A method and device for multi-color micro-arc oxidation on the surface of an alloy

Abstract

The present invention belongs to the technical field of micro-arc oxidation on the surface of alloy materials, and particularly relates to a method and device for multi-color micro-arc oxidation on the surface of alloys. Aiming at the defects such as uneven or discontinuous distribution of the film layer formed during post-micro-arc oxidation in the prior art during multi-color micro-arc oxidation, a method and device for multi-color micro-arc oxidation on the surface of alloys are proposed. After processes such as uniformly cooling the alloy, freeze-drying, uniformly heating, and constant-temperature treatment, the physical and chemical states of the alloy workpiece are effectively adjusted, and the uniformity of the film layer formed during post-micro-arc oxidation is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of micro-arc oxidation on the surface of alloy materials, and particularly relates to a method and device for multi-color micro-arc oxidation on the surface of alloys. Background Art

[0002] As an efficient metal surface treatment technology, micro-arc oxidation technology can in-situ grow a ceramic film layer with excellent wear resistance, corrosion resistance and insulation performance on the surface of valve metals by utilizing the instantaneous high temperature and high pressure generated by arc discharge. This technology has been widely applied in the fields of aviation, automotive, medical equipment and electronic products, etc. because it can significantly improve the mechanical and chemical properties of the material surface.

[0003] With the continuous improvement of market requirements for product appearance and functionality, multi-color micro-arc oxidation treatment on the surface of alloys can not only enhance the beauty of products, meet the needs of consumers for personalization and aesthetics, but also endow specific functional markings on products through film layers of different colors. This is particularly important in the appearance parts of electronic products, precision handicrafts and the markings of industrial equipment, where different functional areas or specific usage states can be distinguished by colors.

[0004] Although significant achievements have been made in the formation of single-color film layers by micro-arc oxidation technology, there are still many challenges in realizing multi-color film layers. Current technologies often can only form a single-color film layer on the metal surface, which is difficult to meet the market's demand for diversified designs and decoration. In addition, in some methods, deionized water is used to clean the electrolyte on the surface of alloy workpieces, and then high-temperature drying is used to remove the deionized water on the surface of alloy workpieces, resulting in defects such as micro-cracks or deformation inside and on the surface of alloy workpieces, and further leading to defects such as uneven or discontinuous distribution of the film layer formed by subsequent micro-arc oxidation. In addition, some technologies require the use of expensive additives or special equipment, which not only increases the production cost but also limits their application in industrial-scale production.

[0005] Therefore, the present invention proposes a micro-arc oxidation preparation method and system capable of achieving a color gradient effect, improving the effect of the prior art in color gradient control. Summary of the Invention

[0006] Aiming at the defects such as uneven or discontinuous distribution of the film layer formed by subsequent micro-arc oxidation during multi-color micro-arc oxidation in the prior art, a method and device for multi-color micro-arc oxidation on the surface of alloys are proposed. After uniformly cooling the alloy, freeze-drying, uniformly heating and constant-temperature treatment, etc., the physical and chemical state of the alloy is effectively adjusted, and the uniformity of the film layer formed by subsequent micro-arc oxidation is improved.

[0007] To achieve the above object, the technical solutions adopted are as follows:

[0008] In a first aspect, the present invention provides a method for multi-color micro-arc oxidation on the surface of an alloy, comprising the following steps:

[0009] S1. Pretreatment of the workpiece, subjecting the alloy workpiece to degreasing, cleaning, and activation treatments;

[0010] S2. Placing the alloy workpiece into electrolyte a, forming a first-color film layer after micro-arc oxidation, and taking the alloy workpiece out of electrolyte a;

[0011] S3. Cleaning the surface of the alloy workpiece with deionized water to remove electrolyte a, and then removing the deionized water on the surface of the alloy workpiece after uniform temperature reduction, freeze-drying, uniform temperature increase, and constant temperature treatments;

[0012] S4. Placing the alloy workpiece into electrolyte b, forming a second-color film layer after micro-arc oxidation, and taking the alloy workpiece out of electrolyte b;

[0013] S5. Cleaning the surface of the alloy workpiece with deionized water to remove electrolyte b, and then removing the deionized water on the surface of the alloy workpiece after uniform temperature reduction, freeze-drying, uniform temperature increase, and constant temperature treatments;

[0014] S6. Repeating steps S2 to S5 to form film layers of multiple colors on the surface of the alloy workpiece.

[0015] Further, in step S3 and / or S5, the rate of uniform temperature reduction is 1 to 3 °C / min.

[0016] Further, in step S3 and / or S5, the temperature of freeze-drying is 5 to 7 °C, and the time of freeze-drying is 30 to 360 min.

[0017] Further, in step S3 and / or S5, the rate of uniform temperature increase is 1 to 3 °C / min.

[0018] Further, in step S3 and / or S5, the surface of the alloy workpiece can be rinsed with deionized water and a cleaning agent multiple times to remove the electrolyte.

[0019] Further, in step S1, the oil stains and impurities on the surface of the alloy workpiece are removed by soaking with an organic solvent or an alkaline degreasing agent. The organic solvent includes one or more of acetone and gasoline, and the alkaline degreasing agent includes one or more of sodium hydroxide solution, sodium carbonate solution, and sodium phosphate solution. The soaking time is 5 to 15 min.

[0020] Further, in step S1, the fine particles and residual impurities on the surface of the alloy workpiece are removed by using deionized water and ultrasonic waves. The time of ultrasonic treatment is 3 to 10 min, and the ultrasonic frequency is 30 to 60 kHz.

[0021] Further, in step S1, the surface of the alloy workpiece is activated using an acidic solution, where the acidic solution includes one or more of dilute nitric acid solution, hydrofluoric acid solution, nitric acid solution, and sulfuric acid solution, and the activation treatment time is 1 - 5 min.

[0022] In a second aspect, the present invention also provides an apparatus for multi - color micro - arc oxidation on the surface of an alloy, including: a plurality of electrolytic cells, each of which is filled with a different type of electrolyte; a plurality of power supply boxes, each of which is electrically connected to a corresponding one of the plurality of electrolytic cells; a circulating cooling box, which is connected to the outer shell of each electrolytic cell through an inlet pipe and an outlet pipe respectively, and the circulating cooling box is used to maintain the constant temperature state of the electrolyte in each electrolytic cell; a cleaning box, which is used to clean the electrolyte adhering to the surface of the alloy workpiece; and a temperature control box, which has functions of uniform cooling, uniform heating, and constant temperature treatment; the plurality of electrolytic cells, the plurality of power supply boxes, the circulating cooling box, and the temperature control box are connected in sequence according to the industrial production order.

