Box-type resistance furnace for metal heat treatment

Abstract

The box-type resistance furnace comprises a furnace body and door plates arranged at a front furnace opening and a rear furnace opening of the furnace body, and a front partition cavity and a rear partition cavity are formed between a front inner partition door and a rear inner partition door and between the front door plate and the rear door plate correspondingly; a sliding block is slidably arranged on the inner side of the door plate in the circumferential direction, and a first groove is formed in the inner wall of the sliding block. Second grooves are formed in the circumferential directions of the front furnace opening and the rear furnace opening of the furnace body. A pipeline communicated with the second grooves is arranged in the furnace body. The sliding block moves in the first direction, so that the first groove and the second groove are buckled to form a negative pressure sealing cavity. The sliding block moves in the second direction, so that the circumferential inner side of the first groove protrudes out of the furnace body, and a gap is formed between the first groove and the furnace body. The invention relates to the technical field of resistance furnaces, and by optimizing the furnace body structure, the resistance furnace has good sealing performance, heat loss is reduced, heat treatment efficiency is improved, heating and cooling time is shortened, and energy consumption is reduced. And the temperature in the workshop is effectively controlled, and the working environment of workers is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of resistance furnaces, and specifically relates to a box-type resistance furnace for heat treatment of metals. Background Art

[0002] The chain-type stepping box-type resistance furnace, as a commonly used equipment for heat treatment of titanium alloy bars, plays an important role in the metal processing industry in our country. This equipment mainly consists of front and rear furnace doors, a furnace body, a heating system, a transmission system, etc. The titanium alloy bars enter the furnace body from the front door, and after being heat-treated in the furnace, are exported from the rear door, and then transferred to the next process after cooling down to 500°C - 600°C. However, the existing chain-type stepping box-type resistance furnace has the following problems in actual application: 1. Long heating and cooling time: After the room-temperature bars enter the furnace body, it takes a certain amount of time to heat up to 1300°C. Similarly, it also takes a long time for the bars to cool down to 500°C - 600°C after leaving the furnace. This not only affects the production efficiency but also causes energy waste.

[0003] 2. Increase in temperature in the workshop: Since heat will be dissipated into the workshop during the heating and cooling process of the chain-type stepping box-type resistance furnace, the temperature in the workshop will increase, affecting the working environment of the staff and the performance of the equipment.

[0004] 3. Poor sealing performance of the furnace door: The furnace door of the existing equipment adopts a single-plate design. Although a clamping mechanism is used to fix the door panel, there are still gaps, resulting in serious heat loss and reducing the heating efficiency of the furnace body.

[0005] In view of the above problems, it is necessary to improve the chain-type stepping box-type resistance furnace to improve the heat treatment efficiency, reduce energy consumption, and improve the workshop environment. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides a box-type resistance furnace for heat treatment of metals, which solves the problems of long heating and cooling time, affecting the working environment, and poor sealing performance of the furnace door of the existing chain-type stepping box-type resistance furnace.

[0007] To achieve the above object, the present invention is realized through the following technical solutions: A box-type resistance furnace for heat treatment of metals includes a furnace body and door panels provided at the front and rear furnace openings of the furnace body. Inner partition doors connected to the door panels by chains are provided at both the front and rear ends of the inner cavity of the furnace body. Front and rear partition cavities are respectively formed between the front and rear inner partition doors and the front and rear door panels; Sliders are circumferentially and slidably provided on the inner sides of the door panels, and first grooves are formed on the inner walls of the sliders; Second grooves are circumferentially provided at the front and rear furnace openings of the furnace body, and pipelines communicating with the second grooves are provided in the furnace body. The pipelines communicate the front partition cavity and the rear partition cavity; Wherein, when the gas in the pipeline is aspirated to make it in a negative pressure state, the slider moves in the first direction, so that the first groove and the second groove are buckled to form a negative pressure sealing cavity; when gas is sent into the pipeline, the slider moves in the second direction, so that the inner circumference of the first groove protrudes from the furnace body and forms a gap with the furnace body.

[0008] Preferably, the first direction in which the slider moves is to move along the outer circumference of the door panel, the second direction in which the slider moves is to move along the inner circumference of the door panel, and the first direction and the second direction in which the slider moves are opposite to each other.

[0009] Preferably, the first groove is semi-elliptical, the second groove is semi-circular, and the length of the major axis of the first groove is greater than the diameter of the second groove.

