Vacuum sintering furnace

Abstract

The utility model discloses a vacuum sintering furnace which comprises a vacuum furnace shell, a heating chamber, a material box uncovering device, a vacuum system and an inflation system. The heating chamber is arranged in the vacuum furnace shell and comprises a heat preservation screen, a heater, an uncovering assembly and a furnace hearth assembly from outside to inside. A sintering material box is placed on the furnace hearth assembly; the uncovering assemblies are located on the inner side of the heater and distributed on the two sides of the sintering material box. The material box uncovering device is located on the upper portion of the vacuum furnace shell, and a guide shaft penetrates through the vacuum furnace shell and the heat preservation screen of the heating chamber to be connected with the uncovering assembly. The material box uncovering device can drive the guide shaft to drive the uncovering assembly to move up and down. More than three layers of sintering material boxes are arranged in the vertical direction, each layer of sintering material box is provided with more than one sintering material box cover, and the cover opening assembly can drive the multiple sintering material box covers to ascend or descend at the same time, so that the sintering material box covers of the multiple layers of sintering material boxes are opened or closed at the same time in the vacuum sintering process.

Description

Technical Field

[0001] This utility model belongs to the field of rare earth permanent magnet production equipment, and specifically relates to a vacuum sintering furnace that can be used for vacuum sintering of rare earth permanent magnets and other materials. Background Technology

[0002] Rare earth permanent magnet materials are important functional materials, especially sintered NdFeB rare earth permanent magnet materials, which are widely used in medical MRI, computer hard disk drives, audio equipment, consumer electronics, automobiles, air conditioning compressors, energy-saving motors, wind power and other fields.

[0003] The industrial-scale preparation of sintered NdFeB rare-earth permanent magnet materials generally employs powder metallurgy technology, which involves vacuum sintering NdFeB alloy powder in a vacuum environment. During the vacuum sintering process, sintered NdFeB materials typically undergo several holding temperature stages, including stages designed to allow gas release and sintering stages to facilitate particle sintering. After heating, rapid air cooling is generally required, as this is crucial for achieving high intrinsic coercivity (Hcj) in batches of sintered NdFeB materials. However, current vacuum sintering furnaces often struggle to achieve the desired processing effect across all temperature stages during heating, and air cooling suffers from poor cooling efficiency and inconsistent magnetic properties, presenting significant industry challenges. Summary of the Invention

[0004] To address the aforementioned technical problems, this utility model provides a vacuum sintering furnace device that can improve the material heating and cooling efficiency during the vacuum sintering process and significantly improve the temperature uniformity and consistency of stacked materials during heating and air cooling.

[0005] The vacuum sintering furnace includes a vacuum furnace shell, a heating chamber, a material box opening device, a vacuum system, and a gas filling system. In a preferred embodiment, the vacuum sintering furnace has a horizontal structure, with the vacuum furnace shell equipped with a water-cooling jacket. The vacuum sintering furnace also includes a cooling system that provides cooling to the vacuum furnace shell. The heating chamber is located inside the vacuum furnace shell and includes, from the outside to the inside, a heat insulation screen, a heater, an opening assembly, and a furnace bed assembly. The sintering material box is placed on the furnace bed assembly. In a more preferred embodiment, the sintering material box is located in the central area of ​​the heating chamber. The opening assembly is located inside the heater and is distributed on both sides of the sintering material box. The material box opening device is located at the top of the vacuum furnace shell, with a guide shaft passing through the heat insulation screen of the vacuum furnace shell and the heating chamber and connecting to the opening assembly. The material box opening device can drive the guide shaft to move the opening assembly up and down. The heating chamber can be square or cylindrical, etc.

[0006] The sintering material boxes are arranged in three or more layers vertically, and each layer has one or more sintering material box covers. The cover opening assembly can drive multiple sintering material box covers to rise or fall simultaneously, so that the covers of the multi-layer sintering material boxes can be opened or closed at the same time. The material box cover opening device includes a motor, a reducer, and a lifting device; there are three or more lifting devices; the motor, reducer, and lifting devices are connected together, and the lifting devices rise or fall synchronously under the drive of the motor.

