A cleaning method for an aviation aluminum alloy sheet part before spot welding

Abstract

The application relates to an aluminum alloy surface treatment technology, in particular to a cleaning method before spot welding of an aviation aluminum alloy sheet part. The method is performed according to a certain treatment procedure, mainly including manual cleaning, degreasing, alkali cleaning, acid cleaning, drying and water washing treatment between procedures. The method can significantly shorten the treatment time and improve the cleaning efficiency on the premise of ensuring the cleaning quality through the improvement of procedures, process parameters and treatment solutions, so that the method is more suitable for collinear production and automatic production; meanwhile, the method solves the problem of traditional Cr 6+ containing aluminum alloy spot welding cleaning process, reduces the pollution to the environment and achieves the effects of cost reduction and environmental protection promotion.

Description

TECHNICAL FIELD

[0001] The application relates to an aluminum alloy surface treatment technology, in particular to a cleaning method for an aviation aluminum alloy sheet part before spot welding. BACKGROUND

[0002] In aviation manufacturing, aluminum alloy sheets are widely used in aircraft fuselages, wings, cabin walls and other structures due to their good strength and toughness, easy processability and corrosion resistance. Spot welding, as the main way of fixing and connecting sheet parts, has high welding quality, small deformation, high energy efficiency and fast welding speed, and can provide a firm connection without adding too much weight. The main influencing factor of spot welding quality is the contact resistance, so all spot welding parts need to be cleaned before spot welding to remove the surface oxide film or contaminants, thereby reducing the contact resistance. At present, there are various ways to clean before spot welding, and the commonly used method is multiple pickling. For example, the spot welding pre-cleaning process currently used by Xifi contains two mixed acid treatment processes, namely nitrochromic acid pickling and phosphor-chromic acid pickling. If the process contains an alkali washing process, an additional nitrochromic acid pickling is also required, and the main process time (alkali washing + acid pickling) is nearly 30 minutes. Although multiple pickling has good effect, it will lead to too long process time, and there is a risk of too large part thinning and size out-of-tolerance. In addition, it will seriously affect the production efficiency during mass production, especially for automated production lines, which require short pulse beats. Multiple pickling will seriously affect the production rhythm and is difficult to adapt to automated production. In addition, in aviation production, due to the involvement of multi-model and multi-process inline production, the spot welding pre-pickling solution of aluminum alloy sheets is often not compatible with the pre-anodizing acid pickling, and a separate tank or line needs to be built, increasing the construction and maintenance costs. In addition, the current aluminum alloy spot welding pre-pickling method often involves Cr 6+ , which seriously pollutes the environment and greatly increases the wastewater treatment cost. For example, the patent 'Aluminum Alloy Aircraft Skin Spot Welding Pre-Cleaning Method' with the application number 201310145488.2 uses chromium sulfate pickling and three-acid mixed acid pickling as the two pickling processes, and both contain Cr 6+ , which cannot meet the growing environmental protection needs. SUMMARY

[0003] The purpose of the present application is to overcome the shortcomings of the existing process, and provide a high-efficiency, inline production and automated production suitable, Cr 6+ -free spot welding pre-cleaning method for aviation aluminum alloy sheet parts, to improve production efficiency, reduce cost and promote environmental protection.

[0004] The purpose of the present application is achieved by the following method: a method for cleaning aluminum alloy sheet parts before spot welding, which can be used for surface cleaning of 0.5mm-2mm sheet parts before spot welding, the process flow includes manual cleaning process, degreasing process, alkaline cleaning process, pickling process, drying process and water washing treatment between processes, characterized in that it comprises the following steps:

[0005] 1 Manual cleaning process: wipe the surface of aluminum alloy sheet parts with white cotton cloth dipped in organic solvent to remove surface contaminants such as residual glue and oil stains;

[0006] 2 Degreasing process: soak the parts in a degreasing solution for 1-20min, the degreasing solution is an aqueous solution of Isoprep44, the concentration of Isoprep44 is 45g / L-75g / L, the temperature of the degreasing solution is 55-65℃, compressed air is used for stirring during soaking, and the purpose of degreasing is to further remove residual grease contaminants;

[0007] 3 Warm water washing process: rinse the degreased parts in warm water for 1-5min, water temperature 30-60℃, to remove residual degreasing solution on the surface of the parts;

[0008] 4 Cold water washing process: rinse the parts after warm water washing in cold water for 1-5min, water temperature 10-30℃, to further remove residual degreasing solution;

[0009] 5 Alkaline cleaning process: soak the parts in an alkaline cleaning solution for 0.5-3min, the alkaline cleaning solution is a mixture of NaOH and NaCO3, the concentration of NaOH is 20g / L-35g / L, the concentration of NaCO3 is 20g / L-30g / L, the temperature of the alkaline cleaning solution is 40-55℃, compressed air is used for stirring during alkaline cleaning, and the purpose of alkaline cleaning is to remove the surface scale and contaminants of the parts;