[0010] Preferably, the pipeline includes: An upper circulation cavity, located above the interior of the furnace body, one end is communicated with the front partition cavity, and the other end is communicated with the second groove at the rear end of the furnace body; a first circulation pump is communicated with the upper circulation cavity. A lower circulation cavity, located below the interior of the furnace body, one end is communicated with the rear partition cavity, and the other end is communicated with the second groove at the front end of the furnace body; a second circulation pump is communicated with the lower circulation cavity. Wherein, circumferential pipes are arranged at the communication positions of the upper circulation cavity and the lower circulation cavity with the second groove.

[0011] Preferably, a first pipeline and a first air inlet pipeline are communicated at the first pipe orifice of the first circulation pump, and a second pipeline is communicated at the second pipe orifice; wherein, electromagnetic valves are arranged in both the first pipeline and the first air inlet pipeline.

[0012] Preferably, a second air inlet pipeline is communicated at the first pipe orifice of the second circulation pump, and a third pipeline and a fourth pipeline are communicated at the second pipe orifice; wherein, electromagnetic valves are arranged in both the third pipeline and the fourth pipeline.

[0013] Preferably, the door panel includes an outer door panel and an inner door panel, and the inner door panel and the outer door panel respectively abut against the inside and outside of the furnace mouth of the furnace body; a groove capable of accommodating the slider is circumferentially formed on the inner wall surface of the inner door panel, and a sealing surface is formed outside the groove.

[0014] Preferably, a linkage assembly is arranged between the outer door panel and the inner door panel, the linkage assembly includes parallel connecting rods, and two ends of the connecting rods are respectively hinged to the outer door panel and the inner door panel; a spring is sleeved outside the connecting rods. Wherein, when the bottom end of the inner door panel abuts against the furnace mouth of the furnace body, the outer door panel continuously descends, so that the connecting rods are parallel and push the inner door panel to translate and tightly abut against the furnace mouth of the furnace body.

[0015] Preferably, a resisting member is provided at the furnace mouth of the furnace body, the bottom end of the inner door panel resists against the top surface of the resisting member, and the inner wall surface of the outer door panel resists against the outer wall surface of the resisting member.

[0016] Preferably, a plurality of tracks are arranged at intervals in the furnace body along the direction from the front furnace opening to the rear furnace opening, and the bottom of the inner partition door is tooth-shaped and matched with the tracks.

[0017] Beneficial effects of the present invention: By using a box-type resistance furnace for heat treatment of metals provided by the present invention, compared with the prior art, firstly, a front cavity and a rear cavity are formed between the front and rear inner partition doors and the front and rear door panels, respectively, to preheat the rod-shaped metal to be heated and to dissipate the heat of the rod-shaped metal in the rear cavity. The pipeline design enables the front cavity and the rear cavity to be connected to form a circulation, so that the temperatures in the two cavities tend to be consistent, thereby increasing the temperature of the rod-shaped metal to be heated and reducing the temperature of the rod-shaped metal in the rear cavity, thereby achieving the purpose of preheating and pre-cooling. Secondly, by moving the slider in the first direction, the first groove and the second groove are engaged to form a negative pressure state of the negative pressure sealing cavity, thereby achieving double sealing at the inner door panel and the furnace mouth of the furnace body; in conjunction with the sealing of the outer door panel and the outside of the furnace body, a triple seal is formed, which effectively reduces heat loss and increases the temperature rise rate inside the furnace body. When the airflow circulates in the front and rear compartments, the slider moves in the second direction under the influence of the airflow, so that the inner side of the first groove protrudes from the furnace body and forms a gap with the furnace body. The gas enters the front compartment or the rear compartment uniformly in the circumference of the door panel through the gap, so that the rod-shaped metal in the front compartment is preheated uniformly or the rod-shaped metal in the rear compartment is cooled uniformly. Finally, by optimizing the furnace structure, the present invention has better sealing performance, reduces heat loss, improves heat treatment efficiency, shortens heating and cooling time, and reduces energy consumption. In addition, the temperature in the workshop is effectively controlled, which improves the working environment of the staff. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the front view of the present invention; Figure 2 It is a right side view of the present invention; Figure 3 This is a state diagram of the door panel of the present invention rising and driving the inner partition door to rise; Figure 4 It is a schematic diagram of the gas flow state of the present invention; Figure 5 For the present invention Figure 2 The enlarged structural diagram at A in the middle; Figure 6 This is a motion state diagram of the door panel of the present invention being closed on the furnace body; Figure 7 This is a schematic diagram of the inner wall surface of the door panel of the present invention; Figure 8 This is a schematic diagram of the structure of the first vacuum pump of the door panel of the present invention; Figure 9 This is a schematic diagram of the second vacuum pump structure of the door panel of the present invention.

