CN111223623B - Large-thickness neodymium iron boron magnetic steel and preparation method thereof - Google Patents
Large-thickness neodymium iron boron magnetic steel and preparation method thereof Download PDFInfo
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Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
- H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
- H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
- H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
- H01F41/0266—Moulding; Pressing
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
- H01F41/0293—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets diffusion of rare earth elements, e.g. Tb, Dy or Ho, into permanent magnets
Abstract
The invention discloses a large-thickness neodymium iron boron magnetic steel and a preparation method thereof. The preparation method comprises the following steps: s1, sintering a neodymium iron boron green compact to obtain a neodymium iron boron sintered body; the neodymium iron boron pressed compact is of a layered structure and comprises a base layer and a separating layer, and a paraffin layer or a polyethylene glycol layer is arranged between the base layer and the separating layer; s2, putting the neodymium iron boron sintered body in inert gas and H2And after activation under the condition, carrying out grain boundary diffusion treatment by taking the heavy rare earth element as a diffusion source. The method can prepare the magnetic remanence Br of more than 14.8kGs and the coercive force HcjAbove 20kOe, direction of orientation>20mm of large-thickness magnetic steel, less heavy rare earth addition and low cost.
Description
Technical Field
The invention relates to a large-thickness neodymium iron boron magnetic steel and a preparation method thereof.
Background
At present, most of the preparation methods of sintered neodymium iron boron magnetic steel are to prepare finished products through the working procedures of smelting, powder making, pressing, cold isostatic pressing, sintering, processing (including diffusion), electroplating and the like. In order to increase the high-temperature resistance of the product, the traditional process adds heavy rare earth dysprosium Dy, terbium Tb and the like in the smelting stage to increase the coercive force of the product. However, the addition of a large amount of heavy rare earth causes the cost of the material to increase, and on the other hand, because the heavy rare earth elements of Dy and Tb atoms and Fe atoms are antiferromagnetic, the residual magnetism of the sintered neodymium iron boron is reduced, and a product with high residual magnetism and high coercivity cannot be prepared at the same time.
In the prior art, for example, patent CN107026003A, the grain boundary diffusion method can significantly increase the sheet magnet (orientation direction)<5mm) and at the same time has less influence on the remanence of the product. However, grain boundary diffusion is affected by the thickness of the materialAnd the product with the thickness more than 10mm has a poor effect by adopting a grain boundary diffusion method. Along with the gradual increase of installed capacity of the wind power market, the performance requirement on the sintered neodymium iron boron with large thickness (larger than 10mm) is higher and higher, and Br needs to reach>14.7kGs, and coercivity H of the productcJ>17kOe, while the neodymium iron boron sintering process in the prior art cannot meet the requirements, other processes are urgently needed to break through. In addition, the sintered nd-fe-b is usually formed by vertical pressing or parallel pressing, and the orientation degree of the product is damaged more or less in the pressing process, so that the residual magnetism of the product is influenced. With the market increasing demand for high remanence and high coercivity dual high yield products, the problems of pressing process and thickness diffusion are urgently needed to be solved.
Therefore, a process is needed to be found, which can prepare the sintered neodymium iron boron magnetic steel with high coercivity and high remanence and large thickness.
Disclosure of Invention
The invention aims to solve the problem that in the prior art, a high-coercivity, high-remanence and large-thickness sintered neodymium iron boron magnetic steel cannot be prepared by a grain boundary diffusion method, and provides a large-thickness neodymium iron boron magnetic steel and a preparation method thereof. The method can prepare the magnetic remanence Br of more than 14.8kGs and the coercive force HcjAbove 20kOe, direction of orientation>20mm of large-thickness magnetic steel, less heavy rare earth addition and low cost.
The invention solves the technical problems through the following technical scheme.
The invention provides a preparation method of neodymium iron boron magnetic steel, which comprises the following steps:
s1, sintering a neodymium iron boron green compact to obtain a neodymium iron boron sintered body;
the neodymium iron boron pressed compact is of a layered structure and comprises a base layer and a separating layer, wherein a paraffin layer or a polyethylene glycol layer is arranged between the base layer and the separating layer;
the raw materials of the substrate layer comprise: 28.2-29.2% of Nd and/or Pr; 0.9-1% of B; 0.01-2% of Cu; 0.01-2% of Co; 0.01-0.2% of Ga; 0.1-1% RH; 0.01 to 0.2% of a high melting point metal;
the raw materials of the separation layer comprise: 29-30% of Nd and/or Pr; 0.9-1% of B; 0.01-2% of Cu; 0-2% of Co; 0.01-0.2% of Ga; 0-0.5% RH; 0.01 to 0.2% of a high melting point metal;
wherein RH is one or more of Dy, Tb, Ho and Gd; the high-melting-point metal is one or more of Nb, Zr, Ti and Hf; the percentage is mass percentage;
s2, putting the neodymium iron boron sintered body in inert gas and H2And after activation under the condition, carrying out grain boundary diffusion treatment by taking the heavy rare earth element as a diffusion source.
In the invention, the neodymium iron boron green compact is preferably of a 3-5-layer structure, and comprises 3 layers of a separating layer, a paraffin layer or a polyethylene glycol layer and a base layer from top to bottom, or 5 layers of a separating layer, a paraffin layer or a polyethylene glycol layer, a base layer, a paraffin layer or a polyethylene glycol layer and a separating layer.
In order to obtain the neodymium iron boron green compact, in a preferred embodiment of the invention, the raw materials of the base layer and the raw materials of the separation layer are poured into a mold with a paraffin partition plate for pressing. During the pressing process, most of the paraffin partition is extruded or melted. In the neodymium iron boron green compact obtained by the method, the base layer raw material and the separating layer raw material are not mixed with each other due to the paraffin layer. Wherein, the paraffin that is extruded can be in the neodymium iron boron pressed compact top layer prevents the oxidation of pressed compact.
