CN111383833A - Grain boundary diffusion method for rare earth neodymium iron boron magnet - Google Patents
Grain boundary diffusion method for rare earth neodymium iron boron magnet Download PDFInfo
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- CN111383833A CN111383833A CN201911096499.XA CN201911096499A CN111383833A CN 111383833 A CN111383833 A CN 111383833A CN 201911096499 A CN201911096499 A CN 201911096499A CN 111383833 A CN111383833 A CN 111383833A
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- 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
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- 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
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- 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
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Abstract
The invention relates to the technical field of permanent magnet preparation, and discloses a rare earth neodymium iron boron magnet grain boundary diffusion method, which comprises the following steps: preparing an RTM alloy casting sheet containing heavy rare earth elements; preparing a neodymium iron boron magnet blank and processing the blank into a blank square sheet; carrying out surface activation on the blank square sheet; overlapping the RTM alloy casting sheet and the blank square sheet with the activated surface in a graphite box up and down until the graphite box is filled; and carrying out vacuum heat treatment on the graphite box filled with the product to obtain the neodymium iron boron magnet after diffusion treatment. The invention adopts the crystal boundary diffusion process, so that heavy rare earth elements in the RTM alloy cast sheet enter the magnet from the surface of the magnet through the crystal boundary diffusion and exist in the grain boundary region, the magnetic hardening of the surface region of the main phase grains is realized, and the prepared sintered neodymium-iron-boron magnet with high intrinsic coercivity has small remanence decline amplitude and obviously reduces the consumption of the heavy rare earth elements.
Description
Technical Field
The invention relates to the technical field of permanent magnet preparation, in particular to a grain boundary diffusion method of a rare earth neodymium iron boron magnet.
Background
The sintered Nd-Fe-B magnet is a permanent magnet material with excellent magnetic performance, is also an important basic functional material, and is widely applied to the high-tech fields of wind power generation equipment, electric vehicles, hybrid electric vehicles, variable frequency electrical devices, industrial energy-saving motors and the like. With the rapid development of high technology fields, the demand for sintered nd-fe-b magnets with high magnetic performance, high use temperature, and high working stability is increasing. The sintered neodymium iron boron magnet with high intrinsic coercivity is a basic condition that the sintered neodymium iron boron magnet has high use temperature and high working stability, and in the prior art, the addition of heavy rare earth elements such as Dy and Tb is a main technical means for improving the intrinsic coercivity of the sintered neodymium iron boron magnet produced industrially.
At present, the intrinsic coercive force of the magnet can also be effectively improved by adding a certain amount of oxide, fluoride, hydride powder of the heavy rare earth elements Dy and Tb or alloy powder thereof in the powder preparation step generally through adding the heavy rare earth elements Dy and Tb in the alloy preparation step or applying a double-alloy process. For example, a "neodymium iron boron magnet and a method for manufacturing the same" disclosed in chinese patent literature, whose publication number CN108364739A, is made of a first neodymium iron boron alloy and a second neodymium iron boron alloy of two formulations through secondary press forming and high temperature sintering, where the first and second neodymium iron boron alloys are, by mass: (Nd, RE)aBbMcFe100-a-b-cWherein a is more than or equal to 26 and less than or equal to 33, b is more than or equal to 0.88 and less than or equal to 1.1, c is more than or equal to 0 and less than or equal to 10, RE is one or more of rare earth elements La, Ce, Pr, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and M is one or more of Co, Al, Cu, Ga, Nb, Mo, Ti, Zr and V.
In the alloy preparation link, heavy rare earth elements such as Dy and Tb are added, and the heavy rare earth elements such as Dy and Tb are used for partially replacing Nd elements in the neodymium iron boron magnet, so that the anisotropy field of main phase magnetic crystal can be improved, and the intrinsic coercive force of the magnet can be improved; in addition, the reserves of heavy rare earth elements are limited, and the material cost is greatly increased by adopting the traditional method for replacement.
