A pin core vacuum fractional quenching device

Abstract

The application discloses a kind of nail core vacuum fractional quenching device, and double-valve transition bin and vertical pipe are respectively the import and export of vacuum tank body, vertical pipe is communicated tank body and water pool, bottom is inserted below water surface of water pool, and water column seals tank body.Chain transmission device, heating furnace and isothermal pool are set in tank body, chain is connected through pin shaft rotation frame bottom, can be moved on the support roller of the formation conveyor belt, loading station and heating furnace are set on the conveyor belt, driven sprocket and isothermal pool are set below the heating furnace outlet door, and the material frame is quickly turned over at the driven sprocket position, and the nail core falls into the colander in the isothermal pool, and the colander turns over and quickly sends the nail core into the vertical pipe for quenching.At driven sprocket position, the material frame hung on chain is turned over into the loading station of conveyor belt by the rotation of upper frame cylinder.The application realizes vacuum fractional quenching, intermittent feeding and discharging, and realizes continuous production.

Description

Technical Field

[0001] This invention is applied to the field of blind rivet production, and relates to the vacuum quenching of rivet cores, specifically a device for vacuum graded quenching of rivet cores. Background Technology

[0002] Blind rivets are primarily used for joining thin plates. They pass through a connecting hole from one side, and a rivet gun is used to hold the rivet head. Pulling the rivet head causes the rivet tube to expand and plastically deform, forming a riveting connection with the rivet head. Except for special applications where stainless steel is used, the rivet head is mostly made of cold-heading steel grade SWRCH22A, with a carbon content between 0.18% and 0.23%, possessing both good cold-working formability and potential for subsequent heat treatment strengthening. The applicant uses spheroidizing annealing on the rivet head raw material strips to maximize their cold deformation capacity. They also perform ion-spray surface modification treatment to form a graphite layer on the outer surface, increasing lubrication performance, reducing friction with the cold-heading die, and extending the die's service life. Vacuum staged quenching is used on the rivet head to reduce quenching deformation and obtain products with high dimensional accuracy.

[0003] Vacuum heating quenching not only effectively prevents decarburization and oxidation of the workpiece surface, but also helps improve the uniformity of temperature inside and outside the workpiece, reducing the risk of quenching deformation and cracking. Stage quenching involves rapidly lowering the workpiece from its high austenitizing temperature to above the martensitic transformation temperature but below the pearlitic transformation temperature, holding it at that temperature for a certain time to ensure uniform temperature inside and outside the workpiece. Before the supercooled austenite begins to transform, the workpiece is rapidly lowered to below the martensitic transformation temperature for quenching. The workpiece undergoes martensitic transformation at a lower supercooled austenite temperature, reducing thermal stress, minimizing workpiece deformation, and obtaining workpieces with high-precision dimensions.

[0004] CN103710503B, a chain-bucket type vacuum water quenching furnace for titanium alloys, primarily addresses the issues of slow workpiece transfer speed and workpiece oxidation. The hopper moves back and forth between the discharge channel and the loading position, constituting a periodic quenching process, not a continuous quenching process. Two points in this application are unclear: the quenching temperatures for Ti-6Al-4V and BT16 titanium alloys are typically above 800℃; and the transmission chain is located within the vacuum heating tube. How to achieve high-temperature transport of the transmission shaft, transmission wheel, and transmission chain is unclear. Furthermore, under vacuum conditions, when the vacuum gate valve is opened, the workpiece falls through the discharge channel onto the elevator in the quenching water tank. How to prevent water in the water tank from entering the vacuum heating tube under atmospheric pressure is unclear. In addition, some other vacuum quenching furnace patent applications, such as CN211120665U (a continuous vacuum furnace material transfer and positioning lifting device), CN104451065A (a vacuum quenching furnace), and CN103627863A (a vertical vacuum quenching furnace), are not suitable for isothermal rapid cooling operations before low-temperature austenitic transformation. Summary of the Invention

[0005] The technical problem solved by this invention is to provide a vacuum graded quenching device for nail cores, which enables continuous production under the condition of meeting the process parameters of vacuum quenching and graded quenching.

