Magnetorheological polishing solution for processing inner walls of small stainless steel pipes as well as preparation method and use method of magnetorheological polishing solution

Abstract

The invention discloses a magneto-rheological polishing solution for machining the inner wall of a small stainless steel pipe. The magneto-rheological polishing solution comprises the following raw material components: 1 part of a stabilizer, 9-20 parts of abrasive particles, 45-50 parts of magnetic particles and 34-45 parts of water, alumina powder with the average particle size of 3.5-10 [mu] m is selected as the abrasive particles, the average particle size of the magnetic particles is 7-10 [mu] m, and hydroxypropyl methyl cellulose is selected as the stabilizer. The obtained magnetorheological polishing solution has excellent dispersion stability, is beneficial to long-time use, is suitable for ultra-precision polishing of the inner wall of a 316L stainless steel small pipe, and can obtain a nanoscale surface, so that the machined inner wall achieves a mirror surface effect.

Description

Technical Field

[0001] The invention relates to the technical field of magnetorheological polishing fluid, in particular to a magnetorheological polishing fluid for processing the inner wall of a stainless steel fine tube, and the preparation and application of the magnetorheological polishing fluid. Background Art

[0002] For the inner wall processing of small tubes (inner diameter less than 10mm, length to inner diameter aspect ratio greater than 15), the existing polishing tools cannot completely reach the inner wall surface, so effective processing cannot be achieved through traditional processing methods. At present, abrasive flow polishing or magnetic particle grinding process can be used to remove the burrs on the inner wall surface and polish the inner wall of small tubes, but both methods have some shortcomings in practical application. For example, abrasive flow polishing technology relies on the good flow characteristics of the fluid to achieve effective polishing of the inner flow channel. During the processing, the abrasive medium exerts a pressure of MPa on the surface of the target workpiece. The polishing effect is obvious when passing through a variable cross-section and variable curvature channel, but the polishing effect on the straight channel surface is poor; the magnetic particle grinding process uses the magnetic field characteristics to assist the abrasive particles in polishing, which has the advantage of high adaptability, but when polishing the inner hole of a small tube with a large aspect ratio, the filling amount of magnetic abrasive particles is small, and it is difficult to ensure the grinding efficiency and uniformity of the 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 processed. It uses the rheological effect of magnetorheological polishing fluid under a magnetic field as a "flexible polishing head" to achieve non-contact processing of the workpiece. The polishing process can be precisely controlled by adjusting the magnetic field intensity, polishing fluid composition and polishing time. Since magnetorheological polishing mainly relies on the shearing effect of abrasive particles for polishing, the pressure on the workpiece surface is small and stress concentration is not prone to occur, which has certain advantages in application.

[0004] General magnetorheological polishing method, refer to Figure 1 As shown, a certain gap is maintained between the magnetic polishing head 1 and the workpiece surface 4 to be processed, and the magnetorheological polishing fluid 5 is passed into the gap. Under the action of the magnetic field, it is coated on the surface of the magnetic polishing head 1 to form a flexible polishing pad. Since the magnetic field is stronger as it is closer to the polishing head, the magnetic particles 2 in the magnetorheological polishing fluid 5 are attracted to the side close to the polishing head, and the abrasive particles 3 are squeezed to the side away from the polishing head 1, that is, close to the surface 4 to be processed. The pressure of the abrasive particles 3 on the surface 4 to be processed is adjusted by adjusting the polishing gap between the polishing head 1 and the surface 4 to be processed, and the high-speed rotation of the polishing head 1 generates relative motion to achieve polishing of the surface 4 to be processed.

