Gradient Nd—Fe—B magnet and a method of production
12080478 · 2024-09-03
Assignee
Inventors
Cpc classification
H01F41/0293
ELECTRICITY
International classification
B22F3/24
PERFORMING OPERATIONS; TRANSPORTING
Abstract
A gradient NdFeB magnet includes an NdFeB magnet block extending along a magnetization direction and having a plurality of surfaces perpendicular to the magnetization direction. A first film, is disposed on one of the surfaces. A second film is disposed on another one of the surfaces, opposite of the one of the surfaces. The first film and the second film are diffused into the NdFeB magnet block dividing the NdFeB magnet block into an edge region, a transition region, and a central region along a plane perpendicular to the magnetization direction wherein the edge region has a coercivity that remains constant in a direction perpendicular to the magnetization direction, and the coercivity, along said magnetization direction, gradually decreases from the one of the surfaces and the another one of the surfaces towards a point located therebetween. A method of making the gradient NdFeB magnet is disclosed herein.
Claims
1. A gradient NdFeB magnet comprising: an NdFeB magnet block extending along a magnetization direction and having a plurality of surfaces perpendicular to said magnetization direction; a first film containing at least one heavy rare earth element, disposed on one of said surfaces, attached to said NdFeB magnet block and extending along a periphery of said one of said surfaces and wherein said first film only covers an area of 10% to 65% of said one of said surfaces; and a second film containing at least one heavy rare earth element, disposed on another one of said surfaces, opposite of said one of said surfaces, attached to said NdFeB magnet block and extending along a periphery of said another one of said surfaces and wherein said second film only covers an area of 10% to 65% of said another one of said surfaces; and said first film and said second film being diffused into said NdFeB magnet block dividing said NdFeB magnet block into an edge region, a transition region, and a central region along a plane extending perpendicular to said magnetization direction; wherein said edge region has a coercivity that remains constant in a direction perpendicular to said magnetization direction, and said coercivity of said edge region, along said magnetization direction, gradually decreases from said one of said surfaces and said another one of said surfaces towards a point located between said one of said surfaces and said another one of said surfaces; and wherein said transition region extends about said center region and said edge region extends about said transition region in concentric relationship.
2. The gradient NdFeB magnet as set forth in claim 1 wherein said transition region has a coercivity that decreases toward said central portion in said direction perpendicular to said magnetization direction and said coercivity of said transition region, along said magnetization direction, gradually decreases from said one of said surfaces and said another one of said surfaces to said point between said one of said surfaces and said another one of said surfaces.
3. The gradient NdFeB magnet as set forth in claim 1 wherein said center region has a coercivity that remains constant in said direction perpendicular to said magnetization direction and along said magnetization direction.
4. The gradient NdFeB magnet as set forth in claim 1 wherein an average of said coercivity of said edge region is greater than an average of said coercivity of said transition region and said average of said coercivity of said transition region is greater than an average of said coercivity of said central region.
5. The gradient NdFeB magnet as set forth in claim 1 wherein said NdFeB magnet block has a thickness of between 2-10 mm along said magnetization direction.
6. The gradient NdFeB magnet as set forth in claim 1 wherein said NdFeB magnet block has a length and a width of at least 10 mm.
7. The gradient NdFeB magnet as set forth in claim 1 wherein said at least one heavy rare earth element is selected from Tb, Dy, and an alloy containing Dy or Tb.
8. The gradient NdFeB magnet as set forth in claim 1 wherein said first film and said second film are attached to said NdFeB magnet block by melting a powder containing said at least one heavy rare earth metal on said one and said another one of the surfaces and along said periphery using a laser.
9. The gradient NdFeB magnet has set forth in claim 8 wherein said at least one heavy rare earth element is selected from Tb, Dy, and an alloy containing Dy or Tb and is present in said powder in an amount of 0.1 wt. % and 2 wt. %.
10. The gradient NdFeB magnet a set forth in claim 8 wherein said powder has an average particle size of between 1 ?m and 300 ?m.
11. The gradient NdFeB magnet a set forth in claim 8 wherein said powder melted into said first film only forms said first film along the periphery of said one of the surfaces and the excess powder not melted into said first film is removed from said one of the surfaces.
12. The gradient NdFeB magnet a set forth in claim 11 wherein said powder melted into said second film only forms said second film along the periphery of said another one of the surfaces and the excess powder not melted into said second film is removed from said another one of the surfaces.
