JPH068488B2 - Permanent magnet alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a permanent magnet alloy for thin materials, in which the magnet characteristics do not deteriorate even when at least one main surface of a sintered magnet is processed by grinding, etc. The present invention relates to a permanent magnet alloy for thin products of 3 mm or less.

[Prior Art] Typical permanent magnet materials at present are Alnico, hard ferrite, and rare earth cobalt magnets. With the destabilization of the raw material situation of cobalt in recent years, 20 to 30 wt% of cobalt
Demand for Alnico magnets, including these, has decreased, and inexpensive hard ferrites, whose main component is iron oxide, have become the mainstream of magnet materials.

On the other hand, the rare earth cobalt magnet is very expensive because it contains 50 to 60 wt% of cobalt and uses Sm which is rarely contained in rare earth ore, but it has much higher magnetic characteristics than other magnets. ， It has come to be used mainly for small size and high value-added magnetic circuits.

The present inventor has previously proposed a permanent magnet based on a Fe-BR ternary compound having magnetic anisotropy as a new high-performance permanent magnet containing no expensive Sm or Co (Japanese Patent Laid-Open No. 59-4600).
8). This permanent magnet uses a light rare earth element, which is rich in resources centered on Nd and Pr as R, and has 25MGOe containing Fe as a main component.
It is an excellent permanent magnet that exhibits the extremely high energy product described above. Furthermore, as a development of the FeBR basic system, the above Fe-
The Curie temperature was raised by substituting a part of Fe in the Fe-BR alloy based on the BR ternary compound with Co (Fe, Co)
Those having magnetic anisotropy based on -BR quaternary compound (Japanese Patent Laid-Open No. 59-64733), and those having increased coercive force by inclusion of additional elements M (Al, Ti, V, etc.) 59-89401), Co, M
The present applicant has developed a series of permanent magnets (alloys) such as those including both (JP-A-59-132104).

Recently, as the performance and size of magnetic circuits have increased, Fe-B-
R-type permanent magnets have been attracting more and more attention, and there has been a demand for magnets for thin products having a thickness of 3 mm or less.

[Problems to be Solved by the Invention] Therefore, it is necessary to remove the uneven surface and the strained surface on the surface of the compacted and sintered compact magnet body to flatten it, and to grind to remove the oxide layer on the surface. There is the above-mentioned Fe-BR
For example, for sintered sintered magnets, material thickness is 10mm, product thickness is 1mm, 2
It was found that the magnet characteristics deteriorate as the product thickness becomes smaller by grinding to mm, 4 mm, 6 mm, and 8 mm, as shown in FIG.

The present invention aims to solve the above problems.

[Means for Solving the Problems] The permanent magnet alloy according to the first aspect of the present invention has at least one kind of boride in atomic% and one boride molecule as one.
It is contained in 0.05 to 3.0% in terms of atoms, 10 to 24% R (R is N
d, Pr, Dy, Ho, Tb, or at least one of these, and La, Ce, Sm, Gd, Er, Eu, Tm, Yb, La, and Y). 4 to 24% B, (excluding B in the boride) 65 to 81% Fe as the main component, and the main phase is FeBR
It consists of a tetragonal system and is characterized in that the main phase has an average grain size of 9.0 μm or less. (However, the boride is FeB
R-based ternary compound is not included) As the second aspect of the present invention, the first aspect (FeBR basic system)
Based on, and containing Co (excluding 0% Co) by substituting 50% or less of Fe, and as a third aspect, containing a predetermined M or less of M element described later in place of a part of Fe (M0% And excluding 50% or less of Fe as Co (Co0
(Excluding%), and containing a predetermined% of the above M element in place of a part of Fe.

The element M replaces a part of Fe, and the element M (M
(Except 0%): 5.0% Al, 3.0% Ti, 5.5% V, 6.0% Ni, 4.5% Cr, 5.0% Mn, 5.0% Bi, 9.0% Nb, 7.0% Ta , 5.2% Mo, 5.0% W, 1.0% Sb, 3.5% Ge, 1.5% Sn, 3.3% Zr, 3.3% Hf, and 5.0% Si (however, the total amount of M elements has the maximum value among the added elements. But above the specified percentage).

[Preferred Embodiment and Operation and Effect] As a result of various studies on the cause of deterioration of the magnetic properties of the Fe-BR sintered magnet, the present inventor has found that the surface of the processed Fe-BR sintered magnet is It was found that the reason for the further decrease in coercive force of the crystal group is that there is no necessary and optimum grain boundary phase for the appearance of high coercive force.

