A cavitation polishing device and method for the inner wall of a slender tube

Abstract

The present invention discloses a cavitation polishing device and method for the inner wall of a slender tube. The device includes a high-pressure fluid generating unit, a variable-diameter cavitation unit, a magnetically controlled displacement unit, and a work platform. There are two high-pressure fluid generating units, which are symmetrically installed on the left and right sides of the work platform; the left and right ends of the slender tube are respectively connected to the high-pressure fluid generating units on the left and right sides; the high-pressure fluid generating unit contains polishing liquid. The present invention utilizes a typical Venturi tube structure formed by a magnetic hollow tube in the slender tube, so that the high-pressure polishing liquid flowing through the area produces a cavitation effect, and utilizes the high temperature and high pressure generated by the annihilation of cavitation bubbles to polish the inner wall of the slender tube, which can achieve efficient polishing of slender tubes with millimeter and submillimeter calibers and an aspect ratio greater than 100. The present invention can effectively control the cavitation effect generated in different areas of the tube to achieve uniform polishing inside the tube. The device of the present invention has a novel structure and is particularly suitable for slender tubes with uneven inner wall roughness.

Description

Technical Field

[0001] The invention belongs to the field of fluid precision processing, and in particular relates to a cavitation polishing device and method for the inner wall of a slender tube. Background technology;

[0003] With the trend toward miniaturization and integration of modern high-end precision equipment, slender tubular parts are widely used in precision fluid transportation and long-distance transportation in aerospace, biomedicine, and chemical engineering due to their structural characteristics. They are often used for sample extraction, fluid transportation, and heat conduction and heat dissipation. In order to ensure the stability of fluid transportation, reduce internal flow resistance, improve the uniformity of the internal fluid, and prevent material residues, the inner wall of the slender tube often needs to have a high degree of finish. At present, the manufacturing of slender tubular parts inevitably produces wrinkles during the drawing and extrusion molding processes, resulting in an inner surface roughness that cannot meet industrial requirements, and therefore requires further polishing.

[0004] Currently, the following methods are mainly used to polish the inner wall of slender tubes: mechanical polishing, abrasive flow polishing, magnetic grinding, and electrolytic polishing. The tool head commonly used in mechanical polishing has poor accessibility for slender tubes with a diameter of 1 mm or less, and it is difficult to move flexibly inside the tube, making it difficult to ensure polishing uniformity. Abrasive flow polishing, a common polishing process that uses high-pressure, high-viscosity non-Newtonian fluids for polishing, also has certain limitations. It has high requirements for the initial inner surface quality. As the length of the tube increases, the pressure inside the slender tube will seriously decrease, resulting in uneven polishing effect. At the same time, excessive pressure can cause some thin-walled parts to deform, affecting their dimensional tolerances. Magnetic grinding uses magnets to drive magnetic particles inside the tube for polishing. However, due to the difficulty of magnetic particles flowing, they cannot effectively and evenly cover the inner wall. Electrolytic polishing uses a redox reaction to dissolve the workpiece as the anode in the electrolyte. However, it is difficult for the cathode to penetrate deep into the interior of the slender tube, making it difficult to avoid short circuits. Its poor environmental performance is also a key drawback that has been criticized.