Preferably, the step S1 includes the following steps: respectively pouring the raw materials of the substrate layer and the separating layer into a mould, prepressing, vacuum sealing, and in a pulse magnetic field, orienting, demagnetizing and hot isostatic pressing to obtain the neodymium iron boron green compact; wherein, a paraffin partition board vertical to the orientation direction is arranged in the mould; the magnetic field intensity of the pulse magnetic field is more than 4T.
Wherein the mold is conventional in the art. More preferably, the mold is a rubber mold or a plastic mold.
Wherein the pre-pressing is conventional in the art.More preferably, after the pre-pressing, the density of the raw material of the base layer and the raw material of the separation layer is 2-3 g/cm3E.g. 2, 2.5 or 3g/cm3。
Wherein said orientation and said demagnetization are conventional in the art. More preferably, said orientation and said demagnetization are performed in a pulsed magnetic field a plurality of times, preferably more than 3 times, for example 5 times.
Wherein the hot isostatic pressing is conventional in the art. The hot isostatic pressing can improve the orientation degree of the product compared with the damage of the traditional vertical or horizontal pressing process to the orientation degree.
More preferably, the hot isostatic pressing is performed at an oil temperature of 70 to 200 ℃, for example, 70, 130 or 200 ℃.
More preferably, the hot isostatic pressing time is 1-30 min, such as 1, 15 or 30 min.
Wherein, more preferably, the density of the neodymium iron boron green compact is 4.0-5.5 g/cm3E.g. 4.0, 5.0 or 5.5g/cm3。
Wherein, the paraffin partition plate is a conventional paraffin partition plate.
More preferably, the thickness of the paraffin partition is 0.1-2 mm, such as 0.1, 0.5 or 2 mm.
More preferably, the paraffin partition contains a dispersant, and the dispersant is preferably cyclohexane or cyclopentane; the dispersant accounts for 0.5 to 1.5 wt%, for example 0.5, 1.0 or 1.5 wt% of the paraffin partition. The dispersing agent plays a role in preventing the raw material alloy powder from agglomerating, and simultaneously escapes in the subsequent sintering process, so that a wider diffusion channel is provided for the subsequent grain boundary diffusion treatment, and the grain boundary diffusion speed and the grain boundary diffusion depth are increased.
More preferably, the thickness of the matrix layer is 6-10mm, for example 8 mm.
More preferably, the thickness of the separation layer is 4-8mm, for example 6 mm.
Preferably, the raw materials of the separation layer comprise: the content of Al is less than 0.08%; the percentage is mass percentage. It should be noted that Al in the above-mentioned spacer layer raw material is not actively added, and particularly due to the very small amount of impurities in the equipment and/or raw materials used in the manufacturing process, the Al content is less than 0.08%.
Preferably, when the raw material of the separation layer comprises Nd and Pr, the ratio of Pr: the mass ratio of Nd is 1: 3-1: 4.
In a preferred embodiment of the present invention, the raw material of the separator layer includes: the content of Nd is 29.294%; the content of B is 0.948%; the content of Cu is 0.049%; the content of Co is 0%; the content of Ga is 0%; the RH content is 0%; the Zr content is 0.112%; the Fe content is 69.597%; the percentage is mass percentage.
In a preferred embodiment of the present invention, the raw material of the separator layer includes: the content of Nd was 29.3%; the content of B is 0.92%; the Cu content is 0.4%; the content of Co is 0%; the content of Ga is 0.1%; the RH content is 0%; the Zr content is 0.1%; the content of Al is 0.04%; the Fe content is 69.14%; the percentage is mass percentage.
In a preferred embodiment of the present invention, the raw material of the separator layer includes: the content of Nd was 29.3%; the content of B is 0.92%; the Cu content is 0.2%; the content of Co is 0%; the content of Ga is 0.4%; the RH content is 0%; the Zr content is 0.1%; the content of Al is 0.04%; the Fe content is 69.04%; the percentage is mass percentage.
In a preferred embodiment of the present invention, the raw material of the separator layer includes: the content of Nd was 29.3%; the content of B is 0.945%; the Cu content is 0.08%; the content of Co is 0%; the content of Ga is 0.1%; the RH content is 0%; the Zr content is 0.1%; the content of Al is 0.04%; the Fe content is 69.435%; the percentage is mass percentage.
Preferably, the raw materials of the separation layer are prepared by smelting, hydrogen crushing and pulverizing alloy powder which satisfies the same components and content of the raw materials of the separation layer.
Preferably, when the raw material of the base layer comprises Nd and Pr, the ratio of Nd: the mass ratio of Pr is 1: 3-1: 4.
In a preferred embodiment of the present invention, the raw material of the substrate layer includes: the content of Nd and Pr is 28.828%; pr: the mass ratio of Nd is 1: 3; the content of Tb is 0.489%; the content of B is 0.947%; the Fe content is 69.031%; the content of Cu is 0.049%; the content of Co is 0.544%; the Zr content is 0.112%; the content of Ga is 0%; the percentage is mass percentage.
In a preferred embodiment of the present invention, the raw material of the substrate layer includes: the content of Nd and Pr was 29.25%; pr: the mass ratio of Nd is 1: 3; the content of Tb is 0.55%; the content of B is 0.92%; the Fe content is 68.48%; the Cu content is 0.06%; the content of Co is 0.5%; the Zr content is 0.14%; the content of Ga is 0.1%; the percentage is mass percentage.
