Aluminum alloy, preparation method thereof and motor rotor

Abstract

The invention provides an aluminum alloy, a preparation method of the aluminum alloy and a motor rotor, the aluminum alloy comprises the following components in percentage by mass: 0.38-0.60% of Si, not more than 0.15% of Fe, not more than 0.05% of Cu, not more than 0.05% of Zn, 0.005-0.01% of Ti, not more than 0.03% of Ga, 0.01-0.1% of Sm, 0.005-0.05% of Er, 0.5-0.8% of Mg and the balance of Al and other elements, the total amount of the other elements is less than 0.1%, and the single content of the other elements is less than 0.01%. According to the aluminum alloy provided by the invention, the high-temperature yield strength of the aluminum alloy can be improved on the premise of keeping good conductivity through reasonable proportioning of all the element components, and when the aluminum alloy is used for preparing the motor rotor of the electric vehicle, the obtained motor rotor can run for a long time under the conditions of high rotating speed and high acceleration and is not prone to deformation or failure.

Description

Technical Field

[0001] The present invention relates to the field of aluminum alloy materials, and in particular to an aluminum alloy and a preparation method thereof, and a motor rotor. Background Art

[0002] Among metals, aluminum's electrical and thermal conductivity are second only to silver, copper, and gold. Compared with silver, copper, and gold, aluminum is not only abundant in resources and low in cost, but it is also the metal with the strongest thermal and electrical conductivity per unit weight, and its lightweight advantage is very obvious.

[0003] The speed of ordinary motors is generally below 3000rpm, and the aluminum rotor materials they use are all pure aluminum of Al99.70. The speed of the drive motor of electric vehicles has already exceeded 10000rpm and is developing towards 30000rpm or even higher, which is close to 10-40 times the speed of ordinary motors. Although pure aluminum has strong conductivity, it has low strength and can no longer meet the requirements of high-speed motors for mechanical properties. At the same time, the higher the rotor speed, the longer the rotor works at high temperature. Therefore, high-speed motors also have higher requirements for the high-temperature performance of materials. Summary of the invention

[0004] The present invention provides an aluminum alloy, which can improve the high-temperature yield strength of the aluminum alloy while maintaining good electrical conductivity by reasonably proportioning various components.

[0005] The present invention also provides a method for preparing the aluminum alloy. The method can prepare the aluminum alloy and has a simple process.

[0006] The present invention also provides a motor rotor. Since the motor rotor is prepared by using the above-mentioned aluminum alloy, the motor rotor can operate under high speed and high acceleration conditions without being easily deformed or failed.

[0007] In a first aspect, the present invention provides an aluminum alloy, which comprises, by mass percentage, 0.38-0.60% Si, not more than 0.15% Fe, not more than 0.05% Cu, not more than 0.05% Zn, 0.005-0.01% Ti, not more than 0.03% Ga, 0.01-0.1% Sm, 0.005-0.05% Er, 0.5-0.8% Mg, and the remainder Al and other elements, the total amount of the other elements being less than 0.1%, and the individual content of the other elements being less than 0.01%.

[0008] Furthermore, its composition includes: 0.42-0.46% Si, 0.68-0.75% Fe, 0.004-0.006% Cu, 0.015-0.020% Zn, 0.005-0.007% Ti, 0.012-0.015% Ga, 0.04-0.1% Sm, and 0.02-0.05% Er.

[0009] Further, 0.42-0.45% Si, 0.69-0.72% Fe, 0.004-0.006% Cu, 0.017-0.018% Zn, 0.005-0.007% Ti, 0.013-0.014% Ga, 0.04-0.1% Sm, and 0.02-0.05% Er.

[0010] Furthermore, the other elements include V and / or Cr, and the total amount of V and Cr accounts for a mass ratio of m to the aluminum alloy, where m≤0.008%.

[0011] Further, 0.0035≤m≤0.0037.

[0012] In a second aspect, the present invention provides a method for preparing an aluminum alloy, comprising the following steps:

[0013] 1) Mix the raw materials other than Ti, Sm and Er, and heat to 760-780°C to obtain the first aluminum liquid;

[0014] 2) Adding aluminum-boron alloy to the first aluminum liquid, and keeping the aluminum liquid at a temperature of M°C for 30-60 minutes, separating the solid and the liquid, to obtain a second aluminum liquid; wherein the liquidus temperature of the first aluminum liquid is N°C, N°C+10°C≤M°C≤N°C+20°C;

[0015] 3) adding aluminum-titanium master alloy, aluminum-erbium master alloy and aluminum-samarium master alloy to the second aluminum liquid at 710-750° C. and mixing to obtain a third aluminum liquid;

[0016] 4) The third aluminum liquid is cast after refining, deslagging and refining, and degassing to obtain the aluminum alloy.