The double-alloy method is to separately process the main phase alloy and the rare earth-rich phase alloyThe composition design is carried out, and the composition measurement of the main phase alloy is closer to Nd2Fe14The method can well distribute medium-heavy rare earth elements at the grain boundary of the main phase, but inevitably diffuse part of heavy rare earth elements into the main phase in the high-temperature sintering process to thicken the epitaxial layer of the main phase grains, thereby reducing the remanence. Therefore, the coercive force of the magnet is ensured to be improved, and meanwhile, the remanence is not reduced or is reduced little, so that the problems of how to reasonably and effectively distribute elements such as Dy, Tb and Ho at the boundary of the main phase of the magnet and how to reduce the addition amount of the elements such as Dy, Tb and Ho are urgently needed to be solved.
Disclosure of Invention
The invention provides a rare earth neodymium iron boron magnet grain boundary diffusion method, aiming at overcoming the problems that the remanence of a magnet is obviously reduced, the consumption quantity of heavy rare earth elements is large and the manufacturing cost of a product is increased when the intrinsic coercive force of an industrially produced sintered neodymium iron boron magnet is improved by adding the heavy rare earth elements such as Dy, Tb and the like in the prior art, so that the original remanence and the maximum magnetic energy product of the magnet are not obviously reduced while the intrinsic coercive force of the neodymium iron boron magnet is effectively improved, the use amount of the heavy rare earth elements is controlled, and the production cost is saved.
In order to achieve the purpose, the invention adopts the following technical scheme:
a grain boundary diffusion method for a rare earth neodymium iron boron magnet comprises the following steps:
(1) preparing an RTM alloy casting sheet containing heavy rare earth elements by using a powder metallurgy method;
(2) preparing a neodymium iron boron magnet blank through smelting, milling, forming and sintering, and processing the blank into a blank square sheet;
(3) carrying out surface activation on the blank square sheet;
(4) the RTM alloy casting sheet is flatly laid at the bottom of the graphite box, and the blank square sheet after surface activation is placed on the RTM alloy casting sheet, so that the RTM alloy casting sheet and the blank square sheet after surface activation are overlapped up and down until the graphite box is filled;
(5) and carrying out vacuum heat treatment on the graphite box filled with the product, and forming the neodymium iron boron magnet after diffusion treatment by using blank square sheets.
The invention is characterized in that an RTM alloy casting piece containing heavy rare earth elements and a neodymium iron boron magnet blank square piece with activated surface are overlapped up and down, after vacuum heat treatment, the heavy rare earth elements such as Dy, Tb and the like in the RTM alloy casting piece penetrate through the crystal boundary of the magnet from the surface of the blank square piece to enter the interior of a sintered body, and the heavy rare earth elements are oriented to a main phase Nd from the crystal boundary2Fe14B, internal diffusion, after the treatment by the method, heavy rare earth elements can be effectively distributed in a grain boundary region, magnetic hardening of a main phase grain surface region is realized, the magnetic crystal anisotropy field of a grain boundary phase and a main phase transition region is improved, the formation of a reverse magnetization domain nucleus is inhibited, and the intrinsic coercivity is improved.
In the grain boundary diffusion heavy rare earth process, heavy rare earth elements are firstly made into RTM alloy cast pieces, and then the RTM alloy cast pieces are overlapped with the neodymium iron boron magnet blank square pieces up and down for vacuum heat treatment, so that the addition of the heavy rare earth elements is convenient to control, the heavy rare earth elements can be effectively prevented from diffusing into a main phase and only distributed in a grain boundary region, and the sintered neodymium iron boron magnet with high intrinsic coercive force prepared in the way has small residual magnetism reduction amplitude and obviously reduces the consumption of the heavy rare earth elements such as Dy and Tb.
