Heat treatment free die cast aluminium alloy, method for manufacturing the same and aluminium alloy die cast

Abstract

The application provides a heat treatment-free die-casting aluminum alloy, a method for manufacturing the same and an aluminum alloy die-casting product. The method for manufacturing the heat treatment-free die-casting aluminum alloy comprises the following steps: preparing raw materials in the following proportions: Si 7.5-10wt.%, Mn 0.4-0.8wt.%, Mg 0.1-0.4wt.%, Ti 0.05-0.22wt.%, Sr 0.008-0.03wt.%, Fe≤0.18wt.%, the rest being aluminum and impurities, wherein the content of each of other impurity elements in the impurities is ≤0.05wt.% and the total content of the other impurities is ≤0.3wt.%; sequentially performing the following steps on the raw materials: melting, deslagging, modification, refining, degassing and first detection, wherein an Al-RE-B refiner is added in the refining step, and RE is a rare earth metal element.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum alloy, in particular to a heat treatment-free die casting aluminum alloy, a method for manufacturing the same and an aluminum alloy die casting. BACKGROUND

[0002] In terms of materials, the integration of multiple parts leads to the large-scale of die castings, greatly increasing the difficulty of heat treatment and the rejection rate. Therefore, heat treatment-free aluminum alloy materials suitable for large-scale and thin-walled die castings become the only choice for integrated die casting. With the increase of the size and complexity of integrated products, the long die casting process characteristics reduce the qualification rate of castings and increase the performance heterogeneity.

[0003] Common die casting structural parts usually use AlSiMnMg series alloy. The addition of Si element can significantly improve the fluidity of the alloy, reduce defects such as porosity and shrinkage, and the Si phase has good chemical stability and higher hardness, which can increase the corrosion resistance and wear resistance of the aluminum alloy. However, the Si phase is also prone to aggregation, which affects the overall performance of the structural part. The addition of Mn element can improve the strength and hardness of the structural part, and a small amount of Mg can improve the fluidity, corrosion resistance and reduce the sticking tendency of the alloy. However, the addition of Mn and Mg elements will affect the uniformity of the alpha-Al grains.

[0004] Integrated aluminum alloy die castings require excellent mechanical properties such as high yield strength and high toughness. Currently, it has become an inevitable trend to use heat treatment-free die casting aluminum alloy to prepare integrated structural parts. However, when the strength deviation of different parts of the die casting is greater than 30%, it is difficult to meet the actual performance requirements of the structural part. The main influencing factor of mechanical properties is the microstructure morphology of the aluminum alloy material. The pre-crystallization and normal die casting grains are the main reasons for the difference in structure. The pre-crystallization structure is the structure before entering the cavity, which will grow after entering the cavity. Normal alpha-Al grains are also generated in the cavity. In the metallographic structure of the final product, the grains with a size greater than 30 μm are called pre-crystallization, and the grains with a size less than 30 μm are called normal grains. Due to the characteristics of die casting, the structure of different parts of the die casting is significantly different. The larger the size and the more the number of pre-crystallization, the larger the normal grain size and the larger the eutectic Si size, the more likely it is to produce segregation, and the worse the performance of the die casting. The size of the pre-crystallization and normal grain and the volume fraction of the pre-crystallization are related to the mold, die casting process and grain refinement method. By adjusting the three, the size of the pre-crystallization and normal grain and the volume fraction of the pre-crystallization can be reduced. However, the traditional method of refining grains will cause Sr poisoning, which will affect the performance of the die casting. Therefore, how to improve the uniformity of the heat treatment-free high-vacuum die casting aluminum alloy and make it have more excellent uniform performance is of great significance for improving the qualification rate of die casting structural parts, promoting the industrialization of integrated die casting, and further promoting the development of the automobile industry.

[0005] In view of the above problems, it is necessary to develop a method for manufacturing heat treatment-free die-casting aluminum alloy which can avoid Sr poisoning while reducing the size of pre-crystallization and making the grain structure more uniform. SUMMARY

[0006] The main purpose of the present application is to provide a method for manufacturing heat treatment-free die-casting aluminum alloy to solve the problems of large grain size, poor uniformity, and poor performance of aluminum alloy caused by Sr poisoning in the process of refining in the prior art method for manufacturing die-casting aluminum alloy.

[0007] To achieve the above-mentioned purpose, the present application provides a method for manufacturing heat treatment-free die-casting aluminum alloy, characterized in that the method for manufacturing heat treatment-free die-casting aluminum alloy comprises: preparing raw materials in the following proportions: Si 7.5-10wt.%, Mn 0.4-0.8wt.%, Mg 0.1-0.4wt.%, Ti 0.05-0.22wt.%, Sr 0.008-0.03wt.%, Fe≤0.18wt.%, the rest being aluminum and impurities, the proportion of each impurity element in the raw materials is ≤0.05wt.%, and the total proportion of impurities is ≤0.3wt.%; sequentially melting, deslagging, modifying, refining, and degassing the raw materials, and first detecting, wherein Al-RE-B refiner is added in the refining step, and RE is a rare earth metal element.

[0008] Further, the Al-RE-B refiner includes Al-La-B refiner or Al-Y-B refiner; preferably, the amount of Al-RE-B refiner is greater than 0, ≤1.0wt.%, based on the total weight of the heat treatment-free die-casting aluminum alloy.