[0005] However, due to the small diameter and long length of the small tube, the magnetic polishing head cannot effectively contact the inner wall surface, and the magnetorheological polishing fluid can only be passed into the tube and a magnetic field can be applied to the outside of the tube to achieve the polishing purpose. Since the magnetic field is outside the tube and the magnetorheological polishing fluid is passed into the tube, the magnetic field force, magnetic field gradient distribution and grinding force are significantly different from those of general magnetorheological polishing conditions. Therefore, when general magnetorheological polishing fluid is used for processing the inner wall of small tubes, the polishing effect is significantly worse, and even after adjustment, the polishing requirements cannot be met. Therefore, the development of magnetorheological polishing fluids specifically for processing the inner wall of small tubes has a wide range of application needs. Summary of the invention

[0006] In order to solve the shortcomings of existing magnetorheological polishing fluid when processing the inner wall surface of stainless steel thin tubes, the present invention develops a magnetorheological polishing fluid suitable for processing the inner wall of thin tubes, which can significantly improve the polishing quality of stainless steel, especially the inner wall of 316L stainless steel thin tubes, realize nanometer-level ultra-precision polishing, and make the surface of the processed workpiece reach a mirror effect.

[0007] To achieve the above-mentioned purpose, the magnetorheological polishing liquid for processing the inner wall of a stainless steel fine tube provided by the present invention comprises the following raw material components in parts by volume:

[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 aluminum oxide 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 hydroxypropyl methylcellulose.

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

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

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

[0012] As a limitation of the above technical solution, it is applicable to 316L stainless steel thin tubes.

[0013] The present invention is based on the particularity of the processing method for the inner wall of a thin tube. It takes into account many aspects such as the type of abrasive particles, the particle size of abrasive particles, the particle size of magnetic particles, the amount of abrasive particles and magnetic particles, and the type of stabilizer that constitute the polishing liquid. It comprehensively considers the influence of the flow properties of the polishing liquid, the shear yield strength, the clamping ability of the magnetic particles on the abrasive particles, and the stability of the polishing liquid on the polishing effect, and optimizes the magnetorheological polishing liquid suitable for the processing of the inner wall of a thin tube of stainless steel, especially 316L stainless steel.

[0014] The magnetic particles in the polishing fluid form a chain structure under the action of the magnetic field to provide processing pressure and stabilize the distribution of abrasive particles. 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 fluid are tools for removing materials and directly act on the surface of the workpiece. The particle size and number 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 make the number of abrasive particles relatively insufficient, resulting in uneven distribution of abrasive particles, and the magnetic particles directly contact the surface to be processed, affecting the processing effect; increasing the particle size of magnetic particles can enhance the rigidity of the chain structure. The larger the particle size of magnetic particles, the greater the shear yield stress, but the density of the number of magnetic chains decreases, the gap of the chain structure increases, the dispersion stability is poor, the abrasive particles are unevenly distributed, and grooves are prone to appear on the processed surface; on the contrary, if the particle size of magnetic particles is small, the rigidity of the magnetic chain is weak, and it is difficult to provide sufficient processing pressure, resulting in a decrease in processing efficiency. Increasing the abrasive ratio can increase the number of abrasives actually involved in grinding per unit volume and improve polishing efficiency, but it may reduce the stability of the chain structure, resulting in insufficient processing pressure and uneven processing; reducing the abrasive ratio will result in fewer abrasives involved in grinding per unit volume and lower polishing efficiency; increasing the abrasive particle size can improve the grinding removal efficiency, but it will cause uneven distribution of abrasive particles in the magnetic chain, easily causing larger surface scratches and affecting the quality of the processed surface; reducing the abrasive particle size can help achieve fine polishing, but the grinding removal efficiency is low, the abrasive particles may agglomerate, reducing the uniformity of abrasive distribution and resulting in uneven removal of material on the workpiece surface.

[0015] The magnetorheological polishing fluid of the present invention can not only significantly enhance the stability of the polishing fluid, effectively reduce the agglomeration of solid particles and slow down the sedimentation rate of particles during the magnetorheological polishing process, but also improve the supporting effect of magnetic particles on abrasive particles and enhance the grinding and polishing effect, thereby ensuring the processing efficiency and surface quality, realizing nano-level ultra-precision polishing, and making the surface of the processed workpiece reach a mirror effect.

