WO2019148882A1

WO2019148882A1 - Device and method for continuous heat treatment of alloy workpiece or metal workpiece

Info

Publication number: WO2019148882A1
Application number: PCT/CN2018/109524
Authority: WO
Inventors: 王清江; 骆溁; 吴建鹏
Original assignee: 福建省长汀金龙稀土有限公司
Priority date: 2018-02-01
Filing date: 2018-10-09
Publication date: 2019-08-08

Abstract

Disclosed are a device and method for continuous heat treatment of a sintered Nd-Fe-B-based magnet workpiece. The device comprises a first heat treatment chamber, a first cooling chamber, a second heat treatment chamber and a second cooling chamber which are successively and continuously arranged, and a conveying system arranged between the chambers and used for conveying the alloy workpiece or the metal workpiece, wherein the first cooling chamber and the second cooling chamber both use an air-cooling system, the temperature of cooling air inside the first cooling chamber is above 25 ℃ and differs from the temperature for heat treatment inside the first heat treatment chamber by at least 450 ℃, and the temperature of cooling air inside the second cooling chamber is above 25 ℃ and differs from the temperature for heat treatment inside the second heat treatment chamber by at least 300 ℃. The device and method for the continuous heat treatment can increase the cooling rate and the production efficiency, and improve the performance and uniformity of a product.

Description

Continuous heat treatment device and method for alloy workpiece or metal workpiece

Technical field

The present invention relates to a heat treatment apparatus and a heat treatment method, and in particular to a continuous heat treatment apparatus for an alloy workpiece or a metal workpiece and a continuous heat treatment method.

Background technique

NdFeB rare earth permanent magnet material is the largest mass-produced magnet with the highest magnetic energy product. It is widely used in wind power generation, servo motors, home appliance compressors and new energy vehicle motors. It has small volume and high efficiency compared with other magnets. Advantage.

NdFeB materials usually require smelting, crushing, pressing, sintering, heat treatment and other processes to obtain the desired properties of the magnet. Wherein, the heat treatment comprises a first-stage heat treatment and a second-stage heat treatment, and is usually in the range of 800 ° C to 950 ° C and 400 ° C to 650 ° C, respectively.

In the prior art, a single-chamber heat treatment furnace is used to heat-treat the NdFeB material, and the temperature rise and the temperature drop are repeated, and the rate of temperature rise and temperature drop is difficult to control, and the energy consumption is increased. Therefore, the existing single-chamber heat treatment furnace is difficult to produce a high-performance NdFeB material with good performance and consistency. In addition, since the single-chamber furnace is generally a cylindrical furnace body, the heat source is the inner wall of the cylindrical furnace body, and the materials are mostly arranged in a multi-column three-dimensional stacking manner, which results in different distances of materials at different locations from each other, so the temperature in the furnace is uniform. Sexuality and uniformity are poor, especially in the temperature difference between the core material and the peripheral material. This placement also limits the ability of the single chamber furnace to cool quickly.

Summary of the invention

In view of the above problems, the present invention provides a continuous heat treatment apparatus for an alloy workpiece or a metal workpiece which can improve cooling rate and production efficiency and improve product consistency.

The technical solution adopted by the present invention is as follows:

A continuous heat treatment device for an alloy workpiece or a metal workpiece, comprising: a first heat treatment chamber, a first cooling chamber, a second heat treatment chamber, a second cooling chamber, and each chamber disposed in sequence by an airtight device a transport system for transporting the alloy workpiece or the metal workpiece, wherein the first cooling chamber and the second cooling chamber each adopt an air cooling system, and the cooling air temperature of the first cooling chamber is above 25 ° C And the heat treatment temperature of the first heat treatment chamber is at least 450 ° C, the cooling air temperature of the second cooling chamber is above 25 ° C, and the heat treatment temperature of the second heat treatment chamber is at least 300 ° C, The pressure in the cooling chamber is 50 kPa to 100 kPa.

In the present invention, the heat treatment chamber and the cooling chamber are separately provided (using an air-cooling system), and the cooling air temperature of the cooling chamber is defined. After the heat treatment of the material is completed, the high-temperature section after the heat treatment can be quickly and uniformly obtained according to the required cooling process. Cooling optimizes the grain boundary microstructure and distribution of alloy or metal workpieces. The air-cooling system can force convection heat transfer and quickly remove the heat of the material, which can be controlled according to the speed of the fan.

In the present invention, the pressure of the cooling chamber is from 50 kPa to 100 kPa, which is a conventional choice in the industry. Therefore, in the examples, the above content range was not tested and verified.