[0019] Description of the reference numerals in the figure 1. Furnace body, 2. Door panel, 201. Outer door panel, 202. Inner door panel, 3. Linkage assembly, 301. Connecting rod, 302. Spring, 4. Circumferential pipe, 5. Chain, 6. Upper circulation cavity, 7. Inner partition door, 8. First circulation pump, 81. First pipeline, 82. First intake pipeline, 83. Second pipeline, 9. Front partition cavity, 10. Lower circulation cavity, 11. Second circulation pump, 111. Third pipeline, 112. Second intake pipeline, 113. Fourth pipeline, 12. Rear partition cavity, 13. Sealing surface, 14. Groove, 15. Slide block, 16. First groove, 17. Gap, 18. Second groove, 19. Contact member. Detailed implementation manners

[0020] The present invention provides a box-type resistance furnace for metal heat treatment, which includes a furnace body and door panels provided at the front and rear furnace openings of the furnace body. Inner partition doors connected to the door panels by chains are provided at both the front and rear ends of the inner cavity of the furnace body. A front partition cavity and a rear partition cavity are respectively formed between the front and rear inner partition doors and the front and rear door panels. The front partition cavity is used to place the rod-shaped metal to be heated, and the rear partition cavity is used to place the heated rod-shaped metal. A slide block is circumferentially and slidably arranged on the inner side of the door panel, and a first groove is formed in the inner wall of the slide block; a second groove is circumferentially arranged at the front and rear furnace openings of the furnace body, and a pipeline communicating with the second groove is arranged in the furnace body, and the pipeline communicates the front partition cavity and the rear partition cavity. Among them, when the gas in the suction pipeline is sucked to make it in a negative pressure state, the slide block moves in the first direction, so that the first groove and the second groove are buckled to form a negative pressure sealing cavity; when gas is sent into the pipeline, the slide block moves in the second direction, so that the inner side of the first groove protrudes circumferentially from the furnace body and forms a gap with the furnace body. The present invention changes the buckling state of the first groove and the second groove through the slidable slide block. When it is necessary to ensure the sealing of the furnace body, the gas in the suction pipeline is sucked to make the first groove and the second groove in a negative pressure state of the negative pressure sealing cavity, so as to improve the sealing performance at the door panel and the furnace body; when it is necessary to preheat the rod-shaped metal to be heated in the front partition cavity and dissipate the heat of the rod-shaped metal in the rear partition cavity, the pipeline design can communicate the front partition cavity and the rear partition cavity and make the heat circulate, and finally make the temperatures in the two partition cavities tend to be consistent, improve the temperature of the rod-shaped metal to be heated, and at the same time reduce the temperature of the rod-shaped metal in the rear partition cavity, so as to achieve the purpose of one preheating and one pre-cooling.

[0021] In order to better understand the above technical solution, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. As long as the effects of the present invention can be exerted, various changes can be made to the implementation scheme.

[0022] By those skilled in the art, the components in this case are connected in sequence. The specific connection and operation sequence should refer to the following working principle. The detailed connection means are well-known technologies in the art. The following mainly introduces the working principle and process.

[0023] Reference Figure 1-7 A box-type resistance furnace for heat treatment of metals according to the present embodiment will be described.

[0024] like Figure 1 and Figure 2 As shown, the box-type resistance furnace includes a furnace body 1 and door panels 2 arranged at the front and rear furnace openings of the furnace body 1. The front and rear ends of the inner cavity of the furnace body 1 are both provided with inner partition doors 7 connected to the door panels 2 through chains 5. The front and rear inner partition doors 7 and the front and rear door panels 2 respectively form a front compartment 9 and a rear compartment 12. The above-mentioned inner partition door 7 is a folding door, specifically composed of two hinged plates. The chain 5 is overlapped on a guide pulley at the top of the front compartment 9 and the rear compartment 12, one end of which is connected to the door panel 2, and the other end is connected to the plate located at the upper part. When the door panel 2 rises, the chain 5 is pulled up, thereby pulling the folded inner partition door 7 up, so as to realize the connection between the front compartment 9 or the rear compartment 12 and the inside of the furnace body 1. When the front compartment 9 is connected to the inside of the furnace body 1, an external mechanical claw is used to push the rod-shaped metal to be processed into the front compartment 9 horizontally, and the rod-shaped metal in the front compartment 9 close to the furnace body 1 is pushed into the furnace body 1, and then the front door panel 2 is closed. Correspondingly, when the rear compartment 12 is connected to the inside of the furnace body 1, an external mechanical claw is used to push the rod-shaped metal cooled to 500℃-600℃ onto the external conveying roller, and the rod-shaped metal heated in the furnace body 1 is pushed into the rear compartment 12, and then the rear door panel 2 is closed. The design of the front compartment 9 and the rear compartment 12 can provide a space for preheating and precooling of the rod-shaped metal, and ensure the temperature in the furnace body 1.