[0023] Further, the apparatus for multi - color micro - arc oxidation on the metal surface further includes a robotic arm and a console, where the robotic arm is used to stably hold the alloy workpiece, and the console is used to control the operation of the apparatus for multi - color micro - arc oxidation on the metal surface.

[0024] Adopting the above - mentioned technical solution, the beneficial effects obtained are as follows:

[0025] ① In the present invention, after the alloy workpiece undergoes the first micro - arc oxidation, through uniform cooling treatment, the internal thermal stress of the alloy material can be effectively controlled, preventing material deformation or rupture caused by too rapid temperature change, and helping to maintain the structural integrity and micro - structure stability of the alloy workpiece.

[0026] ② Each time the micro - arc oxidation film layer is formed, thermal stress has been introduced into the alloy workpiece. The present invention reduces the accumulation of thermal stress caused by drastic temperature changes through freeze - drying treatment of the alloy, helping to maintain the original mechanical properties of the alloy workpiece and reducing micro - cracks or deformations caused by thermal stress.

[0027] ③ In the present invention, after the freeze - drying of the alloy workpiece is completed, the freeze - dried alloy workpiece is uniformly heated to the working temperature through uniform heating, avoiding local overheating of the alloy workpiece, thereby reducing the internal stress caused by uneven temperature, and further preventing defects such as micro - cracks and deformations from occurring in the alloy workpiece during the heating process, providing a good working premise for the subsequent micro - arc oxidation on the surface of the alloy workpiece.

[0028] ④In the present invention, after the alloy workpiece is heated to the working temperature at a uniform speed, the alloy workpiece is subjected to a constant temperature treatment, so that the alloy workpiece completely eliminates the change in the physical and chemical properties of the material caused by temperature fluctuations, ensuring the stable structural performance of the alloy workpiece;

[0029] ⑤The present invention utilizes a plurality of independent electrolytic cells and precisely controlled micro-arc oxidation parameters to stably generate film layers of various colors on the surface of the alloy workpiece. It effectively meets the diverse design and decoration requirements, and significantly improves the market added value of the product;

[0030] ⑥The design of a plurality of independent electrolytic cells and a plurality of independent power supply boxes in the present invention enables the device to independently control the micro-arc oxidation process of each color electrolyte. This design greatly improves the accuracy and stability of color control, ensuring the consistency of the quality and color of different color film layers. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments of the present invention will be briefly introduced below. Among them, the drawings are only used to show some embodiments of the present invention, rather than limiting all embodiments of the present invention thereto.

[0032] Figure 1 It is a schematic structural diagram of a device for multi-color micro-arc oxidation on the surface of an alloy of the present invention.

[0033] The meanings represented by the serial numbers in the figure are as follows:

[0034] 1. Electrolytic cell, 101. First stirrer, 2. Power supply box;

[0035] 3. Circulating cooling box, 301. Water inlet pipe, 302. Water outlet pipe, 303. Cooling box operation console;

[0036] 4. Manipulator, 5. Console;

[0037] 6. Liquid preparation barrel, 601. Slide rail, 602. Second stirrer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] In the following, the exemplary solutions of the embodiments of the present invention will be clearly and completely described in conjunction with the drawings of the specific embodiments of the present invention. Unless otherwise defined, the technical terms or scientific terms used in the present invention should be the ordinary meanings understood by those of ordinary skill in the art.

[0039] In the first aspect, the present invention provides a method for multi-color micro-arc oxidation on the surface of an alloy, including the following steps:

[0040] S1. Workpiece pretreatment, subjecting the alloy workpiece to degreasing, cleaning and activation treatments;

[0041] S2. Place the alloy workpiece into electrolyte a. After micro-arc oxidation, a first color film layer is formed. Then take the alloy workpiece out of electrolyte a;

[0042] S3. Wash the electrolyte a on the surface of the alloy workpiece with deionized water. Subsequently, after the alloy workpiece undergoes uniform temperature reduction, freeze-drying, uniform temperature increase, and constant temperature treatment, remove the deionized water on the surface of the alloy workpiece;

[0043] S4. Place the alloy workpiece into electrolyte b. After micro-arc oxidation, a second color film layer is formed. Then take the alloy workpiece out of electrolyte b;

[0044] S5. Wash the electrolyte b on the surface of the alloy workpiece with deionized water. Subsequently, after the alloy workpiece undergoes uniform temperature reduction, freeze-drying, uniform temperature increase, and constant temperature treatment, remove the deionized water on the surface of the alloy workpiece;

[0045] S6. Repeat steps S2 - S5 to form film layers of multiple colors on the surface of the alloy workpiece.

[0046] First, in the present invention, after the alloy workpiece undergoes the first micro-arc oxidation, through uniform temperature reduction treatment, the internal thermal stress of the alloy material can be effectively controlled, preventing material deformation or rupture caused by too rapid temperature change, and helping to maintain the structural integrity and microstructural stability of the alloy workpiece.

[0047] Second, each time a micro-arc oxidation film layer is formed, thermal stress has been introduced into the alloy workpiece. In the present invention, by subjecting the alloy to freeze-drying treatment, the accumulation of thermal stress caused by drastic temperature changes is reduced, which helps to maintain the original mechanical properties of the alloy workpiece and reduce microcracks or deformations caused by thermal stress.

[0048] Third, in the present invention, after the freeze-drying of the alloy workpiece is completed, the freeze-dried alloy workpiece is uniformly heated to the working temperature by uniform temperature increase, avoiding local overheating of the alloy workpiece, thereby reducing the internal stress caused by uneven temperature, and further preventing defects such as microcracks and deformations from occurring in the alloy workpiece during the heating process, providing a good working premise for the subsequent micro-arc oxidation on the surface of the alloy workpiece.

