Patent Application
20240368798
This application claims the benefit of priority to Taiwan Patent Application No. 112116222, filed on May 2, 2023. The entire content of the above identified application is incorporated herein by reference.
Some references, which may include patents, patent applications and various publications, may be cited and discussed in the description of this disclosure. The citation and/or discussion of such references is provided merely to clarify the description of the present disclosure and is not an admission that any such reference is “prior art” to the disclosure described herein. All references cited and discussed in this specification are incorporated herein by reference in their entireties and to the same extent as if each reference was individually incorporated by reference.
The present disclosure relates to a processing method, and more particularly to a processing method of a magnesium alloy appearance part.
Currently, portable electronic devices are required to have thin and light structures, and magnesium alloy has become a popular material for housings and parts of the portable electronic devices due to its excellent mechanical properties and lightweight. In addition, after mechanical processing (such as drilling, polishing, and laser engraving), magnesium alloy materials can show a metallic luster in appearance, thereby enabling a product to have a high-quality texture.
Since the magnesium alloy is easily corroded, its surface usually needs to be anodized for formation of an anodized film, so as to prevent the magnesium alloy from being directly exposed to the air. However, after a user contacts the product multiple times, electrochemical corrosion on the surface is still likely to occur, such that the product is unable to maintain its metallic luster for a long time.
Therefore, how to improve corrosion resistance of magnesium alloy objects through improvements in processing steps, so as to maintain lightness, thinness, functionality, and long-term corrosion resistance (the metallic luster) for overcoming the above-mentioned problems, has become an important issue yet to be solved in this field.
In response to the above-referenced technical inadequacies, the present disclosure provides a processing method of a magnesium alloy appearance part, which enables a machined surface of the magnesium alloy appearance part to have corrosion resistance and maintain a certain glossiness for a long time.
The technical concept of the present disclosure is to soak a machined magnesium alloy substrate in an anti-oxidation treatment solution for preventing a machined surface of the magnesium alloy substrate from contacting the air, so as to avoid the risk of oxidation. In addition, no acidic agent or solution is used in the processing method of the present disclosure, which is beneficial for maintaining a high gloss and corrosion resistance.
More specifically, in order to solve the above-mentioned problems, one of the technical aspects adopted by the present disclosure is to provide a processing method of a magnesium alloy appearance part, which includes: providing a magnesium alloy substrate; performing a machining process on the magnesium alloy substrate to form a machined surface on the magnesium alloy substrate; performing an antioxidant treatment on the magnesium alloy substrate after the machining process; performing an electrolysis treatment on the magnesium alloy substrate after the antioxidant treatment, so as to form a porous oxide layer on the magnesium alloy substrate; and performing an electro-sealing treatment on the magnesium alloy substrate after the electrolysis treatment to form a sealing layer on the porous oxide layer, so as to obtain the magnesium alloy appearance part. The machined surface of the magnesium alloy appearance part has a glossiness ranging from 250 GU to 450 GU and no acidic agent or solution is used in the processing method.
In one of the possible or preferred embodiments, the machining process includes applying a cutting oil to the magnesium alloy substrate, and the cutting oil does not contain water.
In one of the possible or preferred embodiments, the antioxidant treatment includes impregnating the magnesium alloy substrate in an alkaline antioxidant solution.
In one of the possible or preferred embodiments, the alkaline antioxidant solution includes 1 wt % to 50 wt % of sodium hydroxide or potassium hydroxide.
In one of the possible or preferred embodiments, an electrolytic solution used in the electrolysis treatment includes 5 wt % to 15 wt % of potassium hydroxide, and conditions of the electrolysis treatment include an operating voltage from 40 V to 80 V, a temperature from 25° C. to 40° C., and a treatment time from 20 minutes to 60 minutes.
In one of the possible or preferred embodiments, the electrolysis treatment is an anodizing treatment using a pulse current, a pulse voltage ranges from 40 V to 80V, a frequency ranges from 5,000 Hz to 100,000 Hz, a duty cycle ranges from 40% to 90%, and the treatment time ranges from 20 minutes to 60 minutes.
