CN110871267A - Secondary die-casting metal product with improved appearance defects, preparation method of secondary die-casting metal product, mobile phone middle frame and mobile phone - Google Patents
Secondary die-casting metal product with improved appearance defects, preparation method of secondary die-casting metal product, mobile phone middle frame and mobile phone Download PDFInfo
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- CN110871267A CN110871267A CN201810997502.4A CN201810997502A CN110871267A CN 110871267 A CN110871267 A CN 110871267A CN 201810997502 A CN201810997502 A CN 201810997502A CN 110871267 A CN110871267 A CN 110871267A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D19/00—Casting in, on, or around objects which form part of the product
- B22D19/0081—Casting in, on, or around objects which form part of the product pretreatment of the insert, e.g. for enhancing the bonding between insert and surrounding cast metal
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D19/00—Casting in, on, or around objects which form part of the product
- B22D19/08—Casting in, on, or around objects which form part of the product for building-up linings or coverings, e.g. of anti-frictional metal
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M1/00—Substation equipment, e.g. for use by subscribers
- H04M1/02—Constructional features of telephone sets
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Abstract
The invention relates to the field of amorphous alloy die-casting forming, and discloses a secondary die-casting metal product with improved appearance defects, a preparation method thereof, a mobile phone middle frame and a mobile phone, wherein the method comprises the following steps: injecting molten metal to the surface of the die-casting metal product with the appearance defects to perform secondary die-casting on the surface of the die-casting metal product with the appearance defects and form a secondary die-casting layer, wherein the secondary die-casting layer is formed on the surface of the die-casting metal product with the appearance defects and the defects, and then maintaining pressure under injection pressure; after the pressure maintaining is finished, taking the thickness of a secondary die-casting layer formed on the surface of the die-casting metal product with the appearance defects as a reference, and completely removing the secondary die-casting layer to obtain a secondary die-casting metal product with improved appearance defects; the metal selected from the molten state is the same as the metal selected from the die cast metal product having the appearance defect. The method can effectively improve the defect with larger diameter, and the surface color of the secondary die-casting product after the improvement is uniform, and the filler at the defect is firmly combined.
Description
Technical Field
The invention relates to the field of improvement of appearance defects of die-cast products, in particular to a secondary die-cast metal product with improved appearance defects, a preparation method of the secondary die-cast metal product, a mobile phone middle frame and a mobile phone.
Background
Amorphous alloys have been the hot spot of alloy material research since the first discovery in 1960. In the 90 s of the 20 th century, a multielement alloying method is adopted, so that the critical cooling speed of the amorphous alloy is reduced, the preparation of the bulk amorphous alloy is realized, and the engineering application of the material becomes possible. The amorphous alloy has a short-range ordered and long-range unordered atomic arrangement structure, so that the material has excellent mechanical properties such as high strength, high elastic limit, good abrasion resistance and the like.
Chinese patent application CN201310751623 (a method for forming amorphous alloy) discloses an existing common process for amorphous forming. The method comprises the following steps: (1) under the protection of inert gas, heating the amorphous alloy cast ingot in a crucible arranged in a vacuum chamber; (2) vacuumizing the vacuum chamber to enable the pressure in the vacuum chamber to reach the vacuum pressure below 5000Pa, wherein the temperature when the vacuum pressure is reached is lower than the melting point of the amorphous alloy cast ingot; (3) under the vacuum pressure reached in the step (2), continuously heating the amorphous alloy cast ingot in the crucible to melt the amorphous alloy cast ingot into a molten liquid; (4) and (4) adding the molten liquid obtained in the step (3) into a forming die under a vacuum condition to obtain a formed amorphous alloy product.
The die-casting forming process is suitable for forming products with thin walls, and appearance defects such as sand holes, cracks, shrinkage and the like are high in proportion when the products with thick walls are formed. At present, physical processes such as polishing, sand blasting, wire drawing, spraying and the like are commonly adopted in the industry to reduce and cover products with poor appearance, but the physical processes are limited to cover fine sand holes with the diameter of less than 0.15mm, and the defect covering rate of the diameter of more than 0.15mm is low. In addition, a 'feeding' process (mainly laser cladding) can be adopted, laser local melting is carried out on the appearance defect position and the periphery of the product, the defect is filled, and the defect position is ground flat by mechanical modes such as grinding and polishing, so that the defect is improved, but the process mainly has 3 defects: (1) the defect diameter required to be improved by the process is not more than 0.2mm, and if the defect diameter is too large, the defect cannot be filled; (2) the position of the defect on the product is irregular, so that the defect cannot be accurately processed in a mechanical positioning mode, and the control is difficult to improve the effect; (3) local discoloration may occur after the process treatment, resulting in other appearance defects.
