Finishing method for additively manufactured micro-complex internal runner

Abstract

The application provides a finishing method for additive manufacturing of a micro complex inner flow channel, and the finishing method comprises the following steps: step one, configuring a chemical polishing solution; step two, preheating the chemical polishing solution; step three, starting polishing operation, and stopping the chemical polishing when the flow value of the chemical polishing solution reaches a first set value; step four, performing cleaning and drying operation; step five, selecting the viscosity and abrasive particle size of a high-speed abrasive flow polishing medium; step six, starting high-speed abrasive flow polishing operation, and stopping the high-speed abrasive flow polishing when the discharge mass flow value of the high-speed abrasive flow polishing medium reaches a second set value; and step seven, performing cleaning and drying. The application can realize that the surface roughness of the micro inner flow channel reaches Ra<1.6μm after polishing, and the roughness difference between the upper and lower surfaces and the roughness difference between the inner and outer sides of the turning are within 15%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of precision machining of parts, and particularly relates to a finishing method for additive manufacturing of micro-complex internal flow channels. BACKGROUND

[0002] Parts with micro-complex internal flow channel structures have extremely wide applications in the industrial field. In particular, parts related to fluid power systems often have complex internal cavity structures such as micro flow channels, deep small holes, and micro flow channels connected with deep small holes, which play the functions of transporting, exchanging, or applying hydraulic pressure to fluids. For example, various engine fuel nozzles, heat exchangers, hydraulic components, and oil control restrictors. The process technologies that can machine micro-complex internal flow channels include precision machining, femtosecond / water guide / long pulse laser machining, electrical discharge machining, and additive manufacturing (3D printing). Additive manufacturing (3D printing) is a technology that discretizes a complex three-dimensional structure part model into a two-dimensional structure for layer-by-layer stacking forming. It makes it possible to integrally form complex micro-complex internal flow channel parts, and thus the application of additive manufacturing in the industrial field is increasing. However, due to the process characteristics of additive manufacturing technology such as temperature gradient and layer-by-layer forming, there are semi-sintered or bonded powder particles and surface "step" effects on the internal flow channel surface of the part. This rough internal flow channel can cause turbulent flow, vortex flow, and a sharp increase in fluid resistance along the way during fluid movement, and even cause fluid to lose control, produce vibration, and reduce the service life of the part. Rough surfaces can also generate a large number of cavitation bubbles in the fluid, affecting combustion and hydraulic force, and even causing cavitation corrosion. Therefore, the internal flow channels of most additive manufacturing parts need to be finished before they can be used in actual engineering applications. Additive manufacturing complex internal flow channel finishing technology has become an internationally recognized industry difficult technology.

[0003] Current technology utilizes hydraulic thrust to drive a water-based polishing medium with a viscosity less than 1000 cP to flow at a velocity >5 m / s within a micro-channel. The abrasive particles, moving at high speed with the water-based fluid, generate high-speed, high-frequency micro-cutting, ultimately achieving efficient polishing of complex micro-channels with an aperture ≤3 mm and an aspect ratio ≥50:1. However, when the initial roughness difference between the upper (overhanging) and lower (non-overhanging) surfaces of complex internal channels formed by additive manufacturing (3D printing) is significant, water-based two-phase flow polishing results in a relatively low flow velocity in the rougher surface area due to greater frictional resistance, while the flow velocity is relatively high in the less rough surface area. This velocity difference directly causes uneven polishing; the surface with lower initial roughness is more easily polished, while the surface with higher initial roughness is only slightly polished, and the roughness difference between the upper and lower surfaces after polishing is even greater than in the initial state. Furthermore, due to the inertial centrifugal force, water-based two-phase flow technology is prone to uneven radial distribution of abrasive grains along the inner channel bends during high-speed polishing. Specifically, the number of abrasive grains near the outer wall at the inner channel bend is significantly higher than that on the inner wall. This phenomenon is more severe at higher polishing media velocities and smaller bend angles / radii, resulting in uneven polishing at the bends and even dimensional deviations or damage to the outer wall due to over-polishing. Therefore, new solutions or improvements are needed to address the problems of uneven polishing at channel bends and on surfaces with large initial roughness differences, particularly in the additive manufacturing of micro-complex inner channels using water-based two-phase flow technology, which can lead to dimensional deviations and damage. Summary of the Invention

[0004] In view of this, embodiments of this specification provide a finishing method for additive manufacturing of micro-complex internal channels to improve the polishing effect.

[0005] This specification provides the following technical solution through its embodiments: a finishing method for additive manufacturing of micro-complex internal flow channels, comprising the following steps:

[0006] Step 1: Prepare the chemical polishing solution;

[0007] Step 2: Pour the prepared chemical polishing solution into the chemical polishing solution container, and start the constant temperature heating device to heat the chemical polishing solution to the set temperature;

[0008] Step 3: Adjust the pump pressure of the chemical polishing slurry container, read the flow rate of the chemical polishing slurry flowing out of the inner channel of the workpiece at the beginning, and calculate the initial flow rate of the chemical polishing slurry; start the polishing operation when the flow rate of the chemical polishing slurry is adjusted to the set flow rate, and stop the chemical polishing operation when the flow rate of the chemical polishing slurry increases to the first set increase value.