[0049] Finally, in the present invention, after the alloy workpiece is uniformly heated to the working temperature, by subjecting the alloy workpiece to constant temperature treatment, the change in the physical and chemical properties of the material caused by temperature fluctuations is completely eliminated, ensuring the stable structural performance of the alloy workpiece.

[0050] It should be noted that in the present invention, the alloy workpiece is a magnesium alloy workpiece, an aluminum alloy workpiece, a titanium alloy workpiece, or other common alloy workpieces.

[0051] In some embodiments, in step S3 and / or S5, the rate of uniform temperature decrease is 1 to 3 °C / min. When the rate of uniform temperature decrease is too high, it may cause an increase in internal stress in the alloy workpiece, leading to microcracks or other structural damages. When the rate of uniform temperature decrease is too low, it results in low efficiency and an increase in the production cycle.

[0052] In some embodiments, in step S3 and / or S5, the temperature of freeze-drying is 5 to 7 °C. When the temperature of freeze-drying is too high, it may cause the moisture to fail to sublimate effectively and remain on the surface or inside of the alloy workpiece, affecting the uniformity and adhesion of the subsequent micro-arc oxidation film layer. When the temperature of freeze-drying is too low, it may cause the moisture on the surface or inside of the alloy workpiece to freeze too quickly, increasing the internal stress and triggering microcracks on the surface of the alloy workpiece.

[0053] In some embodiments, in step S3 and / or S5, the time of freeze-drying is 30 to 360 min. When the time of freeze-drying is too short, the moisture inside or on the surface of the alloy workpiece is not completely removed, affecting the effect of subsequent micro-arc oxidation; when the time of freeze-drying is too long, it will reduce the production efficiency and waste energy.

[0054] In some embodiments, in step S3 and / or S5, the rate of uniform temperature increase is 1 to 3 °C / min. When the rate of uniform temperature increase is too high, it will cause a sharp increase in internal stress in the alloy workpiece, resulting in deformation or microcracks in the alloy workpiece; when the rate of uniform temperature increase is too low, it will cause the entire production process to be prolonged and the efficiency to be reduced.

[0055] It should be noted that in the present invention, both the starting temperature of the uniform temperature decrease and the ending temperature of the uniform temperature increase of the alloy workpiece are in the range of 20 to 35 °C, and the actual temperature is the same as the working temperature of the electrolyte.

[0056] In some embodiments, in step S3 and / or S5, the surface of the alloy workpiece can be rinsed with deionized water and a cleaning agent multiple times to ensure that all residual electrolyte is completely removed, so as not to affect the subsequent micro-arc oxidation treatment.

[0057] In some embodiments, in step S1, an organic solvent or an alkaline degreaser is used to soak and remove oil stains and impurities on the surface of the alloy workpiece. The organic solvent includes one or more of acetone and gasoline, and the alkaline degreaser includes one or more of sodium hydroxide solution, sodium carbonate solution, and sodium phosphate solution. The soaking time is 5 - 15 min. By soaking the alloy workpiece with an organic solvent or an alkaline degreaser, the grease, dust, and other impurities on the surface of the alloy workpiece are removed, thereby improving the adhesion and overall quality of the film layer. When the soaking time is too long, the surface of the alloy workpiece will be chemically damaged or over-corroded, affecting its structural integrity; when the soaking time is too short, not all grease and impurities can be fully removed, affecting the effect of subsequent processing steps and the quality of the coating.

[0058] In some embodiments, in step S1, deionized water and ultrasonic waves are used to remove fine particles and residual impurities on the surface of the alloy workpiece. The time of ultrasonic treatment is 3 - 10 min, and the ultrasonic frequency is 30 - 60 kHz. When the ultrasonic treatment time is too long or the ultrasonic frequency is too high, the surface of the alloy workpiece will be subjected to excessive mechanical vibration, resulting in micro-damage or changing the surface properties of the alloy workpiece; when the ultrasonic treatment time is too short or the ultrasonic frequency is too low, it is difficult to completely remove the fine impurity particles on the surface of the alloy workpiece, affecting the adhesion of the subsequent film layer and the overall quality of the film layer.

[0059] In some embodiments, in step S1, the surface of the alloy workpiece is activated using an acidic solution. The acidic solution includes one or more of dilute nitric acid solution, hydrofluoric acid solution, nitric acid solution, and sulfuric acid solution.

[0060] It should be noted that when operating reagents such as dilute nitric acid solution, hydrofluoric acid solution, nitric acid solution, and sulfuric acid solution, protective equipment needs to be worn, and the waste liquid is treated according to environmental protection standards.

[0061] In the present invention, by activating the surface of the alloy workpiece, the chemical reactivity of the alloy surface is improved and the surface roughness is increased, thereby enhancing the adhesion of the film layer during the subsequent micro-arc oxidation process. At the same time, by removing surface impurities and forming more active sites, the micro-arc oxidation film layer is made more uniform and adherent, improving the mechanical and anti-corrosion properties of the film layer.

[0062] In some embodiments, in step S1, the time for activating the surface of the alloy workpiece using an acidic solution is 1 - 5 min. When the activation time is too short, it may cause the surface of the alloy workpiece to be not fully cleaned or activated, thereby affecting the adhesion and uniformity of the subsequent micro-arc oxidation film layer. When the activation time is too long, the alloy workpiece will be over-corroded, damaging the microstructure of the alloy workpiece and reducing its mechanical strength and durability.

[0063] It should be noted that after the surface of the alloy workpiece is activated by an acidic solution, the alloy workpiece needs to be rinsed with deionized water to remove the acidic solution on the surface of the alloy workpiece and avoid excessive corrosion of the surface of the alloy workpiece by the acidic solution.

[0064] In a second aspect, the present invention provides a device for multi-color micro-arc oxidation of a metal surface, which is used to implement the method for multi-color micro-arc oxidation of a metal surface described in any one of the above, and includes a plurality of electrolytic cells 1, a plurality of power supply boxes 2, a circulating cooling box 3, a cleaning box (not shown in the figure), and a temperature adjustment box (not shown in the figure). Among them, different types of electrolytes are respectively contained in each electrolytic cell 1; each power supply box 2 is electrically connected to a corresponding one of the plurality of electrolytic cells 1; the circulating cooling box 3 is respectively communicated with the outer shells of each electrolytic cell 1 through a water inlet pipe 301 and a water outlet pipe 302, and the circulating cooling box 3 is used to maintain the constant temperature state of the electrolyte in each electrolytic cell 1; the cleaning box is used to clean the electrolyte attached to the surface of the alloy workpiece; the temperature adjustment box has functions of uniform temperature reduction, uniform temperature increase, and constant temperature treatment; the plurality of electrolytic cells 1, the plurality of power supply boxes 1, the circulating cooling box 3, and the temperature adjustment box are connected in sequence according to the industrial production order.

