JP2826016B2 - Water jet peening method for underwater structures - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for reducing the residual stress of underwater structures on which fine solid particles such as oxide scale are deposited on the surface.
In connection with the technology of improving using peening and coating, precision peening or coating by means of accurate removal and removal of the solid particles from the structure (plasma coating is also used for peening in a broad sense because molten particles collide with the surface. Included) law.

[0002]

2. Description of the Related Art The surface stress of an existing structure having a heat affected zone (HAZ) having a potential to cause stress corrosion cracking (SCC) is caused by shot blast in which small steel balls are blown by the force of air current, sand blast using sand particles, A so-called peening process using cryoblast using ice particles is applied to pull the stress (the direction to enlarge the crack)
To improve in the compression direction. Such a peening technique is widely used at the time of processing various mechanical structures or parts such as gears as a measure for improving residual stress.

[0003] However, there are many structures that must be peened by all means even in such an environment where blast operation cannot be performed. For example, special heat exchangers and reactors that are filled with water, such as nuclear reactors, or welds of underwater and lake structures are physically or economically required to remove water. Is also nearly impossible. Recovering blast particles from water is a very difficult task. If ice particles are used, recovery is not required, but economical merit is less likely.

[0004] The use of high-speed water jets is known as a unique processing, mining or washing technique, but there is an attempt to use this technique for improving surface stress (Japanese Patent Application Laid-Open No. 62-63614). Peening using a water jet also has the advantage of having a water cooling effect and preventing a local temperature rise. However, this is an effect only for the work in the atmosphere in which the axial dynamic pressure of the water jet can be effectively used, and it is difficult to directly apply the stress to this technique for underwater peening. In water, the decay of the jet axial dynamic pressure is quite fast.

[0005] This is because diffusion is fast because the liquid phase is the same as the resistance of the surrounding water. In water, an ultra-high pressure pump is required to obtain axial power comparable to that of a gaseous water jet. Further, it becomes more difficult to increase the capacity of the pump as the pressure becomes higher. Therefore, it is a very disadvantageous technology in terms of cost.

On the other hand, in high-speed water jets in water, cavitation is generated due to a sharp pressure gradient and severe turbulence of the jets. If this cavitation is promoted and the collapse impact pressure of a large amount of generated bubbles can be used effectively, there is a possibility that a peening effect comparable to that of a water vapor jet in a gas phase can be achieved with a modest injection pressure.

FIGS. 12 and 13 show two examples of the prior art.
The nozzle of FIG. 12 is a nozzle proposed to promote cavitation in water. In the figure, 1
201 is a nozzle body, 1202 is an orifice part, 120
Reference numeral 3 denotes a conical opening, 1204 denotes a conical cavity, 1205 denotes a pipe member, 1206 denotes a high-pressure jetting device, and 1207 denotes an object to be jet-processed.

The example shown in FIG. 13 embodies an idea of removing dirt such as sludge adhered to a component in water by using cavitation. In the technique shown in FIG. 13, if the distance between the nozzle 1303 and the part to be cleaned 1302 (stand-off distance), the injection pressure or the specifications of the nozzle are not properly determined, not only the adhering matter cannot be removed well, but also the part to be cleaned can be removed. Can cause problems. In the figure, 1301 is a water tank, 1303 a is a nozzle tip, 1303 a
Reference numeral 3b denotes an ejection hole, 1304 denotes water, and 1305 denotes a pipe.

[0009]

Here, a light water reactor type reactor is taken up, and problems in the prior art are outlined.

[0010] At the bottom of the reactor pressure vessel or inside the reactor, a substance similar to oxide scale called a clad adheres and deposits in the form of flakes. This clad is composed of fine particles mainly composed of an iron-based oxide such as Fe ₂ O ₃ , and has a high radioactivity. By the way, 90% of the dose received during the periodic inspection is due to the activity of Co-60, but it is said that most of Co-60 is associated with iron-based cladding [Otoha et al .; 5 persons; "BWR"
Reduction of Dose and Waste Volume by Improving Plant Water Quality Management "Thermal Nuclear Power, Vol. 42, no. 12, (1
991-12), 1734].