[0010] 6 Warm water washing process: rinse the parts after alkaline cleaning in warm water for 1-5min, water temperature 30-60℃, to remove residual alkaline cleaning solution on the surface of the parts;

[0011] 7 Cold water washing process: rinse the parts after warm water washing in cold water for 1-5min, water temperature 10-30℃, to further remove residual alkaline cleaning solution;

[0012] 8. Pickling process: the parts are soaked in pickling solution for 2-15 min, the pickling solution is a mixed solution of Bonderite C-IC2310 Aero and nitric acid, the volume fraction of Bonderite C-IC2310 Aero is 10-20%, the volume fraction of nitric acid is 20-30%, and the rest is deionized water. The temperature of the pickling solution is 10-35℃. When the copper content reaches 0.2g / L or as needed, 2% volume of Bonderite C-AD Deoxlm 2315 Aero can be added to prevent the redeposition of copper. The purpose of pickling is to further remove the oxide scale, and on the other hand, it plays a role in lightening after alkaline cleaning;

[0013] 9. Cold water washing process: the parts after pickling are rinsed in cold water for 1-5 min, the water temperature is 10-30℃, to remove the residual pickling solution on the surface of the parts;

[0014] 10. Deionized water washing process: the parts are washed in deionized water for 1-5 min, the water temperature is 10-30℃, to further remove the residual pickling solution;

[0015] 11. Drying process: the parts are dried in an oven at 50-70℃ for at least 30 min.

[0016] The aluminum alloy parts described in the present application refer to aluminum alloy sheet parts of 2A12, LF2, LF21, LF6, etc., but can not be limited to this system, this form of aluminum alloy.

[0017] The organic solvent described in step 1 of the present application includes ethanol, acetone, butanone, ethyl acetate and commonly used commercial cleaning agents.

[0018] The cold water washing of step 4 and the deionized water washing process of step 10 described in the present application should be based on the standard of achieving continuous water film state, and then the next process can be carried out.

[0019] The washing process described in the present application, the parts should not be stationary during the process, but should be continuously moved for cleaning to ensure clean cleaning.

[0020] The deionized water cleaning of step 10 described in the present application includes rinsing and spraying.

[0021] The beneficial effects achieved by the present application are:

[0022] 1. The process time required for cleaning aluminum alloy sheet parts before spot welding is greatly reduced, and the main process (including alkaline cleaning and pickling) only needs 2.5 min at the shortest. This parameter can meet the cleaning requirements of most aluminum alloy sheet parts, can significantly improve the production efficiency, and is more suitable for automated production.

[0023] 2. The process solution used can also be used as a treatment solution in other surface treatment processes such as anodic oxidation, and can be used for co-line production, without the need to build or modify a production line, to achieve convenience.

[0024] 3. The process solution used does not contain Cr 6+ , reduces environmental pollution, has good environmental protection effect, and reduces wastewater treatment cost. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a process flowchart of the embodiment of the present application. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present application will be described in more detail below in combination with the results of the embodiments of the present application. The described embodiments are part of the embodiments of the present application, rather than all the embodiments. The embodiments described below are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present application.

[0027] Embodiment 1

[0028] Select 2A12 aluminum clad aluminum alloy test pieces, the thickness of the test pieces is 1.5 mm, the test piece numbers are 1-1, 1-2 and 1-3, and the test pieces are cleaned according to the following steps:

[0029] 1. Manual cleaning process: wipe the surface of the aluminum alloy sheet part with white cotton cloth dipped in butanone to remove surface residues, oil stains and other pollutants.

[0030] 2. Degreasing process: immerse the aluminum alloy test piece in an aqueous solution of Isoprep44 for 15 min, the concentration of Isoprep44 is 50.9 g / L, the solution temperature is 57℃, and compressed air is used for stirring during immersion.

[0031] 3. Warm water washing process: put the degreased aluminum alloy test piece into warm water for 2 min, and the water temperature is 47℃.

[0032] 4. Cold water washing process: put the aluminum alloy test piece washed in warm water into cold water for 1 min, and the water temperature is 25℃.

[0033] 5. Alkaline cleaning process: immerse the aluminum alloy test piece in a mixed solution of NaOH and NaCO3 for 1 min, the concentration of NaOH is 25.1 g / L, the concentration of NaCO3 is 24.9 g / L, the solution temperature is 50℃, and compressed air is used for stirring during the alkaline cleaning process.

[0034] 6. Warm water rinsing step: the aluminum alloy test piece after alkaline cleaning is put into warm water for 2 minutes, water temperature 47°C.

