A muffle tank structure with pressure relief device applied to a super duplex stainless steel needle carburizing furnace and application thereof

Abstract

This invention relates to the field of metal heat treatment equipment technology, specifically to a muffle furnace structure with a pressure-reducing device for use in a super duplex stainless steel knitting carburizing furnace, and its application. The furnace includes a heat treatment furnace, a pressure-reducing cover for sealing the furnace, and a lifting device for driving the opening and closing of the cover. The pressure-reducing cover includes a pull rod that slides through its central chamber and is driven to rise and fall by the lifting device, a set of limiters on both sides of the pull rod's rising path, and a set of telescopic parts that slide symmetrically in the two halves of the cover's interior. This invention, through the linkage of the limiters and the telescopic parts, constructs a dual pressure-reducing mechanism that prioritizes volume buffering followed by exhaust. During exhaust, the airflow is dispersed and released after multi-stage throttling, resulting in a smooth and controllable process. This avoids the violent atmosphere disturbance caused by the full opening of traditional safety valves, ensuring the quality of the knitting carburizing process.

Description

Technical Field

[0001] This invention relates to the field of metal heat treatment equipment technology, and more specifically, to a muffle tank structure with a pressure-relieving device for use in a super duplex stainless steel knitting furnace and its application. Background Technology

[0002] Super duplex stainless steel knitting needles are core precision parts in knitting machinery. Their material combines the high toughness of austenitic stainless steel with the high strength and stress corrosion resistance of ferrite. To improve the surface hardness and wear resistance of the knitting needles, they need to be carburized in a carburizing furnace. The carburizing process is carried out in a muffle tank, a sealed container, where a specific carburizing atmosphere is introduced and a pyrolysis reaction occurs at high temperature.

[0003] Patent application number CN202521042616.5 discloses a vertical annealing equipment and operating method for ultra-thin metal strips, including a furnace body device, a tension measuring device, a directional roller, an unwinding device, a winding device, a straightening device, and a deviation correction device. The furnace body device includes a muffle furnace and a furnace shell. Multiple sets of elastic supports that are fixedly connected to the furnace shell are provided on the outer side of the muffle furnace along its length. The top of the muffle furnace is fixedly connected to the top of the inner side of the furnace shell through a top elastic support, thereby improving the service life of the muffle furnace.

[0004] In actual production, as the furnace temperature rises or the carburizing atmosphere decomposes and produces gas, the internal pressure of the muffle can fluctuates drastically. If the pressure inside the can is too high, it may cause seal failure and atmosphere leakage, or even cause can deformation or safety accidents. If the pressure drops sharply, it may cause air to backflow into the can, resulting in workpiece oxidation and scrapping, or local carbon potential fluctuations may affect the uniformity of the carburized layer. Traditional safety valves cannot solve the problem of secondary pressure fluctuations and atmosphere instability caused by sudden large-scale exhaust, and are especially unsuitable for high-end workpieces such as super duplex stainless steel knitting needles that are extremely sensitive to surface carbon concentration and uniformity.

[0005] In view of this, this application proposes a muffle tank structure with a pressure-relieving device for use in a super duplex stainless steel knitting furnace and its application. Summary of the Invention

[0006] The purpose of this invention is to provide a muffle tank structure with a pressure-reducing device for use in a super duplex stainless steel knitting carburizing furnace and its application. Through the multi-level linkage of positioning components, limiters, and telescopic parts, a dual pressure-reducing mechanism is constructed with volume buffering as the priority and exhaust as the secondary priority, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A muffle tank structure with a pressure-reducing device for use in a super duplex stainless steel knitting carburizing furnace includes a heat treatment furnace, a pressure-reducing cover for sealing the heat treatment furnace, and a lifting device for driving the opening and closing of the pressure-reducing cover. The pressure relief cover includes a pull rod that slides through its central chamber and is driven to rise and fall by a lifting device, a set of limiters set on both sides of the pull rod's lifting path, and a set of telescopic parts that slide symmetrically in the two halves of the pressure relief cover. The telescopic part includes a sector-shaped piston that bears the pressure inside the furnace and several exhaust pipes that are rotatably disposed on the top surface of the sector-shaped piston. The bottom end of the pull rod is provided with a pressure head, and the limiter includes a shrink frame embedded in the spacer layer of the pressure relief cover cavity and a pair of limit blocks slidably embedded on both sides of the shrink frame. The two limit blocks extend and retract in the upper channels of the two telescopic parts respectively. In the above configuration, during normal operation, the fan-shaped piston adjusts the internal volume of the heat treatment furnace by its own lifting and lowering to buffer pressure fluctuations. When the pressure inside the furnace exceeds the set threshold, the lifting device drives the pull rod to press down, and the pressure head triggers the shrinkage frame to make the limit block exit the upward channel. The fan-shaped piston continues to move upward under the pressure inside the furnace, and when it moves to the preset position, it drives the exhaust pipe to rotate, opening the gas passage and discharging the gas inside the furnace from the top of the pressure relief cover.

