Vacuum anodic oxidation device and oxidation method thereof

Abstract

The invention discloses a vacuum anodic oxidation device and an oxidation method thereof. The vacuum anodic oxidation device comprises a furnace body assembly, at least one group of anode assemblies and at least one group of cathode assemblies. Wherein at least one group of anode assembly comprises an anode plate, an anode conducting rod and a first locking assembly; each cathode assembly comprises a cathode plate, a cathode conducting rod and a second locking assembly; wherein the cathode plate is arranged above the anode plate, the anode plate and the anode conducting rod are fixed through a first locking assembly, and the cathode plate and the cathode conducting rod are fixed through a second locking assembly. Therefore, according to the vacuum anodic oxidation device and the oxidation method thereof, the corrosion resistance, the surface hardness and the wear resistance of the workpiece can be improved while the thickness, the uniformity and the surface smoothness of the workpiece infiltrated layer are ensured.

Description

Technical Field

[0001] This invention relates to the field of vacuum heat treatment of metallic material surfaces, and particularly to a vacuum anodizing apparatus and its oxidation method. Background Technology

[0002] Aluminum alloys are widely used in the manufacturing of mobile phone frames due to their lightweight, high specific strength, good machinability, and heat dissipation properties. However, aluminum alloys have a relatively low surface hardness, only 100 HV. 0.025 Its properties are limited, and its wear resistance and corrosion resistance are insufficient, which restricts its application in high-end mobile phones.

[0003] Traditional anodizing technology forms an oxide film on the surface of aluminum alloys through electrochemical methods. However, this oxidation method not only pollutes the environment, but also has problems such as weak film adhesion, complex process, and insufficient surface gloss, making it difficult to meet the requirements of high-end mobile phone frames for high hardness, high wear resistance, and aesthetics.

[0004] Vacuum anodizing technology, as a clean and pollution-free advanced surface treatment method, generates plasma in a vacuum environment through glow discharge, enabling oxygen ions to grow directly on the substrate surface in situ to form an oxide layer. This results in advantages such as strong film adhesion, high hardness, and good wear resistance. Therefore, there is an urgent need for a vacuum anodizing device and method suitable for strengthening aluminum alloy mobile phone frames to improve the surface properties of mobile phone frames and meet the demands of the high-end market. Summary of the Invention

[0005] The present invention aims to at least solve one of the aforementioned problems existing in the prior art. Therefore, one objective of the present invention is to provide a vacuum anodizing apparatus capable of achieving uniform discharge and efficient oxidation, thereby improving the corrosion resistance of workpieces while simultaneously enhancing their surface hardness and wear resistance. A second objective of the present invention is the oxidation method employing the vacuum anodizing apparatus of the present invention.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a vacuum anodizing apparatus, comprising:

[0007] A furnace body assembly, the furnace body assembly including a source interface, the inner wall of the furnace body assembly being connected to the positive terminal of a power supply;

[0008] At least one anode assembly, the anode assembly including an anode plate, an anode conductive rod and a first locking assembly; wherein, the anode plate is used to place the workpiece, the anode conductive rod is connected to the positive terminal of the power supply, and the anode conductive rod is symmetrically arranged on both sides of the anode plate to support the anode plate; the anode plate and the anode conductive rod are fixed by the first locking assembly;

[0009] At least one cathode assembly, the cathode assembly including a cathode plate, a cathode conductive rod, and a second locking assembly; wherein, the cathode plate is disposed above the anode plate, the cathode conductive rod is connected to the negative terminal of the power supply, and the cathode conductive rod is symmetrically disposed on both sides of the cathode plate for supporting the cathode plate; the cathode plate and the cathode conductive rod are fixed by the second locking assembly.

