Vacuum sintering furnace

Abstract

The invention 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] The invention belongs to the field of rare earth permanent magnet production equipment, and in particular relates to a vacuum sintering furnace which can be used for vacuum sintering of rare earth permanent magnet and other materials. Background Art

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

[0003] The industrial preparation of sintered NdFeB rare earth permanent magnet materials generally adopts powder metallurgy technology, that is, the NdFeB alloy powder is vacuum sintered in a vacuum environment. When the temperature of sintered NdFeB materials rises in the vacuum sintering process, they generally go through several insulation temperature sections, including certain insulation temperature sections set up to allow the material to discharge gas, and sintering temperature sections set up to achieve the sintering process between material particles. After the heating and temperature rise is completed, it should generally be quickly cooled by air cooling. The cooling effect is crucial for the batch sintering of sintered NdFeB materials to obtain high intrinsic coercivity (Hcj). However, the vacuum sintering furnace equipment currently used in the industry is often difficult to make the material achieve the desired treatment effect in each temperature section during the heating and temperature rise process when sintering a large amount of NdFeB materials stacked in the furnace. In the air cooling process, there are problems such as poor cooling effect and poor consistency of magnetic properties of the material, which has become an industry problem that needs to be solved urgently. Summary of the invention

[0004] In view of the above technical problems, the present invention provides a vacuum sintering furnace equipment, which can improve the material heating and cooling efficiency during the vacuum sintering process, and significantly improve the temperature uniformity and consistency of the stacked materials during the heating and air cooling process.

[0005] The vacuum sintering furnace includes a vacuum furnace shell, a heating chamber, a material box cover opening device, a vacuum system and an air charging system. In a preferred embodiment, the vacuum sintering furnace is a horizontal structure, the vacuum furnace shell is provided with a water cooling jacket, and the vacuum sintering furnace also includes a cooling system, and the cooling system provides cooling for the vacuum furnace shell. The heating chamber is arranged in the vacuum furnace shell, and the heating chamber includes a heat preservation screen, a heater, a cover opening assembly and a furnace bed assembly from the outside to the inside; a sintering material box is placed on the furnace bed assembly, and in a more preferred embodiment, the sintering material box is located in the central area of ​​the heating chamber. The cover opening assembly is located on the inner side of the heater and is distributed on both sides of the sintering material box; the material box cover opening device is located at the upper part of the vacuum furnace shell, and a guide shaft passes through the vacuum furnace shell and the heat preservation screen of the heating chamber to connect with the cover opening assembly; the material box cover opening device can drive the guide shaft to drive the cover opening assembly to move up and down. The heating chamber can be in a square or cylindrical form.

[0006] The sintering material boxes are arranged in more than 3 layers in the vertical direction, and each layer of sintering material boxes has more than one sintering material box cover. The cover opening assembly can drive multiple sintering material box covers to rise or fall at the same time, so that the sintering material box covers of the multi-layer sintering material boxes are opened or closed at the same time. The material box cover opening device includes a motor, a reducer and a lifter; there are more than 3 lifters; the motor, the reducer and the lifter are connected together, and the lifter rises or falls synchronously under the drive of the motor.

[0007] The vacuum furnace shell is connected to a gas charging system; the gas charging system includes a gas charging valve and a pressure instrument. Protective gas can be charged into the vacuum furnace shell by opening the gas charging valve.

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

[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 is divided into two pipelines before passing through the vacuum furnace shell, each pipeline is provided with a valve, and the pipeline is respectively connected to the left and right sides of the heating chamber after passing through the vacuum furnace shell; nozzles are provided on both sides of the heating chamber, and the nozzles extend to the interior of the heating chamber through the heat preservation screen of the heating chamber; the two valves are switched on and off simultaneously or alternately, and the airflow direction in the heating chamber can be switched during air cooling.

[0010] The vacuum sintering furnace comprises a first isolation valve, which is arranged 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 the present invention, the vacuum sintering furnace further includes a second vacuum furnace shell and a second isolation valve; the second isolation valve is arranged at the other end of the vacuum furnace shell; the first isolation valve is opened, and the sintering material box can be moved from the outside of the first isolation valve to the heating chamber; the second isolation valve is opened, and the sintering material box can be moved from the heating chamber to the outside of the second isolation valve and enter the second vacuum furnace shell. After the sintering material box filled with materials 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 arranged behind the second vacuum furnace shell to form a continuous vacuum sintering furnace. The process environments of the two vacuum furnace shells can be isolated by setting a vacuum isolation valve between two adjacent vacuum furnace shells. Different and same process environments can be set in different vacuum furnace shells, and materials undergo different stages of process in different vacuum furnace shells.

