Surface finishing method for fine internal flow passages, fine internal flow passage workpiece and finishing medium

Abstract

The present invention relates to a surface finishing method for a fine internal flow passage, a fine internal flow passage workpiece, and a finishing medium. Here, the diameter of the fine internal flow passage is 3 mm or less, the length-to-diameter ratio is 50:1 or more, the finishing method uses a liquid-solid two-phase flow finishing medium, the liquid phase viscosity of the finishing medium is less than 1000 cP, and the solid phase of the finishing medium is abrasive grains (1), a predetermined pressure is applied to the finishing medium so that the finishing medium flows through the fine internal flow passage at a flow rate of more than 5 m / s, and the flow rate of the finishing medium flowing into the fine internal flow passage from one end thereof reaches a saturation value of the flow rate that can be accommodated by the diameter of the fine internal flow passage so that the liquid pressure inside the internal flow passage is in a pressure-trapping state. The surface finishing method for the fine internal flow passage realizes target processing of rough surface convex points, and can obtain a super-mirror quality in which the optimal roughness of the surface coincides with the average cutting edge contact length range of the abrasive grains without being limited by the material of the fine internal flow passage.

Description

[Technical field]

[0001] The present invention relates to the field of precision machining of internal flow passages, and more particularly to a surface finishing method for fine internal flow passages, a fine internal flow passage workpiece, and a finishing medium. [Background technology]

[0002] Components having fine and complex internal flow passage structures are widely used in industrial fields such as aerospace, marine, nuclear, automotive, and mold industries. In particular, components related to fluid power systems often have complex internal cavity structures such as fine flow passages, small-diameter deep holes, and connections between fine flow passages and small-diameter deep holes, and perform functions such as transporting, exchanging, or applying hydraulic pressure to fluids, such as fuel nozzles, heat exchangers, hydraulic modules, and oil passage control throttles in various aviation / space / marine / automotive engines.

[0003] Process technologies that can fabricate fine and complex internal flow passages include precision machining, femtosecond / water jet guided / long pulse laser processing, spark processing, and additive manufacturing (3D printing), etc. Except for additive manufacturing technology, the fine and complex internal flow passage structures fabricated by other single processes are relatively simple and have a small length-to-diameter ratio, and need to be combined with other combination processes such as welding to fabricate fine and complex internal flow passages. The fine and complex internal flow passages produced by precision machining have problems such as burrs, sharp corners, and steps at the joints of the processed parts, the surface of the internal flow passage produced by femtosecond laser processing has the effect of attached residual particles and the surface "step", and the surface of the internal flow passage produced by water jet guided / long pulse laser and spark processing has the effect of remelting.Additive manufacturing (3D printing) is a technology that separates a complex 3D structure part model into a 2D structure and superimposes them layer by layer to form it, and it has become possible to form complex, fine and complex internal flow passage parts in one piece, so it is increasingly being applied in industrial fields such as aerospace, automobiles, and molds.However, additive manufacturing technology has its own process characteristics such as temperature gradient and layer by layer forming during the part forming process, so the surface of the internal flow passage of the part has the effect of semi-sintered or bonded powder particles and the surface "step".

[0004] Burrs during machining, particles sintered on internal flow paths during femtosecond laser processing, and adhesive powder on the surface of internal flow paths during additive manufacturing affect the performance and safety of parts. When burrs, attached residual particles, or adhesive powder fall off due to high-speed friction between the fluid flowing into the internal flow path and the surface, they become redundant and spread with the fluid, block the oil path, or cause mechanical wear failure, resulting in serious safety accidents. Inner surfaces with high roughness are prone to becoming the source of fatigue cracks during long-term use, and carbon accumulation is also likely to occur in high-temperature oil path systems. Traces of cutting edges on the surface of the flow path during machining, sharp corners or steps at the processing joints, and the "step" phenomenon on the surface of the internal flow path during femtosecond laser and additive manufacturing processing cause turbulence, vortexes, and a sudden increase in fluid friction resistance (Frictional Drag) in the fluid movement process, and further cause fluid runaway, generating vibrations and shortening the service life of parts. Rough surfaces can generate a large number of cavitation bubbles in the fluid, affecting combustion and hydraulic power, and can also cause cavitation corrosion. For internal flow paths and small connecting holes of parts made of specific materials such as hollow blades, fine cracks are likely to occur on the surface of the remelted layer, causing early failure of the parts, so it is necessary to reduce the thickness of the remelted layer or not allow the appearance of the remelted layer.

[0005] Therefore, when processing the internal flow passage surface of fluid power components by technologies such as precision machining, femtosecond / water jet guided / long pulse laser machining, spark machining, additive manufacturing (3D printing), etc., it will bring about adverse problems such as burrs, adhesive powder, sintered particle residues, rough surface, remelted layer, etc., and it is necessary to use appropriate surface finishing technologies to remove these adverse effects and meet the performance requirements of the product.

[0006] However, at present, the technology for effectively finishing the surfaces of fine and complex internal passages has not yet emerged, and as a result, the inner surface roughness of fine and complex internal passage workpieces made by additive manufacturing generally only has an original average roughness Ra after additive manufacturing of 6.3 μm or more, and there are no products with an optimum surface roughness Ra of 1.6 μm or less for internal passages, and no products with an optimum surface roughness Ra of 0.8 μm or less for fine and complex internal passage workpieces made by laser processing or spark processing have appeared. In addition, with regard to machined workpieces with fine and complex internal passages, there are no products with an optimum internal passage surface roughness Ra of 0.4 μm or less. However, currently, when fine and complex internal passages have complex, irregularly shaped passages such as S-shaped, L-shaped, U-shaped, or O-shaped bends, this cannot be achieved by machining, which only allows for linear feed, and can only be achieved by methods such as additive manufacturing. Therefore, at present, there are no products with an optimum internal passage surface roughness Ra of 1.6 μm or less produced by additive manufacturing. Summary of the Invention

[0007] An object of the present application is to provide a surface finishing method for a fine internal flow passage, a fine internal flow passage workpiece, and a finishing medium.

[0008] In a first aspect, the present application provides a surface finishing method for a fine internal flow passage, the fine internal flow passage having a diameter of 3 mm or less and a length to diameter ratio of 50:1 or more, the finishing method using a liquid-solid two-phase flow finishing medium, the liquid phase viscosity of the finishing medium being less than 1000 cP, the solid phase of the finishing medium being abrasive grains, a predetermined pressure being applied to the finishing medium such that the finishing medium flows through the fine internal flow passage at a flow velocity of greater than 5 m / s, and a flow rate of the finishing medium flowing into the fine internal flow passage from one end thereof reaches a saturation value of a flow rate that can be accommodated by the diameter of the fine internal flow passage so that the liquid pressure inside the internal flow passage is in a pressure-trapping state.

[0009] In the technical proposal of the embodiment of the present application, the viscosity of the liquid phase of the finishing medium is less than 1000 cP, the flow rate of the two-phase finishing medium in the fine internal flow passage is more than 5 m / s, and the flow rate flowing into one end of the fine internal flow passage reaches the saturation value of the flow rate that can be accommodated by the diameter of the fine internal flow passage, thereby creating a pressure-trapping state of the liquid pressure inside the internal flow passage, thereby forming a means for efficiently polishing the fine internal flow passage with liquid-carrying abrasive grains, and thus solving the difficult problem of finishing the fine internal flow passage through the synergistic action of the three factors of the low-viscosity liquid phase, the fluid flow rate, and the saturation flow rate. The principle is that, first, due to the synergistic action of the three factors of the low viscosity liquid phase, the flow rate of the finishing medium and the saturation flow rate, the finishing medium can smoothly enter the fine internal flow passage and form a state similar to a non-Newtonian fluid in the fine internal flow passage. The fluid boundary layer is parallel to the surface of the internal flow passage, and the abrasive grains in the "blade-like" hard non-Newtonian fluid realize the target processing of the rough surface convex points through shear friction. In addition, due to the synergistic action of the above three factors, frictional fine cutting force is generated between the abrasive grains in the finishing medium and the surface of the fine internal flow passage, so that it is possible to obtain a super-mirror quality in which the optimal roughness of the surface matches the average cutting edge contact length range of the abrasive grains, regardless of the material of the fine internal flow passage.

[0010] In some embodiments, the liquid phase of the finishing medium is an aqueous liquid.

[0011] In some embodiments, the abrasive grains have a surface sharp corner structure, the average cutting depth of the cutting edge of the abrasive grains is 1.4 nm to 14 nm, and the average contact length of the cutting edge of the abrasive grains is 50 nm to 1000 nm.

[0012] In some embodiments, the finishing medium finishes the microscopic internal passages in a reference period until an optimum surface roughness of the microscopic internal passages reaches a target value, the reference period being obtained by the following steps: the finishing medium finishes the microscopic internal passages in an initial period, detects an optimum surface roughness of the microscopic internal passages, if the optimum surface roughness matches the target value, the initial period is the reference period, if the optimum surface roughness does not reach the target value, sequentially increase a step period until the optimum surface roughness reaches the target value, and the corresponding total period is the reference period, where the initial period and the step period are obtained based on a one-side thinning rate corresponding to the abrasive grain and an initial average surface roughness of the microscopic internal passages.

[0013] In some embodiments, the predetermined pressure P satisfies the following equation:

number

[0014] where Ra0 is the initial average surface roughness of the fine internal flow passage, Ra is the target value of the surface optimum roughness of the fine internal flow passage after finishing, and t is the initial period. L is the average cutting depth of the abrasive cutting edge, b is the average contact length of the abrasive cutting edge, ρl is the aqueous liquid phase density, ρp is the abrasive solid phase density, σw is the yield limit of the workpiece material, χ is the boost ratio at which the saturation flow rate is reached, Re is the Reynolds number of the liquid phase, l is the length of the internal flow passage, D is the aperture of the internal flow passage, d is the abrasive grain diameter, and k is the uneven grinding ratio coefficient.

[0015] In some embodiments, the finishing method further includes, after finishing the internal passage, an optimum surface roughness corresponding to the internal passage diameter expansion value satisfies the following formula:

number

[0016] Here, Ra* is the optimum surface roughness when the internal flow passage is finished and the port diameter is enlarged, Ra0 is the initial average surface roughness of the fine internal flow passage, δ is the port diameter enlargement value, and k is the asperity grinding ratio coefficient.

[0017] In some embodiments, the finishing method further includes injecting a cleaning medium into the fine internal channels at the predetermined pressure after the optimal surface roughness of the fine internal channels reaches a target value, and the liquid phases of the cleaning medium and the finishing medium dissolve in each other until the Tyndall effect appears in the cleaning medium flowing out of the fine internal channels.

[0018] In some embodiments, the finishing method further includes performing finishing by gradually increasing the liquid phase viscosity, solid phase abrasive grain size, and solid phase abrasive grain mass concentration of the finishing medium based on lower limit values ​​of the liquid phase viscosity, solid phase abrasive grain size, and abrasive grain mass concentration until the flow rate or flow rate of the two-phase finishing medium is 1 to 5% lower than the flow rate or flow rate corresponding to the lower limit values, thereby obtaining optimal value ranges for the viscosity, abrasive grain size, and abrasive grain mass concentration.

[0019] In some embodiments, the finishing medium finishes the fine internal flow passages during a reference period, a flow rate or flow rate of the finishing medium in the fine internal flow passages is determined, and when the flow rate or flow rate reaches a predetermined value, the optimal surface roughness reaches the target value.

[0020] In some embodiments, the fine internal channels are three-dimensionally elongated and have bent structures including S-shaped bends, L-shaped bends, U-shaped bends, O-shaped bends, spiral bends, and the liquid phase of the finishing medium contains a polymeric thickener.

[0021] In a second aspect, the present application provides a fine internal channel workpiece obtained via the finishing method described in the first aspect above.

[0022] In some embodiments, the fine internal flow passage workpiece has a fine internal flow passage with a diameter of 3 mm or less and a length-to-diameter ratio of 50:1 or more, the fine internal flow passage workpiece is obtained by additive manufacturing, casting, laser processing, spark processing, etc., and the fine internal flow passage has an inner surface with an optimal surface roughness Ra of 1.6 μm or less after finishing.

[0023] In some embodiments, the fine internal flow passage workpiece has a fine internal flow passage with a diameter of 3 mm or less and a length-to-diameter ratio of 50:1 or more, the fine internal flow passage workpiece is obtained by precision machining, and the fine internal flow passage has an inner surface with an optimal surface roughness Ra of 0.4 μm or less after finishing.