[0016] The present invention provides a method for preparing the magnetorheological polishing liquid for inner wall processing of a stainless steel fine tube as described above, comprising the following preparation steps:

[0017] a. Take some deionized water, heat it, slowly add the stabilizer while stirring, stir it thoroughly until it dissolves, then add the remaining deionized water, stir evenly to obtain the base liquid;

[0018] b. Add abrasive particles to the base liquid and stir evenly, then add magnetic particles and continue stirring until evenly dispersed to obtain magnetorheological polishing fluid.

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

[0020] As a limitation of the above technical solution, the stirring time after adding the stabilizer in step a is continued for 0.5 to 1 hour; the stirring time after adding the abrasive in step b is continued for 0.5 to 1 hour, and the stirring time after adding the magnetic particles is continued for 2 to 3 hours.

[0021] The preparation of the magnetorheological polishing liquid of the invention is simple and convenient to operate and is conducive to preparation and application.

[0022] In addition, the present invention also provides a method for using the magnetorheological polishing fluid for processing the inner wall of a stainless steel capillary tube as described above, which is to pass the magnetorheological polishing fluid into the lumen of the capillary tube and keep the magnetorheological polishing fluid flowing continuously in the lumen, place a magnetic head on the outside of the capillary tube, and use the relative movement of the capillary tube and the magnetic head to enable the magnetorheological polishing fluid to complete the polishing of the inner wall of the capillary tube.

[0023] As a limitation of the above technical solution, the magnetic head includes a pair of permanent magnets with the same poles arranged opposite to each other around the thin tube, the permanent magnets rotate relative to the thin tube, and the thin tube reciprocates up and down relative to the permanent magnets, the upper end of the tube cavity of the thin tube is connected to the discharge port of the stirring barrel via a first peristaltic pump, and the lower end of the tube cavity of the thin tube is connected to the return port of the stirring barrel via a second peristaltic pump, and the rotation speed of the first peristaltic pump is greater than the rotation speed of the second peristaltic pump;

[0024] The magnetic field size generated by the permanent magnet on the inner surface of the thin tube is 0.3T~0.4T, the rotation speed of the permanent magnet is 90rpm~100rpm, the reciprocating stroke of the thin tube is 20mm, the reciprocating speed is 1mm / s~1.2mm / s, the rotation speed of the first peristaltic pump is 65rpm~75rpm, and that of the second peristaltic pump is 50rpm~60rpm.

[0025] As a limitation of the above technical solution, after the inner wall of the 316L stainless steel fine tube is processed, the inner wall roughness Sa is reduced to below 150nm, the inner wall can achieve a mirror effect and obtain a nano-scale surface.

[0026] Compared with the traditional magnetorheological polishing method, the present invention passes magnetorheological fluid into the lumen of a small tube, and places a magnetorheological polishing head on the outside of the lumen of the workpiece to be processed, i.e., the small tube. The inner wall is polished through the relative movement of the small tube and the head to adapt to the particularity of the inner wall processing of the small tube and improve the processing quality.

[0027] In summary, the present invention screens and optimizes the composition of the magnetorheological polishing fluid, and changes the traditional magnetorheological polishing method, that is, placing the polishing head and the magnetorheological fluid on both sides of the surface to be processed for processing, thereby completing the effective processing of the inner wall of the 316L stainless steel fine tube, which can significantly improve the inner wall polishing effect and improve the quality of the surface to be processed. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 , Schematic diagram of the principle of magnetorheological polishing of traditional permanent magnetic head;

[0029] Figure 2 , schematic diagram of the principle of magnetorheological polishing of the inner wall of a small tube;

[0030] Figure 3 , schematic diagram of processing in stages;

[0031] Figure 4 , Experiment 1-0: White light interference image of the inner surface of the workpiece after processing (left) and a photo of the upper layer of the magnetorheological polishing fluid after it was left to stand for 3 hours (right);

[0032] Figure 5 , Experiment 1-1: Comparison photos of the inner surface of the workpiece after processing (the lower sample in the figure) and the inner surface of the unprocessed section (the upper sample in the figure);

[0033] Figure 6 , Photos of the inner surface of the workpiece after processing in Experiment 1-2;

[0034] Figure 7 , White light interference image (left) and super depth of field image (right) of the inner surface of the workpiece after processing in Experiment 1-3;

