welded grain boundary 20 are confined in the new grain boundary 23 created by the above-mentioned treatment.
Therefore, the crack propagation speed becomes slow, and the damage propagation speed can be reduced. As described above, also in the HAZ part 4, the life of the pipe welded part can be extended.

In the above-described embodiment, the regenerator 1 was used to heat the welded portion 3. However, in the case of a large structure, the expansion of the heated portion is restricted by the unheated portion, so that Even if the regenerating apparatus 1 is not used, it is possible to regenerate the welded portion only by heating the welded portion.

Although the high-frequency heating coil has been described as the heating means, it is needless to say that the heating means is not limited to the high-frequency heating coil as long as it can locally and rapidly heat.

Next, FIG. 6 shows an example in which the high-temperature pressure-resistant welded portion 3 of the pipe 2 is repaired and welded, and then regenerated by using the regenerating apparatus 1.

That is, as described above, repair welding can generally be applied only to a depth of 0.2 t of the plate thickness t of the pipe 2, so that damage such as creep voids at a deeper portion can be completely removed. It is something that cannot be done. Then, due to the strength difference (mismatch) between the repair welded portion 30 (strong in strength) and the deteriorated portion that could not be repair-welded (weak in strength), cracks are generated at their boundaries, and these cracks are accelerated by thermal stress. Therefore, it was not practical.

Therefore, in the present embodiment, reference numeral 30 indicates a portion in the high-temperature pressure-resistant welding portion 3 which is a creep deterioration portion where damage such as creep voids can be removed (a portion having a depth of 0.2 t of the plate thickness t of the pipe 2). Repair welding is performed as shown in FIG. 3, and then the entire weld 3 including the repair weld 30 is heated by the high frequency heating coil 10, whereby the repair weld 3
The strength difference (mismatch) between 0 and the deteriorated portion that could not be repair-welded is reduced to enhance the life prolonging effect.

Next, FIG. 7 shows another embodiment of the present invention, which is applied to a header 40 such as a boiler. The pipe header 40 (the illustrated pipe header has a circular cross-section, but there is also a rectangular cross-section) is a container that collects a large number of pipes and distributes the flow, and a pipe base 41 for mounting each pipe is provided. It is attached by welding. In such a configuration, the root portion of the nozzle 41 swells as indicated by the reference numeral 42 due to insufficient strength due to defective material, corrosion, wear, or the like, that is, bulges, and the wall thickness becomes thin, resulting in creep deterioration. Is the easiest to proceed. Therefore, the creep-expanded bulged portion 42 at the base of the nozzle base is locally heated at a high frequency to a temperature equal to or higher than the transformation point by the regenerator 1 ′ so that the structure becomes equivalent to that of the unused material and the life is extended. can do.

That is, in the reproducing apparatus 1 ′, the high frequency heating coil 10 and the clamp 16 are attached to the nozzle base 41 by the joining device 17 at the creep-expanded bulging portion 42 at the nozzle base. The other end (not shown) of the joining device 17 is rigidly attached to the header 40 or other structure. As a result, when the high-frequency heating coil 10 heats the bulged portion 42 that has undergone creep deterioration at the base of the nozzle base,
Since the expansion of the creep-deteriorated bulging portion 42 at the base of the nozzle is restricted by the clamp 16 and the joining device 17,
The pressure due to the thermal expansion force acts on the heating portion itself. As a result, creep voids and cracks are pressed in the same manner as above,
It can be repaired.

In addition, in the header 40 shown in FIG.
Since each nozzle 41 is attached to the header 40 by welding, even when these welds deteriorate in creep, the creep voids / cracks are pressed by the regenerating apparatus 1 ′ in the same manner as described above. Can be repaired.

In a boiler, a turbine, etc., as a portion where creep deterioration is most likely to proceed, as shown in FIG. 8, a bent portion 51 of a pipe such as a U-shaped pipe (boiler pipe, heating pipe, etc.) 50 is used. There is a peripheral portion 52. That is, since such a U-shaped pipe 50 is made by bending one pipe, the outer peripheral portion 52 of the bent portion 51 extends more than the inner peripheral portion 53, and the outer peripheral portion 52 has an inner peripheral portion as illustrated. Since the wall thickness is made thinner than that of the portion 53 and bending is performed, creep deterioration is most likely to proceed. Therefore,
The creep-deteriorated outer peripheral portion 52 of the bent pipe portion 51 is locally heated to a temperature higher than the transformation point by a high frequency by the regenerating device, so that the structure can be made equal to that of an unused material and life can be extended.