[0010] Therefore, the vacuum anodizing apparatus of the present invention has at least the following beneficial effects:

[0011] First, in the vacuum anodizing process, under the action of a DC high-voltage electric field, gas atoms in the vacuum container are ionized into ions. Negatively charged oxygen ions collide with the anode workpiece at high speed, lose energy, are absorbed by the workpiece, and diffuse inward to form an oxide layer. Compared to existing technologies, the vacuum anodizing device of this invention optimizes the design of the anode and cathode plates, placing the cathode plate correspondingly above the anode plate. This results in a more uniform distribution of ions and the electric field, increases the average density and energy of ions on the workpiece surface, promotes the aggregation, absorption, and penetration of oxygen ions, reduces the edge effects generated on the workpiece surface during oxidation, and produces an oxide layer with high consistency in thickness.

[0012] Secondly, the vacuum anodizing apparatus of the present invention can adjust the height and spacing of the cathode plate and the anode plate by means of the first locking component and the second locking component, thereby adjusting the heating effect of the glow discharge on the workpiece and ensuring the effectiveness and uniformity of the glow discharge on the workpiece.

[0013] Third, the vacuum anodizing device of the present invention has a simple structure, and the number and spacing of its cathode plate and anode plate can be flexibly adjusted according to actual conditions to meet the processing needs of workpieces of different quantities, specifications and complex shapes.

[0014] According to some embodiments of the present invention, the cathode plate and the anode plate are alternately arranged along the height direction of the furnace body assembly, and the diameter of the anode plate is smaller than the diameter of the cathode plate;

[0015] When the vacuum anodizing apparatus includes an anode plate and a cathode plate, the anode conductive rod is disposed between the anode plate and the inner wall of the furnace body assembly via the first locking assembly;

[0016] When the vacuum anodizing apparatus includes N anode plates and N cathode plates, the anode conductive rod passes through both sides of the cathode plate disposed between adjacent anode plates to support the anode plates; wherein, N > 1, and N is a natural number.

[0017] According to some embodiments of the present invention, the at least one set of cathode assemblies further includes an insulating component, which is disposed at the junction of the cathode conductive rod and the furnace body assembly, for fixing the cathode conductive rod to the furnace body assembly.

[0018] According to some embodiments of the present invention, the anode plate, the anode conductive rod, the cathode plate, and the cathode conductive rod are all made of pure titanium, and the surfaces of the materials are all polished.

[0019] Given the operating temperature and oxygen-containing plasma environment of the vacuum anodizing process, the selected pure titanium material exhibits excellent high-temperature stability and corrosion resistance, which can extend the service life of the anode plate, anode conductive rod, cathode plate, and cathode conductive rod. Furthermore, the surface polishing treatment of the material helps reduce localized hot spots and electric field concentration problems during glow discharge, further improving discharge uniformity and oxide film quality.

[0020] A second aspect of the present invention provides an oxidation method using the vacuum anodizing apparatus described in the first aspect of the present invention, comprising the following steps:

[0021] S11. Process the workpiece to be oxidized, and then dry it for later use;

[0022] S22. Adjust the height, spacing and number of the cathode plate and the anode plate; then place the workpiece on the anode plate of the vacuum anodizing device, close the furnace assembly, and evacuate the vacuum so that the pressure inside the furnace assembly drops to below 10-3 Pa.

[0023] S33. Introduce a mixture of argon and oxygen into the furnace assembly; monitor the vacuum level inside the furnace assembly through the control system; after the vacuum level stabilizes within the target range, set the processing temperature through the control system, turn on the source and cathode power supplies, and set and maintain the output of the cathode power supply.

[0024] S44. The temperature change is monitored by the control system, and the source power output is adjusted so that the internal temperature of the furnace body assembly gradually rises and is finally maintained at 300-400°C.

[0025] S55. Oxidation reaction: After oxidation is complete, turn off the power, stop the gas supply, cool to room temperature, and remove the workpiece.

[0026] According to some embodiments of the present invention, in step S33, the volume ratio of argon to oxygen is 1:5 to 1:7.

