Accurate pressure control type low-pressure carburizing treatment device

Abstract

The utility model provides a precise pressure control type low-pressure carburizing treatment device, which relates to the technical field of low-pressure carburizing and comprises a mounting base plate, a vacuum carburizing furnace arranged at the top end of the mounting base plate, a sealing furnace cover arranged at the top end of the vacuum carburizing furnace, and a penetrant heating box arranged above the mounting base plate; the flow uniformizing assembly comprises a fixing ring which is fixedly installed in the center of the bottom end of the sealing furnace cover, an arc-shaped concave face cover is fixedly installed at the bottom end of the fixing ring, a rotating column is rotationally installed in the center of the inner bottom end of the arc-shaped concave face cover, a flow uniformizing fan is fixedly installed at the top end of the rotating column, and a plurality of air passing holes are evenly formed in the fixing ring at equal intervals. According to the flow uniformizing device for the vacuum carburizing furnace, the flow uniformizing assembly is arranged, a penetrating agent conveyed into the vacuum carburizing furnace through the communicating pipe impacts into the fixing ring and the arc-shaped concave face cover, the penetrating agent impacts on the arc-shaped protrusions firstly, the flow uniformizing fan is driven to rotate on the rotating column, and the penetrating agent is scattered into the arc-shaped concave face cover; and the gas uniformly enters the vacuum carburizing furnace through a plurality of gas passing holes.

Description

Technical Field

[0001] This utility model relates to the field of low-pressure carburizing technology, and in particular to a precision pressure-controlled low-pressure carburizing treatment device. Background Technology

[0002] The workpiece is placed in a vacuum furnace, evacuated and heated to purify the furnace. Once the carburizing temperature is reached, hydrocarbons (such as propane) are introduced for carburizing. After a certain time, the carburizing agent is cut off, and the furnace is evacuated again for diffusion. This method can achieve high-temperature carburizing (1040℃), shorten the carburizing time, prevent internal oxidation in the carburized layer, and avoid the problem of the carbon content on the surface of the carburized layer being lower than that of the sublayer. Furthermore, vacuum carburizing can be performed in a pulse manner to obtain a uniform carburized layer for blind holes and small holes. Heavy-duty gears are required to withstand greater forces, so they need to be treated with a vacuum low-pressure carburizing heat treatment device to improve the strength and performance of heavy-duty gears.

[0003] Announcement No. CN219547064U discloses a heavy-duty gear vacuum low-pressure carburizing heat treatment device, including a base, a vacuum carburizing furnace, a vertical plate, and a furnace cover. The vacuum carburizing furnace is mounted on the top of the base via support legs. A vertical plate is welded to one end of the top of the base, and a servo motor is mounted on one side of the bottom of the vertical plate via a mounting base. The output shaft of the servo motor is connected to a lead screw via a coupling, and a lead screw is fitted onto the lead screw. The furnace cover is mounted on one side of the lead screw via a linkage rod and bolts. A lifting rod is bolted to the bottom of the furnace cover, and a material tray is fitted at the bottom of the lifting rod. The bottom of the material tray has through holes, and a support column is welded inside the material tray. This novel gear vacuum low-pressure carburizing heat treatment device has an automatic feeding and discharging structure, which can automatically feed and discharge materials when using the vacuum carburizing furnace, and close the furnace cover while feeding materials, making it suitable for widespread use.

[0004] The aforementioned device delivers the penetrant into the vacuum furnace through an air inlet. The penetrant's direct delivery into the furnace impacts the workpiece, resulting in uneven distribution of the penetrant across different areas of the furnace and affecting the carburizing effect on different parts of the workpiece. Therefore, a precise pressure-controlled low-pressure carburizing treatment device is needed. Utility Model Content

[0005] The technical problem to be solved by this utility model is to overcome the defect of the existing technology where the penetrant in each area of ​​the vacuum furnace is not uniform, which affects the carburizing effect of different parts of the workpiece. This utility model proposes a precise pressure-controlled low-pressure carburizing treatment device.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is: a precision pressure-controlled low-pressure carburizing treatment device, comprising: a mounting base plate, a vacuum carburizing furnace at the top of the mounting base plate, a sealed furnace cover at the top of the vacuum carburizing furnace, a flow equalization component extending into the top of the vacuum carburizing furnace below the sealed furnace cover, a penetrant heating box above the mounting base plate, a uniform heating component inside the penetrant heating box, and a movable component for moving the sealed furnace cover above the mounting base plate.

