Low-cost high-toughness brazed aluminum alloy and preparation method thereof

Abstract

The invention provides a low-cost high-toughness brazed aluminum alloy and a preparation method thereof, and relates to the technical field of die-casting aluminum alloys. Wherein the aluminum alloy comprises the following components in percentage by weight: 0 to 0.5 weight percent of silicon, 0.5 to 2.0 weight percent of iron, 0 to 0.05 weight percent of manganese, 0 to 0.15 weight percent of chromium, 0.01 to 0.5 weight percent of strontium, 0 to 0.1 weight percent of magnesium, 0 to 0.15 weight percent of titanium, 0 to 0.5 weight percent of nickel, 0.02 to 0.5 weight percent of calcium, 5.0 to 10.0 weight percent of RE, at most 0.05 weight percent of single impurity element and the balance of Al; wherein when the silicon is less than or equal to 0.1, the contents of Ca and Sr are not required, and when the silicon is greater than or equal to 0.1, the weight ratio of (Ca + Sr) to Si is controlled to be 1.0-1.7. The obtained aluminum alloy can meet the brazability of the aluminum alloy under the condition that the cost is controlled.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of die-cast aluminum alloys, in particular to a low-cost high-strength and tough brazable aluminum alloy and a preparation method thereof. BACKGROUND

[0002] With the large-scale popularization of new energy vehicles, high-pressure cast brazable aluminum alloys have obvious advantages over traditional profile processing methods in terms of cost reduction and popularization of applications due to their excellent thermal conductivity, high-temperature stability and processability, and have achieved large-scale application in multiple fields, showing great market potential.

[0003] The battery package shell made of Al-Si-Mg-Cu-Zr high-pressure cast aluminum alloy can realize multi-module integration through brazing process while ensuring structural strength, effectively control the temperature gradient of the battery cell by utilizing the high thermal conductivity of the material.

[0004] The use of high solidus aluminum alloy (solidus ≥ 610℃) in the electric drive system, including the manufacture of motor end covers, can maintain strength (tensile strength ≥ 280MPa) under long-term operation at 200℃; the aluminum alloy water cooling channel integrated by brazing process can achieve high heat dissipation efficiency; the aluminum alloy reducer shell connected by brazing can replace traditional cast iron parts, reducing weight while optimizing the flow channel design and reducing gear oil temperature.

[0005] The technology disclosed in Chinese patent (publication number CN 113913650 A) published on January 11, 2022 adds Y, Sc and Ag elements to the aluminum alloy to improve the brazability of the aluminum alloy; however, the added elements increase the overall cost of the aluminum alloy; at the same time, the silicon content needs to be controlled at a low level, so the amount of recycled material added during die casting production is limited, also leading to an increase in overall cost.

[0006] The technology disclosed in Chinese patent (publication number CN 118792551 A) published on October 18, 2024 controls the content of Fe, Ni, Mn and Cr elements in the aluminum alloy to improve the high-temperature brazability of the aluminum alloy; however, this technology does not consider the influence of the silicon element component in the aluminum alloy material on brazing performance.

[0007] Therefore, under the premise of controlling cost, it is still a technical problem to be solved for high-pressure cast brazable aluminum alloys to improve the solidus temperature of die-cast aluminum alloys to ensure their brazability. SUMMARY

[0008] In view of the problems existing in the prior art, the present application provides a low-cost, high-pressure die-cast aluminum alloy with excellent casting performance and brazability, and a preparation method thereof.

[0009] The principle of the present application is that:

[0010] For alloys composed of pure metals, eutectics and intermetallic compounds, under normal casting conditions, the more latent heat is released, the slower the solidification process is, and the better the fluidity is. RE rare earth elements have obvious strengthening effects in aluminum alloys, mainly including fine grain strengthening, limited solid solution strengthening and second phase strengthening of rare earth compounds. At the same time, they can improve the fluidity of the alloy, reduce the liquid hydrogen content of the aluminum alloy, reduce the probability of gas impurity defects, and play a better role in purifying the aluminum liquid. Die casting itself easily causes the casting to contain gas. If the gas content is too much, it will lead to poor brazing properties, seriously affecting the subsequent brazing production. Adding rare earth elements can play a significant improvement role. The Al-RE eutectic point is 9.0%-10.0%, which is not reached during the casting process. The more latent heat of solidification, the better the fluidity. In the brazable heat-free die-cast aluminum alloy provided in this application, the mass content of RE is controlled to be 5.0-10.0%.