[0005] Cavitation polishing refers to a technology that uses the cavitation effect to generate high-temperature and high-pressure impacts to remove a small amount of workpiece material. The generation of liquid cavitation effect is common in geometric structures such as throttle valves, orifice plates, and venturi tubes where the fluid pressure can change. Due to structural limitations, the fluid flow rate rises sharply and the pressure drops sharply. When the pressure drops below the saturated vapor pressure of the liquid, cavitation bubbles are generated. As the fluid continues to flow, the pressure rises, and the cavitation bubbles generated in the early stage collapse and disintegrate, forming a local high-temperature and high-pressure environment around it, accompanied by a series of cavitation effects such as high-speed jets and impacts, which can mechanically remove the workpiece surface material. For example, Chinese patent CN115741442A proposes a device and method for polishing and strengthening the inner surface of non-uniform cross-section micropores, which is used in the field of polishing and strengthening processing. It involves a device that generates cavitation effect by alternating the volume in a closed body cavity, releasing a large amount of energy and heat to polish and strengthen the inner surface of the micropores. The device consists of a cross-shaped piston cylinder and an opposite through-hole piston cylinder. The reciprocating motion of the piston continuously changes the volume of the enclosed space, utilizing the fluidity and magnetic properties of the magnetic fluid to achieve uniform polishing and strengthening of the micropores. This device can solve the problem of uneven strengthening on both sides of the inner surface of micropores with non-uniform cross-sections, but it has low removal efficiency, high processing costs, and requires high strength and sealing performance of the enclosed space.

[0006] Other polishing techniques for the inner surface of elongated holes are as follows:

[0007] Chinese patent CN206632769U proposes a polishing device for the inner surface of a slender tube with a large aspect ratio, which is used in the field of magnetic grinding. The device adds ultrasonic vibration to the traditional magnetic grinding process, so that the magnetic grinding particles produce a high-frequency impact on the inner surface of the slender tube, and adds auxiliary magnetic poles to the inner cavity of the slender tube. The auxiliary magnetic poles can form a magnetic circuit with the external magnetic poles, increasing the magnetic induction intensity per unit space. As the magnetic induction intensity per unit space increases, the grinding pressure also increases accordingly, and the material removal amount is approximately 1.5 times that of traditional magnetic grinding. The device has high grinding efficiency and large material removal volume, but the device has a complex structure, is difficult to coordinate ultrasound and magnetic force, and is expensive, making it unsuitable for actual production and processing.

[0008] Chinese patent CN2756647Y proposes an electrochemical device for the inner surface of slender tubes used in the electrical field. The device features an electrolyte tank equipped with a workpiece support connected to a workpiece support and a tube rotator. The electrolyte tank is connected to left and right cable drivers, each connected to a guide pulley. The cathode cable is connected to the right cable driver via the left cable driver, the left cable driver guide pulley, the cathode, and the right cable driver guide pulley. The cathode is equipped with a cathode positioning ring, a cathode cable connecting ring, and a polishing head. A DC power supply is connected to the cathode and anode on the upper side of the electrolyte tank. A tube rotator is also connected to the upper side of the electrolyte tank and is drive-connected to the tube rotator via a transmission chain. An electrolyte filter is located at the lower portion of the electrolyte tank and is connected to an electrolyte filter pump and an electrolyte return line. While this device offers good polishing quality, it suffers from issues such as uneven polishing, overlapping, and poor production efficiency. Furthermore, it is not suitable for slender tubes made of materials such as ceramic and quartz, limiting its application.

[0009] Chinese patent CN102211295A proposes a magnetorheological polishing device for the inner wall of a capillary tube. This device uses a piston to inject magnetorheological fluid into the capillary tube, while simultaneously activating a vibration drive system to vibrate the capillary tube and improve the fluidity of the magnetorheological fluid. After the capillary tube is completely filled with magnetorheological fluid, an electromagnet is activated to generate a magnetic field, forming a cylindrical polishing mold within the capillary tube. This mold rotates around the capillary tube and moves along the axis of the capillary tube, polishing the inner wall of the capillary tube. Although this device introduces a magnetic field and magnetorheological fluid, it uses electromagnets to drive extremely small magnetic particles to grind the tube wall, resulting in extremely low polishing efficiency.

[0010] The polishing tools of the above patents and other slender tube inner surface polishing devices are mostly polishing ropes and polishing rods, which cannot meet the polishing requirements of small-diameter slender holes. Therefore, it is urgent to provide a slender hole polishing device and method for smaller apertures to ensure polishing efficiency and polishing accuracy. Summary of the Invention

[0011] In view of the problems existing in the existing polishing methods, the present invention provides a slender tube inner wall cavitation polishing device and method that can solve the problems of limited, uneven and low efficiency of the existing slender tube workpiece inner surface polishing.

