Patent Application
20130093551
1. Field of Invention
The present invention relates to a rare-earth permanent magnetic material, and more particularly to an R—Fe—B based magnet having gradient electric resistance and method for producing the same.
2. Description of Related Arts
In the conventional technologies, a permanent-magnet rotating motor mainly utilizes a ferrite magnet of low price. In recent years, with the miniaturization and high performance of various motors, application amount of R—Fe—B based sintered magnets with higher performance is increasing year by year. In particular, as countries around the world concern about issues of energy conservation and environmental protection recently, application range of the R—Fe—B based sintered magnet has expanded to areas such as home appliances, industrial equipments, electric vehicles and wind turbines. However, the R—Fe—B based sintered magnet is a metallic magnet with low resistance value. Thus, when the R—Fe—B based sintered magnet is applied to a rotating motor, problems of great eddy current loss, and drop of motor efficiency caused by the great eddy current loss appear.
In order to increase the electric resistance of the R—Fe—B based sintered magnet,
a Japanese patent of publication number JP9232122 discloses a high electric resistive magnet produced by adding Ge (Germanium) powder to R—Fe—B based magnetic powder, and by a process of plasma activated sintering;
a Japanese patent of publication number JP9186010 discloses a high electric resistive magnet produced by adding powder of fluoride or oxide of at least one element selected from the group consisting of Li, Na, Mg, Ca, Ba and Sr to R—Fe—B based magnetic powder;
a Japanese patent of publication number JP2006310659 discloses a high electric resistive magnet produced by adding DyF3 and/or TbF3 to R—Fe—B based magnetic powder;
a Japanese patent of publication number JP2006310660 discloses a high electric resistive magnet produced by adding DyF3 and/or TbF3, and Al2O3 to R—Fe—B based magnetic powder; and
a Japanese patent of publication number JP2008060241 discloses a high electric resistive magnet produced by forming a rare-earth fluoride insulating layer on surfaces of R—Fe—B based magnetic particles which are obtained by HDDR processing.
However, all kinds of magnets mentioned above increase the electric resistance of the magnets at the expense of a sharp decline of magnetic property of the magnets simultaneously, which makes it difficult to apply the magnets to a high-power rotating motor.
In order to solve technical problems mentioned above, an R—Fe—B based magnet having gradient electric resistance which is capable of maintaining high electric resistance and excellent magnetic performance simultaneously, and method for producing the same are provided.
A method of producing an R—Fe—B based magnet having gradient electric resistance of the present invention, comprises steps of:
composition of the powder A is Ra-Tb-Bc-Md-Ne, wherein R is at least one rare-earth element selected from the group consisting of Nd, Pr, Dy and Tb; T is at least one element selected from the group consisting of Fe and Co; B is Boron; M is at least one element selected from the group consisting of Cu, Ga and Al; N is at least one element selected from the group consisting of Zr, Ti, Nb and Hf; values of a, b, c, d and e which present weight percent of corresponding elements of the magnet are within scopes as following: 26≦a≦33, 0.9≦c≦1.1, 0.01≦d≦1.5, 0.01≦e≦1.5, and b is a balance,
composition of the powder B is Rm-Tn-BxMy-Oz, wherein:
R is at least one element selected from the group consisting of Nd, Pr, Dy, Tb Ce and Y;
T is at least one element selected from the group consisting of Fe and Co;
B is Boron;
M is at least one element selected from the group consisting of Mn, In, Ge, Ti, V, Cr, Ni, Ga, Ca, Cu, Zn, Si, P, S, C, Al, Mg, Zr, Nb, Ta, W, Mo, Pd, Ag, Cd, Sn and Sb;
O is oxygen;
values of m, n, x, y and z which present weight percent of corresponding elements of layers of the magnet are within scopes as following: 29≦m≦36, 0.9≦x≦1.1, 0.01≦y≦3, 0.02≦z≦1, n is a balance;
In the method of producing the R—Fe—B based magnet having gradient electric resistance of the present invention, raw materials for preparation of the powder A and the powder B in the step (1) comprise alloy α, alloy β and metal oxide,
wherein composition of the alloy α is Ra-Tb-Bc-Md-Ne,
wherein R is at least one rare-earth element selected from the group consisting of Nd, Pr, Dy and Tb,
T is at least one element selected from the group consisting of Fe and Co; B is Boron,
M is at least one element selected from the group consisting of Cu, Ga and Al,
