Continuous spontaneous heating graphitization treatment device and method for mesophase pitch-based carbon fibers

Abstract

The invention relates to the technical field of high-temperature equipment and high-performance carbon fibers, in particular to a mesophase pitch-based carbon fiber continuous self-heating graphitization treatment device and method.The device comprises an inlet filament guiding machine, a high-temperature furnace, an induction coil and an outlet filament guiding machine which are sequentially arranged, and conductive graphite rollers are arranged in the inlet filament guiding machine and the outlet filament guiding machine; the conductive graphite roller is grounded, and the induction coil is connected with an external power supply. Carbon fibers continuously pass through a high-temperature furnace through a conductive graphite roller, an induction current is formed on the carbon fibers by an electromagnetic induction device along the fiber feeding direction, Joule heat is generated by using the resistance value of the carbon fibers, and a certain amount of temperature rise is formed and directly acts on the carbon fibers; under the superposition effect of the running temperature of the high-temperature hearth and the heating temperature of the carbon fiber resistor, a required fiber heat treatment temperature field is formed, high-temperature heat treatment of conductive and continuous materials such as carbon fibers and the like is completed under the low power load of the high-temperature furnace, and a high-performance carbon fiber product is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of high-temperature equipment and high-performance carbon fiber, in particular to a continuous self-heating graphitization treatment method for mesophase asphalt-based carbon fiber. Background Art

[0002] Carbon fiber is a fibrous carbon material with a lower density than aluminum but higher strength than steel, and has the characteristics of corrosion resistance and high modulus. Graphite fiber generally refers to carbon fiber with a carbon content of more than 99%. Compared with carbon fiber, graphite fiber not only has a high carbon content, but also a high tensile modulus. It also has excellent properties such as a small thermal expansion coefficient, good thermal stability, and dimensional stability. Therefore, it is used to manufacture rigid, thin, and dimensionally stable composite components, which are widely used in spacecraft and aerospace fields.

[0003] Manufacturing graphite fiber is the integration of high temperature technology and high temperature equipment. How to extend the high temperature service life at 2200~3200℃ becomes the technical key of continuous graphitization. Carbon Fiber and Graphite Fiber (Hefu, ISBN-978-7-122-8802-4) proposed an induction graphitization furnace for producing continuous carbon fiber. However, due to the problems of maintaining the furnace atmosphere and the short high temperature service life of the heating element caused by the fiber inlet and outlet, this furnace type has never been widely used under ultra-high temperature conditions above 2800℃.

[0004] The utility model patent CN210030982U proposes a graphitization furnace, which solves the problems of overall air tightness of the equipment and expansion damage of the heating element. However, when the heating element undergoes a certain degree of ablation during high-temperature operation, its resistance value increases, the operating power of the equipment increases, the current load on the surface of the heating element increases, and the ablation damage of the heating element is accelerated, limiting the service life and reliability in the high-temperature state. Summary of the invention

[0005] In view of the problem that the heating element of the graphitization furnace in the prior art cannot operate continuously and stably under high temperature due to ablation, the present invention provides a continuous self-heating graphitization treatment method for mesophase asphalt-based carbon fibers.

[0006] The present invention is achieved through the following technical solutions: A continuous self-heating graphitization processing device for mesophase asphalt-based carbon fiber comprises an inlet wire drawing machine, a high-temperature furnace, an induction coil and an outlet wire drawing machine which are arranged in sequence and at the same height. Rotating conductive graphite rollers are arranged inside the inlet wire drawing machine and the outlet wire drawing machine, and the conductive graphite rollers are connected to power terminals for grounding. The induction coil is connected to an external power supply, and the induction coil is used to generate an induced current in the length direction of the carbon fiber. When in use, the fiber running height is flush with the upper edge of the conductive graphite roller, the induced current is derived from the power terminal closest to the high-temperature furnace end, and the induction coil is connected in series with the running carbon fiber to form an effective overlap of the radiant heat in the effective temperature zone of the high-temperature furnace and the Joule heat generated by the carbon fiber current.