Therefore, if this cladding increases in the reactor and in the water circulation system, the radiation dose of the reactor will increase as a result. If the radiation dose can be reduced by removing this clad, it can be used for steam turbines, condensers and circulation pumps in the case of boiling water reactors (BWRs), and in the case of pressurized water reactors (PWRs). Operations such as maintenance and inspection of the steam generator (steam generator) and replacement of parts are simplified.

On the other hand, if the clad adheres and accumulates, water stays in minute gaps between the furnace wall and the surface of the furnace internal structure and the clad, and stress corrosion cracking easily occurs due to an electrochemical effect, so-called galvanic action. This clad is removed and the surface of the steel material, especially the heat affected zone (HAZ) such as the welded section
Contact with flowing water will prevent stress corrosion cracking. Thus, by removing the clad from the inside of the reactor, it is possible to greatly improve the safety and reliability of the reactor.

[0013] Further, if the clad is deposited, it is impossible to narrow down the "target" of the peening work for colliding the high-speed water jet. It is difficult to find a part requiring peening even by an endoscope TV camera. As a result, if peening is performed at an unnecessary part, the construction cost is increased and the construction efficiency is reduced. If the clad is thickly deposited, the stand-off distance (the distance between the nozzle and the surface to be processed), which is extremely important for peening, cannot be set appropriately.

The stand-off distance has an optimum condition (a large amount of stress improvement and no damage) for peening. If the stand-off distance is too short, peening occurs in a portion where the energy of the cavitation concentrates in the jet with the cavitation, and there is a possibility that damage to the cavitation / erosion or the like may be caused on the surface to be processed. On the other hand, if the stand-off distance is too long, even if the collision time of the jet is lengthened, there is also a problem that the improvement of the stress does not progress easily. SUMMARY OF THE INVENTION An object of the present invention is to provide a water jet peening method for an underwater structure having a nozzle structure for removing a clad in a furnace and accurately peening by a high-speed water jet in view of the above problems. Is to provide.

Although not physical means as in the present invention, means for reducing contaminants in the furnace by chemicals has already been proposed (Japanese Patent Publication No. 3-80279). In the furnace,
It is known that activated contaminants may penetrate deeply into metal structures (so-called hard scale reaching several tens of microns from the surface layer) [for example, Kawahara et al. 5; Ishikawajima Harima Technical Report, Vol. 32 , No. 2, (March 1992),
P. 106]. The present invention does not cover such radiation contaminant peeling that has penetrated deep into the metal structure.

[0016]

In order to solve the above-mentioned problem, the present invention employs the following method.

First, the energy generated due to the cavitation
Prior to peening using foam (residual stress improvement), the structure
The cladding attached to the object surface is removed. Means to remove
Then, use the water jet which will be described in detail
There is a way .

Further, the clad adhering to the surface of the structure is
The flow velocity is lower than that of a low-velocity jet jetting from a nozzle (a high-speed water jet used for peening exceeding 300 m / sec. For this reason, the expression “low speed” is used for convenience hereinafter. To be released from the surface. Next, the pump is switched as the opening of the nozzle that has ejected the low-velocity jet and the opening that sucks water at a low velocity, and the cloud floating in the water is sucked out of the system together with the water and discharged. The endoscope is used to check the steel surface from which the clad has been removed, position the nozzle at the optimum stand-off distance (distance between the nozzle and the processing surface), and make a high-speed water jet collide with the processing surface at a predetermined injection pressure. Peening (stress improvement).

In order to perform such an operation, the structure of the nozzle and the water injection / suction system are as follows. First, the nozzle is sprayed with a main orifice that injects a high-speed water jet (to be described later, a bypass is provided in the discharge line from the high-pressure pump so that it can be jetted at a low speed) and a low-speed water jet that blows off the clad. And a low-speed jet hole for sucking the clad together with water. The diameter of the main jet hole is small because high-pressure water is jetted at high speed. On the other hand, the low-velocity flow ejection hole has a large flow path area at the opening. The low-velocity flow outlet serves as both blowing and suction.