Preferably, R in the RTM alloy cast piece in the step (1) is selected from one or more of heavy rare earth elements; t is Fe and/or Co; m is one or more selected from Al, Si, Cu, Nb, Zr and Ga. Heavy rare earth elements are added into the alloy casting sheet, so that the intrinsic coercive force of the neodymium iron boron magnet can be improved; the temperature resistance of the magnet can be improved by adding Fe and/or Co; the addition of Al can refine alloy grains, reduce the lumpiness of Nd-rich phase and B-rich phase, and improve Nd-rich phase and Nd phase by introducing Al into Nd-rich phase2Fe14The wetting angle of the phase B enables the Nd-rich phase to be distributed more uniformly along the grain boundary, so that the coercive force of the magnet is improved; ga and B have positive enthalpy of mixing and repel each other with B, so that Ga is difficult to enter Nd2Fe14B phase and Ga and Nd have large negative mixing enthalpy, and from a binary phase diagram, Ga reacts with Nd phase to form a low-melting-point compound,therefore, the distribution of Ga in the sintered Nd-Fe-B magnet is mainly concentrated at grain boundaries and grain boundary intersections, the densification of liquid phase sintering is promoted, and the Nd-rich phase relative to Nd is improved2Fe14The wetting action of the B main phase crystal grains and the Nd-rich phase reaction improve the microstructure of the magnet, and better play a role in decoupling the magnetism among the main phase crystal grains, thereby improving the coercive force of the magnet; the addition of Si, Cu, Nb and Zr can refine grains and reduce the melting point of the alloy, which is beneficial to subsequent diffusion.
Preferably, in the RTM alloy cast piece in the step (1), the mass fraction of R is 60-100%, the mass fraction of T is 0-35 wt%, and the mass fraction of M is 0-5 wt%. In the RTM alloy cast sheet, the mass of each element is in the proportion range, so that the intrinsic coercive force of the finally obtained neodymium iron boron magnet is optimal, and the influence on the remanence of the magnet is minimum.
Preferably, the thickness of the RTM alloy cast sheet in the step (1) is 0.1-100 mm. In the thickness range, each element in the RTM alloy cast sheet can effectively diffuse into the magnet through the surface of the blank square sheet, the quantity of the heavy rare earth elements distributed in the grain boundary area meets the requirement, and the consumption quantity of the heavy rare earth elements is small.
Preferably, the powder metallurgy method in the step (1) adopts a vacuum rapid solidification process. The RTM alloy cast sheet prepared by the vacuum rapid hardening process has good diffusion performance of each element, and can effectively enter the magnet when being overlapped with the blank square sheet for vacuum heat treatment.
Preferably, the thickness of the blank square sheet in the step (2) is 0.1-10 mm. The thickness of the blank square piece is adopted, so that elements in the RTM alloy cast piece can be enabled to diffuse into the magnet from the surface of the blank square piece, and the intrinsic coercive force of the finally prepared neodymium iron boron magnet is effectively improved.
Preferably, the surface activation method in step (3) is: putting the blank square slices into 10-30 g/L degreasing solution at the temperature of 50-80 ℃ for degreasing for 2-5 minutes; putting the deoiled blank square sheet into a 2-4% nitric acid solution for pickling for 30-60 s; and finally, putting the pickled product into alcohol to be soaked for 10-20 s, and drying. After surface activation, oxide skin on the surfaces of the blank square sheets can be removed, so that the surfaces of the blank square sheets are in an activated state, and heavy rare earth elements in the RTM alloy cast sheets can effectively enter the inside of the magnet during subsequent diffusion treatment.
Preferably, the vacuum heat treatment method in the step (4) is: diffusing at the high temperature of 800-1000 ℃ for 10-20 h, and then tempering at the low temperature of 450-600 ℃ for 2-8 h. Under the vacuum heat treatment process, heavy rare earth elements in the RTM alloy cast sheet can effectively enter the blank square sheet through crystal diffusion and are distributed in a grain boundary area, and the prepared neodymium iron boron magnet has the best magnetic property.