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

[0013] In another embodiment of the present invention, there is a roller at the lower part of the heat preservation screen on the lower side of the heating chamber, and the furnace bed assembly is arranged on the heat preservation screen on the lower side of the heating chamber. The furnace bed assembly and the heat preservation 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 heat preservation 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 mobile material box is also arranged outside the vacuum sintering furnace, and the mobile material box is filled with protective gas. The mobile material box includes a third isolation valve, a material box shell and a lifting device; the third isolation valve is arranged at one end of the material box shell, and the lifting device is arranged inside the material box shell; the mobile material box can be moved to the opposite side of the vacuum sintering furnace, and then, the mobile material box and the vacuum sintering furnace are docked, and the third isolation valve and the first isolation valve are opened, and the sintering material box can be moved between the mobile material box and the vacuum sintering furnace. After the mobile material box and the vacuum sintering furnace are docked, 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 blanks in the mobile material box, and then returns to the vacuum sintering furnace with the sintering material box. Then, the mobile material box and the vacuum sintering furnace are separated, and the vacuum sintering furnace performs the vacuum sintering process. After the vacuum sintering process is completed, the mobile material box and the vacuum sintering furnace are docked again, and the heat preservation 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 to the mobile material box, and then the vacuum sintering furnace and the mobile material box are separated. Before the mobile material box and the vacuum sintering furnace are separated, close the first isolation valve and the third isolation valve first. Before and after the vacuum sintering furnace and the mobile material box are docked, the atmosphere in the transfer box and the vacuum sintering furnace is kept isolated from the atmosphere.

[0014] The applicant found that in ordinary vacuum sintering furnaces, sintering boxes are generally stacked densely, and there is no gap between two adjacent layers of sintering boxes in the vertical direction, and the sintering box cover is always on the sintering box, which makes the heat during heating and the cooling gas during air cooling have poor circulation in the multi-layer sintering boxes. In large-scale vacuum sintering production, the materials in the inner layer of the stack have a large temperature difference with the materials in the outer layer of the stack when heated or air-cooled, which affects the heating and air-cooling efficiency of vacuum sintering, and more importantly, affects the uniformity and consistency of the performance of NdFeB materials sintered in the same furnace. In addition, the applicant also found that when the material undergoes the degassing and heat preservation section in the heating curve, it is often difficult to reduce the content of impurities such as oxygen and carbon in the sintered NdFeB blank due to insufficient degassing, which affects the magnetic properties of the material and limits the further improvement of the performance of rare earth permanent magnet materials. When the material is going through the sintering temperature section, due to the high temperature and vacuum, if the material box is not tightly closed, the material is easily oxidized by the residual oxygen in the furnace and deteriorated, and the rare earth elements in the material are volatilized and lost, which will have a certain impact on the magnetic properties of the sintered NdFeB. If the sintering material box is always uncovered, the material is easy to be heated, and when the temperature and vacuum are high, the rare earth components in the material are easy to be slightly volatilized, which will have a certain impact on the magnetic properties of the sintered NdFeB.

[0015] In a preferred embodiment of the present invention, the sintering material box used in the vacuum sintering furnace has two side plates that are higher than the other two side plates. When the sintering material boxes are stacked in the heating chamber, the bottom of the upper sintering material box is supported on the higher side plate of the lower sintering material box, so that there is a certain distance between the two layers of sintering material boxes. This gap is not only conducive to improving the heating and air cooling efficiency of vacuum sintering, so that the materials in the inner and outer layers of the stack can be evenly heated or air cooled, but also provides space for the sintering material box cover in the present invention to be opened or closed during the vacuum sintering process.

[0016] In the present invention, the lid opening assembly can drive multiple sintering box lids to rise or fall at the same time, so that the opening or closing of the sintering box lids of the multi-layer sintering box can be freely controlled during the vacuum sintering process. When the material is undergoing the degassing and heat preservation section in the heating curve, the sintering box lid is in an open state, so that the harmful gas in the material is fully discharged, reducing the impurity content in the sintered blank. When the material is undergoing the sintering temperature section, the sintering box lid is controlled to be in a closed state to avoid oxidation or volatilization of the NdFeB material in the sintering box. The above factors make the sintered NdFeB rare earth permanent magnet material obtained by vacuum sintering have higher magnetic properties and mechanical properties.

[0017] Beneficial effects of the present invention: The vacuum sintering furnace of the present invention solves the inherent problems in the industry, and enables the opening or closing of the sintering box cover of the multi-layer sintering box to be freely controlled during the vacuum sintering process, which not only improves the heating and air cooling efficiency of vacuum sintering, saves energy and production time, and improves production efficiency, but also enables the sintered NdFeB rare earth permanent magnet material produced to have higher magnetic properties such as intrinsic coercivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the main structure of a vacuum sintering furnace of an embodiment of the present invention.

[0019] Figure 2 It is a schematic diagram of the top structure of another embodiment of the vacuum sintering furnace of the present invention.

