Cleaning method for selective paint removal based on ultralow-temperature flake ice gas jet

Abstract

The invention discloses a cleaning method for selective paint removal based on ultralow-temperature flake ice air jet, which comprises the following steps: ultralow-temperature flake ice is conveyed into an ice particle airflow cleaning device, the ice particle airflow cleaning device is started, the ultralow-temperature flake ice is accelerated by high-speed airflow in a conveying pipeline to form ice jet, and the ice jet is sprayed on the ultralow-temperature flake ice; and the length direction of the ultralow-temperature flake ice in the nozzle is consistent with the spraying direction, the ice jet flow is sprayed out and washes the workpiece, and the purpose of selective paint and rust removal of the upper layer of the workpiece anodic oxide film is achieved. By the adoption of the sheet shape with the multi-corner-angle structure, local stress is more concentrated, the shearing force proportion is higher, the long axis direction of the sheet ice is consistent with the spraying direction, the shearing effect of the sharp edge of the sheet ice is utilized to the maximum degree, and the method has the advantage that a large-thickness paint layer or high-binding-force primer is efficiently and rapidly stripped; and after cleaning is finished, waste water containing stripping substances can be frozen and used again after being filtered, cyclic utilization of water resources is achieved, and energy conservation and environment protection are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of machining, and particularly relates to a cleaning method for selectively removing paint based on cryogenic flake ice gas jet. Background Art

[0002] Due to advantages such as low density, good mechanical properties, and good machining performance, aluminum alloys are often used in aviation products. Aviation aluminum alloy products are usually first anodized and then coated with waterproof and corrosion-resistant paint coatings to improve the corrosion resistance of the substrate. The purpose of anodization is to form a dense anodic oxide film on the surface of the aluminum alloy to improve the bonding strength between the paint coating and the substrate. Once the paint coating is locally damaged, existing coating removal techniques such as paint removers, sandblasting, abrasive water jet, and laser cleaning often damage the anodic oxide film while removing the paint coating, increasing the difficulty of subsequent coating repair. Selectively removing only the paint coating while retaining the underlying anodic oxide film can reduce the coating repair workload and cost, so it is of great significance. Currently, the dry ice particle jet technology using solid carbon dioxide particles as raw materials and the ice particle jet technology using solid water ice particles as raw materials have been successfully applied to the removal of paint coatings. Since the hardness of dry ice particles and ice particles is lower than that of anodic aluminum oxide, the dry ice particle jet technology and the ice particle jet technology are expected to be applied to selectively remove the paint coating on the surface of aviation aluminum alloy products without damaging the surface anodic oxide film. Patent CN102380491A discloses the use of dry ice particle jet technology to remove paint films formulated from epoxy resin, polyurethane, and acrylic resin materials. Patent CN211707605U discloses an automated device for paint removal using dry ice particle jet cleaning technology. However, the dry ice particle jet technology emits a large amount of carbon dioxide, posing a serious life threat to all personnel in the workshop, so there are significant problems. Compared with the dry ice particle jet technology, the consumable of the ice particle jet technology is water, and there are no such problems. Li Deyu et al. first prepared spherical ice particles with diameters of 75 - 425 μm by cooling and atomizing water droplets with liquid nitrogen, and then combined with high-pressure gas injection to achieve paint removal on an aluminum alloy substrate (Fluid Machinery, 2014, 42(6): 1 - 5).

[0003] However, in the cleaning project of thick paint layers or primers with strong bonding force, small-sized spherical ice may have situations where the kinetic energy of a single ice particle is insufficient and the impact depth is limited, resulting in defects such as a high paint layer residue rate and low cleaning efficiency (low paint layer removal rate); on the other hand, due to the smooth edges of the spherical ice, the impact energy is dispersed, and the shear force accounts for a relatively small proportion, further reducing its cleaning efficiency.

[0004] Therefore, there is an urgent need for a cleaning method that can achieve a high removal rate of the paint layer within the spraying area. Summary of the Invention

[0005] The present invention provides a cleaning method based on cryogenic sheet ice gas jet selective paint removal to solve the above problems.

[0006] To achieve the above object, the technical solution of the present invention is:

[0007] A cleaning method based on cryogenic sheet ice gas jet selective paint removal, comprising the following steps:

[0008] Transport the cryogenic sheet ice to the ice particle gas flow cleaning device, set the spraying parameters, start the ice particle gas flow cleaning device, accelerate the cryogenic sheet ice in the conveying pipeline by high-speed gas flow to form an ice jet, the length direction of the cryogenic sheet ice in the nozzle is consistent with the spraying direction, and the ice jet sprays out and erodes the workpiece to complete the purpose of selectively removing paint and rust on the upper layer of the anodic oxidation film of the workpiece.

