Umbrella-shaped diffuse flow type self-circulation micro-arc oxidation device and process
The umbrella-shaped diffused self-circulating micro-arc oxidation device solves the problems of electrolyte waste and high heat dissipation energy consumption, and achieves reduced electrolyte consumption and improved film uniformity. It is suitable for the efficient processing of expensive electrolytes and small workpieces.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-04-30
- Publication Date
- 2026-06-12
AI Technical Summary
Existing micro-arc oxidation devices suffer from serious electrolyte waste, high heat dissipation energy consumption, and poor flow field uniformity, resulting in high costs, low efficiency, and unstable film quality.
An umbrella-shaped, diffused, self-circulating micro-arc oxidation device is adopted. The electrolyte is diffused through the inclined surface of the umbrella-shaped guide platform using a self-circulating conveying system to form a uniform flowing liquid layer for micro-arc oxidation reaction. Natural heat dissipation is achieved through heat dissipation fins or condensation pipes, which reduces the amount of electrolyte used and improves the uniformity of the flow field.
It significantly reduces electrolyte consumption by more than 90%, increases the contact area between the flowing liquid layer and air by 8 to 12 times, controls the coefficient of variation of film thickness to within 1.5%, and the film quality is significantly better than that of traditional devices. It is especially suitable for the efficient processing of expensive electrolytes and small workpieces.
Smart Images
Figure CN122189801A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of metal surface treatment technology, and in particular to an umbrella-shaped diffused self-circulating micro-arc oxidation device and process. Background Technology
[0002] Micro-arc oxidation (MAO) is an advanced surface treatment technology that uses high-voltage pulsed discharge to grow ceramic coatings in situ on the surfaces of light metals such as magnesium, aluminum, and titanium. It can significantly improve the corrosion resistance, wear resistance, and functional properties of workpieces, and has broad application prospects in high-end manufacturing fields such as aerospace, biomedicine, and electronics. However, existing industrial and laboratory equipment generally uses a tank immersion structure, meaning the workpiece must be completely submerged in a tank filled with electrolyte. This traditional configuration has the following three prominent drawbacks: (1) Electrolyte waste is serious and costs are extremely high. For processing small-sized samples of φ20 mm×30 mm, traditional soaking tanks need to maintain a working liquid volume of 10~20 L, while the actual electrolyte volume in contact with the workpiece is less than 1% of the total tank volume. In the research of electrolyte systems involving high-value additives such as rare earth salts (such as cerium nitrate, lanthanum nitrate), nanoparticles (such as ZrO2, Al2O3), and graphene, the "large tank for small samples" solution preparation mode makes the cost of a single experiment as high as several thousand yuan, which seriously restricts the research and development efficiency of new functional electrolytes.
[0003] (2) High heat dissipation energy consumption and bulky equipment size. The intense Joule heat generated by the micro-arc discharge process causes the temperature of the large volume electrolyte in the immersion tank to rise continuously; due to the large heat capacity of the electrolyte and the low natural heat dissipation efficiency, it is very easy to cause heat accumulation effect. In order to maintain the stability of the process temperature, traditional equipment must be equipped with a high-power industrial refrigeration unit of 750~1500 W, which increases the size and weight of the equipment and causes huge auxiliary energy consumption, resulting in high overall processing energy consumption.
[0004] (3) Poor flow field uniformity and unstable film quality. Static tank environments or those relying solely on mechanical stirring cannot guarantee the uniformity of the flow field on the workpiece surface. Complex areas such as grooves and inner holes in the workpiece often form flow dead zones, leading to polarization of reactant concentration or sedimentation of solid particles. This results in quality defects such as uneven film growth thickness (coefficient of variation CV as high as 8%~12%), poor density, and high porosity (approximately 5%~10%), affecting product reliability.
[0005] To address the aforementioned drawbacks, there is an urgent need to develop a compact device that abandons the cumbersome immersion method, utilizes a very small amount of electrolyte to achieve dynamic fluid film formation, and possesses self-heating capabilities, in order to reduce research costs, improve processing efficiency, and enhance film quality. Summary of the Invention
[0006] The purpose of this invention is to provide an umbrella-shaped diffused self-circulating micro-arc oxidation device and process to solve the technical problems existing in the background art.
