JPH11200076A - Stress corrosion cracking introduction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and surely introduce the stress corrosion cracking(SCC) meeting test conditions into the fillet weld zones of test specimens. SOLUTION: In the method for artificially introducing the SCC into the fillet weld zone 6 formed between a pair of base metals 1 and 2 welded to have an approximate L shape to each other; the base metal 2 is arranged at the end of the base metal 1 so as to stand up approximately perpendicular thereto. Restraining materials 3 are so assembled as to prevent the base metal 2 from tilting to the base metal 1 side. A pad 7 consisting of a fibrous material of a conductor is brought into contact with the suitable position of the fillet weld zone 6 formed by welding a groove 4 and is fixed thereto. The base metals 1 and 2 are boiled in this state by high-pressure high-temp. water to form the SCC in the fillet weld zone 6. When the length and depth thereof do not meet the test conditions, the restraint by the restraining materials 3 is released and the groove 5 on the rear side of the groove 4 is subjected to welding. A tensile stress is imparted to the existing fillet weld zone 6 and both base metals 1 and 2 are again boiled to grow the SCC.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for introducing stress corrosion cracking into a fillet weld of a test piece artificially.

[0002]

2. Description of the Related Art In a nuclear power plant or the like, nondestructive inspections such as ultrasonic inspection are performed on various parts of various equipments, and among them, it is said that it is difficult to detect defects in welded joints. At present, inspection technology has not been established.

[0003] Therefore, it is desired to improve the inspection technology in the future.
(Stress corrosion cracking) artificially introduced test specimens,
It is necessary to improve the inspection technique by repeating the nondestructive inspection test using the test specimen.

[0004]

However, a technique for artificially introducing SCC into a weld joint of a test piece has not been established.
Regarding a specimen in which a CC is generated, there is a problem that, despite a high demand for performing a nondestructive inspection test, it is not possible to easily and reliably introduce an SCC that meets the test conditions. there were.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a method for introducing stress corrosion cracking into a fillet weld of a test body, which can easily and surely introduce stress corrosion cracking meeting test conditions. It is an object.

[0006]

SUMMARY OF THE INVENTION The present invention provides a method for introducing stress corrosion cracking into a fillet weld formed between a pair of base materials welded so as to form a substantially L-shape. A method, wherein the other base material is disposed so as to be substantially upright with respect to the end of one base material, and a restraining member is assembled between the base materials so that the other base material does not tilt toward the one base material side. The welding is performed by dissolving the welding material in the groove formed between the two base materials so as to open toward the corner forming side, and welding is performed. And contacting and fixing the pad, and in this state, both base materials are boiled with high-pressure and high-temperature water to generate stress corrosion cracking in the fillet weld.

Therefore, in the present invention, when welding is performed on a groove formed between both base materials, the corners are narrowed by the base material due to shrinkage in the cooling process of the molten material melted into the groove. Although a force that tends to deform in the direction is generated, the deformation due to this force is constrained by the restraining material, and as a result, the fillet weld formed by the cooled molten material has a corner portion between both base materials. The tensile stress in the direction in which the cracks are spread remains as residual stress, and a state in which cracks easily occur in the fillet weld is created.

When both base materials are boiled with high-pressure and high-temperature water, high-pressure and high-temperature water stays at the pad contact portion in the fillet weld and corrodes due to a potential difference generated between the fillet weld and the pad. Since environmental conditions are easily provided, and thereby the generation of stress corrosion cracking is promoted, a stress is applied to the contact portion of the pad in the fillet weld in combination with the action of the tensile stress remaining as a residual stress in the fillet weld as described above. Corrosion cracking will occur.

Further, in the present invention, after the stress corrosion cracking is initially generated, the restraint by the restraining material is released, and a preformed hole is formed on the back side of the previously welded groove so as to open toward the opposite corner forming side. It is possible to apply a tensile stress to the existing fillet weld by applying welding to another groove that has been set, and then to boil both base materials again with high-pressure high-temperature water to grow stress corrosion cracking.

In this way, even if stress corrosion cracking is initially generated and the tensile stress in the fillet weld is reduced, the tensile stress is reduced by applying welding to the back side of the fillet weld. Because of the new addition, it is possible to grow stress corrosion cracks and generate stress corrosion cracks of a length and depth that meet the test conditions.

