A tube furnace and heat treatment method

Abstract

The present application belongs to the technical field of heat treatment, and particularly relates to a tubular furnace and a heat treatment method. The tubular furnace provided by the present application comprises a furnace body, a furnace tube penetrating through the furnace body, and an atmosphere control device arranged at the end of the furnace tube. The atmosphere control device has an annular gas distribution cavity and a plurality of jet holes in communication with the gas distribution cavity. The through axes of the jet holes are arranged obliquely relative to the axial direction of the atmosphere control device. The gas in the gas distribution cavity is directed to be sprayed out towards the central passage through the jet holes, and the gas sprayed out by each jet hole converges in the central passage to form an axial gas flow. By forming an axial barrier gas flow at the end of the furnace tube, the present application can effectively inhibit the overflow of the furnace atmosphere and the infiltration of external air, maintain the stability and purity of the internal atmosphere of the furnace tube while allowing the continuous material to pass through without contact, realize the balance between continuous and efficient production and high-quality control of the heat treatment atmosphere, and is suitable for the continuous heat treatment operation of various types of continuous long-strip workpieces under a protective atmosphere.

Description

Technical Field

[0001] This invention belongs to the field of heat treatment technology, specifically relating to a tubular furnace and a heat treatment method. Background Technology

[0002] In the fields of metal processing and fiber material preparation such as carbon fiber, heat treatment is a key process for controlling microstructure, eliminating internal stress, and improving mechanical properties. Its process effect has a crucial impact on the final quality of the product. For continuous long strip workpieces such as copper alloy wire, stainless steel strip, and carbon fiber precursor, which are prone to oxidation or reaction with other atmospheric components at high temperatures, the composition and purity of the furnace atmosphere during heat treatment are crucial. Even a trace amount of oxygen infiltration can trigger surface oxidation, decarburization, or grain boundary embrittlement, leading to product performance degradation or even scrapping.

[0003] Currently, commonly used heat treatment equipment in industry can be broadly classified into two categories. The first category is the closed-loop batch furnace, typically represented by the atmosphere-sealed box furnace. This type of equipment has a sealed furnace structure, which allows for precise atmosphere control through pre-vacuuming or long-term gas replacement, reducing oxygen content to extremely low levels and providing excellent protection. However, its batch operation mode of loading, heating, holding, cooling, and unloading results in low production efficiency and makes it difficult to match with upstream continuous production lines (such as wire drawing, braiding, and winding). Especially for strips, wires, or fiber bundles that are hundreds or even thousands of meters long, batch furnaces not only cannot accommodate them but also cannot achieve continuous processing, resulting in significant limitations in adaptability.

[0004] The second type is the open continuous furnace, such as a horizontal tube furnace with open ends. This type of equipment allows workpieces to continuously pass through the heating zone, offering high throughput and easy integration into automated production lines. Therefore, it is the preferred equipment for continuous annealing, carbonization, or sintering processes of long workpieces. However, due to the requirement that workpiece inlets and outlets must be left at both ends of the furnace tubes, the furnace chamber cannot be completely sealed. In actual operation, if a protective gas (such as nitrogen or argon) is introduced into the furnace, the protective gas will continuously escape from the pipe openings due to the pressure difference and concentration gradient between the furnace chamber and the outside atmosphere. At the same time, outside air will also seep into the furnace in the opposite direction through diffusion and thermal convection, resulting in significant fluctuations in the oxygen partial pressure of the furnace atmosphere. Even increasing the protective gas flow rate often only reduces the infiltration ratio and cannot completely isolate the furnace. Furthermore, excessive airflow can disturb the temperature field inside the furnace, affecting the uniformity of heat treatment. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a tubular furnace and a heat treatment method.

[0006] The purpose of this invention is to alleviate the contradiction between continuous heat treatment and stable atmosphere control, and to improve the stability of the furnace atmosphere while ensuring continuous and efficient production.