[0007] To achieve the above objectives, the technical solution of the present invention is as follows: An umbrella-shaped, diffused, self-circulating micro-arc oxidation device includes: a collection tank and a power source. The collection tank contains an electrolyte. A hollow support column is vertically installed in the center of the bottom of the collection tank. An umbrella-shaped flow guide platform is fixedly installed at the top of the hollow support column. The umbrella-shaped flow guide platform is a frustum-shaped structure with an upper diameter smaller than its lower diameter. A liquid distributor is installed at the top of the umbrella-shaped flow guide platform. Several workpiece clamping interfaces for clamping workpieces are evenly arranged along the circumferential direction at the bottom edge of the umbrella-shaped flow guide platform. A self-circulating conveying system for continuously conveying the electrolyte in the collection tank to the liquid distributor is provided inside the hollow support column. The anode of the power source is connected to the workpieces clamped on the several workpiece clamping interfaces, and the cathode of the power source is connected to the flow guide slope of the umbrella-shaped flow guide platform. The electrolyte overflows evenly from the liquid distributor and diffuses downward along the flow guide slope under the action of gravity, forming a uniformly thick flowing liquid layer. The flowing liquid layer continuously flows over the surface of the workpiece and carries out a micro-arc oxidation reaction.
[0008] Furthermore, the liquid distributor is cylindrical and its diameter is equal to the diameter of the upper end face of the umbrella-shaped guide platform. The liquid distributor has a flow stabilizing cavity inside, the height of which is 25mm. The side wall of the liquid distributor is evenly provided with several overflow holes along the circumferential direction. The overflow holes are connected to the flow stabilizing cavity, and the diameter of the overflow holes is 1.5mm.
[0009] Furthermore, the workpiece clamping interface includes an insulating mounting base and a conductive spring. The insulating mounting base is embedded at the bottom edge of the umbrella-shaped flow guide platform. The bottom end of the insulating mounting base has a through hole for inserting the workpiece. The conductive spring is disposed inside the through hole and can contact the workpiece. The conductive spring is electrically connected to the anode of the power supply.
[0010] Furthermore, the bottom sidewall of the hollow support column is provided with several reflux suction ports, which are connected to the input end of the self-circulating conveying system.
[0011] Furthermore, a filter assembly is detachably and fixedly installed at the reflux suction port. The filter assembly includes a coarse filter screen and a precision filter element, wherein the pore size of the precision filter element is 50 μm.
[0012] Furthermore, the self-circulating delivery system includes: a suction pipe, a circulation pump, and a delivery pipe. The suction pipe, circulation pump, and delivery pipe are all installed inside the hollow support column. One end of the suction pipe is connected to several return suction ports, and the other end of the suction pipe is connected to the input end of the circulation pump. The output end of the circulation pump is connected to one end of the delivery pipe, and the other end of the delivery pipe passes through the umbrella-shaped guide platform and is connected to the flow stabilizing cavity of the distributor.
[0013] Furthermore, the amount of electrolyte in the collection tank is 0.8~1.2 L; the outer wall of the collection tank is provided with heat dissipation fins or the collection tank has built-in condenser pipes.
[0014] Furthermore, the flow guiding slope is made of a conductive and corrosion-resistant material, the cone half-angle θ of the flow guiding slope is 30°, and the surface roughness Ra of the flow guiding slope is 0.4~0.8μm.
[0015] Furthermore, the hollow support column is made of a corrosion-resistant, high-molecular-weight rigid material.
[0016] A pervasive, self-circulating micro-arc oxidation process, utilizing a pervasive, self-circulating micro-arc oxidation device, includes the following steps: Step 1: Inject electrolyte into the collection tank until it submerges the reflux suction port, insert the workpiece into the workpiece clamping interface, connect the power supply anode, and connect the guide slope to the power supply cathode. Step 2: Start the circulation pump and adjust the flow rate to 1.2~2.0 L / min to form a uniform flowing liquid layer with a thickness of 2.0~3.1 mm on the guide slope. After the flowing liquid layer has been formed stably, proceed to Step 3. Step 3: Turn on the power supply to allow the current to pass through the flowing liquid layer and cause breakdown discharge on the surface of the workpiece, forming a micro-arc oxidation ceramic coating. Step 4: After the set time is reached, first turn off the power, and after the discharge stops, turn off the circulation pump, remove the workpiece, and the processing is complete.
