Water-based two-phase flow polishing medium, polishing method, and method for determining shear thinning characteristics

Abstract

The present invention belongs to the technical field of the precision machining of metal components and parts, and provides a water-based two-phase flow polishing medium, a polishing method, and a method for determining shear thinning characteristics. The water-based two-phase flow polishing medium comprises, in parts by weight: 89.1-94% of deionized water, 2-6% of silicon carbide abrasive particles and 2.4-3.3% of a dispersing agent. In the present invention, by improving the shear thinning characteristics of the water-based two-phase flow polishing medium, the surface roughness of a molded internal flow passage after being polished can reach Ra1.6 μm or below compared with the prior art; and the percentage reduction in the difference between the roughness of the upper and lower surfaces of the internal flow passage molded by means of additive manufacturing after the upper and lower surfaces are polished, compared with the difference between the roughness of the original upper and lower surfaces, and the percentage reduction in the difference between the roughness of the inner and outer sides at a bend after the inner and outer sides are polished, compared with the difference between the roughness of the original inner and outer sides are both greater than 60%.

Description

Water-based two-phase flow polishing media, polishing methods and methods for determining shear thinning characteristics Technical Field

[0001] This specification relates to the field of precision machining technology for metal parts, specifically to a water-based two-phase flow polishing medium, a polishing method, and a method for measuring shear thinning characteristics. Background Technology

[0002] Parts with intricate and complex internal flow channel structures have extremely wide applications in industrial fields, especially components related to fluid power systems. These components often possess complex internal cavity structures such as micro-channels, deep orifices, and connections between micro-channels and deep orifices, serving functions such as fluid transport, exchange, or application of hydraulic pressure. Examples include various engine fuel nozzles, heat exchangers, hydraulic components, and oil circuit control throttles. Processing technologies for machining intricate and complex internal flow channels include precision machining, femtosecond / water-conducting / long-pulse laser processing, electrical discharge machining, and additive manufacturing (3D printing). Except for additive manufacturing, other single-process machining of intricate and complex internal flow channel structures is relatively simple and has a small length-to-diameter ratio, requiring the combination of welding and other combined processes to machine such structures. Precision machining of intricate internal flow channels can lead to problems such as burrs, sharp corners, or tool-joint steps; femtosecond laser machining can result in adhered residue particles and surface "step" effects on the surface of internal flow channels; water-guided / long-pulse laser and EDM machining can produce remelted layers on the surface of internal flow channels. Additive manufacturing (3D printing) is a technology that discretizes complex three-dimensional part models into two-dimensional structures and then stacks them layer by layer to form a complete product. It makes it possible to integrally form complex, intricate internal flow channel parts, and therefore its application in the industrial field is increasing. However, due to the inherent characteristics of additive manufacturing technology, such as temperature gradients and layer-by-layer forming, the surface of internal flow channels in parts may have semi-sintered or adhered powder particles and surface "step" effects.

[0003] Machined burrs, femtosecond laser-processed internal flow channels with sintered particles, and additive manufacturing internal flow channel surface powder all affect the performance and safety of parts. When the fluid flowing into the internal flow channel rubs against the surface at high speed, causing burrs, adhering residue particles, or powder to fall off, they become excess material that spreads with the fluid, either blocking oil passages or causing mechanical wear failures, thus leading to major safety accidents. Rough internal surfaces are prone to becoming fatigue crack sources during long-term use, and in high-temperature oil circuit systems, they are also prone to carbon buildup. Tool marks, sharp corners, or tool steps on the surface of machined flow channels, as well as the "step" phenomenon on the surface of internal flow channels processed by femtosecond laser and additive manufacturing, can all cause turbulence, eddies, and a sharp increase in fluid friction resistance during fluid movement, even causing fluid runaway, vibration, and reduced part lifespan. Rough surfaces can also generate numerous cavitation bubbles in the fluid, affecting combustion and hydraulics, and even causing cavitation corrosion. The remelted layer formed on the surface of internal flow channels after water-guided / long-pulse laser and EDM machining is prone to microcracks, leading to premature failure of parts operating under complex conditions. Therefore, appropriate surface finishing techniques are needed to eliminate these adverse effects in order to meet product performance requirements. Summary of the Invention

[0004] In view of this, embodiments of this specification provide a water-based two-phase flow polishing medium, a polishing method, and a method for measuring shear thinning characteristics, in order to solve the problem that non-uniform polishing, or even dimensional deviations and damage, can easily occur at the bends of the flow channel and at the upper and lower surfaces with large differences in initial roughness when smoothing fine and complex internal flow channels.

