Graphite-based wire material, preparation method, graphite-based electromagnetic coil and application

Abstract

The invention discloses a graphite-based wire material, a preparation method, a graphite-based electromagnetic coil and application, the wire material is formed by mixing crystalline flake graphite and electrolytic copper powder, the carbon content of the crystalline flake graphite is larger than or equal to 99.5%, the copper purity of the electrolytic copper powder is larger than or equal to 99.9%, and the weight part ratio range of the crystalline flake graphite to the electrolytic copper powder is (3-4): (6-7); the preparation method comprises the following steps: mixing crystalline flake graphite and electrolytic copper powder in proportion, putting the mixture into a ball mill, and carrying out ball milling for 5-8 hours at the rotating speed of 300-400 revolutions per minute to realize full and uniform mixing; putting the mixed powder into a mold, and pressing the mixed powder into a wire blank under the pressure of 100-150 MPa; placing the wire blank in an inert atmosphere high-temperature furnace, sintering at 1500 DEG C for 2-3 hours, and then placing in air for natural cooling; the prepared wire blank is wound, connected and combined to form a coil, and the coil is arranged in a drainage port base of a steel ladle tapping hole and can work in a high-temperature environment of 1800 DEG C.

Description

Technical Field

[0001] This invention belongs to the field of conductive materials technology within "new materials technology" and "electrical engineering technology", and specifically relates to a graphite-based conductor material, its preparation method, a graphite-based electromagnetic coil, and its applications. Background Technology

[0002] In high-temperature industrial sectors such as iron and steel metallurgy and non-ferrous metal smelting, critical components like the bottom of steel ladles are subjected to extreme high-temperature environments exceeding 1800℃ for extended periods. Under these conditions, traditional copper-based electromagnetic coils exhibit the following prominent problems: copper's melting point is only 1083℃, far below the operating temperature, leading to easy melting of the conductors and overall coil failure; simultaneously, the resistivity of copper conductors increases dramatically with rising temperature. For example, in actual production at a steel plant, when the temperature at the bottom of the ladle reaches 1500℃, the resistance of the copper-based coil increases several times compared to room temperature. This not only significantly reduces energy conversion efficiency but also generates a large amount of heat due to the Joule effect, accelerating the aging and damage of insulation materials, leading to insulation failure and short-circuit faults. Statistics show that equipment downtime caused by electromagnetic coil failures results in huge economic losses for the steel industry annually, severely impacting production continuity and safety.

[0003] While some existing high-temperature resistant materials (such as nickel-based alloy wires) can withstand high temperatures to a certain extent, their electrical conductivity decreases significantly with increasing temperature. For example, the conductivity of GH600 nickel-based superalloy is approximately 14.2% IACS at room temperature, but drops to approximately 8.1% IACS when the temperature rises to 1000℃. These materials cannot meet the requirements for efficient electrical energy transmission and conversion in applications such as electromagnetic induction heating, thus limiting their widespread application in high-temperature industrial equipment.

[0004] Traditional electromagnetic coils primarily rely on metal wires such as copper and aluminum, which exhibit excellent conductivity at room temperature. However, in high-temperature environments, the increased thermal vibration of metal atoms and the increased resistance to electron migration lead to an exponential increase in resistivity, hindering the effective transmission of electrical energy. Furthermore, metal wires lack sufficient oxidation resistance at high temperatures, easily forming a high-resistivity oxide film on their surface (such as copper oxide on copper wires), further deteriorating conductivity and mechanical strength.

[0005] Currently, there is an urgent market demand for electromagnetic materials capable of stable operation in high-temperature environments. Whether in traditional high-temperature industries such as steel and non-ferrous metals, or emerging fields like new energy and aerospace, there is a pressing need for electromagnetic materials that combine high-temperature resistance with stable conductivity to overcome existing technological bottlenecks and improve equipment performance and production efficiency. However, ideal high-temperature conductive materials are currently unavailable in the market, becoming one of the key factors restricting the development of related industries. Summary of the Invention

[0006] The purpose of this invention is to address the above-mentioned problems by providing a graphite-based conductor material, a preparation method, a graphite-based electromagnetic coil, and its application. The electromagnetic coil can operate stably and continuously in an extreme high-temperature environment of 1800℃.

[0007] To achieve the above objectives, the solution of the present invention is as follows:

[0008] A graphite-based conductor material is composed of a mixture of flake graphite and electrolytic copper powder, wherein: the carbon content of the flake graphite is ≥99.5%, the copper purity of the electrolytic copper powder is ≥99.9%, and the weight ratio of flake graphite to electrolytic copper powder is in the range of 3~4:6~7.