[0009] Further, the melting step comprises preheating the raw materials to 100-300℃, and then performing melting treatment to obtain a melt, wherein the temperature of the melt is controlled at 740-780℃.

[0010] Further, the deslagging step comprises adding a deslagging agent to the melt, the deslagging agent accounting for 0.1-0.5wt.% of the weight of the melt, and controlling the temperature of the melt at 730-750℃.

[0011] Further, the modifying step comprises second detecting the melt obtained in the deslagging step, when the detection result meets the proportion of each element in the raw materials except Sr, adding a strontium modifier, controlling the temperature of the melt at 720-740℃, and stirring and standing for 10-20min after stirring, preferably, the amount of metallic strontium in the strontium modifier is 0.008-0.03wt.% of the weight of the melt; preferably, the strontium modifier is aluminum-strontium intermediate alloy.

[0012] Furthermore, the temperature of the melt is controlled at 700-750℃ during the refinement process.

[0013] Furthermore, the degassing step includes degassing the melt obtained in the refining step using N2 or Ar gas at a temperature of 720-740℃ for 10-20 minutes.

[0014] Furthermore, the first testing process includes: performing composition testing, density testing, and slag content testing on the melt obtained from the degassing step. The test results must meet the following criteria: the composition conforms to the specified proportions of each element in the raw material, and the density value is greater than 2.61 g / cm³. 3 When the K modulus value is not higher than 1 / 20, the preparation process ends. If the test result does not meet the standard, repeat the melting, slag removal, deterioration, refinement and degassing and the first test step.

[0015] To achieve the above objectives, another aspect of the present invention provides a heat-free die-cast aluminum alloy having a pre-crystallized average grain size of >30μm and ≤60μm, a pre-crystallized maximum grain size of ≤60μm, and a normal average grain size of ≤10μm, wherein the heat-free die-cast aluminum alloy is manufactured by the method described above.

[0016] Another aspect of the present invention provides an aluminum alloy die casting part, which is obtained by high vacuum die casting of the above-mentioned heat-free die casting aluminum alloy.

[0017] By applying the technical solution of this invention, a highly efficient grain refiner containing rare earth elements is added during the production of die-cast aluminum alloys. This refiner has a strong effect on refining α-Al in the alloy, is unaffected by Sr poisoning, does not affect the modification effect of Sr, and can reduce the aspect ratio of Si to a certain extent. The refining effect of boron (B) on the aluminum alloy promotes heterogeneous nucleation and inhibits grain growth. The addition of rare earth elements (RE) inhibits the growth of grains towards dendrites and the growth of Si phase towards increasing aspect ratio, reducing the size of pre-crystallized grains and making the grain structure more uniform. Furthermore, most rare earth elements have relatively weak bonding with Sr and will not react with Sr. The heat-free high-vacuum die-cast aluminum alloy produced by this method has a finer and more uniform microstructure compared to other similar products, and achieves superior and more stable performance without heat treatment. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0019] Figure 1 Metallographic image of the microstructure of the aluminum alloy manufactured according to Example 1;

[0020] Figure 2 Metallographic image of the microstructure of the aluminum alloy manufactured according to Example 2;

[0021] Figure 3 Metallographic image of the microstructure of the aluminum alloy manufactured according to Example 3;

[0022] Figure 4 Metallographic image of the microstructure of the aluminum alloy manufactured according to Example 4;

[0023] Figure 5 Metallographic image of the microstructure of the aluminum alloy manufactured according to Example 5;

[0024] Figure 6 Metallographic diagram of the microstructure of the aluminum alloy manufactured according to Comparative Example 1;

[0025] Figure 7 Metallographic diagram of the microstructure of the aluminum alloy manufactured according to Comparative Example 2. Detailed Implementation

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0027] As described in the background art, the existing methods for manufacturing die-cast aluminum alloys suffer from problems such as large grain size, poor uniformity, and Sr poisoning during the grain refinement process, resulting in poor aluminum alloy performance. To address the aforementioned technical problems, this application provides a method for manufacturing heat-free die-cast aluminum alloys. The method comprises: preparing raw materials in the following proportions by weight percentage: Si 7.5-10 wt.%, Mn 0.4-0.8 wt.%, Mg 0.1-0.4 wt.%, Ti 0.05-0.22 wt.%, Sr 0.008-0.03 wt.%, Fe ≤0.18 wt.%, with the remainder being aluminum and impurities. The proportion of each impurity element in the raw materials is ≤0.05 wt.%, and the total proportion of impurities is ≤0.3 wt.%. The raw materials are then subjected to smelting, slag removal, modification, refining, degassing, and a first detection, wherein an Al-RE-B refining agent is added in the refining step, where RE represents a rare earth metal element.