[0035] Figure 8 , Experiment 1-4: Super depth of field image of the inner surface of the workpiece after processing;

[0036] Fig. 9 , White light interference image (left) and super depth of field image (right) of the inner surface of the workpiece after processing in Experiment 1-5;

[0037] Fig.10 , Experiment 1-5: Relationship between workpiece inner surface roughness Sa and processing time;

[0038] Fig.11 , Experiment 1-6 White light interference images of the inner surfaces of both sides of the workpiece after processing;

[0039] Fig.12 , Experiment 1-7 White light interference image of the inner surface of the workpiece after processing;

[0040] Fig.13 , Experiment 1-8 White light interference image of the inner surface of the workpiece after processing;

[0041] Fig.14 , Experiment 1-9: White light interference image of the inner surface of the workpiece after processing;

[0042] Fig.15 , Experiment 1-10 (1) White light interference image of the inner surface of the workpiece after processing;

[0043] Fig.16, Experiment 1-10(2) White light interference image of the inner surface of the workpiece after processing;

[0044] Fig.17 , Experiment 1-10 (3) White light interference image of the inner surface of the workpiece after processing;

[0045] Fig.18 , Experiment 1-10: Relationship between the decrease of the workpiece inner surface roughness Sa relative to the initial surface and the volume content of carbonyl iron powder;

[0046] Fig.19 , Experiment 1-11 (1) White light interference image of the inner surface of the workpiece after processing;

[0047] Fig. 20 , Experiment 1-11(2) White light interference image of the inner surface of the workpiece after processing;

[0048] Fig.21 , Experiment 1-11(3) White light interference image of the inner surface of the workpiece after processing;

[0049] Fig. 22 , Experiment 1-11(4) White light interference image of the inner surface of the workpiece after processing;

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

[0051] Fig.24 , White light interference image of the inner surface of the workpiece after processing with the optimal formula magnetorheological polishing fluid (left) and the mirror effect photo of the inner surface of the workpiece (right);

[0052] Fig.25 , Experiment 2-1 Photo of the stratified state of the magnetorheological polishing fluid after standing;

[0053] Fig.26 , Experiment 2-2 Photo of the stratified state of the magnetorheological polishing fluid after standing;

[0054] Fig. 27 , Experiment 2-3: Photos of the stratified state of the magnetorheological polishing fluid after standing (left and right) and the precipitation caused by particle agglomeration (middle);

[0055] Fig.28 , Experiment 2-4: Photo of the stratified state of the magnetorheological polishing fluid after standing;

[0056] Fig.29 , Experiment 3-1: White light interference image of the inner surface of the workpiece after processing (left) and a photo of the stratified state of the magnetorheological polishing fluid after standing still (right);

[0057] Fig.30, Experiment 3-2: White light interference image of the inner surface of the workpiece after processing (left) and a photo of the stratified state of the magnetorheological polishing fluid after standing still (right);

[0058] Fig.31 , Experiment 3-3: White light interference image of the inner surface of the workpiece after processing (left) and a photo of the stratified state of the magnetorheological polishing fluid after standing still (right);

[0059] Fig.32 , Table 4 Relationship between the decrease of the roughness Sa of the inner surface of the workpiece after experimental processing relative to the initial surface and the particle size of carbonyl iron powder;

[0060] Fig.33 , Experiment 4-1: White light interference image of the inner surface of the workpiece after processing (left) and a photo of the stratified state of the magnetorheological polishing fluid after standing still (right);

[0061] Fig.34 , Experiment 4-2: White light interference image of the inner surface of the workpiece after processing (left) and a photo of the stratified state of the magnetorheological polishing fluid after standing still (right);

[0062] Fig.35 , Experiment 4-3: White light interference image of the inner surface of the workpiece after processing (left), actual photo of the inner surface of the workpiece (middle), and photo of the stratified state of the magnetorheological polishing fluid after standing (right);

[0063] Fig.36 , Table 5 Relationship between the decrease of the roughness Sa of the inner surface of the workpiece after experimental processing relative to the initial surface and the abrasive particle size;

[0064] Note: All the above white light interference images are images of an area of ​​834.37μm*834.37μm measured by a 10x lens.

