Anodizable die cast aluminum alloy material with natural age strengthening

Abstract

The application provides a natural aging strengthened anodizable die-casting aluminum alloy material, which comprises the following components in percentage by mass: Si is less than or equal to 0.15; Fe is less than or equal to 0.15; Cu is less than or equal to 0.05%; Mn is 1.85-2.5; Mg is 0.4-1.0; Zn is 2.0-4.0; Ti is less than or equal to 0.1; Ni is less than or equal to 0.1; Pb is less than or equal to 0.1; Sn is less than or equal to 0.01; and Cd is less than or equal to 0.01. The natural aging strengthened anodizable die-casting aluminum alloy material provided by the application not only can realize very beautiful color anodization effect, but also has relatively high strength. Compared with the anodizable die-casting aluminum alloy material in the prior art, the strength of the alloy material is further significantly improved after two months of natural aging, and the alloy material has very good natural aging strengthening characteristics. Moreover, the material can pass the heat resistance test of 500 DEG C*3 hours without discoloration and deformation, and has good heat resistance.

Description

Technical Field

[0001] This invention belongs to the field of die-cast aluminum alloy technology, specifically relating to anodizable die-cast aluminum alloy materials with natural aging strengthening. Background Technology

[0002] Die casting can produce products with complex structures and thin walls, but the aluminum alloy materials suitable for die casting need to have good fluidity and die-casting filling properties. Commonly used aluminum alloys for die casting are aluminum-silicon alloys, which have good fluidity due to their high silicon content. However, these alloys are not suitable for anodizing because the high silicon content can cause flow marks and dust accumulation on the surface of die-cast parts during anodizing, resulting in color differences in the surface finish.

[0003] Currently, there are also some anodized aluminum alloy materials that can be used for die casting, such as DX24 and DX21 from Japan. DX24 has a good anodizing effect, but its strength and hardness are very low, with a tensile strength of only 117MPa and a hardness of only 20HBW. It also has poor die casting fluidity, making die casting difficult. Furthermore, it requires the use of relatively expensive titanium dioxide (W) as a nucleating agent. DX21's anodizing effect is not as good as DX24's. It has slightly higher strength, with a tensile strength of 170MPa, but its hardness is also relatively low, at only 33HBW. For thinner product parts, it is prone to deformation during die casting.

[0004] Our company has also applied for numerous patents related to anodizable die-cast aluminum alloys. For example, patent application number 201610859177.6 discloses a method for preparing anodizable die-cast aluminum alloys. This alloy has a high iron, manganese, and zinc content, which improves hardness but reduces tensile strength to only 150 MPa. Furthermore, due to the high iron content, the colored anodizing effect is poor, and it is mainly used for natural color and hard anodizing. Another example is patent application number 201610859319.9, which discloses anodizable die-cast aluminum alloys with a lower zinc content, resulting in good anodizing performance but low strength and hardness. Yet another example is patent application number 201911281977.4, which discloses a method for preparing and die-casting anodizable die-cast aluminum alloys. This alloy has a very low zinc content, resulting in significant improvements in die-casting performance and the ability to produce a glowing finish after anodizing. However, it cannot achieve good strength.

[0005] It is difficult for existing anodizable die-cast aluminum alloys to simultaneously achieve excellent anodizing coloring effects and high strength. Simply increasing the zinc and iron content sacrifices the colored anodizing effect, while reducing the zinc content results in poor strength. Existing technologies struggle to simultaneously achieve a very beautiful colored anodizing effect, high strength, and further natural aging strengthening properties. Even more challenging is the simultaneous achievement of good heat resistance, which poses a significant challenge to the field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides an anodizable die-cast aluminum alloy material with natural aging strengthening.

[0007] This invention provides an anodizable die-cast aluminum alloy material with natural age hardening, wherein the die-cast aluminum alloy material comprises, by mass percentage: Si≤0.15; Fe≤0.15; Cu≤0.05%; Mn 1.85-2.5%; Mg 0.4-1.0%; Zn 2.0-4.0%; Ti≤0.1%; Ni≤0.1%; Pb≤0.1%; Sn≤0.01%; Cd≤0.01%.

