Magnetorheological polishing fluid for processing inner wall of stainless steel fine tube and preparation and use method thereof

Abstract

The application discloses a magnetorheological polishing liquid for processing the inner wall of a stainless steel small tube, which is prepared from the following raw materials in parts by weight: a stabilizer 1 part, abrasive grains 9-20 parts, magnetic particles 45-50 parts and water 34-45 parts. The abrasive grains are alumina powder with an average particle size of 3.5-10 microns, the average particle size of the magnetic particles is 7-10 microns, and the stabilizer is hydroxypropyl methyl cellulose. The obtained magnetorheological polishing liquid has excellent dispersion stability and is suitable for long-time use, and is suitable for the ultra-precision polishing of the inner wall of a 316L stainless steel small tube, so that a nanometer-level surface can be obtained and the processed inner wall can reach a mirror surface effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of magnetorheological polishing fluid, in particular to a magnetorheological polishing fluid for machining the inner wall of a small stainless steel tube and preparation and application of the magnetorheological polishing fluid. BACKGROUND

[0002] The inner wall of a small tube (with an inner diameter less than 10 mm and a length-diameter ratio greater than 15) cannot be effectively machined by traditional machining methods because existing polishing tools cannot completely touch the inner wall surface. Currently, the inner wall of a small tube can be polished by abrasive flow polishing or magnetic particle grinding process to remove burrs on the inner wall surface, but both methods have some deficiencies in practical application. For example, the abrasive flow polishing technology realizes effective polishing of the inner flow channel by relying on the good flow characteristics of the fluid. In the machining process, the pressure of the abrasive medium on the target workpiece surface is MPa, and the polishing effect is obvious when passing through a variable cross-section and variable curvature channel, but the polishing effect is poor on the straight channel surface. The magnetic particle grinding process uses the characteristics of a magnetic field to assist abrasive particles in polishing, and has the advantage of high self-adaptability, but when polishing a small tube with a large length-diameter ratio, the filling amount of magnetic abrasive particles is small, making it difficult to ensure the uniformity of grinding efficiency and surface quality.

[0003] Magnetorheological polishing is a non-contact polishing method that does not require the polishing tool to be in direct contact with the surface to be machined. It uses the rheological effect of magnetorheological polishing fluid under a magnetic field as a "flexible polishing head" to realize non-contact machining of the workpiece. The polishing process is precisely controlled by adjusting the magnetic field strength, polishing fluid composition, and polishing time. Since magnetorheological polishing mainly relies on the shearing action of abrasive particles for polishing, the pressure on the workpiece surface is small, and stress concentration problems are less likely to occur, making it advantageous in applications.

[0004] A general magnetorheological polishing method, as shown in Figure 1 , keeps a certain gap between the magnetic polishing head 1 and the surface to be machined 4 of the workpiece, and passes the magnetorheological polishing fluid 5 into the gap. The magnetorheological polishing fluid 5 is coated on the surface of the magnetic polishing head 1 to form a flexible polishing pad due to the stronger magnetic field closer to the polishing head. The magnetic particles 2 in the magnetorheological polishing fluid 5 are attracted to the side closer to the polishing head, and the abrasive particles 3 are squeezed to the side away from the polishing head 1, i.e., the side closer to the surface to be machined 4. The pressure of the abrasive particles 3 on the surface to be machined 4 is adjusted by adjusting the polishing gap between the polishing head 1 and the surface to be machined 4, and the relative motion is generated by the high-speed rotation of the polishing head 1 to realize polishing of the surface to be machined 4.

[0005] But due to the small caliber and long length of the small tube, the magnetic polishing head cannot effectively contact the inner wall surface, and only the magnetorheological polishing liquid can be passed into the tube, and the magnetic field is applied outside the tube to achieve the polishing purpose. Compared with the general magnetorheological polishing working condition, the magnetic field force, the magnetic field gradient distribution and the grinding force are significantly different because the magnetic field is located outside the tube and the magnetorheological polishing liquid is passed into the tube. Therefore, when the general magnetorheological polishing liquid is used for machining the inner wall of the small tube, the polishing effect is obviously poor, and even after adjustment, the polishing requirement cannot be met. Therefore, the development of the magnetorheological polishing liquid specially used for machining the inner wall of the small tube has wide application demand. SUMMARY

[0006] In order to solve the problems of the existing magnetorheological polishing liquid in machining the inner wall of the small stainless steel tube, the magnetorheological polishing liquid suitable for machining the inner wall of the small tube is developed, which can significantly improve the polishing quality of the small stainless steel tube, especially the 316L stainless steel tube, realize nanometer ultra-precision polishing, and make the surface of the machined workpiece reach mirror effect.

