JP3296507B2 - Rare earth permanent magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high performance rare earth permanent magnet used for a VCM (voice coil motor), a rotating device, and the like.

[0002]

2. Description of the Related Art Nd-Fe-B magnets (patent publication No. 6)
No. 3-65742) has been used in a wide range of applications because of its high saturation magnetization and high energy product. Problems such as heat resistance and corrosion resistance, which have been problematic until now, have been solved to some extent, and some problems have been solved in practical use. Products with a maximum energy product of 30 to 40 MGOe have been produced.

[0003]

Recently, there has been a demand for further downsizing of a device using a permanent magnet, and accordingly, a permanent magnet having a higher energy product has been desired. Therefore, an object of the present invention is to provide a rare earth magnet having a high energy product.

[0004]

In order to improve the performance of the Nd-Fe-B magnet, the degree of orientation of crystal grains is improved, and the amount of oxygen is reduced to reduce the total rare earth element content. It is essential to improve the volume ratio. Here, the degree of orientation is a numerical value indicating how much the easy axis of magnetization is aligned in each crystal grain, and is usually expressed by the ratio (Br / Ms) between the residual magnetic flux density Br and the saturation magnetization Ms. In order to improve the degree of orientation, the finely pulverized powder magnetically aggregates when it is oriented in a magnetic field during the molding process. Therefore, it is necessary to reduce the magnetic aggregation and to perform molding without disturbing the orientation. In order to improve the volume fraction of the main phase, the Nd-rich phase, B-rich phase, oxide phase, N
b It is necessary to minimize non-magnetic phases such as precipitates and pores. However, even when the volume fraction of the main phase is increased, good magnetic properties cannot be obtained without the Nd-rich phase, and when the B-rich phase disappears, Fe is generated, deteriorating the squareness. For this reason, the Nd-rich phase and the B-rich phase have ranges for obtaining good magnetic characteristics.

The present invention has been made on the basis of the above-mentioned findings, and is directed to an R ₂ T ₁₄ B compound (R is a rare earth metal element, T
Is a R-T-B rare earth permanent magnet composed of a main phase mainly composed of a transition metal element) and a non-magnetic phase, and has an orientation degree (Br / Ms) of 0.90 to 0.97. 8 phase volume fraction
It is characterized by comprising a sintered body having a volume ratio of 3 to 10% of a nonmagnetic phase having 9 to 97% and an Nd-rich phase and a B-rich phase as essential.

Hereinafter, the present invention will be described in more detail. The rare earth permanent magnet of the present invention has an orientation degree (Br / Ms) of 0.90 to 0.9.
7, the volume fraction of the main phase is 89 to 97%, and the volume fraction of the non-magnetic phase essentially including the Nd-rich phase and the B-rich phase is 3 to 10%.
Where the degree of orientation (Br / Ms) is 0.90 to 0.94.
, The main phase volume fraction is 89 to 95%, the Nd-rich phase and B
When the volume fraction of the non-magnetic phase that requires a rich phase is 5 to 10%, the characteristic of (BH) max = 40 to 46 MGOe is
Further, the degree of orientation (Br / Ms) is 0.92 to 0.97, the volume ratio of the main phase is 92 to 97%, and the volume ratio of the nonmagnetic phase which essentially includes the Nd-rich phase and the B-rich phase is 3 to 7%. %, A characteristic of (BH) max = 42 to 53 MGOe is obtained.

In the non-magnetic phase other than the main phase, the volume ratio of the Nd-rich phase is 2 to 8%, and the volume ratio of the B-rich phase is 0.1 to 8%.
It is preferable that If the Nd-rich phase has a volume ratio of less than 2%, liquid phase sintering cannot be performed and good characteristics cannot be obtained, so the volume ratio is set to 2% or more. Desirably, it is 2.3% or more. When the B-rich phase does not exist, Fe is formed and the squareness is deteriorated. If the volume ratio is 0.1% or more, no Fe is formed and excellent magnetic properties can be obtained. Therefore, the volume ratio is 0.5
% Or more. However, it is not preferable that the Nd-rich phase and the B-rich phase each exceed 8%, since magnetic properties are deteriorated.