[0007] The flow equalization component includes a fixed ring, which is fixedly installed at the center of the bottom of the sealed furnace cover. An arc-shaped concave cover is fixedly installed at the bottom of the fixed ring. A rotating column is rotatably installed at the center of the bottom of the arc-shaped concave cover. A flow equalization fan is fixedly installed at the top of the rotating column. An arc-shaped protrusion is fixedly installed at the center of the top of the flow equalization fan. Several air passage holes are evenly and equidistantly opened on the fixed ring.

[0008] The penetrant delivered to the vacuum carburizing furnace impacts the fixed ring and the arc-shaped concave hood. The penetrant drives the uniform flow fan to rotate on the rotating column, dispersing the penetrant into the arc-shaped concave hood. Gradually, the penetrant enters the vacuum carburizing furnace evenly through several air passages.

[0009] Preferably, an air inlet pipe is connected to the outer wall of the penetrant heating chamber, an oil outlet pipe is connected to the outer wall of the penetrant heating chamber, and several electric heating tubes are fixedly installed at equal intervals at the bottom of the penetrant heating chamber.

[0010] Preferably, the uniform heating assembly includes a fixed partition and several fixed air passage plates. The fixed partition and several fixed air passage plates are fixedly installed inside the penetrant heating chamber. Several fixed air passage plates are arranged above the fixed partition. An air passage cavity is formed between the fixed partition and the lowest fixed air passage plate. An air passage cavity is formed between several adjacent fixed air passage plates. An air passage cavity is formed between the highest fixed air passage plate and the top surface inside the penetrant heating chamber.

[0011] Preferably, the air intake pipe is positioned between the fixed partition and the lowest fixed air passage plate. Several air passage holes are evenly spaced on one side of the fixed air passage plate. The air passage holes on the lowest fixed air passage plate are positioned on the side away from the air intake pipe, and the air passage holes on adjacent fixed air passage plates are symmetrically arranged.

[0012] The penetrant enters the lowest air passage chamber through the air inlet pipe. The penetrant in the air passage chamber flows through air outlets at different positions. Several sets of air outlets arranged symmetrically increase the path of the penetrant and are finally delivered to the uppermost air passage chamber.

[0013] Preferably, the bottom of the fixed air passage plate is fixedly installed with interconnected circulating heating pipes. One end of the circulating heating pipe extends through the hot oil chamber and into the heated oil. A circulating pump is fixedly installed at the top of the mounting base plate. The other end of the circulating heating pipe is connected to the circulating pump. The circulating pump is connected to the liquid extraction pipe, which extends through the hot oil chamber.

[0014] Preferably, the top of the penetrant heating box is connected to a connecting pipe, one end of which extends into the uppermost air passage chamber, and the other end of which extends through the sealed furnace cover into the vacuum carburizing furnace.

[0015] When the circulation pump is started, the heating oil in the hot oil chamber is transported to the circulating heating pipe through the liquid extraction pipe. The heating oil moves in the circulating heating pipe and is eventually transported back to the hot oil chamber, thereby heating the penetrant. This allows the penetrant to be transported to the vacuum carburizing furnace through the connecting pipe, and the carburizing gas can diffuse to all corners of the furnace more quickly, reducing the gas diffusion time and thus accelerating the carburizing process.

[0016] Preferably, the moving component includes a vertical plate, which is fixedly installed on the top of the mounting base plate. A pair of fixing blocks are fixedly installed on the side of the vertical plate near the vacuum carburizing furnace. A threaded rod is rotatably installed between the pair of fixing blocks. A lead screw block is threaded onto the threaded rod. A fixed mounting plate is fixedly installed on the side of the lead screw block near the vacuum carburizing furnace. The fixed mounting plate is fixedly installed on the top surface of the sealed furnace cover. Several limiting rods are fixedly installed between the pair of fixing blocks. The lead screw block is slidably sleeved on the several limiting rods. A forward and reverse motor is fixedly installed on the top of the mounting base plate. The output shaft of the forward and reverse motor is coaxially fixedly connected to the threaded rod.

