A vacuum furnace used in NdFeB heavy rare earth grain boundary diffusion process

Abstract

The present application relates to a vacuum furnace used in a NdFeB heavy rare earth grain boundary diffusion process, comprising a furnace body, a strip-shaped resistance heater arranged in the furnace body, and a reflection screen located between the furnace body and the strip-shaped resistance heater; the furnace body comprises a furnace shell, a front furnace door hinged at one end of the furnace shell, and a rear furnace door fixed at the other end of the furnace shell; the strip-shaped resistance heater comprises a front heater, a furnace shell heater, and a rear heater; the reflection screen comprises a front reflection screen fixed on the front furnace door, a furnace shell reflection screen separately arranged in the furnace shell, and a rear reflection screen fixed on the rear furnace door; a first flexible fixing component flexibly connected to the furnace shell heater is provided on the furnace shell reflection screen, and a second flexible fixing component flexibly connected to the front heater and the rear heater is provided on the side of the front reflection screen and the rear reflection screen facing the furnace shell. The present application has the effect of reducing the degree of hard collision and extrusion of the resistance heater due to high-temperature expansion, thereby improving the service life.

Description

Technical Field

[0001] The present application relates to the field of NdFeB heavy rare earth grain boundary diffusion technology, and in particular to a vacuum furnace applied to NdFeB heavy rare earth grain boundary diffusion technology. Background Art

[0002] In the industrial production of magnetic materials, it is common to increase the coercivity by doping heavy rare earth materials during the smelting process. In order to more effectively obtain higher performance of magnets, the heavy rare earth grain boundary diffusion process is then used to effectively reduce the use of heavy rare earths, so that the heavy rare earth elements only exist in the grain boundaries, which makes it easier to obtain high-performance magnets.

[0003] The current heavy rare earth diffusion process mainly includes: forming a thin film containing heavy rare earth elements on the surface of the workpiece by evaporation or coating, and then subjecting the workpiece to high-temperature thermal diffusion and tempering treatment through magnetic material sintering equipment, so that the heavy rare earth elements penetrate into the magnetic material to complete the heavy rare earth diffusion. In order to ensure sufficient heating temperature, magnetic material sintering equipment usually uses resistance heaters for high-temperature heating, and the resistance heaters are mainly fixed to the inner wall of the magnetic material sintering equipment through some fastening components.

[0004] With respect to the above-mentioned related technologies, the inventors believe that the method of rigidly connecting the resistance heater through a fastening assembly has the following defects: when the temperature is too high, the resistance heater will produce heating expansion, resulting in hard collision and extrusion between the resistance heater and the fastening assembly, affecting the service life. Summary of the invention

[0005] In order to reduce the degree of hard collision and extrusion of the resistance heater due to high-temperature expansion, thereby increasing the service life, the present application provides a vacuum furnace applied to the NdFeB heavy rare earth grain boundary diffusion process.

[0006] The present application provides a vacuum furnace for use in a NdFeB heavy rare earth grain boundary diffusion process, which adopts the following technical solution:

[0007] A vacuum furnace used in a NdFeB heavy rare earth grain boundary diffusion process, comprising a furnace body, a strip-shaped resistance heater arranged in the furnace body, and a reflection screen located between the furnace body and the strip-shaped resistance heater;

[0008] The furnace body comprises a furnace shell with a hollow structure inside, a front furnace door hinged to one end of the furnace shell, and a rear furnace door fixed to the end of the furnace shell opposite to the front furnace door;

[0009] The strip resistance heater includes a front heater, a furnace shell heater and a rear heater; the reflection screen includes a front reflection screen fixed on the front furnace door, a furnace shell reflection screen which is separately arranged in the furnace shell and is cylindrical, and a rear reflection screen fixed on the rear furnace door;

[0010] A first flexible fixing component is provided on the furnace shell reflective screen to fix the furnace shell heater in the furnace shell reflective screen in a flexible connection manner, and a second flexible fixing component is respectively provided on the side of the front reflective screen and the rear reflective screen facing the furnace shell, and the second flexible fixing component respectively fixes the front heater on the front reflective screen in a flexible connection manner and fixes the rear heater on the rear reflective screen in a flexible connection manner.