In addition, CN201906813, CN201147834 and CN206839107 all disclose a method for improving surface defects of amorphous alloys in a one-time die casting process. The method is not only used for products with defects in appearance (mainly because a proper amount of hammerhead oil or a release agent is added in one die casting process to improve demoulding, which causes the appearance of die castings after demoulding to be rough, and small defects cannot be directly distinguished through observation, namely, whether defects exist after the products formed by the first die casting need to be processed by grinding, polishing and the like, in addition, a certain margin is generally reserved in the die design stage of the die castings for post-processing, sand holes on the appearance surface of the actual size of the products cannot be directly observed and distinguished after the products are formed by the first die casting, and the sand holes can be observed after the processing of CNC, grinding, polishing and the like), but the method is used for all the products, so that great waste of manpower, material resources and financial resources is caused. In addition, the above methods cannot sufficiently improve the appearance defects of the product, and still require subsequent processes to compensate for the defects.
The above complement, therefore, has led to the application of amorphous materials being limited mainly to structural components or to products with low appearance requirements, which cannot be opened later in the application of products with high appearance requirements.
Disclosure of Invention
The invention aims to overcome the problem that the prior art can not effectively improve the appearance defect of the amorphous alloy surface with the diameter of more than 0.2mm, and on one hand, the invention provides a method for improving the appearance defect of a die-casting metal product, which comprises the following steps: under the vacuum condition, injecting molten metal to the surface of a die-casting metal product with the appearance defects to perform secondary die-casting on the surface and the defects of the die-casting metal product with the appearance defects and form a secondary die-casting layer, and then maintaining pressure under injection pressure; after the pressure maintaining is finished, taking the thickness of a secondary die-casting layer formed on the surface of the die-casting metal product with the appearance defects as a reference, and completely removing the secondary die-casting layer to obtain a secondary die-casting metal product with improved appearance defects;
wherein the molten metal is selected from the same metals as the die cast metal product having the appearance defect.
Preferably, the thickness of the secondary die-cast layer is 0.1 to 1.2 mm.
Preferably, the temperature of the molten metal is 0-200 ℃ above the melting point of the metal.
Preferably, the secondary die-casting is performed in a secondary die-casting mold, and the temperature of the secondary die-casting mold is 150-.
In a second aspect, the present invention provides a secondary die cast metal product with improved appearance defects prepared by the method as described above.
In a third aspect, the invention provides a mobile phone middle frame, which is prepared from the secondary die-cast metal product.
In a fourth aspect, the present invention provides a mobile phone, which includes the mobile phone middle frame as described above.
The inventor of the present invention has tried to make the die casting thick in one die casting process and then remove the defect by CNC machining, but this requires, on one hand, to prepare the die casting mold again, which consumes a lot of money, and on the other hand, the die casting without appearance defect also requires CNC machining to form the required thickness, which wastes manpower, material resources, and money, and may expose potential internal defects to be unreliated. The invention takes the product with the appearance of the defect (the hole with the diameter more than 0.2 mm) which can not be repaired by the prior art as the bad base body, the same metal material is adopted on the bad base body for secondary die casting forming, and the same metal material is refilled in the defect. The same material has complete intimacy, and is completely fused and combined with a poor matrix at high temperature and high pressure. And the redundant secondary die-casting layer after the secondary die-casting molding is removed, so that the product has no defects in the prior art, and is uniform in color and luster and free of different colors. The invention improves and recycles the products to be scrapped due to poor appearance, thereby improving the product yield and reducing the production cost.
Drawings
FIG. 1 is a schematic view of an amorphous alloy product with an appearance having defects that cannot be repaired by the prior art.
FIG. 2 is a cross-sectional view of a defect in an amorphous alloy product having an appearance with defects that cannot be repaired by the prior art.
Fig. 3 is a secondary die cast metal product having a secondary die cast layer formed in accordance with the method of the present invention.