[0017] Preferably, the vacuum carburizing furnace is provided with several mounting rings, several mounting rods are fixedly inserted through the mounting rings, the mounting rods are fixedly installed at the bottom of the sealed furnace cover, a bearing plate is fixedly installed inside the mounting rings, several ventilation holes are evenly spaced on the bearing plate, and support columns are evenly spaced on the top surface of the bearing plate.

[0018] The workpiece to be processed is placed on the support column, and the forward and reverse motor is started. The forward and reverse motor drives the threaded rod to rotate. As the bolt rod rotates, the lead screw block moves synchronously. The lead screw block moves through the fixed mounting plate to seal the furnace cover, so that the sealing furnace cover seals the vacuum carburizing furnace. After processing is completed, the forward and reverse motor reverses to remove the workpiece from the support plate.

[0019] Compared with the prior art, the beneficial effects of this utility model include: by setting a flow equalization component, the penetrant delivered to the vacuum carburizing furnace through the connecting pipe impacts the fixed ring and the arc-shaped concave mask. The penetrant first impacts the arc-shaped protrusion, and the penetrant drives the flow equalization fan to rotate on the rotating column, dispersing the penetrant into the arc-shaped concave mask. Gradually, the penetrant enters the vacuum carburizing furnace evenly through several air holes, making the processing of the workpiece more uniform. Attached Figure Description

[0020] The disclosure of this utility model is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this utility model. In the drawings, the same reference numerals are used to refer to the same parts. Wherein:

[0021] Figure 1 The schematic diagram shows a three-dimensional structure of a precision pressure-controlled low-pressure carburizing treatment device according to one embodiment of the present invention. Figure 1 .

[0022] Figure 2 The schematic diagram shows a side view of a precision pressure-controlled low-pressure carburizing treatment device according to one embodiment of the present invention. Figure 2 .

[0023] Figure 3 The diagram illustrates the internal structure of a vacuum carburizing furnace in a precision pressure-controlled low-pressure carburizing treatment device according to one embodiment of the present invention.

[0024] Figure 4 The diagram illustrates the flow uniform component structure of a precision pressure-controlled low-pressure carburizing treatment device according to one embodiment of the present invention.

[0025] Figure 5 The diagram illustrates an exploded view of the flow uniform component of a precision pressure-controlled low-pressure carburizing treatment device according to one embodiment of the present invention.

[0026] Figure 6 The diagram illustrates the internal structure of the penetrant heating chamber of a precision pressure-controlled low-pressure carburizing treatment device according to one embodiment of the present invention.

[0027] Figure 7 The diagram schematically shows a side view of the penetrant heating chamber of a precision pressure-controlled low-pressure carburizing treatment device according to one embodiment of the present invention.

[0028] Figure 8 The diagram illustrates the exploded structure of a uniform heating component in a precision pressure-controlled low-pressure carburizing treatment device according to one embodiment of the present invention.

[0029] Figure 9 The diagram illustrates the structure of a moving component of a precision pressure-controlled low-pressure carburizing treatment device according to one embodiment of the present invention.

[0030] Numbered in the diagram: 1. Mounting base plate; 2. Vacuum carburizing furnace; 21. Mounting ring; 22. Mounting rod; 23. Support plate; 24. Vent hole; 25. Support column; 3. Sealed furnace cover; 4. Flow equalization assembly; 41. Fixing ring; 42. Arc-shaped concave cover; 43. Rotating column; 44. Flow equalization fan; 45. Arc-shaped protrusion; 46. Vent hole; 5. Penetrant heating box; 51. Air inlet pipe; 52. Oil outlet pipe; 53. Electric heating element 54. Connecting pipe; 6. Uniform heating component; 61. Fixed partition; 62. Fixed air passage plate; 63. Hot oil chamber; 64. Heating oil; 65. Air passage chamber; 66. Air outlet; 67. Circulating heating pipe; 68. Circulating pump; 69. Liquid extraction pipe; 7. Moving component; 71. Vertical plate; 72. Fixed block; 73. Threaded rod; 74. Lead screw block; 75. Fixed mounting plate; 76. Limiting rod; 77. Forward and reverse motor. Detailed Implementation

[0031] It is readily understood that, based on the technical solution of this utility model, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of this utility model. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative descriptions of the technical solution of this utility model and should not be considered as the entirety of this utility model or as limitations or restrictions on the technical solution of this utility model.