Another object of the present invention is to provide a continuous heat treatment method for an alloy workpiece or a metal workpiece. This continuous heat treatment method can increase the cooling rate and production efficiency and improve the performance and consistency of the product.

The technical solution adopted by the present invention is as follows:

A method for continuously heat-treating an alloy workpiece or a metal workpiece, comprising: a first-stage heat treatment, a first-stage air cooling treatment, a second-stage heat treatment, and a second-stage air cooling, which are sequentially performed in mutually airtight compartments Processing, the cooling air temperature of the first stage air cooling treatment is above 25 ° C, and is at least 450 ° C different from the heat treatment temperature of the first stage heat treatment, and the cooling air temperature of the second stage air cooling treatment is 25 ° C The temperature above and above the heat treatment of the second stage is at least 300 °C.

It should be noted that the numerical ranges disclosed in the present invention include all point values within this range.

Detailed ways

The present invention will be further described in detail below with reference to the embodiments.

In a preferred embodiment, the alloy workpiece is a Nd-Fe-B based sintered magnet. This is because the applicant discovered during the research that the Nd-Fe-B sintered magnet can improve the squareness, intrinsic coercivity and product consistency of the product after heat treatment in the chamber and rapid cooling in the high temperature section, especially The intrinsic coercivity is significantly improved. This mechanism of action is still unclear at this stage.

In a preferred embodiment, the air cooling system is an air cooling system that employs an inert gas. The inert gas herein is selected from gases such as helium, neon, argon, neon, xenon, krypton or nitrogen which do not react with the alloy workpiece or the metal workpiece in the above heat treatment or cooling treatment.

In a preferred embodiment, the first heat treatment chamber has a heat treatment temperature of 800 ° C to 950 ° C, the first cooling chamber has a cooling air temperature of 25 ° C to 150 ° C, and the second treatment chamber has a heat treatment temperature of The cooling air temperature of the second cooling chamber is from 400 ° C to 100 ° C from 400 ° C to 650 ° C. This allows the NdFeB material to pass through the eutectic point quickly, achieving good squareness and coercivity.

Among them, the temperature of the first heat treatment chamber is 800 ° C - 950 ° C and the temperature of the second heat treatment chamber is 400 ° C - 650 ° C, etc., which is a conventional selection of the heat treatment process in the field of Nd-Fe-B sintered magnets, and therefore, In the examples, the above range of contents was not tested and verified.

Generally, the initial temperatures of the first cooling chamber and the second cooling chamber are the same as the corresponding cooling air temperatures.

In a preferred embodiment, the first heat treatment chamber exhibits a square structure and includes two heating regions disposed opposite to the inner wall of the square structure, and the alloy workpiece or the metal workpiece is directly placed in the middle of the square structure. On the rack, or the alloy workpiece or the metal workpiece is placed in the cartridge first, and then the cartridge is placed on the rack in the middle of the square structure; likewise, the second heat treatment chamber presents a square a structure and including two heating regions disposed opposite to an inner wall of the square structure, the alloy workpiece or the metal workpiece being placed directly on a rack in the middle of the square structure, or the alloy workpiece or the metal The workpiece is placed first in the cartridge and then placed on the magazine in the middle of the square structure. Through the above structure, high uniformity of material temperature is achieved, and temperature fluctuation is controlled.

In a preferred embodiment, the area of the heated zone exceeds the longitudinal cross-sectional area of the rack. In this way, it is ensured that all the cartridges can be uniformly heat treated, so that the performance of the alloy workpiece or the metal workpiece after heat treatment tends to be uniform.

In a preferred embodiment, in the second heat treatment chamber, the cartridge or alloy workpiece or metal workpiece has the same distance from the two oppositely disposed heating regions, and is 2 cm to 30 cm, preferably 5 cm to 20 cm. Applicants found in the production process that Nd-Fe-B magnets are extremely sensitive to the secondary tempering temperature difference. The control of the secondary tempering temperature difference can significantly improve the performance of Nd-Fe-B magnets and Nd-Fe-B in various regions. The consistency of the magnets. In the present application, the cartridge is selected to be placed close to the heating zone, especially after the distance is controlled to be between 5 cm and 20 cm. In the preferred embodiment, each region of the cartridge or each region of the alloy workpiece or the metal workpiece of each region or The temperature difference in different areas of the cartridge is controlled within ±5 °C to achieve high uniformity of material temperature, which greatly improves the performance consistency of the same batch of Nd-Fe-B magnets.