[0008] Preferably, Mn is 2.02-2.5.

[0009] Preferably, the zinc content is 2.5-4.0.

[0010] Preferably, Si ≤ 0.05.

[0011] Preferably, the Fe content is ≤ 0.1.

[0012] Preferably, the Cu content is ≤0.01%.

[0013] Preferably, the zinc content is 2.8-3.5.

[0014] Preferably, the preparation of the naturally age-strengthened anodizable die-cast aluminum alloy material includes the following steps:

[0015] S1. First, put in 92% electrolytic aluminum ingots, heat to 825-850℃, and add manganese element additives in 2-3 batches.

[0016] S2. Add 8% of electrolytic aluminum ingots to the aluminum liquid to cool it down. When the temperature of the aluminum liquid is controlled at 760-780℃, add the preheated zinc ingots in 4 batches and let it stand for 5-10 minutes.

[0017] S3. Add the preheated magnesium ingots in two batches. After the test results are qualified, add 0.3-1% of the total amount of aluminum liquid seed crystals (aluminum-titanium-carbon-boron) when the temperature of the aluminum liquid is 700-750℃.

[0018] S4. Aluminum alloy ingots are cast using a bottom water-cooled mold.

[0019] Preferably, the submicron-sized aluminum-titanium-carbon-boron seed crystals are composed of the following components by weight percentage: Ti: 4.5-5.5%, C: 0.10-0.20%, B: 0.15-0.25%, Ce: 0.4-0.6%, with the remainder being Al.

[0020] Preferably, when the anodizable die-cast aluminum alloy material with natural aging strengthening is die-cast, the proportion of recycled material is controlled to be less than 30% and not exceeding 3 cycles when the recycled material is remelted and reused during the die-casting process.

[0021] The anodizable die-cast aluminum alloy material with natural aging strengthening provided by this invention not only achieves a very beautiful colored anodizing effect, but also maintains high strength. Compared with existing anodizable die-cast aluminum alloy materials, the strength of this alloy material can be significantly improved after two months of natural aging, exhibiting excellent natural aging strengthening characteristics. Furthermore, it can pass a heat resistance test at 500℃ for 3 hours without discoloration or deformation, while also demonstrating good heat resistance. Attached Figure Description

[0022] The above and other objects, features, and advantages of the invention will become clearer through a more detailed description of the preferred embodiments illustrated in the accompanying drawings. The same reference numerals denote the same parts throughout the drawings, and the drawings are not intentionally drawn to scale with actual dimensions; the focus is on illustrating the gist of the invention.

[0023] Figure 1 The image shows a high-end headphone accessory obtained by die-casting and anodizing the aluminum alloy material of Example 1 using the die-casting method of Example 2.

[0024] Figure 2 Photographs of the final product obtained by anodizing and coloring treatment after die casting the material of Comparative Example 1 using the method of Example 2;

[0025] Figure 3 The photograph shows the final product obtained by die-casting the material of Comparative Example 3 into a die-cast part using the method of Example 2, followed by anodizing and coloring treatment. Detailed Implementation

[0026] The technical solution of the present invention will be further described in detail below with reference to specific embodiments, so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0027] This invention provides an anodizable die-cast aluminum alloy material with natural age hardening, characterized in that the die-cast aluminum alloy material, by mass percentage, comprises: Si≤0.15; Fe≤0.15; Cu≤0.05%; Mn 1.85-2.5%; Mg 0.4-1.0%; Zn 2.0-4.0%; Ti≤0.1%; Ni≤0.1%; Pb≤0.1%; Sn≤0.01%; Cd≤0.01%.

[0028] In a preferred embodiment, Mn is 2.02-2.5.

[0029] In a preferred embodiment, the zinc content is 2.5-4.0; in a more preferred embodiment, the zinc content is 2.8-3.5.