[0024] In some embodiments, the fine internal passage workpiece is an additively manufactured high temperature alloy fuel nozzle for an aircraft engine, the fuel nozzle has the fine internal passage structure, the diameter of the fine internal passage is less than 2.5 mm, the structure has straight lines, L-shaped bends and O-shaped bends, and the optimum surface roughness Ra of the fine internal passage is 1.6 μm or less. Alternatively, the fine internal passage workpiece is an additively manufactured aluminum alloy heat exchanger, the heat exchanger has a fine internal passage structure, the diameter of the passage is less than 3 mm, the fine internal passage structure has straight lines, L-shaped bends, S-shaped bends and U-shaped bends, and the optimum surface roughness Ra of the fine internal passage is 1.6 μm or less. Alternatively, the fine internal flow passage workpiece is a hydraulic module of titanium alloy by additive manufacturing, the hydraulic module has a fine internal flow passage structure, a diameter of 3 mm, the fine internal flow passage structure has a straight line, an S-shaped bend, and an L-shaped bend, and the optimum surface roughness Ra of the fine internal flow passage is 1.6 μm or less. Alternatively, the fine internal flow passage workpiece is a stainless throttle by additive manufacturing, the throttle has a fine internal flow passage structure, a diameter of less than 1 mm, the fine internal flow passage structure has a spiral bend, and the optimum surface roughness Ra of the fine internal flow passage is 0.8 μm or less.

[0025] In some embodiments, the fine internal passage workpiece is a hollow blade of a high-temperature alloy cast for an aircraft engine, and the hollow blade has an inner cavity structure in which the fine internal passage communicates with a small hole, and the optimum roughness Ra of the inner surface of the small hole after finishing is 0.8 μm or less, there is no remelted layer, and the chamfer radius of the hole is greater than 0.1 mm.

[0026] In a third aspect, the present application provides a finishing medium for use in the finishing method of the first aspect, the finishing medium comprising a liquid phase and a solid phase, the liquid phase having a viscosity of less than 1000 cP, and the solid phase being an abrasive grain.

[0027] In some embodiments, the liquid phase of the finishing medium includes the addition of a polymeric thickener.

[0028] In some embodiments, the liquid phase further comprises an antifoaming agent, and during the machining of fine internal channels by the finishing method, the ratio of the volume of the surface foam slurry of the finishing medium to the volume of the liquid phase does not exceed 0.3:1.

[0029] In some embodiments, the liquid phase of the finishing medium also includes a lubricant, which may include one or more combinations of inorganic compounds, inorganic compounds, and polymeric compounds. [Brief description of the drawings]

[0030] The above and other features, properties and advantages of the present invention will become more apparent from the following description in conjunction with the accompanying drawings and embodiments. It should be noted that the accompanying drawings are all illustrative and not drawn to scale, and should not be considered as limiting the scope of protection actually claimed by the present invention.

[0031] [Figure 1] 1 is a flowchart of a finishing method according to some embodiments of the present application. [Diagram 2] Schematic diagram of the micro-cutting force principle of the finishing method according to some embodiments of the present application. [Diagram 3]1 is a flowchart of a finishing method according to another embodiment of the present application. [Figure 4] 1 is a flowchart of a finishing method according to another embodiment of the present application. [Diagram 5] 1 is a flowchart of a finishing method according to a further embodiment of the present application. [Figure 6A] Image of a part to be finished by the finishing method according to the first embodiment of the present application [Figure 6B] Image of a part to be finished by the finishing method according to the first embodiment of the present application [Figure 6C] Image of a part to be finished by the finishing method according to the first embodiment of the present application [Figure 7A] Image of a part to be finished by a finishing method according to a second embodiment of the present application [Figure 7B] Image of a part to be finished by a finishing method according to a second embodiment of the present application [Figure 7C] Image of a part to be finished by a finishing method according to a second embodiment of the present application [Figure 8A] Image of a part to be finished by a finishing method according to a third embodiment of the present application [Figure 8B] Image of a part to be finished by a finishing method according to a third embodiment of the present application [Figure 8C] Image of a part to be finished by a finishing method according to a third embodiment of the present application [Figure 9A] Image of a part to be finished by a finishing method according to a fourth embodiment of the present application [Figure 9B] Image of a part to be finished by a finishing method according to a fourth embodiment of the present application [Figure 10A] Image of a part to be finished by a finishing method according to a fifth embodiment of the present application [Figure 10B] Image of a part to be finished by a finishing method according to a fifth embodiment of the present application [Figure 11A] Image of a part to be finished by a finishing method according to a sixth embodiment of the present application [Figure 11B] Image of a part to be finished by a finishing method according to a sixth embodiment of the present application [Figure 12A]2. A part image to be finished by a finishing method according to a comparative example corresponding to the finishing method according to the second embodiment of the present application. [Figure 12B] 2. A part image to be finished by a finishing method according to a comparative example corresponding to the finishing method according to the second embodiment of the present application. [Figure 13] Schematic diagram of the bending structure of the fine internal flow passage DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] Various embodiments or examples of the above-mentioned technical proposal are disclosed below. In order to simplify the disclosure, specific examples of each element and arrangement are described below, but these are merely examples and do not limit the scope of protection of the present invention. "An embodiment", "one embodiment", and / or "several embodiments" refer to features, structures, or special features related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "one embodiment" or "alternative embodiments" mentioned twice or more times in different positions in this specification do not necessarily refer to the same embodiment. Furthermore, some features, structures, or special features in expressions such as some embodiments, other embodiments, and further other embodiments of the present application may be appropriately combined.

[0033] In this application, flow charts are used to explain the operations performed by the system according to the embodiment of this application. It should be understood that the operations above or below are not necessarily performed in a precise order. Other operations can be added to these processes, or certain steps or operations can be removed from these processes.

[0034] Moreover, the average roughness described below refers to the case where multiple areas on the surface to be measured are selected and measured, the average value is taken, and the average roughness of the measured surface is obtained. The optimum roughness described below refers to the case where multiple areas on the surface to be measured are selected and measured, the minimum value is taken, and the optimum roughness of the measured surface is obtained. For example, when performing roughness measurement, an area for roughness measurement is a pipe segment having a length of 8 mm, and multiple pipe segments having a length of 8 mm are selected and measured in the pipe to be measured, and the minimum value is obtained.

[0035] Components with fine and complex internal flow passage structures are widely used in industrial fields such as aerospace, marine, nuclear, automotive, and molds. However, current machining processes, such as precision machining, femtosecond / waterjet guided / long pulse laser machining, spark machining, and additive manufacturing (3D printing), can result in adverse problems such as burrs, adhesive powder, sintered particle residues, rough surfaces, and remelted layers when processing the surfaces of internal flow passages in fluid power components. It is necessary to use appropriate surface finishing techniques to eliminate these adverse effects and meet the performance requirements of the products.

[0036] At present, there is no product with an optimum surface roughness Ra of 1.6μm or less for fine internal flow passage workpieces produced by additive manufacturing, no product with an optimum surface roughness Ra of 0.8μm or less for fine internal flow passage workpieces produced by laser processing or spark processing, and no product with an optimum surface roughness Ra of 0.4μm or less for fine internal flow passage workpieces produced by machining, but if the fine internal flow passage has an irregular flow passage structure such as S-shaped bend, L-shaped bend, U-shaped bend, or O-shaped bend, it cannot be realized by linear feed machining and can only be realized by additive manufacturing, etc., so there is still no product with an optimum surface roughness Ra of 1.6μm or less for fine internal flow passages produced by additive manufacturing. The inventor has conducted in-depth research, tried and compared various types of finishing methods for the internal flow passage surface, and discovered the following. When the internal flow passages of a part are large in diameter (>3mm), have a small length-to-diameter ratio (<50:1), and extend in a generally straight line, they can be finished using common methods such as manual polishing, chemical, electrochemical, plasma, magnetic, magnetorheological, abrasive flow, water jet, and ultrasonic. However, when the internal flow passages are small in diameter (<3mm) and have a large length-to-diameter ratio (>50:1), the finishing process is difficult. (1) The abrasive flow technology was adopted, and the inner cavity was finished by a pressing grinding mechanism using a semi-solid ointment finishing medium with high rigidity. The inventor discovered that the creep fluid with an extremely small Reynolds number is difficult to achieve uniform processing through complex long-distance fine channels, and is prone to blockage at bends and dead corners, and that forcibly passing through the channel may cause the channel to deform or tear. Even if it barely passes through an internal channel with a length-to-diameter ratio of 50:1 or more, the pressure and flow rate will rapidly attenuate with the increase in fluid stroke, and the port of the internal channel will be "excessively grinded and polished", while the inside will be "unground and polished" due to excessive pressure and flow rate losses. In addition, the colloidal abrasive flow medium, which is insoluble in water, is prone to remaining in the curves and dead corners of the internal channel, and is difficult or impossible to completely remove after processing. (2) Abrasive water jet technology, also known as fine abrasive slurry jet, high-velocity flow, and high-velocity water particle finishing, is adopted. By applying liquid pressure to the water jet nozzle, a water jet containing abrasive particles is ejected from the nozzle, and the surface material of the workpiece is washed away by the impact kinetic energy. However, since the distance between the water jet nozzle and the part surface is short, the abrasive water jet technology is not effective on the fine internal flow passages with small internal flow passage diameters (less than 3 mm) and large length-to-diameter ratios (more than 50:1). (3) Although magnetic finishing technology was adopted, it can only perform a slight polishing process on the surface of an internal flow passage that is larger than 3 mm in diameter and extends in an approximately linear manner, and cannot perform an effective surface finishing process on a fine and complex internal flow passage that is 3 mm or less in diameter and extends in three dimensions, such as S-shaped bends, L-shaped bends, U-shaped bends, O-shaped bends, and spiral bends. The reasons are as follows. Magnetic finishing is a flexible process that uses relatively large magnetic needle abrasive grains and is based on the principle that surface convex and concave points are simultaneously processed under the action of an applied magnetic field. Therefore, these flexible processing means can only perform a slight polishing improvement on the surface, and even if a large amount of material is removed, it cannot significantly improve the "step" effect on the surface, reduce the surface roughness, significantly peel off the powder and particles attached to the surface, and improve burrs. In addition, since this method is restricted by the movement of the magnetic field, it cannot be used to finish complex internal flow passages that extend in three dimensions in parts. (4) Although a chemical finishing method was adopted, the small diameter of the internal flow passages meant that only a small amount of corrosive solution could be accommodated, making the efficiency of the chemical finishing method extremely low, and even making finishing impossible due to localized accumulation of reactive bubbles. (5) Electrochemical, plasma finishing and ultrasonic methods have been adopted, but they are unable to finish the fine and complex internal flow paths because it is difficult to place tracing electrodes inside the flow paths which are narrow and extend three-dimensionally and include S-shaped bends, L-shaped bends, U-shaped bends, O-shaped bends, spiral bends, etc.

[0037] In addition, for (4) and (5), chemical, electrochemical, plasma finishing methods can cause various corrosion and layer defects on the microstructure of the flow path substrate, and the corrosive liquid and reactive gas also have adverse effects on the environment and equipment. At the same time, (4) and (5) are also flexible processing methods, and have the same disadvantages as (3), which can only make a slight polishing improvement to the surface, and even if the amount of material removed is large, the "step" effect on the surface cannot be significantly improved, the surface roughness can be reduced, and the powder, particles and burrs attached to the surface cannot be significantly removed.

[0038] Based on the above, the inventor conducted intensive research and discovered that the above-mentioned processing methods are difficult to apply to finishing processing of fine internal flow paths because they all face problems such as difficulty in finishing deep parts of fine internal flow paths and / or the finishing quality is not ideal when it comes to the structure of fine internal flow paths.

[0039] Based on the above, the inventor has further researched and invented a surface finishing method for fine internal flow passages, which uses a two-phase flow finishing medium with a viscosity of less than 1000cP, makes the flow rate of the two-phase flow finishing medium in the fine internal flow passage greater than 5m / s, and makes the flow rate flowing into one end of the fine internal flow passage reach the saturation value of the flow rate that can be accommodated by the diameter of the fine internal flow passage, so that the liquid pressure inside the internal flow passage is in a pressure-filled state, thereby forming a means for the liquid to reach the saturation flow rate for the fine internal flow passage, that is, the synergistic action of the low-viscosity liquid phase, the fluid flow rate of the finishing medium, and the saturation flow rate solves the difficult problem of finishing the fine internal flow passage. The principle is described below. First, the synergistic action of the three factors, low viscosity liquid phase, fluid flow rate and saturation flow rate, allows the finishing medium to smoothly enter the fine and complex internal flow passage and form a state similar to a non-Newtonian fluid in the fine and complex internal flow passage, the fluid boundary layer is parallel to the surface of the internal flow passage, and the abrasive grains in the hard non-Newtonian fluid "like a blade" realize target processing of the surface convex points by shear friction. In addition, the synergistic action of the above three factors provides a micro-cutting force due to friction between the abrasive grains in the finishing medium and the surface of the fine and complex internal flow passage, so that the surface optimum roughness can be matched with the range of the average contact length of the abrasive grain cutting edge without being limited by the material of the fine and complex internal flow passage, and even a super-mirror quality with an optimum surface roughness Ra of 0.05 μm can be achieved, breaking through the limitations of the principles of abrasive flow and water jet technology. The principle is described below. Since the cutting mechanism of abrasive flow technology is based on the volume force generated by the pressing of the abrasive grains against the surface, when processing low-hardness metals and polymer flexible materials, dents and pits are likely to occur (Ra>0.8 μm). The cutting force in abrasive waterjet technology is the erosive force caused by the impact of abrasive grains on the surface, and when machining soft metals, the surface is prone to roughening (Ra>0.8μm).