[0065] It should be noted that during the actual production process, each power supply box 2 should be grounded to reduce the risk of high-voltage discharge.

[0066] Furthermore, the temperature of the electrolyte in the electrolytic cell 1 is in the range of 20-35 °C.

[0067] In some embodiments, the device for multi-color micro-arc oxidation of a metal surface further includes a robotic arm 4 and a console 5. The robotic arm 4 is used to stably grasp and hold the alloy workpiece, and the console 5 is used to control the operation of the device for multi-color micro-arc oxidation of a metal surface.

[0068] In the present invention, after the alloy workpiece completes micro-arc oxidation in a certain electrolytic cell 1 each time, it will be grabbed by the robotic arm 4 and sequentially placed in the cleaning box and the temperature adjustment box to clean the electrolyte and moisture on the surface of the alloy workpiece for subsequent micro-arc oxidation.

[0069] Specifically, the robotic arm 4 grabs the alloy workpiece from a certain electrolytic cell 1 and places it in the cleaning box. The alloy workpiece is sprayed with deionized water, ultrasonically oscillated, and circulated with a cleaning agent in the cleaning box. After ensuring that there is no residual electrolyte, the alloy workpiece is placed in the temperature adjustment box. The alloy workpiece undergoes uniform temperature reduction, freeze-drying, uniform temperature increase, and constant temperature treatment in the temperature adjustment box to remove the deionized water on the surface of the alloy workpiece.

[0070] Furthermore, each electrolytic cell 1 is independent of each other, and each electrolytic cell 1 is made of materials with good corrosion resistance and insulation performance, such as high-strength engineering plastics or metal materials treated with anti-corrosion. Different components of electrolyte are respectively installed inside each electrolytic cell 1, and various electrolytes are specifically used to produce micro-arc oxidation film layers of different colors. In addition, each electrolytic cell 1 is equipped with a temperature regulating device and a first stirrer 101. The temperature regulating device can control the temperature of the electrolyte within the working temperature range, and the working temperature is 20~35°C to ensure the stability of the micro-arc oxidation reaction. The first stirrer 101 can make the components of the electrolyte evenly distributed, avoiding the influence of local concentration differences on the film layer quality.

[0071] In the present invention, each power supply box 2 is respectively electrically connected to each electrolytic cell 1 in one-to-one correspondence. That is to say, each electrolytic cell 1 is controlled by an independent power supply box 2, so as to accurately control the micro-arc oxidation parameters in each electrolytic cell 1. The micro-arc oxidation parameters include voltage, current, frequency, etc. In addition, each power supply box 2 adopts advanced digital control technology, which can monitor and adjust parameters in real time to ensure the stability and accuracy of the micro-arc oxidation process. By presetting different parameter modes, it can quickly adapt to the processing requirements of different electrolytes and colors.

[0072] In the present invention, the robotic arm 4 can accurately grasp the alloy workpiece and move it to different electrolytic cells 1 for processing according to the set program. The movement accuracy of the robotic arm 4 is ±0.1 mm, and it has high-precision positioning and movement control capabilities to ensure accurate grasping of the alloy workpiece; the robotic arm 4 also has an automatic identification and correction function to ensure the accuracy and efficiency of workpiece transfer between each electrolytic cell 1. In addition, the device of the present invention also has a fixture for clamping the alloy workpiece. The fixture is designed according to the shape and size of the alloy workpiece, and can firmly clamp the workpiece without damaging the surface of the alloy workpiece.

[0073] In the present invention, it also includes a slide rail 601 and a plurality of liquid preparation barrels 6. The plurality of liquid preparation barrels 6 are used to respectively prefabricate different types of electrolytes; the slide rail 601 is fixedly installed directly above each electrolytic cell 1. Pipettes connected to each liquid preparation barrel 6 through connecting hoses are respectively slidably installed on the slide rail 601. During actual production, each pipette slides on the slide rail 601 to directly above the corresponding electrolytic cell 1, so as to transfer the electrolytes in each liquid preparation barrel 6 to the corresponding electrolytic cell 1.

[0074] Furthermore, a second stirrer 602 is installed at the bottom of each liquid preparation barrel 6. The second stirrer 602 continuously rotates to drive the prefabricated electrolyte in the liquid preparation barrel 6 to rotate, ensuring the uniformity and stability of the prefabricated electrolyte.

[0075] Table 1

[0076]

[0077] Furthermore, the electrolytes and production process parameters used to prepare micro-arc oxidation film layers of different colors in the present invention are shown in Table 1. Table 1 discloses the electrolyte compositions and dosage ranges for micro-arc oxidation film layers of various colors such as black, gold, blue, red, green, white, yellow, and orange, as well as the corresponding voltage, current, frequency, and time ranges during the micro-arc oxidation process.

[0078] The present invention will be further described below through examples.

[0079] Example 1. Two-color (white + black) micro-arc oxidation of magnesium alloy workpieces

[0080] S1. Workpiece pretreatment:

[0081] 1) Degreasing: A basic degreasing agent is prepared by mixing NaOH solution and Na 2 CO 3 solution, where NaOH is 30 g / L and Na 2 CO 3 is 20 g / L. The magnesium alloy workpiece is immersed in the basic degreasing agent for 10 min at an immersion temperature of 60 °C;

[0082] 2) Cleaning: The magnesium alloy workpiece is cleaned cyclically using deionized water combined with ultrasonic waves. The ultrasonic treatment time is 5 min and the ultrasonic frequency is 40 kHz. The cyclic cleaning is performed 3 times, each time for 5 min;

[0083] 3) Activation: The magnesium alloy workpiece is immersed in a mixed solution of hydrofluoric acid (volume fraction 5%) and nitric acid (volume fraction 15%) for 1.5 min, and then rinsed thoroughly with deionized water.