[0017] Furthermore, the refining and slag removal specifically includes the following processes:

[0018] At 710-750° C., solid flux is sprayed into the third aluminum liquid. After standing or stirring, solid on the surface of the third aluminum liquid is scraped off.

[0019] Furthermore, the refining and degassing comprises the steps of introducing argon into the third aluminum liquid at 700-740° C. and leaving the third aluminum liquid to stand.

[0020] Furthermore, the casting specifically includes the following process:

[0021] After the third aluminum liquid is cast into the launder, argon is used to remove hydrogen, and the third aluminum liquid after dehydrogenation is filtered to remove impurities larger than 20 microns.

[0022] In a third aspect, the present invention provides an electrode rotor, which is prepared from the aluminum alloy of the first aspect or the aluminum alloy prepared by the preparation method of the second aspect.

[0023] The aluminum alloy provided by the present invention can improve its high-temperature yield strength while maintaining good electrical conductivity by reasonably proportioning various element components. The motor rotor of an electric vehicle prepared by the aluminum alloy can run for a long time under high speed and high acceleration conditions without being easily deformed or failed. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0025] Figure 1 The present invention is a process flow chart for preparing aluminum alloy according to a specific embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below. The specific implementation methods listed below are only for describing the principles and features of the present invention. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0027] In a first aspect, the present invention provides an aluminum alloy, which comprises, by mass percentage, 0.38-0.60% Si, not more than 0.15% Fe, not more than 0.05% Cu, not more than 0.05% Zn, 0.005-0.01% Ti, not more than 0.03% Ga, 0.01-0.1% Sm, 0.005-0.05% Er, 0.5-0.8% Mg, and the remainder Al and other elements, the total amount of the other elements being less than 0.1%, and the individual content of the other elements being less than 0.01%.

[0028] According to the aluminum alloy provided by the present invention, by controlling the ratio of each element in the aluminum alloy, the aluminum alloy has a higher yield strength and electrical conductivity, and its yield strength is still at a high level when the temperature rises to 180°C. Specifically, at room temperature, the yield strength of the aluminum alloy provided by the present invention is not less than 95Mpa, and at 180°C, its yield strength is not less than 90Mpa.

[0029] It should be noted that the above-mentioned other elements refer to elements other than Si, Fe, Cu, Ti, Zn, Ga, Sm, Er, Mg, and Al.

[0030] In detail, the aluminum alloy of the present invention adopts Ti+Er and other combined grain refinement, and the grain refinement can strengthen and stabilize the yield strength of the aluminum alloy; the reason is that according to the Hall-Petch formula σ=σ0+k / d (1 / 2) The yield strength is inversely proportional to the square root of the grain diameter, that is, the finer the grain, the higher the yield strength. However, using Ti as a grain refining element will seriously reduce the electrical conductivity of the aluminum alloy. In order to ensure the electrical conductivity of the aluminum alloy, only a small amount can be added, and the grain refining effect is weak. The obtained aluminum alloy not only has a low yield strength, but also has poor stability of the yield strength. For this reason, the present invention utilizes Ti, Er, Sm and other elements to cooperate with each other to form a metal compound, which can not only ensure the electrical conductivity of the aluminum alloy, but also effectively hinder the yield drop caused by grain deformation at high temperature; on the other hand, since the aluminum alloy of the present invention includes the rare earth element Sm, it can reduce the dissolved hydrogen in the aluminum alloy, thereby reducing the probability and size of pinholes in the casting, which is beneficial to improve the density of the casting, thereby improving the electrical conductivity and yield strength of the aluminum alloy.

[0031] In order to further ensure the high temperature yield strength of the aluminum alloy, in a specific embodiment, its composition includes: 0.42-0.46% Si, 0.68-0.75% Fe, 0.004-0.006% Cu, 0.015-0.020% Zn, 0.005-0.007% Ti, 0.012-0.015% Ga, 0.04-0.1% Sm, and 0.02-0.05% Er.

[0032] In another specific embodiment, 0.42-0.45% Si, 0.69-0.72% Fe, 0.004-0.006% Cu, 0.017-0.018% Zn, 0.005-0.007% Ti, 0.013-0.014% Ga, 0.04-0.1% Sm, 0.02-0.05% Er.