[0006] The technical solution adopted in this invention is as follows: The nail core vacuum grading quenching device of this invention includes a transition chamber, a tank body, and a vertical pipe, as well as a material frame, support rollers, a chain drive device, a heating furnace, an isothermal pool, and a strainer disposed within the tank body. The tank body is under vacuum, and the transition chamber and the vertical pipe are the inlet and outlet for the nail cores, respectively. The chain drive device includes a driving sprocket, a chain, and a driven sprocket; the drive shaft of the driving sprocket extends out of the tank body and is connected to the tank body via a sealing element, which is fixedly connected to the tank body and rotatably seals against the drive shaft. The chain connects to both sides of the bottom of the material frame via a connecting element, which is fixedly connected to the chain and rotatably connected to the bottom of the material frame via a pin. The material frames are evenly distributed on the chain, meaning the spacing between the material frames is consistent, ensuring consistent positioning of each material frame during movement at each station. Support rollers forming a horizontal conveyor belt are disposed above the chain, supporting the horizontal movement of the material frames. The heating furnace has a double-door structure, disposed above the support rollers; the furnace outlet door is near the driving sprocket, and the furnace inlet door is near the loading station. An isothermal pool is installed below the furnace exit door. A strainer is placed inside the isothermal pool, and the strainer has perforations machined into its body to allow the isothermal liquid to flow through, preventing the nail core from falling into the isothermal pool. The handle of the strainer is fixedly connected to a strainer shaft, which extends out of the tank and is connected to the tank via a seal. The cross-section of the handle is grooved, so that when the strainer is flipped, the nail core falls from the strainer into the vertical pipe for quenching and cooling.

[0007] Furthermore, the transition chamber has a dual-valve structure, installed on the top of the tank above the conveyor belt loading station, with the upper and lower valves located outside the tank body. The alternating opening of the dual valves allows for intermittent continuous feeding into the tank without disrupting the vacuum within the tank.

[0008] Furthermore, the vertical pipe is located at one end of the tank body. The structure of the tank's end cap facilitates the design of the vertical pipe's position. This vertical pipe connects the tank body and the water pool, with its bottom inserted below the water surface in the pool, using a water column to seal the tank body into a vacuum. The water pool is located under atmospheric or negative pressure, and the height of the vertical pipe above the water surface is determined by atmospheric or negative pressure. A vacuum port is provided at the end of the tank body where the vertical pipe is located to promptly remove water vapor and flue gas from the isothermal liquid.

[0009] Furthermore, the drive shaft of the driving sprocket is wrapped with insulating cotton to cushion the impact on the drive shaft when the material frame flips and drops material, while also isolating heat transfer. An upper frame cylinder is installed on the drive shaft of the driven sprocket. The upper frame cylinder is located between the two driven sprockets, and a gap is maintained between the circumferential surface of the upper frame cylinder and the bottom surface of the material frame. When the material frame is suspended downwards and enters the driven sprocket with the chain, it can be flipped under the action of the upper frame cylinder, with the opening facing upwards, and enter the conveyor belt for horizontal transport to the dropping station.

[0010] In another embodiment, the drive shaft of the driving sprocket is mounted on the driven sprocket, which does not affect the conveying of the material frame on the chain drive device.

[0011] In another embodiment, the chain drive device can also be changed to a gear drive device, replacing the driving and driven sprockets with gears and the chain with a flexibly connected rack, which can also achieve fixed-point conveying of the material frame.

[0012] Furthermore, to prevent radiative heat transfer within the tank, a furnace door or curtain is installed at the furnace entrance. If a furnace door is used, its lifting hinge extends out of the tank and is connected to the tank via a seal. If a curtain is used, multiple layers are preferable, with the top and bottom, and left and right curtain gaps alternately covered.

[0013] Furthermore, to improve production efficiency, a preheating furnace is set up between the loading station and the heating furnace. Preheating before austenitizing heating helps to reduce heating deformation.