In the above-described reproduction of the heading nozzle stub and the bent portion of the pipe, their base materials are 9Cr or 12C.
In the case of r, it is necessary to heat the material by regenerative heat treatment by heating, that is, after heating it preferably repeatedly over 3 times the A3 transformation point, and then tempering. For example, 650
Approximately 1 hour tempering is required per inch (25.4 mm) at a heating temperature of ~ 800 ° C, and a thickness of 9 mm of 9Cr
For about 15 minutes, for 9Cr with a thickness of 80 mm, about 3 hours.

[0053]

As described above, according to the present invention, the following effects can be obtained.

According to the first aspect of the present invention, in the method of regenerating the creep deteriorated portion, the internal pressure of thermal expansion generated by heating the creep deteriorated portion while restraining the expansion of the creep deteriorated portion is set. Utilizing this, it is possible to extend the life by pressing and repairing creep voids and cracks. As a result, the life can be extended until the next regular inspection (2 years later), the reliability of the equipment is improved, and the periodic inspection cycle is changed from 2 years to 4 years for the parts that can extend the life to 4 years. It can be extended and the maintenance cost can be significantly reduced.

According to the present invention as set forth in claims 2, 3 and 4, in particular, the high temperature pressure-resistant welded portion where creep deterioration is most advanced, the root bulging portion of the header and the outer peripheral portion of the bent pipe are heated. By utilizing the internal pressure of thermal expansion generated by, the creep voids and cracks can be pressed and repaired to prolong the life.

According to the fifth aspect of the present invention, the welded portion, which is the creep-deteriorated portion to be regenerated, can be pressure-welded with the creep void that could not be removed by the repair welding by combining the repair welding and the regenerative heat treatment by heating. At the same time, it is possible to reduce the difference in strength (mismatch) between the repaired welded portion (having a high strength) and the deteriorated portion (weakened strength) that could not be repaired and to further prolong the life.

According to the sixth aspect of the present invention, by using a high frequency wave for heating, heating can be performed locally and rapidly. By heating rapidly, the diffusion of heat is prevented and the heating is performed locally. By doing so, the thermal expansion force can be concentrated on the heating portion.

According to the seventh aspect of the present invention, the cracks that have been oxidized cannot be pressed, but the cracks can be pressed by pre-pickling the cracks.

According to the present invention of claim 8, by heating the creep-deteriorated portion to be regenerated above the transformation point of the material, the creep voids / cracks can be more effectively pressure-contacted,
It can be repaired. The hardened structure such as the HAZ part has the same structure as the base metal, and the root bulge of the header and the bent outer periphery of the U-shaped pipe have the same structure as the unused material, and the damage progress rate. Can slow down
Further, at that time, the newly-generated grain boundaries trap the precipitates and the impurity segregates in the new grain boundaries, which can slow the crack propagation rate. This can also extend the life.

According to the present invention described in claim 9, by repeating the heat treatment in the vicinity of the transformation point, the precipitate and the impurity segregate can be more effectively confined in a new grain boundary.

According to the present invention as set forth in claims 10 and 11, the creep deteriorated portion to be regenerated is heated or annealed or gradually cooled to room temperature to have the same structure as that of the base material, and the residual stress Occurrence can also be prevented.

According to a twelfth aspect of the present invention, in a device for regenerating a creep deteriorated portion, the creep deteriorated portion is heated by heating the creep deteriorated portion while restraining expansion of the creep deteriorated portion to be regenerated by a clamp. Using the internal pressure of thermal expansion, creep voids and cracks can be pressed and repaired to prolong life.

The present invention as set forth in claim 13 can heat locally and rapidly by using a high frequency for heating. By heating rapidly, the diffusion of heat can be prevented and the heating can be performed locally. By doing so, the thermal expansion force can be concentrated on the heating portion.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of regenerating a high temperature pressure-resistant welded portion of a pipe by a regenerating device according to the present invention.

