Method for casting aluminum alloy smart phone middle frame anodized mirror surface highlight appearance product

Abstract

The invention belongs to the technical field of cast aluminum alloy anodic oxidation, and discloses a method for manufacturing a mirror surface bright appearance part through die-casting aluminum alloy electro-deposition aluminum anodic oxidation. The die-casting aluminum alloy mobile phone middle frame is subjected to ionic liquid anode activation and rack plating in ionic liquid to obtain a high-purity aluminum plating layer with a certain thickness, after mechanical polishing treatment is conducted to achieve the mirror surface bright appearance, anodic oxidation, dyeing, hole sealing and other treatment are conducted, and the highlight anodic oxidation mobile phone middle frame is obtained. By means of the method, the problems that an aluminum alloy anodic oxidation highlight appearance part is cast, CNC machining efficiency is low, cost is high and the like can be solved, the binding force between the obtained high-purity aluminum layer and an aluminum alloy base body is high, and an oxidation film obtained through anodic oxidation is high in transparency, high in specular reflectance, uniform, free of cracks and holes, high in hardness and resistant to corrosion. The anodic oxidation mobile phone middle frame has a good mirror reflection effect and can meet the requirement of highlight anodic oxidation.

Description

Technical Field

[0001] The invention belongs to the technical field of cast aluminum alloy anodizing, and in particular relates to a method for anodizing a cast aluminum alloy smartphone middle frame to produce a product with a mirror-like high-gloss appearance. Background Art

[0002] With the update and iteration of smart phone products and the advent of the 5G era, mobile phone manufacturers have higher and higher requirements and demands for the quality of integrated molding of mobile phone middle frames. Die-cast aluminum alloy middle frames have the advantages of high dimensional accuracy, good thermal conductivity, high strength, etc., and the production efficiency is much higher than CNC processing, and the cost is lower. However, the aluminum alloy used in the integrated mobile phone middle frame with high die-casting precision and complex structure usually has a high silicon content and is not suitable for the production of appearance parts using anodizing process.

[0003] At present, the high-end mobile phones of major mobile phone manufacturers all use aluminum anodizing technology to obtain beautiful, metallic, safe, durable and easy-to-clean mobile phone frames. However, these mobile phone frames generally use CNC processed aluminum alloy profiles with high production costs and low efficiency, such as patents CN106400083A, CN104105374 A, and CN109161950A, and most of them are mainly matte anodizing processes, and high-gloss anodizing, which has a higher market demand, is less common. High-gloss anodizing requires that the aluminum alloy be polished to a mirror finish before anodizing, and the anodized film has high transparency and few defects. This requires that the aluminum alloy has a low impurity content and fine grains to ensure that the aluminum alloy maintains the mirror reflection brightness before anodizing after anodizing, and avoids problems such as low brightness, whitening, and corrosion spots of the oxide film. This seriously limits the application of die-cast aluminum alloy frames in the high-end mobile phone market. Summary of the invention

[0004] The purpose of the present invention is to provide a method for casting an aluminum alloy smartphone middle frame anodized mirror high-gloss appearance product to solve the above-mentioned technical problems.

[0005] In order to solve the above technical problems, the specific technical solution of the method for casting an aluminum alloy smartphone middle frame anodized mirror high-gloss appearance product of the present invention is as follows: A method for casting an aluminum alloy smartphone middle frame anodized mirror high-gloss appearance product comprises the following steps: Step 1: Grinding and polishing: Mechanically grind and polish the die-cast mobile phone middle frame to remove a small amount of burrs and defects on the surface to make the surface uniform and flat; Step 2: Degreasing: Degreasing the cast aluminum alloy parts with residual oil on the surface; Step 3: Anode activation: Anode activation is performed under an inert gas environment; Step 4: Electroplating pure aluminum: electroplating pure aluminum in an ionic liquid electroplating solution; Step 5: Mirror polishing: polish the cast aluminum alloy after electrodeposition of pure aluminum to a mirror finish; Step 6: Cleaning: After mirror polishing, clean the surface of the phone's middle frame to remove surface oil and stains to keep the surface clean; Step 7: Anodizing: Anodizing in a sulfuric acid anodizing tank; Step 8: Dyeing: Dyeing is performed after anodizing; Step 9: Sealing: After dyeing, the anodized film is sealed in a solution containing a sealing agent.