[0028] By applying the technical solution of this invention, a highly efficient grain refiner containing rare earth elements is added during the production of die-cast aluminum alloys. This refiner has a strong effect on refining α-Al in the alloy, is unaffected by Sr poisoning, does not affect the modification effect of Sr, and can reduce the aspect ratio of Si to a certain extent. The refining effect of B on the aluminum alloy promotes heterogeneous nucleation and inhibits grain growth. The addition of RE elements inhibits the growth of grains towards dendrites and the growth of Si phase towards increasing aspect ratio, reducing the size of pre-crystallized grains and making the grain structure more uniform. Most rare earth elements have relatively weak bonding with Sr and will not react with Sr, thus achieving a more uniform and finer structure without affecting Sr modification, effectively improving the uniformity of the product structure and giving the product superior performance. Compared with other similar products, the heat-free high-vacuum die-cast aluminum alloy produced by this method has a finer and more uniform microstructure and achieves superior and more stable performance without heat treatment. This reduces the number of heat treatment steps, shortens the production process, saves time, and reduces costs. Furthermore, the method of the present invention is applicable to more aluminum alloy structural components, including but not limited to structural components that are large in size, complex in shape, and difficult to heat treat.

[0029] In summary, this invention proposes a method for manufacturing die-cast aluminum alloys. Without increasing equipment, altering mold structure and die-casting conditions, or eliminating heat treatment, it optimizes the microstructure uniformity of the product, resulting in superior performance. Simultaneously, it improves production efficiency and reduces production costs. Using this method, the technical problems of existing die-cast aluminum alloys in simultaneously meeting requirements such as ultra-large size, complex structure, and excellent performance are solved, further enhancing the overall performance of the product.

[0030] The Al-RE-B refining agent used in the above method is a mixture of compounds containing Al, RE, and B elements. In a preferred embodiment, the mass percentages of RE and B elements in the Al-RE-B refining agent are 1%-3% and 0.1%-2%, respectively. In a preferred embodiment, the Al-RE-B refining agent used in the above method includes Al-La-B refining agents or Al-YB refining agents. Taking Al-La-B refining agents as an example, the stable compound LaB6, composed of rare earth elements La and B, has a mismatch degree of less than 5 wt.% with a specific Al crystal plane. Primary Al will directly nucleate and grow on the LaB6 surface, which can significantly improve the nucleation rate of α-Al.

[0031] In a preferred embodiment, the amount of Al-RE-B refining agent used in the above method is greater than 0 and ≤1.0 wt.%.

[0032] In a preferred embodiment, the smelting step in the above method includes preheating the raw material to 100-300°C and then performing a melting process to obtain a melt, wherein the melt temperature is controlled at 740-780°C.

[0033] In a preferred embodiment, the raw materials used to manufacture the heat-free die-cast aluminum alloy include aluminum, silicon, manganese, magnesium, titanium, and strontium. In another preferred embodiment, the aluminum raw material is pure aluminum ingots or electrolytic aluminum; the silicon raw material is an aluminum-silicon master alloy or industrial silicon; the manganese raw material is an aluminum-manganese master alloy or manganese agent; the titanium raw material is pure titanium, titanium agent, or an aluminum-titanium master alloy; the magnesium raw material is pure magnesium; and the strontium raw material is an aluminum-strontium master alloy. The strontium raw material is the strontium modifier mentioned below. The Fe in the raw materials comes from the Fe contained in the aluminum raw material.

[0034] In a preferred embodiment, the order of feeding the raw materials in the above smelting step is: aluminum, silicon, manganese, and magnesium. If other feeding orders are used, such as adding magnesium earlier, prolonged smelting will lead to magnesium loss due to burning, resulting in a decrease in magnesium content.

[0035] In a preferred embodiment, the slag removal step in the above method includes adding a slag remover to the melt, the slag remover accounting for 0.1-0.5 wt.% of the melt weight, and controlling the temperature of the melt at 730-750°C. In a preferred embodiment, the slag remover used is a sodium-free, low-calcium refining agent.

[0036] In a preferred embodiment, the modification step in the above method includes performing a second test on the melt obtained from the slag removal step. When the test result satisfies that the composition of the melt obtained from the slag removal step, except for Sr, meets the proportions of each element in the above raw materials, a strontium modifier is added, and the temperature of the melt is controlled at 720-740°C. After stirring, the melt is allowed to stand for 10-20 minutes. Preferably, the amount of metallic strontium in the strontium modifier is 0.008-0.03 wt.% of the melt weight. Preferably, the strontium modifier is an aluminum-strontium master alloy.

[0037] In a preferred embodiment, the qualification criterion for the second test is that the content of elements other than Sr meets the proportion of the above-mentioned raw materials.

[0038] In a preferred embodiment, the temperature of the melt is controlled at 700-750°C during the refining step of the above method.

[0039] In a preferred embodiment, the degassing step in the above method includes degassing the melt obtained in the refining step using N2 or Ar gas, with the temperature of the degassing step being 720-740°C and the time being 10-20 min.

[0040] In the method for manufacturing heat-free die-cast aluminum alloys according to the present invention, the temperature and melting time of each raw material are strictly controlled during raw material feeding. In the refining and degassing stage, the amount of Al-RE-B refining agent used is controlled, and the refining temperature and time are strictly controlled. The refining effect of B on the aluminum alloy promotes heterogeneous nucleation and inhibits grain growth. The addition of RE element inhibits grain growth towards dendrites and suppresses the growth of the Si phase towards a larger aspect ratio. Combined with the effect of Sr element, the aspect ratio of the Si phase can be further reduced. This results in an alloy with a uniform microstructure, ultimately yielding high-vacuum die-cast aluminum alloy structural parts with excellent mechanical properties.

