JP2000237868A - Method and device for forming stress corrosion crack on inside of tube joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a stress corrosion crack whose depth is deep and which is in an open state even after welding working has been completed. SOLUTION: After applying zinc paint 4 on a heat-affected zone near a penetration welding part on the inside surface of a tube 1 on the one side, and after the zinc paint 4 has dried, the tip part of the tube 1 on the one side is butted to that of a tube 2 on another side, and full periphery welding is performed to them at least once from the outside surface side. While cooling the vicinity of a place applied with the zinc paint 4 of the joint part 5 of these tubes by using cooling liquid 13 from the outside surface sides of the tubes 1, 2 and forming a gas shield in the cooling liquid 13, by welding the joint part 5 of the tubes from the outside surface sides of the tubes 1, 2, and by giving a compression stress on the outside surface side of the joint part 5 of the tubes, a tensile stress given on the inside surface side of the joint part 5 of the tubes is increased, and gaps generated among metallic grain lumps are enlarged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for forming a stress corrosion crack on an inner surface of a pipe joint.

[0002]

2. Description of the Related Art In a nuclear power plant, nondestructive inspections such as ultrasonic inspection are periodically performed on various members.
Although it is determined whether or not the inspection target member is sound, it is not easy to detect a defect in the pipe joint.

[0003] Therefore, an ultrasonic flaw inspection is performed by artificially forming stress corrosion cracks in a test pipe joint, and the relationship between the reflection waveform of the ultrasonic wave obtained thereby and the shape and position of a defect in the pipe joint. It has been attempted to figure out.

FIG. 2 is a cross-sectional view showing an example of a current method of forming a stress corrosion crack on the inner surface side of a pipe joint. In this stress corrosion crack formation method, the same material (for example, stainless steel S) is used.
US304), using tubes 1 and 2 having the same diameter, and applying a zinc paint 4 containing zinc powder to a heat-affected portion near the backside welded portion 3 on the inner surface of one of the tubes 1. After drying, the ends of the tubes 1 and 2 are butt-welded from the outer surface to
2 are connected by a pipe joint 5.

As a result, zinc melted by the welding heat enters between the metal agglomerates constituting the tube 1, and stress corrosion cracks are formed on the inner surface of the tube 1 according to the length of application of the zinc paint 4.

[0006]

However, in the above-described method of forming a stress corrosion crack on the inner surface of a pipe joint, the depth of the stress corrosion crack cannot be increased to about 2 mm or more.
Further, after the welding operation is completed, stress corrosion cracking may be apparently closed, making it difficult to perform ultrasonic inspection.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to enable formation of stress corrosion cracks having a large crack depth and being opened even after completion of welding work.

[0008]

In order to achieve the above object, in the method for forming a stress corrosion crack on the inner surface side of a pipe joint according to the first aspect of the present invention, the inner surface of one of the pipes is formed near the uranami weld. After the zinc paint is applied to the heat-affected zone and the zinc paint is dried, the end of the one pipe and the end of the other pipe are butted and welded at least once from the outer surface to the entire circumference. The vicinity of the portion where the zinc paint is applied is cooled by the cooling liquid from the outer surface side of the pipe, and the pipe joint is welded from the outer surface side of the pipe while forming a gas shield in the cooling liquid.

In the stress corrosion cracking forming method according to a second aspect of the present invention, a zinc paint is applied to a heat-affected portion of the inner surface of one of the pipes near a backwash weld and the zinc paint is dried. The end of one of the pipes and the end of the other pipe are butt-butted and welded at least once all around from the outer surface side, and the vicinity of the portion where the zinc paint is applied to the pipe joint is cooled with a coolant from the outer surface side of the pipe. And, while forming the gas shield in the cooling liquid, the pipe joint portion is welded from the outer surface side of the pipe, further, the zinc paint is applied to the zinc paint application location and the zinc paint is dried,
The area near the zinc paint application point of the pipe joint is cooled with a coolant from the outer surface of the pipe, and the pipe joint is welded again from the outer face of the pipe while forming a gas shield in the coolant.

Further, in the apparatus for forming a stress corrosion crack on the inner surface side of a pipe joint according to a third aspect of the present invention, the apparatus has a cooling liquid inlet and a cooling liquid outlet and can cover a predetermined area of the outer surface of the pipe joint. A cooling liquid tank; and a torch disposed in the cooling liquid tank and welding the pipe joint while forming a gas shield.

In the method for forming a stress corrosion crack on the inner surface side of a pipe joint according to claim 1 or 2 of the present invention, when welding near the zinc paint applied portion of the pipe joint portion, a coolant is used. By cooling the pipe joint from the outer side, a compressive stress is applied to the outer side of the pipe joint to increase the tensile stress applied to the inner side of the pipe joint.