[0007] Preferably, a plurality of parallel U-shaped grooves are arranged at intervals on the surface of the conductive graphite roller, and when in use, the fiber filaments pass through the U-shaped grooves.

[0008] Preferably, the conductive graphite roller is arranged inside the inlet wire drawing machine or the outlet wire drawing machine through a rotating shaft and a bearing, wherein the rotating shaft is arranged inside the conductive graphite roller.

[0009] Preferably, the rotating shaft is made of copper and the bearing is made of graphite.

[0010] Preferably, the rotating shaft is a hollow structure, a fin heat sink is arranged on the end surface of the rotating shaft, and the fin heat sink is connected to an external cooling source.

[0011] Preferably, it also includes a sealed box body arranged between the inlet wire drawing machine and the wire inlet of the high-temperature furnace or between the outlet wire drawing machine and the wire outlet of the high-temperature furnace, the conductive graphite roller, the rotating shaft and the graphite bearing are arranged in the sealed box body, and the rotating shaft is installed in the sealed box body through an insulating shaft seat.

[0012] Preferably, an air hole is provided on the sealed box body, and the air hole is connected to an external inert gas source.

[0013] Preferably, the wire-guiding channel of the high-temperature furnace is sprayed with high-temperature resistant ceramics.

[0014] Preferably, the length of the induction coil is 600-1800 mm, and the inner diameter of the induction coil matches the size of the high-temperature furnace.

[0015] A method for continuous self-heating graphitization of mesophase pitch-based carbon fibers, using the device for continuous self-heating graphitization of mesophase pitch-based carbon fibers, wherein the carbon fibers are guided by a conductive graphite roller in an inlet drawing machine to an inlet gas seal, a high-temperature furnace, an induction coil, and an outlet drawing machine in sequence; Among them, the carbon fiber is a conductive carbon fiber that has been carbonized at more than 1200°C, and the resistivity of the carbon fiber is below 40μΩm; the pulling speed of the conductive graphite roller is ~m / min, the total envelope angle of the carbon fiber on the conductive graphite roller is 360~720°, the operating tension of the carbon fiber is 50~300cN, and the carbon fiber is always kept in a straight and taut state in the furnace to ensure good contact between the conductive graphite roller and the carbon fiber.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The carbon fiber of the present invention is continuously passed through a high-temperature furnace via a conductive graphite roller, an induction current is formed on the carbon fiber along the length direction of the fiber by an induction coil, Joule heat is generated by utilizing the resistance of the carbon fiber itself, a certain amount of temperature increase is formed to directly act on the carbon fiber, and the required fiber heat treatment temperature field is formed under the superposition effect of the operating temperature of the high-temperature furnace itself and the resistive heating temperature of the carbon fiber, so that the high-temperature furnace can complete the high-temperature heat treatment of conductive and continuous materials such as carbon fiber under a relatively low power load, thereby obtaining a high-performance carbon fiber product.

[0017] Furthermore, the U-shaped groove improves the current conduction efficiency while facilitating the fiber filaments to pass through and increasing the contact area.

[0018] Furthermore, the rotating shaft is a hollow structure, which can be connected to an external cooling source (gas source or liquid source) in combination with a fin heat sink, thereby effectively preventing overheating caused by resistance thermal effect or friction.

[0019] Furthermore, the design of the sealed box ensures the sealing of the carbon fiber path. At the same time, the sealed box is connected to an external inert gas source through air holes. Inert gas is introduced into the sealed box to maintain positive pressure to prevent the carbon fiber from being oxidized by air at high temperatures.

[0020] Furthermore, the high-temperature furnace itself can achieve continuous and stable operation at 2000~2800℃.

