Preparation method for highlight surface of MIM metal watchcase

Abstract

The invention relates to a preparation method for a highlight surface of an MIM metal watchcase. The preparation method comprises the following steps that S1, a metal watchcase blank is prepared through an MIM preparation technology; s2, oxide skin removal; s3, surface activation is conducted, specifically, the leveled blank is placed in a surface activation tank, the metal surface is activated through an activating agent, active sites are formed, and an activated blank is obtained; s4, air hole filling and leveling, wherein a metal transition material is deposited on the surface of the activated blank, and blank air holes are filled and leveled; s5, rough polishing is conducted, specifically, the blank deposited with the metal transition material is placed in an electrochemical polishing solution to be preliminarily polished, and a preliminarily polished blank is obtained; s6, electroplating is conducted, specifically, the primarily-polished blank is placed in electroplating liquid to be electroplated with a high-hardness plating layer; and S7, fine polishing is conducted, specifically, the high-hardness plating layer is subjected to manual light receiving, and the high-brightness surface is obtained through preparation. The volume fraction of surface oxides can be greatly reduced, the defects of product pits, fogging and the like are reduced, and the product with the good polishing effect can be prepared.

Description

Technical Field

[0001] The present invention relates to the field of polishing processes, and particularly to a method for preparing a high-gloss surface of a MIM metal watch case. Background Art

[0002] Metal injection molding (MIM) is a near-net-shape forming technology developed in recent decades. It has advantages such as high production efficiency, high material utilization rate, low production cost, high forming accuracy, and high degree of freedom in component design. It is an energy-saving, efficient, and environmentally friendly green manufacturing technology. Although MIM-prepared products are inexpensive and can process products with complex structures, due to their density not reaching 100%, and impurities such as silicon oxide, aluminum oxide, and chromium oxide being introduced during the atomization powder-making process, these impurities cause defects such as surface pitting, fogging, and sand holes to easily appear after surface polishing. Therefore, it is difficult to apply in fields such as smart wearables and jewelry, such as metal watch cases, mobile phone frames, and brand logos. How to achieve a high-gloss surface has become a technical difficulty in the current MIM industry. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing a high-gloss surface of a MIM metal watch case. This method can greatly reduce the volume fraction of surface oxides, reduce defects such as product pits and fogging, and can prepare products with better polishing effects.

[0004] The technical solution for achieving the purpose of the present invention is as follows: The present invention includes the following steps: S1. Blank preparation: Prepare a metal watch case blank through the MIM preparation process; S2. Oxide scale removal: Place the metal watch case blank in a rotary polishing machine, remove the surface oxide scale through abrasives, and simultaneously initially level the metal surface to obtain a leveled blank; S3. Surface activation: Place the leveled blank in a surface activation tank, activate the metal surface through an activator to form active sites, and obtain an activated blank; S4. Pore filling: Deposit a metal transition material on the surface of the activated blank to fill the pores of the blank; S5. Rough polishing: Place the blank deposited with the metal transition material in an electro-chemical polishing solution for preliminary polishing to obtain a preliminarily polished blank; S6. Electroplating: Place the preliminarily polished blank in an electroplating solution to electroplate a high-hardness coating; S7. Fine polishing: Manually polish the high-hardness coating to obtain a high-brightness surface.

[0005] Further, the material of the above metal watch case blank is SUS316L or titanium alloy or cobalt alloy or high-nitrogen nickel-free stainless steel or 17-4PHN or 304L.

[0006] Further, in the above step S2, the abrasive is one or a combination of more than one of corn kernels, walnut shells, and nylon particles.

[0007] Further, in the above step S3, the surface activation liquid is one or a combination of more than one of hydrochloric acid, nitric acid, and sulfuric acid.

[0008] As an optimized design, the surface activation liquid is a mixed solution of hydrochloric acid and sulfuric acid, the concentration of sulfuric acid is 10% - 20%, and the concentration of hydrochloric acid is 5% - 10%.

[0009] Further, in the above step S4, the metal transition material is one of an aluminum film, a copper film, and a nickel film.