[0035] 7. Cold water rinsing step: the aluminum alloy test piece after warm water rinsing is put into cold water for 1 minute, water temperature 20°C.

[0036] 8. Acid pickling step: the aluminum alloy test piece is soaked in a mixed solution of Bonderite C-IC2310 Aero and nitric acid for 6 minutes, the volume fraction of Bonderite C-IC2310 Aero is 12.6%, the volume fraction of nitric acid is 28.3%, and the solution temperature is 20°C.

[0037] 9. Cold water rinsing step: the aluminum alloy test piece after acid pickling is put into cold water for 1 minute, water temperature 20°C.

[0038] 10. Deionized water rinsing step: the aluminum alloy test piece is put into deionized water for 2 minutes, water temperature 20°C.

[0039] 11. Drying step: the part is dried in a 55°C oven for 30 minutes.

[0040] The contact resistance value, surface roughness and thinning amount obtained are shown in the following table:

[0041]

[0042] The results show that the method can obtain qualified contact resistance and surface roughness, and the thinning amount is far less than 50% of the aluminum cladding layer. (The aluminum cladding layer on one side accounts for at least 4% of the total thickness, about 0.06mm)

[0043] Example 2:

[0044] Select 2A12 aluminum alloy test pieces with aluminum cladding, the test piece thickness is 2.0mm, and the test piece numbers are 2-1, 2-2 and 2-3. The cleaning is carried out according to the following steps:

[0045] 1. Manual cleaning step: the surface of the aluminum alloy sheet part is wiped with white cotton cloth dipped with butanone to remove surface contaminants such as residual glue, oil stains, etc.

[0046] 2. Degreasing step: the aluminum alloy test piece is soaked in an aqueous solution of Isoprep44 for 10 minutes, the concentration of Isoprep44 is 52.3g / L, the solution temperature is 60°C, and compressed air stirring is used during soaking.

[0047] 3. Warm water rinsing step: the aluminum alloy test piece after degreasing is put into warm water for 2 minutes, water temperature 50°C.

[0048] 4. Cold water rinsing step: the aluminum alloy test piece after warm water rinsing is put into cold water for 1 minute, water temperature 20°C.

[0049] 5. Alkaline cleaning step: The aluminum alloy test piece is immersed in a mixed solution of NaOH and NaCO3 for 0.5 min, the concentration of NaOH is 26.7 g / L, the concentration of NaCO3 is 26.9 g / L, the solution temperature is 50°C, and compressed air is used for stirring during the alkaline cleaning process.

[0050] 6. Warm water cleaning step: The aluminum alloy test piece after alkaline cleaning is put into warm water for 2 min, and the water temperature is 50°C.

[0051] 7. Cold water cleaning step: The aluminum alloy test piece after warm water cleaning is put into cold water for 1 min, and the water temperature is 20°C.

[0052] 8. Acid cleaning step: The aluminum alloy test piece is immersed in a mixed solution of Bonderite C-IC2310 Aero and nitric acid for 2 min, the volume fraction of Bonderite C-IC2310 Aero is 12.6%, the volume fraction of nitric acid is 28.3%, and the solution temperature is 20°C.

[0053] 9. Cold water cleaning step: The aluminum alloy test piece after acid cleaning is put into cold water for 1 min, and the water temperature is 20°C.

[0054] 10. Deionized water cleaning step: The aluminum alloy test piece is put into deionized water for 2 min, and the water temperature is 20°C.

[0055] 11. Drying step: The part is dried in a 55°C oven for 30 min.

[0056] The contact resistance value, surface roughness, and thinning amount obtained are shown in the following table:

[0057]

[0058] The results show that the method can obtain qualified contact resistance and surface roughness, and the thinning amount is also much smaller than 50% of the aluminum cladding layer. (The aluminum cladding layer on one side accounts for at least 4% of the total thickness, about 0.08 mm)

[0059] Example 3:

[0060] An LF6 aluminum alloy test piece is selected, the test piece thickness is 1.5 mm, the test piece numbers are 3-1, 3-2, and 3-3, and the cleaning is carried out according to the following steps:

[0061] 1. Manual cleaning step: The surface of the aluminum alloy sheet part is wiped with a white cotton cloth dipped in acetone to remove surface residues, oil stains, and other contaminants.

[0062] 2. Degreasing: The aluminum alloy test piece was immersed in an aqueous solution of Isoprep 44 for 10 min, the concentration of Isoprep 44 was 50.9 g / L, the solution temperature was 57℃, and compressed air was used for stirring during the immersion.

[0063] 3. Warm water washing: The degreased aluminum alloy test piece was rinsed in warm water for 2 min, the water temperature was 47℃.

