Protection application of strippable coating in chemical milling of large titanium alloy structural member

Abstract

The invention relates to the field of chemical milling of titanium alloy structural parts, in particular to protection application of strippable paint in chemical milling of large titanium alloy structural parts. At present, a film layer prepared by a chemical milling process has the problems of difficulty in stripping, difficulty in laser engraving, residue on the surface of a part and the like. After the part is subjected to oil removal and sand blasting, the paint is sprayed on the surface of the part, and a paint film is formed on the surface of the part; by controlling the breaking strength, the elongation at break, the peel strength, the etching ratio and the like of the paint film, the carved line of the paint film is smooth, the milled edge is straight, and the paint film at the chemical milling part on the surface of the part and the paint film at the protection part after chemical milling can be stripped manually.

Description

Technical Field

[0001] This invention relates to the field of chemical milling of titanium alloy structural parts, and in particular to the protective application of a peelable coating in the chemical milling of large titanium alloy structural parts. Background Technology

[0002] Before chemical milling, titanium alloy structural components need to be coated with a peelable coating on all surfaces to protect the non-machined surfaces during the chemical milling process. The coating prepared by the existing chemical milling process has poor adhesion to the component substrate and is not easy to laser-etch. After etching, the coating on the surface to be milled is not easy to peel off. During the chemical milling process, the coating on the non-milled surface has poor resistance to strong acid (nitric acid and hydrofluoric acid) corrosion, resulting in blistering and delamination. After the coating on the non-milled surface is peeled off after chemical milling, there are residues on the surface of the component, resulting in irregular corrosion marks. Summary of the Invention

[0003] To address the aforementioned issues, this invention explores a peelable coating chemical milling process for large titanium alloy structural components, determining the process route and construction parameters to obtain parts with smooth substrate surfaces, clearly defined chemical milling lines, and no irregular corrosion marks, thus meeting engine usage requirements.

[0004] To achieve the above objectives, the present invention provides a protective application of peelable coating in chemical milling of large titanium alloy structural parts, comprising the following steps:

[0005] Step 1: Degrease the parts;

[0006] Step 2: Sandblasting of parts;

[0007] Step 3: Peelable coating application; After the coating is mixed, it is sprayed onto the surface of the part to form a paint film.

[0008] Step 4: Shape the paint film surface; after shaping, remove the paint film from the milled surface of the part by manual peeling.

[0009] Step 5: Chemical milling; chemical milling is performed in chemical milling fluid. After chemical milling, the paint film on the non-chemically milled surfaces of the parts is removed by manual peeling.

[0010] In step 1, organic solvents such as acetone are used to remove grease from the surface of the parts;

[0011] The main process parameters for sandblasting in step 2 are as follows: 200 mesh corundum sand, pressure 0.5MPa~1.0MPa, sand flow rate 2kg / min~4kg / min, spray gun moving speed 200mm / min~400mm / min, nozzle to part distance 100mm~200mm, turntable speed 20r / min~30r / min;

[0012] In step 3, the spraying pressure is approximately 0.5 MPa, and the spraying distance is 200 mm to 500 mm. The paint film should be smooth and even, without pinholes, bulges, bubbles, wrinkles, or peeling. The drying time is: surface dry (23℃±2℃) ≤ 1 h, and fully dry (23℃±2℃) ≤ 24 h. The paint film thickness is ≥ 0.25 mm, the tensile strength is ≥ 4.0 MPa, the elongation at break is 300% to 600%, the peel strength is 150 N / m to 800 N / m, and the etching ratio is 0.6 to 0.9.

[0013] If the paint film is resistant to strong acidic chemical milling fluid, the paint film will be free of bubbles and bumps, and the paint film can be manually peeled off from the surface of the metal parts, with no damage to the metal substrate caused by the corrosion of the acidic chemical milling fluid.

[0014] In step 4, a laser engraving machine is used for engraving. After engraving, the paint film on the surface of the part is removed. An electrical discharge tester is used to check the integrity of the paint film and measure the thickness of the surface of the part. Any leaks are repaired with the original paint and cured.

[0015] The total time for chemical milling in step 5 is 7 hours.

[0016] In step 4, when engraving, the lines should be smooth, without any burrs, expansion, or tearing; in step 5, after chemical milling, the milled edges should be straight and without obvious serrations.

[0017] The method of this invention applies peelable coatings to the chemical milling process protection of large titanium alloy structural parts. By controlling the fracture strength, elongation at break, peel strength, and etching ratio of the coating film, the film layer has good adhesion to the part substrate, is easy to laser-etch, and the etched lines are smooth. After etching, the coating on the milled surface is easy to peel off manually. During the chemical milling process, the coating on the non-milled surface can resist the corrosion of strong acids (nitric acid and hydrofluoric acid) without blistering or delamination. After chemical milling, the protective film layer on the protected area is also easy to peel off manually without residue. Moreover, the surface of the part substrate after chemical milling is smooth, the outline of the chemical milling line is clear, and there are no irregular etching marks. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the milling process of the present invention.

[0019] Figure 2 This is a photograph of a part that has been milled after being shaped. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. It should be noted that the embodiments described in this invention are only for further explanation and illustration, and not for limiting their application scope. Based on this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this invention.

[0021] Example 1

[0022] Chemical milling process flow as follows Figure 1 As shown.