[0007] The vacuum furnace shell is connected to a gas filling system; the gas filling system includes a gas filling valve and a pressure gauge. Opening the gas filling valve allows protective gas to be filled into the vacuum furnace shell.

[0008] The vacuum furnace shell is connected to the vacuum system; the vacuum system includes a mechanical vacuum pump that directly exhausts to the atmosphere and a Roots vacuum pump that further enhances the vacuum level.

[0009] The vacuum sintering furnace includes an air-cooled heat exchange system; the air inlet pipe of the air-cooled heat exchange system is connected to the vacuum furnace shell; the air outlet pipe of the air-cooled heat exchange system splits into two pipes before passing through the vacuum furnace shell, each pipe is equipped with a valve, and after passing through the vacuum furnace shell, the pipes are connected to the left and right sides of the heating chamber respectively; nozzles are installed on both sides of the heating chamber, and the nozzles extend into the heating chamber through the insulation screen of the heating chamber; the two valves can be opened and closed simultaneously or alternately, and the airflow direction in the heating chamber can be switched during air cooling.

[0010] The vacuum sintering furnace includes a first isolation valve, which is located at one end of the vacuum furnace shell; when the first isolation valve is opened, the sintering material box can be moved to the outside of the vacuum sintering furnace, or the sintering material box can be moved from the outside of the vacuum sintering furnace to the heating chamber.

[0011] In one embodiment of this utility model, the vacuum sintering furnace further includes a second vacuum furnace shell and a second isolation valve; the second isolation valve is located at the other end of the vacuum furnace shell; when the first isolation valve is opened, the sintering material box can move from the outside of the first isolation valve to the heating chamber; when the second isolation valve is opened, the sintering material box can move from the heating chamber to the outside of the second isolation valve and enter the second vacuum furnace shell. After the sintering material box containing the material finishes the heating process in the vacuum furnace shell, it can be moved from the vacuum furnace shell to the second vacuum furnace shell for the next heating or cooling process. More vacuum furnace shells can be set behind the second vacuum furnace shell to form a continuous vacuum sintering furnace. The process environment of the two adjacent vacuum furnace shells can be isolated by setting a vacuum isolation valve. Different or the same process environment can be set in different vacuum furnace shells, and the material undergoes different stages of process in different vacuum furnace shells.

[0012] The furnace bed assembly includes rollers, and the sintering box can be moved on the furnace bed assembly via the rollers.

[0013] In another embodiment of this utility model, rollers are provided at the lower part of the insulation screen on the lower side of the heating chamber, and the furnace bed assembly is mounted on the insulation screen on the lower side of the heating chamber. The furnace bed assembly and the insulation screen on the lower side of the heating chamber can move together along the axis of the heating chamber. After the first isolation valve is opened, the insulation screen on the lower side of the heating chamber drives the furnace bed assembly to move to the outside of the vacuum sintering furnace. A movable material box is also provided outside the vacuum sintering furnace, and the movable material box is filled with protective gas. The movable material box includes a third isolation valve, a material box shell, and a lifting device; the third isolation valve is located at one end of the material box shell, and the lifting device is located inside the material box shell; the movable material box can be moved to the opposite side of the vacuum sintering furnace, and then the movable material box and the vacuum sintering furnace are docked, the third isolation valve and the first isolation valve are opened, and the sintering material box can move between the movable material box and the vacuum sintering furnace. After the moving material box is connected to the vacuum sintering furnace, the insulation screen on the lower side of the heating chamber moves the furnace bed assembly into the moving material box to carry the sintering material box containing the pressed blanks. The sintering material box is then returned to the vacuum sintering furnace. The moving material box and the vacuum sintering furnace then separate, and the vacuum sintering furnace performs the vacuum sintering process. After the vacuum sintering process is completed, the moving material box is connected to the vacuum sintering furnace again. The insulation screen on the lower side of the heating chamber moves the furnace bed assembly to transfer the sintering material box containing the sintered blanks from the vacuum sintering furnace to the moving material box. Then, the vacuum sintering furnace and the moving material box separate. Before the moving material box and the vacuum sintering furnace separate, the first and third isolation valves are closed. Before and after the vacuum sintering furnace is connected to the moving material box, the atmosphere inside both the conveying box and the vacuum sintering furnace remains isolated from the atmosphere.