Further, in the present invention, the inner surface of a groove for forming a fillet weld where stress corrosion cracking is to be generated is welded to the inner surface of a groove using a material having a large resistance index for stress corrosion cracking, It is preferable that the remaining portion of the groove is welded using a material having a small stress corrosion cracking resistance index.

In this case, stress corrosion cracking is less likely to be generated at the boundary between the base material and the fillet weld, and stress corrosion cracking is more likely to be generated inside the fillet weld.

[0013]

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

FIGS. 1 to 8 show an embodiment of the present invention. As shown in FIGS. 1 and 2, a pair of elongated metal base materials 1 and 2 having a relatively large thickness are used. Is prepared, and the other base material 2 is disposed so as to be substantially upright in the vertical direction with respect to the end of one base material 1 arranged so as to be laid down in the horizontal direction, and substantially L
The two base materials 1 and 2 are restrained by assembling them between both longitudinal ends of the base materials 1 and 2 so that the other base material 2 does not incline toward the one base material 1.

Here, between the upper surface of one end of the base material 1 and the lower end of the other base material 2, a corner forming side (the right side in the drawing) formed by the two base materials 1 and 2 is provided. Grooves 4 and 5 are formed on both the opposite side (the left side in the figure), respectively, so that it is a so-called K-shaped square joint type.

Then, as shown in FIG. 3, a molten material is melted and welded into a groove 4 formed so as to open toward the formation side of the corner, thereby forming a fillet weld between the base materials 1 and 2. 6
To form

At the time of welding the groove 4, SC
As shown in FIG. 4, the position at which C (stress corrosion cracking) is to be introduced (the contact position of the pad 7 described later) is defined by the stress corrosion cracking resistance index SCR on the inner surface of the groove 4.
It is preferable to perform welding using the welding material 6a having a large I, and then welding the remaining portion of the groove 4 using the welding material 6b having a small stress corrosion cracking resistance index SCRI. SC at the boundary between fillet weld 2 and 2
C is hardly generated, and SC is formed inside the fillet welded portion 6.
C is easily generated.

The stress corrosion cracking resistance index SCRI is
An index that assesses susceptibility to SCC,

SCRI = [% Cr] +5 [% Nb] +10
[% Ti] -116.5 [% C].

When welding is performed on the groove 4 formed between the base materials 1 and 2 in this way, as shown by an arrow A in FIG. Of the base materials 1 and 2 is deformed in the direction of narrowing the corners due to the shrinkage of the base material. As shown by an arrow B in FIG. 3, a tensile stress in the direction of expanding the corner between the base materials 1 and 2 remains as residual stress in the fillet weld 6 formed by 6, a state in which cracks easily occur is created.

Then, as shown in FIG. 5, a pad 7 made of graphite fiber wool is attached to an appropriate position in the longitudinal direction of the fillet welded portion 6 (see a position shown by a two-dot chain line in FIG. 1) using a clevis jig 8. Contact and fix.

In the illustrated example, the clevis jig 8
Is a diagonal member 10 fastened by bolts 9 to opposite ends of the base materials 1 and 2 by a bolt 9, and a through screw is attached to a middle part of the diagonal member 10 so as to face the surface of the fillet weld 6. The pad 7 is attached to the tip of the screw rod 11 via a pad holder 12.

After the pad 7 is brought into contact with an appropriate position of the fillet welded portion 6 and fixed as described above, as shown in FIG. 6, both base materials 1 and 2 are housed in an autoclave 13 (pressure cooker) and a pressure of 45 is applied. ~ 80kg / cm ² , temperature is 250 ~ 28
The high-pressure high-temperature water 14 of about 8 ° C.
Boil over 500 hours by circulating feed to 3.

When both base materials 1 and 2 are boiled with high-pressure and high-temperature water 14, contact portions of pad 7 in fillet weld 6
As the high-pressure high-temperature water 14 stays and the potential difference between the fillet weld 6 and the pad 7 gives an environmental condition that is susceptible to corrosion and thereby promotes the generation of SCC, as shown in FIG. The SCC is generated as indicated by x at the contact portion of the fillet weld 6 with the pad 7 in combination with the action of the tensile stress remaining as the residual stress in the fillet weld 6.

