Brazeable casting aluminum alloy with high solidus line and preparation method therefor, casting and article

Abstract

A brazeable casting aluminum alloy with a high solidus line, the aluminum alloy comprising the following components in percentages by mass: Mn: 1.5-2.5%, Zn: 2.2-3.5%, Fe: 0.5-1.0%, Ni: 1.8-2.5%, Ti: 0.05-0.10%, Zr: 0.2-0.5%, Cr: 0.2-0.35%, Si:≤0.2%, and the balance of aluminum and inevitable impurities. The brazeable casting aluminum alloy material with a high solidus line has the advantages of a high solidus line, good castability, low hot cracking tendency, good mechanical properties, etc., can serve as a brazing aluminum alloy material for direct brazing, and meets the use requirements of the market for brazeable casting aluminum alloys.

Description

High solids line brazable cast aluminum alloys, their preparation methods, castings and products Technical Field

[0001] This invention relates to the field of aluminum alloy technology, and more specifically, to high solids line brazable cast aluminum alloys, their preparation methods, castings, and products. Background Technology

[0002] Currently, brazing aluminum alloys can be used to manufacture electric vehicle components and charging piles, especially for electric vehicle thermal management systems. Aluminum alloys are divided into two types: wrought aluminum alloys and cast aluminum alloys. Brazing is divided into soft brazing and hard brazing. Automotive components with thicker joints or higher operating temperatures typically use hard brazing. Hard brazing requires higher temperatures, generally around 600℃, and the welding time is generally around 30 minutes. Therefore, hard brazing requires a higher solidus line of the aluminum alloy. Commonly used cast aluminum alloys have a solidus line below 600℃, which cannot meet the requirements of hard brazing. Therefore, most manufacturers use wrought aluminum alloys (such as 6063 thick aluminum plates) to be CNC machined into various shapes and then welded to the wrought aluminum alloy. However, this manufacturing method is inefficient, time-consuming, and CNC machining wastes materials, resulting in high manufacturing costs. Technical issues

[0003] The purpose of this invention is to overcome the defects of the prior art and provide a high solids line brazable cast aluminum alloy, its preparation method, castings and products. Technical solutions

[0004] The technical problem solved by this invention is achieved by the following technical solution.

[0005] This invention provides a high solids-line brazable cast aluminum alloy comprising the following components by mass percentage: Mn: 1.5-2.5%, Zn: 2.2-3.5%, Fe: 0.5-1.0%, Ni: 1.8-2.5%, Ti: 0.05-0.10%, Zr: 0.2-0.5%, Cr: 0.2-0.35%, Si: ≤0.2%, with the balance being aluminum and unavoidable impurities.

[0006] This invention also provides a method for preparing the above-mentioned high solids line brazable cast aluminum alloy, comprising the following steps:

[0007] S1. Put the pure aluminum ingots into the furnace and heat them up to melt them;

[0008] S2. Add aluminum-iron master alloy, aluminum-manganese master alloy, aluminum-nickel master alloy, aluminum-zirconium master alloy, aluminum-chromium master alloy and aluminum-titanium master alloy in batches to the aluminum liquid obtained in step S1, and stir thoroughly until completely melted.

[0009] S3. Add pure zinc ingots to the aluminum alloy liquid obtained in step S2;

[0010] S4. Degas and remove slag from the aluminum alloy liquid obtained in step S3. After the composition is qualified, insert the ultrasonic vibration tool head into the aluminum liquid for ultrasonic treatment, and then filter to obtain pure metal melt.

[0011] S5. Cool the pure molten metal obtained in step S4 to obtain a high solids line brazable cast aluminum alloy ingot.

[0012] The present invention also provides a casting, which is obtained by extrusion casting after melting the above-mentioned high solids line brazable castable aluminum alloy ingot, wherein the extrusion casting temperature is 740-760℃, the pressure is 105MPa, and the holding time is 15sec.