[0041] In a preferred embodiment, the first detection process in the above method includes: performing composition detection, density detection, and slag content detection on the melt obtained from the degassing step. The detection results are determined when the following criteria are met: the composition conforms to the proportions of each element in the raw material, and the density value is greater than 2.61 g / cm³. 3 When the K-modulus value is no higher than 1 / 20, the preparation process ends. If the test results do not meet the standards, the melting, slag removal, modification, refinement, degassing, and first test steps are repeated. Specifically, if the composition is unqualified, it needs to be remelted. If the density value is unqualified, it needs to be degassed again. If the K-modulus value is unqualified, it needs to be slag removed again. The K-modulus value is a score obtained by using a K-mold to test the slag content of the aluminum alloy; the lower the K-modulus value, the lower the slag content of the aluminum alloy.

[0042] The smelting, slag removal, modification, refining, degassing, and detection steps in the above method can be implemented using commonly used equipment and processes in this field.

[0043] Another aspect of this application provides a heat-free die-cast aluminum alloy having a pre-crystallized average grain size of >30μm and ≤60μm, a pre-crystallized maximum grain size of ≤60μm, and a normal average grain size of ≤10μm, manufactured using the above-described method for manufacturing heat-free die-cast aluminum alloys.

[0044] Another aspect of this application provides an aluminum alloy die casting obtained by high-vacuum die casting of the aforementioned heat-free die-cast aluminum alloy.

[0045] In a preferred embodiment, the heat-free die-cast aluminum alloy that has passed the first test in the above method is allowed to cool to 690-720°C, and then the die-casting part is obtained by high vacuum die casting.

[0046] By applying the technical solution of this invention, a highly efficient grain refiner containing rare earth elements is added during the production of die-cast aluminum alloys. This refiner has a strong effect on refining α-Al in the alloy, is unaffected by Sr poisoning, does not affect the modification effect of Sr, and can reduce the aspect ratio of Si to a certain extent. The refining effect of B on the aluminum alloy promotes heterogeneous nucleation and inhibits grain growth. The addition of RE elements inhibits the growth of grains towards dendrites and the growth of Si phase towards increasing aspect ratio, reducing the size of pre-crystallized grains and making the grain structure more uniform. Most rare earth elements have relatively weak bonding with Sr and will not react with Sr, thus achieving a more uniform and finer structure without affecting Sr modification, effectively improving the uniformity of the product structure and giving the product superior performance. Compared with other similar products, the heat-free high-vacuum die-cast aluminum alloy produced by this method has a finer and more uniform microstructure and achieves superior and more stable performance without heat treatment. This reduces the number of heat treatment steps, shortens the production process, saves time, and reduces costs. Furthermore, the method of the present invention is applicable to more aluminum alloy structural components, including but not limited to structural components that are large in size, complex in shape, and difficult to heat treat.

[0047] In summary, this invention proposes a method for manufacturing die-cast aluminum alloys. Without increasing equipment, altering mold structure and die-casting conditions, or eliminating heat treatment, it optimizes the microstructure uniformity of the product, resulting in superior performance. Simultaneously, it improves production efficiency and reduces production costs. Using this method, the technical problems of existing die-cast aluminum alloys in simultaneously meeting requirements such as ultra-large size, complex structure, and excellent performance are solved, further enhancing the overall performance of the product.

[0048] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0049] Example 1

[0050] A heat-free, high-vacuum die-cast aluminum alloy is manufactured. This alloy is an Al-Si-Mn alloy, composed of the following components: Si 8.8 wt.%, Mn 0.55 wt.%, Mg 0.22 wt.%, Ti 0.1 wt.%, Sr 0.011 wt.%, Fe 0.1 wt.%, with the remainder being aluminum and unavoidable impurities. The content of any single element in these trace impurities is ≤0.003 wt.%, and the total amount of trace impurities is ≤0.03 wt.%. The manufacturing steps are as follows:

[0051] (1) Mix pure aluminum ingots, aluminum-silicon master alloy, aluminum-manganese master alloy, pure magnesium ingots, and aluminum-strontium master alloy in the above proportions and preheat to 180±10℃. Place the preheated aluminum ingots, aluminum-silicon master alloy, and aluminum-manganese master alloy into a melting furnace to dissolve them. Control the solution temperature at 735±10℃, then add pure magnesium ingots, melt and stir evenly.

[0052] (2) The melt is subjected to slag removal treatment at a temperature of 738°C. The slag removal agent is a sodium-free, low-calcium refining agent (Sichuan Lande High-Tech Industry Co., Ltd.), and the amount is 0.3 wt.% of the total melt volume.

[0053] (3) The composition of the melt was tested. After the composition was qualified, the aluminum-strontium master alloy Al-10Sr (Sichuan Lande High-tech Industry Co., Ltd.) was added. The melt temperature was controlled at 730±10℃. After stirring, it was allowed to stand for 15 minutes. Then, Al-La-B refining agent was added, in which La accounted for 1.5wt.% of the refining agent, B accounted for 0.8wt.% of the refining agent, and the weight of the refining agent accounted for 0.5wt.% of the total melt. The melt temperature was controlled at 730±10℃. The alloy melt was degassed with N2 gas. The degassed temperature was controlled at 730±10℃. The degassed process was carried out twice, with a time of 10 minutes each time.