[0025] Several tracks are arranged in the furnace body 1 from the front furnace opening to the rear furnace opening to allow the inner rod-shaped metal to roll and move in the furnace body 1. The bottom of the partition door 7 is tooth-shaped and matched with the track to ensure the normal closing of the partition door 7 and the relative tightness after closing.

[0026] like Figure 5 As shown, a slider 15 is circumferentially slidably arranged on the inner side of the door panel 2, and a first groove 16 is formed on the inner wall of the slider 15; a second groove 18 is circumferentially arranged at the front and rear furnace openings of the furnace body 1, and a pipeline communicating with the second groove 18 is arranged in the furnace body 1, and the pipeline communicates the front compartment 9 with the rear compartment 12.

[0027] During implementation, when the gas in the suction pipeline creates a negative pressure state, the slider 15 moves in the first direction, causing the first groove 16 to engage with the second groove 18 to form a negative pressure sealing cavity, achieving vacuum sealing at the furnace opening between the door panel 2 and the furnace body 1, facilitating rapid heating inside the furnace body 1 in a short period of time; when gas is supplied to the pipeline, the slider 15 moves in the second direction, causing the inner circumferential side of the first groove 16 to protrude from the furnace body 1 and form a gap 17 with the furnace body 1, and the gas enters the front partition cavity 9 or the rear partition cavity 12 through this gap 17.

[0028] In an exemplary embodiment, the gas blown out from the gap 17 is ejected circumferentially and uniformly enters the front partition cavity 9 or the rear partition cavity 12 to ensure uniform preheating of the rod-shaped metal in the front partition cavity 9 or uniform cooling of the rod-shaped metal in the rear partition cavity 12.

[0029] Among them, the first direction in which the slider 15 moves is to move along the outer circumferential side of the door panel 2, the second direction in which the slider 15 moves is to move along the inner circumferential side of the door panel 2, and the first direction and the second direction in which the slider 15 moves are opposite.

[0030] In a preferred embodiment, the first groove 16 is semi-elliptical, the second groove 18 is semi-circular, and the major axis length of the first groove 16 is greater than the diameter of the second groove 18. When the slider 15 moves in the first direction, the inner edge of the first groove 16 contacts the inner edge of the second groove 18 at this time; when moving in the second direction, the outer edge of the first groove 16 contacts the outer edge of the second groove 18, causing the inner edge of the first groove 16 to be exposed at the front partition cavity 9 or the rear partition cavity 12.

[0031] As Figure 7 shown, the sliders 15 located on the inner circumference of the door panel 2 are all independent to ensure that each slider 15 can slide normally.

[0032] As Figure 2 shown, the pipeline includes an upper circulation cavity 6 and a lower circulation cavity 10, and both the upper circulation cavity 6 and the lower circulation cavity 10 are formed inside the furnace body 1. The upper circulation cavity 6 is located above the furnace body 1, one end is connected to the front partition cavity 9, and the other end is connected to the second groove 18 at the rear end of the furnace body 1; a first circulation pump 8 is connected to the upper circulation cavity 6; the lower circulation cavity 10 is located below the furnace body 1, one end is connected to the rear partition cavity 12, and the other end is connected to the second groove 18 at the front end of the furnace body 1; a second circulation pump 11 is connected to the lower circulation cavity 10; among them, circumferential pipes 4 are provided at the connection points of the upper circulation cavity 6 and the lower circulation cavity 10 with the second groove 18, and the function of the circumferential pipe 4 is to enable the upper circulation cavity 6 or the lower circulation cavity 10 to communicate with the circumferentially arranged second groove 18.

