Aluminum alloy for rotor casting and asynchronous motor cast-aluminum rotor

Abstract

The invention discloses an aluminum alloy for rotor casting and an asynchronous motor cast-aluminum rotor, and relates to the technical field of aluminum alloys. The silicon content is controlled within the low range of 0.04%-0.1%, the restriction of the high silicon content of a traditional cast aluminum alloy on the conductivity is broken through, meanwhile, 0.02%-0.08% of the silver element is introduced and forms an Al3MgAg nanometer strengthening phase with 0.02%-0.08% of magnesium, 0.004%-0.013% of the titanium element is combined, and through the interaction among the elements, the conductivity of the aluminum alloy is improved, and the conductivity of the aluminum alloy is improved. The motor rotor obtained by casting the aluminum alloy for rotor casting provided by the embodiment of the invention has relatively high conductivity and relatively high tensile strength.

Description

Technical Field

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

[0002] In related technologies, with the vigorous development of the new energy vehicle market, 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] When the rotor of the current squirrel cage motor is cast, the alloy used is difficult to achieve both electrical conductivity and tensile strength, resulting in poor mechanical and electrical properties of the squirrel cage motor rotor.

[0004] Therefore, how to make the motor rotor have both excellent electrical conductivity and mechanical properties is a problem that needs to be solved urgently. Summary of the Invention

[0005] The main purpose of this application is to provide an aluminum alloy for rotor casting and an aluminum cast rotor for an asynchronous motor, aiming to solve the technical problem of how to make the motor rotor have both excellent electrical conductivity and mechanical properties.

[0006] To achieve the above objectives, the present application proposes an aluminum alloy for rotor casting, which comprises 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 Less than or equal to 0.15% impurity elements.

[0007] In some embodiments, the aluminum alloy for rotor casting uses high-purity 99.9% aluminum as the formulation basis for the aluminum liquid raw material.

[0008] In some embodiments, the mass percentage of silicon in the aluminum alloy for rotor casting is 0.04-0.09%.

[0009] In some embodiments, the mass percentage of magnesium in the aluminum alloy for rotor casting is 0.02-0.06%.

[0010] In some embodiments, the mass percentage of silver in the aluminum alloy for rotor casting is 0.01-0.05%.

[0011] In some embodiments, the mass percentage of titanium in the aluminum alloy for rotor casting is 0.005-0.01%.

[0012] In some embodiments, the impurity element includes iron and / or copper.

[0013] In some embodiments, the mass percentage of the copper impurities is less than or equal to 0.03%.

[0014] In some embodiments, the mass percentage of the iron impurities is less than or equal to 0.1%.

[0015] In some embodiments, the mass percentage of the impurity elements other than the copper impurities and the iron impurities is less than or equal to 0.02%.

[0016] One or more technical solutions proposed in this application have at least the following technical effects: By controlling the silicon content in the low range of 0.04-0.1%, the restriction of high silicon content on conductivity of traditional cast aluminum alloys is broken through. At the same time, 0.02-0.08% of silver elements are introduced to form Al3MgAg nano-reinforced phase with 0.02-0.08% of magnesium, combined with 0.004-0.013% of titanium elements, through the interaction between the elements, the motor rotor cast by using the aluminum alloy for rotor casting provided by this embodiment can have both high conductivity and high tensile strength. 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] In recent years, the new energy vehicle market has developed vigorously. In order to improve the power performance and energy efficiency of new energy vehicles, more and more new energy vehicles adopt multi-motor systems. 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 requirements of high speed of motors, the market has put forward higher requirements on the materials of squirrel cage motor rotors.

[0024] Aluminum alloy is one of the common squirrel cage asynchronous motor materials. It has high electrical conductivity, good thermal conductivity and mechanical strength. It also has the advantages of light weight, strong casting processability and low price. It is widely used in new energy vehicle motor rotors. In order to meet market demand, an invention and preparation method of a high-strength motor rotor aluminum alloy formula is provided. The material formula has excellent electrical conductivity and mechanical properties, meeting the high speed and high performance requirements of the squirrel cage motor rotor.

[0025] Squirrel-cage asynchronous motors are gaining market share, and the market is placing higher demands on motor rotors. Currently, the vast majority of motor rotors used on the market are produced to the GB99.7 composition standard. However, due to differences in production processes between manufacturers, the impurity elements in 99.7% pure aluminum vary significantly, making it difficult to consistently guarantee the product's electrical conductivity. Furthermore, excessive impurities can cause significant fluctuations in the mechanical properties of cast rotors. To ensure the required electrical conductivity and mechanical properties of motor rotors, this application proposes an aluminum alloy for rotor casting, aiming to improve the composition of the aluminum alloy to significantly enhance the electrical conductivity and mechanical properties of the motor rotor.

[0026] The present application provides a solution that can break through the restriction of high silicon content on conductivity of traditional cast aluminum alloys by controlling the silicon content in a low range of 0.04~0.1%. At the same time, 0.02~0.08% of silver elements are introduced to form Al3MgAg nano-reinforced phase with 0.02~0.08% of magnesium, combined with 0.004~0.013% of titanium elements. Through the interaction between the elements, the motor rotor obtained by casting the aluminum alloy for rotor casting provided by this embodiment can have both high conductivity and high tensile strength.

[0027] The present application is described and introduced in detail below through a number of embodiments.