[0054] (4) The composition of the refined alloy melt was tested and found to be qualified; the density of the alloy melt was tested and found to be 2.66 g / cm³. 3 The alloy melt was tested for slag content, and the K-modulus value was 0 / 20. If the melt was qualified, it was allowed to stand and cool down to 700±10℃ to obtain the aluminum alloy melt.

[0055] (5) The die casting was prepared by high vacuum die casting process, with a vacuum degree of 30±5mbar, a die casting temperature of 690±10℃, an injection speed of 2.2m / s, and an injection pressure of 102MPa.

[0056] Example 2

[0057] A heat-treatable, high-vacuum die-cast aluminum alloy is manufactured. This alloy is an Al-Si-Mn alloy, composed of the following components: Si 8.6 wt.%, Mn 0.5 wt.%, Mg 0.25 wt.%, Ti 0.1 wt.%, Sr 0.012 wt.%, Fe 0.12 wt.%, with the remainder being aluminum and unavoidable impurities. The content of any single element in these trace impurities is ≤0.05 wt.%, and the total amount of trace impurities is ≤0.02 wt.%. The manufacturing steps are as follows:

[0058] (1) Mix pure aluminum ingots, aluminum-silicon master alloy, aluminum-manganese master alloy, pure magnesium ingots, and aluminum-strontium master alloy in the above proportions and preheat to 180±10℃. Place the preheated aluminum ingots, aluminum-silicon master alloy, and aluminum-manganese master alloy into a melting furnace to dissolve them. Control the solution temperature at 735±10℃, then add pure magnesium ingots, melt and stir evenly.

[0059] (2) The melt is subjected to slag removal treatment at a temperature of 742°C. The slag removal agent is a sodium-free, low-calcium refining agent, and the amount is 0.4 wt.% of the total melt volume.

[0060] (3) The composition of the melt was tested. After the composition was qualified, the aluminum-strontium master alloy Al-10Sr was added. The solution temperature was controlled at 730±5℃. After stirring, it was allowed to stand for 15 minutes. Then, Al-La-B refining agent was added, in which the proportion of La in the refining agent was 1.0wt.% and the proportion of B in the refining agent was 1.2wt.%. The weight of the refining agent accounted for 0.1wt.% of the total melt. The melt temperature was controlled at 730±10℃. The alloy melt was refined and degassed using Ar gas. The refining and degassed temperature was controlled at 730±10℃. The process was carried out twice, with a time of 10 minutes each time.

[0061] (4) The composition of the refined alloy melt was tested and found to be qualified; the density of the alloy melt was tested and found to be 2.635 g / cm³. 3 The alloy melt was tested for slag content, and the K-modulus value was 0 / 20. If the melt was qualified, it was allowed to stand and cool down to 700±10℃ to obtain the aluminum alloy melt.

[0062] (5) Aluminum alloy die castings were prepared by high vacuum die casting process, with a vacuum degree of 35±5mbar, a casting temperature of 690±10℃, an injection speed of 2.2m / s, and a casting pressure of 105MPa.

[0063] Example 3

[0064] A heat-treatable, high-vacuum die-cast aluminum alloy is manufactured. This alloy is an Al-Si-Mn alloy, composed of the following components: Si 8.6 wt.%, Mn 0.62 wt.%, Mg 0.3 wt.%, Ti 0.1 wt.%, Sr 0.14 wt.%, Fe 0.12 wt.%, with the remainder being aluminum and unavoidable impurities. The content of any single element in these trace impurities is ≤0.05 wt.%, and the total amount of trace impurities is ≤0.02 wt.%. The manufacturing steps are as follows:

[0065] (1) Mix pure aluminum ingots, aluminum-silicon master alloy, aluminum-manganese master alloy, pure magnesium ingots, and aluminum-strontium master alloy in the above proportions and preheat to 180±10℃. Place the preheated aluminum ingots, aluminum-silicon master alloy, and aluminum-manganese master alloy into a melting furnace to dissolve them. Control the solution temperature at 735±10℃, then add pure magnesium ingots, melt and stir evenly.

[0066] (2) The melt is subjected to slag removal treatment at a temperature of 737°C. The slag removal agent is a sodium-free, low-calcium refining agent, and the amount is 0.4 wt.% of the total melt volume.

[0067] (3) The composition of the melt was tested. After the composition was qualified, the aluminum-strontium master alloy Al-10Sr was added, the solution temperature was controlled at 730±5℃, and after stirring, it was allowed to stand for 15 min. Al-YB refining agent was added, in which Y accounted for 2wt.% of the refining agent, B accounted for 1wt.% of the refining agent, and the weight of the refining agent accounted for 0.1wt.% of the total melt. The melt temperature was controlled at 730±10℃. Ar gas was used to refine and degas the alloy melt. The refining and degassing temperature was controlled at 730±10℃. The process was carried out twice, with a time of 10 min each time.

[0068] (4) The composition of the refined alloy melt was tested and found to be qualified; the density of the alloy melt was tested and found to be 2.63 g / cm³. 3 The alloy melt was tested for slag content, and the K-modulus value was 0 / 20. If the melt was qualified, it was allowed to stand and cool down to 700±10℃ to obtain the aluminum alloy melt.

[0069] (5) Aluminum alloy die castings were prepared by high vacuum die casting process, with a vacuum degree of 35±5mbar, a casting temperature of 690±10℃, an injection speed of 2.2m / s, and a casting pressure of 105MPa.