[0032] According to one embodiment of the present invention, in conjunction with Figures 1 to 5 As shown. A precision pressure-controlled low-pressure carburizing treatment device includes: a mounting base plate 1, a vacuum carburizing furnace 2 disposed at the top of the mounting base plate 1, a sealed furnace cover 3 disposed at the top of the vacuum carburizing furnace 2, a flow equalization component 4 disposed below the sealed furnace cover 3 extending into the top of the vacuum carburizing furnace 2, a flow equalization component 4 disposed at the top of the vacuum carburizing furnace 2, a penetrant heating box 5 disposed above the mounting base plate 1, a uniform heating component 6 disposed inside the penetrant heating box 5, and a moving component 7 disposed above the mounting base plate 1 to move the sealed furnace cover 3;

[0033] The flow equalization component 4 includes a fixed ring 41, which is fixedly installed at the center of the bottom of the sealed furnace cover 3. An arc-shaped concave cover 42 is fixedly installed at the bottom of the fixed ring 41. A rotating column 43 is rotatably installed at the center of the bottom of the arc-shaped concave cover 42. A flow equalization fan 44 is fixedly installed at the top of the rotating column 43. An arc-shaped protrusion 45 is fixedly installed at the center of the top of the flow equalization fan 44. Several air passage holes 46 are evenly spaced on the fixed ring 41. The vacuum pump outside the vacuum carburizing furnace 2 evacuates the vacuum carburizing furnace 2. The penetrant delivered to the vacuum carburizing furnace 2 impacts the fixed ring 41 and the arc-shaped concave cover 42. The penetrant first impacts the arc-shaped protrusion 45. The penetrant drives the flow equalization fan 44 to rotate on the rotating column 43, dispersing the penetrant into the arc-shaped concave cover 42. Gradually, the penetrant enters the vacuum carburizing furnace 2 evenly through the several air passage holes 46, making the processing of the workpiece more uniform.

[0034] According to one embodiment of the present invention, in conjunction with Figures 6 to 8 As shown. An air inlet pipe 51 is connected to the outer wall of the penetrant heating box 5, an oil outlet pipe 52 is connected to the outer wall of the penetrant heating box 5, and several electric heating tubes 53 are fixedly installed at equal intervals at the bottom of the penetrant heating box 5.

[0035] The uniform heating component 6 includes a fixed partition 61 and several fixed air passage plates 62. The fixed partition 61 and several fixed air passage plates 62 are fixedly installed inside the penetrant heating box 5. Several fixed air passage plates 62 are arranged above the fixed partition 61. The fixed partition 61 and the bottom surface of the penetrant heating box 5 form a hot oil cavity 63. The hot oil cavity 63 is filled with heating oil 64. The fixed partition 61 and the bottommost fixed air passage plate 62 form an air passage cavity 65. Several adjacent fixed air passage plates 62 form an air passage cavity 65. The topmost fixed air passage plate 62 and the top surface of the penetrant heating box 5 each form an air passage cavity 65.

[0036] The air intake pipe 51 is located between the fixed partition 61 and the lowest fixed air passage plate 62. Several air passage holes 66 are evenly spaced on one side of the fixed air passage plate 62. The air passage holes 66 on the lowest fixed air passage plate 62 are located on the side away from the air intake pipe 51. The air passage holes 66 on adjacent fixed air passage plates 62 are symmetrically arranged.

[0037] The bottom of the fixed air passage plate 62 is fixedly installed with interconnected circulating heating pipes 67. One end of the circulating heating pipe 67 passes through the hot oil chamber 63 and extends into the heating oil 64. The top of the mounting base plate 1 is fixedly installed with a circulating pump 68. The other end of the circulating heating pipe 67 is connected to the circulating pump 68. The circulating pump 68 is connected to the liquid extraction pipe 69, which passes through the hot oil chamber 63.

[0038] The top of the penetrant heating box 5 is connected to a connecting pipe 54. One end of the connecting pipe 54 extends into the uppermost air passage 65, and the other end of the connecting pipe 54 extends into the vacuum carburizing furnace 2 through the sealed furnace cover 3.