[0033] As Figure 8As shown, a first pipe 81 and a first intake pipe 82 are connected to the first pipe orifice of the first circulation pump 8, and a second pipe 83 is connected to the second pipe orifice; wherein, solenoid valves are provided in both the first pipe 81 and the first intake pipe 82.

[0034] As Figure 9 shown, a second intake pipe 112 is connected to the first pipe orifice of the second circulation pump 11, and a third pipe 111 and a fourth pipe 113 are connected to the second pipe orifice; wherein, solenoid valves are provided in both the third pipe 111 and the fourth pipe 113.

[0035] As Figure 4 shown, the upper circulation chamber 6 and the lower circulation chamber 10 and the front partition chamber 9 and the rear partition chamber 12 form a gas circulation path. By the first-direction operation of the first circulation pump 8 and the second circulation pump 11, when the first pipe 81 and the third pipe 111 are closed, the gas in the front partition chamber 9 can enter the rear partition chamber 12 through the upper circulation chamber 6, and the gas in the rear partition chamber 12 can enter the front partition chamber 9 through the lower circulation chamber 10. When the first circulation pump 8 and the second circulation pump 11 operate in the second direction (i.e., reverse rotation), at this time the first pipe 81 and the third pipe 111 are opened, the first intake pipe 82 and the fourth pipe 113 are closed, the gas at the second groove 18 is sucked, and the slider 15 slides under the drive of the air flow so that the first groove 16 and the second groove 18 are buckled to form a negative pressure sealing chamber. At the same time, in an implementable case, when the first circulation pump 8 transports the gas in the front partition chamber 9 to the rear partition chamber 12, the valve of the first pipe 81 can be fully opened or partially opened or intermittently opened, so that the external cold gas is transported to the rear partition chamber 12 to accelerate the cooling rate of the rod-shaped metal.

[0036] As Figure 6 shown, the door panel 2 includes an outer door panel 201 and an inner door panel 202, and the inner door panel 202 and the outer door panel 201 respectively abut against the inside and outside of the furnace mouth of the furnace body 1; it should be noted that a sunk groove for accommodating the inner door panel 202 is opened on the inner side of the outer door panel 201, the above-mentioned chain 5 is connected to the inner door panel 202, and when the door panel 2 rises, the chain 5 is also located in the sunk groove under the side view projection; at the same time, the slider 15 is also provided on the inner door panel 202. And the lifting device of the door panel 2 is connected to the outer door panel 201.

[0037] The inner wall surface of the inner door panel 202 is circumferentially provided with a groove 14 for accommodating the slider 15, and a sealing surface 13 is formed on the outer side of the groove 14. When the first groove 16 and the second groove 18 are engaged with each other to form a negative pressure sealing chamber, the sealing surface 13 is tightly fitted to the inner side of the furnace mouth of the furnace body 1. The sealing surface 13 cooperates with the negative pressure sealing chamber to form a double seal between the inner door panel 202 and the furnace mouth of the furnace body 1, and cooperates with the seal between the outer door panel 201 and the outer side of the furnace body 1 to form a triple seal. After the front and rear door panels 2 are closed, the internal temperature of the furnace body 1 can be quickly locked, and the air circulation work can be carried out when the temperature rises to the set temperature.

[0038] In a preferred implementation, a linkage assembly 3 is provided between the outer door panel 201 and the inner door panel 202, and the linkage assembly 3 includes mutually parallel connecting rods 301, and the two ends of the connecting rod 301 are respectively hinged on the outer door panel 201 and the inner door panel 202; a spring 302 is sleeved on the outer side of the connecting rod 301; When the bottom end of the inner door panel 202 contacts the furnace opening of the furnace body 1, the outer door panel 201 continues to descend, and the continuously descending outer door panel 201 drives the connecting rod 301 to be parallel, and pushes the inner door panel 202 to be translated and pressed against the furnace opening of the furnace body 1. The design of the linkage assembly 3 can push the inner door panel 202 to be translated horizontally when the outer door panel 201 vertically descends, and after the outer door panel 201 is locked, the inner door panel 202 is continuously pushed by the connecting rod 301 in a horizontal state, so that it fits tightly against the furnace opening of the furnace body 1. When the door panel 2 rises, the outer door panel 201 rises first, and then as the outer door panel 201 rises and the spring 302 pulls back, the inner door panel 202 is driven to retract into the sink, and rises together with the outer door panel 201.

