High-conductivity aluminum alloy high-voltage electric appliance shell casting and preparation method thereof

Abstract

The invention provides a high-conductivity aluminum alloy high-voltage electric appliance shell casting and a preparation method thereof. The high-conductivity aluminum alloy high-voltage electric appliance shell casting comprises, by weight, 7.0%-7.5% of Si, 0.25%-0.45% of Mg, 0.08%-0.20% of Ti, smaller than or equal to 0.15% of Fe, smaller than or equal to 0.1% of Cu, smaller than or equal to 0.1% of Zn, smaller than or equal to 0.10% of Mn, smaller than or equal to 0.20% of Zr, smaller than or equal to 0.01% of Sn, smaller than or equal to 0.03% of Pb and the balance Al and inevitable impurities. The casting method comprises the following steps: carrying out initial burdening and melting, then adding an alterant and a refiner to carry out modification treatment on molten aluminum alloy, then carrying out refining treatment, and pouring the molten aluminum alloy into a mold at 720-730 DEG C to prepare a casting; and finally, the casting is subjected to solid solution and aging treatment. According to the prepared high-conductivity aluminum alloy high-voltage electric appliance shell casting, the conductivity is larger than or equal to 41.11% IACS, the tensile strength is larger than or equal to 221 MPa, the elongation is larger than or equal to 7.65%, and the casting yield reaches 95% or above.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloy preparation and processing, and specifically relates to a high-conductivity aluminum alloy high-voltage electrical appliance housing casting and a preparation method thereof. Background Art

[0002] In the power and electrical industry, for the material selection of some structural components such as power hardware, electrical control, switches, etc., there are not only requirements for the electrical conductivity of the material, but also requirements for mechanical properties and corrosion resistance. With the continuous development of the power transmission and distribution industry, the ultra / extra-high voltage power transmission and distribution industry has put forward higher requirements for the material strength and conductivity of some structural components such as power hardware, electrical control, switches, etc. At present, the conductivity of the casting aluminum alloy ZL101A-T6 used in the high-voltage electrical appliance industry is generally between 33% and 36% IACS, and it is difficult to meet the improvement requirements of products in the ultra / extra-high voltage power transmission and distribution industry.

[0003] In recent years, with the in-depth research on the electrical conductivity of aluminum alloys in the industry, it has been found that the conductivity of aluminum alloys mainly depends on their heat treatment process, alloying elements and microstructure. Among them, the heat treatment process has a particularly significant impact on the conductivity. The heat treatment of aluminum alloys includes solution treatment and aging treatment. As the artificial aging temperature increases, the conductivity gradually increases. This is because when the aging temperature increases, the supersaturated solid solution obtained by quenching will gradually precipitate solute atoms, reducing the distortion degree of the alloy and lowering the internal stress, thereby making the electron movement easier and the conductivity gradually increasing. However, as the temperature further increases, the density of the precipitated transition phase decreases, making the changes in strength and conductivity tend to level off. Therefore, appropriately increasing the artificial aging temperature is an effective way to develop high-conductivity aluminum alloy products.

[0004] For the Chinese patent with the patent number ZL2017101253133 and the name of a high-conductivity casting aluminum alloy, the content of added Si element is 4.5-6.5%, and trace special elements boron and lanthanum are added. The solution treatment temperature is 540±5°C, and the solution time is 2-8 hours; the aging treatment temperature is 223±5°C, and the aging time is 3-7 hours. The conductivity of the alloy at room temperature is 46.5-50.7% IACS, the tensile strength > 260 MPa, the yield strength > 210 MPa, the elongation > 5%, and the hardness value reaches above 62 HBS. While obtaining the conductivity, because of adding high-cost boron and lanthanum elements, the economic benefits of production and application are reduced, and at the same time, the tensile strength, yield strength and elongation of the material are relatively low.

[0005] A Chinese patent with the application number CN2023110059034 and the title "A High Conductivity Aluminum Alloy Casting and Its Preparation Method" prepares an aluminum alloy casting by adjusting the composition of alloying elements and the heat treatment process. It has the advantage of good conductivity. The conductivity of this high conductivity aluminum alloy casting at room temperature is not less than 50% IACS, and the tensile strength is not lower than 275 MPa, solving the problem of low conductivity of cast aluminum alloy castings. Since there are no measured data in this application, it is difficult to determine whether it can ensure a tensile strength of not less than 275 MPa while ensuring a conductivity of not less than 50% IACS.

[0006] A Chinese patent with the patent number ZL2021115927744 and the title "A Cast Aluminum Alloy and Its Preparation Method", the aluminum alloy contains: Si: 1.8 - 4 wt%, Ni: 0.5 - 3.0 wt%, Mg: 0.1 - 0.8 wt%, Zn: 0.1 - 1.0 wt%, Cu: 0.5 - 1.0 wt%, Fe: 0.4 - 0.9 wt%, Sr: 0.02 - 0.1 wt%, La: 0.1 - 0.3 wt%, the total content of Cr, Mn, V, Ti is less than 0.01 wt%, and the rest is Al and inevitable impurities; its preparation steps include stock preparation, melting aluminum ingots, smelting and melting purification, degassing and casting. Compared with existing cast aluminum alloys, the present invention has a higher thermal conductivity, which can reach a thermal conductivity greater than 180 W / (m·K) and a conductivity greater than 43.8% IACS in the as-cast state. After short-time T5 heat treatment, the thermal conductivity reaches 200 W / (m·K) and the conductivity reaches 48.6% IACS, and the yield strength can reach 205 MPa.