At this stage, the two base materials 1 and 2 are taken out of the autoclave 13 and the clevis jig 8 is removed, and the SCC generation state of the fillet welded portion 6 of the two base materials 1 and 2 is inspected intermediately. The depth is checked to see if the test conditions are met. If SCCs that meet the test conditions have been generated, the portions near the longitudinal ends of both base materials 1 and 2 are left except for the site where the SCCs are generated. And the like are cut and removed to obtain a regular-sized test body in which stress corrosion cracking is introduced into the fillet weld 6 between the base materials 1 and 2.

However, as a result of the intermediate inspection, if the length and depth of the SCC are not sufficient for the test conditions, as shown in FIG.
The other base material 2 and the constraining member 3
Is released, if necessary, a wedge 15 is driven into the cut portion, and another groove 5 previously formed on the back side of the previously welded groove 4 is welded, as described above. Such deformation due to shrinkage in the cooling process of the molten material is intentionally induced to apply a tensile stress to the existing fillet welded portion 6.

Next, the clevis jig 8 is attached again, the base materials 1 and 2 are stored again in the autoclave 13 (see FIG. 6), and the base materials 1 and 2 are again boiled with the high-pressure high-temperature water 14 to grow the SCC. Let it.

That is, even if the tensile stress of the fillet weld 6 is relaxed by the initial generation of SCC, the tensile strength can be increased by applying welding to the back side of the fillet weld 6. With the new stress applied, the SCC can be grown to produce a length and depth of SCC that meets the test conditions.

Therefore, according to the above embodiment, it is possible to easily and surely introduce the SCC that meets the test conditions into the fillet welded portion 6 of the test specimen. By repeating the destructive inspection test, the inspection technology can be greatly improved.

The method for introducing stress corrosion cracking of the present invention is not limited to the above embodiment, and the pad may be made of a conductive fiber material, and is not necessarily made of graphite fiber wool. Of course, various changes can be made without departing from the scope of the present invention.

[0030]

According to the method for introducing stress corrosion cracking of the present invention described above, stress corrosion cracking that meets the test conditions can be easily and reliably introduced into the fillet weld of the test body. By repeating the nondestructive inspection test using such a test body, an excellent effect that the inspection technique can be greatly improved can be achieved.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating an example of an embodiment of the present invention.

FIG. 2 is a side view of FIG.

FIG. 3 is a side view showing a state in which welding is performed on a groove on a corner forming side.

FIG. 4 is a detailed cross-sectional view of a fillet weld at an expected SCC generation position.

FIG. 5 is a cross-sectional view showing a state where clevis jigs are attached to both base materials.

FIG. 6 is a partial sectional view showing a state in which both base materials are boiled with high-pressure and high-temperature water.

FIG. 7 is a perspective view showing a state in which SCC has been generated in the fillet weld.

FIG. 8 is a side view showing a state where the back side of the fillet weld is welded.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base material 2 Base material 3 Restraint material 4 Groove 5 Groove 6 Fillet weld 6a Solvent 6b Solvent 7 Pad 14 High pressure high temperature water

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hiroyuki Sakamoto 1 Shin-Nakahara-cho, Isogo-ku, Yokohama-shi, Kanagawa Ishikawashima Harima Heavy Industries, Ltd. Yokohama Engineering Center

Claims (3)

[Claims] 1. A stress corrosion cracking introducing method for artificially introducing stress corrosion cracking into a fillet weld formed between a pair of base materials welded so as to form a substantially L-shape with each other. The other base material is disposed so as to be substantially upright with respect to the end of the base material, and a restraining member is assembled between the base materials so that the other base material does not incline toward the one base material. The molten material is melted into the groove formed so as to open toward the corner forming side and welded, and the pad made of conductive fiber material is contacted and fixed to the appropriate position of the fillet weld formed by this Then, a stress corrosion cracking introducing method is characterized in that both base materials are boiled in high pressure and high temperature water in such a state to generate stress corrosion cracking in the fillet weld. 2. After the stress corrosion cracking is initially generated, the restraint by the restraining material is released, and another pre-formed so as to open to the opposite corner forming side on the back side of the previously welded groove. The method according to claim 1, wherein the groove is welded to apply a tensile stress to the existing fillet weld, and then the both base materials are again boiled with high-pressure high-temperature water to grow stress corrosion cracking. How to introduce stress corrosion cracking. 3. An inner surface of a groove for forming a fillet weld in which stress corrosion cracking is to be generated is welded using a material having a large resistance index for stress corrosion cracking. The method according to claim 1 or 2, wherein the portions are welded using a material having a small resistance index for stress corrosion cracking.