A niobium-containing non-heat-treated aluminum alloy and a method for manufacturing the same

Abstract

The application discloses a niobium-containing heat treatment-free aluminum alloy and a preparation method thereof, and belongs to the aluminum alloy field. The mass percentage of each component in the alloy is as follows: 7-10% of Si, 0.2-2% of Mg, 0.4-0.75% of Mn, 0.1-0.3% of Fe, 0.05-0.1% of Ti, 0.03-0.1% of Nb, 0.15-0.9% of B, 0.01-0.02% of Sr, the content of other uncontrollable impurity elements is controlled to be less than or equal to 0.5%, and the balance is Al. The ratio of Fe and Mn elements in the alloy is controlled to be 1:2.5-4, the ratio of Nb and B elements is controlled to be 1:5-9, and the ratio of Ti and Nb elements is controlled to be 1:1-2. The Nb and Ti are added in the form of Al-Nb-B intermediate alloy and Al-Ti intermediate alloy respectively. Correspondingly, the application also provides a smelting method of the aluminum alloy. The aluminum alloy prepared by the application has the characteristics of small and uniform grain structure, small and dispersed distribution of eutectic Si particles, improved size and form of Fe-rich phase, high strength and high toughness, and guaranteed fluidity of the alloy material.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy technology, specifically relating to a novel niobium-containing heat-free aluminum alloy and its preparation method. Background Technology

[0002] Improving quality and efficiency is a key driving force behind the transformation of new energy vehicle body manufacturing. The heavy weight of new energy vehicle batteries creates an urgent need for lightweight structural components, making low-density, high-ductility, and corrosion-resistant aluminum alloy castings the optimal choice. Currently, solution treatment and artificial aging heat treatment are the most widely used methods for alloy castings, achieving a good balance between strength and ductility. However, high-temperature solution treatment often leads to surface blistering and deformation in thin-walled structural components, a bottleneck that severely limits their application in automotive structural parts. Therefore, heat-treatment-free aluminum alloys that do not undergo solution treatment or artificial aging have gradually emerged in recent years, with major alloy grades including Castasil 37, C611, and Aural6.

[0003] The thin-walled and complex structures of new energy vehicle components place higher demands on the fluidity, demolding properties, microstructure, and mechanical properties of heat-free aluminum alloys. However, current heat-free aluminum alloys still face many challenges, including coarse grain structure, discontinuous and uneven distribution of Si phase transformation caused by the easy burning of Sr, and the unavoidable large-size lamellar β-Al5FeSi phase. These issues reduce the alloy's strength or plasticity, becoming bottlenecks restricting the development of heat-free cast aluminum alloys.

[0004] Therefore, how to improve the plasticity of an alloy while ensuring its fluidity and strength without heat treatment is a problem that engineers urgently need to solve. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a novel niobium-containing, heat-free aluminum alloy and its smelting method. The Si content in the alloy is close to the eutectic composition to ensure the alloy's strength, fluidity, and castability; the addition of Nb, an anti-Si poisoning element, effectively refines the grains; the addition of trace amounts of Ti, a solute element, inhibits dendrite growth and increases the nucleation rate in the early stages of solidification; in the later stages of solidification, to reduce the secondary dendrite arm spacing and obtain a finely dispersed Mg2Si phase, the Mg content is appropriately increased; simultaneously, the Fe content and Fe / Mn ratio in the alloy are controlled to reduce the possibility of the formation of large-sized lamellar Fe-rich phases.

[0006] Accordingly, the present invention is achieved through the following technical solutions.

[0007] This invention relates to a heat-free aluminum alloy, wherein the specific contents of each element in the alloy, calculated by mass percentage, are: 7%–10% Si; 0.2%–2% Mg; 0.4%–0.75% Mn; 0.1%–0.3% Fe; 0.05%–0.1% Ti; 0.03%–0.1% Nb; 0.15%–0.9% B; 0.01%–0.02% Sr; and the contents of other uncontrollable impurity elements are controlled to be ≤0.5%, with the balance being Al.

[0008] The ratio of Fe to Mn in the alloy is controlled at 1:2.5 to 4, the ratio of Nb to B is controlled at 1:5 to 9, and the ratio of Ti to Nb is controlled at 1:1 to 2.

[0009] The present invention relates to a specific method for smelting the given alloy, which is described in detail as follows:

[0010] Step 1, Ingredient preparation and smelting:

[0011] Si, Mn, Ti, and Al are weighed according to their respective mass percentages and placed in a melting furnace. The temperature is raised to 790℃~810℃ until the alloy is completely melted. The temperature is then lowered to 775℃~785℃, and Nb and B are added. After they are completely melted, the mixture is stirred for 30s~40s. Nb and Ti are added in the form of Al-Nb-B master alloy and Al-Ti master alloy, respectively.