FIG. 2 is a cross-sectional view showing a high temperature pressure resistant welded portion of the pipe.

FIG. 3 is a photograph showing a structure of a welded portion before being regenerated and after being regenerated by the above regenerating apparatus, where (a) is heated to a temperature higher than A3 transformation point and (b) is heated to a temperature lower than A3 transformation point. That is the case.

FIG. 4 is a diagram showing an example of a heating / cooling process by the regeneration device.

FIG. 5 is a schematic view showing a grain boundary of a welded portion reproduced by the reproducing apparatus.

FIG. 6 is a view similar to FIG. 2, showing another example of regenerating the high temperature pressure-resistant welded portion of the pipe according to the present invention.

FIG. 7 is a perspective view showing a case in which a modified example of the reproducing device is applied to a heading nozzle.

8A is a diagram showing a U-shaped pipe to be regenerated according to the present invention, and FIG. 8B is a sectional view taken along line bb of FIG. 8A.

[Explanation of symbols]

1,1 'Playback device 2 piping 3 High temperature pressure resistant weld 4 HAZ part 5,6 clamp 10 High frequency heating coil (heating means) 16 clamps 30 Repair weld 40 control 41 nozzle 42 bulge 50 U-shaped piping 51 bend 52 Outer periphery 53 Inner circumference

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Fumitoshi Sakata             3-5-1, 717-1, Fukahori-cho, Nagasaki-shi, Nagasaki             Hishi Heavy Industries Ltd. Nagasaki Research Center (72) Inventor Masaaki Fujita             1-1 Satinoura Town, Nagasaki City, Nagasaki Prefecture Mitsubishi Heavy Industries             Nagasaki Shipyard Co., Ltd. (72) Inventor Masahiro Kobayashi             1-1 Satinoura Town, Nagasaki City, Nagasaki Prefecture Mitsubishi Heavy Industries             Nagasaki Shipyard Co., Ltd. (72) Inventor Kei Shiibashi             2-5-3 Marunouchi, Chiyoda-ku, Tokyo             Hishi Heavy Industries Ltd. (72) Inventor Yasuhiro Mori             1-1 Satinoura Town, Nagasaki City, Nagasaki Prefecture Mitsubishi Heavy Industries             Nagasaki Shipyard Co., Ltd. F-term (reference) 4K042 AA24 BA04 BA11 DA06

Claims (13)

[Claims] 1. A method of regenerating a creep-deteriorated portion, wherein the creep-deteriorated portion is heated and regenerated by heat treatment while restraining expansion of the creep-deteriorated portion. 2. The method according to claim 1, wherein the creep-deteriorated portion to be regenerated is a high-temperature pressure-resistant welded portion. 3. The method according to claim 1, wherein the creep-deteriorated portion to be regenerated is a root bulge portion of the header. 4. The method according to claim 1, wherein the creep-deteriorated portion to be regenerated is an outer peripheral portion of a bent pipe portion. 5. The method according to claim 2, wherein after repair welding of a high temperature pressure resistant welded portion which is a creep deteriorated portion to be regenerated, the repaired welded portion is heated. 6. The method according to claim 1, wherein the heating is high frequency heating. 7. The method according to claim 1, wherein the creep-deteriorated portion to be regenerated is pickled and then heated. 8. The method according to claim 1, wherein the creep-deteriorated portion to be regenerated is heated above the transformation point of the material. 9. The method according to claim 8, wherein the creep-deteriorated portion to be regenerated is heated to three times or more over the transformation point and then returned to room temperature. 10. The method according to claim 8 or 9, wherein the creep-deteriorated portion to be regenerated is annealed after being heated and then returned to room temperature. 11. The method according to claim 8 or 9, wherein the creep-deteriorated portion to be regenerated is heated and then gradually cooled to room temperature. 12. An apparatus for regenerating a creep deteriorated portion, comprising a clamp for restraining expansion of the creep deteriorated portion to be regenerated and heating means for heating the creep deteriorated portion. 13. The apparatus according to claim 12, wherein the heating means is a high frequency heating coil.