Cast aluminum alloy material with low creep deformation and good toughness and preparation method thereof

Abstract

The invention discloses a cast aluminum alloy material with low creep deformation and good toughness and a preparation method of the cast aluminum alloy material, and belongs to the technical field of motors for new energy automobiles. The aluminum alloy comprises the following components in parts by weight: 0.7-1.0 wt% of Si, 0.4-0.8 wt% of Cu, 0.15-0.4 wt% of a group VIII element, and the balance of Al and inevitable impurities. The cast aluminum rotor prepared from the cast aluminum alloy material can keep toughness and reduce creep deformation at the speed of more than 25,000 rpm, so that the crack generation rate during high-speed rotation is reduced, the shape of the rotor is kept, the rotor can normally operate under high-speed rotation, and the service life of the rotor is prolonged.

Description

TECHNICAL FIELD

[0001] The application relates to a cast aluminum alloy material with low creep and good toughness and a preparation method thereof, and belongs to the technical field of motors for new energy vehicles. BACKGROUND

[0002] The cast aluminum rotor for a new energy vehicle adopts aluminum as a base material, adds a certain amount of metal elements to improve the strength or electrical conductivity of the cast aluminum rotor, and the casting process mainly adopts high-pressure casting and centrifugal casting. At present, more elements are added in the cast aluminum rotor, usually more than five kinds, which will cause the increase of production cost, and the poor casting uniformity of the castings due to the difficulty in smelting and casting caused by too many elements.

[0003] In order to solve the technical problem, the prior art develops a binary motor rotor or a ternary motor patent to reduce the production cost and improve the performance of the castings. For example, in the patents CN114790527A and CN114752830A, one or two elements are added in aluminum to improve the mechanical and electrical properties of the castings.

[0004] Since the cast aluminum rotor is used in the motor of a new energy vehicle, the performance of the cast aluminum rotor varies with the speed, and the applicant finds that the cast aluminum rotor in the current patent can maintain good electrical and mechanical properties below 25000 rpm, but above 25000 rpm, the following problems exist: 1. Insufficient toughness: due to high-speed rotation, the friction on the cast aluminum rotor is intensified and the centrifugal force is quadratically increased, and the cyclic stress frequency is greatly improved, so that the crack is repeatedly stressed, and the crack is easily rapidly expanded along the grain boundary or defect, thereby causing brittle fracture; 2. Creep is intensified: high-speed rotation friction intensifies the temperature rise of the rotor, which can reach above 150 DEG C locally, the grain boundary atom activity is significantly enhanced at high temperature, and the high centrifugal force as a continuous stress will drive the grain boundary to rapidly slip, which will intensify the deformation of the rotor and make the rotor creep worse, and it is difficult to maintain the normal operation of the rotor.

[0005] Therefore, there is a lack of a cast aluminum alloy material with low creep and good toughness for rotation above 25000 rpm. SUMMARY

[0006] In order to solve the above problems, a cast aluminum alloy material with low creep and good toughness is provided, and the cast aluminum rotor prepared by the cast aluminum alloy material can maintain toughness and reduce creep above 25000 rpm, thereby reducing the crack generation rate at high speed rotation and maintaining the shape of the rotor, so that the rotor can normally operate at high speed rotation and prolong the service life of the rotor.

[0007] According to one aspect of the present application, a cast aluminum alloy material with low creep and good toughness is provided, comprising 0.7-1.0 wt% of Si, 0.4-0.8 wt% of Cu, 0.15-0.4 wt% of Group VIII element, and the rest being Al and inevitable impurities.

[0008] The added component Si in the cast aluminum alloy material can form an aluminum silicon phase, i.e. an α-Al-Si solid solution, in the cast aluminum, which can play a strengthening role to improve the mechanical strength and wear resistance of the rotor, and can also significantly reduce the melting point of the aluminum alloy, improve the fluidity of the aluminum liquid, facilitate casting forming, and due to good fluidity, it will not quickly solidify, which can ensure that the gas is discharged in time during casting; the added Cu can precipitate θ'-Al2Cu phase after heat treatment, which can play a role in refining the grain and improving the grain uniformity in combination with the Group VIII element, thereby improving the strength uniformity of the rotor and reducing the risk of brittle fracture under high-speed rotation of the rotor; the added Group VIII element can form Al3Fe, Al3Ni and other metal phases and solid solutions, which can not only improve the strength of the rotor, but also improve the high-temperature stability, stabilize the grain boundary structure and reduce the grain boundary sliding, thereby reducing the high-temperature creep of the rotor.

