WO2015058654A1

WO2015058654A1 - Powder composition and method for preparing r-fe-b-series sintered magnet

Info

Publication number: WO2015058654A1
Application number: PCT/CN2014/088848
Authority: WO
Inventors: 陈国安; 赵玉刚; 胡伯平; 饶晓雷; 张瑾; 钮萼; 陈治安
Original assignee: 北京中科三环高技术股份有限公司; 三环瓦克华（北京）磁性器件有限公司
Priority date: 2013-10-22
Filing date: 2014-10-17
Publication date: 2015-04-30
Also published as: CN104575896B; CN104575896A

Abstract

The present invention provides a powder composition and a method for preparing an R-Fe-B-series sintered magnet. The powder composition consists of a component (A), a component (B), and a component (C). The component (A) is selected from one or more of fluoride powder, oxide powder, and oxyfluoride powder of heavy rare earth. The component (B) is rare earth-transition intermetallic compound powder having a MgCu₂ crystal structure. The component (C) is selected from one or more of rare earth hydrated nitrate powder. The method for preparing an R-Fe-B-series sintered magnet provided by the present invention comprises: coating a conditioning fluid containing the powder composition on the magnet, which has the technical effect of using a tiny amount of heavy rare earth dysprosium (Dy) or terbium (Tb) to significantly improve the coercivity of the magnet under the premise of basically keeping remanence and a maximum magnetic energy product of the R-Fe-B-series sintered magnet.

Description

Powder composition and method for preparing R-Fe-B based sintered magnet

Technical field

The present invention relates to a powder composition and method for preparing an R-Fe-B based sintered magnet.

Background technique

In recent years, due to the high comprehensive magnetic properties of R-Fe-B sintered magnets, the application of high-performance motors in the fields of automobiles and home appliances has received more and more attention. These high performance motors require R-Fe-B sintered magnets to have both high remanence and high intrinsic coercivity.

A large amount of heavy rare-earth elements RH (Dy(镝), Tb(铽)) is added to the R-Fe-B based sintered magnet to replace the rare earth element R in the R ₂ Fe ₁₄ B phase, and the coercive force of the magnet can be remarkably improved. This is because Dy ₂ Fe ₁₄ B or Tb ₂ Fe ₁₄ B has a higher magnetocrystalline anisotropy field than Nd ₂ Fe ₁₄ B, so that the intrinsic coercive force of the magnet may be further improved. The magnetocrystalline anisotropy field ratio Nd ₂ of the solid solution phase (Nd, Dy) ₂ Fe ₁₄ B or (Nd, Tb) ₂ Fe ₁₄ B formed after the Dy/Tb moiety replaces the Nd in the main phase Nd ₂ Fe ₁₄ B The Fe ₁₄ B is large, so that the coercive force of the sintered magnet can be remarkably improved.

However, in the R-Fe-B based sintered magnet, if the light rare earth element (Pr, Nd) is replaced by the heavy rare earth element RH (Dy (镝), Tb (铽)), although the coercive force is increased, the remanence is inevitable. The ground is greatly reduced. Because the magnetic moments of Nd and Fe are arranged in parallel in the main phase of Nd ₂ Fe ₁₄ B, the magnetic moments of the two are enhanced superposition, while Dy/Tb and Fe are ferrimagnetic coupling, and the magnetic moment of Dy/Tb and Fe magnetic The moments are arranged anti-parallel, partially canceling the total magnetic moment of the main phase. Thus, the saturation magnetization of the magnet is significantly reduced, and the remanence and maximum magnetic energy product of the magnet are also significantly reduced. In addition, since Dy and Tb are rare and expensive elements, they cannot be added in a large amount from the viewpoint of cost.

Patent document CN 200610089124.7 shows a method for preparing high-coercivity Nd-Fe-B sintered magnets by using nano Dy and Tb powders as the second phase and mixing with the main alloy powder. law. Under the same conditions, the method can save the use of heavy rare earth to a certain extent, but the coercive force is less increased and the remanence is significantly reduced.

Patent document CN 201110024823.4 provides a method for thermally diffusing a powder of heavy rare earth fluoride, nitrate and phosphate on the surface of a magnet, solving the problem of uneven distribution of molten material remaining on the surface after thermal diffusion of the magnet, thereby solving the coating problem. The problem that the bonding strength between the coated substrate and the plating layer is deteriorated and the corrosion resistance is lowered. However, the composition of the powder and the state of the surface of the magnet and the like may affect the effect of the coercive force very sensitively.

Experiments have shown that if the Dy or Tb compound is diffused into the sintered magnet by diffusion alone, and the activity of the powder and the surface state of the magnet are neglected, it is difficult to ensure that the heavy rare earth diffuses into the magnet on the surface of the magnet, and it is difficult to ensure the diffusion process. The repeatability and process stability make it difficult to industrially prepare a magnet whose coercive force can be stably stabilized. Experiments have also shown that the effect of one of the fluorides, oxides and oxyfluorides of Dy and Tb alone to increase the coercivity is very limited.

Summary of the invention

In view of the above problems, an object of the present invention is to provide a powder composition for preparing an R-Fe-B based sintered magnet and a method for producing an R-Fe-B based sintered magnet using the powder composition, having a substantially holding magnet Under the premise of remanence and maximum magnetic energy product, the technical effect of the coercive force of the magnet is remarkably improved by using a very small amount of heavy rare earth Dy (镝) or Tb (铽).

The powder composition for producing an R-Fe-B based sintered magnet provided by the present invention is composed of the component (A), the component (B) and the component (C). The component (A) is one or more powders selected from the group consisting of fluorides, oxides, and oxyfluorides of heavy rare earths. The component (B) is a rare earth-transition intermetallic compound powder having a MgCu ₂ crystal structure. The component (C) is selected from one or more of the rare earth hydrated nitrate powders.