[0009] Step four, the inner flow channel of the workpiece is cleaned by ultrasonic immersion cleaning, after the cleaning is completed, the workpiece is dried after being rinsed with pure water for several times;

[0010] Step five, the viscosity and abrasive particle size of the high-speed abrasive flow polishing medium are selected;

[0011] Step six, the high-speed abrasive flow hydraulic thrust is adjusted, when the mass flow through the regulated hydraulic thrust is greater than the set threshold value, the high-speed abrasive flow polishing operation is started, and when the discharge mass flow of the high-speed abrasive flow polishing medium at the outlet of the inner flow channel of the workpiece is monitored to reach a second set increase value, the high-speed abrasive flow polishing operation is stopped;

[0012] Step seven, the high-speed abrasive flow polishing medium in the inner flow channel of the workpiece is blown out by using a high-pressure air gun, and then the inner flow channel of the workpiece is cleaned by ultrasonic immersion cleaning, after the cleaning is completed, the workpiece is dried after being rinsed with pure water for several times.

[0013] Further, step one is specifically: the chemical polishing liquid is configured by deionized water, hydrochloric acid, nitric acid, ferric chloride, cerium oxide and sodium molybdate.

[0014] Further, step three is specifically:

[0015] The set flow rate of the chemical polishing liquid is 0.5-2m / s;

[0016] The first set increase value is 15%-50%.

[0017] Further, step three further includes that when the chemical polishing operation is performed, the chemical etching layer depth should be controlled between 100μm and 200μm.

[0018] Further, in step four, the immersion liquid for cleaning the workpiece is configured by synthetic fatty acid monoethanolamide polyalkoxy ether, alkyl polyoxyethylene ether phosphate ester salt, sodium metasilicate, sodium tripolyphosphate and sodium carbonate.

[0019] Further, in step five, the viscosity of the high-speed abrasive flow polishing medium ranges from 1000cP to 8000cP, and the abrasive particle size ranges from 60 to 1200 mesh.

[0020] Further, step five further includes: the viscosity of the high-speed abrasive flow polishing medium is regulated by adding ethylene-propylene branched copolymer in the high-speed abrasive flow polishing medium.

[0021] Further, the set threshold value in step six is 30Mpa.

[0022] Further, the second set increase value in step six is 15%-60%.

[0023] Compared with the prior art, the beneficial effects that can be achieved by at least one of the above-mentioned technical solutions adopted in the embodiments of this specification include at least the following: the present invention is aimed at micro-complex internal flow channels with a diameter of 1.5mm to 3mm and an aspect ratio of ≥50:1 manufactured by additive manufacturing. Through a finishing method for micro-complex internal flow channels manufactured by additive manufacturing, the surface roughness of the micro-internal flow channels is polished to Ra<1.6μm, and the difference in roughness between the upper and lower surfaces with large roughness differences and the inner and outer sides of the bends is <15%. Attached Figure Description

[0024] 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.

[0025] Figure 1 This is a flowchart illustrating an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of the chemical polishing apparatus in an embodiment of the present invention;

[0027] Figure 3 This is a polishing effect diagram of Example 1;

[0028] Figure 4 This is a polishing effect diagram of the upper surface in Example 2;

[0029] Figure 5 This is a diagram showing the surface polishing effect of Example 2.

[0030] The attached figures are labeled as follows: 1. Chemical polishing liquid container; 2. Constant temperature heating device; 3. Flow pump; 4. Valve; 5. Workpiece; 6. Flow meter; 7. First flow guide pipe; 8. Sealing assembly; 9. Tooling; 10. Chemical polishing liquid recovery device; 11. Chemical polishing liquid; 12. Return pump; 13. Second flow guide pipe. Detailed Implementation

[0031] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0032] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0033] like Figure 1 As shown, this embodiment of the invention provides a finishing method for additively manufactured micro-complex internal channels, used to polish additively manufactured micro-complex internal channels with an aperture of 1.5mm to 3mm and an aspect ratio ≥ 50:1, specifically including the following steps:

[0034] Step one, configure the chemical polishing solution;

[0035] Step two, pour the prepared chemical polishing solution into the chemical polishing solution container, and start the constant temperature heating device to heat the chemical polishing solution to the set temperature;

[0036] Step three, adjust the pump pressure of the chemical polishing solution container, read the flow value of the chemical polishing solution flowing out of the inner channel of the workpiece at the beginning, and calculate the initial flow rate of the chemical polishing solution; adjust the flow rate of the chemical polishing solution to the set flow rate to start the polishing operation, and stop the chemical polishing operation when the flow value of the chemical polishing solution reaches the first set value.

[0037] Step four, use ultrasonic immersion to clean the inner channel of the workpiece, and then use pure water to rinse several times and dry;

[0038] Step five, select the viscosity and abrasive particle size of the high-speed abrasive flow polishing medium;

[0039] Step six, adjust the hydraulic thrust of the high-speed abrasive flow, and start the high-speed abrasive flow polishing operation when the mass flow through the regulated hydraulic thrust is greater than the set threshold; stop the high-speed abrasive flow polishing operation when the discharge mass flow of the high-speed abrasive flow polishing medium at the outlet of the inner channel of the workpiece is monitored to reach the second set value.

[0040] Step seven, use a high-pressure air gun to blow out the high-speed abrasive flow polishing medium in the inner channel of the workpiece, then use ultrasonic immersion to clean the inner channel of the workpiece, and then use pure water to rinse several times and dry.

[0041] First, the chemical polishing process is used to remove the residual powder and particles in the micro inner channel of the additive manufacturing, further improve the passability of the inner channel to the high-speed abrasive flow polishing medium, and reduce the initial roughness difference between the upper and lower surfaces of the additive manufacturing inner channel. On this basis, the high-speed abrasive flow polishing is used to realize uniform polishing of the upper and lower surfaces and the corners of the inner channel and achieve higher surface polishing quality.

