Cavitation surface treatment method

Abstract

To increase the grinding speed of a surface by a cavitation processing method.SOLUTION: In the cavitation surface treatment method, an abrasive material 7 is suspended in a treatment liquid 5, a workpiece 3 and a flat spray nozzle 12 are immersed in the treatment liquid 5, the flat spray nozzle 12 sprays a cavitation jet 32 spreading on a plane toward the surface of the workpiece 3 while rotating around a spray axis 1, the surface of the workpiece 3 is smoothed, and compressive residual stress is given to the surface of the workpiece 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cavitation surface treatment method. [Background technology]

[0002] A cavitation surface treatment method called cavitation abrasive surface finishing (CASF) is known, which uses a cavitation jet to smooth the roughness of the workpiece surface and perform peening (US2024 / 0001509A1). Summary of the Invention [Problem to be solved by the invention]

[0003] Conventional cavitation treatment methods sometimes result in slow surface grinding speeds. An object of the present invention is to increase the surface grinding speed achieved by cavitation treatment methods. [Means for solving the problem]

[0004] A first aspect of the present invention is Abrasives are mixed into the processing liquid, Immerse the workpiece and the flat projection nozzle in the treatment liquid, The flat nozzle rotates around the jet axis and jets a cavitation jet that spreads on a plane toward the surface of the workpiece, smoothing the surface of the workpiece and imparting compressive residual stress to the surface of the workpiece; This is a cavitation surface treatment method.

[0005] A second aspect of the present invention is The cavitation jet, which has a spiral ribbon-like cavity, picks up abrasives and collides with the workpiece surface, which is the surface to be treated. The cavity collapses near the surface to be treated, and the cavity cloud with the abrasive flows along the surface to be treated, scraping the surface to be treated and applying residual compressive stress to the surface to be treated. This is a cavitation surface treatment method. [Effects of the Invention]

[0006] According to the cavitation treatment method of the present invention, the surface grinding rate is increased. [Brief explanation of the drawings]

[0007] [Figure 1] Schematic diagram of a cavitation treatment device according to embodiment 1 [Figure 2] FIG. 1 is a longitudinal cross-sectional view of a nozzle according to a first embodiment. [Figure 3] View of arrow III in Figure 2 [Figure 4] Sequential photographs of the cavitation jet of embodiment 1 [Figure 5] Schematic diagram of a cavitation treatment device according to a second embodiment DETAILED DESCRIPTION OF THE INVENTION

[0008] <Embodiment 1> As shown in Fig. 1, a cavitation treatment apparatus 10 of this embodiment includes a treatment tank 11, a nozzle 12, a pump 23, and a moving device 21. The treatment tank 11 has an opening at the top. The treatment tank 11 stores a treatment liquid 5 and an abrasive 7. The abrasive 7 is suspended in the treatment liquid 5.

[0009] The nozzle 12 is disposed on a moving device 21. The moving device 21 freely moves the nozzle 12 in the left-right direction (X), the front-back direction (Y), and the up-down direction (Z). The nozzle 12 is connected to a pump 23. The nozzle 12 is a flat nozzle.

[0010] Fig. 2 is a cross-sectional view of the nozzle 12 taken along the ZX plane passing through the injection axis 1. As shown in Fig. 2 and Fig. 3, the nozzle 12 has a nozzle head 13 and a nozzle tip 17. The nozzle head 13 is in the shape of a round pipe.

[0011] The nozzle head 13 has, in order from the base end (upper side in Figure 2), a flow path 13a, a nozzle chamber 13b, and a jet flow passage port 13c. The flow path 13a is a cylindrical hole. The nozzle chamber 13b is a right cylinder. The nozzle chamber 13b is connected to the flow path 13a. For example, the nozzle chamber 13b has a smaller diameter than the flow path 13a. The jet flow passage port 13c is located at the tip of the nozzle head 13 and is connected to the nozzle chamber 13b. The jet flow passage port 13c is a cylindrical hole. The jet flow passage port 13c has a smaller diameter than the nozzle chamber 13b.