[0070] Example 4

[0071] A heat-treatable, high-vacuum die-cast aluminum alloy is manufactured. This alloy is an Al-Si-Mn alloy, composed of the following components: Si 8.4 wt.%, Mn 0.45 wt.%, Mg 0.27 wt.%, Ti 0.1 wt.%, Sr 0.012 wt.%, Fe 0.12 wt.%, with the remainder being aluminum and unavoidable impurities. The content of any single element in these trace impurities is ≤0.05 wt.%, and the total amount of trace impurities is ≤0.02 wt.%. The manufacturing steps are as follows:

[0072] (1) Mix pure aluminum ingots, aluminum-silicon master alloy, aluminum-manganese master alloy, pure magnesium ingots, and aluminum-strontium master alloy in the above proportions and preheat to 180±10℃. Place the preheated aluminum ingots, aluminum-silicon master alloy, and aluminum-manganese master alloy into a melting furnace to dissolve them. Control the solution temperature at 735±10℃, then add pure magnesium ingots, melt and stir evenly.

[0073] (2) The melt is subjected to slag removal treatment at a temperature of 740°C. The slag removal agent is a sodium-free, low-calcium refining agent, and the amount is 0.4 wt.% of the total melt volume.

[0074] (3) The composition of the melt was tested. After the composition was qualified, the aluminum-strontium master alloy Al-10Sr was added. The solution temperature was controlled at 730±5℃. After stirring, it was allowed to stand for 15 minutes. Then, Al-La-B refining agent was added, in which La accounted for 2wt.% of the refining agent, B accounted for 1.2wt.% of the refining agent, and the weight of the refining agent accounted for 0.7wt.% of the total melt. The melt temperature was controlled at 730±10℃. The alloy melt was refined and degassed using Ar gas. The refining and degassed temperature was controlled at 730±10℃. The process was carried out twice, with a time of 10 minutes each time.

[0075] (4) The composition of the refined alloy melt was tested and found to be qualified; the density of the alloy melt was tested and found to be 2.66 g / cm³. 3 The alloy melt was tested for slag content, and the K-modulus value was 0 / 20. If the melt was qualified, it was allowed to stand and cool down to 700±10℃ to obtain the aluminum alloy melt.

[0076] (5) Aluminum alloy die castings were prepared by high vacuum die casting process, with a vacuum degree of 35±5mbar, a casting temperature of 690±10℃, an injection speed of 2.2m / s, and a casting pressure of 105MPa.

[0077] Example 5

[0078] A heat-treatable, high-vacuum die-cast aluminum alloy is manufactured. This alloy is an Al-Si-Mn alloy, composed of the following components: Si 9.2 wt.%, Mn 0.63 wt.%, Mg 0.4 wt.%, Ti 0.1 wt.%, Sr 0.02 wt.%, Fe 0.1 wt.%, with the remainder being aluminum and unavoidable impurities. The content of any single element in these trace impurities is ≤0.05 wt.%, and the total amount of trace impurities is ≤0.02 wt.%. The manufacturing steps are as follows:

[0079] (1) Mix pure aluminum ingots, aluminum-silicon master alloy, aluminum-manganese master alloy, pure magnesium ingots, and aluminum-strontium master alloy in the above proportions and preheat to 180±10℃. Place the preheated aluminum ingots, aluminum-silicon master alloy, and aluminum-manganese master alloy into a melting furnace to dissolve them. Control the solution temperature at 735±10℃, then add pure magnesium ingots, melt and stir evenly.

[0080] (2) The melt is subjected to slag removal treatment at a temperature of 740°C. The slag removal agent is a sodium-free, low-calcium refining agent, and the amount is 0.4 wt.% of the total melt volume.

[0081] (3) The composition of the melt was tested. After the composition was qualified, the aluminum-strontium master alloy Al-10Sr was added. The solution temperature was controlled at 730±5℃. After stirring, it was allowed to stand for 15 minutes. Then, Al-La-B refining agent was added, in which the proportion of La in the refining agent was 1wt.% and the proportion of B in the refining agent was 0.6wt.%. The weight of the refining agent accounted for 1.0wt.% of the total melt. The melt temperature was controlled at 730±10℃. The alloy melt was refined and degassed using Ar gas. The refining and degassed temperature was controlled at 730±10℃. The process was carried out twice, with a time of 10 minutes each time.

[0082] (4) The composition of the refined alloy melt was tested and found to be qualified; the density of the alloy melt was tested and found to be 2.635 g / cm³. 3 The alloy melt was tested for slag content, and the K-modulus value was 0 / 20. If the melt was qualified, it was allowed to stand and cool down to 700±10℃ to obtain the aluminum alloy melt.

[0083] (5) Aluminum alloy die castings were prepared by high vacuum die casting process, with a vacuum degree of 35±5mbar, a casting temperature of 690±10℃, an injection speed of 2.2m / s, and a casting pressure of 105MPa.