[0005] The technical solution of the present invention is as follows: a water-based two-phase flow polishing medium, which, by weight, comprises 89.1% to 94% deionized water, 2% to 6% silicon carbide abrasive particles, and 2.4% to 3.3% dispersant.

[0006] Furthermore, the dispersant includes one or more combinations of polyvinyl alcohol, sodium silicate, and polystyrene.

[0007] Furthermore, the dispersant includes polyvinyl alcohol, sodium silicate, and polystyrene, wherein polyvinyl alcohol is 0.7%–1%, sodium silicate is 1.2%–1.5%, and polystyrene is 0.5%–0.8%.

[0008] Furthermore, the water-based two-phase flow polishing medium also includes 0.2%–0.3% tackifier, 0.05%–0.1% rust inhibitor, 0.4%–0.5% defoamer, 0.4%–0.5% lubricant, and 0.1%–0.2% antifreeze.

[0009] The present invention also includes a polishing method using the above-mentioned water-based two-phase flow polishing medium. The polishing method includes:

[0010] Step 1: Prepare water-based two-phase flow polishing media;

[0011] Step 2: Place the prepared water-based two-phase flow polishing medium into the material cylinder, adjust the pressure to the first set value, and start the plunger pump to polish the workpiece.

[0012] Step 3: Stop processing when the flow rate of the polishing operation reaches the second set value;

[0013] Step 4: Clean and dry the polished workpiece.

[0014] Further, step one: the specific preparation of the water-based two-phase flow polishing medium is as follows: the order of adding each component in the water-based two-phase flow polishing medium is as follows: deionized water, silicon carbide abrasive particles, dispersant, thickener, rust inhibitor, defoamer, lubricant and antifreeze.

[0015] Furthermore, the first setting value is 45-55 MPa; the second setting value is 45%-55%.

[0016] Furthermore, step four: cleaning and drying the polished workpiece specifically involves:

[0017] The water-based two-phase flow polishing medium inside the micro-channels of the polished workpiece is blown out using a high-pressure air gun, then ultrasonically immersed and cleaned, rinsed several times with pure water, and then dried.

[0018] This invention also provides a method for determining shear thinning characteristics, which measures the shear thinning characteristics of the above-mentioned water-based two-phase flow polishing medium. The method for determining shear thinning characteristics includes the following steps:

[0019] Measure the pressure value p1 of the water-based two-phase flow polishing medium at the center of the inner channel of the workpiece and the pressure value p2 of the water-based two-phase flow polishing medium near the wall of the inner channel.

[0020] The pressure gradient of the flow field from the center of the inner channel to the near wall is calculated using the formula (p1-p2) / r, where r is the radius of the inner channel.

[0021] When the pressure gradient of the flow field is greater than the first set threshold, the shear thinning characteristics of the water-based two-phase flow polishing medium are significantly measured.

[0022] Furthermore, a piezoelectric sensor probe was used to measure the pressure value p1 of the water-based two-phase flow polishing medium at the center of the inner flow channel.

[0023] Furthermore, a piezoelectric sensor contact is attached to the outer wall of the inner flow channel to measure the pressure value p2 of the water-based two-phase flow polishing medium near the wall of the inner flow channel of the workpiece.

[0024] This invention also provides a method for determining shear thinning characteristics, which measures the shear thinning characteristics of the above-mentioned water-based two-phase flow polishing medium. The method for determining shear thinning characteristics includes the following steps:

[0025] Measure the surface roughness R' of the inner side of the flow channel bend in the workpiece. a1 The original surface roughness Ra1 on the inner side of the inner flow channel bend, and the current surface roughness R' on the outer side of the inner flow channel bend. a2 The original surface roughness Ra2 on the outer side of the inner flow channel bend of the workpiece;

[0026] The formula calculates the percentage reduction in the roughness difference between the inner and outer sides of the turn after polishing compared to the original roughness difference.

[0027] When the percentage reduction of the roughness difference between the inner and outer sides of the turn after polishing compared to the original roughness difference between the inner and outer sides of the turn is greater than the second threshold, the shear thinning characteristics of the water-based two-phase flow polishing medium are significantly measured.

[0028] This invention also provides a method for determining shear thinning characteristics, which measures the shear thinning characteristics of the above-mentioned water-based two-phase flow polishing medium. The method for determining shear thinning characteristics includes the following steps:

[0029] Polishing operations were performed using a shear-thinned water-based two-phase flow polishing medium and an unshear-thinned water-based two-phase flow polishing medium, respectively. Under the same polishing time and the same polishing effect, the proportion of the first driving pressure difference reduction and the proportion of the second driving pressure difference reduction were obtained.