[0012] After further reducing the furnace temperature to 730℃~735℃, Mg and Sr are added.

[0013] Step 2, Refining and Casting:

[0014] After degassing and refining for 30 to 35 minutes, remove the slag, let it stand for 15 to 20 minutes, and then cast it at a temperature of 680℃ to 720℃.

[0015] Furthermore, the elements selected in step 1 are added in the following forms: Al-Si master alloy, Al-Mn master alloy, Al-Ti master alloy, industrial pure aluminum with a purity of 99.9%, Al-Nb-B master alloy, pure magnesium with a purity of 99.9%, and Al-Sr master alloy.

[0016] Furthermore, the refining gas used in step 2 is argon, and the gas flow rate is 8L / min to 12L / min.

[0017] Compared with the prior art, the present invention has the following advantages and positive effects:

[0018] The alloy in this invention contains NbAl3 and NbB2 particles that are resistant to poisoning and can serve as effective nucleation substrates, refining the grain structure, reducing segregation, and promoting the fine, uniform, and dispersed distribution of the eutectic Si phase, Mg2Si phase, and Fe-rich phase.

[0019] Conventionally, the mass percentage of Mg in alloys is only 0.1% to 0.3% to meet the requirements of solidification and aging precipitation during heat treatment. Without considering heat treatment, this invention increases the mass percentage of Mg in the alloy to a maximum of 2%, which effectively promotes the refinement of the α-Al secondary dendrite arm spacing in the later stages of solidification, forming a dispersed Mg2Si phase, while simultaneously inhibiting the nucleation and growth of the eutectic Si phase and promoting its refinement.

[0020] The alloy of this invention has a yield strength of up to 194.82 MPa, a tensile strength of up to 285.79 MPa, and an elongation of up to 8.1% under the condition of extrusion casting without heat treatment.

[0021] The alloy of this invention is applicable to various processes such as extrusion casting, high-pressure casting, and semi-solid casting, which can significantly shorten production steps, reduce manufacturing costs, and improve production efficiency, meeting the development requirements of dual-carbon technology. Attached Figure Description

[0022] Figure 1 These are metallographic images of the alloy from Example 1 of the present invention (the alloy contains 8% Si by mass).

[0023] Figure 2 This is a metallographic image of the alloy in Example 2 of the present invention (the mass percentage of Si in the alloy is 10%). Detailed Implementation

[0024] The embodiments of the present invention are described in detail below: These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0025] Example 1:

[0026] The mass percentages of each component in this novel niobium-containing heat-free aluminum alloy are as follows: 8% Si; 0.2% Mg; 0.5% Mn; 0.05% Ti; 0.1% Nb; 0.9% B; 0.01% Sr; Fe is an impurity element with a content controlled between 0.1% and 0.3%; the content of other uncontrollable impurity elements is controlled at ≤0.5%, and the balance is Al.

[0027] In this embodiment, a heat-free aluminum alloy is prepared according to the following steps:

[0028] Material preparation: According to the alloy composition ratio, elements such as Si, Mn, Ti, Nb, B, Mg, Sr, and Al are added in the form of Al-Si master alloy, Al-Mn master alloy, Al-Ti master alloy, Al-Nb-B master alloy, 99.9% pure industrial magnesium, Al-Sr master alloy, and 99.9% pure industrial aluminum, respectively.

[0029] Melting: Al-Si master alloy, Al-Mn master alloy, Al-Ti master alloy, and 99.9% pure industrial aluminum are placed in a resistance melting furnace and heated to 790℃~810℃ until the alloy is completely melted; then the temperature is lowered to 775℃~785℃, and Al-Nb-B master alloy is added. After it is completely melted, it is stirred for 30s~40s; the temperature of the melting furnace is further reduced to 730℃~735℃, and 99.9% pure industrial magnesium and Al-Sr master alloy are added. In order to prevent oxidation and burn-off, the magnesium ingot is wrapped with aluminum foil and pressed into the aluminum melt with a graphite bell jar.

[0030] Refining: Argon gas is used for degassing and refining at a flow rate of 8L / min to 12L / min. After degassing for 30 to 35 minutes, the slag is removed and the mixture is allowed to stand for 15 to 20 minutes.