[0084] S2. First micro-arc oxidation (white): The magnesium alloy workpiece is grasped by the robotic arm 4 and placed in the first electrolytic cell 1 for micro-arc oxidation to generate a white micro-arc oxidation film layer. The electrolyte in the first electrolytic cell 1 is composed of 4 g / L zinc sulfate solution, 3 g / L boric acid solution, and 2 g / L sodium sulfate solution; the voltage of this micro-arc oxidation is 240 V, the current is 2.5 A, the frequency is 750 Hz, the treatment time is 7 min, and the temperature is 25 °C.

[0085] S3. Cleaning of magnesium alloy workpiece:

[0086] 1) The magnesium alloy workpiece is taken out of the first electrolytic cell 1 by the robotic arm 4 and placed in the cleaning box, and is cleaned cyclically by deionized water spraying, ultrasonic waves, and cleaning agent until there is no electrolyte residue;

[0087] 2) Use the robotic arm 4 to take out the magnesium alloy workpiece from the cleaning tank and place it in the temperature adjustment tank. After undergoing uniform temperature reduction, freeze-drying, uniform temperature increase, and constant temperature treatment in sequence, the deionized water on the surface of the alloy workpiece is removed. The rate of uniform temperature reduction is 1 °C / min, the temperature of freeze-drying is 5 °C, the time of freeze-drying is 60 min, the rate of uniform temperature increase is 1 °C / min, and the temperature of constant temperature treatment is 25 °C.

[0088] S4. Second micro-arc oxidation (black): After using the robotic arm 4 to grasp the magnesium alloy workpiece, place some of the magnesium alloy workpieces into the second electrolytic cell 1 for micro-arc oxidation to generate a black micro-arc oxidation film layer. The electrolyte in the second electrolytic cell 1 consists of an 8 g / L manganese sulfate solution, a 4 g / L sodium hydroxide solution, and a 3 g / L sodium phosphate solution; the voltage of this micro-arc oxidation is 310 V, the current is 5.5 A, the frequency is 1050 Hz, the treatment time is 11 min, and the temperature is 30 °C.

[0089] S5. Cleaning of magnesium alloy workpiece:

[0090] 1) Use the robotic arm 4 to take out the magnesium alloy workpiece from the second electrolytic cell 1 and place it in the cleaning tank. After spraying with deionized water, ultrasonic cleaning, and circulating cleaning with a cleaning agent until there is no electrolyte residue;

[0091] 2) Use the robotic arm 4 to take out the magnesium alloy workpiece from the cleaning tank and place it in the temperature adjustment tank. After undergoing uniform temperature reduction, freeze-drying, uniform temperature increase, and constant temperature treatment in sequence, the deionized water on the surface of the alloy workpiece is removed. The rate of uniform temperature reduction is 2 °C / min, the temperature of freeze-drying is 6 °C, the time of freeze-drying is 30 min, the rate of uniform temperature increase is 2 °C / min, and the temperature of constant temperature treatment is 30 °C.

[0092] At this point, two-color film layers of white and black are formed on the surface of the magnesium alloy workpiece. The color boundary is clear, the film layer thickness is uniform, (the white film layer is 10 μm, the black film layer is 15 μm), and the surface hardness ≥ 600 HV. The boundary line between the white film layer and the black film layer is straight and uniform, without a curved boundary line. The distribution of the white film layer and the black film layer is continuous and uniform, without defects such as crack gaps.

[0093] Example 2. Three-color (blue + red + green) micro-arc oxidation of titanium alloy workpiece

[0094] S1. Workpiece pretreatment:

[0095] 1) Degreasing: Immerse the titanium alloy workpiece in an acetone organic solution and perform ultrasonic cleaning simultaneously to remove the oil stains on the surface of the titanium alloy workpiece. The immersion time is 5 min, and the immersion temperature is 60 °C;

[0096] 2) Cleaning: Use deionized water combined with ultrasonic waves to clean the titanium alloy workpiece cyclically. The time for ultrasonic treatment is 5 min, and the ultrasonic frequency is 50 kHz. Clean cyclically 3 times, 5 min each time;

[0097] 3) Activation: Immerse the titanium alloy workpiece in a mixed solution of hydrofluoric acid (volume fraction 3%) and sulfuric acid (volume fraction 10%) for 2 min, and then rinse it thoroughly with deionized water.

[0098] S2. First micro-arc oxidation (blue): Use the robotic arm 4 to grasp the titanium alloy workpiece and place it in the first electrolytic cell 1 for micro-arc oxidation to generate a blue micro-arc oxidation film layer. The electrolyte in the first electrolytic cell 1 consists of a copper sulfate solution at 6 g / L, a borax solution at 4 g / L, and a potassium hydroxide solution at 3 g / L; the voltage for this micro-arc oxidation is 280 V, the current is 4.5 A, the frequency is 900 Hz, the treatment time is 10 min, and the temperature is 30 °C.

[0099] S3. Cleaning of titanium alloy workpiece:

[0100] 1) Use the robotic arm 4 to take the titanium alloy workpiece out of the first electrolytic cell 1 and place it in the cleaning box, and perform cyclic cleaning with deionized water spraying, ultrasonic waves, and cleaning agent until there is no electrolyte residue;

[0101] 2) Use the robotic arm 4 to take the titanium alloy workpiece out of the cleaning box and place it in the temperature adjustment box. After experiencing uniform temperature reduction, freeze-drying, uniform temperature increase, and constant temperature treatment in sequence, remove the deionized water on the surface of the alloy workpiece. The rate of uniform temperature reduction is 2 °C / min, the temperature for freeze-drying is 6 °C, the time for freeze-drying is 180 min, the rate of uniform temperature increase is 2 °C / min, and the temperature for constant temperature treatment is 30 °C.

[0102] S4. Second micro-arc oxidation (red): After using the robotic arm 4 to grasp the titanium alloy workpiece, place part of the titanium alloy workpiece in the second electrolytic cell 1 for micro-arc oxidation to generate a red micro-arc oxidation film layer. The electrolyte in the second electrolytic cell 1 consists of a ferric sulfate solution at 3 g / L, a sodium aluminate solution at 4 g / L, and an EDTA-2Na solution at 2 g / L; the voltage for this micro-arc oxidation is 260 V, the current is 3.8 A, the frequency is 890 Hz, the treatment time is 11 min, and the temperature is 35 °C.