[0007] The present invention first provides a tubular furnace, including a furnace body, a furnace tube penetrating the furnace body, and an atmosphere control device disposed at the end of the furnace tube; the atmosphere control device has an annular gas distribution chamber and multiple jet holes communicating with the gas distribution chamber, the through axis of the jet holes is inclined relative to the axial direction of the atmosphere control device, the gas in the gas distribution chamber is directionally ejected from the jet holes toward the central channel of the atmosphere control device, and the gas ejected from each jet hole merges in the central channel to form an axial airflow.

[0008] As a further optimization, the atmosphere control device includes an outer shell and an inner liner. The outer shell has an annular hollow structure, and the inner liner is located inside the outer shell. The inner liner has a lining wall, and there is an annular gap between the lining wall and the outer shell wall. After the two ends of the annular gap are closed, a gas distribution cavity is formed, and the jet hole is opened on the inner liner.

[0009] As a further optimization, the outer shell is provided with two gas distribution chambers, and each gas distribution chamber is provided with a corresponding liner. The axial components of the air outlets on the liner corresponding to the two gas distribution chambers are opposite, so that the directions of the two axial airflows are opposite.

[0010] As a further optimization, a stop ring is provided on the inner side of the shell peripheral wall of the outer shell. The stop ring is located at the axial center of the outer shell. The two gas distribution chambers are located at the two axial ends of the stop ring and are separated by the stop ring. A first air inlet and a second air inlet are provided on the shell peripheral wall of the outer shell. The first air inlet is connected to one of the gas distribution chambers on one side, and the second air inlet is connected to the other gas distribution chamber.

[0011] As a further optimization, a stop ring is provided on the inner side of the outer shell peripheral wall, and an end sealing ring is provided at the other axial end of the gas distribution cavity. The stop ring and the end sealing ring are located on the two axial sides of the gas distribution cavity, respectively, and together they form the double-sided axial sealing end wall of the gas distribution cavity.

[0012] As a further optimization, the angle A between the through axis of the jet orifice and the axis of the atmosphere control device is 15°~75°.

[0013] As a further optimization, the outer edge of the lining wall of the inner liner is provided with a positioning part, which protrudes radially and abuts against the inner wall of the outer shell to limit the radial position of the inner liner.

[0014] As a further optimization, the jet holes are distributed in a ring array along the circumference.

[0015] As a further optimization, a connecting ring is provided at the end of the outer shell, and multiple connecting holes are provided on the connecting ring along the circumference. The atmosphere control device is detachably connected to the end of the furnace tube through the connecting ring.

[0016] As a further optimization, an atmosphere control device is installed at each end of the furnace tube.

[0017] The present invention also provides a heat treatment method, wherein the above-mentioned tubular furnace is used, comprising the following steps: Step 1: Introduce protective gas into the atmosphere control device. After the protective gas is pressurized in the gas distribution chamber, it is directionally ejected from the jet hole, forming an axial airflow in the central channel. Step 2: Start the furnace body heating to raise the temperature inside the furnace tubes to the preset heat treatment temperature; Step 3: Insert the continuous material through the central channel of the atmosphere control device at one end of the furnace tube, complete the heat treatment inside the furnace tube, and then exit through the central channel of the atmosphere control device at the other end of the furnace tube.

[0018] As a further optimization, the atmosphere control devices at both ends of the tubular furnace tubes each have two gas distribution chambers and two sets of jet holes with opposite gas outlet directions. After the protective gas is introduced, two axial airflows with opposite directions are formed in the central channel of each atmosphere control device. The axial airflow towards the inside of the furnace tube prevents the atmosphere inside the furnace from overflowing, while the axial airflow away from the outside of the furnace tube prevents external air from seeping in.

[0019] As a further optimization, the protective gas is an inert gas, preferably nitrogen or argon.

[0020] Beneficial effects Compared with existing technologies, this invention, by configuring an atmosphere control device with dual gas distribution chambers and a bidirectional injection structure at the end of the furnace tube of a tubular furnace, allows the protective gas to be uniformly pressurized and then directionally injected, converging into two axial airflow barriers in opposite directions in the central channel. Under the condition of continuous material passing through without contact, it simultaneously achieves bidirectional isolation of the overflow of high-temperature atmosphere inside the furnace and the infiltration of external air, significantly improving the stability and purity of the atmosphere inside the furnace tube. This enables continuous heat treatment operations to be carried out efficiently in a stable and controllable atmosphere, and overall improves the reliability of the heat treatment process and the consistency of product quality. Attached Figure Description

[0021] Figure 1 This is a three-dimensional schematic diagram of an atmosphere control device.