13. A method of making the gradient NdFeB magnet of claim 1, said method including the steps of: providing the NdFeB magnet block having a thickness of between 2-10 mm along the magnetization direction and having the surfaces perpendicular to the magnetization direction; placing the NdFeB magnet block in a chamber containing an inert gas of argon with the magnetization direction of the NdFeB magnet block being arranged in a vertical direction; depositing a powder, containing at least one heavy rare earth element, on the one of the surfaces; forming the first film containing the at least one heavy rare earth element on the one of the surfaces and along the periphery of the one of the surfaces; said step of forming the first film further including a step of melting the powder on the one of the surfaces and along the periphery using a laser to form the first film and adhering the first film to the periphery; removing excess powder from the one of the surfaces; rotating the NdFeB magnet block 180?; depositing the powder, containing at least one heavy rare earth element, on the another one of the surfaces opposite of the one of the surfaces; forming the second film containing the at least one heavy rare earth element on the another one of the surfaces and along the periphery of the another one of the surfaces; said step of forming the second film further including a step of melting the powder on the another one of the surfaces and along the periphery using a laser to form the second film and adhering the second film to the periphery; removing excess powder from the another one of the surfaces; diffusing the first film and the second film into the NdFeB magnet block under a vacuum environment or an inert environment containing argon and at a predetermined temperature.
14. The method as set forth in claim 13 wherein the NdFeB magnet block has a length and a width of at least 10 mm.
15. The method as set forth in claim 13 wherein the powder has an average particle size of between 1 ?m and 300 ?m.
16. The method as set forth in claim 13 wherein the at least one heavy rare earth element is selected from a group consisting of Tb, Dy, or an alloy containing Dy or Tb and the powder is present in an amount of 0.1 wt. % and 2 wt. % of the total mass of the NdFeB magnet block.
17. The method as set forth in claim 13 wherein an area covered by the first film is 10% to 65% of an area covered by the powder on one of the surfaces of the NdFeB magnet block.
18. The method as set forth in claim 13 wherein an area covered by the second film is 10% to 65% of an area covered by the powder on the another one of the surfaces of the NdFeB magnet block.
19. The method set forth in claim 13 wherein said step of diffusing is further defined as heating the NdFeB magnet block including the first film and the second film at the predetermined temperature of between 850? ? C. and 950? C. at a diffusing time of between 6 hours and 72 hours.
20. The method as set forth in claim 19 wherein said step of diffusing further including a step of aging the NdFeB magnet block including the first film and the second film at an aging temperature of between 450? C. and 650? C. at an aging time of between 3 hours and 15 hours.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
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DESCRIPTION OF THE ENABLING EMBODIMENT
(15) Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, it is one aspect of the present invention to provide a gradient NdFeB magnet. The gradient NdFeB magnet includes an NdFeB magnet block extending along a magnetization direction and having a plurality of surfaces perpendicular to the magnetization direction. According to one embodiment of the present invention, the NdFeB magnet block can have a thickness of between 2-10 mm along the magnetization direction. According to another embodiment, the NdFeB magnet block can have a length and a width of at least 10 mm.
(16) A first film containing at least one heavy rare earth element, disposed on one of the surfaces, attaches to the NdFeB magnet block and extends along a periphery of the one of the surfaces. A second film containing at least one heavy rare earth element, disposed on another one of the surfaces, opposite of the one of the surfaces, attaches to the NdFeB magnet block and extending along a periphery of the another one of the surfaces. The at least one heavy rare earth element is selected from a group consisting of Tb, Dy, or an alloy containing Dy or Tb. Preferably, the first film and the second film are attached and formed on the NdFeB magnet block by melting a powder containing the at least one heavy rare earth metal on the one and the another one of the surfaces and along the periphery using a laser. In other words, the first film and the second film are only formed along the periphery of the one of the surfaces and the another one of the surfaces. According to one embodiment of the present invention, the powder containing the least one heavy rare earth element is selected from a group consisting of Tb, Dy, or an alloy containing Dy or Tb and is present in the powder in an amount of 0.1 wt. % and 2 wt. %. Preferably, according to one embodiment of the present invention, the powder has an average particle size of between 1 ?m and 300 ?m.
(17) The first film and the second film are diffused into the NdFeB magnet block dividing the NdFeB magnet block into an edge region, a transition region, and a central region along a plane extending perpendicular to the magnetization direction. The central portion is located at the center of the NdFeB magnet block. The transition region is located about the NdFeB magnet block. The edge region is located about the transition region. In other words, the central, transition, and edge regions of the NdFeB magnet block are disposed in a concentric relationship with one another with the central regions being disposed at the center region, the transition region extending about the center region, and the edge region extending about the transition region.