[0014] The applicant discovered that in conventional vacuum sintering furnaces, sintering boxes are typically stacked densely, with no gaps between adjacent layers in the vertical direction. Furthermore, the sintering box lids remain constantly on top of the boxes. This results in poor heat flow during heating and cooling gas flow during air cooling within the multi-layered sintering boxes. In large-scale vacuum sintering production, a significant temperature difference exists between the material in the inner layers of the stack and the material in the outer layers during heating or air cooling, affecting the heating and air cooling efficiency of vacuum sintering. More importantly, it impacts the uniformity and consistency of the performance of NdFeB materials sintered in the same furnace. Additionally, the applicant found that during the venting and heat preservation phase of the heating curve, insufficient venting often makes it difficult to reduce the content of impurities such as oxygen and carbon in the sintered NdFeB blanks, affecting the magnetic properties of the material and limiting further improvements in the performance of rare-earth permanent magnet materials. When the material is undergoing sintering at high temperatures and vacuum levels, if the material box is not properly sealed, it is susceptible to oxidation and deterioration due to residual oxygen in the furnace, as well as the volatilization and loss of rare earth elements. These factors all negatively impact the magnetic properties of the sintered NdFeB. Furthermore, if the sintering material box remains uncovered, the rare earth components in the material are prone to slight volatilization during heating, especially at higher temperatures and vacuum levels, which also affects the magnetic properties of the sintered NdFeB.

[0015] In a preferred embodiment of this invention, the sintering cassette used in the vacuum sintering furnace has two side plates that are higher than the other two. When the sintering cassettes are stacked in the heating chamber, the bottom of the upper sintering cassette is supported on the higher side plate of the lower sintering cassette, creating a gap between the two layers. This gap not only improves the heating and air-cooling efficiency of vacuum sintering, ensuring uniform heating or air-cooling of the materials in the inner and outer layers of the stack, but also provides space for the sintering cassette lid to open or close during the vacuum sintering process.

[0016] In this invention, the opening and closing mechanism can simultaneously raise or lower multiple sintering box lids, allowing for free control of the opening and closing of the multi-layer sintering box lids during vacuum sintering. When the material passes through the venting and heat preservation section of the heating curve, the sintering box lids are open, allowing harmful gases to be fully discharged and reducing the impurity content in the sintered blank. When the material passes through the sintering temperature section, the sintering box lids are kept closed to prevent oxidation or volatilization of the NdFeB material within the sintering box. All these factors contribute to the superior magnetic and mechanical properties of the sintered NdFeB rare earth permanent magnet material obtained through vacuum sintering.

[0017] The beneficial effects of this utility model are:

[0018] This invention's vacuum sintering furnace solves a long-standing problem in the industry, allowing for free control of the opening and closing of the sintering box lid during the vacuum sintering process. This not only improves the heating and air-cooling efficiency of vacuum sintering, saving energy and production time, and increasing production efficiency, but also enables the produced sintered NdFeB rare earth permanent magnet materials to have higher intrinsic coercivity and other magnetic properties. Attached Figure Description

[0019] Figure 1 This is a front view structural schematic diagram of one embodiment of the vacuum sintering furnace of this utility model.

[0020] Figure 2 This is a top view schematic diagram of another embodiment of the vacuum sintering furnace of this utility model.

[0021] Figure 3 This is a front view schematic diagram of another embodiment of the vacuum sintering furnace of this utility model.