[0022] Figure 2 This is a three-dimensional sectional view of an atmosphere control device.

[0023] Figure 3 This is an axial sectional view of an atmosphere control device.

[0024] Figure 4 This is a three-dimensional sectional view of the housing of an atmosphere control device.

[0025] Figure 5This is a three-dimensional schematic diagram of the lining of an atmosphere control device.

[0026] Figure 6 for Figure 5 A three-dimensional sectional view of a single segment of the lining shown.

[0027] Figure 7 This is a schematic diagram showing the angle between the jet hole axis and the atmosphere control device axis.

[0028] Figure 8 This is a schematic diagram of the airflow direction inside an atmosphere control device.

[0029] Figure 9 This is an axial sectional view of another type of atmosphere control device.

[0030] Figure 10 This is a schematic diagram of a tubular furnace.

[0031] Figure 11 for Figure 10 The diagram shows the connection between the furnace tubes and the atmosphere control device of the tubular furnace.

[0032] Figure 12 For continuous material to pass through Figure 10 The diagram shows a tubular furnace.

[0033] Figure 13 This is a schematic diagram of the airflow distribution experienced by the continuous material at the atmosphere control device.

[0034] In the figure, 1 is the outer shell; 2 is the inner lining; 3 is the furnace tube; 4 is the furnace body; 5 is the continuous material; 11 is the shell peripheral wall; 12 is the first air inlet; 14 is the stop ring; 15 is the connecting ring; 16 is the second air inlet; 19 is the gas distribution chamber; 21 is the lining peripheral wall; 22 is the jet hole; 23 is the positioning part; and 25 is the end sealing ring. Detailed Implementation

[0035] The present invention is further illustrated below through embodiments, which are intended to more clearly illustrate the technical solutions of the present invention, and should not be construed as a limitation.

[0036] Reference Figures 1 to 9 The atmosphere control device mainly includes an outer shell 1 and an inner liner 2.

[0037] The outer shell 1 is a hollow, annular load-bearing body with an overall cylindrical structure. The outer shell 1 has an integrally formed peripheral wall 11. Connecting rings 15 can be installed at both ends or one section of the outer shell 1, with multiple connecting holes along the circumference of each ring 15. Through the connecting rings 15, the entire atmosphere control device can be sealed and fixed to the mounting end face, such as the inlet end face of a heating furnace, achieving a detachable connection between the atmosphere control device and the heating furnace.

[0038] The inner wall of the outer casing 1 is provided with an annular gas distribution cavity 19. Gas can enter the gas distribution cavity 19 through the through hole on the peripheral wall 11 of the casing and then flow into the center of the outer casing 1. The structure of the gas distribution cavity 19 can be integrally formed with the outer casing 1 or formed by assembling multiple parts.

[0039] In some embodiments, an inner liner 2 is assembled inside the outer shell 1. The inner liner 2 is an annular flow divider, which is integrally nested inside the outer shell 1. The inner liner 2 has a peripheral wall 21, which is located inside the peripheral wall 11 of the shell. An annular gap exists between the peripheral wall 21 and the peripheral wall 11, and the gap is closed at both ends to form the gas distribution cavity 19. Air jet holes 22 are provided on the peripheral wall 21, and the air jet holes 22 are arranged in an annular array along the peripheral wall 21. The through axis of the air jet holes 22 forms an inclined angle A with the axial direction of the atmosphere control device, such as... Figure 7 As shown, the gas in the gas distribution chamber 19 is ejected directionally towards the central channel of the outer shell 1 through the jet holes 22, and the gas ejected from each jet hole 22 merges in the central channel to form an axial airflow.