[0020] Figure 3 It is a schematic diagram of the main structure of another embodiment of the vacuum sintering furnace of the present invention.

[0021] Figure 4 It is a schematic diagram of the top structure of another embodiment of the vacuum sintering furnace of the present invention. DETAILED DESCRIPTION

[0022] The embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

[0023] like Figure 1 As shown, the vacuum sintering furnace of the present invention includes a vacuum furnace shell 1, a heating chamber 2, a material box cover opening device 3, a vacuum system 4 and an inflation system 5. The vacuum furnace shell 1 is connected to the vacuum system 4. The heating chamber 2 is arranged in the vacuum furnace shell 1, and the heating chamber 2 includes a heat preservation screen 6, a heater 7, a cover opening assembly 8 and a furnace bed assembly 9 from the outside to the inside; a sintering material box 10 is placed on the furnace bed assembly 9. In a more preferred embodiment, the sintering material box 10 is located in the central area of ​​the heating chamber 2. The cover opening assembly 8 is located on the inner side of the heater 7 and is distributed on both sides of the sintering material box 10; the material box cover 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 cover opening assembly 8; the material box cover opening device 3 can drive the guide shaft 11 to drive the cover opening assembly 8 to move up and down.

[0024] exist Figure 1 In the embodiment shown, the vacuum sintering furnace is a horizontal structure, the vacuum furnace shell is a square structure, and is provided with a water cooling jacket. The vacuum sintering furnace also includes a cooling system, which provides cooling for the vacuum furnace shell.

[0025] The heating chamber in the present invention can be in the form of a square or cylindrical shape. Figure 1 The heating chamber shown is a square heating chamber.

[0026] The sintering material boxes are arranged in more than three layers in the vertical direction, and each layer of the sintering material boxes has more than one sintering material box cover. The cover opening assembly can drive multiple sintering material box covers to rise or fall at the same time, so that the sintering material box covers of the multiple layers of sintering material boxes can be opened or closed at the same time.

[0027] The material box cover opening device 3 includes a motor, a reducer and a lifter 12; there are more than four lifters 12; the motor, the reducer and the lifter 12 are connected together, and under the drive of the motor, the lifter 12 rises or falls synchronously.

[0028] The vacuum furnace shell 1 is connected to a gas charging system 5 ; the gas charging system 5 comprises a gas charging valve 13 and a pressure meter 14 . The protective gas can be charged into the vacuum furnace shell 1 by opening the gas charging valve 13 .

[0029] In the present invention, Figure 2 and Figure 3 In the illustrated embodiment, a roller 16 is provided at the lower part of the heat preservation screen 15 at the lower side of the heating chamber, and the furnace bed assembly 9 is arranged on the heat preservation screen 15 at the lower side of the heating chamber. The furnace bed assembly 9 and the heat preservation screen 15 at 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 is arranged 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 heat preservation screen 15 at the lower side of the heating chamber drives the furnace bed assembly 9 to move to the outside of the vacuum sintering furnace. A mobile material box 18 is also arranged outside the vacuum sintering furnace, and the mobile material box 18 is filled with protective gas. The mobile material box 18 includes a third isolation valve 19, a material box shell 20 and a lifting device; the third isolation valve 19 is arranged at one end of the material box shell 20, and the lifting device is arranged inside the material box shell 20; the mobile material box 18 can be moved to the opposite side of the vacuum sintering furnace, and then the mobile material box 18 and the vacuum sintering furnace are docked, the third isolation valve 19 and the first isolation valve 17 are opened, and the sintering material box 10 can be moved between the mobile material box 18 and the vacuum sintering furnace.

[0030] After the mobile material box and the vacuum sintering furnace are docked, the heat preservation screen on the lower side of the heating chamber drives the hearth assembly to move into the mobile material box to carry the sintering material box containing the compact in the mobile material box, and then returns to the vacuum sintering furnace with the sintering material box. After that, the mobile material box and the vacuum sintering furnace are separated, and the vacuum sintering furnace performs the vacuum sintering process.

[0031] After the vacuum sintering process is completed, the mobile material box is docked with the vacuum sintering furnace again, and the heat preservation screen on the lower side of the heating chamber drives the hearth assembly to transfer the sintering material box containing the sintered blank from the vacuum sintering furnace to the mobile material box, and then the vacuum sintering furnace and the mobile material box are separated. Before the mobile material box and the vacuum sintering furnace are separated, close the first isolation valve and the third isolation valve. Before and after the vacuum sintering furnace and the mobile material box are docked, the atmosphere in the transfer box and the vacuum sintering furnace is kept isolated from the atmosphere.

[0032] exist Figure 2 In the illustrated embodiment, the vacuum system 4 includes a mechanical vacuum pump 21 that directly exhausts to the atmosphere and a Roots vacuum pump 22 that further increases the vacuum degree.