[0030] In a preferred embodiment, Si ≤ 0.05.

[0031] In a preferred embodiment, the Fe content is ≤ 0.1.

[0032] In a preferred embodiment, the Cu ≤ 0.01%.

[0033] The anodizable die-cast aluminum alloy material provided by this invention reduces the content of Si, Fe, and Cu impurities in the material, resulting in a transparent and uniform oxide film effect during anodizing. Mn improves high-temperature strength, reduces deformation during die casting, and an appropriate amount of Mn enhances the flow properties of molten aluminum and the die-casting performance; it also provides good corrosion resistance and a colored or natural hue from the anodized appearance. A relatively high Zn content improves the material's flow properties and die-casting performance, while also providing high strength and hardness, and good natural aging strengthening, making the die-cast products suitable for applications requiring relatively high strength. An appropriate amount of Mg increases the anodizing color effect, strength, and hardness of the product. Trace amounts of submicron-sized aluminum-titanium-carbon-boron seed crystals effectively refine the α-Al phase grains, strengthening the material from both grain refinement and coherence perspectives, eliminating casting defects, and improving the effect and uniformity of the anodizing color. The high-melting-point elements in these crystals act as excellent nucleating agents for this anodized material.

[0034] The lower Pb, Sn, and Cd content makes the material more environmentally friendly, and its die-cast parts have a wider range of applications after anodizing. This alloy is a high solidus temperature aluminum alloy, with a solidus temperature of 650℃ and a liquidus temperature of 656℃. This alloy possesses a variety of excellent performance characteristics, including good heat resistance, and can withstand a heat resistance test at 500℃ for 3 hours without discoloration or deformation.

[0035] In a preferred embodiment, the preparation of the naturally age-strengthened anodizable die-cast aluminum alloy material includes the following steps:

[0036] S1. First, put in 92% aluminum ingots, heat to 825-850℃, and add manganese additive in 2-3 batches.

[0037] S2. Add 8% aluminum ingots to the molten aluminum to cool it down. When the temperature of the molten aluminum is controlled at 760-780℃, add the preheated zinc ingots in 4 batches and let it stand for 5-10 minutes.

[0038] S3. Add the preheated magnesium ingots in two batches. After the test results are qualified, add 0.3-1% of the total amount of aluminum liquid seed crystals (aluminum-titanium-carbon-boron) when the temperature of the aluminum liquid is 700-750℃.

[0039] S4. Aluminum alloy ingots are cast using a bottom water-cooled mold.

[0040] In a preferred embodiment, the submicron-sized aluminum-titanium-carbon-boron seed crystals are composed of the following components by weight percentage: Ti: 4.5-5.5%, C: 0.10-0.20%, B: 0.15-0.25%, Ce: 0.4-0.6%, with the remainder being Al. The nucleating agent used in this embodiment is a low-cost, high-performance novel aluminum-titanium-carbon-boron seed crystal. Its composition differs from previous aluminum-titanium-carbon-boron seed crystal alloys. Through a reasonable submicron-sized aluminum-titanium-carbon-boron seed crystal composition, better results are achieved. It forms a novel, high-performance seed crystal structure material with a relatively high Ti content, low C and B content, and a suitable Ce content. This not only achieves a very beautiful colored anodizing effect but also maintains high strength and excellent natural aging strengthening characteristics. Furthermore, it can withstand a heat resistance test at 500℃ for 3 hours without discoloration or deformation, demonstrating good heat resistance.

[0041] In a preferred embodiment, when the anodizable die-cast aluminum alloy material with natural aging strengthening is die-cast, the proportion of recycled material is controlled to be less than 30% and not exceeding 3 cycles during the die-casting process.

[0042] In a preferred embodiment, the method for preparing anodizable die-cast aluminum alloy material with natural age strengthening provided by the present invention includes the following steps:

[0043] (1) The furnace bottom and furnace wall must be thoroughly cleaned before smelting to prevent impurities from the previous furnace from entering and affecting the composition of the molten aluminum.