[0017] Compared with the prior art, the beneficial effects of the present invention are: In this invention, the electrolyte is pumped to the top distributor via a self-circulating delivery system built into the hollow support column. After being evenly distributed by the distributor, it flows downwards along the inclined surface of the umbrella-shaped guide platform, forming a continuous and uniform flowing liquid layer with a thickness of 2.0~3.1 mm. The workpiece to be treated is installed at the workpiece clamping interface on the edge of the umbrella-shaped guide platform. When the flowing liquid layer flows through, an electric current is applied to perform a micro-arc oxidation reaction. The electrolyte after the reaction naturally flows back to the base collection tank, is filtered, and then participates in the circulation again. This invention abandons the traditional large-volume immersion electrolytic cell and utilizes the dynamic diffused reaction principle to reduce the amount of electrolyte used by more than 90%. The flowing liquid layer has a large contact area with the air, and the effective heat dissipation area is 8~12 times that of the immersion device, eliminating the need for external cooling equipment. The coefficient of variation (CV) of the film thickness can be controlled within 1.5%, and the uniformity is significantly better than that of traditional devices. This invention has a compact structure and is particularly suitable for the formulation research of precious electrolytes containing rare earth salts, nanoparticles, etc., and for the efficient surface treatment of small workpieces. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of the overall structure of an umbrella-shaped diffused self-circulating micro-arc oxidation device provided by the present invention; Figure 2 This is a schematic diagram of the structure of the umbrella-shaped diffused self-circulating micro-arc oxidation device provided by the present invention after removing the collection tank; Figure 3 This is a schematic diagram of the self-circulating conveying system in this invention.
[0019] Figure 4 This is a process flow diagram of an umbrella-shaped diffused self-circulating micro-arc oxidation process provided by the present invention.
[0020] The labels in the attached diagram are as follows: 1-Collection tank, 2-Hollow support column, 201-Return suction port, 3-Umbrella-shaped guide platform, 4-Distributor, 5-Workpiece clamping interface, 6-Suction pipe, 7-Circulation pump, 8-Transfer pipe. Detailed Implementation
[0021] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.
[0022] like Figures 1-3As shown, an umbrella-shaped, diffused, self-circulating micro-arc oxidation device includes: a collection tank 1 and a power supply. The collection tank 1 contains electrolyte. A hollow support column 2 is vertically installed in the center of the bottom of the collection tank 1. The hollow support column 2 is made of corrosion-resistant high-molecular rigid material. An umbrella-shaped flow guide platform 3 is fixedly installed at the top of the hollow support column 2. The umbrella-shaped flow guide platform 3 is a frustum structure with an upper diameter smaller than a lower diameter. A liquid distributor 4 is installed at the top of the umbrella-shaped flow guide platform 3. Several workpiece clamping interfaces 5 are evenly arranged along the circumferential direction at the bottom edge of the umbrella-shaped flow guide platform 3 for clamping workpieces. The hollow support column 2 is equipped with a self-circulating conveying system for continuously transporting the electrolyte in the collection tank 1 to the distributor 4. The anode of the power supply is connected to several workpieces clamped on the workpiece clamping interfaces 5, and the cathode of the power supply is connected to the guide slope of the umbrella-shaped guide platform 3 or an auxiliary electrode mesh set on the guide slope. The electrolyte overflows evenly from the distributor 4 and flows downward along the guide slope under the action of gravity, forming a uniformly thick flowing liquid layer. The flowing liquid layer continuously flows over the surface of the workpiece and carries out a micro-arc oxidation reaction. Afterward, it flows into the collection tank 1, completes heat dissipation and filtration, and enters the next cycle.
[0023] The liquid distributor 4 is cylindrical and its diameter is equal to the diameter of the upper end face of the umbrella-shaped guide platform 3. The liquid distributor 4 has a flow stabilizing cavity inside, and the height of the flow stabilizing cavity is 25mm. Several overflow holes are evenly opened along the circumference of the side wall of the liquid distributor 4. The overflow holes are connected to the flow stabilizing cavity and the diameter of the overflow holes is 1.5mm. The machining error of the hole spacing of the overflow holes does not exceed 0.05mm. The overflow holes are used to evenly disperse the pumped electrolyte so that it covers the entire guide slope in a diffuse state. The difference in the outflow velocity of each overflow hole does not exceed 3.2% to ensure the circumferential consistency of the initial distribution of the flowing liquid layer (liquid film).