In one of the possible or preferred embodiments, before forming the porous oxide layer on the magnesium alloy substrate by performing the electrolysis treatment on the magnesium alloy substrate after the antioxidant treatment, the processing method further includes performing a pretreatment on the magnesium alloy substrate. The pretreatment includes alkaline degreasing, decarburization, hot alkali cleaning, or a combination thereof.
In one of the possible or preferred embodiments, before forming the sealing layer on the porous oxide layer, the processing method further includes performing a dyeing treatment on the magnesium alloy substrate. The dyeing treatment includes using an alkaline reactive dye to fill a plurality of holes in the porous oxide layer.
In one of the possible or preferred embodiments, a solid content of a resin composition used in the electro-sealing treatment ranges from 5 wt % to 20 wt %. Furthermore, conditions of the electro-sealing treatment include an operating voltage from 10 V to 100 V, a temperature from 25° C. to 35° C., and a treatment time from 1 minute to 5 minutes.
In one of the possible or preferred embodiments, the resin composition includes an epoxy resin or an acrylic resin.
Therefore, in the processing method of the magnesium alloy appearance part provided by the present disclosure, by virtue of “performing an antioxidant treatment on the magnesium alloy substrate after the machining process” and “performing an electro-sealing treatment on the magnesium alloy substrate after the electrolysis treatment to form a sealing layer on the porous oxide layer,” the risk of the machined surface of the magnesium alloy substrate being in contact with the air during processing can be reduced. Accordingly, the machined surface of the magnesium alloy appearance part has corrosion resistance, and can maintain a certain glossiness for a long time.
These and other aspects of the present disclosure will become apparent from the following description of the embodiment taken in conjunction with the following drawings and their captions, although variations and modifications therein may be affected without departing from the spirit and scope of the novel concepts of the disclosure.
The described embodiments may be better understood by reference to the following description and the accompanying drawings, in which:
The present disclosure is more particularly described in the following examples that are intended as illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. Like numbers in the drawings indicate like components throughout the views. As used in the description herein and throughout the claims that follow, unless the context clearly dictates otherwise, the meaning of “a,” “an” and “the” includes plural reference, and the meaning of “in” includes “in” and “on.” Titles or subtitles can be used herein for the convenience of a reader, which shall have no influence on the scope of the present disclosure.
The terms used herein generally have their ordinary meanings in the art. In the case of conflict, the present document, including any definitions given herein, will prevail. The same thing can be expressed in more than one way. Alternative language and synonyms can be used for any term(s) discussed herein, and no special significance is to be placed upon whether a term is elaborated or discussed herein. A recital of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification including examples of any terms is illustrative only, and in no way limits the scope and meaning of the present disclosure or of any exemplified term. Likewise, the present disclosure is not limited to various embodiments given herein. Numbering terms such as “first,” “second” or “third” can be used to describe various components, signals or the like, which are for distinguishing one component/signal from another one only, and are not intended to, nor should be construed to impose any substantive limitations on the components, signals or the like.
It should be noted that, although various steps in a flowchart of a method are described herein in a specific order, this does not indicate or imply that the steps need to be performed in that specific order, or that all steps need to be performed to achieve desired results. Optionally, multiple steps can be combined into one step for execution, or one step can be divided into multiple steps for execution.
Referring to
Referring to
First, in step S100, the provided magnesium alloy substrate 1 may be a metal containing magnesium or a combination thereof, such as magnesium alloy and magnesium-aluminum alloy. In order to shape the magnesium alloy appearance part into the desired appearance (such as casings, covers, and back plates of electronic devices), the magnesium alloy substrate 1 can first be formed into the shape substantially required for practical application by extrusion, die casting, forging, or cutting. However, the aforementioned details are not meant to limit the scope of the present disclosure.
In step S102, the machining process is performed on the magnesium alloy substrate 1 to form a machined surface 11 on the magnesium alloy substrate 1, so that the machined surface 11 can exhibit a metallic texture (having a glossiness greater than 250 GU). The machined surface 11 can be formed by using a diamond cutter to process the surface of the magnesium alloy substrate 1 under high-speed and low-feed conditions, but the present disclosure is not limited thereto. In this embodiment, the machined surface 11 is formed after the magnesium alloy substrate 1 is die-cast, subjected to a spray surface treatment, and then drilled. In some other embodiments, the machining process can also be performed by using computer numerical control (CNC) cutting. Alternatively, the magnesium alloy substrate 1 can also be polished, sandblasted, or a combination of both to obtain special surface effects. However, the aforementioned details are disclosed for exemplary purposes only, and are not meant to limit the scope of the present disclosure.
