Preparation method of high-purity oxygen-free copper rod for flat wire motor of new energy automobile

Abstract

The invention discloses a preparation method of a high-purity oxygen-free copper rod for a flat wire motor of a new energy automobile, and belongs to the technical field of copper rod preparation, and the preparation method comprises the following preparation steps: S1, raw material pretreatment: carrying out surface cleaning and drying treatment on a high-purity cathode copper plate; s2, smelting treatment: smelting the pretreated cathode copper plate under the protection of vacuum or inert gas; s3, continuous casting and rolling, wherein a casting blank is obtained through an up-drawing continuous casting method or a wheel belt continuous casting method; s4, anaerobic treatment: carrying out online annealing and cooling in a protective atmosphere; and S5, finishing treatment is conducted, specifically, a copper rod finished product with the surface smoothness Ra smaller than or equal to 0.8 micrometer is obtained through drawing and polishing. According to the preparation method of the high-purity oxygen-free copper rod for the flat wire motor of the new energy automobile, a foundation is laid for preparing the high-purity copper rod through strict raw material pretreatment; and by adding the fused salt with specific components, copper is effectively prevented from being in contact with oxygen, oxidation hydrogen absorption is reduced, the purity and quality of the copper rod are remarkably improved, and the advantage of high preparation quality is achieved.

Description

Technical Field

[0001] This invention relates to the field of copper rod preparation technology, specifically a method for preparing high-purity oxygen-free copper rods for flat wire motors in new energy vehicles. Background Technology

[0002] With the rapid development of the new energy vehicle industry, the performance requirements for drive motors, as their core components, are becoming increasingly stringent. Flat wire motors, with their significant advantages such as high power density, high efficiency, and miniaturization, are gradually becoming the mainstream development direction for drive motors in new energy vehicles. In flat wire motors, the flat wire winding is a key component, and high-purity oxygen-free copper rod is the basic material for manufacturing the flat wire winding.

[0003] New energy vehicles, especially motor systems using 800V and above high-voltage platforms, place extremely stringent demands on the performance of copper rods. In terms of conductivity, the copper rods must possess extremely low resistivity to reduce energy losses during transmission, improve motor efficiency, and thus extend the driving range of new energy vehicles. Regarding purity, the copper rods need to have ultra-high purity, with strict control over the content of impurity elements. This is because impurity elements can form scattering centers, increasing resistance to electron movement, reducing conductivity, and potentially affecting the mechanical and processing properties of the copper rods.

[0004] Traditional copper rod manufacturing methods have several shortcomings in meeting the performance requirements of flat wire motors for new energy vehicles. In the raw material pretreatment stage, traditional methods may only employ a single cleaning method, which is insufficient to completely remove impurities and oxides from the surface of high-purity cathode copper plates. This leads to impurities being incorporated into the copper rod during subsequent processing, affecting its purity. During the smelting process, traditional methods are typically carried out under a normal atmosphere, which easily causes copper to react with oxygen in the air, resulting in an increased oxygen content in the copper rod. Furthermore, traditional smelting methods lack precise control over smelting temperature and time, potentially failing to achieve uniform melting of the copper liquid and affecting the microstructure and performance uniformity of the copper rod. In the continuous casting and rolling stage, the traditional process lacks precise control over the casting speed and rolling passes, easily leading to defects such as cracks and porosity in the billet and copper rod, affecting the mechanical properties of the copper rod. Simultaneously, the rolling temperature control is not strict enough, which may result in uneven grain size in the copper rod, reducing its strength and toughness. In terms of oxygen-free processing, traditional methods struggle to control the oxygen content in copper rods to extremely low levels, failing to meet the stringent oxygen content requirements of flat wire motors for new energy vehicles. During finishing, traditional drawing processes lack scientific basis for controlling drawing temperature and the number of drawing passes, easily leading to defects such as scratches and cracks on the copper rod surface, affecting its surface quality and processing performance.

[0005] Therefore, there is an urgent need to develop a method for preparing high-purity oxygen-free copper rods with ultra-low oxygen content, high strength and high conductivity, and excellent surface quality, in order to meet the stringent requirements of flat wire motors for key materials in new energy vehicles. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for preparing high-purity oxygen-free copper rods for flat wire motors in new energy vehicles. This method offers advantages such as high preparation quality, high preparation efficiency, and good energy-saving and environmental benefits, thus solving the problems mentioned in the background section.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for preparing a high-purity oxygen-free copper rod for a flat wire motor in new energy vehicles includes the following preparation steps:

[0009] S1. Raw material pretreatment: The high-purity cathode copper plate is surface cleaned and dried.

