JP2005254367A - Peening method and peening device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide peening method and peening device, simply performing peening in a small-sized device. <P>SOLUTION: A vibrator 5 set opposite to the surface of a workpiece 3 at a predetermined distance in liquid 2 is vibrated with high frequency to generate cavitation in the liquid, and compressive stress is made to remain on the surface of the workpiece 3 by collapsing impact force of cavitation bubbles. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a peening processing method and apparatus for improving a residual stress existing in a metal member.

The peening treatment is used as a treatment method to improve the residual stress existing on the surface of the metal member by improving the residual stress existing on the metal member surface and improving the fatigue strength by hardening. As typical peening methods, shot peening, laser peening, water jet peening and the like are known. Among these, the shot peening treatment method is a technique for leaving a compressive stress on the metal surface by applying small metal balls (shots) to the surface of the metal member at a high speed as described in Patent Document 1 and the like. Further, the laser peening treatment method is a technique for leaving a compressive stress on the metal surface by irradiating the surface of the metal member with pulse laser light in a liquid as described in Patent Document 2 and the like. Further, as described in Patent Document 3 and the like, the water jet peening treatment method causes compressive stress to remain on the metal surface by applying a high pressure fluid from the nozzle in the liquid to apply the cavitation jet to the surface of the metal member. Technology.
JP-A-3-170268 (page 4-5, FIG. 8) Japanese Patent Laid-Open No. 7-246483 (page 3-5, FIG. 1) JP-A-6-114735 (page 4-6, Fig. 1-4)

  The shot peening described in Patent Document 1 requires a high-pressure air generation source for ejecting metal particles (shots), a metal particle recovery device, and the like, and requires a large apparatus. Further, even laser peening described in Patent Document 2 requires a large laser generator. Furthermore, the water jet peening described in Patent Document 3 also requires a large apparatus for generating a high-pressure liquid flow.

As described above, all of the current peening methods require a large apparatus, and no method and apparatus that can be easily peened with a small apparatus have been found so far.
The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a peening processing method and apparatus capable of easily performing peening processing with a small apparatus.

  In order to achieve the above object, the invention of the peening method according to claim 1 is directed to cavitation in a liquid by vibrating a vibrator installed in a liquid so as to face a surface at a predetermined distance from a surface of a workpiece. And compressive stress remains on the surface of the workpiece by the collapsing impact force of the cavitation bubbles.

  Further, the invention of the peening apparatus according to claim 6 is installed at a predetermined distance with respect to the surface of the workpiece in the retained liquid and a liquid retaining portion that retains the liquid on the surface of the workpiece. A vibrator, and an actuator that vibrates the vibrator at a high frequency, and a power source that drives the actuator to generate a high-frequency vibration by supplying an operation signal. And compressive stress remains on the surface of the workpiece by the collapsing impact force of the cavitation bubbles.

  The peening treatment method and the peening apparatus according to the present invention can provide a simple peening treatment method and a small peening apparatus by using cavitation generated by high-frequency vibration.

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

  FIG. 1 is a schematic view showing a peening experiment method using the peening apparatus of the present invention. In FIG. 1, a workpiece 3 and a vibrator 5 attached to the tip of an actuator 4 are disposed opposite to each other in a liquid 2 (for example, water or a solvent having a low boiling point such as alcohol or acetone) stored in a water tank 1. The actuator 4 causes the vibrator 5 to vibrate at a high frequency, thereby generating cavitation between the vibrator 5 and the workpiece 3 and peening the workpiece 3. By using a giant magnetostrictive material for the actuator 4, a vibrator having a large area can be vibrated, so that peening by cavitation can be simultaneously performed on a large area of the workpiece. Reference numeral 6 denotes a power source for supplying an electric signal for vibrating the actuator 4.

  Here, the super magnetostrictive material means a material having a strain amount larger by two digits or more than that of a conventional magnetostrictive material. That is, the strain amount obtained by the conventional magnetostrictive material is about several tens of μm at most, but the super magnetostrictive material used in the present invention can obtain a strain amount of about 2000 μm. One example of such a magnetostrictive material is a single crystal material composed of terbium, dysprosim, and iron. Another example is RTx (where R is one or more of lanthanoid elements, T is one or more of iron, cobalt, nickel, and x is 0 <x <10). There are also giant magnetostrictive materials formed of the intermetallic compounds described.

In this experiment, the cavitation generation test was performed under various conditions, and as a result, many cavitations were generated under the following conditions (1) to (3), and a high peening effect could be obtained.
(1) Keep the distance between the vibrator 5 and the workpiece 3 to 5 mm or less.
(2) The amplitude width of the high-frequency vibration is set to 10 μm or more.
(3) The frequency of the high frequency vibration is set to 1 kHz or more.