[0021] Furthermore, the induced current on the carbon fiber is generated by the induction coil, which is connected in series with the carbon fiber passing through the high-temperature furnace and is led out at the ends of the rotating shafts of the inlet wire drawing machine and the outlet wire drawing machine, forming an effective overlap of the radiant heat in the effective temperature zone of the high-temperature furnace and the Joule heat generated by the current of the fiber filaments.

[0022] Furthermore, the use of high temperature resistant ceramics for spraying treatment can achieve insulation between the wire channel and the fiber filaments, and further improve the high temperature resistance and stability of the device.

[0023] In a method for continuous self-heating graphitization of mesophase asphalt-based carbon fibers of the present invention, the carbon fibers continuously pass through a high-temperature furnace, and an induction coil forms an induced current along the fiber running direction on the fiber filaments, and the resistance of the carbon fibers themselves is used to generate Joule heat, forming a certain amount of temperature increase that directly acts on the carbon fibers. Under the superposition of the operating temperature of the high-temperature furnace itself and the resistance heating temperature of the fiber filaments, the required fiber heat treatment temperature field is formed, and the high-temperature furnace is used to complete the high-temperature heat treatment of conductive and continuous materials such as carbon fibers under a relatively low power load, thereby obtaining high-performance carbon fiber products. Among them, the traction speed of the conductive graphite roller, the total envelope angle of the fiber filaments on the conductive graphite roller, the running tension of the fiber filaments and other parameters are all precisely controlled to ensure the uniformity and stability of the graphitization treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of the high temperature furnace and the heating compensation device in the present invention.

[0025] Figure 2 It is a schematic diagram of the inlet / outlet wire drawing machine in the present invention.

[0026] In the figure: 101-inlet wire drawing machine; 102-inlet air seal; 103-high temperature furnace; 104-induction coil; 105-exit wire drawing machine; 201-fin heat sink; 202-insulating shaft seat; 203-bearing; 204-sealing box; 205-conductive graphite roller; 206-rotating shaft; 207-electrical terminal. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0028] The present invention discloses a continuous self-heating graphitization treatment device for mesophase asphalt-based carbon fibers, referring to Figure 1 , 2 , including an inlet wire drawing port 101, an inlet gas seal 102, a high-temperature furnace 103, an induction coil 104 and an outlet wire drawing machine 105 which are arranged in sequence and at the same height. The high-temperature furnace 103 itself can achieve continuous and stable operation at 2000~2800℃.

[0029] Conductive graphite rollers 205 are arranged inside the inlet wire drawing machine 101 and the outlet wire drawing machine 105. The conductive graphite rollers 205 not only serve as a traction mechanism for the carbon fiber, but also ensure that the carbon fiber passes smoothly through the high-temperature furnace 103 at a precise speed of 1-6 m / min. In this embodiment, the conductive graphite rollers 205, the bearings 203 and the rotating shaft 206 are arranged concentrically, and the rotating shaft 206 is made of copper, and the bearings 203 are made of graphite. The conductive graphite rollers 205 are connected to the rotating shaft 206 through the bearings 203, and the rotating shaft 206 is fixed to the wire drawing machine sealing box 204 through the insulating shaft seat 202. The end of the rotating shaft 206 is provided with an electrical terminal 207 for effective grounding, so that the induced current only exists in the carbon fiber, the conductive graphite rollers 205, the bearings 203 and the rotating shaft 206. The insulating shaft seat 202 is connected to the shaft hole of the sealing box 204, which ensures the safety and stability of the system.

[0030] Among them, the rotating shaft 206 is a hollow structure, and a fin heat sink 201 is provided at the end of the rotating shaft 206. The rotating shaft can be cooled by air cooling or water cooling, which effectively reduces the resistance thermal effect and friction heat generation. The fin heat sink 201 can further enhance the heat dissipation effect and extend its service life.

