Aluminum alloy and preparation method thereof

Abstract

In order to solve the problem of self-piercing riveting cracking of die-casting aluminum alloy parts, the invention provides an aluminum alloy which is characterized by comprising the following components in percentage by mass: 8.0 to 9.5 percent of Si, 0.01 to 0.4 percent of Cu, 0.01 to 0.15 percent of Fe, 0.35 to 0.65 percent of Mn, 0.01 to 0.15 percent of Zn, 0.05 to 0.3 percent of Nb, 0.01 to 0.15 percent of B, 0.005 to 0.015 percent of Sr and the balance of aluminum and inevitable impurities. The balance is aluminum and other elements, and the total amount of the other elements is less than 0.15%. Meanwhile, the invention further discloses a preparation method of the aluminum alloy. The preparation process of the aluminum alloy does not need heat treatment, and the aluminum alloy has good tensile strength and yield strength and meanwhile is high in impact toughness.

Description

Technical Field

[0001] The invention belongs to the technical field of die-casting aluminum alloys, and in particular relates to an aluminum alloy and a preparation method thereof. Background Art

[0002] Die casting is a precision casting method that uses high pressure to force molten metal into a complex-shaped metal mold. Large die castings are severely deformed after heat treatment, and their components are very rigid, so they cannot meet the precision requirements through shaping. Therefore, it is urgent to develop new high-strength and tough die-cast aluminum alloy materials that do not require heat treatment to meet the mechanical properties and connection requirements.

[0003] In the prior art, alloying elements such as Si, Mn, Mg, Cu, V, Zr, TCB refiner, rare earth and Sr are added to the aluminum alloy to ensure high fluidity, high strength and high toughness of the aluminum alloy, but the impact toughness of the alloy is not significantly improved.

[0004] In the automotive industry, impact toughness is an important performance indicator of aluminum alloy die-cast parts for vehicle bodies. Aluminum alloy die-cast parts and other overlapping steel plates or aluminum plates around them are usually connected by self-piercing riveting (SPR). The SPR connection process can be simplified to the high-speed impact process of rivets on aluminum alloy castings. In the prior art, large thin-walled parts made of aluminum alloy often suffer from riveting cracking during the SPR process due to insufficient impact toughness. Summary of the invention

[0005] In view of the problem of self-piercing riveting cracking of existing die-cast aluminum alloy parts, the present invention provides an aluminum alloy and a preparation method thereof.

[0006] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0007] In one aspect, the present invention provides an aluminum alloy comprising the following components in percentage by mass:

[0008] The Si content is 8.0-9.5%, the Cu content is 0.01-0.4%, the Fe content is 0.01-0.15%, the Mn content is 0.35-0.65%, the Zn content is 0.01-0.15%, the Nb content is 0.05-0.3%, the B content is 0.01-0.15%, the Sr content is 0.005-0.015%, and the balance is aluminum and other elements, and the total amount of the other elements is less than 0.15%.

[0009] Optionally, the aluminum alloy includes the following components in percentage by mass:

[0010] The Si content is 8.25-9.0%, the Cu content is 0.1-0.3%, the Fe content is 0.05-0.11%, the Mn content is 0.45-0.55%, the Zn content is 0.05-0.13%, the Nb content is 0.10-0.15%, the B content is 0.05-0.10%, the Sr content is 0.005-0.012%, and the balance is aluminum and other elements, and the total amount of the other elements is less than 0.10%.

[0011] Optionally, the other elements include one or more of Ni and Cr.

[0012] Optionally, the content of a single element in the other elements is less than 0.05%.