Fig. 4 is a secondary die cast metal product with improved appearance defects formed according to the method of the present invention.
Fig. 5 shows a flow chart of the present invention for improving the appearance defect of the die-cast metal product.
Description of the reference numerals
1-defective pit 2-die cast metal product interface 3-die cast metal product appearance
4-secondary die-casting layer
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
According to a first aspect of the present invention, there is provided a method of improving an appearance defect of a die-cast metal product, the method comprising: under the vacuum condition, injecting molten metal to the surface of a die-casting metal product with the appearance defects to perform secondary die-casting on the surface and the defects of the die-casting metal product with the appearance defects and form a secondary die-casting layer, and then maintaining pressure under injection pressure; after the pressure maintaining is finished, taking the thickness of a secondary die-casting layer formed on the surface of the die-casting metal product with the appearance defects as a reference, and completely removing the secondary die-casting layer to obtain a secondary die-casting metal product with improved appearance defects;
wherein the molten metal is selected from the same metals as the die cast metal product having the appearance defect.
In the present invention, a die-cast metal product (hereinafter referred to as a metal base) having an appearance defect is subjected to secondary die-casting using the same metal material, and the defect is refilled with the same metal material. The same material has complete intimacy, and can be completely fused and combined with the die-casting metal product with the appearance defect at high temperature and high pressure, so that the secondary die-casting metal filled in the defect part of the prior die-casting metal can be tightly combined together, and the surface of the product can not generate different colors.
The method of the present invention can be applied to an arbitrary alloy material die casting having defects on the surface, for example, a zirconium alloy die casting, a copper alloy die casting, an iron alloy die casting, an aluminum alloy die casting, a magnesium alloy die casting, a zinc alloy die casting, and the like. That is, the die-cast metal product having the appearance defect is selected from the group consisting of a zirconium alloy die-cast part, a copper alloy die-cast part, an iron alloy die-cast part, an aluminum alloy die-cast part, a magnesium alloy die-cast part, and a zinc alloy die-cast part. However, the cost of materials such as aluminum alloy, magnesium alloy and the like is relatively low, products with serious appearance defects can be directly scrapped, the cost of post-treatment processing such as CNC and polishing is high due to high material cost and high material hardness of the amorphous alloy, and the waste of directly scrapping defective products after polishing is large, so that the method is particularly suitable for amorphous alloy die-casting metal products in view of cost.
Wherein the material selection of the molten metal is determined according to the selection of the metal material of the die-casting metal product with the appearance defect, for example, when the die-casting metal product with the appearance defect is a zirconium-based amorphous alloy die-casting piece with the appearance defect, the molten metal is a zirconium-based amorphous alloy.
The method of the invention is particularly suitable for improving the recessed defects with the diameter of more than 0.2mm, preferably 0.2-0.5mm, which are the defects with recessed characteristics existing on the surface of the product, such as the product appearance recessed due to sand holes, air holes, shrinkage, appearance cracks and other reasons on the surface of the product.
In the present invention, the degree of vacuum of the vacuum condition may be selected within a wide range as long as oxidation of the metal in the secondary die casting process can be prevented. However, the inventors of the present invention have found that, in the secondary die casting process, by setting the vacuum degree under vacuum to 300Pa or less, it is possible to effectively avoid the occurrence of defects such as voids in the secondary die casting process, and further improve the melt bonding strength between the metal base and the filler metal, and improve the color uniformity of the surface of the secondary die cast product.
Wherein, because of the sealing problem of the die casting environment, there is usually vacuum leakage during the die casting process, and the vacuum leakage rate is preferably lower than 10 Pa/s. The degree of vacuum under the vacuum condition is achieved by a balance between the degree of vacuum pumping and the vacuum leak rate.
In the present invention, the thickness of the secondary die-cast layer may be selected from a wide range as long as the defect on the metal substrate can be filled. However, the inventors of the present invention have found that by setting the thickness of the secondary die-cast layer to less than 1.2mm on the premise that the defect site can be filled, the defects such as shrinkage and blisters of the secondary die-casting are greatly reduced, which contributes to an improvement effect. Thus, according to a preferred embodiment of the present invention, the thickness of the secondary die-cast layer is 0.1 to 1.2mm, for example, 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, 1.1mm, 1.2mm, and more preferably, the thickness of the secondary die-cast layer is 0.3 to 0.7 mm.
