JPS63166944A - Corrosion-resisting permanent magnet - Google Patents

Abstract

PURPOSE:To easily obtain a corrosion-resisting permanent magnet excellent in durability and dimensional accuracy, by providing oxidation-resistant resin containing metal foil to the surface of a sintered permanent magnet body having a specific composition principally composed of rare earth elements, B, and Fe and also having a tetragonal phase as a main phase. CONSTITUTION:The oxidation-resistant resin layer containing metal foil is provided to the surface of the sintered permanent magnet body composed principally of, by atom, 10-30% R (R means at least one element among Nd, Pd, Dy, Ho, and Tb or further at least one element among La, Ce, Sm, Gd, Er, Eu, Tm, Yb, Lu, and Y), 2-28% B, and 65-80% Fe and having a main phase consisting of a tetragonal phase so as to improve corrosion resistance. s the above metal foil, about <=1mum-thick foil of metal or alloy having superior corrosion resistance, such as stainless steel, Al, etc., is used by about 0.01-60PHR. Moreover, epoxy resin, thermosetting acrylic resin, etc., are suitably used as the above resin.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application This invention relates to Fe-B-R rare permanent magnets with high magnetic properties, and the corrosion resistance of the permanent magnets is significantly improved by its specific composition and simple surface treatment. Regarding rare earth, boron, and iron-based permanent magnets.

BACKGROUND ART The applicant previously used light rare earths, which are abundant in resources such as Nd and Pr, to make expensive Sm+
Fe-B is a new high-performance permanent magnet that does not contain cobalt and significantly exceeds the best properties of conventional rare earth cobalt magnets.
-R series permanent magnets were proposed (Japanese Unexamined Patent Publication No. 59-46008, JP-A No. 59-89401).

The Curie point of the magnetic alloy is generally 300°C to 37°C.
0°C, but by replacing a part of Fe with Co, a Fe-B-R permanent magnet with a higher Curie point was obtained (JP-A-59-64733, JP-A-59-13).
No. 2104), furthermore, it has a Curie point equal to or higher than the Co-containing Fe-B-R rare earth permanent magnet and a higher (BH)max, and its temperature characteristics, especially 1I-I
In order to improve c, Nd and P are used as rare earth elements (R).
By containing at least one kind of heavy rare earths such as Dy and Tb in a part of R of the Co-containing Fe-B-R rare earth permanent magnet mainly consisting of light rare earths such as r, 25MG
proposed a Co-containing Fe-BR-based rare earth permanent magnet that further improved iHc while maintaining extremely high (BH) max of Oe or higher (Japanese Patent Laid-Open No. 60-34005).

However, Fe-
Permanent magnets made of B-R magneto-optical anisotropic sintered bodies contain rare earth elements and iron, which tend to oxidize in the air and gradually form stable oxides, so when incorporated into a magnetic circuit. Furthermore, the oxides generated on the magnet surface cause a decrease in the output of the magnetic circuit and variations between the magnetic circuits, and there is also the problem of contamination of peripheral equipment due to the falling off of the surface oxide.

Therefore, in order to improve the corrosion resistance of the above-mentioned Fe-B-R permanent magnet, the applicant has developed a permanent magnet (patent application filed in 1983) whose surface is coated with a corrosion-resistant metal plating layer by electroless plating or electrolytic plating. -162350) was proposed, but
In this plating method, the permanent magnet material is sintered and porous, so
Acidic or alkaline solutions from plating pretreatment may remain in these holes, leading to corrosion over time.Also, since the magnet body has poor chemical resistance, the magnet surface may be corroded during plating, resulting in poor adhesion and corrosion resistance. There was a problem of inferiority. Therefore, we proposed a permanent magnet whose surface was coated with a thick corrosion-resistant resin layer by spraying or dipping.
No. 8-171907), however, the corrosion-resistant resin layer had a problem in that its corrosion resistance was insufficient and it could not be used for a long time under harsh environmental conditions.

Purpose of the Invention The purpose of the present invention is to improve the corrosion resistance of Fe-B-R permanent magnet materials.
-Aimed at BR-based permanent magnets.

Structure and Effects of the Invention The present invention was developed as a result of various studies on surface treatments to be applied to the surface of Fe-BR permanent magnets, with the aim of producing Fe-BR permanent magnets that exhibit excellent corrosion resistance. on the surface of the body,
This invention was completed based on the finding that corrosion resistance can be significantly improved by providing an oxidation-resistant resin layer containing metal flakes.

That is, the present invention provides R (R is at least one of Nd, Pr, Dy, Ho, Tb, or furthermore, La, Ce, Sm
, Gd, Er, Eu.