[0044] (2) First, put in 92% electrolytic aluminum ingots, heat to 825-850℃, and add manganese element additives in 2-3 batches;

[0045] (3) After adding the melted product, stir thoroughly three times and let it stand for at least 10 minutes each time.

[0046] (4) Add 8% aluminum ingots to the molten aluminum for cooling. Control the temperature of the molten aluminum at 760-780℃;

[0047] (5) When the temperature of the aluminum liquid is 760-780℃, add the preheated zinc ingots in 4 batches. After melting, stir thoroughly and let stand for 5-10 minutes.

[0048] (6) Add sodium-free refining agent at 740-760℃ for refining and purification (addition amount is 0.15-0.25%). The inert gas carrier is injected into the refining agent at a rate of 0.5 kg / min;

[0049] (7) After refining, let it stand for 10 minutes to remove slag;

[0050] (8) Add the preheated magnesium ingot in two batches, stir thoroughly after melting, and let stand for 5-10 minutes.

[0051] (9) After thorough mixing, take a sample for testing;

[0052] (10) After the composition is qualified, nitrogen or argon is used to degas for 20-30 minutes. After completion, the slag on the surface of the aluminum liquid is removed.

[0053] (11) When the temperature of the aluminum liquid is 700-750℃, add 0.3-1% of the total amount of aluminum liquid submicron-sized aluminum-titanium-carbon-boron seed crystals (composition: Ti: 4.5-5.5%, C: 0.10-0.20%, B: 0.15-0.25%, Ce: 0.4-0.6%, the remainder being Al), let it stand for 5-10 minutes, and then cast the aluminum alloy ingot using a bottom water-cooled mold;

[0054] (12) During the casting process, a filter box is used to filter the gas before the distributor, and nitrogen or argon is used to degas the gas online through the breathable brick with a pore size of 15-40μm at the bottom for further purification.

[0055] (13) All the stirring described above shall be carried out using non-iron tools.

[0056] In a preferred embodiment, the die-casting method for anodizable die-castable aluminum alloy materials with natural age strengthening provided by the present invention includes the following steps:

[0057] Pre-die casting remelting process:

[0058] (1) It has a high melting point, and the appropriate smelting temperature for remelting is 700-750℃.

[0059] (2) Avoid the mixing of other alloys and impurities.

[0060] (3) Do a good job of removing slag and gas.

[0061] (4) When recycled materials are remelted and reused in the die casting process, the proportion of recycled materials shall be controlled to be less than 30% and shall not exceed 3 cycles. Slag bags and exhaust parts shall not be recycled.

[0062] Die casting process:

[0063] (1) To prevent die casting from sticking to the mold, the gate speed should be 20-25 m / s. The gate area should be 1-2 cm² per 100g of product weight. 2 (Proportional)

[0064] (2) The solidification shrinkage rate of the die casting parts considered in the design of the die casting mold is about 0.5-1%.

[0065] (3) The draft angle is more than twice that of ADC12.

[0066] (4) The ejector pins should be thicker than those of ADC12, and there should be more of them.

[0067] (5) Due to the high liquidus temperature, the temperature of the die-cast aluminum liquid should be between 700 and 750℃.

[0068] (6) The temperature of the die-casting mold is 250-350℃. However, due to the high temperature of die casting, care should be taken to prevent the mold from overheating.

[0069] (7) Generally, the faster the piston speed, the smoother the casting surface, provided that sticking to the mold does not occur. When setting the piston speed, it can be gradually adjusted from slow to fast.

[0070] (8) Use water-soluble release agent for casting.

[0071] In a preferred embodiment, the naturally age-strengthened anodizable die-cast aluminum alloy material provided by the present invention is suitable for surface anodizing and corrosion-resistant anodizing of die-cast parts with high strength and moderate toughness. It can be widely used in decorative components, electronic communication materials, hardware, food, and other industries for die-cast aluminum alloy parts requiring corrosion-resistant anodizing and surface coloring anodizing.