Therefore, the invention has the following beneficial effects:
(1) by adopting a grain boundary diffusion method, Dy, Tb and other heavy rare earth elements in the RTM alloy cast piece penetrate through the grain boundary of the magnet from the surface of a blank square piece to enter the interior of a sintered body and are transferred from the grain boundary to a main phase Nd2Fe14B, internal diffusion, after the treatment by the method, heavy rare earth elements can be effectively distributed in a grain boundary region, magnetic hardening of a main phase grain surface region is realized, the magnetic crystal anisotropy field of a grain boundary phase and a main phase transition region is improved, the formation of a reverse magnetization domain nucleus is inhibited, and the intrinsic coercivity is improved;
(2) in the grain boundary diffusion process, heavy rare earth elements are firstly made into RTM alloy cast pieces, and then the RTM alloy cast pieces are overlapped with square pieces of a neodymium iron boron magnet blank up and down for vacuum heat treatment, so that the addition of the heavy rare earth elements is convenient to control, the heavy rare earth elements can be effectively prevented from diffusing into a main phase and are only distributed in a grain boundary region, and the sintered neodymium iron boron magnet with high intrinsic coercivity prepared in the way has small residual magnetism reduction amplitude and obviously reduces the consumption of the heavy rare earth elements such as Dy, Tb and the like;
(3) the RTM alloy cast sheet is made of R, T, M three metals, the heavy rare earth element R can improve the coercive force of the neodymium iron boron magnet, the T element selected from Fe and/or Co can improve the temperature resistance of the magnet, and the M element selected from one or more of Al, Si, Cu, Nb, Zr and Ga can refine grains and reduce the melting point of the alloy to facilitate subsequent diffusion, so that the coercive force of the neodymium iron boron magnet is further improved.
Detailed Description
The invention is further described with reference to specific embodiments.
Example 1:
a grain boundary diffusion method for a rare earth neodymium iron boron magnet comprises the following steps:
(1) the RTM alloy cast sheet with the thickness of 0.3mm is prepared by a vacuum rapid hardening process according to the following formula: r is Tb, T is Fe, M is Al, and the mass percentages of Tb, Fe and Al in the powder are 75%, 20% and 5% respectively;
(2) preparing an N48H neodymium iron boron magnet blank through smelting, milling, molding and sintering steps, and processing the blank into a blank square sheet with the size of 42 × 31 × 3mm (3mm is the orientation direction);
(3) surface activation is carried out on the blank square sheet: putting the blank square slices into a degreasing solution with the temperature of 60 ℃ and the concentration of 20g/L for degreasing for 3 minutes; putting the deoiled blank square slice into a 3% nitric acid solution for pickling for 45 s; finally, putting the product after the acid washing into alcohol to be soaked for 15s and then drying;
(4) the RTM alloy casting sheet is flatly laid at the bottom of the graphite box, and the blank square sheet after surface activation is placed on the RTM alloy casting sheet, so that the RTM alloy casting sheet and the blank square sheet after surface activation are overlapped up and down until the graphite box is filled;
(5) putting the graphite box filled with the product into a sintering furnace, and vacuumizing to 10 DEG-2Heating to 900 ℃ below Pa for high-temperature diffusion treatment for 18h, and then performing low-temperature tempering secondary treatment for 5h at 500 ℃ to form the neodymium-iron-boron magnet after diffusion treatment by blank square pieces.
Example 2:
a grain boundary diffusion method for a rare earth neodymium iron boron magnet comprises the following steps:
(1) the RTM alloy cast sheet with the thickness of 0.28mm is prepared by a vacuum rapid hardening process according to the following formula: r is Dy, T is Co, and M is Cu; the mass percentages of Dy, Co and Cu in the powder are respectively 80%, 5% and 5%;
(2) preparing an N42SH neodymium iron boron magnet blank through smelting, milling, molding and sintering steps, and processing the blank into blank square sheets with the size of 50 × 20 × 4mm (4mm is the orientation direction);
(3) surface activation is carried out on the blank square sheet: putting the blank square slices into 25g/L degreasing solution at the temperature of 60 ℃ for degreasing for 3.5 minutes; putting the deoiled blank square sheet into 3.5% nitric acid solution for pickling for 50 s; finally, putting the product after the acid washing into alcohol to be soaked for 18s and then drying;
(4) the RTM alloy casting sheet is flatly laid at the bottom of the graphite box, and the blank square sheet after surface activation is placed on the RTM alloy casting sheet, so that the RTM alloy casting sheet and the blank square sheet after surface activation are overlapped up and down until the graphite box is filled;
(5) putting the graphite box filled with the product into a sintering furnace, and vacuumizing to 10 DEG-2Heating to 890 ℃ below Pa, performing high-temperature diffusion treatment for 20h, performing low-temperature tempering secondary treatment for 5h at 490 ℃, and forming the neodymium-iron-boron magnet after diffusion treatment by blank square pieces.