The blow-out section and the suction section can be configured differently, but there is a problem that the nozzle becomes large and manual management (moving operation) of a narrow portion becomes difficult. High-pressure water is supplied to the main outlet from a high-pressure pump. A low-pressure suction pump is connected to the line to the low-speed jet port via a switching valve, similarly to the low discharge pressure pump. A filter is provided at the outlet of the suction pump so that the clad can be removed (although omitted, this clad removing operation naturally takes measures against the radiation of the clad).

[0021]

[Action] bottom or furnace structure of the reactor pressure vessel etc.
An oxide scale called a clad is separated from the underwater structure by a low-pressure water jet that is jetted at a low speed from a jet part provided on the outer periphery of the nozzle. The water does not stay in the gaps.

Accordingly, the galvanic action is also eliminated, so that stress corrosion cracking can be prevented. Since the radiation is concentrated in this clad, the amount of radiation in the furnace is reduced by sucking the clad floating in the water inside the furnace by washing from the suction part opened on the outer periphery of the nozzle and removing it outside the furnace. You can do it. By removing the clad from the furnace wall and the surface of the structure, the heat-affected zone (HAZ), that is, the welded portion can be captured by the endoscope TV camera.

This makes it possible to accurately determine the location where the water jet collides. In other words, peening with a water jet can be performed with higher efficiency. In addition, problems such as peening unnecessary portions and erroneous standoff distance (distance between the nozzle and the processing target surface) to cause damage (erosion) are eliminated. Also, in the present invention, for peening
Peening members that spray high-speed water jets
The adhering matter removing member that ejects the jet to remove
Use a nozzle connected to the body. Peening material and adhesion
The material removal members can be used individually,
After putting in the kimono removing member to remove the deposits,
Process for removing adhering substances by putting cleaning members in water
Finding an elephant location and peening that location
Become. However, the water becomes turbid due to suspended matter when removing the attached matter.
Therefore, it is necessary to properly find the processing target location from which
It takes time to work and the work is complicated. Moreover, adhesion
Peening at a position shifted from the processing target location where the object was removed
When the components are installed and processed,
Business, and the peening effect is not fully exhibited. That
Point As in the present invention, the peening member and the adhering matter removing portion
In the structure where the materials are connected integrally, the positional relationship between the two is clear.
Yes, as in the embodiment, a pin
If the nozzle structure has cleaning members
There is no need to move the nozzle after removing objects, and
Nozzle with kimono removal member and peening member next to each other
For structures, move by known dimensions
To the center position of the processing target area from which deposits have been removed.
Can be set for
The rolling effect can be reliably exhibited. After removing such deposits
Position of the peening member
Especially difficult and heavy water is turbid due to suspended matter.
This is an important task.

[0024]

FIG. 1 shows an embodiment of the present invention, in which a high-speed water jet impinges on a processing target portion (heat affected zone) 15 of a structure in water (ambient water) 19 in a container. BRIEF DESCRIPTION OF THE DRAWINGS It is the outline of the processing method which improves stress, and the structure of the nozzle used is shown as sectional drawing. FIG. 2 is a front view of the nozzle.

The nozzle is provided with a high-pressure water ejection section 2 to which high-pressure water 3 is supplied at the center, and low-pressure water 9 is supplied outside thereof. 1) is provided as a casing for the nozzle. In the high-pressure water jetting section 2, high-pressure water 3 is guided through a high-pressure water supply line 4, passes through a high-pressure water supply channel 5, and flows into a high-pressure water jet 6.
, The high-speed water jet 7 is injected into the water 19 at high speed. The high-speed water jet 7 collides with the processing target portion (heat-affected zone) 15 in the present embodiment with severe cavitation in the water 19. The collision causes the cavitation bubbles to collapse, generating an explosive impact pressure. By this impact pressure, the residual stress in the tensile direction of the processing target portion (heat affected zone) 15 is improved in the compression direction.