The component (A) is from 1% to 98% by weight of the powder composition, and the component (B) is from 1% to 98% by weight of the powder composition, the component (C) is from 1% to 98% by weight of the powder composition.

In the component (B), the content of the rare earth element is ≥55% by weight, and the weight percentage of the sum of lanthanum, cerium or lanthanum and cerium is ≥10%, and iron, cobalt or iron and cobalt in the transition metal element And the weight percentage is ≥ 40%, and the balance is at least one selected from the group consisting of copper, titanium, chromium, zinc, and nickel.

The component (A) has an average particle diameter of ≤ 50 μm.

The component (B) has an average particle diameter of from 2 to 10 μm.

The component (C) has an average particle diameter of ≤ 100 μm.

The present invention also provides a method of preparing an R-Fe-B based sintered magnet, comprising the steps of: dissolving the powder composition according to any one of claims 1 to 6 in an organic solvent to prepare a treatment liquid; The treatment liquid is applied to the magnet; and the magnet after the treatment liquid is applied is subjected to vacuum heat treatment.

The content of the powder composition in the treatment liquid is 0.01 to 1.0 g/mL. The treatment liquid further includes a dispersant, and the volume ratio of the dispersant to the organic solvent is less than 1%.

The organic solvent is selected from the group consisting of alcohols, alkanes or esters having 5 to 16 carbon atoms.

The step of applying the treatment liquid to the magnet includes immersing the magnet in the treatment liquid in a stirred state for a immersion time of 1 to 60 minutes.

The vacuum heat treatment comprises the steps of: placing the magnet after coating the treatment liquid into a vacuum sintering furnace, evacuating to a vacuum of 10 ^-2 Pa; heating to 820 to 1050 ° C, and holding for 1 to 8 hours; The argon gas is cooled to below 100 ° C, the cooling is stopped, and the vacuum is evacuated to a vacuum of 10 ^-2 Pa; the temperature is raised to 450 ° C to 620 ° C, and the temperature is maintained for 1 to 5 hours; and the argon gas is cooled to 80 ° C or less.

The present invention also provides an R-Fe-B based sintered magnet comprising a magnet portion and a coating portion on an outer surface of the magnet portion, the coating portion being formed of the above powder composition.

The present invention also provides an R-Fe-B based sintered magnet prepared by the above method.

Detailed ways

The technical solutions of the present invention will be described below by way of specific embodiments.

In the present embodiment, component A is one or more powders selected from the group consisting of fluorides, oxides and/or oxyfluorides of cerium and/or cerium, and component B is a rare earth having a crystal structure of MgCu ₂ - The transition metal intermetallic compound powder, component C, is one or more selected from the group consisting of rare earth hydrated nitrate powders.

The above components A, B and C were mixed in a certain ratio to prepare a powder composition. Component A is from 1% to 98% by weight of the powder composition, Component B is from 1% to 98% by weight of the powder composition, and Component C is from 1% to 98% by weight of the powder composition. .

Component A has an average particle diameter of not more than 50 μm.

In the component B, the content of the rare earth element is not less than 55% by weight, and the weight percentage of the sum of Dy, Tb or Dy and Tb is not less than 10%, and Fe, Co or Fe and Co in the transition metal element The weight percentage is not less than 40%, and the balance is at least one of Cu, Ti, Cr, Zn, Ni, and the like. Component B has an average particle diameter of 2 to 10 μm.

Component C has an average particle diameter of not more than 100 μm.

The powder composition obtained by mixing the components A, B and C in proportion, after the grain boundary diffusion treatment, uniformly distributes the heavy rare earth elements in the surface layer and the epitaxial layer of the main phase grains of the magnet, and the main phase grains are fine The structure is uniform, which reduces the amount of heavy rare earth used, thereby saving manufacturing costs.

In addition, the above powder composition can be processed for different specifications and different grades of magnets, and the powder can be uniformly distributed on the surface of the magnet during the coating process, and no large melt residue remains after the heat treatment is diffused, and the powder can be remarkably improved. Coercive force, and almost no reduction of remanence and maximum magnetic energy product, to ensure uniformity and consistency of coercivity improvement of magnets of different specifications and different grades, as well as stability and consistency of coercivity improvement of different batches of products. Specifically, the uniformity of remanence is ≤0.9%, the uniformity of coercive force is ≤2%, and the uniformity of maximum magnetic energy product is ≤2.5%. Here, uniformity is expressed using (very poor/average value) × 100 (%), and the larger the numerical value, the lower the uniformity; the smaller the numerical value, the higher the uniformity.

The above powder composition was used to prepare an R-Fe-B based sintered magnet by referring to the following process.

First, the components A, B and C are mixed in a certain ratio to prepare a powder composition. The powder composition is stored, configured and used under the protection of an inert gas.

Dispersing the above powder composition in an organic solvent at a ratio of 0.01 to 1.0 g/mL. Stir well to form a slurry. It is also possible to add a dispersing agent to the slurry in a volume ratio of less than 1% by weight of the dispersing agent to the organic solvent used.

The slurry is used as a mixed powder slurry for grain boundary diffusion and permeation, and is coated on a magnet which is subjected to surface cleaning treatment or conversion film treatment such as phosphating or oxidation after machining, without adding metal, non-metal or organic The magnet of the protective layer, and the oxygen content of the magnet is 4000 ppm or less, and the magnetization direction of the magnet (ie, the orientation direction of the magnet) is 10 mm or less.

Subsequent vacuum heat treatment is then performed.

The above organic solvent may be an alcohol or an alkane or an ester having 5 to 16 carbon atoms. The alcohol may be selected from the group consisting of ethanol, propanol, isopropanol, butanol, and butanol. The alkane may be selected from cyclohexane and cyclooctane. The esters may be selected from ethyl acetate and isobutyl acetate.