[0040] In some embodiments, a positioning portion 23 is provided on the outer edge of the liner wall 21. The positioning portion 23 protrudes radially and abuts against the inner wall of the shell peripheral wall 11, defining the radial position of the inner liner 2 and maintaining the flow gap of the gas distribution cavity 19. The positioning portion 23 and the inner wall of the shell peripheral wall 11 are preferably interference-fitted to prevent the inner liner 2 from loosening and falling off. Preferably, there are 3 to 4 positioning portions 23 on each liner wall 21, evenly distributed circumferentially. The inner liner 2 can be integrally molded, or it can be processed as follows: Figure 5 and Figure 6 The diagram shows a structure assembled from multiple ring-shaped units continuously spliced ​​along the axial direction.

[0041] In some embodiments, a stop ring 14 is provided on the inner side of the shell peripheral wall 11, and the stop ring 14 is preferably integrally formed with the shell peripheral wall 11. The stop ring 14 is an annular sealing member, and the stop ring 14 forms an axially sealed end wall on one side of the gas distribution cavity 19, preventing gas in the gas distribution cavity 19 from overflowing axially. The stop ring 14 also forms a central through hole, allowing material to pass through, and the stop ring 14 also provides axial restraint for the inner liner 2. An end sealing ring 25 is also provided at the other end of the gas distribution cavity 19. The end sealing ring 25 and the stop ring 14 are located on opposite sides of the axial direction of the gas distribution cavity 19. The end sealing ring 25 and the stop ring 14 together form the double-sided axially sealed end wall of the gas distribution cavity 19, preventing gas in the gas distribution cavity 19 from overflowing axially from both ends. The end sealing ring 25 can be a separate part as shown in the figure, and can be detachably installed in a preset position. In other embodiments, the end sealing ring 25 can also be integrally formed with the liner peripheral wall 21.

[0042] In some embodiments, a gas distribution chamber 19 is provided inside the outer casing 1, and the corresponding jet holes 22 of the inner liner 2 blow air in one direction, forming a unidirectional axial airflow. In this case, such as Figure 9 As shown, the stop ring 14 is offset towards one end of the outer shell 1, and the inner liner 2 and gas distribution chamber 19 are only provided on one side of the stop ring 14. A first air inlet 12 is provided on the side wall of the outer shell 1, and the first air inlet 12 communicates with the gas distribution chamber 19. External gas is sent into the gas distribution chamber 19 through the first air inlet 12. Usually, one first air inlet 12 is provided, but multiple inlets can also be provided as needed. The inclination direction of the jet nozzle 22 is consistent with the blowing direction, so that the ejected gas forms an axial airflow facing the same side in the central channel, blocking the gas in the opposite direction from flowing in the opposite direction along the central channel.

[0043] In other embodiments, the outer shell 1 has two gas distribution chambers 19, and the jet holes 22 of the corresponding two sets of inner liners 2 blow air in two opposite directions, forming a bidirectional axial airflow. In this case, the baffle ring 14 is located at the axial middle position of the outer shell 1. Each side of the baffle ring 14 has a set of inner liners 2 and a gas distribution chamber 19. The two gas distribution chambers 19 are separated by the baffle ring 14 and are not interconnected. The side wall of the outer shell 1 has a first air inlet 12 and a second air inlet 16. The first air inlet 12 communicates with one of the gas distribution chambers 19, and the second air inlet 16 communicates with the other gas distribution chamber 19, allowing independent air supply to both sides. Usually, one first air inlet 12 and one second air inlet 16 are provided, but multiple inlets can also be provided as needed. The jet holes 22 of the inner liners 2 on both sides have opposite air outlet directions and are inclined away from the baffle ring 14, so that the gas ejected from both sides blows in two opposite directions to form an axial airflow, blocking the gas at both ends from exchanging from one side to the other, achieving a better blocking effect.