[0042] The polishing method of the embodiment of the application can realize that the surface roughness of the micro inner channel after polishing reaches Ra<3.2μm, and the roughness difference between the upper and lower surfaces and the turning inner and outer sides is within 15%.

[0043] In another embodiment, the method specifically includes the following steps:

[0044] Step one, high-speed water-based two-phase flow polishing is performed on the inner channel of the workpiece, and the high-speed water-based two-phase flow polishing is stopped when the flow of the high-speed water-based two-phase flow medium reaches the third set value.

[0045] Step two, configure the chemical polishing solution;

[0046] Step three, pour the prepared chemical polishing solution into the chemical polishing solution container, and start the constant temperature heating device to heat the chemical polishing solution to the set temperature;

[0047] Step four, adjust the pump pressure of the chemical polishing solution container, read the flow value of the chemical polishing solution flowing out of the inner channel of the workpiece at the beginning, and calculate the initial flow rate of the chemical polishing solution; adjust the flow rate of the chemical polishing solution to the set flow rate to start the polishing operation, and stop the chemical polishing operation when the flow rate of the chemical polishing solution reaches the first set increase value;

[0048] Step five, use ultrasonic immersion to clean the inner channel of the workpiece, and then use pure water to rinse several times and dry;

[0049] Step six, select the viscosity and abrasive particle size of the high-speed abrasive flow polishing medium;

[0050] Step seven, adjust the hydraulic thrust of the high-speed abrasive flow, and start the high-speed abrasive flow polishing operation when the mass flow through the hydraulic thrust control is greater than the set threshold; stop the high-speed abrasive flow polishing operation when the monitored mass flow of the high-speed abrasive flow polishing medium at the outlet of the inner channel of the workpiece reaches the second set increase value;

[0051] Step eight, use a high-pressure air gun to blow out the high-speed abrasive flow polishing medium in the inner channel of the workpiece, and then use ultrasonic immersion to clean the inner channel of the workpiece, and then use pure water to rinse several times and dry.

[0052] First, the water-based two-phase flow is used to slightly polish the micro inner channel, locally chamfer the sharp edge, and micro-finish, which significantly improves the passability of the inner channel to the chemical polishing solution and the high-speed abrasive flow fluid polishing medium; then the chemical polishing process is used to further remove the powder and particles locally remaining in the inner channel after water-based two-phase flow polishing, further improve the passability of the inner channel to the high-speed abrasive flow fluid polishing medium, and reduce the initial roughness difference between the upper and lower surfaces of the additive manufacturing inner channel; finally, the high-speed abrasive flow polishing is used to achieve uniform polishing and higher polishing quality of the surfaces of the inner channel and its corners.

[0053] The third set increase value is 5% to 15%, the water-based two-phase flow and the high-speed abrasive flow belong to the same working condition of fluid dynamic polishing method, the local sharp edge chamfering and micro-finish of the water-based two-phase flow to the micro inner channel will significantly improve the fluid passability of the subsequent chemical polishing solution and high-speed abrasive flow polishing medium, and improve the polishing efficiency. The flow increase of the inner channel after water-based two-phase flow polishing exceeding 15% will result in too large difference between the upper and lower surfaces and the inside and outside of the turn, and the flow increase less than 5% will not significantly affect the fluid passability and polishing efficiency of the subsequent chemical polishing solution and high-speed abrasive flow polishing medium.

[0054] Further, the high-speed water-based two-phase flow medium is configured by deionized water, aluminum oxide and rosin resin emulsion.

[0055] In the present application, the chemical polishing liquid is configured by deionized water, hydrochloric acid, nitric acid, ferric chloride, cerium oxide and sodium molybdate. The specific components are shown in Table 1.

[0056] Table 1 Preferred chemical polishing liquid formula for nickel-based superalloy

[0057]

[0058] Among them, the preferred HCl and HNO3 mainly play a role in corrosion, because through engineering tests, it is found that for nickel-based superalloy, the selection of HCl and HNO3 can have good oxidation and dissolution effect (thinning amount is 0.8 mm / 30 min), and the oxidation and dissolution reagent can also be selected from H2SO4, HF, BH3O3, HClO4, HI, HBr, HIO3, H3PO4, etc.; the catalyst is preferably FeCl3, because FeCl3 as a catalyst can greatly improve the reaction rate, about 70% to 75%. The catalyst can also be selected from iron powder, MnO2, Al2O3, Fe2O3, CuO, AlCl3, etc.; the film former is preferably Na2MoO4, because Na2MoO4 as a film former can effectively prevent the nickel-based superalloy from being over-corroded to appear corrosion pits, and the use of Na2MoO4 as a film former can significantly reduce the number of chemical corrosion pits, the reduction rate is about 80% to 85%, significantly alleviating the pitting degree and corrosion layer depth of the polishing liquid on the nickel-based superalloy, and the film former can also be selected from NaHO3, Na2CrO4, As2O3, SbCl3, Na2SiO3, etc. In addition, compared with the traditional nickel-based superalloy chemical polishing liquid, the unique addition of CeO2 component, when the inner flow channel diameter is small and long, the bubbles generated by the chemical reaction will make the corrosion solution that can be contained in the flow channel less, and the efficiency of the chemical polishing will be very low, the addition of CeO2 component can accelerate the dissolution rate of the chemical reaction bubbles in the polishing liquid, thereby improving the polishing rate of the chemical polishing liquid on the nickel-based superalloy micro inner flow channel.