[0013] The present invention also provides an article, which is made by joining the above-mentioned casting with other metal materials by brazing. Beneficial effects

[0014] The present invention has the following beneficial effects:

[0015] This invention provides a high solids-line brazable cast aluminum alloy, its preparation method, castings, and finished products. The high solids-line brazable cast aluminum alloy provided by this invention comprises the following components by mass percentage: Mn: 1.5-2.5%, Zn: 2.2-3.5%, Fe: 0.5-1.0%, Ni: 1.8-2.5%, Ti: 0.05-0.10%, Zr: 0.2-0.5%, Cr: 0.2-0.35%, Si: ≤0.2%, with the balance being aluminum and unavoidable impurities. The above-mentioned high solids-line brazable cast aluminum alloy provided by this invention has the characteristics of high solids-liquid lines, good casting performance, good resistance to hot cracking, and excellent mechanical properties. It can be directly brazed as a brazing aluminum alloy material, meeting the market demand for brazable cast aluminum alloys. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 shows photographs of three types of castings produced according to an embodiment of the present invention: end plates, φ6mm test bars, and φ10mm test bars.

[0018] Figure 2 is a metallographic image of the end plate cast in Embodiment 6 of the present invention;

[0019] Figure 3 shows photographs of the castings produced in Embodiments 4, 5 and 6 of the present invention after salt spray testing.

[0020] Figure 4 is a metallographic diagram of the casting produced in Embodiment 4 of the present invention;

[0021] Figure 5 shows the potential polarization curves of the castings produced in Embodiments 4, 5 and 6 of the present invention;

[0022] Figure 6 is a schematic diagram of the sampling locations of the brazed joints in different areas of the part after the end plate cast in Example 6 was brazed with 6063 deformed aluminum alloy.

[0023] Figure 7 shows the metallographic structure of the brazed joint in region B1 after the end plate cast in Example 6 was brazed with 6063 wrought aluminum alloy.

[0024] Figure 8 shows the metallographic structure of the brazed joint in region B2 after the end plate cast in Example 6 was brazed with 6063 wrought aluminum alloy.

[0025] Figure 9 shows the metallographic structure of the brazed joint in region B3 after the end plate cast in Example 6 was brazed with 6063 wrought aluminum alloy.

[0026] Figure 10 shows the metallographic structure of the brazed joint in region B4 after the end plate cast in Example 6 was brazed with 6063 wrought aluminum alloy.

[0027] Figure 11 shows the metallographic structure of the brazed joint in region B5 after the end plate cast in Example 6 was brazed with 6063 wrought aluminum alloy.

[0028] Figure 12 shows the metallographic structure of the brazed joint in region B6 after the end plate cast in Example 6 was brazed with 6063 deformed aluminum alloy.

[0029] Figure 13 shows the metallographic structure of the brazed joint in region B7 after the end plate cast in Example 6 was brazed with 6063 wrought aluminum alloy.

[0030] Figure 14 shows the metallographic structure of the brazed joint in region B8 after the end plate cast in Example 6 was brazed with 6063 wrought aluminum alloy.

[0031] Figure 15 shows the metallographic structure of the brazed joint in region B9 after the end plate cast in Example 6 was brazed with 6063 wrought aluminum alloy.

[0032] Figure 16 shows the first metallographic structure of the fusion zone of the end plate cast in Example 6 and the brazed joint of 6063 wrought aluminum alloy.

[0033] Figure 17 is a second metallographic diagram of the fusion zone of the end plate cast in Example 6 and the brazed joint of 6063 deformed aluminum alloy.

[0034] Figure 18 is a third metallographic diagram of the fusion zone of the end plate cast in Example 6 and the brazed joint of 6063 deformed aluminum alloy.

[0035] Figure descriptions: 100-AlMnFeCrNi, 200-Al9FeNi, 300-AlMnCr, 400-AlZrTi, 500-6063 base material, 600-fusion line, 700-brazing aluminum base material, 800-Al(MnFe), 900-melted metal flowing downwards along the casting wall. Embodiments of the present invention

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Unless otherwise specified, specific conditions are applied in the embodiments. Reagents or instruments used without a specified manufacturer are all commercially available conventional products.

[0037] Aluminum alloys are divided into two types: wrought aluminum alloys and cast aluminum alloys. In the field of aluminum alloy welding, wrought aluminum alloys are currently mostly used for welding. This is because the solidus temperature of existing cast aluminum alloys is relatively low, while brazing requires the solidus temperature of the aluminum alloy material to be welded to be at least 600°C. Therefore, using existing cast aluminum alloy materials for welding results in deformation of the parts after welding. As a result, most manufacturers have turned to using wrought aluminum alloys for welding. However, wrought aluminum alloy parts have large machining allowances, resulting in low manufacturing efficiency, high costs, and material waste.

