Novel efficient energy-saving pit type carburizing furnace

Abstract

The invention provides a novel efficient energy-saving pit type carburizing furnace, and relates to the technical field of pit type carburizing furnaces, the novel efficient energy-saving pit type carburizing furnace comprises a main carburizing furnace body, an upper sealing furnace cover, a permeating agent pipe and an inner circulating fan, the upper sealing furnace cover is attached to the top of the main carburizing furnace body in a sealed mode, and the permeating agent pipe is fixedly arranged on the upper portion of the upper sealing furnace cover; an inner circulation fan is arranged below the upper sealing furnace cover, an inner heat insulation furnace lining is fixedly arranged in the main carburizing furnace body, an inner spiral air guide groove is formed in the inner side of the inner heat insulation furnace lining, and an inner carburizing boss is arranged at the bottom of the inner heat insulation furnace lining in an upward protruding mode. Air flow is guided by the inner spiral air guide groove to flow downwards, the air flow carries the carbonitriding agent flowing out of the lower extension pipe to flow downwards while flowing downwards, uniform distribution of the carbonitriding agent in the inner heat insulation furnace lining is promoted, the time for uniformizing the internal carbon potential atmosphere is shortened, and the problem that downward air flow is prone to counteracting upward hot air, and the service life of the furnace lining is prolonged is solved. And therefore, airflow is difficult to reach the bottommost part of the pit type carburizing furnace, and a carburizing agent needs longer time to be uniform.

Description

Technical Field

[0001] The invention relates to the technical field of pit carburizing furnaces, and in particular to a novel high-efficiency and energy-saving pit carburizing furnace. Background Art

[0002] The pit carburizing furnace is a device used for surface carburizing of cast iron and steel parts. It uses a bottom opening design to achieve carburizing through natural convection and diffusion. The pit carburizing furnace is widely used in the automotive, machinery manufacturing and other industries to improve product quality and performance.

[0003] A furnace cover is set at the top opening of the pit carburizing furnace for sealing. The furnace cover is lifted away from the pit carburizing furnace by a lifting device. A fan is set on the top of the furnace cover to blow the air circulation inside the pit carburizing furnace. The airflow driven by the fan blows downward. The airflow lacks path planning, and the downward airflow is easily offset by the upward hot air, which makes it difficult for the airflow to reach the bottom of the pit carburizing furnace. It takes a longer time to evenly distribute the carburizing agent. The longer the pit carburizing furnace runs, the higher the power consumption of the pit carburizing furnace. Summary of the invention

[0004] The disclosed embodiment relates to a novel high-efficiency and energy-saving pit-type carburizing furnace, in which the airflow of the outlet pipe is guided by the inner spiral air guide groove to flow downward, and the airflow carries the carburizing agent flowing out of the lower extension pipe downward while the airflow flows downward. The downward flow distance of the airflow is longer, which promotes the uniform distribution of the carburizing agent inside the inner insulation furnace lining, shortens the time for the internal carbon potential atmosphere to be uniform, shortens the processing time of the carburizing furnace, and achieves the purpose of energy conservation and emission reduction. The inner spiral air guide groove guides the external airflow to move downward, and the internal air inlet of the isolation pipe outside the lower air inlet of the internal circulation fan guides the airflow in the middle to move upward, forming an airflow trend of external descending and middle rising, and the external heat quickly gathers toward the location of the components in the middle, accelerating the heating rate of the components in the middle. At the same time, the carburizing agent carried by the airflow contacts the components in the middle, further accelerating the carburizing speed of the components and shortening the processing time of the carburizing furnace.