In the stress corrosion cracking forming apparatus for the inner surface side of a pipe joint according to a third aspect of the present invention, the cooling liquid is supplied into a cooling liquid tank arranged so as to cover the vicinity of the zinc paint application portion of the pipe joint from the outer surface. By supplying, the pipe joint is cooled from the outer surface side, and the pipe joint is welded while forming a gas shield with a torch.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing an example of an embodiment of a stress corrosion crack forming apparatus for an inner surface side of a pipe joint according to the present invention.
Numeral 6 is a cooling liquid tank made of transparent acrylic, and the bottom of the cooling liquid tank 6 is open, and the peripheral edge of the bottom is formed along the outer surface side of the tubes 1 and 2 having the same diameter.

A coolant inlet 7 is formed in the lower portion of the left side surface of the coolant tank 6 in FIG. 1, and a coolant supply pipe 8 is provided outside the coolant inlet 7.

A coolant outlet 9 is formed in the upper portion of the right side surface in FIG. 1 of the coolant tank 6, and a coolant discharge pipe 10 is provided outside the coolant outlet 9.

Reference numeral 11 denotes a torch for TIG welding. The torch 11 is capable of ejecting a shielding gas for forming a gas shield around the torch, and is attached to the cooling liquid tank 6. ing.

Also, a pipe 1 and a pipe 1
A packing 12 that can be in close contact with the outer peripheral surface of the second member 2 is attached.

When stress corrosion cracking is formed on the inner surface side of the pipe joint using the above-described apparatus, zinc powder is contained in the heat-affected portion of the inner surface of one of the pipes 1 in the vicinity of the Uranami weld. The zinc paint 4 is applied in such a length that a stress corrosion crack is formed, and the zinc paint 4 is dried.

After the zinc paint 4 applied to the inner surface of the tube 1 is dried, the ends of the tubes 1 and 2 are butt-welded at least once from the outer surface to the extent that the ends of the tubes 1 and 2 are butted and liquid-tight can be maintained. Then, the pipes 1 and 2 are connected by the pipe joint 5.

Next, the packing 12 around the bottom edge of the cooling liquid tank 6 is brought into close contact with the outer surface of the tubes 1 and 2 so as to include the location where the zinc paint 4 is applied, and the cooling liquid tank 6 is attached to the tubes 1 and 2 by a belt or the like. Shackle.

In this state, a coolant 13 such as water is continuously supplied from the coolant supply pipe 8 into the coolant tank 6, and the coolant 13 is supplied from the coolant outlet 9 to the outside of the coolant tank 6. Discharge to

Further, while forming a gas shield around the torch 11, the pipe joint portion 5 near the zinc paint 4 application location is subjected to underwater welding from outside the pipes 1 and 2, but the zinc paint 4 application location is Since it is sufficient to give the thermal effect of the welding, the range of underwater welding is limited to the pipe joint 5 near the zinc paint 4 application point.
It is not necessary to carry out over the entire circumference of the pipe joint portion 5 only.

At this time, since the pipe joint portion 5 is cooled from the outer surface side with the cooling liquid 13, a compressive stress due to shrinkage is applied to the outer surface side of the pipe joint portion 5. On the inner surface side of 5, the tensile stress applied by expansion is increased, and large voids are generated between adjacent metal granules, and molten zinc in the voids enters.

As a result, a stress corrosion crack having a greater depth than before is formed at the location where the zinc paint 4 is applied on the inner surface of the tube 1.

The tensile stress on the inner surfaces of the tubes 1 and 2 is
Since the flow rate of the cooling liquid 13 depends on the cooling rate, the throttle valve is provided in the cooling liquid supply pipe 8 and the cooling liquid discharge pipe 10 to adjust the flow rate of the cooling liquid 13, or the cooling liquid 13 is stagnated in the cooling liquid tank 6. By changing the cooling rate by the cooling liquid 13, it is possible to adjust the depth of the stress corrosion crack formed at the place where the zinc paint 4 is applied on the inner surface of the pipe 1.

Further, when it is necessary to form a stress corrosion crack having a large depth, the stress corrosion crack is formed once by the above-described operation, and then the zinc paint 4 is applied again to the previously applied zinc paint 4 on the inner surface of the pipe 1. I do.

The tubes 1 and 2 are used to form the joint 5 for the test and have a short overall length. Even when the tubes 1 and 2 are connected, the zinc paint 4 is applied again to the previously applied location of the zinc paint 4. Can be applied.

The zinc paint 4 was applied again to the previously applied zinc paint 4
Is applied and dried, and then the coolant 1 is placed in the coolant tank 6.
When the underwater welding is performed while supplying the pipe joint 3 and cooling the pipe joint portion 5 near the location where the zinc paint 4 is applied from the outside of the pipes 1 and 2, the stress corrosion cracking formed last time is larger and deeper, and the inner surface of the pipe 1 Zinc will penetrate deeper between the metal agglomerates.