A nozzle body (low-speed flow path) 1 constituting a low-speed water flow channel outside the high-pressure water jetting section 2 adheres to a processing target portion (heat affected portion) 15 and a processing target portion (base material) 14. It serves as a flow path for the low-pressure water 9 that blows off the accumulated clad (oxidized scale) 30 and disperses and floats, and the suction water 11 that sucks the clad (oxidized scale) dispersed and suspended in water. The low-speed water jet part 8 at the tip end of the nozzle body (low-speed flow path) 1 has a slightly divergent shape, and the clad (oxidized scale) 30 is dispersed / floated or dispersed / floated over a wide area. It is easy to inhale the clad (oxidized scale).

[0027] Clad (oxide scale) 3
The low-pressure water 9 for blowing off the pressure 0 and the suction water 11 for sucking the clad are supplied to a low-pressure water supply line 10 which is a common conduit.
Through the means depending on the means. On the side of the nozzle body (low-speed flow channel) 1, an endoscope TV camera 16 with built-in illumination is provided. The information from the endoscope TV camera 16 is displayed as a screen in the remote control room so that an operator (operator) can monitor the information.

In the operation according to the embodiment of the present invention, first, based on the image from the endoscope TV camera 16, the surface layer of the clad (oxidized scale) 30 adhered and deposited on the processing target (base material) 14. Check the part, and bring the nozzle body (low-speed flow channel) 1 close to a predetermined position. The nozzle body (low-speed flow channel) 1 is moved by a manipulator (not shown) via the nozzle support 18. Next, a low-speed water jet 12 is jetted to blow off a softly deposited clad (oxidized scale) 30 on the processing target portions 14 and 15, and to be dispersed and suspended in the water 19.
The degree of dispersion / floating is confirmed by the fact that the image from the endoscope TV camera 16 looks turbid. further,
The cloud (oxide scale) 30 dispersed and suspended in the water 19 by the suction water flow 13 is sucked from the nozzle. By such a suction, it is possible to immerse in the water or the processing target locations 14 and 1.
5 is also determined based on the video from the endoscope TV camera 16 as to whether or not the cladding (oxidized scale) has been removed.

After the processing target portion (heat affected zone) 15 is accurately determined, the nozzle main body 1 is moved to an optimum stand-off distance (distance between the outlet of the high-speed water jet and the processing target surface) [nozzle shape and Although it differs somewhat depending on the flow velocity, x / D = 60 to 150 (x; distance, D; ejection hole diameter) as a dimensionless distance
Is the optimum standoff distance for stress improvement. When x / D = 10 to 30, the breaking force of the cavitation is large, but the area that affects the machined surface is small.
Since the energy is focused, the processing surface may be damaged), and the high-speed water jet 7 collides with the processing target portion at a predetermined injection pressure for a predetermined time. 1
7 is a fiber probe.

FIG. 3 shows an example of a water injection, supply and circulation system embodying the present invention. The high-pressure water 3 is supplied from a water supply line 22 to a high-pressure pump 20 by using water 21 in a reservoir.
Is pumped up by the high-pressure pump 20 and further pressurized. As described above, the high-pressure water 3 is supplied from the high-pressure water ejection section 2 installed in the nozzle body 1 to the cavitation jet 36 accompanied by intense cavitation.
Is injected into the surrounding water 19 and collides with the processing target portion 14. As will be described later (FIG. 6), a low-pressure water jet is also injected from the high-pressure water jet unit 2 for assisting the suction of the clad, so that a return line from the switching valve 23 to the reservoir is also provided.

The low-speed water jet 12 for floating and dispersing the clad is pumped up by the low-pressure injection pump 25 through the water supply line 22 to the low-pressure pump, and then to the nozzle body 1 via the switching valve 26 and the low-pressure water supply line 10. Be guided. The low-speed water flow is supplied from the low-speed water flow jetting portion 8 in the nozzle body 1 to the processing target location 1 where the clad is deposited.
Injected toward 4. When sucking the water with Kuratsudo from Roh nozzle body 1 to the switching valve 26 is used in common supply line of the low-speed water flow.