[0039] The furnace body 1 is provided with a resisting member 19 at the furnace mouth, the bottom end of the inner door panel 202 resists against the top surface of the resisting member 19, and the inner wall surface of the outer door panel 201 resists against the outer wall surface of the resisting member 19. The resisting member 19 is used to receive the bottom of the inner door panel 202 and to fit the sealing surface of the outer door panel 201.

[0040] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A box-type resistance furnace for heat treatment of metals, comprising a furnace body and door panels arranged at the front and rear furnace openings of the furnace body, characterized in that: The front and rear ends of the furnace body cavity are both provided with inner partition doors connected to door panels by chains, and a front partition cavity and a rear partition cavity are formed between the front and rear inner partition doors and the front and rear door panels respectively; A slider is provided on the inner side of the door panel for circumferential sliding, and a first groove is provided on the inner wall of the slider; a second groove is provided on the circumference of the front and rear furnace openings of the furnace body, and a pipeline communicating with the second groove is provided in the furnace body, and the pipeline communicates the front compartment and the rear compartment; When the gas in the pipeline is sucked to make it in a negative pressure state, the slider moves in a first direction, so that the first groove and the second groove are engaged to form a negative pressure sealed cavity; when air is supplied to the pipeline, the slider moves in a second direction, so that the first groove protrudes inwardly from the furnace body and forms a gap between the first groove and the furnace body.

2. A box-type resistance furnace for heat treatment of metals according to claim 1, characterized in that: The first direction of movement of the slider is along the outer side of the door panel, and the second direction of movement of the slider is along the inner side of the door panel. The first direction of movement of the slider is opposite to the second direction.

3. The box-type resistance furnace for heat treatment of metals according to claim 1, characterized in that: The first groove is semi-elliptical, the second groove is semi-circular, and the major axis length of the first groove is greater than the diameter of the second groove.

4. The box-type resistance furnace for heat treatment of metals according to claim 1, characterized in that: The pipeline comprises: An upper circulation chamber is located above the furnace body, one end of which is connected to the front compartment, and the other end of which is connected to the second groove at the rear end of the furnace body; the upper circulation chamber is connected to a first circulation pump; A lower circulation chamber is located at the lower part of the furnace body, one end of which is connected to the rear compartment, and the other end of which is connected to the second groove at the front end of the furnace body; the lower circulation chamber is connected to a second circulation pump; Wherein, circumferential tubes are provided at the connection points between the upper circulation chamber, the lower circulation chamber and the second groove.

5. A box-type resistance furnace for heat treatment of metals according to claim 4, characterized in that: The first pipe opening of the first circulation pump is connected with the first pipeline and the first air intake pipeline, and the second pipe opening is connected with the second pipeline; wherein the first pipeline and the first air intake pipeline are both provided with solenoid valves.

6. A box-type resistance furnace for heat treatment of metals according to claim 4, characterized in that: The first pipe opening of the second circulation pump is connected to a second air intake pipeline, and the second pipe opening is connected to a third pipeline and a fourth pipeline; wherein solenoid valves are provided in the third pipeline and the fourth pipeline.

7. The box-type resistance furnace for heat treatment of metals according to claim 1, characterized in that: The door panel comprises an outer door panel and an inner door panel, and the inner door panel and the outer door panel respectively abut against the inner and outer positions of the furnace body furnace mouth; the inner wall surface of the inner door panel is circumferentially provided with a groove for accommodating a slider, and a sealing surface is formed on the outer side of the groove.

8. The box-type resistance furnace for heat treatment of metals according to claim 7, characterized in that: A linkage assembly is provided between the outer door panel and the inner door panel, and the linkage assembly includes connecting rods parallel to each other, and the two ends of the connecting rods are respectively hinged on the outer door panel and the inner door panel; a spring is sleeved on the outer side of the connecting rod; When the bottom end of the inner door panel abuts against the furnace opening of the furnace body, the outer door panel continues to descend, so that the connecting rod is parallel and pushes the inner door panel to translate and abut against the furnace opening of the furnace body.

9. A box-type resistance furnace for heat treatment of metals according to claim 8, characterized in that: A resisting piece is arranged at the furnace mouth of the furnace body, the bottom end of the inner door panel resists against the top surface of the resisting piece, and the inner wall surface of the outer door panel resists against the outer wall surface of the resisting piece.

10. The box-type resistance furnace for heat treatment of metal according to claim 1, characterized in that: A plurality of tracks are arranged in the furnace body at intervals along the direction from the front furnace opening to the rear furnace opening, and the bottom of the inner partition door is tooth-shaped and matched with the tracks.

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