Processing technology of alloy die casting for camera production

Abstract

The invention relates to the technical field of die-casting aluminum alloy, in particular to a machining process of an alloy die casting for camera production, which comprises the following steps: taking a polished alloy die casting, and ultrasonically cleaning by using different cleaning solutions; activating with a sodium hydroxide solution and treating with hot water; transferring the alloy die casting into an aluminum phosphate conversion film material for dipping, carrying out water vapor treatment, then immersing the alloy die casting into a passivation solution for passivation, and applying a primer and a finish paint to obtain the alloy die casting for camera production. The aluminum alloy die casting is treated through the aluminum phosphate conversion film material, a uniform and compact aluminum phosphate film is formed, good adhesive force is provided, tiny defects are filled, the surface flatness is improved, tiny crystals of a phosphate film can also be embedded into a subsequent coating, preliminary curing of the phosphate conversion film is promoted through water vapor treatment, and the surface smoothness of the aluminum alloy die casting is improved. A layer of compact passivation film is formed on the surface of the aluminum phosphate conversion film through passivation treatment, and finally paint spraying treatment is carried out, so that the corrosion resistance and the protection performance of the alloy die casting are enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of die-casting aluminum alloys, and in particular to a processing technology for alloy die-castings used in camera production. Background Art

[0002] Cameras are widely used in many fields such as consumer electronics, security monitoring, and the automotive industry. Key components of cameras such as lens holders and housings are usually made of aluminum alloy die-castings. Aluminum alloy die-castings have the advantages of light weight, high strength, good processing performance, and low cost, and are particularly suitable for large-scale production and the manufacture of parts with complex shapes. In actual applications, aluminum alloy die-castings have problems such as surface quality, corrosion resistance, and aesthetics. They have inherent and unavoidable casting defects such as pores, cracks, inclusions, local depressions, and flow marks. The alloy die-castings used in cameras have requirements for mechanical strength, corrosion resistance, and impact resistance. Therefore, during the processing of aluminum alloy die-castings, they will undergo pretreatment such as grinding, surface treatment, and painting to improve the surface quality and protective performance of aluminum alloy die-castings.

[0003] Among them, the most commonly used surface treatment is the electrodeposition film layer, but the electrodeposition film layer uniformity and adhesion are insufficient. Although the electrodeposition can form a dense film layer, due to the uneven current distribution or the complex shape of the parts, the film layer in some areas is too thin or too thick. Especially on some surfaces with complex shapes or minor defects, the poor or uneven adhesion of the film layer will lead to poor local protection performance, affecting the overall corrosion resistance and aesthetics. In addition, the additives in the electrodeposition liquid may decompose or precipitate after long-term use, affecting the electrodeposition effect, and the interface bonding strength and long-term stability between the electrodeposition film and the plastic powder cured film are also poor, resulting in poor corrosion resistance and protection performance of the final product. Therefore, the present invention provides a processing technology for alloy die castings for camera production to solve the above problems. Summary of the invention

[0004] In view of the deficiencies in the prior art, the object of the present invention is to provide a processing technology for alloy die-castings for camera production.

[0005] A processing technology for alloy die castings for camera production comprises the following steps:

[0006] S1. Polishing and grinding: taking an alloy die-casting for camera production, and performing polishing and grinding treatment on it to obtain a pre-treated alloy die-casting;

[0007] S2. Surface treatment: Use an ultrasonic cleaning machine to clean the alloy die castings with tap water, alcohol anhydrous organic solvents and surfactants in sequence;

[0008] Use 10-30g / L sodium hydroxide solution to activate the alloy die castings, then place the alloy die castings in deionized water and heat to 70-80°C for 1-5 minutes;

[0009] The activated alloy die casting is immersed in an aluminum phosphate conversion film material for 2-3 minutes to perform an aluminum phosphate treatment, and then the alloy die casting is placed in a water vapor environment for treatment;

[0010] The alloy die casting treated with aluminum phosphate is immersed in a passivation solution for passivation treatment to obtain a surface treated alloy die casting;

[0011] S3. Painting treatment: Use electrostatic spraying or dipping to apply primer on the alloy die-casting to ensure uniform coverage of the coating; then use the topcoat to apply it to the surface of the alloy die-casting in the same way, place the painted alloy die-casting in a curing furnace for heating and curing, and obtain the finished alloy die-casting for camera production.