[0005] According to a first aspect of the present disclosure, a new type of high-efficiency and energy-saving pit-type carburizing furnace is provided, which specifically includes: a main carburizing furnace body, an upper closed furnace cover, a carburizing agent pipe and an internal circulation fan, wherein the top of the main carburizing furnace body is sealed with an upper closed furnace cover, a carburizing agent pipe is fixedly arranged on the upper part of the upper closed furnace cover, an internal circulation fan is arranged below the upper closed furnace cover, an inner insulation furnace lining is fixedly arranged inside the main carburizing furnace body, the inner insulation furnace lining is made of fireproof and heat-insulating material, the inner insulation furnace lining forms a cylindrical structure inside the main carburizing furnace body, an inner spiral air guide groove is arranged on the inner side of the inner insulation furnace lining, an inner spiral heating element is fixed on the inner side of the inner insulation furnace lining, a lower sealing ring is fixed on the outer side of the top of the main carburizing furnace body, and an inner carburizing boss is convexly arranged on the bottom of the inner insulation furnace lining.

[0006] In at least some embodiments, the inner spiral air guide groove of the inner insulation furnace lining is concave, the inner spiral air guide groove and the inner spiral heating element are staggered, the inner spiral air guide groove and the inner spiral heating element are both surrounded by the outer side of the inner carburized boss, and the airflow of the outlet pipe is guided by the inner spiral air guide groove to flow downward, and the airflow flows downward in a spiral shape along the inner spiral air guide groove. The guidance of the inner spiral air guide groove makes the downward flow distance of the airflow longer.

[0007] In at least some embodiments, a lower boss frame is protruding from the bottom of the upper closed furnace cover, an upper sealing ring is fixedly provided at the bottom of the upper closed furnace cover, an outer telescopic insulation ring is fixedly provided at the outer side of the bottom of the upper closed furnace cover, and an exhaust pipe is fixedly passed through the upper closed furnace cover.

[0008] In at least some embodiments, the upper sealing ring is wrapped around the outer side of the lower boss frame, the upper sealing ring and the lower sealing ring slide vertically together to seal, the outer telescopic insulation ring is wrapped around the outer side of the upper sealing ring, the lower end of the exhaust pipe passes through to the outer side of the bottom of the lower boss frame, and the lower end of the outer telescopic insulation ring is extended and fits against the top of the main carburizing furnace body.

[0009] In at least some embodiments, the lower end of the permeation agent tube is slidably connected to a lower extension tube, a bracket fixed on the outer side of the lower extension tube is threadedly connected to a threaded lifting rod, and the top end of the permeation agent tube is connected to an upper connecting tube.

[0010] In at least some embodiments, the three penetrant tubes connected to the upper connecting tube are arranged in an interval array, and the three penetrant tubes and the lower extension tube arranged in a horizontal ring interval expand the carbon penetrant discharge range in the horizontal position. The number of penetrant tubes can be adjusted as needed, the lower extension tube and the lower boss frame are axially slidingly connected, the threaded lifting rod and the upper closed furnace cover are rotatably connected, and the lower end of the lower extension tube extends to the outside of the bottom of the lower boss frame.

[0011] In at least some embodiments, the outer side of the internal circulation fan is connected to an exhaust pipe, a lower air inlet outer isolation pipe is fixed to the bottom of the internal circulation fan, the central fan blades of the internal circulation fan are fixed to the main shaft of the upper drive motor, and the upper drive motor is fixed to the top of the upper closed furnace cover.

[0012] In at least some embodiments, the air outlet pipe is a circular curved pipe structure, the tail end of the air outlet pipe faces the inner spiral air guide groove, the outer isolation pipe of the lower air inlet surrounds the outer side of the bottom inlet of the internal circulation fan, the lower air inlet outer isolation pipe isolates the bottom inlet of the internal circulation fan to prevent the air from the air outlet pipe from being directly introduced into the bottom inlet of the internal circulation fan, the lower air inlet outer isolation pipe is located vertically above the inner carburized boss, and the internal air inlet of the lower air inlet outer isolation pipe of the internal circulation fan guides the middle airflow to move upward.