[0040] It can be understood that the surface finishing method of the internal flow passage disclosed in the embodiment of the present application solves the problem that the internal flow passage has a small diameter (less than 3 mm), a large length-to-diameter ratio (more than 50:1), and a fine and complex internal flow passage cannot be surface-finished, and a fine internal flow passage workpiece with an inner surface optimum surface roughness Ra of 1.6 μm or less can be obtained, and the workpiece can have a fine and complex internal flow passage workpiece that is three-dimensionally stretched and includes S-shaped bending, L-shaped bending, U-shaped bending, O-shaped bending, and spiral bending, such as various engine fuel nozzles, heat exchangers, hydraulic units, and oil passage control throttles for aviation / space / ships / automobiles. It can also be understood that the surface finishing method of the internal flow passage disclosed in the embodiment of the present application can be used not only for the use of fine and complex internal flow passage workpieces, but also for the processing of internal flow passage materials of other dimensions.

[0041] It is necessary to explain that the terms "diameter" and "length" in the context mean equivalent diameter and equivalent length, and the ratio of length to diameter is the ratio of equivalent length to equivalent diameter. Regarding the equivalent diameter, the cross-sectional shape of the internal flow passage may be a circle, an ellipse, etc., whose cross-sectional outline is composed of a closed curve (non-broken line). The cross-sectional shape of the internal flow passage may be a rectangle, a triangle, etc., whose cross-sectional outline is composed of a closed broken line. Since the cross-sectional outline is composed of any closed curve (non-broken line) or a closed broken line, and the cross-sectional outline is an irregular shape, the equivalent diameter is introduced and the equivalent diameter is defined as follows: For any cross-sectional shape, an ideal circle is taken that is equal to the actual cross-sectional area of ​​the any cross-sectional shape, and the diameter of this ideal circle is the equivalent diameter. The equivalent length refers to the entire path that the fluid in the internal flow passage actually flows between two ports of the internal flow passage.

[0042] According to some embodiments of the present application, and referring to FIG. 1 , the present application provides a method for finishing a surface of an internal flow passage, the method comprising: Using a liquid-solid two-phase flow finishing medium, the liquid phase of which has a viscosity of less than 1000 cP and the solid phase of which is an abrasive; A predetermined pressure is applied to the finishing medium so that the finishing medium flows through the fine internal flow passage at a flow velocity of greater than 5 m / s, the flow rate of the finishing medium flowing into the fine internal flow passage from one end thereof reaches a saturation value of the flow rate that can be accommodated by the diameter of the fine internal flow passage, and the liquid pressure inside the internal flow passage is in a pressure-trapping state.

[0043] The liquid here has a viscosity of less than 1000 cP, and all descriptions of viscosity values ​​in this application refer to the Ubbelohde viscosity at room temperature (around 25°C). The optimum value of the viscosity of the liquid phase corresponding to the finishing method corresponding to the fine internal flow passages with different materials, dimensions, and initial average roughness can be obtained by constantly increasing the viscosity based on the lower limit. Currently, the lower limit of the viscosity in the embodiment is about 50 cP, and the inventors have found through a large amount of test data that for the fine internal flow passages of common materials such as titanium alloys, high temperature alloys, steel, ceramics, aluminum alloys, and polymer materials, the viscosity of the liquid phase needs to be at least 50 cP to reach the target value of roughness after finishing. A specific method for obtaining the optimum value of the viscosity will be described in the embodiment described later, but the critical value of 1000 cP here is not a general optimum value, but a limit value at which the finishing medium flows continuously, smoothly, and stably through the fine internal flow passages.

[0044] The liquid phase described in the examples is, for example, an aqueous liquid phase, in which a certain thickener is added to deionized water so that the aqueous liquid has a certain viscosity. The beneficial effects of using an aqueous liquid are that it is low-cost, easy to obtain, environmentally friendly, and the finishing medium is easy to wash after finishing is completed. However, it is understood that the liquid phase here is not limited to an aqueous liquid as long as it is a liquid with a viscosity μ of less than 1000 cP.

[0045] The material of the solid phase abrasive grains may be a common abrasive material, such as carbide ceramics including silicon carbide, tungsten carbide, etc., oxide ceramics including aluminum oxide, zirconium oxide, cerium oxide, etc., nitride ceramics including boron nitride, chromium nitride, etc., and natural minerals including diamond / sand, mica, quartz, olivine, etc. Preferably, the material may be one or more combinations of diamond / sand and oxide ceramics.

[0046] When selecting the particle size and mass concentration of the abrasive grains, it is common to gradually increase them based on the lower limit value to obtain the optimal value range. If the particle size and mass concentration of the abrasive grains are below the lower limit value, the expected finishing effect cannot be achieved, that is, the fine internal flow passage cannot achieve the target value of surface roughness. The principle is that if the particle size is too small, the mass of the abrasive grains themselves is too low to generate enough kinetic energy to achieve effective abrasive grinding, and if the mass concentration is too small, the grinding probability of the surface processing point is reduced and effective abrasive grinding cannot be achieved. The selection of the lower limit value is generally conservative, for example, any lower limit value can be conservatively selected on the premise that it does not exceed the upper limit value of the particle size, and the lower limit of the ratio of the internal flow passage diameter to the particle size of the abrasive grains is usually 20, that is, the internal flow passage diameter must ensure that at least 20 abrasive grains are not clogged when passing through in parallel, that is, the upper limit of the particle size of the abrasive grains is usually 1 / 20 of the internal flow passage diameter, and the lower limit of the abrasive grains is generally 1 / 5 of the upper limit value. The lower limit of the mass concentration of the abrasive grains is generally 10g / L, and the selection of the lower limit is generally relatively conservative, because the pressure of the system is relatively large, and the occurrence of clogging of the abrasive grains may cause the scrapping of the workpiece and the system, or may cause cracking and explosion. Therefore, the particle size and mass concentration of the abrasive grains are gradually increased according to the predetermined lower limit until the particle size and mass concentration of the abrasive grains are too large and cause significant flow resistance, resulting in a decrease in the flow rate, and the mutual collision between the abrasive grains affects the flow rate, reducing the flow rate and the grinding effect, that is, the optimum value can be obtained by testing according to the lower limit, and the specific method will be described in the following examples.

[0047] A predetermined pressure is applied to the finishing medium so that the finishing medium flows through the fine internal flow passage at a flow rate of more than 5 m / s. The predetermined pressure here means a pressure that allows the finishing medium to flow through the fine internal flow passage at a flow rate of more than 5 m / s even in the initial state of the finishing process, and as the finishing progresses, the internal flow passage surface roughness decreases, and under the same pressure conditions, the flow rate of the finishing medium in the fine internal flow passage becomes faster and faster. It can be understood that the realized flow rate is in a certain range, so the predetermined pressure here is a concept of a range, and not that only a specific value can be applied to the finishing medium. To measure the flow rate of the finishing medium inside the fine internal flow passage, immersion measurement cannot be adopted, otherwise the abrasive grains may damage the sensor probe. The method of ultrasonic velocity measurement can be adopted, and indirect measurement can also be performed using the Hagen-Poiseuille law of viscous fluid (see below). In the formula, D is the internal passage diameter, l is the length of the fine internal passage, p is the pressure difference acting on both ends of the fine internal passage, i.e., the hydraulic pressure p, Re is the Reynolds number, um is the flow velocity of the liquid phase in the aqueous two-phase flow, ρl is the density of the liquid phase, and the flow velocity of the liquid phase is approximately equal to the flow velocity of the completion medium.

number

[0048] The flow rate of the finishing medium is greater than 5m / s, based on the theoretical critical conditions for forming non-Newtonian fluid and the critical value obtained by the inventor through long-term practice. According to engineering fluid mechanics data (e.g., book data: Yang Shuren, Wang Zhiming, He Guangyu, etc., Engineering Fluid Mechanics [M]. Petroleum Industry Press, 2006), the viscosity of pure water is 1cP, and the critical flow rate of non-Newtonian fluid is greater than 16.6m / s, but the lower limit of the viscosity of the liquid phase in this embodiment is 50cP, which is greater than 1cP, so the critical flow rate of non-Newtonian fluid is less than 16.6m / s. At the same time, combining the results of practice, the inventor found that the ideal processing effect cannot be obtained when the viscosity is less than 5m / s, so the critical value is 5m / s.

[0049] The flow rate at which the finishing medium flows into one end of the fine internal flow passage reaches a saturation value of the flow rate that can be accommodated by the diameter of the fine internal flow passage, and the liquid pressure inside the internal flow passage becomes high, that is, the so-called saturated flow rate state in this field.

[0050] The saturation value of the capacity flow rate and the state of saturation flow rate herein refer to the state in which the fluid fills the cross section of the pipe when it flows into the pipe, and the cross section of the pipe can accommodate the maximum number of fluid molecules in parallel.

[0051] It can be seen that the beneficial effects of the finishing method of the above embodiment are as follows:

[0052] The viscosity of the liquid phase of the finishing medium is less than 1000cP, the flow rate of the two-phase finishing medium in the fine internal passage is greater than 5m / s, the flow rate of the fine internal passage at one end reaches the saturation value of the flow rate that can be accommodated by the diameter of the fine internal passage, the liquid pressure inside the internal passage is in a pressure-trapping state, and a means is formed for the liquid to reach the saturation flow rate for the fine internal passage, that is, the synergistic effect of the low viscosity liquid phase, the fluid flow rate, and the saturation flow rate solves the difficult problem of finishing the fine internal passage. The principle is described below. First, due to the synergistic effect of the three factors of low viscosity liquid phase, fluid flow rate and saturation flow rate, the finishing medium is in a state of low viscosity and high flow rate, so it can smoothly enter the fine internal flow passage and form a non-Newtonian fluid in the fine internal flow passage, the fluid boundary layer is parallel to the surface of the internal flow passage, and the abrasive grains in the "blade-like" hard liquid phase realize target processing of the surface convex points by shear friction, and in principle overcome the problem that the surface convex points and concave points are processed simultaneously during flexible processing, which can only be slightly polished. At the same time, due to the micro-cutting force caused by the friction between the abrasive grains of the finishing medium and the surface of the fine internal flow passage, it is possible to obtain an optimal surface roughness that matches the average contact length range of the abrasive grain cutting edge without being limited by the material of the fine internal flow passage, and break through the limitations of the principles of abrasive flow and water jet technology. The principle is described below. Since the cutting mechanism of abrasive flow technology is based on the volume force generated by the pressing of the abrasive grains against the surface, when processing metals and polymer flexible materials with low hardness, dents and pits are likely to occur (Ra>0.8μm). The cutting force in abrasive waterjet technology is the erosion force caused by the impact of abrasive grains on the surface, and when processing soft metals, the surface is easily roughened (Ra>0.8μm). In addition, in the low viscosity and high flow rate fluid dynamics conformal processing method, the steps, sharp corners, geometric contour curvatures, and other locations that do not conform to fluid engineering on the internal flow channel surface are polished more, and the corners, sharp edges, internal flow channel contour curvatures, and hole shapes are geometrically streamlined, further improving the fluid movement performance of the internal flow channel. In addition, the above example proposed that the critical flow velocity is 5m / s to realize a blade-like hard non-Newtonian fluid using the flow rate of the finishing medium and to realize target processing of surface convex points by the shear friction of the abrasive grains.

[0053] Regarding the machining time of the finishing medium in the fine internal flow passage, the finishing medium may finish the fine internal flow passage during a reference period until the surface optimum roughness of the fine internal flow passage reaches a target value. The reference period here may be a predetermined continuous period, or may be a plurality of intermittent periods, or the finishing process may be automatically stopped after detecting that the flow rate of the finishing medium reaches the flow rate corresponding to when the surface optimum roughness of the fine internal flow passage is the target value after a non-predetermined continuous period after starting. For example, as described above, in some embodiments, after starting machining, the flow rate or flow rate of the finishing medium in the fine internal flow passage is measured to indirectly obtain the surface optimum roughness in the characteristic representation, and when the flow rate or flow rate value reaches a predetermined value, the corresponding surface optimum roughness reaches the target value, so that the finishing process is stopped manually or automatically at this time. The meaning of the surface optimum roughness being the target value here does not necessarily mean that the surface optimum roughness does not necessarily need to be measured directly, but may be indirectly characterized, for example, as introduced above, it may be a method of characterizing the flow rate, flow rate, etc. of the finishing medium inside the fine internal flow passage. The above target values ​​refer to the set optimum surface roughness values, and generally refer to the requirements for the final optimum surface roughness of the fine internal flow passages, but it is not excluded that further finishing may be carried out after the above finishing steps, and what is set at this time is not the requirement for the final optimum surface roughness.