However, it is not easy to give the necessary and optimum grain boundary phase to the crystal group of the processed surface, and in order to reduce the volume ratio of the crystal group of the surface layer with a low coercive force, the crystal grain of the sintered body must be reduced. We have found that it is effective to make the diameter as small as possible.

Generally, the crystal grain size of the sintered body can be reduced by reducing the grain size of the finely pulverized powder before molding. In order to minimize the deterioration of the magnetic properties of sintered magnets for thin products with a thickness of 3 mm or less and to stably mass-produce it, it is necessary to keep the particle size of the raw material powder below 2 μm. Since the raw material powder for a magnet contains a large amount of rare earth elements,
Fine powder with a particle size of 2 μm or less is chemically active, difficult to handle, and is not suitable for stable mass production.

As a result of various studies, the inventor suppresses grain growth during sintering and increases iHc (increase by 1 to 2 KOe) by including a specific amount of boride in a Fe—BR system sintered magnet. In addition to the above, the present invention provides a permanent magnet material having excellent characteristics that does not deteriorate the magnet characteristics of the sintered magnet even when the thickness is reduced to about 3 mm or less by processing.

The present invention is characterized in that at least one boride is added. As boride, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo,
There are W, borides of metals such as rare earth (R), and BN. Of these borides, ZrB ₂ , ZrB ₁₂ , HfB ₂ , VB ₂ ,
NbB, NbB ₂ , TaB, TaB ₂ , TiB ₂ , CrB ₂ , MoB,
MoB ₂ B, Mo ₂ B, WB, W ₂ B, BN, NdB ₆ , PrB ₆
Etc. are practical. The boride has a high melting point and is a very stable compound. For example, the melting point of ZrB ₂ is about 3000 ℃
Is.

The permanent magnet material of the present invention comprises at least 50 Vo1 FeBR or FeCoBR compound having a tetragonal crystal structure with an average crystal grain size of 9.0 μm or less and magnetic anisotropy.
% Or more and a volume ratio of 1% to 50% of a nonmagnetic phase (excluding oxide phase). In this invention magnet,
When the average crystal grain size exceeds 9 μm, the volume ratio of the crystal group on the surface having a low coercive force is increased, which is not preferable. The average crystal grain size is preferably 7 μm or less, and further 3 to 5 μm.

Therefore, the permanent magnet of the present invention mainly uses Nd and Pr-rich light rare earths as R, contains boride, and contains Fe, B, and R as the main components, so that
An excellent permanent magnet that has an extremely high energy product above Oe, a high residual magnetic flux density and a high coercive force, and that prevents deterioration of characteristics due to processing can be obtained at low cost.

The rare earth element R used in the permanent magnet of the present invention is Nb, Pr, D
At least one of y, Ho, Tb is included, or one or more of these are further added to La, Ce, Sm, Gd, Er, Eu, Pm, Tm, Yb, Y
Among them, those containing at least one kind are preferable. Also, one type of R (particularly Nd, Pr, Dy, Ho, Tb, etc.) is usually sufficient,
Nd and Pr are particularly preferable, but in practice, a mixture of two or more kinds (Misch metal, didymium, etc.) can be used for reasons such as convenience in availability. However, Sm and La in R of the alloy forming the main phase should be as small as possible (eg Sm1
Atomic% or less, further 0.5% or less). As an R mixed system, especially Nd, Pr, or a small amount thereof (0.05 to 5 atom% in the total alloy,
A combination of Dy, Ho, Tb, etc. of 0.2 to 3 atomic% is particularly preferable in terms of temperature characteristics. It is preferable that R is 50 atomic% or more (more preferably 80 atomic%) in total of Nd and Pr from the viewpoint of characteristics, cost and resources.

It should be noted that this R does not have to be a pure rare earth element, and may contain impurities that are unavoidable in manufacturing within the industrially available range.

R is an essential element in the novel permanent magnet, and if it is less than 10 atomic%, a large number of cubic crystal structures having the same crystal structure as α-iron are produced, so that high magnetic properties, especially high coercive force, are obtained. If it exceeds 24 at%, the R-rich non-magnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet with excellent characteristics cannot be obtained. Therefore, the rare earth element R
Is in the range of 10 atom% to 24 atom%.

B is an essential element in the new permanent magnets of the above-mentioned system. When it is less than 4 atomic%, a lot of rhombohedral structure is generated and a high coercive force (iHc) cannot be obtained. An excellent permanent magnet cannot be obtained because the rich nonmagnetic phase increases and the residual magnetic flux density (Br) decreases. Therefore, B is
The range is from 4 atom% to 24 atom%.