In a preferred embodiment, the Nd-Fe-B based magnet is a Nd-Fe-B based magnet having a TRE (total rare earth content) of 28.8 wt% to 34.0 wt%, preferably TRE (total total rare earth content) of 28.8 A wt%-30.5 wt% Nd-Fe-B based magnet. During the research, it was found that the magnet with TRE (total content of rare earth) of 28.8wt%-30.5wt% is most sensitive to the temperature difference of secondary tempering, and the control of heat treatment temperature is higher.

The Nd-Fe-B based magnet mentioned in the present invention is a magnet including a Nd ₂ Fe ₁₄ B type main phase.

In a preferred embodiment, the first temperature rising chamber, the second temperature increasing chamber, the first heat treatment chamber, the first cooling chamber, the third temperature increasing chamber, the second heat treatment chamber, and the second cooling chamber are sequentially disposed by the airtight device. . This is because the temperature rise to 800 ° C - 950 ° C is about twice the heat treatment time of the first heat treatment chamber. By providing two temperature rising chambers, the processing time of the two temperature rising chambers is adjusted to be equivalent to the heat treatment time of the first heat treatment chamber. The beats are consistent, so that the production continues.

In a preferred embodiment, in the second stage heat treatment, the temperature difference of the alloy workpiece or the metal workpiece in different regions is below ±5 °C.

In a preferred embodiment, in the first stage cooling process, the average cooling rate of the alloy workpiece or the metal workpiece in the first 10 minutes is 6 ° C / min - 15 ° C / min, the second stage cooling treatment The average cooling rate of the alloy workpiece or the metal workpiece for the first 10 minutes is 6 ° C / min - 15 ° C / min.

In the present invention, the average cooling rate of the first 10 minutes is selected and monitored by continuous test verification. Of course, the average cooling rate of the first 5 min to 30 min can be selected according to the needs of the product.

The sintered magnets obtained in the respective examples were all measured by the following detection methods.

Magnetic performance evaluation process: The sintered magnet was magnetically tested using the NIM-10000H BH bulk rare earth permanent magnet non-destructive measurement system of China Metrology Institute.

Example 1

The continuous heat treatment apparatus includes a first temperature rising chamber, a second temperature increasing chamber, a first heat treatment chamber, a first cooling chamber, a third temperature increasing chamber, a second heat treatment chamber, and a second cooling chamber, which are sequentially disposed in sequence, and a first temperature increasing chamber, a gas-tight valve is disposed between the two temperature rising chambers, the first heat treatment chamber, the first cooling chamber, the third temperature increasing chamber, the second heat treatment chamber, and the second cooling chamber, and is disposed between the respective chambers for transporting Nd-Fe- A delivery system for B-based sintered magnets.

The continuous heat treatment process is as follows:

(1) Loading

According to the mass percentage wt%, the composition is Pr 7.25%, Nd is 21.75%, Dy is 1.5%, Fe is bal., B is 0.97%, Cu is 0.15%, Ga is 0.2%, Nb is 0.2%, Co. The Nd-Fe-B sintered magnet was prepared by using 0.8% of raw materials and using smelting, enthalpy, hydrogen crushing, gas flow crushing, pressing and sintering.

The properties of the Nd-Fe-B sintered magnet were determined to be Hcj=16.50 kOe, Br=13.70 kGs, and the squareness was 98%.

The Nd-Fe-B sintered magnets were placed in a cartridge with through holes, and the cartridges were stacked in a double row, placed on a rack, and fed into a first temperature rising chamber. It is worth mentioning that, in accordance with different production requirements, a closed cartridge can also be used in the alternative embodiment.

(2) The first stage of heating

When the degree of vacuum of the first temperature rising chamber reached 100 Pa, the heating procedure was started, and the temperature was raised from room temperature for 165 minutes, and after the temperature reached 370 ° C to 400 ° C, the temperature was kept for 15 minutes. After the end of the heat preservation, the rack containing the cartridge is transported from the first temperature rising chamber to the second temperature increasing chamber.

(3) Second stage heating

After the rack containing the cartridge enters the second heating chamber, when the vacuum reaches 100 Pa, the heating is heated for 165 min, and after the temperature reaches 800 ° C - 850 ° C, the temperature is maintained for 15 min. After the end of the heat preservation, the rack containing the cartridge is transported from the second temperature rising chamber to the first heat treatment chamber.

(4) First stage heat treatment

The first heat treatment chamber exhibits a square structure and includes two heating regions disposed opposite to each other on the inner wall of the square structure, the area of the heating region exceeding the longitudinal cross-sectional area of the rack. After entering the first heat treatment chamber, the cartridge was placed at a distance of 25 cm from both heating zones.