[0022] Figure 4 This is a top view of another embodiment of the vacuum sintering furnace of this utility model. Detailed Implementation

[0023] The embodiments of this utility model will be further described below with reference to the accompanying drawings.

[0024] like Figure 1 As shown, the vacuum sintering furnace of this utility model includes a vacuum furnace shell 1, a heating chamber 2, a material box opening device 3, a vacuum system 4, and a gas filling system 5. The vacuum furnace shell 1 is connected to the vacuum system 4. The heating chamber 2 is disposed inside the vacuum furnace shell 1, and from the outside to the inside, the heating chamber 2 includes a heat preservation screen 6, a heater 7, an opening assembly 8, and a furnace bed assembly 9; a sintering material box 10 is placed on the furnace bed assembly 9. In a preferred embodiment, the sintering material box 10 is located in the central area of ​​the heating chamber 2. The opening assembly 8 is located inside the heater 7 and is distributed on both sides of the sintering material box 10; the material box opening device 3 is located at the upper part of the vacuum furnace shell 1, and a guide shaft 11 passes through the vacuum furnace shell 1 and the heat preservation screen 6 of the heating chamber and is connected to the opening assembly 8; the material box opening device 3 can drive the guide shaft 11 to move the opening assembly 8 up and down.

[0025] exist Figure 1 In the illustrated embodiment, the vacuum sintering furnace has a horizontal structure, and the vacuum furnace shell has a square structure with a water-cooling jacket. The vacuum sintering furnace also includes a cooling system that provides cooling to the vacuum furnace shell.

[0026] The heating chamber in this invention can be square or cylindrical, etc. For example... Figure 1 The heating chamber shown is a square-shaped heating chamber.

[0027] The sintering boxes are arranged in three or more layers in the vertical direction. Each layer of sintering boxes has one or more sintering box covers. The cover opening component can drive multiple sintering box covers to rise or fall simultaneously, so that the sintering box covers of the multi-layer sintering boxes can be opened or closed at the same time.

[0028] The material box opening device 3 includes a motor, a reducer, and a lifting device 12; there are more than four lifting devices 12; the motor, reducer, and lifting device 12 are connected together, and the lifting devices 12 rise or fall synchronously under the drive of the motor.

[0029] The vacuum furnace shell 1 is connected to the gas filling system 5; the gas filling system 5 includes a gas filling valve 13 and a pressure gauge 14. Opening the gas filling valve 13 can fill the vacuum furnace shell 1 with protective gas.

[0030] In this utility model, such as Figure 2 and Figure 3 In the illustrated embodiment, rollers 16 are located at the lower part of the insulation screen 15 on the lower side of the heating chamber, and the furnace bed assembly 9 is mounted on the insulation screen 15 on the lower side of the heating chamber. The furnace bed assembly 9 and the insulation screen 15 on the lower side of the heating chamber can move together along the axis of the heating chamber 2. The vacuum sintering furnace includes a first isolation valve 17, which is connected to the vacuum furnace shell 1 and located at one end of the vacuum furnace shell 1; when the first isolation valve 17 is opened, the sintering material box 10 can be moved to the outside of the vacuum sintering furnace. After the first isolation valve 17 is opened, the insulation screen 15 on the lower side of the heating chamber drives the furnace bed assembly 9 to move to the outside of the vacuum sintering furnace. A movable material box 18 is also provided outside the vacuum sintering furnace, and the movable material box 18 is filled with protective gas. The movable material box 18 includes a third isolation valve 19, a material box housing 20, and a lifting device; the third isolation valve 19 is located at one end of the material box housing 20, and the lifting device is located inside the material box housing 20; the movable material box 18 can be moved to the opposite side of the vacuum sintering furnace, and then the movable material box 18 and the vacuum sintering furnace are connected, the third isolation valve 19 and the first isolation valve 17 are opened, and the sintering material box 10 can move between the movable material box 18 and the vacuum sintering furnace.