[0009] Further, the length of the cryogenic sheet ice is l, the thickness is h, and the temperature is T, and the length l satisfies 2 mm ≤ l ≤ 10 mm, and 1.1 mm ≤ h ≤ 1.3 mm, T ≤ -86 °C.

[0010] Further, the Mohs hardness of the cryogenic sheet ice should be greater than 3.

[0011] Further, the mass of the cryogenic sheet ice with a length l ≥ 6 mm accounts for more than 50% of the total mass of the cryogenic sheet ice.

[0012] Further, the parameters of the ice particle gas flow cleaning device are: the incident angle is α, the spraying target distance is d, and the spraying pressure is P, and 0° < α ≤ 90°, 0 mm < d ≤ 100 mm, 0.6 MPa < P ≤ 0.8 MPa.

[0013] Further, the incident angle α is 45°, the spraying target distance d is 40 mm, and the spraying pressure P is 0.8 MPa.

[0014] Further, during the transportation of the cryogenic sheet ice, a compressed air precooling system is used to maintain the stability of the hardness of the cryogenic sheet ice.

[0015] The beneficial effects of the present invention are:

[0016] A cleaning method based on cryogenic sheet ice gas jet selective paint removal disclosed in the present invention, by using a sheet with a multi-edge structure, makes the local stress more concentrated and the shear force ratio higher. Moreover, during the process of the sheet ice flowing through the nozzle, the long axis direction of the sheet ice is consistent with the spraying direction, maximizing the use of the shear effect of its sharp edge, making this method have the advantages of efficiently and quickly stripping thick paint layers or primers with strong bonding force. At the same time, this solution does not require the use of dry ice, which can reduce carbon dioxide emissions. After the cleaning, the wastewater containing the stripped substances can be filtered and then frozen for reuse, realizing the recycling of water resources, energy conservation and environmental protection. Brief Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1 Photograph of the ultra-low temperature flake ice adopted by the present invention;

[0019] Figure 2 Schematic structural diagram of the ice particle air flow cleaning device used in the present invention;

[0020] Figure 3 Schematic diagram of the position of the rectangular nozzle of the ice particle air flow cleaning device used in the present invention and the flake ice;

[0021] Figure 4 Photographs of the anodic oxidation films on the surface of aluminum alloy before and after cleaning in Embodiment 1 of the present invention. Among them, 4A is the photograph of the anodic oxidation film before cleaning, and 4B is the photograph of the anodic oxidation film after cleaning;

[0022] Figure 5 Scanning electron microscope photographs of the anodic oxidation films on the surface of aluminum alloy before and after cleaning in Embodiment 1 of the present invention. Among them, 5A is the electron microscope photograph of the anodic oxidation film before cleaning, and 5B is the electron microscope photograph of the anodic oxidation film after cleaning;

[0023] Figure 6 Photograph of the workpiece after cleaning in Embodiment 1 of the present invention;

[0024] Figure 7 Photograph of the workpiece after cleaning in Embodiment 2 of the present invention;

[0025] Figure 8 Photograph of the workpiece after cleaning in Embodiment 3 of the present invention;

[0026] Figure 9 Photograph of the workpiece after cleaning in Comparative Example 1 of the present invention;

[0027] Figure 10 Photograph of the workpiece after cleaning in Comparative Example 2 of the present invention;

[0028] Figure 11 Photograph of the workpiece after cleaning in Comparative Example 3 of the present invention.

[0029] In the figure: 1. Air compressor; 2. Air storage tank; 3. First filter; 4. Refrigerated dryer; 5. Second filter; 6. Third filter; 7. Ice particle jet cleaning device; 8. Clean booth; 9. Control cabinet; 10. Motor; 11. Rectangular nozzle; 13. Conical hopper; 14. Waste liquid collection device; 15. Ultra-low temperature flake ice. Detailed implementation manners

[0030] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0031] Embodiment

[0032] Embodiment 1:

[0033] A cleaning method based on selective paint removal by ultra-low temperature flake ice gas jet includes the following steps:

[0034] Load the ultra-low temperature flake ice into the ice particle gas flow cleaning device, set the spraying parameters, start the ice particle gas jet device, and accelerate the ultra-low temperature flake ice in the conveying pipeline by the high-speed gas flow to form an ice jet. The length direction of the ultra-low temperature flake ice in the nozzle is consistent with the spraying direction. The ice jet sprays out and erodes the workpiece, achieving the purpose of selective paint and rust removal on the upper layer of the anodic oxidation film of the workpiece. The schematic diagram of the position and direction of the rectangular nozzle and the ejected flake ice is as Figure 3 shown. The form of the flake ice used in this embodiment is as Figure 1 shown. The structure diagram of the existing ice particle gas flow cleaning device adopted is as Figure 2 shown, including an air compressor 1, an air storage tank 2, a first filter 3, a refrigerated dryer 4, a second filter 5, a third filter 6, an ice particle jet cleaning device 7, a clean booth 8, a control cabinet 9, a motor 10, a rectangular nozzle 11, a conical hopper 13 and a waste liquid collection device 14 connected in sequence. Below the rectangular nozzle 11 is the workpiece 12 to be cleaned; the air compressor 1, the air storage tank 2 and the refrigerated dryer 4 form a compressed air precooling system, so that the temperature of the ultra-low temperature flake ice 15 is maintained at the target temperature during the conveying process, thereby ensuring the stability of its hardness and thus ensuring the cleaning effect.