[0011] By adopting the above technical scheme, in the present application, by setting up three independent individuals, namely the front heater, the furnace shell heater and the rear heater, different positions in the furnace body can be heated respectively to ensure the uniformity of the temperature in the furnace body; by setting up the first flexible fixing component and the second flexible fixing component, the front heater, the furnace shell heater and the rear heater can be fixed one by one on the front furnace door, the furnace shell and the rear furnace door respectively in a flexible connection manner, and when the strip resistance heater expands at high temperature, the first flexible fixing component and the second flexible fixing component can provide a certain expansion space for the strip resistance heater, which greatly reduces the degree of hard collision and extrusion of the strip resistance heater due to high-temperature expansion and improves its service life.

[0012] Preferably, the first flexible fixing component includes a column located inside the furnace shell reflective screen, a first through rod fixedly connected to one end of the column and radially extending through the furnace shell reflective screen, a second through rod fixedly connected to the other end of the column and passing through the furnace shell heater, and B-type cotter pins respectively plugged into one end of the first through rod extending out of the furnace shell reflective screen and one end of the second through rod passing through the furnace shell heater; there is a spacing between one end of the column close to the furnace shell heater and the B-type cotter pin plugged into the second through rod for the furnace shell heater to expand.

[0013] By adopting the above technical solution, during installation, the first flexible fixing component is first fixed to the furnace shell reflector screen by the first through rod and the B-type cotter pin, and then the second through rod is passed through the furnace shell heater and fixed by the B-type cotter pin. Since there is a distance between the end of the column close to the furnace shell heater and the B-type cotter pin inserted on the second through rod, sufficient expansion space can be provided for the high-temperature expansion of the furnace shell heater, thereby reducing the degree of hard collision and extrusion of the furnace shell heater due to high-temperature expansion.

[0014] Preferably, elastic gaskets are respectively provided on the rod bodies of the second penetration rod located on both sides of the furnace shell heater, and a telescopic gap is reserved between the two elastic gaskets.

[0015] By adopting the above technical solution, the furnace shell heater can be protected and, at the same time, a retractable space is provided for the expansion of the furnace shell heater, thereby reducing the degree of hard collision and extrusion of the furnace shell heater caused by high-temperature expansion.

[0016] Preferably, the second flexible fixing assembly includes a vertical plate fixedly connected to the front reflective screen or the rear reflective screen on the side facing the furnace shell, supporting members arranged on both sides of the vertical plate and movable relative to or toward each other, fixing bolts connecting the supporting members to the vertical plate, and limiting bolts arranged between the two supporting members to limit the front heater or the rear heater from falling.

[0017] By adopting the above technical solution, during installation, the two supporting members are first mounted on the vertical plate by fixing bolts, and then the front heater or the rear heater is placed between the two supporting members and fixed by limiting bolts.

[0018] Preferably, the supporting member includes a side plate parallel to the vertical plate, a transition plate integrally formed on the side plate at one end facing the furnace shell, and a bent plate integrally formed on the free end of the transition plate and extending back to the side plate. The two bent plates of the two supporting members are arranged opposite to each other and form a supporting cavity for placing the front heater or the rear heater. At least two pairs of fixing holes for fixing bolts to pass through are provided at corresponding positions of the side plates and the vertical plates, and the diameter of the fixing holes is larger than the diameter of the fixing bolts. The bent plates are provided with mounting holes for inserting limit bolts, and the diameter of the mounting holes is larger than the diameter of the limit bolts.

[0019] By adopting the above technical solution, when the front heater or the rear heater expands due to heating, since the diameter of the fixing hole is larger than the diameter of the fixing bolt and the diameter of the mounting hole is larger than the diameter of the limiting bolt, the two supporting parts are stretched open and move toward each other, ensuring that the front heater or the rear heater has a certain amount of lateral expansion and contraction.