[0039] The circulating pump 68 is started, and the heating oil 64 in the hot oil chamber 63 is transported to the circulating heating pipe 67 through the liquid extraction pipe 69. The heating oil 64 moves within the circulating heating pipe 67 and is eventually transported back to the hot oil chamber 63. The penetrant enters the lowest gas passage chamber 65 through the air inlet pipe 51. The penetrant in the gas passage chamber 65 flows through the gas outlets 66 at different positions. The symmetrically arranged sets of gas outlets 66 increase the path of the penetrant, thereby heating it. The penetrant is then transported to the vacuum carburizing furnace 2 through the connecting pipe 54. The carburizing gas can diffuse to all corners of the furnace more quickly, reducing the gas diffusion time and thus accelerating the carburizing process. The increased temperature intensifies the thermal motion of gas molecules and increases their kinetic energy. The preheated gas enters the furnace and, due to its higher molecular motion speed, diffuses more quickly, filling the furnace space in a shorter time. This reduces uneven distribution caused by slow diffusion, allowing the gas to reach a more uniform distribution state more quickly and improving the processing effect on the workpiece.

[0040] According to one embodiment of the present invention, in conjunction with Figure 3 and Figure 9 As shown. The moving component 7 includes a vertical plate 71, which is fixedly mounted on the top of the mounting base plate 1 by fixing bolts. A pair of fixing blocks 72 are fixedly mounted on the side of the vertical plate 71 near the vacuum carburizing furnace 2 by fixing bolts. A threaded rod 73 is rotatably mounted between the pair of fixing blocks 72. A lead screw block 74 is threaded onto the threaded rod 73. A fixed mounting plate 75 is fixedly mounted on the side of the lead screw block 74 near the vacuum carburizing furnace 2. The fixed mounting plate 75 is fixedly mounted on the top surface of the sealed furnace cover 3. A number of limiting rods 76 are fixedly mounted between the pair of fixing blocks 72. The lead screw block 74 is slidably sleeved on the number of limiting rods 76. A forward and reverse motor 77 is fixedly mounted on the top of the mounting base plate 1. The output shaft of the forward and reverse motor 77 is coaxially fixedly connected to the threaded rod 73.

[0041] The vacuum carburizing furnace 2 is equipped with several mounting rings 21, and several mounting rods 22 are fixedly inserted through the mounting rings 21. The mounting rods 22 are fixedly installed at the bottom of the sealed furnace cover 3. A bearing plate 23 is fixedly installed inside the mounting rings 21. Several ventilation holes 24 are evenly spaced on the bearing plate 23. Support columns 25 are evenly spaced on the top surface of the bearing plate 23.

[0042] The workpiece to be processed is placed on the support column 25, and the forward and reverse motor 77 is started. The forward and reverse motor 77 drives the threaded rod 73 to rotate. As the threaded rod 73 rotates, the lead screw block 74 moves synchronously. The lead screw block 74 moves through the fixed mounting plate 75 to seal the furnace cover 3, so that the sealing furnace cover 3 seals the vacuum carburizing furnace 2. After processing is completed, the forward and reverse motor 77 reverses to remove the workpiece from the bearing plate 23.

[0043] The technical scope of this utility model is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this utility model, and all such modifications and variations should fall within the protection scope of this utility model.

Claims

1. A precision pressure-controlled low-pressure carburizing treatment device, characterized in that, include: Mounting substrate (1), a vacuum carburizing furnace (2) is provided at the top of the mounting substrate (1), a sealing furnace cover (3) is provided at the top of the vacuum carburizing furnace (2), a uniform flow component (4) is provided below the sealing furnace cover (3) and extends into the top of the vacuum carburizing furnace (2), a penetrant heating box (5) is provided above the mounting substrate (1), a uniform heating component (6) is provided inside the penetrant heating box (5), and a moving component (7) for moving the sealing furnace cover (3) is provided above the mounting substrate (1). The flow equalization component (4) includes a fixing ring (41), which is fixedly installed at the center of the bottom of the sealed furnace cover (3). An arc-shaped concave cover (42) is fixedly installed at the bottom of the fixing ring (41). A rotating column (43) is rotatably installed at the center of the bottom of the arc-shaped concave cover (42). A flow equalization fan (44) is fixedly installed at the top of the rotating column (43). An arc-shaped protrusion (45) is fixedly installed at the center of the top of the flow equalization fan (44). Several air passage holes (46) are evenly and equidistantly opened on the fixing ring (41).

