A hard anodizing process method for the inner surface of a 7075 aluminum alloy spherical part

Abstract

The present invention belongs to the technical field of surface treatment of metal materials, and particularly relates to a hard anodizing process method for the inner surface of 7075 aluminum alloy spherical parts. The process route is as follows: using potassium alum to adjust the Al concentration in the hard anodizing bath, part acceptance, pre-degreasing, hanging the parts, coating with an insulating isolation adhesive solution, mounting the parts, alkaline degreasing, deionized water washing, deoxidizing pickling, deionized water washing, hard anodizing, deionized water washing, drying, removing the insulating isolation adhesive, and inspection (including the hardness and thickness of the hard anodizing film layer, the diameter of the inner surface of the part, the distance from the center of the sphere to the spherical surface, and coaxiality), ensuring the service life of the part and eliminating the problems of eccentric wear and jamming that may occur due to out-of-tolerance dimensions during the flight of the aircraft, and ensuring the flight safety of the aircraft. 3+ The process route is as follows: using potassium alum to adjust the Al concentration in the hard anodizing bath, part acceptance, pre-degreasing, hanging the parts, coating with an insulating isolation adhesive solution, mounting the parts, alkaline degreasing, deionized water washing, deoxidizing pickling, deionized water washing, hard anodizing, deionized water washing, drying, removing the insulating isolation adhesive, and inspection (including the hardness and thickness of the hard anodizing film layer, the diameter of the inner surface of the part, the distance from the center of the sphere to the spherical surface, and coaxiality), ensuring the service life of the part and eliminating the problems of eccentric wear and jamming that may occur due to out-of-tolerance dimensions during the flight of the aircraft, and ensuring the flight safety of the aircraft.

Description

Technical Field

[0001] The present invention belongs to the technical field of surface treatment of metal materials, and particularly relates to a hard anodizing process method for the inner surface of 7075 aluminum alloy spherical parts. Background Art

[0002] The ball seat material of the Z9 / Z19 type machine is 7075. This part belongs to a high-precision spherical part. According to the design requirements, only the inner surface needs to be subjected to hard anodizing treatment. Before the hard anodizing treatment of this part, the dimensional accuracy is relatively high. And after the hard anodizing treatment, the hardness, thickness, inner surface diameter, distance from the ball center to the spherical surface, and coaxiality of the hard anodized film layer of this part must meet the requirements of the drawing. It cannot be reworked or repaired. If the hard anodizing process is not properly handled, it is very easy to reduce the service life of the part, cause the dimensional tolerance of the part, and then cause a large number of parts to be scrapped. And this part has a dynamic fit requirement and needs to rotate at high speed during the flight of the aircraft. If the above indicators do not meet the design requirements, problems such as eccentric wear and jamming will occur during the use of this part, which will seriously affect the flight safety of the aircraft. Summary of the Invention

[0003] The technical problem solved by the present invention: This part is a high-precision dimensional spherical part made of 7075, with a high fit precision with the hemispherical support. The hard anodizing area of a single part is 0.4 dm 2 , and after the hard anodizing treatment, it is necessary to ensure that there is no fixture mark on the surface of each part. The hard anodized film layer should be continuous and the thickness should be uniform. The thickness of each hard anodizing area of each part should meet 45 μm - 65 μm. The hardness of the hard anodized film layer > 300 HV. At the same time, it is necessary to ensure that the inner surface diameter of each part after the hard anodizing treatment should be φ140 mm + 0.05 mm, the distance from the ball center to the spherical surface should be -0.03 mm - -0.09 mm, and the coaxiality should be φ0 mm - 0.03 mm. All indicators should meet the design requirements, so as to ensure the service life of this part and eliminate the eccentric wear and jamming problems that may occur due to dimensional tolerance during the flight of the aircraft, and ensure the flight safety of the aircraft.