Preferably, the raw material of the substrate layer is prepared by smelting, hydrogen crushing and pulverizing alloy powder which satisfies the same components and content of the raw material of the substrate layer.
Preferably, the smelting is carried out in a medium-frequency vacuum induction rapid hardening melt-spun furnace for smelting and casting; the thickness of the throwing sheet is 0.15-0.4 mm, preferably 0.20-0.27 mm, such as 0.2, 0.25 or 0.27 mm.
More preferably, the hydrogen breaking is divided into hydrogen absorption treatment and dehydrogenation treatment; the hydrogen absorption treatment is carried out under the condition that the hydrogen pressure is 0.1-0.15 MPa, such as 0.1, 0.12 or 0.15 MPa; the dehydrogenation treatment is carried out at a temperature of 500 ℃ to 600 ℃, for example 500, 550 or 600 ℃; the time of the dehydrogenation treatment is 2-4 h, for example 4 h; after the dehydrogenation treatment, the hydrogen content of the powder is 500-2000 ppm, for example 500-1500 ppm.
In a preferred embodiment of the present invention, the hydrogen absorption treatment is considered to be completed when the hydrogen burst pressure variation range is less than 0.04MPa/10 min.
More preferably, the milling is jet milling.
More preferably, before milling, an antioxidant and/or a lubricant are also added.
Preferably, the antioxidant constitutes 0.5-1.5 wt%, more preferably 0.8-1.2 wt% of the mass of the fine powder.
Preferably, the lubricant comprises 0.5 to 1.5 wt%, more preferably 0.8 to 1.2 wt% of the mass of the fine powder.
The antioxidant and the lubricant are known to those skilled in the art, and generally should not react with the raw materials in the neodymium iron boron permanent magnet material, and are preferably special antioxidant and lubricant for magnetic materials produced by new Tianjin Yuesheng material research institute.
In S1, the sintering may be conventional in the art. It will be appreciated by those skilled in the art, in view of the present invention, that during sintering, paraffin decomposes and interdiffusion between the spacer layer and the base layer occurs, but to a lesser extent (less than 0.2 mm).
Preferably, the sintering can be divided into 3 processes, which are sequentially decomposing and discharging the organic matter at 200-. Wherein the organic matter is paraffin, a dispersant, an antioxidant and a lubricant; the redundant gas is mainly hydrogen in the hydrogen breaking stage.
More preferably, the atmosphere is an inert gas atmosphere. The inert gas may be one conventional in the art and typically includes one or more of helium, neon, argon, krypton, xenon, and radon, such as argon.
In a preferred embodiment of the present invention, after the sintered nd-fe-b body is obtained, post-treatment is performed on the sintered nd-fe-b body in order to remove an oxide layer and a surface degradation layer on the surface of the sintered nd-fe-b body and to create conditions for adhesion of a diffusion layer during subsequent grain boundary diffusion. In S1, preferably, the sintered nd-fe-b body is ground, acid-washed, and sand-blasted for use.
In the present invention, the raw material of the separation layer is designed to be an easily diffusible alloy powder. In the presence of inert gas and H2And under the condition, further exciting the activity of the surface layer (namely the surface layer of the easy-diffusion separation layer) of the neodymium iron boron sintered body by adopting a low-temperature hydrogen activation method. The inventors of the present application found that the surface layer of the activated sintered nd-fe-b absorbs H2H, during the grain boundary diffusion treatment, by high temperature and inert gas pressure infiltration2Can quickly escape when heated and is heavy and thinThe earth element diffusion source provides a diffusion channel, the grain boundary diffusion speed and the grain boundary diffusion depth are increased, heavy rare earth elements diffuse along the grain boundary and form a heavy rare earth-rich shell structure in the surface area of the main phase boundary, Nd atoms are replaced to enter the grain boundary phase, the grain boundary phase volume is increased, meanwhile, the distribution of the rare earth-rich phase at the grain boundary is more continuous and uniform, and therefore the H of the surface layer of the separation layer is greatly improvedcjAnd the Br reduction amplitude of the surface layer of the separation layer is smaller. Furthermore, the raw materials of the substrate layer are designed according to the composition and the performance of the separation layer subjected to grain boundary diffusion treatment, so that the performance of the innermost layer (close to the substrate layer) of the separation layer after the grain boundary diffusion treatment is close to that of the substrate layer, the gradient difference of performances such as coercive force, residual magnetism and the like does not exist in the prepared large-thickness neodymium iron boron magnetic steel, the problem that the residual magnetism and the coercive force of the large-thickness magnetic steel do not reach the standard can be solved, and the grain boundary diffusion method can only be applied to the production of the large-thickness neodymium iron boron magnetic steel with the orientation direction<5mm magnetic steel. In the large-thickness magnetic steel prepared by the invention, the residual C content in paraffin decomposition is still existed between the separating layer magnetic steel and the substrate layer magnetic steel, so that the resistance between the separating layer magnetic steel and the substrate layer magnetic steel is greatly increased compared with that of the normal whole piece of magnetic steel, the eddy current loss can be reduced in the motor operation process, and the heat productivity can be reduced.
In S2, the inert gas preferably includes one or more of helium, neon, argon, krypton, xenon, and radon, such as argon.
In S2, preferably, the inert gas and H2Is at a pressure of 0.03 to 1MPa, for example 0.05MPa, and the H2The ratio of the mass volume concentration of (a) to the mass volume concentration of the neodymium iron boron sintered body is 0.03-0.1%, for example 0.03%.
In S2, the activation time is preferably 0.5 to 10 hours.
In S2, the activating temperature is preferably 200 to 300 ℃, for example 200, 250 or 300 ℃.
