A cleaning method based on selective paint removal by super-low-temperature flake ice gas jet

Abstract

The application discloses a kind of based on super low temperature sheet ice gas jet selective paint removal cleaning method, including steps: super low temperature sheet ice is transported to ice particle gas flow cleaning device, ice particle gas flow cleaning device is started, and high-speed airflow in conveying pipeline accelerates super low temperature sheet ice to form ice jet, the length direction of super low temperature sheet ice in nozzle is consistent with the direction of injection, and ice jet is sprayed and erodes workpiece, and the purpose of selective paint removal rust on workpiece anodic oxidation film is completed.By adopting the sheet with multi-angled structure, the local stress is more concentrated, the shear force is higher, the long axis direction of the sheet ice is consistent with the direction of injection, and the shear effect of the sharp edge is maximized, so that the method has the advantages of efficient, fast peeling of thick paint layer or strong adhesion primer. The present scheme does not need to use dry ice, can reduce carbon dioxide emission, after cleaning, the wastewater containing the stripping material can be reused after filtration, realizing the recycling of water resources, energy saving and environmental protection.

Description

Technical Field

[0001] This invention relates to the field of machining technology, and in particular to a cleaning method based on selective paint removal using ultra-low temperature ice jet. Background Technology

[0002] Aluminum alloys, due to their low density, excellent mechanical properties, and good machinability, are frequently used in aerospace products. Aerospace aluminum alloy products often undergo anodizing followed by coating with a waterproof and corrosion-resistant paint to improve the substrate's corrosion resistance. The purpose of anodizing is to form a dense anodic oxide film on the aluminum alloy surface, enhancing the adhesion between the paint coating and the substrate. Once the paint coating is partially damaged, existing coating removal technologies such as paint removers, sandblasting, abrasive waterjet cleaning, and laser cleaning often damage the anodic oxide film while removing the paint, increasing the difficulty of subsequent coating repair. Selectively removing only the paint coating while preserving the underlying anodic oxide film can reduce the workload and cost of coating repair, thus being of great significance. Currently, dry ice particle jet technology using solid carbon dioxide particles as raw material and ice particle jet technology using solid water ice particles as raw material 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 anodized aluminum, dry ice particle jet technology and ice particle jet technology are expected to be applied to selectively remove paint coatings from the surface of aerospace aluminum alloy products without damaging the surface anodized film. Patent CN102380491A discloses the use of dry ice particle jet technology to remove paint films made of epoxy resin, polyurethane and acrylic resin materials. Patent CN211707605U discloses an automated device for paint removal using dry ice particle jet cleaning technology. However, dry ice particle jet technology emits a large amount of carbon dioxide, posing a serious life-threatening risk to all personnel in the workshop, thus posing a significant problem. Compared with dry ice particle jet technology, ice particle jet technology uses water as its consumable, and does not have the above-mentioned problems. Li Deyu et al. first prepared spherical ice particles with a diameter of 75-425μm by cooling and atomizing water droplets with liquid nitrogen, and then combined it with high-pressure gas jet to achieve paint removal on aluminum alloy substrates (Fluid Machinery, 2014, 42(6): 1-5).

[0003] However, in cleaning processes involving thick paint layers or strong-bonding primers, small-sized ice balls may result in insufficient kinetic energy per ice particle and limited impact depth, leading to high paint residue and low cleaning efficiency (low paint removal rate). On the other hand, the smooth edges of the ice balls cause their impact energy to be dispersed, resulting in a smaller proportion of shear force, which further reduces their cleaning efficiency.

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

[0005] This invention provides a cleaning method based on ultra-low temperature sheet ice jet selective paint removal to solve the above problems.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A cleaning method for selective paint removal based on ultra-low temperature ice jet includes the following steps:

[0008] The cryogenic flake ice is transported to the ice particle airflow cleaning device. The spraying parameters are set, and the ice particle airflow cleaning device is started. The high-speed airflow in the conveying pipeline accelerates the cryogenic flake ice to form an ice jet. The length direction of the cryogenic flake ice in the nozzle is consistent with the spraying direction. The ice jet is sprayed out and erodes the workpiece, completing the purpose of selectively removing paint and rust from the upper layer of the anodized film on the workpiece.