[0007] A Chinese invention patent with the application number CN2022116285848 and the title "A Preparation Method of an Aluminum Alloy Casting" includes the following steps: performing low-pressure casting on the aluminum alloy melt; the aluminum alloy casting is composed of the following components by percentage: Si: 1.7 - 1.9 wt%, Mg: 0.4 - 0.6 wt%, Zn: 0.05 - 0.1 wt%, Cu: 0.4 - 0.6 wt%, Fe: 0.05 - 0.1 wt%, B: 0.05 - 0.07 wt%, Mn: 0.02 - 0.04 wt%, and Sr: 0.02 - 0.04 wt%, and the balance is Al and other inevitable impurities. The tensile strength and conductivity of the aluminum alloy conductor casting prepared by this invention meet the standard requirements of 180 MPa and 45% IACS.

[0008] The Chinese invention patent with the application number CN2022116276069 and the name of a high-conductivity cast aluminum alloy material, its preparation method and application. The high-conductivity cast aluminum alloy material consists of the following components by percentage: Si: 0.6 - 1.6wt%, Mg: 0.34 - 0.63wt%, Zn: 0.09 - 0.13wt%, Cu: 0.11 - 0.16wt%, Fe: 0.09 - 0.13wt%, B: 0.04 - 0.06wt%, Sr: 0.03 - 0.05wt%, Mn: 0.03 - 0.04wt%, Cr: 0.03 - 0.04wt%, and the rest is Al and other inevitable impurities. The cast aluminum alloy of this invention has a relatively high conductivity and yield strength (after the prepared aluminum alloy conductor casting is subjected to T6 heat treatment, the conductivity can reach 50% - 53% IACS, the tensile strength ≥ 240MPa, the elongation rate ≥ 1%, and the hardness ≥ 70HB). It can form conductor parts for high-voltage switches through ordinary gravity casting process, and the forming effect, production cost, etc. are the same as those of traditional ZL101A. Compared with ZL101A, it has a higher conductivity.

[0009] However, generally speaking, the above methods all improve the conductivity of cast aluminum alloy by reducing the silicon content. Although the conductivity of the cast aluminum-silicon alloy is improved by using the above methods, due to the reduction of its fluidity and the deterioration of casting performance, it is difficult to meet the casting requirements of large, complex and thin-walled electrical components. At the same time, it will also reduce the strength and plasticity of large, complex and thin-walled electrical components. Summary of the Invention

[0010] The purpose of the present invention is to provide a high-conductivity aluminum alloy high-voltage electrical housing casting and its preparation method to solve the problems existing in the above background technology.

[0011] To achieve the above purpose, the present invention provides the following technical solutions: A high-conductivity aluminum alloy high-voltage electrical housing casting, characterized in that it includes the following components by weight percentage: Si 7.0% - 7.5%, magnesium Mg 0.25% - 0.45%, titanium Ti 0.08% - 0.20%, iron Fe ≤ 0.15%, copper Cu ≤ 0.1%, zinc Zn ≤ 0.1%, manganese Mn ≤ 0.10%, zirconium Zr ≤ 0.20%, tin Sn ≤ 0.01%, lead Pb ≤ 0.03%, and the rest is aluminum Al and inevitable impurities; S1: Initial batching. Batch according to the formula requirements, put the prepared aluminum ingots into the melting furnace, evacuate and fill with protective gas, then heat up to 740 - 750 °C to melt the raw materials; cool down to 715 - 725 °C, stir evenly, add the modifier Al-10Sr master alloy, the grain refiner Al-5Ti-1B, use a rotating impeller to blow nitrogen and add a sodium-free refining agent for melt treatment, control the Sr content at 0.006% - 0.012%, control the Ti content at 0.08% - 0.20%, the addition amount of the refining agent is 3‰ of the aluminum liquid, the degassing time is not less than 20 minutes, the degassing temperature shall not be lower than 720 - 750 °C, let it stand for 10 min after degassing, and skim the slag after heat preservation and standing; S2: Hydrogen measurement. Measure hydrogen with a hydrogen measuring instrument. When the density of the solidified sample of the aluminum alloy liquid ≥ 2.62 g / cm3 and the temperature is 720 - 730 °C, pour the aluminum alloy liquid into the mold to prepare a casting; S3: Heat-treat the casting obtained in step S2. The heat treatment includes solution treatment and aging treatment; the temperature of the solution treatment is 530 - 540 °C, and the duration is 6 - 10 hours; the temperature of the aging treatment is 200 - 230 °C, and the duration is 6 - 10 hours.

[0012] As an improvement to the above technical solution, the total sum of inevitable impurities ≤ 0.7%.

