Highly flexible enameled copper round wire and method for manufacturing the same

Abstract

The present application belongs to the technical field of enameled copper round wire, and particularly relates to a high-softness enameled copper round wire and a preparation method thereof, which comprises the following steps: low-oxygen copper rod material selection and inspection, continuous drawing and continuous annealing to prepare soft wire blank, multi-pass drawing, annealing, painting and repeated baking of a continuous drawing and continuous enameling machine, and sample performance inspection and microstructure detection after cooling; meanwhile, the low-oxygen copper rod and the soft wire blank are limited in terms of yield ratio and elongation, and key process parameters of drawing, annealing and painting and baking are limited, and the finished product is required to have an average grain size of greater than or equal to 9.0 microns, a dislocation density of less than or equal to 1*10 14 m ‑2 The present application improves the softness of the enameled copper round wire by accurately limiting the performance of the base material and the process parameters, solves the problems of hard wire, easy breakage and serious springback during winding, and has the advantages of simple operation and stable mass production.

Description

Technical Field

[0001] This invention belongs to the technical field of enameled copper round wire, specifically relating to a highly flexible enameled copper round wire and its preparation method, which is suitable for the industrial production of enameled copper round wires used in compressors, power tools, digital motors and other fields. Background Technology

[0002] With the increasing level of industrial automation, products such as compressors, power tools, and digital motors are developing towards lightweight, miniaturization, and high performance. Downstream manufacturers generally adopt high-speed winding machines with linear speeds exceeding 1000m / min to improve production efficiency. Enameled copper round wire will undergo 8%-10% deformation during high-speed winding, which places stringent requirements on the comprehensive performance of enameled copper round wire. In addition to having good insulation, heat resistance, surface smoothness, and mechanical strength, high flexibility has become a core performance indicator.

[0003] Currently, enameled copper round wires produced using existing technologies often suffer from stiffness, leading to problems such as easy breakage, a stiff feel, and severe springback during high-speed winding. This results in decreased motor winding quality, failing to meet the production demands of downstream high-end equipment. Therefore, some motor customers require enameled wire manufacturers to increase the springback angle of their products by more than 5% beyond the national standard. A review of existing literature and patents reveals that current methods for improving the flexibility of enameled wire mainly focus on adjusting the annealing process, optimizing the cross-sectional shrinkage rate, and adjusting the coating material. However, there is a lack of precise selection and limitation of the copper rod base material's properties, and core process parameters such as drawing and annealing are not correlated with the flexibility indicators of enameled copper round wire, thus failing to effectively guide the improvement of enameled wire flexibility.

[0004] Therefore, developing a simple, industrially mass-producible preparation method for enameled copper round wire that can fundamentally improve its flexibility has become a pressing technical problem in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of insufficient flexibility and easy problems in the winding process of enameled copper round wire in the prior art, and to provide a method for preparing highly flexible enameled copper round wire. By screening the properties of the base material, precisely controlling the process parameters and limiting the microstructure indicators, the flexibility of the enameled copper round wire is significantly improved, ensuring the smooth high-speed winding of downstream customers.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing highly flexible enameled copper round wire includes the following steps: (1) Selection of raw material: Low oxygen copper rods with a diameter of 6mm-10mm, elongation ≥42%, and yield strength ≤0.55 are selected as raw materials; (2) Continuous drawing and annealing: The spare low oxygen copper rod is fed into the continuous drawing and annealing machine for multiple drawing passes, and then annealed by resistance heating to obtain a soft copper wire blank with a diameter of 1.0mm-3.0mm, an elongation of ≥40%, and a yield strength ratio of ≤0.55. (3) Continuous drawing and wrapping: The soft copper wire blank is fed into the continuous drawing and wrapping enameling machine. It is first drawn in multiple passes, and then annealed, coated, and baked and cured after each coating. After sufficient cooling, enameled copper round wire with a diameter of 0.3mm-2.0mm is obtained. (4) Performance and microstructure testing: The cooled enameled copper round wires were subjected to performance and microstructure testing. Wires with a springback angle more than 12% tighter than the national standard, an average grain size ≥9.0μm, and a dislocation density ≤1×10⁻⁶ were selected. 14 m -2 Highly flexible enameled copper round wire.