[0009] Furthermore, 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℃.

[0010] Furthermore, the Mohs hardness of the ultra-low temperature sheet ice should be greater than 3.

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

[0012] Furthermore, the parameters of the ice particle airflow cleaning device are: incident angle α, spray target distance d, spray pressure P, and 0° < α ≤ 90°, 0 mm <d≤100mm,0.6MPa<P≤0.8MPa。

[0013] Furthermore, the incident angle α is 45°, the distance from the target to the spray is 40 mm, and the spray pressure P is 0.8 MPa.

[0014] Furthermore, a compressed air pre-cooling system is used in conjunction with the ultra-low temperature flake ice during the transport process to maintain the stability of the hardness of the ultra-low temperature flake ice.

[0015] The beneficial effects of this invention are:

[0016] This invention discloses a cleaning method for selective paint removal based on ultra-low temperature flake ice jets. By employing flakes with multi-faceted structures, local stress is more concentrated and the proportion of shear force is higher. Moreover, as the flake ice flows through the nozzle, its long axis is aligned with the jet direction, maximizing the shearing effect of its sharp edges. This method has the advantages of efficiently and quickly peeling off thick paint layers or strong-adhesion primers. At the same time, this solution does not require the use of dry ice, which reduces carbon dioxide emissions. After cleaning, the wastewater containing the peeled material can be filtered and then re-frozen for reuse, realizing the recycling of water resources and saving energy and protecting the environment. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a photograph of the ultra-low temperature flake ice used in this invention;

[0019] Figure 2 This is a schematic diagram of the ice particle airflow cleaning device used in this invention;

[0020] Figure 3 This is a schematic diagram showing the position of the rectangular nozzle and flake ice in the ice particle airflow cleaning device used in this invention.

[0021] Figure 4 These are photographs of the anodic oxide film on the aluminum alloy surface before and after cleaning in Embodiment 1 of the present invention, wherein 4A is a photograph of the anodic oxide film before cleaning and 4B is a photograph of the anodic oxide film after cleaning.

[0022] Figure 5 These are scanning electron microscope (SEM) images of the anodic oxide film on the aluminum alloy surface before and after cleaning in Embodiment 1 of the present invention, wherein 5A is an SEM image of the anodic oxide film before cleaning, and 5B is an SEM image of the anodic oxide film after cleaning.

[0023] Figure 6 This is a photograph of the workpiece after cleaning in Embodiment 1 of the present invention;

[0024] Figure 7 This is a photograph of the workpiece after cleaning in Embodiment 2 of the present invention;

[0025] Figure 8 This is a photograph of the workpiece after cleaning in Embodiment 3 of the present invention;

[0026] Figure 9 This is a photograph of the cleaned workpiece in Comparative Example 1 of the present invention;

[0027] Figure 10 This is a photograph of the cleaned workpiece in Comparative Example 2 of the present invention;

[0028] Figure 11 This is a photograph of the cleaned workpiece in Comparative Example 3 of the present invention.

[0029] In the diagram: 1. Air compressor; 2. Air tank; 3. First filter; 4. Freeze dryer; 5. Second filter; 6. Third filter; 7. Ice 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

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example

[0032] Example 1:

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

[0034] Cryogenic flake ice is loaded into an ice particle gas jet cleaning device. The spray parameters are set, and the ice particle gas jet device is activated. High-speed airflow accelerates the cryogenic flake ice within the delivery pipeline, forming an ice jet. The length direction of the cryogenic flake ice within the nozzle is aligned with the spray direction. The ice jet is ejected and erodes the workpiece, achieving selective paint and rust removal from the anodized film. A schematic diagram showing the position and direction of the rectangular nozzle and the ejected flake ice is shown below. Figure 3 As shown. The flake ice form used in this embodiment is as follows. Figure 1 As shown in the diagram, the existing ice particle airflow cleaning device is structurally illustrated as follows: Figure 2 As shown, the system includes an air compressor 1, an air tank 2, a first filter 3, a freeze dryer 4, a second filter 5, a third filter 6, an ice 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, all connected in sequence. The workpiece 12 to be cleaned is located below the rectangular nozzle 11. The air compressor 1, the air tank 2, and the freeze dryer 4 form a compressed air pre-cooling system, which maintains the temperature of the ultra-low temperature flake ice 15 at the target temperature during the conveying process, thereby ensuring the stability of its hardness and thus ensuring the cleaning effect.

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

[0036] The parameters of the ice particle airflow cleaning device are as follows: under the process parameters of 0.8MPa spray pressure, 45° spray angle, 40mm spray target distance, and 50s spray time, paint removal and cleaning are performed on the aluminum alloy surface;

[0037] like Figure 6 As shown, the epoxy silicone coating on the aluminum alloy surface was completely removed within the ultra-low temperature flake ice jet spraying area, and the anodized film at the bottom remained intact; the paint removal rate within the spraying area was approximately 91.6%, and the area of ​​paint removed reached 2.43 cm². 2 Figure 4 shows a comparison of the anodic oxide film before and after cleaning. Figure 4 Photo A shows the anodized film before cleaning. Figure 4 B is a photograph of the anodic oxide film after cleaning; scanning electron microscope (SEM) images of the anodic oxide film before and after cleaning are shown below. Figure 5 As shown, Figure 5 A is a scanning electron microscope image of the anodic oxide film before cleaning. Figure 5 B is a scanning electron microscope image of the anodic oxide film after cleaning.

[0038] Example 2:

[0039] The only difference between this embodiment and Embodiment 1 is that, in this embodiment, an ultra-low temperature flake ice of -86℃ with a length l of 6±4mm and a thickness of 1.2±0.1mm and a Mohs hardness of 3.5 is used to remove paint from the aluminum alloy surface under the process parameters of 0.8MPa spray pressure, 45° spray angle, 20mm spray target distance and 50s spray time.

[0040] like Figure 7 As shown, the epoxy silicone coating on the aluminum alloy surface was completely removed within the ultra-low temperature flake ice jet spraying area, and the underlying anodized film remained intact; the paint removal rate within the spraying area was approximately 90.1%, and the area of ​​paint removed reached 1.82 cm². 2 .

[0041] Example 3

[0042] The only difference between this embodiment and Embodiment 1 is that, in this embodiment, an ultra-low temperature flake ice of -86℃ with a length l of 6±4mm and a thickness of 1.2±0.1mm and a Mohs hardness of 3.5 is used to remove paint from the aluminum alloy surface under the process parameters of 0.8MPa spray pressure, 90° spray angle, 40mm spray target distance and 50s spray time.

[0043] like Figure 8 As shown, the epoxy silicone coating on the aluminum alloy surface was completely removed within the ultra-low temperature flake ice jet spraying area, and the underlying anodized film remained intact. The paint removal rate within the spraying area was approximately 95.1%, and the area of ​​paint removed reached 1.75 cm². 2 .

[0044] Comparative Example

[0045] Comparative Example 1:

[0046] The only difference between this comparative example and Example 1 is that, in this comparative example, -86°C cryogenic flake ice particles with a length l of 3±1mm, a thickness of 1.2±0.1mm, a Mohs hardness of 3.5, and a length greater than 6mm have a mass of less than 50% of the total mass of cryogenic flake ice, are used to remove paint from the aluminum alloy surface under the process parameters of 0.8MPa spray pressure, 45° spray angle, 40mm spray target distance, and 50s spray time.