[0084] Comparative Example 1

[0085] A heat-free, high-vacuum die-cast aluminum alloy is manufactured. This alloy is an Al-Si-Mn alloy, composed of the following components: Si 8.8 wt.%, Mn 0.46 wt.%, Mg 0.3 wt.%, Ti 0.08 wt.%, Sr 0.01 wt.%, Fe 0.11 wt.%, with the remainder being aluminum and unavoidable impurities. The content of any single element in these trace impurities is ≤0.003 wt.%, and the total amount of trace impurities is ≤0.01 wt.%. The manufacturing steps are as follows:

[0086] (1) Mix pure aluminum ingots, aluminum-silicon master alloy, aluminum-manganese master alloy, pure magnesium ingots, and aluminum-strontium master alloy in the above proportions and preheat to 180±10℃. Place the preheated aluminum ingots, aluminum-silicon master alloy, and aluminum-manganese master alloy into a melting furnace to dissolve them. Control the solution temperature at 735±10℃, then add pure magnesium ingots, melt and stir evenly.

[0087] (2) The melt is subjected to slag removal treatment at a temperature of 744℃. The slag removal agent is a sodium-free, low-calcium refining agent, and the amount is 0.4 wt.% of the total melt volume.

[0088] (3) The composition of the melt was tested. After the composition was qualified, the aluminum-strontium master alloy Al-10Sr was added, the solution temperature was controlled at 730±5℃, and after stirring, it was allowed to stand for 15 min. Then, Al-Ti-B refining agent was added, accounting for 0.7wt.% of the total melt weight, and the melt temperature was controlled at 730±10℃. The alloy melt was refined and degassed using N2 gas, and the refining and degassed temperature was controlled at 730±10℃. The process was carried out twice, with a time of 10 min each time.

[0089] (4) The composition of the refined alloy melt was tested and found to be qualified; the density of the alloy melt was tested and found to be 2.60 g / cm³. 3 The alloy melt was tested for slag content, and the K-modulus value was 0 / 20. If the melt was qualified, it was allowed to stand and cool down to 700±10℃ to obtain the aluminum alloy melt.

[0090] (5) Aluminum alloy die castings were prepared by high vacuum die casting process, with a vacuum degree of 40±5mbar, a casting temperature of 690±10℃, an injection speed of 2.2m / s, and a casting pressure of 105MPa.

[0091] Comparative Example 2

[0092] A heat-free, high-vacuum die-cast aluminum alloy is manufactured. This alloy is an Al-Si-Mn alloy, composed of the following components: Si 8.74 wt.%, Mn 0.47 wt.%, Mg 0.25 wt.%, Ti 0.08 wt.%, Sr 0.012 wt.%, Fe 0.09 wt.%, with the remainder being aluminum and unavoidable impurities. The content of any single element in these trace impurities is ≤0.003 wt.%, and the total amount of trace impurities is ≤0.01 wt.%. The manufacturing steps are as follows:

[0093] (1) Mix pure aluminum ingots, aluminum-silicon master alloy, aluminum-manganese master alloy, pure magnesium ingots, and aluminum-strontium master alloy in the above proportions and preheat to 180±10℃. Place the preheated aluminum ingots, aluminum-silicon master alloy, and aluminum-manganese master alloy into a melting furnace to dissolve them. Control the solution temperature at 735±10℃, then add pure magnesium ingots, melt and stir evenly.

[0094] (2) The melt is subjected to slag removal treatment at a temperature of 738°C. The slag removal agent is a sodium-free, low-calcium refining agent, and the amount is 0.4 wt.% of the total melt volume.

[0095] (3) The composition of the melt was tested. After the composition was qualified, the aluminum-strontium master alloy Al-10Sr was added, the solution temperature was controlled at 730±5℃, and after stirring, it was allowed to stand for 15 min. Then, Al-Ti-B refining agent was added, accounting for 0.3wt.% of the total melt, and the melt temperature was controlled at 730±10℃. The alloy melt was refined and degassed using N2 gas, and the refining and degassed temperature was controlled at 730±10℃. The process was carried out twice, with a time of 10 min each time.

[0096] (4) The composition of the refined alloy melt was tested and found to be qualified; the density of the alloy melt was tested and found to be 2.59 g / cm³. 3 The alloy melt was tested for slag content, and the K-modulus value was 0 / 20. The melt was qualified, and it was allowed to stand and cool down to 700±10℃ to obtain aluminum alloy melt.

[0097] (5) Aluminum alloy die castings were prepared by high vacuum die casting process, with a vacuum degree of 40±5mbar, a casting temperature of 690±10℃, an injection speed of 2.2m / s, and a casting pressure of 105MPa.

[0098] The aluminum alloy die castings manufactured in Examples 1-5 and Comparative Examples 1-2 were subjected to the following tests, and the results are given in Table 1:

[0099] Precrystallized microstructure size test: The cross section of the aluminum alloy die casting sample was observed using a metallographic microscope. Ten fields of view were selected, and the maximum caliper diameter of the precrystallized (greater than 30 μm) in all fields of view was calculated. The average value and the maximum value were taken to obtain the average grain size and the maximum grain size of the precrystallized.

[0100] Normal grain average size test: As above, select 10 fields of view and calculate the average value of the maximum caliper diameter of all normal grains (less than 30μm).

[0101] Eutectic silicon shape factor test: As above, 10 fields of view were selected, and the ratio of the minimum caliper diameter to the maximum caliper diameter of the eutectic silicon phase was measured. The average value was calculated. A higher eutectic silicon shape factor value indicates that the eutectic silicon phase is approximately spherical, suggesting a better modification effect.