The slurry may be applied to the surface of the magnet by immersing the magnet in a slurry in a stirred state for a immersion time of 1 to 60 minutes. Then, the processed magnet is placed in a metal box and sealed, and the material of the metal box is iron, steel, molybdenum, tungsten, tantalum.

The vacuum heat treatment can be carried out in the following manner. First, the cartridge was placed in a vacuum sintering furnace and evacuated to a vacuum of 10 ^-2 Pa. Next, the temperature was raised to 820 to 1050 ° C, and the temperature was kept for 1 to 8 hours. Then, when the argon gas was cooled to below 100 ° C, the cooling was stopped, and the vacuum was evacuated until the degree of vacuum reached 10 ^-2 Pa. The temperature was raised again to 450 ° C to 620 ° C, and the temperature was kept for 1 to 5 hours. After that, it was cooled by argon gas to below 80 °C.

When the R-Fe-B based sintered magnet material is prepared, the above powder composition is used as a diffusion permeation source, which can significantly improve the coercive force of the magnet, and is advantageous for controlling the stability and consistency of the coercivity between batches. The reproducibility of the diffusion process to achieve the purpose of industrial preparation.

The above specific embodiments will be described in more detail below with reference to the embodiments.

Example 1

Component A: cesium fluoride powder having an average particle diameter of 10 μm.

Component B: Rare earth-transition intermetallic compound powder having a MgCu ₂ crystal structure having an average particle diameter of 2 μm, specific components and weight percentages are 15% Nd, 12% Pr, 30% Dy, 42% Fe, 1% Cu .

Component C: cerium nitrate pentahydrate powder having an average particle diameter of 100 μm.

The above components were mixed in a weight ratio of A:B:C = 1:1:1: 98 to obtain a powder composition.

The powder composition was dispersed in ethanol at a ratio of 0.01 g/mL to form a slurry, that is, 0.01 g of the powder composition was mixed per 1 mL of ethanol.

The sintered NdFeB blank machine without aging treatment is processed into a circular magnetic piece having a diameter of 10 mm and a height of 3.5 mm, and then subjected to conventional degreasing treatment, pickling in a 5% (volume%) concentration of nitric acid, ultrasonic cleaning and Blow dry.

The treated magnetic sheet was completely immersed in the slurry in a stirred state for 1 minute, and the impregnated magnet was placed in a tinplate box to be sealed.

The cartridge was placed in a vacuum sintering furnace, evacuated, and heated to 820 ° C when the degree of vacuum reached 10 ^-2 Pa or more, and kept for 3 hours. Then the heating was stopped and the argon gas was cooled to below 100 °C. After that, the cooling was stopped, and the vacuum was evacuated to 10 ^-2 Pa, and then heated to 450 ° C for 3 hours. Then, the heating was stopped and argon gas was charged, and the mixture was cooled to 80 ° C or lower.

At the same time, the control magnet 1 was prepared, except that the slurry impregnation magnet was not used, and the other process steps were the same as those of the magnet of Example 1.

The remanence, coercive force, and maximum magnetic energy product of the magnet of Example 1 and the control magnet 1 were measured, and the results are shown in Table 1.

Table 1

Example 2

Component A: cerium oxide powder having an average particle diameter of 20 μm.

Component B: Rare earth-transition intermetallic compound powder having a MgCu ₂ crystal structure having an average particle diameter of 6 μm, specific components and weight percentages of 10% Nd, 12% Pr, 35% Dy, 41% Fe and 2% Co .

Component C: cerium nitrate hexahydrate powder having an average particle diameter of 50 μm.

The components were mixed in a weight ratio of A:B:C=10:10:80 to obtain a powder composition.

The powder composition was dispersed in pentanol at a ratio of 0.05 g/mL to form a slurry, that is, 0.05 g of the above powder composition was dispersed per 1 mL of pentanol.

The sintered NdFeB blank without aging treatment is machined into a magnetic piece having a diameter of 10 mm and a height of 5 mm, and the magnetic piece is subjected to conventional degreasing, pickling in a 5% (volume%) concentration of nitric acid, ultrasonic cleaning and drying. .

The treated magnetic sheet was completely immersed in the slurry in a stirred state for 60 minutes, and the impregnated magnet was placed in a stainless steel container and sealed.

The cartridge was placed in a vacuum sintering furnace, evacuated, and heated to 1050 ° C when the degree of vacuum reached 10 ^-2 Pa or more, and kept for 1 hour. Then the heating was stopped and the argon gas was cooled to below 100 °C. After that, the cooling was stopped, and the vacuum was applied to 10 ^-2 Pa, heated to 620 ° C, and kept for 1 hour. Next, the heating was stopped, argon gas was charged, and the temperature was cooled to below 80 °C.

At the same time, the control magnet 2 was prepared, and the other process steps were the same as those of the magnet of Example 2 except that the slurry was not impregnated with the slurry containing the powder composition.

The remanence, coercive force, and maximum magnetic energy product of the magnet of Example 2 and the control magnet 2 were measured, and the results are shown in Table 2.

Table 2

Example 3

Component A: bismuth oxyfluoride powder having an average particle diameter of 30 μm.

Component B: Rare earth-transition intermetallic compound powder having a MgCu ₂ crystal structure having an average particle diameter of 3 μm, specific components and weight percentages of 10% Nd, 15% Pr, 25% Dy, 7% Tb, 41.9% Fe , 1% Co and 0.1% Cu.

Component C: 3.5 hydrate cerium nitrate powder having an average particle diameter of 30 μm.

The components were mixed in a weight ratio of A:B:C=10:20:70 to obtain a powder composition.