[0047] Within the ultra-low temperature flake ice jet spraying area, the epoxy silicone paint coating on the aluminum alloy surface was partially removed, while the underlying anodized film remained intact; the paint removal rate within the spraying area was approximately 85.7%, and the area of ​​paint removed was 1.86 cm². 2 Furthermore, a certain amount of flocculent residual paint layer exists within the sprayed area, such as Figure 9 As shown.

[0048] Comparative Example 2:

[0049] The only difference between this comparative example and Example 1 is that, in this comparative example, ordinary low-temperature flake ice particles with a length l of 6±4mm and a temperature of -28℃, a thickness of 1.2±0.1mm, and a Mohs hardness of 3.5 were used to remove paint from the aluminum alloy surface under the process parameters of 0.8MPa spray pressure, 45° spray angle, 40mm spray target distance, and 50s spray time.

[0050] like Figure 10 As shown, the anodized film at the bottom of the paint layer on the aluminum alloy surface within the ultra-low temperature flake ice particle jet spraying area remained intact. The paint removal rate within the spraying area was approximately 89.5%, and the area of ​​paint removed reached 1.49 cm². 2 .

[0051] Comparative Example 3:

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

[0053] Within the ultra-low temperature flake ice jet spraying area, the anodic oxide film at the bottom of the epoxy silicone paint coating on the aluminum alloy surface remained intact. The paint removal rate within the spraying area was approximately 87.0%, and the area of ​​paint removed reached 1.16 cm². 2 Furthermore, a large amount of flocculent residual paint layer exists in the sprayed area, such as Figure 11 As shown.

[0054] Data from Examples 1-3 and Comparative Example 1 show that when the mass of ice flakes with a length l ≥ 6 mm is less than 50% of the total mass, the paint removal rate is significantly reduced. Comparing the data from Examples 1-3 and Comparative Examples 2-3, it is evident that when the temperature of the ice flakes used is above -86°C, the paint removal rate is significantly reduced. Furthermore, at an ice flake temperature of -2°C, a large amount of flocculent residual paint layer exists in the spraying area, and the area of ​​paint layer removed is only 1.16 cm². 2 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, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cleaning method for selective paint removal based on ultra-low temperature sheet ice jet, characterized in that, Includes the following steps: The ultra-low temperature flake ice is transported to the ice particle airflow cleaning device. The spraying 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 spraying direction. The ice jet is sprayed out and erodes the workpiece, completing the purpose of selectively removing paint and rust from the upper layer of the anodized film of the workpiece. The length of the ultra-low temperature flake ice is l Thickness is h The temperature is T and length l Satisfying 2mm≤ l ≤10mm, and 1.1mm≤ h ≤1.3mm, T ≤-86℃; length l The mass of the ultra-low temperature flake ice with a diameter of ≥6mm accounts for more than 50% of the total mass of the ultra-low temperature flake ice.

2. The cleaning method for selective paint removal based on ultra-low temperature sheet ice jet according to claim 1, characterized in that, The Mohs hardness of the ultra-low temperature flake ice should be greater than 3.

3. The cleaning method for selective paint removal based on ultra-low temperature sheet ice jet according to claim 1, characterized in that, The parameters of the ice particle airflow cleaning device are: incident angle is... α The distance to the spray target is d The injection pressure is P And 0° < α ≤90°, 0mm< d ≤100mm, 0.6MPa< P ≤0.8MPa.

4. The cleaning method for selective paint removal based on ultra-low temperature sheet ice jet according to claim 3, characterized in that, angle of incidence α The angle is 45°, and the distance from the target is [missing information]. d 40mm, injection pressure P It is 0.8 MPa.

5. The cleaning method for selective paint removal based on ultra-low temperature sheet ice jet according to claim 1, characterized in that, The cryogenic flake ice is transported in conjunction with a compressed air pre-cooling system to maintain the stability of the cryogenic flake ice's hardness.

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