JPH01228111A - Permanent magnet and manufacture thereof - Google Patents

Abstract

PURPOSE:To enhance the workability of the title permanent magnet and to make it possible to obtain high corrosion-resisting property by a method wherein a protective layer is formed by containing dispersion substance in a metal matrix, and the melting point of the metal matrix is set higher than that of the dispersion substance or than its softening point. CONSTITUTION:In a permanent magnet having a protective layer on the surface, the protective layer has a dispersion substance contained in a metal matrix, and the melting point of the metal matrix is higher than that of a dispersion substance or than its softening point. In this case, it is desirable that the dispersion substance contains glass or resin. Also, it is desirable that the metal matrix contains a kind of Ni or Co in the above-mentioned case. As a result, the generation of pinholes, through holes and the like when a film is formed can be prevented, and the improvement in corrosion-resisting property can be accomplished.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to a permanent magnet containing R (wherein R is one or more rare earth elements including Y), Fe and B, and which has particularly excellent corrosion resistance. .

<Prior art> As a rare earth magnet with high performance, an Sm-Co magnet made by powder metallurgy has an energy product of 32 MGOe.
are being mass-produced.

However, this method has the disadvantage that the cost of raw materials for Sm and cm is high. Among the rare earth elements, those with smaller atomic weights, such as cerium, praseodymium, and neodymium, are more abundant and cheaper than samarium. Also, F
e is cheap.

Therefore, in recent years, Nb-Fe-B magnets have been developed, and JP-A No. 59-46008 discloses a sintered magnet, and JP-A No. 60-9852 discloses a magnet using a high-speed quenching method. .

This magnet is a high-performance magnet that exhibits a high energy product of 25 MGOe or more, but since it contains rare earth elements and iron, which are easily oxidized, as its main components, it has low corrosion resistance, causing problems such as performance deterioration and variation. There is.

In order to improve the low corrosion resistance of R-Fe-B magnets, permanent magnets having various corrosion-resistant films on their surfaces and their manufacturing methods have been proposed (Japanese Patent Laid-Open No. 60-54406). Publication No. 60-63901,
60-63902, 61-130453, 61-150201, 61-16611
Publication No. 5, Publication No. 61-166116, Publication No. 61-16
No. 6117, No. 61-185910, No. 61
-270308, etc.).

<Problems to be Solved by the Invention> However, even with these corrosion-resistant films, the corrosion resistance of R-Fe-B magnets cannot be said to be sufficient.

In particular, since the corrosion-resistant film of metal or alloy disclosed in JP-A-60-54406 is formed by plating, holes, through holes, etc. occur during film formation, especially when the film is formed by electroplating. corrosion resistance is insufficient.

An object of the present invention is to solve these problems and provide an R-Fe-B permanent 61 stone with excellent corrosion resistance and a method for producing the same.

Means to solve problems〉 Such an object is achieved by the second aspect of the present invention described below.

That is, the present invention provides a permanent material containing R (wherein R is one or more rare earth elements including Y), Fe, and B, having a substantially tetragonal main phase, and having a protective layer on the surface. A permanent magnet in which the protective layer contains a dispersion in a metal matrix, the melting point of the metal matrix being higher than the melting point or softening point of the dispersion.

In this case, it is preferable that the dispersion contains glass or resin.

Also, in these cases, the metal matrix is made of Ni and Co.
It is preferable to contain one or more of the following.

Furthermore, another invention of the present invention is a method for manufacturing these permanent magnets, in which the protective layer is provided by vapor phase plating or liquid phase plating, and the plating bath used for this liquid phase plating is a metal This is a method for manufacturing a permanent magnet that contains metal ions and a dispersion that constitute a matrix.

In these cases, it is preferable to perform heat treatment after forming the protective layer.

Further, in these cases, it is preferable that the temperature of the heat treatment is lower than the melting point of the metal matrix and higher than the melting point or softening point of the dispersion.

The permanent magnet of the present invention has a protective layer on the surface of the permanent magnet having the composition described above.

This protective layer has the function of imparting corrosion resistance to the permanent magnet.

This protective layer contains a dispersion in a metal matrix, and the melting point of the metal matrix is higher than the melting point or softening point of the dispersion.

The metal constituting the metal matrix used in the present invention is not particularly limited as long as it has such physical properties, but from the relationship with the melting point or softening point of the dispersion described later, N
i, Co, Cu%Fe, among which Ni due to its high corrosion resistance
It is preferable to use 1Co, especially Ni.

The metal matrix may be composed of these metals alone, or may be an alloy containing two or more of these metals.

The alloys used include N1-Co, Ni-Zn% Fe-Zn, etc. are preferred.

The dispersion dispersed in such a metal matrix is preferably glass or resin.