[0009] A further aspect of the scheme is that the weight ratio of the flake graphite to the electrolytic copper powder is 3.5:6.5.

[0010] The solution further states that the weight ratio of the flake graphite to the electrolytic copper powder is 3.8:6.3.

[0011] A method for preparing a graphite-based conductive wire, comprising the above-mentioned graphite-based conductive wire material, wherein the preparation method includes ball milling, molding, and high-temperature sintering;

[0012] The ball milling process involves mixing flake graphite and electrolytic copper powder in a specific ratio, placing the mixture in a ball mill, and milling it at 300–400 rpm for 5–8 hours.

[0013] The compression molding process involves placing the mixed powder in a mold and pressing it into a wire blank under a pressure of 100–150 MPa.

[0014] The high-temperature sintering process involves placing the wire blank in an inert atmosphere high-temperature furnace and sintering it at 1500℃ for 2–3 hours, followed by natural cooling in air.

[0015] A further provision is that the inert atmosphere is argon.

[0016] A graphite-based electromagnetic coil, wherein the coil is formed by winding and connecting the prepared conductor blanks, and insulation is provided between the conductor blanks.

[0017] A further aspect of the solution is that the insulation is a nano-ceramic insulating layer sprayed and coated onto the surface of the conductor blank.

[0018] A further aspect of the solution is that the aforementioned nano-ceramic insulating layer contains... A nano-ceramic insulating layer with SiO2, the thickness of which is 0.1–0.2 mm.

[0019] A further aspect of the solution is that a graphite heat-conducting sheet is embedded between the upper and lower layers of the conductor blank.

[0020] An application of a graphite-based electromagnetic coil includes a molten steel ladle in a steel plant, with a molten steel outlet at the lower end of the ladle, and an electromagnetic induction heating coil disposed in the base of the molten steel outlet, wherein the electromagnetic induction heating coil is the aforementioned graphite-based electromagnetic coil.

[0021] The beneficial effects of this invention are:

[0022] (I) Three core performance advantages

[0023] 1. Adaptability to ultra-high temperature environments

[0024] This graphite-doped copper powder electromagnetic coil can operate stably for over 4000 hours in an extreme high-temperature environment of 1800℃. Traditional copper coils typically have a temperature resistance limit below 600℃ and are prone to softening and melting at high temperatures. This invention successfully solves the problem of high-temperature morphological stability through a graphite skeleton and composite structure design. Practical application shows that in a steel plant's ladle heating system, the continuous operating time of the equipment was significantly extended after using this coil, effectively avoiding frequent downtime caused by coil failure.

[0025] 2. Excellent in both electrical conductivity and heat dissipation.

[0026] At room temperature, the conductivity of this conductor can reach 4.5 × 10⁻⁶. 7 Its conductivity is approximately 85% of that of pure copper; even at a high temperature of 1800℃, its conductivity remains at 3.2 × 10⁻⁶. 7 The S / m ratio ensures efficient power transmission. In the composite structure, graphite provides a stable electron transport path, while copper powder forms a continuous conductive network.

[0027] In terms of heat dissipation, the high heat resistance of graphite is utilized, and the coil's thermal resistance is reduced by 60% through structural design, effectively avoiding the vicious cycle caused by resistive heating. Actual tests show that electromagnetic devices using this coil have an induction efficiency that is more than 15% higher than traditional devices, resulting in a significant improvement in energy utilization.

[0028] 3. Long lifespan and low maintenance costs

[0029] Through its anti-oxidation coating and multi-layer sealing structure design, this coil's resistance to high-temperature oxidation is increased by approximately 5 times, and its service life is 3-5 times that of traditional coils. Taking the electromagnetic heating system of a high-temperature reactor in a chemical plant as an example, traditional coils require maintenance every 2 months on average and need to be replaced 2-3 times a year; after adopting this coil, the maintenance cycle is extended to 6-8 months, requiring only one replacement per year, reducing annual maintenance costs by approximately 60%, and significantly reducing equipment downtime.

[0030] (II) Revolutionary impact on high-temperature industrial sectors

[0031] This invention breaks the traditional understanding that "high-temperature resistant materials are not conductive and conductive materials are not heat resistant," and provides a brand-new solution for high-temperature industries such as steel, metallurgy, and chemicals.

[0032] • Steel industry: After adopting this coil, the continuous operating time of the ladle heating system has been increased from 8 hours to 72 hours, the annual maintenance cost has been reduced by 40%, and the production efficiency and product stability have been significantly improved.

[0033] • In the metallurgical field: In non-ferrous metal smelting, this coil provides stable conductivity and electromagnetic induction efficiency, helping to achieve precise control of temperature and process parameters and improve product purity.

