Preparation method of aluminum alloy for rotor casting and aluminum alloy for rotor casting

Abstract

The invention discloses a preparation method of an aluminum alloy for rotor casting and the aluminum alloy for rotor casting, and relates to the technical field of aluminum alloys. According to the technical scheme, by mass percent, 0.04%-0.09% of silicon, 0.02%-0.06% of magnesium, 0.01%-0.05% of silver, 0.005%-0.01% of titanium and 99.7% of aluminum ingots are adopted; an aluminum ingot is heated to be in a molten state, the silicon, the magnesium, the silver and the titanium are added into molten aluminum in the molten state, refining is performed after sufficient mixing, and therefore the aluminum alloy material with the electrical conductivity and the mechanical strength is obtained, and the excellent performance of a rotor can be guaranteed when the aluminum alloy material is used for manufacturing the rotor of the squirrel cage asynchronous motor.

Description

Technical Field

[0001] The present application relates to the technical field of aluminum alloys, and in particular to a method for preparing an aluminum alloy for rotor casting and an aluminum alloy for rotor casting. Background Art

[0002] In related technologies, in order to improve the power performance and energy efficiency of new energy vehicles, more and more new energy vehicles adopt multi-motor systems, and squirrel cage asynchronous motors are widely used in new energy vehicle systems as auxiliary drive motors, working in conjunction with permanent magnet synchronous motors. In order to improve the mechanical properties of squirrel cage motors and meet the high speed requirements of motors, the market has put forward higher requirements on the materials of squirrel cage motor rotors.

[0003] Aluminum alloy is a common material for squirrel-cage asynchronous motors and is widely used in rotors for new energy vehicles. However, the aluminum alloys used in related technologies struggle to balance electrical conductivity and mechanical strength, limiting the performance of the resulting rotors.

[0004] Therefore, how to make aluminum alloy have both electrical conductivity and mechanical strength is an urgent problem to be solved. Summary of the Invention

[0005] The main purpose of this application is to provide a method for preparing an aluminum alloy for rotor casting and an aluminum alloy for rotor casting, aiming to solve the technical problem of how to make the aluminum alloy have both electrical conductivity and mechanical strength.

[0006] To achieve the above objectives, the present application proposes a method for preparing an aluminum alloy for rotor casting, the method comprising: Obtaining an ingot containing 0.04-0.09% by mass of silicon, 0.02-0.06% by mass of magnesium, 0.01-0.05% by mass of silver, 0.005-0.01% by mass of titanium, and 99.7% by mass of aluminum; The aluminum ingot is heated to a molten state; The silicon, magnesium, silver and titanium are added to the molten aluminum liquid, fully mixed and then refined.

[0007] In some embodiments, the adding of the silicon, the magnesium, the silver, and the titanium into the molten aluminum liquid, fully mixing, and then refining comprises: The silicon, the magnesium, the titanium, and the silver are added to the molten aluminum in stages, wherein adjacent stages are separated by a specified time interval; After thorough mixing, the mixture is refined.

[0008] In some embodiments, the specified duration is 5 minutes.

[0009] In some embodiments, after the thorough mixing and before refining the mixture, the method for preparing the aluminum alloy for rotor casting further comprises: Electromagnetic stirring is continuously performed with a magnetic induction intensity of 0.5 Tesla to fully mix the aluminum liquid, the silicon, the magnesium, the titanium, and the silver to obtain the mixture.

[0010] In some embodiments, refining the mixture comprises: The mixture is rotationally sprayed with argon gas, and the flow rate of the argon gas is 10 L / min.

[0011] In some embodiments, during the rotary blowing process, a composite refining agent is simultaneously added to refine and purify the mixture.

[0012] In some embodiments, the refining and purification process lasts from 15 minutes to 20 minutes.

[0013] In some embodiments, heating the aluminum ingot to a molten state comprises: The aluminum ingot is heated to a molten state at a temperature between 740 and 760 degrees.