[0007] In order to achieve the above purpose, the magnetorheological polishing liquid for machining the inner wall of the small stainless steel tube provided by the present application comprises the following volume parts of raw material components:

[0008] 1 part of stabilizer, 9-20 parts of abrasive particles, 45-50 parts of magnetic particles and 34-45 parts of water; the abrasive particles are selected from alumina powder with an average particle size of 3.5-10 μm, the average particle size of the magnetic particles is 7-10 μm, and the stabilizer is selected from hydroxypropyl methyl cellulose.

[0009] As a limitation of the above technical solution, the average particle size of the abrasive particles is selected to be 7-10 μm, and the average particle size of the magnetic particles is selected to be 7 μm.

[0010] As a limitation of the above technical solution, the dosage ratio of the abrasive particles to the magnetic particles is 1:2.25-1:5.55.

[0011] As a limitation of the above technical solution, the magnetic particles are selected from carbonyl iron powder.

[0012] As a limitation of the above technical solution, it is suitable for 316L stainless steel small tube.

[0013] The present application is based on the particularity of the machining method of the inner wall of the small tube, and considers the types of abrasive particles, the particle size of abrasive particles, the particle size of magnetic particles, the dosage of abrasive particles and magnetic particles and the types of stabilizers, etc. from many aspects, and comprehensively considers the influences of the flow performance, the shear yield strength, the clamping capacity of the magnetic particles to the abrasive particles and the stability of the polishing liquid on the polishing effect, and optimizes the magnetorheological polishing liquid suitable for machining the inner wall of the small stainless steel tube, especially the 316L stainless steel tube.

[0014] The magnetic particles in the polishing liquid form a chain structure under the action of a magnetic field to provide machining pressure and stabilize the distribution of abrasive particles, and the content and particle size of the magnetic particles directly affect the shear yield stress of the magnetorheological fluid; the abrasive particles in the polishing liquid are tools for removing material and directly act on the surface of the workpiece being machined, and the particle size and quantity of the abrasive particles directly affect the grinding effect of the material. Increasing the proportion of magnetic particles can enhance the rigidity of the chain structure and provide higher shear force, but too high a proportion of magnetic particles will result in a relatively insufficient number of abrasive particles, leading to uneven distribution of the abrasive particles, and the magnetic particles directly contact the surface to be machined, affecting the machining effect; increasing the particle size of the magnetic particles can increase the rigidity of the chain structure, and the larger the particle size of the magnetic particles, the greater the shear yield stress, but the number density of the magnetic chains decreases, the gap between the chain structures increases, the dispersion stability is poor, the abrasive particles are unevenly distributed, and grooves are easily formed on the machined surface; on the contrary, the smaller the particle size of the magnetic particles, the weaker the rigidity of the magnetic chain, and it is difficult to provide sufficient machining pressure, resulting in a decrease in machining efficiency. Increasing the proportion of abrasive particles can increase the number of abrasive particles actually participating in grinding in a unit volume and improve the polishing efficiency, but it may reduce the stability of the chain structure, resulting in insufficient machining pressure and uneven machining; reducing the proportion of abrasive particles results in a smaller number of abrasive particles participating in grinding in a unit volume and lower polishing efficiency; increasing the particle size of the abrasive particles can improve the grinding removal efficiency, but it may result in uneven distribution of the abrasive particles in the magnetic chain, easily causing larger surface scratches and affecting the quality of the machined surface; reducing the particle size of the abrasive particles is helpful for fine polishing, but the grinding removal efficiency is low, the abrasive particles may agglomerate, reducing the uniformity of the abrasive particle distribution, and leading to uneven removal of the material on the surface of the workpiece.