Generally speaking, a metal cutting oil is applied to metal parts during the machining process, which has the effects of cooling, lubricating, and improving processing precision. The metal cutting oil can be classified into an oily cutting oil, a water-based cutting oil, and a synthetic cutting oil. Here, the water-based cutting oil is an emulsion obtained by diluting a concentrated mineral oil with water in proportion, and the synthetic cutting oil is a mixture of polymers, organic substances, inorganic substances, and water. Since magnesium alloys are easily oxidized (whether being exposed to the air or aqueous solutions), an oxide film may be formed on the surface of the magnesium alloys, thereby resulting in a decrease of surface gloss. Therefore, in step S102, the machining process includes applying a cutting oil that does not contain water to the magnesium alloy substrate 1. That is to say, in order to maintain the high gloss of the machined surface 11, the processing method of the present disclosure uses a 100% crude oil (such as a mineral oil), which can have a higher anti-oxidation effect as compared with the water-based cutting oil and the synthetic cutting oil that contain water.
In step S104, the antioxidant treatment includes immersing the magnesium alloy substrate 1 after the machining process in an alkaline antioxidant solution, so as to prevent the machined surface 11 of the magnesium alloy substrate 1 from contacting the air and avoid the risk of oxidation. Specifically, the alkaline antioxidant solution can contain 1 wt % to 50 wt % of sodium hydroxide or potassium hydroxide. Preferably, the alkaline antioxidant solution can be 5 wt % of a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution.
In step S106, the electrolysis treatment of the magnesium alloy substrate 1 after the antioxidant treatment is performed in an electrolyzer (not shown), so as to form a porous oxide layer 2 on the magnesium alloy substrate 1. In this embodiment, the electrolysis treatment is an anodizing treatment. During the treatment process, the magnesium alloy substrate 1 is used as an anode, and is electrically connected to a positive electrode of a high-voltage power supply. A cathode (such as a stainless steel electrode) of the electrolyzer is electrically connected to a negative electrode of the high-voltage power supply. The conditions for the electrolysis treatment include an operating voltage from 40 V to 80 V, a temperature from 25° C. to 40° C., and a treatment time from 20 minutes to 60 minutes. However, the aforementioned details are disclosed for exemplary purposes only, and are not meant to limit the scope of the present disclosure.
In some other embodiments, the electrolysis treatment can be an anodizing treatment using a pulse current, so that the porous oxide layer 2 can have a relatively smooth surface. In this way, the surface of the magnesium alloy substrate can maintain a high gloss and uniformity in appearance. Furthermore, in the anodizing treatment using the pulse current, a pulse voltage is optimally 60 V, a temperature is 30±5° C. (i.e., from 25° C. to 35° C., and preferably 30° C.), the treatment time is 40 minutes (which can be 20 minutes to 60 minutes), a duty cycle is 40% to 90%, and a frequency is 5,000 Hz to 100,000 Hz.
In embodiments of the present disclosure, during the anodizing treatment using the pulse current, the pulse voltage can be 40 V, 45 V, 50 V, 55 V, or 60 V, the frequency can be 5,000 Hz, 5,500 Hz, 6,000 Hz, 6,500 Hz, 7,000 Hz, 7,500 Hz, 8,000 Hz, 8,500 Hz, 9,000 Hz, 9,500 Hz, or 100,000 Hz, and the duty cycle can be 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90%.
Referring to
Referring to
Referring to
In the embodiment of the present disclosure, the glossiness of the machined surface 11 of the magnesium alloy substrate 1 can be 250 GU, 275 GU, 300 GU, 325 GU, 350 GU, 375 GU, 400 GU, 410 GU, 420 GU, 430 GU, 440 GU, or 450 GU. The machined surface 11 of the magnesium alloy substrate 1 has gloss after the machining process. After the above-mentioned steps S100 to S108, the machined surface 11 of the magnesium alloy appearance part still maintains the gloss.