[0030] The proportion of the first driving pressure difference reduction is compared with the proportion of the second driving pressure difference reduction. When the proportion of the first driving pressure difference reduction is greater than the proportion of the second driving pressure difference reduction, the shear thinning characteristics of the shear-thinned water-based two-phase flow polishing medium are determined to be more significant than those of the unshear-thinned water-based two-phase flow polishing medium.

[0031] This invention also provides a method for determining shear thinning characteristics, which measures the shear thinning characteristics of the above-mentioned water-based two-phase flow polishing medium. The method for determining shear thinning characteristics includes the following steps:

[0032] Polishing operations were performed using shear-thinned and unshear-thinned water-based two-phase flow polishing media respectively. Under the same polishing effect, the first processing time and the second processing time were obtained.

[0033] Comparing the first processing time with the second processing time, when the first processing time is shorter than the second processing time, the shear thinning characteristics of the shear-thinned water-based two-phase flow polishing medium are found to be more significant than those of the unshear-thinned water-based two-phase flow polishing medium.

[0034] Compared with the prior art, the beneficial effects that can be achieved by the above-mentioned at least one technical solution adopted in the embodiments of this specification include at least the following: By improving the shear thinning characteristics of the water-based two-phase flow polishing medium, the present invention can achieve a surface roughness of Ra1.6μm or less after polishing of the inner flow channel compared with the prior art. The percentage reduction of the roughness difference between the upper and lower surfaces after polishing of the inner and lower surfaces of the additive manufacturing inner flow channel compared with the original roughness difference between the upper and lower surfaces and the percentage reduction of the roughness difference between the inner and outer surfaces after polishing of the inner and outer surfaces of the bend compared with the original roughness difference between the inner and outer surfaces are both greater than 60%. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 is a comparison diagram of the shear thinning effect principle in the present invention and the prior art;

[0037] Figure 2 is a flowchart of an embodiment of the present invention;

[0038] Figure 3 is a photograph of the workpiece after polishing according to Embodiment 1 of the present invention;

[0039] Figure 4 is a comparison view of the upper and lower surfaces of the workpiece in Embodiment 2 of the present invention. Detailed Implementation

[0040] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0041] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0042] This invention provides a water-based two-phase flow polishing medium, which, by weight, comprises 89.1% to 94% deionized water, 2% to 6% silicon carbide abrasive particles, and 2.4% to 3.3% dispersant.

[0043] The dispersant in the embodiments of the present invention can significantly improve the shear thinning characteristics, and can achieve a surface roughness of Ra1.6μm or less after polishing of the inner flow channel. The percentage reduction of the roughness difference between the upper and lower surfaces after polishing of the inner flow channel after additive manufacturing compared with the original roughness difference between the upper and lower surfaces, and the percentage reduction of the roughness difference between the inner and outer surfaces after polishing of the inner and outer surfaces of the bend compared with the original roughness difference between the inner and outer surfaces are both greater than 60%.

[0044] Specifically, the dispersant includes one or more combinations of polyvinyl alcohol, sodium silicate, and polystyrene.

[0045] The rheological properties of the original polishing medium were detected using a rheometer. The results showed that its viscosity did not exhibit significant shear thinning with increasing shear rate; the viscosity decay rate (the amount of viscosity decrease per unit increase in shear rate) was 0.035–0.2 dB / dec. When polyvinyl alcohol, sodium silicate, and polystyrene were used as dispersants, the viscosity decay rate was approximately 20–50 dB / dec. Since a viscosity decay rate exceeding 20 dB / dec is considered to indicate significant shear properties, it can be concluded that polyvinyl alcohol, sodium silicate, and polystyrene all have significant shear thinning effects when used as dispersants.

[0046] The magnitude of shear thinning characteristics can be characterized by the pressure gradient of the flow field from the center of the inner channel to the near-wall surface when the shear-thinning fluid flows through the inner channel, i.e., the pressure difference between the flow field at the center of the inner channel and the flow field near the wall surface per unit distance along the pipe normal direction. The larger the pressure gradient from the center of the inner channel to the near-wall surface, the more significant the shear thinning effect. Referring to Figure 1 (the left side is the prior art, and the right side is the present invention), the pressure gradient expression is (p1-p2) / r, where p2 is the pressure value of the water-based two-phase flow polishing medium near the wall surface of the inner channel, p1 is the pressure value of the water-based two-phase flow polishing medium at the center of the inner channel, and r is the radius of the inner channel.

