WO2021051297A1

WO2021051297A1 - Cutting fluid for chamfering

Info

Publication number: WO2021051297A1
Application number: PCT/CN2019/106350
Authority: WO
Inventors: Qingyong GUO; Yongyong Xu; Yacheng CHUANG; Kuan-Ting Wu
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2019-09-18
Filing date: 2019-09-18
Publication date: 2021-03-25

Abstract

Example of a cutting fluid (106) for chamfering(103) is described. In an example, a cutting fluid (106) includes at least one silicate in an amount of from about 0.5 wt% to about 3.0 wt% based on the total weight of the cutting fluid (106); at least one base in an amount of from about 1.0 wt% to about 5.0 wt% based on the total weight of the cutting fluid (106); and at least one phosphate in an amount of from about 0.5 wt% to about 2.0 wt% based on the total weight of the cutting fluid (106), wherein the cutting fluid (106) has a pH of from about 9 to about 13.

Description

CUTTING FLUID FOR CHAMFERING

BACKGROUND

Electronic devices, such as mobile phones, tablets, laptops, and the like are housed within a casing that is manufactured to exhibit desired physical properties and appearance. Casings made up of Mg alloy may be chamfered at one or more peripheral edges for enhancing both visual and tactile appeal. Chamfering in presence of cutting fluid greatly reduces the frictional resistance in both metal deformation and in chip formation, as well as reducing the heat produced in overcoming friction.

BRIEF DESCRIPTION OF DRAWINGS

The following detailed description references the drawings, wherein:

Fig. 1 illustrates a schematic showing a process for forming a chamfered substrate, according to an example of the present disclosure;

Fig. 2 illustrates a flow chart showing a process for forming a Mg alloy casing comprising the passivation of Mg alloy substrate by chemical treatment, according to an example of the present disclosure;

Fig. 3 illustrates a flow chart showing a process for forming a Mg alloy casing comprising the passivation of Mg alloy substrate by electro-chemical treatment, according to another example of the present disclosure

Fig. 4 illustrates a flow chart showing a process for forming a Mg alloy casing comprising second passivation by chemical treatment, according to another example of the present disclosure;

Fig. 5 illustrates a flow chart showing a process of forming a Mg alloy casing comprising second passivation by electrolytic treatment, according to another example of the present disclosure.

Fig. 6 illustrates a process for forming a chamfered substrate with chamfered edge 602 in presence of a cutting fluid, according to another example of the present disclosure.

DETAILED DESCRIPTION

Definitions

For convenience, before further description of the present disclosure, certain terms employed in the specification, and examples are described here. These definitions should be read in the light of the remainder of the present disclosure. The terms used herein have the meanings recognized and known to those of skilled in the art, however, for convenience and completeness, particular terms and their meanings are set forth below.

The articles “a” , “an” , and “the” are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article.

The term “about” when referring to a numerical value is intended to encompass the values resulting from variations that can occur during the normal course of performing a method. Such variations are usually within plus or minus 5 to 10 percent of the stated numerical value.

The term “alloy” refers to the class material that may be referred to as a solid solution of metals. The alloy in the present disclosure refers to a magnesium alloy selected from AZ91D, AZ31B, LZ91, ALZ991, AZ60, AZ61, AZ63, AZ80, AZ81, AZ92, AM50, AM60, AM100, LZ141, ALZ691, or combinations thereof.

The term “substrate” , used herein refers to a metal enclosure or body for electronic devices made up of Mg alloy that is usable to obtain the casing of the present disclosure. The substrate may be corrosion resistant. The substrate may further include a passivating layer, a finishing layer, or any other layer employed by a known process, so as to obtain a patterned surface.

The term "finishing layer" used herein refers to a coating provided on the underlying substrate which also provide various useful features, such as a certain degree of wear resistance, scratch resistance, anti-tarnish and/or corrosion resistance, in addition to providing aesthetic appeal. Such coatings may also be used for other functional purposes, such as increasing the strength of cutting edge, or to improve abrasion resistance of the surface.

The term “chamfered substrate” used herein refers to substrates obtained after chamfering of the Mg alloy substrate, with or without a passivation layer or finishing layer. The chamfering may be carried out at suitable regions such as edges, sidewall region, fingerprint scanner region, clickpad region, among others. The chamfering may be carried out in presence of a cutting fluid having a pH of from about 9 to about 13. Chamfering in presence of cutting fluid may assist in preventing discoloration and formation of corrosion spots on the Mg alloy substrate, so as to obtain a chamfered substrate with high gloss finish at the edges. Chamfering may be carried out by a computerized numerical control (CNC) diamond cutting machine. Chamfering may be carried out at a speed of from about 300 mm/minute to 2000 mm /minute.

The term “alkaline chemical 606” used herein refers to an aqueous solution having pH of from about 9 to about 13. The alkaline chemical may comprise sodium hydroxide and sodium carbonate in an amount of from about 0.5 -3.0 wt %based on the total weight of the alkaline chemical. The alkaline chemical may comprise sodium hexametaphosphate and sodium phosphate in an amount of from about 0.3 -2.0 wt %based on the total weight of the alkaline chemical. The alkaline chemical may comprise surfactants selected from diethanolamine, diglycolamine, ethylenediamine, or triethanolamine in an amount of from about 0.3 -5.0 wt %based on the total weight of the alkaline chemical.

The term “high gloss finish” used herein refers to chamfered surfaces (in particular the edges) of the substrate that reveal shiny edges. It also includes the chamfered appearance.

The phrase “chelating agent and salts thereof” used herein refers to metal salt of a chelating agent selected from ethylenediaminetetraaceticacid, ethylendiamine, nitriloacetic acid, diethylenetriaminepenta (methylenephosphonic acid) , nitrilotris (methylenephosphonic acid) , or 1-hydroxyethane-1, 1-diphosphonic acid. The metal may be selected from aluminum, nickel, chromium, tin or zinc. In an example, the at least one chelating agent may be selected from zinc (II) EDTA complex, nickel (II) EDTA complex, and the like.