[0014] Furthermore, an inlet is provided above the water surface in the vertical pipe to promote the circulation of cooling water within the vertical pipe.

[0015] Furthermore, a stirring device is installed at the bottom of the isothermal pool to promote temperature homogenization of the isothermal liquid. A cooling water pipe is installed below the strainer inside the isothermal pool, or a cooling water nozzle is installed on the outside of the steel plate of the pool wall to prevent the temperature of the isothermal liquid inside the pool from exceeding the process temperature. Alternatively, a cavity can be formed outside the isothermal pool, and the isothermal liquid can be placed inside the cavity, with cooling water nozzles installed outside to indirectly cool the isothermal pool by cooling the isothermal liquid inside the cavity. Although this cooling method is slightly more complex in structure, it provides better temperature control of the isothermal liquid inside the pool, with less drastic temperature drop and good structural safety.

[0016] The beneficial effects of this invention are as follows: This invention uses a chain drive device to drive the material frame to achieve intermittent movement at multiple stations. After the nail core is heated for austenitization, it is quickly poured into an isothermal tank for isothermal cooling. After the processing time, a strainer can quickly send the nail core into a vertical tube for quenching and cooling, achieving vacuum staged quenching. The tank is intermittently fed and discharged without disrupting the tank vacuum, thus achieving continuous production. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the main structure of Embodiment 1; Figure 2 This is a left-side view of the structure of the present invention; Figure 3 This is a schematic diagram of the material frame exiting the furnace and the nail core exiting the frame; Figure 4 This is a schematic diagram of the material frame returning to its original position; Figure 5 This is a schematic diagram of the main structure of Embodiment 2; Figure 6 This is a schematic diagram of the main structure of Example 3; In the diagram: 1-Transition chamber, 2-Tank body, 3-Material frame, 4-Support roller, 5-Driven sprocket, 6-Upper frame cylinder, 7-Chain, 8-Connector, 9-Isothermal pool, 10-Strainer, 11-Strainer shaft, 12-Vertical pipe, 13-Discharge machine, 14-Water pool, 15-Drive sprocket, 16-Heating furnace, 17-Power unit, 18-Sealing component, 19-Pin shaft, 20-Insulation cotton, 21-Door curtain, 22-Preheating furnace. Detailed Implementation

[0018] The observation holes, manholes, vacuum ports, and liquid filling ports on the tank body, as well as the maintenance operation platform inside the tank, reinforcing ribs, support rods, and brackets, are simplified and not shown in the attached drawings. Structures not described in detail below, components not shown in detail in the attached drawings, and purchased equipment are all existing technology.

[0019] The difference between "driving sprocket" and "driven sprocket" mentioned below is only in their installation position. Example 1

[0020] The structure of the vacuum graded quenching device in this embodiment is shown in the attached figure. Figure 1 and attached Figure 2 As shown, the system includes a transition chamber 1, a tank body 2, and a vertical pipe 12, as well as a material frame 3, support rollers 4, a chain drive device, a heating furnace 16, an isothermal pool 9, and a strainer 10, all housed within the tank body. It also includes a water tank 14 and a discharge machine 13. The tank body 2 is a vacuum tank. To enhance its compressive strength, axial and circumferential reinforcing ribs, or an operating platform, can be welded to the inner and outer surfaces of the tank body. The tank body is connected to two vacuum pumps via pipes. The larger vacuum pump is used to quickly evacuate the air from the tank body, saving production preparation time, while the smaller vacuum pump is used to maintain the vacuum within the tank body, saving energy.