Consisting of at least one of Tm, Yb, Lu, and Y) 10% to 30 atomic%, B2 atomic% to 28 atomic%, Fe65) M % to 80 atomic%, and the main phase is a tetragonal phase. This is a corrosion-resistant permanent magnet characterized by having an oxidation-resistant resin layer containing metal flakes on the surface of a sintered permanent magnet body made of the following.

The oxidation-resistant resin layer in this invention is made of a metal flake and a resin, and due to the excellent water resistance of the metal flake, simply forming a thin film on the permanent magnet body has a large rust prevention effect.

Preferred Embodiments of the Invention The metal flakes used in this invention include metal 2 alloys, metal compounds, etc. with good corrosion resistance, such as stainless steel and AI
, Zn5TiSZr, V, Nb, Cr, Mo
.

Metals such as W, Mn, Co, and Ni and alloys thereof can be used.

Further, the size of the metal flakes is 1pm or less in thickness, 2 to 200pm in width and length, and 0.1pm in thickness.
It is preferable that the thickness is 5 pm or less and the width and length are 5 to 1100 pm in order to form a homogeneous resin layer.

Further, as the resin in this invention, epoxy resin,
Synthetic resins for paints, such as thermosetting acrylic resins, phenolic resins, urethane resins, melamine resins, silicone resins, and vinyl resins, or composite resins thereof.

The amount of metal flakes contained in the resin is 0.01 PHR to 60 PHR1, preferably IPHR to 30 PHR1, from the viewpoint of corrosion resistance and the formation of a homogeneous resin layer.In addition, zinc oxide, zinc chromate, lead, etc. for rust prevention are added to the above resin. It may contain a pigment or it may contain benzotriazole.

In addition, in the present invention, the resin layer is coated on the surface of the permanent magnet by coating it by a spray method, brush coating method, dipping method, etc., and then baking it, but it is sufficient that the resin layer has a thickness of 5 μm or more, which is excellent. In order to obtain high dimensional accuracy, the thickness is preferably 25 pm or less.

Reason for limiting the components of permanent magnet The rare earth element R used in the permanent magnet of the present invention accounts for 10 to 30 at% of the 411 element, including Nd, Pr,
At least one of Dy, Ho, Tb, or in addition, La, Ce, Sm, Gd, Er, E
Preferably, it contains at least one of u, Tm, Yb, Lu, and Y.

Also, normally one type of R is sufficient, but in practice two types are sufficient.
A mixture of more than one species (Mitushmetal, Didim, etc.) can be used for reasons such as availability.

Note that this R does not have to be a pure rare earth element, and may contain impurities that are unavoidable in production within an industrially available range.

R is an essential element in the above permanent magnet, and 1
If it is less than 0 atomic %, the crystal structure becomes a cubic structure with the same structure as α-iron, so high magnetic properties, especially high 1-magnetic force, cannot be obtained, and if it exceeds 30 atomic %, RIJ The magnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet with excellent characteristics cannot be obtained. Therefore, rare earth elements are
The range is 10 atomic % to 30 atomic %.

B is an essential element in the permanent magnet according to the present invention. If it is less than 2 at %, the rhombohedral structure becomes the main phase and high coercive force (iHc) cannot be obtained, and if it exceeds 28 at %, B-rich The number of non-magnetic phases increases, and the residual magnetic flux density (Br
) decreases, making it impossible to obtain an excellent permanent magnet. Therefore, B is in the range of 2 atomic % to 28 atomic %.

Fe is an essential element in the above-mentioned permanent magnet, and 6
If it is less than 5 at%, the residual magnetic flux density (Br) decreases, and 80
If it exceeds atomic%, high coercivity cannot be obtained, so Fe
The content is 65 atomic % to 80 atomic %.

Moreover, in the permanent magnet of this invention, a part of Fe is co
Substitution with Co can improve the temperature characteristics without impairing the magnetic properties of the resulting magnet, but if the amount of Co substitution exceeds 20% of Fe, the magnetic properties will deteriorate, so it is preferable. do not have. When the amount of Co substitution is 5 at % to 15 at % in total of Fe and Co, (Br) increases compared to the case where no substitution is made, which is preferable in order to obtain a high magnetic flux density.

In addition, the permanent magnet of the present invention can tolerate the presence of unavoidable impurities in industrial production in addition to R, B, and Fe; P, 2
．． By replacing at least one of S at 5 atomic % or less and Cu at 3.5 atomic % or less, with a total amount of 4.0 atomic % or less, it is possible to improve the manufacturability and lower the price of permanent magnets. .

Furthermore, at least one of the following additional elements is R-B-
It can be added to Fe-based permanent magnets because it is effective in improving the coercive force and squareness of the demagnetization curve, improving manufacturability, and reducing costs.