2. The precision pressure-controlled low-pressure carburizing treatment device according to claim 1, characterized in that, The outer wall of the penetrant heating box (5) is connected to an air inlet pipe (51), the outer wall of the penetrant heating box (5) is connected to an oil outlet pipe (52), and a number of electric heating tubes (53) are evenly and uniformly fixedly installed at the bottom of the penetrant heating box (5).

3. The precision pressure-controlled low-pressure carburizing treatment device according to claim 2, characterized in that, The uniform heating assembly (6) includes a fixed partition (61) and several fixed air passage plates (62). The fixed partition (61) and several fixed air passage plates (62) are fixedly installed inside the penetrant heating box (5). Several of the fixed air passage plates (62) are arranged above the fixed partition (61). The fixed partition (61) and the bottom surface of the penetrant heating box (5) form a hot oil cavity (63). The hot oil cavity (63) is filled with heating oil (64). The fixed partition (61) and the bottom fixed air passage plate (62) form an air passage cavity (65). Several adjacent fixed air passage plates (62) form an air passage cavity (65). The top fixed air passage plate (62) and the top surface of the penetrant heating box (5) all form an air passage cavity (65).

4. The precision pressure-controlled low-pressure carburizing treatment device according to claim 3, characterized in that, The air inlet pipe (51) is located between the fixed partition (61) and the lowest fixed air passage plate (62). A plurality of air delivery holes (66) are evenly spaced on one side of the fixed air passage plate (62). The air delivery hole (66) on the lowest fixed air passage plate (62) is located on the side away from the air inlet pipe (51). The air delivery holes (66) on adjacent fixed air passage plates (62) are symmetrically arranged.

5. The precision pressure-controlled low-pressure carburizing treatment device according to claim 4, characterized in that, The bottom of each fixed air-passing plate (62) is fixedly installed with interconnected circulating heating pipes (67). One end of the circulating heating pipe (67) extends through the hot oil chamber (63) and into the heating oil (64). The top of the mounting base plate (1) is fixedly installed with a circulating pump (68). The other end of the circulating heating pipe (67) is connected to the circulating pump (68). The circulating pump (68) is connected to a liquid extraction pipe (69). The liquid extraction pipe (69) extends through the hot oil chamber (63).

6. The precision pressure-controlled low-pressure carburizing treatment device according to claim 3, characterized in that, The top of the penetrant heating box (5) is connected to a connecting pipe (54). One end of the connecting pipe (54) extends into the uppermost air passage (65), and the other end of the connecting pipe (54) extends through the sealed furnace cover (3) into the vacuum carburizing furnace (2).

7. The precision pressure-controlled low-pressure carburizing treatment device according to claim 4, characterized in that, The moving component (7) includes a vertical plate (71), which is fixedly installed on the top of the mounting base plate (1). A pair of fixing blocks (72) are fixedly installed on the side of the vertical plate (71) near the vacuum carburizing furnace (2). A threaded rod (73) is rotatably installed between the pair of fixing blocks (72). A lead screw block (74) is threaded on the threaded rod (73). A fixed mounting plate (75) is fixedly installed on the side of the lead screw block (74) near the vacuum carburizing furnace (2). The fixed mounting plate (75) is fixedly installed on the top surface of the sealed furnace cover (3). A plurality of limiting rods (76) are fixedly installed between the pair of fixing blocks (72). The lead screw block (74) is slidably sleeved on the plurality of limiting rods (76). A forward and reverse motor (77) is fixedly installed on the top of the mounting base plate (1). The output shaft of the forward and reverse motor (77) is coaxially fixedly connected to the threaded rod (73).

8. The precision pressure-controlled low-pressure carburizing treatment device according to claim 1, characterized in that, The vacuum carburizing furnace (2) is provided with several mounting rings (21), and several mounting rods (22) are fixedly inserted through the mounting rings (21). The mounting rods (22) are fixedly installed at the bottom of the sealed furnace cover (3). A bearing plate (23) is fixedly installed inside the mounting rings (21). Several ventilation holes (24) are evenly and equidistantly opened on the bearing plate (23). Support columns (25) are evenly and equidistantly fixedly installed on the top surface of the bearing plate (23).

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