The powder composition was dispersed in isopropyl alcohol in a ratio of 0.1 g/mL to form a slurry, that is, 0.1 g of the powder composition was mixed per 1 mL of isopropyl alcohol.

The sintered NdFeB blank without aging treatment was machined into a magnetic piece having a diameter of 10 mm and a height of 10 mm, and then subjected to a conventional degreasing treatment, pickled in a 5% (by volume) concentration of nitric acid, ultrasonically washed, and blown dry.

The treated magnetic sheet was completely immersed in the slurry under stirring for 15 minutes, and the impregnated magnet was placed in a molybdenum cartridge and sealed.

The cartridge was placed in a vacuum sintering furnace, evacuated, and heated to 950 ° C when the degree of vacuum reached 10 ^-2 Pa or more, and kept for 8 hours. Then the heating was stopped and the argon gas was cooled to below 100 °C. After that, the cooling was stopped, the vacuum was applied to 10 ^-2 Pa, and the mixture was heated to 500 ° C for 5 hours. Then, the heating was stopped, argon gas was charged, and the temperature was cooled to 80 ° C or lower.

At the same time, a control magnet 3 was prepared, and the other process steps were the same as those of the magnet of Example 3, except that the slurry was not impregnated with the slurry containing the powder composition.

The remanence, coercive force, and maximum magnetic energy product of the magnet of Example 3 and the control magnet 3 were measured, and the results are shown in Table 3.

table 3

Example 4

Component A: cesium fluoride or cerium oxide powder having an average particle diameter of 5 μm.

Component B: Rare earth-transition intermetallic compound powder having a MgCu ₂ crystal structure with an average particle diameter of 4 μm, specific composition and weight percentage of 28% Nd, 25% Dy, 3% Ho, 42.7% Fe, 1% Co , 0.1% Cu, 0.1% Ga and 0.1% Zr.

Component C: cerium nitrate trihydrate powder having an average particle diameter of 20 μm.

The above components were mixed in a ratio of A:B:C=10:30:60 to obtain a powder composition.

Dispersing the powder composition in cyclohexane at a ratio of 0.5 g/mL to form a slurry, that is, each 0.5 g of the above powder composition was mixed into 1 mL of cyclohexane.

The sintered NdFeB blank without aging treatment is machined into a magnetic piece having a diameter of 10 mm and a height of 2 mm, and the magnetic piece is subjected to conventional degreasing treatment, pickled in a 5% (by volume) concentration of nitric acid, ultrasonically washed and blown. dry.

The treated magnetic sheet was completely immersed in the slurry under stirring for 25 minutes, and the impregnated magnet was placed in a tungsten box and sealed.

The cartridge was placed in a vacuum sintering furnace, evacuated, and heated to 920 ° C when the degree of vacuum reached 10 ^-2 Pa or more, and kept for 4 hours. Then the heating was stopped and the argon gas was cooled to below 100 °C. After that, the cooling was stopped, and the vacuum was evacuated to 10 ^-2 Pa, and then heated to 550 ° C for 3 hours. Then, the heating was stopped, and the argon gas was cooled to 80 ° C or lower.

At the same time, a control magnet 4 was prepared, and the other process steps were the same as those of the magnet of Example 4, except that the slurry was not impregnated with the slurry containing the powder composition.

The remanence, coercive force, and maximum magnetic energy product of the magnet of Example 4 and the control magnet 4 were measured, and the results are shown in Table 4.

Table 4

Example 5

Component A: cesium fluoride, cerium oxide, cerium oxyfluoride powder having an average particle diameter of 1 μm.

Component B: Rare earth-transition intermetallic compound powder having a MgCu ₂ crystal structure with an average particle diameter of 5 μm, specific composition and weight percentage of 22% Pr, 30% Dy, 6% Ho, 38.1% Fe, 3% Co , 0.5% Cu, 0.2% Ga, 0.1% Cr and 0.1% Mn.

Component C: cerium nitrate hexahydrate powder having an average particle diameter of 20 μm.

The above components were mixed in a ratio of A:B:C = 1:98:1 to obtain a powder composition.

The powder composition was dispersed in ethyl acetate at a ratio of 1 g/mL to form a slurry, that is, 1 g of the above powder composition was mixed per 1 mL of ethyl acetate.

The sintered NdFeB blank without aging treatment is machined to a diameter of 10 mm and height A magnetic sheet of 1 mm was subjected to conventional degreasing treatment, pickled in a 5% (by volume) concentration of nitric acid, ultrasonically washed and blown dry.

The treated magnetic sheet was completely immersed in the slurry under stirring for 40 minutes, and the impregnated magnet was placed in a stainless steel case and sealed.

The cartridge was placed in a vacuum sintering furnace, evacuated, and heated to 1000 ° C when the degree of vacuum reached 10 ^-2 Pa or more, and kept for 5 hours. Then the heating was stopped and the argon gas was cooled to below 100 °C. After that, the cooling was stopped, and the vacuum was evacuated to 10 ^-2 Pa, and then heated to 480 ° C for 2.5 hours. Next, the heating was stopped, and the argon gas was cooled to 80 ° C or lower.

The control magnet 5 was simultaneously prepared, and the other process steps were the same as those of the magnet of Example 5 except that the slurry was not impregnated with the slurry containing the powder composition.

The remanence, coercive force, and maximum magnetic energy product of the magnet of Example 5 and the control magnet 5 were measured, and the results are shown in Table 5.

table 5

Example 6

Component A: cesium fluoride or cerium oxide powder having an average particle diameter of 1 μm.

Component B: Rare earth-transition intermetallic compound powder having a MgCu ₂ crystal structure having an average particle diameter of 2 μm, specific components and weight percentages of 3% La, 1% Ce, 7% Pr, 11% Nd, 21% Dy 6% Tb, 6% Ho, 41% Fe, 3% Co, 0.5% Cu, 0.1% Ni, 0.2% Ga, 0.1% Cr and 0.1% Ti.