[0027] In vacuum anodizing, oxygen is the core reactant gas. However, if only oxygen is introduced, its high electronegativity may lead to unstable discharge, requiring a higher voltage to propel the reaction and increasing equipment load and energy consumption. Therefore, introducing an appropriate amount of argon as an auxiliary gas not only promotes ionization and plasma formation but also lowers the voltage threshold required for discharge, resulting in more uniform and stable glow discharge. Although argon ions do not participate in the chemical reaction, their kinetic energy is converted into heat energy in the electric field, which synergizes with the heating effect of oxygen ion bombardment to improve heating efficiency. Furthermore, in step S33, an argon-to-oxygen volume ratio of 1:5 to 1:7 is selected. A higher oxygen ratio ensures sufficient oxygen ions participate in the oxidation reaction, while a small amount of argon increases plasma density and discharge stability, while avoiding excessive dilution of oxygen by inert gas, thus reducing oxidation efficiency.

[0028] Furthermore, selecting an oxidation temperature range of 300–400°C in step S44 provides suitable thermal activation energy for the diffusion of oxygen atoms on the aluminum alloy surface, promoting the penetration of oxygen atoms into the matrix. At this temperature, the aluminum alloy matrix exhibits good thermal stability, while enhanced surface atomic activity facilitates the chemical reaction between oxygen and aluminum atoms, resulting in a more uniform and dense oxide film. If an excessively high oxidation temperature is selected, the aluminum alloy may undergo microstructural changes, such as coarse grains or decomposition of precipitated phases, leading to softening or embrittlement of the matrix and a decrease in mechanical properties. Simultaneously, excessively high temperatures may accelerate the oxidation reaction, causing the oxide film to grow too quickly, forming pores, cracks, or a loose structure, reducing the adhesion and density of the film layer. If an excessively low oxidation temperature is selected, the thermal activation energy of oxygen atoms is insufficient, limiting their adsorption and diffusion effects on the aluminum alloy surface, slowing down the oxide layer growth rate, and reducing process efficiency. At low temperatures, the oxide film may also form an inhomogeneous or amorphous structure with weak adhesion, making it prone to peeling or micropores, affecting its appearance and performance.

[0029] According to some embodiments of the present invention, the oxidation method includes at least one of the following reaction conditions:

[0030] 1) In step S33, the vacuum level inside the furnace assembly is monitored to maintain the total gas pressure at 90–110 Pa.

[0031] 2) The output voltage of the source in step S44 is 300-400V;

[0032] 3) The output voltage of the cathode power supply in step S44 is 500-600V;

[0033] 4) The oxidation reaction in step S55 takes 4 to 5 hours.

[0034] According to some embodiments of the present invention, the distance between the cathode plate and the anode plate is 150 to 450 mm.

[0035] Glow discharge requires a low-pressure environment; excessively high or low pressure will affect the stability of the discharge. In step S33, selecting a pressure range of 90–110 Pa ensures that the mixed gas can be effectively ionized under the DC high-voltage electric field, generating stable plasma with a suitable density. This also avoids excessive molecular collisions leading to ion energy loss, improving bombardment efficiency and maintaining a relatively high oxidation reaction rate. Using too low a pressure may result in insufficient ion density, making it difficult to maintain glow discharge; while too high a pressure may lead to excessively high gas molecule density, causing unstable arc discharge, resulting in workpiece surface defects or electrode damage.

[0036] The primary function of the source power supply is to heat and maintain the temperature within the vacuum furnace. Therefore, selecting a source voltage output range of 300–400V in step S44 optimizes the electric field distribution and balances the oxidation efficiency and safety stability of the equipment. If an excessively high source voltage is selected, the strong electric field will increase the risk of arc discharge and raise the positive potential of the furnace wall, potentially attracting too many ions to bombard the furnace wall, leading to localized overheating of the furnace wall instead of concentrated heating of the workpiece on the anode plate. Conversely, if an excessively low source voltage is selected, it will result in insufficient electric field strength, inadequate heating of the workpiece, and unstable glow discharge.