[0012] To achieve the above object, the present invention provides the following technical solutions:

[0013] A cavitation polishing device for the inner wall of a slender tube comprises a high-pressure fluid generating unit, a variable-diameter cavitation unit, a magnetically controlled displacement unit, and a work platform. Two high-pressure fluid generating units are symmetrically mounted on the left and right sides of the work platform. The left and right ends of the slender tube are connected to the high-pressure fluid generating units on each side, respectively. The high-pressure fluid generating units contain polishing fluid.

[0014] The high-pressure fluid generating unit includes a piston cylinder, a piston rod, a piston, a connector, and a piston cylinder bracket. The piston cylinder is fixedly connected to the work platform via the piston cylinder bracket; the inner end of the piston rod is fixedly connected to the piston and slidably connected to the opening at the outer end of the piston cylinder; the piston is slidably connected to the inner surface of the piston cylinder, and the cavity between the inner side of the piston and the inner surface of the piston cylinder is filled with polishing fluid; the outlet at the inner end of the piston cylinder is connected to one end of the connector, and the other end of the connector is connected to one end of the slender tube workpiece via an internal snap.

[0015] The variable diameter cavitation unit is a magnetic hollow tube located inside the slender tube. The outer diameter of the magnetic hollow tube is smaller than the inner diameter of the slender tube and larger than half of the inner diameter of the slender tube, while the inner diameter is smaller than half of the inner diameter of the slender tube. This allows the flow channel in the slender tube to form a typical Venturi tube structure, i.e., a structure with large diameters at both ends and a small diameter in the middle. The magnetically controlled displacement unit includes a magnet, a guide rail, a guide rail bracket, and a yoke. The guide rail bracket is located below the slender tube and is fixedly connected to the processing platform. The two ends of the guide rail are fixed and suspended below the slender tube by the guide rail bracket. The axial direction of the guide rail is parallel to the axial direction of the slender tube, determining the direction and range of movement of the magnet. The yoke is a circular ring structure that surrounds the slender tube. The yoke is slidably connected to the guide rail through a slot and moves axially on the guide rail. The magnet is fixed to the yoke, and the magnet pole tip is close to the slender tube.

[0016] Furthermore, there are four magnets with the same structure and are evenly distributed and fixed along the circumference of the inner wall of the yoke. Each magnet includes a magnetic pole and a magnetic pole tip, and the distance between the magnetic pole tip and the slender tube is 1-3 mm.

[0017] Furthermore, the polishing medium in the polishing liquid is selected according to the material of the slender tube: cerium oxide is selected when the slender tube material is quartz glass, aluminum oxide is selected when the slender tube material is stainless steel, and diamond powder is selected when the slender tube material is cast iron.

[0018] Furthermore, the material of the magnetic hollow tube is pure iron, carbon steel or Ru-Fe-B.

[0019] A cavitation polishing method for the inner wall of a slender tube is provided, wherein the cavitation polishing device for the inner wall of the slender tube is used for polishing, and the polishing method comprises the following steps:

[0020] Step 1: Select polishing medium according to the material of the slender tube to prepare polishing liquid, stir the prepared polishing liquid evenly and then suck it into the inner cavity of the piston cylinder, and place a magnetic hollow tube inside the slender tube.

[0021] Step 2: Connect the piston cylinder outlet to the connector through a threaded connection, and connect the two ends of the slender tube through the internal buckle of the connector. After the overall connection, check the sealing.

[0022] Step 3: Place the magnet on the yoke so that the distance between the magnetic pole tip and the outer wall of the slender tube is 1-3 mm.

[0023] Step 4: Use an external push rod to push the piston rods at both ends to move synchronously, ensuring that the polishing liquid is pushed out by the piston cylinder on one side while the polishing liquid is sucked into the piston cylinder on the other side. Under the push of the piston rod, the polishing liquid passes back and forth through the area where the magnetic hollow tube is located, causing cavitation, thereby polishing the inner surface of the slender tube.