[0023] 1. Use organic solvents such as acetone to degrease the parts;

[0024] 2. Use 200-mesh corundum sand, pressure 0.5MPa~1.0MPa, sand flow rate 2kg / min~4kg / min, spray gun moving speed 200mm / min~400mm / min, nozzle to part distance 100mm~200mm, turntable speed 20r / min~30r / min to sandblast the part;

[0025] 3. Before use, the paint should be thoroughly stirred and mixed evenly, then poured into the feed tank. During the spraying process, the stirrer should be kept running continuously. Spraying should be carried out at a spraying pressure of about 0.5MPa and a spraying distance of 200mm~500mm to form a paint film on the surface of the parts.

[0026] The paint film has a smooth and even appearance, free from pinholes, bulges, bubbles, wrinkles, peeling, etc.; the drying time of the paint film is: surface dry (23℃±2℃) ≤1h, and hard dry (23℃±2℃) ≤24h; the paint film thickness is ≥0.25mm, the tensile strength is ≥4.0MPa, the elongation at break is 300%~600%, the peel strength is 150N / m~800N / m, and the etching ratio is 0.6~0.9.

[0027] 4. The laser engraving machine is used for engraving, resulting in smooth lines without burrs, expansion, or tearing. After engraving, an electrical discharge tester is used for inspection, and any leaks are repaired with the original paint and cured.

[0028] After the engraving is complete, use a small knife (such as a scalpel) to peel off one end of the paint film in each area (do not damage the paint film on the non-chemically milled surface during peeling), then peel off the paint film in that area by hand. After peeling, check the paint film in the protected area for any damage; if any is found, repair it. Before chemical milling, after peeling off the paint film, use an EDM (Electrical Discharge Machining) tester to check the protective paint film on the test piece surface again. If any spots are found, recoat is required. See the actual image below. Figure 2 As shown;

[0029] 5. Chemical milling; the initial temperature of the part entering the chemical milling tank is controlled at 24℃. No refrigeration is required during the entire process. After chemical milling, the milled edges are straight and without obvious serrations. The total time the part spends in the chemical milling tank is 7 hours. After chemical milling, the paint film is manually peeled off.

Claims

1. The protective application of a peelable coating in the chemical milling of large titanium alloy structural parts, characterized in that, Includes the following: Step 1: Degrease the parts; Step 2: Sandblasting of parts; Step 3: Peelable coating application; After the coating is mixed, it is sprayed onto the surface of the part to form a paint film. Step 4: Shape the paint film surface; after shaping, remove the paint film from the milled surface of the part by manual peeling. Step 5: Chemical milling; chemical milling is performed in chemical milling fluid. After chemical milling, the paint film on the non-chemically milled surfaces of the parts is removed by manual peeling.

2. The application of a peelable coating as described in claim 1 in the protective milling of large titanium alloy structural parts, characterized in that, In step 1, organic solvents are used to remove grease from the surface of the parts.

3. The application of a peelable coating as described in claim 1 in the protective milling of large titanium alloy structural parts, characterized in that, The sandblasting process parameters in step 2 are as follows: 200-mesh corundum sand, pressure 0.5MPa~1.0MPa, sand flow rate 2kg / min~4kg / min, spray gun moving speed 200mm / min~400mm / min, nozzle to part distance 100mm~200mm, turntable speed 20r / min~30r / min.

4. The application of a peelable coating as described in claim 1 in the protective process of chemical milling of large titanium alloy structural parts, characterized in that, The spraying pressure in step 3 is 0.5 MPa, and the spraying distance is 200 mm to 500 mm.

5. The application of a peelable coating as described in claim 1 in the protective milling of large titanium alloy structural parts, characterized in that, The paint film described in step 3 has a smooth and even appearance, free from pinholes, bulges, bubbles, wrinkles, and peeling. The drying time of the paint film is: surface dry ≤ 1h, and fully dry ≤ 24h. The thickness of the paint film is ≥ 0.25mm.

6. The application of a peelable coating as described in claim 1 in the protective process of chemical milling of large titanium alloy structural parts, characterized in that, The paint film described in step 3 has a tensile strength ≥ 4.0 MPa, an elongation at break of 300%~600%, a peel strength of 150 N / m~800 N / m, and an etching ratio of 0.6~0.

9.

7. The application of a peelable coating as described in claim 1 in the protective milling of large titanium alloy structural parts, characterized in that, When the paint film mentioned in step 3 is a paint film resistant to strong acidic chemical milling fluid, the paint film is free of bubbles and protrusions, the paint film can be manually peeled off from the surface of the metal parts, and there are no places on the surface of the metal parts that are damaged by the corrosion of acidic chemical milling fluid.

8. The application of a peelable coating according to claim 1 in the protective milling of large titanium alloy structural parts, characterized in that, In step 4, a laser engraving machine is used for engraving. After engraving, the paint film on the surface of the part is removed. An electrical discharge tester is used to check the integrity of the protective paint film on the surface of the part and to measure the thickness of the surface of the part. Any areas with leaks in the paint film are touched up with the original paint and then cured.

9. The protective application of a peelable coating according to claim 1 in the chemical milling of large titanium alloy structural parts, characterized in that, The total time for chemical milling in step 5 is 7 hours.

10. The protective application of a peelable coating according to claim 1 in the chemical milling of large titanium alloy structural parts, characterized in that, In step 4, the lines are smooth during the engraving process, without any burrs, expansion, or tearing; in step 5, the milled edges are straight after chemical milling, without any jagged shapes.

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