Example 3:
a grain boundary diffusion method for a rare earth neodymium iron boron magnet comprises the following steps:
(1) an RTM alloy cast sheet with the thickness of 0.32mm is prepared by a vacuum rapid hardening process according to the following formula: r is Nd, T is Co, and M is Al; the mass percentages of Nd, Co and Cu in the powder are respectively 75%, 15% and 10%;
(2) preparing an N50 neodymium iron boron magnet blank through smelting, pulverizing, molding and sintering, and processing the blank into blank square sheets with the size of 50 × 20 × 2.5mm (2.5mm is the orientation direction);
(3) surface activation is carried out on the blank square sheet: putting the blank square slices into 26g/L degreasing solution at the temperature of 65 ℃ for degreasing for 4 minutes; putting the deoiled blank square piece into a 3.6% nitric acid solution for pickling for 45 s; finally, putting the product after the acid washing into alcohol to be soaked for 16s and then drying;
(4) the RTM alloy casting sheet is flatly laid at the bottom of the graphite box, and the blank square sheet after surface activation is placed on the RTM alloy casting sheet, so that the RTM alloy casting sheet and the blank square sheet after surface activation are overlapped up and down until the graphite box is filled;
(5) putting the graphite box filled with the product into a sintering furnace, and vacuumizing to 10 DEG-2Heating to 910 ℃ below Pa for 16h of high-temperature diffusion treatment, and then carrying out low-temperature tempering secondary treatment at 495 ℃ for 5h to obtain the blank square piece which is subjected to diffusion treatment.
Example 4:
a grain boundary diffusion method for a rare earth neodymium iron boron magnet comprises the following steps:
(1) the RTM alloy cast sheet with the thickness of 0.3mm is prepared by a vacuum rapid hardening process according to the following formula: r is Dy and Tb, T is Fe, M is Al, and the mass percentages of Dy, Tb, Fe and Al in the powder are respectively 50%, 25%, 20% and 5%;
(2) preparing an N48H neodymium iron boron magnet blank through smelting, milling, molding and sintering steps, and processing the blank into a blank square sheet with the size of 42 × 31 × 3mm (3mm is the orientation direction);
(3) surface activation is carried out on the blank square sheet: putting the blank square slices into a degreasing solution with the temperature of 60 ℃ and the concentration of 20g/L for degreasing for 3 minutes; putting the deoiled blank square slice into a 3% nitric acid solution for pickling for 45 s; finally, putting the product after the acid washing into alcohol to be soaked for 15s and then drying;
(4) the RTM alloy casting sheet is flatly laid at the bottom of the graphite box, and the blank square sheet after surface activation is placed on the RTM alloy casting sheet, so that the RTM alloy casting sheet and the blank square sheet after surface activation are overlapped up and down until the graphite box is filled;
(5) putting the graphite box filled with the product into a sintering furnace, and vacuumizing to 10 DEG-2Heating to 900 ℃ below Pa for high-temperature diffusion treatment for 18h, and then performing low-temperature tempering secondary treatment for 5h at 500 ℃ to form the neodymium-iron-boron magnet after diffusion treatment by blank square pieces.
Example 5:
a grain boundary diffusion method for a rare earth neodymium iron boron magnet comprises the following steps:
(1) the RTM alloy cast sheet with the thickness of 0.3mm is prepared by a vacuum rapid hardening process according to the following formula: r is Tb, T is Fe, M is Al and Ga, and the mass percentages of Tb, Fe, Al and Ga in the powder are 75%, 20%, 3% and 2% respectively;
(2) preparing an N48H neodymium iron boron magnet blank through smelting, milling, molding and sintering steps, and processing the blank into a blank square sheet with the size of 42 × 31 × 3mm (3mm is the orientation direction);
(3) surface activation is carried out on the blank square sheet: putting the blank square slices into a degreasing solution with the temperature of 60 ℃ and the concentration of 20g/L for degreasing for 3 minutes; putting the deoiled blank square slice into a 3% nitric acid solution for pickling for 45 s; finally, putting the product after the acid washing into alcohol to be soaked for 15s and then drying;
(4) the RTM alloy casting sheet is flatly laid at the bottom of the graphite box, and the blank square sheet after surface activation is placed on the RTM alloy casting sheet, so that the RTM alloy casting sheet and the blank square sheet after surface activation are overlapped up and down until the graphite box is filled;
(5) putting the graphite box filled with the product into a sintering furnace, and vacuumizing to 10 DEG-2Heating to 900 ℃ below Pa for high-temperature diffusion treatment for 18h, and then performing low-temperature tempering secondary treatment for 5h at 500 ℃ to form the neodymium-iron-boron magnet after diffusion treatment by blank square pieces.