[0047] Good shear thinning effects can be obtained by adding polyvinyl alcohol, sodium silicate, or polystyrene alone to the polishing medium. When polyvinyl alcohol is added alone at a concentration of 7–10 g / L, the shear thinning effect is significant, with a pressure gradient of 0.66–0.71 MPa / mm; when sodium silicate is added alone at a concentration of 12–15 g / L, the shear thinning effect is significant, with a pressure gradient of 0.63–0.69 MPa / mm; and when polystyrene is added alone at a concentration of 5–8 g / L, the shear thinning effect is significant, with a pressure gradient of 0.7–0.73 MPa / mm.

[0048] Adding any two of polyvinyl alcohol (PVA), sodium silicate, or polystyrene to the polishing medium can achieve good shear thinning effects, with the combination of two substances showing better shear thinning than adding a single substance. When PVA and sodium silicate are added in combination, a concentration of 7–10 g / L for PVA and 12–15 g / L for sodium silicate results in better shear thinning than adding either substance alone, with a pressure gradient of 0.75–0.79 MPa / mm. Similarly, when PVA and polystyrene are added in combination, a concentration of 7–10 g / L for PVA and 5–8 g / L for polystyrene results in a pressure gradient of 0.81–0.83 MPa / mm. Likewise, when sodium silicate and polystyrene are added in combination, a concentration of 12–15 g / L for sodium silicate and 5–8 g / L for polystyrene results in a pressure gradient of 0.83–0.85 MPa / mm.

[0049] The best shear thinning effect can be obtained when polyvinyl alcohol, sodium silicate, or polystyrene is added to the polishing medium. When polyvinyl alcohol, sodium silicate, and polystyrene are added in combination, the optimal shear thinning effect is achieved when the polyvinyl alcohol content is 7-10 g / L (0.7%-1% by weight), the sodium silicate content is 12-15 g / L (1.2%-1.5% by weight), and the polystyrene content is 5-8 g / L (0.5%-0.8% by weight), with a pressure gradient of 0.88-0.91 MPa / mm. In addition, this dispersant combination can effectively maintain the suspension of abrasive particles in water-based two-phase flow polishing media.

[0050] Preferably, the water-based two-phase flow polishing medium further includes 0.2%–0.3% thickener, 0.05%–0.1% rust inhibitor, 0.4%–0.5% defoamer, 0.4%–0.5% lubricant, and 0.1%–0.2% antifreeze. It should be noted that the sum of all the above components should be 100%.

[0051] As shown in Figure 2, the present invention also provides a polishing method using the above-mentioned water-based two-phase flow polishing medium. The polishing method includes:

[0052] Step 1: Prepare water-based two-phase flow polishing media;

[0053] Step 2: Place the prepared water-based two-phase flow polishing medium into the material cylinder, adjust the pressure to the first set value, and start the plunger pump to polish the workpiece.

[0054] Step 3: Stop processing when the flow rate of the polishing operation reaches the second set value;

[0055] Step 4: Clean and dry the polished workpiece.

[0056] It should be noted that the first setting value is 45-55 MPa; the second setting value is 45%-55%.

[0057] The following are two specific examples for illustration.

[0058] Example 1: This example is a two-dimensional internal flow channel sample with bends. The internal flow channel to be finished is manufactured using laser additive manufacturing technology. The structure is a micro-internal flow channel with a diameter D = 1.5 mm, a total length of approximately 80 mm, and an aspect ratio greater than 50:1. The flow channel includes two bends. The material is a high-temperature alloy. The original roughness of the outer side of the bend is Ra 7.8 μm, and the original roughness of the inner side is Ra 10.2 μm. The specific processing method is as follows:

[0059] Step 1: Prepare a shear-thinned water-based two-phase flow polishing medium. The order and amount of each substance added are as follows: deionized water, silicon carbide abrasive (50g / L), dispersant (polyvinyl alcohol 7-10g / L, sodium silicate 12-15g / L, polystyrene 5-8g / L), tackifier (3g / L), rust inhibitor (1g / L), defoamer (5g / L), lubricant (5g / L), and antifreeze (2g / L).

[0060] Step 2: Place the shear-thinning polishing medium prepared in Step 1 into the material cylinder, and set the plunger pump pressure to 51 MPa.

[0061] Step 3: Stop processing when the flow rate increases by 50%.