The water and the clad sucked through the switching valve 26 are pumped up by a suction pump 27, and after the clad is removed by a filter 28, only the water returns through a water circulation line 29. This water is reused as used water 21 in the reservoir. In this system, a high-pressure discharge and small-capacity plunger pump is used as a high-pressure pump, and a low-pressure and large-capacity centrifugal pump is used as a low-pressure injection suction pump. 24 is a water supply line to the low pressure pump.

FIGS. 8 and 9 show two examples of nozzles to be used. The structure shown in FIG.
The nozzle is provided with a cavitator (door groove-shaped slot) 807 at a connection portion between the reference numeral 06 and the diameter contraction portion (restriction portion) 805.
The high-pressure water 802 is guided through a high-pressure water supply channel 804, decompressed and accelerated in a radially contracted portion (restriction portion) 805, and is jetted from a jet hole 806 as a high-speed water jet. 8
01 is a nozzle main body, and 803 is a center axis.

The nozzle whose structure is shown in FIG. 9 is provided with a cavitator (door groove-shaped slot) 907 at the center of a straight type ejection hole 906. In this nozzle as well, high-pressure water 902 is supplied through a high-pressure water supply channel 904, is rapidly accelerated in a diameter contraction portion (restriction portion) 905, and has a high-speed water jet accompanied by intense cavitation from an ejection hole 906 (ejection speed is 300 m Per second). Reference numeral 901 denotes a nozzle main body, and 903 denotes a central axis.

In each of the nozzles, a subcavity (in the form of a narrow tube-shaped cavity) is generated from the cavity (door groove-shaped slot), and is supplied into the high-speed water jet as an inflow nucleus. Is done. The provision of such a sub-cavitation as an inflow nucleus greatly promotes the cavitation of the high-speed water jet. Therefore, if a nozzle having a structure is used here, the effect of peening (improving stress) can be significantly improved.

FIG. 4 schematically shows a state in which the clad (oxidized scale) deposited on the surface of the processing object is blown off by the low-speed water flow and dispersed and suspended in the surrounding water in the embodiment of the present invention. Things.

The low-speed water jet 12 is jetted from the low-speed water jet 8 at an initial velocity of about 40 to 160 m / sec. This flow velocity is not necessarily “slow”, but the high-speed water jet used for peening has an initial velocity of more than 300 m / sec, and is expressed as “slow” for comparison.
When the initial velocity exceeds 40 m / sec, cavitation starts to be generated although the jet is not intense, and the effect of peeling the scale increases rapidly. On the other hand, when the initial speed is 160 m / sec or more, the cavitation becomes considerably intense, which affects not only the scale removal but also the base material.

The low-speed water jet 12 collides with a clad (oxidized scale) 30 which is attached and deposited. Due to the turbulence during collision and the action of the cavitation, the clad 30
Are blown off and dispersed and suspended in water 19. It is not necessary to perform continuous jetting of the low-speed water jet for removing such a clad, and it is sufficient that intermittent jetting of about 3 to 4 seconds is repeated once or several times as necessary. Reference numeral 31 denotes a clad floating by a water jet.

FIG. 5 illustrates a situation in which the clad 34 dispersed and suspended in the water 19 is sucked from the low-speed water jet unit 8. In this case, as described above, the low-pressure pump to be used is switched from discharge to suction. The clad 34 dispersed and suspended in the water by the blowing operation as shown in FIG. 4 is sucked into the nozzle body (low-speed flow path) 1 by the suction water flow 33 and discharged from the low-pressure water supply line 10 as suction water 32. You. In the case of suction, the flow velocity when passing through the low-speed water jet unit 8 is set substantially equal to that in the case of injection as shown in FIG.

In the above-described operation of dispersing / floating and suctioning the clad, the image reflected on the endoscope becomes cloudy, but the appearance of particles or flocks, which are clumps of particles, are observed to flow violently. This confirms the effect of removing the clad.

FIG. 6 illustrates a method for assisting the suction of a clad.
A situation in which a low-speed water jet 35 is jetted from the high-speed water jet orifice 6 which should originally jet a high-speed water jet for peening (this switching is performed by the switching valve 23 as shown in FIG. 3) is schematically depicted. It is a thing.