[0011] In the composition of aluminum alloy materials, iron plays a vital role. An appropriate amount of iron can significantly improve the hardness of aluminum alloys. When the iron content is controlled between 0.5% and 2%, the hardness of the aluminum alloy will be significantly improved. In addition, the solid solution formed by iron and aluminum not only enhances the strength of the aluminum alloy, but also improves its corrosion resistance. Under high temperature conditions, aluminum alloys with higher iron content exhibit better strength and corrosion resistance. However, the iron content must be controlled within a reasonable range. Too high will inhibit the grain boundary activity of aluminum, affect the strength and ductility of the aluminum alloy, and increase the difficulty of processing; too low will lead to a decrease in the strength and heat resistance of the aluminum alloy, and have an adverse effect on its mechanical properties and corrosion resistance. Therefore, in the production process of aluminum alloys, precise control of the iron content is the key to ensuring optimal performance and processing technology. For this alloy system, iron is preferably controlled at 0.5-1.5%.

[0012] Manganese can improve the strength and hardness of aluminum alloys. The strength and hardness of aluminum alloys are determined by their grain size. Manganese can effectively refine the grains of aluminum alloys, making them denser and more uniform. The addition of manganese forms a phase called MnAl6, which has high hardness and can inhibit grain growth, thereby improving the strength and hardness of aluminum alloys. Manganese also effectively alters the iron phase, preventing the effects of excessive acicular iron on the properties and fluidity of the aluminum matrix. The preferred manganese content is 0.2-1.0%.

[0013] In aluminum alloys, chromium combines with elements such as iron and manganese to form intermetallic compounds such as (CrFe)Al7 and (CrMn)Al12. These compounds not only hinder the nucleation and growth of recrystallization, strengthening the alloy, but also improve its toughness and reduce its sensitivity to stress corrosion cracking. However, it should be noted that the addition of chromium will slightly increase the quenching sensitivity and cause the anodic oxide film to appear yellow. Therefore, in aluminum alloys, the addition of chromium is usually controlled within 0.35%, and is adjusted according to the content of other transition elements in the alloy. The preferred chromium content is controlled within 0-0.15%.

[0014] By controlling the Si content to <0.5, Sr can be added to the aluminum alloy to bind the Si element, thereby inhibiting the precipitation of the eutectic silicon phase and ensuring that the alloy has a higher solidus temperature, thus ensuring the brazing ability of the alloy under conventional processes.

[0015] Calcium can also be added to form the CaAl₄ phase (melting point approximately 1050°C) in aluminum alloys, serving as a heterogeneous nucleation core and significantly refining the cast structure. For example, adding 0.1-0.3% calcium to Al-Si alloys can reduce grain size from 200 μm to below 50 μm, reducing dendritic segregation. Furthermore, by refining the grains and regulating the distribution of secondary phases, the alloy's thermal expansion coefficient is lowered. Calcium preferentially combines with oxygen to form CaO (melting point 2572°C), forming a loose oxide layer on the alloy surface, reducing the density of the oxide film. The addition of calcium alters the alloy's solidification path and can slightly increase the solidus temperature (due to the formation of high-melting-point phases such as CaSi₂). However, its impact on the overall solidus temperature is relatively limited, as its primary function is to optimize the structure rather than significantly alter the alloy's basic phase diagram. By forming an interfacial reaction layer (such as CaAl₂), calcium inhibits the diffusion of silicon from the brazing filler metal into the base metal. The optimal calcium content is controlled between 0.01-0.15%.