Component C: cerium nitrate hexahydrate or cerium nitrate pentahydrate powder having an average particle diameter of 10 μm.

The above components were mixed in a weight ratio of A:B:C=20:40:40 to obtain a powder composition.

The powder composition was dispersed in cyclooctane at a ratio of 0.2 g/mL to form a slurry, that is, 0.2 g of the above powder composition was mixed per 1 mL of cyclooctane.

The sintered NdFeB blank without aging treatment is machined to a diameter of 10 mm and height A 3.5 mm magnetic piece was subjected to conventional degreasing treatment, pickled in a 5% (by volume) concentration of nitric acid, ultrasonically washed, and blown dry.

The treated magnetic sheet was completely immersed in the slurry under stirring for 5 minutes, and the impregnated magnet was placed in a stainless steel cartridge and sealed.

The cartridge was placed in a vacuum sintering furnace, evacuated, and heated to 850 ° C when the degree of vacuum reached 10 ^-2 Pa or more, and kept for 2.5 hours. Then the heating was stopped and the argon gas was cooled to below 100 °C. After that, the cooling was stopped, and the vacuum was evacuated to 10 ^-2 Pa, and then heated to 490 ° C for 2 hours. Next, the heating was stopped, and the argon gas was cooled to 80 ° C or lower.

At the same time, a control magnet 6 was prepared, and the other process steps were the same as those of the magnet of Example 6, except that the slurry was not impregnated with the slurry containing the powder composition.

The remanence, coercive force, and maximum magnetic energy product of the magnet of Example 6 and the control magnet 6 were measured, and the results are shown in Table 6.

Table 6

Example 7

Component A: bismuth oxyfluoride powder having an average particle diameter of 40 μm.

Component B: Rare earth-transition intermetallic compound powder having a MgCu ₂ crystal structure having an average particle diameter of 3 μm, specific components and weight percentages of 0.5% La, 3.5% Ce, 17% Pr, 30% Dy, 5% Ho 41.2% Fe, 2.5% Co, 0.3% Cu.

Component C: cerium nitrate trihydrate, cerium nitrate hexahydrate, cerium nitrate pentahydrate having an average particle diameter of 5 μm.

The above components were mixed in a weight ratio of A:B:C=30:40:30 to obtain a powder composition.

The powder composition was dispersed in isobutyl acetate in a ratio of 0.3 g/mL to form a slurry, that is, 0.3 g of the above powder composition was mixed per 1 mL of isobutyl acetate.

The sintered NdFeB blank without aging treatment is machined into a magnetic piece having a diameter of 10 mm and a height of 1.0 mm, and the magnetic piece is subjected to conventional degreasing treatment at a concentration of 5% by volume. The nitric acid is pickled, ultrasonically cleaned and blown dry.

The treated magnetic sheet was completely immersed in the slurry under stirring for 10 minutes, and the impregnated magnet was placed in a stainless steel cartridge and sealed.

The cartridge was placed in a vacuum sintering furnace, and a vacuum was applied. When the degree of vacuum reached 10 ^-2 Pa or more, the temperature was raised to 820 ° C and the temperature was maintained for 8 hours. Then the heating was stopped and the argon gas was cooled to below 100 °C. After that, the cooling was stopped, and the vacuum was applied to 10 ^-2 Pa, and then heated to 510 ° C for 3 hours. Next, the heating was stopped, and the argon gas was cooled to 80 ° C or lower.

At the same time, a control magnet 7 was prepared, and the other process steps were the same as those of the magnet of Example 7, except that the slurry was not impregnated with the slurry containing the powder composition.

The remanence, coercive force, and maximum magnetic energy product of the magnet of Example 7 and the control magnet 7 were measured, and the results are shown in Table 7.

Table 7

Example 8

Component A: cerium oxide powder having an average particle diameter of 15 μm.

Component B: Rare earth-transition intermetallic compound powder having a MgCu ₂ crystal structure with an average particle diameter of 4 μm, specific components and weight percentages of 2% Ce, 22% Nd, 16% Dy, 15% Tb, 2% Ho 40.8% Fe, 1% Co, 0.1% Cu, 0.5% Ni, 0.2% Ga, 0.2% Cr and 0.2% Ti.

Component C: cerium nitrate pentahydrate or cerium nitrate hexahydrate having an average particle diameter of 80 μm.

The above components were mixed in a ratio of A:B:C=50:10:40 to obtain a powder composition.

The powder composition was dispersed in propanol at a ratio of 0.6 g/mL to form a slurry, that is, 0.6 g of the above powder composition was mixed per 1 mL of propanol.

The sintered NdFeB blank without aging treatment is machined into a magnetic piece having a diameter of 10 mm and a height of 5.0 mm, and the magnetic piece is subjected to conventional degreasing treatment, pickled in a 5% (by volume) concentration of nitric acid, and ultrasonically cleaned. Blow dry.

The treated magnetic sheet was completely immersed in the slurry under stirring for 30 minutes, and the impregnated magnet was placed in a stainless steel case and sealed.

The cartridge was placed in a vacuum sintering furnace, evacuated, and the temperature was raised to 830 ° C when the degree of vacuum reached 10 ^-2 Pa or more, and the temperature was maintained for 7 hours. Then the heating was stopped and the argon gas was cooled to below 100 °C. After that, the cooling was stopped, and the vacuum was evacuated to 10 ^-2 Pa, and then heated to 520 ° C for 4 hours. Next, the heating was stopped, and the argon gas was cooled to 80 ° C or lower.

At the same time, a control magnet 8 was prepared, and the other process steps were the same as those of the magnet of Example 8, except that the slurry was not impregnated with the slurry containing the powder composition.