[0007] In a preferred example, in step (2), the number of drawing passes is 6 to 15, and the drawing elongation coefficient is 1.05 to 1.50.

[0008] In a preferred example, in step (2), the annealing voltage is 35V-45V, the annealing current is 3500A-5000A, and the annealing time is 1s-10s.

[0009] In a preferred example, in step (3), the number of drawing passes is 5 to 12, the drawing elongation coefficient is 1.15 to 1.30, and the total drawing deformation is 70% to 90%.

[0010] In a preferred example, in step (3), the annealing temperature is 450℃-600℃ and the annealing line speed is 50m / min-120m / min.

[0011] In a preferred example, in step (3), the paint is applied using polyesterimide paint and polyamideimide paint, and the number of paint coats is 12-24.

[0012] In a preferred example, in step (3), the baking curing temperature is 480℃-580℃, the baking linear speed is the same as the annealing linear speed, the single baking time is 2s-10s, and the baking atmosphere is an air atmosphere.

[0013] Based on a general inventive concept, another objective of this invention is to provide a highly flexible enameled copper round wire prepared by the above method, with an elongation ≥39.8%, a springback angle more than 12% tighter than the national standard, an average grain size ≥9.0μm, and a dislocation density ≤1×10⁻⁶. 14 m -2 The electrical performance meets the GB / T 6109.1-2008 standard.

[0014] The core mechanism of this invention is as follows: On the one hand, by selecting low-oxygen copper rods and controlling the performance of soft wire rods, the yield strength ratio and elongation of the copper material are limited, laying the foundation for subsequent process control and microstructure optimization, thus ensuring the plasticity of the copper material from the source; on the other hand, by synergistically controlling the total deformation during continuous drawing, annealing, and baking processes, the copper material undergoes complete recrystallization, controlling grain growth to above 9.0 μm, while simultaneously reducing the dislocation density to 1×10⁻⁶. 14 m -2 The following steps reduce the number of grain boundaries, eliminate internal stress, and minimize stress concentration during winding, thus avoiding the problems of wire stiffness and breakage during high-speed winding and significantly improving the flexibility of enameled wire. The synergistic effect of substrate selection, process control, and microstructure constraints jointly achieves the high flexibility of enameled copper round wire.

[0015] Compared with the prior art, the advantages and positive effects of the present invention are as follows: 1. Performance screening is conducted from the source of the base material to limit the yield strength ratio and elongation of low-oxygen copper rods and soft copper wire blanks, ensuring the plastic forming ability of copper materials in subsequent processing and laying the foundation for the high flexibility of enameled copper round wires. 2. The core process parameters such as drawing, annealing, coating and baking in the continuous drawing and annealing and continuous drawing and wrapping processes are precisely quantified and limited, realizing process controllability of the entire process of enameled copper round wire preparation and effectively regulating the microstructure of the finished product; 3. By limiting the average grain size and dislocation density of enameled copper round wire, the high flexibility of the product is ensured at the microstructure level, solving the technical problems of existing enameled copper round wires being hard, easy to break, and having severe springback during winding. The springback angle of the finished product is 12.8%-23.5% tighter than that of the national standard GB / T 6109.1-2008. 4. The preparation method is simple to operate. The continuous drawing and undrawing machine and the continuous drawing and wrapping enameling machine used are conventional equipment in the field of enameled wire production. No additional modification is required. It can directly realize industrialized, large-scale and stable production with low production cost, which is suitable for large-scale promotion. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is further described in conjunction with specific embodiments. However, this invention is not limited to these embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments. In this invention, unless otherwise specified, all parts and percentages are units of mass, and the equipment and raw materials used are commercially available or commonly used in the art. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art.

[0017] The terms “comprising,” “including,” “containing,” or any other variations thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0018] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether such range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within the range.

[0019] The average grain size was determined according to GB / T 6394-2017 "Method for Determination of Average Grain Size of Metals"; the dislocation density was determined by transmission electron microscopy (TEM), and the average value was calculated by selecting at least 5 fields of view through TEM image analysis software; the springback angle was tested according to the method in GB / T 6109.1-2008 "Enameled Copper Round Wire Part 1: General Provisions".