After the stress-corrosion cracking is formed by underwater welding while cooling the pipe joint portion 5 near the location where the zinc paint 4 is applied from outside the pipes 1 and 2 as described above, even after the welding operation is completed, A compressive stress is applied to the outer surface of the pipe 1 and the pipe 1
Since the state where the tensile stress is applied to the inner surface continues and zinc penetrates deeply into the stress corrosion cracks, the stress corrosion cracks do not close, and a good ultrasonic inspection is performed. The relationship between the reflection waveform of the sound wave and the shape and position of the defect in the pipe joint can be grasped.

The method and apparatus for forming stress corrosion cracks on the inner surface of a pipe joint according to the present invention are not limited to the above-described embodiment, but may be modified without departing from the scope of the present invention. Obviously you can get it.

[0032]

As described above, according to the method and apparatus for forming a stress corrosion crack on the inner surface side of a pipe joint according to the present invention, the following various excellent effects can be obtained.

(1) Claim 1 or Claim 2 of the present invention
In any of the methods for forming stress corrosion cracks on the inner surface side of the pipe joint described in the above, when welding near the zinc paint application point of the pipe joint part, by cooling the pipe joint part from the outer surface side with a coolant, the pipe Since a compressive stress is applied to the outer surface of the joint to increase the tensile stress applied to the inner surface of the pipe joint, a large void is formed between adjacent metal agglomerates. Even after the work is completed, stress corrosion cracks in an open state can be formed, and the relationship between the reflection waveform of the ultrasonic inspection inspection and the shape and position of the defect can be grasped.

(2) In the method for forming a stress corrosion crack on the inner surface side of a pipe joint according to the second aspect of the present invention, zinc paint is applied, cooling from the outer side of the pipe joint part, and welding of the pipe joint part. Is repeated, so that stress corrosion cracking with a larger crack depth can be formed.

(3) In the apparatus for forming a stress corrosion crack on the inner surface side of the pipe joint according to the third aspect of the present invention, the apparatus is provided in a cooling liquid tank arranged so as to cover the area near the zinc paint application portion of the pipe joint from the outer surface. Since the coolant is supplied, the depth of the stress corrosion crack to be formed on the inner surface side of the pipe joint can be controlled by appropriately adjusting the flow rate of the coolant.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of an embodiment of an apparatus for forming a stress corrosion crack on an inner surface side of a pipe joint according to the present invention.

FIG. 2 is a cross-sectional view showing an example of a current method of forming a stress corrosion crack on the inner surface side of a pipe joint.

[Explanation of symbols]

 1, 2 pipe 3 Uranami welding part 4 zinc paint 5 pipe joint part 6 coolant tank 7 coolant inlet 9 coolant outlet 11 torch 13 coolant

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C21D 9/50 102 C21D 9/50 102A G21C 17/003 G21C 17/00 EF term (Reference) 2G075 AA01 BA17 CA13 DA14 DA16 FA10 FA16 FA18 FC14 GA01 4E001 AA03 BB06 CA03 CC02 DC09 DD01 4E081 BA03 BA19 BA27 CA07 DA05 DA11 DA31 DA81 4K042 AA24 BA07 DD03

Claims (3)

[Claims] 1. After applying a zinc paint to a heat-affected zone near a backside weld on the inner surface of one tube and drying the zinc paint,
The end of the one pipe and the end of the other pipe are abutted and welded at least once all around from the outer surface side, and the area near the zinc paint applied portion of this pipe joint is cooled with a coolant from the outer surface side of the pipe. A method of forming a stress corrosion crack on an inner surface of a pipe joint, wherein the pipe joint is welded from an outer surface side of the pipe while forming a gas shield in a coolant. 2. A method for applying zinc paint to a heat-affected zone near the backside welded portion on the inner surface of one of the tubes and drying the zinc paint,
The end of the one pipe and the end of the other pipe are abutted and welded at least once all around from the outer surface side, and the area near the zinc paint applied portion of this pipe joint is cooled with a coolant from the outer surface side of the pipe. At the same time, the pipe joint is welded from the outer surface side of the pipe while forming a gas shield in the coolant, and further, the zinc paint is applied to a place where the zinc paint is applied and the zinc paint is dried. Cooling the vicinity of the zinc paint application area with a coolant from the outer surface of the pipe, and re-welding the pipe joint portion from the outer surface of the pipe while forming a gas shield in the coolant, Method of forming stress corrosion cracks on steel. 3. A cooling liquid tank having a cooling liquid inlet and a cooling liquid outlet and capable of covering a predetermined area of an outer surface of a pipe joint, and said pipe arranged in the cooling liquid tank and forming a gas shield. An apparatus for forming a stress corrosion crack on an inner surface side of a pipe joint, comprising: a torch for welding a joint portion.