[0033] In a specific embodiment, the other elements include V and / or Cr, and the total amount of V and Cr accounts for m, m≤0.008% of the mass ratio of the aluminum alloy. Among them, V and / or Cr exist in the form of solid solution, which will increase the degree of lattice distortion of the aluminum alloy, hinder the movement of electrons, and thus reduce the electrical conductivity of the aluminum alloy. Therefore, the total amount of V and Cr should not be too high, especially within the scope of the above embodiment, it can be ensured that the electrical conductivity of the aluminum alloy is not affected by V and Cr.

[0034] In a specific embodiment, 0.0035≤m≤0.0037.

[0035] In a second aspect, the present invention provides a method for preparing the above aluminum alloy, Figure 1 , including the following steps:

[0036] 1) Mix the raw materials other than Ti, Sm and Er, and heat to 760-780°C to obtain the first aluminum liquid;

[0037] 2) Adding aluminum-boron alloy to the first aluminum liquid, and keeping the aluminum liquid at a temperature of M°C for 30-60 minutes, separating the solid and the liquid, to obtain a second aluminum liquid; wherein the liquidus temperature of the first aluminum liquid is N°C, N°C+10°C≤M°C≤N°C+20°C;

[0038] 3) adding aluminum-titanium master alloy, aluminum-erbium master alloy and aluminum-samarium master alloy to the second aluminum liquid at 710-750° C. and mixing to obtain a third aluminum liquid;

[0039] 4) The third aluminum liquid is cast after refining, deslagging and refining, and degassing to obtain the aluminum alloy.

[0040] The above-mentioned preparation method can obtain the aluminum alloy described in the first aspect by adding materials in batches and coordinating the processing temperature, slag removal and hydrogen removal and other treatments in each step. In detail, the above-mentioned preparation method first melts part of the raw materials at a certain temperature, and then uses aluminum-boron alloy to react with impurity elements such as V in the aluminum liquid that are not conducive to thermal conductivity to generate precipitates and remove them, thereby achieving the effect of reducing the content of impurity elements; secondly, the remaining raw materials are added at a certain temperature, and slag removal and hydrogen removal treatment are performed to reduce the inclusions and hydrogen content in the third aluminum liquid to an extremely low level, thereby reducing the adverse effects of inclusions on the mechanical properties and electrical conductivity of the aluminum alloy.

[0041] It can be understood that the addition amount of the above-mentioned aluminum-boron alloy can be calculated based on the molecular weight of TiB2, VB2, CrB2, and ZrB2. If too much is added, the remaining B content needs to be lower than 0.01% to avoid affecting the conductivity of the aluminum alloy.

[0042] In a specific embodiment, the refining and slag removal specifically includes the following process:

[0043] At 710-750° C., solid flux is sprayed into the third aluminum liquid. After standing or stirring, solid on the surface of the third aluminum liquid is scraped off.

[0044] Among them, solid flux is sprayed into the third aluminum liquid. After the solid flux is liquefied, it will absorb metal oxides (alumina, silicon dioxide, magnesium oxide, etc.) in the aluminum liquid during the process of floating to the surface of the aluminum liquid, so as to be finally removed; illustratively, the above-mentioned solid flux can be commonly used solid fluxes such as sodium chloride and potassium chloride. In some embodiments, the solid solvent is composed of sodium chloride, potassium chloride, sodium fluoroaluminate (Na3AlF6) and other salts; wherein the total mass of sodium chloride and potassium chloride accounts for 50%-95% of the total weight of the solid solvent.

[0045] In a specific embodiment, the refining and degassing comprises: introducing argon gas into the third aluminum liquid at 700-740° C. and allowing the third aluminum liquid to stand.

[0046] Among them, argon gas is introduced into the third aluminum liquid to form bubbles, and hydrogen in the aluminum liquid will enter the argon bubbles under the action of penetration. During the static process, it will float to the surface of the aluminum liquid and then enter the air.

[0047] In a specific embodiment, the casting specifically includes the following process:

[0048] After the third aluminum liquid is cast into the launder, argon is used to remove hydrogen, and the third aluminum liquid after dehydrogenation is filtered to remove impurities larger than 20 microns.

[0049] The above-mentioned argon gas dehydrogenation can use a rotary degassing method, a breathable brick degassing method or a combination of the two.