[0020] Preferably, the two ends of the fixing bolt do not press against the two side plates, and the two ends of the limiting bolt do not press against the two bending plates.

[0021] By adopting the above technical solution, after installation, the fixing bolts and the limiting bolts can still move along their own axial direction, so that the front heater or the rear heater can have a certain longitudinal expansion and contraction when heated and expanded.

[0022] Preferably, elastic gaskets are respectively provided on both sides of the vertical plate and at positions between the two side plates corresponding to where the fixing bolts pass through.

[0023] By adopting the above technical solution, relative collision and friction between the two side plates caused by the front heater or the rear heater recovering their deformation can be avoided, thereby achieving a flexible buffering effect.

[0024] Preferably, the furnace shell comprises an inner shell and an outer shell, which are assembled by welding, and a water inlet and a water outlet are provided on the outer shell.

[0025] By adopting the above technical solution, the water inlet and the water outlet can be connected to the water cooling circulation system as needed to cool the furnace shell.

[0026] Preferably, the first flexible fixing components are provided in a plurality of groups, and the plurality of groups of first flexible fixing components are distributed in a circle with the axis of the furnace shell reflective screen as the center.

[0027] By adopting the above technical solution, the furnace shell reflective screen can be stably installed on the inner wall of the furnace shell.

[0028] Preferably, a plurality of groups of the second flexible fixing components are provided along the arrangement direction of the front heater or the rear heater.

[0029] By adopting the above technical solution, the front heater or the rear heater can be stably installed on the front reflection screen or the rear reflection screen. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the overall structure of the vacuum furnace in an embodiment of the present application;

[0031] Figure 2 It is an exploded schematic diagram showing the structure and position relationship of the reflective screen and the heater after the furnace shell is hidden;

[0032] Figure 3 It is a structural diagram showing the positional relationship between the furnace shell reflector screen, the support frame and the tray device;

[0033] Figure 4 It is a structural schematic diagram after the furnace shell heater and the first flexible fixing component fixing the furnace shell heater are taken out from the furnace shell reflection screen;

[0034] Figure 5 is a structural schematic diagram showing the connection relationship between the front heater and the second flexible fixing component;

[0035] Figure 6 It is a schematic diagram of the specific structure of the second flexible fixing component.

[0036] Explanation of the accompanying drawings: 1. furnace body; 11. furnace shell; 12. support seat; 13. front furnace door; 14. rear furnace door; 2. heater; 21. front heater; 22. furnace shell heater; 23. rear heater; 3. reflection screen; 31. front reflection screen; 32. furnace shell reflection screen; 33. rear reflection screen; 34. partition; 4. tray device; 41. support rod; 42. disk; 43. support plate; 5. first flexible fixing component; 51. column; 52. first through rod; 53. second through rod; 54. B-type cotter pin; 6. second flexible fixing component; 61. vertical plate; 62. supporting member; 621. side plate; 622. transition plate; 623. bending plate; 63. fixing bolt; 64. limiting bolt; 7. elastic gasket; 8. support frame; 81. annular plate; 82. connecting plate; 83. reinforcing plate. DETAILED DESCRIPTION

[0037] The following is combined with Figure 1-6 This application is described in further detail.

[0038] The present application embodiment discloses a vacuum furnace for use in a NdFeB heavy rare earth grain boundary diffusion process. Figure 1 and Figure 2 The vacuum furnace includes a furnace body 1, a heater 2 arranged in the furnace body 1, and a reflective screen 3 located between the furnace body 1 and the heater 2; the furnace body 1 is mainly used for placing workpieces to be processed; the heater 2 is mainly used for high-temperature heating of the workpieces; the reflective screen 3 is mainly used for heat preservation and insulation of the furnace body 1.