[0062] Step 4: First, use a high-pressure air gun to blow out the high-speed water-based two-phase flow polishing medium inside the micro-channels, then use ultrasonic immersion cleaning, then rinse several times with pure water and dry.

[0063] As shown in Figure 3, the two-dimensional inner flow channel sample with bends after polishing was cut. The inner surface of the flow channel clearly shows a near-machined surface flattening and a significant polishing effect, resulting in a smooth and glossy surface. Metallographic analysis revealed no residual, embedded, or semi-sintered additive manufacturing powder. Roughness testing showed that the outer roughness of the inner flow channel bend was Ra 1.1 μm, and the inner roughness was Ra 1.5 μm, achieving the target requirement of a roughness Ra < 3.2 μm after polishing and a roughness difference of more than 60% between the inner and outer sides of the bend.

[0064] Example 2: This example describes the finishing of a two-dimensional O-shaped internal flow channel sample. The internal flow channel to be finished is manufactured using laser additive manufacturing technology. The structure consists of a micro-channel with a diameter D = 1.5 mm, a total channel length of 160 mm, and an aspect ratio greater than 100:1. It includes an O-shaped bend structure and is made of a high-temperature alloy. The original roughness Ra of the internal flow channel is approximately 7.4 (non-overhanging surface) to 11.3 μm (overhanging surface). The specific processing method is as follows:

[0065] Step 1: Prepare a shear-thinned water-based two-phase flow polishing medium. The order and amount of each substance added are as follows: deionized water, silicon carbide abrasive (50g / L), dispersant (polyvinyl alcohol 7-10g / L, sodium silicate 12-15g / L, polystyrene 5-8g / L), tackifier (3g / L), rust inhibitor (1g / L), defoamer (5g / L), lubricant (5g / L), and antifreeze (2g / L).

[0066] Step 2: Place the shear-thinning polishing medium prepared in Step 1 into the material cylinder, and set the plunger pump pressure to 51 MPa.

[0067] Step 3: Stop processing when the flow rate increases by 50%.

[0068] Step 4: First, use a high-pressure air gun to blow out the high-speed water-based two-phase flow polishing medium inside the micro-channels, then use ultrasonic immersion cleaning, then rinse several times with pure water and dry.

[0069] As shown in Figure 4 (left image shows the upper surface, right image shows the lower surface), the two-dimensional O-shaped inner channel sample after polishing was cut. The inner surface of the channel clearly shows a near-machined surface flattening and a significant polishing effect, resulting in a smooth and glossy surface. Metallographic analysis revealed no residue, embedding, or semi-sintered additive manufacturing powder. Roughness testing showed that the surface roughness Ra of the overhanging O-shaped inner channel was 3.1 μm, and the surface roughness Ra of the non-overhanging surface was 1.8 μm, meeting the target requirement of roughness Ra < 3.2 μm and a roughness difference of more than 60% after polishing of the initially large differences between the upper and lower surfaces. In the order of material addition, the dispersant should be added after deionized water and abrasive particles, but before other additives. This is because the dispersant is a surfactant, while most subsequent additives are organic. Adding the surfactant first, followed by other additives, can significantly improve the dissolution rate of the subsequent organic additives.

[0070] This invention also provides a method for determining shear thinning characteristics, which measures the shear thinning characteristics of the above-mentioned water-based two-phase flow polishing medium. The method for determining shear thinning characteristics includes the following steps:

[0071] Measure the pressure value p2 of the water-based two-phase flow polishing medium near the wall of the inner channel of the workpiece and the pressure value p1 of the water-based two-phase flow polishing medium at the center of the inner channel.

[0072] The pressure gradient of the flow field from the center of the inner channel to the near wall is calculated using the formula (p1-p2) / r, where r is the radius of the inner channel.

[0073] When the pressure gradient of the flow field exceeds a first preset threshold, the shear thinning characteristics of the water-based two-phase flow polishing medium are significantly measured. The first preset threshold can be 0.5 MPa / mm. Of course, the first preset threshold in this embodiment can be adjusted according to different needs.

[0074] Specifically, a piezoelectric sensor contact is used to measure the pressure value p2 of the water-based two-phase flow polishing medium near the wall of the inner flow channel. A piezoelectric sensor probe is used to measure the pressure value p1 of the water-based two-phase flow polishing medium at the center of the inner flow channel.