[0020] Example 1

[0021] A method for preparing highly flexible enameled copper round wire includes the following steps: (1) Selection of raw material: Low oxygen copper rods with a diameter of 8mm, an elongation of 42.4% and a yield strength ratio of 0.508 are selected as raw materials and are prepared for use after surface grinding, cleaning and drying; (2) Continuous drawing and annealing: The spare low oxygen copper rod is fed into the continuous drawing and annealing machine for multiple drawing passes, and then annealed by resistance heating to obtain a soft copper wire blank with a diameter of 2.6 mm, an elongation of 42.6%, and a yield strength ratio of 0.540. The drawing process involved 7 passes with a drawing elongation coefficient of 1.42; the annealing voltage was 42V, the annealing current was 4600A, and the annealing time was 8s.

[0022] (3) Continuous drawing and wrapping: The soft copper wire blank is fed into the continuous drawing and wrapping enameling machine. It is first drawn in multiple passes, and then annealed, coated with enamel (polyester imide enamel: polyamide imide enamel = 7:9) in sequence. After each coating, it is baked and cured. After sufficient cooling, a 1.2mm enameled copper round wire with a 2-grade enamel film is obtained. The drawing process involved 7 draw passes, a drawing elongation coefficient of 1.26, and a total drawing deformation of 78.7%. The annealing temperature was 590℃, and the annealing speed was 60m / min. The painting process involved 16 paint passes. The baking and curing temperature was 510℃, the baking speed was the same as the annealing speed, the baking time was 6s per pass, and the baking atmosphere was an air atmosphere. (4) Performance and microstructure testing: The enameled copper round wire was tested for performance and microstructure. The elongation was 43.6%, the springback angle was 30°, which is 18.9% tighter than the national standard (37°), the average grain size was 11.0 μm, and the dislocation density was 4.9 × 10⁻⁶. 13 m -2 The electrical performance meets the GB / T 6109.1-2008 standard.

[0023] Example 2

[0024] A method for preparing highly flexible enameled copper round wire includes the following steps: (1) Selection of raw material: Low oxygen copper rods with a diameter of 8mm, an elongation of 42.4% and a yield strength ratio of 0.508 are selected as raw materials and are prepared for use after surface grinding, cleaning and drying; (2) Continuous drawing and annealing: The spare low-oxygen copper rod is fed into the continuous drawing and annealing machine for multiple drawing passes, and then annealed by resistance heating to obtain a soft copper wire blank with a diameter of 2.0 mm, an elongation of 40.6%, and a yield strength ratio of 0.506. The drawing process involved 9 passes with a drawing elongation coefficient of 1.35; the annealing voltage was 40V, the annealing current was 3900A, and the annealing time was 10s.

[0025] (3) Continuous drawing and wrapping: The soft copper wire blank is fed into the continuous drawing and wrapping enameling machine. It is first drawn in multiple passes, and then annealed and coated in sequence (polyester imide paint: polyamide imide paint = 10:11). After each coating, it is baked and cured. After sufficient cooling, 0.80mm enameled copper round wire with 2-level paint film is obtained. The drawing process involved 8 draw passes, a drawing elongation coefficient of 1.26, and a total drawing deformation of 84.0%. The annealing temperature was 520℃, and the annealing speed was 99 m / min. The painting process involved 21 paint passes. The baking and curing temperature was 570℃, the baking speed was the same as the annealing speed, the baking time was 5 seconds per pass, and the baking atmosphere was an air atmosphere. (4) Performance and microstructure testing: The enameled copper round wire was tested for performance and microstructure. The elongation was 39.8%, the springback angle was 35°, which is 18.6% tighter than the national standard (43°), the average grain size was 9.9 μm, and the dislocation density was 3.6 × 10⁻⁶. 13 m -2 The electrical performance meets the GB / T 6109.1-2008 standard.