(18) The edge region has a coercivity that remains constant in a direction perpendicular to the magnetization direction, and the coercivity of the edge region, along the magnetization direction, gradually decreases from the one of the surfaces and the another one of the surfaces towards a point located between the one of the surfaces and the another one of the surfaces. The transition region also has a coercivity that decreases toward the central portion in the direction perpendicular to the magnetization direction and the coercivity of the transition region, along the magnetization direction, gradually decreases from the one of the surfaces and the another one of the surfaces to the point between the one of the surfaces and the another one of the surfaces. The center region has a coercivity that remains constant in the direction perpendicular to the magnetization direction and along the magnetization direction. It should be appreciated that an average of the coercivity of the edge region is greater than an average of the coercivity of the transition region and the average of the coercivity of the transition region is greater than an average of the coercivity of the central region. In other words, by diffusing the first film and the second film into the periphery of the NdFeB magnet block improves the coercivity of the edge portion of the NdFeB thereby improves the de-magnetization resistance of the NdFeB magnet.
(19) It is another aspect of the present invention to provide a method of making the gradient NdFeB magnet. The method includes a first step of providing an NdFeB magnet block having a plurality of surfaces that are perpendicular to a magnetization direction. According to one embodiment of the present invention, the NdFeB magnet block can have a thickness of between 2-10 mm along the magnetization direction. According to another embodiment, the NdFeB magnet block can have a length and a width of at least 10 mm. The method then proceeds with placing the NdFeB magnet block in a chamber containing an inert gas of argon with the magnetization direction of the NdFeB magnet block being arranged in a vertical direction. The next step of the method includes depositing a powder, containing at least one heavy rare earth element, on the one of the surfaces. According to one embodiment of the present invention, the powder containing the least one heavy rare earth element is selected from a group consisting of Tb, Dy, or an alloy containing Dy or Tb and the powder is present in an amount of 0.1 wt. % and 2 wt. % of the NdFeB magnet block. Preferably, according to one embodiment of the present invention, the powder has an average particle size of between 1 ?m and 300 ?m.
(20) Then, the method follows with a step of forming the first film containing the at least one heavy rare earth element on the one of the surfaces and along the periphery of the one of the surfaces. The step of forming the first film further includes a step of melting the powder on the one of the surfaces and along the periphery using a laser to form the first film and adhering the first film to the periphery. Preferably, an area covered by the first film is 10% to 65% of an area covered by the powder on one of the surfaces of the NdFeB magnet block. Next, excess powder are removed from the one of the surfaces. In other words, the powder of the heavy rare earth elements only forms the first film along the periphery of the one of the surfaces. This significantly reduces the amount of heavy rare earth elements used during the manufacturing process. After removing the excess powder, the NdFeB magnet block is rotated 180?.
(21) After rotating the magnet block, the powder, containing at least one heavy rare earth element, is deposited on the another one of the surfaces opposite of the one of the surfaces. Then, the method proceeds with forming the second film containing the at least one heavy rare earth element on the another one of the surfaces and along the periphery of the another one of the surfaces. The step of forming the second film further including a step of melting the powder on the another one of the surfaces and along the periphery using a laser to form the second film and adhering the second film to the periphery. Preferably, an area covered by the second film is 10% to 65% of an area covered by the powder on the another one of the surfaces of the NdFeB magnet block. Next, the excess powder is removed from the another one of the surfaces. Similar to the first film, the powder of the heavy rare earth elements only forms the second film along the periphery of the another one of the surfaces. This also significantly reduces the amount of heavy rare earth elements used during the manufacturing process. Then, the first film and the second film are diffused into the NdFeB magnet block under a vacuum environment or an inert environment containing argon and at a predetermined temperature. The step of diffusing is further defined as heating the NdFeB magnet block including the first film and the second film at the predetermined temperature of between 850? C. and 950? C. at a diffusing time of between 6 hours and 72 hours. The diffusing further includes a step of aging the NdFeB magnet block including the first film and the second film at an aging temperature of between 450? C. and 650? C. at an aging time of between 3 hours and 15 hours.
(22) The examples below provide a better illustration of the present invention. The examples are used for illustrative purposes only and do not limit the scope of the present invention.