[0008] In the technical solution of the present invention, the pressure relief cover further includes a circular frame placed on the top surface of the heat treatment furnace and a sealing assembly fixedly connected to the top of the circular frame by bolts. The interior of the circular frame is provided with a pressure relief groove for the telescopic part to slide up and down. The center of the circular frame is provided with a central hole for the pull rod to move. The interior of the circular frame is provided with a placement groove for accommodating the limiter. The circular frame is provided with a square opening in the placement groove that communicates with the pressure relief groove. A pin inserted into the placement groove is fixedly connected to the outer wall of the circular frame by bolts.

[0009] In the above configuration, the circular frame serves as the supporting skeleton for the pressure-relieving cover, enabling all moving parts to coordinate and cooperate under a unified standard.

[0010] In the technical solution of the present invention, the sealing assembly includes a cover body fixedly connected to the top surface of a circular frame by bolts and several circular tubes welded to the bottom surface of the cover body and extending downward. The pull rod is slidably inserted through the center of the cover body. A circular groove communicating with the circular tubes is opened on the top surface of the cover body, and an air vent cover is fixedly engaged in the circular groove.

[0011] In the above configuration, the sealing assembly forms a top seal on the tank through the fixed connection between the cover and the circular frame, the circular tube provides external protection for the pull rod, and the small exhaust hole on the vent cover constitutes the end throttle orifice of the exhaust channel, ensuring that the discharged high-temperature gas is dispersed and released rather than concentratedly injected.

[0012] In the technical solution of the present invention, the limiter further includes a second spring that provides elastic force for the shrink frame to extend into the central cavity of the pressure relief cover, and the inner end of the shrink frame is provided with an inclined chamfer that cooperates with the conical surface of the pressure head.

[0013] In the technical solution of the present invention, the shrinking frame of the limiter is provided with two front and rear symmetrical limit blocks, and the two limit blocks extend into the front and rear pressure relief grooves respectively; the shrinking frame is also provided with two symmetrically arranged inclined grooves, and the ends of the limit blocks are engaged with protruding rods that slide with the inclined grooves.

[0014] In the above setup, the travel of the telescopic part is controlled in stages by the limit switch, thus realizing a dual pressure relief mechanism that prioritizes volume buffering and then exhaust.

[0015] In the technical solution of the present invention, the telescopic part further includes an exhaust cover that is fixedly connected to the bottom surface of the sector piston by bolts. The exhaust cover has a plurality of exhaust grooves, the exhaust pipe has a plurality of cam grooves on its pipe wall, and the bottom surface of the exhaust pipe has a plurality of ventilation grooves. The exhaust pipe rotates on the top surface of the sector piston and is sleeved on the inner side of the circular pipe. The outer wall of the circular pipe is fixed with an insert rod, and the head of the insert rod extends into the cam groove.

[0016] In the technical solution of the present invention, the cam groove is composed of an upper straight groove section and a lower spiral groove section; when the limiting block does not exit the upward channel, the insert rod is limited to sliding within the straight groove section, and the exhaust pipe does not rotate; after the limiting block exits the upward channel, the fan-shaped piston drives the exhaust pipe to continue to move upward, the insert rod enters the spiral groove section and forces the exhaust pipe to rotate, so that the exhaust groove is aligned with the ventilation groove.

[0017] In the technical solution of the present invention, a third spring is also sleeved on the outside of the round pipe and the exhaust pipe. The upper end of the third spring abuts against the bottom surface of the cover and the lower end abuts against the top surface of the fan-shaped piston.

[0018] The above settings achieve pressure regulation while maintaining a stable atmosphere inside the tank, fundamentally avoiding the drawbacks of traditional safety valves that discharge all the way through and cause pressure overshoot.