[0039] Reference Figure 1 The furnace body 1 includes a furnace shell 11 which is hollow inside and open at both ends. The furnace shell 11 is cylindrical and horizontally arranged. A support seat 12 is fixedly connected to the circumference of the furnace shell 11. The support seat 12 can be designed according to needs, and the specific shape and structure are not limited. A front furnace door 13 is hinged at one end of the furnace shell 11, and a rear furnace door 14 is fixedly connected to the other end of the furnace shell 11 by bolts. The front furnace door 13 can be opened and closed. After closing, a closed heating space is formed between the front furnace door 13, the furnace body 1 and the rear furnace door 14.

[0040] The furnace shell 11 is a double-layer structure, specifically including an inner shell and an outer shell, which are welded together. The outer shell is provided with a vacuum port, an air charging port, a water inlet and a water outlet. The vacuum port is used to connect with the vacuum system for vacuuming; the air charging port is used to connect with the air charging system so as to fill argon gas into the furnace shell 11; the water inlet is used to connect with the output end of the water cooling circulation system; the water outlet is used to connect with the input end of the water cooling circulation system. After the cooling water is passed into the furnace shell 11 through the water inlet, it can absorb most of the heat and be taken out of the furnace shell 11 through the water outlet to achieve cooling.

[0041] Reference Figure 1 and Figure 2 The heater 2 is a strip resistance heater, and its material is a high-temperature molybdenum strip. More specifically, the strip resistance heater includes a front heater 21 arranged on the front furnace door 13, a furnace shell heater 22 arranged in the furnace shell 11, and a front heater 23 arranged on the rear furnace door 14. The front heater 21, the furnace shell heater 22 and the front heater 23 are three independent individuals, each of which can be operated separately, so as to ensure the uniformity of the temperature in the furnace body 1.

[0042] The reflective screen 3 is of full metal structure, with six layers in total. The first two layers from the inside to the outside are molybdenum, and the remaining four layers are stainless steel. More specifically, the reflective screen 3 includes a front reflective screen 31 disposed between the front furnace door 13 and the front heater 21, a furnace shell reflective screen 32 disposed between the furnace shell 11 and the furnace shell heater 22, and a rear reflective screen 33 disposed between the rear furnace door 14 and the front heater 23. The furnace shell reflective screen 32 is a cylindrical structure with a hollow interior and openings at both ends. The front reflective screen 31 and the rear reflective screen 33 are plate-like structures that match the openings at both ends of the furnace shell reflective screen 32. When the furnace door is closed, a closed space is formed between the front reflective screen 31, the furnace shell reflective screen 32, and the rear reflective screen 33. It should be noted here that the side of the front reflective screen 31 and the rear reflective screen 33 facing the furnace shell 11 is the inner side.

[0043] Furthermore, the length of the molybdenum layer of the furnace shell reflection screen 32 is smaller than the length of the stainless steel layer, forming a high and low staggered edge. At the same time, the diameter of the molybdenum layer of the front reflection screen 31 and the rear reflection screen 33 is smaller than the diameter of the stainless steel layer. Such a structural design can greatly improve the sealing performance of the reflection insulation device.

[0044] Reference Figure 3 Between two adjacent layers of the furnace shell reflective screen 32, a plurality of circumferentially distributed partitions 34 are equidistantly arranged with the axis of the reflective screen 3 as the center. The arrangement of the partitions 34 forms a heat insulation cavity between the two adjacent layers of the structure, which can achieve better heat preservation and insulation effects.

[0045] A tray device 4 is provided inside the furnace shell reflective screen 32 for placing workpieces. The tray device 4 includes two groups of support rods 41 fixed on the inner wall of the furnace shell reflective screen 32 and arranged side by side in parallel, and a tray placed on the two groups of support rods 41. The support rods 41 are staggered with the furnace shell heater 22, and each group of support rods 41 is equidistantly distributed along the axial direction of the furnace shell reflective screen 32; the tray includes a disk surface 42 and two support plates 43 formed on one side of the disk surface 42. The free end of each group of support rods 41 is provided with a groove penetrating along the axial direction of the furnace shell reflective screen 32, and the tray is stably fixed by the support plate 43 and the groove.