Example 6:
a grain boundary diffusion method for a rare earth neodymium iron boron magnet comprises the following steps:
(1) the RTM alloy cast sheet with the thickness of 0.1mm is prepared by a vacuum rapid hardening process according to the following formula: r is Tb, T is Fe, M is Al, and the mass percentages of Tb, Fe and Al in the powder are 75%, 20% and 5% respectively;
(2) preparing an N48H neodymium iron boron magnet blank through smelting, milling, molding and sintering steps, and processing the blank into a blank square sheet with the size of 42 × 31 × 3mm (3mm is the orientation direction);
(3) surface activation is carried out on the blank square sheet: putting the blank square slices into 10g/L degreasing solution at the temperature of 50 ℃ for degreasing for 2 minutes; then putting the deoiled blank square slice into a 2% nitric acid solution for pickling for 30 s; finally, putting the product after the acid washing into alcohol to be soaked for 10s and then drying;
(4) the RTM alloy casting sheet is flatly laid at the bottom of the graphite box, and the blank square sheet after surface activation is placed on the RTM alloy casting sheet, so that the RTM alloy casting sheet and the blank square sheet after surface activation are overlapped up and down until the graphite box is filled;
(5) putting the graphite box filled with the product into a sintering furnace, and vacuumizing to 10 DEG-2Heating to 800 ℃ below Pa for high-temperature diffusion treatment for 10h, and then performing low-temperature tempering secondary treatment for 2h at 450 ℃, so that the blank square piece forms the neodymium-iron-boron magnet after diffusion treatment.
Example 7:
a grain boundary diffusion method for a rare earth neodymium iron boron magnet comprises the following steps:
(1) preparing an RTM alloy cast sheet with the thickness of 10mm by a vacuum rapid hardening process according to the following formula: r is Tb, T is Fe, M is Al, and the mass percentages of Tb, Fe and Al in the powder are 75%, 20% and 5% respectively;
(2) preparing an N48H neodymium iron boron magnet blank through smelting, milling, molding and sintering steps, and processing the blank into a blank square sheet with the size of 42 × 31 × 10mm (10mm is the orientation direction);
(3) surface activation is carried out on the blank square sheet: putting the blank square slices into a degreasing solution with the temperature of 80 ℃ and the concentration of 30g/L for degreasing for 5 minutes; then putting the deoiled blank square slice into 4% nitric acid solution for pickling for 60 s; finally, putting the product after the acid washing into alcohol to be soaked for 20s and then drying;
(4) the RTM alloy casting sheet is flatly laid at the bottom of the graphite box, and the blank square sheet after surface activation is placed on the RTM alloy casting sheet, so that the RTM alloy casting sheet and the blank square sheet after surface activation are overlapped up and down until the graphite box is filled;
(5) putting the graphite box filled with the product into a sintering furnace, and vacuumizing to 10 DEG-2Heating to 1000 ℃ below Pa for 20h of high-temperature diffusion treatment, and then carrying out low-temperature tempering secondary treatment at 600 ℃ for 8h to form the neodymium-iron-boron magnet after diffusion treatment on the blank square pieces.