A large-capacity low-speed water jet 3 having an injection velocity of 5 to 200 m / sec, more preferably 40 to 160 m / sec.
Numeral 5 collides with the processing target portion 15 and plays a role of keeping the clad in a forcibly dispersed / floated state at an interference portion (shear vortex portion 35 a) with the flow of the suction water flow 33. If the flow rate is too low, the clad cannot be separated from the surface of the steel material, and if the flow rate is too high, the clad will blow away far, making suction impossible. The clad dispersed and suspended in the vicinity of the nozzle body 1 as described above is efficiently sucked into the nozzle body (low-speed flow path) 1 as the suction water flow 33.

If the clad is removed by the above operation, the position of the processing target portion (heat affected zone) 15 becomes clear. Next, as described above, the optimal standoff distance x
The positions the nozzle body 1, for injecting high velocity water jets 7 from the high-speed water jet ejection holes 6 at a predetermined injection pressure P _1. Injection pressure P ₁ is due connexion different kinds and necessary processing conditions of the processing target section is selected within the range of 30～150MPa. High velocity water jets are accompanied by severe cavitation, as shown in FIG. At the optimal standoff distance xopt for stress improvement, the cavitation cloud splits (1004) and the vortex cavitation 1005
Is actively generated. This vortex cavitation 1005
Decays explosively on or near the surface to be machined, generating numerous shock pulses. The impact pulse generated in this manner causes the plastic grains to undergo compression plastic deformation such that the crystal grains on the surface layer of the steel material are crushed, and the residual stress in the tensile direction is improved in the compression direction. 1001 is high-pressure water, 1002 is a nozzle, 1003 is a continuous flow of the cavitation cloud, 1
006 is fine bubbles, and 1007 is ambient water.

FIG. 7 shows an actual peening execution state. 36 Kiyabiteshiyon jets, 37 rebounds jet, P ₁ is the injection pressure, xopt is the optimal stand-off distance. FIG. 11 shows the results of verifying the stress improvement effect by the water jet peening (WJP) as described above. The residual stress is dimensionlessly described based on the absolute value σ ^* of the residual stress in the tensile direction before peening. Before the peening, the tensile residual stress at the level of σ / σ ^* = − 1 was increased by water jet peening (WJP) embodying the present invention to σ / σ ^* ≦ +
It can be seen that the compression side has been improved to 1.14. By improving the stress on the steel surface to the compression side, stress corrosion cracking (S
The occurrence of CC) and the accompanying crack propagation are greatly suppressed. Even if such water jet peening (WJP) processing is performed on the surface of a steel material in which minute cracks are already present, there is no problem that the cracks are enlarged, and the same stress improving effect is produced.

The technology according to the present invention can be applied to construction of underwater structures such as the ocean where scales and the like are remarkably adhered. The scale of a structure in seawater or lake water is often a matter to which not only oxides but also small aquatic organisms are attached. The present technology, which combines a technology for removing (cleaning) such deposits with cutting for peening (improving stress) or dismantling, is useful.

However, for cutting in water, the stand-off distance of the submerged water jet (the distance from the nozzle to the workpiece) is set to one of the stand-off distances in peening in order to concentrate the destructive force of the cavitation on the material.
It may be set to / 3 to 1/5. That is, the nozzle is much closer to the workpiece than the peening.

[0047]

The effect of the present invention is particularly large when applied to peening (stress improvement) and cleaning in an aged nuclear reactor. The specific effects are summarized as follows.

(1) The welding residual stress of the members constituting the reactor pressure vessel or the internal structure of the reactor can be improved with high accuracy. This is because, by removing the scale, the field of view of the endoscope is extended, and the location to be peened, that is, the target can be determined. Thereby, stress corrosion cracking (SCC) can be prevented and the fatigue strength is improved. In this way, the life of the reactor is extended.

(2) In connection with the above effect (1), since there is no error in the position where the high-speed water jet impinges, there is no adverse effect on equipment / members that do not require peening (damage due to cavitation, etc.). Thereby, the reliability of peening construction is improved.