[0024] The workpiece clamping interface 5 includes an insulating mounting base and a conductive spring. The insulating mounting base is embedded at the bottom edge of the umbrella-shaped flow guide platform 3. The bottom end of the insulating mounting base has a through hole for inserting the workpiece. The conductive spring is disposed inside the through hole and can contact the workpiece. The conductive spring is electrically connected to the anode of the power supply.
[0025] Several reflux suction ports 201 are provided on the bottom side wall of the hollow support column 2, and the reflux suction ports 201 are connected to the input end of the self-circulating conveying system.
[0026] A filter assembly is detachably and fixedly installed at the reflux suction port 201. The filter assembly includes a coarse filter screen and a precision filter element. The precision filter element has a pore size of 50 μm and is used to trap micro-arc oxidation reaction particles and precipitates carried by the electrolyte during reflux.
[0027] The self-circulating delivery system includes: a suction pipe 6, a circulation pump 7, and a delivery pipe 8. The suction pipe 6, circulation pump 7, and delivery pipe 8 are all installed inside the hollow support column 2. One end of the suction pipe 6 is connected to several return suction ports 201, and the other end of the suction pipe 6 is connected to the input end of the circulation pump 7. The output end of the circulation pump 7 is connected to one end of the delivery pipe 8, and the other end of the delivery pipe 8 passes through the umbrella-shaped guide platform 3 and is connected to the flow stabilizing chamber of the distributor 4. The circulation pump 7 adopts a magnetic drive or diaphragm pumping structure to achieve water and electricity separation.
[0028] The electrolyte volume in the collection tank 1 is 0.8~1.2 L, which reduces the electrolyte consumption by more than 90% compared with the traditional immersion tank. The outer wall of the collection tank 1 is equipped with heat dissipation fins or the collection tank 1 has built-in condenser pipes. Physical cooling is achieved by utilizing the large-area diffusion of the electrolyte on the guide slope and the heat exchange effect with the base collection tank. Under the condition of circulation flow rate Q=1.5 L / min, no external refrigeration equipment is required and the electrolyte working temperature can be maintained below 45℃.
[0029] The guide slope is made of conductive and corrosion-resistant materials (such as stainless steel, titanium alloy, etc.) and serves directly as the counter electrode (cathode) for the micro-arc oxidation reaction; or a flexible stainless steel mesh or titanium mesh is laid on the guide slope made of insulating material as the cathode to ensure uniform electric field distribution in the flowing liquid layer; the cone half angle θ of the guide slope is 30°, the surface roughness Ra of the guide slope is 0.4~0.8μm, and under the condition that the circulation flow rate Q is 1.2~2.0 L / min, the thickness δ of the flowing liquid layer formed on the guide slope is 2.0~3.1 mm, and the optimal operating condition is Q=1.5 L / min, δ=2.5 mm; the circumferential thickness difference of the flowing liquid layer (liquid film) does not exceed 0.11 mm.
[0030] like Figure 4 As shown, an umbrella-shaped diffused self-circulating micro-arc oxidation process includes the following steps: (1) Equipment preparation: Inject electrolyte into the collection tank 1 until it submerges the return suction port 201, insert the workpiece into the workpiece clamping interface 5, connect the power anode, and connect the guide slope to the power cathode. (2) Establishing circulation: Start the circulation pump 7 and adjust the flow rate to 1.2~2.0 L / min to form a uniform flowing liquid layer with a thickness of 2.0~3.1 mm on the guide slope. After the flowing liquid layer is stably formed, proceed to the next step. (3) Micro-arc oxidation: Turn on the power, set the process parameters, and let the current pass through the flowing liquid layer to break down and discharge on the surface of the workpiece to form a micro-arc oxidation ceramic coating; maintain a continuous self-circulation of "liquid absorption-filtration-pumping-flooding-reaction-heat dissipation" during the process; (4) End of processing: After the set time is reached, turn off the power first, and after the discharge stops, turn off the circulation pump 7, remove the workpiece, and the processing is completed.
[0031] The present invention will now be described in further detail with reference to experimental data.