N is at least one element selected from the group consisting of Zr, Ti, Nb and Hf, and
values of a, b, c, d and e which present weight percent of corresponding elements of the magnet are within scopes as following: 26≦a≦33, 0.9≦c≦1.1, 0.01≦d≦1.5, 0.01≦e≦1.5, b is a balance,
composition of the alloy β is Rm-Tn-Bx-My-Oz, wherein
R is at least one element selected from the group consisting of Nd, Pr, Dy, Tb Ce and Y,
T is at least one element selected from the group consisting of Fe and Co,
B is Boron,
M is at least one element selected from the group consisting of Mn, In, Ge, Ti, V, Cr, Ni, Ga, Ca, Cu, Zn, Si, P, S, C, Al, Mg, Zr, Nb, Ta, W, Mo, Pd, Ag, Cd, Sn and Sb,
O is oxygen, and
values of m, n, x, y and z which present weight percent of corresponding elements of layers of the magnet are within scopes as following: 29≦m≦36, 0.9≦x≦1.1, 0.01≦y≦3, 0.02≦z≦1, n is a balance,
wherein preparation methods of the powder A and the powder B are selected from one or combination of the following methods:
(i) processing the alloy α and the alloy β respectively by hydrogen decrepitation with a hydrogen furnace, grinding flakes of the alloy α to form the powder A in an environment under protection of inert gas or nitrogen; grinding the alloy β with a jet mill to form fine powder B in an environment having oxygen content of at least 1%;
(ii) processing the alloy α by hydrogen decrepitation with a hydrogen furnace, processing fine-grinding with a jet mill to obtain the powder A in an environment under protection of inert gas or nitrogen, then mixing the powder A and metal oxide to obtain the powder B, wherein the weight of the metal oxide mixed is more than 1% of the total weight of the powder A and the metal oxide;
(iii) separating the grinded powder formed by processing the alloy α in a hydrogen furnace into two parts; fine-grinding one part of the powder with a jet mill to form powder A in an environment under protection of insert gas or nitrogen, fine-grinding the other part with a jet mill to form powder B in an environment having oxygen content of at least 1%;
(iv) grinding the alloy α and the alloy β respectively, grinding the alloy α to obtain the powder A in an environment under protection of inert gas or nitrogen, mixing the alloy α and the alloy β with a certain proportion, wherein a ratio of the alloy α to the alloy β is not less than 10:1, processing fine-grinding with a jet mill to obtain the powder B in an environment having oxygen content of at least 1%;
(V) grinding the alloy α, processing fine-grinding with a jet mill to obtain the powder A in an environment under protection of inert gas or nitrogen, then mixing part of the powder A and metal oxide to obtain the powder B, wherein the weight of the metal oxide mixed is not less than 1% of the total weight of the part of powder A mixed and the metal oxide; and
(vi) separating grinded powder formed by grinding the alloy α into two parts, fine-grinding one part of the powder with a jet mill to form the powder A in an environment under protection of inert gas or nitrogen, fine-grinding the other part of the powder with a jet mill to obtain the powder B in an environment having oxygen content of at least 1%.
In the method of producing the R—Fe—B based magnet having gradient electric resistance, thickness of the filled layer of the powder B in the step (2) accounts for less than 50% of total thickness.
The R—Fe—B based magnet having gradient electric resistance comprises an exterior layer G and a main body layer H, wherein the exterior layer G is connected with the main body layer H via a sintered layer I; oxygen content of the exterior layer G is more than that of the main body layer H, and electrical resistivity of the exterior layer G is not lower than that of the main body layer H.
In the R—Fe—B based magnet having gradient electric resistance, thickness of the exterior layer G accounts for less than 50% of total thickness of the R—Fe—B based magnet in a direction of magnetic field orientation.
In the R—Fe—B based magnet having gradient electric resistance, oxygen content of the exterior layer G is more than 0.2%.
In the R—Fe—B based magnet having gradient electric resistance, coercive force of the exterior layer G is larger than that of the main body layer H.
The manufacturing method of the R—Fe—B based magnet having gradient electric resistance provides an R—Fe—B based permanent magnet material having characteristics of high electric resistance, high coercive force and excellent magnetic performance Applying the R—Fe—B based permanent magnet in a rotor of a middle/high-power and high-speed rotating motor can reduce loss of the rotating motor, and improve efficiency thereof.