[0013] On the other hand, the present invention provides a method for preparing the aluminum alloy as described above, comprising the following steps:

[0014] After the pure aluminum ingot is completely melted, add AlSi, AlCu, and AlMn master alloys to obtain aluminum alloy liquid, and the temperature is controlled at 730-750℃;

[0015] Add refining agent to carry out the first deslagging and degassing of aluminum liquid under argon, and control the temperature at 730-750℃;

[0016] Add AlSr alloy and AlNbB refiner, control the temperature at 720-730°C, and obtain alloy melt;

[0017] The alloy melt is transferred into a container, and a refining agent is added for refining, and the second slag removal and degassing are performed. The degassing time is 5-20 minutes, and the temperature is controlled at 720-730°C;

[0018] After the refined alloy melt is qualified by composition analysis, the alloy melt is cooled to 680-700°C for high vacuum pressure casting to obtain an aluminum alloy sample.

[0019] Optionally, after the first slag removal and degassing, the aluminum alloy liquid is subjected to a composition test, and after the composition analysis is qualified, the AlSr master alloy is added, the temperature is controlled at 720-730°C, and after stirring and standing for 5-10 minutes, the AlNbB refiner is added, and then stirred for 20-30 minutes, and the temperature is controlled at 720-730°C.

[0020] Optionally, the AlSr content accounts for 0.1-0.5% of the total amount of the alloy melt, and the AlNbB refiner content accounts for 0.1-0.5% of the total amount of the alloy melt.

[0021] Optionally, the AlNbB refiner is selected from an AlNbB master alloy wire rod, and based on 100% of the mass of the AlNbB master alloy wire rod, the content of Nb is 3-10%, and the content of B is 0.10-0.30%.

[0022] Optionally, the amount of the refining agent added each time is 0.1-0.4% of the total amount of the alloy melt.

[0023] Optionally, during high vacuum pressure casting, the mold cavity vacuum degree is 60-80Mbar, the casting pressure is 50-70MPa, the injection speed is 3-4m / s, and the mold temperature is 170-190℃.

[0024] According to the aluminum alloy provided by the present invention, by adjusting the ratio of each strengthening element in the aluminum alloy, the aluminum alloy has higher impact toughness, and ensures good elongation without sacrificing strength. The silicon content of 8.0-9.5% of the hypoeutectic is used to improve the fluidity of the melt; the Fe content is strictly controlled to avoid the influence of the relative performance of the needle, but at the same time, in order to ensure that it avoids sticking to the mold, the Mn element is used to fill it; the heterogeneous nucleation effect of NbAl3 and NbB2 in the Al-Nb-B refiner on α-Al can refine the α-Al grain size to less than 20μm, effectively hindering the growth of grains, and can prepare aluminum alloy castings with good tensile strength and yield strength without heat treatment. At the same time, the impact toughness is high, and it can be used for self-piercing riveting of large die-casting structural parts, with broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the metallographic structure of the aluminum alloy die-cast state according to Example 1 of the present invention;

[0026] Figure 2 This is a schematic diagram of the impact fracture of the aluminum alloy die-cast state according to Example 1 of the present invention;

[0027] Figure 3 This is a schematic diagram of the metallographic structure of the aluminum alloy die-cast state according to Example 2 of the present invention;

[0028] Figure 4 This is a schematic diagram of the impact fracture of the aluminum alloy die-cast state according to Example 2 of the present invention;

[0029] Figure 5 This is a schematic diagram of the metallographic structure of the aluminum alloy die-casting state according to Example 3 of the present invention;

[0030] Figure 6 This is a schematic diagram of the impact fracture of the aluminum alloy die-cast state according to Example 3 of the present invention;

[0031] Figure 7 This is a schematic diagram of the metallographic structure of the aluminum alloy die-casting state of Comparative Example 1 of the present invention;

[0032] Figure 8 This is a schematic diagram of the impact fracture of the die-cast aluminum alloy of Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0033] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] An embodiment of the present invention provides an aluminum alloy, comprising the following components in percentage by mass:

[0035] The Si content is 8.0-9.5%, the Cu content is 0.01-0.4%, the Fe content is 0.01-0.15%, the Mn content is 0.35-0.65%, the Zn content is 0.01-0.15%, the Nb content is 0.05-0.3%, the B content is 0.01-0.15%, the Sr content is 0.005-0.015%, and the balance is aluminum and other elements, and the total amount of the other elements is less than 0.15%.