[0031] Pouring: The hydrogen content of the melt is measured using a hydrogen analyzer, and the pinholes are no greater than grade 1 as specified in GB / T7946.3 for pinholes of cast aluminum alloys. After passing the test, pouring is carried out, and the pouring temperature is controlled between 680℃ and 720℃.

[0032] Extrusion casting: The molten aluminum is transferred to an extrusion casting machine. The extrusion equipment is a SCH-550 horizontal indirect extrusion casting machine with an extrusion pressure of 150 MPa and an extrusion speed of 110 mm / s.

[0033] The aluminum alloys prepared in Example 1 were observed using a metallographic microscope. The microstructure of the alloys was as follows: Figure 1 and Figure 2 As shown, from Figure 1 and Figure 2 As can be seen, the grains are fine and uniform, the eutectic Si phase is evenly distributed, and there are no large-sized lamellar Fe-rich phases, indicating that the aluminum alloy microstructure in this invention is excellent.

[0034] Example 2:

[0035] The mass percentages of each component in this novel niobium-containing heat-free aluminum alloy are as follows: 10% Si; 0.2% Mg; 0.5% Mn; 0.05% Ti; 0.05% Nb; 0.4% B; 0.01% Sr; Fe is an impurity element with a content controlled between 0.1% and 0.3%; the content of other uncontrollable impurity elements is controlled at ≤0.5%, and the balance is Al.

[0036] In this embodiment, a heat-free aluminum alloy is prepared according to the following steps:

[0037] Material preparation: According to the alloy composition ratio, elements such as Si, Mn, Ti, Nb, B, Mg, Sr, and Al are added in the form of Al-Si master alloy, Al-Mn master alloy, Al-Ti master alloy, Al-Nb-B master alloy, 99.9% pure industrial magnesium, Al-Sr master alloy, and 99.9% pure industrial aluminum, respectively.

[0038] Melting: Al-Si master alloy, Al-Mn master alloy, Al-Ti master alloy, and 99.9% pure industrial aluminum are placed in a resistance melting furnace and heated to 790℃~810℃ until the alloy is completely melted; then the temperature is lowered to 775℃~785℃, and Al-Nb-B master alloy is added. After it is completely melted, it is stirred for 30s~40s; the temperature of the melting furnace is further reduced to 730℃~735℃, and 99.9% pure industrial magnesium and Al-Sr master alloy are added. In order to prevent oxidation and burn-off, the magnesium ingot is wrapped with aluminum foil and pressed into the aluminum melt with a graphite bell jar.

[0039] Refining: Argon gas is used for degassing and refining at a flow rate of 8L / min to 12L / min. After degassing for 30 to 35 minutes, the slag is removed and the mixture is allowed to stand for 15 to 20 minutes.

[0040] Pouring: The hydrogen content of the melt is measured using a hydrogen analyzer, and the pinholes are no greater than grade 1 as specified in GB / T7946.3 for pinholes in cast aluminum alloys. After passing the test, pouring is carried out, and the pouring temperature is controlled between 680℃ and 720℃.

[0041] Extrusion casting: The molten aluminum is transferred to an extrusion casting machine. The extrusion equipment is a SCH-550 horizontal indirect extrusion casting machine with an extrusion pressure of 150 MPa and an extrusion speed of 110 mm / s.

[0042] Comparative Example 1:

[0043] The comparative example involves the following components of a niobium-containing, heat-free aluminum alloy: 8% Si; 0.2% Mg; 0.5% Mn; 0.01% Sr; Fe is an impurity element with a content controlled between 0.1% and 0.3%; the content of other uncontrollable impurity elements is controlled at ≤0.5%; and the balance is Al.

[0044] In this comparative example, a heat-free aluminum alloy was prepared according to the following steps:

[0045] Material preparation: According to the alloy composition ratio, elements such as Si, Mn, Mg, Sr, and Al are added in the form of Al-Si master alloy, Al-Mn master alloy, 99.9% pure industrial magnesium, Al-Sr master alloy, and 99.9% pure industrial aluminum, respectively.

[0046] Melting: Al-Si master alloy, Al-Mn master alloy, and 99.9% pure industrial aluminum are placed in a resistance melting furnace and heated to 790℃~810℃ until the alloy is completely melted; after the melting furnace temperature is reduced to 730℃~735℃, 99.9% pure industrial magnesium and Al-Sr master alloy are added. To prevent oxidation and burn-off, the magnesium ingots are wrapped in aluminum foil and pressed into the molten aluminum using a graphite bell jar.

[0047] Refining: Argon gas is used for degassing and refining at a flow rate of 8L / min to 12L / min. After degassing for 30 to 35 minutes, the slag is removed and the mixture is allowed to stand for 15 to 20 minutes.