Fe is an essential element in the FeBR basic permanent magnet. If less than 65 atomic%, the residual magnetic flux density (Br) decreases, and if it exceeds 81 atomic%, a high coercive force cannot be obtained.
In the BR basic system, the content is 65 atom% to 81 atom%.

In the present invention, the characteristic boride is important for refining the crystal grains of the sintered magnet, but if it is less than 0.05 atom%, the effect of refining the crystal grains is small, and the deterioration of the magnet properties during the main surface processing of the sintered body is suppressed. The effect of prevention is small, and if it exceeds 3.0 atom%, the residual magnetic flux density and the maximum energy product decrease, which is not preferable. The boride content is preferably 0.3 to 1 atomic%.

In the alloy for permanent magnets based on the FeBR ternary compound having magnetic anisotropy according to the present invention, a part of Fe is Co
By substituting with ((Fe, Co) -BR system quaternary compound), the temperature characteristics can be improved without impairing the magnetic characteristics of the obtained magnet, but the Co substitution amount is 50% of that of Fe. If it exceeds%, on the contrary, the magnetic properties deteriorate, which is not preferable.

The temperature coefficient of Br is 0.1% / at 5 atomic% or more of Co in the alloy.
Below 25 ° C, 25 atom% or less contributes to the increase in Curie temperature Tc without substantially deteriorating other properties. Also
Co is effective even in a small amount (0.1 to 1 atom%) depending on the content, and increases the Curie temperature Tc to Tc of 300 to 370 ° C. of the FeBR basic system, corresponding to the content. IH even at around 20% Co
Also increase c. It also has the effect of improving squareness.

In addition, at least one of the following additional elements is Fe-BR
It is added to the system-based permanent magnet because it is effective in improving its coercive force, etc., improving manufacturability, and lowering the price. However,
Since the residual magnetic flux density (Br) decreases with the addition for improving the coercive force, it is necessary to add Br in at least 9KG in order to achieve (BH) max20MGOe or more.

In addition, at least one of the following additional elements M is Fe-B
-R-based permanent magnets are added because they are effective in improving the coercive force, improving the manufacturability, and reducing the cost. However, since the residual magnetic flux density (Br) generally decreases with the addition for improving the coercive force, addition in the following range is desirable in order to obtain Br 9 KG or more.

5.0 atomic% or less Al, 3.0 atomic% or less Ti, 5.5 atomic% or less V, 6.0 atomic% or less N
i, 4.5 atomic% or less Cr, 5.0 atomic% or less Mu, 5.0 atomic% or less Bi, 9.0 atomic% or less Nb, 7.0 atomic% or less Ta, 5,2 atomic% or less Mo, 5.0 atomic% or less W, S of 1.0 atomic% or less
b, Ge of 3.5 atomic% or less, Sn of 1.5 atomic% or less, Zr of 3.3 atomic% or less, Hf of 3.3 atomic% or less, and Si of 5.0 atomic% or less are added at least one kind (However, two kinds are included. When the above content is included, the maximum content of the additive element is the atomic% or less of the one having the maximum value), so that the coercive force of the permanent magnet can be increased. The limits of Ni and Mn are determined from iHc. However, the content of the additional element M can generally be appropriately selected within the above range depending on the desired site of Br, and generally 0.1 to 3 atomic% or less (particularly 1% or less) is effective. This M can also be alloyed and added to the grain boundary phase component. As the additive element M, V, Nb, Ta, Mo,
W, Cr and Al are preferred.

At least the main phase of the crystal phase of the alloy powder in this invention is
A tetragonal crystal of 50 vo1% or more (preferably 80 vo1% or more) and at least a grain boundary of the main phase surrounded by a non-magnetic phase is essential for producing a sintered permanent magnet with excellent magnetic properties. Is. The nonmagnetic phase is mainly composed of an R-rich phase (R 90 atomic% or more of metal) or a B-rich phase (R ₂ Fe ₇ B ₆ to R ₁ Fe ₄ B ₄ etc.), and is effective even in a slight amount, for example, 1 vo1%. The above is a sufficient amount. The parameter of the tetragonal lattice is a about 8.8Å, c
It is about 12.2Å and its central composition is considered to be R ₂ Fe ₁₄ B. Also in the case of the FeCoBR system containing Co, according to the FeBR basic system, Fe is partially replaced by Co and has a similar crystal structure. It is considered that the addition of the M element (within the predetermined range) does not change the basic crystal structure.