[0032] I. Optimization Experiment of Flow Film Thickness and Circulation Flow Rate Experimental conditions: Half-angle θ of the umbrella-shaped guide platform cone = 30°, effective inner diameter D of the distributor outlet = 80 mm, electrolyte is a silicate system (kinematic viscosity ν ≈ 1.05 × 10⁻⁶). -6 m 2 / s, density ρ ≈ 1020 kg / m 3 The room temperature was 25℃. The thickness of the liquid film (flowing liquid layer) was measured using a laser displacement sensor with a measurement accuracy of ±0.05 mm. The theoretical relationship between the liquid film thickness δ and the circulation flow rate Q is based on the Nusselt liquid film model, as shown in the following equation:
[0033] In the formula: The kinematic viscosity of the electrolyte (m) 2 / s); Volumetric flow rate (m³) 3 / s); Acceleration due to gravity (m / s²) 2 ); R is the angle of inclination of the guide slope (°). eff The effective flow radius (m) is given. The experimental results are shown in Table 1.
[0034] Table 1 Relationship between circulation flow rate and liquid film parameters
[0035] As shown in Table 1, the circulation flow rate Q has a decisive influence on the liquid film flow state and the surface coverage quality of the workpiece. When Q < 1.2 L / min, the driving force of the liquid film is insufficient, the continuity of the liquid layer on the inclined surface cannot be guaranteed, local flow interruptions occur on the workpiece surface, the coverage rate is less than 98.5%, and the interrupted areas cannot undergo effective discharge due to the lack of conductive medium, resulting in missing film growth in these areas. When Q > 2.0 L / min, the liquid film gradually evolves from stable laminar flow to wavy flow and even turbulent flow, the thickness fluctuation amplitude increases, and splash loss occurs, leading to a decrease in film uniformity. Therefore, the preferred circulation flow rate range is Q = 1.2~2.0 L / min, within which the liquid film maintains a stable laminar flow state, and the surface coverage rate of the workpiece is not less than 98.5%.
[0036] II. The Influence of the Cone Angle of the Guide Surface on the Uniformity of the Liquid Film With Q = 1.5 L / min, the effect of different cone half-angles θ on the circumferential uniformity of the liquid film was investigated, and the results are shown in Table 2.
[0037] Table 2. Effect of the half-angle of the guide slope cone on the uniformity of the liquid film.
[0038] Experiments show that when the cone half-angle θ=30°, the ratio of gravity-driven component to viscous resistance is optimal, the liquid film velocity is moderate (0.087 m / s), the thickness difference in the circumferential direction is the smallest (0.11 mm), and the film thickness CV value is the lowest (3.8%), making it the preferred cone half-angle.
[0039] III. The Influence of Liquid Film Thickness on Overall Film Quality With θ=30° fixed, different liquid film thicknesses δ were obtained by adjusting Q. Micro-arc oxidation was carried out under the same electrical parameters (voltage 400 V, frequency 500 Hz, duty cycle 40%, processing time 20 min, workpiece material: magnesium alloy AZ31B, sample size: φ20 mm×30 mm). The results are shown in Table 3.
[0040] Table 3. Comparison of overall quality of micro-arc oxidation films under different liquid film thicknesses
[0041] Table 3 shows that when δ=2.5 mm, the standard deviation of the film thickness is only 0.8 μm (coefficient of variation CV=4.1%), the film hardness reaches a peak of 412 HV, the pinhole rate drops to 1.7%, and the salt spray resistance is optimal (384 h). When the liquid film is too thin (δ<1.9 mm), the conductive channel cross-section is insufficient, and the micro-arc discharge is unstable; when the liquid film is too thick (δ>3.1 mm), the liquid film enters a wavy flow, the liquid thickness fluctuation increases, and the increased equivalent IR drop leads to a decrease in the effective working voltage on the workpiece surface, both resulting in a decline in film quality. Therefore, δ=2.5 mm is the optimal liquid film thickness recommended for engineering applications.
[0042] IV. Comprehensive Verification Experiment of Film Thickness Uniformity To verify the uniformity of film thickness of this device, under optimal operating conditions (Q=1.5 L / min, δ=2.5 mm), a 40-point comprehensive measurement was performed on a φ20 mm×30 mm magnesium alloy AZ31B cylindrical sample: 5 sections were uniformly taken along the axial direction (Z-axis) (Z1 is the top, Z5 is the bottom, with a spacing of 7.5 mm), and 8 measurement points were evenly distributed along the circumference of each section (angular spacing of 45°). The measurement was performed using an eddy current thickness gauge (accuracy ±0.1 μm). The results are shown in Table 4.