[0072] To provide a better understanding of the technical solution of the present invention, several preferred embodiments are listed below for further detailed description.

[0073] Example 1

[0074] By weight percentage, silicon: 0.043%, iron: 0.077%, copper: 0.003%, manganese: 2.02%, magnesium: 0.53%, zinc: 2.92%, titanium: 0.0108%, lead: 0.0016%, tin: 0.001%, cadmium: 0.0013%.

[0075] The aluminum alloy is prepared according to the above proportions, and the steps are as follows:

[0076] According to the production plan, ensure proper transitions between different alloy grades. Use a scraper to remove and clean the furnace walls and bottom from the previous furnace. Add 92% of the weight of No. 1 electrolytic aluminum ingots to the furnace. Heat and melt the ingots into molten aluminum, raising the temperature to 833°C. Add preheated manganese additives in three batches. After melting, mechanically stir with graphite, alternating with settling three times, each time for 10 minutes, to ensure effective alloying. Then add the remaining 8% of No. 1 electrolytic aluminum ingots to the furnace, melt them, and mechanically stir with graphite. Reduce the temperature of the molten aluminum to 767°C, and add preheated zinc ingots in four batches. After melting, stir evenly and settling for 5 minutes. Subsequently, using nitrogen as the carrier gas, inject 0.2% of the total weight of sodium-free refining agent into the molten aluminum at a rate of 0.5 kg / min for refining. After refining, settling for 10 minutes to remove slag. Preheated magnesium ingots were added in two batches, melted, stirred thoroughly, and allowed to stand for 5 minutes. After thorough stirring with graphite, samples were taken for composition testing. Next, nitrogen was used to degas the molten aluminum for 30 minutes to remove slag. Once the composition test was satisfactory, 0.3% of submicron-sized aluminum-titanium-carbon-boron seed crystals were added to the molten aluminum. After melting and stirring thoroughly, the mixture was allowed to stand for 5 minutes, and slag was removed again. The molten aluminum was kept at 720℃, and aluminum alloy ingots were cast using a bottom-cooled mold. Throughout the casting process, nitrogen was used for online degassing and further purification before the distributor, passing through permeable bricks with 15-40μm pore sizes at the bottom of the filter box.

[0077] The aluminum alloy material was tested and found to have the following characteristics: pinhole level 1, grain size level 1, porosity level 1, conductivity 18.45% IACS, density 2.67 g / cm³, tensile strength 195 MPa, and hardness 50.27 HBW.

[0078] After two months of natural aging, the aluminum alloy material was tested and found to have a tensile strength of 253 MPa and a hardness of 68.47 HBW, demonstrating a good natural aging strengthening effect.

[0079] It passed a heat resistance test at 500℃ for 3 hours and did not change color or deform.

[0080] Example 2

[0081] The aluminum alloy material prepared in Example 1 is then die-cast into die-cast parts using a die-casting machine according to the die-casting process. After anodizing and coloring treatment, the final high-end headphone product accessories are obtained.

[0082] Pre-die casting remelting process:

[0083] During remelting, the melting temperature should be 750℃. Avoid the mixing of other alloys and impurities. Ensure proper slag and gas removal. The proportion of recycled material should be controlled to be less than 30%, and the total amount should not exceed 3 cycles. Slag bags and venting areas must not be recycled.

[0084] Die casting conditions:

[0085] The gate velocity is 20-25 m / s. The gate area is 1-2 cm² per 100g of product weight. 2 (Proportional);

[0086] The solidification shrinkage rate of die-cast parts considered in the design of die-casting molds is approximately 1%;

[0087] The draft angle during die casting must be controlled to be ≥1.5. 0 ;

[0088] The ejector pins should be thicker than those of ADC12, and there should be more of them.

[0089] The temperature of the die-cast aluminum melt is 700-750℃;

[0090] The temperature of the die-casting mold is 250-350℃;

[0091] Water-soluble release agent for casting.