[0012] Furthermore, in the surface treatment of step S2, tap water, anhydrous alcohol organic solvent and surfactant are used to clean the alloy die castings respectively, and the treatment time is 5-20 minutes, the power is 50-200W, the frequency is 10-100KHz, and the anhydrous alcohol organic solvent is ethanol or isopropanol.

[0013] Furthermore, in the surface treatment of step S2, the temperature of the activation treatment using sodium hydroxide solution is 40-60° C., and the treatment time is 10-20 minutes.

[0014] Furthermore, in the surface treatment of step S2, the aluminum phosphate conversion film material is prepared using aluminum dihydrogen phosphate, aluminum oxide with a particle size less than 500 meshes and pure water as raw materials.

[0015] Furthermore, in the surface treatment step S2, the alloy die casting is placed in a water vapor environment at a treatment temperature of 120-150° C. and a treatment time of 1-3 minutes.

[0016] Furthermore, in the surface treatment of step S2, the passivation solution uses a chromium-free passivating agent, and the chromium-free passivating agent is one of silane, titanate and molybdate.

[0017] Furthermore, in the paint spraying process in step S3, the primer is an epoxy primer or a polyurethane primer.

[0018] Furthermore, in the painting process in step S3, the topcoat is polyester powder coating or acrylic topcoat.

[0019] Furthermore, in the paint spraying process of step S3, the heating curing temperature is 140-160° C. and the time is 10-20 minutes.

[0020] Furthermore, the alloy die-casting is an aluminum alloy die-casting.

[0021] The beneficial effects achieved by the present invention are as follows: 1. The present invention forms a uniform and dense aluminum phosphate film on the metal surface through a chemical reaction between the aluminum phosphate conversion film material and the aluminum alloy surface, which can provide good adhesion, fill tiny defects and improve surface flatness. The phosphate film is composed of tiny crystals, which can be embedded in the subsequent coating. Even on surfaces with complex shapes or tiny defects, the uniformity and adhesion of the film layer can be ensured. The initial solidification of the phosphate conversion film is promoted by water vapor environment treatment, and a dense passivation film is formed on the surface of the aluminum phosphate conversion film by passivation treatment. This film works together with the phosphate film to provide double protection. Finally, the paint treatment is performed to improve the corrosion resistance and protective performance of the alloy die-casting.

[0022] 2. The present invention uses epoxy primer or polyurethane primer. These two primers have excellent adhesion and chemical resistance and can firmly adhere to the aluminum phosphate conversion film to form a solid base layer. Polyester powder coating or acrylic topcoat is used. These coatings not only have good weather resistance and decorative properties, but also can form a close bond with the primer during high-temperature curing to ensure long-term stability. The coated alloy die-casting is placed in a curing furnace for heating and curing, so that the coating is completely cross-linked to form a hard and stable protective layer, thereby improving the interface bonding strength and long-term stability.

[0023] 3. The present invention ensures good protection of alloy die-castings through the optimized combination of various processes, improves the good bonding force between the film layer and the paint, and the adhesion of the film layer to the substrate, increases the service life of the alloy die-castings, and uses a chromium-free passivating agent to improve environmental protection performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The figure is a schematic flow chart of a processing technology for alloy die-castings for camera production adopted in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below in conjunction with specific embodiments.