Casing of electronic devices are made of metal alloy substrate, in which both strength and aesthetic appeal are desirable. Metal alloys, such as magnesium alloy substrates are prone to corrosion and, also suffer from poor tensile strength. However, their Iow density and compatibility with associated techniques, such as spray coating and/or electrophoretic deposition makes such alloys attractive choices for enhancing the aesthetic appeal of casings. Based on the application, selected portions of the casing of the electronic devices, may be chamfered or otherwise trimmed for aesthetic and/or tactile purposes. Chamfering however, may lead to discoloration and formation of corrosion spots (white spots) on the metal alloy substrate.

While, enhancement of aesthetics is desirable for electronic device casing, the aesthetically pleasing rounded edges of laptops, tablets, mobile phones and the like, are noted to possess relatively inferior gloss finish, owing to surface corrosion occurring on chamfered areas of magnesium alloy materials. In the process of chamfering a reactive metal, appropriate choice of cutting fluid may play a role in lubrication, cooling, cleaning and rust-removal, thereby improving the tool life, chamfering accuracy and chamfering quality, increasing productivity, and reduced costs.

The present subject matter describes examples of a cutting fluid comprising: (a) at least one silicate in an amount of from about 0.5 wt %to about 3.0 wt %based on the total weight of the cutting fluid; (b) at least one base in an amount of from about 1.0 wt %to about 5 wt %based on the total weight of the cutting fluid; and (c) at least one phosphate in an amount of from about 0.3 wt %to about 2.0 wt %based on the total weight of the cutting fluid, wherein the cutting fluid has a pH of from about 9 to about 13. In an example, chamfering a Mg alloy substrate in presence of the cutting fluid greatly reduces the frictional resistance in both metal deformation and in chip formation, as well as reducing the heat produced in overcoming friction.

The substrate on which chamfering may be done may be made up of Mg alloys selected from AZ31, AZ31B, AZ61, AZ60, AZ80, AM60, AZ91D, LZ91, LZ141, ALZ691, ALZ931, or combinations thereof. The Mg alloy substrate may be of a thickness from about 0.3 mm to about 2.0 mm. In an example, the Mg alloy substrate may have a thickness from about 0.5 mm to about 1.8 mm. In another example, the alloy substrate 102, may have a thickness from about 0.5 mm to about 0.8 mm. In another example, the alloy substrate 102, may have a thickness of about 0.6 mm. The alloy substrate having a thickness beyond 2.0 mm leads to substrates that are unsuitable for forming casing of electronic devices owing to excess weight. On the other hand, an alloy substrate having a thickness lower than 0.3 mm is too weak and mechanically unstable. In an example, the tensile strength of the alloy substrate may be of from about 800 to about 1200 MPa as measured by American Society for Testing and Materials (ASTM) D790. The alloy may be a magnesium alloy selected from AZ31, AZ31B, AZ61, AZ60, AZ80, AM60, AZ91D, LZ91, LZ141, ALZ691, ALZ931, or combinations thereof. Further, the Mg alloy is readily usable in processing techniques, such as electrophoretic deposition or spray coating, thus allowing relatively easy deposition of a finishing layer that can provide enhancement of aesthetic appeal of the thus obtained Mg alloy casing. Said enclosure is particularly suitable for electronic devices.

The aesthetic quality of thus obtained casing may be quantified by measuring a gloss value. In an example, the gloss value of the chamfered enclosure may be of from about 80 to about 100 units as measured by American Society for Testing and Materials (ASTM) D523 at a viewing angle of about 20°. This is found to be a clear enhancement from the unchamfered enclosures that result in a gloss value of from about 60 to about 75 units as measured by American Society for Testing and Materials (ASTM) D523 at a viewing angle of about 60°. In another example, the gloss value of the chamfered surface decoration layer may be of from about 87 to about 95 units as measured by ASTM D523 at a viewing angle of about 20°.

The following detailed description refers to the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the following description to refer to the same or similar parts. While several examples are described in the description, modifications, adaptations, and other implementations are possible. Accordingly, the following detailed description does not limit the disclosed examples. Instead, the proper scope of the disclosed examples may be defined by the appended claims.

Fig. 1 illustrates a schematic 100 showing a process for forming a chamfered substrate, according to an example of the present disclosure. As shown in Fig. 1 the Mg alloy substrate 102, may be subject to chamfering 103, at a portion in the presence of a cutting fluid 106, which has a pH of from about 9 to about 13, to obtain a chamfered substrate 104. In an example, the chamfering 103, may be carried out at portions such as edges, side wall, fingerprint scanner, clickpad, among others of the substrate 102. In an example, the chamfering 103, in presence of the cutting fluid 106, may result in an enhanced gloss value of from about 80 to about 100 units as measured by American Society for Testing and Materials (ASTM) D523 at a viewing angle of about 20°. In an example, the chamfering 103, in presence of the cutting fluid 106, may result in a gloss value of from about 85 to about 95 units. In another example, the chamfering 103, in presence of the cutting fluid 106, may result in a gloss value of about 85 units. In an example, the chamfering 103, in presence of cutting fluid 106, may avoid discoloration and formation of corrosion spots (white spots) on the Mg alloy substrate. Although depicted as a block, the Mg alloy substrate 102, in an example, may be of any pattern, shape, and structure, depending on the application.

Further, chamfering 103, of the Mg alloy substrate in presence of the cutting fluid 106, may provide high gloss finish at the edges. Chamfering may be carried out by a CNC diamond cutting machine or a laser engraving machine. In an example, the chamfering may be carried out with a laser engraving machine having a Nd: YAG laser under a laser power from about 20 to about 200 W and an engraving speed from about 100 to about 300 mm/minute. In another example, the laser etching may be carried out under a laser power of from about 50 to about 150 W and an engraving speed from about 120 to about 280 mm/minute. In another example, the laser etching may be carried out at a laser power of about 100 W and an engraving speed of about 200 mm/minute. In another example, the chamfering may be carried out with a CNC diamond cutting machine at speed from about 5,000 to about 90,000 rpm. In an example, chamfering in presence of the cutting fluid 106 results in an etching that reveals the underlying shiny Mg alloy surface. In an example, the substrate is subjected to chamfering using a CNC laser machine.