When the degree of vacuum reaches 100 Pa, the heating is heated for 10 min, and the heat treatment temperature of the first heat treatment chamber (detected at different positions in different boxes) is 880 ° C - 895 ° C, and the temperature is maintained for 170 min. After the end of the heat preservation, the rack containing the cartridge is transported from the first-stage heat treatment chamber to the first cooling chamber.

(5) First stage cooling

After the rack containing the cartridge enters the first cooling chamber, a vacuum is applied, and the cooling chamber is filled with 78 kPa of inert gas, and then the fan is circulated and cooled, and the cooling time is 180 min. The inert gas temperature of the first cooling chamber is as shown in Table 1, and the inert gas temperature is detected at the gas outlet of the aspirating circulating air.

(6) Third stage heating

After the double-column stacked cartridge enters the third heating chamber, when the vacuum reaches 100 Pa, the heating is heated for 165 min, and after the temperature reaches 460 ° C - 470 ° C, the temperature is maintained for 15 min. After the end of the heat preservation, the rack containing the cartridge is transported from the third temperature rising chamber to the second heat treatment chamber.

(7) Second stage heat treatment

The second heat treatment chamber has a square structure and includes two heating regions disposed opposite to each other on the inner wall of the square structure, the area of the heating region exceeding the longitudinal cross-sectional area of the rack. After the cartridge entered the second heat treatment chamber, it was placed at a distance of 25 cm from both heating zones.

When the degree of vacuum reaches 100 Pa, the heating is heated for 15 min, and after the heat treatment temperature (detected at different positions in different boxes) reaches 500 ° C - 515 ° C, the temperature is maintained for 165 min. After the end of the heat preservation, the rack containing the cartridge is transported from the second heat treatment chamber to the second cooling chamber.

(8) Second stage cooling

After the rack containing the cartridge enters the second-stage cooling chamber, a vacuum is applied, and the cooling chamber is filled with 78 kPa of inert gas, and then the fan is circulated and cooled, and the cooling time is 180 min. The rack containing the cartridge is taken out of the oven. The inert gas temperature of the second cooling chamber is as shown in Table 1, and the inert gas temperature is detected at the gas outlet of the aspirating circulating air.

In this way, the rack equipped with the cartridge is heated in the first temperature rising chamber and short-term heat-insulated, and then enters the second heating chamber for temperature rise and short-time heat preservation. After that, it enters the first heat treatment chamber for a short time to heat up and keep warm. After the first heat treatment chamber is insulated, the first cooling chamber is cooled. After the cooling of the first cooling chamber is completed, the third temperature rising chamber is introduced to perform temperature rise and short-time heat preservation. After the third temperature rising chamber is insulated, the second stage heat treatment chamber is entered for short-term temperature rise and heat preservation. After the heat preservation is completed, the second cooling chamber is entered for cooling. After the cooling is completed, the material is discharged.

After the above heat treatment and cooling treatment, the properties of the magnets are shown in Table 1.

Table 1 Inert gas temperature of the first and second cooling chambers, and magnet properties after heat treatment and cooling treatment

The average cooling rate of the Nd-Fe-B based sintered magnet in the first 10 minutes of the first stage cooling treatment of Example 1.4, Example 1.5 and Example 1.6 was 6 ° C / min - 15 ° C / min, examples 1.3. In the second-stage cooling treatment of Example 1.4, Example 1.5 and Example 1.6, the average cooling rate of the Nd-Fe-B based sintered magnet for the first 10 minutes was 6 ° C / min - 15 ° C / min. In the first-stage cooling treatment of Example 1.1, Example 1.2 and Example 1.3, the average cooling rate of the first 10 min of the Nd-Fe-B based sintered magnet was less than 6 ° C/min, and the results of Example 1.1 and Example 1.2 were In the secondary cooling treatment, the average cooling rate of the Nd-Fe-B based sintered magnet for the first 10 minutes was also less than 6 ° C / min.

It can be seen from Table 1 that the cooling air temperature of the first cooling chamber is higher than 25 ° C and lower than the heat treatment temperature of the first heat treatment chamber by at least 450 ° C, while the inert gas temperature of the second cooling chamber is higher than 25 ° C, and Below the heat treatment temperature of the second heat treatment chamber is at least 300 ° C, the magnetic properties of the magnet after heat treatment are better, especially Hcj is significantly improved, and SQ is improved. This is because the above-mentioned temperature range contributes to the improvement of the cooling rate of the high temperature section after the heat treatment of the magnet, thereby optimizing the phase composition and distribution of the grain boundary microstructure.