[0024] Step 5: Move the magnet along the guide rail, and the magnetic hollow tube adsorbed on the inner surface of the slender tube will change the processing area as it moves.

[0025] Step 6. After processing, remove the slender tube and put it into an ultrasonic cleaning machine for cleaning.

[0026] Step 7: The processed slender tube is inspected and its inner surface quality reaches the expected target, and the polishing process is completed.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] 1. The present invention utilizes a typical Venturi tube structure formed by a magnetic hollow tube within a slender tube, causing the high-pressure polishing liquid flowing through the area to produce a cavitation effect. The high temperature and high pressure generated by the annihilation of cavitation bubbles are used to polish the inner wall of the slender tube. This can achieve efficient polishing of slender tubes with millimeter and submillimeter calibers and an aspect ratio greater than 100.

[0029] 2. This invention utilizes a magnetic hollow tube with controlled movement within the tube, using magnet poles to attract it. This effectively controls the cavitation effect in different regions within the tube, adjusting the cavitation intensity and polishing effect in each region to achieve uniform polishing within the tube. The novel structure of this device makes it particularly suitable for slender tubes with uneven inner wall roughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the three-dimensional structure of the device of the present invention.

[0031] Figure 2 It is a front cross-sectional view of the device of the present invention (section lines are not shown).

[0032] Figure 3 for Figure 1 Top view of the variable diameter cavitation unit.

[0033] Figure 4 for Figure 1 A partial enlarged side view of the .

[0034] In the figure: 1. Piston rod; 2. Piston cylinder; 3. Piston cylinder bracket; 4. Connector; 5. Slender tube; 6. Magnetic yoke; 7. Magnetic pole; 8. Magnetic pole tip; 9. Guide rail bracket; 10. Guide rail; 11. Working platform; 12. Piston; 13. Magnetic hollow tube. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present application is described in detail below with reference to the accompanying drawings. The following description is only exemplary and explanatory and should not have any limiting effect on the scope of protection of the present application.

[0036] like Figure 1-4 As shown, a cavitation polishing device for the inner wall of a slender tube includes a high-pressure fluid generating unit, a variable-diameter cavitation unit, a magnetically controlled displacement unit, and a work platform 11. Two high-pressure fluid generating units are symmetrically mounted on the left and right sides of the work platform 11. The left and right ends of the slender tube 5 are respectively connected to the left and right high-pressure fluid generating units. The high-pressure fluid generating units contain polishing fluid.

[0037] The high-pressure fluid generating unit includes a piston cylinder 2, a piston rod 1, a piston 12, a connector 4, and a piston cylinder bracket 3. The piston cylinder 2 is fixedly connected to the work platform 11 via the piston cylinder bracket 3; the inner end of the piston rod 1 is fixedly connected to the piston 12, and the piston rod 1 is slidably connected to the opening at the outer end of the piston cylinder 2; the piston 12 is slidably connected to the inner surface of the piston cylinder 2, and the cavity between the inner side of the piston 12 and the inner surface of the piston cylinder 2 is filled with polishing liquid; the outlet at the inner end of the piston cylinder 2 is connected to one end of the connector 4, and the other end of the connector 4 is connected to one end of the slender tube 5 workpiece via an internal snap.

[0038] The variable diameter cavitation unit is a magnetic hollow tube 13, which is located inside the slender tube 5. The outer diameter of the magnetic hollow tube 13 is smaller than the inner diameter of the slender tube 5 and larger than half of the inner diameter of the slender tube 5, and the inner diameter is less than half of the inner diameter of the slender tube 5, so that the flow channel inside the slender tube 5 forms a typical Venturi tube structure, that is, a structure with large diameters at both ends and a small diameter in the middle.