In the present invention, the temperature of the molten metal can be selected within a wide range as long as the metal can be maintained in a molten state and can be smoothly injected into the metal base. According to a preferred embodiment of the present invention, in order to improve the fusion of the secondary die-cast layer with the metal matrix while avoiding the splashing of the amorphous alloy raw material at the time of melting, the temperature of the molten metal is 0 to 200 ℃ higher than the melting point of the metal, more preferably 50 to 100 ℃ higher, for example, 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃. Here, the "melting point" is a temperature at which the metal is just in a molten state (flowing state).
In the present invention, the pressure of the injection may be selected within a wide range as long as the molten metal can be efficiently injected to the surface of the metal base body to form the secondary die-cast layer. According to a preferred embodiment of the present invention, in order to improve the bonding force between the molten metal and the metal matrix, the pressure of the injection is 100-300MPa, and may be, for example, 100MPa, 110MPa, 120 MPa, 130MPa, 140MPa, 150MPa, 160MPa, 170MPa, 180MPa, 190MPa, 200MPa, 210MPa, 220MPa, 230MPa, 240MPa, 250MPa, 260MPa, 270MPa, 280MPa, 290MPa, 300 MP. Preferably, the pressure of the injection is 150-250 MPa.
In the present invention, the time for the pressure holding may be selected within a wide range as long as the secondary die-cast layer can be stably fused on the metal substrate. Preferably, the dwell time is 1 to 20s, and may be, for example, 1s, 3s, 5s, 8s, 10s, 12s, 14s, 16s, 18s, 20 s. Further preferably, the dwell time is 5 to 15 s.
In the present invention, the die-cast metal product having the appearance defect may be a metal casting of primary die-casting or a metal casting of secondary die-casting, and the improvement can be made by the method of the present invention as long as the surface has the defect as described above. Preferably, the metal base is a die-cast part having a defect in appearance obtained after a primary die-casting in a primary die-casting mold. The temperature of the primary die-casting die is generally 150-250 ℃.
In the invention, the secondary die-casting is carried out in a secondary die-casting die, and the secondary die-casting die and the primary die-casting die can be the same or different. For cost reasons, the secondary die casting mold is identical to the primary die casting mold. Preferably, the temperature of the secondary die-casting mold is 150-350 ℃, preferably 230-300 ℃. Under such temperature, the one shot die-casting shaping product of location in the mould can not produce local crystallization to can not change material property, and can also improve the cohesion between secondary die-casting layer and the one shot die-casting product, promote the homogeneity of color and luster.
According to a preferred embodiment of the invention, the temperature of the secondary die casting mould is higher than the temperature of the primary die casting mould, preferably 30-80 ℃ higher, for example 30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃, in which case the secondary die casting layer is more tightly bonded to the primary die cast product.
In the present invention, before the metal base is subjected to the secondary die casting, the method preferably further includes a step of cleaning and degreasing the metal base. The cleaning and degreasing can be performed in a manner known in the art, for example, cleaning and degreasing can be performed by an alkaline substance (preferably, an aqueous solution of sodium hydroxide).
In the present invention, before the die-casting metal product with the appearance defects is placed under the vacuum condition, the method further preferably comprises heating the die-casting metal product with the appearance defects to the temperature of 100-. Preferably, the heating is preferably performed after the cleaning and degreasing, and thus, the drying of the metal substrate cleaned and degreased can also be simultaneously performed.
In the invention, after the pressure maintaining is finished, the step of deflating the secondary die-casting grinding tool is further included, after the deflation is finished and the product is cooled, the secondary die-casting layer can be removed by adopting a method known in the art, for example, the secondary die-casting layer can be removed by adopting a mechanical method of CNC, grinding and polishing.
As shown in fig. 5, a specific flow chart for improving the appearance defects of die-casting metal products according to the present invention is provided, in which a metal substrate to be improved in appearance is first cleaned, then dried and preheated to a predetermined temperature, and then the metal substrate is fixed in a cavity of a secondary die-casting mold through a positioning hole, and after mold closing, a system is vacuumed to a predetermined vacuum degree and the vacuum degree is maintained. At the moment, the same metal used for forming the die-casting layer is smelted to a preset temperature to obtain molten metal, the molten metal is injected to the surface of the metal base body under injection pressure to form secondary die-casting, then the temperature and pressure are kept for a certain time under the system temperature and the injection pressure, the secondary die-casting layer is deflated and opened after being stabilized to obtain an excessive product, the excessive product is taken out to be cooled, and the secondary die-casting layer is removed through a conventional process, so that the secondary die-casting metal product with improved appearance defects is obtained.