[0075] In one specific embodiment, the inner flow channel sample is selected from a CoCrMo high-temperature alloy inner flow channel with a diameter of 3 mm and an aspect ratio of 100:1. The hydraulic drive pressure of the water-based two-phase flow device is 50 MPa, and the hydraulic drive mode is constant pressure mode. The water-based two-phase flow polishing medium is selected as a dispersant with different mass concentrations that does not contain abrasive particles. The reason why the polishing medium of the two-phase flow to be measured does not contain abrasive particles is that if abrasive particles are added, they will cause abrasive erosion damage to the piezoelectric sensor contacts and piezoelectric sensor probes.

[0076] This invention also provides a method for determining shear thinning characteristics, which measures the shear thinning characteristics of the above-mentioned water-based two-phase flow polishing medium. The method for determining shear thinning characteristics includes the following steps:

[0077] Measure the surface roughness R' of the inner side of the flow channel bend in the workpiece. a1 The original surface roughness Ra1 on the inner side of the inner flow channel bend, and the current surface roughness R' on the outer side of the inner flow channel bend. a2 The original surface roughness Ra2 on the outer side of the inner flow channel bend of the workpiece;

[0078] The percentage reduction in the roughness difference between the inner and outer sides of the bend after polishing is calculated using a formula, compared to the original roughness difference between the inner and outer sides of the bend.

[0079] When this percentage is greater than the second threshold, the shear thinning characteristics of the water-based two-phase flow polishing medium are determined to be significant.

[0080] The shear thinning effect can be characterized by the percentage reduction in the roughness difference between the upper and lower surfaces after polishing the inner flow channel after additive manufacturing compared to the original roughness difference, and the percentage reduction in the roughness difference between the inner and outer surfaces after polishing the inner and outer surfaces of the bend compared to the original roughness difference. This percentage can be greater than a second threshold (generally 60%). The larger this percentage is, the more significant the shear thinning characteristics are.

[0081] Specifically, when the pressure gradient is between 0.63 and 0.91 MPa / mm, the percentage reduction in the roughness difference between the upper and lower surfaces after polishing of the inner flow channel in additive manufacturing compared to the original roughness difference, and the percentage reduction in the roughness difference between the inner and outer surfaces after polishing of the inner and outer surfaces of the bends compared to the original roughness difference, are both greater than 60%, and these percentages increase with the increase of the pressure gradient. When the pressure gradient is less than 0.63, the percentage reduction in the roughness difference between the upper and lower surfaces after polishing of the inner flow channel in additive manufacturing compared to the original roughness difference, and the percentage reduction in the roughness difference between the inner and outer surfaces after polishing of the inner and outer surfaces of the bends compared to the original roughness difference, are both less than 60%, and these percentages decrease with the decrease of the pressure gradient. This is because shear-thinned non-Newtonian fluids have a higher pressure in the central flow field region of the inner flow channel, which gradually decreases from the central region along the vertical direction near the wall. Particles near the wall of the inner flow channel move faster, while particles in the center of the inner flow channel move slower. This is equivalent to the flow field at the center of the inner channel continuously applying abrasive particles with a thrust to both sides through the vertical pressure gradient and the difference in abrasive particle concentration distribution. This causes the abrasive particles to migrate and accumulate near the walls on both sides of the inner channel, which is beneficial for increasing the thrust generated by the shear thinning of abrasive particles at the bend of the inner channel, pushing them towards and accumulating on the inner and outer walls. This overcomes the problem that abrasive particles are mainly distributed on the outer wall of the bend due to the difference in mass density and inertia between the solid phase of the abrasive particles and the water-based liquid phase. It increases the distribution of abrasive particles in the inner part of the bend area of ​​the micro-inner channel, improving and reducing the difference in polishing effect between the outer and inner walls of the bend area of ​​the inner channel. In addition, since there are more abrasive particles on the lower surface of the inner channel and the outer side of the bend, the concentration gradient makes it easier for the abrasive particles to diffuse to the upper surface of the inner channel and the area with less abrasive particle distribution on the inner side of the bend, enhancing the polishing effect on the upper surface of the inner channel and the inner side of the bend, and improving and reducing the difference in roughness after polishing the upper and lower surfaces of the inner channel and the inner and outer sides of the bend.

[0082] This invention further provides a method for determining shear thinning characteristics, which measures the shear thinning characteristics of the above-mentioned water-based two-phase flow polishing medium. The method for determining shear thinning characteristics includes the following steps:

[0083] Polishing operations were performed using a shear-thinned water-based two-phase flow polishing medium and an unshear-thinned water-based two-phase flow polishing medium, respectively. Under the same polishing time and the same polishing effect, the proportion of the first driving pressure difference reduction and the proportion of the second driving pressure difference reduction were obtained.