[0039] The magnetically controlled displacement unit includes a magnet, a guide rail 10, a guide rail bracket 9, and a yoke 6. The guide rail bracket 9 is located below the slender tube 5 and is fixedly connected to the work platform 11. The two ends of the guide rail 10 are fixed and suspended below the slender tube 5 by the guide rail bracket 9. The axial direction of the guide rail 10 is parallel to the axial direction of the slender tube 5, determining the direction and range of movement of the magnet. The yoke 6 is a circular structure that surrounds the slender tube 5. The yoke 6 is slidably connected to the guide rail 10 through a slot and moves axially on the guide rail 10. The magnet is fixed to the yoke 6, and the magnetic pole tip 8 of the magnet is close to the slender tube 5.

[0040] Furthermore, there are four magnets with the same structure, which are evenly distributed and fixed along the circumference of the inner wall of the yoke 6. Each magnet includes a magnetic pole 7 and a magnetic pole tip 8. The distance between the magnetic pole tip 8 and the slender tube 5 is 1-3 mm.

[0041] Furthermore, the polishing medium in the polishing liquid is selected according to the material of the slender tube 5: cerium oxide is selected when the slender tube 5 is made of quartz glass, aluminum oxide is selected when the slender tube 5 is made of stainless steel, and diamond powder is selected when the slender tube 5 is made of cast iron.

[0042] Furthermore, the material of the magnetic hollow tube 13 is pure iron, carbon steel or Ru-Fe-B.

[0043] The working principle of the present invention is as follows:

[0044] The present invention provides two high-pressure fluid generating units, and the piston cylinder 2 outlets of the high-pressure fluid generating units are arranged relatively to each other, and the slender tube 5 is located in the middle of the two high-pressure fluid generating units, ensuring that the polishing liquid in the inner cavity of the piston cylinder 2 can pass through the inner surface of the slender tube 5 in a straight-through manner during operation, reducing the pressure and speed loss along the process, and maximizing the cavitation efficiency and processing efficiency; the end of the piston rod 1 is fixedly connected to the piston 12 by a thread, ensuring that the piston rod 1 and the piston 12 can withstand a certain pressure and impact in the axial direction; the piston 12 is in sealing contact with the inner wall of the piston cylinder 2, and the piston 12 and the inner cavity of the piston cylinder 2 form a volume-variable sealed cavity for holding Polishing liquid; the piston rod 1 can move axially along the piston rod 1 in the piston cylinder 2, and then push the piston 12 at the end of the piston rod 1 to move in the same direction, changing the volume of the sealed cavity containing the polishing liquid, thereby applying pressure to the polishing liquid for processing movement, ensuring that the polishing liquid can be pressurized to work under the action of the piston rod 1, and accelerating the generation and collapse of cavitation; the outlet of the piston cylinder 2 is connected to the connecting piece 4 by a threaded connection, and the other end of the connecting piece 4 is clamped with the slender tube 5 by a threaded rotary clamping device; the two ends of the slender tube 5 are respectively clamped and fixed by a connecting piece 4 to ensure the sealing of the polishing device and to clamp the slender tube 5 to determine its position.

[0045] The high-pressure fluid generating unit contains polishing liquid. Under the action of the high-pressure fluid generating unit, the polishing liquid enters the interior of the slender tube 5 at a certain pressure. Subsequently, under the action of the variable-diameter cavitation unit, the actual flow diameter of the polishing liquid in this area changes, forming a Venturi tube structure with two-end diameters significantly larger than the middle diameter. When the polishing liquid flows through this area, a cavitation effect is generated, including the occurrence and collapse of cavitation. The cavitation collapse mainly occurs in the section after the fluid flows out of the variable-diameter cavitation unit, generating high temperature and releasing high-pressure jets, thereby driving the abrasive particles in the polishing liquid to scratch, plow and wear the inner surface of the slender tube 5 to be processed, thereby achieving polishing of the inner wall of the slender tube 5.