[0028] Example 1: 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 less than or equal to 0.15% impurity elements.

[0029] 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. The impurity 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%.

[0030] 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.

[0031] This embodiment controls the silicon content in the low range of 0.04-0.1%, breaking through the restriction of high silicon content on conductivity of traditional cast aluminum alloys. At the same time, 0.02-0.08% of silver elements are introduced to form Al3MgAg nano-reinforced phase with 0.02-0.08% of magnesium, thereby ensuring high conductivity and high tensile strength.

[0032] 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 alleviating the lattice distortion caused by the Si-Al solid solution, significantly improving conductivity compared to the commonly used cast aluminum alloys in related art.

[0033] 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.

[0034] 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) through the addition of 0.004~0.013% 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.

[0035] 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.

[0036] 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 0.004-0.013% 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.

[0037] 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.

[0038] 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.

[0039]

[0040] 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%.

[0041] 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 temperature of 180°C, its tensile strength is no less than 100 MPa, its elongation after fracture is no less than 18%, and its electrical conductivity is 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, it achieves higher tensile strength while maintaining electrical conductivity.

[0042] Example 2: The metal ratio of aluminum alloy for rotor casting includes: Silicon, the mass percentage of the silicon is 0.04-0.09%; magnesium, the mass percentage of the magnesium is 0.02-0.06%; silver, the mass percentage of the silver is 0.01-0.05%; titanium, the mass percentage of the titanium is 0.005-0.01%; aluminum, the mass percentage of the aluminum is 99.7%; impurity elements, the mass percentage of the impurity elements is less than or equal to 0.15%.

[0043] The mass percentage of copper impurities is strictly controlled below 0.03%, the mass percentage of iron impurities does not exceed 0.1%, and the total content of other impurity elements is ≤ 0.02%. Using 99.9% high-purity aluminum liquid as the matrix, under smelting conditions of 750°C, silicon, magnesium, titanium, and silver are added in this order for microalloying, and an argon rotary degassing process is used to reduce the hydrogen content.

[0044] Compared to Example 1, this example further limits the mass percentage range of silicon, magnesium, and silver. By controlling the silicon content within the optimized range of 0.04-0.09% and reducing the silver content to 0.01-0.05%, this example found that when the silver / magnesium mass ratio reaches 0.5-0.8, the precipitation density of the Al3MgAg strengthening phase can be further increased.

[0045] At the same time, the titanium content is optimized to 0.005-0.01%, and the grain size is further refined to below 40μm by forming a TiB2-TiAl3 composite nucleating agent. Testing has shown that this aluminum alloy achieves a tensile strength of 112MPa at 180°C, an electrical conductivity of 62% IACS, and an elongation above 17.5%, achieving synergistic optimization of strength and conductivity.

[0046] Example 3: 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.

[0047] For the description of the related mechanism, please refer to the relevant part in the aforementioned embodiment, which will not be repeated here.

[0048] Step S120: heating the aluminum ingot to a molten state.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] In this embodiment, silicon, magnesium, titanium, and silver may be added to the aluminum liquid in this order.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] As an example, the specified duration may be 5 minutes.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] After the elements are sufficiently mixed to obtain a mixture according to the above embodiment, the mixture is refined.

[0065] Specifically, during the refining process, argon gas may be used to perform rotational spraying on the mixture, wherein the flow rate of the argon gas is 10 L / min.

[0066] 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.

[0067] 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%.

[0068] In some embodiments, during the rotary spraying process, a composite refining agent may be added to the mixture to refine and purify the mixture.

[0069] 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.

[0070] 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.

[0071] In this embodiment, the refining and purification process using argon and a composite refining agent can last from 15 to 20 minutes. Specifically, 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.

[0072] After refining and purification, the aluminum alloy for rotor casting provided in this embodiment can be obtained.

[0073] 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.

[0074] 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.

[0075] 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. An aluminum alloy for rotor casting, characterized in that: The rotor casting aluminum alloy comprises 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 Less than or equal to 0.15% impurity elements.

2. The aluminum alloy for rotor casting according to claim 1, wherein The aluminum alloy for rotor casting uses high-purity 99.9% aluminum as the formulation basis for the aluminum liquid raw material.

3. The aluminum alloy for rotor casting according to claim 1, wherein In the aluminum alloy for rotor casting, the mass percentage of silicon is 0.04-0.09%.

4. The aluminum alloy for rotor casting according to claim 1, wherein In the aluminum alloy for rotor casting, the mass percentage of magnesium is 0.02-0.06%.

5. The aluminum alloy for rotor casting according to claim 1, wherein In the aluminum alloy for rotor casting, the mass percentage of silver is 0.01-0.05%.

6. The aluminum alloy for rotor casting according to claim 1, wherein In the aluminum alloy for rotor casting, the mass percentage of titanium is 0.005-0.01%.

7. The aluminum alloy for rotor casting according to claim 1, wherein The impurity elements include iron and / or copper.

8. The aluminum alloy for rotor casting according to claim 7, wherein: The mass percentage of the copper impurities is less than or equal to 0.03%.

9. The aluminum alloy for rotor casting according to claim 7, wherein: The mass percentage of the iron impurities is less than or equal to 0.1%.

10. A cast aluminum rotor for an asynchronous motor, characterized in that: The material of the cast aluminum rotor of the asynchronous motor is the aluminum alloy for rotor casting as described in any one of claims 1 to 9.

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