[0034] • Chemical Industry: In high-temperature and high-pressure reaction environments, this coil meets stringent temperature resistance and conductivity requirements, providing reliable support for the efficient and stable operation of chemical equipment and promoting technological progress in the industry.

[0035] IV. Application Scenarios and Market Prospects

[0036] (I) Core Application Areas

[0037] 1. Metallurgical smelting equipment

[0038] Steel ladle electromagnetic induction heating coil: It operates stably in the 1800℃ environment at the bottom of the steel ladle, ensuring precise control of the molten steel temperature, reducing downtime, and improving production efficiency and molten steel quality.

[0039] Blast furnace tuyere temperature measuring wire: Maintains conductivity and structural stability in the harsh environment inside the blast furnace (1500–1800℃), enabling accurate measurement of tuyere temperature. After application by a certain enterprise, blast furnace energy utilization increased by 8% and the defect rate decreased by 5%.

[0040] 2. High-Temperature Industrial Testing Instruments

[0041] • High-temperature sensor leads: Stable signal transmission in highly corrosive environments such as petrochemical reactors (800–1200℃) to ensure sensor measurement accuracy.

[0042] • Furnace temperature measuring coil: Operates stably in ceramic firing furnaces (1000–1400℃), aiding in precise temperature control. After application by a ceramic company, the product yield increased from 80% to 90%, and quality indicators were significantly improved.

[0043] 3. New Energy and Aerospace

[0044] High-temperature hydrogen fuel cell stacks: Maintain conductivity and stability at 80–120℃ and in complex chemical environments, improve battery power generation efficiency and lifespan, and support the development of the new energy vehicle industry.

[0045] Aircraft engine temperature measurement coil: accurately measures temperature in environments of 1500–2000℃, high-speed rotation and vibration, providing key data for engine condition monitoring and fault diagnosis, and contributing to the localization of aerospace equipment.

[0046] The invention will be further explained in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the conductor blank;

[0048] Figure 2 This is a schematic diagram of a drainage seat. Detailed Implementation

[0049] Example 1:

[0050] A graphite-based conductive wire material is composed of a mixture of flake graphite and electrolytic copper powder. Through nanoscale surface modification technology, a copper-based conductive layer is uniformly coated onto the surface of the graphite flakes, forming a "graphite-copper" composite powder structure. The flake graphite has a carbon content ≥99.5%, the electrolytic copper powder has a copper purity ≥99.9%, and the weight ratio of flake graphite to electrolytic copper powder is in the range of 3~4:6~7. At this ratio, the composite wire can utilize the morphological stability of the graphite skeleton at high temperatures and form an effective conductive path by filling the interlayer gaps with copper powder. For example, when the mass ratio is 3:7, the conductivity of the composite wire can be stably maintained at 3.2×10⁻⁶ at 1800℃. 7 S / m, meeting the requirements for use in extreme high-temperature environments.

[0051] The following are two preferred formulations: the weight ratio of the flake graphite to the electrolytic copper powder is 3.5:6.5. The weight ratio of the flake graphite to the electrolytic copper powder is 3.8:6.3.

[0052] Example 2:

[0053] A method for preparing graphite-based conductive wires includes the graphite-based conductive wire material described in Example 1, wherein the content of Example 1 shall be used as the content of this embodiment; the preparation method includes ball milling, molding, and high-temperature sintering;

[0054] The ball milling process involves mixing flake graphite and electrolytic copper powder in a specific ratio, placing them in a ball mill, and milling at 300–400 rpm for 5–8 hours to achieve thorough and uniform mixing.

[0055] The compression molding process involves placing the mixed powder in a mold and pressing it into a wire blank under a pressure of 100–150 MPa. Figure 1 The illustration shows a circular wire blank 1. Terminals 101 and 102 are machined on the upper and lower surfaces of the ends of the circular wire blank 1. Of course, in addition to... Figure 1The circle shown can also be any other shape, depending on the application.

[0056] The high-temperature sintering process involves placing the wire blank in an inert atmosphere high-temperature furnace and sintering at 1500℃ for 2–3 hours. This promotes the formation of an interfacial bonding structure between graphite and copper, characterized by wetting, penetration, and mechanical interlocking, resulting in a stable bond and improved material density and performance. The blank is then allowed to cool naturally in air.

[0057] Wherein: the inert atmosphere is argon.

[0058] Example 3:

[0059] A graphite-based electromagnetic coil is provided, wherein the coil is formed by winding and connecting the conductor blanks prepared as described in Example 2. The content of Example 2 should be used as the content of this embodiment. Insulation is provided between the conductor blanks.