[0059] The chemical polishing liquid needs to flow in the micro inner flow channel for polishing, and the set flow rate of the chemical polishing liquid is 0.5-2 m / s; the micro inner flow channel is directly immersed in the chemical polishing liquid, even if the polishing liquid is stirred, vibrated or assisted by ultrasonic waves, the fresh polishing liquid contained in the micro inner flow channel is still little, the chemical reaction and polishing efficiency are low, and even the micro inner flow channel cannot be polished due to local reaction bubble blockage. The bubbles generated by the chemical reaction are taken away from the micro inner flow channel by the rapid flow of the polishing liquid, and the contact area between the polishing liquid and the inner flow channel surface is increased. In addition, the fresh polishing liquid is continuously introduced into the cycle, and the locally failed polishing liquid is quickly discharged, thereby improving the chemical reaction rate and polishing efficiency. Through engineering tests, if the flow rate of the polishing liquid in the inner flow channel is lower than 0.5 m / s, the bubbles generated by the chemical polishing liquid in the micro inner flow channel and the failed polishing liquid cannot be quickly taken away and discharged by the flow field, which leads to a decrease in the chemical reaction and polishing efficiency or even no polishing. In addition, if the flow rate of the polishing liquid in the inner flow channel is higher than 2 m / s, the chemical reaction time of the chemical polishing liquid with the superalloy material is too short, which also leads to an insufficient chemical reaction, thereby leading to a decrease in the chemical polishing efficiency or even no polishing. Therefore, the flow rate of the chemical polishing liquid is 0.5-2 m / s. The chemical polishing liquid and the metal material are chemically reacted, the bubbles generated by the chemical polishing liquid in the micro inner flow channel and the failed polishing liquid are effectively discharged, and the chemical polishing efficiency is not affected. The smaller the diameter of the micro inner flow channel, the larger the length-diameter ratio, the more the local turning deformation characteristics, and the higher the flow rate of the chemical polishing liquid.

[0060] Preferably, the present application uses the flow change of the chemical polishing solution through the micro internal flow channel as the online monitoring method and effect evaluation standard of chemical polishing. If the front chemical polishing reaction is excessive, the corrosion layer is too deep, and the subsequent high-speed abrasive flow polishing cannot fully remove the corrosion layer and defect layer generated by the front chemical polishing, if the front chemical polishing reaction is insufficient, it cannot achieve sufficient removal of the floating powder of additive manufacturing, cannot significantly reduce the sintered or semi-sintered particle size of the surface after printing, cannot significantly reduce the roughness difference between the upper and lower surfaces and the inside and outside of the turning, is insufficient to improve the passability of the high-speed abrasive flow polishing medium to the micro internal flow channel, resulting in that the high-speed abrasive flow polishing medium is still difficult to pass through the micro internal flow channel with a diameter of 1.5mm-3mm and a length-diameter ratio of ≥50:1 to achieve uniform polishing, and the polishing medium is easy to be blocked in the turning and dead angle of the micro internal flow channel, and forced passing will cause deformation or even burst of the flow channel. In addition, due to the solution composition, solution temperature and solution volume of the chemical polishing process will change constantly with the chemical reaction and the natural placement of the polishing solution, resulting in inconsistent effects of each chemical polishing under the same chemical polishing time and temperature. For the micro internal flow channel, the flow monitoring value of the polishing solution flowing through the micro internal flow channel during the reaction is used as the basis for the standard of chemical polishing. The reason is that no matter how the chemical solution changes with the reaction or natural placement, the flow or flow resistance change of the chemical polishing solution of the micro internal flow channel can reflect the final effect of the chemical polishing, because the essence of the flow or flow resistance improvement is the final removal amount of the high-temperature alloy material under the chemical polishing, and the final removal amount of the material in the chemical polishing can represent the final reaction amount of the chemical reaction, which is irrelevant to the intermediate process of the chemical reaction, and irrelevant to the changes of the polishing solution composition, temperature, concentration, volume and placement time.

[0061] When performing the chemical polishing operation, the chemical corrosion layer depth should be controlled between 100μm-200μm. And the flow of the micro internal flow channel in the chemical polishing is improved by 15%-50% (the first set improvement value).

[0062] When the chemical corrosion depth is less than 100μm, the chemical polishing of the micro internal flow channel is not enough, the chemical reaction degree is not enough, the surface roughness improvement and the flow channel smoothness are still low, and the subsequent high-speed abrasive flow polishing medium is still difficult to pass through the micro internal flow channel, resulting in low high-speed abrasive flow polishing efficiency or even no polishing. When the chemical corrosion depth is greater than 200μm, the chemical corrosion layer and defect layer are too deep, and the subsequent high-speed abrasive flow will be difficult to fully remove the residual corrosion layer and defect layer. Specifically, the data relationship between the chemical polishing corrosion layer depth and the flow improvement of the micro internal flow channel is shown in Table 2.

[0063] Table 2 Chemical polishing internal flow channel surface corrosion layer depth and corresponding flow improvement data

[0064]

[0065] Further, the soaking liquid for soaking and cleaning workpieces is prepared by using 2% to 6% of synthetic fatty acid monoethanolamide polyalkoxy ether, 1% to 3% of alkyl polyoxyethylene ether phosphate, 24% to 30% of sodium metasilicate, 24% to 28% of sodium tripolyphosphate, and 10% of sodium carbonate.