Implementing Example 1
(23) In implementing example 1, a plurality of NdFeB magnet blocks 1, each having a dimension of 20 mm*20 mm*5 mm are provided. Each of the NdFeB magnet blocks 1 has a plurality of surfaces that are perpendicular to a magnetization direction. Each of the NdFeB magnet blocks 1 are then placed in a chamber containing an inert gas of argon with the magnetization direction of the NdFeB magnet block 1 being arranged in a vertical direction. Then, as best illustrated in
(24) After rotating the NdFeB magnet block, the powder 1, containing at least one heavy rare earth element of Tb, is deposited on the another one of the surfaces opposite of the one of the surfaces. A second film containing the at least one heavy rare earth element of Tb is formed on the another one of the surfaces and along the periphery of the another one of the surfaces. In particular, the NdFeB magnet block containing the heavy rare earth element is move under a laser wherein the laser melts the powder, in a strip extending approximately 2 mm along the periphery of the another one of the surfaces, to form the second film and adhering the second film to the periphery. Excess powder are then removed from the another one of the surfaces.
(25) Then, the first film and the second film are diffused into the NdFeB magnet block under a vacuum environment and at a predetermined temperature. In particular, the NdFeB magnet block including the first film and the second film is heated at the predetermined temperature of between 900? C. at a diffusing time of 24 hours. Then, the NdFeB magnet block including the first film and the second film is subjected to an aging treatment at an aging temperature of between 500? C. at an aging time of 6 hours.
(26) After diffusing the NdFeB magnet block, the gradient NdFeB magnet is formed and includes an edge region 4, a transition region 5, and a central region 6 along a plane extending perpendicular to the magnetization direction. The edge region 4 has a coercivity that remains constant in a direction perpendicular to the magnetization direction, and the coercivity of the edge region 4, along the magnetization direction, gradually decreases from the one of the surfaces and the another one of the surfaces towards a point located between the one of the surfaces and the another one of the surfaces. The transition region 5 also has a coercivity that decreases toward the central portion 6 in the direction perpendicular to the magnetization direction and the coercivity of the transition region 5, along the magnetization direction, gradually decreases from the one of the surfaces and the another one of the surfaces to the point located between the one of the surfaces and the another one of the surfaces. The center region 6 has a coercivity that remains constant in the direction perpendicular to the magnetization direction and along the magnetization direction. An average of the coercivity of the edge region 4 is greater than an average of the coercivity of the transition region 5 and the average of the coercivity of the transition region 6 is greater than an average of the coercivity of the central region 6.
(27) After forming the gradient NdFeB magnet, the gradient magnet is sliced along the in the length or width direction forming a plurality of 20 mm*1 mmm*5 mm NdFeB magnets as best illustrated in
Implementing Example 2
(28) In implementing example 2, a plurality of NdFeB magnet blocks, each having a dimension of 40 mm*40 mm*10 mm are provided. Each of the NdFeB magnet blocks has a plurality of surfaces that are perpendicular to a magnetization direction. Each of the NdFeB magnet blocks are then placed in a chamber containing an inert gas of argon with the magnetization direction of the NdFeB magnet block being arranged in a vertical direction. Then, a powder, containing at least one heavy rare earth element of Tb and having an average particle size of 100 ?m, is disposed on the one of the surfaces. The heavy rare earth element is 2.0 wt. % of the total mass of the NdFeB magnet block. Next, a first film, containing the at least one heavy rare earth element of Tb, is formed on the one of the surfaces and along the periphery of the one of the surfaces. More specifically, the NdFeB magnet block containing the heavy rare earth element is move under a laser wherein the laser melts the powder, in a strip extending approximately 3 mm along the periphery of the one of the surfaces, to form the first film and adhering the first film to the periphery. The area covered by the first film is approximately 28% the area covered by the powder on one of the surfaces of the NdFeB magnet block. Excess powder are then removed from the one of the surfaces. The NdFeB magnet block is rotated 180?.
(29) After rotating the magnet block, the powder, containing at least one heavy rare earth element of Tb, is deposited on the another one of the surfaces opposite of the one of the surfaces. A second film containing the at least one heavy rare earth element of Tb is formed on the another one of the surfaces and along the periphery of the another one of the surfaces. In particular, the NdFeB magnet block containing the heavy rare earth element is move under a laser wherein the laser melts the powder, in a strip extending approximately 3 mm along the periphery of the another one of the surfaces, to form the second film and adhering the second film to the periphery. Excess powder are then removed from the another one of the surfaces.
(30) Then, the first film and the second film are diffused into the NdFeB magnet block under a vacuum environment and at a predetermined temperature. In particular, the NdFeB magnet block including the first film and the second film is heated at the predetermined temperature of between 850? C. at a diffusing time of 72 hours. Then, the NdFeB magnet block including the first film and the second film is subjected to an aging treatment at an aging temperature of between 500? C. at an aging time of 15 hours.