[0013] The present invention also provides a preparation method for the high conductivity aluminum alloy high voltage electrical appliance housing casting. The steps of this method are: S1: Initial batching. Batch according to the formula requirements, put the prepared aluminum ingots into the melting furnace, evacuate and fill with protective gas, then heat up to 740 - 750 °C to melt the raw materials; cool down to 715 - 725 °C, stir evenly, add the modifier Al-10Sr master alloy, the grain refiner Al-5Ti-1B, use a rotating impeller to blow nitrogen and add a sodium-free refining agent for melt treatment, control the Sr content at 0.006% - 0.012%, control the Ti content at 0.08% - 0.20%, the addition amount of the refining agent is 3‰ of the aluminum liquid, the degassing time is not less than 20 minutes, the degassing temperature shall not be lower than 720 - 750 °C, let it stand for 10 min after degassing, and skim the slag after heat preservation and standing; S2: Hydrogen measurement. Measure hydrogen with a hydrogen measuring instrument. When the density of the solidified sample of the aluminum alloy liquid ≥ 2.62 g / cm 3 and the temperature is 720 - 730 °C, pour the aluminum alloy liquid into the mold to prepare a casting; S3: Heat-treat the casting obtained in step S2. The heat treatment includes solution treatment and aging treatment; the temperature of the solution treatment is 530 - 540 °C, and the duration is 6 - 10 hours; the temperature of the aging treatment is 200 - 230 °C, and the duration is 6 - 10 hours.

[0014] As an improvement to the above technical solution, the cooling method for solution treatment in step S3 is water cooling.

[0015] As an improvement to the above technical solution, the cooling method for aging treatment in step S3 is air cooling.

[0016] As an improvement to the above technical solution, the protective gas in step S1 is argon.

[0017] As an improvement to the above technical solution, the holding time for heat preservation and static setting in step S1 is 15 to 20 minutes.

[0018] As an improvement to the above technical solution, the mold in step S2 is preheated to 275 - 285 °C before pouring, and a release agent is sprayed.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: The high - conductivity aluminum alloy high - voltage electrical appliance housing casting obtained by the present invention has a conductivity ≥ 41.11% IACS, a tensile strength ≥ 221 MPa, an elongation rate ≥ 7.65%, and the casting yield rate reaches more than 95%; achieving the coordinated unity of conductivity, casting yield rate, casting strength, and plasticity. Brief Description of the Drawings

[0020] Figure 1 is a three - dimensional structural schematic diagram of the high - conductivity aluminum alloy high - voltage electrical appliance housing casting cast by the present invention; Figure 2 is a sectional structural schematic diagram of the high - conductivity aluminum alloy high - voltage electrical appliance housing casting cast by the present invention. Detailed Embodiments

[0021] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a 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 those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0022] The high - conductivity aluminum alloy high - voltage electrical appliance housing casting to be cast by the present invention is as Figure 1 and 2 shown. The thickness of the flange of this casting is 33 mm, the wall thickness of the housing part is 10 mm and 12 mm. The wall thickness of the part is uneven and the wall - thickness difference is large. The ratio of the thin - wall part of the housing to the overall length, width, and height of the part is 10 - 12:899:650:744, belonging to a large - scale complex thin - wall aluminum alloy housing casting. From the overall structure, the casting process is difficult. Shrinkage cavities, shrinkage porosity, gas holes and other casting defects are likely to appear in the thick - wall part, while misruns, cold shuts and other casting defects are likely to appear in the thin - wall part, resulting in a low yield rate.

[0023] The technical requirements for the high-conductivity aluminum alloy high-voltage electrical appliance housing casting are to improve the conductivity while ensuring the strength required for the use of the housing, so as to meet the demand for the improvement of conductivity in conductor products in the ultra / extra-high voltage power transmission and distribution industry. In addition, in other technical requirements, the demanding party has relatively high requirements for the withstand voltage strength and material density of the parts.

[0024] The applicant of the present invention tried various methods and various material formulas introduced in the above background technology for trial production, but no good results were obtained. It is mainly reflected that the casting yield, conductivity, tensile strength and elongation rate of the aluminum alloy casting cannot be coordinated and matched with each other, and it is difficult to stably meet the requirements in the pressure test and airtightness test. Specifically, using the formulas and methods in the above background technology to manufacture the above large and complex thin-walled aluminum alloy casting, its casting yield is less than 50%, and it is difficult to stably meet the requirements for the withstand voltage strength and material density.

[0025] Through a large number of practical studies, the applicant of the present invention determined the raw material formula for the high-conductivity aluminum alloy high-voltage electrical appliance housing casting of the present invention, including the following components by weight percentage: Si 7.0% - 7.5%, magnesium Mg 0.25% - 0.45%, titanium Ti 0.08% - 0.20%, iron Fe ≤ 0.15%, copper Cu ≤ 0.1%, zinc Zn ≤ 0.1%, manganese Mn ≤ 0.10%, zirconium Zr ≤ 0.20%, tin Sn ≤ 0.01%, lead Pb ≤ 0.03%, and the rest is aluminum Al and inevitable impurities, and the total sum of the inevitable impurities ≤ 0.7%.