Example 8:
a grain boundary diffusion method for a rare earth neodymium iron boron magnet comprises the following steps:
(1) an RTM alloy cast sheet with the thickness of 50mm is prepared by a vacuum rapid hardening process according to the following formula: r is Tb, T is Fe, M is Al, and the mass percentages of Tb, Fe and Al in the powder are 75%, 20% and 5% respectively;
(2) preparing an N48H neodymium iron boron magnet blank through smelting, milling, molding and sintering steps, and processing the blank into a blank square sheet with the size of 42 × 31 × 10mm (10mm is the orientation direction);
(3) surface activation is carried out on the blank square sheet: putting the blank square slices into a degreasing solution with the temperature of 80 ℃ and the concentration of 30g/L for degreasing for 5 minutes; then putting the deoiled blank square slice into 4% nitric acid solution for pickling for 60 s; finally, putting the product after the acid washing into alcohol to be soaked for 20s and then drying;
(4) the RTM alloy casting sheet is flatly laid at the bottom of the graphite box, and the blank square sheet after surface activation is placed on the RTM alloy casting sheet, so that the RTM alloy casting sheet and the blank square sheet after surface activation are overlapped up and down until the graphite box is filled;
(5) putting the graphite box filled with the product into a sintering furnace, and vacuumizing to 10 DEG-2Heating to 1000 ℃ below Pa for 20h of high-temperature diffusion treatment, and then carrying out low-temperature tempering secondary treatment at 600 ℃ for 8h to form the neodymium-iron-boron magnet after diffusion treatment on the blank square pieces.
Example 9:
a grain boundary diffusion method for a rare earth neodymium iron boron magnet comprises the following steps:
(1) preparing an RTM alloy casting sheet with the thickness of 100mm by a vacuum rapid hardening process according to the following formula: r is Tb, T is Fe, M is Al, and the mass percentages of Tb, Fe and Al in the powder are 75%, 20% and 5% respectively;
(2) preparing an N48H neodymium iron boron magnet blank through smelting, milling, molding and sintering steps, and processing the blank into a blank square sheet with the size of 42 × 31 × 10mm (10mm is the orientation direction);
(3) surface activation is carried out on the blank square sheet: putting the blank square slices into a degreasing solution with the temperature of 80 ℃ and the concentration of 30g/L for degreasing for 5 minutes; then putting the deoiled blank square slice into 4% nitric acid solution for pickling for 60 s; finally, putting the product after the acid washing into alcohol to be soaked for 20s and then drying;
(4) the RTM alloy casting sheet is flatly laid at the bottom of the graphite box, and the blank square sheet after surface activation is placed on the RTM alloy casting sheet, so that the RTM alloy casting sheet and the blank square sheet after surface activation are overlapped up and down until the graphite box is filled;
(5) putting the graphite box filled with the product into a sintering furnace, and vacuumizing to 10 DEG-2Heating to 1000 ℃ below Pa for 20h of high-temperature diffusion treatment, and then carrying out low-temperature tempering secondary treatment at 600 ℃ for 8h to form the neodymium-iron-boron magnet after diffusion treatment on the blank square pieces.
Example 10:
a grain boundary diffusion method for a rare earth neodymium iron boron magnet comprises the following steps:
(1) the RTM alloy cast sheet with the thickness of 0.1mm is prepared by a vacuum rapid hardening process according to the following formula: r is Tb, T is Fe, M is Al, and the mass percentages of Tb, Fe and Al in the powder are 75%, 20% and 5% respectively;
(2) preparing an N48H neodymium iron boron magnet blank through smelting, pulverizing, molding and sintering, and processing the blank into a blank square sheet with the size of 42 × 31 × 0.1.1 mm (0.1mm is the orientation direction);
(3) surface activation is carried out on the blank square sheet: putting the blank square slices into 10g/L degreasing solution at the temperature of 50 ℃ for degreasing for 2 minutes; then putting the deoiled blank square slice into a 2% nitric acid solution for pickling for 30 s; finally, putting the product after the acid washing into alcohol to be soaked for 10s and then drying;
(4) the RTM alloy casting sheet is flatly laid at the bottom of the graphite box, and the blank square sheet after surface activation is placed on the RTM alloy casting sheet, so that the RTM alloy casting sheet and the blank square sheet after surface activation are overlapped up and down until the graphite box is filled;
(5) putting the graphite box filled with the product into a sintering furnace, and vacuumizing to 10 DEG-2Heating to 800 ℃ below Pa for high-temperature diffusion treatment for 10h, and then performing low-temperature tempering secondary treatment for 2h at 450 ℃, so that the blank square piece forms the neodymium-iron-boron magnet after diffusion treatment.