In order to obtain a high residual magnetic flux density and a high coercive force in the FeBR basic system of the present invention, the maximum energy product (BH) ma in the case of R12.0 to 20 atom%, B5 to 15 atom% and Fe65 to 83 atom% is obtained.
It is a preferable range that x25 MGOe or more can be obtained. Furthermore, when R12.0 to 19 atom% and B5.5 to 12 atom%, (BH) max30MG
You can get more than Oe.

At R12.0 to 16 atom% and B5.5 to 10 atom%, 35 MGOe or more,
Furthermore, 40 MGOe for R12-14.5 atom% and B5.8-8 atom%
The above (up to 44 MGOe) is achieved.

Co in the alloy is 35% or less (at atomic%), 25 MGOe or more, 25
% Below 30MGOe, below 23% below 35MGOe, below 15% below 40MGOe.

Further, the permanent magnet of the present invention can be generally manufactured by a powder metallurgy method, and a magnetically anisotropic magnet can be obtained by pressure molding in a magnetic field. Thus, a magnetically isotropic magnet can be obtained. Sintering can be carried out under normal pressure or pressure, but under known conditions such as reduced pressure atmosphere or vacuum (for example, JP-A-59-59).
215460).

Further, the alloy according to the present invention contains R, B, Fe (or Co,
In addition to (M element), the presence of impurities that are unavoidable in industrial production can be allowed. For example, P can be contained in an amount of 2 atomic% or less, S in an amount of 2 atomic% or less, Cu in an amount of 2 atomic% or less, and a total amount of 2 atomic% or less can be contained, whereby the manufacturability of the magnet alloy can be improved and the cost can be reduced. is there. However, these elements generally reduce Br so that it is preferable that the amount is small, and the above range is for Br 9 KG or more, and the permissible limit is small according to the required Br (total 1% or 0.5% or less).

[Example] Example 1 Electrolytic iron, ferroboron alloy, and Nd metal were used as starting materials, and Nd, F was added so that the final composition was 14Nd8B78Fe.
First, e and B were melted by high frequency and then cast in a water-cooled copper mold to obtain a 1 kg ingot.

After that, the ingot is put into a stamp mill, coarsely crushed, and then finely crushed with a ball mill. The final composition of BN having a particle size of 50 μm or less and purity of 99.5% or more and TiB ₂ having a purity of 99% or more is 13.93 Nd.
7.96B77.61FeO.50BN (or TiB ₂ ) was added and blended and finely pulverized to obtain a differentially pulverized powder having a particle size of 3.0 μm.

The Nd-B-Fe alloy powder, the BN-containing Nd-B-Fe alloy powder, and the TiB ₂ -containing Nd-B-Fe alloy powder were placed in a mold and oriented in a magnetic field of 10 KOe and perpendicular to the magnetic field. 2T / c in direction
Molded at a pressure of m ² .

The obtained molded body is sintered at 1100 ° C for 1 hour in Ar, then allowed to cool, and then subjected to an aging treatment at 600 ° C for 2 hours in Ar to obtain a size of 10 mm × 5 mm × thickness 10 mm. The test piece of was obtained.

Table 1 shows the composition and crystal grain size of the magnet, and FIG. 2 shows the results of the magnetic characteristics when the thickness of the test piece was ground to 6 mm, 4 mm, 2 mm, and 1 mm (both sides). In the magnet of the present invention, BN, TiB ₂ etc. boride may be compounded and added at the time of finely pulverizing the raw material powder as in the example, but when the compounded raw materials are dissolved, boride such as TiB ₂ etc. is generated in the molten metal, A boride may be contained in the ingot.

Example 2 Nd ₁₅ B shown in Table 2 obtained in the same manner as in Example 1
A test piece measuring 10 mm × 10 mm × thickness 10 mm was obtained from a sintered magnet of ₈ Fe _76.7 (additive) 0.3. Furthermore, the thickness of this magnet is 1.
Table 2 shows the magnetic properties and the average crystal grain size (D) when polished to 5 mm (both sides).