[0026] At the same time, the preparation method for the high-conductivity aluminum alloy high-voltage electrical appliance housing casting of the present invention was determined, including the following steps: S1: Initial batching, batch according to the formula requirements, put the prepared aluminum ingots into the melting furnace, evacuate and fill with protective gas, and then heat up to 740 - 750 °C to melt the raw materials; cool down to 715 - 725 °C, stir evenly, and then add the modifier Al-10Sr master alloy, the grain refiner Al-5Ti-1B, rotate the impeller to blow nitrogen and add the sodium-free refining agent for melt treatment, control the Sr content at 0.006% - 0.012%, control the Ti content at 0.08% - 0.20%, the addition amount of the refining agent is 3‰ of the aluminum liquid, the degassing time is not less than 20 minutes, the degassing temperature shall not be lower than 720 - 750 °C, stand for 10 min after degassing, and skim the slag after heat preservation and standing; S2: Hydrogen measurement, use a hydrogen measuring instrument to measure hydrogen. When the density of the solidified sample of the aluminum alloy liquid ≥ 2.62 g / cm 3 , and the temperature of the aluminum alloy liquid is 720 - 730 °C, pour the aluminum alloy liquid into the mold to prepare the casting; at the same time, pour it into the mold to prepare the conductive sample and the tensile sample; S3: Heat-treat the castings, conductive specimens, and tensile specimens obtained in step S2. The heat treatment includes solution treatment and aging treatment. The temperature of the solution treatment is 530 - 540 °C, and the duration is 6 - 10 hours. The temperature of the aging treatment is 200 - 230 °C, and the duration is 6 - 10 hours.

[0027] In step S3, the cooling method for the solution treatment is water cooling, and the cooling method for the aging treatment is air cooling. The protective gas in step S1 is argon. The holding time in step S1 is 15 - 20 minutes. Before pouring in step S2, the mold is preheated to 275 - 285 °C and a mold release agent is sprayed.

[0028] To verify the authenticity and effectiveness of the preparation method in the above specific embodiments, four examples and three comparative examples were set up in the production experiment (referring to the heat treatment process specifications of national standard GB / T1173 - 2013 and existing research reports). The specific processes and results of the examples and comparative examples are as follows: Example 1: S1: Initial batching, batching according to the formula requirements. In the formula, silicon Si is 7.0%, magnesium Mg is 0.25%, titanium Ti is 0.08%, iron Fe ≤ 0.15%, copper Cu ≤ 0.1%, zinc Zn ≤ 0.1%, manganese Mn ≤ 0.10%, zirconium Zr ≤ 0.20%, tin Sn ≤ 0.01%, lead Pb ≤ 0.03%, and the rest is aluminum Al and inevitable impurities; Put the prepared aluminum ingots into a melting furnace. After evacuating and filling with a protective gas, heat up to 740 °C to melt the raw materials. Cool down to 715 °C, stir evenly, then add the modifier Al-10Sr master alloy, the grain refiner Al-5Ti-1B, and carry out melt treatment by blowing nitrogen with a rotating impeller and adding a sodium-free refining agent. Control the Sr content at 0.006%, control the Ti content at 0.08%, the addition amount of the refining agent is 3‰ of the aluminum liquid, the degassing time is not less than 20 minutes, the degassing temperature is not lower than 720 °C, let it stand for 10 min after degassing, and skim the slag after holding. S2: Hydrogen measurement, measure hydrogen using a hydrogen meter. When the density of the solidified specimen of the aluminum alloy liquid ≥ 2.62 g / cm 3 , and the temperature of the aluminum alloy liquid is 720 °C, pour the aluminum alloy liquid into the mold to prepare castings; at the same time, pour it into the mold to prepare conductive specimens and tensile specimens; S3: Heat-treat the castings, conductive specimens, and tensile specimens obtained in step S2. The heat treatment includes solution treatment and aging treatment. The temperature of the solution treatment is 530 °C, and the duration is 8 hours. The temperature of the aging treatment is 230 °C, and the duration is 8 hours.

[0029] The cooling method for solution treatment described in step S3 is water cooling, and the cooling method for aging treatment is air cooling. The protective gas described in step S1 is argon. The mold described in step S2 is preheated to 275 - 285 °C before pouring and a mold release agent is sprayed. Example

[0030] S1: Initial batching. Batching is carried out according to the formula requirements. In the formula, silicon Si is 7.5%, magnesium Mg is 0.45%, titanium Ti is 0.20%, iron Fe ≤ 0.15%, copper Cu ≤ 0.1%, zinc Zn ≤ 0.1%, manganese Mn ≤ 0.10%, zirconium Zr ≤ 0.20%, tin Sn ≤ 0.01%, lead Pb ≤ 0.03%, and the rest is aluminum Al and inevitable impurities. Put the prepared aluminum ingots into a melting furnace. After evacuating and filling with a protective gas, heat up to 750 °C to melt the raw materials; cool down to 725 °C, stir evenly, then add a modifying agent Al-10Sr master alloy, a grain refiner Al-5Ti-1B, blow nitrogen with a rotating impeller and add a sodium-free refining agent for melt treatment. Control the Sr content at 0.012%, control the Ti content at 0.20%, the addition amount of the refining agent is 3‰ of the aluminum liquid, the degassing time is not less than 20 minutes, the degassing temperature shall not be lower than 750 °C, let it stand for 10 min after degassing, and skim the slag after heat preservation and standing. S2: Hydrogen measurement. Measure hydrogen with a hydrogen measuring instrument. When the density of the solidified sample of the aluminum alloy liquid ≥ 2.62 g / cm 3 , and the temperature of the aluminum alloy liquid is 730 °C, pour the aluminum alloy liquid into the mold to prepare a casting; at the same time, pour it into the mold to prepare a conductive sample and a tensile sample. S3: Heat-treat the casting, conductive sample, and tensile sample obtained in step S2. The heat treatment includes solution treatment and aging treatment; the temperature of the solution treatment is 540 °C and the duration is 8 hours; the temperature of the aging treatment is 220 °C and the duration is 8 hours.