In an example, the Mg alloy substrate 102, may be cleaned, washed, polished, degreased, and/or activated before chamfering. The Mg alloy substrate 102, may be chemically cleaned using an alkaline agent, for example, sodium hydroxide. The Mg alloy substrate 102, may be washed in a buffer solution. The cleaning and washing of the metal substrate may help in removing foreign particles, if any, present on the surface of the Mg alloy substrate. Further, the Mg alloy substrate may be chemically polished using abrasives to remove irregularities that may be present on the surface of the Mg alloy substrate. The Mg alloy substrate may also be degreased through ultrasonic degreasing to remove impurities, such as fat, grease, or oil from the surface of the Mg alloy. Further, the Mg alloy substrate may also be activated through acid treatment for removing the natural oxide layer, if any, present on the surface of the Mg alloy substrate.

In an example, the Mg alloy substrate 102, may be of a thickness of from about 0.3 mm to 2.0 mm. In another example, the Mg alloy substrate 102, may be of a thickness of from about 0.5 to 1.8 mm. In another example, the Mg alloy substrate 102, may be of a thickness of 0.7 mm.

In an example, the Mg alloy which is used to prepare the Mg alloy substrate 102, may be selected from AZ31, AZ31B, AZ61, AZ60, AZ80, AM60, AZ91D, LZ91, LZ14, ALZ691, ALZ931, or combinations thereof. In an example, the alloy 104, may be AZ91D. In another example, the Mg alloy 102, may be made of AZ31B.

In an example, Mg alloy substrate 102, may include a passivation layer. The passivation layer may be formed on a portion or on the entire surface of Mg alloy substrate. In an example, the passivation layer may have a thickness of from about 1.0 μm to about 15.0 μm. In another example, the passivation layer may have a thickness of from about 2.0 μm to about 12.0 μm.

In an example, the Mg alloy substrate 102, including the passivation layer may be of a thickness of from about 0.3 mm to 2.0 mm. In another example, the Mg alloy substrate 102, including the passivation layer may be of a thickness of from about 0.5 to 1.8 mm. In another example, the Mg alloy substrate 102, including the passivation layer may be of a thickness of 0.7 mm.

In an example, the Mg alloy substrate 102, may include a finishing layer. The finishing layer may be formed on to the passivation layer which is present on the Mg alloy substrate or may be directly formed on the Mg alloy substrate 102. The finishing layer may have a thickness of from about 15.0 μm to about 65.0 μm. In another example, the finishing layer may have a thickness of from about 30.0 μm to about 60.0 μm.

In an example, the Mg alloy substrate 102, including the finishing layer may be of a thickness of from about 0.3 mm to 2.0 mm. In another example, the Mg alloy substrate 102, including the finishing layer may be of a thickness of from about 0.5 to 1.8 mm. In another example, the Mg alloy substrate 102, including the finishing layer may be of a thickness of 0.7 mm.

In an example, the Mg alloy substrate 102, may include both, a passivation layer as well as the finishing layer. In another example, the Mg alloy substrate 102, including the passivation layer and the finishing layer may be of a thickness of from about 0.3 mm to 2.0 mm. In another example, the Mg alloy substrate 102, including the passivation layer and the finishing layer may be of a thickness of from about 0.5 to 1.8 mm. In another example, the Mg alloy substrate 102, including the passivation layer and the finishing layer may be of a thickness of 0.7 mm.

In an example, the Mg alloy substrate 102, before chamfering 103, may be deposited with a passivation layer and/or finishing layer for providing corrosion resistance, wear resistance, and to obtain a desired appearance.

As shown in Fig. 1, the chamfering 103, is carried out in the presence of a cutting fluid 106. In an example, the cutting fluid 106, comprises at least one silicate in an amount of from about 0.5 %to about 3.0 %based on the total weight of the cutting fluid. In an example, the cutting fluid 106, comprises at least one silicate in an amount of from 1.0 %to about 2.5 %based on the total weight of the cutting fluid. In an example, the cutting fluid 106, comprises at least one silicate is in an amount of 2.0 %.

In an example, the cutting fluid 106, may have a pH of from about about 9 to about 13. In another example, the cutting fluid 106, may have a pH of from about about 10 to about 12. In another example, the cutting fluid 106, may have a pH of 11.

In an example the cutting fluid comprises (a) at least one silicate in an amount of from about 0.5 wt %to about 3.0 wt %based on the total weight of the cutting fluid; (b) at least one base in an amount of from about 1.0 wt %to about 5 wt %based on the total weight of the cutting fluid; and (c) at least one phosphate in an amount of from about 0.3 wt %to about 2.0 wt %based on the total weight of the cutting fluid, wherein the cutting fluid has a pH of from about 9 to about 13. In an example, the cutting fluid 106, may effectively maintain the metallic luster of the chamfered surface.

Additional suitable surface treatments, including surface treatments, such as, passivation layer, finishing layer, a second passivation layer including transparent chemical passivation treatment or electrolytic passivation treatment may be applied to Mg alloy substrate 102, or the chamfered substrate 104. Examples of setups and procedures used for the treatment on the Mg alloy substrate 102, are described in detail with reference to Fig. 2, Fig. 3, Fig. 4, Fig. 5 and Fig. 6. In another example, the chamfered substrate 104, may have chamfered edges 604, on to which surface treatments may be done.

Further details of the process of forming a Mg alloy casing for an electronic device 200, is described with reference to Fig. 2. Fig. 2 illustrates a flow chart showing a process for obtaining a Mg alloy casing comprising the passivation of Mg alloy substrate by chemical treatment, according to an example, of the present disclosure. The chemical treatment, i.e., dip coating may be done for a period of from about 20 seconds to about 180 seconds. In an example, the passivation process 202, may be carried out by a process of dip coating for a period of from about 40 seconds to about 90 seconds. In an example, the passivation process 202, may be carried out by dip coating may have a thickness of from about 1 μm to about 5 μm. In another example, the passivation process 202, may be carried out by dip coating may have a thickness of from about 1.5 μm to about 4.5 μm.