[0021] The transition chamber 1 and the vertical pipe 12 are the inlet and outlet for the continuous entry and exit of the nail cores into and out of the tank 2. The transition chamber 1 has a double-valve structure, located above the loading station, and is sealed to the top of the tank. It is equipped with two valves, an upper valve and a lower valve. The upper valve connects the transition chamber to the outside. Opening the upper valve allows the nail cores to be added into the transition chamber, and the valve is closed after a measured amount of nail cores has been added. The lower valve connects the transition chamber to the tank. When the material frame is being loaded, the lower valve is opened, and the nail cores in the transition chamber fall into the material frame. After the material falls, the lower valve is closed. Since the volume of the transition chamber is much smaller than that of the tank, intermittent continuous feeding through the transition chamber will not adversely affect the vacuum level inside the tank. The vertical pipe 12 is located at the end of the tank, and its end spherical arc end cap facilitates the flipping design of the strainer. The vertical pipe connects the tank and the water pool 14 vertically, using the water column inside the vertical pipe to isolate it from external atmospheric pressure. The bottom of the vertical pipe is inserted below the water surface of the water pool 14. To prevent atmospheric pressure from forcing water from the water pool into the tank, the height of the vertical pipe above the water surface in the water pool is no less than 10 meters. The volume of the water tank above the water surface should be greater than the volume of the vertical pipe above the water surface to ensure that the bottom of the vertical pipe is always lower than the water surface of the tank. The discharge machine 13 in the water tank is purchased externally and is used to receive the nail cores falling from the vertical pipe and carry the nail cores out of the water tank, into the hopper or the tempering furnace conveyor belt, and into the tempering heat treatment process.

[0022] The chain drive device is installed inside the tank and includes two symmetrically arranged sets of driving sprockets 15, chains 7, and driven sprockets 5. The drive shaft of the driving sprocket 15 extends out of the tank and is connected to the power unit 17. Under the drive of the power unit 17, the driving sprocket 15 rotates, thereby driving the chain 7 to move and the driven sprocket 5 to rotate. The drive shaft is connected to the tank through a seal 18, which is fixedly connected to the tank and provides a rotatable sealing connection with the drive shaft. The two chains 7 are respectively connected to both sides of the material frame 3 through connectors 8, as shown in the attached diagram. Figure 2 In the enlarged view, connector 8 is fixedly connected to chain 7 and rotatably connected to the bottom of the material frame via pin 19. Above the chain, multiple support rollers 4 are fixed horizontally at the same height. The rotation axis of the support rollers 4 is perpendicular to the transmission direction of the chain. The support rollers 4 are used to support the material frame 3, forming a conveyor belt, so that the material frame can be driven by the chain to move horizontally on the support rollers.

[0023] The heating furnace 16 has a double-door structure, located above the support roller 4. In the material conveying direction, it has an inlet door and an outlet door, with the outlet door near the drive sprocket 15. The inlet and outlet doors (referring to the door openings) are covered by a lifting furnace door (referring to the component). One end of a steel wire rope is connected to the upper part of the furnace door, and the other end is connected to a counterweight. The door is moved up and down by a fixed wheel fixed to a rotating shaft. This structure is commonly used for furnace doors in box-type heat treatment furnaces. The furnace door lifting shaft extends out of the tank body and is connected to the power unit. The connection method between the furnace door lifting shaft and the tank body is the same as the connection method between the drive sprocket drive shaft and the tank body.

[0024] Below the furnace outlet door of the heating furnace, an isothermal pool 9 is installed, and a strainer 10 is placed inside the isothermal pool 9. The body of the strainer 10 is used to catch the nail core falling from the material frame. The body of the strainer is machined with a large number of holes, the diameter of which is smaller than the diameter of the nail core rod, so that the isothermal liquid in the isothermal pool 9 can flow through it, but it can prevent the nail core from passing through and falling into the isothermal pool, or getting stuck in the holes. The handle of the strainer is fixedly connected to the strainer shaft 11, which extends out of the tank body and is sealed and rotatably connected to the tank body by a sealing element 18, the connection method being the same as that of the aforementioned drive sprocket drive shaft and furnace door lifting shaft. The end of the strainer shaft is connected to a hydraulic cylinder or other power device. The drive of the hydraulic cylinder or other power device can realize the rapid rotation of the strainer around the strainer shaft. The handle is grooved, so that when the strainer is rapidly rotated, the nail core can slide quickly from the body of the strainer through the groove of the handle into the vertical tube 12. The position of the strainer shaft, the size of the strainer handle, and the design of the upper opening of the vertical pipe should ensure that the strainer can tip freely without colliding with the drive sprocket shaft or the tank body. The isothermal solution uses inexpensive nitrates and nitrites, which are melted by electric heating before use.