[0046] A support frame 8 made of high temperature resistant material is sleeved on the outside of the furnace shell reflective screen 32 to ensure the strength of the furnace shell reflective screen 32 and to limit the deformation of the furnace shell reflective screen 32. The support frame 8 includes an annular plate 81 sleeved near both ends of the furnace shell reflective screen 32, a plurality of connecting plates 82 fixedly connected between the two annular plates 81 and evenly distributed, and a reinforcing plate 83 fixedly connected to the middle of two adjacent connecting plates 82. The annular plate 81 is adapted to the outer contour of the furnace shell reflective screen 32, and the connecting plate 82 and the reinforcing plate 83 are closely attached to the outer wall of the furnace shell reflective screen 32. When the furnace shell reflective screen 32 has a tendency to expand after being subjected to high temperature, the support frame 8 can limit the furnace shell reflective screen 32 and reduce the possibility of deformation of the furnace shell reflective screen 32.

[0047] Reference Figure 2 and Figure 4 A first flexible fixing component 5 is provided on the furnace shell reflection screen 32, which is used to fix the furnace shell heater 22 on the furnace shell reflection screen 32 in a flexible connection manner. The furnace shell heater 22 is installed outside the furnace shell 11 and is placed inside the furnace shell 11 after installation.

[0048] Reference Figure 2 The front reflecting screen 31 is fixed on the front furnace door 13, and the rear reflecting screen 33 is fixed on the rear furnace door 14. A second flexible fixing component 6 is respectively provided on the side of the front reflecting screen 31 and the rear reflecting screen 33 facing the furnace shell 11, for fixing the front heater 21 on the front reflecting screen 31 in a flexible connection manner, and fixing the front heater 23 on the rear reflecting screen 33 in a flexible connection manner.

[0049] The provision of the first flexible fixing component 5 and the second flexible fixing component 6 can greatly reduce the degree of hard collision and extrusion of the strip-shaped resistance heater 2 due to high-temperature expansion, thereby increasing the service life.

[0050] Reference Figure 3 and Figure 4 The first flexible fixing component 5 is provided with multiple groups, which are distributed in a circle with the axis of the furnace shell reflective screen 32 as the center. The first flexible fixing component 5 includes a column 51 located inside the furnace shell reflective screen 32, and the first through rod 52 and the second through rod 53 coaxially arranged with the column 51 are respectively fixed at both ends of the column 51. The first through rod 52 and the second through rod 53 are both provided with through holes, and the through holes are plugged with B-type cotter pins 54. The first through rod 52 passes through the radial direction of the furnace shell reflective screen 32 and is plugged and fixed by the B-type cotter pin 54, so that one end of the column 51 is against the inner wall of the furnace shell reflective screen 32; and the second through rod 53 passes through the furnace shell heater 22 and is plugged and fixed by the B-type cotter pin 54, so that the furnace shell heater 22 is fixed on the second through rod 53, and there is a spacing between the end of the column 51 and the B-type cotter pin 54 plugged on the second through rod 53 for the furnace shell heater 22 to expand.

[0051] In order to avoid damage caused by direct contact between the various components of the first flexible fixing component 5 and the furnace shell reflective screen 32 and the furnace shell heater 22, high-temperature resistant elastic gaskets 7 are respectively arranged at the positions where the various components of the first flexible fixing component 5 contact the furnace shell reflective screen 32 and the furnace shell heater 22, that is, one is arranged between the outer wall of the furnace shell reflective screen 32 and the B-type cotter pin 54, one is arranged between the inner wall of the furnace shell reflective screen 32 and the end face of the column 51, and one is arranged on each side of the furnace shell heater 22.

[0052] An expansion gap is reserved between the elastic gaskets 7 located on both sides of the furnace shell heater 22. When the furnace shell heater 22 is heated and expanded, the furnace shell heater 22 can expand and contract within the expansion gap, and after expansion and contraction, it is still in flexible contact with the elastic gasket 7, which greatly reduces the degree of hard collision and extrusion of the furnace shell heater 22 during heating and expansion.