[0031] The cooling method for solution treatment described in step S3 is water cooling, and the cooling method for aging treatment is air cooling. The protective gas described in step S1 is argon. The mold described in step S2 is preheated to 275 - 285 °C before pouring and a mold release agent is sprayed. Example

[0032] S1: Initial batching. Batching is carried out according to the formula requirements. In the formula, silicon Si is 7.2%, magnesium Mg is 0.3%, titanium Ti is 0.1%, iron Fe ≤ 0.15%, copper Cu ≤ 0.1%, zinc Zn ≤ 0.1%, manganese Mn ≤ 0.10%, zirconium Zr ≤ 0.20%, tin Sn ≤ 0.01%, lead Pb ≤ 0.03%, and the rest is aluminum Al and inevitable impurities. Put the prepared aluminum ingots into a melting furnace. After evacuating and filling with a protective gas, heat up to 745 °C to melt the raw materials; cool down to 720 °C, stir evenly, then add the modifier Al-10Sr master alloy, the grain refiner Al-5Ti-1B, and use a rotating impeller to blow nitrogen and add a sodium-free refining agent for melt treatment. Control the Sr content at 0.010%, control the Ti content at 0.10%, the addition amount of the refining agent is 3‰ of the aluminum liquid, the degassing time is not less than 20 minutes, the degassing temperature shall not be lower than 730 °C, let it stand for 10 min after degassing, and skim the slag after heat preservation and standing; S2: Hydrogen measurement. Use a hydrogen measuring instrument to measure hydrogen. When the density of the solidified sample of the aluminum alloy liquid ≥ 2.62 g / cm 3 , and when the temperature of the aluminum alloy liquid is 725 °C, pour the aluminum alloy liquid into a mold to prepare a casting; at the same time, pour it into the mold to prepare a conductive sample and a tensile sample; S3: Heat-treat the casting, conductive sample and tensile sample obtained in step S2. The heat treatment includes solution treatment and aging treatment; the temperature of the solution treatment is 535 °C and the duration is 8 hours; the temperature of the aging treatment is 210 °C and the duration is 8 hours.

[0033] In step S3, the cooling method for solution treatment is water cooling, and the cooling method for aging treatment is air cooling. The protective gas in step S1 is argon. The mold in step S2 is preheated to 275 - 285 °C before pouring and a mold release agent is sprayed. Example

[0034] S1: Initial batching. Batch according to the formula requirements. In the formula, silicon Si is 7.4%, magnesium Mg is 0.4%, titanium Ti is 0.15%, iron Fe ≤ 0.15%, copper Cu ≤ 0.1%, zinc Zn ≤ 0.1%, manganese Mn ≤ 0.10%, zirconium Zr ≤ 0.20%, tin Sn ≤ 0.01%, lead Pb ≤ 0.03%, and the rest is aluminum Al and unavoidable impurities; Put the prepared aluminum ingots into a melting furnace. After evacuating and filling with a protective gas, heat up to 748 °C to melt the raw materials; cool down to 718 °C, stir evenly, then add the modifier Al-10Sr master alloy, the grain refiner Al-5Ti-1B, and use a rotating impeller to blow nitrogen and add a sodium-free refining agent for melt treatment. Control the Sr content at 0.008%, control the Ti content at 0.014%, the addition amount of the refining agent is 3‰ of the aluminum liquid, the degassing time is not less than 20 minutes, the degassing temperature shall not be lower than 720 - 750 °C, let it stand for 10 min after degassing, and skim the slag after heat preservation and standing; S2: Hydrogen measurement. Use a hydrogen measuring instrument to measure hydrogen. When the density of the solidified sample of the aluminum alloy liquid ≥ 2.62 g / cm 3 , and when the temperature of the aluminum alloy liquid is 740 °C, pour the aluminum alloy liquid into a mold to prepare a casting; at the same time, pour it into the mold to prepare a conductive sample and a tensile sample; S3: Heat-treat the castings, conductive specimens, and tensile specimens obtained in step S2. The heat treatment includes solution treatment and aging treatment. The temperature of the solution treatment is 530 °C, and the duration is 6 - 10 hours. The temperature of the aging treatment is 200 °C, and the duration is 6 - 10 hours.

[0035] In step S3, the cooling method for the solution treatment is water cooling, and the cooling method for the aging treatment is air cooling. The protective gas in step S1 is argon. In step S2, the mold is preheated to 275 - 285 °C before pouring, and a mold release agent is sprayed.