[0004] The technical solution of the present invention:

[0005] A hard anodizing process method for the inner surface of 7075 aluminum alloy spherical parts, the method comprising:

[0006] S1, using chemically pure potassium alum to adjust the Al concentration in the hard anodizing bath; 3+ concentration;

[0007] S2, inspecting the parts;

[0008] S3, pre-degreasing the parts;

[0009] S4, hanging part;

[0010] S5, coating the outer surface of the part with insulating isolation glue;

[0011] S6, hanging the part;

[0012] S7, degreasing the part surface with alkali;

[0013] S8, performing the first deionized water wash on the part;

[0014] S9, performing deoxidation treatment on the part surface;

[0015] S10, performing the second deionized water wash on the part;

[0016] S11, performing hard anodizing treatment on the part surface;

[0017] S12, performing the third deionized water wash on the part;

[0018] S13, drying the part, removing the insulating isolation glue, and performing quality inspection on the hard anodized film layer of the part.

[0019] The features and further improvements of the technical solution of the present invention are as follows:

[0020] (1) The specific acceptance of the part in S2 is as follows:

[0021] There are no scratches, bumps, burrs, visible heavy oil stains and corrosion on the part surface, and the surface roughness value Ra ≤ 0.8.

[0022] (2) S3, pre-degreasing the part, specifically:

[0023] Using a white cotton cloth dipped in alcohol, acetone, and methyl ethyl ketone to wipe the part for pre-degreasing.

[0024] (3) S4, hanging the part, specifically:

[0025] Using LY1Y aluminum wire with a diameter of 2 mm to clamp the outer surface of the part, and winding a single aluminum wire around the outer surface of the part for one circle.

[0026] (4) The specific content of S5 is as follows:

[0027] Coating the outer surface of the part with insulating isolation glue, and ensuring that the edge of the joint between the insulating isolation glue isolation area and the part exposed area is neat, the insulating isolation glue is tightly bonded to the part substrate, and there are no bubbles and leakage points.

[0028] (5) The specific content of S6 is as follows:

[0029] The number of parts inserted into the slot each time is 12. Every 3 parts form a column. The aluminum wire wound around 3 parts is wound into a strand and hung on the copper bar in 4 columns.

[0030] (6) S7 specifically is: Perform alkaline degreasing on the surface of the parts. The concentration of TURCO 4215NC-LT is 37.5 g / L to 59.5 g / L, the temperature is 50°C to 60°C, and the time is 5 min to 10 min.

[0031] After that, rinse with deionized water for a time ≥ 2 min. Then, conduct a water film continuity test, requiring that the water film continuously remains unbroken within 30 s.

[0032] (7) S9 specifically is:

[0033] Perform deoxidation treatment on the surface of the parts, ensuring that the single-sided corrosion rate is 20.3 μm / h to 25.4 μm / h. The concentration of chromic acid is 22.5 g / L to 37.5 g / L, the concentration of nitric acid is 210 g / L to 230 g / L, and hydrofluoric acid with a volume fraction of 40%; the temperature is room temperature, and the time is 3 min to 5 min.

[0034] After that, rinse with deionized water for a time ≥ 2 min. Then, conduct a water film continuity test, requiring that the water film continuously remains unbroken within 30 s.

[0035] (8) S11 specifically is:

[0036] Perform hard anodizing treatment on the surface of the parts: The concentration of sulfuric acid is 160 g / L to 170 g / L, Al 3+ 2.5 g / L to 2.7 g / L, the temperature is -5°C to -8°C, and the current density parameter is controlled as follows: 0 min to 5 min: gradually increase to 2.5 A, 5 min to 10 min: gradually increase to 5 A, 15 min to 20 min: gradually increase to 7.5 A, 15 min to 20 min: gradually increase to 10 A, the time is 90 min to 120 min. After 20 min, the current is allowed to be adjusted during the hard anodizing process, and the voltage increase per 5 min needs to be controlled between 0.7 V and 3 V;

[0037] After that, rinse with deionized water for a time ≥ 2 min.

[0038] The advantages of the present invention are:

[0039] 1. Use an aluminum wire with a diameter of 2 mm and a material of LY1Y to hang the parts from the outer surface of the spherical parts, fundamentally eliminating the hanging marks on the inner surface of the spherical products, ensuring the continuity and integrity of the film layer. At the same time, a special aluminum wire suitable for hanging aluminum alloy anodized parts is provided. This aluminum wire is of moderate hardness and softness, simple in structure, easy to process, and can be used for hanging aluminum alloy parts of various material grades and various shapes. It can also be wound into a spring and is specially used for hanging parts in the anodizing processes such as chromic acid anodizing, sulfuric acid anodizing, hard anodizing, boric acid-sulfuric acid anodizing, and tartaric acid-sulfuric acid anodizing of aluminum alloys, which can effectively reduce production costs and effectively reduce the problem of electric shock burns of parts during anodizing.