[0054] In summary, the finishing method introduced in the above examples solves the long-standing industry challenge of finishing fine internal passages with a diameter of 3 mm or less and a length-to-diameter ratio of 50:1 or more by combining measures such as constructing a hydraulic system at both ends of the internal passage to be processed, utilizing a low-viscosity, high-speed solid-liquid two-phase fluid, reaching a saturation flow rate of the internal passage to be processed, and a fine cutting mechanism generated by the abrasive grains in the two-phase flow rubbing against the internal passage surface at high speed.

[0055] In some embodiments, as shown in FIG. 2, the structure of the abrasive grain 1 of the two-phase flow finishing media may have a surface cusp structure 2 so as to play the role of fine cutting, and the structural parameters of the abrasive grain may be the average cutting depth L of the abrasive grain cutting edge of 1.4 nm to 14 nm and the average contact length b of the abrasive grain cutting edge of 50 nm to 1000 nm. It can be understood that since the particle size of a single abrasive grain is generally small, in reality, the abrasive grain generally undergoes local aggregation, and the abrasive grain structure model shown in FIG. 2 is not the atoms or molecules of a single abrasive grain in a physical sense, but an equivalent abrasive grain group in which local aggregation occurs. That is, the above-mentioned average cutting depth of the abrasive grain cutting edge is the average cutting depth of the cutting edge of the equivalent abrasive grain group, and the average contact length of the abrasive grain cutting edge is the average contact length of the cutting edge of the equivalent abrasive grain group, and in order to clearly show the average cutting depth L of the abrasive grain cutting edge and the average contact length b of the abrasive grain cutting edge, FIG. 2 is not drawn in equal proportions. In addition, the average cutting depth L of the abrasive cutting edge is 1.4nm to 14nm, and the average contact length b of the abrasive cutting edge is 50nm to 1000nm, which are not directly observed by an electron microscope, but are statistically calculated from data obtained by the inventor through long-term practice. The inventor found that when the finishing method of the above embodiment is adopted, the one-side thinning speed for the internal flow passage diameter is 5μm / h to 50μm / h, and the corresponding one-side thinning speed per second is 1.4nm / s to 14nm / s, that is, the average cutting depth of the abrasive cutting edge where the equivalent abrasive grain group contacts the fine internal flow passage surface in one second is 1.4nm / s to 14nm / s, that is, the corresponding average cutting depth L of the abrasive cutting edge is 1.4nm to 14nm. In this way, not only is the finishing effect ensured, but the fine cutting speed is not too fast to cause excessive polishing and grinding, and the dimensional accuracy requirements of the finishing process are met and tolerance deviation is avoided. In addition, the inventors found that when the finishing method of the above embodiment is adopted, the achievable surface optimum roughness Ra is 0.05μm~1μm, and the corresponding average contact length of the abrasive cutting edge is 50nm~1000nm, since the average contact length of the abrasive cutting edge determines the final optimum roughness. Obtaining the structural parameters of the equivalent abrasive group through a large amount of practice can play an important role in the calculation of parameters such as a predetermined pressure.The specific value of the average cutting depth of the abrasive cutting edge that contacts the fine internal flow passage surface in 1 second, between 1.4nm and 14nm, and the specific value of the average contact length of the abrasive cutting edge that is between 50nm and 1000nm, can be obtained correspondingly based on the specific particle size approximation of the abrasive grains. The larger the particle size of the abrasive grains, the larger the average cutting depth and average contact length of the cutting edge that contacts the fine internal flow passage surface in 1 second will be. The specific corresponding values ​​are obtained from long-term experimental data of the one-side thinning speed corresponding to the abrasive grain size, i.e., the average cutting depth and average contact length of the abrasive cutting edge that contacts the fine internal flow passage surface in 1 second, i.e., the optimal roughness after finishing.

[0056] In another embodiment, as shown in Fig. 3, the finishing medium finishes the fine internal flow passages in a reference period, and the specific value of this reference period may be a reference period obtained by a pre-test or a reference period obtained by a field test. The procedure for obtaining this reference period is as follows.

[0057] The finishing medium finishes the micro internal passage in an initial period, and detects an optimum surface roughness of the micro internal passage. If the optimum surface roughness matches the target value, the initial period is the reference period, and if not, the step period is successively increased until the optimum surface roughness reaches the target value, and the corresponding total period is the reference period. Here, the initial period and the step period are obtained from the one-side thinning speed of the abrasive grinding and the initial average surface roughness of the micro internal passage.

[0058] The above initial period is generally calculated based on the initial surface average roughness of the fine internal flow passage and the average cutting depth of the abrasive cutting edge that contacts the fine internal flow passage surface in 1 second. For example, the initial surface average roughness Ra of the internal flow passage of the part is 10 μm, the average height difference between the surface convex points and concave points is about 10 μm, and the average cutting depth of the abrasive cutting edge that contacts the fine internal flow passage surface in 1 second is 1.4 nm to 14 nm, that is, the one-side thinning speed is 5 μm / h to 50 μm / h, and if estimated with a lower limit of 5 μm / h, the reference period is at least 2 h, so the initial period is set to 2 h. And the selection of the step period is generally calculated based on the dimensional tolerance requirement of the part and the one-side thinning speed. For example, if the tolerance is plus or minus 5 μm, if the one-side thinning speed is 5 μm / h to 50 μm / h and estimated with a lower limit of 5 μm / h, the step time will be 1 h accordingly, to avoid the time step being too large to cause tolerance deviation.

[0059] It can be understood that the above process can be obtained by field testing during the finishing process, that is, if it is necessary to determine the initial period corresponding to a certain fine internal flow passage, a reference period can be obtained by finishing the initial period and step period according to the above method, and at the same time, the fine internal flow passage processing of this structure is also completed while obtaining this reference period. Then, when finishing this kind of fine internal flow passage, the total processing time can be directly obtained from the reference period. There is no need to test the initial period and step period.

[0060] In some embodiments, as a method for detecting the optimum surface roughness of the fine internal flow passage after the finishing medium finishes the fine internal flow passage in the initial period, a method for indirectly detecting the optimum surface roughness of the fine internal flow passage based on the value of the optimum surface roughness corresponding to the aperture expansion value may be used, which satisfies the following formula:

number

[0061] Here, Ra* is the optimum surface roughness after the port diameter is enlarged, Ra0 is the initial surface average roughness, δ is the port diameter enlargement value, which is generally 0.01 mm to 0.5 mm, and k is the asperity grinding ratio coefficient, which is generally 0.2 to 0.4.

[0062] Here, the uneven grinding ratio coefficient k indicates the distribution probability ratio of the abrasive grains located at the ridges to the abrasive grains located at the valleys, and can be measured by the ratio of the grinding thinning amount at the valleys and ridges. In the case of cutting tools for machining, the cutting tools perform directional machining only on the convex points with rigid positioning, so k ≒ 0. In the case of abrasive flow, the convex points and valley areas are both pressed by the abrasive grains and ground by contact, so k ≒ 0.6 to 0.8. Flexible methods such as chemical / electrochemical / magnetic / ultrasonic + abrasive grains are isotropic machining for the convex points and valley areas, so k ≒ 0.9 to 1, that is, even if the machining takes a long time and the average thinning amount of the surface is large, the surface roughness is not significantly improved, and only a glossy orange peel-like surface morphology is left. In the case of the two-phase flow finishing method introduced in the above examples, the non-Newtonian fluid has a high-speed shear motion of the surface by the rigid cutting tool, so it has a higher directional grinding for the convex points, so k ≒ 0.2 to 0.4. In general, first calculate the target diameter expansion value corresponding to the target value of the surface optimum roughness, and then compare the actual diameter expansion value with this initial period. If the actual diameter expansion value is 90% or more of the target diameter expansion value, it means that the surface optimum roughness Ra* after the diameter expansion corresponding to this diameter expansion value matches the target value, so this initial period is the reference period, while if it does not match the target value, the step period is increased successively until the surface optimum roughness reaches a predetermined value.

[0063] When the optimum surface roughness of the fine internal flow passage is indirectly detected by the optimum surface roughness corresponding to the aperture enlargement value, the detection process is convenient and can be directly detected on site.

[0064] In yet another embodiment, as shown in FIG. 4, the finishing method further includes cleaning the finished fine internal flow passage after setting the optimal surface roughness of the fine internal flow passage as the target value, and specifically includes the following steps:

[0065] A cleaning medium is injected into the fine internal passages through the ports at a predetermined pressure, and the cleaning medium dissolves in the aqueous liquid of the finishing medium until the Tyndall effect appears in the cleaning medium flowing out of the fine internal passages.

[0066] The cleaning medium and the aqueous liquid are mutually soluble, for example, when the finishing medium is an aqueous two-phase flow, the cleaning medium is correspondingly deionized water, so that the aqueous liquid phase of the finishing medium can be sufficiently cleaned, and the defects such as the bend of the internal flow path caused by the abrasive flow technology, the residue in the dead angle, and the defects which are difficult or impossible to completely remove after the processing is completed can be avoided. Meanwhile, the pressure of the cleaning medium is the same as the predetermined pressure, so that the cleaning medium can remove the solid phase of the finishing medium. As a principle, the inventors have found that the residual position of the solid phase is generally related to the applied pressure, so that by applying the same pressure, the cleaning medium can "find" and remove the residual solid phase.

[0067] As a method for determining whether cleaning is complete, it is not necessary to disassemble the workpiece and observe the characteristic expression, but only to characterize the occurrence of the Tyndall phenomenon in the cleaning medium flowing out of the fine internal flow path after cleaning. For example, the flowing cleaning medium may be put into a transparent drainage container and then discharged from the transparent drainage container. During this process, the deionized water in the transparent drainage container is always irradiated with a spotlight, so the state of the light in the cleaning deionized water is observed. If the spotlight light in the deionized water after cleaning is in a turbid state and the Tyndall effect, which is a linear milky light beam, does not occur, it indicates that the cleaning at this time is not yet complete, and deionized water is continued to be added until the spotlight light in the deionized water in the transparent drainage container becomes a linear milky light beam, that is, the Tyndall effect appears. It can be understood that after the above cleaning process, ultrasonic cleaning and drying in a drying box may be performed sequentially.

[0068] In some embodiments, referring to FIG. 5 , in a step of obtaining optimal values ​​for the viscosity of the aqueous liquid phase of the finishing medium, and the abrasive grain size and abrasive mass concentration of the solid phase, the liquid phase viscosity, the solid phase abrasive grain size, and the solid phase abrasive grain mass concentration of the finishing medium may be gradually increased based on the lower limit values ​​of the liquid phase viscosity, the solid phase abrasive grain size, and the abrasive grain mass concentration until the flow rate or flow rate of the two-phase finishing medium is 1% to 5% lower than the corresponding lower limit values.

[0069] For example, the viscosity of the liquid phase is tested using an Ubbelohde viscometer in the pure water liquid phase, and the thickener is gradually increased to adjust the aqueous viscosity to a lower limit of 50 cP. Then, test processing is performed on the internal flow path of the fine internal flow path workpiece to be processed, the initial flow rate or flow rate data corresponding to the finishing medium is read as the reference value, the thickener is increased by 1 g / L and the corresponding viscosity increment is increased by about 10 cP, and the test processing on the internal flow path to be processed is continued, and the increase step is repeated until the initial flow rate or flow rate data is less than 1-5% of the flow rate or flow rate reference value, and the thickener concentration at this time is optimal, and the viscosity of the corresponding finishing medium is optimal. Table 1 can be referred to for the optimal value range of viscosity corresponding to different calibers of the fine internal flow path. Table 1: Optimal range of viscosity of the liquid phase of the finishing medium for different diameters of fine internal channels [Table 1]

[0070] Also, for example, for the grain size of the solid phase, one of the lower limits is conservatively selected on the premise that the upper limit is not exceeded, and the lower limit of the ratio of the internal flow passage diameter to the grain size of the abrasive is usually 20, that is, it is necessary to ensure that at least 20 grains do not clog when passing through the internal flow passage diameter in parallel, so that the lower limit of the grain size corresponding to the different internal flow passage diameter is obtained. For example, if the corresponding internal flow passage diameter is 3 mm, the corresponding upper limit of the grain size is 3 / 20 mm, that is, 150 μm. Based on this upper limit, in order to ensure the safety of the test, the lower limit is generally set to 1 / 5 of the upper limit, that is, the grain size is increased based on the lower limit of 30 μm. The inventor discovered that if the grain size of the abrasive is smaller than the lower limit, the mass of the abrasive itself is too low to generate sufficient kinetic energy to realize highly efficient polishing and grinding. After selecting the lower limit of the grain size, test processing is carried out, the initial flow rate or flow rate data corresponding to the finishing medium is taken as the reference value, then the grain size increment is increased by 1μm~10μm based on the lower limit of the grain size, and the test processing of the internal flow path to be processed is continued, and the increase process is repeated until the initial flow rate or flow rate data is less than 1~5% of the flow rate or flow rate reference value, at this time the grain size of the grain is the optimum value. Table 2 can be referred to for the grain size ranges corresponding to different apertures of the fine internal flow path. Table 2: Optimal range of abrasive grain size for finishing media corresponding to different diameters of fine internal channels [Table 2]