Combined with the accompanying drawings, the R—Fe—B based magnet having gradient electric resistance and method for producing the same, according to preferred embodiments of the present invention, are further illustrated as following
Prepare a raw material having a purity of over 99 wt % according to the following composition (weight percentage): (Nd21Pr5Dy4.5)Co2Cu0.15Al0.1Nb0.2B1Febalance, melt in a vacuum strip continuous casting furnace, and send flakes into a hydrogen furnace to form hydrogen decrepitation particles;
in an oxygen-free environment with oxygen content close to 0%, send the particles after hydrogen decrepitation into a jet mill to process fine-grinding, so as to obtain a powder A with an average particle size of d=3.3 μm, add Dy2O3 powder with an average particle size of d=3.2 μm to a part of the powder A, wherein the weight of the Dy2O3 powder added is 3% of the total weight of the part of the powder A added and the Dy2O3 powder, and mix them uniformly to form powder B;
in an environment having oxygen content of less than 1% send the powder A and the powder B into a magnet oriented molding device, fill along a magnetizing direction layer by layer with spacing boards, wherein volume ratio of the powder A to the powder B is 3.6:1, and compact the filled powder in a magnetic field for alignment; in an environment having oxygen content of less than 1% sinter the compact under 1080° C. for 4 hrs followed by fast cooling, and perform aging under 900° C. for 3 hrs and under 520° C. for 4 hrs respectively to form a rectangular magnet A1 having a size of 51×51×22 mm, wherein thickness of an exterior layer G is 6 mm, and thickness of a main body layer H is 16 mm. Produce a D10×20 cylinder for measuring magnetic property thereof. Produce a tall and slender rod having a size of 1×1×5 mm along the magnetizing direction in the exterior layer G and the main body layer H for measuring resistivity thereof. Measuring results are shown in Table 1.
SEM (scanning electron microscope) analysis image is shown in
The magnet obtained in the embodiment 1 has characteristics of high electric resistance, high coercive force and excellent magnetic performance. When the magnet is applied to a rotor in a rotating motor having a high-speed and middle/high-power, eddy current loss of the rotating motor can be reduced and electrical efficiency of the rotating motor thus can be improved.
Comparison 1
Prepare a raw material having a purity of over 99 wt % according to the following composition (weight percentage): (Nd21Pr5Dy4.5)Co2Cu0.15Al0.1Nb0.2B1Febalance, melt in a vacuum strip continuous casting furnace, and send flakes into a hydrogen furnace to form hydrogen decrepitation particles;
in an oxygen-free environment with oxygen content close to 0%, send the particles after hydrogen decrepitation into a jet mill to process fine-grinding, so as to obtain a powder with an average particle size of d=3.3 μm;
in an environment having oxygen content of less than 1%, send the powder into a magnet oriented molding device to compact; in an environment having oxygen content of less than 1% sinter the compact under 1080° C. for 4 hrs followed by fast cooling, and perform aging under 900° C. for 3 hrs and under 520° C. for 4 hrs respectively to form a rectangular magnet B1 having a size of 51×51×22 mm. Produce a tall and slender rod having a size of 1×1×5 mm for measuring resistivity thereof. Measure results are shown in Table 1.
It can be seen from Table 1 that the magnet A1 produced by the method of the embodiment 1 has only about half of the eddy current loss of the magnet B1 produced by conventional method.
Prepare a raw material having a purity of over 99 wt % according to the following composition (weight percentage): (Nd21Pr5Dy4.5)Co2Cu0.15Al0.1Nb0.2B1Febalance, melt in a vacuum strip continuous casting furnace, and send flakes into a hydrogen furnace to form hydrogen decrepitation particles;
in an oxygen-free environment with oxygen content close to 0%, send one part of particles after hydrogen decrepitation into a jet mill to process fine-grinding, so as to obtain a powder A with an average particle size of d=3.3 μm; send the other part of the particles after hydrogen decrepitation into a jet mill to process fine-grinding in an environment with oxygen content of 1.5%, so as to obtain a powder B with an average particle size of d=3.4 μm; send the powder A and the powder B into a magnet oriented molding device in an environment having oxygen content of less than 1%, fill along a magnetizing direction layer by layer with spacing boards, wherein volume ratio of the powder A to the powder B is 3.6:1, magnetize and mold after the powder is filled; send the compact into a sintering furnace in an environment having oxygen content of less than 1%, sinter the compact under 1075° C. for 4 hrs followed by fast cooling, and perform aging under 900° C. for 3 hrs and under 510° C. for 4 hrs respectively to form a rectangular magnet A2 having a size of 51×51×22 mm, wherein thickness of an exterior layer G is 6 mm, and thickness of a main body layer H is 16 mm. Produce a D10×20 cylinder for measuring magnetic property thereof. Produce a tall and slender rod having a size of 1×1×5 mm along a magnetizing direction in the exterior layer G and the main body layer H for measuring resistivity thereof. Measuring results are shown in Table 1.