[0025] The vacuum graded quenching process for H22A nail cores is as follows: the furnace temperature is 840-860℃, the holding time is 10-20 minutes, the nail cores are quickly taken out of the furnace and sent into the isothermal pool, the isothermal liquid temperature is 300-350℃, the holding time is 15-30 seconds, and then quickly poured into the cooling water in the vertical pipe for quenching.

[0026] In this embodiment, the movement of a material frame is used as an example. The nail core falls from the transition chamber into the material frame at the loading station. The furnace inlet door of the heating furnace is opened, and the chain drives the material frame into the heating furnace. The furnace inlet door is closed, and after the nail core heating and heat preservation process time, the furnace outlet door of the heating furnace is opened, and the chain drives the material frame out of the furnace, as shown in the attached diagram. Figure 3 As shown, when the drive sprocket turns the chain, the material frame loses the support of the support rollers. Under the gravity of the material frame and the nail core, the material frame flips and buckles around the pin shaft. The side plate of the material frame collides with the drive shaft of the drive sprocket and comes to a relative stop. At this time, all the nail cores in the material frame fall into the ladle body in the isothermal pool for isothermal cooling. To buffer the impact of the material frame on the drive shaft, insulation cotton 20 is wrapped around the drive shaft, which also prevents the high-temperature material frame from transferring heat to the drive shaft. During the isothermal cooling process of the nail core, the material frame has been moved away from the top of the isothermal pool to avoid affecting the flipping of the ladle. After the nail core in the ladle body isothermally cooled, the ladle shaft rotates under the action of the hydraulic cylinder or other power device, the ladle flips, and the nail core in the ladle body is quickly transferred from the groove of the ladle handle to the vertical tube. After water quenching in the vertical tube, the nail core descends to the bottom of the pool and is retrieved by the discharge machine and sent to the tempering station. After the nail cores are tilted and tilted, the material frame is conveyed by a chain to the driven sprocket position, as shown in the attached diagram. Figure 4 As shown in the attached diagram. An upper frame cylinder 6 is mounted on the drive shaft of the driven sprocket. The center of the upper frame cylinder 6 coincides with the center of the driven sprocket drive shaft, and a gap is maintained between its circumferential surface and the bottom surface of the material frame. The width of the upper frame cylinder is located between the two driven sprockets, as shown in the attached diagram. Figure 2 As shown. When the chain drives the material frame to turn at the driven sprocket, the outer circumferential surface of the upper frame cylinder 6 contacts the bottom surface of the material frame, causing the material frame to flip from a suspended state with its opening facing down to a horizontal state with its opening facing up. Supported by the support roller 4, it moves horizontally on the conveyor belt and enters the loading station, completing one chain drive cycle for a material frame. To achieve continuous production, multiple material frames can be evenly distributed on the chain, that is, the material frames are installed at equal intervals on the chain to ensure that the position of the material frame is consistent each time it moves to a different station. The moving speed of the material frame is not less than the speed at which the material frame moves from the unloading position to a position that does not affect the tilting of the strainer during the isothermal cooling process in the isothermal bath. In other words, the movement of the material frame between stations is completed within 15 to 30 seconds of isothermal bath heat preservation.

[0027] illustrate: 1) To facilitate valve maintenance and replacement, the upper and lower valves of the transition chamber should preferably be located outside the tank body. In this invention, apart from the static cables for heating the furnace and isothermal liquid, and the temperature measuring cable, which are inserted into the tank body, all other power transmission devices are located outside the tank body. These include power devices connected to the furnace door lifting shaft, the drive sprocket shaft, and the strainer shaft. This structure facilitates both the maintenance and replacement of the power devices and the determination of the equipment's operating status.