[0013] The present invention provides a novel high-efficiency and energy-saving pit-type carburizing furnace, which has the following beneficial effects: The airflow of the air outlet pipe is guided by the inner spiral air guide groove to flow downward. The airflow carries the carburizing agent flowing out of the lower extension pipe downward at the same time. The downward flow distance of the airflow is longer, which promotes the uniform distribution of the carburizing agent inside the inner insulation furnace lining, shortens the time for the internal carbon potential atmosphere to be uniform, shortens the processing time of the carburizing furnace, and achieves the purpose of energy saving and emission reduction.

[0014] The inner spiral air guide groove guides the external air flow to move downward, and the inner air inlet of the isolation tube outside the lower air inlet of the internal circulation fan guides the air flow in the middle to move upward, forming an air flow trend of descending outside and rising in the middle. The external heat quickly gathers toward the location of the components in the middle, accelerating the heating rate of the components in the middle. At the same time, the carburizing agent carried by the airflow contacts the components in the middle, further accelerating the carburizing speed of the components and shortening the processing time of the carburizing furnace.

[0015] The three lower extension tubes expand the carburizing agent discharge range in the horizontal position. The threads of the threaded lifting rod guide the lower extension tubes to move axially. The lower extension tubes move deeper into the inner insulation furnace lining to expand the carburizing agent range at different vertical depths and accelerate the carburizing agent diffusion efficiency.

[0016] During the upward movement of the upper closed furnace cover, the outer telescopic insulation ring moves up and fits the top of the main carburizing furnace body. The outer telescopic insulation ring isolates the flame between the upper closed furnace cover and the main carburizing furnace body to prevent the flame from escaping outward along the gap between the upper closed furnace cover and the main carburizing furnace body and endangering surrounding personnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the drawings of the embodiment are briefly introduced below.

[0018] The drawings described below are only related to some embodiments of the present invention, but are not intended to limit the present invention.

[0019] In the attached picture: Figure 1 A schematic diagram showing the overall structure of the present application; Figure 2 A schematic diagram showing a longitudinal half-section structure of the main carburizing furnace body and the inner heat-insulating furnace lining of the present application is shown; Figure 3 A schematic diagram showing the structure of the inner spiral heating element of the present application is shown; Figure 4 A schematic diagram showing the internal circulation fan structure of the present application is shown; Figure 5 The schematic diagram of the structure of the permeation agent tube of the present application is shown; Figure 6 A schematic structural diagram of the external telescopic heat-insulating ring of the present application is shown; Figure 7The schematic diagram of the structure of the inner spiral air guide groove of the present application is shown; Figure 8 The schematic diagram of the structure shows the main carburizing furnace body and the upper closed furnace cover of the present application in a separated state.