[0103] S5. Cleaning of titanium alloy workpiece:

[0104] 1) Use the robotic arm 4 to take the titanium alloy workpiece out of the second electrolytic cell 1 and place it in the cleaning box, and perform cyclic cleaning with deionized water spraying, ultrasonic waves, and cleaning agent until there is no electrolyte residue;

[0105] 2) Use the robotic arm 4 to take out the titanium alloy workpiece from the cleaning tank and place it in the temperature adjustment tank. The alloy workpiece is successively subjected to uniform temperature reduction, freeze-drying, uniform temperature increase, and constant temperature treatment to remove the deionized water on the surface of the alloy workpiece. The rate of uniform temperature reduction is 2 °C / min, the temperature of freeze-drying is 7 °C, the time of freeze-drying is 180 min, the rate of uniform temperature increase is 2 °C / min, and the temperature of constant temperature treatment is 35 °C.

[0106] S6. Third micro-arc oxidation (green): After using the robotic arm 4 to grasp the titanium alloy workpiece, place some of the titanium alloy workpieces in the third electrolytic cell 1 for micro-arc oxidation to generate a green micro-arc oxidation film layer. The electrolyte in the third electrolytic cell 1 is composed of a potassium dichromate solution of 6 g / L, a sodium silicate solution of 4 g / L, and a sodium fluoride solution of 2.5 g / L; the voltage of this micro-arc oxidation is 290 V, the current is 4.2 A, the frequency is 890 Hz, the treatment time is 9 min, and the temperature is 25 °C.

[0107] S7. Cleaning of titanium alloy workpiece:

[0108] 1) Use the robotic arm 4 to take out the titanium alloy workpiece from the third electrolytic cell 1 and place it in the cleaning tank, and perform deionized water spraying, ultrasonic, and cleaning agent circulation cleaning until there is no electrolyte residue;

[0109] 2) Use the robotic arm 4 to take out the titanium alloy workpiece from the cleaning tank and place it in the temperature adjustment tank. The alloy workpiece is successively subjected to uniform temperature reduction, freeze-drying, uniform temperature increase, and constant temperature treatment to remove the deionized water on the surface of the alloy workpiece. The rate of uniform temperature reduction is 1 °C / min, the temperature of freeze-drying is 5 °C, the time of freeze-drying is 180 min, the rate of uniform temperature increase is 1 °C / min, and the temperature of constant temperature treatment is 25 °C.

[0110] At this point, film layers of three colors, blue, red, and green, are formed on the surface of the titanium alloy workpiece. The color boundaries are clear, the film layer thickness is uniform, (the blue film layer is 12 μm, the red film layer is 15 μm, and the green film layer is 18 μm), the salt spray test resistance > 500 h, and the color fastness reaches level 4. The boundary lines between the blue film layer, the red film layer, and the green film layer are straight and uniform, without curved boundaries. The distributions of the blue film layer, the red film layer, and the green film layer are continuous and uniform, without defects such as cracks and gaps.

[0111] Example 3. Four-color (white + yellow + brown + black) micro-arc oxidation of aluminum alloy workpiece

[0112] S1. Workpiece pretreatment:

[0113] 1) Degreasing: Use a NaOH solution and a Na 2 CO 3 solution mixture to make an alkaline degreasing agent, where NaOH is 30 g / L, Na 2 CO3 It is 20 g / L. Immerse the magnesium alloy workpiece in the alkaline degreaser for 10 min at an immersion temperature of 60 °C;

[0114] 2) Cleaning: Use deionized water combined with ultrasonic waves to circulate and clean the aluminum alloy workpiece. The time for ultrasonic treatment is 3 min, and the ultrasonic frequency is 60 kHz. Circulate and clean 3 times, 3 min each time;

[0115] 3) Activation: Immerse the aluminum alloy workpiece in a nitric acid solution (volume fraction 10%) for 2 min, and then rinse it thoroughly with deionized water.

[0116] S2. First micro-arc oxidation (white): Use the robotic arm 4 to grasp the aluminum alloy workpiece and place it in the first electrolytic cell 1 for micro-arc oxidation to generate a white micro-arc oxidation film layer. The electrolyte in the first electrolytic cell 1 consists of a 4 g / L zinc sulfate solution, a 3 g / L boric acid solution, and a 2 g / L sodium sulfate solution; the voltage for this micro-arc oxidation is 240 V, the current is 2.5 A, the frequency is 750 Hz, the treatment time is 7 min, and the temperature is 20 °C.

[0117] S3. Cleaning of the aluminum alloy workpiece:

[0118] 1) Use the robotic arm 4 to take out the aluminum alloy workpiece from the first electrolytic cell 1 and place it in the cleaning box. After circulating and cleaning with deionized water spraying, ultrasonic waves, and cleaning agent until there is no electrolyte residue;

[0119] 2) Use the robotic arm 4 to take out the aluminum alloy workpiece from the cleaning box and place it in the temperature adjustment box. After experiencing uniform temperature reduction, freeze-drying, uniform temperature increase, and constant temperature treatment in sequence, remove the deionized water on the surface of the alloy workpiece. The rate of uniform temperature reduction is 2 °C / min, the temperature for freeze-drying is 7 °C, the time for freeze-drying is 360 min, the rate of uniform temperature increase is 2 °C / min, and the temperature for constant temperature treatment is 20 °C.

[0120] S4. Second micro-arc oxidation (yellow): After using the robotic arm 4 to grasp the aluminum alloy workpiece, place part of the aluminum alloy workpiece in the second electrolytic cell 1 for micro-arc oxidation to generate a yellow micro-arc oxidation film layer. The electrolyte in the second electrolytic cell 1 consists of a 4 g / L sodium molybdate solution, a 3 g / L disodium hydrogen phosphate solution, and a 2 g / L potassium sodium tartrate solution; the voltage for this micro-arc oxidation is 270 V, the current is 3.5 A, the frequency is 850 Hz, the treatment time is 9 min, and the temperature is 30 °C.