[0028] 2) Because there is an extremely thin graphite layer on the surface of the nail core to increase lubrication, even if there is a small amount of oxygen in the tank during the heating process, the graphite layer can react with the oxygen without oxidizing the nail core. Therefore, the intermittent switching of the transition chamber has no effect on the heat treatment of the nail core. In addition, the vacuum degree can be appropriately reduced, thereby reducing the energy consumption cost of production.

[0029] 3) An inlet is installed above the water surface in the vertical pipe to inject cooling water into it. Water pressure forces the hot water in the vertical pipe into the water tank, thus achieving water flow within the pipe. Relatively speaking, the core material in the vertical pipe cools from 300-350℃ to the water temperature; the cooling water carries away only a small amount of heat, and a small amount of circulating cooling water is sufficient to meet the water temperature requirements. Furthermore, the small amount of water vapor generated is removed by a vacuum pump, which will not adversely affect the heating elements inside the tank. The vacuum port of the tank should preferably be located near the vertical pipe opening to facilitate the removal of water vapor and flue gas from the isothermal liquid.

[0030] 4) A stirring device is installed at the bottom of the isothermal pool to ensure uniform temperature of the isothermal liquid within the pool. Simultaneously, a cooling water pipe is installed below the strainer within the isothermal pool, intermittently circulating cooling water to cool the isothermal liquid and prevent it from exceeding the process temperature range due to continuous operation of the high-temperature core. This cooling method places high demands on the pressure resistance of the cooling pipes, as the outside of the pipes is a vacuum environment while the inside is subjected to rapid cooling water vapor pressure. Alternatively, cooling water nozzles can be installed on the outside of the steel plate of the isothermal pool wall, using sprayed water to cool the steel plate and thus lower the temperature of the isothermal liquid within the pool. This method places high demands on the steel plate of the isothermal pool wall and requires a faster cooling rate. The best approach is indirect cooling, forming a cavity outside the isothermal pool connected to atmospheric pressure. Isothermal liquid is placed inside the cavity, and the outer wall of the cavity is water-cooled. The cooling of the isothermal liquid within the cavity slowly cools the isothermal liquid in the pool, and the temperature of the isothermal liquid in the cavity is controlled by the temperature of the isothermal liquid within the isothermal pool. In other words, the electric heating and temperature measurement of the isothermal liquid inside the tank are all moved to the cavity outside the tank, which facilitates the maintenance and replacement of the electric heating element and the temperature measuring thermocouple.

[0031] 5) The chain drive can also be changed to a gear drive, with the driving and driven sprockets replaced by gears and the chain replaced by a flexibly connected rack, as long as the positioning transmission is satisfied.

[0032] 6) Alternatively, the drive shaft of the drive sprocket can be installed on the driven sprocket. That is, the power unit drives the driven sprocket and drives the drive sprocket through the chain. As long as the moving direction of the material frame on the conveyor belt remains unchanged, it will not affect the transmission of the material frame by the chain. The difference between the drive and driven sprockets is only in their positions. The upper frame cylinder is still set on the driven sprocket near the loading station.

[0033] 7) If the water tank is set under negative pressure, the height of the water column in the riser is related to the negative pressure. This can reduce the height of the riser, thereby reducing the installation height of the tank. Alternatively, salt can be dissolved in the water in the tank to increase the quenching capacity and, by increasing the density of the cooling water, reduce the water level in the riser.

[0034] 8) The inner surface of the tank and its internal reinforcing ribs are covered with insulating cotton and wrapped with high-temperature reflective materials such as thin-walled stainless steel or aluminum foil. This reduces radiative heat dissipation after the material frame exits the furnace, helping to save energy. More importantly, it prevents the tank and reinforcing ribs from overheating, which could lead to a decrease in strength and thus ensure the safety of the vacuum tank. Other internal components of the tank and the operating platform should also adopt the above-mentioned insulation and heat dissipation prevention methods.