[0006] Furthermore, in step 2, acetone or degreasing powder is used for ultrasonic cleaning and degreasing, the degreasing temperature is room temperature, the degreasing time is 5-30 minutes, and water washing is performed three times after degreasing.

[0007] Furthermore, in step 3, the mobile phone middle frame is used as the anode and the pure aluminum plate is used as the cathode, and 10-50 mA / cm 2 The current was activated for 10-60s each time, and the activation was repeated twice.

[0008] Furthermore, the ionic liquid electroplating solution in step 4 is composed of aluminum chloride (AlCl 3 ) and 1-ethyl-3-methylimidazole chloride (EMIC) in a molar ratio of 1.5-2. The activated mobile phone middle frame was used as the cathode and the pure aluminum plate was used as the anode. In the ionic liquid protected by inert gas, the current was turned on for 50-180 min with a current density of 5-30 mA / cm 2 The plating solution temperature is 10-60℃, and the thickness of the pure aluminum coating obtained by electroplating is 20-50 μ m.

[0009] Furthermore, in step 5, the cast aluminum alloy after electrodeposition of pure aluminum is polished to a mirror finish using a polishing wheel and a silica sol polishing solution. The polishing equipment may be a CNC polishing machine for automatic polishing, or a polishing machine for manual polishing.

[0010] Furthermore, the cleaning process in step 6 is performed using water and ethanol.

[0011] Furthermore, the anodization in step 7 is carried out in a 180-200 g / L sulfuric acid anodizing tank, the anodizing temperature is controlled at 15-24°C, the anodizing voltage is 10-15V, the anodizing time is 20-60min, and the film thickness is 8-20 μ m of anodized film.

[0012] Furthermore, the dyeing time in step 8 is between 10 and 120 seconds, and the dyeing temperature is room temperature.

[0013] Furthermore, in step 9, the sealing liquid temperature is 60-100° C., and the sealing time is 10-60 min.

[0014] The method of casting an aluminum alloy smartphone middle frame anodized with a mirror-like high-gloss appearance product of the present invention has the following advantages: the present invention adopts an ionic liquid anode to activate the die-cast aluminum alloy mobile phone middle frame, ionic liquid electroplating high-purity aluminum, mirror-polishing the pure aluminum coating, and finally anodizing the high-gloss mobile phone middle frame. The advantages of aluminum alloy ionic liquid electroplating aluminum with strong bonding force, high purity, few defects, and good uniformity are utilized to solve the problem of anodizing the high-gloss appearance frame of the integrated molded mobile phone middle frame, while retaining the advantages of the aluminum alloy die-casting process. The anodized mobile phone middle frame has a good mirror reflection effect and can meet the requirements of high-gloss anodization. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Appearance picture of electroplating high-purity aluminum for die-cast mobile phone middle frame; Figure 2 This is the appearance of the mobile phone middle frame that is electroplated with high-purity aluminum and then anodized with high gloss; Figure 3 This is the cross-sectional SEM image of the oxide layer after anodization of the electroplated pure aluminum layer. DETAILED DESCRIPTION

[0016] In order to better understand the purpose, structure and function of the present invention, the following is a further detailed description of a method for casting an aluminum alloy smartphone middle frame anodized mirror high-gloss appearance product of the present invention in conjunction with the accompanying drawings.

[0017] A method for casting an aluminum alloy smartphone middle frame anodized mirror-finished high-gloss appearance product of the present invention comprises the following steps: Step 1: Grinding and Polishing Mechanical grinding and polishing of the die-cast mobile phone middle frame removes a small amount of burrs and defects on the surface, making the surface uniform and smooth, and avoiding burrs that affect the quality and appearance of the coating after electroplating.

[0018] Step 2: Degreasing Cast aluminum alloy parts with residual oil on the surface need to be degreased. Use acetone or degreasing powder to ultrasonically clean and degrease. The degreasing temperature is room temperature and the degreasing time is 5-30 minutes. After degreasing, wash with water three times to keep the surface as clean as possible.

[0019] Step 3: Anodic Activation The activation process is carried out in an inert gas (nitrogen or argon) environment to avoid the problem of re-oxidation of the die-cast aluminum alloy after activation. During anodic activation, the mobile phone middle frame is used as the anode and the pure aluminum plate is used as the cathode. 20-50 mA / cm 2 The current was activated for 10-60 s each time, and the activation was repeated twice.