[0015] The magnetorheological polishing liquid of the application can significantly enhance the stability of the polishing liquid, effectively reduce the agglomeration between solid particles during magnetorheological polishing machining, delay the sedimentation rate of the particles, improve the supporting effect of the magnetic particles on the abrasive particles, and improve the grinding and polishing effect, thereby ensuring the machining efficiency and surface quality, achieving nanoscale ultra-precision polishing, and achieving mirror surface effect on the machined workpiece surface.

[0016] The application provides a preparation method of the magnetorheological polishing liquid for machining the inner wall of a small stainless steel tube as described above, which comprises the following preparation steps:

[0017] a. Take part of deionized water, heat, and slowly add a stabilizer under stirring, fully stir until dissolved, then add the remaining deionized water, and stir uniformly to obtain a base liquid;

[0018] b. Add abrasive particles to the base liquid and stir uniformly, then add magnetic particles and continuously stir until uniformly dispersed to obtain the magnetorheological polishing liquid.

[0019] As a limitation to the above technical solution, the deionized water in step a is heated to 90-100 DEG C.

[0020] As a limitation of the above technical solution, the stirring time after adding the stabilizer in step a lasts for 0.5-1h; the stirring time after adding the abrasive particles in step b lasts for 0.5-1h, and the stirring time after adding the magnetic particles lasts for 2-3h.

[0021] The preparation of the magnetorheological polishing liquid of the present application is simple and convenient, and is beneficial to preparation and application.

[0022] In addition, the present application also provides a method for using the magnetorheological polishing liquid for processing the inner wall of a small stainless steel pipe as described above, which comprises the following steps: introducing the magnetorheological polishing liquid into the lumen of the small pipe, and keeping the magnetorheological polishing liquid continuously flowing in the lumen; placing a magnetic head outside the small pipe; and moving the small pipe and the magnetic head relative to each other, so that the magnetorheological polishing liquid completes the polishing treatment of the inner wall of the small pipe.

[0023] As a limitation of the above technical solution, the magnetic head comprises a pair of permanent magnets which are arranged in a same-pole opposite manner around the small pipe, the permanent magnets rotate relative to the small pipe, the small pipe reciprocates up and down relative to the permanent magnets, the upper end of the lumen of the small pipe is connected to the discharge port of the stirring barrel through a first peristaltic pump, the lower end of the lumen of the small pipe is connected to the return port of the stirring barrel through a second peristaltic pump, and the rotating speed of the first peristaltic pump is greater than that of the second peristaltic pump.

[0024] The magnetic field generated by the permanent magnets on the inner surface of the small pipe is 0.3T-0.4T, the rotating speed of the permanent magnets is 90rpm-100rpm, the reciprocating stroke of the small pipe is 20mm, the reciprocating speed is 1mm / s-1.2mm / s, the rotating speed of the first peristaltic pump is 65rpm-75rpm, and the rotating speed of the second peristaltic pump is 50rpm-60rpm.

[0025] As a limitation of the above technical solution, after the inner wall of the small 316L stainless steel pipe is processed, the inner wall roughness Sa is reduced to below 150nm, the inner wall can achieve a mirror effect, and a nanoscale surface is obtained.

[0026] Compared with the traditional magnetorheological polishing method, the magnetorheological liquid is introduced into the lumen of the small pipe, the magnetorheological polishing head is placed outside the lumen of the small pipe to be processed, and the relative movement of the small pipe and the magnetic head is used to complete the polishing treatment of the inner wall, so as to adapt to the particularity of the inner wall processing of the small pipe and improve the processing quality.