In an example, the passivation process 202, may be carried out by dip coating in the presence of at least one salt of manganese, molybdates, vanadate, phosphate, chromate, stannate, and combinations thereof to obtain a passivated Mg alloy substrate. In another example, the passivation process 202, may be carried out by dip coating in the presence of at least one salt of manganese. In an example, the salt may be dispersed in the form of an aqueous solution having a concentration of from about 3%to about 15%based on total weight. In an example, the salt may be dispersed in the form of an aqueous solution having a concentration of from about 5%to about 12%based on total weight.

Further, the passivated Mg alloy substrate may be cleaned, washed, polished, degreased, and/or activated, in a manner as described above, before the deposition process 204, i.e., depositing a finishing layer on the passivated Mg alloy substrate to obtain a finished Mg alloy substrate.

As shown in Fig. 2 the deposition process 204, may be carried out for obtaining a finished Mg alloy substrate by depositing a finishing layer on the passivated Mg alloy substrate. In an example, the depositing process may be carried out by spray coating or electrophoretic deposition.

In an example, depositing process 204, carried out by spray coating may result in a finishing layer having a thickness of from about 25.0 μm to about 65.0 μm. In another example, depositing process 204, carried out by spray coating may result in a finishing layer having a thickness of from about 25.0 μm to about 60.0 μm. In another example, depositing process 204, carried out by spray coating may result in a finishing layer having a thickness of from about 35.0 μm to about 55.0 μm. In another example, depositing process 204, carried out by spray coating may result in a finishing layer having a thickness of about 44.0 μm.

The depositing process 204, carried out by spray coating may be carried out in a manner, whereby the finishing layer thus formed may comprise multiple layers, such as primer, base coat and top coat. In an example, the spray coated finishing layer comprises sequentially deposited coats of primer having a thickness of from about 5.0 μm to about 20.0 μm, followed by base coat having a thickness of from about 10.0 μm to about 20.0 μm, followed by top coat having a thickness of from about 10.0 μm to about 25.0 μm.

The passivated Mg alloy substrate may be cleaned, dried, degreased and washed prior to deposition of the finishing layer 206. The finishing layer may comprise primer, either alone or in combination with one or more other layers. The primer may also be applied as single or multiple coats to achieve desired thickness and finish. In an example, the primer may have a thickness of from about 5.0 μm to about 20.0 μm. In another example, the primer may have a thickness of from about 8.0 μm to about 18.0 μm. In another example, the primer may have a thickness of about 12.0 μm. In an example, the primer may be deposited on the passivated Mg alloy substrate by spray coating polyurethanes followed by heat treatment at a temperature of from about 60 ℃ to about 80 ℃ for period of from about 15 to about 40 minutes. In another example, the primer may be deposited by spray coating polyurethane followed by heat treatment at a temperature of from about 62 ℃ to about 78 ℃ for period of from about 18 to about 38 minutes. In another example, the primer may be deposited by spray coating thermoplastics, such as polyurethanes followed by heat treatment at a temperature of about 70 ℃ for period of about 25 minutes.

In an example, the finishing layer may comprise base coat, in combination with one or more other layers. The base coat may also be applied as single or multiple coats to achieve desired thickness and finish. In an example, the base coat may have a thickness of from about 10.0 μm to about 20.0 μm. In another example, the base coat may have a thickness of from about 12.0 μm to about 18.0 μm. In another example, the base coat may have a thickness of about 15.0 μm. In an example, the base coat may be a polyurethane containing pigments selected from carbon black, titanium dioxide, clay, mica, talc, barium sulfate, calcium carbonate, aluminum oxide, plastic bead, dyes, and combinations thereof. In an example, the spray coated base coat comprises polyurethane containing carbon black. In another example, the spray coated base coat comprises polyurethane containing titanium dioxide. In another example, the spray coated base coat comprises polyurethane containing clay.

In another example, the base coat deposited by spray coating may be followed by heat treatment at a temperature of from about 60 ℃ to about 80 ℃ for period of from about 15 to about 40 minutes. In another example, the base coat deposited by spray coating may be followed by heat treatment at a temperature of from about 62 ℃ to about 78 ℃ for period of from about 18 to about 38 minutes. In another example, the base coat deposited by spray coating may be followed by heat treatment at a temperature of about 70 ℃ for period of about 25 minutes.

The finishing layer may comprise top coat, in combination with one or more other layers. The top coat may also be applied as single or multiple coats to achieve desired thickness and finish. In an example, the top coat may have a thickness of from about 10.0 μm to about 25.0 μm. In another example, the top coat may have a thickness of from about 12.0 μm to about 22.0 μm. In another example, the top coat may have a thickness of about 17.0 μm. In an example, the top coat may be made of polyacrylic acid, polyurethane, urethane acrylates, acrylic acrylates, epoxy acrylates, or combinations thereof. In an example, the top coat is made of polyacrylic acid. In another example, the top coat may be made of polyurethane. In another example, the top coat may be made of urethane acrylates.

In an example, the top coat deposited by spray coating may be followed by UV treatment of from about 700 mJ/cm ² to about 1200 mJ/cm ² for a period of from about 10 seconds to about 30 seconds. In another example, the top coat deposited by spray coating may be followed by UV treatment of from about 800 mJ/cm ² to about 1100 mJ/cm ² for a period of from about 15 seconds to about 25 seconds. In another example, the top coat deposited by spray coating may be followed by UV treatment of about 950 mJ/cm ² for a period of about 20 seconds.

In another example, the top coat deposited by spray coating a polyurethane may be followed by heat treatment at a temperature of from about 60 ℃ to about 80 ℃ for period of from about 15 to about 40 minutes. In another example, the base coat deposited by spray coating may be followed by heat treatment at a temperature of from about 62 ℃ to about 78 ℃ for period of from about 18 to about 38 minutes. In another example, the base coat deposited by spray coating may be followed by heat treatment at a temperature of about 70 ℃ for period of about 25 minutes.

The depositing process 204, may be carried out by electrophoretic deposition. In an example, an electrophoretic deposition may be carried out subsequent to formation of the passivation layer to introduce colors and to provide aesthetically improved finish prior to chamfering. In an example the electrophoretic deposition may be carried out on the Mg alloy substrate 102, to introduce colors and to provide aesthetically improved finish prior to chamfering. In an example, the electrophoretic deposition may result in deposition of a finishing layer having a thickness of from about 15.0 μm to about 40.0 μm. In another example, the electrophoretically deposited finishing layer may have a thickness of from about 17.0 μm to about 38.0 μm. In another example, the electrophoretically deposited finishing layer may have a thickness of from about 20.0 μm to about 35.0 μm. In another example, the electrophoretically deposited finishing layer may have a thickness of about 20 μm.