[0014] In some embodiments, after adding the silicon, magnesium, silver, and titanium to the molten aluminum, fully mixing, and then refining, the method for preparing the aluminum alloy for rotor casting further includes: The refined mixture is centrifugally cast at a rotation speed of 400-800 rpm; After the casting is completed, the asynchronous motor rotor is obtained by step-by-step cooling and solidification.

[0015] In addition, to achieve the above-mentioned purpose, the present application also proposes an aluminum alloy for rotor casting, which is prepared by the method for preparing the aluminum alloy for rotor casting as described above.

[0016] One or more technical solutions proposed in this application have at least the following technical effects: By obtaining 0.04-0.09% by mass of silicon, 0.02-0.06% by mass of magnesium, 0.01%-0.05% by mass of silver, 0.005%-0.01% by mass of titanium and 99.7% by mass of an aluminum ingot; heating the aluminum ingot to a molten state, adding the silicon, magnesium, silver and titanium to the molten aluminum liquid, fully mixing and then refining, an aluminum alloy material with both conductive properties and mechanical strength is obtained, and the aluminum alloy material used for manufacturing a squirrel cage asynchronous motor rotor can ensure the excellent performance of the rotor. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0018] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0019] Figure 1 A schematic flow chart of a method for preparing an aluminum alloy for rotor casting provided in one embodiment of the present application is shown.

[0020] The purpose, features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0021] It should be understood that the specific embodiments described herein are merely used to explain the technical solutions of the present application and are not intended to limit the present application.

[0022] In order to better understand the technical solution of the present application, a detailed description will be given below in conjunction with the accompanying drawings and specific implementation methods.

[0023] The main solution of the embodiment of the present application is: obtaining an aluminum ingot with a mass percentage of 0.04-0.09% silicon, a mass percentage of 0.02-0.06% magnesium, a mass percentage of 0.01%-0.05% silver, a mass percentage of 0.005%-0.01% titanium and a mass percentage of 99.7% aluminum; heating the aluminum ingot to a molten state; adding the silicon, the magnesium, the silver and the titanium to the molten aluminum liquid, and refining after thorough mixing.

[0024] In related technologies, in order to improve the power performance and energy efficiency of new energy vehicles, more and more new energy vehicles adopt multi-motor systems, and squirrel cage asynchronous motors are widely used in new energy vehicle systems as auxiliary drive motors, working in conjunction with permanent magnet synchronous motors. In order to improve the mechanical properties of squirrel cage motors and meet the high speed requirements of motors, the market has put forward higher requirements on the materials of squirrel cage motor rotors.

[0025] Aluminum alloy is a common material for squirrel-cage asynchronous motors and is widely used in rotors for new energy vehicles. However, the aluminum alloys used in related technologies struggle to balance electrical conductivity and mechanical strength, limiting the performance of the resulting rotors.

[0026] In summary, how to make aluminum alloy have both electrical conductivity and mechanical strength is a problem that needs to be solved urgently.

[0027] To solve this problem, the present application proposes a method for preparing an aluminum alloy for rotor casting and an aluminum alloy for rotor casting, aiming to make the aluminum alloy take into account both conductivity and mechanical strength. The motor rotor obtained by casting the aluminum alloy of this embodiment can meet the requirements of high conductivity and high mechanical strength.

[0028] For ease of understanding, an embodiment is provided herein to illustrate the mechanism of aluminum alloy for rotor casting.

[0029] The aluminum alloy for rotor casting includes the following components by mass percentage: 0.04~0.1% silicon; 0.02~0.08% magnesium; 0.02~0.08% silver; 0.004-0.013% titanium; Greater than or equal to 99.7% aluminum; and impurity elements less than or equal to 0.15%.

[0030] Among them, the aluminum alloy used for rotor casting uses high-purity 99.9% aluminum as the blending basis of the aluminum liquid raw material. Other elements include iron impurities and / or copper impurities. The mass percentage of copper impurities is less than or equal to 0.03%, and the mass percentage of iron impurities is less than or equal to 0.1%.

