Method for repairing hard anodized film layer of aluminum alloy part

Abstract

The invention discloses a method for repairing a hard anodized film layer of an aluminum alloy part, which is characterized in that an original hard anodized film layer on the surface of the aluminum alloy part is reserved, and a new hard anodized film layer is continuously generated on the surface of the original hard anodized film layer. The clamping position required by hard anodizing is re-processed, so that the clamping position contains exposed matrix metal, and when a new hard anodizing film layer continues to be generated on the surface of the original hard anodizing film layer, a method of increasing voltage in a segmented manner is adopted, so that the film layer is thickened, and meanwhile, the hardness of the film layer is improved. The method solves the problem that when the part has a poor film layer, the part is scrapped due to the fact that the original film layer of the part cannot be removed and hard anodizing repair is carried out again.

Description

Technical Field

[0001] The invention belongs to the technical field of aviation aircraft environmental control systems, and in particular relates to a method for repairing a hard anodized film layer of an aluminum alloy part. Background Art

[0002] When the aluminum alloy hard anodized parts used in the aircraft environmental control system have a bad hard anodized film, the parts need to be re-de-filmed or re-made and hard anodized. If the part size cannot be removed and re-repaired, the cost of re-processing the part and then hard anodizing it is high and the cycle is long.

[0003] Aluminum alloy hard anodizing has inherent characteristics of film formation, such as Figure 1 As shown, the increase in the size of one side of the part is about half of the film thickness. Figure 1 The substrate will corrode about half of the film thickness ( Figure 1 Therefore, in most cases, the bad film layer is generally not suitable for repair, unless the part size tolerance allows, then the film layer can be repaired by removing the hard anodized film and then re-hard anodizing. Summary of the invention

[0004] The present invention aims to provide a method for repairing the hard anodized film layer of an aluminum alloy part, so as to solve the problem of parts being scrapped due to a poor hard anodized film layer of the part and the inability to remove the original film layer and re-hard anodize the part for repair.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for repairing the hard anodized film layer of aluminum alloy parts, including:

[0007] The original hard anodized film layer on the surface of the aluminum alloy parts is retained, and a new hard anodized film layer continues to be generated on the surface of the original hard anodized film layer.

[0008] Furthermore, the method for repairing the hard anodized film layer of an aluminum alloy part also includes: processing a new clamping position on the aluminum alloy part according to the requirements of hard anodizing clamping and conductivity, or repairing the original clamping position of the aluminum alloy part to obtain a new clamping position for hard anodizing. Generally speaking, the original clamping point / clamping position is usually selected for repair, because the film layer at this position is relatively thin, or even almost non-existent, and the appearance presented is a white or slightly white surface, and repairing this position is relatively convenient and feasible.

[0009] Further, the new clamping location includes exposed base metal.

[0010] Furthermore, the method for repairing the hard anodized film layer of an aluminum alloy part also includes: performing a film stripping process on a fixture used for hard anodizing to ensure the conductive performance of the fixture during hard anodizing.

[0011] Furthermore, when a new hard anodized film layer is generated, the hard anodizing treatment is divided into multiple stages to perform voltage boosting, and the voltage is maintained for a period of time after each boosting.

[0012] Furthermore, after each voltage boost, the current does not change suddenly during the time when the voltage remains unchanged.

[0013] Furthermore, the hard anodizing is performed using sulfuric acid.

[0014] Compared with the prior art, the present invention adopts the following film repair scheme for the situation where the hanger has been removed before the parts are repaired: that is, the required film layer is added to the surface of the original hard anodized film. The repair method of the present invention solves the cost and cycle problems of reprocessing parts, and is particularly suitable for the situation where aluminum alloy parts are scrapped because the original film layer cannot be removed and re-hard anodized for repair.

[0015] The present invention is different from the traditional method of removing the hard anodized film and then hard anodizing again, and is also different from the supplementary hard anodizing treatment performed when the parts are not hung because the film thickness is insufficient during the hard anodizing process. The hard anodized film layer of the aluminum alloy parts repaired by the present invention is continuous, uniform and complete, and the hardness and thickness can meet the technical requirements, opening up a new way to repair the hard anodized film layer of aluminum alloy parts.