[0043] In comparison, when treated with the same electrical parameters and workpiece specifications in a traditional immersion apparatus (15 L tank, mechanical stirring), the film thickness CV value is approximately 8.5%~12.3%, and the maximum-minimum film thickness difference is 3.5~6.2 μm. The film thickness uniformity of this apparatus is 5~8 times better than that of the traditional immersion apparatus.
[0044] Table 4. MAO film thickness distribution on the workpiece surface under optimized working conditions
[0045] V. Quantitative Analysis of Resource Advantages Based on the Flow Principle (1) Comparison of electrolyte usage and cost Table 5 compares the single-batch solution preparation cost of this device and a traditional immersion tank under different electrolyte systems, taking the processing of a single workpiece with a diameter of φ20 mm × 30 mm as an example. The minimum working fluid volume required by the traditional immersion tank to maintain complete immersion of the workpiece is approximately 15 L, while the effective working fluid volume of the base collection tank of this device is only 1.0 L. For common electrolyte systems such as silicate base solutions, the cost difference between the two is relatively limited; however, in electrolyte systems involving high-value functional additives such as rare earth salts (e.g., La(NO3)3, Ce(NO3)3), zirconia nanoparticles (ZrO2), and graphene, the difference in solution preparation cost is extremely significant.
[0046] Table 5. Comparison of single-experiment solution preparation costs under different electrolyte systems
[0047] (2) Energy consumption comparison The power consumption of the fixed micro-arc oxidation power supply is 500 W, and the single processing time is 20 min. The energy consumption of each component is shown in Table 6.
[0048] Table 6 Comparison of Comprehensive Energy Consumption per Single Processing Session between This Device and Traditional Immersion Device
[0049] Note: This device utilizes a large-area contact between the diffused liquid layer and the air (the effective heat dissipation area is approximately 8 to 12 times that of the immersion type). During the 20-minute treatment process, the electrolyte temperature rise does not exceed 17°C, and the maximum temperature is below 45°C, so no external cooling is required.
[0050] The following describes the micro-arc oxidation treatment of magnesium alloy AZ31B (silicate-based solution). (1) Equipment preparation stage: Pour about 1.0 L of the prepared silicate electrolyte system (Na2SiO3 12 g / L, KOH 2 g / L, prepared with deionized water, pH=12.5) into the collection tank 1. The liquid level should be at least 10 mm higher than the reflux suction port 201. Drill a hole (M4 thread) in the bottom of the φ20 mm×30 mm magnesium alloy AZ31B cylindrical sample and screw it into the workpiece clamping interface 5; the sealing ring in the interface holds the workpiece tightly to prevent leakage, the conductive spring contacts the metal substrate of the workpiece, and connects to the anode of the micro-arc oxidation power supply. The guide slope of the umbrella-shaped guide platform 3 is made of 316L stainless steel and is connected to the cathode of the power supply.
[0051] (2) Circulation Establishment Stage: Start the circulation pump 7 built into the hollow support column 2. The electrolyte is drawn in from the bottom return suction port 201, filtered by the 50 μm pore size filter assembly, and rises along the suction pipe 6 and delivery pipe 8 inside the hollow support column 2, overflowing evenly from the 24 overflow holes of the distributor 4. Adjust the flow rate of the circulation pump 7 to 1.5 L / min, observe the formation of a uniform flowing liquid layer on the guide slope, and confirm the liquid film thickness is 2.5 mm using a laser displacement sensor. The liquid film stably covers the surface of the workpiece (coverage rate 99.8%), and finally falls back into the collection tank, completing the circulation establishment.
[0052] (3) Micro-arc oxidation stage: Turn on the power supply, set the voltage to 400 V, the frequency to 500 Hz, the duty cycle to 40%, and the processing time to 20 min. The current passes through the flowing liquid layer and discharges on the surface of the workpiece to form a ceramic film layer. Under dynamic diffuse flow conditions, the Joule heat generated by the reaction is quickly carried away (the electrolyte temperature rise rate is about 0.85℃ / min), and the bubbles are continuously washed away from the surface by the liquid flow. After 20 min of treatment, the highest temperature of the electrolyte is 42.0℃, and no cooling intervention is required. The entire process maintains a continuous self-circulation of "liquid absorption - filtration - pumping - diffuse flow - reaction - heat dissipation".