[0019] In the technical solution of the present invention, the lifting device includes a support frame, a cylinder fixedly connected to the support frame by bolts, a lifting frame driven by the cylinder, and a fixing rod fixedly connected to the top of the pull rod by bolts.

[0020] In the above setup, the lifting frame is driven by a cylinder, which in turn moves the pull rod up and down, thus enabling the active switching between the pressure relief cover's locked state and its venting state.

[0021] On the other hand, the present invention also provides an application of a muffle tank structure with a pressure-relieving device in a carburizing furnace for super duplex stainless steel knitting, which is the application of the above-mentioned muffle tank structure with a pressure-relieving device in a carburizing furnace for super duplex stainless steel knitting during the carburizing process.

[0022] Compared with the prior art, the beneficial effects of the present invention are: 1. The structure and application of the muffle tank with pressure relief device applied to the super duplex stainless steel knitting needle carburizing furnace, through the cooperation of a sector piston and a third spring, dynamically adjusts the internal volume of the tank by adaptively raising and lowering the piston within the normal pressure fluctuation range, so as to achieve lossless pressure stabilization by buffering only and not discharging, which is different from the disadvantages of traditional safety valves that cause atmosphere loss and sharp pressure drop due to one-time exhaust.

[0023] 2. The structure and application of the muffle tank with pressure relief device applied to the super duplex stainless steel knitting needle carburizing furnace, through the linkage of the limiter and the telescopic part, constructs a dual pressure relief mechanism with volume buffering as the priority and exhaust as the secondary priority. During exhaust, the airflow is dispersed and released after passing through multiple throttling stages. The process is smooth and controllable, avoiding the violent atmosphere disturbance caused by the full opening of the traditional safety valve, and ensuring the quality of knitting needle carburizing.

[0024] 3. The structure and application of the muffle tank with pressure relief device applied to the super duplex stainless steel knitting furnace adopts a cylinder-driven triggering method. When overpressure occurs, the pull rod presses down to further tighten the pressure relief cover, and at the same time triggers the limiter to release the exhaust channel. The action is precise and controllable. After exhaust, all components automatically reset without manual intervention. The pressure relief device is integrated into the pressure relief cover on the top of the tank, and the lifting device is placed outside the furnace body, which does not occupy the effective space of the furnace chamber. The modular design facilitates the upgrading and transformation of existing carburizing furnaces. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a cross-sectional schematic diagram of the heat treatment furnace in this invention; Figure 3 This is a cross-sectional schematic diagram of the pressure-relieving cover in this invention; Figure 4 This is a sectional side view of the pressure-relieving cover in this invention; Figure 5 This is a cross-sectional view of the circular frame structure in this invention; Figure 6 This is one of the cross-sectional schematic diagrams of the sealing component in this invention; Figure 7 This is the second cross-sectional schematic diagram of the sealing component in this invention; Figure 8 This is a schematic diagram of the tie rod structure in this invention; Figure 9 This is a schematic diagram of the limiter in this invention; Figure 10 This is one of the structural breakdown diagrams of the telescopic part in this invention; Figure 11 This is the second structural breakdown diagram of the telescopic part in this invention; Figure 12 This is a schematic diagram of the lifting device in this invention; Explanation of reference numerals in the attached figures: 100. Heat treatment furnace; 200. Pressure-relieving cover; 210. Circular frame; 211. Pressure-relieving groove; 212. Shaft hole; 213. Placement groove; 214. Square opening; 220. Sealing assembly; 221. Cover body; 2210. Circular groove; 222. Circular tube; 223. Insert rod; 224. Gas cover; 230. Pull rod; 231. Contact head; 240. Limiter; 241. Retractable frame; 2410. Inclined groove; 242. Second spring; 243. Limiting block; 244. Protruding rod; 250. Telescopic part; 251. Sector piston; 252. Exhaust cover; 2520. Exhaust groove; 253. Exhaust pipe; 2530. Cam groove; 2531. Vent groove; 260. Third spring; 270. Pin; 300. Lifting device; 310. Support frame; 320. Cylinder; 330. Lifting frame; 340. Fixing rod. Detailed Implementation

[0026] The technical solutions of this invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0027] Please see Figures 1-2 As shown, this embodiment provides a technical solution: A muffle tank structure with a pressure relief device is used in a carburizing furnace for super duplex stainless steel knitting needles. It is applied in the carburizing process of super duplex stainless steel knitting needles. It includes a heat treatment furnace 100, with a pressure relief cover 200 and a lifting device 300 for driving the opening and closing of the pressure relief cover 200 respectively on the top and the outside of the heat treatment furnace 100. Furthermore, the heat treatment furnace 100 includes a sealed outer shell and a muffle tank disposed within the sealed outer shell. The tank is a cylindrical heat-resistant steel container with an opening at the top. A pressure sensor is installed inside the tank to detect whether the pressure inside the tank exceeds a set safety threshold.