Example 2

The continuous heat treatment process is as follows:

(1) Loading

According to the mass percentage wt%, the composition was Pr 7.12%, Nd was 21.38%, Tb was 1.5%, Fe was bal., B was 0.96%, Cu was 0.15%, Ga was 0.2%, Nb was 0.2%, Co. The Nd-Fe-B sintered magnet was prepared by using 0.8% of raw materials and using smelting, enthalpy, hydrogen crushing, gas flow crushing, pressing and sintering.

The properties of the Nd-Fe-B sintered magnet were determined to be Hcj=16.5 kOe, Br=14.2 kGs, and the squareness was 97%.

The Nd-Fe-B sintered magnets were placed in a grid box, and the cartridges were stacked in a single row, placed on a rack, and fed into a first temperature rising chamber.

(2) The first stage of heating

When the degree of vacuum of the first temperature rising chamber reached 150 Pa, the heating procedure was started, and the temperature was raised from room temperature for 150 minutes, and after the temperature reached 350-380 ° C, the temperature was kept for 30 minutes. After the end of the heat preservation, the rack containing the cartridge is transported from the first temperature rising chamber to the second temperature increasing chamber.

(3) Second stage heating

After the rack containing the cartridge enters the second heating chamber, when the vacuum reaches 150 Pa, the heating is heated for 150 min, and after the temperature reaches 820-860 ° C, the temperature is maintained for 30 min. After the end of the heat preservation, the rack containing the cartridge is transported from the second temperature rising chamber to the first heat treatment chamber.

(4) First stage heat treatment

The first heat treatment chamber exhibits a square structure and includes two heating regions disposed opposite to each other on the inner wall of the square structure, the area of the heating region exceeding the longitudinal cross-sectional area of the rack. After entering the first heat treatment chamber, the cartridge was placed at a distance of 2-30 cm from both heating zones, as shown in Table 2.

When the degree of vacuum reached 150 Pa, the heating was heated for 5 min, and the heat treatment temperature at different positions in different boxes in each region was detected, as shown in Table 2, and the temperature was maintained for 175 min. After the end of the heat preservation, the rack containing the cartridge is transported from the first-stage heat treatment chamber to the first cooling chamber.

(5) First stage cooling

After the rack containing the cartridge enters the first cooling chamber, vacuum is applied, vacuum is applied, and the cooling chamber is filled with an inert gas of 76 kPa at 40 ° C to 50 ° C, and then cooled by a fan, and the cooling time is 180 min, Nd-Fe- The average cooling rate of the B-based sintered magnet for the first 10 minutes was 15 ° C / min. The inert gas temperature is detected at the air outlet of the aspirating circulating air.

(6) Third stage heating

After the rack containing the cartridge enters the third heating chamber, when the vacuum reaches 150 Pa, the heating is heated for 170 min, and after the temperature reaches 380 ° C - 420 ° C, the temperature is maintained for 10 min. After the end of the heat preservation, the rack containing the cartridge is transported from the third temperature rising chamber to the second heat treatment chamber.

(7) Second stage heat treatment

The second heat treatment chamber exhibits a square structure and includes two heating regions disposed opposite each other on the inner wall of the square structure, the area of the heating region exceeding the longitudinal cross-sectional area of the rack. After entering the second heat treatment chamber, the cartridge was placed at a distance of 2-30 cm from both heating zones, as shown in Table 2.

When the degree of vacuum reached 150 Pa, the heating was heated for 10 min, and the heat treatment temperature at different positions in different boxes in each zone was detected, as shown in Table 2, and the temperature was maintained for 170 min. After the end of the heat preservation, the rack containing the cartridge is transported from the second heat treatment chamber to the second cooling chamber.

(8) Second stage cooling

After the rack containing the cartridge enters the second-stage cooling chamber, vacuum is applied, and the cooling chamber is filled with an inert gas of 76 kPa at 40 ° C to 50 ° C, and then cooled by a fan, and the cooling time is 180 min, Nd-Fe- The average cooling rate of the B-based sintered magnet for the first 10 minutes was 9.0 ° C / min. The rack containing the cartridge is taken out of the oven. The inert gas temperature is detected at the air outlet of the aspirating circulating air.

After the above heat treatment and cooling treatment, the properties of the magnet were as shown in Table 2. The distance in Table 2 is the distance between the single-column stacked cartridge and the heated areas on both sides.

Twenty Nd-Fe-B sintered magnets were taken from different regions, and Br, Hcj, BH(max) and SQ were measured, and the consistency was measured. Consistency is described by the volatility of product performance metrics, defined as (maximum-minimum)/minimum. The smaller the volatility, the better the consistency.