[0036] In some specific embodiments, the Si content is 8.4%, 8.6%, 8.8%, 9.2% or 9.35%, the Cu content is 0.03%, 0.05%, 0.2% or 0.35%, the Fe content is 0.03%, 0.07%, 0.09%, 0.10% or 0.13%, the Mn content is 0.4%, 0.5% or 0.6%, the Zn content is 0.03%, 0.07%, 0.09% or 0.1%, the Nb content is 0.07%, 0.09%, 0.13%, 0.2% or 0.25%, the B content is 0.03%, 0.07%, 0.09% or 0.13%, and the Sr content is 0.007%, 0.009%, 0.01% or 0.013%.

[0037] According to the aluminum alloy provided by the present invention, by adjusting the ratio of each strengthening element in the aluminum alloy, the aluminum alloy has higher impact toughness, and ensures good elongation without sacrificing strength. The silicon content of 8.0-9.5% of the hypoeutectic is used to improve the fluidity of the melt; the Fe content is strictly controlled to avoid the influence of the relative performance of the needle, but at the same time, in order to ensure that it avoids sticking to the mold, the Mn element is used to fill it; the heterogeneous nucleation effect of NbAl3 and NbB2 in the Al-Nb-B refiner on α-Al can refine the α-Al grain size to less than 20μm, effectively hindering the growth of grains, and can prepare aluminum alloy castings with good tensile strength and yield strength without heat treatment. At the same time, the impact toughness is high, and it can be used for self-piercing riveting of large die-casting structural parts, with broad application prospects.

[0038] In some preferred embodiments, the aluminum alloy includes the following components in mass percentage: Si content is 8.25-9.0%, Cu content is 0.1-0.3%, Fe content is 0.05-0.11%, Mn content is 0.45-0.55%, Zn content is 0.05-0.13%, Nb content is 0.10-0.15%, B content is 0.05-0.10%, Sr content is 0.005-0.012%, and the balance is aluminum and other elements, and the total amount of the other elements is less than 0.10%.

[0039] In some embodiments, the other elements include one or more of Ni and Cr.

[0040] In some embodiments, the content of a single element of the other elements is less than 0.05%.

[0041] Another embodiment of the present invention provides a method for preparing the aluminum alloy as described above, comprising the following steps:

[0042] After the pure aluminum ingot is completely melted, add AlSi, AlCu, and AlMn master alloys to obtain aluminum alloy liquid, and the temperature is controlled at 730-750℃;

[0043] Add refining agent to carry out the first deslagging and degassing of aluminum liquid under argon, and control the temperature at 730-750℃;

[0044] Add AlSr alloy and AlNbB refiner, control the temperature at 720-730°C, and obtain alloy melt;

[0045] The alloy melt is transferred into a container, and a refining agent is added for refining, and the second slag removal and degassing are performed. The degassing time is 5-20 minutes, and the temperature is controlled at 720-730°C;

[0046] After the refined alloy melt is qualified by composition analysis, the alloy melt is cooled to 680-700°C for high vacuum pressure casting to obtain an aluminum alloy sample.

[0047] In some embodiments, after the first slag removal and degassing, the aluminum alloy liquid is subjected to component detection. After the component analysis is qualified, the AlSr master alloy is added, the temperature is controlled at 720-730°C, and after stirring, the AlNbB refiner is added after standing for 5-10 minutes, and then stirred for 20-30 minutes, and the temperature is controlled at 720-730°C.

[0048] In some embodiments, the AlSr content accounts for 0.1-0.5% of the total amount of the alloy melt, and the AlNbB refiner content accounts for 0.1-0.5% of the total amount of the alloy melt.

[0049] In some embodiments, the AlNbB refiner is selected from an AlNbB master alloy wire rod, and based on 100% of the mass of the AlNbB master alloy wire rod, the content of Nb is 3-10%, and the content of B is 0.10-0.30%.

[0050] In some embodiments, the refining agent includes one or more of hexafluoroethane and aluminum refining agent ZS-AJ01C.