[0053] (4) End of processing: After the set time is reached, turn off the power first, and after the discharge stops, turn off the circulation pump, take out the workpiece, rinse it with deionized water and then dry it.
[0054] (5) Test results: average film thickness 19.6 μm, total standard deviation 0.24 μm, coefficient of variation CV=1.23%, film hardness 412 HV, pinhole rate 1.7%, neutral salt spray (5% NaCl) corrosion resistance time 384 h.
[0055] The following section verifies the energy-saving advantages of micro-arc oxidation treatment of 6061 aluminum alloy (containing Ce(NO3)3 precious rare earth electrolyte). (1) Experimental objective: To verify the application value and economic efficiency of this device in electrolyte systems containing precious additives.
[0056] (2) Equipment preparation stage: Prepare an aluminum alloy micro-arc oxidation electrolyte containing 2 g / L Ce(NO3)3 (Na2SiO3 12 g / L + KOH 2 g / L + Ce(NO3)3 2 g / L), and inject about 0.9 L into the collection tank 1. The cost of preparing the electrolyte once is about 156 yuan. Compared with the traditional 20 L immersion tank, the cost of preparing the electrolyte with the same formula is about 3120 yuan, and the saving rate of this device is 95.0%. Clamp a φ15 mm×25 mm 6061 aluminum alloy cylindrical sample on the workpiece clamping interface 5 and connect it to the power supply anode; connect the guide slope to the cathode.
[0057] (3) Circulation establishment stage: Adjust the circulation pump flow rate to 1.5 L / min to form a uniform flowing liquid layer with a thickness of 2.5 mm and a coverage rate of 99.8%.
[0058] (4) Micro-arc oxidation stage: set voltage 450 V, frequency 600 Hz, duty cycle 35%, and processing time 25 min. The highest temperature of the electrolyte during the process is 42.3℃ (only relying on natural heat dissipation through diffuse flow, without external cooling), and it maintains continuous self-circulation throughout the process.
[0059] (5) Test results: average film thickness 22.4 μm, coefficient of variation CV = 1.35%, film hardness 1180 HV. 0.1 (Aluminum alloy MAO film), pinhole rate 1.5%, neutral salt spray corrosion resistance time exceeding 500 h. Ce2O3 particles are uniformly dispersed in the film layer, and the rare earth uniformity of the film layer is good, proving that the diffuse dynamic renewal mechanism effectively inhibits Ce. 3+ Concentration polarization sedimentation.
[0060] (6) Summary of economic benefits: In terms of electrolyte cost alone, this device saves about 2,964 yuan per experiment. In the scenario of conducting 100 formula screening experiments, the cost can be saved by about 296,000 yuan, which has significant economic value.
[0061] In the description of this invention, it should be noted that the terms "upper", "lower", "left", "right", "inner", "outer", "top / bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.
[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent substitutions, and improvements made by those skilled in the art to the above embodiments without departing from the scope of the technical solution of the present invention, based on the technical essence of the present invention, shall still fall within the protection scope of the technical solution of the present invention.
Claims
1. An umbrella-shaped, diffused, self-circulating micro-arc oxidation device, characterized in that, include: The liquid collection tank (1) and the power supply are provided. The liquid collection tank (1) is filled with electrolyte. A hollow support column (2) is vertically installed in the middle of the bottom of the liquid collection tank (1). An umbrella-shaped guide platform (3) is fixedly installed at the top of the hollow support column (2). The umbrella-shaped guide platform (3) is a frustum structure with a diameter at the top smaller than that at the bottom. A liquid distributor (4) is installed at the top of the umbrella-shaped guide platform (3). Several workpiece clamping interfaces (5) for clamping workpieces are evenly arranged along the circumferential direction at the bottom edge of the umbrella-shaped guide platform (3). A self-circulating conveying system for continuously conveying the electrolyte in the liquid collection tank (1) to the liquid distributor (4) is provided inside the hollow support column (2). The anode of the power supply is connected to the workpieces clamped on several workpiece clamping interfaces (5). The cathode of the power supply is connected to the guide slope of the umbrella-shaped guide platform (3). The electrolyte overflows uniformly from the distributor (4) and flows downward along the guide slope under the action of gravity, forming a uniformly thick liquid layer. The liquid layer continuously flows over the surface of the workpiece and undergoes a micro-arc oxidation reaction.