[0026] Embodiment 1: A processing technology for alloy die castings for camera production, such as Figure 1 As shown, the following steps are included:

[0027] S1. Polishing and grinding: Take the aluminum alloy die-casting for camera production, use a light grinding tool to grind the edges and complex structure parts to ensure that the surface is flat and smooth, and obtain the pre-treated aluminum alloy die-casting;

[0028] S2. Surface treatment: Use an ultrasonic cleaning machine to clean the aluminum alloy die castings with tap water, 50% ethanol and a surfactant (polyoxyethylene alkyl ether) in sequence. The treatment time of each cleaning solution is 10 minutes, the power is 100 W, and the frequency is 50 KHz;

[0029] Use 20g / L sodium hydroxide solution to activate the aluminum alloy die casting at 45°C for 15 minutes, then put the aluminum alloy die casting into deionized water and heat it to 75°C for 3 minutes;

[0030] Aluminum dihydrogen phosphate, alumina with a particle size of less than 500 meshes and pure water are used as raw materials to prepare an aluminum phosphate conversion film material, and the activated aluminum alloy die casting is immersed in the aluminum phosphate conversion film material for 2.5 minutes to perform an aluminum phosphate treatment, and then the aluminum alloy die casting is placed in a water vapor environment for treatment at a temperature of 130° C. for 2 minutes;

[0031] The aluminum alloy die casting treated with aluminum phosphate is immersed in a chromium-free passivation solution containing silane for passivation treatment at room temperature for 10 minutes to obtain a surface-treated aluminum alloy die casting;

[0032] S3. Painting treatment: Use electrostatic spraying to apply epoxy primer on the aluminum alloy die-casting to ensure uniform coverage of the coating; then use topcoat (polyester powder coating) to apply it to the surface of the aluminum alloy die-casting in the same way, and place the painted aluminum alloy die-casting in a curing furnace for heating and curing at a temperature of 150°C for 15 minutes to obtain a finished aluminum alloy die-casting for camera production.

[0033] Embodiment 2: A processing technology for alloy die castings for camera production, such as Figure 1 As shown, the following steps are included:

[0034] S1. Polishing and grinding: Take the aluminum alloy die-casting for camera production, use a light grinding tool to grind the edges and complex structure parts to ensure that the surface is flat and smooth, and obtain the pre-treated aluminum alloy die-casting;

[0035] S2. Surface treatment: Use an ultrasonic cleaning machine to clean the aluminum alloy die castings with tap water, 70% isopropyl alcohol and a surfactant (polyoxyethylene alkyl ether) in sequence. The treatment time of each cleaning solution is 15 minutes, the power is 150W, and the frequency is 80KHz;

[0036] Use 25g / L sodium hydroxide solution to activate the aluminum alloy die casting at 50°C for 12 minutes, then put the aluminum alloy die casting into deionized water and heat it to 80°C for 4 minutes;

[0037] Aluminum dihydrogen phosphate, alumina with a particle size of less than 500 meshes and pure water are used as raw materials to prepare an aluminum phosphate conversion film material, and the activated aluminum alloy die casting is immersed in the aluminum phosphate conversion film material for 2 minutes to perform an aluminum phosphate treatment, and then the aluminum alloy die casting is placed in a water vapor environment for treatment at a temperature of 140° C. for 1.5 minutes;

[0038] The aluminum alloy die casting treated with aluminum phosphate is immersed in a chromium-free passivation solution containing titanate for passivation treatment at a temperature of 40° C. for a treatment time of 8 minutes to obtain a surface-treated aluminum alloy die casting;

[0039] S3. Painting treatment: Apply polyurethane primer to the aluminum alloy die-casting by dipping to ensure uniform coverage of the coating; then apply acrylic topcoat to the surface of the aluminum alloy die-casting in the same manner, place the painted aluminum alloy die-casting in a curing furnace for heating and curing at 140°C for 10 minutes to obtain a finished aluminum alloy die-casting for camera production.