The following are desirable as the composition of the rare earth permanent magnet of the present invention. _{(Nd 1-XYZ Ce X Pr} Y Dy Z) a Fe b Co c B d AD e
M _f Al _g (where 0.001 ≦ X ≦ 0.1, 0.05 ≦ Y ≦
0.5, 0.001 ≦ Z ≦ 0.25, AD is Cu, Z
n is at least one of Ga and M is V, Mo, N
at least one of b and W, 5 ≦ a ≦ 18 at%;
65 ≦ b ≦ 85 at%, 0 ≦ c ≦ 20 at%,
4 ≦ d ≦ 15 at%, 0 ≦ e ≦ 7 at%, 0 ≦ f ≦
(7 at%, 0 ≦ g ≦ 5 at%) The rare earth element R is contained in a range of 5 at% or more and 18 at% or less, preferably 10 at% or more and 16 at% or less. Excessive addition of Ce is not preferred, and 0.001 ≦
X ≦ 0.1 is desirable. If Pr is used in the range of 0.05 ≦ Y ≦ 0.5, it is effective in improving coercive force and heat resistance. However, addition of Pr further reduces saturation magnetization and also reduces corrosion resistance. A large coercive force is obtained when Dy is included, and N
The ratio of d + Ce + Pr to Dy is 99.95: 0.
The range of 05 to 75:25 is desirable because a high coercive force can be obtained without significantly lowering the saturation magnetization.

Fe is contained in a range of 65 ≦ b ≦ 85 at%. If it is less than 65 at%, the saturation magnetization is low.
If it exceeds t%, the coercive force is significantly reduced.

[0010] Co is an element that contributes to improvement in thermal stability, and is contained in a range of 20 at% or less. If the content exceeds 20 at%, the saturation magnetization and the coercive force decrease. In addition,
The ratio between Fe and Co is preferably in the range of 99.95: 0.05 to 77:23 in order to maintain appropriate squareness and coercive force.

The amount of B is preferably 4 ≦ d ≦ 15 at%,
Outside this range, the residual magnetic flux density and the coercive force become small.

AD is an element for improving the coercive force, but if it exceeds 7 at%, the residual magnetic flux density is reduced, so that it is set to 7 at% or less. It is preferable that the range is 0.01 ≦ e ≦ 4 at%.

The M element is an element effective for suppressing the growth of crystal grains and improving the thermal stability. However, if it is contained excessively, it reduces the saturation magnetization. Therefore, when added, the content is preferably 7 at% or less.

Al is effective in improving the coercive force, and Ferro-
From B and upon dissolution. However, excessive addition lowers the Curie temperature.
t% or less.

Next, a method for manufacturing the magnet of the present invention will be described. The magnet of the present invention can be manufactured by a sintering method. It is obtained by preparing a melted ingot, subjecting the ingot to a hydrogen storage / dehydrogenation treatment, finely pulverizing, then forming, sintering, and heat-treating in a magnetic field.

[0016]

【Example】

(Example 1) Metal Nd, metal Dy, Fe, Co, fer
ro-B and ferro-Nb were weighed so as to have the following composition, and were melted under vacuum to produce an ingot weighing 10 kg. Nd _x Dy _0.4 Fe _88.1-x Co _4.5 B ₆ Nb _0.5
Al _0.5 (X = 12.1 to 15.0) After crushing this ingot with a hammer, it was further coarsely crushed in an inert gas atmosphere using a coarse crusher to obtain a coarse powder having a particle size of 500 μm or less. . The coarse powder was similarly pulverized in an inert gas atmosphere using a jet mill to obtain a fine powder. This fine powder had an average particle size of 4.0 μm (FSSS). next,
This fine powder was press-molded in a magnetic field to produce a 20 × 20 × 15 compact. This molded body was sintered and subjected to a heat treatment to obtain a permanent magnet. FIG. 1 shows a change in (BH) max depending on the amount of Nd, and the amount of Nd is 12.7 at.
%, Good characteristics cannot be obtained due to a decrease in the Nd-rich phase. Also, as is clear from FIG. 1, the degree of orientation (Br
/ Ms) is 0.91, (BH) max = 45M
Although GOe was not obtained, it can be seen that (BH) max = 45 MGOe was obtained when the degree of orientation was 0.93. FIG. 2 shows Nd _12.8 Dy _0.4 Fe _75.3 Co _4.5 B _6.0
Oxygen content and B-rich phase in composition of Nb _0.5 Al _0.5 , N
The change of the volume ratio of a d-rich phase, an oxide phase, and Nb precipitate is shown. The oxide phase increases with an increase in the amount of oxygen, but Nd
The rich phase decreases. The Nb precipitate and the B-rich phase are almost constant irrespective of the amount of oxygen. The oxygen content is 0.3wt
%, The volume fraction of the main phase was 94.28%.