In S2, the grain boundary diffusion treatment may be conventional in the art, and may generally be heating after preparing a layer of diffusion source on the substrate, and this method may reduce the usage amount of heavy rare earth and reduce the cost.
S2, preferably, the method is performed by thermal spraying, coating or vapor deposition on H2And forming a layer of diffusion source on the surface layer of the activated neodymium iron boron sintered body. More preferably, the thickness of the diffusion source is 0.1-3 mm, such as 0.1, 0.5 or 3 mm.
In S2, preferably, the heavy rare earth element is Dy and/or Tb. More preferably, the heavy rare earth elements are from heavy rare earth powders, including Dy powder and/or Tb powder, and/or heavy rare earth fluorides, including terbium fluoride and/or dysprosium fluoride; alternatively, the heavy rare earth element is from a heavy rare earth hydride comprising dysprosium hydride and/or terbium hydride.
In S2, the heating temperature for the grain boundary diffusion treatment is preferably 800 to 1000 DEG C
In S2, the heating time for the grain boundary diffusion treatment is preferably 5 to 20 hours, for example, 5, 10, or 20 hours.
The invention also provides neodymium iron boron magnetic steel which is prepared by the preparation method.
The invention also provides a raw material of the neodymium iron boron magnetic steel, which comprises the following components: 29-30% of Nd and/or Pr; 0.9-1% of B; 0.01-2% of Cu; 0-2% of Co; 0.01-0.2% of Ga; 0-0.5% RH; 0.01 to 0.2% of a high melting point metal;
wherein RH is one or more of Dy, Tb, Ho and Gd; the high-melting-point metal is one or more of Nb, Zr, Ti and Hf; the percentage is mass percentage.
In a preferred embodiment of the present invention, the raw material comprises: the content of Nd is 29.294%; the content of B is 0.948%; the content of Cu is 0.049%; the content of Co is 0%; the content of Ga is 0%; the RH content is 0%; the Zr content is 0.112%; the Fe content is 69.597%; the percentage is mass percentage.
In a preferred embodiment of the present invention, the raw material comprises: the content of Nd was 29.3%; the content of B is 0.92%; the Cu content is 0.4%; the content of Co is 0%; the content of Ga is 0.1%; the RH content is 0%; the Zr content is 0.1%; the content of Al is 0.04%; the Fe content is 69.14%; the percentage is mass percentage.
In a preferred embodiment of the present invention, the raw material comprises: the content of Nd was 29.3%; the content of B is 0.92%; the Cu content is 0.2%; the content of Co is 0%; the content of Ga is 0.4%; the RH content is 0%; the Zr content is 0.1%; the content of Al is 0.04%; the Fe content is 69.04%; the percentage is mass percentage.
In a preferred embodiment of the present invention, the raw material comprises: the content of Nd was 29.3%; the content of B is 0.945%; the Cu content is 0.08%; the content of Co is 0%; the content of Ga is 0.1%; the RH content is 0%; the Zr content is 0.1%; the content of Al is 0.04%; the Fe content is 69.435%; the percentage is mass percentage.
On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.
The reagents and starting materials used in the present invention are commercially available.
The positive progress effects of the invention are as follows:
according to the invention, through the design of the formula elements of the substrate layer and the separation layer, the obtained neodymium iron boron sintered body is subjected to low-temperature hydrogenation treatment, and then subjected to grain boundary diffusion treatment, so that the performance of the innermost layer of the separation layer subjected to the grain boundary diffusion treatment is close to that of the substrate layer, the performance jump problem of large-thickness magnetic steel subjected to the grain boundary diffusion is reduced, meanwhile, the resistance between the separation layer magnetic steel and the substrate layer magnetic steel is greatly increased compared with that of the normal whole magnetic steel, the eddy current loss can be reduced in the motor operation process, and the heat productivity is reduced. The method can prepare the magnetic remanence Br of more than 14.8kGs and the coercive force HcjAbove 20kOe, direction of orientation>20mm of large-thickness magnetic steel, less heavy rare earth addition and low cost.
Drawings
Fig. 1 shows the properties of the magnetic steel prepared in example 1.
FIG. 2 is an EPMA plot of the cross-section of the magnetic steel prepared in example 1.
Detailed Description
The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.
Example 1
Step 1:
in order to solve the defects that the remanence and the coercive force of the large-thickness magnetic steel do not reach the standard and the grain boundary diffusion method can only be suitable for producing the magnetic steel with the orientation direction of less than 5mm, the raw materials of the substrate layer are designed according to the composition and the performance of the separation layer subjected to the grain boundary diffusion treatment, so that the performance of the innermost layer (namely, the layer close to the substrate) of the separation layer after the grain boundary diffusion treatment is close to that of the substrate layer.
The raw material of the substrate layer is prepared by smelting, hydrogen crushing and pulverizing alloy powder with the same components and content as the raw material of the substrate layer.
The raw material of the separation layer is prepared by smelting, hydrogen crushing and pulverizing alloy powder with the same components and content as the raw material of the separation layer.
The base layer comprises the following raw materials in percentage by weight:
| example 1 | PrNd | Tb | B | Fe | Cu | Co | Zr | Ga |
| Weight ratio (%) | 28.828 | 0.489 | 0.947 | 69.031 | 0.049 | 0.544 | 0.112 | 0 |
The separating layer comprises the following raw materials in percentage by weight:
| example 1 | Nd | Tb | B | Fe | Cu | Co | Zr | Ga |
| Weight ratio (%) | 29.294 | 0 | 0.948 | 69.597 | 0.049 | 0 | 0.112 | 0 |
(1) Smelting: smelting and casting in a medium-frequency vacuum induction rapid hardening melt-spun furnace; the thickness of the obtained throwing piece is 0.25 mm.