[0044] In some embodiments, the cross-sectional shape of the jet orifice 22 is preferably circular. The through axis of the jet orifice 22 is inclined at an angle A to the axial direction of the atmosphere control device. The inclined angle A is preferably in the range of 15° to 75°, and more preferably 25° to 65°. The inclined angle A can be adjusted according to specific working conditions: when the atmosphere control device has sufficient axial distance, a smaller angle A is preferred, such as 25° to 45°. At this time, the axial velocity component of the airflow is larger and the radial velocity component is smaller. The airflow needs to flow through a longer axial path before converging into a whole. The axial velocity of the airflow is large, and the blocking effect is better. When the axial space of the atmosphere control device is limited, or when it is necessary to quickly form a complete blocking airflow in a shorter distance, a larger angle A is preferred, such as 45° to 65°. At this time, the radial velocity component of the airflow is larger. After being ejected, it can quickly converge towards the center and form a continuous and dense airflow barrier in a shorter axial distance. However, the energy loss is larger, which is suitable for compact installation requirements.

[0045] Reference Figures 10 to 13 A tubular furnace is provided, comprising a furnace body 4, furnace tubes 3, and the aforementioned atmosphere control device.

[0046] The furnace body 4 is the main heating and insulation structure of the tubular furnace. Heating elements and insulation layers are installed inside the furnace body 4 to provide the required high-temperature environment for heat treatment. The furnace tube 3 is located inside the furnace body 4 and runs through the furnace body 4. The furnace tube 3 is a high-temperature resistant tubular component. If it is made of a suitable material, a through-processing cavity is formed inside. The continuous material 5 to be heat treated passes through the inside of the furnace tube 3 and completes the heat treatment.

[0047] An atmosphere control device is installed at the end of the furnace tube 3, and is connected to the end of the furnace tube 3 via a connecting ring 15. In some embodiments, an atmosphere control device is installed at each end of the furnace tube 3, located on the feed side and discharge side of the furnace body 4, respectively. The two atmosphere control devices operate independently, respectively isolating the feed end and the discharge end.

[0048] In some embodiments, the atmosphere control device adopts a dual-chamber structure, that is, two gas distribution chambers 19 are provided inside the outer shell 1, and the jet holes 22 on both sides of the baffle ring 14 spray in two opposite directions. After the atmosphere control device with this structure is installed at the end of the furnace tube 3, the axial airflow towards the furnace tube 3 prevents the gas inside the furnace from overflowing, and the axial airflow away from the furnace tube 3 prevents external air from seeping into the furnace tube 3 in the opposite direction, thereby realizing bidirectional atmosphere control, improving the stability and purity of the atmosphere inside the furnace tube 3, and allowing the workpiece to be heat-treated to smoothly enter and pass through the furnace tube to achieve continuous heat treatment operation.

[0049] In other embodiments, the atmosphere control device adopts a single-cavity structure, that is, a gas distribution cavity 19 is provided inside the outer shell 1, and the installation direction is set as needed so that the jet hole 22 sprays towards the inside or outside of the furnace tube 3.

[0050] The following describes a heat treatment method using an atmosphere control device with bidirectional control installed at both ends of furnace tube 3 as an example. The method includes the following steps: S1. After setting up the device, protective gas is introduced into the first air inlet 12 and the second air inlet 16 of the atmosphere control device at both ends. After the gas is pressurized by the corresponding gas distribution chamber 19, it is ejected directionally from the jet hole 22 on the inner liner 2. The jet holes 22 on both sides of the stop ring 14 are ejected in opposite directions, forming two axial airflows in opposite directions in the central channel of the device. S2. Start heating the furnace body 4 to raise the temperature inside the furnace tube 3 to the preset heat treatment temperature; insert the continuous material 5 through the central channel of the atmosphere control device at the feeding end, complete the heat treatment inside the furnace tube 3, and then exit through the central channel of the atmosphere control device at the discharging end; during the feeding process, the continuous material 5 is surrounded by bidirectional axial airflow from the feeding end and the discharging end, and the high-temperature atmosphere inside the furnace tube 3 is blocked by the axial airflow towards the furnace and does not overflow or only overflows slowly in small amounts, while the external air is blocked by the axial airflow towards the furnace and does not penetrate into the furnace tube 3, thereby maintaining the basic stability of the atmosphere inside the furnace tube 3 under the premise that the continuous material 5 passes through without contact.

[0051] In some embodiments, the protective gas can be selected according to process requirements, and is generally an inert gas (nitrogen, argon, etc.).