[0092] The aluminum alloy material prepared in Example 1 exhibited good fluidity during die casting, with no sticking to the mold, resulting in smooth die casting. After anodizing, the die-cast parts showed uniform color with no color difference or flow marks. See attached product photos. Figure 1 As shown.

[0093] Comparative Example 1

[0094] Compared to Example 1, in Comparative Example 1, Mn was changed to 0.8%, while the remaining formulation and preparation method were the same as in Example 1. Furthermore, the die-casting process was followed by anodizing and coloring treatment to obtain the final product. The anodizing coloring effect of the die-cast parts was poor. See attached product photos. Figure 2 As shown.

[0095] Comparative Example 2

[0096] Compared to Example 1, Zn was changed to 1%, while the remaining formulation and preparation method were the same as in Example 1. The aluminum alloy material was tested and found to have a tensile strength of 166 MPa and a hardness of 45.22 HBW. The tensile strength of the aluminum alloy material decreased by 15%, and the hardness decreased by 10%.

[0097] After undergoing the same two-month natural aging process as in Example 1, the aluminum alloy material was tested and found to have a tensile strength of 169 MPa and a hardness of 48.34 HBW, indicating that natural aging did not significantly strengthen the material.

[0098] Comparative Example 3

[0099] Compared to Example 1, the submicron-sized aluminum-titanium-carbon-boron seed crystals have the following composition: Ti: 1.8-2.2%, C: 0.28-0.35%, B: 0.28-0.35%, with the remainder being Al. The remaining formulation and preparation method are the same as in Example 1. Furthermore, the die-cast parts were obtained using the method of Example 2, followed by anodizing and coloring treatment to obtain the final product. The die-cast parts produced by the method in Comparative Example 3 have coarse grains, poor and uneven anodizing coloring effect, and flow marks. See attached product photos. Figure 3 As shown.

[0100] In summary, it can be seen that the anodizable die-cast aluminum alloy material with natural aging strengthening provided by this invention has a reasonable formula and preparation method, which not only achieves a very beautiful colored anodizing effect, but also maintains high strength. Compared with existing anodizable die-cast aluminum alloy materials, this alloy material shows a significant further increase in strength after two months of natural aging, exhibiting excellent natural aging strengthening characteristics. Furthermore, this material can withstand a heat resistance test at 500℃ for 3 hours without discoloration or deformation, while also possessing good heat resistance.

[0101] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A naturally age-strengthened anodizable die-cast aluminum alloy material, characterized in that, The die-cast aluminum alloy material, by mass percentage, includes Si≤0.05; Fe≤0.1; Cu≤0.01%; Mn 2.02-2.5; Mg 0.4-1.0; Zn 2.8-3.5; Ti≤0.1; Ni≤0.1; Pb≤0.1; Sn≤0.01; Cd≤0.

01. The preparation of the naturally age-strengthened anodizable die-cast aluminum alloy material includes the following steps: S1. First, put in 92% electrolytic aluminum ingots, heat to 825-850℃, and add manganese element additives in 2-3 batches. S2. Add 8% of electrolytic aluminum ingots to the aluminum liquid to cool it down. When the temperature of the aluminum liquid is controlled at 760-780℃, add the preheated zinc ingots in 4 batches and let it stand for 5-10 minutes. S3. Add the preheated magnesium ingots in two batches. After the test results are qualified, add 0.3-1% of the total amount of aluminum liquid seed crystals (aluminum-titanium-carbon-boron) when the temperature of the aluminum liquid is 700-750℃. S4. Aluminum alloy ingots are cast using a bottom water-cooled mold; The submicron-sized aluminum-titanium-carbon-boron seed crystals, by weight percentage, consist of the following components: composition: Ti: 4.5-5.5%, C: 0.10-0.20%, B: 0.15-0.25%, Ce: 0.4-0.6%, with the remainder being Al.

2. The anodizable die-cast aluminum alloy material with natural age hardening as described in claim 1, characterized in that, When the anodizable die-cast aluminum alloy material with natural age strengthening is die-cast, the proportion of recycled material is controlled to be less than 30% and not more than 3 cycles.

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