[0016] Compared with the prior art, the present invention has the following technical effects:

[0017] The present invention achieves tensile strength of ≥210MPa, yield strength of ≥95MPa, and elongation of ≥5% in the cast state by adding Si, Fe, Cr, Mn, Sr, and RE elements within a specific range. Under the condition of simulating a brazing temperature of 610 degrees and maintaining heat, the yield strength can reach above 60Mpa, achieving the alloy properties required for brazing.

[0018] The tolerance of the present invention to Si reaches 0.5%, and a higher proportion of recycled aluminum can be used for production, saving costs and lowering carbon emissions. At the same time, customers can use 100% recycled materials during use, reducing production and operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1A 200 times metallographic structure chart of the low-cost high-tenacity brazing aluminum alloy material disclosed in Embodiment 3 of the present application.

[0020] Figure 2 A 100 times metallographic structure chart of the low-cost high-tenacity brazing aluminum alloy material disclosed in Embodiment 3 of the present application. DETAILED DESCRIPTION

[0021] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely with reference to the drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. In the described embodiments of the present application, steps 1, step 2, … do not limit the only execution steps of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0022] In a first aspect, the present application provides an aluminum alloy, the alloy composition is as follows: 0-0.5wt% of silicon, 0.5-2.0wt% of iron, 0-0.05wt% of manganese, 0-0.15wt% of chromium, 0.01-0.5wt% of strontium, 0-0.1wt% of magnesium, 0-0.15wt% of titanium, 0-0.5wt% of nickel, 0.02-0.5wt% of calcium, 5.0-10.0wt% of RE, and the maximum of single impurity element is 0.05wt%, and the rest is Al.

[0023] When Si≤0.1, the content of Ca and Sr is not required; when Si≥0.1, the ratio of (Ca+Sr) / Si is controlled between 1.0-1.7.

[0024] Preferably, the added amount of iron element is 1.5-2.0wt%.

[0025] Preferably, the added amount of strontium element is 0.11-0.5wt%.

[0026] Preferably, the added amount of manganese element is 0-0.02wt%.

[0027] Preferably, the added amount of calcium element is 0.02-0.1wt%.

[0028] Preferably, RE is selected from the combination of La and Ce elements.

[0029] It should be noted that any numerical value within the weight percentage range of the aluminum alloy component belongs to the protection scope of the present application, and the exemplary,

[0030] The weight% of silicon can be: 0, 0.1, 0.2, 0.3, 0.4, 0.5;

[0031] The weight % of iron can be: 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5;

[0032] The weight % of manganese can be: 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0;

[0033] The weight percent of chromium may be: 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15;

[0034] The weight percent of strontium can be: 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24 , 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5;

[0035] The weight % of magnesium can be: 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1;

[0036] The weight % of titanium may be: 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15;

[0037] The weight % of nickel can be: 0, 0.1, 0.2, 0.3, 0.4, 0.5;

[0038] The weight % of calcium can be: 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0. 25, 0.26, 0.27, 0.28, 0.29, 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5;

[0039] The weight % of RE can be: 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10.0;

[0040] In a second aspect, the present invention provides a method for preparing the above-mentioned aluminum alloy, that is, preparing the high-strength and toughness heat-treatment-free aluminum alloy casting according to the following steps:

[0041] Step 1: According to the above mass percentage, gradually increase the temperature in the furnace to bake out the water vapor in the furnace. During the heating process, place the A00 weighed according to the proportion on the side of the furnace for baking. After baking for 30 minutes, put the A00 into the furnace and heat it up to melt. The aluminum liquid temperature is set to 720 degrees and the furnace temperature is set to 780 degrees.

[0042] Step 2: After A00 is dissolved, first place the master alloys such as AlFe20, AlCr20, and AlRE40 on the side of the furnace for baking. After baking for 30 minutes, put them into the furnace and stir them several times to fully dissolve them; let them stand for 30 minutes, and then use a mobile rotary degasser to press in the aluminum alloy sodium-free refining agent for refining. The refining agent ratio is 0.1%-0.2%, and 99.999% argon is introduced for degassing time of 15 minutes. Then, the slag is skimmed and the mixture is allowed to stand; after refining and degassing, the AlSr10 master alloy is added according to the proportion.