[Effects of the Invention] According to the present invention, a predetermined amount of boride is contained in the Fe-BR permanent magnet alloy to suppress grain growth during sintering and increase iHc (1 to 2 kOe increase). In addition, the magnet characteristics of the sintered magnet do not deteriorate even when the thickness is reduced to about 3 mm or less by processing.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the thickness t of a 14Nd-7B-Fe magnet and the magnetic characteristics, and FIG. 2 is an embodiment of the present invention, 14Nd8B77.5Fe0.5 (Ti).
B ₂₎ and a graph showing the relationship between the thickness t and the magnetic properties of the magnet of 14Nd8B77.5Fe0.5 (BN).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Hirosawa 2-15-17 Egawa, Shimamoto-machi, Mishima-gun, Osaka Prefecture 15-17 Sumitomo Special Metals Co., Ltd. Yamazaki Manufacturing (72) Masato Sagawa 2 Egawa, Shimamoto-cho, Mishima-gun, Osaka Prefecture 15-17 17 Sumitomo Special Metals Co., Ltd. Yamazaki Works (56) Reference JP 60-119701 (JP, A) JP 60-91601 (JP, A) JP 60-63903 (JP, A) )

Claims (4)

[Claims] 1. In atomic%, at least one kind of boride is contained in an amount of 0.05 to 3.0% by converting one boride molecule into one atom, and 10 to 24% R (R is Nd, Pr, Dy). , Ho, Tb at least 1
Species, or one or more of these and further La, Ce, Sm, Gd, Er, Eu,
Consists of at least one of Tm, Yb, La and Y) 4-24%
B (excluding B in the boride), 65 to 81% Fe as a main component, the main phase is FeBR tetragonal phase, and the average crystal grain size of the main phase is 9.0 μm or less. Characteristic permanent magnet alloy (however, the boride does not include FeBR ternary compound). 2. In atomic%, at least one kind of boride is contained in an amount of 0.05 to 3.0% by converting one boride molecule into one atom, and 10 to 24% R (R is Nd, Pr, Dy). , Ho, Tb at least 1
Species, or one or more of these and further La, Ce, Sm, Gd, Er, Eu,
Consists of at least one of Tm, Yb, La and Y) 4-24%
B (excluding B in the boride), 65 to 81% Fe as a main component, and replace 50% or less of Fe with Co (excluding 0%),
A permanent magnet alloy in which the main phase is composed of a FeCoBR type tetragonal phase, and the average crystal grain size of the main phase is 9.0 μm or less (however, the boride does not include a FeCoB type quaternary compound). 3. In atomic%, at least one kind of boride is contained in an amount of 0.05 to 3.0% in terms of one boride molecule, and 10 to 24% R (R is Nd, Pr, Dy). , Ho, Tb at least 1
Species, or one or more of these and further La, Ce, Sm, Gd, Er, Eu,
Consists of at least one of Tm, Yb, La and Y) 4-24%
B (excluding B in the above boride), 65 to 81% Fe as a main component, and one or more kinds of the following M elements (excluding M0%) of the following predetermined% or less in place of a part of Fe A permanent magnet alloy in which the main phase is a FeBR tetragonal phase and the average crystal grain size of the main phase is 9.0 μm or less (however, the boride does not include the FeBR ternary compound). (M element) 5.0% Al, 3.0% Ti, 5.5% V, 6.0% Ni, 4.5% Cr, 5.0% Mn, 5.0% Bi, 9.0% Nb, 7.0% Ta, 5.2% Mo, 5.0% W, 1.0% S
b, 3.5% Ge, 1.5% Sn, 3.3% Zr, 3.3% Hf, 5.0% Si (However, the total amount of M elements is the above specified% or less of the maximum amount of the additive elements) 4. In atomic%, at least one kind of boride is contained in an amount of 0.05 to 3.0% in terms of one boride molecule, and 10 to 24%.
R (R is at least one of Nd, Pr, Dy, Ho, Tb, or one or more of these and at least one of La, Ce, Sm, Gd, Er, Eu, Tm, Yb, La, Y) 4) to 24% B (excluding B in the boride), 65 to 81% Fe as the main component, and 5% of Fe.
Substituting 0% or less with Co (excluding Co0%), and containing one or more of the following M elements (excluding M0%) of the following predetermined% in place of a part of Fe, and the main phase is FeBR BR tetragonal phase Consists of
A permanent magnet alloy characterized in that the average crystal grain size of the main phase is 9.0 μm or less (however, the boride does not include a FeCoBR-based quaternary compound). (M element) 5.0% Al, 3.0% Ti, 5.5% V, 6.0% Ni, 4.5% Cr, 5.0% Mn, 5.0% Bi, 9.0% Nb, 7.0% Ta, 5.2% Mo, 5.0% W, 1.0% Sb, 3.5% Ge, 1.5% Sn, 3.3% Zr, 3.3% Hf, 5.0% Si (however, the total amount of M elements is the above specified% or less of the maximum amount of the additive elements)