[0020] Reference numerals list 1. Main carburizing furnace body; 101. Inner heat-insulating furnace lining; 102. Inner spiral air guide groove; 103. Inner spiral heating element; 104. Lower sealing ring; 105. Inner carburizing boss; 2. Upper closed furnace cover; 201. Lower boss frame; 202. Upper sealing ring; 203. External telescopic heat insulation ring; 204. Exhaust pipe; 3. Penetrant tube; 301. Lower extension tube; 302. Threaded lifting rod; 303. Upper connecting tube; 4. Internal circulation fan; 401. Exhaust pipe; 402. Lower air inlet outer isolation pipe; 403. Upper drive motor. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Example 1: Please refer to Figures 1 to 8 : The present invention proposes a novel high-efficiency and energy-saving pit-type carburizing furnace, comprising: a main carburizing furnace body 1, an upper closed furnace cover 2, a carburizing agent pipe 3 and an internal circulation fan 4, an inner heat-insulating furnace lining 101 is fixedly arranged inside the main carburizing furnace body 1, the inner heat-insulating furnace lining 101 is made of fireproof and heat-insulating materials, the inner heat-insulating furnace lining 101 forms a cylindrical structure inside the main carburizing furnace body 1, an inner spiral air guide groove 102 is arranged on the inner side of the inner heat-insulating furnace lining 101, an inner spiral heating element 103 is fixed on the inner side of the inner heat-insulating furnace lining 101, a lower sealing ring 104 is fixed on the outer side of the top of the main carburizing furnace body 1, an inner carburizing boss 105 is convexly arranged on the bottom of the inner heat-insulating furnace lining 101, the top of the main carburizing furnace body 1 is sealed with an upper closed furnace cover 2, and a lower boss frame 2 is convexly arranged on the bottom of the upper closed furnace cover 2 01, an upper sealing ring 202 is fixedly provided at the bottom of the upper closed furnace cover 2, an outer telescopic insulation ring 203 is fixedly provided on the outer side of the bottom of the upper closed furnace cover 2, an exhaust pipe 204 is fixedly passed through the upper closed furnace cover 2, a permeate tube 3 is fixedly provided on the upper part of the upper closed furnace cover 2, the lower end of the permeate tube 3 is slidably connected with a lower extension tube 301, the bracket fixed on the outer side of the lower extension tube 301 is screwed with a threaded lifting rod 302, the top of the permeate tube 3 is connected with the upper connecting tube 303, an internal circulation fan 4 is provided below the upper closed furnace cover 2, the outer side of the internal circulation fan 4 is connected with an outlet pipe 401, a lower air inlet outer isolation tube 402 is fixed to the bottom of the internal circulation fan 4, the central fan blade of the internal circulation fan 4 is fixed to the main shaft of the upper drive motor 403, and the upper drive motor 403 is fixed to the top of the upper closed furnace cover 2.

[0023] In the embodiment of the present disclosure, the inner spiral air guide groove 102 of the inner heat-insulating furnace lining 101 is concavely arranged, the inner spiral air guide groove 102 and the inner spiral heating element 103 are staggered, the inner spiral air guide groove 102 and the inner spiral heating element 103 are both surrounded by the outer side of the inner carburized boss 105, and the airflow of the air outlet pipe 401 is guided by the inner spiral air guide groove 102 to flow downward, and the airflow flows downward in a spiral shape along the inner spiral air guide groove 102. The guidance of the inner spiral air guide groove 102 makes the downward flow distance of the airflow The distance is longer, the upper connecting pipe 303 is connected to the supply pipeline of the carburizing agent, the carburizing agent is connected to the carburizing agent pipe 3 and the lower extension pipe 301 through the upper connecting pipe 303, the carburizing agent flows out of the lower extension pipe 301, and the airflow of the outlet pipe 401 flows downward while carrying the carburizing agent flowing out of the lower extension pipe 301 to flow downward, thereby promoting the uniform distribution of the carburizing agent in the vertical direction inside the inner insulation furnace lining 101, shortening the time for the internal carbon potential atmosphere to be uniform, shortening the processing working time and processing energy consumption of the carburizing furnace, and saving energy and reducing emissions.

[0024] In the disclosed embodiment, the upper sealing ring 202 surrounds the outer side of the lower boss frame 201, and the upper sealing ring 202 and the lower sealing ring 104 slide vertically to fit and seal. The outer telescopic insulation ring 203 surrounds the outer side of the upper sealing ring 202, and the lower end of the exhaust pipe 204 passes through to the outer side of the bottom of the lower boss frame 201. After the outer telescopic insulation ring 203 is extended, the lower end fits with the top of the main carburizing furnace body 1. The outer telescopic insulation ring 203 isolates the flame that emerges outward from the upper closed furnace cover 2 and the main carburizing furnace body 1 to prevent the flame from escaping outward along the gap between the upper closed furnace cover 2 and the main carburizing furnace body 1 and endangering the surrounding personnel.