[0035] The ultra-low temperature flake ice used in this embodiment is flaky (flake ice particles), that is, a polyhedron structure. The maximum span (the length of the diagonal) of the polyhedron in the plane is defined as the length l of the ultra-low temperature flake ice. The parameters of the ultra-low temperature flake ice are as follows: l is 6 ± 4 mm, the temperature is -86 °C, the thickness is 1.2 ± 0.1 mm, the Mohs hardness is 3.5, and the mass of the ultra-low temperature flake ice with a length l ≥ 6 mm is greater than 50% of the total mass of the ultra-low temperature flake ice;

[0036] The parameters of the ice particle air flow cleaning device are as follows: under the process parameters of 0.8 MPa jet pressure, 45° jet angle, 40 mm jet target distance, and 50 s jet time, the aluminum alloy surface is degreased and cleaned;

[0037] As Figure 6 shown, the epoxy organosilicon paint coating on the aluminum alloy surface within the ultra-low temperature flake ice particle jet spraying area is removed cleanly, and the anodic oxidation film at the bottom is not damaged; the paint layer removal rate within the spraying area is about 91.6%, and the area of the removed paint layer reaches 2.43 cm 2 ; The comparison of the anodic oxidation film before and after cleaning is shown in Figure 4. Figure 4 A is a photo of the anodic oxidation film before cleaning. Figure 4 B is a photo of the anodic oxidation film after cleaning; the scanning electron microscope images of the anodic oxidation film before and after cleaning are as Figure 5 shown. Figure 5 A is the scanning electron microscope image of the anodic oxidation film before cleaning. Figure 5 B is the scanning electron microscope image of the anodic oxidation film after cleaning.

[0038] Example 2:

[0039] The difference between this embodiment and Example 1 is only that in this embodiment, ultra-low temperature flake ice at -86 °C with a length l of 6 ± 4 mm is used, the thickness is 1.2 ± 0.1 mm, and the Mohs hardness is 3.5. Under the process parameters of 0.8 MPa jet pressure, 45° jet angle, 20 mm jet target distance, and 50 s jet time, the aluminum alloy surface is degreased and cleaned;

[0040] As Figure 7 shown, the epoxy organosilicon paint coating on the aluminum alloy surface within the ultra-low temperature flake ice particle jet spraying area is removed cleanly, and the anodic oxidation film at the bottom is not damaged; the paint layer removal rate within the spraying area is about 90.1%, and the area of the removed paint layer reaches 1.82 cm 2 .

[0041] Example 3

[0042] The difference between this embodiment and Embodiment 1 is only that, in this embodiment, ultra-low temperature sheet ice at -86°C with a length l of 6 ± 4 mm, a thickness of 1.2 ± 0.1 mm, and a Mohs hardness of 3.5 is used. Under the process parameters of a spraying pressure of 0.8 MPa, a spraying angle of 90°, a spraying target distance of 40 mm, and a spraying time of 50 s, the aluminum alloy surface is degreased and cleaned.

[0043] As Figure 8 shown, the epoxy organosilicon paint coating on the aluminum alloy surface within the ultra-low temperature sheet ice particle jet spraying area is completely removed, and the anodic oxidation film at the bottom is not damaged. The paint layer removal rate within the spraying area is approximately 95.1%, and the area of the removed paint layer reaches 1.75 cm 2 .

[0044] Comparative example

[0045] Comparative example 1:

[0046] The difference between this comparative example and Embodiment 1 is only that, in this comparative example, ultra-low temperature sheet ice particles at -86°C with a length l of 3 ± 1 mm, a thickness of 1.2 ± 0.1 mm, and a Mohs hardness of 3.5 are used, and the mass of ultra-low temperature sheet ice with a length greater than 6 mm is less than 50% of the total mass of the ultra-low temperature sheet ice. Under the process parameters of a spraying pressure of 0.8 MPa, a spraying angle of 45°, a spraying target distance of 40 mm, and a spraying time of 50 s, the aluminum alloy surface is degreased and cleaned.