[0046] The magnetically controlled displacement unit ensures that the magnetic hollow tube 13 can be stably adsorbed within the slender tube 5 under the influence of the magnetic field, and its position is not affected by the high-pressure, high-speed polishing fluid. The yoke 6 contacts the guide rail 10 through the hole groove below it, and the yoke 6 can move axially on the guide rail 10. The magnet is fixed to the yoke 6 to ensure that it can move axially under the slender tube 5, thereby controlling the magnetic field range. The top surface of the magnet must be as close as possible to the slender tube 5 to ensure that the polishing fluid in the slender tube 5 is subjected to a sufficiently large magnetic field force. The magnetic field applied by the magnetic pole 7 controls the movement of the magnetic hollow tube 13, achieving the effect of controlling the cavitation polishing area.

[0047] A cavitation polishing method for the inner wall of a slender tube comprises the following steps:

[0048] Step 1: Place the pure iron magnetic hollow tube 13 inside the stainless steel slender tube 5, then mix 200 grams of polishing liquid with 50 micron alumina, 30% hydrochloric acid solution, citric acid and deionized water in a ratio of 30:10:5:55, stir the prepared polishing liquid evenly and then absorb it into the inner cavity of the piston cylinder 2.

[0049] Step 2: Connect the outlet of the piston cylinder 2 to the connector 4 through a threaded connection, and connect the connector 4 to the two ends of the slender tube 5 through the internal buckle. After the overall connection, check the sealing.

[0050] Step 3: Place the magnet on the yoke 6 so that the distance between the magnetic pole tip 8 and the outer wall of the slender tube 5 is 1-3 mm.

[0051] Step 4: Use an external push rod to push the piston rods 1 at both ends to move synchronously in the same direction, ensuring that the polishing liquid is pushed out by the piston cylinder 2 on one side while the polishing liquid is sucked into the piston cylinder 2 on the other side. Under the pushing action of the piston rod 1, the polishing liquid flushes the inner surface of the slender tube 5 back and forth for 1 hour to polish the inner surface of the slender tube 5.

[0052] Step 5: Move the magnet along the guide rail 7 to adsorb the magnetic hollow tube 13 in the slender tube 5 and adhere it to the tube wall to produce a blocking effect and change the processing area.

[0053] Step 6: After the processing is completed, stop the rotation, remove the slender tube 5, and put it into the ultrasonic cleaning machine for cleaning.

[0054] Step 7: The processed slender tube 5 is inspected, and its inner surface quality reaches the expected target, and the polishing process is completed.

[0055] The present invention uses specific examples to illustrate the principles and implementation methods of this application. The above examples are only used to help understand the method and core ideas of this application. The above is only the preferred implementation method of this application. It should be pointed out that due to the limitations of textual expression, there are objectively infinite specific structures. For ordinary technicians in this technical field, without departing from the principles of this application, they can make several improvements, modifications or changes, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the concept and technical solution of this application to other occasions without improvement, should be regarded as the scope of protection of this application.