[0025] In the disclosed embodiment, the three impregnating agent tubes 3 connected by the upper connecting tube 303 are arranged in an interval array, and the three impregnating agent tubes 3 arranged in a horizontal ring interval and the lower extension tube 301 expand the carbon impregnating agent discharge range in the horizontal position. The number of impregnating agent tubes 3 can be adjusted as needed. The lower extension tube 301 is axially slidingly connected to the lower boss frame 201, and the threaded lifting rod 302 is rotationally connected to the upper closed furnace cover 2. The lower end of the lower extension tube 301 extends to the outer side of the bottom of the lower boss frame 201, and the lower extension tube 301 moves deeper into the inner insulation furnace lining 101. The lower extension tube 301 is set at different heights to expand the carbon impregnating agent range at different vertical depths, thereby accelerating the diffusion efficiency of the carbon impregnating agent.

[0026] In the disclosed embodiment, the air outlet pipe 401 is a circular curved pipe structure, the tail end of the air outlet pipe 401 faces the inner spiral air guide groove 102, the lower air inlet outer isolation pipe 402 surrounds the outer side of the bottom inlet of the inner circulation fan 4, and the lower air inlet outer isolation pipe 402 isolates the bottom inlet of the inner circulation fan 4 to prevent the air outlet of the air outlet pipe 401 from being directly introduced into the bottom inlet of the inner circulation fan 4. The lower air inlet outer isolation pipe 402 is located vertically above the inner carburized boss 105, and the internal air inlet of the lower air inlet outer isolation pipe 402 of the inner circulation fan 4 guides the airflow in the middle to move upward The inner insulation furnace lining 101 has a downward trend in the outer part of the inner spiral air guide groove 102 and an upward trend in the middle airflow on one side of the inner carburizing boss 105. The airflow circulates up and down, and the external heat of the inner spiral air guide groove 102 quickly gathers and flows upward toward the position of the components on the upper part of the middle inner carburizing boss 105, thereby accelerating the heating rate of the middle components. At the same time, in the process of airflow gathering and flowing upward, the carburizing agent carried in the airflow contacts the components in the middle, thereby further accelerating the carburizing rate of the components. The operation time of the pit-type carburizing furnace is shorter and the power consumption of the pit-type carburizing furnace is lower.

[0027] Embodiment 2, on the basis of embodiment 1, the upper and lower edges of the inner spiral air guide groove 102 are protruding to set air guide walls, the air guide walls increase the air guiding capacity of the inner spiral air guide groove 102, enhance the downward flow capacity of the airflow, and promote the uniform speed of the internal carbon potential atmosphere. The inner spiral heating element 103 can be further integrated in the inner spiral air guide groove 102, and the width of the inner spiral air guide groove 102 is further expanded, which further promotes the ability to guide the airflow, and also promotes uniform heating and temperature rise inside.