[0010] Further, in the above step S4, the metal transition material uses a copper film; in step S6, the initial polished blank is placed into a copper salt electroplating bath, and a copper film blank is prepared by electroplating. The electroplating solution formula is 10 - 30 g / L of copper sulfate, 10 - 30 ml / L of formaldehyde, and 30 - 50 g / L of disodium ethylenediaminetetraacetate Further, in the above step S6, the electroplating process is as follows: add 200 - 300 g / L of nickel sulfate, 40 - 60 g / L of nickel chloride, 1 - 3 g / L of saccharin, 0.3 - 0.5 g / L of 1,4 - butynediol, and the current density is 3 - 6 A / dm2; the temperature of the electrolyte is 50 - 60 °C, and electroplating is carried out for 20 - 30 minutes.

[0011] Further, the above manual polishing uses a cloth wheel and polishing white wax, and is processed into a high - brightness surface by manual grinding. The present invention has positive effects: (1) The present invention effectively solves the problems of poor polishing of MIM blanks, such as pits and sand holes; through a suitable electroplating solution formula, pH value, electroplating time, and electroplating temperature, a uniformly distributed and dense and wear - resistant coating layer can be obtained. Sand holes and pits can serve as nucleation sites. During electroplating, free metal ions preferably fill the sand holes, tightly combine with extremely fine pits, and gradually spread around and grow crystallographically to form a dense coating layer.

[0012] (2) The present invention forms active sites through surface activation. The active sites form a layer of catalytic centers with high activity on the surface of the substrate, providing favorable conditions for the reduction and deposition of metal ions during the subsequent electroless plating process, contributing to the uniform reduction and deposition of metal ions on the surface of the substrate during the electroless plating process, thereby obtaining a uniform, continuous, and dense coating. Description of the Drawings

[0013] In order to make the content of the present invention easier to be clearly understood, the following further details the present invention according to specific embodiments in combination with the drawings, where Figure 1 Figure 28 is a polishing comparison diagram between Example 1 and the control example. Detailed Description of the Embodiments

[0014] (Example 1) This example includes the following steps: S1. Blank preparation: Prepare a metal watch case blank through the MIM preparation process; S2. Scale removal: Place the metal watch case blank in a tumbling polishing machine, and remove the surface scale through abrasives. At the same time, preliminarily finish the leveling of the metal surface to obtain a leveled blank; S3. Surface activation: Place the leveled blank in a surface activation tank, activate the metal surface through an activator to form active sites, and obtain an activated blank; S4. Pore filling: Deposit a metal transition material on the surface of the activated blank to fill the pores of the blank; S5. Rough polishing: Place the blank deposited with the metal transition material in an electro-chemical polishing solution for preliminary polishing to obtain a preliminarily polished blank; S6. Electroplating: Place the preliminarily polished blank in an electroplating solution to electroplate a high-hardness coating; S7. Fine polishing: Manually polish the high-hardness coating to obtain a high-brightness surface.

[0015] The material of the metal watch case blank is SUS316L.

[0016] In step S2, the leveled blank is obtained through rough grinding, medium grinding, and fine grinding; among them, nylon particles are used as the abrasive for rough grinding, corn kernels are used as the abrasive for medium grinding, and walnut shells are used as the abrasive for fine grinding.

[0017] In step S3, the surface activation solution is a mixed solution of hydrochloric acid and sulfuric acid, the concentration of sulfuric acid is 10% - 20%, and the concentration of hydrochloric acid is 5% - 10%.

[0018] In step S4, the metal transition material is a copper film with a thickness of 10 - 20 μm. The copper film can play a role in filling pores and can also improve the adhesion of the nickel layer. When the copper film is too thin, polishing will expose the bottom. When the copper film is too thick, it not only wastes materials, but also the filling effect is not ideal. Therefore, it is most reasonable to choose a film thickness of 10 - 20 μm.

[0019] In step S6, place the preliminarily polished blank in a copper salt electroplating tank and prepare a copper film-containing blank through electroplating.

[0020] In the electroplating process of step S6, add 200 - 300 g / L of nickel sulfate, 40 - 60 g / L of nickel chloride, 1 - 3 g / L of saccharin, 0.3 - 0.5 g / L of 1,4-butyne diol, and the current density is 6 A / dm 2 ; the temperature of the electrolyte is 60 °C, and electroplating is carried out for 30 minutes.