[0052] The above embodiments are exemplary and are intended to illustrate the technical concept and features of the present invention, so that those skilled in the art can understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A tubular furnace, characterized in that, The furnace includes a furnace body (4), a furnace tube (3) passing through the furnace body (4), and an atmosphere control device disposed at the end of the furnace tube (3). The atmosphere control device has an annular gas distribution chamber (19) and a plurality of jet holes (22) communicating with the gas distribution chamber (19). The through axis of the jet holes (22) is inclined relative to the axial direction of the atmosphere control device. The gas in the gas distribution chamber (19) is ejected directionally towards the central channel of the atmosphere control device through the jet holes (22). The gas ejected from each jet hole (22) merges in the central channel to form an axial airflow.

2. The tubular furnace according to claim 1, characterized in that, The atmosphere control device includes an outer shell (1) and an inner liner (2). The outer shell (1) has an annular hollow structure. The inner liner (2) is disposed inside the outer shell (1). The inner liner (2) has a lining wall (21). There is an annular gap between the lining wall (21) and the shell lining wall (11) of the outer shell (1). The two ends of the annular gap are closed to form the gas distribution cavity (19). The jet hole (22) is opened on the inner liner (2).

3. The tubular furnace according to claim 2, characterized in that, The outer shell (1) is provided with two gas distribution chambers (19), and each gas distribution chamber (19) is provided with a corresponding inner liner (2). The axial components of the air outlets (22) on the inner liner (2) corresponding to the two gas distribution chambers (19) are opposite, so that the directions of the two axial airflows are opposite.

4. The tubular furnace according to claim 3, characterized in that, A stop ring (14) is provided on the inner side of the shell peripheral wall (11) of the outer shell (1). The stop ring (14) is located at the axial center of the outer shell (1). The two gas distribution chambers (19) are located at the two axial ends of the stop ring (14) and are separated by the stop ring (14). A first air inlet (12) and a second air inlet (16) are provided on the shell peripheral wall (11) of the outer shell (1). The first air inlet (12) is connected to one of the gas distribution chambers (19) on one side, and the second air inlet (16) is connected to the other gas distribution chamber (19).

5. The tubular furnace according to claim 4, characterized in that, The outer shell (1) has a stop ring (14) on the inner side of the shell peripheral wall (11), and the gas distribution cavity (19) has an end sealing ring (25) on the other axial end. The stop ring (14) and the end sealing ring (25) are located on the axial sides of the gas distribution cavity (19) respectively, and together they form the double-sided axial sealing end wall of the gas distribution cavity (19).

6. The tubular furnace according to claim 1, characterized in that, The angle A between the through axis of the jet hole (22) and the axial direction of the atmosphere control device is 15°~75°.

7. The tubular furnace according to any one of claims 1-6, characterized in that, An atmosphere control device is installed at each end of the furnace tube (3).

8. A heat treatment method, characterized in that, The process, performed using the tubular furnace as described in claim 7, includes the following steps: Step 1: Introduce protective gas into the atmosphere control device. After being pressurized by the gas distribution chamber (19), the protective gas is directionally ejected from the jet hole (22) to form an axial airflow in the central channel. Step 2: Start the furnace body (4) to heat up, so that the inside of the furnace tube (3) rises to the preset heat treatment temperature; Step 3: Insert the continuous material (5) through the central channel of the atmosphere control device at one end of the furnace tube (3), and after heat treatment inside the furnace tube (3), it exits through the central channel of the atmosphere control device at the other end of the furnace tube (3).

9. The heat treatment method according to claim 8, characterized in that, The atmosphere control devices at both ends of the furnace tube (3) of the tubular furnace each have two gas distribution chambers (19) and two sets of jet holes (22) with opposite gas outlet directions. After the protective gas is introduced, two axial airflows with opposite directions are formed in the central channel of each set of atmosphere control devices. The axial airflow towards the inside of the furnace tube (3) prevents the atmosphere inside the furnace from overflowing, while the axial airflow away from the outside of the furnace tube (3) prevents external air from seeping in.

10. The heat treatment method according to claim 8, characterized in that, The protective gas is an inert gas.

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