[0066] In the high-speed abrasive flow polishing stage, the polishing effect of the micro internal flow channel in the high-speed abrasive flow polishing process cannot be observed and measured by direct visualization method, and the unique viscous polishing medium of the high-speed abrasive flow cannot be detected by the traditional fluid flow method. The mass / weight flow of the polishing medium per unit time flowing out of the internal flow channel is used as the online monitoring and evaluation standard of the high-speed abrasive flow polishing effect of the micro internal flow channel, and the mass balance weighing method is used to measure and characterize the flow of the high-speed abrasive flow polishing medium.

[0067] Specifically, for the micro internal flow channel with a caliber of 1.5mm to 3mm and a length-diameter ratio of ≥50:1, the preferred value of the high-speed abrasive flow polishing medium flow is in the range of 10 to 25g / min. If the high-speed abrasive flow polishing medium flow is too low, the polishing medium cannot reach the sufficient passability, pressure and flow rate for the micro internal flow channel, resulting in very low polishing efficiency or even no polishing. If the high-speed abrasive flow polishing medium flow is too high, the fluid flow rate is too fast to directly impact the wall and cause over-polishing deformation at the turning part. The polishing medium flow increases with the decrease of the caliber of the internal flow channel, the increase of the length-diameter ratio and the increase of the local turning deformation characteristics. Specifically, the preferred value data relationship between the micro internal flow channel of different caliber and the high-speed abrasive flow polishing medium flow is shown in Table 3.

[0068] Table 3 Preferred value of high-speed abrasive flow polishing medium flow corresponding to micro internal flow channel of different caliber

[0069]

[0070] The viscosity range of the high-speed abrasive particle flow polishing medium is 1000 cP~8000 cP for the micro internal flow channel with a caliber of 1.5mm~3mm and a length-diameter ratio of ≥50:1. The viscosity of the polishing medium decreases with the decrease of the caliber of the internal flow channel, the increase of the length-diameter ratio and the increase of the local turning deformation characteristics. The reason is that the smaller the caliber of the micro internal flow channel, the larger the length-diameter ratio and the more the local turning deformation characteristics, the worse the passing performance of the high-speed abrasive particle flow polishing medium, which leads to the decrease of the polishing efficiency or even the failure of polishing. Therefore, the viscosity of the high-speed abrasive particle flow polishing medium needs to be reduced to improve the passing performance of the micro internal flow channel, so as to improve the polishing efficiency. However, the viscosity of the high-speed abrasive particle flow polishing medium should not be too low. If the viscosity is too low, the extrusion force of the polishing medium on the internal flow channel wall surface will be reduced, which leads to the decrease of the polishing efficiency. At the same time, the polishing medium is easy to be blocked due to the "wall sticking effect", which also reduces the binding effect of the polishing medium on the abrasive particles, leading to the over-polishing, deformation and the increase of the roughness difference between the upper and lower surfaces at the turning part of the internal flow channel. Specifically, the viscosity of the high-speed abrasive particle flow polishing medium corresponding to the micro internal flow channel with different caliber is shown in Table 4.

[0071] Table 4 The viscosity of the high-speed abrasive particle flow polishing medium corresponding to the micro internal flow channel with different caliber

[0072]

[0073] Preferably, the viscosity of the high-speed abrasive particle flow polishing medium is adjusted by adding ethylene-propylene branched copolymer in the high-speed abrasive particle flow polishing medium. The reason is that the ethylene-propylene branched copolymer has better solubility and high-temperature stability for the high-speed abrasive particle flow polishing medium.

[0074] In the high-speed abrasive particle flow polishing stage, the abrasive particle size range of the high-speed abrasive particle flow medium is 60~1200 mesh for the micro internal flow channel with a caliber of 1.5mm~3mm and a length-diameter ratio of ≥50:1. And the abrasive particle size of the high-speed abrasive particle flow polishing medium gradually decreases with the decrease of the caliber of the micro internal flow channel, the increase of the length-diameter ratio and the increase of the local turning deformation characteristics. The reason is that the smaller the caliber of the micro internal flow channel, the larger the length-diameter ratio and the more the local turning deformation characteristics, the worse the passing performance of the high-speed abrasive particle flow polishing medium, which leads to the decrease of the polishing efficiency or even the failure of polishing. Therefore, the abrasive particle size needs to be lower than the upper limit to ensure the passing performance of the high-speed abrasive particle flow polishing medium, so as to avoid the decrease of the flowability of the polishing medium or even the blockage and rupture of the internal flow channel. However, the abrasive particle size of the high-speed abrasive particle flow polishing medium should not be too low. If the abrasive particle size is too small, the effective friction area on the internal flow channel wall surface will be reduced, which leads to the decrease of the polishing efficiency. Specifically, the data relationship between the micro internal flow channel with different caliber and the abrasive particle size is shown in Table 5.

[0075] Table 5 The abrasive particle size corresponding to the micro internal flow channel with different caliber

[0076]

[0077] The set threshold value in the embodiment of the application is 30 MPa.

[0078] Specifically, for the micro internal flow channel with a caliber of 1.5 mm to 3 mm and a length-diameter ratio of greater than or equal to 50:1, the high-speed abrasive flow polishing medium preferably provides a hydraulic thrust greater than 30 MPa, and the hydraulic thrust of the high-speed abrasive flow increases with the decrease of the caliber of the micro internal flow channel, the increase of the length-diameter ratio, and the increase of the local turning deformation characteristics. The reason is that for the micro internal flow channel with a caliber of 1.5 mm to 3 mm and a length-diameter ratio of greater than or equal to 50:1, it is necessary to provide a hydraulic thrust greater than 30 MPa to the high-speed abrasive flow polishing medium to ensure the high-speed passing property and polishing efficiency of the polishing medium to the micro internal flow channel, and this pressure exceeds the hydraulic thrust range (0.7 MPa-22.4 MPa) of the traditional abrasive flow. It should be noted that the machining can also be achieved by using the traditional abrasive flow pressure range (0.7 MPa-22.4 MPa), but the efficiency is lower. Specifically, the data relationship between the micro internal flow channel with different caliber and the driving pressure of the high-speed abrasive flow equipment is shown in Table 6.