Next, the material surface hardening graph by this experiment is shown in FIG. In the figure, Data1 is data before peening processing, and Data2 is data after peening processing.
This experiment was conducted under the following conditions (a) to (e).
(A) Work piece; SUS316L austenitic stainless steel (b) Actuator; Giant magnetostrictive material (c) Distance between vibrator and work piece; 1.0 (mm)
(D) Amplitude of vibrator; 30 (μm)
(E) Vibrator frequency: 2 (kHz)
(F) Cavitation time: 3 minutes Here, the hardness is measured by Knoop hardness (Hk) with a load of 100 (g).

  As is clear from the graph of the experimental results shown in FIG. 2, in the case of the workpiece subjected to the peening process by cavitation, it is cured to a depth range of about 100 (μm) from the surface of the material. Sufficient peening effect was obtained.

Next, FIG. 3 shows an embodiment of a handy type peening apparatus manufactured based on the principle of FIG.
In the principle diagram of FIG. 1, the workpiece 3 and the vibrator 5 are opposed to each other in the liquid 2 stored in the water tank 1, but the workpiece 3 actually peened at the site is a large structure. There are many cases. Therefore, since it is not practical to accommodate the large-sized workpiece 3 in the water tank 1, the following configuration is used instead of adopting the configuration in which the liquid 2 is stored in the water tank 1 in this embodiment. Is adopted.

  In FIG. 3, the elements indicated by reference numerals 2 to 6 are the same elements as in the principle diagram of FIG. 1, but in this embodiment, when the peening device case 7 is placed on the surface of the workpiece 3 during the peening process. The liquid reservoir 8 is formed in the space formed by the case 7 and the surface of the workpiece 3, and the vibrator 5 is opposed to the surface of the workpiece 3 in the liquid reservoir 8. It is composed.

  By the way, the peening device case 7 has a cylindrical actuator housing portion 7a having one end closed with a lid and the other end opened, and the opening side of the actuator housing portion 7a. That is, it is composed of a pedestal portion 7 b that is integrally fixed to the lower portion of the actuator housing portion 7 a and forms the liquid storage portion 8.

This pedestal portion 7b has a cylindrical leg portion 7b1 having a sufficient height to form the liquid storage portion 8 between the pedestal portion 7b and the surface of the workpiece 3. When the peening apparatus is moved by attaching an annular sealing material 10 made of an elastic body to the lower end of the leg portion 7b1, the liquid 2 stored in the liquid storage portion 8 is exposed to the outside. Suppressing leakage. For this sealing material 10, for example, rubber or resin rich in elasticity such as butadiene rubber, urethane rubber, or silicon rubber is used.
The cylindrical leg 7b1 has a hole 7b2 at a position slightly higher than the position of the vibrator 5 (height from the workpiece surface), and the liquid 2 overflows from the hole 7b2.

  The pedestal 7b has such a length that supports the load of the peening device at a position surrounding the vibrator 5 inside the cylindrical leg 7b1 so that the sealing material 10 is properly adhered to the surface of the workpiece 3. The supporting portion 7b3 is provided, and a plurality of moving rollers 9 for smoothly moving the peening apparatus are provided at the tip of the supporting portion 7b3. The support portion 7b3 may have a cylindrical shape similar to the leg portion 7b1 or a shape obtained by dividing the cylinder into a plurality of portions in the circumferential direction.

  On the other hand, the actuator accommodating portion 7a is provided with a moving handle 11 to be gripped when moving the peening device on the upper side, that is, on the side opposite to the pedestal portion 7b, and further, the side is connected to the liquid storing portion 8 to replenish liquid. A liquid supply hole 7a1 is provided.

  With respect to the peening apparatus case 7 configured as described above, the actuator 4 is inserted into the actuator housing portion 7a from the leg portion 7b1 side of the pedestal portion 7b, and the vibrator 5 is placed in the liquid storage portion 8 in the workpiece 3. It is attached so as to be located at a predetermined distance from the surface.

  In the simple peening apparatus configured as described above, first, the vibrator 5 is adjusted so as to be positioned at a predetermined distance (for example, 5 mm or less) from the surface of the workpiece 3, and then the liquid 2 is discharged from the liquid supply hole 7a1. It is injected into the liquid storage unit 8 so that the vibrator 5 is immersed in the liquid 2.

  Note that the closer the distance between the vibrator 5 and the surface of the workpiece 3 is, the more cavitation energy is applied to the workpiece 3 by the vibrator 5, so that even if the energy given to the vibrator is small, the necessary compression is applied. Although stress can remain, it becomes difficult to control the position of the vibrator 5 itself. Therefore, in this embodiment, the distance is preferably 5 mm or less, and a distance of at least about 1 mm is secured.

  The liquid 2 is always injected, and a gap between the support portion 7b3 and the surface of the workpiece 3 or between the support portions 7b3 when the support portion 7b3 is divided in the circumferential direction. It passes through the gap, enters an annular gap formed by the leg portion 7b1 and the support portion 7b3, and flows out through the hole 7b2 provided in the leg portion 7b1. For this reason, the liquid level of the liquid storage part 8 is always maintained at the liquid level of the hole 7b2.