[0084] The proportion of the reduction in the first driving pressure difference is compared with the proportion of the reduction in the second driving pressure difference. When the proportion of the reduction in the first driving pressure difference is greater than the proportion of the reduction in the second driving pressure difference, the shear thinning characteristics of the shear-thinned water-based two-phase flow polishing medium are more significant than those of the unshear-thinned water-based two-phase flow polishing medium.

[0085] The shear-thinning effect is characterized by the reduction in driving pressure differential under the same time and polishing effect, achieving a reduction of 16%–23%. The greater the reduction in driving pressure differential under the same time and polishing effect, the more significant the shear-thinning characteristic. Specifically, when the pressure gradient value is 0.63–0.91 MPa / mm, under the same polishing effect, the driving pressure differential can be reduced by 16%–23% compared to the unshear-thinned water-based two-phase flow polishing medium. Furthermore, without affecting the final polishing effect, the driving pressure differential decreases with increasing pressure gradient value. When the pressure gradient value is <0.63, the driving pressure differential reduction is <16%, and the driving pressure differential increases with decreasing pressure gradient value. The reduction in feed driving pressure differential will reduce the flow velocity of the water-based two-phase flow polishing medium and the inertia of the abrasive particles, thereby further mitigating the roughness differences after polishing on the upper and lower sides of the inner flow channel and the outer and inner sides of the turning area.

[0086] This invention also provides a method for determining shear thinning characteristics, which measures the shear thinning characteristics of the above-mentioned water-based two-phase flow polishing medium. The method for determining shear thinning characteristics includes the following steps:

[0087] Polishing operations were performed using shear-thinned and unshear-thinned water-based two-phase flow polishing media respectively. Under the same polishing effect, the first processing time and the second processing time were obtained.

[0088] Comparing the first processing time with the second processing time, when the first processing time is shorter than the second processing time, the shear thinning characteristics of the shear-thinned water-based two-phase flow polishing medium are found to be more significant than those of the unshear-thinned water-based two-phase flow polishing medium.

[0089] The shear thinning effect can also be characterized by the reduction in processing time under the same driving pressure difference and polishing effect, with time reductions reaching 80% to 270%. The greater the reduction in processing time under the same driving pressure difference and polishing effect, the more significant the shear thinning characteristics. This is because the shear stress of shear-thinned non-Newtonian fluids increases rapidly at first, then slowly, and tends to stabilize as the driving pressure and flow shear rate increase, while the shear stress of non-shear-thinned non-Newtonian fluids decreases as the driving pressure and flow shear rate increase. Therefore, under high shear rate conditions, the shear-thinning rheological properties can maintain a relatively stable shear stress on the wall surface by the abrasive particles, thereby improving the polishing efficiency of the water-based two-phase flow polishing medium on the inner channel wall. In addition, the shear-thinned non-Newtonian fluid continuously applies pressure gradients in the vertical direction to the abrasive particles, causing them to migrate and accumulate from the center of the inner channel to the two side walls. This effectively increases the distribution probability and collision frequency of the abrasive particles on the inner channel wall, especially on rough walls, further contributing to the efficient micro-cutting polishing of the channel wall by the abrasive particles. The efficiency is significantly improved compared to the high-speed water-based two-phase flow polishing medium without shear thinning.

[0090] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A water-based two-phase flow polishing medium, characterized in that, By weight, the water-based two-phase flow polishing medium comprises 89.1% to 94% deionized water, 2% to 6% silicon carbide abrasive particles, and 2.4% to 3.3% dispersant.

2. The water-based two-phase flow polishing medium according to claim 1, characterized in that, The dispersant includes one or more of polyvinyl alcohol, sodium silicate, and polystyrene.

3. The water-based two-phase flow polishing medium according to claim 2, characterized in that, The dispersant comprises polyvinyl alcohol, sodium silicate, and polystyrene, wherein polyvinyl alcohol is 0.7%–1%, sodium silicate is 1.2%–1.5%, and polystyrene is 0.5%–0.8%.

4. The water-based two-phase flow polishing medium according to claim 3, characterized in that, The water-based two-phase flow polishing medium also includes 0.2%–0.3% thickener, 0.05%–0.1% rust inhibitor, 0.4%–0.5% defoamer, 0.4%–0.5% lubricant, and 0.1%–0.2% antifreeze.

5. A polishing method, using the water-based two-phase flow polishing medium according to any one of claims 1 to 4, characterized in that, The polishing method includes: Step 1: Prepare water-based two-phase flow polishing media; Step 2: Place the prepared water-based two-phase flow polishing medium into the material cylinder, adjust the pressure to the first set value, and start the plunger pump to polish the workpiece. Step 3: Stop processing when the flow rate of the polishing operation reaches the second set value; Step 4: Clean and dry the polished workpiece.

