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Nd-fe-b magnet with modified grain boundary and process for producing the same

An intergranular and modified technology, which is applied in the manufacture of inductors/transformers/magnets, magnetic objects, magnetic materials, etc., can solve the problems of reduced saturation magnetization, reduced maximum energy product residual magnetic flux density, etc., and achieves improved demagnetization and improved correction Coercive force, the effect of solving resource problems

Inactive Publication Date: 2007-11-21
JAPAN SCI & TECH CORP +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In terms of general sintered magnets, by using anisotropic magnetic field compared with Nd 2 Fe 14 B compound big Dy 2 Fe 14 B or Tb 2 Fe 14 The magnetism of the B compound makes the magnet alloy contain several mass % to 10 mass %. Although a high coercive force can be realized, as the content of Dy or Tb increases, a sharp decrease in saturation magnetization is incurred, and some Make the maximum energy product ((BH) 最大 ) and remanent flux density (Br) decrease problems exist

Method used

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  • Nd-fe-b magnet with modified grain boundary and process for producing the same
  • Nd-fe-b magnet with modified grain boundary and process for producing the same
  • Nd-fe-b magnet with modified grain boundary and process for producing the same

Examples

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Embodiment 1

[0071] Hereinafter, the present invention will be described in detail with reference to examples.

[0072] by Nd 12.5 Fe 79.5 B 8 Composed alloy ingots were made into alloy flakes with a thickness of about 0.2 mm according to the strip casting method. Next, by filling this flake in a container and releasing it after absorbing 300 kPa of hydrogen gas at room temperature, an amorphous powder with a size of 0.1 to 0.2 mm can be obtained, and jet milling is continuously performed to produce a fine powder of about 3 μm. This fine powder was filled into a mold, shaped by applying a pressure of 100 MPa while applying a magnetic field of 800 kA / m, filled into a vacuum furnace, and sintered at 1080° C. for 1 hour. This sintered body was cut and processed to produce a plurality of 5 mm x 5 mm x 3 mm plate-shaped samples having anisotropy in the thickness direction, and one of them was used as a comparative sample (1).

[0073] Second, the mixed Dy 2 o 3 Powder 2g and CaH 2 0.7 g ...

Embodiment 2

[0082] to the mixed Dy 2 o 3 Powder 1g and CaH 2 A small amount of methanol was added to 0.3 g of the powder as a slurry, which was applied to each plate-shaped sample similar to that used in Example 1 and dried. On the other hand, as for the comparative example, only Dy 2 o 3 1 g of the powder is the same as a slurry, and the same is applied and dried. Each of these was filled in a stainless steel crucible, and solid phase reduction and diffusion infiltration were performed by heat treatment at 920° C. and 1000° C. for 2 hours each in a blanket gas flowing with Ar gas.

[0083] The treated magnet sample is to remove the CaO powder on the surface, wash it with pure water and alcohol, and then dry it. Those who have used the former mixed powder are used as samples (7) to (8) of the present invention, and those who have used the latter Dy 2 o 3 Individual powders were used as comparative samples (2) to (3).

[0084] Table 2 shows the magnetic property values ​​and the am...

Embodiment 3

[0090] Mixed DyF 3 3 g of powder, 0.9 g of metal Ca particles, and 5 g of LiF powder were filled in a graphite crucible, and the plate magnet sample used in Example 1 was embedded in the middle of the powder. Next, install it in a shrouded gas furnace with Ar gas flow, control the temperature of the furnace, and perform a molten liquid phase reduction reaction and diffusion infiltration treatment at a maximum temperature of 900° C. in the crucible for 5 to 60 minutes and cool it down.

[0091] After each sample was taken out from the crucible and the reaction residue on the surface of the magnet was removed with a brush, the CaF powder was dissolved and removed with dilute hydrochloric acid, washed with pure water and alcohol, and pre-dried. The obtained samples were treated as samples (9) to (14) of the present invention in the order of processing time of 5 to 60 minutes, and their magnetic properties were measured in the same manner as in Example 1. And, tentatively assumin...

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Abstract

In the conventional process, a coercitivity increase is realized by effecting selective presence of, for example, Dy metal in crystal grain boundary zones of sintered magnet. However, as this process employs a physical film forming technique using a vacuum vessel, such as sputtering, there has been a difficulty in mass productivity in the performing of vast quantities of magnet treatment. Further, from the viewpoint, for example, that an expensive high-purity Dy metal or the like must be employed as a film forming material, there has been a drawback in magnet cost. There is provided a method of modifying the grain boundary of Nd-Fe-B magnet, characterized in that a fluoride, oxide or chloride of metal element M (M: Pr, DY, Tb or Ho) is subjected to reduction treatment so that there is effected diffusion infiltration of the metal element M from the surface of Nd-Fe-B sintered magnet having an Nd rich crystal grain boundary phase surrounding the circumferential part of Nd2Fe14B main crystal into the grain boundary phase.

Description

technical field [0001] The present invention relates to a high-performance magnet with excellent mass productivity and a manufacturing method thereof, in which Dy or Tb elements are diffused from the surface of the magnet into the crystalline intergranular phase of Nd-Fe-B magnets to perform intergranular modification. Background technique [0002] Rare earth-iron-boron magnets are widely used as voice coil motors (VCM) of hard disk drives or magnetic circuits of magnetic tomography (MRI), etc. In recent years, the scope of application is also expanding to drive motors of electric vehicles. Especially in automotive applications, heat resistance is required. In order to avoid high temperature demagnetization at an ambient temperature of 150-200°C, magnets with higher coercive force are required. [0003] Nd-Fe-B system sintered magnet is surrounded by Nd-rich intergranular phase Nd 2 Fe 14 It is formed by the fine structure of the main phase of the B compound, and the compo...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01F41/02B22F3/24H01F1/053H01F1/08
CPCC22C29/14H01F1/0577H01F41/0293B22F3/24H01F1/053H01F1/08
Inventor 町田宪一铃木俊治
Owner JAPAN SCI & TECH CORP
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