[0010] S2. Melting treatment: The pretreated cathode copper plate is melted under vacuum or inert gas protection, and the melting temperature is controlled at 1150-1250℃.

[0011] S3. Continuous casting and rolling: The billet is obtained by using the upward continuous casting method or the wheel belt continuous casting method, and then multiple passes of continuous rolling are performed, with the rolling temperature maintained at 800-950℃.

[0012] S4. Oxygen-free treatment: Online annealing and cooling are carried out in a protective atmosphere, with the oxygen content controlled to ≤5ppm;

[0013] S5. Finishing: A copper rod with a surface finish Ra≤0.8μm is obtained through drawing and polishing;

[0014] The relationship between drawing temperature and number of drawing passes follows the formula M=(4.7-8.6)×N, where M is the difference between the drawing temperature and the recrystallization temperature of the billet, and N is the number of drawing passes.

[0015] Furthermore, the purity of the high-purity cathode copper plate in S1 is ≥99.99%; the surface cleaning in S1 adopts a combination of acid washing and ultrasonic cleaning; the drying treatment in S1 is carried out at 80-120℃ for 30-60 minutes.

[0016] Furthermore, the smelting equipment in S2 is a vacuum induction furnace; the vacuum degree in S2 is ≤10. -3 Pa, or high-purity argon as a protective gas; rare earth elements are added for microalloying during the smelting process in S2, with an addition amount of 0.01-0.05wt.

[0017] Furthermore, the continuous casting speed in S3 is 0.5-1.5 m / min; the number of continuous rolling passes in S3 is 8-12; and the final rolling temperature in S3 is controlled at 800±20℃.

[0018] Furthermore, the protective atmosphere in S4 is a nitrogen-hydrogen mixture with a hydrogen content of 2-5%; the annealing temperature in S4 is 450-550℃ for 2-4 hours; and rapid cooling is used in S4 with a cooling rate ≥100℃ / min.

[0019] Furthermore, the drawing deformation in S5 is 80-90%; S5 employs multi-pass continuous drawing, with the deformation per pass controlled at 15-25%; and S5 uses electrolytic polishing or mechanical polishing for polishing.

[0020] Furthermore, molten salt may be added during the S2 smelting process, and the molten salt comprises, by weight percentage:

[0021] Sodium fluorosilicate 17-30%, anhydrous borax 10-25%, calcium fluoride 5-10%, cryolite 15-30%, rare earth carbonate 12-25%, lithium oxide 5-10%, and titanium dioxide 1-5%.

[0022] Furthermore, the method for preparing the molten salt is as follows:

[0023] Sodium fluorosilicate, anhydrous borax, calcium fluoride, cryolite, rare earth carbonate, lithium oxide, and titanium dioxide are added to a stainless steel crucible according to the above weight percentages. The crucible is kept at 250-280℃ for 3-5 hours and then ground in a ball mill at 300-400 r / min for 4-6 hours. After casting, molten salt is obtained. The amount of molten salt is 0.15-0.25% of the mass of electrolytic copper.

[0024] This invention also provides a high-purity oxygen-free copper rod for flat wire motors in new energy vehicles, comprising:

[0025] Oxygen content ≤3ppm;

[0026] Hydrogen content ≤1ppm;

[0027] Surface finish Ra≤0.6μm;

[0028] Grain size ≥ 0.05 mm;

[0029] Total impurity element content ≤30ppm;

[0030] The content of a single impurity element is ≤5ppm;

[0031] Room temperature resistivity ≤ 1.724 × 10⁻⁶ -8 Ω·m.

[0032] This invention also provides an application of high-purity oxygen-free copper rod for the manufacture of flat wire windings for drive motors in new energy vehicles, which is particularly suitable for motor systems on high-voltage platforms of 800V and above.

[0033] Compared with the prior art, the present invention provides a method for preparing high-purity oxygen-free copper rods for flat wire motors in new energy vehicles, which has the following beneficial effects:

[0034] 1. This method for preparing high-purity oxygen-free copper rods for flat wire motors in new energy vehicles involves rigorous raw material pretreatment, employing a combination of acid washing and ultrasonic cleaning to thoroughly remove impurities and oxides from the surface of the high-purity cathode copper plate, laying the foundation for preparing high-purity copper rods. Furthermore, by adding molten salts of specific components, contact between copper and oxygen is effectively prevented, reducing oxidation and hydrogen absorption. This controls the oxygen content in the copper rod to ≤3ppm and the hydrogen content to ≤1ppm, significantly lower than copper rods prepared using traditional methods. This method significantly improves the purity and quality of the copper rod, achieving the advantage of high-quality preparation.