[0009] Optionally, the weight ratio of Si, Cu and Group VIII element is (2-2.5):(1-1.5):1.

[0010] The addition amount of Si in the above-mentioned cast aluminum alloy material is greater than that of Cu and Group VIII element, and the combination of the three components can further reduce the size of the grain and the difference in grain size, so that the mechanical properties of the casting are optimized. If the Si is lower than the above-mentioned proportion, the tensile strength and yield strength will decrease, and if the Si is higher than the above-mentioned proportion, the improvement of the tensile strength and yield strength is not great, but there will be excess free silicon, which will make the grain size larger, leading to an increase in the brittleness of the rotor, which will increase the crack formation at high speed, and cannot meet the use requirements above 25000 rpm, and will also reduce the thermal conductivity of the rotor, making it difficult to conduct the heat generated at high speed, and reducing the anti-creep ability of the rotor. If the Cu is lower than the above-mentioned proportion, the θ'-Al2Cu strengthening phase will decrease, which will reduce the mechanical strength of the rotor, and if the Cu is higher than the above-mentioned proportion, the toughness of the rotor will decrease significantly, and excessive Cu will make the θ'-Al2Cu phase larger, which is easy to continuously precipitate along the grain boundary, forming a brittle grain boundary layer, which is easy to crack, and will also reduce the high-temperature stability of the rotor, thereby increasing the creep.

[0011] Optionally, the Group VIII element is selected from at least one of iron, cobalt and nickel.

[0012] The production cost of the above elements is low, and the processing performance of the elements added to the rotor is good, facilitating the casting forming of the rotor, reducing the generation of defects such as impurities, inclusions or pores in the rotor, thereby avoiding the defects as stress concentration points to inhibit the generation of cracks from the root.

[0013] The addition of the iron element has the following advantages: 1. Reducing the sticking tendency: the hard and brittle intermetallic compound formed by the iron element can reduce the adhesion of the casting on the mold, facilitating demolding; 2. Improving the strength and hardness: the AlFeSi and Al3Fe phases formed by the iron element can improve the strength and hardness of the casting.

[0014] The addition of the nickel element has the following advantages: 1. Improving high-temperature performance: nickel can form stable intermetallic compounds (such as Al3Ni and Al9FeNi) with aluminum, iron and copper, which can maintain their structure at high temperatures. Al3Ni can effectively pin the grain boundaries, preventing grain growth and softening, thus making the structure less prone to coarsening and softening, thereby improving the strength retention rate and creep resistance of the rotor at high speed.

[0015] 2. Reducing the thermal expansion coefficient: the addition of the nickel element can inhibit the volume deformation of the rotor at high temperature, thereby reducing the thermal expansion of the rotor and maintaining the normal rotation of the rotor.

[0016] 3. Improving high-temperature wear resistance: the addition of the nickel element can improve the high-temperature wear resistance of the rotor, thereby reducing surface damage caused by friction during high-speed rotation, making the rotor surface smooth to further avoid the increase of friction, and if the content of nickel element is low, the wear resistance of the rotor surface will decrease, and the rotor will produce surface damage during operation, making the surface roughness of the rotor increase. The increased surface roughness will further increase the friction force on the rotor during high-speed rotation, thereby further increasing the temperature of the rotor, and the vicious cycle will reduce the creep resistance of the rotor.

[0017] Optionally, the Group VIII element includes iron and nickel in a weight ratio of 1: (1.2-1.5).

[0018] With the addition of the above Group VIII element, the toughness and creep resistance of the rotor can be improved, and when iron and nickel in a weight ratio of 1:1.5 are used as the Group VIII element, the Al9FeNi, Al3Fe and Al3Ni phases can be balanced, and the phase separation in the cast aluminum alloy material can be reduced.

[0019] Optionally, the Group VIII element includes iron, nickel and cobalt in a weight ratio of 1:1.5:0.5.