There are no particular restrictions on the glass as long as it has a softening point lower than the melting point of the metal matrix.It depends on the melting point of the metal matrix, but if a glass of various known compositions with a working temperature of about 300 to 900°C is used. good.

Specifically, S i O, -B, O, -Cab.

5i02-B20. PbO1 S i 02- B203 A l1203, S i
02-B2O3ZnO1 PbOB20s -ZnO5 S i O2-B 203 P b O-A 422
03 etc.

Further, the resin used is not particularly limited as long as it is a thermoplastic resin whose softening point is lower than the melting point of the metal matrix.

Kono J: As a thermoplastic resin, the softening point is 100~
Nylon, polyamide, polyphenylene sulfide, polybutylene terephthalate, liquid crystal, etc., which have a temperature of about 300° C., can be suitably used.

These dispersions exist dispersed in the metal matrix, and more specifically, they are caused by pinholes in the metal matrix that occur when the protective layer is formed by vapor phase plating or liquid phase plating as described below. It is present at least in the protective layer and enhances the corrosion resistance improving function of the protective layer, and also improves the mechanical strength of the protective layer.

The volume ratio of the dispersion in the protective layer is preferably 5 to 50%, particularly 10 to 30% by volume.

If this value is less than 5 vofL%, the pinhole sealing effect after heat treatment will be small, and if it exceeds 50 VOU%, it will be difficult to form a layer, especially in liquid phase plating.

The thickness of the protective layer is 1 to 50 μm, more preferably 5 to 1 μm.
The thickness is preferably about 0 μm.

This is because if the thickness is less than 1 μm, pin-pole sealing becomes difficult, and if it exceeds 50 μm, the decrease in surface magnetic flux becomes large.

Note that, before the protective layer is formed, a base layer may be formed on the surface of the permanent magnet that is the layered body.

From the viewpoint of high reliability, sputtering, CVD,
Vapor phase plating layers such as vacuum evaporation are preferred, but electroplating,
Liquid phase plating such as electroless plating may be used. The materials constituting the base layer are Cu, Ni%Co, 5iOz, "rto2
, AIL203, etc., and the thickness of the base layer is preferably about 0.05 to 5 μm.

The protective layer as described above is provided by liquid phase plating or vapor phase plating.

As the liquid phase plating, it is preferable to use electroplating.

In the present invention, the plating bath contains metal ions constituting the metal matrix and the above dispersion.

Metal ions may normally be supplied using a metal lump.

The dispersion is preferably dispersed in the plating bath as a powder with a particle size of 0.01 to 5 μm, particularly 0.1 to 1 μm.
Preferably, the particle size is m.

If the particle size is less than 0.01 μm, it will be difficult to disperse in the plating film, and if it exceeds 5 μm, the dispersion in the plating film will be poor.

In addition, the volume ratio of the plating solution and the dispersion is 100% of the plating solution.
It is preferable that the amount of dispersion is about 0.01 to 10.

If this value is less than 0.01, the volume ratio of the dispersion in the protective layer will be less than 5%, and even if it exceeds 10, the volume ratio of the dispersion in the protective layer will not increase.

These other conditions may be in accordance with ordinary electroplating methods.

Note that it is preferable to pre-treat the surface of the permanent magnet before applying the protective layer.

As for pretreatment, it is preferable to perform degreasing with an organic solvent in the same manner as in normal plating, and then perform acid treatment (activation).

As the vapor phase plating, known ordinary methods such as sputtering, ion blating, and vacuum evaporation can be used, but it is preferable to use sputtering because it allows a dense protective layer to be formed.

When depositing the above-mentioned protective layer by sputtering, a target made of, for example, a dispersion of metal constituting the metal matrix and a dispersion of glass, resin, etc. can be suitably used; Multi-source sputtering can also be used in which the metals constituting the metal matrix and the dispersion are each targeted.

Other sputtering conditions may be appropriately selected within generally known ranges.

The protective layer formed by liquid phase plating or vapor phase plating as described above is preferably subjected to heat treatment.

Preferably, the heat treatment temperature is below the melting point of the metal matrix and below the melting or softening point of the dispersion.

For example, when the metal constituting the metal matrix is Ni and the dispersion is glass with a softening point of 600°C, the heat treatment temperature is preferably about 600 to 90°C, and
When the dispersion is a resin with a softening point of 150°C, the heat treatment temperature is preferably about 150 to 250°C.

The heat treatment time is preferably increased by 0.1 to 2 hours.

The atmosphere during the heat treatment is air or Ar.

This may be carried out in an inert gas atmosphere such as N2 gas, but if lead-containing glass is used as a dispersion, lead will be reduced and precipitated, so it is preferable to avoid an inert gas atmosphere.