[0031] The surface of the conductive graphite roller 205 is provided with a plurality of parallel U-shaped grooves, which are arranged along the circumference of the conductive graphite roller 205, and the plane of the U-shaped groove is perpendicular to the length axis of the conductive graphite roller 205, and the carbon fiber passes through the U-shaped groove. The grooves are evenly distributed along the circumference of the conductive graphite roller 205, and their planes are perpendicular to the length axis of the conductive graphite roller 205. Such a design not only increases the contact area between the fiber filaments and the conductive graphite roller 205, but also ensures the uniform distribution of the current, thereby improving the efficiency and uniformity of the graphitization process.

[0032] The wire-running channel of the high-temperature furnace 103 is sprayed with high-temperature resistant ceramics (such as boron nitride) to achieve insulation between the wire-running channel and the fiber filaments, thereby avoiding the risk of current leakage.

[0033] The induction coil 104 is connected in series with the carbon fiber passing through the high temperature furnace 103, and the induction coil 104 is used to form an induced current on the carbon fiber. In this embodiment, the length of the induction coil 104 is 600-1800 mm, and the inner diameter matches the furnace size of the high temperature furnace 103. As a key component for generating an alternating magnetic field, the induction coil 104 is limited in length and inner diameter to ensure that the radiant heat and the Joule heat generated by the carbon fiber current can efficiently overlap to form the required graphitization treatment temperature field.

[0034] In order to maintain the pure atmosphere in the high temperature furnace 103 and prevent the outside air from interfering with the graphitization process, a sealed box is provided between the inlet wire drawing machine 101 and the wire inlet 102 of the high temperature furnace 103 or between the outlet wire drawing machine 105 and the wire outlet of the high temperature furnace 103, and the outer sides of the conductive graphite roller 205, the rotating shaft 206 and the bearing 203 are wrapped by the sealed box 204. The sealed box 204 is tightly connected to the insulating shaft seat 202, and the sealed box 204 is respectively provided at the front end of the inlet gas seal 102 and the rear end of the induction coil 104, forming a relatively closed processing space.

[0035] The sealed box 204 is provided with air holes, which are connected to an external inert gas source (such as an inert gas), thereby providing a stable protective atmosphere for the graphitization treatment of the fiber filaments and further improving the treatment quality.

[0036] In the continuous self-heating graphitization treatment device for mesophase asphalt-based carbon fiber of the present invention, the carbon fiber passes through the high-temperature furnace 103 continuously through the conductive graphite roller 205, and the induction coil 104 forms an induced current along the fiber wire running direction on the carbon fiber, and the resistance of the carbon fiber itself is used to generate Joule heat, forming a certain amount of temperature rise directly acting on the carbon fiber. Under the superposition of the operating temperature of the furnace of the high-temperature furnace 103 and the temperature of the carbon fiber resistance heating, the required fiber heat treatment temperature field is formed, and the high-temperature furnace 103 is realized under a relatively low power load. The high-temperature heat treatment of conductive and continuous materials such as carbon fiber is completed to obtain a high-performance carbon fiber product, and the continuous self-heating graphitization treatment of the mesophase asphalt-based carbon fiber is realized, which not only improves the processing efficiency and stability, but also effectively solves the problem of easy ablation of the heating body in the traditional technology. The induced current on the carbon fiber is derived from the power terminal 207 at the end of the rotating shaft 206, and the induction coil 104 is connected in series with the running carbon fiber, forming an effective overlap of the radiation heat in the effective temperature zone of the high-temperature furnace 103 and the Joule heat generated by the carbon fiber current.