[0121] S5. Cleaning of the aluminum alloy workpiece:

[0122] 1) Use the robotic arm 4 to take out the aluminum alloy workpiece from the second electrolytic cell 1 and place it in the cleaning box. After circulating and cleaning with deionized water spraying, ultrasonic waves, and cleaning agent until there is no electrolyte residue;

[0123] 2) Use the robotic arm 4 to take out the aluminum alloy workpiece from the cleaning tank and place it in the temperature adjustment tank. The workpiece undergoes uniform temperature reduction, freeze-drying, uniform temperature increase, and constant temperature treatment in sequence to remove the deionized water on the surface of the alloy workpiece. The rate of uniform temperature reduction is 1 °C / min, the temperature of freeze-drying is 5 °C, the time of freeze-drying is 180 min, the rate of uniform temperature increase is 1 °C / min, and the temperature of constant temperature treatment is 30 °C.

[0124] S6. Third micro-arc oxidation (brown): After using the robotic arm 4 to grasp the aluminum alloy workpiece, place some of the aluminum alloy workpieces in the third electrolytic cell 1 for micro-arc oxidation to generate a brown micro-arc oxidation film layer. The electrolyte in the third electrolytic cell 1 is composed of a 5 g / L ferric sulfate solution, a 3 g / L sodium aluminate solution, and a 2 g / L EDTA-2Na solution; the voltage of this micro-arc oxidation is 260 V, the current is 3.5 A, the frequency is 850 Hz, the treatment time is 10 min, and the temperature is 20 °C.

[0125] S7. Cleaning of aluminum alloy workpiece:

[0126] 1) Use the robotic arm 4 to take out the aluminum alloy workpiece from the third electrolytic cell 1 and place it in the cleaning tank. After spraying with deionized water, ultrasonic cleaning, and circulating cleaning with a cleaning agent until there is no electrolyte residue;

[0127] 2) Use the robotic arm 4 to take out the aluminum alloy workpiece from the cleaning tank and place it in the temperature adjustment tank. The workpiece undergoes uniform temperature reduction, freeze-drying, uniform temperature increase, and constant temperature treatment in sequence to remove the deionized water on the surface of the alloy workpiece. The rate of uniform temperature reduction is 1.5 °C / min, the temperature of freeze-drying is 6 °C, the time of freeze-drying is 60 min, the rate of uniform temperature increase is 1.5 °C / min, and the temperature of constant temperature treatment is 20 °C.

[0128] S8. Fourth micro-arc oxidation (black): After using the robotic arm 4 to grasp the aluminum alloy workpiece, place some of the aluminum alloy workpieces in the fourth electrolytic cell 1 for micro-arc oxidation to generate a black micro-arc oxidation film layer. The electrolyte in the fourth electrolytic cell 1 is composed of an 8 g / L manganese sulfate solution, a 4 g / L sodium hydroxide solution, and a 3 g / L sodium phosphate solution; the voltage of this micro-arc oxidation is 310 V, the current is 5.5 A, the frequency is 1050 Hz, the treatment time is 11 min, and the temperature is 25 °C.

[0129] S9. Cleaning of aluminum alloy workpiece:

[0130] 1) Use the robotic arm 4 to take out the aluminum alloy workpiece from the third electrolytic cell 1 and place it in the cleaning tank. After spraying with deionized water, ultrasonic cleaning, and circulating cleaning with a cleaning agent until there is no electrolyte residue;

[0131] 2) Use the robotic arm 4 to take out the aluminum alloy workpiece from the cleaning tank and place it in the temperature adjustment tank. After experiencing uniform cooling, freeze-drying, uniform heating, and constant temperature treatment in sequence, the deionized water on the surface of the alloy workpiece is removed. The rate of uniform cooling is 2.5 °C / min, the temperature of freeze-drying is 5 °C, the time of freeze-drying is 240 min, the rate of uniform heating is 2.5 °C / min, and the temperature of constant temperature treatment is 25 °C.

[0132] So far, four-color film layers of white, yellow, brown, and black are formed on the surface of the aluminum alloy workpiece. The color boundaries are clear, and the film layer thickness is uniform (white film layer 12 μm, yellow film layer 14 μm, brown film layer 16 μm, black film layer 18 μm). The intersection lines between the white film layer, yellow film layer, brown film layer, and black film layer are straight and uniform, without curved boundaries. The distribution of the white film layer, yellow film layer, brown film layer, and black film layer is continuous and uniform, without defects such as cracks and gaps.

[0133] Comparison 1. Micro-arc oxidation of magnesium alloy workpiece with two colors (white + black)

[0134] S1. Workpiece pretreatment:

[0135] 1) Degreasing: Mix NaOH solution and Na 2 CO 3 solution to make an alkaline degreasing agent, where NaOH is 30 g / L and Na 2 CO 3 is 20 g / L. Immerse the magnesium alloy workpiece in the alkaline degreasing agent for 10 min, and the immersion temperature is 60 °C;

[0136] 2) Cleaning: Use deionized water combined with ultrasonic waves to circulate and clean the magnesium alloy workpiece. The time of ultrasonic treatment is 5 min, and the ultrasonic frequency is 40 kHz. Circulate and clean 3 times, 5 min each time;

[0137] 3) Activation: Immerse the magnesium alloy workpiece in a mixed solution of hydrofluoric acid (volume fraction 5%) and nitric acid (volume fraction 15%) for 1.5 min, and then rinse it clean with deionized water.

[0138] S2. First micro-arc oxidation (white): Use the robotic arm 4 to grab the magnesium alloy workpiece and place it in the first electrolytic cell 1 for micro-arc oxidation to generate a white micro-arc oxidation film layer. The electrolyte in the first electrolytic cell 1 is composed of 4 g / L zinc sulfate solution, 3 g / L boric acid solution, and 2 g / L sodium sulfate solution; the voltage of this micro-arc oxidation is 240 V, the current is 2.5 A, the frequency is 750 Hz, the treatment time is 7 min, and the temperature is 25 °C.

[0139] S3. Cleaning of magnesium alloy workpiece:

[0140] Use the robotic arm 4 to take out the magnesium alloy workpiece from the first electrolytic cell 1, and perform conventional deionized water cleaning and high-temperature drying. The temperature of the high-temperature drying is 105°C, and the time of the high-temperature drying is 120 min.