[0037] In addition, the cathode power supply drives ion bombardment to provide heat, which, in conjunction with the source power supply, adjusts the discharge intensity. In step S44, a cathode voltage output range of 500–600V is selected, allowing ions to acquire suitable kinetic energy and maintain a relatively efficient oxidation reaction under stable glow discharge conditions. Using excessively high cathode voltage will significantly enhance the electric field strength, causing excessive ionization of gas molecules, potentially leading to a more intense arc discharge and increasing power consumption and load. Localized high temperatures and uneven discharge caused by arc discharge can result in microcracks or burns on the workpiece surface, affecting the surface finish of the film. Overheating of the workpiece may also reduce its mechanical properties. Excessively high kinetic energy acquired by ions at high voltage may cause surface atomic sputtering when bombarding the workpiece, leading to defects such as porosity or uneven thickness in the oxide film. Using excessively low cathode voltage will result in insufficient discharge, reducing gas ionization efficiency and causing low plasma density, affecting the growth rate, depth, and density of the oxide layer.

[0038] In addition, the oxidation time of 4-5 hours selected in step S55 provides sufficient conditions for oxygen atoms to diffuse into the substrate, while balancing oxidation efficiency and production efficiency. If the oxidation time is too long, it may lead to the formation of a loose structure in the oxide film, increasing surface defects, prolonging the process cycle, and reducing production efficiency; while if the oxidation time is too short, it will result in insufficient oxygen atom diffusion, uneven oxidation, and the film thickness and performance will not meet the process requirements.

[0039] According to some embodiments of the present invention, the workpiece is an aluminum alloy workpiece. Preferably, the aluminum alloy workpiece is an aluminum alloy mobile phone frame.

[0040] According to some embodiments of the present invention, the step S11 of treating the workpiece to be oxidized includes placing the workpiece in an alcohol solution and a cleaning agent for ultrasonic cleaning, and then drying it with cold air for later use. Preferably, the cleaning agent is a metal cleaning agent.

[0041] Therefore, the vacuum anodizing method of the present invention has at least the following beneficial effects: by performing vacuum anodizing treatment on the workpiece using the vacuum anodizing device of the present invention, the depth, uniformity and surface smoothness of the diffusion layer can be ensured, thereby improving the corrosion resistance of the workpiece while also improving its surface hardness and wear resistance. Attached Figure Description

[0042] Figure 1 This is a cross-sectional view of a vacuum anodizing apparatus according to a first aspect embodiment of the present invention;

[0043] Figure 2 for Figure 1 Sectional view at point AA.

[0044] Reference numerals: 11-furnace body assembly, 21-cathode conductive rod, 22-cathode plate, 23-second locking assembly, 24-insulation assembly, 31-anode conductive rod, 32-anode plate, 33-first locking assembly, 41-workpiece. Detailed Implementation

[0045] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0046] In the description of the embodiments of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," 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 the embodiments of this application 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 limitations on the embodiments of this application. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0047] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a replaceable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0048] The specific implementation of the present invention will be further described below with reference to the accompanying drawings and embodiments, but the implementation and protection of the present invention are not limited thereto.

[0049] like Figures 1-2 As shown, a vacuum anodizing apparatus includes a furnace body assembly 11 and at least one set of anode assemblies and at least one set of cathode assemblies. The furnace body assembly 11 has an internal cavity for placing the anode assemblies, cathode assemblies, and workpiece 41, and provides a sealed environment for vacuum anodizing.

[0050] The furnace body assembly 11 is provided with a source interface, and the inner wall of the furnace body assembly 11 is connected to the positive terminal of the power supply. When the source power supply and the cathode power supply are turned on, current flows into the interior of the furnace body assembly 11, and the temperature of the internal cavity of the furnace body assembly 11 will gradually rise, heating the workpiece 41. Exemplarily, the positive terminal of the power supply is the positive terminal of the DC high voltage power supply.

[0051] The anode assembly includes at least two anode conductive rods 31, at least one anode plate 32, and a first locking assembly 33. Exemplarily, the first locking assembly 33 may be a locking nut or other locking assembly, without specific limitations herein.