[0027] In summary, the present application selects and optimizes the composition of the magnetorheological polishing liquid, changes the traditional magnetorheological polishing method, i.e., the polishing head and the magnetorheological liquid are respectively placed on both sides of the surface to be processed for processing, and effectively processes the inner wall of the small 316L stainless steel pipe, which can significantly improve the polishing effect of the inner wall and improve the quality of the surface to be processed. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 Fig. 1-0 Schematic diagram of the principle of traditional permanent magnet head magnetorheological polishing;

[0029] Figure 2 Fig. 1-0 Schematic diagram of the principle of traditional permanent magnet head magnetorheological polishing;

[0030] Figure 3 Fig. 1-0 Schematic diagram of the principle of traditional permanent magnet head magnetorheological polishing;

[0031] Figure 4 Fig. 1-0 Schematic diagram of the principle of traditional permanent magnet head magnetorheological polishing;

[0032] Figure 5 Fig. 1-0 Schematic diagram of the principle of traditional permanent magnet head magnetorheological polishing;

[0033] Figure 6 Fig. 1-0 Schematic diagram of the principle of traditional permanent magnet head magnetorheological polishing;

[0034] Figure 7 Fig. 1-0 Schematic diagram of the principle of traditional permanent magnet head magnetorheological polishing;

[0035] Figure 8 Fig. 1-0 Schematic diagram of the principle of traditional permanent magnet head magnetorheological polishing;

[0036] Figure 9 Fig. 1-0 Schematic diagram of the principle of traditional permanent magnet head magnetorheological polishing;

[0037] Figure 10 Fig. 1-0 Schematic diagram of the principle of traditional permanent magnet head magnetorheological polishing;

[0038] Figure 11 Fig. 1-0 Schematic diagram of the principle of traditional permanent magnet head magnetorheological polishing;

[0039] Figure 12 Fig. 1-0 Schematic diagram of the principle of traditional permanent magnet head magnetorheological polishing;

[0040] Figure 13 Fig. 1-0 Schematic diagram of the principle of traditional permanent magnet head magnetorheological polishing;

[0041] Figure 14 Fig. 1-0 Schematic diagram of the principle of traditional permanent magnet head magnetorheological polishing;

[0042] Figure 15 Fig. 1-0 Schematic diagram of the principle of traditional permanent magnet head magnetorheological polishing;

[0043] Figure 16, Experiment 1-10 (2) White light interferometry image of inner surface of workpiece after processing;

[0044] Figure 17 , Experiment 1-10 (3) White light interferometry image of inner surface of workpiece after processing;

[0045] Figure 18 , Experiment 1-10 Relationship between the reduction of inner surface roughness Sa relative to the initial surface and the volume content of carbonyl iron powder;

[0046] Figure 19 , Experiment 1-11 (1) White light interferometry image of inner surface of workpiece after processing;

[0047] Figure 20 , Experiment 1-11 (2) White light interferometry image of inner surface of workpiece after processing;

[0048] Figure 21 , Experiment 1-11 (3) White light interferometry image of inner surface of workpiece after processing;

[0049] Figure 22 , Experiment 1-11 (4) White light interferometry image of inner surface of workpiece after processing;

[0050] Figure 23 , Experiment 1-11 Relationship between the reduction of inner surface roughness Sa relative to the initial surface and the volume content of abrasive particles;

[0051] Figure 24 , White light interferometry image (left) and mirror effect photo (right) of inner surface of workpiece after processing using the optimal formulation of magnetorheological polishing fluid;

[0052] Figure 25 , Experiment 2-1 Photograph of the stratification state of magnetorheological polishing fluid after standing;

[0053] Figure 26 , Experiment 2-2 Photograph of the stratification state of magnetorheological polishing fluid after standing;

[0054] Figure 27 , Experiment 2-3 Photographs of the stratification state of magnetorheological polishing fluid after standing (left and right) and the sedimentation caused by particle agglomeration (middle);

[0055] Figure 28 , Experiment 2-4 Photograph of the stratification state of magnetorheological polishing fluid after standing;

[0056] Figure 29 , Experiment 3-1 White light interferometry image (left) of inner surface of workpiece after processing and photograph of the stratification state of magnetorheological polishing fluid after standing (right);

[0057] Figure 30, the white light interferometer image of the inner surface of the workpiece after processing (left) and the photograph of the stratification state of the used MRF liquid after standing (right) of experiment 3-2;

[0058] Figure 31 , the white light interferometer image of the inner surface of the workpiece after processing (left) and the photograph of the stratification state of the used MRF liquid after standing (right) of experiment 3-3;

[0059] Figure 32 , the relationship between the roughness Sa of the inner surface of the workpiece after processing and the particle size of the carbonyl iron powder of experiment 4-1;