[0051] In some embodiments, the amount of the refining agent added each time is 0.1-0.4% of the total amount of the alloy melt.

[0052] In some embodiments, during high vacuum pressure casting, the vacuum degree of the mold cavity is 60-80 Mbar, the casting pressure is 50-70 MPa, the injection speed is 3-4 m / s, and the mold temperature is 170-190°C.

[0053] The present invention is further described below by way of examples.

[0054] Table 1

[0055]

[0056]

[0057] Example 1

[0058] This embodiment is used to illustrate the aluminum alloy and the preparation method thereof disclosed in the present invention, and includes the following steps:

[0059] As shown in Table 1, the aluminum alloy composition is calculated by mass content: Si content is 8.25%, Cu content is 0.01%, Fe content is 0.11%, Mn content is 0.45%, Zn content is 0.13%, Nb content is 0.15%, B content is 0.01%, Sr content is 0.012%, and the balance is aluminum and other elements, and the total amount of the other elements is less than 0.15%. The masses of various master alloys, refiners and metal elements required are calculated based on the mass contents of the above aluminum alloy components.

[0060] Add industrial pure aluminum ingots into a crucible resistance furnace for heating, with the preset temperature at 730°C. After the pure aluminum ingots are completely melted, add AlSi, AlCu, and AlMn intermediate alloys in sequence to obtain aluminum alloy liquid, with the temperature controlled at 730-750°C.

[0061] A refining agent of 15% relative to the total amount of the alloy melt is added to carry out the first deslagging and degassing of the aluminum liquid under argon, and the temperature is controlled at 730-750°C.

[0062] The aluminum alloy liquid is subjected to component detection. After the component analysis is qualified, the AlSr master alloy is added, the temperature is controlled at 720-730° C., and after stirring, the AlNbB refiner is added after standing for 5-10 minutes, and then stirred for 20-30 minutes, and the temperature is controlled at 720-730° C. to obtain an alloy melt.

[0063] The alloy melt is transferred into a container and refined by adding a refining agent. The second slag removal and degassing are carried out. The degassing time is 5-20 minutes and the temperature is controlled at 720-730°C.

[0064] After the refined alloy melt composition analysis is qualified, the alloy melt is cooled to 680-700℃ for high vacuum pressure casting to obtain aluminum alloy samples. The pressure casting process parameters are: mold cavity vacuum degree is 60-80Mbar, casting pressure is 50-70MPa, injection speed is 3-4m / s, mold temperature is 170-190℃, and alloy melt temperature is 690℃.

[0065] Embodiments 2 to 7

[0066] Examples 2 to 7 are used to illustrate the aluminum alloy and the preparation method thereof disclosed in the present invention, and include most of the operating steps in Example 1, except that:

[0067] The aluminum alloy compositions shown in Examples 2 to 7 in Table 1 were used.

[0068] Comparative Example 1

[0069] This comparative example is used to compare and illustrate the aluminum alloy and the preparation method thereof disclosed in the present invention, and includes the following steps:

[0070] As shown in Table 1, the aluminum alloy composition is calculated by mass content: Si content is 8.25%, Cu content is 0.01%, Fe content is 0.11%, Mn content is 0.45%, Zn content is 0.13%, Sr content is 0.012%, and the balance is aluminum and other elements, and the total amount of the other elements is less than 0.15%. The masses of various required master alloys and metal elements are calculated based on the mass contents of the above aluminum alloy components.

[0071] Add industrial pure aluminum ingots into a crucible resistance furnace for heating, with the preset temperature at 730°C. After the pure aluminum ingots are completely melted, add AlSi, AlCu, and AlMn intermediate alloys in sequence to obtain aluminum alloy liquid, with the temperature controlled at 730-750°C.

[0072] A refining agent of 15% relative to the total amount of the alloy melt is added to carry out the first deslagging and degassing of the aluminum liquid under argon, and the temperature is controlled at 730-750°C.