[0047] The epoxy organosilicon paint coating on the aluminum alloy surface within the ultra-low temperature sheet ice particle jet spraying area is partially removed, and the anodic oxidation film at the bottom is not damaged; the paint layer removal rate within the spraying area is approximately 85.7%, and the area of the removed paint layer is 1.86 cm 2 , and there is a certain amount of flocculent residual paint layer within the spraying area, as Figure 9 shown.

[0048] Comparative example 2:

[0049] The difference between this comparative example and Embodiment 1 is only that, in this comparative example, ordinary low-temperature sheet ice at -28°C with a length l of 6 ± 4 mm, a thickness of 1.2 ± 0.1 mm, and a Mohs hardness of 3.5 is used. Under the process parameters of a spraying pressure of 0.8 MPa, a spraying angle of 45°, a spraying target distance of 40 mm, and a spraying time of 50 s, the aluminum alloy surface is degreased and cleaned.

[0050] As Figure 10 shown, the anodic oxidation film at the bottom of the paint layer on the aluminum alloy surface within the ultra-low temperature sheet ice particle jet spraying area is not damaged, the paint layer removal rate within the spraying area is approximately 89.5%, and the area of the removed paint layer reaches 1.49 cm 2 .

[0051] Comparative example 3:

[0052] The difference between this comparative example and Example 1 is only that, in this comparative example, ordinary low-temperature flake ice particles at -2°C with a length l of 6 ± 4 mm are used, the thickness is 1.2 ± 0.1 mm, the Mohs hardness is 2, and under the process parameters of a spraying pressure of 0.8 MPa, a spraying angle of 45°, a spraying target distance of 40 mm, and a spraying time of 50 s, the aluminum alloy surface is degreased and cleaned;

[0053] The anodic oxidation film at the bottom of the epoxy organosilicon paint coating on the aluminum alloy surface within the ultra-low temperature flake ice particle jet spraying area is not damaged, the paint layer removal rate within the spraying area is about 87.0%, and the area of the removed paint layer reaches 1.16 cm 2 And there are a large number of flocculent residual paint layers within the spraying area, as Figure 11 shown.

[0054] From the data of Examples 1 - 3 and Comparative Example 1, it can be seen that when the mass of the flake ice with a length l ≥ 6 mm used is less than 50% of the total mass, the paint layer removal rate will be significantly reduced. By comparing the data of Examples 1 - 3 and Comparative Examples 2 - 3, it can be seen that when the temperature of the flake ice used is higher than -86°C, the paint layer removal rate is significantly reduced, and when the temperature of the flake ice is -2°C, there are a large number of flocculent residual paint layers within the spraying area, and the area of the removed paint layer is only 1.16 cm 2 , and the removal effect is poor.

[0055] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cleaning method based on ultra-low temperature flake ice gas jet selective paint removal, characterized in that: The steps include: The ultra-low temperature flake ice is transported to the ice particle airflow cleaning device, the injection parameters are set, and the ice particle airflow cleaning device is started. The high-speed airflow in the conveying pipeline accelerates the ultra-low temperature flake ice to form an ice jet. The length direction of the ultra-low temperature flake ice in the nozzle is consistent with the injection direction. The ice jet is ejected and erodes the workpiece to complete the purpose of selective paint and rust removal on the upper layer of the workpiece anodized film.

2. The cleaning method based on ultra-low temperature flake ice gas jet selective paint removal according to claim 1 is characterized in that: The ultra-low temperature flake ice has a length of l, a thickness of h, and a temperature of T, and the length l satisfies 2mm≤l≤10mm, 1.1mm≤h≤1.3mm, and T≤-86°C.

3. The cleaning method based on ultra-low temperature flake ice gas jet selective paint removal according to claim 2 is characterized in that: The Mohs hardness of the ultra-low temperature flake ice should be greater than 3.

4. The cleaning method based on ultra-low temperature flake ice gas jet selective paint removal according to claim 2, characterized in that: The mass of the ultra-low temperature flake ice with a length of l≥6 mm accounts for more than 50% of the total mass of the ultra-low temperature flake ice.

5. The cleaning method based on ultra-low temperature flake ice gas jet selective paint removal according to claim 1, characterized in that: The parameters of the ice particle airflow cleaning device are: the incident angle is α, the spray target distance is d, the spray pressure is P, and 0°<α≤90°, 0mm <d≤100mm,0.6MPa<P≤0.8MPa。 6. The cleaning method based on ultra-low temperature flake ice gas jet selective paint removal according to claim 5, characterized in that: The incident angle α is 45°, the spray target distance d is 40 mm, and the spray pressure P is 0.8 MPa.

7. The cleaning method based on ultra-low temperature flake ice gas jet selective paint removal according to claim 1, characterized in that: During the transportation of the ultra-low temperature flake ice, a compressed air pre-cooling system is used to maintain the stability of the hardness of the ultra-low temperature flake ice.

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