[0012] The nozzle tip 17 is cylindrical and disposed in the nozzle chamber 13b. Preferably, the nozzle tip 17 abuts against the nozzle chamber 13b. The nozzle tip 17 is made of, for example, a gem, an artificial gem, or a sintered body of an artificial gem. The nozzle tip 17 has, in order from the base end, an inlet 17a, a restrictor 17b, and a discharge groove 17c. The inlet 17a and the restrictor 17b are disposed around the injection axis 1. The inlet 17a is a right circular cone whose diameter decreases toward the tip. The restrictor 17b is a right elliptical cylinder. As shown in FIG. 3, the major axis of the restrictor 17b extends in the X direction. The restrictor 17b is directly connected to the inlet 17a. The restrictor 17b opens into the discharge groove 17c. As shown in FIG. 3, the discharge groove 17c is disposed on the tip surface of the nozzle tip 17 and extends in the X direction. As shown in FIG. 2, the YZ cross section of the ejection groove 17c is semicircular.

[0013] 1, the collision area 34 between the cavitation jet 32 ​​and the workpiece 3 is, for example, an elongated ellipse. The collision angle 37 of the cavitation jet 32 ​​is 5 to 10 degrees.

[0014] The workpiece 3 has a processing target surface 3a. The processing target surface 3a is a flat surface. The workpiece 3 is, for example, additively manufactured using a powder bed method. The processing target surface 3a is given tensile residual stress. The processing target surface 3a has unmelted powder (α case). The processing target surface 3a is the surface of the workpiece 3. The processing target surface 3a is the target portion from which the unmelted powder is removed and to which compressive residual stress is given.

[0015] The cavitation treatment method of this embodiment will be described with reference to FIG. 1. First, a workpiece 3 is placed at the bottom of a treatment tank 11. The workpiece 3 is immersed in a treatment liquid 5. A surface 3a to be treated extends in the XY plane. A nozzle 12 is positioned by a moving device 21 at an offset distance 35 away from the surface 3a to be treated. The nozzle 12 is immersed in the treatment liquid 5. The injection axis 1 extends in the Z direction. The moving device 21 rotates the nozzle 12 at a rotational speed 31. Preferably, the rotational speed 31 is between 100 and 200 revolutions per minute.

[0016] The pump 23 then pressurizes the processing liquid 5 and sends it to the nozzle 12. The processing liquid 5 passes through the flow path 13a, the inlet 17a, and the opening of the orifice 17b and is ejected as a cavitating jet 32. The processing liquid 5 is accelerated at the inlet 17a, and when it is ejected from the orifice 17b, the cavitating jet 32 ​​spreads out into a plate shape. The velocity difference near the interface between the processing liquid 5 stored in the processing tank 11 and the cavitating jet 32 ​​generates a vortex, which creates a pressure difference and promotes the formation of cavities. The cavitating jet 32 ​​contains many cavities. The cavitating jet 32 ​​passes through the jet passage opening 13c and collides with the workpiece 3. The moving device 21 may move the nozzle 12 at a constant speed along a predetermined moving path 33 while maintaining the offset distance 35.

[0017] Figure 4 shows a series of photographs taken with a high-speed camera of the state of the cavitating jet 32. The photographs were taken continuously every 0.024 seconds with no abrasive in the tank. The results are shown in the order of photographs 411 to 415. The cavities contained in the cavitating jet 32 ​​appear as white clouds. As shown in Figure 4, the cavitation jet 32 ​​moves toward the workpiece 3 like a thin, twisted ribbon. The cavity collapses near the workpiece 3. The abrasive 7 is caught up in the cavitation jet 32. The abrasive 7 is subjected to the fluid drag of the cavitation jet 32 ​​and flows along the cavitation jet 32. The abrasive 7 collides with the workpiece 3 and flows radially around the jet axis 1 along the workpiece 3.