(2) Hydrogen breaking: hydrogen breaking is divided into hydrogen absorption treatment and dehydrogenation treatment; the hydrogen absorption treatment was carried out under a hydrogen pressure of 0.12 MPa. The dehydrogenation treatment is carried out at a temperature of 550 ℃; the time of dehydrogenation treatment is 4 h; after dehydrogenation treatment, the hydrogen content of the powder is generally 500-1500 ppm. When the hydrogen breaking pressure variation range is less than 0.04MPa/10min, the hydrogen absorption treatment is considered to be completed.
(3) The pulverization is carried out by jet milling. Before jet milling, an antioxidant and/or a lubricant are also added, wherein the antioxidant and/or the lubricant are special antioxidants and lubricants (the type of the antioxidant is No. 3, and the type of the lubricant is No. 6) for magnetic materials produced by New Tianjin Yuesheng material research institute. The antioxidant accounts for 0.8 wt% of the fine powder. The lubricant accounts for 0.8 wt% of the mass of the fine powder.
The raw material for the base layer and the raw material for the separation layer are prepared separately.
Step 2:
the mold was divided into three layers perpendicular to the orientation direction by a rubber mold under Ar gas protection with two paraffin spacers in the middle (1.0% dispersant in the paraffin spacer). Respectively, separation layer-substrate layer-separation layer. The thickness of the separation layer is 6mm, the thickness of the base layer is 8mm, and the thickness of the paraffin partition is 0.5 mm.
The source of the separating layerThe materials are uniformly poured into the separation layer, and the raw materials of the substrate layer are uniformly poured into the substrate layer. The pre-compaction density is 2.5g/cm3Followed by 5 times orientation and demagnetization in a pulsed magnetic field, and then vacuum sealing.
And step 3:
putting the magnet sealed in vacuum into isostatic pressing with oil temperature of 130 ℃, keeping the pressure for 15 minutes, and obtaining a neodymium iron boron green compact with the density of 5g/cm3And most of the paraffin in the middle interlayer is extruded or melted.
And 4, step 4:
and (2) placing the neodymium iron boron green compact in a vacuum sintering furnace, wherein the sintering can be divided into 3 processes, namely decomposing and discharging organic matters at the temperature of 200-plus-400 ℃, discharging redundant gas of the neodymium iron boron green compact at the temperature of 500-plus-900 ℃, and sintering the neodymium iron boron green compact in Ar gas or vacuum at the temperature of 1000-plus-1200 ℃ to obtain the neodymium iron boron sintered body.
And 5:
and grinding, pickling and sandblasting the neodymium iron boron sintered body for later use.
Step 6:
placing the post-treated neodymium iron boron sintered body in a diffusion treatment furnace, introducing Ar gas, adding hydrogen gas, inert gas and H after the temperature in the furnace is 250 DEG C2Pressure of 0.05MPa, H2The ratio of the mass volume concentration of the neodymium iron boron sintered body to the mass volume concentration of the neodymium iron boron sintered body is 0.03%, the activation time is 0.5h, the activity of the surface layer (namely the surface layer of the easy-to-diffuse separation layer) of the neodymium iron boron sintered body is excited through low-temperature hydrogen activation treatment, and favorable conditions are created for subsequently improving the diffusion speed and the diffusion depth.
And 7:
and forming a heavy rare earth diffusion source Tb layer with the thickness of 0.5mm on the surface layer of the interlayer magnet by adopting a thermal spraying method on the neodymium iron boron sintered body subjected to hydrogenation activity treatment.
Then heated to 800-. At a temperature range of 800-2H absorbed by surface layer of sintered Nd-Fe-B body during activation treatment2Quickly escape, and simultaneously provide diffusion channels for Dy or Tb diffusion sources, thereby increasing the diffusion speed and diffusion depth of interlayer magnetic steel。
The thickness of the prepared neodymium iron boron magnetic steel in the orientation direction is 20 mm.
Example 2
The parameters in the preparation process were the same as those in example 1 except that hydrogen was added in a volume fraction of 0.065% in step 6.
Example 3
The parameters in the remaining manufacturing process were the same as those in example 1 except for the raw material of the base layer and the raw material of the separation layer.
The base layer comprises the following raw materials:
| example 3 | PrNd | Tb | B | Fe | Cu | Co | Zr | Ga |
| Weight ratio (%) | 29.25 | 0.55 | 0.92 | 68.48 | 0.06 | 0.5 | 0.14 | 0.1 |
The raw material formula of the separating layer is as follows:
| example 3 | Nd | Tb | B | Fe | Cu | Co | Zr | Ga | Al |
| Weight ratio (%) | 29.3 | 0 | 0.92 | 69.14 | 0.4 | 0 | 0.1 | 0.1 | 0.04 |
Example 4
The parameters in the remaining manufacturing process were the same as those in example 1 except for the raw material of the base layer and the raw material of the separation layer.
The base layer comprises the following raw materials:
| example 4 | PrNd | Tb | B | Fe | Cu | Co | Zr | Ga |
| Weight ratio (%) | 29.25 | 0.55 | 0.92 | 68.48 | 0.06 | 0.5 | 0.14 | 0.1 |
The raw material formula of the separating layer is as follows:
| example 4 | Nd | Tb | B | Fe | Cu | Co | Zr | Ga | Al |
| Weight ratio (%) | 29.3 | 0 | 0.92 | 69.04 | 0.2 | 0 | 0.1 | 0.4 | 0.04 |
Example 5
The parameters in the remaining manufacturing process were the same as those in example 1 except for the raw material of the base layer and the raw material of the separation layer.