[0035] 2. This method for preparing high-purity oxygen-free copper rods for flat wire motors in new energy vehicles ensures the uniformity of the copper rod's microstructure and performance by precisely controlling various process parameters during the preparation process, thereby improving the product's qualification rate and stability. The method also allows for the reasonable determination of drawing temperature and drawing passes through formula calculations, avoiding surface defects and performance degradation of the copper rod caused by improper drawing processes, thus improving drawing efficiency and quality and achieving the advantage of high preparation efficiency.

[0036] 3. The method for preparing high-purity oxygen-free copper rods for flat wire motors in new energy vehicles, through rapid continuous casting and rolling and online annealing processes, is estimated to reduce energy consumption by more than 30% compared to traditional multi-pass intermittent production; the molten salt system and process used produce no toxic or harmful gas emissions, meeting the requirements of green manufacturing and achieving the advantages of good energy-saving and environmental protection benefits. Attached Figure Description

[0037] Figure 1 This is a schematic flowchart illustrating a method for preparing high-purity oxygen-free copper rods for flat wire motors in new energy vehicles, as proposed in this invention. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1 (Standard Preparation Process):

[0040] Please see Figure 1This embodiment describes a method for preparing a high-purity oxygen-free copper rod for a flat wire motor in new energy vehicles, which includes the following raw materials and equipment:

[0041] Main ingredients:

[0042] High-purity cathode copper plate: purity 99.995% (compliant with GB / T 467-2010 standard);

[0043] Rare earth additive: Cerium-Lanternium mixed rare earth (Ce:La=1:1);

[0044] Protective gas: High-purity argon (99.999% purity);

[0045] Molten salt composition: sodium fluorosilicate 22%, anhydrous borax 18%, calcium fluoride 8%, cryolite 20%, rare earth carbonate 18%, lithium oxide 8%, titanium dioxide 4%.

[0046] Main equipment:

[0047] Vacuum induction melting furnace (capacity 500kg);

[0048] Tire continuous casting unit (casting speed adjustable);

[0049] Three-roll Y-type continuous rolling mill (8 passes);

[0050] Protective atmosphere annealing furnace (nitrogen-hydrogen mixed atmosphere);

[0051] Multi-die drawing machine (21 dies continuous drawing);

[0052] Electrolytic polishing production line.

[0053] In this embodiment, the method for preparing high-purity oxygen-free copper rods includes the following preparation steps:

[0054] S1. Raw material pretreatment:

[0055] S1-1, Pickling treatment:

[0056] Use a 10% sulfuric acid solution at a temperature of 60℃;

[0057] Processing time: 5 minutes;

[0058] Remove the surface oxide layer and impurities.

[0059] S1-2, Ultrasonic Cleaning:

[0060] Frequency: 40kHz;

[0061] Time: 10 minutes;

[0062] Cleaning agent: deionized water + neutral detergent.

[0063] S1-3. Drying treatment:

[0064] Temperature: 100±5℃;

[0065] Time: 45 minutes;

[0066] Moisture content: ≤50ppm.

[0067] S2, Smelting process:

[0068] S2-1, Smelting parameters:

[0069] Melting temperature: 1200℃;

[0070] Vacuum level: 5e -4 Pa;

[0071] Rare earth content: 0.03wt%.

[0072] S2-2, Preparation and addition of molten salt:

[0073] Weigh each component according to the formula and keep it at 265℃ for 4 hours;

[0074] Ball milling treatment: 350 r / min, 5 hours;

[0075] Dosage: 0.2% of the copper material mass.

[0076] S2-3, Smelting process:

[0077] First, evacuate to a vacuum level of 5×10. -4 Pa;

[0078] High-purity argon gas was introduced to a positive pressure of 0.05 MPa;

[0079] Add rare earth elements and molten salt;

[0080] Refining time: 30 minutes.

[0081] S3, Continuous casting and rolling:

[0082] S3-1, Continuous casting process:

[0083] Casting speed: 1.0 m / min;

[0084] Cooling water pressure: 0.3MPa.