[0028] The working principle of the first embodiment: an inner heat-insulating furnace lining 101 is arranged inside the main carburizing furnace body 1 for heat preservation and insulation, and an inner spiral heating element 103 is used to heat the inner heat-insulating furnace lining 101. The main carburizing furnace body 1 and the inner heat-insulating furnace lining 101 are the entrances, and the upper closed furnace cover 2 is connected to a lifting device. The upper closed furnace cover 2 is automatically lifted by the lifting device and separated from the main carburizing furnace body 1 and rotated to one side. The carburizing parts are placed in a basket, and the basket is placed above the inner carburizing boss 105. The upper closed furnace cover 2 descends, and the upper sealing ring 202 and the lower sealing ring 104 are sealed. The upper drive motor 403 is started to drive the blades of the inner circulation fan 4 to rotate. The air outlet pipe 401 of the inner circulation fan 4 blows air outwards, and the air outlet pipe 401 blows air toward the inner spiral air guide groove 102. The airflow of the air outlet pipe 401 is guided by the inner spiral air guide groove 102 to flow downward, and the airflow flows downward in a spiral shape along the inner spiral air guide groove 102. The guidance of the inner spiral air guide groove 102 makes the downward flow distance of the airflow longer. While the airflow flows downward along the inner spiral air guide groove 102, the circumferential movement further expands the range of influence. The upper connecting pipe 303 is connected to the supply pipeline of the carburizing agent. The carburizing agent is connected to the carburizing agent pipe 3 and the lower extension pipe 301 by the upper connecting pipe 303. The lower extension pipe 301 flows out the carburizing agent. The air outlet pipe 401 While flowing downward, it carries the carburizing agent flowing out of the lower extension pipe 301 downward, promoting the uniform distribution of the carburizing agent in the vertical direction inside the inner insulation furnace lining 101. While the airflow flows downward along the inner spiral air guide groove 102, the circumferential movement further expands the impact range, shortens the time for the internal carbon potential atmosphere to be uniform, shortens the processing working time and processing energy consumption of the carburizing furnace, and achieves the purpose of energy saving and emission reduction; when the inner spiral air guide groove 102 guides the external air flow to move downward, the air flow flows along the inner spiral air guide groove 102 to the bottom and then moves upward along the inclined surface of the bottom, and the internal air inlet of the isolation pipe 402 outside the lower air inlet of the internal circulation fan 4 guides the middle air flow upward The inner heat-insulating furnace lining 101 is formed such that the outer portion of the inner spiral air guide groove 102 which opens into the inner carburizing boss 105 descends while the middle airflow on one side of the inner carburizing boss 105 rises. The airflow performs an upward and downward diversion cycle. The external heat of the inner spiral air guide groove 102 quickly gathers toward the position of the components on the upper part of the middle inner carburizing boss 105 and flows upward, thereby accelerating the heating rate of the middle components. At the same time, during the process of the airflow gathering and flowing upward, the carbonizing agent carried in the airflow contacts the components in the middle, thereby further accelerating the carburizing rate of the components and shortening the processing time of the carburizing furnace. The carburizing of the components is more efficient, the operation time of the pit-type carburizing furnace is shorter, and the power consumption of the pit-type carburizing furnace is lower. The three carburizing agent tubes 3 and the lower extension tube 301 arranged at intervals in the horizontal annular shape expand the horizontal carbonizing agent discharge range. The threads of the threaded lifting rod 302 guide the axial movement of the lower extension tube 301, and the lower extension tube 301 moves deeper into the inner heat-insulating furnace lining 101. The lower extension tube 301 is set at different heights to expand the carburizing agent range at different vertical depths, thereby accelerating the carburizing agent diffusion efficiency and the uniform diffusion of the carburizing agent. After carburizing is completed, during the upward movement of the upper closed furnace cover 2, the outer telescopic heat-insulating ring 203 will move upward under gravity. Extend, the lower end of the outer telescopic insulation ring 203 is fitted with the top of the main carburizing furnace body 1 after extension, and the outer telescopic insulation ring 203 isolates the flame coming out from between the upper closed furnace cover 2 and the main carburizing furnace body 1 to prevent the flame from coming out along the gap between the upper closed furnace cover 2 and the main carburizing furnace body 1 and endangering the surrounding personnel. After the gap between the upper closed furnace cover 2 and the main carburizing furnace body 1 expands to the point where the upper closed furnace cover 2 and the main carburizing furnace body 1 are completely separated, the flame will become vertical instead of spreading all around, which has less impact on the surrounding personnel and improves the working environment of the staff.

[0029] In this article, there are a few points to note: 1. The drawings of the embodiments of the present disclosure only involve structures related to the embodiments of the present disclosure, and other structures may refer to general designs.

[0030] 2. In the absence of conflict, the embodiments of the present disclosure and the features therein may be combined with each other to obtain new embodiments.