(Example 2) In the same manner as in Example 1, the composition N
d _12.4 Dy _0.4 Fe _75.9 Co _4.5 B _5.9 Nb _0.4 Al
_{At 0.5} , a magnet having an oxygen content of 0.1 wt% and a pore volume of _0.5 vol% was obtained. FIG. 3 shows a change in (BH) max depending on the degree of orientation of the magnet. In this composition, the degree of orientation is 0.958.
With the above, it can be seen that the characteristic of (BH) max = 50 MGOe can be obtained. The main phase volume at this time was 95.96.
%, B-rich phase 0.1%, Nd-rich phase 2.62
%, The oxide phase was 0.65%, and the Nb precipitate was 0.17%.

[0018]

According to the present invention, a high-performance magnet can be obtained by optimizing the orientation degree, the main phase volume ratio, and the Nd-rich phase and the B-rich phase in the RTB-based magnet.

[Brief description of the drawings]

FIG. 1 Nd _x Dy _0.4 Fe _88.1-x Co _4.5 B ₆ Nb _0.5 A
Nd for a magnet of l _0.5 (x = 12.1 to 15.0)
It is a graph which shows the change of (BH) max with quantity.

FIG. 2 Nd _12.8 Dy _0.4 Fe _75.3 Co _4.5 B _6.0 Nb _0.5
B-rich phase when the oxygen content is changed with the composition of Al _0.5 ,
It is a graph which shows the relationship of the volume ratio of a Nd rich phase, an oxide phase, and a Nb precipitate.

FIG. 3 Nd _12.4 Dy _0.4 Fe _75.9 Co _4.5 B _5.9 Nb _0.4
Al _0.5 , oxygen content 0.1 wt%, pore 0.5 vol
5 is a graph showing a change in (BH) max depending on the degree of orientation in the case of%.

Claims (4)

(57) [Claims] An R ₂ T ₁₄ B compound (R is a rare earth metal element,
T is an RTB-based rare earth permanent magnet composed of a main phase mainly composed of a transition metal element) and a nonmagnetic phase, and has a degree of orientation (Br / Ms) of 0.90 to 0.97; Main phase volume ratio is 8
9-97%, Nd-rich phase and B-rich phase are essential
Non rare earth permanent magnet magnetic phase volume fraction is characterized by comprising the sintered body is 3-10% that. 2. An R ₂ T ₁₄ B compound (R is a rare earth metal element,
T is a transition metal element) from the main phase and the non-magnetic phase
It is an RTB-based rare earth permanent magnet composed of
(Br / Ms) is 0.90 to 0.97 and the main phase volume ratio is 8
9-95%, Nd-rich phase and B-rich phase are essential
A non-magnetic phase having a volume fraction of 5 to 10% and a (BH) max of 38 to 46 MGOe. 3. A main phase volume ratio of 92 to 97%, Nd rich
Phase and a non-magnetic phase having a B-rich phase as essential volume ratio of 3
The rare-earth permanent magnet according to claim 1, wherein (BH) max is 42 to 53 MGOe at 〜7%. 4. The method according to claim 1, wherein the volume fraction of the Nd-rich phase is 2 to 8%,
The volume ratio of the rich phase is 0.05 to 8%.
A rare earth permanent magnet according to any one of the above.