9.5 at% or less Al, 4.5 at% or less Ti, 9
．． 5 at% or less V, 8.5 at% or less Cr, 8.0
Mn of atomic% or less, Bi of 5.0 atomic% or less, Nb of 9.5 atomic% or less, Ta of 9.5 atomic% or less, Mo of 9.5 atomic% or less, W of 9.5 atomic% or less , 2.5 atom% or less sb, 7 atom% or less Ge, 3.5 atom% or less Sn, 5.5 atom% or less Zr, 9.0 atom% or less N
i, 9.0 at% or less Si, 1.1 at% or less Zn
, 5.5 atomic % or less of Hf, provided that 2f! If the content is more than If, the maximum content is less than atomic % of the one having the maximum value among the added elements, thereby increasing the permanent magnet's high Vl=
, m power becomes possible.

It is essential that the crystal phase is mainly tetragonal in order to produce a sintered permanent magnet with superior magnetic properties than a fine and uniform alloy powder.

In addition, the 7J (kumagnet) of this invention has an average crystal grain size of 1 to 8.
It is characterized by having a compound having a tetragonal crystal structure in the range of 0 pm as the main phase, and containing a non-magnetic phase (excluding the oxide phase) in a volume ratio of 1% to 50%.

The permanent magnet according to the present invention has fR611 force iHc≧1 kOe, residual magnetic flux density Br>
4kG, and the maximum energy product (BH) max is
(BH)max≧10MGOe, maximum value is 25M
Reach GOe or higher.

Further, the main components of the permanent magnet according to the present invention are the 5
In the case where 0% or more is occupied by metals mainly composed of Nd and Pr, R12 atomic % to 20 atomic %, B44 atomic % to
When the main component is 24 at% Fe and 74 at% to 80 at% Fe, it exhibits excellent magnetic properties of (BH)max 35MGOe or more, and especially when the light rare earth metal is Nd, the maximum value is 45MGOe. reach more than that.

In addition, in this invention, as a permanent magnet that shows extremely high corrosion resistance in a corrosion resistance test where it is left in an environment of 60°C and a relative temperature of 90% for a long time, Nd 1lat% to 15at%, DyO, 2at% to 3
．． Oat%, and the total amount of Nd and Dy is 12at,%~1
7at%, B 5at% to 8at%, CoO,
5at%~13at%, AeO, 5at%~4at%
, C1000 ppm or less, with the remainder being Fe and unavoidable impurities.

Example starting materials include electrolytic iron with a purity of 99.9%, ferroboron alloy, Nd, Dy, Co, with a purity of 99.7% or more,
Using Al, these were mixed and high-frequency melted, then cast in a water-cooled copper mold, and 14Nd -0,5Dy 7B
An ingot having a composition of 6Co-2AI-remaining Fe (at%) was obtained.

The ingot was then coarsely crushed, then finely crushed, with an average particle size of 3
A fine powder of pm was obtained.

This fine powder was inserted into a mold, oriented in a 12 KOe magnet, and molded at a pressure of 1.5 t/cm 2 in a direction perpendicular to the magnetic field.

The obtained colored body was heated to 1' in Ar at 1100°C for 1 hour.
1-, then allowed to cool, and then sintered at 580° in Ar.
A permanent magnet was produced by performing an aging treatment for C12 hours.

From the obtained permanent magnet, length 2Orrun x width 10mm
A test piece was cut out to a size of x thickness 8 x nm.

Next, after washing this test piece with a solvent and drying it, an epoxy resin in which stainless steel flakes with an average thickness of 0.3 pm, an average width of 8 pm, and an average length of 10 pm were dispersed was applied using a sprayer, and then left at room temperature for 3 hours. After drying, a baking treatment was performed at 90° C. for 1 hour, and a resin layer of 20 pm to 25 pm was coated on the surface to obtain a permanent magnet of the present invention.

In addition, the above fat layer contains 18PHR of stainless steel flakes.
It was included.

For comparison, an epoxy resin containing no stainless steel flakes was applied by spraying, dried at room temperature for 3 hours, and then
Baking treatment at ℃ for 1 hour to give 20pm to 30pm on the surface.
A comparative test piece was prepared with a resin layer of m.

Next, the above test was left in an atmosphere at a temperature of 60°C and a relative humidity of 90% for 1000 hours, and the state of rust and the magnetic properties before and after the corrosion resistance test of the permanent magnet material were measured. The results are shown in Table 1.

Margin below Table 1

Claims (1)

[Claims] 1 R (R is at least one of Nd, Pr, Dy, Ho, Tb, or furthermore, La, Ce, Sm, Gd, Er
, Eu, Tm, Yb, Lu, Y) 10 atomic % to 30 atomic %, B2 atomic % to 28 atomic %, Fe65 atomic % to 80 atomic %, and the main phase is square. A corrosion-resistant permanent magnet characterized by having an oxidation-resistant resin layer containing metal flakes on the surface of a sintered permanent magnet body consisting of a crystalline phase.