[0031] In this embodiment, in response to the technical demand for synergistic improvement of high conductivity and high strength of aluminum alloys used in motor rotor casting, a technical route of "ultra-high purity aluminum matrix + nano-level multi-element synergistic strengthening" was constructed.

[0032] This embodiment controls the silicon content in the low range of 0.04-0.09%, breaking through the restriction of high silicon content on conductivity of traditional cast aluminum alloys. At the same time, 0.01-0.05% of silver elements are introduced to form Al3MgAg nano-reinforced phase with 0.02-0.06% of magnesium, thereby ensuring high conductivity while guaranteeing high tensile strength.

[0033] Specifically, silicon atoms form a Si-Al solid solution in an aluminum matrix. The difference in atomic radius (Si: 0.118nm, Al: 0.143nm) causes lattice distortion, significantly increasing the probability of electron scattering and reducing conductivity. This embodiment reduces the silicon content, thereby reducing the lattice distortion caused by the Si-Al solid solution, significantly improving conductivity compared to the commonly used cast aluminum alloys in related art.

[0034] Silver (Ag) and magnesium (Mg) in a 1:1 molar ratio can form a metastable L12-type Al3MgAg phase. This phase has a face-centered cubic structure and forms a semi-coherent interface with the aluminum matrix, reducing the interfacial energy barrier. The Al3MgAg phase hinders dislocation motion and significantly improves tensile strength.

[0035] In addition, this embodiment uses 99.9% high-purity aluminum liquid as the matrix, and accurately controls the grain size (grain refinement to below 45μm) by adding 0.005~0.01% titanium element, supplemented by strict control of the mass proportion of other impurity elements, which can effectively suppress the formation of β-Al5FeSi needle-like phase.

[0036] Among them, needle-like phases (such as β-Al5FeSi phase) have a sharp geometric morphology and are prone to causing stress concentration when subjected to stress, leading to crack initiation and significantly reducing tensile strength. By inhibiting their nucleation, the risk of brittle fracture of the material can be reduced and the tensile strength of the material can be improved.

[0037] In this example, the 99.9% high-purity aluminum melt contains an extremely low Fe impurity content, fundamentally reducing the Fe ratio required to form the β-Al5FeSi phase. The formation of the β-Al5FeSi phase requires a specific Fe / Si atomic ratio (typically close to 5:1), and the high-purity aluminum matrix suppresses Fe enrichment, reducing the driving force for nucleation of this phase. Furthermore, when 0.005-0.01% titanium is added, titanium and aluminum form a metastable TiAl3 phase, which forms a semi-coherent interface with the α-Al matrix. According to peritectic reaction theory, TiAl3, as a nucleation substrate, promotes epitaxial growth of α-Al grains, thereby refining the grain size to below 45μm. It is understood that fine grains disperse the distribution of Fe / Si elements, reducing their local concentration, thereby suppressing the formation of the β-Al5FeSi phase.

[0038] In summary, the formula system provided in this embodiment can enable the motor rotor cast using the aluminum alloy for rotor casting provided in this embodiment to have both high electrical conductivity and high tensile strength through the interaction of elements.

[0039] As a verification, the aluminum alloy for casting the motor rotor provided in this embodiment is numbered 1, and the aluminum alloy for casting the motor rotor of comparative example 1 is numbered 2.

[0040]

[0041] In the alloy formula of Comparative Example 1, the mass percentage of aluminum is 99.5%, the mass percentage of silicon is 0.25%, and among other components, the mass percentage of iron is 0.3%, and the mass percentage of copper is 0.015%.