[0043] Step 3: Use an electric spark direct reading spectrometer to detect whether the aluminum alloy composition meets the usage standard. If so, proceed to step 4. If not, it means that a certain original mass percentage in the aluminum alloy liquid does not meet the above-mentioned preset mass percentage, and an additional mass percentage of elements needs to be added to adjust the mass percentage of the element in the effective aluminum alloy liquid so that the mass percentage of the element meets the usage standard, that is, reaches the preset mass percentage.

[0044] Step 4: Detect the gas content with a hydrogen meter, and when the density equivalent is ≤0.2%, die-cast it using high-pressure die-casting equipment. If the gas content does not meet the standard, continue with the refining and degassing in step 2.

[0045] Step 5: High-pressure die casting was performed using a LK 280T die-casting machine equipped with a vacuum system, oil-circulating mold temperature controller, and barrel heating device to produce a 3mm × 80mm × 200mm flat die specimen. The high-pressure casting process parameters were as follows: mold cavity vacuum ≤ 50Mbar, injection speed 2.5 ± 0.5m / s, mold temperature 130 ± 10°C, and aluminum alloy liquid temperature 700 ± 10°C.

[0046] The present invention provides a low-cost, high-strength and tough brazable aluminum alloy and a preparation method thereof, the technical effects of which are:

[0047] 1. By adding Si, Fe, Cr, Mn, Sr, and RE elements within a specific range, the tensile strength in the cast state is ≥210MPa, the yield strength is ≥95MPa, and the elongation is ≥5%. Under the simulated brazing temperature of 610 degrees and insulation, the yield strength can reach above 60Mpa, meeting the brazing requirements.

[0048] 2. The tolerance of the present invention to Si reaches 0.5%, and a higher proportion of recycled aluminum can be used for production, saving costs and lowering carbon emissions. At the same time, customers can use 100% recycled materials during use, reducing production and operating costs.

[0049] Example 1:

[0050] An aluminum alloy having the following alloy compositions in percentage by weight: 0.016 weight percent silicon, 1.9 weight percent iron, 0.014 weight percent manganese, 0.018 weight percent chromium, 0.0023 weight percent strontium, 0.0014 weight percent magnesium, 0.0041 weight percent titanium, 0.027 weight percent nickel, 0.08 weight percent calcium, 2.48 weight percent La, 5.25 weight percent Ce, a maximum of 0.05 weight percent of a single impurity element, and the remainder being Al.

[0051] The alloy preparation method comprises the following steps:

[0052] Step 1: According to the above mass percentage, gradually increase the temperature in the furnace to bake out the water vapor in the furnace. During the heating process, place the A00 weighed according to the proportion on the side of the furnace for baking. After baking for 30 minutes, put the A00 into the furnace and heat it up to melt. The aluminum liquid temperature is set to 720 degrees and the furnace temperature is set to 780 degrees.

[0053] Step 2: After A00 is dissolved, first place the master alloys such as AlFe20, AlCr20, and AlRE40 on the furnace side for baking. After baking for 30 minutes, put them into the furnace and stir them several times to fully dissolve them. Let them stand for 30 minutes, then use a mobile rotary degasser to press in the aluminum alloy sodium-free refining agent for refining. The refining agent ratio is 0.1%-0.2%. 99.999% argon is introduced for degassing for 15 minutes, then the slag is skimmed and the mixture is allowed to stand. After refining and degassing, the AlSr10 master alloy is added according to the proportion.