[0053] Reference Figure 5 and Figure 6 The second flexible fixing assembly 6 is provided with a plurality of groups along the arrangement direction of the front heater 21 or the front heater 23. The second flexible fixing assembly 6 includes a vertical plate 61 fixedly connected to the side of the front reflective screen 31 or the rear reflective screen 33 facing the furnace shell 11, supporting members 62 arranged on both sides of the vertical plate 61 and movable relative to or toward each other, fixing bolts 63 connecting the supporting members 62 to the vertical plate 61, and a limiting bolt 64 arranged between the two supporting members 62 to limit the front heater 21 or the front heater 23 from falling; the supporting member 62 includes a vertical plate 61 fixedly connected to the vertical plate 61 and a fixing bolt 63 connecting the supporting members 62 to the vertical plate 61 ... A side plate 621 parallel to the plate 61, a transition plate 622 integrally formed at one end of the side plate 621 facing the furnace shell 11, and a bent plate 623 integrally formed at the free end of the transition plate 622 and extending away from the side plate 621, the two bent plates 623 of the two supporting members 62 are arranged opposite to each other and form a supporting cavity for placing the front heater 21 or the front heater 23, and mounting holes are opened on the bent plates 623, and the limiting bolts 64 pass through the mounting holes of the two bent plates 623 at the same time to limit the front heater 21 or the front heater 23.

[0054] At least two fixing holes are provided at corresponding positions of the side plate 621 and the vertical plate 61. The two supporting parts 62 are fixed by two fixing bolts 63 passing through the fixing holes on the side plate 621 and the vertical plate 61. Elastic gaskets 7 are respectively provided at the positions corresponding to the fixing bolts 63 passing through the two sides of the vertical plate 61 and between the two side plates 621. The fixing bolts 63 also pass through the elastic gaskets 7 to avoid direct contact between the side plate 621 and the vertical plate 61.

[0055] In this embodiment, the fixing bolt 63 and the limiting bolt 64 are always in a loose connection state, that is, the two ends of the fixing bolt 63 are not pressed against the two side plates 621, and the two ends of the limiting bolt 64 are not pressed against the two bent plates 623. After installation, the fixing bolt 63 and the limiting bolt 64 can still move along their own axial direction, so as to ensure that the front heater 21 or the front heater 23 can have a certain longitudinal expansion when heated and expanded; at the same time, the aperture of the installation hole and the fixing hole is larger than the diameter of the fixing bolt 63 and the limiting bolt 64, so as to ensure that the front heater 21 or the front heater 23 can have a certain lateral expansion when heated and expanded. By reserving the lateral expansion and longitudinal expansion, the front heater 21 or the front heater 23 is flexibly fixed, and the degree of hard collision and extrusion of the front heater 21 or the front heater 23 due to high-temperature expansion is reduced.

[0056] The implementation principle of the embodiment of the present application is: when working, the workpiece is placed on the tray and heated at high temperature by the heater 2. According to needs, one, two or three heaters 2 can be selectively turned on to ensure the uniformity of the temperature in the furnace body 1; during the heating process, if the furnace shell heater 22 generates heating expansion, the furnace shell heater 22 expands and contracts in the expansion gap between the two elastic gaskets 7; during the heating process, if the front heater 21 or the front heater 23 generates heating expansion, the front heater 21 or the front heater 23 expands and contracts laterally and longitudinally between the two supporting parts 62.