The thickness of the finishing layer achieved may be directly related to the potential applied and time for electrophoretic deposition. In an example, the electrophoretic deposition may be carried out by applying a potential of from about 30 to about 150 V for a period of from about 25 to about 120 seconds. In another example, the electrophoretic deposition may be carried out by applying a potential of from about 50 to about 130 V for a period of from about 40 to about 100 seconds. In another example, the electrophoretic deposition may be carried out by applying a potential of about 120 V for a period of about 80 seconds.

The finishing layer deposited by electrophoretic deposition may comprise various dyes selected from red dye, blue dye, orange dye, yellow dye: Quinoline Yellow WS to obtain different colors at portions such as edges, side wall, fingerprint scanner, clickpad, among others. In an example, to obtain red colored finish, red dye may be used and may be selected from Alexa Fluor 594 dye, or Texas Red. In another example to obtain red color a pigment may be used, such as pigment Red 168 MF. In an example to obtain blue colored finish, blue dye may be used, such as Pacific Blue dye. In an example, to obtain orange colored finish, orange dye may be used, such as Pacific Orange. In an example, to obtain yellow colored finish a yellow dye may be used, such as quinoline yellow WS. In another example, to obtain yellow color a pigment may be used, such as Pigment Yellow 191.

In an example, the process for forming Mg alloy casing 200, comprises chamfering 103, a portion of the finished Mg alloy substrate in presence of cutting fluid 106, to obtain an exposed surface. In an example, the chamfering 103, may be carried out at portions such as edges, side wall, fingerprint scanner, clickpad, among others. The process of chamfering 103, may be used to chamfer a portion of the finished Mg alloy substrate, as described above in the description of Fig. 1, so as to obtain the exposed surface.

In an example, the process for forming Mg alloy casing 200, comprises contacting the exposed surface with an alkaline chemical in a chemical bath by a process 208. The alkaline chemical 606, as shown in Fig. 6, has been described in greater detail below. The exposed surface obtained after chamfering a portion of the finished Mg alloy substrate in presence of the cutting fluid (having a pH of from about 9 to about 13) , is immersed in alkaline chemical 606. The alkaline chemical 606, has a pH of from about 9 to about 13. After immersing the exposed surface in the alkaline chemical 606, it may be kept immersed for a period of from about 120 minutes to about 240 minutes. In an example, the degreasing process may be carried out after immersing the exposed surface in the alkaline chemical. In an example, chamfering may be done at, at least a portion of the Mg alloy substrate in presence of cutting fluid 106, to obtain an exposed surface.

In an example, the exposed surface obtained after chamfering in the presence of the cutting fluid may also be degreased by a degreasing process through ultrasonic degreasing to remove impurities (not shown in Fig. 2) , such as fat, grease, or oil from the surface of the exposed surface. The chemicals used in the degreasing process may be selected from sodium caseinate, sodium polyacrylate, sodium polyoxyethylene alkyl ether carboxylate, sodium dodecyl sulfate, or combinations thereof. In an example, the chemicals used in degreasing process may be dispersed in de-ionized water to form an aqueous solution. In an example, the concentration of the aqueous solution used in degreasing process may be from about 1.0 wt %to about 10.0 wt %based on the total weight. In another example, the concentration of the chemical used in degreasing process may be from about 3.0 wt %to 8.0 wt %based on the total weight. In another example, the concentration of the chemical used in degreasing process may be 6 wt %based on the total weight. In an example, the degreasing process may be carried out in a bath comprising the aqueous solution. In an example, the degreasing process may be carried out for a period from about 30 seconds to about 180 seconds at a temperature of from about 25℃ to about 60 ℃. In another example, the degreasing process may be carried out for a period from about 50 seconds to about 160 seconds at a temperature of from about 25℃ to about 60 ℃. In another example, the degreasing process may be carried out for a period from about 30 seconds to about 60 seconds at a temperature of from about 25℃ to about 60 ℃.

In an example, the degreasing process as described above may be carried out after the step of immersing the exposed surface in the alkaline chemical 606 to obtain Mg alloy casing.

In an example, the Mg alloy casing obtained by the process 200, detailed in Fig. 2 may be employed as frames or bodies of electronic devices, such as tablets, mobile phones, smart watches, laptops, and the like.

In an example, the process for forming Mg alloy casing 300, is illustrated in Fig. 3 wherein the flow chart shows a process for obtaining a Mg alloy casing comprising the passivation of Mg alloy substrate by electro-chemical treatment, according to another example of the present disclosure. The passivation process 302, i.e., passivating the Mg alloy substrate to obtain a passivated Mg alloy substrate, may be carried out by electrochemical treatment, i.e., micro-arc oxidation carried out at voltage of from about 150 V to about 550 V at a temperature of from about 10 ℃ to about 45℃ for a period of from about 2 minutes to about 25 minutes. In another example, the passivation process 302 may be carried out by micro arc oxidation carried out at voltage of from about 180 V to about 520 V at a temperature of from about 12 ℃ to about 42℃ for a period of from about 5 minutes to about 22 minutes. In another example, the passivation process 302 may be carried out by micro arc oxidation carried out at voltage of from about 250 V to about 400 V at a temperature of from about 12 ℃ to about 42℃ for a period of from about 5 minutes to about 22 minutes.

In an example, the passivation process 302, carried out by micro arc oxidation may form passivated Mg alloy substrate having a passivation layer with a thickness of from about 2 μm to about 15 μm. In another example, the passivation process 302, carried out by micro-arc oxidation may form a passivation layer having a thickness of from about 4 μm to about 12 μm. In another example, the passivation process 302, carried out by micro-arc oxidation may form a passivation layer having a thickness of from about 3 μm to about 7 μm.