[0141] S4. Second micro-arc oxidation (black): After grasping the magnesium alloy workpiece with the robotic arm 4, place part of the magnesium alloy workpiece into the second electrolytic cell 1 for micro-arc oxidation to generate a black micro-arc oxidation film layer. The electrolyte in the second electrolytic cell 1 is composed of 8 g / L manganese sulfate solution, 4 g / L sodium hydroxide solution, and 3 g / L sodium phosphate solution; the voltage of this micro-arc oxidation is 310 V, the current is 5.5 A, the frequency is 1050 Hz, the treatment time is 11 min, and the temperature is 30°C.

[0142] S5. Cleaning of magnesium alloy workpiece:

[0143] Use the robotic arm 4 to take out the magnesium alloy workpiece from the second electrolytic cell 1, and perform conventional deionized water cleaning and high-temperature drying. The temperature of the high-temperature drying is 105°C, and the time of the high-temperature drying is 120 min.

[0144] So far, film layers of two colors, white and black, are formed on the surface of the magnesium alloy workpiece. Among them, the boundary line between the white film layer and the black film layer is not straight, but has an obvious curved boundary line. In addition, there are defects such as protrusions and gaps on both the white film layer and the black film layer, and the aesthetics of the film layer is poor.

[0145] In Examples 1 to 3, the surface cleaning electrolyte and deionized water of the alloy workpiece are both subjected to uniform temperature reduction, freeze-drying, uniform temperature increase, and constant temperature treatment; while the surface cleaning electrolyte of the alloy workpiece in Comparative Example 1 is subjected to conventional deionized water cleaning and high-temperature drying. Compared with Comparative Example 1, the film layers of various colors on the alloy workpieces in Examples 1 to 3 are more uniform, without defects such as crack gaps, and there is a straight and uniform boundary line between the two-color film layers. This is because, through uniform temperature reduction, freeze-drying, uniform temperature increase, and constant temperature treatment, the accumulation of thermal stress caused by the drastic temperature change of the alloy workpiece is reduced, and defects such as microcracks and protrusion deformation of the alloy workpiece are avoided, thereby ensuring the uniformity of the micro-arc oxidation film layer on the alloy surface.

[0146] It should be understood that in Specific Examples 1 to 3 and Comparative Example 1, the first electrolytic cell 1, the second electrolytic cell 1, the third electrolytic cell 1, and the fourth electrolytic cell 1 mentioned are only for convenience of description in each example. That is to say, in different examples, the first (second / third / fourth) electrolytic cell 1 is not the same electrolytic cell 1.

[0147] It should be noted that when an element is described as "connected", "coupled" or "linked" to another element, it may mean a direct connection, coupling or linkage, but it should be understood that there may be intermediate elements between them; that is, it covers both direct and indirect connection positional relationships.

[0148] It should be noted that the use of words such as "a" or "an" does not necessarily imply a limitation in quantity. Words such as "comprising" or "including" mean that the elements or items appearing before such words cover the elements or items listed after such words and their equivalents, without excluding other elements or items.

[0149] It should be noted that terms indicating orientation or positional relationships such as "upper", "lower", "left", "right", etc. are only used to represent relative positional relationships, which are for the convenience of describing the present invention, rather than the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation; when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0150] The preferred embodiments for implementing the present invention have been described in detail above, but it should be understood that the functions of these embodiments are only for illustration and not for limiting the scope, application or construction of the present invention in any way. The protection scope of the present invention is defined by the appended claims and their equivalents. Those of ordinary skill in the art can make many changes to the foregoing embodiments under the teaching of the present invention, and these changes all fall within the protection scope of the present invention.

Claims

1. A method for multicolor micro-arc oxidation of alloy surface, characterized in that: The following steps are involved: S1. Workpiece pretreatment: degreasing, cleaning and activation of the alloy workpiece; S2. placing the alloy workpiece in electrolyte a, forming a first color film layer after micro-arc oxidation, and removing the alloy workpiece from electrolyte a; S3. The electrolyte a is washed with deionized water on the surface of the alloy workpiece, and then the alloy workpiece is cooled uniformly, freeze-dried, heated uniformly and treated at a constant temperature to remove the deionized water on the surface of the alloy workpiece; S4. The alloy workpiece is placed in electrolyte b, and a second color film layer is formed after micro-arc oxidation, and the alloy workpiece is removed from electrolyte b; S5. The electrolyte b is cleaned on the surface of the alloy workpiece with deionized water, and then the alloy workpiece is cooled uniformly, freeze-dried, heated uniformly, and the deionized water is removed from the surface of the alloy workpiece after constant temperature treatment; S6. Steps S2 to S5 are repeated to form a film layer of various colors on the surface of the alloy workpiece; In step S3 and / or S5, the uniform cooling rate is 1-3°C / min; In step S3 and / or S5, the freeze-drying temperature is 5-7°C, and the freeze-drying time is 30-360 min; In step S3 and / or S5, the uniform heating rate is 1-3°C / min.

2. A method for multicolor micro-arc oxidation of alloy surface according to claim 1, characterized in that: In step S3 and / or S5, deionized water and a cleaning agent may be used to rinse the electrolyte on the surface of the alloy workpiece multiple times.

3. A method for multicolor micro-arc oxidation of alloy surface according to claim 1, characterized in that: In step S1, an organic solvent or an alkaline degreasing agent is used to soak and remove oil stains and impurities on the surface of the alloy workpiece, wherein the organic solvent comprises one or more of acetone and gasoline, and the alkaline degreasing agent comprises one or more of sodium hydroxide solution, sodium carbonate solution and sodium phosphate solution, and the soaking time is 5 to 15 minutes.

4. The method for multicolor micro-arc oxidation of alloy surface according to claim 1, characterized in that: In step S1, deionized water and ultrasonic waves are used to remove tiny particles and residual impurities on the surface of the alloy workpiece. The ultrasonic treatment time is 3 to 10 minutes, and the ultrasonic frequency is 30 to 60 kHz.

5. The method for multicolor micro-arc oxidation of alloy surface according to claim 1, characterized in that: In step S1, an acidic solution is used to activate the surface of the alloy workpiece. The acidic solution includes one or more of a hydrofluoric acid solution, a nitric acid solution and a sulfuric acid solution. The activation treatment time is 1 to 5 minutes.

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