[0052] For example, the anode conductive rod 31 is connected to the positive terminal of a DC high-voltage power supply, and its bottom is fixed to the furnace body assembly 11 by at least two first locking components 33. The anode plate 32 is used to place the workpiece 41, and a space for the workpiece 41 is left between it and the cathode plate 22. The anode conductive rod 31 is used to connect and fix the alternately arranged anode plates 32, and at least two anode conductive rods 31 are connected between every two anode plates 32. At least two first locking components 33 are respectively installed on the lower side of the anode plate 32 to fix it to the anode conductive rod 31.

[0053] The cathode assembly includes at least two cathode conductive rods 21, at least one cathode plate 22, and a second locking assembly 23. Exemplarily, the second locking assembly 23 may be a locking nut or other locking assembly, without specific limitations herein.

[0054] In the vacuum anodizing process, the influence of the cathode plate 22 and anode plate 32 on the glow discharge heating effect is mainly related to the electric field strength, plasma density, and ion collision energy. Specifically, the strength of the DC high-voltage electric field is inversely proportional to the distance between the cathode and anode plates. When the plate distance decreases, the electric field strength increases, and oxygen ions gain higher acceleration energy in the electric field. When they collide with the workpiece 41 on the anode plate 32, they convert more kinetic energy into heat energy, thus enhancing the heating effect. Simultaneously, a smaller plate distance reduces the volume of the discharge region, increasing the ionization probability of the mixed gas molecules within a limited space, raising the plasma density, and allowing more oxygen ions and active particles to participate in the reaction. These particles release energy upon impacting the workpiece 41, further promoting the heating and oxidation process. When the plate distance is close, the free path of ions in the electric field shortens, increasing the collision frequency between ions and gas molecules. More frequent collisions result in a more concentrated transfer of ion energy to the surface of the workpiece 41, leading to a stronger bombardment heating effect.

[0055] Therefore, the vacuum anodizing apparatus of the present invention can adjust the height and spacing of the cathode plate 22 and the anode plate 32 by means of the first locking component 33 and the second locking component 23, thereby adjusting the heating effect of the glow discharge on the workpiece 41 and ensuring the effectiveness and uniformity of the glow discharge on the workpiece 41.

[0056] For example, the cathode conductive rod 21 is connected to the negative terminal of a DC high-voltage power supply to support the alternately arranged cathode plates 22, with at least two cathode conductive rods 21 connecting each pair of cathode plates 22. The cathode plates 22 are positioned above the anode plates 32, and when a bias voltage is applied, they can form an accelerating electric field flowing from the cathode plates 22 to the anode plates 32, so that the heating effect of the electric field acts on the surface of the workpiece 41 to be processed. In addition, the cathode plates 22 and anode plates 32 are arranged alternately, and the cathode plate 22 located between two anode plates 32 has at least two through holes with a diameter slightly larger than the diameter of the anode conductive rod 31, through which the anode conductive rod 31 passes. Furthermore, at least two second locking components 23 are respectively installed below the cathode plates 22 and fixed to the cathode conductive rods 21.

[0057] In another embodiment, when the vacuum anodizing apparatus includes an anode plate and a cathode plate, that is, when only a cathode plate 22 and an anode plate 32 are provided, the anode conductive rod 31 is provided between the anode plate 32 and the inner wall of the furnace body assembly 11 through the first locking assembly 33;

[0058] When the vacuum anodizing apparatus includes N anode plates and N cathode plates, where N > 1 and N is a natural number (in general understanding, the ">" here does not include the number 1), the anode conductive rod 31 passes through both sides of the cathode plate 22 disposed between adjacent anode plates 32 to support the anode plate 32. That is, except for the uppermost cathode plate 22 disposed along the height direction of the furnace body assembly 11, the other cathode plates 22 are provided with through holes on both sides, and the anode conductive rod 31 passes through the through holes to support the anode plate 32.

[0059] In another embodiment, the cathode assembly further includes insulating components 24, with at least two insulating components 24 respectively disposed at the junction of the cathode conductive rod 21 and the furnace body assembly 11, for fixing the cathode conductive rod 21 to the furnace body assembly 11. Exemplarily, the insulating components 24 are made of mica, and the furnace body assembly 11 is made of stainless steel or other suitable materials, without specific limitations herein.