The magnetic properties of the non-diffusion-treated square blank pieces and the diffusion-treated ndfeb magnets in the above examples were measured, and the results are shown in table 1.
Table 1: and (5) testing the magnetic property.
(wherein, the larger the magnetic energy product, the smaller the volume of permanent magnet required to produce the same magnetic field;
remanence (Br) — the magnetic moment retained by a permanent magnet after the external field is removed after the permanent magnet is charged in the external magnetic field. The larger the remanence is, the larger the magnetic energy product is;
coercivity (HcJ) -the loss of magnetism of a permanent magnet, is the strength of the external field applied in the opposite direction to the magnetization direction of the magnet, i.e., the strength of the corresponding reverse magnetic field when Br is 0. The larger the coercive force is, the stronger the anti-interference capability of the magnet, i.e., the capability of keeping magnetism is. ) As can be seen from Table 1, by adopting the method of the present invention, the coercivity of the neodymium iron boron magnet prepared by diffusion treatment can be greatly improved, and the residual magnetism and the maximum magnetic energy product can be ensured to be basically kept unchanged, thereby effectively improving the magnetic performance of the neodymium iron boron magnet.
Claims (8)
1. A grain boundary diffusion method for a rare earth neodymium iron boron magnet is characterized by comprising the following steps:
(1) preparing an RTM alloy casting sheet containing heavy rare earth elements by using a powder metallurgy method;
(2) preparing a neodymium iron boron magnet blank through smelting, milling, forming and sintering, and processing the blank into a blank square sheet;
(3) carrying out surface activation on the blank square sheet;
(4) the RTM alloy casting sheet is flatly laid at the bottom of the graphite box, and the blank square sheet after surface activation is placed on the RTM alloy casting sheet, so that the RTM alloy casting sheet and the blank square sheet after surface activation are overlapped up and down until the graphite box is filled;
(5) and carrying out vacuum heat treatment on the graphite box filled with the product, and forming the neodymium iron boron magnet after diffusion treatment by using blank square sheets.
2. The grain boundary diffusion method of the rare earth neodymium iron boron magnet according to claim 1, wherein in the step (1), R in the RTM alloy casting piece is selected from one or more of heavy rare earth elements; t is Fe and/or Co; m is one or more selected from Al, Si, Cu, Nb, Zr and Ga.
3. The grain boundary diffusion method of the rare earth neodymium iron boron magnet according to claim 1 or 2, wherein in the RTM alloy casting sheet in the step (1), the mass fraction of R is 60-100%, the mass fraction of T is 0-35 wt%, and the mass fraction of M is 0-5 wt%.
4. The grain boundary diffusion method of the rare earth neodymium iron boron magnet according to claim 1 or 2, wherein the thickness of the RTM alloy cast sheet in the step (1) is 0.1-100 mm.
5. The grain boundary diffusion method of the rare earth neodymium iron boron magnet according to claim 1 or 2, wherein the powder metallurgy method in the step (1) adopts a vacuum rapid solidification process.
6. The grain boundary diffusion method of the rare earth neodymium iron boron magnet according to claim 1, wherein the thickness of the blank square piece in the step (2) is 0.1-10 mm.
7. The grain boundary diffusion method of the rare earth neodymium iron boron magnet according to claim 1, wherein the surface activation method in the step (3) is as follows: putting the blank square slices into 10-30 g/L degreasing solution at the temperature of 50-80 ℃ for degreasing for 2-5 minutes; putting the deoiled blank square sheet into a 2-4% nitric acid solution for pickling for 30-60 s; and finally, putting the pickled product into alcohol to be soaked for 10-20 s, and drying.
8. The grain boundary diffusion method of the rare earth neodymium iron boron magnet according to claim 1, wherein the heat treatment method in the step (4) is as follows: diffusing at the high temperature of 800-1000 ℃ for 10-20 h, and then tempering at the low temperature of 450-600 ℃ for 2-8 h.
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