In an example, the passivation process 302, carried out by micro arc oxidation may be carried out in the presence of at least one chemical selected from sodium silicate, metal phosphates, potassium fluoride, potassium hydroxide, sodium hydroxide, fluorozirconates, sodium hexametaphosphate, sodium fluoride, ferric ammonium oxalate, phosphoric acid salt, graphite powder, silicon dioxide powder, aluminum oxide powder, and combinations thereof. In an example, the chemical may be employed at a dosage of from about 0.05%to about 15%in the presence of water at a pH of from about 9 to about 13. In another example, the chemical may be employed at a dosage of from about 0.1%to about 12%in the presence of water at a pH of from about 9.0 to about 13. In another example, the chemical may be employed at a dosage of from about 0.3%to about 15%in the presence of water at a pH of from about 9.0 to about 13. The passivation process by micro-arc oxidation leads to form a passivation layer which offers porous surface and good adhesion strength with the substrate.

In an example, the

process step

204, 103, 208 as depicted in Fig. 3 may be carried out in a similar manner as discussed in detail of Fig. 2. In another example, the degreasing process may also be carried out in the process of formation of a Mg alloy casing 300, comprising the passivation of Mg alloy substrate by electro-chemical treatment. In an example, the Mg alloy casing obtained by the process 300, detailed in Fig. 3 may be employed as frames or bodies of electronic devices, such as tablets, mobile phones, smart watches, laptops, and the like.

Fig. 4 illustrates a flow chart showing a process 400, for forming a Mg alloy casing comprising second passivation by chemical treatment, according to another example of the present disclosure. As shown in Figure 4 the Mg alloy substrate 102, may be passivated by a process step 402. The passivation process 402, may be carried out by a chemical treatment 202, or electrochemical treatment 302, as described earlier to obtain a passivated Mg alloy substrate. Further, a finishing layer 206, chamfering a portion of the finished Mg alloy substrate 103, in the presence of a cutting fluid 106, and immersing in an alkaline chemical 606, by a process 208, may be carried out by processes as described in Fig. 1 and Fig. 2. Further a second passivation may be done by a process 404. In an example, the second passivation treatment may be selected from transparent chemical passivation treatment or electrolytic passivation treatment. In an example, the transparent passivation treatment may be carried out in the presence of at least one chelating agent selected from ethylenediaminetetraacetic acid (EDTA) , ethylenediamine, nitrilotriacetic acid (NTA) , diethylenetriaminepenta (methylenephosphonic acid) (DTPPH) and nitrilotris (methylenephosphonicacid)(NTMP) ,1-hydroxyethane-1, 1-diphosphonic acid (HEDP) , phosphoric acid, and salts thereof. In an example, the transparent passivation treatment may be done throughout the surface of the casing. In another example, the transparent passivation treatment may be done at the exposed surface post immersing in alkaline chemical. In an example, the at least one chelating agent concentration may be of from about 1 wt %to about 10 wt %based on the total concentration. In an example, the at least one chelating agent concentration may be of from about 2 wt %to about 8 wt %based on the total concentration. In an example, the at least one chelating agent concentration may be 6 wt %based on the total concentration. In an example, the transparent passivation treatment may be carried out by immersing in a chemical bath at a temperature of from about 20 ℃to about 40 ℃ for a period of from about 30 seconds to about 180 seconds.

In another example, the transparent passivation treatment may be carried out in the presence of at least one chelating agent selected may be ethylenediaminetetraacetic acid (EDTA) , and salts thereof. In another example, the at least one chelating agent may be selected from zinc (II) EDTA complex or nickel (II) EDTA complex. In an example, the transparent passivation layer may have a thickness of from about 0.03 μm to about 1 μm. In another example, the transparent passivation layer may have a thickness of from about 0.05 μm to about 0.8 μm. In another example, the transparent passivation layer may have a thickness of from about 0.1 μm to about 0.6 μm. In another example, the transparent passivation layer may have a thickness of about 0.5 μm.

Further, transparent passivation layer obtained by a process 404, helps preserving the glossy finish. In an example, the gloss value of the transparent layer formed on at least one chamfered portion of the casing may be of from about 85 to about 100 units as measured by ASTM D523 at a viewing angle of about 20°.

Further, the deposition of ED layer by an electrophoretic deposition 406 to obtain Mg alloy casing may be carried out in the presence of at least one dye at the chamfered portions may provide a multi-colored finish to the chamfered portion of the casing. In an example, the Mg alloy casing is a keyboard casing having a first color as base and a second color at the finger print scanner area and a third color at the touch pad area. The deposition of the ED layer may be carried out by electrophoretic deposition. In an example, an electrophoretic deposition may be carried out subsequent to formation of the transparent passivation layer to introduce colors and to provide aesthetically improved finish. The thickness of the ED layer achieved may be directly related to the potential applied and time for electrophoretic deposition. In an example, the electrophoretic deposition may be carried out by applying a potential of from about 30 to about 150 V for a period of from about 25 to about 120 seconds. In another example, the electrophoretic deposition may be carried out by applying a potential of from about 50 to about 130 V for a period of from about 40 to about 100 seconds. In another example, the electrophoretic deposition may be carried out by applying a potential of about 120 V for a period of about 80 seconds. The method as described hereinabove for the Mg alloy casing of Fig. 4, may be applied conveniently for forming casing for a range of electronic devices such as keyboards, laptops, tablets, mobile phones, among others.

In an example, the ED layer deposited by electrophoretic deposition may comprise various dyes selected from red dye, blue dye, orange dye, yellow dye: Quinoline Yellow WS to obtain different colors at portions such as edges, side wall, fingerprint scanner, clickpad, among others. In an example, to obtain red colored in the ED layer, red dye may be used and may be selected from Alexa Fluor 594 dye, or Texas Red. In another example to obtain red color a pigment may be used, such as pigment Red 168 MF. In an example to obtain blue colored finish in the ED layer, blue dye may be used, such as Pacific Blue dye. In an example, to obtain orange colored finish in the ED layer, orange dye may be used, such as Pacific Orange. In an example, to obtain yellow colored finish in the ED layer a yellow dye may be used, such as quinoline yellow WS. In another example, to obtain yellow color a pigment may be used, such as Pigment Yellow 191.