[0042] As can be seen, the rotor cast from the aluminum alloy provided in this example exhibits excellent mechanical strength and electrical conductivity. At the same test temperature of 180°C, the rotor exhibits a tensile strength of no less than 100 MPa, an elongation after fracture of no less than 18%, and an electrical conductivity of no less than 58 IACS, achieving both excellent mechanical and electrical properties. Compared to Comparative Example 1, by adjusting the proportions of the alloy components and adding magnesium, silver, and titanium, the rotor achieves higher tensile strength while maintaining electrical conductivity.

[0043] Reference Figure 1 , Figure 1 The flowchart of the method for preparing an aluminum alloy for rotor casting provided by one embodiment of the present application is shown. The method for preparing an aluminum alloy for rotor casting can be applied to a device for preparing an aluminum alloy for rotor casting, and includes the following steps S110 to S130: Step S110 , obtaining an aluminum ingot containing 0.04-0.09% by mass of silicon, 0.02-0.06% by mass of magnesium, 0.01-0.05% by mass of silver, 0.005-0.01% by mass of titanium, and 99.7% by mass of aluminum.

[0044] For the description of the related mechanism, please refer to the relevant part in the aforementioned embodiment, which will not be repeated here.

[0045] Step S120: heating the aluminum ingot to a molten state.

[0046] In this embodiment, a 99.9% pure aluminum ingot can be placed in a medium-frequency induction heating furnace crucible for heating and melting. Specifically, a crucible specifically designed for graphite clay sintering can be used. As will be appreciated, graphite has a melting point of up to 3650°C, and the clay forms a dense ceramic phase after sintering, making the crucible less susceptible to cracking when melting the metal in this embodiment. Furthermore, graphite itself does not react with the metal elements involved in this embodiment, improving safety and preventing the introduction of impurities.

[0047] During the heating process, the heating temperature can be maintained between 740 and 760 degrees to fully melt the aluminum ingot and obtain aluminum liquid.

[0048] In step S130 , the silicon, magnesium, silver, and titanium are added to the molten aluminum liquid, and the mixture is fully mixed and then refined.

[0049] In this embodiment, silicon, magnesium, titanium, and silver may be added to the aluminum liquid in this order.

[0050] Specifically, silicon has a high melting point (approximately 1414°C) and requires a relatively high temperature to fully dissolve in the aluminum liquid. Therefore, in this embodiment, the crucible temperature can be raised above the melting point of silicon. As a fundamental alloying element, silicon improves the alloy's fluidity and casting properties, and provides a stable aluminum-based solid solution for the addition of subsequent elements. Adding silicon and melting it first ensures uniform distribution of silicon in the molten liquid, preventing quality fluctuations in subsequent finished products due to uneven distribution.

[0051] Secondly, magnesium has a low melting point (approximately 650°C) but is susceptible to oxidation at high temperatures, so the crucible temperature can be adjusted adaptively. Adding it after silicon shortens the magnesium's exposure time and reduces oxidation losses. Furthermore, magnesium's strengthening effect must be exerted within the silicon matrix. As previously mentioned, it can improve the alloy's strength and corrosion resistance.

[0052] Secondly, titanium has an extremely high melting point (approximately 1668°C), but as a grain refiner, it must refine the grains by forming compounds such as TiAl3. Adding it after magnesium avoids competitive reactions between titanium and magnesium, ensuring that titanium preferentially combines with aluminum to form a uniform nucleus, optimizing the microstructure and improving mechanical properties.

[0053] Finally, the amount of silver added is extremely small and needs to be avoided from premature reaction with elements such as titanium and magnesium. Adding it last can reduce the oxidation or volatilization of silver.

[0054] In this embodiment, to ensure that each element is fully melted and stably mixed with the aluminum liquid, silicon, magnesium, titanium, and silver can be added in stages, wherein each stage is separated by a specified time.

[0055] As an example, the specified duration may be 5 minutes.

[0056] As mentioned above, different alloying elements have significant differences in melting point, oxidation tendency, and compatibility with molten aluminum. If added simultaneously, they may trigger competitive reactions (e.g., Mg and Ti competing for aluminum-based binding sites), leading to compositional segregation or the formation of harmful interphases (e.g., brittle compounds), which can disrupt material homogeneity.