(31) After diffusing the NdFeB magnet block, the gradient NdFeB magnet is formed and includes an edge region, a transition region, and a central region along a plane extending perpendicular to the magnetization direction. The edge region has a coercivity that remains constant in a direction perpendicular to the magnetization direction, and the coercivity of the edge region, along the magnetization direction, gradually decreases from the one of the surfaces and the another one of the surfaces towards a point located between the one of the surfaces and the another one of the surfaces. The transition region also has a coercivity that decreases toward the central portion in the direction perpendicular to the magnetization direction and the coercivity of the transition region, along the magnetization direction, gradually decreases from the one of the surfaces and the another one of the surfaces to the point between the one of the surfaces and the another one of the surfaces. The center region has a coercivity that remains constant in the direction perpendicular to the magnetization direction and along the magnetization direction. An average of the coercivity of the edge region is greater than an average of the coercivity of the transition region and the average of the coercivity of the transition region is greater than an average of the coercivity of the central region.
(32) After forming the gradient NdFeB magnet, the gradient magnet is sliced along the in the length or width direction forming a plurality of 40 mm*1 mmm*10 mm NdFeB magnets. Then, the NdFeB magnets are further sliced into small NdFeB magnets having a dimension of 1 mm*1 mm*1 mm. It should be noted that the NdFeB magnet located in the first row and the first column is referred to as 1, 1. The NdFeB magnet located in the second row and the first column is referred to as 2, 1. The NdFeB magnet located in the third row and the third column is referred to as 3, 3. Properties of the small NdFeB magnets are then tested wherein portions of the properties are listed in Table 1 below.
Implementing Example 3
(33) In implementing example 3, a plurality of NdFeB magnet blocks, each having a dimension of 80 mm*50 mm*5 mm are provided. Each of the NdFeB magnet blocks has a plurality of surfaces that are perpendicular to a magnetization direction. Each of the NdFeB magnet blocks are then placed in a chamber containing an inert gas of argon with the magnetization direction of the NdFeB magnet block being arranged in a vertical direction. Then, a powder, containing at least one heavy rare earth element of Dy and having an average particle size of 200 ?m, is disposed on the one of the surfaces. The heavy rare earth element is 0.5 wt. % of the total mass of the NdFeB magnet block. Next, a first film, containing the at least one heavy rare earth element of Dy, is formed on the one of the surfaces and along the periphery of the one of the surfaces. More specifically, the NdFeB magnet block containing the heavy rare earth element is move under a laser wherein the laser melts the powder, in a strip extending approximately 2 mm along the periphery of the one of the surfaces, to form the first film and adhering the first film to the periphery. The area covered by the first film is approximately 24% the area covered by the powder on one of the surfaces of the NdFeB magnet block. Excess powder are then removed from the one of the surfaces. The NdFeB magnet block is rotated 180?.
(34) After rotating the magnet block, the powder, containing at least one heavy rare earth element of Dy, is deposited on the another one of the surfaces opposite of the one of the surfaces. A second film containing the at least one heavy rare earth element of Dy is formed on the another one of the surfaces and along the periphery of the another one of the surfaces. In particular, the NdFeB magnet block containing the heavy rare earth element is move under a laser wherein the laser melts the powder, in a strip extending approximately 2 mm along the periphery of the another one of the surfaces, to form the second film and adhering the second film to the periphery. Excess powder are then removed from the another one of the surfaces.
(35) Then, the first film and the second film are diffused into the NdFeB magnet block under a vacuum environment and at a predetermined temperature. In particular, the NdFeB magnet block including the first film and the second film is heated at the predetermined temperature of between 950? C. at a diffusing time of 6 hours. Then, the NdFeB magnet block including the first film and the second film is subjected to an aging treatment at an aging temperature of between 450? C. at an aging time of 8 hours.
(36) After diffusing the NdFeB magnet block, the gradient NdFeB magnet is formed and includes an edge region, a transition region, and a central region along a plane extending perpendicular to the magnetization direction. The edge region has a coercivity that remains constant in a direction perpendicular to the magnetization direction, and the coercivity of the edge region, along the magnetization direction, gradually decreases from the one of the surfaces and the another one of the surfaces towards a point located between the one of the surfaces and the another one of the surfaces. The transition region also has a coercivity that decreases toward the central portion in the direction perpendicular to the magnetization direction and the coercivity of the transition region, along the magnetization direction, gradually decreases from the one of the surfaces and the another one of the surfaces to the point between the one of the surfaces and the another one of the surfaces. The center region has a coercivity that remains constant in the direction perpendicular to the magnetization direction and along the magnetization direction. An average of the coercivity of the edge region is greater than an average of the coercivity of the transition region and the average of the coercivity of the transition region is greater than an average of the coercivity of the central region.