Table 2 Heat treatment temperature of the first stage and second stage heat treatment, and the properties of the magnet after heat treatment and cooling treatment

It can be seen from Table 2 that the smaller the fluctuation of the second-stage heat treatment temperature, the more stable Br, and the smaller the fluctuation of Hcj and SQ. This is because the second-stage heat treatment temperature is closely related to the grain boundary microstructure composition and distribution of the magnet, and the greater the temperature fluctuation, the greater the performance fluctuation.

The state of the microstructure has a great influence on the performance of NdFeB. The more uniform the microstructure and the finer the grain, the better the performance of the material. The better the consistency of the microstructure, and the optimization of the microstructure of the sintered NdFeB material mainly occurs in the heat treatment stage. Therefore, the heat treatment process has a great influence on the properties of the material. The same formulation may vary widely in magnetic properties due to the heat treatment process. The present invention improves the uniformity of the tissue by increasing the temperature uniformity and then uniforms the group by rapid cooling rate. Curing makes the organization of each product uniform, from the purpose of improving material properties and uniformity.

Example 3

The continuous heat treatment process is as follows:

(1) Loading

According to the mass percentage wt%, the composition is Pr 8%, Nd is 19%-21.5% (according to TRE in Table 3), Tb is 1.5%, Fe is bal., B is 0.97%, Cu is 0.1%, A raw material having a Ga of 0.1%, a Nb of 0.1%, and a Co of 1% was obtained by melting, twisting, hydrogen breaking, gas flow crushing, pressing, and sintering to obtain a Nd-Fe-B based sintered magnet. The content ratio of the TRE content and the properties of the magnet are shown in Table 3.

(2) The first stage of heating

When the degree of vacuum of the first temperature rising chamber reached 10 ^-1 Pa, the heating procedure was started, and the temperature was raised from room temperature for 130 minutes, and after the temperature reached 360-400 ° C, the temperature was kept for 20 minutes. After the end of the heat preservation, the rack containing the cartridge is transported from the first temperature rising chamber to the second temperature increasing chamber.

(3) Second stage heating

After the rack containing the cartridge enters the second heating chamber, when the vacuum reaches 10 ^-1 Pa, the heating is heated for 130 min, and after the temperature reaches 810-830 ° C, the temperature is maintained for 20 min. After the end of the heat preservation, the rack containing the cartridge is transported from the second temperature rising chamber to the first heat treatment chamber.

(4) First stage heat treatment

The first heat treatment chamber exhibits a square structure and includes two heating regions disposed opposite to each other on the inner wall of the square structure, the area of the heating region exceeding the longitudinal cross-sectional area of the rack. After the rack containing the cartridge enters the first heat treatment chamber, it is placed at a distance of 5 cm from both heating zones.

When the degree of vacuum reaches 10 ^-1 Pa, the heating is heated for 10 min, and the heat treatment temperature of the first heat treatment chamber (detected at different positions in different boxes) is 905 ° C - 910 ° C, and the temperature is maintained for 140 min. After the end of the heat preservation, the rack containing the cartridge is transported from the first-stage heat treatment chamber to the first cooling chamber.

(5) First stage cooling

After the rack containing the cartridge enters the first cooling chamber, when the vacuum reaches 10 ^-1 Pa, the cooling chamber is filled with 80 kPa of inert gas at 70 ° C - 90 ° C, and then the fan is circulated and cooled, and the cooling time is 150 min. The average cooling rate of the Nd-Fe-B based sintered magnet for the first 10 minutes was 6.5 ° C / min. The inert gas temperature is detected at the air outlet of the aspirating circulating air.

(6) Third stage heating

After the rack containing the cartridge enters the third heating chamber, when the vacuum reaches 10 ^-1 Pa, the heating is heated for 140 min, and after the temperature reaches 400 ° C - 425 ° C, the temperature is maintained for 10 min. After the end of the heat preservation, the rack containing the cartridge is transported from the third temperature rising chamber to the second heat treatment chamber.

(7) Second stage heat treatment

The second heat treatment chamber exhibits a square structure and includes two heating regions disposed opposite each other on the inner wall of the square structure, the area of the heating region exceeding the longitudinal cross-sectional area of the rack. After the rack containing the cartridge enters the second heat treatment chamber, it is placed at a distance of 5 cm from both heating zones.

After the rack containing the cartridge enters the second heat treatment chamber, when the vacuum reaches 10 ^-1 Pa, the heating is heated for 10 min, and the heat treatment temperature of the second heat treatment chamber (detected at different positions in different cartridges) reaches 535 ° C - 540 °C, heat preservation for 140min. After the end of the heat preservation, the rack containing the cartridge is transported from the second heat treatment chamber to the second cooling chamber.