[0054] Step 3: Use an electric spark direct reading spectrometer to detect whether the aluminum alloy composition meets the use standard. If so, proceed to step 4. If not, it means that a certain original mass percentage in the aluminum alloy liquid does not meet the above-mentioned preset mass percentage, and an additional mass percentage of an element needs to be added to adjust the mass percentage of the element in the effective aluminum alloy liquid so that the mass percentage of the element meets the use standard, that is, reaches the preset mass percentage;

[0055] Step 4: Use a hydrogen meter to detect the gas content, and when the density equivalent is ≤0.2%, use high-pressure die-casting equipment to die-cast. If the gas content does not meet the standard, continue with the refining and degassing in step 2;

[0056] Step 5: High-pressure die casting was performed using a LK 280T die-casting machine equipped with a vacuum system, oil-circulating mold temperature controller, and barrel heating device to produce a 3mm × 80mm × 200mm flat die specimen. The high-pressure casting process parameters were as follows: mold cavity vacuum ≤ 50Mbar, injection speed 2.5 ± 0.5m / s, mold temperature 130 ± 10°C, and aluminum alloy liquid temperature 700 ± 10°C.

[0057] Example 2:

[0058] An aluminum alloy having alloy components in percentage by weight: 0.132 weight percent silicon, 1.85 weight percent iron, 0.0149 weight percent manganese, 0.023 weight percent chromium, 0.0153 weight percent strontium, 0.0016 weight percent magnesium, 0.0038 weight percent titanium, 0.029 weight percent nickel, 0.075 weight percent calcium, 2.62 weight percent La, 5.46 weight percent Ce, a maximum of 0.05 weight percent of a single impurity element, and the remainder being Al.

[0059] The alloy preparation method is the same as that in Example 1.

[0060] Example 3:

[0061] An aluminum alloy having alloy compositions in percentage by weight: 0.162 weight percent silicon, 1.84 weight percent iron, 0.0144 weight percent manganese, 0.0023 weight percent chromium, 0.176 weight percent strontium, 0.0016 weight percent magnesium, 0.0037 weight percent titanium, 0.029 weight percent nickel, 0.1 weight percent calcium, 2.62 weight percent La, 5.45 weight percent Ce, a maximum of 0.05 weight percent of a single impurity element, and the remainder being Al.

[0062] The alloy preparation method is the same as that in Example 1.

[0063] Example 4:

[0064] An aluminum alloy having alloy compositions in percentage by mass: 0.164 weight percent silicon, 1.77 weight percent iron, 0.014 weight percent manganese, 0.002 weight percent chromium, 0.183 weight percent strontium, 0.1 weight percent magnesium, 0.101 weight percent titanium, 0.028 weight percent nickel, 0.09 weight percent calcium, 2.52 weight percent La, 5.27 weight percent Ce, a maximum of 0.05 weight percent of a single impurity element, and the remainder being Al.

[0065] The alloy preparation method is the same as that in Example 1.

[0066] Example 5:

[0067] An aluminum alloy having the following alloy compositions in percentage by weight: 0.165 weight percent silicon, 1.74 weight percent iron, 0.013 weight percent manganese, 0.003 weight percent chromium, 0.169 weight percent strontium, 0.083 weight percent magnesium, 0.074 weight percent titanium, 0.229 weight percent nickel, 0.09 weight percent calcium, 2.5 weight percent La, 5.27 weight percent Ce, a maximum of 0.05 weight percent of a single impurity element, and the remainder being Al.

[0068] The alloy preparation method is the same as that in Example 1.

[0069] Example 6:

[0070] An aluminum alloy having alloy compositions in percentage by weight: 0.173 weight percent silicon, 1.76 weight percent iron, 0.0155 weight percent manganese, 0.0033 weight percent chromium, 0.168 weight percent strontium, 0.087 weight percent magnesium, 0.116 weight percent titanium, 0.318 weight percent nickel, 0.1 weight percent calcium, 2.56 weight percent La, 5.34 weight percent Ce, a maximum of 0.05 weight percent of a single impurity element, and the remainder being Al.

[0071] The alloy preparation method is the same as that in Example 1.