In addition, when the aging treatment temperature of the permanent magnet described below is lower than the melting point of the metal matrix, the formation of the protective layer and the heat treatment may be performed before or after the aging treatment. When the melting point or softening point is lower than the aging treatment temperature, the heat treatment after the formation of the protective layer can be performed simultaneously with the aging treatment. However, since aging treatment is performed in an inert gas atmosphere, if a protective layer is to be applied before aging treatment, it is preferable to avoid using lead-containing glass as a dispersion for the same reason as above. .

Further, when the melting point of the metal matrix is lower than the aging treatment temperature of the permanent magnet, the protective layer is provided after the aging treatment.

Such heat treatment melts or softens the dispersion dispersed in the metal matrix, and in particular, the dispersion present at the grain boundaries of the metal matrix closes the through holes in the metal matrix due to this melting or softening.

The permanent magnet on which the protective layer is formed as described above contains R (where R is 1 fi or more of a rare earth element including Y), Fe, and B.

The content of R, Fe and B is 5.5at%≦R≦30at% 42at%≦Fe　≦90at% 2at%≦B≦28at% It is preferable that

In particular, when producing a magnet by a sintering method, it is preferable that the magnet has the following composition.

As the rare earth element R, at least one of Nd, Pr, Ho, and Tb, or furthermore, La, Sm, Ce,
Gd, Er% Eu% Pm.

Those containing one or more of Tm, Yb%Y are preferred.

In addition, when using two or more types of elements as R, a mixture such as mitshu metal can also be used as a raw material.

The content of R is preferably 8 to 30 at%.

If it is less than 8 at%, the crystal structure becomes a cubic structure that is the same as α-iron, so a high coercive force (iHc) cannot be obtained,
When it exceeds 30 at%, the R-rich nonmagnetic phase increases and the residual magnetic flux density (Br) decreases.

The content of Fe is preferably 42 to 90 at%.

When Fe is less than 42at%, Br decreases and 90at%
%, iHc decreases.

The content of B is preferably 2 to 28 at%.

If B is less than 2 at%, it will result in interstitial body tissue, so iHc
is insufficient, and if it exceeds 28 at %, the B-rich nonmagnetic phase increases, resulting in a decrease in Br.

Note that by replacing a portion of Fe with Co, the temperature characteristics can be improved without impairing the magnetic characteristics.
In this case, if the Coi replacement amount exceeds 50% of Fe, the magnetic properties will deteriorate, so the Co replacement amount is preferably 50% or less.

In addition to R%Fe and B, N is an unavoidable impurity.
i%Si, AJ2, Cu, Ca, etc. may be contained in an amount of 3 at% or less of the total.

Furthermore, by replacing a part of B with one or more of C, P, S, and Cu, productivity can be improved and costs can be reduced. In this case, the amount of substitution is 4at% of the total
It is preferable that it is below.

In addition, in order to improve coercive force, improve productivity, and reduce costs, A1, T 1 % V % Cr s M n 1
Bi, Nb, Ta, Mo, W% Sb, Ge.

1 fi or more of Sn, Zr, Ni, St, Hf, etc. may be added. In this case, the total amount added is preferably 10 at% or less.

Such a permanent magnet used in the present invention has a main phase with a substantially tetragonal crystal structure.

The particle size of this main phase is preferably about 1 to 100 μm.

It usually contains a non-magnetic phase of 1 to 50% by volume.

Such a permanent magnet suitably used in the present invention is disclosed in the above-mentioned Japanese Patent Laid-Open Publication No. 185910/1983.

The above permanent magnet is preferably manufactured by a sintering method as described below.

First, an alloy having a desired composition is cast to obtain an ingot.

The obtained ingot is milled with a stamp mill etc. to a particle size of 10
It is coarsely ground to about 100 μm, and then finely ground to a particle size of about 0.5 to 5 μm using a ball mill or the like.

The obtained powder is preferably compacted in a magnetic field. In this case, the magnetic field strength is 10 kOe or more, and the molding pressure is 1 to 5
Preferably, t/cm is 2 degrees.

The obtained molded body was heated to 0.5 to 5 at 1000 to 1200°C.
Sinter for an hour and quench. Note that the sintering atmosphere is preferably an inert gas atmosphere such as Ar gas.

After this, preferably in an inert gas atmosphere,
Aging treatment is performed at 00°C for 1 to 5 hours.

Note that the present invention is suitably applicable not only to permanent magnets manufactured by the above-mentioned sintering method but also to bulk magnets manufactured by a so-called quenching method.