[0020] When the three elements of iron, nickel and cobalt are used as the group VIII elements in the above weight ratio, the amount of Al3Fe, NiAl3 phases remains unchanged, the added Co element can be dissolved in the crystal lattice of aluminum to form a solid solution, which plays a role in strengthening the matrix and further improves the strength and hardness of the rotor. The formation of the solid solution can also hinder the lattice slip, thereby keeping the Al3Fe, Al3Ni phases in a fine and dispersed state during high-speed operation, avoiding the coarsening or dissolution of the strengthening phase caused by local high temperature, and further improving the high-temperature creep resistance and deformation resistance of the rotor.

[0021] The iron element in the group VIII elements can form α phase (α-Al8Fe2Si) and β phase (β-Al5FeSi) with Si element, the α phase is relatively "blunt" and has less harm to mechanical properties and plasticity, which is the desired form, the β phase is a harmful phase which can seriously split the matrix and is the main source of stress concentration, and excessive content of the β phase can significantly reduce the strength and plasticity of the alloy. Therefore, for the cast aluminum alloy material, it is desired to reduce the β phase and increase the α phase under the same amount of iron and Si addition. By adding the total content of group VIII elements and limiting the group VIII elements to include iron, nickel and cobalt in a weight ratio of 1:1.5:0.5, and combining with the heat treatment process, the beneficial α phase can be promoted and the harmful β phase can be inhibited, so that the creep resistance and toughness of the rotor under high-speed rotation are optimally improved.

[0022] Optionally, the cast aluminum alloy material satisfies at least one of the following conditions: yield strength ≥ 75 MPa; tensile strength ≥ 130 MPa.

[0023] According to a second aspect of the present application, a preparation method of the low-creep and good-toughness cast aluminum alloy material described in any one of the above is provided, comprising the following steps: (1) The aluminum liquid is heated to 720-740℃, and the weighed Si and Cu are added. After complete dissolution, uniform stirring is performed, and the temperature is maintained at 710-730℃ for primary refining. The slag is removed, and the intermediate liquid A is obtained after standing; (2) The intermediate liquid is heated to 720-740℃ again, and the weighed group VIII elements are added. After complete dissolution, uniform stirring is performed, and the temperature is maintained at 720-740℃ for secondary refining. The slag is removed, and the intermediate liquid B is obtained after standing; (3) The casting mold is preheated, and then the intermediate liquid B is cooled to 720℃, and then poured into the casting mold for centrifugation. After the rotor solidifies, the pouring equipment stops rotating, and natural cooling is performed for 60-120s, and then air cooling is performed to room temperature to obtain the casting; (4) After the casting is heat treated, it is naturally cooled to room temperature, and the process is completed.

[0024] The preparation method can avoid the formation of inclusions among the elements, reduce the impurity content in the melt, improve the purity and element distribution uniformity of the intermediate liquid B, and further improve the microstructure uniformity of the casting.

[0025] Optionally, the centrifugal speed of step (3) is 150-300 r / min, and the centrifugal time is 45-60 s.

[0026] The centrifugal casting has a low speed and a long casting time, so that the gas in the mold can be discharged in time, the gas pores in the casting can be avoided, and the grains in the rotor can be slowly formed, so that the grain size uniformity is improved while the grain size is refined.

[0027] Optionally, in the casting mold, the temperature of the upper mold is 520-540 DEG C, and the temperature of the lower mold is 340-360 DEG C.

[0028] The temperature of the upper mold is lower than that of the lower mold, so that the intermediate liquid B can be more uniformly filled into the mold and the exhaust effect is good, the generation of bubbles in the casting is reduced, and the grains are gradually formed during the casting and solidification forming process, so that a finer and more uniform structure is obtained.

[0029] Optionally, the primary refining in step (1) is specifically: rotating and spraying gas, and the refining time is 10-15 min.

[0030] Step (1) adopts the rotating and spraying gas refining to complete the preliminary refining, remove the bubbles and a small amount of impurities in the aluminum liquid, and however, some impurities remain and need to be refined by the refining agent, but since the impurities do not form inclusions with the group VIII elements, they can be removed together in the secondary refining to reduce the production cost.

[0031] Optionally, the secondary refining of step (2) includes a first stage and a second stage, the first stage rotates and sprays gas, and the refining time is 5-8 min, and the second stage adds 0.7-0.9 wt% of the total mass of the melt of the refining agent, and the refining time is 5-10 min.