[0020] Step 4: Electroplating Pure Aluminum Ionic liquid electroplating solution is made of aluminum chloride (AlCl 3 ) and 1-ethyl 3-methylimidazole chloride (EMIC) in a molar ratio of 1.5-2. The activated mobile phone middle frame is used as the cathode and the pure aluminum plate is used as the anode. In the ionic liquid protected by inert gas, the current is applied for 50-180 min with a current density of 5-30 mA / cm 2 The plating solution temperature is 10-60℃, and the thickness of the pure aluminum coating obtained by electroplating is 20-50 μ m.

[0021] Step 5: Mirror Polishing Use polishing wheels and silica sol polishing liquid to polish the cast aluminum alloy after electrodeposition of pure aluminum to a mirror finish. The polishing equipment can be a CNC polishing machine for automatic polishing, or a polishing machine for manual polishing.

[0022] Step 6: Cleaning After mirror polishing, the surface of the mobile phone frame needs to be cleaned to remove surface oil and stains to keep the surface clean. The cleaning process mainly uses water and ethanol for cleaning.

[0023] Step 7: Anodizing Anodization is carried out in a 180-200 g / L sulfuric acid anodizing tank, the anodizing temperature is controlled at 15-24 °C, the anodizing voltage is 10-15 V, the anodizing time is 20-60 min, and the film thickness can be 8-20 μ m of anodized film.

[0024] Step 8: Dyeing In order to further improve the aesthetics of the anodized film, it can be dyed after anodizing to obtain various colors such as black, purple, red, green, pink, etc. The dye is configured according to the required color requirements, the dyeing time is between 10-120s, and the dyeing temperature is room temperature.

[0025] Step 9: Sealing the Holes After dyeing, the anodized film is sealed in a solution containing a sealing agent, the sealing liquid temperature is 60-100° C., and the sealing time is 10-60 minutes.

[0026] Examples of the present invention are as follows: The polished die-cast aluminum mobile phone middle frame was ultrasonically cleaned in acetone solution for 20 min, deionized and cleaned three times, and then dried and placed in an ionic liquid activation chamber protected by nitrogen. 3 -In the EMIC ionic liquid, the mobile phone middle frame is used as the anode and the aluminum plate is used as the cathode. The current density is 40 mA / cm 2The anode was activated twice, each time for 10-15 seconds.

[0027] After anodic activation, most of the oxide film on the surface of the cast aluminum alloy was dissolved, exposing the aluminum surface. 3 -EMIC ionic liquid electroplating for 80 min, applying 8 mA / cm 2 The current density of the mobile phone middle frame is 40-50mm thick. μ m. After electroplating, the appearance of the cast aluminum alloy mobile phone middle frame is as follows Figure 1 As shown, the appearance is uniform silver-white with a certain metallic luster.

[0028] Use a polishing wheel and silica sol polishing liquid to manually polish the coating on a polishing machine until it is mirror-bright. During the polishing process, the amount of aluminum coating removed must be controlled and the remaining coating thickness must be greater than the thickness of the oxide film after anodizing.

[0029] After polishing, the aluminum-plated mobile phone middle frame is thoroughly cleaned with water and anhydrous ethanol to remove the polishing liquid and stains remaining during polishing. The cleaning order is to wash with water twice and wash with anhydrous ethanol once.

[0030] After the aluminum-plated mobile phone middle frame is cleaned, it is anodized in a 200 g / L sulfuric acid oxidation tank for 30 minutes, the oxidation temperature is 20°C, and the oxidation voltage is 12 V. After dyeing at room temperature, it is heat-sealed in a sealing liquid at 65°C for 20 minutes. Figure 2 As shown, the middle frame of the mobile phone has a high mirror reflection ability, and can achieve mirror imaging for the front sample.

[0031] The microstructure of the anodic oxide film is Figure 3 As shown, the anodized film is uniform and dense, showing a porous structure, without looseness, holes and other defects formed by anodization of cast aluminum alloy. The thickness of the anodized film is 8-9 μ m.