[0035] In this embodiment, the nail cores are intermittently added to the material frame using a transition chamber, without disrupting the vacuum of the tank. A chain drive device drives the material frame to achieve intermittent movement at multiple stations. After the nail cores are heated and kept at a certain temperature, the material frame can be quickly flipped to pour the nail cores into an isothermal bath for isothermal cooling. A strainer can quickly send the isothermally cooled nail cores into the cooling water in the vertical pipe for quenching and cooling, thereby achieving continuous vacuum staged quenching of the nail cores. Example 2

[0036] The heating furnace inside the tank of this invention heats the nail core under a vacuum negative state. In a vacuum state, conduction, convection, and radiation heating methods are eliminated. Since the heating element is not in contact with the material frame, only radiation heating is available. The furnace door is closed only to prevent radiative heat loss from the heating element; the furnace door is replaced with a door curtain 21, as shown in the attached diagram. Figure 5 As shown, the flexible door curtain does not affect the entry and exit of the material frame. This eliminates the need for the furnace door lifting structure, reducing the tank height and thus the tank volume, improving tank safety, and saving on material investment. It also reduces the drop height of the charging core at the loading station, mitigating core impact and protecting the core's outer surface.

[0037] To prevent heat loss through radiation from gaps between door curtains, multi-layered curtains are recommended, allowing the gaps at the top, bottom, left, and right to alternately cover the curtains and eliminate radiation. Stainless steel with a smooth, highly reflective surface is a suitable material for the curtains. Example 3

[0038] Based on Example 2, to improve production efficiency and further reduce nail core heating deformation, a preheating furnace 22 can be added between the loading station and the heating furnace, as shown in the attached figure. Figure 6 As shown. The structure of the preheating furnace 22 is similar to that of the heating furnace, also with two doors, the inlet door and the outlet door located on the conveyor belt. The preheating furnace temperature is 500-600℃, and the heating furnace temperature is 840-860℃, with a holding time of 8-10 minutes for both. The nail core is heated twice. After being heated in the preheating furnace, the temperature difference for austenitization in the heating furnace is reduced, resulting in lower thermal stress during austenitization transformation and less heating deformation. Two material frames have been added to the chain, doubling the material unloading efficiency at the loading station and increasing production efficiency by double.

[0039] In this embodiment, the active sprocket is positioned vertically below the furnace outlet door, reducing the interval time between the nail core falling into the isothermal pool and shortening the distance from the material frame inside the furnace to the position that does not affect the flipping of the strainer. This is equivalent to reducing the distance between material frames, which helps to reduce the length of the cylinder and the volume of the tank.

[0040] This invention employs a chain drive to move the material frame intermittently and simultaneously across multiple stations. After austenitizing heating, the nail cores are rapidly poured into an isothermal bath for isothermal cooling. Subsequently, a strainer quickly feeds the nail cores into a vertical tube for quenching and cooling, combining vacuum quenching and staged quenching. This helps reduce quenching deformation of the nail cores, resulting in products with high dimensional accuracy. The tank is fed and discharged intermittently without disrupting the vacuum, enabling continuous production to meet the requirements of mass production of nail cores. A preheating furnace is recommended to improve production efficiency and reduce heating deformation of the nail cores. This invention uses sealing components to house all power units outside the tank, facilitating maintenance and replacement. The tank interior uses insulation cotton and high-temperature reflective materials to reduce heat transfer from the tank interior to the outside, contributing to energy conservation and ensuring tank safety.

[0041] This invention uses H22A nail cores as an example to illustrate the structure of a vacuum graded quenching device, but it is not limited to H22A material or nail core products. The only changes are in the heating temperature and holding time, without altering the overall structure of the device. When used in conjunction with an automatic control system, this invention enables unmanned operation based on automatic weighing, automatic temperature control, time control, and power unit control. This device can be installed before a controlled atmosphere mesh belt tempering furnace to achieve continuous vacuum graded quenching and tempering.