[0028] Furthermore, by installing a pressure sensor inside the tank, real-time monitoring of the tank pressure is achieved, providing a signal basis for the active triggering of the lifting device 300, thus forming a prerequisite for closed-loop control.

[0029] Please see Figures 3-5 As shown, in this embodiment, the pressure relief cover 200 includes a circular frame 210 placed on the top surface of the heat treatment furnace 100, a sealing assembly 220 fixedly connected to the top of the circular frame 210 by bolts, a pull rod 230 that slides through the inside of the pressure relief cover 200 and is driven to rise and fall by the lifting device 300, a set of limiters 240 provided on both sides of the lifting path of the pull rod 230, and a set of telescopic parts 250 that slide symmetrically in the two halves of the cavity inside the pressure relief cover 200.

[0030] Furthermore, the interior of the circular frame 210 is provided with a pressure-relieving groove 211 for the telescopic part 250 to slide up and down. The center of the circular frame 210 is provided with a central hole 212 for the pull rod 230 to move. The interior of the circular frame 210 is provided with a placement groove 213 for accommodating the limiter 240. The circular frame 210 is provided with a square opening 214 through the placement groove 213, which is connected to the pressure-relieving groove 211. The square opening 214 provides a radially contracting sliding space for the structure in the limiter 240. A pin 270 inserted into the placement groove 213 is fixedly connected to the outer wall of the circular frame 210 by bolts. The pin 270 is used to close the external space of the placement groove 213 and provide a limiting support for the limiter 240.

[0031] In the above configuration, the circular frame 210 serves as the supporting skeleton of the pressure relief cover 200, provides a lifting guide rail for the telescopic part 250 through the pressure relief groove 211, constrains the movement axis of the pull rod 230 through the central hole 212, and provides installation space and movement space for the limiter 240 through the placement groove 213 and the square opening 214, so that all moving parts can coordinate and cooperate under a unified reference.

[0032] Please see Figures 6-8 As shown, in this embodiment, the sealing assembly 220 includes a cover 221 fixedly connected to the top surface of the circular frame 210 by bolts, several circular tubes 222 welded to the bottom surface of the cover 221 and extending downward, and several insert rods 223 snapped and fixed to the outer wall of the circular tubes 222. The pull rod 230 slides through the center of the cover 221. A circular groove 2210 communicating with the circular tubes 222 is opened on the top surface of the cover 221. An air cap 224 is snapped and fixed in the circular groove 2210.

[0033] Furthermore, multiple small vent holes are evenly distributed on the gas cover 224 to disperse and release the discharged gas. The pull rod 230 slides through the center of the cover 221 and moves within the axial hole 212. The bottom end of the pull rod 230 is provided with a pressing head 231, and the bottom of the pressing head 231 is provided with a conical surface, which is used to cooperate with the limiter 240.

[0034] In the above configuration, the sealing assembly 220 forms a top seal of the tank through the fixed connection between the cover 221 and the circular frame 210, the circular tube 222 provides external protection for the pull rod 230, and the exhaust hole on the gas cover 224 constitutes the end throttle port of the exhaust channel, ensuring that the discharged high-temperature gas is dispersed and released rather than concentrated.

[0035] Please see Figure 9 As shown, in this embodiment, the limiter 240 includes a shrinking frame 241 embedded in the chamber spacer of the pressure relief cover 200, a second spring 242 providing elastic force for the shrinking frame 241 to extend into the central chamber of the pressure relief cover 200, and a pair of limiting blocks 243 slidably embedded on both sides of the shrinking frame 241. The two limiting blocks 243 extend and retract within the upward channels of the two telescopic parts 250, respectively. The inner end of the shrinking frame 241 is provided with an inclined chamfer that cooperates with the conical surface of the pressure head 231.