[0050] In the above embodiment, filtering can be achieved by passing the third aluminum liquid through two-stage ceramic filter plates with mesh sizes of 30 and 40, respectively. Among them, the use of multi-stage ceramic filter plates can further filter large-sized solid impurities such as aluminum oxide and magnesium oxide in the aluminum liquid, thereby further improving the conductivity of the aluminum alloy.

[0051] In a third aspect, the present invention provides a motor rotor, which is prepared from the aluminum alloy of the first aspect or the aluminum alloy prepared by the preparation method of the second aspect.

[0052] It can be understood that the motor rotor of the present invention can be used in various devices that need to convert electrical energy into mechanical energy or convert mechanical energy into electrical energy, including but not limited to: electric vehicles, hybrid vehicles, cranes, excavators, concrete mixers, subways, MRI scanners, CT scanners, surgical robots, etc.

[0053] In some embodiments, the aluminum alloy ingot is remelted, refined, and degassed: the aluminum ingot is added to the casting machine side furnace, and after it is completely melted into liquid, slag is removed and degassed; and a centrifugal casting process is used to cast the motor rotor. The centrifugal process includes the following process:

[0054] Mould preparation: Select a suitable mould and fix it in the centrifugal casting machine.

[0055] Injecting liquid metal: Start the equipment and fill the mold under the action of centrifugal force.

[0056] Cooling and solidification: The liquid metal cools and solidifies in the mold to form a preliminary casting.

[0057] Post-processing: cleaning, inspection and necessary post-processing of castings.

[0058] In order to further understand the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0059] Unless otherwise specified, the reagents involved in the embodiments of the present invention are all commercially available products and can be purchased through commercial channels.

[0060] The specifications or sources of some raw materials involved in the following experiments are shown in Table 1.

[0061] Table 1:

[0062]

[0063] Example 1

[0064] This example provides an aluminum alloy, whose composition includes: 0.422% Si, 0.071% Fe, 0.005% Cu, 0.018% Zn, 0.005% Ti, 0.014% Ga, 0.04% Sm, 0.02% Er, 0.061% Mg, V+Cr=0.0037, and the balance Al.

[0065] The preparation method thereof comprises the following steps:

[0066] 1) Mix electrolytic aluminum, magnesium ingot and industrial silicon, preheat and melt them into liquid state, and then heat them to 760-780°C to obtain the first aluminum liquid;

[0067] 2) Adding aluminum-boron master alloy to the first aluminum liquid to make the impurity elements Ti, V, etc. generate metal compounds with high specific gravity such as TiB2 and VB2, and making the aluminum liquid temperature 10-20°C higher than the liquidus temperature of the first aluminum liquid, standing for 30-60 minutes, and separating the solid and liquid to obtain the second aluminum liquid;

[0068] 3) adding aluminum-titanium master alloy, aluminum-erbium master alloy and aluminum-samarium master alloy to the second aluminum liquid at 750° C. and mixing them to obtain a third aluminum liquid;

[0069] 4) At 750°C, solid flux is added to the third aluminum melt in an amount of 1-2% of the weight of the aluminum melt. The solid flux is liquefied and then floats to the surface of the melt, where it absorbs metal oxides (aluminum oxide, silicon dioxide, magnesium oxide, etc.) in the aluminum melt and is finally removed. Argon gas (argon gas flow rate is 15-25L / min) is then introduced into the aluminum melt to form bubbles. The hydrogen in the aluminum melt will form argon bubbles under the action of penetration, float to the surface of the melt, and enter the air.

[0070] 5) At 740℃, after the third aluminum liquid is cast in the launder, a secondary argon gas (argon flow rate is 15-25L / min) is used for dehydrogenation by rotary degassing. After that, the third aluminum liquid will pass through a 2-stage porcelain filter plate with 30 and 40 meshes respectively to completely filter out impurities larger than 20 microns in the aluminum liquid. The aluminum ingot is cast: the aluminum melt enters the aluminum ingot mold and solidifies into an aluminum ingot.

[0071] Example 2-3

[0072] It is basically the same as Example 1, the only difference is the content of the constituent elements of the aluminum alloy, see Table 2 for details.

[0073] Comparative Examples 1-3

[0074] It is basically the same as Example 1, the only difference is the constituent elements or the content of the aluminum alloy, see Table 2 for details.

[0075] Application Examples

[0076] The aluminum alloys of the above-mentioned embodiments and comparative examples are added into the side furnace of the casting machine, and after being completely melted into liquid, slag removal and degassing are carried out; a centrifugal casting process is adopted to cast the motor rotor; the centrifugal process includes the following processes: mold preparation: selecting the mold and fixing it in the centrifugal casting machine; injecting metal liquid: starting the equipment, and filling the mold under the action of centrifugal force; cooling and solidification: the liquid metal is cooled and solidified in the mold to form a preliminary casting; post-processing: cleaning, testing and post-processing the casting.