[0065] Fig.37 , White light interference image of the workpiece surface after processing using the optimal formula at a measurement area of ​​99μm*99μm;

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

[0067] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

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

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

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

[0071] The hydroxypropyl methylcellulose adopts high-quality hydroxypropyl methylcellulose with a commercially available model of HPMC 100,000 viscosity.

[0072] Embodiment 1

[0073] Table 1 below shows the polishing effects of different magnetorheological polishing fluids and polishing methods on the inner wall of 316L stainless steel thin tubes.

[0074] Table 1. Raw material composition of magnetorheological polishing fluid used in different experiments

[0075]

[0076]

[0077]

[0078] (I) The configuration of magnetorheological polishing fluid is as follows:

[0079] a. Take half of the volume of deionized water, heat it to 90°C, add it to the stirring barrel, turn on the stirrer and set the speed to 300rpm, slowly add the stabilizer while stirring to ensure that the stabilizer is completely dissolved. After all the stabilizer is added, continue stirring for 30 minutes, then add the remaining volume of room temperature deionized water to the stirring barrel, stir for 30 minutes until it is evenly mixed, and obtain the base liquid;

[0080] b. Add abrasive particles to the base liquid, stir for 30 minutes, then add magnetic particles, set the stirrer speed to 550 rpm, and continue stirring for 2 hours to obtain magnetorheological polishing liquid, reduce the stirrer speed to 300 rpm, and continue stirring until use.

[0081] (B) Polishing experiment

[0082] Traditional magnetorheological polishing method: Figure 1 As shown, the magnetic polishing head maintains a certain gap with the surface to be processed, and the magnetorheological polishing fluid is introduced into the gap. Under the action of the magnetic field, it is coated on the surface of the magnetic polishing head to form a flexible polishing pad. Since the magnetic field gradient is stronger the closer to the polishing head, the magnetic particles in the magnetorheological polishing fluid are attracted to the side close to the polishing head, and the abrasive particles are squeezed to the side away from the polishing head, that is, the side close to the surface to be processed. Due to the influence of the magnetic field gradient, the flexible polishing pad close to the polishing head has greater rigidity and is softer on the side away from the polishing head. The pressure of the abrasive particles on the surface to be processed is adjusted by adjusting the polishing gap between the polishing head and the workpiece surface, and the high-speed rotation of the polishing head generates relative motion to achieve material removal.

[0083] Magnetorheological polishing of the inner wall of a small tube: 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 fluid is passed into the tube hole and a magnetic field is applied on the outside to achieve the polishing purpose. Figure 2As shown, unlike the traditional 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 to the side away from the magnetic field. In this polishing experiment, the workpiece is placed vertically and reciprocates up and down. The magnetic head includes a pair of permanent magnets with the same poles arranged opposite to each other around the outer periphery of the thin tube. The permanent magnet rotates relative to the thin tube, so that the magnetic field generated by the permanent magnet on the inner surface of the thin tube rotates around the workpiece at a certain speed. Under the action of the first peristaltic pump, the magnetorheological polishing liquid is passed from top to bottom into the tube of the workpiece to be processed and circulates, that is, the magnetorheological polishing liquid is transported from the stirring barrel to the upper end of the workpiece through the first peristaltic pump, flows from the upper end to the lower end inside the workpiece, and is transported back to the stirring barrel from the lower end through the second peristaltic pump. Due to the rotation of the magnetic field and the axial relative movement of the magnetorheological polishing liquid, the abrasive particles produce a spiral relative movement with the inner surface of the workpiece under the support of the magnetic particles, thereby achieving polishing of the inner surface of the thin tube.

[0084] The device that meets the above experimental conditions was used to conduct experiments on stainless steel thin tubes. Specifically, the inventor used a magnetorheological polishing device for thin tubes with variable diameter and large aspect ratio in this laboratory to conduct experiments. The specific device structure is detailed in Chinese patent application: 202410366779.2. The polished workpiece is 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] Corresponding to the polishing liquid in Table 1, a polishing experiment was carried out according to the polishing conditions in Table 2 below. The results are as follows.