[0102] Mechanical property testing: Using the testing standard GB / T 228.1-2010, 5 parallel samples were tested for each product. The (maximum yield strength - minimum yield strength) / maximum yield strength of the 5 parallel samples was calculated to obtain the strength difference between the 5 parallel samples.

[0103] Table 1. Microstructure uniformity of alloy die castings from Examples 1-5 and Comparative Examples 1-2

[0104]

[0105]

[0106] Note: Grain structures with a size > 30 μm are considered pre-crystallized structures.

[0107] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0108] Comparing Examples 1-5 with Comparative Examples 1-2, it can be seen that the method of the present invention for manufacturing heat-treatable die-cast aluminum alloys improves the grain structure of heat-treatable high-vacuum die-cast aluminum alloys by adding a non-poisonous Sr Al-RE-B alloy. The pre-crystallized average grain size is ≤60 μm, and compared to the comparative examples using an Al-Ti-B refining agent that poisons Sr, the maximum grain size is less than half that of the comparative examples. Similarly, the normal average size in Examples 1-5 is also smaller than that in Comparative Examples 1-2. Furthermore, from... Figures 1-7 As can be seen, the grain size of Examples 1-5 is more uniform than that of Comparative Examples 1-2, and the number of grains with a size greater than 50 μm in Examples 1-5 is also significantly less than that in Comparative Examples 1-2. Therefore, the aluminum alloy die castings of Examples 1-5 have smaller strength differences and more stable mechanical properties.

[0109] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0110] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for manufacturing heat-treatable die-cast aluminum alloys, characterized in that, The method for manufacturing heat-free die-cast aluminum alloys includes: The raw materials are prepared according to the following proportions by weight percentage: Si 7.5-10 wt.%, Mn 0.4-0.8 wt.%, Mg 0.1-0.4 wt.%, Ti 0.05-0.22 wt.%, Sr 0.008-0.03 wt.%, Fe ≤0.18 wt.%, with the remainder being aluminum and impurities. The proportion of each impurity element in the raw materials is ≤0.05 wt.%, and the total proportion of the impurities is ≤0.3 wt.%. The raw materials are sequentially subjected to smelting, slag removal, modification, refining and degassing, and first detection. Al-RE-B refining agent is added in the refining step, where RE is a rare earth metal element. The mass percentages of RE and B elements in the Al-RE-B refining agent are 1%-3% and 0.1%-2%, respectively. The Al-RE-B refining agent includes Al-La-B refining agent or Al-YB refining agent; Based on the total weight of the heat-free die-cast aluminum alloy, 0 < the amount of the Al-RE-B refining agent ≤ 1.0 wt.%; The modification step includes a second test on the melt obtained from the slag removal step. When the test result satisfies that the composition of the melt obtained from the slag removal step, excluding Sr, meets the proportion specified by the raw materials, a strontium modifier is added, and the temperature of the melt is controlled at 720-740℃. After stirring, the melt is allowed to stand for 10-20 minutes.

2. The method for manufacturing heat-treatable die-cast aluminum alloys according to claim 1, characterized in that, The smelting step includes preheating the raw material to 100-300°C and then performing a melting process to obtain a melt, wherein the temperature of the melt is controlled at 740-780°C.

3. The method for manufacturing heat-free die-cast aluminum alloys according to claim 2, characterized in that, The slag removal step includes adding a slag remover to the melt, the slag remover accounting for 0.1-0.5 wt.% of the weight of the melt, and controlling the temperature of the melt at 730-750°C.

4. The method for manufacturing heat-free die-cast aluminum alloys according to claim 3, characterized in that, The amount of metallic strontium in the strontium modifier is 0.008~0.03 wt.% of the melt weight.

5. The method for manufacturing heat-treatable die-cast aluminum alloys according to claim 4, characterized in that, The strontium modifier is an aluminum-strontium master alloy.

6. The method for manufacturing heat-treatable die-cast aluminum alloys according to claim 4, characterized in that, During the refining step, the temperature of the melt is controlled at 700-750℃.

7. The method for manufacturing heat-treatable die-cast aluminum alloys according to claim 1, characterized in that, The degassing step includes degassing the melt obtained in the refining step using N2 or Ar gas. The temperature of the degassing step is 720-740℃ and the time is 10-20 min.

8. The method for manufacturing heat-treatable die-cast aluminum alloys according to any one of claims 1 to 7, characterized in that, The first detection process includes: performing composition detection, density detection, and slag content detection on the melt obtained from the degassing step. The detection results are determined when the following criteria are met: the composition conforms to the proportions defined in claim 1, and the density value is greater than 2.61 g / cm³. 3 When the K modulus value is not higher than 1 / 20, the preparation process ends. If the test result does not meet the standard, the smelting, slag removal, modification, refining, degassing and the first test step are repeated.

9. A heat-treatable die-cast aluminum alloy, characterized in that, The heat-free die-cast aluminum alloy has a pre-crystallized average grain size >30μm and ≤60μm, a pre-crystallized maximum grain size ≤60μm, and a normal average grain size ≤10μm. The heat-free die-cast aluminum alloy is manufactured by the method described in any one of claims 1-8.

10. An aluminum alloy die-casting part, characterized in that, The aluminum alloy die casting is obtained by high-vacuum die casting of the heat-free die-cast aluminum alloy as described in claim 9.

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