6. The polishing method according to claim 5, characterized in that, Step one: Configuring the water-based two-phase flow polishing medium specifically involves adding the components in the water-based two-phase flow polishing medium in the following order: deionized water, silicon carbide abrasive particles, dispersant, thickener, rust inhibitor, defoamer, lubricant, and antifreeze.

7. The polishing method according to claim 6, characterized in that, The first setting value is 45-55 MPa; the second setting value is 45%-55%.

8. The polishing method according to claim 6, characterized in that, Step four, cleaning and drying the polished workpiece, specifically involves: The water-based two-phase flow polishing medium inside the micro-channels of the polished workpiece is blown out using a high-pressure air gun, then ultrasonically immersed and cleaned, rinsed several times with pure water, and then dried.

9. A method for determining shear thinning characteristics, comprising determining the shear thinning characteristics of the water-based two-phase flow polishing medium according to any one of claims 1-4, characterized in that, The method for determining shear thinning properties includes the following steps: Measure the pressure value p1 of the water-based two-phase flow polishing medium at the center of the inner channel of the workpiece and the pressure value p2 of the water-based two-phase flow polishing medium near the wall of the inner channel. The pressure gradient of the flow field from the center of the inner channel to the near wall is calculated using the formula (p1-p2) / r, where r is the radius of the inner channel. When the pressure gradient of the flow field is greater than the first set threshold, the shear thinning characteristics of the water-based two-phase flow polishing medium are significantly measured.

10. The method for determining shear thinning properties according to claim 9, characterized in that, The pressure value p1 of the water-based two-phase flow polishing medium at the center of the inner channel was measured using a piezoelectric sensor probe.

11. The method for determining shear thinning characteristics according to claim 9, characterized in that, The pressure value p2 of the water-based two-phase flow polishing medium near the wall of the inner flow channel of the workpiece is measured by attaching the contact plate of the piezoelectric sensor to the outer wall of the inner flow channel.

12. A method for determining shear thinning characteristics, comprising determining the shear thinning characteristics of the water-based two-phase flow polishing medium according to any one of claims 1-4, characterized in that, The method for determining shear thinning properties includes the following steps: Measure the surface roughness R' of the inner side of the flow channel bend in the workpiece. a1 The original surface roughness Ra1 on the inner side of the inner flow channel bend, and the current surface roughness R' on the outer side of the inner flow channel bend. a2 The original surface roughness Ra2 on the outer side of the inner flow channel bend of the workpiece; The formula calculates the percentage reduction in the roughness difference between the inner and outer sides of the turn after polishing compared to the original roughness difference. When the percentage reduction of the roughness difference between the inner and outer sides of the polished turn compared to the original roughness difference is greater than the second threshold, the shear thinning characteristics of the water-based two-phase flow polishing medium are determined to be significant.

13. A method for determining shear thinning characteristics, comprising determining the shear thinning characteristics of the water-based two-phase flow polishing medium according to any one of claims 1-4, characterized in that, The method for determining shear thinning properties includes the following steps: Polishing operations were performed using a shear-thinned water-based two-phase flow polishing medium and an unshear-thinned water-based two-phase flow polishing medium, respectively. Under the same polishing time and the same polishing effect, the proportion of the first driving pressure difference reduction and the proportion of the second driving pressure difference reduction were obtained. The proportion of the first driving pressure difference reduction is compared with the proportion of the second driving pressure difference reduction. When the proportion of the first driving pressure difference reduction is greater than the proportion of the second driving pressure difference reduction, the shear thinning characteristics of the shear-thinned water-based two-phase flow polishing medium are determined to be more significant than those of the unshear-thinned water-based two-phase flow polishing medium.

14. A method for determining shear thinning characteristics, comprising determining the shear thinning characteristics of the water-based two-phase flow polishing medium according to any one of claims 1-4, characterized in that, The method for determining shear thinning properties includes the following steps: Polishing operations were performed using shear-thinned and unshear-thinned water-based two-phase flow polishing media respectively. Under the same polishing effect, the first processing time and the second processing time were obtained. Comparing the first processing time with the second processing time, when the first processing time is shorter than the second processing time, the shear thinning characteristics of the shear-thinned water-based two-phase flow polishing medium are found to be more significant than those of the unshear-thinned water-based two-phase flow polishing medium.

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