Further, details of the process of forming a Mg alloy casing 500, is described with reference to Fig. 5. Fig. 5 illustrates a flow chart showing a process 500, of forming a Mg alloy casing comprising second passivation by electrolytic treatment 502, according to another example of the present disclosure. In an example, electrolytic passivation treatment may be carried out by applying a potential of from about 0.5 to about 15 V for a period of from about 30 to about 180 seconds. In another example, the electrolytic passivation treatment may be carried out by applying a potential of from about 2 to about 8 V for a period of from about 45 to about 120 seconds. In another example, the electrolytic passivation treatment may be carried out by applying a potential of about 6 V for a period of about 90 seconds. In another example, the electrolytic passivation treatment may be carried in presence of an electrolyte comprising KOH solution in a concentration of from about 5 to about 30 wt %, and ZnO in a concentration of from about 1 to about 5 wt %based on the total concentration at a temperature of from about 20 ℃to about 40 ℃.

In an example, to obtain a chamfered substrate with high gloss finish at the chamfered portion and without discoloration and formation of corrosion spots (white spots) , chamfering may be carried out by a process 600. Fig. 6 illustrates a process for forming a chamfered substrate 104, having chamfered edge 604, in presence of a cutting fluid, according to an example of the present disclosure. In an example, the cutting fluid 106, may play a beneficial role in lubrication, cooling, cleaning, and corrosion, thereby improving the tool life, chamfering accuracy and chamfering quality. In an example, cutting fluid 106, may be applied at a portion of the Mg alloy substrate 102, followed by chamfering 103 to obtain a chamfered substrate 104, with chamfered edge 604. In an example, the chamfered substrate 104, with the chamfered edge may be immediately immersed in an alkaline chemical 606, to stabilize the chamfered edge by a process 208.

In an example, the cutting fluid may comprise (a) at least one silicate in an amount of from about 0.5 wt %to about 3.0 wt %based on the total weight of the cutting fluid; (b) at least one base in an amount of from about 1.0 wt %to about 5.0 wt %based on the total weight of the cutting fluid; and (c) at least one phosphate in an amount of from about 0.5 wt %to about 2.0 wt %based on the total weight of the cutting fluid, wherein the cutting fluid has a pH of from about 9 to about 13. In another example, the cutting fluid may comprise (a) at least one silicate in an amount of from about 0.5 wt %to about 3.0 wt %based on the total weight of the cutting fluid; (b) at least one base in an amount of from about 1.0 wt %to about 5 wt %based on the total weight of the cutting fluid; (c) at least one phosphate in an amount of from about 0.5 wt %to about 2.0 wt %based on the total weight of the cutting fluid; (d) at least one surfactant in an amount of from about 1.0 wt %to about 10.0 %based on the total weight of the cutting fluid; and (e) deionized water in an amount of from about 80.0 %to about 97.0 %based on the total weight of the cutting fluid, wherein the cutting fluid has a pH of from about 9 to about 13.

In another example, the cutting fluid may comprise (a) at least one silicate in an amount of from about 0.8 wt %to about 2.5 wt %based on the total weight of the cutting fluid; (b) at least one base in an amount of from about 2.0 wt %to about 4.0 wt %based on the total weight of the cutting fluid; and (c) at least one phosphate in an amount of from about 0.7 wt %to about 1.5 wt %based on the total weight of the cutting fluid, wherein the cutting fluid has a pH of from about 9 to about 13. In another example, the cutting fluid may comprise (a) at least one silicate in an amount of from about 1.0 wt %to about 2.0 wt %based on the total weight of the cutting fluid; (b) at least one base in an amount of from about 2.5 wt %to about 3.5 wt %based on the total weight of the cutting fluid; and (c) at least one phosphate in an amount of from about 1.0 wt %to about 2.0 wt %based on the total weight of the cutting fluid, wherein the cutting fluid has a pH of from about 9 to about 13.

Chamfering of the Mg alloy substrate, when carried out at highspeed leads to deterioration of the surface finish and increase in cutting forces. The chamfering may be done in presence of the cutting fluid during high speed chamfering, in order to effectively eliminate the build-up formation (discoloration and formation of corrosion spots (white spots) ) .

In an example, at least one silicate may be selected from sodium silicate, sodium meta silicate, or combinations thereof. In another example, at least one silicate may be sodium silicate. In another example, at least one silicate may be sodium meta silicate. In another example, the at least one silicate may be in an amount of from about 0.5 wt %to about 3.0 wt %based on the total weight of the cutting fluid. In another example, the at least one silicate may be in an amount of from about 0.7 wt %to about 1.5 wt %based on the total weight of the cutting fluid, wherein the cutting fluid has a pH of from about 9 to about 13.

In an example, the at least one base may be selected from sodium hydroxide, sodium carbonate, or combinations thereof. In another example, the at least one base may be sodium hydroxide. In another example, the at least one base may be sodium carbonate. In another example, the at least one base may be in an amount of from about 1.0 wt %to about 5 wt %based on the total weight of the cutting fluid, wherein the cutting fluid has a pH of from about 9 to about 13. In another example, the at least one base may be in an amount of from about 2.0 wt %to about 4 wt %based on the total weight of the cutting fluid, wherein the cutting fluid has a pH of from about 9 to about 13.

In an example, at least one phosphate may be selected from sodium hexametaphosphate, sodium phosphate, or combinations thereof. In another example, at least one phosphate may be sodium hexametaphosphate. In another example, at least one phosphate may be sodium phosphate. In another example the at least one phosphate may be in an amount of from about 0.5 wt %to about 2.0 wt %based on the total weight of the cutting fluid, wherein the cutting fluid has a pH of from about 9 to about 13. In another example, the at least one phosphate may be in an amount of from about 0.7 wt %to about 1.5 wt %based on the total weight of the cutting fluid, wherein the cutting fluid has a pH of from about 9 to about 13.