[0077] Test Case

[0078] The following performance tests were performed on the aluminum alloys of the embodiments and comparative examples:

[0079] 1: Electrical conductivity, tested using the eddy current method, refer to the national standard GB / T 12966-2022 "Eddy current test method for electrical conductivity of aluminum and aluminum alloys";

[0080] 2: Yield strength at room temperature, tested by tensile test, refer to the national standard GB / T 228.1-2021 "Tensile test of metallic materials Part 1 Room temperature test method";

[0081] 3: Yield strength at 180°C, tested by tensile test, refer to the national standard GB / T 228.2-2015 "Tensile test of metallic materials Part 2: High temperature test method".

[0082] Table 2:

[0083]

[0084] It can be seen from Table 2 that, compared with the comparative example, the aluminum alloy of the embodiment of the present invention has good electrical conductivity and high-temperature yield strength. Therefore, the motor rotor made of the aluminum alloy can operate for a long time under high speed and high acceleration conditions without deformation or failure.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An aluminum alloy, It is characterized in that Measured by mass percentage, its composition includes: 0.38-0.60% Si, not more than 0.15% Fe, not more than 0.05% Cu, not more than 0.05% Zn, 0.005-0.01% Ti, not more than 0.03% Ga, 0.01-0.1% Sm, 0.005-0.05% Er, 0.5-0.8% Mg, and the balance Al and other elements, the total amount of the other elements is less than 0.1%, and the individual content of the other elements is less than 0.01%.

2. The aluminum alloy according to claim 1, It is characterized in that Its composition includes: 0.42-0.46% Si, 0.68-0.75% Fe, 0.004-0.006% Cu, 0.015-0.020% Zn, 0.005-0.007% Ti, 0.012-0.015% Ga, 0.04-0.1% Sm, and 0.02-0.05% Er.

3. The aluminum alloy according to claim 2, It is characterized in that 0.42-0.45% Si, 0.69-0.72% Fe, 0.004-0.006% Cu, 0.017-0.018% Zn, 0.005-0.007% Ti, 0.013-0.014% Ga, 0.04-0.1% Sm, 0.02-0.05% Er.

4. The aluminum alloy according to any one of claims 1 to 3, It is characterized in that The other elements include V and / or Cr, and the total amount of V and Cr accounts for a mass ratio of m to the aluminum alloy, where m≤0.008%.

5. The aluminum alloy according to claim 4, It is characterized in that 0.0035≤m≤0.0037。 6. A method for preparing the aluminum alloy according to any one of claims 1 to 5, It is characterized in that The following steps are involved: 1) Mix the raw materials other than Ti, Sm and Er, and heat to 760-780°C to obtain the first aluminum liquid; 2) Adding aluminum-boron alloy to the first aluminum liquid, and keeping the aluminum liquid at a temperature of M°C for 30-60 minutes, separating the solid and the liquid, to obtain a second aluminum liquid; wherein the liquidus temperature of the first aluminum liquid is N°C, N°C+10°C≤M°C≤N°C+20°C; 3) adding aluminum-titanium master alloy, aluminum-erbium master alloy and aluminum-samarium master alloy to the second aluminum liquid at 710-750° C. and mixing to obtain a third aluminum liquid; 4) The third aluminum liquid is cast after refining, deslagging and refining, and degassing to obtain the aluminum alloy.

7. The preparation method according to claim 6, It is characterized in that The refining and slag removal specifically includes the following processes: At 710-750° C., solid flux is sprayed into the third aluminum liquid. After standing or stirring, solid on the surface of the third aluminum liquid is scraped off.

8. The preparation method according to claim 6, It is characterized in that The refining and degassing comprises the steps of introducing argon into the third aluminum liquid at 700-740° C. and leaving the third aluminum liquid to stand.

9. The preparation method according to claim 6, It is characterized in that The casting specifically includes the following processes: After the third aluminum liquid is cast into the launder, argon is used to remove hydrogen, and the third aluminum liquid after dehydrogenation is filtered to remove impurities larger than 20 microns.

10. A motor rotor, It is characterized in that The aluminum alloy is prepared from the aluminum alloy described in any one of claims 1 to 5 or the aluminum alloy prepared by the preparation method described in any one of claims 6 to 9.

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