[0037] The present invention also discloses a method for continuous self-heating graphitization of mesophase pitch-based carbon fibers. The device for continuous self-heating graphitization of mesophase pitch-based carbon fibers is used. The carbon fibers are guided by an inlet wire drawing machine 101 to sequentially enter an inlet gas seal 102, a high-temperature furnace 103, an induction coil 104, and an outlet wire drawing machine 105. The high-temperature furnace 103 itself can achieve continuous and stable operation at 2000-2800°C. Among them, the carbon fiber has been carbonized at a temperature above 1200°C and has conductivity, and the resistivity of the carbon fiber is below 40μΩm; the pulling speed of the conductive graphite roller 205 is 1~6m / min, the total envelope angle of the carbon fiber on the conductive graphite roller 205 is 360~720°, and the operating tension of the carbon fiber is 50~300cN, which keeps the fiber in a straight and taut state in the furnace at all times, ensuring that the current on the conductive graphite roller 205 is effectively discharged; the fiber running height is flush with the upper edge of the conductive graphite roller 205.

[0038] Specifically, according to Figure 1 and Figure 2 As shown, the carbon fiber passes through the high-temperature furnace 103 and the induction coil 104 in sequence, and the induction coil 104 forms an induced current on the carbon fiber along the fiber running direction, and utilizes the resistance of the carbon fiber to generate Joule heat, thereby forming a certain amount of temperature increase that directly acts on the carbon fiber. Under the superposition of the operating temperature of the furnace of the high-temperature furnace 103 itself and the resistive heating temperature of the carbon fiber, the required carbon fiber heat treatment temperature field is formed, so that the high-temperature furnace 103 can complete the high-temperature heat treatment of conductive and continuous materials such as carbon fiber under a relatively low power load, thereby obtaining a high-performance carbon fiber product.

[0039] Example 1 The furnace temperature of the high-temperature furnace 103 is 2000°C, the carbon fiber running speed is 1m / min, the total envelope angle of the carbon fiber on the conductive graphite roller 205 is 360°, the running tension is 50cN, the induction coil length is 600mm, and after turning on the induction power supply, the effective temperature of 2400°C is achieved under the superposition of the operating temperature of the high-temperature furnace itself and the heating temperature of the carbon fiber.

[0040] Example 2 The furnace temperature of the high-temperature furnace 103 is 2400°C, the carbon fiber operating speed is 3m / min, the total envelope angle of the carbon fiber on the conductive graphite roller 205 is 540°, the operating tension is 150cN, the induction coil length is 1200mm, and after turning on the induction power supply, the effective temperature of 2700°C is achieved under the superposition of the operating temperature of the high-temperature furnace itself and the heating temperature of the carbon fiber.

[0041] Example 3 The furnace temperature of the high-temperature furnace 103 is 2800°C, the carbon fiber running speed is 6m / min, the total envelope angle of the carbon fiber on the conductive graphite roller 205 is 720°, the running tension is 300cN, the induction coil length is 1800mm, and after turning on the induction power supply, the effective temperature of 3000°C is achieved under the superposition of the operating temperature of the high-temperature furnace itself and the heating temperature of the carbon fiber.

[0042] To summarize, the compensating heating device of the present invention arranges conductive graphite rollers on both sides of the air seal of the high-temperature furnace for continuous processing of carbon fibers. The carbon fibers continuously pass through the high-temperature furnace via the conductive graphite rollers, and an induced current is formed on the carbon fibers along the fiber running direction by the induction coil. The resistance of the carbon fibers themselves is used to generate Joule heat, thereby forming a certain amount of temperature increase that directly acts on the carbon fibers. Under the superposition of the operating temperature of the high-temperature furnace itself and the resistive heating temperature of the carbon fibers, the required fiber heat treatment temperature field is formed, so that the high-temperature furnace can complete the high-temperature heat treatment of conductive and continuous materials such as carbon fibers under a relatively low power load, thereby obtaining high-performance carbon fiber products.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A continuous self-heating graphitization treatment device for mesophase pitch-based carbon fibers, characterized in that: The invention comprises an inlet wire drawing machine (101), a high temperature furnace (103), an induction coil (104) and an outlet wire drawing machine (105) which are arranged in sequence and at the same height. A rotating conductive graphite roller (205) is arranged inside the inlet wire drawing machine (101) and the outlet wire drawing machine (105), and the conductive graphite roller (205) is connected to an electrical terminal for grounding. The induction coil (104) is connected to an external power supply. The induction coil is used to generate an induced current in the length direction of the carbon fiber. When in use, the running height of the fiber is flush with the upper edge of the conductive graphite roller (205), the induced current is led out from the electrical terminal (207) closest to the end of the high temperature furnace, and the induction coil (104) is connected in series with the running carbon fiber, so that the radiant heat in the effective temperature zone of the high temperature furnace (103) and the Joule heat generated by the current of the carbon fiber are effectively overlapped.