[0057] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A vacuum furnace used in NdFeB heavy rare earth grain boundary diffusion process, characterized in that: The invention comprises a furnace body (1), a strip-shaped resistance heater arranged in the furnace body (1), and a reflection screen (3) located between the furnace body (1) and the strip-shaped resistance heater: the furnace body (1) comprises a furnace shell (11) with a hollow structure inside, a front furnace door (13) hinged at one end of the furnace shell (11), and a rear furnace door (14) fixed at the end of the furnace shell (11) opposite to the front furnace door (13); the strip-shaped resistance heater comprises a front heater (21), a furnace shell heater (22), and a rear heater (23); the reflection screen (3) comprises a front reflection screen (31) fixed on the front furnace door (13), a cylindrical tube (23) arranged separately in the furnace shell (11) and a rear heater (23); A furnace shell reflection screen (32) is provided on the furnace shell reflection screen (32) and a rear reflection screen (33) fixed on the rear furnace door (14); a first flexible fixing component (5) is provided on the furnace shell reflection screen (32) for fixing the furnace shell heater (22) in the furnace shell reflection screen (32) in a flexible connection manner; a second flexible fixing component (6) is provided on the side of the front reflection screen (31) and the rear reflection screen (33) facing the furnace shell (11); the second flexible fixing component (6) fixes the front heater (21) to the front reflection screen (31) in a flexible connection manner and fixes the rear heater (23) to the rear reflection screen (33) in a flexible connection manner; The first flexible fixing component (5) comprises a column (51) located inside the furnace shell reflection screen (32), a first penetration rod (52) fixedly connected to one end of the column (51) and radially extending from the furnace shell reflection screen (32), a second penetration rod (53) fixedly connected to the other end of the column (51) and extending through the furnace shell heater (22), and a B-type cotter pin (54) respectively plugged into one end of the first penetration rod (52) extending from the furnace shell reflection screen (32) and one end of the second penetration rod (53) extending from the furnace shell heater (22), wherein a spacing for the furnace shell heater (22) to expand exists between one end of the column (51) close to the furnace shell heater (22) and the B-type cotter pin (54) plugged into the second penetration rod (53); The second penetration rod (53) is located on both sides of the furnace shell heater (22) and is provided with elastic gaskets (7) respectively, and a telescopic gap is reserved between the two elastic gaskets (7); The second flexible fixing assembly (6) comprises a vertical plate (61) fixedly connected to the side of the front reflective screen (31) or the rear reflective screen (33) facing the furnace shell (11), supporting members (62) arranged on both sides of the vertical plate (61) and movable relative to or towards each other, fixing bolts (63) connecting the supporting members (62) to the vertical plate (61), and a limiting bolt (64) arranged between the two supporting members (62) to limit the front heater (21) or the rear heater (23) from falling; The support member (62) comprises a side plate (621) parallel to the vertical plate (61), a transition plate (622) integrally formed at one end of the side plate (621) facing the furnace shell (11), and a bent plate (623) integrally formed at the free end of the transition plate (622) and extending away from the side plate (621); the two bent plates (623) of the two support members (62) are arranged opposite to each other and form a support cavity for placing the front heater (21) or the rear heater (23); at least two pairs of fixing holes for the fixing bolts (63) to pass through are provided at corresponding positions of the side plate (621) and the vertical plate (61); the diameter of the fixing hole is larger than the diameter of the fixing bolt (63); the bent plate (623) is provided with a mounting hole for the limit bolt (64) to be inserted; the diameter of the mounting hole is larger than the diameter of the limit bolt (64); Elastic gaskets (7) are respectively provided at positions between the two sides of the vertical plate (61) and the two side plates (621) corresponding to the positions through which the fixing bolts (63) pass; The two ends of the fixing bolt (63) do not abut against the two side plates (621), and the two ends of the limiting bolt (64) do not abut against the two bending plates (623).

2. A vacuum furnace for use in a NdFeB heavy rare earth grain boundary diffusion process according to claim 1, characterized in that: The furnace shell (11) comprises an inner shell and an outer shell, which are welded together, and a water inlet and a water outlet are provided on the outer shell.

3. The vacuum furnace used for NdFeB heavy rare earth grain boundary diffusion process according to claim 1, characterized in that: The first flexible fixing components (5) are provided in a plurality of groups, and the plurality of groups of first flexible fixing components (5) are distributed in a circle with the axis of the furnace shell reflection screen (32) as the center.

4. The vacuum furnace for use in the NdFeB heavy rare earth grain boundary diffusion process according to claim 1, characterized in that: The second flexible fixing components (6) are arranged in multiple groups along the arrangement direction of the front heater (21) or the rear heater (23).

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