[0036] Furthermore, the retraction frame 241 of the limiter 240 is provided with two front and rear symmetrical limit blocks 243, and the two limit blocks 243 extend into the front and rear pressure relief grooves 211 respectively; the retraction frame 241 is also provided with two symmetrically arranged inclined grooves 2410, and the end of the limit block 243 is engaged with a protruding rod 244 that slides with the inclined groove 2410. The limit block 243 extends into the upward channel of the telescopic part 250 to limit the upward stroke of the telescopic part 250.

[0037] Furthermore, when the pressure sensor built into the tank detects that the pressure inside the tank exceeds the set safety threshold, the controller controls the cylinder 320 to drive the pull rod 230 downward through the lifting frame 330. After the pull rod 230 is pressed down, on the one hand, the downward pressure is transmitted to the circular frame 210 through the fixed rod 340 and the lifting frame 330, so that the circular frame 210 is further pressed against the top surface of the heat treatment furnace 100 to prevent the pressure relief cover 200 from loosening or the atmosphere from leaking due to pressure fluctuations inside the tank during the exhaust process; on the other hand, the conical surface of the pressure head 231 contacts the inclined chamfer at the inner end of the shrinkage frame 241, pushing the shrinkage frame 241 radially outward, the protruding rod 244 slides along the inclined groove 2410 for guidance, and the limiting block 243 smoothly exits from the pressure relief groove 211, releasing the stroke restriction on the sector piston 251.

[0038] In the above configuration, the limiter 240 controls the stroke of the telescopic part 250 in stages, realizing a dual pressure relief mechanism with volume buffering as the priority and exhaust as the secondary priority. When the pressure fluctuates normally, the limiter 243 restricts the telescopic part 250 to move within a certain range to absorb the pressure fluctuation. When the pressure is over-pressurized, the pull rod 230 presses down to make the limiter 243 retract, releasing the remaining stroke of the telescopic part 250 to trigger exhaust.

[0039] Please see Figures 10-11As shown, in this embodiment, the telescopic part 250 includes a sector-shaped piston 251 that bears the pressure inside the furnace, an exhaust cover 252 that is fixedly connected to the bottom surface of the sector-shaped piston 251 by bolts, and several exhaust pipes 253 that are rotatably disposed on the top surface of the sector-shaped piston 251. During operation, the sector-shaped piston 251 adjusts the internal volume of the heat treatment furnace 100 by its own lifting and lowering to buffer pressure fluctuations; when the pressure inside the furnace exceeds a set threshold, the lifting device 300 drives the pull rod 230 to press down, and the pressure head 231 triggers the shrink frame 241 to make the limit block 243 exit the upward channel. The sector-shaped piston 251 continues to move upward under the drive of the pressure inside the furnace, and when it moves to the preset position, it drives the exhaust pipes 253 to rotate, opening the gas passage and discharging the gas inside the furnace from the top of the pressure relief cover 200.

[0040] Furthermore, the exhaust cover 252 is provided with several exhaust grooves 2520, the exhaust pipe 253 is provided with several cam grooves 2530 on its pipe wall, and several ventilation grooves 2531 are provided through the bottom surface of the exhaust pipe 253; the exhaust pipe 253 rotates on the top surface of the sector piston 251 and is sleeved inside the round pipe 222, and the head of the insert rod 223 extends into the cam groove 2530.

[0041] Furthermore, the cam groove 2530 consists of an upper straight groove section and a lower spiral groove section; when the limiting block 243 has not exited the upward channel, the insert rod 223 is limited to sliding within the straight groove section, and the exhaust pipe 253 does not rotate; after the limiting block 243 exits the upward channel, the sector piston 251 drives the exhaust pipe 253 to continue moving upward, the insert rod 223 enters the spiral groove section and forces the exhaust pipe 253 to rotate, so that the exhaust groove 2520 is aligned with the ventilation groove 2531.

[0042] Furthermore, a third spring 260 is also fitted on the outside of the round tube 222 and the exhaust pipe 253. The upper end of the third spring 260 abuts against the bottom surface of the cover 221, and the lower end abuts against the top surface of the fan-shaped piston 251.