[0016] The present invention is applicable to all aluminum alloys, as long as the aluminum alloy is designed and structured to allow hard anodizing. However, there are two exceptions. One is that it is limited to aluminum alloy castings, and the other is that the hard anodized film is not applicable to the repair of aluminum alloy thin-walled parts. For the former, it is because the aluminum alloy castings allow pinholes to exist in the matrix structure due to the characteristics of the castings themselves, and there may even be loose tissue deep in the matrix that cannot be observed by the naked eye. When the hard anodized parts are repaired, the repair clamping position is corroded while the anodized film is generated. If the corrosion reaches the place where the matrix is ​​loose, the degree of corrosion will be aggravated, and eventually electric shocks to the parts or corrosion holes will be generated. Therefore, it is not recommended to repair the hard anodized film of aluminum alloy castings when there are defects, that is, it is limited to aluminum alloy castings.

[0017] The repair method of the present invention has the following characteristics:

[0018] (1) There is no need to remove the original hard anodized film, and the film layer continues to be generated on the surface of the existing film layer. The original clamping position on the surface of the hard anodized film layer that needs to be repaired cannot be clamped and restored. After the original clamping position is re-repaired, hard anodizing can be performed;

[0019] (2) The bath liquid composition during hard anodizing treatment is commonly used sulfuric acid. During operation, a voltage stabilization method is adopted. Through multi-stage boosting, voltage and current are controlled to form a hard and wear-resistant oxide film on the surface;

[0020] (3) The hard anodized film layer generated after repair meets the thickness requirements. As the thickness of the anodized film increases, the hardness of the anodized film also increases accordingly;

[0021] (4) The hard anodized film generated after repair was polished on the longitudinal surface by a metallographic polishing machine and observed under a 50x metallographic microscope. The generated film had no interface with the original film and the film was fine and uniform. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the principle of hard anodizing of aluminum alloy parts;

[0023] Figure 2 The invention discloses a hard anodized sample and a metallographic diagram of an aluminum alloy part. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments, but it should not be understood that the scope of the subject matter described in the present invention is limited to the following embodiments. Without departing from the above-mentioned technical ideas of the present invention, various modifications, substitutions and changes made according to the common technical knowledge and customary means in the field are included in the scope of the present invention.

[0025] In the present invention, the method for repairing the hard anodized film layer of an aluminum alloy part comprises the following steps:

[0026] Step 1: Repair the clamping position of the aluminum alloy parts to make the clamping position meet the requirements of hard anodizing clamping and conductivity. Specifically, the original hard anodizing clamping position of the aluminum alloy parts to be repaired is repaired by mechanical processing. The clamping position after repair must meet the requirements of hard anodizing clamping and conductivity.

[0027] Step 2: Clean the aluminum alloy parts to be repaired. Use organic solvents such as alcohol and gasoline to wipe the surface of the aluminum alloy parts to ensure that the surface of the aluminum alloy parts is clean and free of dirt after cleaning.

[0028] Step three, the fixture is stripped by conventional alkaline washing to ensure that the aluminum alloy parts clamped by the fixture have good conductivity during hard anodizing.

[0029] Step 4: When clamping the aluminum alloy parts, ensure that the clamping position is where the newly processed base metal is exposed and ensure that the parts are clamped securely.

[0030] Step 5: Hard anodizing of aluminum alloy parts to generate the required hard anodized film layer on the surface of the original film layer:

[0031] In this embodiment, 2A12 plate (including aluminum layer) is used for verification, and the film thickness of the hard anodized test piece before repair is (20-30) μm. The commonly used sulfuric acid process (H2SO4: 180-200g / L) is used, the temperature is (-2--6) ° C, and the voltage stabilization method is used during operation. The voltage and current (DC) are controlled through a 9-stage boost, as follows:

[0032] Section 1: (0-7) min, the voltage is increased to 20 V within 5 min, the current is increased to 1 A / dm 2, and the voltage is maintained for 2 min;

[0033] Section 2: (7-17) min, the voltage is increased to 25 V within 5 min, the current is increased to 1.25 A / dm 2, and the voltage is maintained for 5 min;

[0034] Section 3: (17-27) min, the voltage is increased to 30 V within 5 min, the current is increased to 1.5 A / dm 2, and the voltage is maintained for 5 min;