[0038] To obtain aluminum alloys with good casting properties, a large amount of silicon is usually added to improve their casting performance. This is because silicon has the highest latent heat of phase transformation of all elements. During phase transformation, silicon absorbs heat when changing from a solid to a liquid phase and releases heat when changing from a liquid to a solid phase. Therefore, adding a large amount of silicon can significantly improve the casting performance of aluminum alloys. However, at the same time, a high silicon content will also lead to a decrease in the solidus line of the aluminum alloy. Thus, directly adding a large amount of silicon to aluminum alloys can improve their casting performance, but it also lowers the solidus line. When using it for welding, the material will soften due to deformation, leading to component failure.

[0039] To obtain a truly high solidsline cast aluminum alloy, the inventors, through long-term practice, have provided the following brazing aluminum, comprising the following components by mass percentage: Mn: 1.5-2.5%, Zn: 2.2-3.5%, Fe: 0.5-1.0%, Ni: 1.8-2.5%, Ti: 0.05-0.10%, Zr: 0.2-0.5%, Cr: 0.2-0.35%, Si: ≤0.2%, with the balance being aluminum and unavoidable impurities. To improve the casting properties of the brazing aluminum, this invention adds a high content of Zn and Mn to the provided aluminum alloy. The addition of Zn and Mn not only improves casting properties but also does not cause a decrease in the solidsline. Numerous experimental results show that the solidus temperature and liquidus temperature of the high solidus line brazable cast aluminum alloy provided by this invention are both higher than 600℃, and it has good high-temperature stability. It is a true high solidus line cast aluminum alloy. When used for welding, no discontinuity is observed between the base material and the brazing filler metal in all fields of view. The brazing filler metal and the base material are well fused, and a complete brazed joint can be formed.

[0040] The following is a detailed description of a high solids line brazable cast aluminum alloy, its preparation method, castings, and products provided by embodiments of the present invention.

[0041] In a first aspect, embodiments of the present invention provide a high solids line brazable cast aluminum alloy comprising the following components by mass percentage: Mn: 1.5-2.5%, Zn: 2.2-3.5%, Fe: 0.5-1.0%, Ni: 1.8-2.5%, Ti: 0.05-0.10%, Zr: 0.2-0.5%, Cr: 0.2-0.35%, Si: ≤0.2%, with the balance being aluminum and unavoidable impurities.

[0042] This invention provides a high solidsline brazable cast aluminum alloy. Adding Zn to this high solidsline brazable cast aluminum alloy improves casting performance, while adding Mn addresses the viscosity of the molten aluminum, reducing its viscosity and increasing high-temperature strength without lowering the solidsline. Furthermore, since the raw materials used to prepare this high solidsline brazable cast aluminum alloy contain little or no Si, resulting in poor castability and hot cracking, Fe is added to improve resistance to hot cracking. Simultaneously, to meet the customer's requirement for low thermal conductivity, Zr and Cr are added to form lamellar or blocky second phases, increasing heat dissipation from electron movement and reducing the alloy's thermal conductivity. To improve strength and hardness, Ti is added; Ti refines the crystal structure, forming TiAl3 grains to increase hardness. Adding Ni forms Al9FeNi, ensuring high-temperature strength and a low coefficient of thermal expansion, meeting the customer's requirement that the internal cavity of the brazed part can withstand a hydrostatic pressure of 3.2 MPa, and improving explosion resistance. Therefore, the high solids-line brazable cast aluminum alloy provided in this embodiment of the invention has the advantages of high solids-line, high liquidus-line, low thermal conductivity, excellent mechanical properties, and good casting performance. It can be used in the field of hard brazing. After welding, the casting does not melt or deform, thus meeting the market demand for high solids-line cast aluminum alloys.

[0043] It is worth noting that the high solids line brazable cast aluminum alloy provided in this embodiment of the invention contains Si: ≤0.2%. The high solids line brazable cast aluminum alloy provided does not contain Si at all. The Si is introduced with the raw materials during the manufacturing process of the high solids line brazable cast aluminum alloy, rather than being added by the inventors during the manufacturing process.

[0044] In an optional embodiment, the solidus temperature of the high solidus line brazable cast aluminum alloy is ≥630℃, the liquidus temperature is ≥650℃, and the thermal conductivity is ≤50W / m*K.