[0079] Table 6: High-speed abrasive flow hydraulic thrust corresponding to micro internal flow channel with different caliber

[0080]

[0081] Further, the second set of promotion values is 15% to 60%. When the discharge mass flow of the high-speed abrasive flow polishing medium through the micro internal flow channel is promoted by 15% to 30%, the roughness of the surface of the internal flow channel of the workpiece is reduced by about one time, the discharge mass flow is promoted by 30% to 50%, the roughness of the surface of the internal flow channel of the workpiece is reduced by about two times, and the discharge mass flow is promoted by more than 50%, the roughness of the surface of the internal flow channel of the workpiece is reduced by about three times. The reason is that the higher the discharge mass of the high-speed abrasive flow polishing medium through the micro internal flow channel, the better the passing property of the internal flow channel surface to the high-speed abrasive flow polishing medium, at this time, the lower the roughness of the micro internal flow channel surface, the higher the surface quality, and the more sufficient the removal of surface particles, powder and steps.

[0082] As shown in Figure 2 The application also provides a chemical polishing liquid device for the chemical polishing operation in the finishing method for the additive manufacturing micro complex internal flow channel, and the chemical polishing liquid device comprises:

[0083] A chemical polishing liquid container 1 for placing a chemical polishing liquid 11;

[0084] A chemical polishing liquid recovery device 10 is arranged at intervals with the chemical polishing liquid container 1, and the chemical polishing liquid recovery device 10 is connected with the chemical polishing liquid container 1 through the flow guide pipeline and the backflow pipeline, and the workpiece 5 is arranged in the flow guide pipeline.

[0085] Further, the flow guide pipeline comprises:

[0086] The flow guide pump 3 is arranged in the chemical polishing liquid container 1.

[0087] The valve 4 is connected with the outlet of the flow guide pump 3, and the outlet of the valve 4 is connected with the inlet of the workpiece 5.

[0088] The flow meter 6 is connected with the outlet of the workpiece 5, and the outlet of the flow meter 6 is connected with the chemical polishing liquid recovery device 10 through the first flow guide pipe 7.

[0089] The backflow pipeline comprises the backflow pump 12 and the second flow guide pipe 13, the backflow pump 12 is arranged in the chemical polishing liquid recovery device 10, one end of the second flow guide pipe 13 is connected with the outlet of the backflow pump 12, and the other end of the second flow guide pipe 13 is connected with the chemical polishing liquid container 1.

[0090] It should be noted that the chemical polishing liquid container 1, the first flow guide pipe 7 and the second flow guide pipe 13, and the chemical polishing liquid recovery device 10 are all made of polytetrafluoroethylene material, and have the properties of strong acid resistance and high temperature resistance.

[0091] Preferably, the chemical polishing liquid container 1 is further provided with a constant temperature heating device 2. The surface of the constant temperature heating device 2 is plated with a corrosion-resistant coating, which can preheat the chemical polishing liquid 11 to the set temperature during use. The surfaces of the flow guide pump 3 and the backflow pump 12 are plated with a corrosion-resistant coating. The flow guide pump 3 functions to press the chemical polishing liquid 11 through the first flow guide pipe 7 into the inner flow channel of the workpiece 5. The backflow pump 12 functions to return the chemical polishing liquid 11 in the chemical polishing liquid recovery device 10 to the chemical polishing liquid container 1, so as to be recycled until the acid in the chemical polishing liquid 11 for corrosion is consumed.

[0092] The valve 4 is an on-off control and is made of polypropylene material and has acid resistance. The flow meter 6 (the pressure rating of the flow meter is 5MPa, the polytetrafluoroethylene lining is corrosion-resistant, and can be widely used in the chemical industry) monitors the flow rate of the chemical polishing liquid 11 at the outlet of the workpiece 5 in real time.

[0093] Further, the embodiment of the present application further comprises a tooling 9 arranged in the flow guide pipeline and used for clamping the workpiece 5. A sealing assembly 8 is further arranged at a position requiring sealing, and the sealing assembly 8 is made of fluorine rubber material to prevent the chemical polishing liquid 11 from leaking. When the chemical polishing liquid 11 flowing through the inner flow channel of the workpiece 5 is collected into the chemical polishing liquid recovery device 10, the sealing through the sealing assembly 8 can prevent environmental pollution.

[0094] The following is described by using an embodiment, and the specific implementation is as follows:

[0095] Embodiment 1: This embodiment is the light finishing of two inner flow channel samples with turning structure in two dimensions. The inner flow channel to be light finished is manufactured by laser additive manufacturing technology. The structure is that the caliber D of the micro inner flow channel is about 1.5 mm, the total length of the flow channel is about 80 mm, the length-diameter ratio is greater than 50:1, each flow channel contains two turning structures, the material is high-temperature alloy, the original roughness Ra of the outer side of the turning of the inner flow channel is 10.3 μm, and the original roughness Ra of the inner side of the turning is 8.1 μm. The specific processing method is as follows:

[0096] First step: high-speed water-based two-phase flow polishing is performed. The high-speed water-based two-phase flow is composed of deionized water, alumina, and tackifier rosin resin emulsion, the viscosity is 180 cP, the alumina abrasive particle size is 43 μm, the abrasive particle mass concentration is 30 g / L, the plunger pump thrust is 53 MPa, and the initial flow rate is 3.5 L / min. The polishing is stopped when the flow rate of the high-speed water-based two-phase flow is increased by 8%.