[0036] Comparative Example 1: S1: Initial batching. Batch according to the formula requirements. In the formula, silicon Si is 7.0%, magnesium Mg is 0.25%, titanium Ti is 0.08%, iron Fe ≤ 0.15%, copper Cu ≤ 0.1%, zinc Zn ≤ 0.1%, manganese Mn ≤ 0.10%, zirconium Zr ≤ 0.20%, tin Sn ≤ 0.01%, lead Pb ≤ 0.03%, and the rest is aluminum Al and unavoidable impurities. Put the prepared aluminum ingots into a melting furnace. After evacuating and filling with a protective gas, heat up to 740 °C to melt the raw materials. Cool down to 715 °C, stir evenly, then add a modifying agent Al-10Sr master alloy, a grain refiner Al-5Ti-1B, and carry out melt treatment by blowing nitrogen with a rotating impeller and adding a sodium-free refining agent. Control the Sr content at 0.006%, control the Ti content at 0.08%, the addition amount of the refining agent is 3‰ of the aluminum liquid, the degassing time is not less than 20 minutes, the degassing temperature shall not be lower than 720 °C, let it stand for 10 min after degassing, and skim the slag after heat preservation and standing. S2: Hydrogen measurement. Measure hydrogen using a hydrogen meter. When the density of the solidified specimen of the aluminum alloy liquid ≥ 2.62 g / cm 3 , and the temperature of the aluminum alloy liquid is 720 °C, pour the aluminum alloy liquid into the mold to prepare castings; at the same time, pour it into the mold to prepare conductive specimens and tensile specimens. S3: Heat-treat the castings, conductive specimens, and tensile specimens obtained in step S2. The heat treatment includes solution treatment and aging treatment. The temperature of the solution treatment is 535 °C, and the duration is 8 hours. The temperature of the aging treatment is 160 °C, and the duration is 8 hours.

[0037] In step S3, the cooling method for the solution treatment is water cooling, and the cooling method for the aging treatment is air cooling. The protective gas in step S1 is argon. In step S2, the mold is preheated to 275 - 285 °C before pouring, and a mold release agent is sprayed.

[0038] Comparative Example 2: S1: Initial batching, batching according to the formula requirements. In the formula, Si is 7.0%, Mg is 0.25%, Ti is 0.08%, Fe ≤ 0.15%, Cu ≤ 0.1%, Zn ≤ 0.1%, Mn ≤ 0.10%, Zr ≤ 0.20%, Sn ≤ 0.01%, Pb ≤ 0.03%, and the rest are Al and inevitable impurities; Put the prepared aluminum ingot into the melting furnace. After evacuating and filling with protective gas, heat up to 740 °C to melt the raw materials; cool down to 715 °C, stir evenly, then add the modifier Al-10Sr master alloy, the grain refiner Al-5Ti-1B, blow nitrogen with a rotating impeller and add a sodium-free refining agent for melt treatment. Control the Sr content at 0.006%, control the Ti content at 0.08%, the addition amount of the refining agent is 3‰ of the aluminum liquid, the degassing time is not less than 20 minutes, the degassing temperature shall not be lower than 720 °C, let it stand for 10 min after degassing, and skim the slag after heat preservation and standing; S2: Hydrogen measurement, measure hydrogen with a hydrogen measuring instrument. When the density of the solidified sample of the aluminum alloy liquid ≥ 2.62 g / cm 3 , and the temperature of the aluminum alloy liquid is at 720 °C, pour the aluminum alloy liquid into the mold to prepare castings; at the same time, pour it into the mold to prepare conductive specimens and tensile specimens; S3: Heat-treat the castings, conductive specimens and tensile specimens obtained in step S2. The heat treatment includes solution treatment and aging treatment; the temperature of the solution treatment is 530 °C and the duration is 8 hours; the temperature of the aging treatment is 170 °C and the duration is 8 hours.

[0039] In step S3, the cooling method for the solution is water cooling, and the cooling method for the aging treatment is air cooling. The protective gas in step S1 is argon. The mold in step S2 is preheated to 275 - 285 °C before pouring and a mold release agent is sprayed.

[0040] Comparative example 3: S1: Initial batching, batching according to the formula requirements. In the formula, Si is 7.0%, Mg is 0.25%, Ti is 0.08%, Fe ≤ 0.15%, Cu ≤ 0.1%, Zn ≤ 0.1%, Mn ≤ 0.10%, Zr ≤ 0.20%, Sn ≤ 0.01%, Pb ≤ 0.03%, and the rest are Al and inevitable impurities; Put the prepared aluminum ingots into a melting furnace. After evacuating and filling with a protective gas, heat up to 740 °C to melt the raw materials; cool down to 715 °C, stir evenly, then add the modifying agent Al-10Sr master alloy, the grain refiner Al-5Ti-1B, and use a rotating impeller to blow nitrogen and add a sodium-free refining agent for melt treatment. Control the Sr content at 0.006% and the Ti content at 0.08%. The addition amount of the refining agent is 3‰ of the aluminum liquid. The degassing time is not less than 20 minutes, the degassing temperature shall not be lower than 720 °C, let it stand for 10 minutes after degassing, and skim the slag after heat preservation and standing; S2: Measure hydrogen. Use a hydrogen measuring instrument to measure hydrogen. When the density of the solidified sample of the aluminum alloy liquid ≥ 2.62 g / cm 3 , and when the temperature of the aluminum alloy liquid is 720 °C, pour the aluminum alloy liquid into a mold to prepare a casting; at the same time, pour it into the mold to prepare a conductive sample and a tensile sample; S3: Perform heat treatment on the castings, conductive samples, and tensile samples obtained in step S2. The heat treatment includes solution treatment and aging treatment; the temperature of the solution treatment is 535 °C, and the duration is 8 hours; the temperature of the aging treatment is 180 °C, and the duration is 8 hours.

[0041] The cooling method for the solution in step S3 is water cooling, and the cooling method for the aging treatment is air cooling. The protective gas in step S1 is argon. The mold in step S2 is preheated to 275 - 285 °C before pouring, and a mold release agent is sprayed.