The remanence, coercive force, and maximum magnetic energy product of the magnet of Example 8 and the control magnet 8 were measured, and the results are shown in Table 8.

Table 8

Example 9

Component A: cerium oxide having an average particle diameter of 25 μm, cerium oxide powder.

Component B: Rare earth-transition intermetallic compound powder having a MgCu ₂ crystal structure with an average particle diameter of 5 μm, specific components and weight percentages of 3% La, 1% Ce, 7% Pr, 30% Nd, 15% Dy , 42.5% Fe, 1.5% Co.

Component C: cerium nitrate hexahydrate or cerium nitrate pentahydrate powder having an average particle diameter of 60 μm.

The above components were mixed in a ratio of A:B:C=40:10:50 to obtain a powder composition.

The powder composition was dispersed in butanol at a ratio of 0.7 g/mL to form a slurry, that is, 0.7 g of the above powder composition was mixed per 1 mL of butanol.

The sintered NdFeB blank without aging treatment is machined into a magnetic piece having a diameter of 10 mm and a height of 8.0 mm, and the magnetic piece is subjected to conventional degreasing treatment, pickled in a 5% (by volume) concentration of nitric acid, and ultrasonically cleaned. Blow dry.

The treated magnetic sheet was completely immersed in the slurry under stirring for 50 minutes, and the impregnated magnet was placed in a stainless steel container and sealed.

The cartridge was placed in a vacuum sintering furnace, vacuum was applied, and the temperature was raised to 920 ° C when the degree of vacuum reached 10 ^-2 Pa or more, and the temperature was maintained for 6.5 hours. Then the heating was stopped and the argon gas was cooled to below 100 °C. After that, the cooling was stopped, and the vacuum was evacuated to 10 ^-2 Pa, and then heated to 610 ° C for 5 hours. Next, the heating was stopped, and the argon gas was cooled to 80 ° C or lower.

At the same time, a control magnet 9 was prepared, and the other process steps were the same as those of the magnet of Example 9, except that the slurry was not impregnated with the slurry containing the powder composition.

The remanence, coercive force, and maximum magnetic energy product of the magnet of Example 9 and the control magnet 9 were measured, and the results are shown in Table 9.

Table 9

Example 10

Component A: cesium fluoride powder having an average particle diameter of 3 μm.

Component B: Rare earth-transition intermetallic compound powder having a MgCu ₂ crystal structure with an average particle diameter of 6 μm, specific components and weight percentages are 25% Nd, 25% Dy, 5% Tb, 1% Ho, 43% Fe , 0.5% Co, 0.1% Cu, 0.1% Ga, 0.2% Cr and 0.1% Ti.

Component C: cerium nitrate pentahydrate, cerium nitrate trihydrate, cerium nitrate hexahydrate having an average particle diameter of 2 μm.

The above components were mixed in a weight ratio of A:B:C=98:1:1 to obtain a powder composition.

The powder composition was dispersed in pentanol at a ratio of 0.8 g/mL to form a slurry, that is, 0.8 g of the above powder composition was mixed per 1 mL of pentanol.

The sintered NdFeB blank without aging treatment is machined into a magnetic piece having a diameter of 10 mm and a height of 2.0 mm, and the magnetic piece is subjected to conventional degreasing treatment, pickled in a 5% (by volume) concentration of nitric acid, and ultrasonically cleaned. Blow dry.

The treated magnetic sheet was completely immersed in the slurry under stirring for 25 minutes, and the impregnated magnet was placed in a stainless steel case and sealed.

The cartridge was placed in a vacuum sintering furnace, evacuated, and heated to 930 ° C when the degree of vacuum reached 10 ^-2 Pa or more, and kept for 5 hours. Then the heating was stopped and the argon gas was cooled to below 100 °C. After that, the cooling was stopped, and the vacuum was evacuated to 10 ^-2 Pa, and then heated to 485 ° C for 6 hours. Next, the heating was stopped, and the argon gas was cooled to 80 ° C or lower.

At the same time, the control magnet 10 was prepared, except that the slurry was impregnated with the slurry containing the powder composition, and the other process steps were the same as those of the magnet of Example 10.

The remanence, coercive force, and maximum magnetic energy product of the magnet of Example 10 and the control magnet 10 were measured, and the results are shown in Table 10.

Table 10

From the above, according to the technical solution of the present invention, the coercive force of the magnet can be remarkably improved while substantially maintaining the remanence and the maximum magnetic energy product.

Example 11

Component A: cerium oxide powder having an average particle diameter of 20 μm.

The components A to C were mixed in a ratio of A:B:C=10:10:80.

The mixed powder composition was dispersed in pentanol at a ratio of 0.05 g/mL to form a slurry, that is, 0.05 g of the above mixed powder was dispersed per 1 mL of pentanol.

The N48M sintered NdFeB blank machine without aging treatment was processed into a D10mm×5mm wafer and a 10mm×10mm×5mm square piece, and the magnetic sheet was subjected to conventional degreasing at a concentration of 5% (volume percent) nitric acid. Pickled, ultrasonically cleaned and blown dry.

At the same time, a control magnet 11 was prepared, and the above-mentioned N48M magnetic sheet was selected as a coating substrate of 10 mm*10 mm*5 mm, except that the magnet was impregnated with a slurry of cerium nitrate, and other process steps were the same as those of the magnet of Example 11.