[0060] Figure 33 , the white light interferometer image of the inner surface of the workpiece after processing (left) and the photograph of the stratification state of the used MRF liquid after standing (right) of experiment 4-1;

[0061] Figure 34 , the white light interferometer image of the inner surface of the workpiece after processing (left) and the photograph of the stratification state of the used MRF liquid after standing (right) of experiment 4-2;

[0062] Figure 35 , the white light interferometer image of the inner surface of the workpiece after processing (left), the photograph of the inner surface of the workpiece (middle) and the photograph of the stratification state of the used MRF liquid after standing (right) of experiment 4-3;

[0063] Figure 36 , the relationship between the roughness Sa of the inner surface of the workpiece after processing and the particle size of the abrasive grain of experiment 4-3;

[0064] Note: all the above white light interferometer images are the area images of 834.37 μm*834.37 μm measured by 10 times lens.

[0065] Figure 37 , the white light interferometer image of the surface of the workpiece after processing using the best formula in the measuring area of 99 μm*99 μm;

[0066] Wherein: 1-polishing head; 2-magnetic particles; 3-abrasive grains; 4-surface to be processed; 5-MRF liquid; 6-rotating magnetic field. DETAILED DESCRIPTION

[0067] The technical solutions of the present application will be described below in conjunction with the embodiments, obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0068] The raw materials used in the following experiments are typical products purchased in the market. Among them, the average particle size of 3.5 μm alumina powder adopts the commercially available type ALPN high-grade alumina polishing powder, and the particle size range is mainly distributed in 2.5-5.5 μm. The average particle size of 7 μm alumina powder adopts the commercially available type ALPN high-grade alumina polishing powder, and the particle size range is mainly distributed in 6-9 μm. The average particle size of 10 μm alumina powder adopts the commercially available type ALPN high-grade alumina polishing powder, and the particle size range is mainly distributed in 9-12 μm. The average particle size of 14 μm alumina powder adopts the commercially available type ALPN high-grade alumina polishing powder, and the particle size range is mainly distributed in 13-16 μm. The average particle size of 22 μm alumina powder adopts the commercially available type ALPN high-grade alumina polishing powder, and the particle size range is mainly distributed in 21-24 μm.

[0069] The average particle size of 7 μm cerium oxide powder adopts the commercially available type KG-CeO2-007 high-quality cerium oxide polishing powder, and the particle size range is mainly distributed in 6-9 μm. The average particle size of 14 μm diamond powder adopts the commercially available type W14 high-quality diamond micro powder, and the particle size range is mainly distributed in 13-16 μm. The average particle size of 2 μm silicon carbide powder adopts the commercially available type ZM-SiC-02 high-purity silicon carbide powder, and the particle size range is mainly distributed in 1-4 μm.

[0070] The carbonyl iron powder adopts the commercially available type MCIP-HD-R-3 high-quality carbonyl iron powder. The average particle size of 3.5 μm carbonyl iron powder, the particle size range is mainly distributed in 2.5-5.5 μm; the average particle size of 7 μm carbonyl iron powder, the particle size range is mainly distributed in 6-9 μm; the average particle size of 10 μm carbonyl iron powder, the particle size range is mainly distributed in 9-12 μm; the average particle size of 14 μm carbonyl iron powder, the particle size range is mainly distributed in 13-16 μm.

[0071] The hydroxypropyl methyl cellulose adopts the commercially available type HPMC 100,000 viscosity high-quality hydroxypropyl methyl cellulose.

[0072] Example one

[0073] The polishing effects of different magnetic fluid polishing liquids and polishing methods on the inner wall of 316L stainless steel fine tube are shown in the following table 1.

[0074] Table 1, raw material composition of different magnetic fluid polishing liquids used in the experiment

[0075]

[0076]

[0077]

[0078] (1) The configuration of the magnetorheological polishing liquid is as follows:

[0079] a. Half of the volume of deionized water is heated to 90°C and added to the stirring barrel. The stirrer speed is set to 300 rpm. The stabilizer is slowly added while stirring to ensure complete dissolution of the stabilizer. After all the stabilizer is added, continue stirring for 30 min. Then, the remaining volume of deionized water at room temperature is added to the stirring barrel and stirred for 30 min until the mixture is uniform. The base liquid is obtained;

[0080] b. Add abrasive particles to the base liquid and stir for 30 min. Then, add magnetic particles. The stirrer speed is set to 550 rpm and continues to stir for 2 hours to obtain the magnetorheological polishing liquid. The stirrer speed is reduced to 300 rpm and continues to stir until use.