[0031] After the mobile material box is connected to the vacuum sintering furnace, the heat preservation screen on the lower side of the heating chamber drives the furnace bed assembly to move into the mobile material box to carry the sintering material box containing the pressed billet. Then, the sintering material box is returned to the vacuum sintering furnace. After that, the mobile material box and the vacuum sintering furnace are separated, and the vacuum sintering furnace performs the vacuum sintering process.

[0032] After the vacuum sintering process is completed, the moving material box reconnects with the vacuum sintering furnace. The insulation screen on the lower side of the heating chamber drives the furnace bed assembly to transfer the sintering material box containing the sintered blanks from the vacuum sintering furnace into the moving material box. Then, the vacuum sintering furnace and the moving material box separate. Before the moving material box and the vacuum sintering furnace separate, the first isolation valve and the third isolation valve are closed. Before and after the vacuum sintering furnace connects with the moving material box, the atmosphere inside both the material box and the vacuum sintering furnace remains isolated from the atmosphere.

[0033] exist Figure 2 In the embodiment shown, the vacuum system 4 includes a mechanical vacuum pump 21 that discharges directly into the atmosphere and a Roots vacuum pump 22 that further enhances the vacuum level.

[0034] The vacuum sintering furnace includes an air-cooled heat exchange system 23; the air inlet pipe of the air-cooled heat exchange system 23 is connected to the vacuum furnace shell 1; the air outlet pipe 24 of the air-cooled heat exchange system splits into two pipes 25 before passing through the vacuum furnace shell 1, each pipe is equipped with a valve 26, and the pipes 25 are connected to the left and right sides of the heating chamber 2 respectively after passing through the vacuum furnace shell 1. Nozzles 27 are installed on both sides of the heating chamber, and the nozzles 27 extend into the heating chamber through the insulation screen 6; the two valves 26 are opened and closed simultaneously or alternately.

[0035] In this utility model, such as Figure 4 In the illustrated embodiment, the vacuum sintering furnace further includes a second vacuum furnace shell 28 and a second isolation valve 29; the second isolation valve 29 is also connected to the vacuum furnace shell 1 and is located at the other end of the vacuum furnace shell 1; when the first isolation valve 17 is opened, the sintering material box 10 can move from the outside of the first isolation valve 17 to the heating chamber 2; when the second isolation valve 29 is opened, the sintering material box 10 can move from the heating chamber 2 to the outside of the second isolation valve 29 and enter the second vacuum furnace shell 28. After the sintering material box 10 containing material finishes the heating process in the vacuum furnace shell 1, it can move from the vacuum furnace shell 1 to the second vacuum furnace shell 28 for the next heating or cooling process. More vacuum furnace shells can be set behind the second vacuum furnace shell 28 to form a continuous vacuum sintering furnace. The process environment of the two adjacent vacuum furnace shells can be isolated by setting a vacuum isolation valve. Different and the same process environment can be set in different vacuum furnace shells, and the material undergoes different stages of process in different vacuum furnace shells. Figure 4 In the embodiment shown, the movable material box 18 is connected to the vacuum sintering furnace, and the first isolation valve 17 and the third isolation valve 19 are opened, so that the sintering material box 10 can be moved from the movable material box 18 outside the first isolation valve 17 to the heating chamber 2.

[0036] The furnace bed assembly includes rollers, and the sintering box can be moved on the furnace bed assembly via the rollers.

[0037] In a preferred embodiment of this invention, the sintering cassette used in the vacuum sintering furnace has two side plates that are higher than the other two. When the sintering cassettes are stacked in the heating chamber, the bottom of the upper sintering cassette is supported on the higher side plate of the lower sintering cassette, creating a gap between the two layers. This gap not only improves the heating and air-cooling efficiency of vacuum sintering, ensuring uniform heating or air-cooling of the materials in the inner and outer layers of the stack, but also provides space for the sintering cassette lid to open or close during the vacuum sintering process.