[0048] Pouring: The hydrogen content of the melt is measured using a hydrogen analyzer, and the pinholes are no greater than grade 1 as specified in GB / T7946.3 for pinholes of cast aluminum alloys. After passing the test, pouring is carried out, and the pouring temperature is controlled between 680℃ and 720℃.

[0049] Extrusion casting: The molten aluminum is transferred to an extrusion casting machine. The extrusion equipment is a SCH-550 horizontal indirect extrusion casting machine with an extrusion pressure of 150 MPa and an extrusion speed of 110 mm / s.

[0050] The aluminum alloy castings prepared in Examples 1-2 and Comparative Example 1 were tested for tensile strength, yield strength, and elongation after fracture. Two parallel experiments were conducted, and the results are shown in Table 1.

[0051] Table 1. Performance testing of aluminum alloys prepared in the examples and comparative examples.

[0052]

[0053] As can be seen from Table 1, the alloys provided by the present invention in Examples 1 and 2 are superior to Comparative Example 1 in terms of various properties in the extrusion casting process.

[0054] In Example 1, the yield strength increased by 42.92%, the tensile strength increased by 5.25%, and the elongation increased by 37.23% compared to Comparative Example 1. In Example 2, the yield strength increased by 11.7%, the tensile strength decreased by 4.2%, and the elongation decreased by 7.8% compared to Example 1. This is attributed to the increase in Si content, which led to an increase in brittle phases in the alloy.

[0055] In summary, the addition of Nb and Ti elements provides excellent resistance to poisoning, effectively refines the grains, reduces the spacing between secondary dendrite arms, and yields a fine, uniformly distributed eutectic Si phase. Furthermore, thanks to the appropriate Fe / Mn ratio, large-sized lamellar Fe-rich phases are not formed, resulting in an overall improvement in the alloy's mechanical properties.

Claims

1. A niobium-containing, heat-treatable-free aluminum alloy, characterized in that, By mass percentage, the contents of each element in the alloy include: 7%–10% Si; 0.2%–2% Mg; 0.4%–0.75% Mn; 0.1%–0.3% Fe; 0.05%–0.1% Ti; 0.03%–0.1% Nb; 0.15%–0.9% B; 0.01%–0.02% Sr; other uncontrollable impurity elements are controlled to be ≤ 0.5%, with the balance being Al; The ratio of Fe to Mn in the alloy is controlled at 1:2.5 to 4, the ratio of Nb to B is controlled at 1:5 to 9, and the ratio of Ti to Nb is controlled at 1:1 to 2. The preparation method of heat-free aluminum alloy includes the following steps: Step 1, Batching and Melting: Si, Mn, Ti, and Al are batched according to their mass percentages and placed into a melting furnace. The temperature is raised to 790℃~810℃ until the alloy is completely melted. The temperature is then lowered to 775℃~785℃, and Nb and B are added. After they are completely melted, the mixture is stirred for 30s~40s. Nb and Ti are added as Al-Nb-B master alloys and Al-Ti master alloys, respectively. The melting temperature is further lowered to 730℃~735℃ before adding Mg and Sr. Step 2, Refining and Casting: After degassing and refining for 30min~35min, the slag is removed. The mixture is allowed to stand for 15min~20min before casting at a casting temperature of 680℃~720℃.

2. The method for preparing a heat-free aluminum alloy according to claim 1, characterized in that, Includes the following steps: Step 1, Batching and Melting: Si, Mn, Ti, and Al are batched according to their mass percentages and placed into a melting furnace. The temperature is raised to 790℃~810℃ until the alloy is completely melted. The temperature is then lowered to 775℃~785℃, and Nb and B are added. After they are completely melted, the mixture is stirred for 30s~40s. Nb and Ti are added as Al-Nb-B master alloys and Al-Ti master alloys, respectively. The melting temperature is further lowered to 730℃~735℃ before adding Mg and Sr. Step 2, Refining and Casting: After degassing and refining for 30min~35min, the slag is removed. The mixture is allowed to stand for 15min~20min before casting at a casting temperature of 680℃~720℃.

3. The preparation method according to claim 2, characterized in that, The elements selected in step 1 are added in the following forms: Al-Si master alloy, Al-Mn master alloy, Al-Ti master alloy, industrial pure aluminum with a purity of 99.9%, Al-Nb-B master alloy, pure magnesium with a purity of 99.9%, and Al-Sr master alloy.

4. The preparation method according to claim 2, characterized in that, The refining gas used in step 2 is argon, with a gas flow rate of 8 L / min to 12 L / min.

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