Prepare a raw material having a purity of over 99 wt % according to the following composition (weight percentage): (Nd21Pr5Dy4.5)Co2Cu0.15Al0.1Nb0.2B1Febalance, melt in a vacuum strip continuous casting furnace, and send flakes into a hydrogen furnace to form hydrogen decrepitation particles;
in an oxygen-free environment with oxygen content close to 0%, send the particles after hydrogen decrepitation into a jet mill to process fine-grinding, so as to obtain a powder A with an average particle size of d=3.3 μm, add Al2O3 powder with an average particle size of d=1.5 μm to a part of the powder A, wherein the weight of the Al2O3 powder added is 1% of the total weight of the part of powder A added and the Al2O3 powder, and mix them uniformly to form a powder B;
in an environment having oxygen content of less than 1%, send the powder A and the powder B into a magnet oriented molding device, fill along a magnetizing direction layer by layer with spacing boards, wherein volume ratio of the powder A to the powder B is 3.6:1, and compact the filled powder in a magnetic field for alignment; in an environment having oxygen content of less than 1%, sinter the compact under 1090° C. for 4 hrs followed by fast cooling, and perform aging under 900° C. for 3 hrs and under 500° C. for 4 hrs respectively to form a rectangular magnet A3 having a size of 51×51×22 mm, wherein thickness of an exterior layer G is 6 mm, and thickness of a main body layer H is 16 mm. Produce a D10×20 cylinder for measuring magnetic property thereof. Produce a tall and slender rod having a size of 1×1×5 mm along a magnetizing direction in the exterior layer G and the main body layer H for measuring resistivity thereof. Measuring results are shown in Table 1.
SEM (scanning electron microscope) analysis results are shown in
Prepare an alloy α with a raw material having a purity of over 99 wt % according to the following composition (weight percentage): Nd24Pr5Co1Al0.1Zr0.2B1Febalance, prepare an alloy β with a raw material having a purity of over 99 wt % according to the following composition (weight percentage): Nd25Dy45Co20Cu2Al2B0.4Febalance,
melt the alloy α and the alloy β in a vacuum strip continuous casting furnace respectively, and send them into a hydrogen furnace to form hydrogen decrepitation particles α and β separately;
in an oxygen-free environment with oxygen content close to 0%, send one part of particles a after hydrogen decrepitation into a jet mill to process fine-grinding, so as to obtain a powder A with an average particle size of d=3.3 μm, and mix the other part of the particles α after hydrogen decrepitation and the particles β after hydrogen decrepitation according to weight percentage of 91:9,
after mixed uniformly, in an environment having oxygen content of 1.2%, fine-grind with a jet mill to form a powder B having an average particle diameter of 3.4 μm;
in an environment having oxygen content of less than 1%, send the powder A and the powder B into a magnet oriented molding device, fill along a magnetizing direction layer by layer with spacing boards, wherein volume ratio of the powder A to the powder B is 3.6:1, and compact the filled powder in a magnetic field for alignment in an environment having oxygen content of less than 1%, sinter the compact under 1085° C. for 5 hrs followed by fast cooling, and perform aging under 900° C. for 3 hrs and under 500° C. for 4 hrs respectively to form a magnet A4 having a size of 51×51×22 mm, wherein thickness of an exterior layer G is 6 mm, and thickness of a main body layer H is 16 mm. Produce a D10×20 cylinder for measuring magnetic property thereof. Produce a tall and slender rod having a size of 1×1×5 mm along a magnetizing direction in the exterior layer G and the main body layer H for measuring resistivity thereof. Measuring results are shown in Table 1.