(8) Second stage cooling

After the rack containing the cartridge enters the second-stage cooling chamber, when the vacuum reaches 10 ^-1 Pa, the cooling chamber is filled with an inert gas of 80 kPa at 30 ° C - 60 ° C, and then the fan is circulated and cooled, and the cooling time is performed. For 150 min, the average cooling rate of the Nd-Fe-B based sintered magnet for the first 10 min was 6.0 ° C/min. The rack containing the cartridge is taken out of the oven. The inert gas temperature is detected at the air outlet of the aspirating circulating air.

After the above heat treatment and cooling treatment, the properties of the magnets are shown in Table 3.

Table 3 TRE content, and magnet properties before and after heat treatment and cooling treatment

The Br fluctuation (%), Hcj fluctuation (%), and SQ fluctuation (%) of the magnet before the heat treatment and the cooling treatment were zero.

In the existing heat treatment process, generally, magnets with a TRE of more than 30.5% have a good consistency during heat treatment, while magnets with a TRE of 28.8 wt% to 30.5 wt% are in the heat treatment process, and Br fluctuations (%) One or more of Hcj volatility (%) and SQ volatility (%) will reach 5% or more, which will affect product consistency.

The Applicant has found that a magnet having a TRE of 28.8 wt% to 30.5 wt% is heat-treated in a heat treatment apparatus having a small temperature difference and an average cooling rate of the first 10 minutes, and Br fluctuation (%), Hcj fluctuation ( Both %) and SQ volatility (%) are reduced, which can significantly improve consistency.

It can be seen from Table 3 that increasing the temperature uniformity of the planar heat treatment equipment and controlling its cooling rate has a very important positive effect on improving the consistency of the low rare earth content of the NdFeB.

Comparative example

The continuous heat treatment apparatus comprises a first heat treatment chamber and a second heat treatment chamber which are sequentially disposed in sequence, a gas tight valve is disposed between the first heat treatment chamber and the second heat treatment chamber, and a Nd-Fe- is disposed between the two chambers for transporting Nd-Fe- A delivery system for B-based sintered magnets.

The continuous heat treatment process is as follows:

The mass percentage wt% composition is Pr 8%, Nd 20%, Tb 1.5%, Fe is bal., B is 0.97%, Cu is 0.1%, Ga is 0.1%, Nb is 0.1%, Co is 1 % of the raw materials, and the use of smelting, ribbon, hydrogen crushing, gas flow crushing, pressing and sintering, the specific process parameters are the same as in the third embodiment, to obtain Nd-Fe-B based sintered magnet.

The Nd-Fe-B sintered magnets were placed in a grid box, and the cartridges were stacked in a single row, placed on a rack, and fed into a first heat treatment chamber.

After the rack containing the cartridge enters the first heat treatment chamber, it is placed at a distance of 5 cm from both heating zones. When the vacuum reaches 10 ^-1 Pa, the heating is heated for 180 min to the heat treatment temperature of the first heat treatment chamber ( Detected at different positions in different boxes) 905 ° C - 910 ° C, heat preservation 140 min. After the end of the heat preservation, the first heat treatment chamber is filled with an inert gas of 80 kPa at 70 ° C - 90 ° C, and then the fan is circulated and cooled, the cooling time is 150 min, and the inert gas temperature is detected at the gas outlet of the aspirating circulating air. The average cooling rate of the Nd-Fe-B based sintered magnet for the first 10 minutes was 5 ° C / min. The rack containing the cartridge is transported from the first heat treatment chamber to the second heat treatment chamber.

After the rack containing the cartridge enters the second heat treatment chamber, it is placed at a distance of 5 cm from both heating zones. When the vacuum reaches 10 ^-1 Pa, the heating is heated for 90 min to the heat treatment temperature of the second heat treatment chamber ( Detected at different positions in different boxes) reached 535 ° C -540 ° C, and kept for 140 min. After the end of the heat preservation, the second heat treatment chamber is filled with an inert gas of 80 kPa at 30 ° C - 60 ° C, and then the fan is circulated and cooled, the cooling time is 150 min, and the inert gas temperature is detected at the gas outlet of the aspirating circulating air. The average cooling rate of the Nd-Fe-B based sintered magnet for the first 10 minutes was 4.5 ° C / min.

Table 4 TRE content, and magnet properties before and after single chamber heat treatment and cooling treatment

The Br fluctuation (%), Hcj fluctuation (%), and SQ fluctuation (%) of the magnet before the heat treatment and the cooling treatment were set to zero.

It can be seen from Table 3 and Table 4 that in the single chamber for heat treatment and cooling treatment, the cooling rate in the high temperature section is low, the Br and SQ in the single chamber treatment are slightly decreased, the Hcj drop is more obvious, and the fluctuation of the three is obvious. Significantly bigger.