[0060] In this embodiment, the anode conductive rod 31, anode plate 32, cathode conductive rod 21, and cathode plate 22 are all made of pure titanium, and the surfaces of all materials are polished. Specifically, this embodiment includes three anode plates 32, three cathode plates 22, two anode conductive rods 31, two cathode conductive rods 21, eight first locking assemblies 33, and six second locking assemblies 23. The anode conductive rods 31 are positioned on both sides of the anode plate 32 to support it, and the cathode conductive rods 21 are positioned on both sides of the cathode plate 22 to support it.

[0061] In another embodiment, the diameter of the cathode plate 22 is slightly larger than that of the anode plate 32 (i.e., the diameter of the anode plate 32 is smaller than that of the cathode plate 22) so that the cathode conductive rod 21 passes through the outside of the anode plate 32. Except for the uppermost cathode plate 22, several lower cathode plates 22 are provided with through holes on both sides. The diameter of the through holes is slightly larger than that of the anode conductive rod 31 so that the anode conductive rod 31 passes through the through holes on both sides of the alternately arranged cathode plates 22 from top to bottom, thereby supporting the anode plate 32 and preventing short circuit between the anode and cathode.

[0062] For example, the workpiece 41 is an aluminum alloy mobile phone frame or other aluminum alloy workpieces, and no specific limitation is made here.

[0063] This invention provides a vacuum anodizing method, which employs the vacuum anodizing apparatus of this invention and includes the following steps:

[0064] S11. Process the workpiece 41 to be oxidized, and then dry it for later use; wherein, processing the workpiece 41 to be oxidized in step S11 includes placing the workpiece 41 in an alcohol solution and cleaning agent for ultrasonic cleaning, and then drying it with cold air for later use. Exemplarily, the cleaning agent can be a metal cleaning agent or other types of cleaning agents, and is not specifically limited here.

[0065] S22. Adjust the height, spacing and number of the cathode plate and the anode plate; then place the workpiece 41 on the anode plate of the vacuum anodizing device, close the furnace body assembly 11, start the vacuum pump group, and evacuate the vacuum so that the pressure inside the furnace body assembly drops to below 10-3 Pa.

[0066] S33. Turn on the argon and oxygen cylinders connected to the furnace assembly 11, and introduce a mixture of argon and oxygen into the furnace assembly 11 through the gas supply system, so that the volume ratio of argon to oxygen in the furnace is 1:7; monitor the vacuum level in the furnace assembly through the control system to maintain the total pressure at 90-110 Pa, and then set the processing temperature through the control system, turn on the source and cathode power supplies, and set the output of the cathode power supply and keep it constant; wherein, the output voltage of the source power supply is 300-400V, and the output voltage of the cathode power supply is 500-600V; for example, the control system can be a PLC control system or other control systems, which are not specifically limited here;

[0067] S44. The temperature change is monitored by the control system, and the source power output is adjusted so that the internal temperature of the furnace gradually rises and is finally maintained at 300-400℃.

[0068] S55. Oxidation reaction for 4-5 hours. After oxidation is complete, turn off the power and stop the gas supply. After the temperature inside the furnace assembly 11 cools down to room temperature, open the furnace assembly 11 and take out the workpiece 41 placed on the anode plate 32.

[0069] The vacuum anodizing method of the present invention will be specifically described below through specific embodiments, and the performance parameters of the sample of the present invention and the traditional anodized sample will be compared and analyzed according to standard test methods.

[0070] First specific embodiment: The workpiece material is 7075 aluminum alloy, and the surface hardness requirement is 300HV. 0.025 The required thickness of the diffusion layer is 2μm or more. Vacuum anodizing is performed according to the following process and parameters: the distance between the cathode and anode plates is adjusted so that the distance between the cathode plate 22 and the anode plate 32 is 300mm; the volume ratio of the gas is Ar:O2 = 1:7; the oxidation temperature is 300℃; the oxidation pressure is 110Pa; the source power supply is 300V; the cathode power supply voltage is 500V; and the oxidation time is 5h.