2. The umbrella-shaped diffused self-circulating micro-arc oxidation device according to claim 1, characterized in that: The liquid distributor (4) is cylindrical and its diameter is equal to the diameter of the upper end face of the umbrella-shaped guide platform (3). The liquid distributor (4) has a flow stabilizing cavity inside, the height of which is 25mm. The side wall of the liquid distributor (4) is evenly provided with several overflow holes along the circumferential direction. The overflow holes are connected to the flow stabilizing cavity, and the diameter of the overflow holes is 1.5mm.
3. The umbrella-shaped diffused self-circulating micro-arc oxidation device according to claim 1, characterized in that: The workpiece clamping interface (5) includes an insulating mounting base and a conductive spring. The insulating mounting base is embedded at the bottom edge of the umbrella-shaped flow guide (3). The bottom end of the insulating mounting base has a through hole for inserting the workpiece. The conductive spring is disposed inside the through hole. The conductive spring can contact the workpiece. The conductive spring is electrically connected to the anode of the power supply.
4. The umbrella-shaped diffused self-circulating micro-arc oxidation device according to claim 2, characterized in that: The hollow support column (2) has several reflux suction ports (201) on its bottom side wall, and the reflux suction ports (201) are connected to the input end of the self-circulating conveying system.
5. The umbrella-shaped diffused self-circulating micro-arc oxidation device according to claim 4, characterized in that: A filter assembly is detachably and fixedly installed at the reflux suction port (201). The filter assembly includes a coarse filter screen and a precision filter element, wherein the pore size of the precision filter element is 50 μm.
6. The umbrella-shaped diffused self-circulating micro-arc oxidation device according to claim 4, characterized in that: The self-circulating delivery system includes: a liquid extraction pipe (6), a circulation pump (7), and a liquid delivery pipe (8). The liquid extraction pipe (6), the circulation pump (7), and the liquid delivery pipe (8) are all installed inside the hollow support column (2). One end of the liquid extraction pipe (6) is connected to several return liquid suction ports (201). The other end of the liquid extraction pipe (6) is connected to the input end of the circulation pump (7). The output end of the circulation pump (7) is connected to one end of the liquid delivery pipe (8). The other end of the liquid delivery pipe (8) passes through the umbrella-shaped guide platform (3) and is connected to the flow stabilizing cavity of the liquid distributor (4).
7. The umbrella-shaped diffused self-circulating micro-arc oxidation device according to claim 1, characterized in that: The amount of electrolyte in the collection tank (1) is 0.8~1.2 L; the outer wall of the collection tank (1) is provided with heat dissipation fins or the collection tank (1) has a built-in condenser pipe.
8. The umbrella-shaped diffused self-circulating micro-arc oxidation device according to claim 1, characterized in that: The flow guiding slope is made of a conductive and corrosion-resistant material, the cone half-angle θ of the flow guiding slope is 30°, and the surface roughness Ra of the flow guiding slope is 0.4~0.8μm.
9. The umbrella-shaped diffused self-circulating micro-arc oxidation device according to claim 1, characterized in that: The hollow support column (2) is made of corrosion-resistant high-molecular hard material.
10. An umbrella-shaped diffused self-circulating micro-arc oxidation process, utilizing the umbrella-shaped diffused self-circulating micro-arc oxidation device according to claim 6, characterized in that: Includes the following steps: Step 1: Inject electrolyte into the collection tank (1) until it submerges the return suction port (201), insert the workpiece into the workpiece clamping interface (5), connect the power anode, and connect the guide slope to the power cathode. Step 2: Start the circulation pump (7) and adjust the flow rate to 1.2~2.0 L / min to form a uniform flowing liquid layer with a thickness of 2.0~3.1 mm on the guide slope. After the flowing liquid layer is stably formed, proceed to step 3. Step 3: Turn on the power supply to allow the current to pass through the flowing liquid layer and cause breakdown discharge on the surface of the workpiece, forming a micro-arc oxidation ceramic coating. Step 4: After the set time is reached, turn off the power first, and then turn off the circulation pump (7) after the discharge stops. Remove the workpiece to complete the processing.