[0032] The secondary refining in step (2) is divided into two stages, the first stage removes the remaining gas in the melt, reduces the dissolved gas in the aluminum liquid, and avoids the generation of pores in the casting, and the second stage adds the refining agent, the refining agent can combine with the solid inclusions, so that the solid inclusions can be separated during the slagging, the content of the inclusions in the intermediate liquid B is reduced, and the foundation for refining the grains and reducing the defects in the casting is laid.

[0033] Optionally, the refining agent is C2Cl6.

[0034] Optionally, the amount of the rotating injection gas in the primary and secondary refining is 3-6 L / min.

[0035] Optionally, the injection gas is compressed air or inert gas.

[0036] Optionally, the heat treatment process of step (4) is: S1: heating the casting to 320-340℃ at a heating rate of 5-10℃ / min, holding for 2-3h, and then heating to 380-420℃ at a heating rate of 20-30℃, holding for 1-2h; S2: cooling the rotor to room temperature in a cooling liquid containing 10-20wt% of the control agent and the rest being water, the cooling rate of the cooling liquid being 15-25℃ / s in the range of 300-420℃, and the cooling rate being 40-80℃ / s below 300℃; S3: heating to 150-160℃ at a heating rate of 5℃ / min and holding for 5h.

[0037] Optionally, the control agent is selected from polyvinyl alcohol, sodium alginate and sulfonated cellulose in a weight ratio of 6:3:1.

[0038] Optionally, the molecular weight of the polyvinyl alcohol is 200-250 thousand, the molecular weight of the sodium alginate is 300-350 thousand, and the molecular weight of the sulfonated cellulose is 20-40 thousand.

[0039] The beneficial effects of the present application include but are not limited to: 1. The low creep and good toughness cast aluminum alloy material according to the present application can improve the creep resistance and toughness at a rotation speed of 25000 rpm or above, and prolong the service life of the cast aluminum rotor at high rotation speed.

[0040] 2. The low creep and good toughness cast aluminum alloy material according to the present application can realize the dual improvement of toughness and creep resistance, avoid brittle fracture of the rotor at high speed rotation, maintain the shape of the rotor, and ensure the normal operation of the rotor.

[0041] 3. The low creep and good toughness cast aluminum alloy material according to the present application can improve the strength and hardness by adding Si, Cu and group VIII elements, reduce the grain size and improve the grain uniformity, reduce the grain boundary area, and greatly improve the toughness.

[0042] 4. The low creep and good toughness cast aluminum alloy material according to the present application can improve the high temperature stability of the rotor by adding group VIII elements, stabilize the grain boundary structure at high temperature and high speed rotation, reduce the grain boundary sliding, and further reduce the high temperature creep of the rotor. DETAILED DESCRIPTION

[0043] The application will be described in detail below with reference to the examples, but the application is not limited to these examples.

[0044] The raw materials in the examples and comparative examples of the present application are commercially available unless otherwise specified.

[0045] The methods used in the examples and comparative examples of the present application are conventional methods in the prior art unless otherwise specified. The control agents used in the following examples and comparative examples are commercially available products, and the preparation method of sulfonated cellulose is also a method known in the prior art, which can be directly purchased or directly prepared by referring to the prior art, for example, refer to patent CN119638854A.

[0046] Example 1 This example relates to a cast aluminum alloy material with low creep and good toughness, which comprises 1.0wt% of Si, 0.4wt% of Cu, 0.4wt% of Fe element, and the rest is Al and unavoidable impurities.