[0097] Second step: configure a chemical polishing solution of 5 L, and the addition sequence and amount of each substance are as follows: H2O (2 L), HCl (2.5 L), HNO3 (0.5 L), FeCl3 (0.76 kg), CeO2 (0.15 kg), and Na2MoO4 (0.23 kg).

[0098] Third step: pour the chemical polishing solution prepared in the second step into the chemical polishing solution container, and start the constant temperature heating device to heat the chemical polishing solution to 50°C.

[0099] Fourth step: adjust the pump pressure of the flow guide pump in the chemical polishing device, read the flow value of the chemical polishing solution flowing out of the micro inner flow channel at the beginning through the flowmeter, and divide the flow value by the cross-sectional area of the inner flow channel to obtain the initial flow rate of the chemical polishing medium. When the flow rate of the chemical polishing solution flowing through the inner flow channel is adjusted to 1 m / s, the chemical polishing is started. After a period of processing, the chemical polishing is stopped when the flow rate of the chemical polishing solution is increased by 50%.

[0100] Fifth step: ultrasonic immersion cleaning is used to clean the inner flow channel of the workpiece. The immersion liquid is an alkaline cleaning agent to neutralize the residual acidic polishing solution, and the material ratio is as follows: synthetic fatty acid monoethanolamide polyalkoxy ether 2%~6%, alkyl polyoxyethylene ether phosphate salt 1%~3%, sodium metasilicate 24%~30%, sodium tripolyphosphate 24%~28%, and sodium carbonate 10%. After rinsing with pure water for several times, the workpiece is finally dried for use.

[0101] Sixth step: the viscosity of the high-speed abrasive flow polishing medium is selected. Since the caliber of the workpiece is 1.8 mm, the viscosity of the high-speed abrasive flow polishing medium is adjusted to 4000 cP.

[0102] Step 7: Select the abrasive grain size of the high-speed abrasive flow polishing medium. Since the workpiece diameter is 1.8 mm, the abrasive grain size of the high-speed abrasive flow polishing medium is selected to be 600 mesh.

[0103] Step 8: Adjust the hydraulic thrust of the high-speed abrasive flow. When the mass flow rate reaches 13 g / min through the regulated hydraulic thrust, start the high-speed abrasive flow polishing. Process for a certain period of time under this hydraulic thrust. When it is monitored that the output mass flow rate of the high-speed abrasive flow polishing medium at the outlet of the micro internal flow channel increases by 60%, stop processing.

[0104] Step 9: First, use a high-pressure air gun to blow out the high-speed abrasive flow polishing medium inside the micro internal flow channel. Then, use ultrasonic immersion cleaning. After several times of pure water rinsing, dry it.

[0105] As shown in Figure 3 cutting the two internal flow channels with a two-dimensional turning structure after triple composite finishing, the internal surface of the flow channel can clearly see the flattening near the machined surface and the significant finishing effect, the surface is smooth and beautiful. Through metallographic detection, there is no residual, inlaying and semi-sintering additive manufacturing powder. Through roughness detection, the roughness of the outer side of the spiral turning is Ra=0.8 μm, and the roughness of the inner side of the spiral turning is Ra=0.7 μm, which meets the target requirement of Ra<1.6 μm and the roughness difference between the inner and outer sides of the turning is less than 15%.

[0106] Example 2: This example is the finishing of a two-dimensional O-shaped internal flow channel sample. The internal flow channel to be finished is made by laser additive manufacturing technology. The structure is a micro internal flow channel with a diameter D=1.5 mm and a total length=160 mm, the aspect ratio is greater than 100:1, containing an O-shaped bending structure, the material is a high-temperature alloy, and the original roughness of the internal flow channel is about Ra=7.4 (non-overhanging surface)~11.3 μm (overhanging surface). The specific processing method is as follows:

[0107] Step 1: Perform high-speed water-based two-phase flow polishing. The high-speed water-based two-phase flow is composed of deionized water, alumina, and tackifier rosin resin emulsion with a viscosity of 150 cP. The abrasive grain size of the alumina is 43 μm, and the plunger pump thrust is 63 MPa. The initial flow rate is 2.8 L / min. Stop polishing when the high-speed water-based two-phase flow rate increases by 12%.

[0108] Step 2: Prepare 5L of chemical polishing solution. The order and amount of each substance added are as follows: H2O (2L), HCl (2.5L), HNO3 (0.5L), FeCl3 (0.76 kg), CeO2 (0.15 kg), Na2MoO4 (0.23 kg).

[0109] Step 3: Pour the chemical polishing solution prepared in Step 2 into the chemical polishing solution container, and start the constant temperature heating device to heat the chemical polishing solution to 50℃.

[0110] Step 4: Adjust the pump pressure of the guide pump in the chemical polishing device. Read the initial flow rate of the chemical polishing solution from the micro-channel using a flow meter. Divide the flow rate by the cross-sectional area of ​​the channel to obtain the initial flow velocity of the chemical polishing medium. Start chemical polishing when the flow velocity is adjusted to 1.5 m / s by the guide pump. After processing for a period of time, stop chemical polishing when the flow rate of the chemical polishing solution increases by 50%.