[0031] The above are only specific embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A new type of high-efficiency and energy-saving pit carburizing furnace, comprising: A main carburizing furnace body (1), an upper closed furnace cover (2), a carburizing agent pipe (3) and an internal circulation fan (4); characterized in that the top of the main carburizing furnace body (1) is sealed with an upper closed furnace cover (2), a carburizing agent pipe (3) is fixedly arranged on the upper part of the upper closed furnace cover (2), an internal circulation fan (4) is arranged below the upper closed furnace cover (2), an inner heat-insulating furnace lining (101) is fixedly arranged inside the main carburizing furnace body (1), an inner spiral air guide groove (102) is arranged on the inner side of the inner heat-insulating furnace lining (101), an inner spiral heating element (103) is fixed on the inner side of the inner heat-insulating furnace lining (101), a lower sealing ring (104) is fixed on the outer side of the top of the main carburizing furnace body (1), and an inner carburizing boss (105) is convexly arranged on the bottom of the inner heat-insulating furnace lining (101).

2. A new type of high-efficiency and energy-saving pit carburizing furnace according to claim 1, characterized in that: The inner spiral air guide groove (102) of the inner heat-insulating furnace lining (101) is concavely arranged, the inner spiral air guide groove (102) and the inner spiral heating element (103) are staggeredly arranged, and the inner spiral air guide groove (102) and the inner spiral heating element (103) are both surrounded by the outer side of the inner carburized boss (105).

3. A new type of high-efficiency and energy-saving pit carburizing furnace according to claim 1, characterized in that: The bottom of the upper closed furnace cover (2) is provided with a lower boss frame (201) protruding therefrom, an upper sealing ring (202) is fixedly provided at the bottom of the upper closed furnace cover (2), an outer telescopic heat insulation ring (203) is fixedly provided at the outer side of the bottom of the upper closed furnace cover (2), and an exhaust pipe (204) is fixedly passed through the upper closed furnace cover (2).

4. A new type of high-efficiency and energy-saving pit carburizing furnace according to claim 3, characterized in that: The upper sealing ring (202) surrounds the outer side of the lower boss frame (201), the upper sealing ring (202) and the lower sealing ring (104) slide vertically to fit and seal, the outer telescopic heat insulation ring (203) surrounds the outer side of the upper sealing ring (202), and the lower end of the exhaust pipe (204) penetrates to the outer side of the bottom of the lower boss frame (201).

5. A new type of high-efficiency and energy-saving pit carburizing furnace according to claim 4, characterized in that: The lower end of the penetrating agent tube (3) is slidably connected to a lower extension tube (301), the lower extension tube (301) and the threaded lifting rod (302) are threadedly connected, and the top end of the penetrating agent tube (3) is connected to an upper connecting tube (303).

6. A new type of high-efficiency and energy-saving pit carburizing furnace according to claim 5, characterized in that: The three penetrant tubes (3) connected to the upper connecting tube (303) are arranged in an interval array, the lower extension tube (301) and the lower boss frame (201) are axially slidably connected, the threaded lifting rod (302) and the upper closed furnace cover (2) are rotationally connected, and the lower end of the lower extension tube (301) extends to the outside of the bottom of the lower boss frame (201).

7. A new type of high-efficiency and energy-saving pit carburizing furnace according to claim 1, characterized in that: The outer side of the internal circulation fan (4) is connected to an air outlet pipe (401), a lower air inlet outer isolation pipe (402) is fixed to the bottom of the internal circulation fan (4), a central fan blade of the internal circulation fan (4) and a main shaft of an upper drive motor (403) are fixed, and the upper drive motor (403) is fixed to the top of the upper closed furnace cover (2).

8. A new type of high-efficiency and energy-saving pit carburizing furnace according to claim 7, characterized in that: The air outlet pipe (401) is a circular curved pipe structure, the tail end of the air outlet pipe (401) faces the inner spiral air guide groove (102), the lower air inlet outer isolation pipe (402) surrounds the outer side of the bottom inlet of the inner circulation fan (4), and the lower air inlet outer isolation pipe (402) is located vertically above the inner carburized boss (105).

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