[0032] The performance of the electroplated aluminum high-gloss anodized mobile phone middle frame is shown in Table 1. The oxide film has high light transmittance, which ensures the excellent mirror reflection and imaging ability of high-gloss anodizing. It can be dyed in various colors, and the oxide film is dense, so that the average hardness reaches 390 HV, which is higher than the 300HV of ordinary pure aluminum anodized film. The neutral salt spray test is completely free of rust for more than 1000 hours, which is much higher than the 48h required for ordinary anodizing.

[0033] Table 1 Performance of electroplated aluminum high-gloss anodized mobile phone middle frame

[0034] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A method for casting an aluminum alloy smartphone middle frame anodized mirror high-gloss appearance product, characterized in that: The steps include: Step 1: Grinding and polishing: Mechanically grind and polish the die-cast mobile phone middle frame to remove a small amount of burrs and defects on the surface to make the surface uniform and flat; Step 2: Degreasing: Degreasing the cast aluminum alloy parts with residual oil on the surface; Step 3: Anode activation: Anode activation is performed under an inert gas environment; Step 4: Electroplating pure aluminum: electroplating pure aluminum in an ionic liquid electroplating solution; Step 5: Mirror polishing: polish the cast aluminum alloy after electrodeposition of pure aluminum to a mirror finish; Step 6: Cleaning: After mirror polishing, clean the surface of the phone's middle frame to remove surface oil and stains to keep the surface clean; Step 7: Anodizing: Anodizing is carried out in a sulfuric acid anodizing tank; Step 8: Dyeing: Dyeing is done after anodizing; Step 9: Sealing: After dyeing, the anodized film is sealed in a solution containing a sealing agent.

2. The method for casting an aluminum alloy smart phone middle frame to produce anodized mirror-finished high-gloss appearance products according to claim 1, characterized in that: In step 2, acetone or degreasing powder is used for ultrasonic cleaning and degreasing. The degreasing temperature is room temperature and the degreasing time is 5-30 minutes. After degreasing, water washing is performed three times.

3. The method for casting an aluminum alloy smart phone middle frame to produce anodized mirror-finished high-gloss appearance products according to claim 1, characterized in that: In step 3, during anode activation, the mobile phone middle frame is used as the anode and the pure aluminum plate is used as the cathode. 20-50 mA / cm 2 The current was activated for 10-60s each time, and the activation was repeated twice.

4. The method for casting an aluminum alloy smart phone middle frame to produce an anodized mirror-finished high-gloss appearance product according to claim 1, characterized in that: The ionic liquid plating solution in step 4 is prepared by aluminum chloride (AlCl3) and 1-ethyl 3-methyl imidazole chloride (EMIC) in a molar ratio of 1.5-2. The activated mobile phone middle frame is used as the cathode and the pure aluminum plate is used as the anode. In the ionic liquid protected by inert gas, the current is applied for 50-180 min at a current density of 5-30 mA / cm 2 The plating solution temperature is 10-60℃, and the thickness of the pure aluminum coating obtained by electroplating is 20-50 μ m.

5. The method for casting an aluminum alloy smart phone middle frame to produce an anodized mirror-finished high-gloss appearance product according to claim 1, characterized in that: Step 5: polishing the cast aluminum alloy after electrodeposition of pure aluminum to a mirror finish using a polishing wheel and a silica sol polishing solution. The polishing equipment may be a CNC polishing machine for automatic polishing or a polishing machine for manual polishing.

6. The method for casting an aluminum alloy smart phone middle frame to produce anodized mirror-finished high-gloss appearance products according to claim 1, characterized in that: The cleaning process in step 6 is performed using water and ethanol.

7. The method for casting an aluminum alloy smart phone middle frame to produce anodized mirror-finished high-gloss appearance products according to claim 1, characterized in that: The anodization in step 7 is carried out in a 180-200 g / L sulfuric acid anodizing tank, the anodizing temperature is controlled at 15-24° C., the anodizing voltage is 10-15 V, the anodizing time is 20-60 min, and the film thickness is 8-20 μ m of anodized film.

8. The method for casting an aluminum alloy smart phone middle frame to produce anodized mirror-finished high-gloss appearance products according to claim 1, characterized in that: The dyeing time in step 8 is between 10 and 120 seconds, and the dyeing temperature is room temperature.

9. The method for casting an aluminum alloy smart phone middle frame to produce anodized mirror-finished high-gloss appearance products according to claim 1, characterized in that: In step 9, the sealing liquid temperature is 60-100° C., and the sealing time is 10-60 min.

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