[0060] Wherein: the insulation is a nano-ceramic insulating layer sprayed and coated onto the surface of the conductor blank. The nano-ceramic insulating layer contains Al2O3 and SiO2, with a thickness controlled between 0.1 and 0.2 mm, and a temperature resistance of ≥2000℃, effectively preventing leakage and short circuits.

[0061] A graphite heat-conducting sheet is embedded between the upper and lower layers of the conductor blank. Utilizing its excellent in-plane thermal conductivity (up to 1500–2000 W / mK), it rapidly dissipates the heat generated during coil operation, preventing localized heat accumulation. This integrated "conductivity-insulation-heat dissipation" structure significantly improves the long-term operational stability of the coil at 1800℃. The graphite heat-conducting sheet is embedded using an adhesive process, ensuring a tight bond with the winding wires and insulation layer, without affecting the overall structural stability.

[0062] Example 4:

[0063] An application of a graphite-based electromagnetic coil is described in Example 3. Since graphite-based electromagnetic coils are particularly suitable for high-temperature operating environments, the content of Example 3 should be considered as the content of this embodiment. Figure 2 As shown, the application of the graphite-based electromagnetic coil includes a molten steel ladle in a steel plant. A molten steel inlet 3 is located at the lower end of the ladle, and an electromagnetic induction heating coil is installed in the base 4 of the molten steel inlet. This electromagnetic induction heating coil is the graphite-based electromagnetic coil described in Example 3. The coil 2, composed of a wire blank arranged and wound, surrounds the molten steel inlet 3 and is placed in the inlet base 4 of the molten steel ladle's outlet. Therefore:

[0064] Steel ladle electromagnetic induction heating coil: It operates stably in the 1800℃ environment at the bottom of the steel ladle, ensuring precise control of the molten steel temperature, reducing downtime, and improving production efficiency and molten steel quality.

[0065] Blast furnace tuyere temperature measuring wire: Maintains conductivity and structural stability in the harsh environment inside the blast furnace (1500–1800℃), enabling accurate measurement of tuyere temperature. After application by a certain enterprise, blast furnace energy utilization increased by 8% and the defect rate decreased by 5%.

Claims

1. A graphite-based conductive material, characterized in that, The conductor material is composed of a mixture of flake graphite and electrolytic copper powder, wherein: the carbon content of the flake graphite is ≥99.5%, the copper purity of the electrolytic copper powder is ≥99.9%, and the weight ratio of flake graphite to electrolytic copper powder is 3~4:6~7.

2. The material according to claim 1, characterized in that, The weight ratio of the flake graphite to the electrolytic copper powder is 3.5:6.

5.

3. The material according to claim 1, characterized in that, The weight ratio of the flake graphite to the electrolytic copper powder is 3.8:6.

3.

4. A method for preparing a graphite-based conductive wire, characterized in that, The graphite-based conductive material according to any one of claims 1 to 3, wherein the preparation method includes ball milling, molding, and high-temperature sintering; The ball milling process involves mixing flake graphite and electrolytic copper powder in a specific ratio, placing the mixture in a ball mill, and milling it at 300–400 rpm for 5–8 hours. The compression molding process involves placing the mixed powder in a mold and pressing it into a wire blank under a pressure of 100–150 MPa. The high-temperature sintering process involves placing the wire blank in an inert atmosphere high-temperature furnace and sintering it at 1500℃ for 2–3 hours, followed by natural cooling in air.

5. The preparation method according to claim 4, characterized in that, The inert atmosphere is argon.

6. A graphite-based electromagnetic coil, characterized in that, The coil is formed by winding and connecting wire blanks formed by the preparation method of claim 4, and insulation is provided between the wire blanks.

7. The graphite-based electromagnetic coil according to claim 6, characterized in that, The insulation is a nano-ceramic insulating layer sprayed and coated onto the surface of the conductor blank.

8. The graphite-based electromagnetic coil according to claim 7, characterized in that, The nano-ceramic insulating layer is a nano-ceramic insulating layer containing Al2O3 and SiO2, and the thickness of the insulating layer is 0.1–0.2 mm.

9. The graphite-based electromagnetic coil according to claim 6, characterized in that, A graphite heat-conducting sheet is embedded between the upper and lower layers of the wire blank.

10. An application of a graphite-based electromagnetic coil, comprising a molten steel ladle in a steel plant, wherein a molten steel outlet is provided at the lower end of the ladle, and an electromagnetic induction heating coil is disposed in the base of the molten steel outlet, characterized in that, The electromagnetic induction heating coil is the graphite-based electromagnetic coil according to any one of claims 6 to 9.

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