The above embodiments are only used to further illustrate several specific embodiments of the present invention, but the present invention is not limited to the embodiments, and any simple modifications, equivalent changes and modifications made to the above embodiments in accordance with the technical spirit of the present invention, All fall within the scope of protection of the technical solution of the present invention.

Claims

A continuous heat treatment device for an alloy workpiece or a metal workpiece, comprising: a first heat treatment chamber, a first cooling chamber, a second heat treatment chamber, a second cooling chamber, and each chamber disposed in sequence by an airtight device a transport system for transporting the alloy workpiece or the metal workpiece, wherein the first cooling chamber and the second cooling chamber each adopt an air cooling system, and the cooling air temperature of the first cooling chamber is above 25 ° C And the heat treatment temperature of the first heat treatment chamber is at least 450 ° C, the cooling air temperature of the second cooling chamber is above 25 ° C, and the heat treatment temperature of the second heat treatment chamber is at least 300 ° C, The pressure in the cooling chamber is 50 kPa to 100 kPa.
A continuous heat treatment apparatus for an alloy workpiece or a metal workpiece according to claim 1, wherein the alloy workpiece is a Nd-Fe-B based sintered magnet.
A continuous heat treatment apparatus for an alloy workpiece or a metal workpiece according to claim 1, wherein the air cooling system is an air cooling system using an inert gas.
A continuous heat treatment apparatus for an alloy workpiece or a metal workpiece according to claim 3, wherein the first heat treatment chamber has a heat treatment temperature of 800 ° C to 950 ° C, and the cooling air temperature of the first cooling chamber The temperature of the second heat treatment chamber is from 400 ° C to 650 ° C and the cooling air temperature of the second cooling chamber is from 25 ° C to 100 ° C.
A continuous heat treatment apparatus for an alloy workpiece or a metal workpiece according to claim 1, wherein the first heat treatment chamber has a square structure and includes two heating regions disposed opposite to each other on the inner wall of the square structure. The alloy workpiece or the metal workpiece is directly placed on a rack in the middle of the square structure, or the alloy workpiece or the metal workpiece is first placed in a cartridge and then the cartridge is placed in the square structure Similarly, the second heat treatment chamber has a square structure and includes two heating regions disposed opposite to the inner wall of the square structure, and the alloy workpiece or the metal workpiece is directly placed on the square The rack in the middle of the structure, or the alloy workpiece or the metal workpiece is placed in the magazine first and then the cartridge is placed on the rack in the middle of the square structure.
A continuous heat treatment apparatus for an alloy workpiece or a metal workpiece according to claim 5, wherein the area of the heating region exceeds the longitudinal sectional area of the rack.
A continuous heat treatment apparatus for an alloy workpiece or a metal workpiece according to claim 1, wherein in said first heat treatment chamber and said second heat treatment chamber, said alloy workpiece or said metal workpiece or said material The distance between the two oppositely disposed heating zones is 5 cm to 20 cm.
A continuous heat treatment apparatus for an alloy workpiece or a metal workpiece according to claim 7, wherein said Nd-Fe-B based magnet is a Nd-Fe-B system having a TRE of 28.8 wt% to 30.5 wt%. magnet.
A method for continuously heat-treating an alloy workpiece or a metal workpiece, comprising: a first-stage heat treatment, a first-stage air cooling treatment, a second-stage heat treatment, and a second-stage air cooling, which are sequentially performed in mutually airtight compartments Processing, the cooling air temperature of the first stage air cooling treatment is above 25 ° C, and is at least 450 ° C different from the temperature of the first stage heat treatment, and the cooling air temperature of the second stage air cooling treatment is above 25 ° C And at least 300 ° C from the temperature of the second stage heat treatment.
A method of continuously heat-treating an alloy workpiece or a metal workpiece according to claim 9, wherein the alloy workpiece is a Nd-Fe-B based sintered magnet.
A method of continuously heat-treating an alloy workpiece or a metal workpiece according to claim 10, wherein in the second-stage heat treatment, the temperature difference between the alloy workpiece or the metal workpiece in different regions is less than ±5 °C.
A method of continuously heat-treating an alloy workpiece or a metal workpiece according to claim 9, wherein in the first-stage cooling treatment, an average cooling rate of the alloy workpiece or the metal workpiece in the first 10 minutes is 6 ° C / min - 15 ° C / min, in the second stage of the alloy workpiece or the metal workpiece cooling process, the average cooling rate of the first 10 min is 6 ° C / min - 15 ° C / min.