[0043] Furthermore, during the energy storage and buffering stage, the bottom surface of the sector piston 251 directly bears the pressure of the atmosphere inside the tank. When the pressure inside the tank increases, the thrust exerted by the gas pressure on the bottom surface of the sector piston 251 increases, overcoming the elastic force of the third spring 260 and pushing the sector piston 251 upward along the pressure-relief groove 211 a certain distance. The upward movement of the sector piston 251 causes a corresponding increase in the volume of the effective gas phase space inside the tank below it. According to the gas law, under the condition that the temperature and the amount of gaseous substance remain unchanged, the increase in volume directly leads to a decrease in pressure, thereby offsetting the pressure increase caused by heating or cracking gas production. When the pressure inside the tank drops, the third spring 260 pushes the sector piston 251 downward to reset, the volume decreases, and the pressure rises again. Through the adaptive raising and lowering of the sector piston 251 with pressure fluctuations, the volume of the gas phase space inside the tank can be dynamically adjusted, achieving flexible absorption of pressure fluctuations and maintaining a relatively stable pressure inside the tank. Unlike traditional safety valves that can only release gas once when there is overpressure, causing a sharp drop in pressure and loss of atmosphere, this solution does not need to release any gas within the normal pressure fluctuation range. It achieves lossless pressure stabilization by buffering without releasing gas through volume adaptive adjustment.

[0044] Furthermore, when the pressure exceeds the upper limit that the volume adjustment can buffer, that is, when the stroke of the sector piston 251 is limited by the limit block 243 and cannot continue to increase the volume, the stroke limitation on the sector piston 251 is released. Driven by the pressure inside the tank, the sector piston 251 continues to push the third spring 260 upward. After the insertion rod 223 completes the straight groove section of the cam groove 2530, it enters the spiral groove section. The head of the insertion rod 223 slides along the spiral groove, forcing the exhaust pipe 253 to rotate around its own axis, so that the exhaust groove 2520 on the exhaust cover 252 is aligned with the vent groove 2531 on the exhaust pipe 253, and the exhaust passage is connected. The excess high-temperature atmosphere inside the tank enters the inner cavity of the exhaust pipe 253 through the exhaust groove 2520 and the vent groove 2531, and then rises through the round pipe 222, and is slowly dispersed into the atmosphere through the exhaust hole on the air cover 224. The exhaust path passes through multiple stages of throttling, including the exhaust channel, ventilation channel, circular pipe, and air cover. The airflow is gradually slowed down, and the discharge process is smooth and controllable, avoiding impact on the carburizing atmosphere inside the tank.

[0045] The above-mentioned settings achieve pressure regulation while maintaining a stable atmosphere inside the tank, fundamentally avoiding the drawbacks of traditional safety valves that allow pressure to overflow. Simultaneously, the downward pressure of the lever 230 during overpressure further tightens the pressure relief cover 200, ensuring that the cover 221 remains firmly attached to the top of the tank during the venting process, and that gas is only discharged through the controlled channel, resulting in higher safety.

[0046] Please see Figure 12As shown, in this embodiment, the lifting device 300 includes a support frame 310, a cylinder 320 fixedly connected to the support frame 310 by bolts, a lifting frame 330 driven by the cylinder 320, and a fixing rod 340 fixedly connected to the top of the pull rod 230 by bolts.

[0047] Furthermore, the lifting frame 330 is a horizontal beam structure, and its end is connected to the top of the tie rod 230 through the fixing rod 340, so that when the cylinder 320 drives the lifting frame 330 to move up and down, it can simultaneously drive the tie rod 230 to move up and down along the central hole 212.

[0048] In the above configuration, the lifting frame 330 is driven by cylinder 320, which in turn moves the lever 230 up and down, thus enabling the active switching between the locked and venting states of the pressure relief cover 200. Unlike traditional safety valves that rely entirely on spring force for passive opening and closing, this solution uses external power for active drive. This allows the triggering timing of the venting action and the travel distance of the lever 230 to be precisely controlled by the controller based on real-time signals from the pressure sensor, thereby achieving multi-stage triggering and controllable pressure relief.