(37) After forming the gradient NdFeB magnet, the gradient magnet is sliced along the in the length or width direction forming a plurality of 20 mm*1 mmm*5 mm NdFeB magnets. Then, the NdFeB magnets are further sliced into small NdFeB magnets having a dimension of 1 mm*1 mm*1 mm. It should be noted that the NdFeB magnet located in the first row and the first column is referred to as 1, 1. The NdFeB magnet located in the second row and the first column is referred to as 2, 1. The NdFeB magnet located in the third row and the third column is referred to as 3, 3. Properties of the small NdFeB magnets are then tested wherein portions of the properties are listed in Table 1 below.
Implementing Example 4
(38) In implementing example 4, a plurality of NdFeB magnet blocks, each having a dimension of 80 mm*80 mm*5 mm are provided. Each of the NdFeB magnet blocks has a plurality of surfaces that are perpendicular to a magnetization direction. Each of the NdFeB magnet blocks are then placed in a chamber containing an inert gas of argon with the magnetization direction of the NdFeB magnet block being arranged in a vertical direction. Then, a powder, containing at least one heavy rare earth element of Dy and having an average particle size of 250 ?m, is disposed on the one of the surfaces. The powder is an alloy powder containing Tb and Co wherein Tb is present at 90 wt. %). The powder is 0.5% of the mass of the NdFeB magnet block. Next, a first film, containing the at least one heavy rare earth element of Tb, is formed on the one of the surfaces and along the periphery of the one of the surfaces. More specifically, the NdFeB magnet block containing the heavy rare earth element is move under a laser wherein the laser melts the powder, in a strip extending approximately 2 mm along the periphery of the one of the surfaces, to form the first film and adhering the first film to the periphery. The area covered by the first film is approximately 10% the area covered by the powder on one of the surfaces of the NdFeB magnet block. Excess powder are then removed from the one of the surfaces. The NdFeB magnet block is rotated 180?.
(39) After rotating the magnet block, the powder, containing at least one heavy rare earth element of Tb, is deposited on the another one of the surfaces opposite of the one of the surfaces. A second film containing the at least one heavy rare earth element of Tb is formed on the another one of the surfaces and along the periphery of the another one of the surfaces. In particular, the NdFeB magnet block containing the heavy rare earth element is move under a laser wherein the laser melts the powder, in a strip extending approximately 2 mm along the periphery of the another one of the surfaces, to form the second film and adhering the second film to the periphery. Excess powder are then removed from the another one of the surfaces.
(40) Then, the first film and the second film are diffused into the NdFeB magnet block under a vacuum environment and at a predetermined temperature. In particular, the NdFeB magnet block including the first film and the second film is heated at the predetermined temperature of between 900? C. at a diffusing time of 24 hours. Then, the NdFeB magnet block including the first film and the second film is subjected to an aging treatment at an aging temperature of between 650? C. at an aging time of 6 hours.
(41) After diffusing the NdFeB magnet block, the gradient NdFeB magnet is formed and includes an edge region, a transition region, and a central region along a plane extending perpendicular to the magnetization direction. The edge region has a coercivity that remains constant in a direction perpendicular to the magnetization direction, and the coercivity of the edge region, along the magnetization direction, gradually decreases from the one of the surfaces and the another one of the surfaces towards a point located between the one of the surfaces and the another one of the surfaces. The transition region also has a coercivity that decreases toward the central portion in the direction perpendicular to the magnetization direction and the coercivity of the transition region, along the magnetization direction, gradually decreases from the one of the surfaces and the another one of the surfaces to the point between the one of the surfaces and the another one of the surfaces. The center region has a coercivity that remains constant in the direction perpendicular to the magnetization direction and along the magnetization direction. An average of the coercivity of the edge region is greater than an average of the coercivity of the transition region and the average of the coercivity of the transition region is greater than an average of the coercivity of the central region.
(42) After forming the gradient NdFeB magnet, the gradient magnet is sliced along the in the length or width direction forming a plurality of 80 mm*1 mmm*5 mm NdFeB magnets. Then, the NdFeB magnets are further sliced into small NdFeB magnets having a dimension of 1 mm*1 mm*1 mm. It should be noted that the NdFeB magnet located in the first row and the first column is referred to as 1, 1. The NdFeB magnet located in the second row and the first column is referred to as 2, 1. The NdFeB magnet located in the third row and the third column is referred to as 3, 3. Properties of the small NdFeB magnets are then tested wherein portions of the properties are listed in Table 1 below.