[0071] Also, for example, for the abrasive mass concentration of the solid phase, the lower limit of the mass concentration is selected based on the mass concentration of the abrasive being 10 g / L. The inventors have found that below this lower limit of the mass concentration, the grinding effect is insufficient due to the decrease in the grinding point probability on the abrasive surface. After selecting the lower limit of the mass concentration, a test process is carried out, and the initial flow rate or flow rate data corresponding to the finishing medium is read as a reference value, and then the abrasive mass concentration is increased by 2 g / L to 5 g / L based on the lower limit of the mass concentration to continue the test process of the internal flow path to be processed, and the increase step is repeated until the initial flow rate or flow rate data is less than 1 to 5% of the flow rate or flow rate reference value, at this time the mass concentration of the abrasive is the optimal value. For the optimal values ​​of the mass concentration range corresponding to different calibers of the fine internal flow path, refer to Table 3. As shown in Table 3, the inventors found that for fine internal flow passages with a diameter of 0.5 mm to 1 mm, the optimal abrasive mass concentration is correspondingly low, at 10 g / L to 15 g / L, whereas for fine internal flow passages with a diameter of more than 1 mm, the abrasive mass concentration has a low correlation with the diameter dimension, at 10 g / L to 35 g / L. Table 3: Optimal range of abrasive mass concentration of finishing media for different diameters of fine internal channels [Table 3]

[0072] It is understood that the above optimal values ​​can be obtained by on-site machining tests, that is, if it is necessary to determine the optimal values ​​of the viscosity of the finishing medium, the abrasive grain size, and the abrasive grain mass concentration corresponding to a certain fine internal passage, they can be obtained by test machining based on the above method. Then, when finishing this kind of fine internal passage, the optimal values ​​can be directly applied, and there is no need to perform test machining.

[0073] In some embodiments, the value of the predetermined pressure P can be calculated according to the following formula:

number

[0074] Here, Ra0 is the initial surface average roughness of the internal flow passage, Ra is the target value of the optimal roughness of the internal flow passage surface after machining, L is the average cutting depth of the abrasive cutting edge, b is the average contact length of the abrasive cutting edge, ρl is the liquid phase density, ρp is the abrasive solid phase density, σw is the yield limit of the workpiece material, t is the initial period mentioned above, which can generally be calculated from the initial surface average roughness of the internal flow passage and the average cutting depth of the abrasive cutting edge that contacts the fine internal flow passage surface in 1 second, χ is the pressure increase ratio when the internal flow passage reaches the saturation flow rate, Re is the Reynolds number of the liquid phase, l is the length of the internal flow passage, D is the diameter of the internal flow passage, d is the grain size of the abrasive grain, and k is the unevenness grinding ratio coefficient.

[0075] Regarding the meaning and specific values ​​of the above parameters, generally, the initial surface average roughness Ra0 is taken as the average value of the roughness of each area of ​​the internal flow path, since the surface roughness of each area in the initial stage after the manufacture of the internal flow path is not completely consistent, and the Ra0 data is usually as follows: 3D printing is 6.3 μm to 30 μm, precision casting is 3.2 μm to 6.4 μm, machining is 0.8 μm to 1.6 μm, laser processing and wire cutting are 1.6 μm to 3.2 μm, and the target value Ra of the optimal surface roughness after finishing (the roughness of each area after polishing is not completely consistent even in the initial difference, so the optimal value of the roughness of each area of ​​the internal flow path is taken), and the normal Ra data is as follows: 3D printing and precision casting are 1.6 μm or less, machining is 0.4 μm or less, and laser processing and wire cutting are 0.8 μm or less. The length of the fine internal flow passage is l, the diameter D is 3mm or less, the length-to-diameter ratio l / D is 50 or more, the Reynolds number Re is 20-200, and can be obtained by calculating the viscosity and flow rate of the liquid phase. The uneven grinding ratio coefficient k is 0.2-0.4, the abrasive grain diameter D is 5μm-150μm, the average cutting depth L of the abrasive cutting edge is 1.4nm-14nm, and the average cutting depth L of the abrasive cutting edge can be measured in terms of the thinning amount per unit time. The thinning speed of one side of the internal flow passage in the finishing technology of aqueous two-phase flow is 5μm / h-50μm / h. The average contact length b of the abrasive cutting edge is 50nm-1000nm, the average contact length b of the abrasive cutting edge can be measured at the final limit scratch and the corresponding optimum roughness, the optimum roughness Ra after abrasive polishing grinding in the finishing technology of aqueous two-phase flow is 0.05μm-1μm, so the contact length b of the abrasive cutting edge is 50nm-1000nm. The liquid phase density ρl is 1200Kg / m3-1500Kg / m3, for aqueous liquid phase it is generally 1500Kg / m3, the abrasive solid phase density ρp is 2200Kg / m3-3300Kg / m3, the specific values ​​are different for different solid abrasives. The yield limit σw of the workpiece material can be obtained by looking up the table, t is the initial period, i.e., calculated from the initial average roughness and the average cutting depth of the abrasive cutting edge, and the intensification ratio χ at the saturation flow rate must be greater than 1 and is generally between 50 and 400.The boost ratio of the saturated flow rate here means the ratio of the inner lumen of the inner flow path at the end of the inner flow path to the cross-sectional area of ​​the inner flow path when the fluid enters the inner flow path from the end of the inner flow path, for example, if the cylinder that propels the polishing medium is at the front end and the inner flow path is at the rear end, the ratio of the cross-sectional area of ​​the cylinder to the cross-sectional area of ​​the inner flow path is 50 to 400. The specific value varies depending on the actual situation.

[0076] The above method has solved the problem of presetting the fine internal passage processing parameters, making the finishing method efficient, safe and reliable. It can be understood that the value of the predetermined pressure P can be obtained by trial and error, as long as the finishing medium flows through the fine internal passage at a flow rate of more than 5m / s, for example, a small lower limit can be estimated based on experience, and then trials can be continued until the flow rate requirement is met, but this method is inefficient, so a data table can be calculated based on this formula or test data, and then the finishing process can be performed by simply consulting the table. After long-term testing, the inventor has obtained the process parameters of the finishing method corresponding to titanium alloy / high temperature alloy / steel, which are shown in Table 4 below. Table 4: Process parameters for finishing methods for titanium alloys / high temperature alloys / steels [Table 4]

[0077] And, for the ceramic / aluminum alloy / polymer material, the corresponding predetermined pressure is 50% to 70% lower than the predetermined pressure P corresponding to the titanium alloy / high temperature alloy / steel material in Table 4.

[0078] In some embodiments, the thickener for providing the above-introduced finishing medium, which provides an aqueous liquid phase with a certain viscosity, may include a polymer thickener, preferably a combination of one or more of polymer long-chain flexible polyoxyethylene and polyacrylamide. The inventors have found that when a polymer thickener is used, as the viscosity increases within a certain range, it actually results in an almost equal flow rate and a uniform polishing and grinding effect in each region of the internal flow path. The principle is probably that the long chain of the polymer provides a turbulent resistance reduction effect, reducing the friction resistance in the internal flow path of the liquid, thereby realizing an almost equal flow rate and a uniform polishing and grinding effect in each region of the internal flow path, and avoiding the difference in the polishing and grinding effect between the port and the inside. The inventors have also found that when a non-polymer thickener is used, the viscosity of the liquid phase increases, but the difference in the polishing and grinding effect between the flow path port and the inside begins to increase, and the flow path port has a higher polishing and grinding effect than the inside. The use of polymer thickeners is particularly suitable for the case where the fine internal flow passage is three-dimensionally stretched and has a structure including S-shaped bends, L-shaped bends, U-shaped bends, O-shaped bends, and spiral bends. Due to the turbulent resistance reduction effect of the polymer thickener, in the process of finishing the structure including S-shaped bends, L-shaped bends, U-shaped bends, O-shaped bends, and spiral bends that are three-dimensionally stretched, the liquid does not significantly reduce its own flow rate due to the increase in friction resistance in the internal flow passage, and ensures that the difference between the worst roughness and the optimal roughness of each region is within 30%, thereby achieving a good uniform finishing effect. It is also understood that if the structure is relatively simple, such as a linear internal flow passage, there is no need to use polymer thickeners.

[0079] In some embodiments, the aqueous liquid phase of the finishing medium may be added with an antifoaming agent in addition to the thickener, so that the volume ratio of the foam slurry on the surface of the two-phase flow polishing medium to the volume of the liquid phase during the finishing process does not exceed 0.3:1, thereby preventing bubbles from interfering with the fine cutting process of the finishing medium and the flow rate and pressure detection system. The antifoaming agent may be selected from non-silicon-based agents including organic substances such as alcohols, fatty acids, fatty acid esters, phosphate esters, mineral oils, and amides. The polyether-based agents include copolymers of ethylene oxide and propylene oxide. The silicone-based agents include polydimethylsiloxane and dimethyl silicone oil. Preferably, the antifoaming agent is a combination of one or more of lauric acid, polymerized propylene oxide, etc., and the mass concentration of the antifoaming agent is 1 g / L to 5 g / L.

[0080] In some embodiments, a lubricant may be added to the finishing medium, and the mass concentration of the lubricant is 1 g / L to 10 g / L. The lubricant may be selected from simple substances or inorganic substances such as MoS2, graphite powder, talc powder, tetraboron mononitride, calcium fluoride, barium fluoride, lead oxide, etc., or may be selected from organic polymer compounds such as polytetrafluoroethylene and polyimide. Preferably, the lubricant is a combination of one or more of MoS2 and graphite powder. The lubricant must ensure that the flow rate and pressure of the finishing medium during finishing do not suddenly decrease by more than 5% due to possible clogging of the abrasive grains, thereby ensuring the reliability of the finishing process.

[0081] In some embodiments, the liquid phase of the finishing medium may contain additives in the following mass concentrations: for example, 1 g / L to 5 g / L of a rust inhibitor may be added to prevent corrosion of the aqueous liquid phase against the part to be processed; 20 g / L to 30 g / L of a dispersant may be added to allow the solid phase abrasive grains and various additives in the finishing medium to be well dispersed in the liquid phase, particularly in aqueous systems; and 1 g / L to 2 g / L of an antifreeze may be added to prevent freezing of the finishing medium due to low temperatures and thus the effect on the finishing process due to a decrease in flow rate or flow rate.

[0082] In light of the above, the finishing method introduced in the above embodiment can obtain a fine internal flow passage workpiece with a diameter of 3 mm or less, a length-to-diameter ratio of 50:1 or more, and an optimal surface roughness Ra of 0.05 μm. Due to its very low surface roughness, the problem of burrs, attached residual particles, or adhesive powder falling off due to high-speed friction between the fluid flowing into the internal flow passage and the surface layer becoming redundant and spreading all over the fluid or blocking the flow passage is avoided, and the problem of the rough inner surface being prone to becoming a source of fatigue cracks during long-term use and prone to carbon accumulation in high-temperature oil passage systems is also avoided. In addition, the "step" phenomenon on the surface of the internal flow passage and other factors cause turbulence and vortexes in the fluid movement process, which rapidly increases the fluid friction resistance, and further causes the fluid to run away and vibration to occur, reducing the service life of the parts. In addition, the occurrence of a large number of cavitation bubbles in the fluid of the fine internal flow passage, which affects combustion and liquid force, and also causes cavitation corrosion is avoided. For example, in some embodiments, the fine internal passage workpiece obtained by the finishing method introduced in the above embodiments is an additively manufactured high-temperature alloy fuel nozzle of an aero engine, whose oil passage is a fine internal passage, with an aperture of less than 2.5 mm, a length-to-diameter ratio of greater than 50:1, and a surface optimum roughness Ra of less than 1.6 μm, and such a low surface optimum roughness is reached after finishing, indicating that the powder particles with semi-sintered or adhesive on the internal passage surface of the part are removed during the finishing process. Compared with an unfinished additively manufactured fuel nozzle, it is possible to avoid the burrs caused by the high-speed friction between the fuel flowing into the internal passage and the surface layer, the adhered residual particles, or the excess when the adhesive powder falls off, which spreads everywhere in the fluid, block the oil passage, cause mechanical wear failure, and cause serious safety accidents. In addition, it is avoided that the inner surface with large roughness is prone to become a fatigue crack source during long-term use, and the carbon accumulation phenomenon is likely to occur in the high-temperature oil passage system. In addition, the "step" phenomenon on the surface of the internal flow passage prevents turbulence and vortexes from occurring in the fluid movement process, causing a sudden increase in fluid friction resistance and even causing the fluid to run out of control, resulting in vibrations and shortening the lifespan of parts.In addition, the rough surface prevents a large number of cavitation bubbles from being generated in the fluid, which affects combustion and hydraulic power, and ultimately causes cavitation corrosion.