[0049] The muffle tank structure with a pressure-reducing device for use in a super duplex stainless steel knitting needle carburizing furnace according to the present invention includes the following steps: Before the carburizing process begins, the pressure relief cover 200 is placed at the top opening of the heat treatment furnace 100, and the cover 221 is fitted to the top surface of the tank to form a seal. At this time, the shrinking frame 241 moves towards the central chamber of the pressure relief cover 200 under the elastic force of the second spring 242, and the limiting block 243 extends into the pressure relief groove 211 through the square opening 214 to limit the upward stroke of the fan-shaped piston 251; the insert rod 223 is located at the bottom of the straight groove section of the cam groove 2530, the exhaust groove 2520 and the ventilation groove 2531 are kept offset, the exhaust passage is closed, and the heat treatment furnace 100 is in a completely sealed carburizing working state; During the carburizing heating process, the temperature inside the tank rises or the carburizing agent decomposes, causing the pressure to gradually increase. The bottom surface of the fan-shaped piston 251 bears the pressure and acts on the third spring 260, moving up and down within the stroke range allowed by the limit block 243. By adjusting the internal volume of the furnace, the pressure fluctuation is buffered and absorbed, achieving lossless pressure stability with only buffering and no discharge. When the pressure sensor built into the heat treatment furnace 100 detects that the pressure inside the heat treatment furnace 100 exceeds the set safety threshold, the controller controls the cylinder 320 to drive the pull rod 230 to move downward through the lifting frame 330. After the pull rod 230 is pressed down, on the one hand, the cover 221 is further pressed against the top surface of the tank to ensure that the gas is discharged only from the controlled channel during the exhaust process; on the other hand, the conical surface of the pressure head 231 contacts the inclined chamfer at the inner end of the shrink frame 241, pushing the shrink frame 241 radially outward, the protruding rod 244 slides along the inclined groove 2410, and the limiting block 243 smoothly exits from the pressure relief groove 211, releasing the stroke restriction on the sector piston 251; After the limit block 243 is removed, the sector piston 251 continues to push the third spring 260 upward under the pressure inside the tank. After the insertion rod 223 completes the straight groove section of the cam groove 2530, it enters the spiral groove section. The head of the insertion rod 223 slides along the spiral groove, forcing the exhaust pipe 253 to rotate around its own axis, so that the exhaust groove 2520 on the exhaust cover 252 is aligned with the vent groove 2531 on the exhaust pipe 253, and the exhaust passage is connected. The excess high temperature atmosphere inside the tank enters the inner cavity of the exhaust pipe 253 through the exhaust groove 2520 and the vent groove 2531, and then rises through the round pipe 222, and is slowly dispersed into the atmosphere through the exhaust hole on the air cover 224. As the gas is discharged, the pressure inside the tank gradually drops back to a safe range. Under the elastic force of the third spring 260, the sector piston 251 moves downward to reset; the exhaust pipe 253 moves downward accordingly, and the insert rod 223 moves in the opposite direction in the spiral groove section of the cam groove 2530, driving the exhaust pipe 253 to rotate in the opposite direction, and the exhaust groove 2520 and the ventilation groove 2531 are re-shunted and closed. After the sector piston 251 is reset, the controller drives the cylinder 320 to pull the lever 230 back to its initial position. The limiter 240 is reset under the action of the second spring 242, and the limit block 243 extends back into the pressure relief groove 211. The entire pressure relief device is restored to its initial sealing state. After the carburizing process is completed, the lifting device 300 drives the pull rod 230 to move upward, so that the bottom surface of the cover 221 is matched with the top end of the pull rod 230, thereby lifting the entire pressure relief cover 200 from the top opening of the tank and taking out the internal workpiece.

[0050] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the specification and its equivalents.

Claims

1. A muffle furnace structure with a pressure-reducing device for use in a super duplex stainless steel knitting carburizing furnace, comprising a heat treatment furnace, characterized in that: It also includes a pressure relief cover for sealing the heat treatment furnace and a lifting device for driving the opening and closing of the pressure relief cover; The pressure relief cover includes a pull rod that slides through its central chamber and is driven to rise and fall by a lifting device, a set of limiters set on both sides of the pull rod's lifting path, and a set of telescopic parts that slide symmetrically in the two halves of the pressure relief cover. The telescopic part includes a sector-shaped piston that bears the pressure inside the furnace and several exhaust pipes that are rotatably disposed on the top surface of the sector-shaped piston. The bottom end of the pull rod is provided with a pressure head, and the limiter includes a shrink frame embedded in the spacer layer of the pressure relief cover cavity and a pair of limit blocks slidably embedded on both sides of the shrink frame. The two limit blocks extend and retract in the upper channels of the two telescopic parts respectively. During operation, the sector piston adjusts the internal volume of the heat treatment furnace by its own lifting and lowering to buffer pressure fluctuations. When the pressure inside the furnace exceeds the set threshold, the lifting device drives the pull rod to press down, and the pressure head triggers the shrinkage frame to make the limit block exit the upward channel. The sector piston continues to move upward under the pressure inside the furnace, and when it moves to the preset position, it drives the exhaust pipe to rotate, opening the gas passage and discharging the gas inside the furnace from the top of the pressure relief cover.