  In this state, an operation signal is sent from the power source 6 to the actuator 4 to operate the actuator 4 to vibrate the vibrator 5 in the liquid 2 at high frequency. At this time, the frequency of the vibrator 5 is 2 (kHz) and the amplitude is 10 (μm).

  Note that it is said that the currently obtained vibrator 5 has a large amplitude of 200 to 500 μm and a frequency of about 50 kHz. However, if the amplitude is too large, it is not preferable for the occurrence of cavitation in a limited space as in the present embodiment. Similarly, the higher the frequency, the greater the cavitation energy, but there is also a relationship between the distance between the vibrator 5 and the workpiece 3, and the maximum frequency is not necessarily required.

  Therefore, in the present embodiment, from the experimental results, the amplitude of the vibrator is desirably 10 μm or more, preferably approximately 30 μm, and the frequency is desirably 1 kHz or more, preferably approximately 2 kHz.

  Due to the vibration of the vibrator 5, cavitation occurs in the liquid 2 in the liquid storage portion 8. Since the collapse impact force of the cavitation bubbles is very large, by compressing the cavitation bubbles on the surface of the workpiece, compressive stress remains on the surface of the workpiece 3, and the fatigue strength of the surface of the workpiece 3 is increased. Improve stress corrosion and release the tensile residual stress of the weld.

  When the peening apparatus is moved, the liquid 2 leaks little by little from the contact surface between the sealing material 10 and the surface of the processing target 3, but the liquid level is constant because the liquid 2 is always supplied from the liquid supply hole 7 a 1. Is maintained.

As described above, according to the peening processing method and apparatus of the present invention, by supplying the liquid from the case, the liquid 2 is stored between the vibrator 5 and the workpiece 3 while being processed. Since the surface of the object 3 can be moved freely to perform peening, and the moving roller 9 is provided on the pedestal portion 7b, the peening apparatus can be easily moved.
Therefore, although the peening apparatus of the present invention is small, it can perform a peening process suitable for on-site construction for releasing tensile residual stress and improving fatigue strength of a welded part of a large plant.

Schematic of peening experiment method. Graph of material surface hardening by peening. The block diagram of one Example of a peening apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Water tank, 2 ... Liquid, 3 ... Workpiece, 4 ... Actuator, 5 ... Vibrator, 6 ... Power supply, 7 ... Peening apparatus case, 7a ... Actuator accommodating part, 7a1 ... Liquid supply hole, 7b ... Base part, 7b1 ... Legs, 7b2 ... Holes, 7b3 ... Supporting part, 8 ... Liquid storage part, 9 ... Moving roller, 10 ... Sealing material, 11 ... Moving handle.

Claims (9)

  A vibrator installed at a predetermined distance from the surface of the work piece in the liquid is vibrated at a high frequency to generate cavitation in the liquid, and the cavitation bubbles collapse to compress the work surface. A peening treatment method characterized by remaining stress.   The peening processing method according to claim 1, wherein the vibrator is vibrated at a high frequency by an actuator using a giant magnetostrictive material.   The peening processing method according to claim 1, wherein a predetermined distance between the vibrator and the workpiece is kept at 5 mm or less.   2. The peening processing method according to claim 1, wherein the amplitude of the high-frequency vibration of the vibrator is 10 μm or more.   2. The peening processing method according to claim 1, wherein the frequency of the high-frequency vibration of the vibrator is 1 kHz or more.   A liquid retaining portion that retains liquid on the surface of the workpiece, a vibrator installed at a predetermined distance from the surface of the workpiece in the retained liquid, and an actuator that vibrates the vibrator at high frequency And a power source that drives the actuator so as to generate a high-frequency vibration by supplying an operation signal. Cavitation is generated in the liquid by the vibration of the vibrator, and the workpiece is processed by the collapse impact force of the cavitation bubble. A peening apparatus characterized in that compressive stress remains on the surface of an object.   The peening apparatus according to claim 6, wherein the vibrator is vibrated at a high frequency by an actuator using a giant magnetostrictive material. A case including an actuator housing portion that houses the actuator, and a pedestal portion that is fixed to an opening located at a lower portion of the actuator housing portion and forms a liquid storage portion in contact with the surface of the workpiece;
An annular sealing material that is attached to the lower end of the leg located below the pedestal and that tightly contacts the surface of the workpiece during peening and prevents leakage of liquid stored in the liquid reservoir to the outside The peening apparatus according to claim 6 or 7, wherein: A supporting part for supporting the load of the peening apparatus provided at a position surrounding the vibrator below the pedestal part, and a peening apparatus provided at the tip of the supporting part and in contact with the surface of the workpiece The peening apparatus according to claim 6, further comprising a moving roller for smoothly moving the roller.

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