[0021] The manual polishing is to use a cloth wheel and polishing white wax to process into a high-brightness surface through manual grinding.

[0022] (Control Example) S1. Blank Preparation: Prepare a metal watch case blank through injection - debinding - sintering; S2. Scale Removal: Place the metal watch case blank in a tumbling machine, and remove the surface scale through abrasives. At the same time, initially finish the leveling of the metal surface to obtain a leveled blank; S3. Rough Polishing: Place the blank with deposited copper material in an electro - chemical polishing solution for preliminary polishing; S4. Fine Polishing: Manually finish the high - hardness coating to prepare a high - brightness surface; In S1, the metal watch case includes a SUS316L watch case; In S2, the abrasives are nylon particles for rough grinding, corn kernels for medium grinding, and walnut shells for fine grinding; The manual polishing in S4 is to use a cloth wheel and white wax, and process it into a high - brightness surface through manual grinding.

[0023] The polishing effect is shown in Figure 1 , on the left is the example, with a better polishing effect and no obvious pitting; on the right is the control group, with more pitting and a poorer mirror effect.

[0024] The above - described specific embodiments have further detailed the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above - described are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a high-gloss surface of a MIM metal watch case; characterized in that The following steps are involved: S1. Blank preparation: A metal watch case blank is prepared by MIM preparation process; S2. Oxide scale removal: The metal case blank is placed in a slip and polishing machine, and the surface oxide scale is removed by abrasives, and the metal surface is preliminarily leveled to obtain a leveled blank; S3, surface activation: placing the flattened blank in a surface activation tank, activating the metal surface with an activator to form active sites, and obtaining an activated blank; S4, pore filling: depositing metal transition material on the surface of the activated blank to fill the blank pores; S5, rough polishing: placing the blank of the deposited metal transition material in an electrochemical polishing solution for preliminary polishing to obtain a rough polished blank; S6, electroplating: placing the initially polished blank in an electroplating solution to electroplate a high hardness coating; S7, Fine Polishing: The high hardness coating is polished manually to obtain a high-gloss surface.

2. A method for preparing a high-gloss surface of a MIM metal watch case according to claim 1, characterized in that: The material of the metal watch case blank is SUS316L or titanium alloy or cobalt alloy or high nitrogen nickel-free stainless steel or 17-4PHN or 304L.

3. The method for preparing a high-gloss surface of a MIM metal watch case according to claim 1, characterized in that: In step S2, the abrasive is a combination of one or more of corn kernels, walnut shells, and nylon particles.

4. The method for preparing a high-gloss surface of a MIM metal watch case according to claim 1, characterized in that: The surfactant in step S3 is one or a combination of hydrochloric acid, nitric acid and sulfuric acid.

5. A method for preparing a high-gloss surface of a MIM metal watch case according to claim 4, characterized in that: The surfactant solution is a mixed solution of hydrochloric acid and sulfuric acid, with the concentration of sulfuric acid being 10% - 20% and the concentration of hydrochloric acid being 5% - 10%.

6. The method for preparing a high-gloss surface of a MIM metal watch case according to claim 1, characterized in that: In the step S4, the metal transition material is one of aluminum film, copper film and nickel film.

7. The method for preparing a high-gloss surface of a MIM metal watch case according to claim 1, characterized in that: In the step S4, the metal transition material is a copper film; in the step S6, the first-polished blank is placed in a copper salt electroplating tank to prepare a copper film blank by electroplating.

8. The method for preparing a high-gloss surface of a MIM metal watch case according to claim 1, characterized in that: The electroplating process in step S6 is as follows: adding 200-300 g / L nickel sulfate, 40-60 g / L nickel chloride, 1-3 g / L saccharin, 0.3-0.5 g / L 1,4-butynediol, current density 3-6 A / dm2; electrolyte temperature 50-60°C, electroplating for 20-30 minutes.

9. The method for preparing a high-gloss surface of a MIM metal watch case according to claim 1, characterized in that: The manual finishing is performed by using a cloth wheel and polishing white wax to produce a high-gloss surface through manual grinding.

Images