[0073] The aluminum alloy liquid is subjected to component detection, and after the component analysis is qualified, the AlSr master alloy is added, and the temperature is controlled at 720-730° C. to obtain an alloy melt.

[0074] The alloy melt is transferred into a container and refined by adding a refining agent. The second slag removal and degassing are carried out. The degassing time is 5-20 minutes and the temperature is controlled at 720-730°C.

[0075] After the refined alloy melt composition analysis is qualified, the alloy melt is cooled to 680-700℃ for high vacuum pressure casting to obtain aluminum alloy samples. The pressure casting process parameters are: mold cavity vacuum degree is 60-80Mbar, casting pressure is 50-70MPa, injection speed is 3-4m / s, mold temperature is 170-190℃, and alloy melt temperature is 690℃.

[0076] Comparative Examples 2 to 9

[0077] Comparative Examples 2 to 9 are used to compare and illustrate the aluminum alloy and the preparation method thereof disclosed in the present invention, and include most of the operating steps in Example 1, except that:

[0078] The aluminum alloy compositions shown in Comparative Examples 2 to 9 in Table 1 were used.

[0079] Performance Testing

[0080] 1. The aluminum alloys prepared in the above-mentioned Example 1, Example 2, Example 3 and Comparative Example 1 were subjected to composition scanning, and the obtained SEM photos are as follows: Figure 1 , Figure 3 , Figure 5 and Figure 7As shown in FIG. 1 , it can be seen that for aluminum alloys with different Si contents, adding NbB refiner can significantly refine the grains. Scanning electron microscope imaging was performed on the impact port of the aluminum alloy parts prepared in the above-mentioned Example 1, Example 2, Example 3, and Comparative Example 1, and the obtained photos are shown in FIG. Figure 2 , Figure 4 , Figure 6 and Figure 8 As shown, it can be seen that the fracture surface with the addition of NbB refiner is obviously ductile fracture.

[0081] 2. The aluminum alloys prepared in the above Examples 1-7 and Comparative Examples 1-9 were subjected to the following performance tests: Tensile strength test

[0082] The tensile strength, yield strength and elongation of the material are tested using "GB / T 228.1-2010 Tensile test of metallic materials Part 1: Room temperature test method".

[0083] The aluminum alloys prepared in Examples 1-36 and Comparative Examples 1-24 were die-cast to form tensile test bars (diameter 6.4 mm*gauge length 50 mm), and tensile properties were tested using an electronic universal testing machine with model CMT5105. The gauge length was 50 mm, and the loading rate was 2 mm / min. The measurement data were recorded, and six samples were tested at each formulation point, where the yield strength, tensile strength and elongation were the average values ​​of the six data. The relative standard deviation of the yield strength was the percentage ratio of the standard deviation of the six yield strength data to the average value, and the relative standard deviation of the tensile strength was the percentage ratio of the standard deviation of the six tensile strength data to the average value.

[0084] Thermal conductivity test:

[0085] Aluminum alloy is made into φ12.7×3mm ingot heat-conducting discs, and graphite coating is evenly sprayed on both sides of the sample to be tested; the treated sample is placed in a laser thermal conductivity instrument for testing. Laser thermal conductivity testing is carried out in accordance with the "ASTM E1461 Standard Method for Determining Thermal Diffusivity by Flash Method".

[0086] Carry out metal Charpy notched impact test according to GB / T 229-2007.

[0087] The test results obtained are entered in Table 2.

[0088] Table 2

[0089]

[0090]

[0091] From the test results of comparative examples 1-7 and comparative examples 1-9, it can be seen that, relative to aluminum alloys outside the element range provided by the present invention, the aluminum alloy provided by the present invention has excellent mechanical properties of large impact toughness in the die-cast state, can meet the requirements of the die-casting process, and at the same time has good yield strength, tensile strength and good elongation.

[0092] It can be seen from Examples 1 to 3, Comparative Examples 2 and 3 that by adjusting the Si content in the aluminum alloy, the yield strength and elongation can be adjusted, and the melt fluidity can be significantly affected.