The processing method of the present disclosure will be further explained in the following examples. However, the aforementioned details are disclosed for exemplary purposes only, and are not meant to limit the scope of the present disclosure.
A die-cast AZ91D magnesium alloy object is CNC drilled under the condition of applying a 100% oily cutting oil, and a machined surface on the magnesium alloy object can have a glossiness of 420 GU. The magnesium alloy object is transferred and immersed in 5 wt % of the sodium hydroxide aqueous solution, and is then cleaned (i.e., alkaline degreasing at 50° C. for 1 minute, decarbonizing at a room temperature for 2 minutes, and then hot alkaline washing at 70° C. for 2 minutes). After cleaning, the magnesium alloy object is immersed in an electrolytic solution containing 5 wt % of the potassium hydroxide. A pulse anodizing treatment is performed with the magnesium alloy object as the anode and a carbon plate or stainless steel plate as the cathode. The pulse voltage is 40 V, the frequency is 9,000 Hz, the duty cycle is 90%, and the treatment time is 20 minutes. The magnesium alloy object is then dried at 100° C. for 15 minutes. With the magnesium alloy object as the cathode and stainless steel as the anode, a resin composition containing a cationic epoxy resin (its solid content is 10%) is used to perform electrical-sealing under the following conditions. The operating voltage is 60 V, and the duration time is 1 minute. Then, the coating film is hardened by baking at a baking temperature of 120° C. and a baking time of 3 hours. After completion, the magnesium alloy object can obtain a transparent machined surface having a high gloss and corrosion resistance.
A die-cast magnesium alloy object is CNC drilled under the condition of applying a 100% oily cutting oil, and a machined surface on the magnesium alloy object can have a glossiness of 450 GU. The magnesium alloy object is transferred and immersed in 15 wt % of the potassium hydroxide aqueous solution, and is then cleaned (i.e., alkaline degreasing at 50° C. for 1 minute, decarbonizing at a room temperature for 2 minutes, and then hot alkaline washing at 70° C. for 2 minutes). After cleaning, the magnesium alloy object is immersed in an electrolytic solution containing 10 wt % of the potassium hydroxide. A pulse anodizing treatment is performed with the magnesium alloy object as the anode and a carbon plate or stainless steel plate as the cathode. The pulse voltage is 60 V, the frequency is 4,500 Hz, the duty cycle is 95%, and the treatment time is 25 minutes. The magnesium alloy object is then immersed in a commercial reactive dye (its pH value being controlled at 9) for the dyeing treatment. With the magnesium alloy object as the cathode and stainless steel as the anode, a resin composition containing a cationic epoxy resin (its solid content is 10%) is used to perform electrical-sealing under the following conditions. The operating voltage is 60 V, and the duration time is 1 minute. Then, the coating film is hardened by baking at a baking temperature of 120° C. and a baking time of 3 hours. After completion, the magnesium alloy object can obtain a machined surface having a blue appearance, a high gloss, and corrosion resistance.
A die-cast AZ91D magnesium alloy object is CNC drilled under the condition of applying a 100% oily cutting oil, and a machined surface on the magnesium alloy object can have a glossiness of 440 GU. The magnesium alloy object is transferred and immersed in 20 wt % of the sodium hydroxide aqueous solution, and is then cleaned (i.e., alkaline degreasing at 50° C. for 1 minute, decarbonizing at a room temperature for 2 minutes, and then hot alkaline washing at 70° C. for 2 minutes). After cleaning, the magnesium alloy object is immersed in an electrolytic solution containing 12 wt % of the potassium hydroxide. A pulse anodizing treatment is performed with the magnesium alloy object as the anode and a carbon plate or stainless steel plate as the cathode. The pulse voltage is 80 V, the frequency is 5,000 Hz, the duty cycle is 50%, and the treatment time is 20 minutes. The magnesium alloy object is then dried at 100° C. for 15 minutes. With the magnesium alloy object as the cathode and stainless steel as the anode, a resin composition containing an anionic epoxy resin (its solid content is 14%) is used to perform electrical-sealing under the following conditions. The operating voltage is 20 V, and the duration time is 2 minutes. Then, the coating film is hardened by baking at a baking temperature of 120° C. and a baking time of 3 hours. After completion, the magnesium alloy object can obtain a transparent machined surface having a high gloss and corrosion resistance.