[0026] Example 3

[0027] A method for preparing highly flexible enameled copper round wire includes the following steps: (1) Selection of raw material: Low oxygen copper rods with a diameter of 6 mm, an elongation of 43.5% and a yield strength ratio of 0.520 are selected as raw materials and are prepared for use after surface grinding, cleaning and drying; (2) Continuous drawing and annealing: The spare low oxygen copper rod is fed into the continuous drawing and annealing machine for multiple drawing passes, and then annealed by resistance heating to obtain a soft copper wire blank with a diameter of 1.12 mm, an elongation of 41.2%, and a yield strength ratio of 0.53. The drawing process consists of 6 passes with a drawing elongation coefficient of 1.26; the annealing voltage is 35V, the annealing current is 3500A, and the annealing time is 8s.

[0028] (3) Continuous drawing and wrapping: The soft copper wire blank is fed into the continuous drawing and wrapping enameling machine. It is first drawn in multiple passes, and then annealed and coated in sequence (polyester imide varnish: polyamide imide varnish = 10: 9). After each coating, it is baked and cured. After sufficient cooling, enameled copper round wire with a diameter of 0.55mm is obtained. The drawing process involved 8 draw passes, a drawing elongation coefficient of 1.19, and a total drawing deformation of 75.8%. The annealing temperature was 470℃, and the annealing speed was 120m / min. The painting process involved 19 paint passes. The baking and curing temperature was 560℃, the baking speed was the same as the annealing speed, the baking time was 2s per baking pass, and the baking atmosphere was an air atmosphere. (4) Performance and microstructure testing: The cooled enameled copper round wire was subjected to performance and microstructure testing. The prepared high-flexibility enameled copper round wire had an elongation of 45.6%, a springback angle that was 22.7% tighter than the national standard (44°), an average grain size of 9.8 μm, and a dislocation density of 5.2 × 10⁻⁶. 13 m -2 The electrical performance meets the GB / T 6109.1-2008 standard.

[0029] Comparative Example 1

[0030] A method for preparing highly flexible enameled copper round wire includes the following steps: (1) Selection of raw material: Low oxygen copper rods with a diameter of 8mm, an elongation of 40.3% and a yield strength ratio of 0.610 are selected as raw materials and are prepared for use after surface grinding, cleaning and drying; (2) Continuous drawing and annealing: The spare low oxygen copper rod is fed into the continuous drawing and annealing machine for multiple drawing passes, and then annealed by resistance heating to obtain a soft copper wire blank with a diameter of 2.6 mm, an elongation of 39.7%, and a yield strength ratio of 0.621. The drawing process involved 7 passes with a drawing elongation coefficient of 1.42; the annealing voltage was 42V, the annealing current was 4600A, and the annealing time was 8s.

[0031] (3) Continuous drawing and wrapping: The soft copper wire blank is fed into the continuous drawing and wrapping enameling machine. It is first drawn in multiple passes, and then annealed, coated with enamel (polyester imide enamel: polyamide imide enamel = 7:9) in sequence. After each coating, it is baked and cured. After sufficient cooling, a 1.2mm enameled copper round wire with a 2-grade enamel film is obtained. The drawing process involved 7 draw passes, a drawing elongation coefficient of 1.26, and a total drawing deformation of 78.7%. The annealing temperature was 590℃, and the annealing speed was 60m / min. The painting process involved 16 paint passes. The baking and curing temperature was 510℃, the baking speed was the same as the annealing speed, the baking time was 6s per pass, and the baking atmosphere was an air atmosphere. (4) Performance and microstructure testing: The enameled copper round wire was tested for performance and microstructure. The elongation was 41.2%, the springback angle was 35°, which is only 5.4% tighter than the national standard (37°), the average grain size was 7.8 μm, and the dislocation density was as high as 2.3 × 10⁻⁶. 14 m -2 .

[0032] Comparative Example 2

[0033] A method for preparing highly flexible enameled copper round wire includes the following steps: (1) Selection of raw material: Low oxygen copper rods with a diameter of 8mm, an elongation of 39.3% and a yield strength ratio of 0.570 are selected as raw materials and are prepared for use after surface grinding, cleaning and drying; (2) Continuous drawing and annealing: The spare low oxygen copper rod is fed into the continuous drawing and annealing machine for multiple drawing passes, and then annealed by resistance heating to obtain a soft copper wire blank with a diameter of 2.6 mm, an elongation of 38.5%, and a yield strength ratio of 0.605. The drawing process involved 8 passes with a drawing elongation coefficient of 1.42; the annealing voltage was 38V, the annealing current was 4200A, and the annealing time was 8s.