[0057] Secondly, elements such as silicon (Si) and magnesium (Mg) must be fully dissolved in the aluminum liquid through electromagnetic stirring. This phased addition allows for targeted treatment based on the physical properties of each element (e.g., higher-melting-point elements require longer dissolution times), thus avoiding compositional fluctuations due to incomplete dissolution.

[0058] Additionally, magnesium (Mg) and silver (Ag) are susceptible to oxidation or volatilization at high temperatures. Adding them in stages shortens their exposure time (especially Mg), and combined with an argon atmosphere for protection, minimizes the loss of active elements.

[0059] Based on these considerations, the inventors discovered that in molten aluminum at around 750°C, elements like Si and Mg can complete initial dissolution and form a homogeneous solid solution within 5 minutes. This 5-minute window ensures sufficient diffusion of the elements while avoiding prolonged melting times that could increase energy consumption or exacerbate aluminum oxidation.

[0060] In some embodiments, during the addition of each element to the molten aluminum, electromagnetic stirring may be continuously performed at a magnetic induction intensity of 0.5 Tesla (T) to thoroughly mix the molten aluminum, silicon, magnesium, titanium, and silver to form a mixture. It is understood that a 0.5 T magnetic field can enhance convection in the molten aluminum, shorten the homogenization time of the elements, and improve mixing efficiency.

[0061] After the elements are sufficiently mixed to obtain a mixture according to the above embodiment, the mixture is refined.

[0062] Specifically, during the refining process of the mixture, argon gas may be used to perform rotational spraying on the mixture, wherein the flow rate of the argon gas is 10 L / min.

[0063] Argon is an inert gas that does not chemically react with metal elements and effectively prevents oxidation and nitridation. During the metal refining process, argon isolates oxygen and moisture from the air, preventing contamination of the melt (i.e., the mixture), thereby improving the purity and performance of the material. In this embodiment, the use of argon injection during the aluminum alloy smelting process can significantly reduce hydrogen content and oxide inclusions.

[0064] In aluminum alloy refining, the argon flow rate is often controlled at a low level (such as 10L / min) through a porous ceramic nozzle to generate micron-sized bubbles, which can increase the hydrogen removal rate to more than 50%.

[0065] In some embodiments, during the rotary spraying process, a composite refining agent may be added to the mixture to refine and purify the mixture.

[0066] Understandably, the purpose of composite refining agents is to further remove hydrogen and oxide inclusions from the mixture. There are many types of composite refining agents, which can generally effectively remove oxide inclusions (such as Al2O3), gases (such as hydrogen), and other impurities from the mixture through physical adsorption, chemical reaction, and slag separation, thereby improving the purity and material properties of the alloy.

[0067] As an example, a composite refining agent can use sodium chloride, potassium chloride, or the like as a base carrier to lower the melting point of the slag and promote the floating of inclusions. Alternatively, sodium fluoroaluminate can be used as a capping agent to reduce aluminum oxidation and adsorb inclusions. The choice of composite refining agent can be determined based on actual needs and is not limited in this embodiment.

[0068] In this embodiment, the refining and purification process using argon and a composite refining agent can last from 15 to 20 minutes. Experimental data shows that over 90% of hydrogen and inclusions can be removed within the first 15 minutes, while the dehydrogenation rate significantly decreases after 15 minutes. Therefore, a refining and purification time of 15 to 20 minutes is ideal.

[0069] After refining and purification, the aluminum alloy for rotor casting provided in this embodiment can be obtained.

[0070] The aluminum alloy for rotor casting provided in this embodiment can then be centrifugally cast. Specifically, the refined mixture can be centrifugally cast at a speed of 400-800 rpm. After casting, the mixture undergoes step-wise cooling and solidification to produce the asynchronous motor rotor. In this embodiment, step-wise cooling and solidification can reduce grain boundary brittleness and improve strength. It also helps promote uniform diffusion of solute elements (such as Si and Mg), reduce dendritic segregation, and avoid localized conductivity loss.