[0081] (2) Polishing experiment

[0082] Traditional magnetorheological polishing method: As shown in Figure 1 , the magnetic polishing head maintains a certain gap with the surface to be processed. The magnetorheological polishing liquid is introduced into the gap and coated on the surface of the magnetic polishing head to form a flexible polishing pad. Due to the stronger magnetic field gradient closer to the polishing head, the magnetic particles in the magnetorheological polishing liquid are attracted to the side close to the polishing head, and the abrasive particles are squeezed to the side away from the polishing head, i.e., the side close to the surface to be processed. Due to the influence of the magnetic field gradient, the flexible polishing pad on the side close to the polishing head is stiffer, and the side away from the polishing head is softer. By adjusting the polishing gap between the polishing head and the workpiece surface, the pressure of the abrasive particles acting on the surface to be processed is adjusted. The relative movement is generated by the high-speed rotation of the polishing head to realize the removal of materials.

[0083] Magnetorheological polishing method for small tube inner wall surface: Due to the small diameter and long length of the small tube, the magnetic polishing head cannot effectively contact the inner surface of the tube to be processed. The magnetorheological polishing liquid is introduced into the tube hole, and a magnetic field is applied on the outside to achieve the polishing purpose. Figure 2As shown, unlike the conventional magnetorheological polishing method, the magnetic field is on the outside, and the magnetic particles are closer to the inner surface of the workpiece to be processed under the action of the magnetic field gradient, while the abrasive particles are squeezed away from the side of the magnetic field. In the polishing experiment, the workpiece is placed vertically and reciprocates up and down, the magnetic head includes a pair of permanent magnets of the same polarity arranged opposite each other around the outer periphery of the small tube, the permanent magnets rotate relative to the small tube, so that the magnetic field generated by the permanent magnets on the inner surface of the small tube rotates around the workpiece at a certain speed, under the action of the first peristaltic pump, the magnetorheological polishing liquid is introduced into the workpiece tube from top to bottom and circulates, that is, the magnetorheological polishing liquid is transported from the stirring barrel to the upper end of the workpiece by the first peristaltic pump, and flows from the upper end to the lower end inside the workpiece, and is transported back to the stirring barrel from the lower end by the second peristaltic pump. Due to the rotation of the magnetic field and the axial relative motion of the magnetorheological polishing liquid, the abrasive particles produce spiral relative motion with the inner surface of the workpiece under the support of the magnetic particles, thereby realizing polishing of the inner surface of the small tube.

[0084] A device meeting the above experimental conditions was used to conduct experiments on stainless steel small tubes. Specifically, the inventors used a magnetorheological polishing device for variable-diameter large-length-ratio inner holes of small tubes in the laboratory to conduct experiments, and the specific device structure is described in detail in Chinese Patent Application 202410366779.2. The polished workpiece was a 316L stainless steel tube with an outer diameter of 10 mm, an inner diameter of 9 mm, and a length of 150 mm.

[0085] According to the polishing liquid in Table 1, the polishing experiments were conducted according to the polishing conditions in Table 2 below, and the results are as follows.

[0086] Table 2

[0087]

[0088]

[0089]

[0090]

[0091]

[0092]

[0093] Analysis of the above results: experiments 1-5, 1-9, 1-10(2), 1-11(1), 1-11(2), and 1-11(3) have good experimental results, with a roughness reduction of greater than or equal to 100 nm, and are considered to have obvious processing effects.

[0094] The optimized magnetorheological finishing fluid formula (by volume) is: 1 part of hydroxypropyl methyl cellulose, 45-50 parts of carbonyl iron powder with an average particle size of 7 μm, 9-20 parts of aluminum oxide powder with an average particle size of 3.5-7 μm, and 34-45 parts of deionized water.