In an example, at least one surfactant may be selected from diethanolamine,diglycolamine,ethylenediamine,triethanolamine,or combinations thereof. In another example, at least one surfactant may be diethanolamine. In another example, at least one surfactant may be diglycolamine. In another example, at least one surfactant may be ethylenediamine. In another example, at least one surfactant may be triethanolamine. In another example, the at least one surfactant may be in an amount of from about 1.0 wt %to about 10.0 %based on the total weight of the cutting fluid, wherein the cutting fluid has a pH of from about 9 to about 13. In another example, the at least one surfactant may be in an amount of from about 4.0 wt %to about 8.0 %based on the total weight of the cutting fluid, wherein the cutting fluid has a pH of from about 9 to about 13.

In an example, cutting fluid may comprise deionized water in an amount of from about 80.0 %to about 97.0 %based on the total weight of the cutting fluid. In another example, cutting fluid may comprise deionized water in an amount of from about 85.0 %to about 95.0 %based on the total weight of the cutting fluid. In another example, cutting fluid may comprise deionized water in an amount of from about 85.0 %to about 96.0 %based on the total weight of the cutting fluid.

In an example, the cutting fluid 106, may be prepared by blending together the at least one silicate, at least one base, at least one phosphate, at least one surfactant, and de-ionized water, in proportions as described above so as to attain a pH of from about 9 to about 13. In another example, the cutting fluid may be prepared by mixing sodium hydroxide and sodium carbonate in an amount of from about 0.5 wt to about 3.0 wt%based on the total weight of the cutting fluid, sodium hexametaphosphate and sodium phosphate in an amount of from about 0.3 to about 2.0 wt%based on the total weight of the cutting fluid, and sodium meta silicate, and sodium silicate in an amount of from about 0.5 to about 3.0 wt%based on the total weight of the cutting fluid to obtain the cutting fluid which may have a pH of from about 9 to about 13 at a temperature of from about 25° C to about 40 ℃. In another example, the cutting fluid may be prepared by addition of deionized water and surfactant

However, a process for preparing the cutting fluid may not be limited by the above. Therefore, a cutting fluid of the present disclosure may be prepared by dissolving salt containing sodium in presence of surfactant and de-ionized water.

Although examples for the present disclosure have been described in a language specific to structural features and/or methods, it is to be understood that the appended claims are not limited to the specific features or methods described herein. Rather, the specific features and methods are disclosed and explained as examples of the present disclosure.

Claims

A process for forming a chamfered substrate, the process comprising:

(a) chamfering at least a portion of a Mg alloy substrate in the presence of a cutting fluid to obtain a chamfered substrate,

wherein the cutting fluid has a pH of from about 9 to about 13 and the cutting fluid comprises at least one silicate in an amount of from about 0.5%to about 3.0%based on the total weight of the cutting fluid.
The process as claimed in claim 1, wherein the Mg alloy is selected from AZ31B, AZ61, AZ60, AZ63, AZ80, AZ81, AM50, AM60, AM100, AZ91D, AZ92, LZ91, LZ141, ALZ691, ALZ931, or combinations thereof and the thickness of the Mg alloy substrate is of from about 0.3 mm to about 2 mm.
The process as claimed in claim 1, wherein the Mg Alloy substrate comprises:

(a) a passivation layer having a thickness of from about 1 μm to about 15 μm; and

(b) a finishing layer having a thickness of from about 25.0 μm to about 65.0 μm.
A process for forming a Mg alloy casing, the process comprising:

(a) passivating a Mg alloy substrate to obtain a passivated Mg alloy substrate;

(b) depositing a finishing layer on the passivated Mg alloy substrate to obtain a finished Mg alloy substrate;

(c) chamfering at least a portion of the finished Mg alloy substrate in the presence of a cutting fluid to obtain an exposed surface; and

(d) contacting the exposed surface with an alkaline chemical to obtain the Mg alloy casing,

wherein the cutting fluid has a pH of from about 9 to about 13.
The process as claimed in claim 4, wherein passivating a Mg alloy substrate is carried out by a process selected from chemical treatment or electro-chemical treatment.
The process as claimed in claim 5, wherein the chemical treatment is carried out in the presence of at least one salt of manganese, molybdate, vanadate, phosphate, chromate, stannate, or combinations thereof for a period of from about 20 seconds to about 120 seconds.
The process as claimed in claim 5, wherein the electrochemical treatment is carried out by a micro arc oxidation.
The process as claimed in claim 4, wherein the cutting fluid comprises at least one silicate in an amount of from about 0.5 wt%to about 3.0 wt%based on the total weight of the cutting fluid.
The process as claimed in claim 4, comprises a second passivation treatment followed by electrophoretic deposition prior to obtaining the Mg alloy casing.
The process as claimed in claim 9, wherein the second passivation treatment comprises a process selected from transparent chemical passivation treatment or electrolytic passivation treatment.
The process as claimed in claim 10, wherein the transparent chemical passivation treatment is carried in the presence of at least one chelating agent selected from ethylenediaminetetraacetic acid (EDTA) , ethylenediamine, nitrilotriacetic acid (NTA) , diethylenetriaminepenta (methylenephosphonic acid) (DTPPH) and nitrilotris (methylenephosphonic acid) (NTMP) , 1-hydroxyethane-1, 1-diphosphonic acid (HEDP) , phosphoric acid, or salts thereof.
The process as claimed in claim 4, wherein depositing a finishing layer on the passivated Mg alloy substrate is carried out by spray coating.
The process as claimed in claim 12, wherein the finishing layer comprises:

a primer having a thickness of from about 5.0 μm to about 20.0 μm;

a base coat having a thickness of from about 10.0 μm to about 20.0 μm; and

a top coat having a thickness of from about 10.0 μm to about 25.0 μm.
A cutting fluid comprising:

(a) at least one silicate in an amount of from about 0.5 wt%to about 3.0 wt%based on the total weight of the cutting fluid;

(b) at least one base in an amount of from about 1.0 wt%to about 5.0 wt%based on the total weight of the cutting fluid; and

(c) at least one phosphate in an amount of from about 0.5 wt%to about 2.0 wt%based on the total weight of the cutting fluid,

wherein the cutting fluid has a pH of from about 9 to about 13.
The cutting fluid as claimed in claim 14, comprises:

(a) at least one surfactant in an amount of from about 1.0 wt%to about 10.0%based on the total weight of the cutting fluid; and

(b) deionized water in an amount of from about 80.0 wt%to about 97.0 wt%based on the total weight of the cutting fluid.