2. The muffle tank structure with a pressure-reducing device applied to a super duplex stainless steel knitting needle carburizing furnace according to claim 1, characterized in that: The pressure relief cover also includes a circular frame placed on the top surface of the heat treatment furnace and a sealing assembly fixedly connected to the top of the circular frame by bolts. The interior of the circular frame is provided with a pressure relief groove for the telescopic part to slide up and down. The center of the circular frame is provided with a central hole for the pull rod to move. The interior of the circular frame is provided with a placement groove for accommodating the limiter. The circular frame is provided with a square opening in the placement groove that communicates with the pressure relief groove. A pin inserted into the placement groove is fixedly connected to the outer wall of the circular frame by bolts.

3. The muffle tank structure with a pressure-reducing device applied to a super duplex stainless steel knitting needle carburizing furnace according to claim 2, characterized in that: The sealing assembly includes a cover body fixedly connected to the top surface of a circular frame by bolts and several circular tubes welded to the bottom surface of the cover body and extending downward. The pull rod is slidably inserted through the center of the cover body. A circular groove communicating with the circular tubes is opened on the top surface of the cover body, and an air vent cover is snapped and fixed in the circular groove.

4. The muffle tank structure with a pressure-reducing device applied to a super duplex stainless steel knitting needle carburizing furnace according to claim 3, characterized in that: The limiter also includes a second spring that provides elastic force for the retractable frame to extend into the central cavity of the pressure relief cover, and the inner end of the retractable frame is provided with an inclined chamfer that mates with the conical surface of the pressure head.

5. The muffle tank structure with a pressure-reducing device applied to a super duplex stainless steel knitting needle carburizing furnace according to claim 4, characterized in that: The shrinking frame of the limiter is provided with two symmetrical limit blocks at the front and rear centers, and the two limit blocks extend into the front and rear pressure relief grooves respectively; the shrinking frame is also provided with two symmetrically arranged inclined grooves, and the ends of the limit blocks are engaged with protruding rods that slide with the inclined grooves.

6. The muffle tank structure with a pressure-reducing device applied to a super duplex stainless steel knitting needle carburizing furnace according to claim 5, characterized in that: The telescopic part also includes an exhaust cover that is fixedly connected to the bottom surface of the sector piston by bolts. The exhaust cover has several exhaust grooves, the exhaust pipe has several cam grooves on its wall, and the bottom surface of the exhaust pipe has several ventilation grooves. The exhaust pipe rotates on the top surface of the sector piston and is sleeved inside the round pipe. The outer wall of the round pipe is fixed with a rod, and the head of the rod extends into the cam groove.

7. The muffle tank structure with a pressure-reducing device applied to a super duplex stainless steel knitting needle carburizing furnace according to claim 6, characterized in that: The cam groove consists of an upper straight groove section and a lower spiral groove section. When the limiting block does not exit the upward channel, the insert rod is limited to sliding within the straight groove section, and the exhaust pipe does not rotate. After the limiting block exits the upward channel, the fan-shaped piston drives the exhaust pipe to continue moving upward, the insert rod enters the spiral groove section and forces the exhaust pipe to rotate, so that the exhaust groove is aligned with the ventilation groove.

8. The muffle tank structure with a pressure-reducing device applied to a super duplex stainless steel knitting needle carburizing furnace according to claim 7, characterized in that: A third spring is also fitted on the outside of the round tube and the exhaust pipe. The upper end of the third spring abuts against the bottom surface of the cover, and the lower end abuts against the top surface of the sector piston.

9. The muffle tank structure with a pressure-reducing device applied to a super duplex stainless steel knitting needle carburizing furnace according to claim 8, characterized in that: The lifting device includes a support frame, a cylinder fixedly connected to the support frame by bolts, a lifting frame driven by the cylinder, and a fixing rod fixedly connected to the top of the pull rod by bolts.

10. An application of a muffle tank structure with a pressure-reducing device in a super duplex stainless steel knitting carburizing furnace, as described in claim 9, characterized in that: It is used in the carburizing process of super duplex stainless steel knitting needles in a carburizing furnace.

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