[0042] Through tests, the performance of the high conductivity aluminum alloy high voltage electrical appliance housing castings prepared by the above formula and method of the present invention is shown in Table 1 below: Table 1: Heat treatment method and performance table of high conductivity aluminum alloy high voltage electrical appliance housing castings

[0043] The applicant of the present invention believes that the reason why the high conductivity aluminum alloy high voltage electrical appliance housing castings of the present application can achieve the following effects is mainly based on the following theoretical basis of the applicant: The casting fluidity of traditional aluminum-silicon alloys is mainly affected by the silicon content. When the silicon content is controlled near the eutectic point of 11-13 wt%, the aluminum-silicon alloy can have a narrow solidification range, which can significantly improve the fluidity of the melt. For example, for the casting aluminum alloy ADC12 with the largest usage ratio, its silicon content is generally about 12%. ADC12 has good casting forming performance and low hot cracking tendency, enabling it to form complex thin-walled parts through the casting process. On the other hand, the conductivity of aluminum alloys decreases significantly with the increase of silicon content. For a pure Al-Si binary alloy, when the silicon content is 12%, the relative conductivity is about 21.9-24.3% IACS. When the silicon content is reduced to about 7%, the relative conductivity is 33.9% IACS-36.3% IACS. When the silicon content is reduced to about 2%, the conductivity is 45.1% IACS-49.2% IACS. On the other hand, if the fluidity at a silicon content of 12% is set to 100, the fluidity at a silicon content of 2% is about 55. It can be seen that although the conductivity is greatly improved when the silicon content is 2%, due to its low fluidity, it is difficult to adapt to the casting of complex thin-walled large structural parts and can only form relatively simple small parts.

[0044] From the analysis of the conductivity principle of aluminum alloys, it can be known that for aluminum alloy materials with a silicon content of 0%-4%, due to the small number of silicon phases with poor conductivity, a complete network fails to wrap the aluminum grains, making the overall conductivity of the material significantly better than that of aluminum alloys with a silicon content of more than 7%. For aluminum alloys with a silicon content less than 4%, the main influencing factor of conductivity is the defects in the crystal lattice of the aluminum matrix metal crystal lattice, the lattice distortion caused by solute atoms or precipitated phases, which accounts for about 70% of the influencing factors of conductivity. These lattice distortions cause changes in the electric field period, resulting in an increase in the scattering probability of free electrons, a decrease in the average free path of electrons, and a decrease in the conductivity of the alloy. The secondary influencing factor of the conductivity of such materials is the microstructure and distribution uniformity of the relevant precipitated second phase. For example, when the morphology of eutectic silicon changes from coarse plate-like to fine fibrous, the scattering probability of free electrons decreases, which is beneficial to the improvement of the conductivity of the material.

[0045] After fully considering the above theoretical basis of the applicant, the implementation of the present invention mainly controls from several aspects such as composition control, modification, melt purification, and heat treatment of material properties, so that the material reaches a high conductivity, while ensuring a high casting yield, and at the same time ensuring the strength and plasticity requirements of the material to ensure the coordinated unity of its four technical indicators.

[0046] First, the present invention controls the silicon content at 7.0 - 7.5%, which can enable the aluminum-silicon alloy to have basic fluidity and reduce the volume shrinkage rate during solidification. The Ni component is not added to avoid the decrease in the conductivity of aluminum alloy castings, enabling it to form complex thin-walled parts through the casting process. The Fe element is controlled at Fe ≤ 0.15%, mainly to prevent sticking to the mold during casting. Appropriate amounts of Mg, Zn, and Cu elements are added to improve the strength of the material to meet a wider range of uses, while their impact on the conductivity is slight.

[0047] Secondly, during the casting process of the present invention, a modifier Al-10Sr master alloy containing Sr is also added. The purpose is to modify the eutectic silicon, changing it from flaky to fine fibrous, which is beneficial to the improvement of the conductivity. The modification effect of Sr generally only lasts for about 4 hours. After adding Sr, casting or pouring should be carried out as soon as possible to avoid the loss of Sr. If the Sr loss is serious due to long-term heat preservation, Sr should be replenished before casting.

[0048] In addition, different elements have different degrees of damage to the conductivity when dissolved in the aluminum matrix. Among them, the dissolution of elements such as Cr, Mn, V, and Ti significantly damages the conductivity of aluminum. When they are dissolved in the aluminum matrix, they strongly absorb the free electrons in the aluminum matrix to fill the incomplete electron layers of Cr, Mn, V, and Ti, resulting in a reduction in the free electrons available for conduction. In the solution state, the harmful effect of every 1% (Cr + Mn + V + Ti) on the conductivity is 5 times that of every 1% silicon on the conductivity of aluminum. Therefore, the content of Cr + Mn + V + Ti in the aluminum alloy with high conductivity requirements should be less than 0.01%. During the casting process of this application, a refining agent containing titanium and boron and a modifier Al-10Sr master alloy are also added. While improving the conductivity of aluminum alloy castings, it ensures the fluidity of the aluminum-silicon alloy and reduces the volume shrinkage rate during solidification, thereby increasing the yield of large-sized high-voltage electrical appliance housing castings with complex thin-walled aluminum alloys.