A die-cast AZ91D magnesium alloy object is CNC drilled under the condition of applying a 100% oily cutting oil, and a machined surface on the magnesium alloy object can have a glossiness of 40 GU. The magnesium alloy object is transferred and immersed in 5 wt % of the sodium hydroxide aqueous solution, and is then cleaned (i.e., alkaline degreasing at 50° C. for 1 minute, decarbonizing at a room temperature for 2 minutes, and then hot alkaline washing at 70° C. for 2 minutes). After cleaning, the magnesium alloy object is immersed in an electrolytic solution containing 20 wt % of the potassium hydroxide. A pulse anodizing treatment is performed with the magnesium alloy object as the anode and a carbon plate or stainless steel plate as the cathode. The pulse voltage is 40 V, the frequency is 8,000 Hz, the duty cycle is 80%, and the treatment time is 40 minutes. The magnesium alloy object is then immersed in a commercial reactive dye (its pH value being controlled at 10) for the dyeing treatment. With the magnesium alloy object as the cathode and stainless steel as the anode, a resin composition containing an anionic epoxy resin (its solid content is 10%) is used to perform electrical-sealing under the following conditions. The operating voltage is 20 V, and the duration time is 2 minutes. Then, the coating film is hardened by baking at a baking temperature of 120° C. and a baking time of 3 hours. After completion, the magnesium alloy object can obtain a machined surface having a yellow-red appearance, a high gloss, and corrosion resistance.
A salt spray test is an artificially accelerated salt spray corrosion resistance assessment method. In this test, parameters of the MIL-STD-810F standard are used as test conditions to conduct tests on Examples 1 to 4. Firstly, an object to be tested (i.e., magnesium alloy appearance parts of Examples 1 to 4) is placed at 35±2° C. for at least 2 hours, and then 5±1 wt % of a salt spray (at a sedimentation rate of from 1 mL/80 cm3/h to 4 mL/80 cm3/h) is added, so that the object to be tested is surrounded by the salt spray. According to the provisions of the test plan, the test is carried out with a test cycle of 24 hours of spraying the salt spray/24 hours of drying/24 hours of spraying the salt spray/24 hours of drying. As for a conversion between the salt spray test and the actual number of days, a 24-hour salt spray test is approximately equivalent to 120 days in the coastal environment, or equal to the number of days in the natural environment in one year (365 days). The results of the salt spray test show that there is no corrosion in the appearance of Examples 1 to 4. Hence, the magnesium alloy appearance parts obtained by the processing method of the present disclosure are proven to have a high salt spray resistance (corrosion resistance) effect.
In conclusion, in the processing method of the magnesium alloy appearance part provided by the present disclosure, by virtue of “performing an antioxidant treatment on the magnesium alloy substrate after the machining process” and “performing an electro-sealing treatment on the magnesium alloy substrate after the electrolysis treatment to form a sealing layer on the porous oxide layer,” the risk of the machined surface of the magnesium alloy substrate being in contact with the air during processing can be reduced. Accordingly, the machined surface of the magnesium alloy appearance part has corrosion resistance, and can maintain a certain glossiness for a long time.
Furthermore, in the present disclosure, a water-free cutting oil is applied during the machining process. In this way, the machined surface of the magnesium alloy substrate will not be easily oxidized.
Moreover, in the processing method of the magnesium alloy appearance part provided by the present disclosure, no acidic agent is used in any processing step. Hence, the surface of the magnesium alloy appearance part can be effectively prevented from oxidation, fogging, and dulling due to the processing steps.
The foregoing description of the exemplary embodiments of the disclosure has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching.
The embodiments were chosen and described in order to explain the principles of the disclosure and their practical application so as to enable others skilled in the art to utilize the disclosure and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present disclosure pertains without departing from its spirit and scope.
| Number | Date | Country | Kind |
|---|---|---|---|
| 112116222 | May 2023 | TW | national |