The second aspect of the present invention also provides a secondary die cast metal product with improved appearance defects prepared by the method as described above.
The third aspect of the invention also provides a mobile phone middle frame, which is prepared from the secondary die-cast metal product.
The fourth aspect of the invention also provides a mobile phone, which comprises the mobile phone middle frame.
The present invention will be described in detail below by way of examples.
Example 1
This example illustrates the method for improving the appearance defect of die-cast metal product provided by the present invention
(1) A zirconium-based amorphous alloy substrate (a schematic diagram is shown in figure 1, a cross-sectional diagram is shown in figure 2, wherein 1 is a defect depression, 2 is a die-casting metal product interface, and 3 is a die-casting metal product appearance surface) with the diameters of the defects of the external appearance sand holes to be improved being 0.1 +/-0.01 mm, 0.2 +/-0.01 mm, 0.3 +/-0.01 mm, 0.4 +/-0.01 mm and 0.5 +/-0.01 mm is respectively placed in a 5 wt% sodium hydroxide solution to be cleaned and degreased, and then, deionized water is used for washing to remove residual sodium hydroxide.
(2) And (2) drying and preheating the cleaned substrate in the step (1) to 250 ℃, fixing the substrate in a secondary die-casting mold cavity (higher than 80 ℃ of a primary die-casting mold) at 300 ℃ through a positioning hole, vacuumizing the system after mold closing until the vacuum degree is 300Pa, and maintaining the vacuum degree, wherein the vacuum leak rate of the secondary die-casting mold is 10 Pa/s.
(3) Heating the same zirconium-based amorphous alloy to a temperature 50 ℃ higher than the melting point of the amorphous alloy, injecting the same zirconium-based amorphous alloy to the surface of a zirconium-based amorphous alloy substrate under the pressure of 250MPa to form a secondary die-casting layer with the thickness of about 0.3mm, and maintaining the temperature and pressure for 5s at the system temperature and the injection pressure to fix the secondary die-casting layer.
(4) After the heat preservation and pressure maintenance are finished, vacuumizing is stopped, the secondary die is deflated and opened to obtain an intermediate transition product (1 is a defect-type dent, 2 is a die-casting metal product interface, 3 is a die-casting metal product appearance surface, and 4 is a secondary die-casting layer as shown in fig. 3), after the transition product is cooled, the secondary die-casting layer is removed by a CNC (computer numerical control), grinding and polishing mechanical method to obtain a secondary die-casting part with improved appearance defects (1 is a defect-type dent, 2 is a die-casting metal product interface, and 3 is a die-casting metal product appearance surface) as shown in fig. 4, and the improvement effect of each defect is shown in table 1.
Example 2
This example illustrates the method for improving the appearance defect of die-cast metal product provided by the present invention
(1) The copper-based amorphous alloy substrates with the grain defect diameters of 0.1 +/-0.01 mm, 0.2 +/-0.01 mm, 0.3 +/-0.01 mm, 0.4 +/-0.01 mm and 0.5 +/-0.01 mm to be improved are marked as a, b, c, d and e, respectively placed in 3 weight percent of sodium hydroxide solution for cleaning and degreasing, and then washed by deionized water to remove residual sodium hydroxide.
(2) And (2) drying and preheating the cleaned base body in the step (1) to 150 ℃, fixing the base body in a secondary die-casting mold cavity (30 ℃ higher than a primary die-casting mold) at 230 ℃ through a positioning hole, vacuumizing the system after mold closing until the vacuum degree is 100Pa, and maintaining the vacuum degree, wherein the vacuum leak rate of the secondary die-casting mold is 10 Pa/s.
(3) Heating the same copper-based amorphous alloy to a temperature higher than the melting point of the amorphous alloy by 100 ℃, injecting the same copper-based amorphous alloy to the surface of the copper-based amorphous alloy substrate under the pressure of 150MPa to form a secondary die-casting layer with the thickness of about 0.7mm, and preserving heat and pressure for 15s at the system temperature and the injection pressure to fix the secondary die-casting layer.