[0095] The magnetorheological finishing fluid formula (by volume) most suitable for processing the inner wall of a 316L stainless steel thin tube is: 1 part of hydroxypropyl methyl cellulose, 45 parts of carbonyl iron powder with an average particle size of 7 μm, 20 parts of aluminum oxide powder with an average particle size of 7 μm, and 34 parts of deionized water.

[0096] The unified polishing process parameter settings are: wall surface magnetic induction intensity 0.35 T (double magnet in opposition), magnet rotating speed 100 rpm, workpiece up-and-down reciprocating speed 1.1 mm / s, workpiece up-and-down reciprocating stroke 20 mm, magnetorheological finishing fluid input end peristaltic pump rotating speed 70 rpm, and output end peristaltic pump rotating speed 55 rpm.

[0097] The optimal processing result is: using the formula of experiment 1-11 (3) for processing, the average roughness Sa of the unpolished area is about 310 nm, the average roughness Sa of the polished surface is about 130 nm, the roughness reduction is about 180 nm, the reduction is 58%, the processing effect is remarkable, the surface large defects are basically removed, and the processed surface reaches the mirror effect, which can clearly reflect the image, as shown in the accompanying Figure 24

[0098] Example Two

[0099] On the basis of the optimized magnetorheological finishing fluid formula, the effects of stabilizers, magnetic particle sizes, and abrasive particle sizes on the performance of the polishing fluid are explored.

[0100] (1) The magnetorheological finishing fluid is prepared according to Table 3 below, and the effects of different stabilizers on the stability of the polishing fluid are observed.

[0101] Stability experiment: the obtained magnetorheological finishing fluid is placed in a 25℃ environment, and the time from uniform mixing to obvious sedimentation and stratification of solid particles and base fluid, and the time from the magnetorheological upper layer to clear liquid are observed, and the stability of each magnetorheological finishing fluid is compared.

[0102] Table 3

[0103]

[0104] Under the condition of the same amount of other components, the magnetorheological finishing fluid prepared using hydroxypropyl methyl cellulose has better dispersion stability than the magnetorheological finishing fluid prepared using other commonly used dispersants, and does not produce non-dispersible agglomeration and precipitation, and better meets the processing and use requirements.

[0105] ​(II) The magnetorheological polishing liquid is prepared according to Table 4 below, and the influence of the particle size of the magnetic particles on the stability and polishing effect of the polishing liquid (the stability experiment and the polishing experiment are the same as above, and the experiment is carried out according to the unified polishing process parameters) is observed.

[0106] Table 4

[0107]

[0108]

[0109] In combination with the optimal processing result of Example 1, the processing results of each experiment in Table 4 are compared, as shown in the accompanying Figure 32 When the average particle size of the carbonyl iron powder is 7 μm, the processing effect is the best.

[0110] (III) The magnetorheological polishing liquid is prepared according to Table 5 below, and the influence of different abrasive particles and particle sizes on the stability and polishing effect of the polishing liquid (the stability experiment and the polishing experiment are the same as above, and the polishing experiment is carried out according to the unified conditions) is observed.

[0111] Table 5

[0112]

[0113]

[0114] In combination with the optimal processing result of Example 1, the processing results of each experiment in Table 5 are compared, and the roughness reduction of the formula greater than 100 nm is: 1-5, 1-9, 1-10 (2), 1-11 (1), (2), (3), 3-2, 4-2; as shown in the accompanying Figure 36 When the average particle size of the abrasive particles is 7 μm, a better processing effect can be obtained.

[0115] Based on the experimental results of Table 2, Table 4 and Table 5, the following conclusions are obtained.

[0116] The optimized magnetorheological polishing liquid formula (by volume) is: hydroxypropyl methyl cellulose 1 part, carbonyl iron powder 45-50 parts, aluminum oxide powder 9-20 parts, and deionized water 34-45 parts.

[0117] The optimized particle size range is: the average particle size of the carbonyl iron powder is 7-10 μm, and the average particle size of the aluminum oxide abrasive particles is 3.5-10 μm; more preferably, the average particle size of the carbonyl iron powder is 7 μm, and the average particle size of the aluminum oxide abrasive particles is 7-10 μm.