2. The continuous self-heating graphitization treatment device for mesophase pitch-based carbon fibers according to claim 1 is characterized in that: A plurality of parallel U-shaped grooves are arranged at intervals on the surface of the conductive graphite roller (205); when in use, the fiber filaments pass through the U-shaped grooves.

3. The continuous self-heating graphitization treatment device for mesophase pitch-based carbon fibers according to claim 1 is characterized in that: The conductive graphite roller (205) is arranged inside the inlet wire drawing machine (101) or the outlet wire drawing machine (105) via a rotating shaft (206) and a bearing (203), wherein the rotating shaft is arranged inside the conductive graphite roller (205).

4. A continuous self-heating graphitization treatment device for mesophase pitch-based carbon fibers according to claim 3, characterized in that: The rotating shaft (206) is made of copper, and the bearing (203) is made of graphite.

5. The continuous self-heating graphitization treatment device for mesophase pitch-based carbon fibers according to claim 3 is characterized in that: The rotating shaft (206) is a hollow structure, and a fin heat sink (201) is arranged on the end surface of the rotating shaft (206), and the fin heat sink (201) is connected to an external cooling source.

6. The continuous self-heating graphitization treatment device for mesophase pitch-based carbon fibers according to claim 3 is characterized in that: It also includes a sealed box (204) arranged between an inlet wire drawing machine (101) and a wire inlet (102) of a high-temperature furnace (103) or between an outlet wire drawing machine (105) and a wire outlet of a high-temperature furnace (103); a conductive graphite roller (205), a rotating shaft (206) and a graphite bearing (203) are arranged in the sealed box (204); and the rotating shaft (206) is installed in the sealed box (204) via an insulating shaft seat (202).

7. The continuous self-heating graphitization treatment device for mesophase pitch-based carbon fibers according to claim 6 is characterized in that: The sealed box body (204) is provided with an air hole, which is connected to an external inert gas source.

8. The continuous self-heating graphitization treatment device for mesophase pitch-based carbon fibers according to claim 1 is characterized in that: The wire-passing channel of the high-temperature furnace (103) is sprayed with high-temperature resistant ceramics.

9. The continuous self-heating graphitization treatment device for mesophase pitch-based carbon fibers according to claim 1, characterized in that: The length of the induction coil (104) is 600-1800 mm, and the inner diameter of the induction coil (104) matches the size of the furnace of the high-temperature furnace (103).

10. A method for continuous self-heating graphitization of mesophase pitch-based carbon fibers, characterized in that: Using the mesophase pitch-based carbon fiber continuous self-heating graphitization processing device as described in any one of claims 1 to 9, the carbon fiber is guided by a conductive graphite roller (205) in an inlet drawing machine (101) to enter a high-temperature furnace (103), an induction coil (104) and an outlet drawing machine (105) in sequence; The carbon fiber is a conductive carbon fiber that has been carbonized at a temperature above 1200°C, and the resistivity of the carbon fiber is below 40 μΩm. The pulling speed of the conductive graphite roller (205) is (1) to (6) m / min, the total envelope angle of the carbon fiber on the conductive graphite roller (205) is 360 to 720°, the operating tension of the carbon fiber is 50 to 300 cN, and the carbon fiber is always kept in a straight and taut state in the furnace, ensuring that the conductive graphite roller (205) is in good contact with the carbon fiber.

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