[0045] In an optional embodiment, the microstructure of the high solids line brazable cast aluminum alloy includes one or more intermetallic compound AlX strengthening phases and (Al+Al9FeNi) eutectic, wherein AlX is a binary to pentagonal intermetallic compound, and X in the intermetallic compound AlX is selected from one or more elements selected from Mn, Zn, Fe, Ni, Ti, Zr, and Cr.

[0046] In an optional embodiment, the mechanical properties of the high solids line brazable cast aluminum alloy annealed at 600°C for 30 min are as follows: tensile strength Rm≥120MPa, yield strength Rp0.2≥60MPa, and elongation after fracture A≥15%.

[0047] Secondly, embodiments of the present invention also provide a method for preparing the above-mentioned high solids line brazable cast aluminum alloy, comprising the following steps:

[0048] S1. Put the pure aluminum ingots into the furnace and heat them up to melt them;

[0049] S2. Add aluminum-iron master alloy, aluminum-manganese master alloy, aluminum-nickel master alloy, aluminum-zirconium master alloy, aluminum-chromium master alloy and aluminum-titanium master alloy in batches to the aluminum liquid obtained in step S1, and stir thoroughly until completely melted.

[0050] S3. Add pure zinc ingots to the aluminum alloy liquid obtained in step S2;

[0051] S4. The aluminum alloy liquid obtained in step S3 is refined and slag is removed. After the composition is qualified, it is subjected to ultrasonic treatment and then filtered to obtain pure metal melt.

[0052] S5. Cool the pure molten metal obtained in step S4 to obtain a high solids line brazable cast aluminum alloy ingot.

[0053] This invention also provides a method for preparing the above-mentioned high solidsline brazable cast aluminum alloy, comprising: mixing and melting various raw materials according to the aluminum alloy composition to obtain an aluminum alloy liquid; then degassing and removing slag from the aluminum alloy liquid; after the composition is qualified, inserting an ultrasonic vibrating tool head into the aluminum liquid for ultrasonic treatment. Because the ultrasonic vibrating head generates pressure fluctuations in the molten metal, forming microbubbles, these microbubbles undergo growth and collapse processes, leading to rapid supercooling and superheating of the molten metal grains, promoting grain nucleation and producing a grain refinement effect. Furthermore, ultrasound can break up large grains and inhibit dendrite growth, while the solute is evenly distributed due to the ultrasonic stirring effect, avoiding segregation. Therefore, ultrasonic treatment of the aluminum alloy liquid, through its unique physical effects, can improve the microstructure of the aluminum alloy liquid, making it more uniform and dense, and promoting grain refinement. The aluminum alloy liquid is then filtered to obtain a pure molten metal, which is then cooled to obtain a high solidsline brazable cast aluminum alloy ingot.

[0054] In an optional implementation, step S1 includes: feeding pure aluminum ingots into a furnace and heating them at 740°C-760°C.

[0055] In an optional embodiment, step S4 includes: using industrial argon and refining agent to spray and refine the aluminum alloy liquid for 15 minutes, removing slag and letting it stand for 20 minutes to obtain an aluminum liquid at a temperature of 720℃-740℃, then inserting an ultrasonic vibration tool head into the aluminum liquid and performing microstructure refinement for 12 minutes under ultrasonic conditions at a frequency of 20kHz and a temperature of 730℃-750℃, followed by filtration to obtain a pure metal melt.

[0056] Thirdly, the present invention also provides a casting, which is obtained by extrusion casting after melting the above-mentioned high solids line brazable castable aluminum alloy ingot, wherein the extrusion casting temperature is 740℃-760℃, the pressure is 105MPa, and the holding time is 15sec.

[0057] Fourthly, the present invention also provides an article of manufacture which is made by joining the above-mentioned casting with other metal materials by brazing.

[0058] In an optional embodiment, the brazing temperature is 590°C-610°C.

[0059] This invention provides a high solids-line brazable cast aluminum alloy with a solidus temperature ≥630℃ and a liquidus temperature ≥650℃. This high solids-line brazable cast aluminum alloy can be directly used in the field of high-temperature brazing. The product obtained by hard brazing the casting with other metal materials in the temperature range of 590℃-610℃ has a high appearance aesthetics and can meet the needs of high-temperature brazing castings in the field of new energy vehicles, such as valve bodies of new energy vehicle thermal management systems or charging piles.