[0072] Example 7:

[0073] An aluminum alloy having alloy compositions in percentage by weight: 0.168 weight percent silicon, 1.58 weight percent iron, 0.0155 weight percent manganese, 0.0033 weight percent chromium, 0.168 weight percent strontium, 0.087 weight percent magnesium, 0.116 weight percent titanium, 0.318 weight percent nickel, 0.02 weight percent calcium, 2.56 weight percent La, 5.34 weight percent Ce, a maximum of 0.05 weight percent of a single impurity element, and the remainder being Al.

[0074] The alloy preparation method is the same as that in Example 1.

[0075] Comparative Example 1:

[0076] An aluminum alloy having alloy compositions in percentage by weight: 0.142 weight percent silicon, 1.75 weight percent iron, 0.0149 weight percent manganese, 0.023 weight percent chromium, 0.0023 weight percent strontium, 0.0016 weight percent magnesium, 0.0038 weight percent titanium, 0.029 weight percent nickel, 0.09 weight percent calcium, 2.62 weight percent La, 5.46 weight percent Ce, a maximum of 0.05 weight percent of a single impurity element, and the remainder being Al.

[0077] The alloy preparation method is the same as that in Example 1.

[0078] Comparative Example 2:

[0079] An aluminum alloy having alloy compositions in percentage by weight: 0.178 weight percent silicon, 1.91 weight percent iron, 0.0155 weight percent manganese, 0.0033 weight percent chromium, 0.168 weight percent strontium, 0.087 weight percent magnesium, 0.116 weight percent titanium, 0.318 weight percent nickel, 0.001 weight percent calcium, 2.56 weight percent La, 5.34 weight percent Ce, a maximum of 0.05 weight percent of a single impurity element, and the remainder being Al.

[0080] The alloy preparation method is the same as that in Example 1.

[0081] Comparative Example 3:

[0082] An aluminum alloy having the following alloy compositions in percentage by weight: 0.07 weight percent silicon, 1 weight percent iron, 0.5 weight percent manganese, 0.35 weight percent chromium, 0.004 weight percent strontium, 0.087 weight percent magnesium, 0.116 weight percent titanium, 2.9 weight percent nickel, 0.11 weight percent calcium, a maximum of 0.05 weight percent of a single impurity element, and the remainder being Al.

[0083] The alloy preparation method is the same as that in Example 1.

[0084] The element addition amount and alloy parameters of each embodiment and comparative example are shown in the following table.

[0085]

[0086] Mechanical property tests were performed on the flat plate mold test pieces obtained from each embodiment and comparative example. The test items included: tensile strength (Mpa), yield strength (Mpa), and elongation (%) tests under as-cast condition; tensile strength, yield strength, and elongation tests under simulated brazing temperature 610 degrees for 30 minutes.

[0087] The present application takes the solidus temperature reaching 610 degrees and the yield strength reaching 60 Mpa under simulated brazing environment as the main evaluation index for meeting the brazability requirement.

[0088] The test results are shown in the following table:

[0089]

[0090]

[0091] From the above table data, the following obvious comparison conclusions can be drawn:

[0092] 1. Verification of the Si, Ca, and Sr content relationship proposed in the present application:

[0093] The present application discloses that when Si≤0.1, the content of Ca and Sr is not required; when Si≥0.1, the ratio of (Ca+Sr) / Si is controlled between 1.0-1.7.

[0094] The Si content of example 1 is 0.016, the Ca content is 0.08, and the Sr content is 0.0023. It belongs to the case of Si≤0.1, at this time, the relationship between the content of Ca+Sr and the content of Si is not required, only the single element range proposed in the present application needs to be met, and the solidus temperature of the obtained alloy reaches 626 degrees.

[0095] Examples 2-8 all belong to the case of Si≥0.1, these embodiments not only meet the single element range proposed in the present application, but also meet the ratio of (Ca+Sr) / Si between 1.0-1.7, and the solidus temperature of the obtained alloy all reaches above 610 degrees.

[0096] Comparative examples 1 and 2 also belong to the case of Si≥0.1, however, in their components, the ratio of (Ca+Sr) / Si does not meet the requirement of 1.0-1.7, and the solidus temperature of the obtained alloy does not reach the requirement of 610 degrees.