[0111] Step 5: Ultrasonic immersion cleaning of the workpiece's internal flow channels. The immersion solution is an alkaline cleaning agent used to neutralize residual acidic polishing solution. Its composition is as follows: synthetic fatty acid monoethanolamide polyalkoxy ether 2%–6%, alkyl polyoxyethylene ether phosphate salt 1%–3%, sodium metasilicate 24%–30%, sodium tripolyphosphate 24%–28%, and sodium carbonate 10%. Afterwards, rinse several times with pure water and finally dry for use.

[0112] Step 6: Select the viscosity of the high-speed abrasive flow polishing medium. Since the workpiece diameter is 1.5mm, the viscosity of the high-speed abrasive flow polishing medium is 4000cP.

[0113] Step 7: Select the abrasive particle size of the high-speed abrasive flow polishing medium. Since the workpiece diameter is 1.5mm, the abrasive particle size of the high-speed abrasive flow polishing medium is 600 mesh.

[0114] Step 8: Adjust the hydraulic thrust of the high-speed abrasive flow. When the mass flow rate reaches 12g / min by adjusting the hydraulic thrust, start high-speed abrasive flow polishing. Process under this hydraulic thrust for a period of time. When the mass flow rate of the high-speed abrasive flow polishing medium at the outlet of the micro-channel increases by 60%, stop processing.

[0115] Step 9: First, use a high-pressure air gun to blow out the high-speed abrasive polishing medium from inside the micro-channels, then use ultrasonic immersion cleaning, rinse several times with pure water, and then dry.

[0116] like Figure 4 and Figure 5 As shown, the two-dimensional O-shaped inner channel sample after triple lamination and finishing was cut. The inner surface of the channel clearly shows a flattening close to the machined surface and a significant finishing effect, resulting in a smooth and glossy surface. Metallographic testing revealed no residual, embedded, or semi-sintered additive manufacturing powder. Roughness testing showed that the surface roughness Ra of the overhanging O-shaped inner channel was 1.5 μm, and the surface roughness Ra of the non-overhanging surface was 1.4 μm, meeting the target requirement of roughness Ra < 1.6 μm and a roughness difference of < 15% after polishing of the initially large differences between the upper and lower surfaces.

[0117] The above merely describes specific embodiments of the present application and cannot be used to limit the scope of the application, so replacement of equivalent components or equivalent changes and modifications made within the scope of the patent protection of the present application should still fall within the scope of the present patent. In addition, the technical features in the present application can be freely combined with each other, and the technical features can be freely combined with each other.

Claims

1. A finishing method of additively manufacturing a micro complex inner runner, characterized by, The method comprises the following steps: Step one, preparing a chemical polishing solution by using deionized water, hydrochloric acid, nitric acid, ferric chloride, cerium oxide and sodium molybdate; Step two, pouring the prepared chemical polishing solution into a chemical polishing solution container, and starting a constant temperature heating device to heat the chemical polishing solution to a set temperature; Step three, adjusting the pump pressure of the chemical polishing solution container, reading the flow value of the chemical polishing solution flowing out of the inner flow channel of the workpiece at the beginning, and calculating the initial flow rate of the chemical polishing solution; adjusting the flow rate of the chemical polishing solution to the set flow rate to start the polishing operation, and stopping the chemical polishing operation when the flow value of the chemical polishing solution reaches the first set increase value; Step four, using ultrasonic immersion to clean the inner flow channel of the workpiece, and then using pure water to rinse several times and drying; Step five, selecting the viscosity and abrasive particle size of the high-speed abrasive flow polishing medium; Step six, adjusting the hydraulic thrust of the high-speed abrasive flow, and starting the high-speed abrasive flow polishing operation when the mass flow through the hydraulic thrust control is greater than the set threshold value; stopping the high-speed abrasive flow polishing operation when the discharge mass flow of the high-speed abrasive flow polishing medium at the outlet of the inner flow channel of the workpiece is monitored to reach the second set increase value; Step seven, using a high-pressure air gun to blow out the high-speed abrasive flow polishing medium in the inner flow channel of the workpiece, and then using ultrasonic immersion to clean the inner flow channel of the workpiece, and then using pure water to rinse several times and drying.

2. The method of claim 1, wherein, The step three is specifically: The set flow rate of the chemical polishing solution is 0.5-2 m / s; The first set increase value is 15%-50%.

3. The method of claim 1, wherein the method is performed by a laser beam machine. The step three further comprises controlling the chemical corrosion layer depth to be between 100 μm and 200 μm during the chemical polishing operation.

4. The method of claim 1, wherein the method is a method of finish machining of a micro complex internal runner by additive manufacturing. In the step four, the immersion cleaning solution for cleaning the workpiece is prepared by using synthetic fatty acid monoethanolamide polyalkoxy ether, alkyl polyoxyethylene ether phosphate ester salt, sodium metasilicate, sodium tripolyphosphate and sodium carbonate.

5. The method of claim 1, wherein the method is performed by a computer system. In the step five, the viscosity of the high-speed abrasive flow polishing medium is in the range of 1000 cP-8000 cP, and the abrasive particle size is in the range of 60-1200 mesh.

6. The method of claim 5, wherein the method further comprises: The step five further comprises adding ethylene-propylene branched copolymer to the high-speed abrasive flow polishing medium to control the viscosity of the high-speed abrasive flow polishing medium.

7. The method of claim 1, wherein the method is a method of finish machining of a micro complex internal runner by additive manufacturing. The set threshold value in the step six is 30 MPa.

8. The method of claim 1, wherein the method is a method of finish machining of a micro complex internal runner by additive manufacturing. The second set increase value in the step six is 15%-60%.

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