[0060] To achieve the above objectives, the present invention provides the following technical solution:

[0061] The following tests are conducted to facilitate the testing of various properties of high solidus line brazable cast aluminum alloys. The aluminum alloy is directly cast into a casting during the forming process and then tested. The difference between the two is that aluminum alloys are made by directly cooling the refined melt of each component, while castings are made by cooling the refined melt of each component into a mold according to a preset shape. Therefore, the performance of the casting can be used to reflect the performance of the cast aluminum alloy.

[0062] In this field, the quantities pre-designed during the preparation of castings may have some error compared with the actual test values ​​later. The test values ​​after casting are used as the standard in the following text, and the content of each metal is measured by a direct-reading spectrometer.

[0063] Specifically: In the following embodiments, the battery end plate (hereinafter referred to as end plate) of a new energy vehicle was used as the test sample because the end plate has a regular plane, does not require processing, and is easy to braze. In addition, the short plate has a complex structure and is prone to cracking during casting, so the thermal crack resistance of aluminum alloy materials can be measured.

[0064] 1. Composition and performance test results of samples obtained from each melting batch in the examples and comparative examples.

[0065] 1.1. The composition of the samples obtained from each furnace melting in the examples is shown in Table 1. Example 1

[0066] A method for preparing a brazable cast aluminum alloy with high solids line includes the following steps:

[0067] S1. According to the composition of the aluminum alloy, put the pure aluminum ingots into the furnace and heat them to 740℃;

[0068] S2. Add aluminum-iron master alloy, aluminum-manganese master alloy, aluminum-nickel master alloy, aluminum-zirconium master alloy, aluminum-chromium master alloy and aluminum-titanium master alloy in batches to the aluminum liquid obtained in step S1, and stir thoroughly until completely melted.

[0069] S3. Add pure zinc ingots to the aluminum alloy liquid obtained in step S2;

[0070] S4. Refine and remove slag from the aluminum alloy liquid obtained in step S3. After the composition is qualified, insert the ultrasonic vibration tool head into the aluminum liquid and ultrasonically treat it for 12 minutes at an ultrasonic frequency of 20kHz and a temperature of 730℃. Then filter to obtain pure metal melt.

[0071] S5. The pure molten metal obtained in step S4 is extruded and cast into a casting at a pouring temperature of 740℃, a pressure of 105MPa, and a holding time of 15sec.

[0072] The casting composition and its mass percentage obtained in this embodiment are as follows: Mn: 2.5%, Zn: 2.32%, Fe: 0.531%, Ni: 1.87%, Ti: 0.051%, Zr: 0.23%, Cr: 0.23%, Si: 0.194%, with the balance being aluminum and unavoidable impurities.

[0073] Table 1. Chemical composition of the high solids line brazable cast aluminum alloys provided in Examples 1-10

[0074]

[0075] 1.2. Sample Casting

[0076] Three types of castings were machined: end plates, φ6mm test bars, and φ10mm test bars. The types of castings cast in each embodiment are shown in Table 2 below:

[0077] Table 2 shows the types of castings produced by the high solidus brazable cast aluminum alloys provided in Examples 1-10.

[0078]

[0079] Taking the high solids-line brazable castable aluminum alloys obtained from Examples 3, 4, and 5 as examples, and casting them into three types of castings—end plates (Figure a), φ6mm test bars (Figure b), and φ10mm test bars (Figure c)—as a reference, and referring to Table 2 and Figure 1, it can be seen that the high solids-line aluminum alloys provided by the embodiments of the present invention can be cast into different types of castings, and the different types of castings have good shape quality, indicating that the high solids-line aluminum alloys provided by the embodiments of the present invention have excellent filling performance and are suitable for preparing castings with different morphologies.

[0080] Using the end plate cast in Example 6 above as a sample, sampling and analysis were performed. Referring to Figure 2, the matrix structure of this sample is an α-Al+(Al+Al9FeNi) eutectic, in which the fine lamellar Al9FeNi (shown as 200 in Figure 2) exhibits good thermal stability and does not participate in the dissolution process during brazing heating. This effectively prevents grain boundary slippage at high temperatures, improving the alloy's high-temperature stability. Adding Mn, Cr, and Ni to the aluminum alloy can form blocky AlMnCr (shown as 300 in Figure 2), lamellar AlMnFeCrNi (shown as 100 in Figure 2), and granular AlZrTi second phase (shown as 400 in Figure 2), increasing the scattering of electron motion and reducing the thermal conductivity of the aluminum alloy.