(4) And after the heat preservation and pressure maintenance are finished, stopping vacuumizing, deflating the secondary die, opening the die to obtain an intermediate transition product, and after the transition product is cooled, removing the secondary die casting layer by a CNC (computer numerical control), grinding and polishing mechanical method to obtain the secondary die casting with improved appearance defects, wherein the improvement effect of each defect part is shown in Table 1.
Example 3
This example illustrates the method for improving the appearance defect of die-cast metal product provided by the present invention
(1) Iron-based amorphous alloy substrates with the grain defect diameters of 0.1 +/-0.01 mm, 0.2 +/-0.01 mm, 0.3 +/-0.01 mm, 0.4 +/-0.01 mm and 0.5 +/-0.01 mm to be improved are marked as a, b, c, d and e, respectively placed in 8 weight percent sodium hydroxide solution for cleaning and degreasing, and then washed by deionized water to remove residual sodium hydroxide.
(2) And (2) drying and preheating the cleaned substrate in the step (1) to 200 ℃, fixing the substrate in a secondary die-casting mold cavity (higher than a primary die-casting mold by 50 ℃) at 250 ℃ through a positioning hole, vacuumizing the system after mold closing until the vacuum degree is 200Pa, and maintaining the vacuum degree, wherein the vacuum leak rate of the secondary die-casting mold is 10 Pa/s.
(3) Heating the same iron-based amorphous alloy to a temperature higher than the melting point of the amorphous alloy by 80 ℃, injecting the same iron-based amorphous alloy to the surface of the iron-based amorphous alloy substrate under the pressure of 200MPa to form a secondary die-casting layer with the thickness of about 0.5mm, and preserving heat and pressure for 10s at the system temperature and the injection pressure to fix the secondary die-casting layer.
(4) And after the heat preservation and pressure maintenance are finished, stopping vacuumizing, deflating the secondary die, opening the die to obtain an intermediate transition product, and after the transition product is cooled, removing the secondary die casting layer by a CNC (computer numerical control), grinding and polishing mechanical method to obtain the secondary die casting with improved appearance defects, wherein the improvement effect of each defect part is shown in Table 1.
Example 4
This example illustrates the method for improving the appearance defect of die-cast metal product provided by the present invention
The appearance defect of the die-cast metal product was improved according to the method of example 1 except that in the step (3), the thickness of the secondary die-cast layer was 1.5 mm. The improvement effect at each defect is shown in table 1.
Example 5
This example illustrates the method for improving the appearance defect of die-cast metal product provided by the present invention
The appearance defects of the die-cast metal product were improved according to the method of example 1, except that, in the step (3), the same zirconium-based amorphous alloy was heated to a temperature at which the amorphous alloy melts. The improvement effect at each defect is shown in table 1.
Example 6
This example illustrates the method for improving the appearance defect of die-cast metal product provided by the present invention
The appearance defect of the die-casting metal product is improved according to the method in the embodiment 1, except that in the step (2), the temperature of the secondary die-casting die cavity is the same as that of the primary die-casting die cavity during primary die-casting of the product. The improvement effect at each defect is shown in table 1.
Example 7
This example illustrates the method for improving the appearance defect of die-cast metal product provided by the present invention
The appearance defect of the die-casting metal product is improved according to the method in the embodiment 1, except that in the step (2), the temperature of the cavity of the secondary die-casting die is 150 ℃ higher than that of the cavity of the primary die-casting die when the product is subjected to primary die-casting. The improvement effect at each defect is shown in table 1.
Comparative example 1
This comparative example is intended to illustrate the existing method of improving the appearance defects of die-cast metal products
In the comparison experiment, zirconium-based amorphous alloy substrates with the diameters of the appearance sand hole defects to be improved being 0.1 +/-0.01 mm, 0.2 +/-0.01 mm, 0.3 +/-0.01 mm, 0.4 +/-0.01 mm and 0.5 +/-0.01 mm are marked as a, b, c, d and e, and a layer of uniform spraying with the thickness of 160 mu m is carried out on the surface of a sample by using ink (the general spraying thickness in the mobile phone manufacturing industry is less than 160 mu m) to obtain a comparison sample. The improvement effect at each defect is shown in table 1.