[0047] The preparation method of the cast aluminum alloy material for producing a cast aluminum rotor comprises the following steps: (1) The aluminum liquid is heated to 720℃, and the weighed Si and Cu are added. After complete dissolution, uniform stirring is performed, and the temperature is maintained at 710℃ for primary refining. Rotating air blowing refining is performed for 10min, the compressed air input amount is 6L / min, and the slag is removed and left to obtain intermediate liquid A; (2) The intermediate liquid is heated to 720℃ again, and the weighed Fe element is added. After complete dissolution, uniform stirring is performed, and the temperature is maintained at 720℃ for secondary refining. The slag is removed and left to obtain intermediate liquid B. The secondary refining includes a first stage and a second stage. The first stage rotating air blowing refining is performed for 5min, the compressed air input amount is 6L / min, and the second stage adds 0.9wt% of C2Cl6refining agent based on the total mass of the melt, and the refining is performed for 5min; (3) The casting mold is preheated, the temperature of the upper mold is 520℃, and the temperature of the lower mold is 340℃. Then the intermediate liquid B is cooled to 720℃, and is poured into the casting mold for centrifugation at a speed of 150r / min for 60s. After the rotor solidifies, the pouring equipment stops rotating, and is naturally cooled for 60s. Then air cooling is performed to room temperature to obtain a casting; (4) After the casting is heat treated, it is naturally cooled to room temperature to obtain the product. The heat treatment process is as follows: S1: The casting is heated to 320℃ at a heating rate of 5℃ / min, and is kept for 3h. Then it is heated to 380℃ at a heating rate of 20℃, and is kept for 2h; S2: cooling the rotor to room temperature in a cooling liquid containing 20wt% of a control agent and the rest water, the control agent being selected from polyvinyl alcohol (molecular weight 200,000), sodium alginate (molecular weight 300,000) and sulfonated cellulose (molecular weight 20,000) in a weight ratio of 6:3:1, the cooling rate of the cooling liquid being 15-25℃ / s in the range of 300-380℃ and the cooling rate below 300℃ being 40-80℃ / s; S3: heating to 160℃ at a heating rate of 5℃ / min and holding for 5h.

[0048] Example 2 The present embodiment relates to a cast aluminum alloy material with low creep and good toughness, comprising 0.7wt% of Si, 0.8wt% of Cu, 0.15wt% of Ni element, and the rest being Al and inevitable impurities.

[0049] The preparation method of the cast aluminum alloy material for producing a cast aluminum rotor comprises the following steps: (1) The aluminum liquid is heated to 740℃, and the weighed Si and Cu are added. After complete dissolution, uniform stirring is performed, and the temperature is maintained at 730℃ for primary refining. Rotating air blowing refining is performed for 20min, the compressed air input amount is 3L / min, and the slag is removed and left to obtain intermediate liquid A; (2) The intermediate liquid is heated to 740℃ again, and the weighed Ni element is added. After complete dissolution, uniform stirring is performed, and the temperature is maintained at 740℃ for secondary refining. The slag is removed and left to obtain intermediate liquid B. The secondary refining includes a first stage and a second stage. The first stage rotating air blowing refining is performed for 5min, the compressed air input amount is 6L / min, and the second stage adds 0.7wt% of C2Cl6refining agent based on the total mass of the melt, and the refining is performed for 10min; (3) The casting mold is preheated, the temperature of the upper mold is 530℃, and the temperature of the lower mold is 350℃. Then the intermediate liquid B is cooled to 720℃, and then poured into the casting mold for centrifugation at a speed of 200r / min for 45s. After the rotor solidifies, the pouring equipment stops rotating, and natural cooling is performed for 100s. Then air cooling is performed to room temperature to obtain a casting; (4) After the casting is heat treated, it is naturally cooled to room temperature to obtain the product. The heat treatment process is as follows: S1: heating the casting to 340℃ at a heating rate of 10℃ / min, holding for 2h, and then heating to 420℃ at a heating rate of 30℃ / min, holding for 1h; S2: cooling the rotor to room temperature in a cooling liquid containing 10wt% of a control agent and the rest water, the control agent being selected from polyvinyl alcohol (molecular weight 200,000), sodium alginate (molecular weight 350,000) and sulfonated cellulose (molecular weight 30,000) in a weight ratio of 6:3:1, the cooling rate of the cooling liquid being 15-25℃ / s in the range of 300-420℃ and the cooling rate below 300℃ being 40-80℃ / s; S3: heating to 150℃ at a heating rate of 5℃ / min and holding for 5h.

[0050] Example 3 The present embodiment relates to a cast aluminum alloy material with low creep and good toughness, comprising 0.8wt% of Si, 0.6wt% of Cu, 0.1wt% of Fe element, 0.12wt% of Ni element, and the rest being Al and unavoidable impurities.