Claims

1. A vacuum graded quenching device for nail cores, characterized in that: It includes a transition chamber (1), a tank (2) and a vertical pipe (12), as well as a material frame (3), a support roller (4), a chain drive device, a heating furnace (16), an isothermal pool (9) and a strainer (10) installed in the tank (2); the tank (2) is a vacuum, and the transition chamber (1) and the vertical pipe (12) are the inlet and outlet of the nail core entering and exiting the tank (2), respectively; The chain drive device includes a drive sprocket (15), a chain (7), and a driven sprocket (5); the drive shaft of the drive sprocket (15) extends out of the tank body (2) and is connected to the tank body (2) through a seal (18); the chain (7) is connected to both sides of the material frame (3) through a connector (8), the connector (8) is fixedly connected to the chain (7), and is rotatably connected to the bottom of the material frame (3) through a pin (19); the material frames (3) are evenly distributed on the chain (7); Above the chain (7), a support roller (4) is provided to form a horizontal conveyor belt, and the support roller (4) supports the material frame (3). The heating furnace (16) has a double door structure and is located above the support roller (4). The furnace outlet door of the heating furnace (16) is close to the drive sprocket (15), and the furnace inlet door is close to the charging station. An isothermal pool (9) is provided below the furnace door, and a strainer (10) is placed in the isothermal pool (9); the handle of the strainer (10) is fixedly connected to the strainer shaft (11), the strainer shaft (11) extends out of the tank body (2) and is connected to the tank body (2) through a sealing element (18); the cross-section of the handle is in the form of a groove, and when the strainer is flipped, the nail core falls from the strainer into the vertical tube (12).

2. The nail core vacuum graded quenching device according to claim 1, characterized in that: The transition chamber (1) has a double valve structure and is installed on the top of the tank above the conveyor belt loading station. The upper and lower valves are located outside the tank body (2). The inner surface of the tank body (2) is covered with insulation cotton, and the outer surface of the insulation cotton is covered with stainless steel or aluminum foil.

3. The nail core vacuum graded quenching device according to claim 1, characterized in that: The vertical pipe (12) is located at one end of the tank (2), connecting the tank (2) and the water pool (14). The bottom of the vertical pipe (12) is inserted below the water surface of the water pool (14). The water pool (14) is located under atmospheric pressure or negative pressure. A vacuum port is provided at the end of the tank where the vertical pipe is installed.

4. The nail core vacuum graded quenching device according to claim 1, characterized in that: Insulating cotton is wrapped around the drive shaft of the drive sprocket (15); an upper frame cylinder (6) is installed on the drive shaft of the driven sprocket (5), the upper frame cylinder (6) is located between the two driven sprockets (5), and the circumferential surface of the upper frame cylinder (6) and the bottom surface of the material frame (3) are kept apart.

5. The nail core vacuum graded quenching device according to claim 4, characterized in that: The drive shaft of the driving sprocket (15) is mounted on the driven sprocket (5).

6. The nail core vacuum graded quenching device according to claim 1, characterized in that: The chain drive device is changed to a gear drive device, the driving sprocket (15) and the driven sprocket (5) are changed to gears, and the chain (7) is changed to a flexibly connected rack.

7. The nail core vacuum graded quenching device according to claim 1, characterized in that: A furnace door or curtain is installed at the entrance of the heating furnace (16); the lifting shaft of the furnace door extends out of the tank (2) and is connected to the tank (2) through a sealing element (18); the upper and lower and left and right curtain gaps of the curtain are alternately covered.

8. The nail core vacuum graded quenching device according to claim 1, characterized in that: A preheating furnace (22) is provided between the loading station and the heating furnace (16).

9. The nail core vacuum graded quenching device according to claim 1, characterized in that: An inlet is provided above the water surface of the vertical pipe (12).

10. The nail core vacuum graded quenching device according to claim 1, characterized in that: A stirring device is provided at the bottom of the isothermal pool (9); a cooling water pipe is provided below the strainer in the isothermal pool (9), or a cooling water nozzle is provided outside the steel plate of the pool wall of the isothermal pool (9), or a cavity is formed outside the isothermal pool (9), and an isothermal liquid is placed in the cavity and a cooling water nozzle is provided outside.

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