[0081] 1.3 Solid-liquid phase temperature and thermal cracking performance testing

[0082] The casting was scanned using a DSC 204F1 differential calorimeter at a speed of 5 K / min. The actual solid-liquid phase temperatures and the proportion of hot cracks in the casting are shown in Table 3 below.

[0083] Table 3 shows the actual solid-liquid phase temperatures and hot cracking ratios of the castings made from the high solidus line brazable cast aluminum alloys provided in Examples 1-10.

[0084]

[0085] Table 4 shows the actual solid-liquid phase temperatures of the castings made from the high solidus line brazable cast aluminum alloys provided in Comparative Examples 1-4.

[0086]

[0087] Table 5 shows the hot cracking rates of castings made from high solids-line brazable cast aluminum alloys provided in Comparative Examples 5-7.

[0088]

[0089] As can be seen from Tables 3 and 4 above, the measured solidus and liquidus temperatures of all aluminum alloys in Examples 1-10 all meet the requirements of a solidus temperature ≥ 630℃ and a liquidus temperature ≥ 650℃. This indicates that the aluminum alloys prepared in the embodiments of the present invention have very high solidus and liquidus lines, and can be directly used for brazing as brazable cast aluminum alloys. However, in Comparative Examples 3-4, when Si content is higher than 0.2%, the solidus temperature is lower than 630℃. This indicates that high silicon content is not conducive to obtaining aluminum alloys with high solidus lines. As can be seen from Tables 3 and 5 above, the hot cracking ratio in Examples 3, 5, 6, and 10 is 0. This shows that the higher the iron content in the aluminum alloy, the lower the hot cracking ratio, indicating that adding Fe can improve the hot cracking resistance of the aluminum alloy.

[0090] 1.4. The mechanical properties of the test bar are shown in Table 6:

[0091] Table 6 shows the mechanical properties of the test bars cast from the high solidus brazable cast aluminum alloys provided in Examples 1-10.

[0092]

[0093] As can be seen from Table 6 above, the alloy composition of Example 9 is similar to that of Example 4. The elongation test value of the casting obtained by casting in the annealed state in Example 4 is lower than that of the casting obtained by casting in Example 9, indicating that the measured mechanical properties of the sample are affected by the sample preparation quality.

[0094] 1.5. Thermal conductivity test

[0095] The thermal conductivity test results are shown in Table 7:

[0096] Table 7 shows the thermal conductivity of the high solidus brazable cast aluminum alloys provided in Examples 4-6.

[0097]

[0098] As can be seen from Table 7 above, the high solidus line brazable cast aluminum alloy provided in the embodiments of the present invention has low thermal conductivity.

[0099] 1.6. Corrosion resistance

[0100] The end plates of Examples 4, 5, and 6 were subjected to a 120-hour neutral salt spray corrosion test. The photos are shown in Figure 3 (Figure a shows the end plate cast in Example 5; Figure b shows the end plate cast in Example 6; Figure c shows the end plate cast in Example 4). As can be seen from Figure 3, the end plate cast in Example 5 had the fewest corrosion products, while the test bar cast in Example 4 had the most corrosion products.

[0101] Referring to Figure 4, the metallographic structure of the casting produced in Example 4 shows that the casting is easily corroded because the large number of blocky second phases on the surface disrupts the continuity of the naturally formed oxide film on the metal surface.

[0102] Figure 5 shows the potentiodynamic polarization curves of the three alloys in a 3.5% NaCl corrosive medium at a rate of 1 mV / s. The self-corrosion current obtained from the figure is: Example 5 < Example 6 < Example 4, indicating that the end plate cast in Example 5 has the best corrosion resistance. The order of corrosion resistance performance evaluated by self-corrosion current is the same as that of salt spray corrosion. Based on the results of the salt spray test, the product must undergo a hard anodizing treatment after brazing to ensure its corrosion resistance.

[0103] 2. Analysis of brazed joints in end plate castings

[0104] The end plate cast in Example 6 was brazed to 6063 wrought aluminum alloy using 4004 wrought aluminum alloy sheet as brazing filler metal. The welding process was carried out in a vacuum brazing furnace. After the furnace was evacuated to a preset vacuum level, the temperature was raised to 500°C and held for 0.5 hours to preheat the sample. Then, the temperature was raised to 600°C and held for 30 minutes. Samples of the brazed workpiece were taken perpendicular to the weld direction, and the brazed joint condition at different locations was observed.