[0040] 2. The process method is simple and easy to operate. Adopting the DC hard anodizing treatment method, it is first proposed to accurately control the number of parts entering the tank and the hanging arrangement method according to the volume of the hard anodizing tank, the cathode area, and the inner diameter size of the parts before hard anodizing during the process, ensuring the conformity of the cathode area and the anode area and the uniformity of the current distribution on a single part during the hard anodizing treatment process. After the soft start stage of hard anodizing, the current can be adjusted to control the voltage increase within every 5 minutes, and the voltage increase is specified, thereby effectively controlling the final time of the hard anodizing treatment, ensuring that the deposition and dissolution rates of different surface film layers are quite the same during the hard anodizing treatment process, and ensuring the uniformity of the film layer thickness. Different operators can immediately master this hard anodizing treatment method, which has extremely high popularization and practicality.

[0041] 3. A method curve for adjusting the hard anodizing bath solution using potassium alum (chemically pure) is proposed, providing theoretical and practical references for the hard anodizing treatment of other materials, and finding the limit value of Al 3+ in the hard anodizing bath solution, making the hard anodizing solution reach the best conductive state, and further ensuring the uniformity of the film layer thickness.

[0042] 4. Greatly reduces the cost savings. This patent provides a hard anodizing process method for high-precision aluminum alloy parts. Only performing hard anodizing treatment can meet the design requirements, without the need for additional processing, reducing the scrap rate of the parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a graph showing the relationship between the Al 3+ concentration and the conductivity of the solution provided by the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0044] The technical solution of the present invention will be described in detail below with reference to the drawings.

[0045] The spherical part is made of 7075 material with high-precision dimensions. It has a high fitting precision with the hemispherical support. The area of the hard anodized region of a single part is 0.4 dm 2 , and after hard anodizing, it is necessary to ensure that there are no fixture marks on the surface of each part. The hard anodized film layer should be continuous and the thickness should be uniform. The thickness of the hard anodized region of each part should meet the requirement of 45 μm to 65 μm. The hardness of the hard anodized film layer > 300 HV. At the same time, it is necessary to ensure that the inner surface diameter of each part after hard anodizing should be φ140 mm + 0.05 mm, the distance from the center of the sphere to the spherical surface should be -0.03 mm to -0.09 mm, and the coaxiality should be φ0 mm to 0.03 mm. All indicators should meet the design requirements, so as to ensure the service life of the part and eliminate the problems of eccentric wear and jamming that may occur due to dimensional tolerance during the flight of the aircraft, and ensure the flight safety of the aircraft.

[0046] The embodiment of the present invention provides a hard anodizing process method for 7075 high-precision aluminum alloy spherical parts, accurately controlling the bath composition (including sulfuric acid concentration, Al 3+ concentration), using LY1Y aluminum wire to hang the outer surface of the part, and controlling the number of parts entering the bath and process parameters.

[0047] The process route is as follows: using potassium alum to adjust the Al 3+ concentration in the hard anodizing bath → part acceptance → pre-degreasing → hanging the part → coating the insulating isolation glue solution → installing and hanging the part → alkaline degreasing → deionized water washing → deoxidizing pickling → deionized water washing → hard anodizing → deionized water washing → drying → removing the insulating isolation glue → inspection (including the hardness, thickness of the hard anodized film layer, the diameter of the inner surface of the part, the distance from the center of the sphere to the spherical surface, and coaxiality).

[0048] Among them, using chemically pure potassium alum to adjust the Al 3+ concentration in the hard anodizing bath, the conductivity of the solution is as Figure 1 shown:

[0049] The specific steps of the hard anodizing process are as follows:

[0050] Step 1. Accept the part: The surface of the part has no scratches, dents, burrs, visible heavy oil stains and corrosion to the naked eye, and the surface roughness Ra value ≤ 0.8.

[0051] Step 2. Pre-degreasing: Provide a clean and clean metal substrate, and use a white cotton cloth dipped in alcohol, acetone, and methyl ethyl ketone to wipe the part for pre-degreasing.