[0083] For example, in some embodiments, the fine internal flow passage workpiece obtained by the finishing method introduced in the above embodiments is a hollow blade cast for an aircraft engine, in which the cooling holes communicating with the pores on the surface of the blade are fine internal flow passages, the length-to-diameter ratio is greater than 50:1, the hole diameter of the pores on the surface of the blade is 0.3 mm to 0.6 mm, the inner wall roughness Ra of the pores is 0.8 μm or less, there is no remelted layer, and the chamfer of the hole is greater than 0.1 mm, thereby avoiding early failure of the part due to the tendency of microcracks to occur on the surface of the remelted layer, prolonging the life of the hollow blade, and improving the aerodynamic performance.

[0084] In order to more clearly explain the effects of the present invention, six specific examples of fine internal flow passage workpieces using the finishing method introduced in the above examples are shown below. Note that the structural schematic diagrams of parts shown in Figures 6A, 7A, 8A, 9A, 10A, and 11A are not drawn to scale.

[0085] (First Example) As shown in Fig. 6A, the target product of this embodiment is a fuel nozzle 100 for a certain type of aircraft engine, and the internal flow passage to be finished is manufactured by laser additive manufacturing technology, the aperture D of the fine internal flow passage is 1.3mm-1.4mm, the total length of the flow passage is 130mm-140mm, the length-to-diameter ratio is 100, and the structure includes a straight line 101, an L-shaped bend 102, and an O-shaped bend 103. As for the bending structure, as shown in Fig. 13, its parameters mainly include a bending radius and a bending angle, the bending point is the point where the deflection first occurs along the axis (straight line), the bending angle is the central angle corresponding to the arc length between two adjacent bending points, and the bending radius is defined as the radius of curvature corresponding to the arc length between two adjacent bending points. As shown in FIG. 13, the bending points of the first bending structure 11 are 111, 112, the bending radius is R1, and the bending angle a1 is an acute angle, the bending points of the second bending structure 12 are 121, 122, the bending radius is R2, and the bending angle a2 is a right angle, and the bending points of the third bending structure are 131, 132, the bending radius is R3, and the bending angle a3 is an obtuse angle. As shown in FIG. 6A, the bending angle of the L-shaped bend 102 is about 90°, the bending radius is about 6mm, the bending angle of the O-shaped bend 103 and the corner 104 of the straight line 101 is about 60°, the bending radius is about 8mm, and the bending angle of the O-shaped bend 103 is 180°, and the bending radius is about 15mm. The material is a high temperature alloy. The specific finishing method is as follows:

[0086] The first step is to prepare the finishing medium. First, add antifreeze, antifoam, rust remover, dispersant and lubricant in deionized water in sequence, and test with Ubbelohde viscometer. Slowly increase the thickener to adjust the aqueous viscosity to 50cP, then perform test processing on the internal flow path of the part to be processed. Take the flow rate or flow rate data as the reference value, and continue to increase the thickener by 1g / L and the corresponding viscosity increase by about 10cP. Continue to test the internal flow path of the part to be processed until the initial flow rate or flow rate data is below 1%-5% of the reference value. At this time, the thickener concentration is optimal and the corresponding finishing medium viscosity is optimal. Tests show that the optimal thickener addition amount for the fuel nozzle is 4g / L-5g / L, that is, the liquid phase viscosity of the finishing medium is 90cP-100cP. Similarly, for the grain size, a lower limit is conservatively selected on the premise that the upper limit is not exceeded, and the lower limit of the ratio of the internal flow passage diameter to the grain size is usually 20, that is, the internal flow passage diameter needs to ensure that at least 20 grains can pass through in parallel without clogging, so the upper limit of the grain size is 70 μm, and the lower limit of the grain size is 13 μm. Then, test processing is performed on the internal flow passage of the part to be processed based on the grain size lower limit, the flow rate or flow rate data is read as the reference value, and the initial grain size is increased by 1 μm to 10 μm, and the test processing of the internal flow passage of the part to be processed is continued until the initial flow rate or flow rate data is less than 1% to 5% of the reference value, at this time the grain size is optimal, and the grain size d is obtained by testing from 30 μm to 32 μm. Similarly, for the mass concentration of abrasive grains, first select 10g / L as the lower limit of the mass concentration of abrasive grains, perform test processing on the internal flow path of the part to be processed, read the reference value of the flow rate or flow rate data, increase 2g / L~5g / L based on the mass concentration of abrasive grains of 10g / L, and continue the internal flow path test processing of the part to be processed until the flow rate or flow rate data is less than 1%~5% of the reference value, at this time, the mass concentration of abrasive grains is optimal. The optimal mass concentration of abrasive grains is 20~22g / L through testing. After adding all the above substances to the deionized water, the production of the two-phase flow finishing medium is completed, and the finishing medium is added to the equipment cylinder.

[0087] Step 2: The specific characteristic parameters of this fuel nozzle are: pipe length l = 130mm~140mm, pipe diameter D = 1.3mm~1.4mm, length to diameter ratio l / D = 100, initial average roughness Ra0 = 10μm, target value of optimal roughness after finishing Ra = 1.6μm, Reynolds number Re = 120, uneven grinding ratio coefficient k = 0.3, average grain diameter d = 30μm, average cutting depth L of the grain cutting edge corresponding to this grain diameter = 3.3 nm, i.e., the one-side thinning rate during the processing is about 12 μm / h, the abrasive cutting edge contact length b = 500 nm, i.e., the final limit scratch and the corresponding optimum roughness Ra are 0.5 μm, the aqueous liquid phase density ρl = 1500 kg / m3, the abrasive solid phase density ρp = 3300 kg / m3, the high-temperature alloy material yield limit σw = 300 MPa, the initial processing time t = 1 h, and the pressure increase ratio χ = 145. These parameters are substituted into the following equation.

number

[0088] Calculating, we obtain the specified pressure P = 46.7 MPa.

[0089] Step 3: The specified pressure P = 46.7 MPa and processing time 1 h in step 2 are input into the equipment to perform prototype processing. After the prototype processing is completed, the diameter of the internal flow passage port of the test piece is measured with a plug gauge, δ is the port diameter expansion value, and after the measurement, δ = 0.04 mm is found, which does not reach the theoretical value of the port diameter expansion δ = 0.096 mm calculated with Ra = 1.6 μm as follows. This means that the internal flow passage roughness does not reach the optimal roughness Ra = 1.6 μm after the above finishing.

number

[0090] Step 4: The step time was increased by 1h each time, and the total processing time was finally 8h, reaching the theoretical aperture enlargement value δ=0.096mm.

[0091] Step 5: Enter the period of 8 hours and the specified pressure P = 46.7 MPa into the equipment to perform the formal processing. When the processing time reaches 8 hours, the equipment will automatically stop and the processing will end.

[0092] Step 6: After the processing is completed, the finishing medium in the cylinder is sucked to clean the cylinder, and deionized water with a cleanliness of 0.1μs / cm~10μs / cm is added to the cylinder as a cleaning medium again. The pressure is set to P=46.7MPa, and the equipment is started to apply this pressure to the deionized water to perform deionized water processing and cleaning. The deionized water discharged through the internal flow path is irradiated with a spotlight beam, and when the Tyndall effect, which is a linear milky light beam, appears, the cleaning is completed.

[0093] Seventh step: The parts are ultrasonically cleaned for 10 minutes, dried with an air gun, and finally dried in an oven to complete the final cleaning.

[0094] As shown in Figure 6B, the finished fuel nozzle was cut along the axis of the passage by wire cutting, and when further enlarged, as shown in Figure 6C, the inner surface of the passage was clearly visible with a flattened surface close to the machined surface and a remarkable finishing effect, and the surface was smooth and bright. Metallographic detection showed that there was no residual, inlaid or semi-sintered additive manufacturing powder, and roughness detection showed that the optimal roughness Ra was 1.3 μm, achieving the target requirement of Ra<1.6 μm.

[0095] (Second Example) As shown in FIG. 7A, the target product of this embodiment is an internal flow passage 200 of a certain type of heat exchanger, and the internal flow passage to be finished is processed by laser additive manufacturing technology. The structural features are that the aperture D of the fine internal flow passage is 2.3mm-2.4mm, the total length l of the flow passage is 500mm, the length-to-diameter ratio l / D is 28, and the structure includes a straight line 201, an L-shaped bend 202, an S-shaped bend 203, and a U-shaped bend 204, and the bending angle of the S-shaped bend 203 is about 60°, that is, the bending angle of the first bending structure 2031 and the second bending structure 2032 of the S-shaped bend 203 shown in FIG. 7A is 60°, the bending radius is about 6mm, the bending angle of the L-shaped bend 202 is 90°, and the U-shaped bend 204 is a structure including two consecutive symmetrical L-shaped bends 202. The material is an aluminum alloy. The specific processing method is as follows:

[0096] First step: As in the first embodiment, no further description is given here. The viscosity of the liquid phase of the obtained two-phase flow finishing medium is 100-120 cP, the abrasive grain size is d=50 μm-52 μm, and the optimal abrasive grain mass concentration is 30 g / L-35 g / L.

[0097] Step 2: The specific characteristic parameters of the internal flow passage of this heat exchanger are "pipe length l = 500 mm, pipe diameter D = 2.3 mm ~ 2.4 mm, length to diameter ratio l / D = 208, initial average roughness Ra0 = 25 μm, target value of optimal roughness after finishing Ra = 1.6 μm, Reynolds number Re = 60, uneven grinding ratio coefficient k = 0.2, abrasive grain diameter d = 50 μm, corresponding average cutting depth L = 10 nm, that is, the machining process Similarly, the above parameters are substituted into the following equation: thinning speed per side at 35 μm / h, average contact length of the abrasive cutting edge b = 800 nm, i.e., the final limit scratch and the corresponding optimum roughness Ra are 0.8 μm, aqueous liquid phase density ρl = 1500 kg / m3, abrasive solid phase density ρp = 3300 kg / m3, aluminum alloy material yield limit σw = 100 MPa, initial processing time t = 1 h, and pressure increase ratio χ = 87.

number

[0098] Calculate and obtain the specified pressure P = 51.5 MPa.

[0099] Step 3: Input the specified pressure P=51.5MPa and initial period 1h in Step 2 into the equipment to perform prototype processing. After the prototype processing is completed, measure the diameter of the internal flow passage port of the test piece with a plug gauge, δ is the port diameter expansion value, and after the measurement, δ=0.22mm is found, which is more than 90% of the theoretical value of the port diameter expansion δ=0.234mm calculated with Ra=3.2μm by the following formula, which means that the desired optimal roughness target value Ra=1.6μm after the above-mentioned finishing process is reached by the finishing process of the internal flow passage for a total time of 1 hour.

number

[0100] Step 4: Input the reference period of 1 hour and the specified pressure P = 51.5 MPa into the equipment and perform the formal processing. When the processing reaches the reference processing time, the equipment will automatically stop and the processing will end.

[0101] Fifth step: After the processing is completed, the finishing medium in the cylinder is sucked to clean the cylinder, and deionized water with a cleanliness of 0.1μs / cm~10μs / cm is added to the cylinder as a cleaning medium again. The pressure is set to P=51.5MPa, and the equipment is started to add this pressure to the deionized water to perform deionized water processing and cleaning. The deionized water discharged through the internal flow path is irradiated with a spotlight beam, and the cleaning is completed when the Tyndall effect, which is a linear milky light beam, appears.

[0102] Sixth step: The parts are ultrasonically cleaned for 10 minutes, dried with an air gun, and finally dried in an oven to complete the final cleaning.

[0103] As shown in Figure 7B, a certain type of heat exchanger after finishing was cut along the axis of the flow passage by wire cutting, and when further enlarged, as shown in Figure 7C, the inner surface of the flow passage was clearly flattened close to the machined surface and had a remarkable finishing effect, and the surface was smooth and bright. Metallographic detection showed that there was no residual, inlaid or semi-sintered additive manufacturing powder, and roughness detection showed that the optimal roughness Ra was 1.08 μm, achieving the target requirement of Ra below 1.6 μm.

[0104] In addition, in one comparative example, the predetermined pressure for the internal flow path structure is 21.2MPa, as in the second embodiment, and as shown in Figures 12A and 12B, taking the area near the first bending structure 2031 of the S-bending of the U-bending attachment 204 as an example, a significant "orange peel effect" appears on the processed surface, and the roughness improvement is not significant. The inventors later calculated the reason for this, and found that the flow rate of the finishing medium is 4.2m / s, which does not reach the critical flow rate of non-Newtonian fluid >5m / s, so target grinding for only the convex points cannot be realized, and the high and low points on the surface can only be ground together, leaving a significant "orange peel effect" on the surface, and the processing effect of target grinding for only the convex points when the flow rate is >5m / s cannot be realized.