Claims

1. A cavitation polishing device for the inner wall of a slender tube, characterized by: It comprises a high-pressure fluid generating unit, a variable diameter cavitation unit, a magnetically controlled displacement unit and a working platform (11); there are two high-pressure fluid generating units, which are symmetrically installed on the left and right sides of the working platform (11); the left and right ends of the slender tube (5) are respectively connected to the high-pressure fluid generating units on the left and right sides; the high-pressure fluid generating unit contains polishing liquid; The high-pressure fluid generating unit comprises a piston cylinder (2), a piston rod (1), a piston (12), a connecting piece (4) and a piston cylinder bracket (3); the piston cylinder (2) is fixedly connected to the working platform (11) via the piston cylinder bracket (3); the inner end of the piston rod (1) is fixedly connected to the piston (12), and the piston rod (1) is slidably connected to the opening of the outer end of the piston cylinder (2); the piston (12) is slidably connected to the inner surface of the piston cylinder (2), and polishing liquid is poured into the cavity between the inner side of the piston (12) and the inner surface of the piston cylinder (2); the outlet of the inner end of the piston cylinder (2) is connected to one end of the connecting piece (4), and the other end of the connecting piece (4) is connected to one end of the slender tube (5) workpiece through an internal snap; The variable diameter cavitation unit is a magnetic hollow tube (13), which is located inside the slender tube (5), with an outer diameter smaller than the inner diameter of the slender tube (5) and larger than half the inner diameter of the slender tube (5), and an inner diameter smaller than half the inner diameter of the slender tube (5), so that the flow channel inside the slender tube (5) forms a typical Venturi tube structure, that is, a structure with large diameters at both ends and a small diameter in the middle; The magnetic control displacement unit comprises a magnet, a guide rail (10), a guide rail bracket (9) and a yoke (6); the guide rail bracket (9) is located below the slender tube (5) and is fixedly connected to the working platform (11); both ends of the guide rail (10) are fixedly suspended below the slender tube (5) by the guide rail bracket (9), and the axial direction of the guide rail (10) is parallel to the axial direction of the slender tube (5), determining the moving direction and moving range of the magnet; the yoke (6) is a circular ring structure, surrounding the slender tube (5); the yoke (6) is slidably connected to the guide rail (10) through a hole groove, and the yoke (6) moves axially on the guide rail (10); the magnet is fixed on the yoke (6), and the magnetic pole tip (8) of the magnet is close to the slender tube (5).

2. The cavitation polishing device for the inner wall of an elongated tube according to claim 1, characterized in that: There are four magnets, each of which has the same structure and is evenly distributed and fixed along the circumference of the inner wall of the yoke (6). Each magnet includes a magnetic pole (7) and a magnetic pole tip (8), and the distance between the magnetic pole tip (8) and the slender tube (5) is 1-3 mm.

3. The cavitation polishing device for the inner wall of an elongated tube according to claim 1, characterized in that: The polishing medium in the polishing liquid is selected according to the material of the slender tube (5): cerium oxide is selected when the slender tube (5) is made of quartz glass, aluminum oxide is selected when the slender tube (5) is made of stainless steel, and diamond powder is selected when the slender tube (5) is made of cast iron.

4. The cavitation polishing device for the inner wall of an elongated tube according to claim 1, characterized in that: The material of the magnetic hollow tube (13) is pure iron, carbon steel or Ru-Fe-B.

5. A method for polishing the inner wall of a slender tube by cavitation, characterized in that: Polishing is performed using the cavitation polishing device for the inner wall of an elongated tube according to claim 1, comprising the following steps: Step 1: Select a polishing medium according to the material of the slender tube (5) to prepare a polishing liquid, stir the prepared polishing liquid evenly and then suck it into the inner cavity of the piston cylinder (2), and place a magnetic hollow tube (13) inside the slender tube (5); Step 2: Connect the outlet of the piston cylinder (2) to the connector (4) through a threaded connection, and connect the connector (4) to the two ends of the slender tube (5) through the internal buckle. After the whole connection is completed, check the sealing performance; Step 3: Place the magnet on the yoke (6) so that the distance between the magnetic pole tip (8) and the outer wall of the slender tube (5) is 1-3 mm; Step 4: The piston rods (1) at both ends are pushed by an external push rod to move synchronously, ensuring that the polishing liquid is pushed out by the piston cylinder (2) on one side while the polishing liquid is sucked into the piston cylinder (2) on the other side. The polishing liquid passes back and forth through the area where the magnetic hollow tube (13) is located under the pushing action of the piston rod (1), and cavitation occurs, thereby polishing the inner surface of the slender tube (5); Step 5: Move the magnet along the guide rail (10), and the magnetic hollow tube (13) adsorbed on the inner surface of the slender tube (5) changes the processing area as it moves; Step 6: After the processing is completed, remove the slender tube (5) and put it into an ultrasonic cleaning machine for cleaning; Step 7: The processed slender tube (5) is inspected and its inner surface quality reaches the expected target, and the polishing process is completed.

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