[0049] Finally, on the basis of increasing the yield of large-sized complex thin-walled aluminum alloy high-voltage electrical appliance housing castings, the present invention optimizes the heat treatment process of the high-voltage electrical appliance housing castings, improving the conductivity of the housing castings. This application uses a method of solution treatment plus aging treatment. The temperature of the solution treatment is 530 - 540 °C, and the duration is 6 - 10 hours; the temperature of the aging treatment is 200 - 230 °C, and the duration is 6 - 10 hours. After the above heat treatment, the conductivity, mechanical properties, and yield of the high-conductivity aluminum alloy high-voltage electrical appliance housing castings of the present invention are as shown in Table 1 above.

[0050] It can be seen from the comparison between the examples and the comparative examples that the cast aluminum alloy of the present invention not only has a high conductivity, but also has high mechanical properties and high finished product rate. As can be seen from Table 1, the conductivity of the high-voltage electrical housing casting of the present invention is ≥41.11% IACS, the tensile strength is ≥221 MPa, the elongation rate is ≥7.65%, and the casting finished product rate reaches more than 95%.

[0051] The preparation method described in the preparation method of the present invention is simple and easy to control.

[0052] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

Claims

1. A high conductivity aluminum alloy high voltage electrical appliance housing casting, characterized in that: The composition includes the following components in weight percentage: Si 7.0% to 7.5%, magnesium Mg 0.25% to 0.45%, titanium Ti 0.08% to 0.20%, iron Fe ≤ 0.15%, copper Cu ≤ 0.1%, zinc Zn ≤ 0.1%, manganese Mn ≤ 0.10%, zirconium Zr ≤ 0.20%, tin Sn ≤ 0.01%, lead Pb ≤ 0.03%, and the rest is aluminum Al and unavoidable impurities; S1: Initial batching, batching is carried out according to the formula requirements, and the prepared aluminum ingots are placed in the smelting furnace, vacuumed and filled with protective gas, and then the temperature is raised to 740-750℃ to melt the raw materials; the temperature is lowered to 715-725℃ and stirred evenly, and then the modifier Al-10Sr master alloy, the refiner Al-5Ti-1B, the rotating impeller blowing nitrogen and the sodium-free refining agent are added for melt treatment, and the Sr content is controlled at 0.006%-0.012%, and the Ti content is controlled at 0.08%-0.20%. The amount of refining agent added is 3‰ of the aluminum liquid, the degassing time is not less than 20 minutes, and the degassing temperature shall not be lower than 720-750℃. After degassing, it is allowed to stand for 10 minutes, and the slag is removed after being kept warm and standing; S2: Hydrogen measurement, hydrogen is measured using a hydrogen meter. When the density of the aluminum alloy liquid solidification sample is ≥2.62g / cm3 and the temperature is 720-730℃, the aluminum alloy liquid is poured into the mold to prepare the casting; S3: heat treating the casting obtained in step S2, wherein the heat treatment includes solution treatment and aging treatment; the temperature of the solution treatment is 530-540°C and the duration is 6-10 hours; the temperature of the aging treatment is 200-230°C and the duration is 6-10 hours.

2. The high conductivity aluminum alloy high voltage electrical appliance housing casting according to claim 1 is characterized in that: The sum of the unavoidable impurities is ≤0.7%.

3. A method for preparing a high conductivity aluminum alloy high voltage electrical appliance housing casting as claimed in claim 1 or 2, the steps of the method are: S1: Initial batching: batch the materials according to the formula requirements, and put the prepared aluminum ingots into the melting furnace. After vacuuming and filling with protective gas, heat it to 740-750℃ to melt the raw materials; cool it to 715-725℃, stir it evenly, add the modifier Al-10Sr master alloy, the refiner Al-5Ti-1B, the rotating impeller blowing nitrogen and the sodium-free refining agent for melt treatment, control the Sr content at 0.006%-0.012%, control the Ti content at 0.08%-0.20%, and the refining agent is added in an amount of 3‰ of the aluminum liquid. The degassing time is not less than 20 minutes, and the degassing temperature shall not be lower than 720-750℃. After degassing, let it stand for 10 minutes, keep it warm and stand it for slag removal; S2: Hydrogen measurement, using a hydrogen meter to measure hydrogen, when the density of the aluminum alloy liquid solidification sample is ≥2.62g / cm 3 When the temperature is between 720°C and 730°C, the aluminum alloy liquid is poured into the mold to prepare the casting; S3: heat treating the casting obtained in step S2, wherein the heat treatment includes solution treatment and aging treatment; the temperature of the solution treatment is 530-540°C and the duration is 6-10 hours; the temperature of the aging treatment is 200-230°C and the duration is 6-10 hours.

4. The method for preparing a high conductivity aluminum alloy casting according to claim 3, characterized in that: The cooling method of the solid solution in step S3 is water cooling.

5. The method for preparing a high conductivity aluminum alloy casting according to claim 3, characterized in that: The cooling method of the aging treatment in step S3 is air cooling.

6. The method for preparing a high conductivity aluminum alloy casting according to claim 3, characterized in that: The protective gas in step S1 is argon.

7. The method for preparing a high conductivity aluminum alloy casting according to claim 3, characterized in that: The heat preservation and standing time in step S1 is 15 to 20 minutes.

8. The method for preparing a high conductivity aluminum alloy casting according to claim 3, characterized in that: In step S2, the mold is preheated to 275-285° C. before pouring and sprayed with a release agent.

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