Comparison 2
Prepare an alloy α with a raw material having a purity of over 99 wt % according to the following composition (weight percentage): Nd24Pr5Co1Al0.1Zr0.2B1Febalance,
prepare an alloy β with a raw material having a purity of over 99 wt % according to the following composition (weight percentage): Nd25Dy45Co20Cu2Al2B0.4Febalance,
melt the alloy α and the alloy β in a vacuum strip continuous casting furnace respectively, and send them into a hydrogen furnace to form hydrogen decrepitation particles α and β separately;
after hydrogen decrepitation mix the particles α and the particles β according to weight ratio of 91:9,
after mixed uniformly, in an environment having oxygen content of 1.2%, fine-grind with a jet mill to form a powder B having an average particle diameter of 3.4 μm;
in an environment having oxygen content of less than 1%, send the powder A and the powder B into a magnet oriented molding device, magnetize and mold after the powder is filled, and compact the filled powder in a magnetic field for alignment; in an environment having oxygen content of less than 1% sinter the compact under 1085° C. for 5 hrs followed by fast cooling, and perform aging under 900° C. for 3 hrs and under 500° C. for 4 hrs respectively to form a magnet B2 having a size of 51×51×22 mm. Produce a tall and slender rod having a size of 1×1×5 mm for measuring resistivity thereof. Measuring results are shown in Table 1.
Prepare a raw material having a purity of over 99 wt % according to the following composition (weight percentage): (Nd21Pr5Dy4.5)Co2Cu0.15Al0.1Nb0.2B1Febalance,
melt in a vacuum strip continuous casting furnace, and send flakes into a hydrogen furnace to form hydrogen decrepitation particles;
in an oxygen-free environment with oxygen content close to 0%, send the particles after hydrogen decrepitation into a jet mill to process fine-grinding, so as to obtain a powder A with an average particle size of d=3.3 μm, add Ce2O3 powder with an average particle size of d=3.2 μm to the powder A, wherein the weight of the Ce2O3 powder added is 4% of the total weight of the powder A and the Ce2O3 powder, and uniformly mix them uniformly to form a powder B;
in an environment having oxygen content of less than 1% send the powder A and the powder B into a magnet oriented molding device, fill along a magnetizing direction layer by layer with spacing boards, wherein volume ratio of the powder A to the powder B is 3.6:1, and compact the filled powder in a magnetic field for alignment; in an environment having oxygen content of less than 1% sinter the compact under 1080° C. for 4 hrs followed by fast cooling, and perform aging under 900° C. for 3 hrs and under 530° C. for 4 hrs respectively to form a magnet A5 having a size of 51×51×22 mm, wherein thickness of an exterior layer G is 6 mm, and thickness of a main body layer H is 16 mm. Produce a D10×20 cylinder for measuring magnetic property thereof. Produce a tall and slender rod having a size of 1×1×5 mm along a magnetizing direction in the exterior layer G and the main body layer H for measuring resistivity thereof. Measuring results are shown in Table 1.
The magnets obtained according to the embodiment 4 and the embodiment 5 not only present excellent magnetic performance but also have characteristics of high electric resistance and low cost. The magnets manufactured by the embodiment 4 and the embodiment 5 have wide application prospects in embedded permanent magnetic motor.
One skilled in the art will understand that the embodiment of the present invention as shown in the drawings and described above is exemplary only and not intended to be limiting.
It will thus be seen that the objects of the present invention have been fully and effectively accomplished. Its embodiments have been shown and described for the purposes of illustrating the functional and structural principles of the present invention and is subject to change without departure from such principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims.
Raw materials adopted by the R—Fe—B based magnet having gradient electric resistance and method for producing the same are all currently existing raw materials for producing permanent magnets, and the production equipments adopted thereby are all currently existing conventional equipments. The R—Fe—B based magnets of the present invention are widely adopted in middle/high power and high speed rotating motors, and have positive effects, and thus have great market prospects and industrial applicability.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201010217943.1 | Jul 2010 | CN | national |
This is a U.S. National Stage under 35 USC 371 of the International Application PCT/CN2010/080239, filed on Dec. 24, 2010.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CN2010/080239 | 12/24/2010 | WO | 00 | 12/20/2012 |