[0040] Embodiment 3: A processing technology for alloy die castings for camera production, such as Figure 1 As shown, the following steps are included:

[0041] S1. Polishing and grinding: Take the aluminum alloy die-casting for camera production, use a light grinding tool to grind the edges and complex structure parts to ensure that the surface is flat and smooth, and obtain the pre-treated aluminum alloy die-casting;

[0042] S2. Surface treatment: Use an ultrasonic cleaning machine to clean the aluminum alloy die castings with tap water, 60% ethanol and a surfactant (polyoxyethylene alkyl ether) in sequence. The treatment time of each cleaning solution is 20 minutes, the power is 200W, and the frequency is 100KHz;

[0043] Use 30g / L sodium hydroxide solution to activate the aluminum alloy die casting at 60°C for 20 minutes, then put the aluminum alloy die casting into deionized water and heat it to 70°C for 5 minutes;

[0044] Aluminum dihydrogen phosphate, alumina with a particle size of less than 500 meshes and pure water are used as raw materials to prepare an aluminum phosphate conversion film material, and the activated aluminum alloy die casting is immersed in the aluminum phosphate conversion film material for 3 minutes to perform an aluminum phosphate treatment, and then the aluminum alloy die casting is placed in a water vapor environment for treatment at a temperature of 150° C. for 3 minutes;

[0045] The aluminum alloy die casting treated with aluminum phosphate is immersed in a chromium-free passivation solution containing molybdate for passivation treatment at a temperature of 60° C. for a treatment time of 15 minutes to obtain a surface-treated aluminum alloy die casting;

[0046] S3. Painting treatment: Use electrostatic spraying to apply epoxy primer on the aluminum alloy die-casting to ensure uniform coverage of the coating; then use topcoat (polyester powder coating) to apply to the surface of the aluminum alloy die-casting in the same way, and place the painted aluminum alloy die-casting in a curing furnace for heating and curing at a temperature of 160°C for 20 minutes to obtain a finished aluminum alloy die-casting for camera production.

[0047] Performance test: The alloy die-castings for camera production after the complete processing of Examples 1 to 3 were taken for relevant performance tests;

[0048] 1. Surface quality and appearance inspection: According to GB / T 9792-2005 "Surface rust grade and rust removal grade of steel before painting", carefully observe the surface of aluminum alloy die-castings at a distance of about 30-50 cm from the sample under a white fluorescent light to check whether there are obvious defects.

[0049] 2. Adhesion test: According to GB / T 9286-1998 "Scratch test for paint and varnish films", use a scribing tool to scratch a 1mm×1mm grid on the coating surface, to a depth of the substrate, and stick a transparent tape that meets the standard requirements (3M No. 600 tape) evenly on the scribing area and roll it with the palm of your hand to ensure that the tape is in full contact with the coating. Quickly tear off the tape in a direction perpendicular to the sample surface, and evaluate according to the rating standard (0-5 levels, 0 is the best adhesion and 5 is the worst) based on the degree of coating being lifted.

[0050] 3. Corrosion resistance test: According to GB / T 10125-2012 "Artificial atmosphere corrosion test salt spray test", the aluminum alloy die castings are cleaned, dried and placed in a salt spray test chamber. The temperature is set to 35±2℃, the salt solution concentration is 5% sodium chloride, the pH value is 6.8, and the spray time is 96 hours. After the test, take out the sample, rinse it with tap water and dry it, and check the corrosion condition of the sample surface.

[0051] 4. Hardness test: According to ASTM D3363 "Determination of Pencil Hardness of Paints and Related Coatings", prepare a set of pencils of different hardness (from 6H to 6B) and arrange them in order from hard to soft; sharpen the pencils to expose about 6mm of lead core, gently push the pencils over the coating surface of the alloy die-casting at a 45° angle, apply a pressure of about 750g, and record the hardest pencil grade that can scratch the coating to evaluate the hardness.