[0033] The vacuum sintering furnace includes an air-cooling heat exchange system 23; the air inlet pipe of the air-cooling heat exchange system 23 is connected to the vacuum furnace shell 1; the air outlet pipe 24 of the air-cooling heat exchange system is divided into two pipelines 25 before passing through the vacuum furnace shell 1, each pipeline is provided with a valve 26, and the pipeline 25 is respectively connected to the left and right sides of the heating chamber 2 after passing through the vacuum furnace shell 1. Nozzles 27 are provided on both sides of the heating chamber, and the nozzles 27 extend to the interior of the heating chamber through the heat preservation screen 6 of the heating chamber; the two valves 26 are switched on and off simultaneously or alternately.

[0034] In the present invention, 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 disposed at the other end of the vacuum furnace shell 1; the first isolation valve 17 is opened, and the sintering material box 10 can be moved from the outside of the first isolation valve 17 to the heating chamber 2; the second isolation valve 29 is opened, and the sintering material box 10 can be moved 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 filled with materials completes the heating process in the vacuum furnace shell 1, it can be moved 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 disposed behind the second vacuum furnace shell 28 to form a continuous vacuum sintering furnace. A vacuum isolation valve can be provided between two adjacent vacuum furnace shells to isolate the process environments of the two vacuum furnace shells. Different and same process environments can be set in different vacuum furnace shells, and materials undergo different stages of process processes in different vacuum furnace shells. In such as Figure 4 In the illustrated embodiment, the mobile 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 mobile material box 18 outside the first isolation valve 17 to the heating chamber 2 .

[0035] The hearth assembly includes rollers, and the sintering material box can be moved on the hearth assembly via the rollers.

[0036] In a preferred embodiment of the present invention, the sintering material box used in the vacuum sintering furnace has two side plates that are higher than the other two side plates. When the sintering material boxes are stacked in the heating chamber, the bottom of the upper sintering material box is supported on the higher side plate of the lower sintering material box, so that there is a certain distance between the two layers of sintering material boxes. This gap is not only conducive to improving the heating and air cooling efficiency of vacuum sintering, so that the materials in the inner and outer layers of the stack can be evenly heated or air cooled, but also provides space for the sintering material box cover in the present invention to be opened or closed 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 cover opening device, a vacuum system and an inflation system; the heating chamber is arranged in the vacuum furnace shell, and the heating chamber includes a heat preservation screen, a heater, a cover opening assembly and a hearth assembly from the outside to the inside; a sintering material box is placed on the hearth assembly; the cover opening assembly is located on the inner side of the heater and distributed on both sides of the sintering material box; the material box cover opening device is located on the upper part of the vacuum furnace shell, and a guide shaft passes through the vacuum furnace shell and the heat preservation screen of the heating chamber and is connected to the cover opening assembly; the material box cover opening device can drive the guide shaft to drive the cover opening assembly to move up and down.

2. The vacuum sintering furnace according to claim 1, characterized in that: The sintering material boxes are arranged in more than three layers in the vertical direction, and each layer of sintering material boxes has more than one sintering material box cover. The cover opening assembly can drive multiple sintering material box covers to rise or fall at the same time, so that the sintering material box covers of the multi-layer sintering material boxes can be opened or closed at the same time 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 charging system; the gas charging system comprises a gas charging valve, and protective gas can be charged into the vacuum furnace shell by opening the gas charging valve.

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 the atmosphere and a Roots vacuum pump that further improves the vacuum degree.

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 is divided into two pipelines before passing through the vacuum furnace shell, each pipeline is provided with a valve, and the pipeline is respectively connected to the left and right sides of the heating chamber after passing through the vacuum furnace shell; nozzles are provided on both sides of the heating chamber, and the nozzles extend to the interior of the heating chamber through the heat preservation screen of the heating chamber; the two valves are switched on and off simultaneously or alternately.

6. The vacuum sintering furnace according to claim 1, characterized in that: The vacuum sintering furnace comprises a first isolation valve, which is arranged 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 arranged at the other end of the vacuum furnace shell; when the first isolation valve is opened, the sintering material box can be moved from the outside of the first isolation valve to the heating chamber; when the second isolation valve is opened, the sintering material box can be moved 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 hearth assembly comprises rollers, and the sintering material box can be moved on the hearth assembly via the rollers.

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

10. The vacuum sintering furnace according to claim 6, characterized in that: A mobile material box is also provided outside the vacuum sintering furnace; the mobile material box includes a third isolation valve, a material box shell and a lifting device; the third isolation valve is arranged at one end of the material box shell, and the lifting device is arranged inside the material box shell; the mobile material box can be moved to the opposite side of the vacuum sintering furnace, and then the mobile 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 be moved between the mobile material box and the vacuum sintering furnace.

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