[0018] According to the cavitation treatment of this embodiment, the abrasive 7 is caught in the cavitation jet 32, so that the amount of the abrasive 7 that collides with the workpiece 3 increases. Also, the amount of the abrasive 7 that flows over the surface of the workpiece 3 increases. This increases the amount of the workpiece 3 that is ground. [Example]

[0019] Cavitation treatment was carried out under the following conditions. The amount of grinding is the depth from the unprocessed workpiece surface to the processed surface. Surface roughness was measured using a stylus surface roughness measuring instrument. The workpiece surface residual stress was measured using X-ray stress measurement (cos α method). The X-ray stress measuring device used was the Pulstec Industrial μ-X360s portable X-ray residual stress measuring device. When the rotation speed was 0 degrees, the direction in which the cavitation jet 32 ​​spread was the X direction, and the movement path 33 was the Y direction. Workpiece: Ti alloy additive manufacturing using the powder bed method Treatment liquid: Water Abrasive: Alumina powder (particle size: 60μm~70μm) Cavitation Jet 32 ​​Flow Rate: 6.5L / min ·Mound angle 37:10 degrees Offset distance 35: 150mm ·Moving speed: 50mm / s Rotation speed: 0~300(1 / min)

[0020] The resulting grinding amounts are shown in Table 1. The grinding amount increased significantly when the rotation speed was 100 to 200 revolutions per minute. The surface residual stress after processing was -609 MPa. [Table 1]

[0021] <Embodiment 2> As shown in FIG. 5, in this embodiment, cavitation treatment is performed on a workpiece 103. The workpiece 103 has a cavity 103b. The cavity 103b has an axis 103c and a wall surface (surface to be treated) 103a. Preferably, the axis 103c is set to the Z direction. The cavity 103b is, for example, a through hole. The axis 103c is aligned with the injection axis 1. The moving device 21 rotates the nozzle 12 at 100 to 200 revolutions per minute. The moving device 21 may also feed the nozzle 12 in the axial direction.

[0022] The cavitation jet 32 ​​spirals into a thin ribbon, entraining the abrasive 7 and entering the cavity 103b. The cavitation jet 32 ​​collides with the wall surface 103a together with the abrasive 7. The abrasive 7 and the cavity cloud then flow along the wall surface 103a. The cavity collapses near the wall surface 103a, imparting compressive residual stress to the surface of the wall surface 103a.

[0023] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present invention, and all technical matters included in the technical ideas described in the claims are subject to the present invention. The above-described embodiments are preferred examples, but a person skilled in the art can realize various alternatives, modifications, variations, or improvements from the contents disclosed in this specification, and these are included in the technical scope described in the appended claims. [Explanation of symbols]

[0024] 1 Injection axis 3 Work 3a Surface to be treated 5 Processing liquid 7 Abrasive material 10. Cavitation treatment device 12 Flat nozzle 32 Cavitation Jet

Claims

1. Abrasives are mixed into the processing liquid, Immerse the workpiece and the flat projection nozzle in the treatment liquid, The flat nozzle rotates around the jet axis and jets a cavitation jet that spreads on a plane toward the surface of the workpiece, smoothing the surface of the workpiece and imparting compressive residual stress to the surface of the workpiece; Cavitation surface treatment method.

2. The flat nozzle rotates at 100 to 200 revolutions per minute. The cavitation surface treatment method according to claim 1.

3. The flat nozzle ejects a cavitation jet having a jet angle of 5° to 10° around the ejection axis. The cavitation surface treatment method according to claim 1 or 2.

4. the workpiece has a surface to be processed; The injection axis extends in a direction perpendicular to the surface to be treated. The cavitation surface treatment method according to any one of claims 1 to 3.

5. the workpiece has a hole to be processed; The injection axis extends in the direction in which the hole to be treated extends. The cavitation surface treatment method according to any one of claims 1 to 3.

6. The cavitation jet, which has a spiral ribbon-like cavity, picks up abrasives and collides with the workpiece surface, which is the surface to be treated. The cavity collapses near the surface to be treated, and the cavity cloud with the abrasive flows along the surface to be treated, scraping the surface to be treated and applying residual compressive stress to the surface to be treated. Cavitation surface treatment method.

7. The treatment liquid flows through the liquid inlet, is rectified and accelerated, passes through the throttle opening, and is ejected in a flat plate shape so as to spread along the discharge groove. The cavitation surface treatment method according to any one of claims 1 to 6.

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