[0105] Referring to Figures 6-15, it is evident that there are no breaks between the base material and the brazing filler metal in all fields of view. The brazing filler metal and the base material are well fused, forming a complete brazed joint. Specifically, as shown in Figure 15, a complete fusion line (as shown in Figure 15, 600) is formed between the 6063 base material (as shown in 500 in Figure 15) and the brazing aluminum base material (as shown in 700 in Figure 15). In the fusion zone of the end plate and the brazing filler metal cast in Example 6, it is visible that the lamellar Al(MnFe) in the end plate (as shown in 800 in Figure 16) spans both the brazing aluminum matrix and the fusion zone (see Figure 16). On both sides of the weld bead, it is visible that the end plate undergoes local melting and fusion with the brazing filler metal to form a large fusion zone (see Figure 17). The partially molten fusion metal flows downward along the outer wall of the end plate (as shown in 900 in Figure 18) (see Figure 18). When the joint cools, the liquid metal solidifies and fills the locally melted part of the end plate, and no bonding defects appear on the outside of the brazed joint.

[0106] The above are merely preferred embodiments of the present invention and are not intended to limit the present 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 high solids line brazable cast aluminum alloy, characterized in that, The composition includes the following components by mass percentage: Mn: 1.5-2.5%, Zn: 2.2-3.5%, Fe: 0.5-1.0%, Ni: 1.8-2.5%, Ti: 0.05-0.10%, Zr: 0.2-0.5%, Cr: 0.2-0.35%, Si: ≤0.2%, with the balance being aluminum and unavoidable impurities. The high solids temperature brazable cast aluminum alloy has a solid phase temperature ≥630℃, a liquid phase temperature ≥650℃, and a thermal conductivity ≤50W / m*K. The microstructure of the brazable cast aluminum alloy with high solids line includes one or more intermetallic compound AlX strengthening phases and (Al+Al9FeNi) eutectic, wherein AlX is a binary to pentagonal intermetallic compound, and X in the intermetallic compound AlX is selected from one or more elements selected from Mn, Zn, Fe, Ni, Ti, Zr, and Cr. The mechanical properties of the high solidus brazable cast aluminum alloy after annealing at 600℃ for 30 min are as follows: tensile strength Rm≥ 120MPa, yield strength Rp0.2≥60MPa, and elongation after fracture A≥15%.

2. A method for preparing a high solidus line brazable cast aluminum alloy according to claim 1, characterized in that, Includes the following steps: S1. Put the pure aluminum ingots into the furnace and heat them up to melt them; S2. Add aluminum-iron master alloy, aluminum-manganese master alloy, aluminum-nickel master alloy, aluminum-zirconium master alloy, aluminum-chromium master alloy and aluminum-titanium master alloy in batches to the aluminum liquid obtained in step S1, and stir thoroughly until completely melted. S3. Add pure zinc ingots to the aluminum alloy liquid obtained in step S2; S4. The aluminum alloy liquid obtained in step S3 is refined and slag is removed. After the composition is qualified, it is subjected to ultrasonic treatment and then filtered to obtain pure metal melt. S5. Cool the pure molten metal obtained in step S4 to obtain a high solids line brazable cast aluminum alloy ingot.

3. The preparation method according to claim 2, characterized in that, Step S1 includes: putting pure aluminum ingots into a furnace and heating them at 740℃-760℃.

4. The preparation method according to claim 2, characterized in that, Step S4 includes: using industrial argon and refining agent to spray and refine the aluminum alloy liquid for 15 minutes, removing slag and letting it stand for 20 minutes to obtain aluminum liquid at a temperature of 720℃-740℃, then inserting an ultrasonic vibration tool head into the aluminum liquid and performing microstructure refinement for 12 minutes under ultrasonic conditions at a frequency of 20kHz and a temperature of 730℃-750℃, followed by filtration to obtain pure metal melt.

5. A casting, characterized in that, The casting is prepared by melting and extruding a high solids line brazable castable aluminum alloy ingot obtained by the preparation method described in claim 2. The extrusion casting temperature is 740℃-760℃, the pressure is 105MPa, and the holding time is 15sec.

6. An article, characterized in that, The product is made by joining the casting described in claim 5 with other metal materials by hard brazing.

7. The article of claim 6, characterized in that, The welding temperature for the brazing is 590℃-610℃.

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