[0093] It can be seen from Examples 1 to 3 and Comparative Example 1 that by adjusting the content of Nb and B in the aluminum alloy, different grain refinement effects can be achieved, which has a significant effect on the impact toughness of the material; under the same content of grain refiner, the grain size is basically the same, and the impact toughness is jointly affected by other alloy elements.

[0094] It can be seen from Examples 1-7, Comparative Examples 5 and 9 that the yield strength and tensile strength of the material can be adjusted by adjusting the content of Mn and Cu in the aluminum alloy and increasing or decreasing the content of the reinforcing phase.

[0095] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An aluminum alloy, characterized in that: The components include the following mass percentages: The Si content is 8.0-9.5%, the Cu content is 0.01-0.4%, the Fe content is 0.01-0.15%, the Mn content is 0.35-0.65%, the Zn content is 0.01-0.15%, the Nb content is 0.05-0.3%, the B content is 0.01-0.15%, the Sr content is 0.005-0.015%, and the balance is aluminum and other elements, and the total amount of the other elements is less than 0.15%.

2. The aluminum alloy according to claim 1, characterized in that The aluminum alloy comprises the following components in percentage by mass: The Si content is 8.25-9.0%, the Cu content is 0.1-0.3%, the Fe content is 0.05-0.11%, the Mn content is 0.45-0.55%, the Zn content is 0.05-0.13%, the Nb content is 0.10-0.15%, the B content is 0.05-0.10%, the Sr content is 0.005-0.012%, and the balance is aluminum and other elements, and the total amount of the other elements is less than 0.10%.

3. The aluminum alloy according to claim 1, characterized in that The other elements include one or more of Ni and Cr.

4. The aluminum alloy according to claim 1, characterized in that The content of a single element of the other elements is less than 0.05%.

5. The method for preparing an aluminum alloy according to any one of claims 1 to 4, characterized in that: The steps include: After the pure aluminum ingot is completely melted, add AlSi, AlCu, and AlMn master alloys to obtain aluminum alloy liquid, and the temperature is controlled at 730-750℃; Add refining agent to carry out the first deslagging and degassing of aluminum liquid under argon, and control the temperature at 730-750℃; Add AlSr alloy and AlNbB refiner, control the temperature at 720-730°C, and obtain alloy melt; The alloy melt is transferred into a container, and a refining agent is added for refining, and the second slag removal and degassing are performed. The degassing time is 5-20 minutes, and the temperature is controlled at 720-730°C; After the refined alloy melt is qualified by composition analysis, the alloy melt is cooled to 680-700°C for high vacuum pressure casting to obtain an aluminum alloy sample.

6. The method for preparing the aluminum alloy according to claim 5, characterized in that: After the first slag removal and degassing, the aluminum alloy liquid is subjected to component detection. After the component analysis is qualified, the AlSr master alloy is added, the temperature is controlled at 720-730°C, and after stirring, the AlNbB refiner is added after standing for 5-10 minutes, and then stirred for 20-30 minutes, and the temperature is controlled at 720-730°C.

7. The method for preparing the aluminum alloy according to claim 5, characterized in that: The AlSr content accounts for 0.1-0.5% of the total amount of the alloy melt, and the AlNbB refiner content accounts for 0.1-0.5% of the total amount of the alloy melt.

8. The method for preparing the aluminum alloy according to claim 5, characterized in that: The AlNbB refiner is selected from the AlNbB master alloy wire rod. Based on 100% of the mass of the AlNbB master alloy wire rod, the content of Nb is 3-10%, and the content of B is 0.10-0.30%.

9. The method for preparing the aluminum alloy according to claim 5, characterized in that: The amount of the refining agent added each time is 0.1-0.4% of the total amount of the alloy melt.

10. The method for preparing the aluminum alloy according to claim 5, characterized in that: During high vacuum pressure casting, the mold cavity vacuum degree is 60-80Mbar, the casting pressure is 50-70MPa, the injection speed is 3-4m / s, and the mold temperature is 170-190℃.

Images