[0034] (3) Continuous drawing and wrapping: The soft copper wire blank is fed into the continuous drawing and wrapping enameling machine. It is first drawn in multiple passes, and then annealed, coated with enamel (polyester imide enamel: polyamide imide enamel = 10: 9) in sequence. After each coating, it is baked and cured. After sufficient cooling, a 0.55mm enameled copper round wire with a 2-grade enamel film is obtained. The drawing process involved 7 draw passes, a drawing elongation coefficient of 1.26, and a total drawing deformation of 92.4%. The annealing temperature was 470℃, and the annealing speed was 118 m / min. The painting process involved 12 paint passes. The baking and curing temperature was 560℃, the baking speed was the same as the annealing speed, the baking time was 6 seconds per pass, and the baking atmosphere was an air atmosphere. (4) Performance and microstructure testing: The enameled copper round wire was tested for performance and microstructure. The elongation was 40.0%, the springback angle was 40°, which is only 9.1% tighter than the national standard (44°), the average grain size was 7.5μm, and the dislocation density was 3.5×10⁻⁶. 14 m -2 .

[0035] The above embodiments are merely preferred embodiments of the present invention. Any simple modifications, alterations, and substitutions made to the above embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing highly flexible enameled copper round wire, characterized in that, Includes the following steps: (1) Selection of raw material: Low oxygen copper rods with a diameter of 6mm-10mm, elongation ≥42%, and yield strength ≤0.55 are selected as raw materials; (2) Continuous drawing and annealing: The spare low oxygen copper rod is fed into the continuous drawing and annealing machine for multiple drawing passes, and then annealed by resistance heating to obtain a soft copper wire blank with a diameter of 1.0mm-3.0mm, an elongation of ≥40%, and a yield strength ratio of ≤0.

55. (3) Continuous drawing and wrapping: The soft copper wire blank is fed into the continuous drawing and wrapping enameling machine. It is first drawn in multiple passes, and then annealed, coated, and baked and cured after each coating. After sufficient cooling, enameled copper round wire with a diameter of 0.3mm-2.0mm is obtained. (4) Performance and microstructure testing: The cooled enameled copper round wires were subjected to performance and microstructure testing. Wires with a springback angle more than 12% tighter than the national standard, an average grain size ≥9.0μm, and a dislocation density ≤1×10⁻⁶ were selected. 14 m -2 Highly flexible enameled copper round wire.

2. The method for preparing a highly flexible enameled copper round wire according to claim 1, characterized in that, In step (2), the number of drawing passes is 6 to 15, and the drawing elongation coefficient is 1.05 to 1.

50.

3. The method for preparing a highly flexible enameled copper round wire according to claim 1, characterized in that, In step (2), the annealing voltage is 35V-45V, the annealing current is 3500A-5000A, and the annealing time is 1s-10s.

4. The method for preparing a highly flexible enameled copper round wire according to claim 1, characterized in that, In step (3), the number of drawing passes is 5 to 12, the drawing elongation coefficient is 1.15 to 1.30, and the total drawing deformation is 70% to 90%.

5. The method for preparing a highly flexible enameled copper round wire according to claim 1, characterized in that, In step (3), the annealing temperature is 450℃-600℃ and the annealing line speed is 50m / min-120m / min.

6. The method for preparing a highly flexible enameled copper round wire according to claim 1, characterized in that, In step (3), polyesterimide paint and polyamide-imide paint are used for painting, and the number of paint coats is 12-24.

7. The method for preparing a highly flexible enameled copper round wire according to claim 5, characterized in that, In step (3), the baking and curing temperature is 480℃-580℃, the baking linear speed is the same as the annealing linear speed, the single baking time is 2s-10s, and the baking atmosphere is an air atmosphere.

8. The highly flexible enameled copper round wire prepared by the preparation method according to any one of claims 1-7, characterized in that, Elongation ≥39.8%, springback angle more than 12% tighter than the national standard, average grain size ≥9.0μm, dislocation density ≤1×10 14 m -2 The electrical performance meets the GB / T 6109.1-2008 standard.