[0052] 5. Weathering test: According to GB / T 1865-2009 "Artificial weathering and artificial radiation exposure of paint and varnish coatings - filtered xenon arc radiation", clean the aluminum alloy die castings, dry them and put them into the xenon arc accelerated aging test chamber. Set the test conditions: irradiation intensity 0.35W / m 2(340nm wavelength), blackboard temperature 65±3℃, relative humidity 50±5%, water spraying for 18 minutes every 102 minutes, and xenon arc accelerated aging test for 500 hours; after the test, take out the samples and check for color change, gloss loss, chalking, cracks, etc.

[0053] The test results are shown in the following table.

[0054] Table 1 Test results of various properties of alloy die castings for camera production

[0055]

[0056]

[0057] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A processing technology for alloy die castings for camera production, characterized in that: The following steps are involved: S1. Polishing and grinding: taking an alloy die-casting for camera production, and performing polishing and grinding treatment on it to obtain a pre-treated alloy die-casting; S2. Surface treatment: Use an ultrasonic cleaning machine to clean the alloy die castings with tap water, alcohol anhydrous organic solvents and surfactants in sequence; Use 10-30g / L sodium hydroxide solution to activate the alloy die castings, then place the alloy die castings in deionized water and heat to 70-80°C for 1-5 minutes; The activated alloy die casting is immersed in an aluminum phosphate conversion film material for 2-3 minutes to perform an aluminum phosphate treatment, and then the alloy die casting is placed in a water vapor environment for treatment; The alloy die casting treated with aluminum phosphate is immersed in a passivation solution for passivation treatment to obtain a surface treated alloy die casting; S3. Painting treatment: Use electrostatic spraying or dipping to apply primer on the alloy die-casting to ensure uniform coverage of the coating; then use the topcoat to apply it to the surface of the alloy die-casting in the same way, place the painted alloy die-casting in a curing furnace for heating and curing, and obtain the finished alloy die-casting for camera production.

2. The processing technology of alloy die casting for camera production according to claim 1 is characterized in that: In the surface treatment of step S2, tap water, anhydrous alcohol organic solvent and surfactant are used to clean the alloy die castings respectively, and the treatment time is 5-20 minutes, the power is 50-200W, the frequency is 10-100KHz, and the anhydrous alcohol organic solvent is ethanol or isopropanol.

3. The processing technology of alloy die casting for camera production according to claim 1 is characterized in that: In the surface treatment step S2, the activation treatment temperature using sodium hydroxide solution is 40-60° C. and the treatment time is 10-20 minutes.

4. The processing technology of alloy die casting for camera production according to claim 1 is characterized in that: In the surface treatment step S2, the aluminum phosphate conversion film material is prepared using aluminum dihydrogen phosphate, aluminum oxide with a particle size less than 500 meshes and pure water as raw materials.

5. The processing technology of alloy die casting for camera production according to claim 1 is characterized in that: In the surface treatment step S2, the alloy die casting is placed in a water vapor environment at a treatment temperature of 120-150° C. and a treatment time of 1-3 minutes.

6. The processing technology of alloy die casting for camera production according to claim 1 is characterized in that: In the surface treatment step S2, the passivation solution uses a chromium-free passivating agent, and the chromium-free passivating agent is one of silane, titanate and molybdate.

7. The processing technology of alloy die casting for camera production according to claim 1 is characterized in that: In the step S3 of spray painting, the primer is an epoxy primer or a polyurethane primer.

8. The processing technology of alloy die casting for camera production according to claim 1 is characterized in that: In the step S3 of spray painting, the topcoat is polyester powder coating or acrylic topcoat.

9. The processing technology of alloy die casting for camera production according to claim 1, characterized in that: In the step S3 of spray painting, the heating curing temperature is 140-160° C. and the time is 10-20 minutes.

10. The processing technology of alloy die casting for camera production according to claim 1, characterized in that: The alloy die casting is an aluminum alloy die casting.

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