[0071] Second specific embodiment: The workpiece material is 6061 aluminum alloy, and the surface hardness requirement is 260HV. 0.025 The required thickness of the diffusion layer is 2μm or more. Vacuum anodizing is performed according to the following process and parameters: the distance between the cathode and anode plates is adjusted so that the distance between the cathode plate 22 and the anode plate 32 is 300mm; the volume ratio of the gas is Ar:O2 = 1:7; the oxidation temperature is 350℃; the oxidation pressure is 90Pa; the source power supply is 350V; the cathode power supply voltage is 550V; and the oxidation time is 4.5h.

[0072] Third specific embodiment: The workpiece material is 6063 aluminum alloy, and the surface hardness requirement is 260HV. 0.025 The required thickness of the diffusion layer is 2μm or more. Vacuum anodizing is performed according to the following process and parameters: the distance between the cathode and anode plates is adjusted so that the distance between the cathode plate 22 and the anode plate is 300mm; the volume ratio of the gas is Ar:O2 = 1:7; the oxidation temperature is 400℃; the oxidation pressure is 100Pa; the source power supply is 400V; the cathode power supply voltage is 600V; and the oxidation time is 4h.

[0073] The performance parameters of the samples from the specific embodiments of this invention and the traditional anodized samples were compared and characterized according to standard testing methods. The specific testing methods are as follows:

[0074] 1. Uniformity test: The treated sample was prepared by cross-sectional metallographic analysis, and the oxide film thickness distribution was measured by SU8600 ultra-high resolution field emission scanning electron microscope (SEM) combined with energy dispersive spectroscopy (EDS).

[0075] 2. Surface finish test: Use a Bruker Icon large sample stage scanning probe microscope (atomic force microscope) to measure the surface roughness of a 500nm×500nm area intercepted from the surface of the specimen. Surface topography imaging is obtained in the tapping mode, and surface roughness data is calculated and analyzed by NanoScope Analysis software.

[0076] 3. Hardness test: Use an SCTMC-HV-1000(Z) type Vickers microhardness tester for hardness measurement. The test load is 25g, the holding time is 10s, and the average value is taken after measuring 3 times.

[0077] 4. Corrosion resistance test: Use a PS-120 type precision salt spray test machine to conduct a salt spray test on the sample. The laboratory temperature is 35°C, the pressure barrel temperature is 45°C, the pressure inside the salt spray test machine is 1000Pa, and the corrosion solution is 5% neutral NaCl solution. The qualified salt spray resistance time is greater than 72h.

[0078] 5. Wear resistance test: Use an MPX-3H friction and wear workstation to conduct a wear resistance test on the sample. The friction pair selects GCr15 material with a diameter of φ4mm, the set load is 5N, the rotation speed is 250r / min, and the rubbing time is 30min. The film layer is qualified if it does not peel or show the bottom.

[0079] The comparison of the performance parameter test results between traditional anodic oxidation and the samples of the specific embodiments of the present invention is shown in Table 1.

[0080] Table 1 Comparison table of performance parameters of traditional anodic oxidation and samples of specific embodiments of the present invention

[0081]

[0082] In summary, in Examples 1-3 of the present invention, compared with traditional anodic oxidation, an oxide layer with higher uniformity and surface finish can be obtained, improving the corrosion resistance, surface hardness and wear resistance of the mobile phone middle frame.

[0083] Therefore, the vacuum anodic oxidation device and its oxidation method of the present invention can ensure the depth, uniformity and surface finish of the infiltration layer, while improving the corrosion resistance of the workpiece, and improving its surface hardness and wear resistance.

[0084] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present application shall be equivalent replacement methods and are all included in the protection scope of the present application.