Implementing Example 5
(43) In implementing example 5, a plurality of NdFeB magnet blocks, each having a dimension of 10 mm*10 mm*2 mm are provided. Each of the NdFeB magnet blocks has a plurality of surfaces that are perpendicular to a magnetization direction. Each of the NdFeB magnet blocks are then placed in a chamber containing an inert gas of argon with the magnetization direction of the NdFeB magnet block being arranged in a vertical direction. Then, a powder, containing at least one heavy rare earth element of Tb and having an average particle size of 10 ?m, is disposed on the one of the surfaces. The powder is a hydrogenated Tb powder wherein the powder is 0.1% of the mass of the NdFeB magnet blocks. Next, a first film, containing the at least one heavy rare earth element of Tb, is formed on the one of the surfaces and along the periphery of the one of the surfaces. More specifically, the NdFeB magnet block containing the heavy rare earth element is move under a laser wherein the laser melts the powder, in a strip extending approximately 2 mm along the periphery of the one of the surfaces, to form the first film and adhering the first film to the periphery. The area covered by the first film is approximately 64% the area covered by the powder on one of the surfaces of the NdFeB magnet block. Excess powder are then removed from the one of the surfaces. The NdFeB magnet block is rotated 180?.
(44) After rotating the magnet block, the powder, containing at least one heavy rare earth element of Tb, is deposited on the another one of the surfaces opposite of the one of the surfaces. A second film containing the at least one heavy rare earth element of Tb is formed on the another one of the surfaces and along the periphery of the another one of the surfaces. In particular, the NdFeB magnet block containing the heavy rare earth element is move under a laser wherein the laser melts the powder, in a strip extending approximately 2 mm along the periphery of the another one of the surfaces, to form the second film and adhering the second film to the periphery. Excess powder are then removed from the another one of the surfaces.
(45) Then, the first film and the second film are diffused into the NdFeB magnet block under a vacuum environment and at a predetermined temperature. In particular, the NdFeB magnet block including the first film and the second film is heated at the predetermined temperature of between 900? C. at a diffusing time of 6 hours. Then, the NdFeB magnet block including the first film and the second film is subjected to an aging treatment at an aging temperature of between 650? C. at an aging time of 3 hours.
(46) After diffusing the NdFeB magnet block, the gradient NdFeB magnet is formed and includes an edge region, a transition region, and a central region along a plane extending perpendicular to the magnetization direction. The edge region has a coercivity that remains constant in a direction perpendicular to the magnetization direction, and the coercivity of the edge region, along the magnetization direction, gradually decreases from the one of the surfaces and the another one of the surfaces towards a point located between the one of the surfaces and the another one of the surfaces. The transition region also has a coercivity that decreases toward the central portion in the direction perpendicular to the magnetization direction and the coercivity of the transition region, along the magnetization direction, gradually decreases from the one of the surfaces and the another one of the surfaces to the point between the one of the surfaces and the another one of the surfaces. The center region has a coercivity that remains constant in the direction perpendicular to the magnetization direction and along the magnetization direction. An average of the coercivity of the edge region is greater than an average of the coercivity of the transition region and the average of the coercivity of the transition region is greater than an average of the coercivity of the central region.
Comparative Example 1
(47) In comparative example 1, a plurality of NdFeB magnet blocks, each having a dimension of 20 mm*20 mm*5 mm are provided. More specifically, the NdFeB magnet blocks are provided using the saw raw powder as the NdFeB magnets from Implementing Example 5. The NdFeB magnet blocks are then sliced along the in the length or width direction forming a plurality of 20 mm*1 mmm*5 mm NdFeB magnets. Then, the NdFeB magnets are further sliced into small NdFeB magnets having a dimension of 1 mm*1 mm*1 mm. It should be noted that the NdFeB magnet located in the first row and the first column is referred to as 1, 1. The NdFeB magnet located in the second row and the first column is referred to as 2, 1. The NdFeB magnet located in the third row and the third column is referred to as 3, 3. Properties of the small NdFeB magnets are then tested wherein portions of the properties are listed in Table 1 below.