Permanent magnets that are bulk magnets manufactured by a rapid cooling method, have particularly excellent magnetic properties, and are suitably used in the present invention are:
Patent application No. 62-90709, No. 62-191380,
It is disclosed in No. 62-259373 and the like.

<Example> Hereinafter, the present invention will be explained in further detail by giving specific examples of the present invention.

[Example 1] An ingot having a composition of 15Nd-7B-78Fe (numbers are atomic ratios) was obtained by casting.

This ingot was coarsely pulverized using a stamp mill and then finely pulverized using a ball mill to obtain an alloy powder with an average particle size of 3.5 μm.

This alloy powder was heated at 1.5t/cm in a 12kOe magnetic field.
'' to obtain a molded product.

This molded body was heated at 1100° C. for 1 hour in an Ar atmosphere and then rapidly cooled to obtain a sintered body.

The obtained sintered body was subjected to aging treatment at 600° C. for 2 hours in an Ar atmosphere to obtain a permanent magnet.

A magnet piece of 20 mm in size was cut out from this permanent magnet, and the surface of this magnet piece was degreased with acetone and then acid-treated (pretreated) with IN hydrochloric acid.

A protective layer was formed on the surface of the pretreated magnet piece by plating the dispersion as glass or resin. Table 1 shows the compositions or names of the plating baths and dispersions used, and their average particle diameters.

Thereafter, heat treatment was performed under the conditions shown in Table 1 to obtain permanent magnet samples of the present invention (Sample Nos. 1 to 3).
Table 1 shows the thickness of the protective layer and the volume ratio of the dispersion in the protective layer of each sample.

For comparison, metal (N i
Samples No. 4 and No. 4 with a protective layer formed only of ) and Sample No. 015 with no protective layer were also prepared.

The following corrosion resistance test was conducted on these samples.

(Corrosion Resistance Test) Magnetic properties were measured after storage at 60° C. and 90% RH for 1000 hours, and changes in appearance were also observed.

The results are shown in Table 1.

In addition, as a result of observing the surface of the protective layer with a scanning electron microscope, pinholes of the same degree were observed on the surface of the protective layer of samples Nos. 1 to 4, but in the samples of the present invention Nos.
The pinhole in No. 3 was filled with glass or resin without any gaps, and the pinhole was closed.

[Example 2] A layer made of Ni containing glass was formed by sputtering on the magnet piece obtained in Example 1, and this layer was heat-treated to form a protective layer with a thickness of 5 μm. The composition of this glass is 652 n O-23820s -12S in atomic ratio.
iO2, heat treatment temperature is 700℃, heat treatment time is 1 hour,
The content ratio of glass in the protective layer was 10vol%.

This was designated as sample No. 11.

For comparison, sample No. 12 was prepared by sputtering a protective layer made only of Ni and having the same layer thickness.
was also created.

Corrosion resistance tests similar to those in Example 1 were conducted on these samples. The results are shown in Table 2.

In addition, as a result of observing the protective layer surface with a scanning electron microscope, pinholes of the same degree were observed on the protective layer surface of samples No. 11 and 12, but sample No.
The pinhole of No. 0111 was filled with glass without any gaps, and the pinhole was closed.

The effects of the present invention are clear from the above examples.

(Effects of the Invention) If electroplating is used to form the metal protective layer, manufacturing is simple, but through holes are likely to be formed. Furthermore, the glass protective layer is prone to cracking during handling.

The present invention compensates for both of these drawbacks, and according to the present invention, a permanent magnet with high workability and high corrosion resistance and a method for manufacturing the same are realized.

Claims (7)

[Claims] (1) A permanent magnet containing R (where R is one or more rare earth elements including Y), Fe, and B, having a substantially tetragonal main phase, and having a protective layer on the surface. A permanent magnet in which the protective layer contains a dispersion in a metal matrix, and the melting point of the metal matrix is higher than the melting point or softening point of the dispersion. (2) The permanent magnet according to claim 1, wherein the dispersion contains glass or resin. (3) The permanent magnet according to claim 1 or 2, wherein the metal matrix contains one or more of Ni and Co. (4) The method for manufacturing a permanent magnet according to any one of claims 1 to 3, wherein the protective layer is formed by liquid phase plating, and the plating bath used for this liquid phase plating coats a metal matrix. Method for producing a permanent magnet containing constituent metal ions and dispersion (5) A method for manufacturing a permanent magnet according to any one of claims 1 to 3, wherein the protective layer is provided by vapor phase plating. (6) Claim 4 or 5, wherein heat treatment is performed after the protective layer is formed.
Method for manufacturing permanent magnets described in (7) Claim 6, wherein the temperature of the heat treatment is lower than the melting point of the metal matrix and higher than the melting point or softening point of the dispersion.
Method for manufacturing permanent magnets described in