Claims

1. A vacuum sintering furnace, characterized in that: It includes a vacuum furnace shell, a heating chamber, a material box opening device, a vacuum system, and a gas filling system; the heating chamber is located inside the vacuum furnace shell, and from the outside to the inside, the heating chamber includes a heat preservation screen, a heater, an opening assembly, and a furnace bed assembly; the sintering material box is placed on the furnace bed assembly; the opening assembly is located inside the heater and is distributed on both sides of the sintering material box; the material box opening device is located at the top of the vacuum furnace shell, and a guide shaft passes through the heat preservation screen of the vacuum furnace shell and the heating chamber and connects to the opening assembly; the material box opening device can drive the guide shaft to move the opening assembly up and down.

2. The vacuum sintering furnace according to claim 1, characterized in that: The sintering boxes are arranged in three or more layers in the vertical direction. Each layer of sintering boxes has one or more sintering box covers. The cover opening component can drive multiple sintering box covers to rise or fall simultaneously, so that the sintering box covers of the multi-layer sintering boxes can be opened or closed simultaneously during the vacuum sintering process.

3. The vacuum sintering furnace according to claim 1, characterized in that: The vacuum furnace shell is connected to a gas filling system; the gas filling system includes a gas filling valve, which, when opened, allows protective gas to be filled into the vacuum furnace shell.

4. The vacuum sintering furnace according to claim 1, characterized in that: The vacuum furnace shell is connected to the vacuum system; the vacuum system includes a mechanical vacuum pump that directly exhausts to the atmosphere and a Roots vacuum pump that further enhances the vacuum level.

5. The vacuum sintering furnace according to claim 1, characterized in that: The vacuum sintering furnace includes an air-cooled heat exchange system; the air inlet pipe of the air-cooled heat exchange system is connected to the vacuum furnace shell; the air outlet pipe of the air-cooled heat exchange system splits into two pipes before passing through the vacuum furnace shell, each pipe is equipped with a valve, and after passing through the vacuum furnace shell, the pipes are connected to the left and right sides of the heating chamber respectively; nozzles are installed on both sides of the heating chamber, and the nozzles extend into the heating chamber through the insulation screen of the heating chamber; the two valves are opened and closed simultaneously or alternately.

6. The vacuum sintering furnace according to claim 1, characterized in that: The vacuum sintering furnace includes a first isolation valve, which is located at one end of the vacuum furnace shell; when the first isolation valve is opened, the sintering material box can be moved from the heating chamber to the outside of the vacuum sintering furnace, or the sintering material box can be moved from the outside of the vacuum sintering furnace to the heating chamber.

7. The vacuum sintering furnace according to claim 6, characterized in that: The vacuum sintering furnace also includes a second vacuum furnace shell and a second isolation valve; the second isolation valve is located at the other end of the vacuum furnace shell; when the first isolation valve is opened, the sintering material box can move from the outside of the first isolation valve to the heating chamber; when the second isolation valve is opened, the sintering material box can move from the heating chamber to the outside of the second isolation valve and enter the second vacuum furnace shell.

8. The vacuum sintering furnace according to claim 1, characterized in that: The furnace bed assembly includes rollers, and the sintering box can be moved on the furnace bed assembly via the rollers.

9. The vacuum sintering furnace according to claim 1, characterized in that: The material box opening device includes a motor, a reducer, and a lifter; there are more than three lifters; the motor, reducer, and lifters are connected together, and the lifters rise or fall synchronously under the drive of the motor.

10. The vacuum sintering furnace according to claim 6, characterized in that: The vacuum sintering furnace is also equipped with a movable material box on its exterior. The movable material box includes a third isolation valve, a material box shell, and a lifting device. The third isolation valve is located at one end of the material box shell, and the lifting device is located inside the material box shell. The movable material box can be moved to the opposite side of the vacuum sintering furnace. Then, the movable material box and the vacuum sintering furnace are connected, the third isolation valve and the first isolation valve are opened, and the sintering material box can move between the movable material box and the vacuum sintering furnace.

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