[0064] 4. Cold water washing: The warm water washed aluminum alloy test piece was rinsed in cold water for 1 min, the water temperature was 20℃.

[0065] 5. Alkaline washing: The aluminum alloy test piece was immersed in a mixed solution of NaOH and NaCO3 for 0.5 min, the concentration of NaOH was 25.1 g / L, the concentration of NaCO3 was 24.9 g / L, the solution temperature was 50℃, and compressed air was used for stirring during the alkaline washing.

[0066] 6. Warm water washing: The alkaline washed aluminum alloy test piece was rinsed in warm water for 2 min, the water temperature was 47℃.

[0067] 7. Cold water washing: The warm water washed aluminum alloy test piece was rinsed in cold water for 1 min, the water temperature was 20℃.

[0068] 8. Acid washing: The aluminum alloy test piece was immersed in a mixed solution of Bonderite C-IC2310 Aero and nitric acid for 10 min, the volume fraction of Bonderite C-IC2310 Aero was 12.4%, the volume fraction of nitric acid was 28.6%, and the solution temperature was 20℃.

[0069] 9. Cold water washing: The acid washed aluminum alloy test piece was rinsed in cold water for 1 min, the water temperature was 20℃.

[0070] 10. Deionized water washing: The aluminum alloy test piece was rinsed in deionized water for 2 min, the water temperature was 20℃.

[0071] 11. Drying: The part was dried in a 55℃ oven for 30 min.

[0072] The contact resistance value, surface roughness, and thinning amount obtained are shown in the following table:

[0073]

[0074] The results show that this method can obtain qualified contact resistance and surface roughness, and the thinning amount is also within the allowable range.

Claims

1. A method for cleaning an aluminum alloy sheet part before spot welding, which is used for surface cleaning of a sheet part with a thickness of 0.5 mm to 2 mm before spot welding, and a process flow includes a manual cleaning process, a degreasing process, an alkaline cleaning process, an acid cleaning process, a drying process, and water washing treatment between each process, characterized in that: Comprising the following steps: ​ 1.1 Manual cleaning process: wipe the surface of the aluminum alloy sheet parts with white cotton cloth dipped in organic solvent to remove surface residual glue, oil contamination; 1.2 Degreasing process: soak the parts in a degreasing solution for 1-20 min, and use compressed air to stir during the soaking process to further remove residual grease contamination; 1.3 Warm water washing process: rinse the degreased parts in warm water for 1-5 min, water temperature 30-60℃, to remove residual degreasing solution on the surface of the parts; 1.4 Cold water washing process: rinse the warm water washed parts in cold water for 1-5 min, water temperature 10-30℃, to further remove residual degreasing solution; 1.5 Alkaline cleaning process: soak the parts in an alkaline cleaning solution for 0.5-3 min, and use compressed air to stir during the alkaline cleaning process, which aims to remove surface scale and contaminants; 1.6 Warm water washing process: rinse the alkaline cleaned parts in warm water for 1-5 min, water temperature 30-60℃, to remove residual alkaline cleaning solution on the surface of the parts; 1.7 Cold water washing process: rinse the warm water washed parts in cold water for 1-5 min, water temperature 10-30℃, to further remove residual alkaline cleaning solution; 1.8 Pickling process: soak the parts in a pickling solution for 2-15 min, and use compressed air to stir during the pickling process, which aims to further remove scale and achieve the lightening effect after alkaline cleaning; the pickling solution is a mixture of Bonderite C-IC2310 Aero and nitric acid, with a volume fraction of Bonderite C-IC2310 Aero of 10-20%, a volume fraction of nitric acid of 20-30%, and the rest being deionized water; the pickling solution temperature is 10-35℃; when the copper content in the pickling solution reaches 0.2g / L or as needed, 2% volume of Bonderite C-AD Deoxlm 2315 Aero can be added to prevent copper redeposition; 1.9 Cold water washing process: rinse the pickled parts in cold water for 1-5 min, water temperature 10-30℃, to remove residual pickling solution on the surface of the parts; 1.10 Deionized water washing process: wash the parts in deionized water for 1-5 min, water temperature 10-30℃, to further remove residual pickling solution; 1.11 Drying process: dry the parts in an oven at 50-70℃ for at least 30 min.

2. The method of claim 1, wherein the method is characterized by The degreasing solution is an aqueous solution of Isoprep44, with a concentration of Isoprep44 of 45g / L -75g / L, and a degreasing solution temperature of 55-65℃.

3. The method of claim 1, wherein the method is characterized by The alkaline cleaning solution is a mixture of NaOH and NaCO3, with a concentration of NaOH of 20g / L -35g / L and a concentration of NaCO3 of 20g / L -30g / L, and an alkaline cleaning solution temperature of 40-55℃.

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