[0097] The main difference between Comparative Example 3 and the Examples is that no RE, ie, rare earth element, is added. In a performance test simulating a brazing environment, the yield strength thereof is 58.4 MPa, which does not meet the brazing requirements.

Claims

1. A low-cost, high-strength, and tough brazable aluminum alloy, characterized in that: The aluminum alloy has the following components and weight percentages: 0-0.5 weight % silicon, 0.5-2.0 weight % iron, 0-0.05 weight % manganese, 0-0.15 weight % chromium, 0.01-0.5 weight % strontium, 0-0.1 weight % magnesium, 0-0.15 weight % titanium, 0-0.5 weight % nickel, 0.02-0.5 weight % calcium, 5.0-10.0 weight % RE, a maximum of 0.05 weight % of a single impurity element, and the remainder being Al; Among them, when silicon ≤ 0.1, the content of Ca and Sr is not required; when silicon ≥ 0.1, the weight ratio of (Ca + Sr) to Si is controlled between 1.0-1.7; The preparation method of the aluminum alloy comprises: Step 1: gradually increase the temperature in the furnace according to the above mass percentage to bake out the water vapor in the furnace. During the heating process, place A00 weighed according to the proportion on the side of the furnace for baking. After baking for 30 minutes, place A00 into the furnace and heat it up to melt. Step 2: After A00 is dissolved, first place the master alloys such as AlFe20, AlCr20, and AlRE40 on the furnace side for baking. After baking for 30 minutes, put them into the furnace and stir them several times to fully dissolve them. Let them stand for 30 minutes, then use a mobile rotary degasser to press in the aluminum alloy sodium-free refining agent for refining. The refining agent ratio is 0.1%-0.2%. 99.999% argon is introduced for degassing for 15 minutes, then the slag is skimmed and the mixture is allowed to stand. After refining and degassing, the AlSr10 master alloy is added according to the proportion. Step 3: Use an electric spark direct reading spectrometer to detect whether the aluminum alloy composition meets the use standard. If so, proceed to step 4. If not, adjust the mass percentage of the element that does not meet the use standard in the effective aluminum alloy liquid so that the mass percentage of the element reaches the preset mass percentage; Step 4: Use a hydrogen meter to detect the gas content, and when the density equivalent is ≤0.2%, use high-pressure die-casting equipment to die-cast. If the gas content does not meet the standard, continue with the refining and degassing in step 2; Step 5: Perform high-pressure die casting through a die casting machine.

2. The aluminum alloy according to claim 1, characterized in that The amount of iron added is 1.5 to 2.0% by weight.

3. The aluminum alloy according to claim 1, characterized in that The amount of strontium added is 0.11 to 0.5% by weight.

4. The aluminum alloy according to claim 1, characterized in that The amount of calcium added is 0.02 to 0.1% by weight.

5. The aluminum alloy according to claim 1, characterized in that The RE is a combination of La and Ce elements.

6. The aluminum alloy according to claim 1, characterized in that In step 1 of the preparation method, the temperature of the molten aluminum is set at 720 degrees and the furnace temperature is set at 780 degrees.

7. The aluminum alloy according to claim 1, characterized in that In step 5 of the preparation method, the die-casting machine is a LK 280T die-casting machine.

8. The aluminum alloy according to claim 1, wherein In step 5 of the preparation method, the die-casting machine is equipped with a vacuum system, an oil circulation mold temperature controller, and a barrel heating device.

9. The aluminum alloy according to claim 1, characterized in that In step 5 of the preparation method, a 3 mm × 80 mm × 200 mm flat die specimen is obtained by the high pressure die casting.

10. The aluminum alloy according to claim 1, wherein In step 5 of the preparation method, the process parameters of the high-pressure casting are as follows: mold cavity vacuum ≤ 50 Mbar, injection speed 2.5±0.5 m / s, mold temperature 130±10°C, and aluminum alloy liquid temperature 700±10°C.

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