[0052] Step 3. Hang the part: Use LY1Y aluminum wire with a diameter of 2 mm to clamp the outer surface of the part, and a single aluminum wire can be wound around the outer surface of the part for one circle.

[0053] Step 4. Coating the insulating and isolating glue solution: Coat the insulating and isolating glue on the outer surface, and ensure that the edge of the joint between the insulating and isolating glue isolation area and the exposed area of the part is neat, the insulating and isolating glue is tightly bonded to the part substrate, and there are no bubbles or leakage points.

[0054] Step 5. Hanging the parts: The number of parts put into the tank each time is 12, with 3 parts in each column (the aluminum wire wound around 3 parts is wound into one strand), and they are hung on the copper bar in 4 columns. (Note: The volume of this tank is 2000L, the tank size is 2m×1m×1m, and the cathode area is 1.8m 2 )

[0055] Step 6. Alkaline degreasing: Alkaline degreasing is carried out on the surface of the part substrate. The concentration of TURCO 4215NC-LT is 37.5g / L - 59.5g / L, the temperature is 50°C - 60°C, and the time is 5min - 10min. Then rinse with deionized water for a time ≥2min, and then conduct a water film continuity test, requiring that the water film does not break within 30s of continuous retention.

[0056] Step 7. Deoxidizing pickling: Deoxidize the surface of the substrate to ensure that the single-sided corrosion rate is 20.3μm / h - 25.4μm / h, the chromic acid concentration is 22.5g / L - 37.5g / L, the nitric acid concentration is 210g / L - 230g / L, and hydrofluoric acid with a volume fraction of 40% is added according to the requirement of the corrosion rate. The temperature is room temperature, and the time is 3min - 5min. Then rinse with deionized water for a time ≥2min, and then conduct a water film continuity test, requiring that the water film does not break within 30s of continuous retention.

[0057] Step 8. Hard anodizing treatment on the surface of the substrate: The sulfuric acid concentration is 160g / L - 170g / L, Al 3+ 2.5g / L - 2.7g / L, the temperature is -5°C - -8°C, and the current density parameters are controlled as follows: 0min - 5min: gradually increase to 2.5A, 5min - 10min: gradually increase to 5A, 15min - 20min: gradually increase to 7.5A, 15min - 20min: gradually increase to 10A, the time is 90min - 120min, and the current is allowed to be adjusted during the hard anodizing process after 20min. It is necessary to control the voltage increase per 5min within the range of 0.7V - 3V. Then rinse with deionized water for a time ≥2min.

[0058] Step 9. Drying: Dry the parts with dry, oil-free, and water-free compressed air or air-dry them naturally at room temperature.

[0059] Step 10. Remove the isolation and protection insulating and isolating glue.

[0060] Step 11. Quality inspection of the hard anodized film layer: including the hardness, thickness of the hard anodized film layer, the diameter of the inner surface of the part, the distance from the center of the ball to the spherical surface, and the coaxiality.

[0061] Specific implementation method example:

[0062] Select 12 ball seat parts with a surface roughness Ra value of 0.7. Hang 3 parts in each column and divide them into 4 columns and hang them on the copper bar; use a white cotton cloth dipped in methyl ethyl ketone to wipe the parts for pre-degreasing; Hang the parts: Use LY1Y aluminum wire with a diameter of 2 mm to clamp the outer surface of the parts, and single aluminum wire can be wound around the outer surface of the parts for one circle; Apply insulating isolation glue: Apply insulating isolation glue on the outer surface, and ensure that the edge of the insulating isolation glue is neat, the bonding is tight, and there are no leakage points. Hang 12 parts into the tank, 3 parts in each column (wind the aluminum wire around 3 parts into one strand), and divide them into 4 columns and hang them on the copper bar; Perform alkaline degreasing: The concentration of TURCO4215NC-LT is 45.5 g / L, the temperature is 55.2 °C, and the time is 8 min. Then rinse with deionized water for 3 min. Then perform a water film continuity test. The water film remains continuous within 30 s without breaking; After the water film inspection is qualified, perform deoxidizing pickling: Add 15.L of hydrofluoric acid with a volume fraction of 40%, the single-sided corrosion rate is 22.7 μm / h, the chromic acid concentration is 32.8 g / L, the nitric acid concentration is 220 g / L, the temperature is room temperature, and the time is 4 min; Then rinse with deionized water for 3 min. Then perform a water film continuity test. The water film remains continuous within 30 s without breaking; After the water film inspection is qualified, perform hard anodizing treatment: The sulfuric acid concentration is 168 g / L, Al 3+ is 2.6 g / L, the temperature is -7.2 °C, and the current density parameter control is 0 min - 5 min: gradually increase to 2.5 A, 5 min - 10 min: gradually increase to 5 A, 15 min - 20 min: gradually increase to 7.5 A, 15 min - 20 min: gradually increase to 10 A, the time is 90 min - 120 min. After 20 min, the current is allowed to be adjusted during the hard anodizing process. The voltage increase per 5 min needs to be controlled between 0.7 V and 3 V; Then rinse with deionized water for 10 min; Then use dry, oil-free, and water-free compressed air to blow dry the parts; Remove the protection of the insulating isolation glue. Send it to the physical and chemical metrology center for film layer and part size quality inspection: The hardness of the hard anodized film layer is 378 kgf / mm 2 , the thickness is 60 μm, the diameters of the inner surfaces of 12 ball seat parts, the distance from the center of the ball to the spherical surface, and the coaxiality are shown in Table 1.

[0063] Table 1

[0064] Number Inner surface diameter (mm) Distance from the center of the sphere to the spherical surface (mm) Coaxiality (mm) 1 φ140.007 -0.060 φ0.003 2 φ140.009 -0.053 φ0.002 3 φ140.019 -0.072 φ0.005 4 φ140.024 -0.054 φ0.005 5 φ140.010 -0.065 φ0.001 6 φ140.003 -0.081 φ0.005 7 φ140.008 -0.044 φ0.004 8 φ140.015 -0.070 φ0.002 9 φ140.020 -0.076 φ0.003 10 φ140.006 -0.066 φ0.008 11 φ140.007 -0.070 φ0.004 12 φ140.010 -0.056 φ0.004

[0065] The advantages of the present invention are as follows:

[0066] 1. Aluminum wire with a diameter of 2 mm and material LY1Y is used to hang parts from the outer surface of spherical parts, fundamentally eliminating the hanging marks on the inner surface of spherical products, ensuring the continuity and integrity of the film layer. At the same time, a special aluminum wire suitable for hanging aluminum alloy anodized parts is provided. This aluminum wire is of moderate hardness and softness, has a simple structure, is easy to process, can be used for hanging aluminum alloy parts of various material grades and various shapes, and can also be wound into springs, which are specifically used for hanging parts during anodizing processes such as chromic acid anodizing, sulfuric acid anodizing, hard anodizing, borosulfuric acid anodizing, and tartaric acid sulfuric acid anodizing of aluminum alloys. It can effectively reduce production costs and also effectively reduce the problem of electric shock burns of parts during anodizing.

[0067] 2. The process method is simple and easy to operate. The direct current hard anodizing treatment method is adopted. For the first time, it is proposed to accurately control the number of parts put into the tank and the hanging arrangement method according to the volume of the hard anodizing tank, the cathode area, and the inner diameter size of the parts before hard anodizing during the process, ensuring the correspondence between the cathode area and the anode area and the uniformity of the current distribution on a single part during the hard anodizing process. After the soft start stage of hard anodizing, the current can be adjusted to control the voltage increase within every 5 minutes. The voltage increase is specified, thereby effectively controlling the final time of the hard anodizing process, ensuring that the deposition and dissolution rates of different surface film layers are comparable during the hard anodizing process, and ensuring the uniformity of the film layer thickness. Different operators can immediately master this hard anodizing treatment method, which has extremely high popularization and practicality.

[0068] 3. A method curve for adjusting the hard anodizing bath solution using potassium alum (chemically pure) is proposed, providing theoretical and practical references for the hard anodizing treatment of other materials, and finding the limit value of Al in the hard anodizing bath solution, enabling the hard anodizing solution to reach the best conductive state, and further ensuring the uniformity of the film layer thickness. 3+ 4. Greatly reduces cost savings. This patent provides a hard anodizing process method for high-precision aluminum alloy parts. Only by performing hard anodizing treatment can the design requirements be met, without the need for additional processing, reducing the scrap rate of parts.