[0105] (Third Example) As shown in FIG. 8A, the target product of this embodiment is an internal flow passage 300 of a certain type of hydraulic module, and the internal flow passage to be finished is processed by laser additive manufacturing technology. The structure has a fine internal flow passage diameter D of 3 mm, a total length l of the flow passage of 150 mm, and a length-to-diameter ratio l / D of 50. It includes a straight line 301, an S-shaped bend 302, and an L-shaped bend 303, in which the S-shaped bend 302 refers to a staircase structure consisting of multiple consecutive L-shaped bends, and the bending angle of the L-shaped bend 303 is about 90° for the inner bend and about 60° for the outer bend, where the inner and outer refer to the distance of the bending area from the center of the circle when the fluid moves and bends, and the inner bend is closer to the center of the circle and the outer bend is farther from the center of the circle. For example, as shown in Fig. 8A, the inner bend 30311 of the first bending structure 3031 of the L-shaped bending 303 is about 90°, the outer bend 30312 is about 60°, the inner bend 30321 of the second bending structure 3032 of the L-shaped bending 303 is about 90°, the outer bend 30322 is about 60°, the bending radius is about 10mm, and the material is titanium alloy. The specific finishing method is as follows:

[0106] First step: As in the first embodiment, no further description is given here. The viscosity of the liquid phase of the obtained two-phase flow finishing medium is 120cP~150cP, the abrasive grain size is d=100μm~120μm, and the optimal abrasive grain mass concentration is 30~35g / L.

[0107] Step 2: The specific characteristic parameters of the internal flow passage of this hydraulic module are "pipe length l=150mm, pipe diameter D=3mm, length to diameter ratio l / D=50, initial average roughness Ra0=25μm, desired optimal roughness target value Ra=3.2μm after finishing, Reynolds number Re=50, unevenness grinding ratio k=0.1, abrasive grain diameter d=100μm, corresponding average cutting depth L=14nm of the abrasive grain cutting edge, that is, the one-side thinning speed during the processing is 50μm / h, average contact length b=1000nm of the abrasive grain cutting edge, that is, the final limit scratch and corresponding optimal roughness Ra are 1μm, aqueous liquid phase density ρl=1500kg / m3, abrasive grain solid phase density ρp=3300kg / m3, titanium alloy material yield limit σw=600MPa, initial period t=0.5h, pressure increase ratio χ=65", and these parameters are substituted into the following equation.

number

[0108] Calculate and obtain the specified pressure P = 40.5 MPa.

[0109] Step 3: The predetermined pressure P=40.5MPa and the initial period of 0.5h in Step 2 are input into the equipment to perform prototype processing. After the prototype processing is completed, the port diameter of the internal flow passage of the test piece is measured with a plug gauge, δ is the port diameter expansion value, and after the measurement, δ=0.2mm is found, which reaches the theoretical value of port diameter expansion δ=0.194mm calculated with Ra=3.2μm as follows. This means that the internal flow passage roughness processing for a total time of 0.5 hours has basically reached the desired optimal roughness target value Ra=3.2μm after the above-mentioned finishing.

number

[0110] Step 4: Input the reference time of 0.5 hours and the specified pressure P = 40 MPa into the equipment to perform the formal processing. When the processing reaches the reference processing time of 0.5 hours, the equipment will automatically stop and the processing will end.

[0111] Fifth step: After the processing is completed, the finishing medium in the cylinder is sucked to clean the cylinder, and deionized water with a cleanliness of 0.1μs / cm~10μs / cm is added to the cylinder again. The pressure is set to P=40MPa, and the equipment is started to add this pressure to the deionized water to perform deionized water processing and cleaning. The deionized water discharged through the internal flow path is irradiated with a spotlight beam, and when the Tyndall effect, which is a linear milky light beam, appears, the cleaning is completed.

[0112] Sixth step: The parts are ultrasonically cleaned for 10 minutes, dried with an air gun, and finally dried in an oven to complete the final cleaning.

[0113] As shown in Figure 8B, the inner surface of the internal flow passage of a certain type of hydraulic module after finishing along the flow passage axis by wire cutting is cut, and when further enlarged, as shown in Figure 8C, the flatness close to the machined surface and the remarkable finishing effect are clearly seen, and the surface is smooth and bright. Metallographic detection shows that there is no residual, inlaid or semi-sintered additive manufacturing powder, and roughness detection shows that the optimal roughness Ra is 2.6 μm, achieving the target requirement of Ra below 3.2 μm.

[0114] (Fourth Example) As shown in FIG. 9A, the target product of this embodiment is a type of throttle internal flow passage 400, and the internal flow passage to be finished is processed by laser additive manufacturing technology. The structure has a fine internal flow passage diameter D of 0.5 mm, a total flow passage length l of 200 mm, a length to diameter ratio l / D of 400, and a spiral bending structure 401, a bending angle of 180°, and a bending radius of 5.5 mm. The material is stainless steel. The specific processing method is as follows:

[0115] First step: Similar to the first embodiment, no further description is given here. The viscosity of the liquid phase of the obtained two-phase flow finishing medium is 50cP~60cP, the abrasive grain size is d=5μm~6μm, and the optimal abrasive grain mass concentration is 10g / L~12g / L.

[0116] Step 2: The specific characteristic parameters of the internal flow passage of this hydraulic module are "pipe length l = 200mm, pipe diameter D = 0.5mm, length to diameter ratio l / D = 400, initial average roughness Ra0 = 6.4μm, target value of optimal roughness after finishing Ra = 0.8μm, Reynolds number Re = 180, unevenness grinding ratio k = 0.4, abrasive grain diameter d = 5μm, corresponding average cutting depth of the abrasive grain cutting edge L = 2nm, that is, the one-side thinning speed in the processing process is 7μm / h, average contact length of the abrasive grain cutting edge b = 100nm, that is, the final limit scratch and corresponding optimal roughness Ra is 0.1μm, aqueous liquid phase density ρl = 1500kg / m3, abrasive grain solid phase density ρp = 3300kg / m3, stainless steel material yield limit σw = 170MPa, initial period t = 1h, pressure increase ratio χ = 500", and these parameters are substituted into the following equation.

number

[0117] Calculate and obtain the specified pressure P = 55.5 MPa.

[0118] Step 3: The predetermined pressure P = 55.5 MPa in Step 2 and the initial period of 1 h are input into the equipment to perform prototype processing. After the prototype processing is completed, the diameter of the internal flow passage port of the test piece is measured with a plug gauge, δ is the port diameter expansion value, and after the measurement, δ = 0.024 mm is found, which does not reach the theoretical value of the port diameter expansion δ = 0.075 mm calculated with Ra = 0.8 μm as follows. This means that the internal flow passage roughness at the initial period of 1 hour does not reach the optimal roughness target value Ra = 0.8 μm after the finishing.

number

[0119] Step 4: The processing step was increased by 1 h each time, and the total accumulated processing time was finally 8 h, reaching the theoretical aperture enlargement value δ = 0.075 mm.

[0120] Step 5: Input the reference period of 8 hours and the specified pressure P = 55 MPa into the equipment and perform the formal processing. When the processing reaches the reference processing time, the equipment will automatically stop and the processing will end.

[0121] Step 6: After the processing is completed, the finishing medium in the cylinder is sucked to clean the cylinder, and deionized water with a cleanliness of 0.1μs / cm~10μs / cm is added to the cylinder as a cleaning medium again. The pressure is set to P=55MPa, and the equipment is started to apply this pressure to the deionized water to perform deionized water processing and cleaning. The deionized water discharged through the internal flow path is irradiated with a spotlight beam, and the cleaning is completed when the Tyndall effect, which is a linear milky light beam, appears.

[0122] Seventh step: The parts are ultrasonically cleaned for 10 minutes, dried with an air gun, and finally dried in an oven to complete the final cleaning.

[0123] After finishing, the workpiece is cut along the axis X1 of the part as shown in Figure 9A by wire cutting, and when further enlarged, the cross section of the spiral-shaped bent passage port is a tilted arrangement of a group of circular holes as shown in Figure 9B, and when the inner surface of the passage is observed through the holes, it is clearly seen that the flatness close to the machined surface and the remarkable finishing effect are observed, and the surface is smooth and bright. Metallographic detection shows that there is no residual, inlaid or semi-sintered additive manufacturing powder, and roughness detection shows that the optimal roughness Ra is 0.7μm, achieving the target requirement of Ra below 0.8μm.

[0124] (Fifth Example) As shown in FIG. 10A, the target product of this embodiment is a high-temperature alloy hollow blade 500 of an aircraft engine, the blade is formed by precision casting, the air film hole 501 is opened by spark processing, the hole diameter of the air film hole 501 is 0.3mm-0.6mm, and the thickness of the remelted layer is 5μm. The fine internal flow passage in the blade communicates with the surface air film hole 501, and the hollow blade 500 has an inner cavity structure 502 in which the fine internal flow passage communicates with the air film hole 501, and the characteristics of the fine internal flow passage structure are that the aperture D is 3mm or less, the total length of the flow passage is 300mm, and the length to diameter ratio is 100 or more. It can be understood that FIG. 10A is an example, and the actual number of the air film holes 501 is generally much more than 3. The specific finishing method of the air film hole 501 on the blade surface is as follows:

[0125] First step: Similar to the first embodiment, no further description is given here. The viscosity of the liquid phase of the obtained two-phase flow finishing medium is 50cP~60cP, the abrasive grain size is d=5μm~6μm, and the optimal abrasive grain mass concentration is 10g / L~12g / L.

[0126] Step 2: The specific characteristic parameters of the internal flow passage of this hydraulic module are "the diameter D of the internal flow passage of the blade is 3 mm, the pipe length l = 300 mm, the ratio of the pipe length to the diameter l / D = 100, the diameter D of the air film hole = 0.5 mm, the initial average roughness Ra0 = 1.6 μm, the target value of the optimal roughness after finishing Ra = 0.8 μm, the Reynolds number Re = 180, the unevenness grinding ratio k = 0.4, the abrasive grain diameter d = 5 μm, and the average cutting depth L of the corresponding abrasive grain cutting edge = 2 nm, i.e., the thinning rate of one side during the processing is 7 μm / h, the average contact length of the abrasive cutting edge b = 50 nm, i.e., the final limit scratch and the corresponding optimum roughness Ra are 0.05 μm, the aqueous liquid phase density ρl = 1500 kg / m3, the abrasive solid phase density ρp = 3300 kg / m3, the stainless steel material yield limit σw = 170 MPa, the initial period t = 30 min, and the pressure increase ratio χ = 400. These parameters are substituted into the following equation.

number

[0127] Calculate and obtain the desired pressure P = 40 MPa.

[0128] Step 3: The predetermined pressure P=40MPa and the initial period of 30min in Step 2 are input into the equipment to carry out trial processing. After the trial processing is completed, the small hole port diameter of the test piece is measured with a plug gauge, δ is the port diameter expansion value, after the measurement, δ=0.01mm is found, the one-side thinning rate has already reached 5μm, the requirement of the remelted layer being fully removed is met, and the roughness reaches more than 90% of the theoretical value of the diameter expansion δ=0.011mm after calculation with Ra=0.8μm as shown in the following formula. This means that the roughness of the small hole inner wall has reached the target value of the optimal roughness Ra=0.8μm after the above finishing.

number

[0129] Step 4: Input the specified time of 30 min and the specified pressure P = 40 MPa into the equipment to perform the formal processing. When the processing reaches the standard processing time, the equipment will automatically stop and the processing will end.

[0130] Fifth step: After the processing is completed, the polishing media in the cylinder is sucked to clean the cylinder, and deionized water with a cleanliness of 0.1μs / cm~10μs / cm is added to the cylinder again. The pressure is set to P=40MPa, the equipment is started to perform deionized water processing and cleaning, and the deionized water discharged from the internal flow path is irradiated with a spotlight beam. When the Tyndall effect, which is a linear milky light beam, appears, the cleaning is completed.

[0131] Sixth step: The parts are ultrasonically cleaned for 10 minutes, dried with an air gun, and finally dried in an oven to complete the final cleaning.

[0132] As shown in FIG. 10B, the surface of the small hole after polishing is observed by a microscope. The inner surface of the small hole is clearly flattened to the machined surface and has a remarkable polishing effect. The surface is smooth and bright, and the hole mouth has a large halation, that is, the chamfer radius of the hole is larger than 0.1 mm, which prevents the occurrence of microcracks due to fatigue corrosion at the tip of the hole when gas passes through. The optimum roughness Ra is 0.8 μm by roughness detection, and the target requirement of Ra of 0.8 μm is achieved. The fifth embodiment is different from the first to fourth embodiments in that it aims to process the surface air film hole 501 rather than the fine internal flow path of the blade. The inventor has found that when the air film hole 501 of an aircraft engine is finished by a finishing method for finishing the fine internal flow path, the effect of completely removing the remelted layer can be obtained, and the use of fluid processing allows the finishing medium to smoothly pass through the internal flow path of the blade to achieve the final finishing of the air film hole.