[0071] This embodiment provides a method for preparing an aluminum alloy for rotor casting, comprising obtaining an aluminum ingot containing 0.04% to 0.09% silicon by mass, 0.02% to 0.06% magnesium by mass, 0.01% to 0.05% silver by mass, 0.005% to 0.01% titanium by mass, and 99.7% aluminum; heating the aluminum ingot to a molten state, adding the silicon, magnesium, silver, and titanium to the molten aluminum liquid, thoroughly mixing, and then refining, thereby obtaining an aluminum alloy material having both electrical conductivity and mechanical strength. The aluminum alloy material can be used to manufacture a rotor for a squirrel-cage asynchronous motor, thereby ensuring excellent rotor performance.

[0072] The above description is only part of the embodiments of the present application and does not limit the patent scope of the present application. All equivalent structural transformations made by using the contents of the present application specification and drawings under the technical concept of the present application, or direct / indirect application in other related technical fields are included in the patent protection scope of the present application.

Claims

1. A method for preparing an aluminum alloy for rotor casting, characterized in that: The preparation method of the aluminum alloy for rotor casting comprises: Obtaining an ingot containing 0.04-0.09% by mass of silicon, 0.02-0.06% by mass of magnesium, 0.01-0.05% by mass of silver, 0.005-0.01% by mass of titanium, and 99.7% by mass of aluminum; The aluminum ingot is heated to a molten state; The silicon, magnesium, silver and titanium are added to the molten aluminum liquid, fully mixed and then refined.

2. The method for preparing an aluminum alloy for rotor casting according to claim 1, wherein: The step of adding the silicon, magnesium, silver, and titanium to the molten aluminum liquid, fully mixing, and then refining the mixture comprises: The silicon, the magnesium, the titanium, and the silver are added to the molten aluminum in stages, wherein adjacent stages are separated by a specified time interval; After thorough mixing, the mixture is refined.

3. The method for preparing an aluminum alloy for rotor casting according to claim 2, wherein: The specified duration is 5 minutes.

4. The method for preparing an aluminum alloy for rotor casting according to claim 2, wherein: After the thorough mixing and before refining the mixture, the method for preparing the aluminum alloy for rotor casting further comprises: Electromagnetic stirring is continuously performed with a magnetic induction intensity of 0.5 Tesla to fully mix the aluminum liquid, the silicon, the magnesium, the titanium, and the silver to obtain the mixture.

5. The method for preparing an aluminum alloy for rotor casting according to claim 2, wherein: The process of refining the mixture includes: The mixture is rotationally sprayed with argon gas, and the flow rate of the argon gas is 10 L / min.

6. The method for preparing an aluminum alloy for rotor casting according to claim 5, wherein: During the rotary spraying process, a composite refining agent is added simultaneously to refine and purify the mixture.

7. The method for preparing an aluminum alloy for rotor casting according to claim 6, wherein: The refining and purification takes 15 to 20 minutes.

8. The method for preparing an aluminum alloy for rotor casting according to claim 1, wherein: The step of heating the aluminum ingot to a molten state comprises: The aluminum ingot is heated to a molten state at a temperature between 740 and 760 degrees.

9. The method for preparing an aluminum alloy for rotor casting according to claim 1, wherein: The method for preparing the aluminum alloy for rotor casting further comprises: adding the silicon, the magnesium, the silver, and the titanium to the molten aluminum liquid, fully mixing, and then refining. The refined mixture is centrifugally cast at a rotation speed of 400-800 rpm; After the casting is completed, the asynchronous motor rotor is obtained by step-by-step cooling and solidification.

10. An aluminum alloy for rotor casting, characterized in that: The rotor casting aluminum alloy is prepared by the method for preparing the rotor casting aluminum alloy according to any one of claims 1 to 8.

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