1000 sheets of the D10 mm × 5 mm wafer of Example 11 and 1000 sheets of 10 mm × 10 mm × 5 mm were placed together with 1000 sheets of the control magnet 11 in the same vacuum sintering furnace for heat treatment. Further, the square piece magnet of Example 11 was separately subjected to heat treatment for 5 batches in 2000 batches. The heat treatment process conditions for all batches were consistent as shown below. The 30 wafers and 30 square sheets of the examples were respectively selected from the batches treated in the examples and the comparative examples, and 30 square sheets were selected in the comparative examples to measure the magnetic properties. The batches of the embodiment square magnets were also treated separately, and 30 magnets were each selected for magnetic property measurement. In addition, 30 pieces of uncoated N48M square piece magnets were selected for magnetic property measurement. The magnetic properties of the comparative examples were different from those of the uncoated magnets and the comparative examples. The performance of the products of the different batches of the examples was consistent, and the performance of the products of different specifications was consistent after the treatment.

The heat treatment process conditions are as follows: the cartridge is placed in a vacuum sintering furnace, vacuum is applied, and the temperature is raised to 1050 ° C when the degree of vacuum reaches 10 ^-2 Pa or more, and the temperature is maintained for 1 hour. Then the heating was stopped and the argon gas was cooled to below 100 °C. After that, the cooling was stopped, and the vacuum was applied to 10 ^-2 Pa, heated to 620 ° C, and kept for 1 hour. Next, the heating was stopped, argon gas was charged, and the temperature was cooled to below 80 °C.

The magnetic properties of the square magnets of the uncoated and heat-treated square magnets, the square magnet of Example 11, and the magnetic specimen of Comparative Magnetic Example 11 were averaged and the calculated range was compared. The results are shown in Table 11-1. . At the same time, the average results of the magnetic properties of the 30 pieces of the wafer and the square piece after the first batch treatment and the extremely poor results are shown in Table 11-2. The magnetic performance results and the extremely poor results of the five batches of treated square sheets are shown in Table 11-3.

Here, uniformity is expressed using (very poor/average value) × 100 (%), and the larger the numerical value, the lower the uniformity; the smaller the numerical value, the higher the uniformity. In each table, the values in parentheses below the range are (very poor/average) × 100 (%), which are used to indicate uniformity.

Table 11-1

Table 11-2

Table 11-3

From the above results, it can be seen that the technical solution of the present invention not only improves the magnet Hcj well, but also reduces the Br and the magnetic energy product, and improves the product consistency of batch production of different batches and different specifications. And uniformity.

Example 12

Component B: Rare earth-transition intermetallic compound powder having a MgCu ₂ crystal structure having an average particle diameter of 2 μm, specific components and weight percentages of 3% La, 1% Ce, 7% Pr, 11% Nd, 21% Dy, 6% Tb, 6% Ho, 41% Fe, 3% Co, 0.5% Cu, 0.1% Ni, 0.2% Ga, 0.1% Cr and 0.1% Ti.

The components A to C were mixed in a ratio of A:B:C=20:40:40.

The N35SH sintered NdFeB blank machine without aging treatment was processed into a D10 mm×5 mm wafer, the magnetic sheet was subjected to conventional degreasing, pickled in a 5% (volume percent) concentration of nitric acid, ultrasonically washed and blown dry.

At the same time, a comparative example magnet 12 was prepared, except that the magnet was impregnated with a slurry of cesium fluoride, and the other process steps were the same as those of the magnet of Example 12.

The D10 mm × 5 mm wafer magnet of Example 12 and the D10 mm * 5 mm wafer magnet of Comparative Example 12 were placed together in the same vacuum sintering furnace for heat treatment. Further, the wafer magnet of Example 12 was separately selected, and a total of 5 batches of heat treatment were performed for each batch of 2000 sheets. The heat treatment process conditions for all batches are consistent as shown below. For the examples and the comparative examples in the batch which was co-processed with the examples, 30 sheets were each selected for measurement of magnetic properties. Batches of the examples were separately processed. 30 magnets were selected per batch for magnetic performance measurements. In addition, 30 pieces of N35SH disk magnets which were not coated and heat-treated were selected for magnetic property measurement. The magnetic properties of the comparative examples were different from those of the uncoated magnets and the comparative examples. Performance consistency of products between different batches of the example. The average value and the extreme difference of the measured values of the magnetic properties of each batch of magnets were compared. The results are shown in Table 12-1 and Table 12-2.

Heat treatment process conditions: The material box is placed in a vacuum sintering furnace, vacuum is applied, and the temperature is raised to 1050 ° C when the degree of vacuum reaches 10 ^-2 Pa or more, and the temperature is kept for 1 hour. Then the heating was stopped and the argon gas was cooled to below 100 °C. After that, the cooling was stopped, and the vacuum was applied to 10 ^-2 Pa, heated to 620 ° C, and kept for 1 hour. Next, the heating was stopped, argon gas was charged, and the temperature was cooled to below 80 °C.

Table 12-1

Table 12-2

It can be seen from the above results that the technical solution of the present invention can not only improve the magnet Hcj, and Br and magnetic properties are reduced less, and can improve the consistency and uniformity of products in batch production.

Example 13

Component B: a rare earth-transition intermetallic compound powder having a MgCu ₂ crystal structure having an average particle diameter of 5 μm, specific components and weight percentages of 22% Pr, 30% Dy, 6% Ho, 38.1% Fe, 3% Co, 0.5% Cu, 0.2% Ga, 0.1% Cr and 0.1% Mn.

The components A to C were mixed in a ratio of A:B:C=5:90:5.

The N40H sintered NdFeB blank machine without aging treatment was processed into a D10 mm×5 mm wafer, the magnetic sheet was subjected to conventional degreasing, pickled in a 5% (volume percent) concentration of nitric acid, ultrasonically washed and blown dry.

At the same time, the control magnet 13 was prepared, except that the magnet was impregnated with only the slurry of the component B, and the other process steps were the same as those of the magnet of Example 13.