Comparative example 2
This comparative example is intended to illustrate the existing method of improving the appearance defects of die-cast metal products
In the comparison experiment, the zirconium-based amorphous alloy substrates with the appearance sand hole defect diameters to be improved of 0.1 +/-0.01 mm, 0.2 +/-0.01 mm, 0.3 +/-0.01 mm, 0.4 +/-0.01 mm and 0.5 +/-0.01 mm are marked as a, b, c, d and e, the defect area of the sample is subjected to laser local melting (the power is 1000W, the aperture is 50 mu m and the pitch is 150 mu m), and then the sample is subjected to re-polishing to obtain a comparison sample. The improvement effect at each defect is shown in table 1.
TABLE 1
Remarking: 1. in the table, "OK" means that the experimental sample has good appearance, uniform surface color and luster and firm combination of fillers at the defect; "NG" means poor appearance of the test specimen, specifically, "NG 1" means no improvement in defects, "NG 2" means no full formation of the secondary die-cast layer, "NG 3" means reduced but no improvement in defects, "NG 4" means increased defects.
2. In example 7, the structural appearance of the sample was OK, but local crystallization occurred inside the amorphous alloy of the samples a, b, and d due to the excessively high mold temperature, which may have a certain effect on the product performance.
As can be seen from the results in table 1, the method of the present invention can effectively improve the defect with a larger diameter compared to the prior art. By comparing example 1 with examples 4 to 7, it can also be seen that the improvement is further improved at the preferred secondary die-casting layer thickness, the preferred molten metal temperature and the preferred secondary die temperature.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (14)
1. A method of improving cosmetic defects in die cast metal products, the method comprising: under the vacuum condition, injecting molten metal to the surface of a die-casting metal product with the appearance defects to perform secondary die-casting on the surface and the defects of the die-casting metal product with the appearance defects and form a secondary die-casting layer, and then maintaining pressure under injection pressure; after the pressure maintaining is finished, taking the thickness of a secondary die-casting layer formed on the surface of the die-casting metal product with the appearance defects as a reference, and completely removing the secondary die-casting layer to obtain a secondary die-casting metal product with improved appearance defects;
wherein the molten metal is selected from the same metals as the die cast metal product having the appearance defect.
2. The method of claim 1, wherein the vacuum condition has a vacuum of less than 300 Pa.
3. The method according to claim 1 or 2, wherein the secondary diecast layer formed on the surface of the diecast metal product having appearance defects has a thickness of 0.1-1.2 mm.
4. A process according to claim 1 or claim 2, wherein the temperature of the molten metal is from 0 to 200 ℃ above the melting point of the metal.
5. The method as defined in claim 1 or 4 wherein the pressure of said shot is 100-300 MPa.
6. The process according to claim 1 or 5, wherein the dwell pressure is for a time of 1-20 s.
7. The method according to claim 1, wherein the metal selected from the molten state and the die-cast metal product having the appearance defect is selected from a zirconium alloy, a copper alloy, an iron alloy, an aluminum alloy, a magnesium alloy or a zinc alloy;
preferably, the die-cast metal product with the appearance defects is an amorphous alloy die-cast metal product with the appearance defects.
8. The method as claimed in claim 1, wherein the secondary die casting is performed in a secondary die casting mold having a temperature of 150 ℃.
9. The method of claim 8, wherein the die-cast metal product having the appearance defect is a primary die-cast metal product die-cast in a primary die-casting mold, wherein a temperature of the secondary die-casting mold is 0-100 ℃ higher than a temperature of the primary die-casting mold; preferably 30-80 ℃ higher;
and the secondary die-casting die and the primary die-casting die are the same or different.
10. The method as set forth in claim 1, wherein prior to subjecting the die cast metal product with cosmetic defects to the vacuum condition, further comprising heating the die cast metal product with cosmetic defects to 100-300 ℃.
11. The method according to claim 1, wherein the appearance defect is a recessed appearance defect, and the secondary die-cast layer is formed on a surface of the die-cast metal product having the appearance defect and filled at the recessed defect.
12. A secondary die cast metal product having improved appearance defects produced by the method of any one of claims 1 to 11.
13. A middle frame of a cellular phone, characterized in that the middle frame of the cellular phone is made of the secondary die-cast metal product of claim 12.
14. A handset comprising the handset bezel of claim 13.
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