[0118] In summary, the magnetorheological polishing liquid for processing the inner wall of a small stainless steel tube has excellent dispersion stability, is suitable for long-term use, is suitable for the ultra-precision polishing of the inner wall of a 316L stainless steel small tube, can obtain a nanoscale surface, and can make the inner wall after processing reach a mirror effect.

Claims

1. A magnetorheological polishing fluid for processing the inner wall of a stainless steel fine tube, characterized by comprising: a magnetic fluid; and a dispersant. The magnetorheological polishing liquid is composed of the following components by volume fraction: The stable agent 1 part, the abrasive particle 9-20 parts, the magnetic particle 45-50 parts, and the water 34-45 parts; the abrasive particle is the alumina powder with the average particle size of 3.5-10 μm, the magnetic particle has the average particle size of 7-10 μm, the stable agent is the hydroxypropyl methyl cellulose, and the magnetic particle is the carbonyl iron powder.

2. The magnetorheological polishing fluid for machining the inner wall of a stainless steel capillary tube according to claim 1, characterized in that: The average particle size of the abrasive particle is 7-10 μm, and the average particle size of the magnetic particle is 7 μm.

3. The magnetorheological polishing fluid for machining the inner wall of a stainless steel capillary tube according to claim 1, characterized in that: The abrasive particle and the magnetic particle are used in the ratio of 1:2.25-1:5.

55.

4. The magnetorheological polishing fluid for machining the inner wall of a stainless steel capillary tube according to any one of claims 1 to 3, characterized by: The magnetorheological polishing liquid is suitable for the 316L stainless steel small tube.

5. A method for preparing the magnetorheological polishing fluid for processing the inner wall of a stainless steel capillary tube according to any one of claims 1 to 4, characterized by, The magnetorheological polishing liquid comprises the following preparation steps: a. Take part of the water, heat, and slowly add the stable agent under stirring, fully stir until dissolved, then add the remaining water, and stir uniformly to obtain the base liquid; b. Add the abrasive particle to the base liquid, stir uniformly, then add the magnetic particle, and continuously stir until uniformly dispersed to obtain the magnetorheological polishing liquid.

6. The method for preparing the magnetorheological polishing fluid for machining the inner wall of the stainless steel capillary tube according to claim 5, characterized in that: In step a, the water is heated to 90-100 ℃.

7. A method of using the magnetorheological polishing fluid for machining the inner wall of a small stainless steel tube according to any one of claims 1 to 4, characterized in that: The magnetorheological polishing liquid is introduced into the lumen of the small tube, the magnetorheological polishing liquid is kept continuously flowing in the lumen, the magnetic head is placed outside the small tube, the relative movement between the small tube and the magnetic head is realized, and the magnetorheological polishing liquid is used to polish the inner wall of the small tube.

8. The method of claim 7, wherein the magnetorheological polishing fluid is used for processing the inner wall of a stainless steel capillary tube. The magnetic head comprises a pair of same-pole opposite permanent magnets surrounding the small tube, the permanent magnets rotate relative to the small tube, the small tube reciprocates up and down relative to the permanent magnets, the upper end of the lumen of the small tube is connected to the discharge port of the stirring barrel through the first peristaltic pump, the lower end of the lumen of the small tube is connected to the return port of the stirring barrel through the second peristaltic pump, and the rotating speed of the first peristaltic pump is greater than that of the second peristaltic pump. The magnetic field generated by the permanent magnets on the inner surface of the small tube is 0.3-0.4 T, the rotating speed of the permanent magnets is 90-100 rpm, the reciprocating stroke of the small tube is 20 mm, the reciprocating speed is 1-1.2 mm / s, the rotating speed of the first peristaltic pump is 65-75 rpm, and the rotating speed of the second peristaltic pump is 50-60 rpm.

9. The method according to claim 8, wherein the magnetorheological polishing fluid for processing the inner wall of a stainless steel capillary tube is used. After the inner wall of the 316L stainless steel small tube is processed, the inner wall roughness Sa is reduced to below 150 nm, the mirror effect is achieved, and the nanoscale surface is obtained.

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