The base layer comprises the following raw materials:
| example 5 | PrNd | Tb | B | Fe | Cu | Co | Zr | Ga |
| Weight ratio (%) | 29.25 | 0.55 | 0.92 | 68.48 | 0.06 | 0.5 | 0.14 | 0.1 |
The raw material formula of the separating layer is as follows:
| example 5 | Nd | Tb | B | Fe | Cu | Co | Zr | Ga | Al |
| Weight ratio (%) | 29.3 | 0 | 0.945 | 69.435 | 0.08 | 0 | 0.1 | 0.1 | 0.04 |
Comparative example 1
Comparative example 1 is a preparation process of a base layer material.
Step 1:
the raw material of the substrate layer is prepared by smelting, hydrogen crushing and pulverizing alloy powder with the same components and content as the raw material of the substrate layer.
The base layer comprises the following raw materials:
| comparative example 1 | PrNd | Tb | B | Fe | Cu | Co | Zr | Ga |
| Weight ratio (%) | 28.828 | 0.489 | 0.947 | 69.031 | 0.049 | 0.544 | 0.112 | 0 |
Step 2:
the base layer material was poured into a rubber mold (not containing a paraffin spacer). The pre-compaction density is 2.5g/cm3Followed by 5 times orientation and demagnetization in a pulsed magnetic field, and then vacuum sealing.
And step 3:
putting the magnet sealed in vacuum into isostatic pressing with oil temperature of 130 ℃, keeping the pressure for 15 minutes, and obtaining a neodymium iron boron green compact with the density of 5g/cm3。
And 4, step 4:
and (2) placing the neodymium iron boron green compact in a vacuum sintering furnace, wherein the sintering can be divided into 3 processes, namely decomposing and discharging organic matters at the temperature of 200-plus-400 ℃, discharging redundant gas of the neodymium iron boron green compact at the temperature of 500-plus-900 ℃, and sintering in Ar gas at the temperature of 1000-plus-1200 ℃ to obtain the neodymium iron boron sintered body.
And 5:
and grinding, pickling and sandblasting the neodymium iron boron sintered body for later use.
The orientation thickness of the prepared neodymium iron boron magnetic steel is 20 mm.
Comparative example 2
Comparative example 2 was not subjected to the low temperature hydrotreating process. Namely, steps 1 to 5 are the same as steps 1 to 5 of example 1.
Step 6:
and forming a heavy rare earth diffusion source Tb layer with the thickness of 0.5mm on the surface layer of the interlayer magnet by adopting a thermal spraying method on the neodymium iron boron sintered body subjected to hydrogenation activity treatment.
Then heated to 800-.
The orientation thickness of the prepared neodymium iron boron magnetic steel is 20 mm.
Comparative example 3
The parameters in the remaining manufacturing process except for the raw material of the base layer were the same as those in comparative example 1.
The base layer comprises the following raw materials:
| comparative example 3 | PrNd | Tb | B | Fe | Cu | Co | Zr | Ga |
| Weight ratio (%) | 29.5 | 1 | 0.947 | 67.848 | 0.049 | 0.544 | 0.112 | 0 |
Comparative example 4
The mold of comparative example 4 was free of paraffin spacers and the parameters in the remaining manufacturing process were the same as the manufacturing process of example 1.
Effects of the embodiment
The magnetic properties of example 1 are shown in fig. 1 and table 1, and the magnetic properties of the remaining examples and comparative examples are shown in table 1. Fig. 2 is an EPMA diagram of the cross section of the magnetic steel prepared in example 1, and the diffusion depth of Tb element (gray white/white bright spot in fig. 2) is obviously increased and Tb distribution is relatively uniform by EPMA detection after Tb element diffusion.
TABLE 1 comparison of magnetic Performance data for examples and comparative examples
Claims (23)
1. A preparation method of neodymium iron boron magnetic steel is characterized by comprising the following steps:
s1, pouring the raw materials of the base layer and the separating layer into a mold with a paraffin partition plate for pressing to obtain a neodymium iron boron green compact; sintering the neodymium iron boron green compact to obtain a neodymium iron boron sintered body;
the neodymium iron boron pressed blank is of a layered structure and comprises a base layer and a separating layer, wherein a paraffin layer is arranged between the base layer and the separating layer;
the raw materials of the substrate layer comprise: 28.2-29.2% of Nd and/or Pr; 0.9-1% of B; 0.01-2% of Cu; 0.01-2% of Co; 0.01-0.2% of Ga; 0.1-1% RH; 0.01-0.2% of high-melting-point metal, and the balance being Fe;
the raw materials of the separation layer comprise: 29-30% of Nd and/or Pr; 0.9-1% of B; 0.01-2% of Cu; 0-2% of Co; 0.01-0.2% of Ga; 0-0.5% RH; 0.01-0.2% of high-melting-point metal, and the balance being Fe;
wherein RH is one or more of Dy, Tb, Ho and Gd; the high-melting-point metal is one or more of Nb, Zr, Ti and Hf; the percentage is mass percentage;
s2, putting the neodymium iron boron sintered body in inert gas and H2After activation under the condition, carrying out grain boundary diffusion treatment by taking heavy rare earth elements as diffusion sources;
the inert gas and H2The pressure of (A) is 0.03 to 1MPa, and H2The ratio of the mass volume concentration of the neodymium iron boron sintered body to the mass volume concentration of the neodymium iron boron sintered body is 0.03-0.1%;
the activation temperature is 200-300 ℃.