[0035] Section 4: (27-37) min, the voltage rises to 35 V and the current rises to 1.75 A / dm2 within 5 min, and the voltage is maintained for 5 min;

[0036] Section 5: (37-44) min, the voltage is increased to 40 V within 5 min, the current is increased to 2 A / dm 2, and the voltage is maintained for 2 min;

[0037] Section 6: (44-49) min, the voltage rises to 45 V within 3 min, the current rises to 2.25 A / dm 2, and the voltage is maintained for 2 min;

[0038] Section 7: (49-54) min, the voltage is increased to 50 V within 3 min, the current is increased to 2.5 A / dm 2, and the voltage is maintained for 2 min;

[0039] Section 8: (54-60) min, the voltage rises to 55 V within 3 min, the current rises to 2.75 A / dm 2, and the voltage is maintained for 3 min;

[0040] Section 9: (60-70) min, within 5 min, the voltage is increased to 60 V, the current is increased to 3 A / dm 2, and the voltage is maintained for 5 min.

[0041] It should be noted that, in the above process, the decrease in current is reliable (the decrease in current means that after the voltage is increased, the current also reaches an instantaneous high current state at this stage. According to the voltage stabilization method adopted by the present invention, according to Ohm's law U=IR, when the voltage remains stable, when the resistance increases (that is, the film layer thickens), the current must maintain a downward trend. When the current suddenly increases, it means that the substrate at the clamping position is instantly too hot and the area has been electrocuted. Therefore, the decrease in current is required to be in a controllable and reliable operation). Once a sudden increase in current is found, the operation must be interrupted, and the parts may have been electrocuted at this time.

[0042] Step six, according to conventional processing methods, complete the washing, filling, drying, and drying processes of the hard anodized aluminum alloy parts.

[0043] Step 7: Disassemble the fixture.

[0044] Step 8: Inspection of hard anodized film, including:

[0045] a. Appearance quality: Figure 2 In the left picture, the film is dark gray, and the film is continuous, uniform, and complete;

[0046] b. Film thickness inspection: Figure 2 In the right figure, the film thickness is 35-45 μm;

[0047] c. Film hardness inspection: film hardness ≥ HV230;

[0048] d. Metallographic microscopic examination of the film: Figure 2 In the right picture, the longitudinal surface of the film layer was polished by a metallographic polisher and observed under a 50x metallographic microscope. There was no dividing line on the surface of the film layer, and the film layer was fine and uniform.

[0049] It needs to be emphasized again that the present invention is limited to the repair of the hard anodized film layer of aluminum alloy castings, and is not applicable to the repair of the hard anodized film layer of aluminum alloy thin-walled parts.

[0050] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for repairing hard anodized film of aluminum alloy parts, characterized in that: include: The original hard anodized film layer on the surface of the aluminum alloy parts is retained, and a new hard anodized film layer continues to be generated on the surface of the original hard anodized film layer.

2. The method for repairing the hard anodized film layer of an aluminum alloy part according to claim 1, characterized in that: Also includes: According to the requirements of hard anodized clamping and conductivity, new clamping positions are processed on aluminum alloy parts.

3. The method for repairing the hard anodized film layer of an aluminum alloy part according to claim 1, characterized in that: The original clamping position of the aluminum alloy parts is repaired to obtain a new clamping position for hard anodizing.

4. The method for repairing the hard anodized film layer of an aluminum alloy part according to claim 2 or 3, characterized in that: The new clamping location includes exposed base metal.

5. The method for repairing the hard anodized film layer of an aluminum alloy part according to claim 1, characterized in that: Also includes: The fixture used for hard anodizing is stripped to ensure the conductive performance of the fixture during hard anodizing.

6. The method for repairing the hard anodized film layer of an aluminum alloy part according to claim 1, characterized in that: When a new hard anodized film layer is generated, the hard anodizing treatment is divided into multiple stages to perform voltage boosting, and the voltage is maintained for a period of time after each boost.

7. The method for repairing the hard anodized film layer of an aluminum alloy part according to claim 6, characterized in that: During the time when the voltage remains constant after each voltage boost, there is no sudden change in the current.

8. The method for repairing the hard anodized film layer of an aluminum alloy part according to claim 1 or 6, characterized in that: The hard anodizing process uses sulfuric acid.

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