Claims

1. A vacuum anodizing apparatus, characterized in that, include: A furnace body assembly, the furnace body assembly including a source interface, the inner wall of the furnace body assembly being connected to the positive terminal of a power supply; At least one anode assembly, the anode assembly including an anode plate, an anode conductive rod and a first locking assembly; wherein, the anode plate is used to place the workpiece, the anode conductive rod is connected to the positive terminal of the power supply, and the anode conductive rod is symmetrically arranged on both sides of the anode plate to support the anode plate; the anode plate and the anode conductive rod are fixed by the first locking assembly; At least one cathode assembly, the cathode assembly including a cathode plate, a cathode conductive rod, and a second locking assembly; wherein, the cathode plate is disposed above the anode plate, the cathode conductive rod is connected to the negative terminal of the power supply, and the cathode conductive rod is symmetrically disposed on both sides of the cathode plate for supporting the cathode plate; the cathode plate and the cathode conductive rod are fixed by the second locking assembly.

2. The vacuum anodizing apparatus according to claim 1, characterized in that, The cathode plate and the anode plate are alternately arranged along the height direction of the furnace body assembly, and the diameter of the anode plate is smaller than the diameter of the cathode plate; When the vacuum anodizing apparatus includes an anode plate and a cathode plate, the anode conductive rod is disposed between the anode plate and the inner wall of the furnace body assembly via the first locking assembly; When the vacuum anodizing apparatus includes N anode plates and N cathode plates, the anode conductive rod passes through both sides of the cathode plate disposed between adjacent anode plates to support the anode plates; wherein, N > 1, and N is a natural number.

3. A vacuum anodizing apparatus according to any one of claims 1 to 2, characterized in that, The at least one set of cathode assemblies further includes an insulating component, which is disposed at the junction of the cathode conductive rod and the furnace body assembly, for fixing the cathode conductive rod to the furnace body assembly.

4. A vacuum anodizing apparatus according to any one of claims 1 to 2, characterized in that, The anode plate, the anode conductive rod, the cathode plate, and the cathode conductive rod are all made of pure titanium, and the surfaces of all the materials have been polished.

5. A vacuum anodizing method, comprising using a vacuum anodizing apparatus as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S11. Process the workpiece to be oxidized, and then dry it for later use; S22. Adjust the height, spacing and number of the cathode plate and the anode plate; then place the workpiece on the anode plate of the vacuum anodizing device, close the furnace assembly, and evacuate the vacuum so that the pressure inside the furnace assembly drops to below 10-3 Pa. S33. Introduce a mixture of argon and oxygen into the furnace assembly; monitor the vacuum level inside the furnace assembly through the control system; after the vacuum level stabilizes within the target range, set the processing temperature through the control system, turn on the source and cathode power supplies, and set and maintain the output of the cathode power supply. S44. The temperature change is monitored by the control system, and the source power output is adjusted so that the internal temperature of the furnace body assembly gradually rises and is finally maintained at 300-400°C. S55. Oxidation reaction: After oxidation is complete, turn off the power, stop the gas supply, cool to room temperature, and remove the workpiece.

6. The vacuum anodizing method according to claim 5, characterized in that, In step S33, the volume ratio of argon to oxygen is 1:5 to 1:

7.

7. A vacuum anodizing method according to any one of claims 5 to 6, characterized in that, The oxidation method includes at least one of the following reaction conditions: 1) In step S33, the vacuum level inside the furnace assembly is monitored to maintain the total gas pressure at 90–110 Pa. 2) The output voltage of the source in step S44 is 300-400V; 3) The output voltage of the cathode power supply in step S44 is 500-600V; 4) The oxidation reaction in step S55 takes 4 to 5 hours.

8. The vacuum anodizing method according to any one of claims 5 to 6, characterized in that, The distance between the cathode plate and the anode plate is 150–450 mm.

9. The vacuum anodizing method according to any one of claims 5 to 6, characterized in that, The workpiece is an aluminum alloy workpiece.

10. The vacuum anodizing method according to any one of claims 5 to 6, characterized in that, The process of treating the workpiece to be oxidized in step S11 includes placing the workpiece in an alcohol solution and cleaning agent for ultrasonic cleaning, and then drying it with cold air for later use.

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