2. The method according to claim 1, wherein the neodymium-iron-boron green compact has a 3-5 layer structure comprising 3 layers of a spacer layer, a paraffin layer and a base layer from top to bottom, or 5 layers of the spacer layer, the paraffin layer, the base layer, the paraffin layer and the spacer layer;
and/or the step of S1 comprises the following steps: respectively pouring the raw materials of the substrate layer and the separating layer into a mould, prepressing, vacuum sealing, and in a pulse magnetic field, orienting, demagnetizing and hot isostatic pressing to obtain the neodymium iron boron green compact; wherein, a paraffin partition board vertical to the orientation direction is arranged in the mould;
and/or the thickness of the substrate layer is 6-10 mm;
and/or the thickness of the separation layer is 4-8 mm;
and/or the raw materials of the separation layer comprise: the content of Al is less than 0.08%;
and/or when the raw material of the separation layer contains Nd and Pr, the ratio of Pr: the mass ratio of Nd is 1: 3-1: 4;
and/or the raw materials of the separation layer are prepared by smelting, hydrogen crushing and pulverizing alloy powder with the same components and content as the raw materials of the separation layer;
and/or when the raw material of the matrix layer comprises Nd and Pr, the ratio of Nd: the mass ratio of Pr is 1: 3-1: 4;
and/or the raw material of the substrate layer is prepared by smelting, hydrogen crushing and pulverizing alloy powder with the same components and content as the raw material of the substrate layer.
3. The method according to claim 2, wherein the pulsed magnetic field has a magnetic field strength of 4T or more;
and/or the mould is a rubber mould or a plastic soft material mould;
and/or after the prepressing, the density of the raw material of the base layer and the raw material of the separation layer is 2-3 g/cm3；
And/or, said orienting and said demagnetizing are performed a plurality of times in a pulsed magnetic field;
and/or the hot isostatic pressing is carried out at the oil temperature of 70-200 ℃;
and/or the hot isostatic pressing time is 1-30 min;
and/or the density of the neodymium iron boron green compact is 4.0-5.5 g/cm3；
And/or the thickness of the paraffin partition plate is 0.1-2 mm;
and/or the paraffin partition contains a dispersant.
4. The method of claim 3, wherein the dispersant is cyclohexane or cyclopentane.
5. The method according to claim 3, wherein the dispersant accounts for 0.5 to 1.5 wt% of the paraffin separator in terms of mass ratio/volume ratio.
6. The method according to claim 3, wherein the orientation and the demagnetization are performed more than 3 times in a pulsed magnetic field.
7. The method of claim 1, wherein the starting materials for the spacer layer comprise: the content of Nd is 29.294%; the content of B is 0.948%; the content of Cu is 0.049%; the content of Co is 0%; the content of Ga is 0%; the RH content is 0%; the Zr content is 0.112%; the Fe content is 69.597%; the percentage is mass percentage;
or, the raw materials of the separation layer comprise: the content of Nd was 29.3%; the content of B is 0.92%; the Cu content is 0.4%; the content of Co is 0%; the content of Ga is 0.1%; the RH content is 0%; the Zr content is 0.1%; the content of Al is 0.04%; the Fe content is 69.14%; the percentage is mass percentage;
or, the raw materials of the separation layer comprise: the content of Nd was 29.3%; the content of B is 0.92%; the Cu content is 0.2%; the content of Co is 0%; the content of Ga is 0.4%; the RH content is 0%; the Zr content is 0.1%; the content of Al is 0.04%; the Fe content is 69.04%; the percentage is mass percentage;
or, the raw materials of the separation layer comprise: the content of Nd was 29.3%; the content of B is 0.945%; the Cu content is 0.08%; the content of Co is 0%; the content of Ga is 0.1%; the RH content is 0%; the Zr content is 0.1%; the content of Al is 0.04%; the Fe content is 69.435%; the percentage is mass percentage;
and/or the raw material of the substrate layer comprises: the content of Nd and Pr is 28.828%; pr: the mass ratio of Nd is 1: 3; the content of Tb is 0.489%; the content of B is 0.947%; the Fe content is 69.031%; the content of Cu is 0.049%; the content of Co is 0.544%; the Zr content is 0.112%; the content of Ga is 0%; the percentage is mass percentage;
or, the raw material of the substrate layer comprises: the content of Nd and Pr was 29.25%; pr: the mass ratio of Nd is 1: 3; the content of Tb is 0.55%; the content of B is 0.92%; the Fe content is 68.48%; the Cu content is 0.06%; the content of Co is 0.5%; the Zr content is 0.14%; the content of Ga is 0.1%; the percentage is mass percentage.
8. The preparation method according to claim 3, wherein the smelting is carried out in a medium-frequency vacuum induction rapid hardening melt-spun furnace for smelting and casting;
and/or the thickness of the throwing piece prepared by smelting is 0.15-0.4 mm;
and/or the hydrogen breaking is divided into hydrogen absorption treatment and dehydrogenation treatment;
and/or the pulverization is airflow milling pulverization;
and/or, before milling, adding antioxidant and/or lubricant;
and/or, the sintering is vacuum sintering or atmosphere sintering at 1000-1200 ℃;
and/or the atmosphere is an inert gas atmosphere and comprises one or more of helium, neon, argon, krypton, xenon and radon;
and/or in S1, grinding, pickling and sand blasting the neodymium iron boron sintered body for later use.
9. The preparation method of claim 8, wherein the thickness of the melt-spun piece prepared by smelting is 0.20-0.27 mm.
10. The production method according to claim 8, wherein the hydrogen absorption treatment is performed under a hydrogen pressure of 0.1 to 0.15 MPa.