[0086] Table 2

[0087]

[0088]

[0089]

[0090]

[0091]

[0092]

[0093] Analyzing the results in the above table: Experiments 1-5, 1-9, 1-10(2), 1-11(1), 1-11(2), and 1-11(3) have good experimental results, with the roughness reduction being greater than or equal to 100nm, and it is believed that they have obvious processing effects.

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

[0095] The formula of magnetorheological polishing fluid most suitable for processing the inner wall of 316L stainless steel fine tube (by volume) is: 1 part of hydroxypropyl methylcellulose, 45 parts of carbonyl iron powder with average particle size of 7μm, 20 parts of alumina powder with average particle size of 7μm, and 34 parts of deionized water.

[0096] The unified polishing process parameters were set as follows: wall magnetic induction intensity 0.35 T (double magnets facing each other), magnet rotation speed 100 rpm, workpiece up and down reciprocating speed 1.1 mm / s, workpiece up and down reciprocating stroke 20 mm, peristaltic pump speed 70 rpm at the input end of magnetorheological polishing fluid, and peristaltic pump speed 55 rpm at the output end.

[0097] The best processing result is: the average roughness Sa of the unpolished area is about 310nm when the recipe of experiment 1-11 (3) is used for processing. The average surface roughness Sa after polishing is about 130nm. The roughness reduction is about 180nm, a reduction of 58%. The processing effect is significant. The larger surface defects are basically removed. The surface after processing has a mirror effect and can clearly reflect the image. Fig.24 shown.

[0098] Embodiment 2

[0099] Based on the optimized formula of magnetorheological polishing fluid, the effects of stabilizer, magnetic particle size and abrasive particle size on the performance of polishing fluid are explored.

[0100] (I) Prepare magnetorheological polishing fluid according to Table 3 below and observe the effect of different stabilizers on the stability of the polishing fluid.

[0101] Stability experiment: The obtained magnetorheological polishing fluid was placed in an environment of 25°C, and the time from the uniformly mixed state to the solid particles and the base liquid producing obvious sedimentation and stratification and the magnetorheological upper layer producing clear liquid was observed to compare the stability of each magnetorheological polishing fluid.

[0102] Table 3

[0103]

[0104] Under the same conditions of other component dosages, the magnetorheological polishing fluid prepared with hydroxypropyl methylcellulose has better dispersion stability than the magnetorheological polishing fluid prepared with other commonly used dispersants, and will not produce non-redispersible agglomerates and precipitation, and can better meet the processing and use requirements.

[0105] (ii) Prepare magnetorheological polishing fluid according to Table 4 below, and observe the influence of magnetic particle size on the stability of polishing fluid and polishing effect (stability experiment and polishing experiment are the same as above, and the experiment is carried out according to unified polishing process parameters).

[0106] Table 4

[0107]

[0108]

[0109] Combined with the optimal processing results of Example 1, the processing results of each experiment in Table 4 are compared, as shown in the attached Fig.32 As shown, the processing effect is best when the average particle size of carbonyl iron powder is 7μm.

[0110] (III) Prepare magnetorheological polishing fluid according to Table 5 below, and observe the influence of different abrasive particles and particle sizes on the stability of the polishing fluid and the polishing effect (the stability experiment and polishing experiment are the same as above, and the polishing experiment conditions are unified).

[0111] Table 5

[0112]

[0113]

[0114] Combining the optimal processing results of Example 1 and comparing the processing results of each experiment in Table 5, the formulas with a roughness reduction greater than 100 nm are: 1-5, 1-9, 1-10 (2), 1-11 (1), (2), (3), 3-2, 4-2; as shown in the attached Fig.36 As shown in the figure, better processing effect can be obtained when the average particle size of the abrasive is 7μm.

[0115] Considering the experimental results in Table 2, Table 4 and Table 5, the following conclusions are obtained.