[0133] (Sixth Example) As shown in FIG. 11A, the target product of this embodiment is a valve 600 with intersecting deep holes, and the internal flow passage to be finished needs to adopt machining technology to deburr the deep hole intersection position. The valve 600 has a first intersecting deep hole group 601 and a second intersecting deep hole group 602, and the intersecting deep hole group 601 includes a first deep hole 6011, and the structural features of the second deep hole 6012 are that the aperture D of the fine internal flow passage is 1.6 mm, the total flow passage length l is 100 mm, the length to diameter ratio l / D is 50, and the structure includes a straight line 603 and an L-shaped bend 604, and the bending angle of the L-shaped bend 604 is 90°, for example, the L-shaped bend 604 formed by the first deep hole 6011 and the second deep hole 6012 of the first intersecting deep hole group 601, and the bending radius of the L-shaped bend is 0.2 mm. The material is an aluminum alloy. The specific processing method is as follows:

[0134] First step: As in the first embodiment, no further description is given here. The viscosity of the liquid phase of the two-phase flow finishing medium obtained was 90 cP-100 cP, the abrasive grain size was d=40 μm-42 μm, and the optimal abrasive grain mass concentration was 20-22 g / L.

[0135] Step 2: The specific characteristic parameters of the internal flow passage of this cross deep hole are "pipe length l = 100mm, pipe diameter D = 1.5mm ~ 2mm, length to diameter ratio l / D = 50, initial average roughness Ra0 = 0.8μm, target roughness after finishing Ra = 0.4μm, burrs at the cross hole position are sufficiently removed under a 40x microscope, Reynolds number Re = 100, unevenness grinding ratio coefficient k = 0.3, abrasive grain diameter d = 40μm, and the flatness of the abrasive blade tip that contacts the fine internal flow passage surface at each second The average cutting depth L=3 nm, i.e., the thinning speed of one side during the machining process is 11 μm / h, the contact length of the abrasive grain cutting edge b=200 nm, i.e., the final limit scratch and the target value Ra of the corresponding optimum roughness are 0.2 μm, the aqueous liquid phase density ρl=1500 kg / m3, the abrasive grain solid phase density ρp=3300 kg / m3, the aluminum alloy material yield limit σw=100 MPa, the initial period t=30 min, and the pressure increase ratio χ=125. Similarly, the above parameters are substituted into the following equation.

number

[0136] Calculating, we obtain the desired pressure P = 42 MPa.

[0137] Step 3: The predetermined pressure P=42MPa and the initial period of 30min in Step 2 are input into the equipment to perform trial processing. After the trial processing is completed, the diameter of the internal flow passage port of the test piece is measured with a plug gauge, δ is the port diameter expansion value, after the measurement, δ=0.05mm is found, which reaches the theoretical value of diameter expansion δ=0.047mm calculated with Ra=0.4μm as follows. By setting the actual processing time of the internal flow passage roughness of the cross deep hole to 30min, it means that the desired optimal roughness target value Ra=0.4μm after the finishing is reached.

number

[0138] Step 4: Input the reference time of 30 min and the specified pressure P = 42 MPa into the equipment and perform the formal processing. When the processing reaches the reference processing time, the equipment will automatically stop and the processing will end.

[0139] Fifth step: After the processing is completed, the finishing medium in the cylinder is sucked to clean the cylinder, and deionized water with a cleanliness of 0.1μs / cm~10μs / cm is added to the cylinder as a cleaning medium again. The pressure is set to P=42MPa, and the equipment is started to add this pressure to the deionized water to perform deionized water processing and cleaning. The deionized water discharged through the internal flow path is irradiated with a spotlight beam, and when the Tyndall effect, which is a linear milky light beam, appears, the cleaning is completed.

[0140] Sixth step: The parts are ultrasonically cleaned for 10 minutes, dried with an air gun, and finally dried in an oven to complete the final cleaning.

[0141] After finishing, the intersecting deep hole position of the valve 600 with intersecting deep holes was cut along the flow path axis by wire cutting, and when further enlarged, as shown in Figure 11B, the remarkable finishing effect was clearly seen on the inner surface of the flow path, the surface was smooth and bright, and the burrs at the deep hole intersection position were sufficiently removed under a 40x microscope. The optimum roughness Ra was 0.4 μm by roughness detection, and the target requirement of Ra being 0.4 μm or less was achieved.

[0142] Although the present invention has been disclosed in the above embodiments, the present invention is not limited to the embodiments, and those skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention and the contents that do not deviate from the technical solution of the present invention are within the scope of protection defined in the claims of the present invention.

Claims

1. A method for finishing a fine internal flow passage, the diameter of the fine internal flow passage is 3 mm or less, and the ratio of length to diameter is 50:1 or more; A liquid-solid two-phase flow finishing medium is used, the liquid phase viscosity of the finishing medium is less than 1000 cP, and the solid phase of the finishing medium is an abrasive grain; A finishing method characterized by including the steps of: applying a predetermined pressure to the finishing medium so that the finishing medium flows through a fine internal flow passage at a flow velocity of greater than 5 m / s; and a flow rate of the finishing medium flowing into the interior of the fine internal flow passage from one end thereof reaching a saturation value of the flow rate that can be accommodated by the diameter of the fine internal flow passage so that the liquid pressure inside the internal flow passage is trapped by pressure.

2. 2. The method of claim 1, wherein the liquid phase of the finishing medium is an aqueous liquid.

3. The finishing method according to claim 1, characterized in that the abrasive grains have a surface acute angle structure, the average cutting depth of the abrasive grain cutting edge is 1.4 nm to 14 nm, and the average contact length of the abrasive grain cutting edge is 50 nm to 1000 nm.

4. The finishing medium finishes the fine internal flow passages in a reference period until an optimum surface roughness of the fine internal flow passages reaches a target value, and the reference period is obtained by the following steps: The finishing method described in claim 3, characterized in that the finishing medium finishes the fine internal flow passage in an initial period, detects the optimal surface roughness of the fine internal flow passage, and if the optimal surface roughness matches the target value, the initial period is the reference period; if the optimal surface roughness does not reach the target value, the step period is successively increased until the optimal surface roughness reaches the target value, and the corresponding total period is the reference period, wherein the initial period and the step period are obtained based on the one-side thinning speed corresponding to the abrasive grain and the initial average surface roughness of the fine internal flow passage.

5. The predetermined pressure P satisfies the following formula: [0010] Here, Ra0 is the initial average surface roughness of the fine internal flow passage, Ra is the target value of the optimal surface roughness of the fine internal flow passage after finishing, t is the initial period, L is the average cutting depth of the abrasive cutting edge, b is the average contact length of the abrasive cutting edge, ρl is the aqueous liquid phase density, ρp is the abrasive solid phase density, σw is the yield limit of the workpiece material, χ is the pressure increase ratio that reaches saturation flow rate, Re is the Reynolds number of the liquid phase, l is the length of the internal flow passage, D is the diameter of the internal flow passage, d is the abrasive grain diameter, and k is the uneven grinding ratio coefficient.

6. Further, after the internal flow passage is finished, the surface optimum roughness corresponding to the diameter expansion value of the internal flow passage satisfies the following formula: [0025] Here, Ra* is the optimum surface roughness when the internal flow passage is finished and the port diameter is enlarged, Ra0 is the initial average surface roughness of the fine internal flow passage, δ is the port diameter enlargement value, and k is the uneven grinding ratio coefficient.

7. 2. The finishing method of claim 1, further comprising injecting a cleaning medium into the fine internal passages at the predetermined pressure after the optimal surface roughness of the fine internal passages reaches a target value, and the liquid phases of the cleaning medium and the finishing medium dissolve in each other until the Tyndall effect appears in the cleaning medium flowing out of the fine internal passages.

8. The finishing method according to claim 1, further comprising performing finishing by gradually increasing the viscosity of the liquid phase, the abrasive grain size and the abrasive grain mass concentration of the solid phase of the finishing medium based on lower limit values ​​of the viscosity of the liquid phase, the abrasive grain size and the abrasive grain mass concentration of the solid phase until the flow rate or flow rate of the two-phase flow finishing medium is reduced by 1 to 5% below the flow rate or flow rate corresponding to the lower limit values, thereby obtaining an optimal value range for the viscosity, the abrasive grain size and the abrasive grain mass concentration.

9. The finishing method described in claim 1, characterized in that the finishing medium finishes the fine internal flow path during a reference period, the flow speed or flow rate of the finishing medium in the fine internal flow path is determined, and when the flow speed or flow rate reaches a predetermined value, the optimal surface roughness reaches a target value.

10. The finishing method according to claim 1, characterized in that the fine internal flow passages are three-dimensionally extended and have bent structures including S-shaped bends, L-shaped bends, U-shaped bends, O-shaped bends and spiral bends, and the liquid phase of the finishing medium contains a polymeric thickener.

11. A fine internal flow passage workpiece obtained by the finishing method according to any one of claims 1 to 10.

12. The fine internal flow passage workpiece described in claim 11 has a fine internal flow passage with a diameter of 3 mm or less and a length-to-diameter ratio of 50:1 or more, the fine internal flow passage workpiece is obtained by additive manufacturing, casting, laser processing, or spark processing, and the fine internal flow passage has an inner surface with an optimal surface roughness Ra of 1.6 μm or less after finishing.

13. The fine internal flow passage workpiece described in claim 11 has a fine internal flow passage with a diameter of 3 mm or less and a length-to-diameter ratio of 50:1 or more, the fine internal flow passage workpiece is obtained by precision machining, and the fine internal flow passage has an inner surface with an optimal surface roughness Ra of 0.4 μm or less after finishing.

14. The fine internal passage workpiece is a high temperature alloy fuel nozzle of an aircraft engine by additive manufacturing, the fuel nozzle has the fine internal passage structure, the diameter of the fine internal passage is less than 2.5 mm, the structure has a straight line, an L-shaped bend and an O-shaped bend, and the surface optimum roughness Ra of the fine internal passage is less than 1.6 μm; or The fine internal flow passage workpiece is an aluminum alloy heat exchanger by additive manufacturing, the heat exchanger has a fine internal flow passage structure, the diameter is less than 3 mm, and the fine internal flow passage structure has a straight line, an L-shaped bend, an S-shaped bend, and a U-shaped bend, and the surface optimum roughness Ra of the fine internal flow passage is 1.6 μm or less, or The fine internal flow passage workpiece is a hydraulic module of a titanium alloy by additive manufacturing, the hydraulic module has a fine internal flow passage structure, a diameter of 3 mm, and the fine internal flow passage structure has a straight line, an S-shaped bend, and an L-shaped bend, and the optimum surface roughness Ra of the fine internal flow passage is 3.2 μm or less, or The fine internal flow passage workpiece described in claim 11, characterized in that the fine internal flow passage workpiece is a stainless steel throttle produced by additive manufacturing, the throttle has a fine internal flow passage structure, a diameter of less than 1 mm, and the fine internal flow passage structure has a spiral bend, and the optimal surface roughness Ra of the fine internal flow passage is 0.8 μm or less.

15. The fine internal passage workpiece is a hollow blade of a high-temperature alloy cast for an aircraft engine, and the hollow blade has an inner cavity structure in which the fine internal passage is connected to a small hole, and the optimal roughness Ra of the inner surface of the small hole after finishing is 0.8 μm or less, there is no remelted layer, and the chamfer radius of the hole is greater than 0.1 mm.

16. A finishing medium for use in the finishing method according to any one of claims 1 to 10, the finishing medium comprising a liquid phase and a solid phase, the liquid phase having a viscosity of less than 1000 cP, the solid phase being an abrasive grain, and a polymeric thickener being added to the liquid phase of the finishing medium, the step of obtaining the finishing medium comprising: A finishing medium comprising: a finishing process in which the viscosity of the liquid phase, the abrasive grain size of the solid phase, and the abrasive grain mass concentration of the finishing medium are gradually increased based on lower limit values ​​of the viscosity of the liquid phase, the abrasive grain size of the solid phase, and the abrasive grain mass concentration, until the flow rate or flow rate of the two-phase flow finishing medium is reduced by 1 to 5% below the flow rate or flow rate corresponding to the lower limit values, thereby obtaining an optimal value range for the viscosity, abrasive grain size, and abrasive grain mass concentration.

17. The finishing medium according to claim 16, characterized in that the liquid phase further contains an antifoaming agent, and during the process of machining fine internal channels by the finishing method, the volume ratio of the surface foam slurry of the finishing medium to the volume of the liquid phase does not exceed 0.3:

1.

18. 17. The finishing medium of claim 16, further comprising a lubricant added to the liquid phase of the finishing medium, the lubricant comprising one or more combinations of inorganic compounds, inorganic elements, and polymeric compounds.

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