The D10 mm × 5 mm wafer magnet of Example 13 and the D10 mm * 5 mm wafer magnet of Comparative Example 13 were placed together in the same vacuum sintering furnace for heat treatment. Further, the wafer magnet of Example 13 was separately selected, and a total of 5 batches of heat treatment were performed for each batch of 2000 sheets. The heat treatment process conditions for all batches are consistent as shown below. For the examples and the comparative examples in the batch which was co-processed with the examples, 30 sheets were each selected for measurement of magnetic properties. Batches of the examples were separately processed. 30 magnets were selected per batch for magnetic performance measurements. In addition, 30 pieces of N40H disk magnets which were not coated and heat-treated were selected for magnetic property measurement. The magnetic properties of the comparative examples were different from those of the uncoated magnets and the comparative examples, and the performance consistency of the products between the different batches of the examples. The average value and the extreme difference of the measured values of the magnetic properties of each batch of magnets were compared. The results are shown in Table 13-1 and Table 13-2.

Table 13-1

Table 13-2

From the above results, it can be seen that the technical solution of the present invention can not only improve the Hcj of the magnet, but also reduce the Br and magnetic properties less, and can improve the consistency and uniformity of the product in batch production.

The technical solutions of the present invention have been described in detail above with reference to the specific embodiments and examples, but the present invention is not limited thereto. Various changes and modifications can be made to the invention without departing from the scope of the invention.

Claims

A powder composition for producing an R-Fe-B based sintered magnet, comprising component (A), component (B) and component (C),

The component (A) is one or more powders selected from the group consisting of fluorides, oxides, and oxyfluorides of heavy rare earths.

The component (B) is a rare earth-transition intermetallic compound powder having a MgCu 2 crystal structure,

The component (C) is selected from one or more of the rare earth hydrated nitrate powders.
The powder composition according to claim 1, wherein

The component (A) accounts for 1% to 98% by weight of the powder composition.

The component (B) accounts for 1% to 98% by weight of the powder composition.

The component (C) is from 1% to 98% by weight of the powder composition.
The powder composition according to claim 1, wherein in the component (B), the content of the rare earth element is ≥ 55% by weight, and the weight percentage of the sum of lanthanum, cerium or lanthanum and cerium is ≥ 10 %, the weight percentage of iron, cobalt or the sum of iron and cobalt in the transition metal element is ≥ 40%, and the balance is at least one selected from the group consisting of copper, titanium, chromium, zinc, and nickel.
The powder composition according to claim 1, wherein the component (A) has an average particle diameter of ≤ 50 μm.
The powder composition according to claim 1, wherein the component (B) has an average particle diameter of from 2 to 10 μm.
The powder composition according to claim 1, wherein the component (C) has an average particle diameter of ≤ 100 μm.
A method for preparing an R-Fe-B based sintered magnet, comprising the steps of:

Dissolving the powder composition according to any one of claims 1 to 6 in an organic solvent to prepare a treatment liquid,

Applying the treatment liquid to a magnet,

The magnet after coating the treatment liquid is subjected to vacuum heat treatment.
The method of preparing an R-Fe-B based sintered magnet according to claim 7, wherein the content of the powder composition in the treatment liquid is 0.01 to 1.0 g/mL,

The treatment liquid further includes a dispersant, and the volume ratio of the dispersant to the organic solvent is less than 1%.
The method of producing an R-Fe-B based sintered magnet according to claim 7, wherein the organic solvent is selected from the group consisting of alcohols, alkanes or esters having 5 to 16 carbon atoms.
The method of preparing an R-Fe-B based sintered magnet according to claim 7, wherein the step of applying the treatment liquid to the magnet comprises:

The magnet was immersed in the treatment liquid in a stirred state, and the immersion time was 1 to 60 minutes.
The method of producing an R-Fe-B based sintered magnet according to claim 7, wherein the vacuum heat treatment comprises the following steps:

The magnet after coating the treatment liquid is placed in a vacuum sintering furnace, and vacuum is applied until the degree of vacuum reaches 10 -2 Pa;

Warm up to 820 ~ 1050 ° C, keep warm for 1 ~ 8 hours;

After cooling with argon gas to below 100 ° C, stop cooling, vacuuming to a vacuum of 10 -2 Pa;

Warming up to 450 ° C 620 ° C, holding 1 to 5 hours;

The argon gas was cooled to below 80 °C.
A method of producing an R-Fe-B based sintered magnet according to any one of claims 7 to 11, wherein after the treatment liquid is applied to the magnet and after the treatment liquid is applied After the magnet is subjected to vacuum heat treatment, the uniformity of the magnetic properties of the magnet satisfies one or more of the following formulas (1) to (3):

The uniformity of remanence is ≤0.9% (1)

Coherence uniformity ≤ 2% (2)

The uniformity of the maximum energy product is ≤ 2.5% (3).
An R-Fe-B based sintered magnet comprising a magnet portion and a coating portion on an outer surface of the magnet portion, the coating portion being formed of the powder composition according to any one of claims 1 to 6. .
The R-Fe-B based sintered magnet according to claim 13, wherein the uniformity of magnetic properties of the R-Fe-B based sintered magnet satisfies one of the following formulas (1) to (3) or Multiple:

The uniformity of remanence is ≤0.9% (1)

Coherence uniformity ≤ 2% (2)

The uniformity of the maximum energy product is ≤ 2.5% (3).
An R-Fe-B based sintered magnet prepared by the method of any one of claims 7 to 11.
The R-Fe-B based sintered magnet according to claim 15, wherein the uniformity of magnetic properties of the R-Fe-B based sintered magnet satisfies one of the following formulas (1) to (3) or Multiple:

The uniformity of remanence is ≤0.9% (1)

Coherence uniformity ≤ 2% (2)

The uniformity of the maximum energy product is ≤ 2.5% (3).