[0116] The optimized magnetorheological polishing fluid formula (by volume) is: 1 part of hydroxypropyl methylcellulose, 45-50 parts of carbonyl iron powder, 9-20 parts of alumina powder, and 34-45 parts of deionized water.

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

[0118] In summary, the magnetorheological polishing fluid for processing the inner wall of a stainless steel fine tube of the present invention has excellent dispersion stability, is conducive to long-term use, is suitable for ultra-precision polishing of the inner wall of a 316L stainless steel fine tube, can obtain a nano-scale surface, and make the processed inner wall achieve a mirror effect.

Claims

1. A magnetorheological polishing fluid for inner wall processing of stainless steel fine tubes, characterized in that: The magnetorheological polishing liquid comprises the following raw material components in parts by volume: 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 aluminum oxide 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 hydroxypropyl methylcellulose.

2. The magnetorheological polishing liquid for inner wall processing of stainless steel fine tubes according to claim 1, characterized in that: The average particle size of the abrasive particles is 7 to 10 μm, and the average particle size of the magnetic particles is 7 μm.

3. The magnetorheological polishing liquid for inner wall processing of stainless steel fine tubes according to claim 1, characterized in that: The ratio of the abrasive particles to the magnetic particles is 1:2.25 to 1:5.

55.

4. The magnetorheological polishing liquid for inner wall processing of stainless steel fine tubes according to claim 1, characterized in that: The magnetic particles are carbonyl iron powder.

5. The magnetorheological polishing liquid for inner wall processing of stainless steel fine tubes according to any one of claims 1 to 4, characterized in that: Suitable for 316L stainless steel small tubes.

6. A method for preparing a magnetorheological polishing liquid for inner wall processing of a stainless steel thin tube as claimed in any one of claims 1 to 5, characterized in that: The method comprises the following preparation steps: a. Take some water, heat it, slowly add the stabilizer while stirring, stir it thoroughly until it dissolves, then add the remaining water and stir evenly to obtain the base liquid; b. Add abrasive particles to the base liquid and stir evenly, then add magnetic particles and continue stirring until evenly dispersed to obtain magnetorheological polishing fluid.

7. The method for preparing the magnetorheological polishing liquid for inner wall processing of stainless steel fine tubes according to claim 6, characterized in that: In step a, water is heated to 90-100°C.

8. A method for using the magnetorheological polishing liquid for inner wall processing of a stainless steel thin tube as claimed in any one of claims 1 to 5, characterized in that: The magnetorheological polishing liquid is introduced into the lumen of the thin tube, and the magnetorheological polishing liquid is kept flowing in the lumen. The magnetic head is placed on the outside of the thin tube. Through the relative movement of the thin tube and the magnetic head, the magnetorheological polishing liquid completes the polishing process of the inner wall of the thin tube.

9. The method for using the magnetorheological polishing fluid for inner wall processing of stainless steel fine tubes according to claim 8, characterized in that: The magnetic head includes a pair of permanent magnets with the same poles arranged opposite to each other around the thin tube, the permanent magnets rotate relative to the thin tube, and the thin tube reciprocates up and down relative to the permanent magnets. The upper end of the tube cavity of the thin tube is connected to the discharge port of the stirring barrel via a first peristaltic pump, and the lower end of the tube cavity of the thin tube is connected to the return port of the stirring barrel via a second peristaltic pump. The rotation speed of the first peristaltic pump is greater than the rotation speed of the second peristaltic pump. The magnetic field size generated by the permanent magnet on the inner surface of the thin tube is 0.3T~0.4T, the rotation speed of the permanent magnet is 90rpm~100rpm, the reciprocating stroke of the thin tube is 20mm, the reciprocating speed is 1mm / s~1.2mm / s, the rotation speed of the first peristaltic pump is 65rpm~75rpm, and that of the second peristaltic pump is 50rpm~60rpm.

10. The method for using the magnetorheological polishing fluid for inner wall processing of stainless steel fine tubes according to claim 8, characterized in that: After being used for inner wall processing of 316L stainless steel thin tubes, the inner wall roughness Sa is reduced to below 150nm, achieving a mirror effect and obtaining a nano-level surface.

Images