(48) TABLE-US-00001 TABLE 1 Magnetic Properties of the Gradient Magnet of Implementing Examples 1-4 and Magnetic Properties of the Magnets of Comparative Example 1 Comparative Sample No. (1, 1) (1, 5) (1, 10) (1, 15) (1, 20) Example Coercivity Br Hcj Br Hcj Br Hcj Br Hcj Br Hcj 13.8 18.9 13.79 18.9 13.8 18.9 13.79 18.9 13.8 18.89 Sample No. (3, 1) (3, 5) (3, 10) (3, 15) (3, 20) Coercivity Br Hcj Br Hcj Br Hcj Br Hcj Br Hcj 13.79 18.9 13.8 18.9 13.8 18.9 13.8 18.9 13.79 18.9 Sample No. (5, 1) (5, 5) (5, 10) (5, 15) (5, 20) Coercivity Br Hcj Br Hcj Br Hcj Br Hcj Br Hcj 13.79 18.9 13.8 18.89 13.8 18.9 13.79 18.89 13.79 18.89 Implementing Sample No. (1, 1) (1, 2) (1, 3) (1, 6) (1, 8) Example 1 Coercivity Br Hcj Br Hcj Br Hcj Br Hcj Br Hcj 13.62 29.6 13.61 29.55 13.66 27.2 13.79 18.9 13.8 18.89 Sample No. (3, 1) (3, 2) (3, 3) (3, 6) (3, 8) Coercivity Br Hcj Br Hcj Br Hcj Br Hcj Br Hcj 13.7 26.4 13.71 26.4 13.75 23.7 13.8 18.88 13.8 18.88 Sample No. (5, 1) (5, 2) (5, 3) (5, 6) (5, 8) Coercivity Br Hcj Br Hcj Br Hcj Br Hcj Br Hcj 13.61 29.58 13.6 29.6 13.65 27.3 13.79 18.89 13.8 18.89 Implementing Sample No. (1, 1) (1, 3) (1, 4) (1, 8) (1, 10) Example 2 Coercivity Br Hcj Br Hcj Br Hcj Br Hcj Br Hcj 13.59 29.58 13.6 29.55 13.65 28.1 13.79 18.88 13.8 18.9 Sample No. (5, 1) (5, 3) (5, 4) (5, 8) (5, 10) Coercivity Br Hcj Br Hcj Br Hcj Br Hcj Br Hcj 13.71 26.42 13.73 26.38 13.76 24.2 13.8 18.89 13.79 18.89 Sample No. (10, 1) (10, 3) (10, 4) (10, 8) (10, 10) Coercivity Br Hcj Br Hcj Br Hcj Br Hcj Br Hcj 13.6 29.57 13.61 29.58 13.66 28.2 13.79 18.9 13.8 18.88 Implementing Sample No. (1, 1) (1, 2) (1, 3) (1, 6) (1, 8) Example 3 Coercivity Br Hcj Br Hcj Br Hcj Br Hcj Br Hcj 13.63 25.68 13.61 25.68 13.67 23.11 13.78 18.9 13.8 18.89 Sample No. (3, 1) (3, 2) (3, 3) (3, 6) (3, 8) Coercivity Br Hcj Br Hcj Br Hcj Br Hcj Br Hcj 13.71 22.21 13.72 22.2 13.76 21.2 13.8 18.9 13.79 18.89 Sample No. (5, 1) (5, 2) (5, 3) (5, 6) (5, 8) Coercivity Br Hcj Br Hcj Br Hcj Br Hcj Br Hcj 13.62 25.65 13.61 25.62 13.66 13.14 13.78 18.9 13.8 18.89 Implementing Sample No. (1, 1) (1, 2) (1, 3) (1, 6) (1, 8) Example 4 Coercivity Br Hcj Br Hcj Br Hcj Br Hcj Br Hcj 13.6 29.62 13.61 29.61 13.66 27.6 13.79 18.9 13.8 18.89 Sample No. (3, 1) (3, 2) (3, 3) (3, 6) (3, 8) Coercivity Br Hcj Br Hcj Br Hcj Br Hcj Br Hcj 13.72 26.51 13.73 26.48 13.76 23.9 13.8 18.89 13.79 18.89 Sample No. (5, 1) (5, 2) (5, 3) (5, 6) (5, 8) Coercivity Br Hcj Br Hcj Br Hcj Br Hcj Br Hcj 13.61 26.63 13.62 29.62 13.66 27.55 13.8 18.89 13.8 18.89
(49) As illustrated in
(50) Obviously, many modifications and variations of the present invention are possible in light of the above teachings and may be practiced otherwise than as specifically described while within the scope of the appended claims. These antecedent recitations should be interpreted to cover any combination in which the inventive novelty exercises its utility. The use of the word said in the apparatus claims refers to an antecedent that is a positive recitation meant to be included in the coverage of the claims whereas the word the precedes a word not meant to be included in the coverage of the claims.