[0085] S3-2, Continuous rolling process:

[0086] Rolling passes: 10;

[0087] Rolling temperature: 920℃;

[0088] Final rolling temperature: 810℃;

[0089] Deformation per pass: 25%, 23%, 21%, 19%, 17%, 15%, 13%, 11%, 9%, 7%.

[0090] S4, Anaerobic treatment:

[0091] S4-1 Annealing process:

[0092] Atmosphere: 95% N2 + 5% H2;

[0093] Temperature: 500℃;

[0094] Time: 3 hours;

[0095] Cooling rate: 120℃ / min.

[0096] S4-2, Oxygen Content Control:

[0097] Online oxygen content monitoring: 2.8 ppm;

[0098] Hydrogen content: 0.8 ppm.

[0099] S5. Finishing process:

[0100] S5-1, Drawing process:

[0101] Total deformation: 85%;

[0102] Deformation per pass: 18-22%;

[0103] Pulling rounds: 21;

[0104] Drawing temperature control: Calculated according to the formula M=(4.7-8.6)×N, with a coefficient of 6.5, and the recrystallization temperature is set to 200℃.

[0105] S5-2 Polishing process:

[0106] Electrolytic polishing was employed.

[0107] Polishing solution: a mixture of phosphoric acid and sulfuric acid;

[0108] Surface finish: Ra 0.55μm.

[0109] In this embodiment, the performance test results of the high-purity oxygen-free copper rod are shown in Table 1.

[0110] Table 1

[0111]

[0112] In this embodiment, the implementation effects are compared as shown in Table 2.

[0113] Table 2

[0114]

[0115] Example 2 (High-end application formulation):

[0116] The method for preparing a high-purity oxygen-free copper rod for a flat wire motor in new energy vehicles in this embodiment differs from that in Embodiment 1 in that:

[0117] 1. Rare earth element addition optimization:

[0118] High-purity cerium (99.9%) is used;

[0119] The addition amount was increased to 0.05 wt%.

[0120] 2. Molten salt formula adjustment:

[0121] Increase lithium oxide to 10%;

[0122] Reduce anhydrous borax to 15%.

[0123] 3. Performance Improvement:

[0124] Electrical conductivity: 102.3% IACS;

[0125] Tensile strength: 268MPa.

[0126] Example 3 (Economic Formula):

[0127] The method for preparing a high-purity oxygen-free copper rod for a flat wire motor in new energy vehicles in this embodiment differs from that in Embodiment 1 in that:

[0128] 1. Raw material adjustment:

[0129] Cathode copper purity: 99.99%;

[0130] Rare earth content: 0.01wt%.

[0131] 2. Simplified process:

[0132] The number of pull-out stages has been reduced to 16.

[0133] Polishing was changed to mechanical polishing.

[0134] 3. Cost reduction:

[0135] Raw material costs reduced by 15%;

[0136] It still meets the basic performance requirements.

[0137] It should be noted that the key process control points of the above embodiments 1-3 are described as follows:

[0138] 1. Smelting control:

[0139] Vacuum degree fluctuation range: ±0.1×10 -3 Pa;

[0140] Temperature control accuracy: ±5℃.

[0141] 2. Rolling control:

[0142] The final rolling temperature is controlled at 810±10℃;

[0143] Deformation error per pass: ≤±1%.

[0144] 3. Drawing temperature control:

[0145] Strictly follow the formula M=(4.7-8.6)×N;

[0146] Select the adjustment coefficient based on the specifications of the copper rod.

[0147] 4. Atmosphere control:

[0148] The hydrogen content is controlled at 5±0.5%;

[0149] Dew point temperature: ≤-60℃.

[0150] It should be noted that the exception handling schemes of the above embodiments 1-3 are explained as follows:

[0151] 1. Oxygen content exceeds the standard:

[0152] Check the sealing of the smelting furnace;

[0153] Adjust the amount of molten salt added.

[0154] 2. Surface defects:

[0155] Adjust the angle of the drawing die;

[0156] Optimize polishing process parameters.

[0157] 3. Uneven performance:

[0158] Check the temperature uniformity of continuous rolling;

[0159] Adjust the distribution of deformation amount per pass.