11. The method of claim 8, wherein the dehydrogenation process is carried out at a temperature of 500 ℃ to 600 ℃.
12. The method according to claim 8, wherein the dehydrogenation treatment is carried out for 2 to 4 hours.
13. The method according to claim 8, wherein after the dehydrogenation treatment, the powder has a hydrogen content of 500 to 2000 ppm.
14. The method according to claim 8, wherein the antioxidant is 0.5 to 1.5 wt% based on the mass of the fine powder obtained after the pulverization by the jet mill.
15. The method of claim 14, wherein the antioxidant is present in an amount of 0.8 to 1.2 wt% based on the mass of the fine powder.
16. The production method according to claim 8, wherein the lubricant is 0.5 to 1.5 wt% based on the mass of the fine powder obtained after the jet mill pulverization.
17. The method of claim 16, wherein the lubricant comprises 0.8 to 1.2 wt% of the fine powder.
18. The method of claim 1, wherein in S2, the inert gas includes one or more of helium, neon, argon, krypton, xenon, and radon;
and/or in S2, the activation time is 0.5-10 h.
19. The method of claim 1, wherein in S2, the thermal spraying, coating or vapor deposition method is used in H2Forming a layer of diffusion source on the surface layer of the activated neodymium iron boron sintered body;
and/or the thickness of the diffusion source is 0.1-3 mm;
and/or, in S2, the heavy rare earth element is Dy and/or Tb;
and/or in S2, the heating temperature of the grain boundary diffusion treatment is 800-1000 ℃;
and/or in S2, the heating time of the grain boundary diffusion treatment is 5-20 h.
20. The method of claim 19, wherein the heavy rare earth element is derived from a heavy rare earth powder comprising Dy powder and/or Tb powder, and/or a heavy rare earth fluoride comprising terbium fluoride and/or dysprosium fluoride; alternatively, the heavy rare earth element is from a heavy rare earth hydride comprising dysprosium hydride and/or terbium hydride.
21. A neodymium iron boron magnetic steel, which is characterized by being prepared by the preparation method in any one of claims 1-20.
22. A raw material for ndfeb magnetic steel as set forth in claim 21, comprising a raw material for a base layer and a raw material for a separation layer, the raw material for the base layer comprising: 28.2-29.2% of Nd and/or Pr; 0.9-1% of B; 0.01-2% of Cu; 0.01-2% of Co; 0.01-0.2% of Ga; 0.1-1% RH; 0.01-0.2% of high-melting-point metal, and the balance being Fe; the raw materials of the separation layer comprise: 29-30% of Nd and/or Pr; 0.9-1% of B; 0.01-2% of Cu; 0-2% of Co; 0.01-0.2% of Ga; 0-0.5% RH; 0.01-0.2% of high-melting-point metal, and the balance being Fe;
wherein RH is one or more of Dy, Tb, Ho and Gd; the high-melting-point metal is one or more of Nb, Zr, Ti and Hf; the percentage is mass percentage.
23. The raw material for ndfeb magnetic steel as set forth in claim 22, wherein said raw material for said substrate layer comprises: the content of Nd and Pr is 28.828%; pr: the mass ratio of Nd is 1: 3; the content of Tb is 0.489%; the content of B is 0.947%; the Fe content is 69.031%; the content of Cu is 0.049%; the content of Co is 0.544%; the Zr content is 0.112%; the content of Ga is 0%; the percentage is mass percentage; the raw materials of the separation layer comprise: the content of Nd is 29.294%; the content of B is 0.948%; the content of Cu is 0.049%; the content of Co is 0%; the content of Ga is 0%; the RH content is 0%; the Zr content is 0.112%; the Fe content is 69.597%; the percentage is mass percentage;
or, the raw material of the substrate layer comprises: the content of Nd and Pr was 29.25%; pr: the mass ratio of Nd is 1: 3; the content of Tb is 0.55%; the content of B is 0.92%; the Fe content is 68.48%; the Cu content is 0.06%; the content of Co is 0.5%; the Zr content is 0.14%; the content of Ga is 0.1%; the percentage is mass percentage; the raw materials of the separation layer comprise: the content of Nd was 29.3%; the content of B is 0.92%; the Cu content is 0.4%; the content of Co is 0%; the content of Ga is 0.1%; the RH content is 0%; the Zr content is 0.1%; the content of Al is 0.04%; the Fe content is 69.14%; the percentage is mass percentage;
or, the raw material of the substrate layer comprises: the content of Nd and Pr was 29.25%; pr: the mass ratio of Nd is 1: 3; the content of Tb is 0.55%; the content of B is 0.92%; the Fe content is 68.48%; the Cu content is 0.06%; the content of Co is 0.5%; the Zr content is 0.14%; the content of Ga is 0.1%; the percentage is mass percentage; the raw materials of the separation layer comprise: the content of Nd was 29.3%; the content of B is 0.92%; the Cu content is 0.2%; the content of Co is 0%; the content of Ga is 0.4%; the RH content is 0%; the Zr content is 0.1%; the content of Al is 0.04%; the Fe content is 69.04%; the percentage is mass percentage;
or, the raw material of the substrate layer comprises: the content of Nd and Pr was 29.25%; pr: the mass ratio of Nd is 1: 3; the content of Tb is 0.55%; the content of B is 0.92%; the Fe content is 68.48%; the Cu content is 0.06%; the content of Co is 0.5%; the Zr content is 0.14%; the content of Ga is 0.1%; the percentage is mass percentage; the raw materials of the separation layer comprise: the content of Nd was 29.3%; the content of B is 0.945%; the Cu content is 0.08%; the content of Co is 0%; the content of Ga is 0.1%; the RH content is 0%; the Zr content is 0.1%; the content of Al is 0.04%; the Fe content is 69.435%; the percentage is mass percentage.
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