[0051] The preparation method of the cast aluminum alloy material for producing a cast aluminum rotor comprises the following steps: (1) The aluminum liquid is heated to 730℃, and the weighed Si and Cu are added. After complete dissolution, uniform stirring is performed, and the temperature is maintained at 720℃ for primary refining. Rotating air blowing refining is performed for 15min, and the compressed air input amount is 4L / min. After slagging and standing, intermediate liquid A is obtained; (2) The intermediate liquid is heated to 730℃ again, and the weighed Fe element and Ni element are added. After complete dissolution, uniform stirring is performed, and the temperature is maintained at 730℃ for secondary refining. After slagging and standing, intermediate liquid B is obtained. The secondary refining includes a first stage and a second stage. In the first stage, rotating air blowing refining is performed for 8min, and the compressed air input amount is 4L / min. In the second stage, 0.8wt% of C2Cl6refining agent based on the total mass of the melt is added, and refining is performed for 10min; (3) The casting mold is preheated, the temperature of the upper mold is 540℃, and the temperature of the lower mold is 360℃. Then the intermediate liquid B is cooled to 720℃, and then poured into the casting mold for centrifugation at a speed of 300r / min for 50s. After the rotor solidifies, the pouring equipment stops rotating, and natural cooling is performed for 120s. Then air cooling is performed to room temperature to obtain a casting; (4) After the casting is heat treated, it is naturally cooled to room temperature to obtain the product. The heat treatment process is as follows: S1: heating the casting to 330℃ at a heating rate of 8℃ / min and holding for 2.5h, and then heating to 400℃ at a heating rate of 25℃ / min and holding for 1.5h; S2: cooling the rotor to room temperature in a cooling liquid containing 15 wt% of a control agent and the rest water, the control agent being selected from polyvinyl alcohol (molecular weight 250,000), sodium alginate (molecular weight 300,000) and sulfonated cellulose (molecular weight 30,000) in a weight ratio of 6:3:1, the cooling liquid having a cooling rate of 15-25 °C / s in the range of 300-400 °C and a cooling rate of 40-80 °C / s below 300 °C; S3: heating to 160 °C at a heating rate of 5 °C / min and holding for 5 h.

[0052] Example 4 The difference between this example and Example 3 is that the content of Ni element is 0.15 wt%.

[0053] Example 5 The difference between this example and Example 3 is that the cast aluminum alloy material further comprises 0.05 wt% Co element.

[0054] Example 6 The difference between this example and Example 3 is that the cast aluminum alloy material further comprises 0.15 wt% Co element.

[0055] Example 7 The difference between this example and Example 3 is that S2 of step (4) is: cooling the rotor to room temperature in water at a temperature of 25 °C.

[0056] Example 8 The difference between this example and Example 3 is that S2 of step (4) is: cooling the rotor to room temperature in a cooling liquid containing 30 wt% of a control agent and the rest water, the control agent being selected from polyvinyl alcohol (molecular weight 200,000), sodium alginate (molecular weight 300,000) and sulfonated cellulose (molecular weight 20,000) in a weight ratio of 6:3:1, the cooling liquid having a cooling rate of 5-10 °C / s in the range of 300-400 °C and a cooling rate of 20-45 °C / s below 300 °C.

[0057] Example 9 The difference between this example and Example 3 is that polyacrylamide is used instead of sulfonated cellulose in S2 of step (4), and the cooling liquid has a cooling rate of 15-25 °C / s in the range of 300-400 °C and a cooling rate of 40-60 °C / s below 300 °C.

[0058] Example 10 The difference between this example and Example 3 is that step S3 of step (4) is not performed.

[0059] Comparative Example 1 The difference between the present comparative example and Example 3 is that 0.1wt% of Mg is used to replace Fe.

[0060] Comparative Example 2 The difference between the present comparative example and Example 3 is that 0.1wt% of Zn is used to replace Ni.

[0061] Comparative Example 3 The difference between the present comparative example and Example 3 is that the amount of Fe element added is 0.3wt%.

[0062] Comparative Example 4 The difference between the present comparative example and Example 3 is that the amount of Ni element added is 0.35wt%.

[0063] Comparative Example 5 The difference between the present comparative example and Example 3 is that the amount of Si element added is 0.6wt%.

[0064] Comparative Example 6 The difference between the present comparative example and Example 3 is that the amount of Si element added is 1.2wt%.

[0065] Comparative Example 7 The difference between the present comparative example and Example 3 is that the amount of Cu element added is 0.3wt%.

[0066] Comparative Example 8 The difference between the present comparative example and Example 3 is that the amount of Cu element added is 0.9wt%.

[0067] Comparative Example 9 The difference between the present comparative example and Example 3 is that step (4) is not performed, and the casting obtained in step (3) is the final product.