[0160] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0161] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high-purity oxygen-free copper rod for a flat wire motor in new energy vehicles, characterized in that, The preparation steps include the following: S1. Raw material pretreatment: The high-purity cathode copper plate is surface cleaned and dried. S2. Melting treatment: The pretreated cathode copper plate is melted under vacuum or inert gas protection, and the melting temperature is controlled at 1150-1250℃. S3. Continuous casting and rolling: The billet is obtained by using the upward continuous casting method or the wheel belt continuous casting method, and then multiple passes of continuous rolling are performed, with the rolling temperature maintained at 800-950℃. S4. Oxygen-free treatment: Online annealing and cooling are carried out in a protective atmosphere, with the oxygen content controlled to ≤5ppm; S5. Finishing: A copper rod with a surface finish Ra≤0.8μm is obtained through drawing and polishing; The relationship between drawing temperature and number of drawing passes follows the formula M=(4.7-8.6)×N, where M is the difference between the drawing temperature and the recrystallization temperature of the billet, and N is the number of drawing passes.

2. The method for preparing a high-purity oxygen-free copper rod for a flat wire motor in new energy vehicles according to claim 1, characterized in that, The purity of the high-purity cathode copper plate in S1 is ≥99.99%; the surface cleaning in S1 adopts a combination of acid washing and ultrasonic cleaning; the drying treatment in S1 is carried out at 80-120℃ for 30-60 minutes.

3. The method for preparing a high-purity oxygen-free copper rod for a flat wire motor in new energy vehicles according to claim 1, characterized in that: The smelting equipment in S2 is a vacuum induction furnace; the vacuum degree in S2 is ≤10. -3 Pa, or high-purity argon as a protective gas; rare earth elements are added for microalloying during the smelting process in S2, with an addition amount of 0.01-0.05wt.

4. The method for preparing a high-purity oxygen-free copper rod for a flat wire motor in new energy vehicles according to claim 1, characterized in that, The continuous casting speed in S3 is 0.5-1.5 m / min; the number of continuous rolling passes in S3 is 8-12; and the final rolling temperature in S3 is controlled at 800±20℃.

5. The method for preparing a high-purity oxygen-free copper rod for a flat wire motor in new energy vehicles according to claim 1, characterized in that: The protective atmosphere in S4 is a nitrogen-hydrogen mixture with a hydrogen content of 2-5%; the annealing temperature in S4 is 450-550℃ for 2-4 hours; and rapid cooling is used in S4 with a cooling rate ≥100℃ / min.

6. The method for preparing a high-purity oxygen-free copper rod for a flat wire motor in new energy vehicles according to claim 1, characterized in that: The drawing deformation in S5 is 80-90%; S5 uses multi-pass continuous drawing, and the deformation per pass is controlled at 15-25%; S5 uses electrolytic polishing or mechanical polishing.

7. The method for preparing a high-purity oxygen-free copper rod for a flat wire motor in new energy vehicles according to claim 1, characterized in that, Molten salt may also be added during the S2 smelting process, and the molten salt comprises, by weight percentage: Sodium fluorosilicate 17-30%, anhydrous borax 10-25%, calcium fluoride 5-10%, cryolite 15-30%, rare earth carbonate 12-25%, lithium oxide 5-10%, and titanium dioxide 1-5%.

8. The method for preparing a high-purity oxygen-free copper rod for a flat wire motor in new energy vehicles according to claim 7, characterized in that, The method for preparing the molten salt is as follows: Sodium fluorosilicate, anhydrous borax, calcium fluoride, cryolite, rare earth carbonate, lithium oxide, and titanium dioxide are added to a stainless steel crucible according to the above weight percentages. The crucible is kept at 250-280℃ for 3-5 hours and then ground in a ball mill at 300-400 r / min for 4-6 hours. After casting, molten salt is obtained. The amount of molten salt is 0.15-0.25% of the mass of electrolytic copper.

9. A high-purity oxygen-free copper rod for a flat-wire motor in new energy vehicles, prepared by the method for preparing a high-purity oxygen-free copper rod for a flat-wire motor in new energy vehicles according to any one of claims 1-8, characterized in that, include: Oxygen content ≤3ppm; Hydrogen content ≤1ppm; Surface finish Ra≤0.6μm; Grain size ≥ 0.05 mm; Total impurity element content ≤30ppm; The content of a single impurity element is ≤5ppm; Room temperature resistivity ≤ 1.724 × 10⁻⁶ -8 Ω·m.

10. An application of the high-purity oxygen-free copper rod as described in claim 9, characterized in that, Used for manufacturing flat wire windings for drive motors in new energy vehicles, especially suitable for motor systems on high voltage platforms of 800V and above.

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