[0069] 4. And greatly reduces the cost. This patent provides a hard anodizing process method for high-precision aluminum alloy parts. Only by performing hard anodizing treatment can the design requirements be met, without the need for additional processing, reducing the scrap rate of parts.

Claims

1. A hard anodizing process method for the inner surface of a 7075 aluminum alloy spherical part, characterized in that, The method includes: S1. Adjust the Al concentration in the hard anodizing bath using chemically pure potassium alum 3+ concentration; S2, inspect the parts; S3, pre-degrease the parts; S4, hang the parts; specifically: use LY1Y aluminum wire with a diameter of 2 mm to clamp the outer surface of the parts, and single aluminum wire winds around the outer surface of the parts for one circle; S5, coat the outer surface of the parts with insulating isolation glue; S6, hang the parts; S6 specifically: the number of parts put into the tank each time is 12, with 3 in each column, wind the aluminum wire around 3 parts into one strand, and hang them on the copper bar in 4 columns; S7, alkaline degrease the surface of the parts; S8, conduct the first deionized water washing on the parts; S9, conduct deoxidation treatment on the surface of the parts to ensure that the single-sided corrosion rate is between 20.3 μm / h and 25.4 μm / h; S10, conduct the second deionized water washing on the parts; S11, conduct hard anodizing treatment on the surface of the parts; S11 specifically: Hard anodizing treatment is carried out on the part surface: sulfuric acid concentration is 160 g / L to 170 g / L, Al 3+ 2.5 g / L to 2.7 g / L, temperature is -5°C to -8°C, current density parameter control is 0 min to 5 min: gradually increase to 2.5 A, 5 min to 10 min: gradually increase to 5 A, 10 min to 15 min: gradually increase to 7.5 A, 15 min to 20 min: gradually increase to 10 A, time is 90 min to 120 min. After 20 min, current adjustment is allowed during the hard anodizing process, and the voltage increase per 5 min needs to be controlled between 0.7 V and 3 V; After that, rinse with deionized water for a time ≥ 2 min; S12, conduct the third deionized water washing on the parts; S13, dry the parts, remove the insulating isolation glue, and conduct quality inspection on the hard anodized film layer of the parts.

2. A hard anodizing process method for the inner surface of a 7075 aluminum alloy spherical part according to claim 1, characterized in that, S2 inspect the parts specifically: There are no scratches, bumps, burrs, visible heavy oil stains and corrosion on the surface of the parts, and the surface roughness value Ra ≤ 0.

8.

3. A hard anodizing process method for the inner surface of a 7075 aluminum alloy spherical part according to claim 1, characterized in that, S3, pre-degrease the parts, specifically: Use a white cotton cloth dipped in alcohol, acetone, and methyl ethyl ketone to wipe the parts for pre-degreasing.

4. A hard anodizing process method for the inner surface of a 7075 aluminum alloy spherical part according to claim 1, characterized in that, S5 specifically: Coat the outer surface of the parts with insulating isolation glue, and ensure that the edge of the joint between the insulating isolation glue isolation area and the exposed area of the parts is neat, the insulating isolation glue is tightly bonded to the part substrate, and there are no bubbles and leakage points.

5. A hard anodizing process method for the inner surface of a 7075 aluminum alloy spherical part according to claim 1, characterized in that, S7 specifically: alkaline degrease the surface of the parts, the concentration of TURCO 4215NC-LT is 37.5 g / L - 59.5 g / L, temperature: 50°C - 60°C, time 5 min - 10 min; After that, rinse with deionized water for a time ≥ 2 min, and then conduct a water film continuity test, requiring that the water film continuously remains unbroken within 30 s.

6. A hard anodizing process method for the inner surface of a 7075 aluminum alloy spherical part according to claim 1, characterized in that, In the S9 deoxidation treatment: Chromic acid concentration is 22.5 g / L - 37.5 g / L, nitric acid concentration: 210 g / L - 230 g / L, hydrofluoric acid with a volume fraction of 40%: added according to the requirement of the corrosion rate, temperature: room temperature, time 3 min - 5 min; After that, rinse with deionized water for a time ≥ 2 min, and then conduct a water film continuity test, requiring that the water film continuously remains unbroken within 30 s.

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