(3) Since radioactivity is concentrated on a scale called a clad (consisting of a group of fine particles) in the reactor, the scale is sucked and removed to the outside of the reactor according to the present technology. Radiation dose in the reactor can be reduced. As a result, maintenance of steam turbines (boiling water reactor (BWR)), steam generators (pressurized water reactor (PWR)), forced circulation pumps, condensers, etc., through which water and steam containing radioactivity pass directly Inspection work becomes easy.

(4) If the scale is accumulated on the members in the nuclear reactor, the flow of water is stagnant in the narrow space between the scale and the steel material, and the stress corrosion cracking (SC) is caused by the galvanic effect.
C) easily occurs. By suctioning and removing the scale according to the present invention, the cause of stress corrosion cracking can be removed, and the soundness of the furnace internal members can be maintained.

[Brief description of the drawings]

FIG. 1 is a structural view of a water jet peening apparatus according to an embodiment of the present invention.

FIG. 2 is a front view of the nozzle shown in FIG.

FIG. 3 is a schematic diagram of water injection, supply and circulation system according to an embodiment of the present invention.

FIG. 4 is a schematic view showing a situation in a clad removing operation method before peening.

FIG. 5 is a schematic diagram showing a situation in a clad removing operation method before peening.

FIG. 6 is a schematic view showing a situation in a clad removal operation method before peening.

FIG. 7 is a structural diagram showing an actual peening construction state.

FIG. 8 is a structural diagram of a nozzle.

FIG. 9 is a structural diagram of a nozzle.

FIG. 10 is a schematic diagram showing the phenomenon of underwater water jets with cavitation.

FIG. 11 is an explanatory diagram showing a stress improvement effect by water jet peening.

FIG. 12 is a structural view showing the prior art.

FIG. 13 is a structural view showing another prior art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nozzle main body (low-speed flow path) 2 High-pressure water ejection part 3 High-pressure water 4 High-pressure water supply line 5 High-pressure water supply path 6 High-speed water jet hole 7 High-speed water jet 8 Low-speed water jet part 9 Low-pressure water 10 Low-pressure water supply line DESCRIPTION OF SYMBOLS 11 Suction water 12 Low-speed water jet 13 Suction jet 14 Processing target part (base material) 15 Processing target part (Heat affected zone) 16 Endoscope TV camera 17 Fiber probe 18 Nozzle support 19 Ambient water (environmental water) 20 High pressure pump 23 Switching valve 25 Low pressure injection pump 27 Suction pump 28 Filter 29 Water circulation line 30 Clad (oxidized scale) 36 Cavitation jet

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B24C 1/10 B24C 1/00 B24C 5/04

Claims (5)

(57) [Claims] 1. A high-pressure water jet for peening.
Jets to remove cleaning materials and deposits
Using a nozzle that is integrally connected to the
A water stream is applied to the surface of the structure with the adhering substance removing member.
To remove the deposits adhering to the structure, and then
A peening member is used to make a water flow faster than the water flow
To generate compressive residual stress on structures
Water Jetpinin for Underwater Structures
Method . 2. The water jet peening method for underwater structures according to claim 1, wherein the jet velocity of the jet for removing the attached matter is 5 m / sec or more and less than 200 m / sec. 3. The method according to claim 1, wherein
An endoscope that puts the workpiece and the jet within the field of view
Water jet peening for underwater structure, characterized in that it has attached to. 4. A high-pressure water jet spraying member is provided at the center of the nozzle, and a ring for removing or adhering deposits is formed around the high-speed water jet spraying member. A water jet peening method for underwater structures, characterized by providing an opening. 5. A method according to claim 1 to 4, wherein, when sucking the particles which deposits Ri by the suction water flow is dispersed and suspended from the annular opening, the ejection hole that opens in the middle,
A water jet peening method for an underwater structure, characterized in that a flow rate is controlled by a bypass line and a switching valve to jet a water flow at a lower speed than a high-speed water jet used for peening.