[0068] Test Example 1 The end face of the cast aluminum rotor prepared from the cast aluminum alloy material of the above examples and comparative examples is sampled for mechanical property and conductivity test. The conductivity sample size meets the requirements of GB / T129662008 and is tested for conductivity. The mechanical property test sample size standard meets ASTM E8 and is analyzed for tensile property. The impact resistance is tested by cantilever beam impact strength tester according to GB / T1843-2008. The results are shown in Table 1.

[0069] Table 1

[0070] Test Example 2 The cast aluminum rotor prepared from the cast aluminum alloy material of the above examples and comparative examples was run at 200℃, 26000 rpm, and the creep limit and fatigue limit of the rotor after 1000h service were tested, and the loss rate of tensile strength and impact strength were tested, and the test results are shown in Table 2.

[0071] The test temperature of the creep limit and fatigue limit of the rotor after 1000h service in Table 2 is 150℃, and the larger the value, the better the anti-creep performance of the rotor.

[0072] The loss rate of tensile strength is [ (T1-T2) / T1] x 100%, T1 is the initial tensile strength, unit: MPa, and T2 is the tensile strength after 1000h running at 200℃, 26000 rpm, unit: MPa.

[0073] The loss rate of impact strength is [ (T3-T4) / T3] x 100%, T3 is the initial impact strength, unit: kJ / m 2 , and T4 is the impact strength after 1000h running at 200℃, 26000 rpm, unit: kJ / m 2 .

[0074] Table 2

[0075] The above is only an embodiment of the present application, and the protection scope of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. The present application can have various changes and variations for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the technical thought and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A cast aluminum alloy material with low creep and good toughness, characterized in that, By weight, it includes 0.7-1.0 wt% Si, 0.4-0.8 wt% Cu, 0.15-0.4 wt% Group VIII elements, with the remainder being Al and unavoidable impurities.

2. The low-creep and high-toughness cast aluminum alloy material according to claim 1, characterized in that, The weight ratio of Si, Cu and Group VIII elements is (2-2.5):(1-1.5):

1.

3. The low-creep and high-toughness cast aluminum alloy material according to claim 1, characterized in that, The group VIII elements are selected from at least one of iron, cobalt, and nickel.

4. The low-creep and high-toughness cast aluminum alloy material according to claim 3, characterized in that, The group VIII elements include iron and nickel in a weight ratio of 1:(1.2-1.5).

5. The low-creep and high-toughness cast aluminum alloy material according to claim 3, characterized in that, The group VIII elements include iron, nickel, and cobalt in a weight ratio of 1:1.5:0.

5.

6. The low-creep and high-toughness cast aluminum alloy material according to claim 1, characterized in that, It meets at least one of the following conditions: Yield strength ≥ 75 MPa; Tensile strength ≥130MPa.

7. The method for preparing the low-creep and high-toughness cast aluminum alloy material according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Heat the aluminum liquid to 720-740℃, add the weighed Si and Cu, stir evenly after it is completely dissolved, maintain the temperature at 710-730℃ for one refining, remove the slag and let it stand to obtain intermediate liquid A. (2) Heat the intermediate liquid again to 720-740℃, add the weighed group VIII element, stir evenly after it is completely dissolved, maintain the temperature at 720-740℃ for secondary refining, remove the slag and let it stand to obtain intermediate liquid B; (3) Preheat the casting mold, then cool the intermediate liquid B to 720°C and pour it into the casting mold for centrifugation. After the rotor solidifies, stop the casting equipment from rotating and allow it to cool naturally for 60-120 seconds. Then air cool it to room temperature to obtain the casting. (4) After heat treatment, the casting is naturally cooled to room temperature to obtain the final product.

8. The preparation method according to claim 7, characterized in that, In step (3), the centrifugation speed is 150-300 r / min and the centrifugation time is 45-60 s.

9. The preparation method according to claim 7, characterized in that, In the casting mold, the temperature of the upper mold is 520-540℃, and the temperature of the lower mold is 340-360℃.

10. The preparation method according to claim 7, characterized in that, The refining process in step (1) specifically involves: rotary blowing of gas for 10-15 minutes; and / or The secondary refining in step (2) includes a first stage and a second stage. In the first stage, gas is sprayed in a rotary kneading motion for 5-8 minutes. In the second stage, a refining agent of 0.7-0.9 wt% of the total mass of the melt is added for 5-10 minutes.

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