JPS62120002A - Permanent magnet with excellent corrosion resistance - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of a permanent magnet by providing a vapor-phase plating layer on the permanent magnet which mainly contains R (R is at least one of rare earth elements including Y) B and Fe, and tetragonal crystal of main phase and producing a diffused layer between the plating layer and the magnet. CONSTITUTION:Rare earth elements R used for a permanent magnet material of this invention are included in a range of 8-30atom%. If less than 8atom%, high magnetic property and hence high coercive force is not obtained, and if more than 30atom%, its remaining magnetic flux density Br decreases. B is included in a range of 2-28atom%. If less than 2atom%, high coercive force (iHc) is not obtained, and if more than 28atom%, its remaining magnetic flux density Br decreases. Fe is included in a range of 42-90atom%. If less than 42atom%, the remaining magnetic flux density Br decreases, and if more than 90atom%, high coercive force is not obtained. A thin corrosion resistance film is formed by vapor-phase plating layer forming means on the surface of the magnet of the above components. A diffused layer is formed between the plating layer and the magnet, and heat treated at 250 deg.C or age hardening tempera ture or lower. The thickness of the diffused layer is preferably 0.01-10mum by consider ing the corrosion resistance and the sealability with a base magnet.

Description

[Detailed description of the invention] Industrial field of application This invention is applicable to R (R is m, Pr, u, Ho, T
At least one of b or further, La, Ce
, Sm.

Ga, Er, Eu, Tm, Yb, Lu, Y
A vapor phase plating phase having a diffusion layer is deposited between the permanent magnet body and the permanent magnet to improve the corrosion resistance of the permanent magnet and the magnet. This article relates to a rare earth/boron/iron permanent magnet that improves the reduction in magnetic flux caused by body forming processing.

BACKGROUND ART The present inventor previously proposed a Fe-BR-based permanent magnet (R is at least one of rare earth elements including Y) as a new high-performance permanent magnet that does not contain expensive Stn or porcelain. (Gan Sho 57-145072). This permanent magnet is an excellent permanent magnet that uses resource-rich light rare earths such as ceramics and circles as R, has Fe as its main component, and exhibits an extremely high energy product of 25 MGOe or more.

However, Fa, which has the above-mentioned excellent magnetic properties,
Permanent magnets made of B R-based magnetically 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, 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 surrounding carriers due to the surface oxide falling off.

Therefore, in order to improve the corrosion resistance of the above-mentioned FEI-B-R permanent magnet, the applicant has previously proposed a permanent magnet (patent application 1982-162350), and proposed a permanent magnet in which the surface of the magnet was coated with a corrosion-resistant resin by spraying or dipping (Japanese Patent Application No. 58-171).
907@) I did.

However, in the former plating method, since the permanent magnet body is a sintered body and has pores, there is a risk that acidic or alkaline solutions from plating pretreatment remain in the pores, leading to corrosion over time. In addition, since the chemical resistance of the magnet body was poor, the magnet surface was corroded during plating, resulting in poor adhesion and corrosion resistance.

In addition, since resin coating using the latter spray method has a directionality, it takes a lot of time and effort to apply a uniform resin coating to the entire surface of the object, especially for irregularly shaped magnets with complex shapes. It is difficult to apply a coating with a uniform thickness, and the dipping method results in uneven resin coating thickness, resulting in poor product dimensional accuracy.

In general, it is possible to eliminate the drawbacks of the above-mentioned plating and spraying methods, and to obtain stable corrosion resistance over a long period of time.
As a -B-R system permanent magnet, we proposed a permanent magnet whose surface was coated with corrosion-resistant vapor phase plating made of various metals or alloys (Japanese Patent Application No. 59-278489@). This vapor phase plating suppresses oxidation on the surface of the magnet body, does not deteriorate the magnetic properties, and does not use or leave corrosive chemicals, so it has the advantage of being stable over a long period of time.

However, when used for a long period of time in a more severe environment, there was a problem in which there was concern that the corrosion-resistant thin film would deteriorate or peel off.

Purpose of the Invention The object of the present invention is to provide a permanent magnet with improved corrosion resistance of a new permanent magnet material mainly composed of rare earth elements, boron, and iron. The purpose of the present invention is to provide a highly corrosion-resistant permanent magnet in which a highly corrosion-resistant thin film is firmly provided on the surface of the magnet material with a uniform thickness.

Structure and Effects of the Invention This invention provides R (R is Na, Pr, D!It, H
At least one of O, Th or further i, C
o, Sm.

C<, Er, Eu, Tm, Yb, Lu, Y
8 at% to 30 at%
, B2 atomic% to 28 atomic%, Fe42 atomic% to 90 atomic% as main components, and the main phase is a tetragonal phase, on the surface of the permanent magnet body, by vacuum evaporation method, ion sputtering method, ion blating method, ion evaporation thin film. M, Zn, NL, Cr, Cu, Co, deposited by IVD (IVD) or CVO (plasma vapor deposition).
Tj, Nb, v, Ta.

It has a corrosion-resistant vapor phase plating layer of metals such as Mo, W, t'In, etc. or their alloys, and is heat-treated in a vacuum or in the atmosphere to form a permanent magnet with the vapor phase plating layer. It is a highly corrosion-resistant permanent magnet characterized by the generation of diffused magnetism between bodies.

The vapor phase plating in this invention physically adsorbs onto the surface of the water-based permanent magnet material and forms a strong coating with a uniform thickness. It was discovered that voids were created, and that water could penetrate into these voids and cause rust, resulting in a problem of mechanical and thermal instability. This problem was solved using a diffusion layer.

In other words, by subjecting a water-based permanent magnet on which vapor phase plating has been formed to a prescribed heat treatment, the voids are filled by sintering and melting effects, and diffusion heat is created between the vapor phase plating phase and the permanent magnet body. By generating and promoting diffusion not only to the crystal grains of the magnet layer but also to the grain boundaries, the corrosion resistance of the grain boundaries is improved, and the mechanical and thermal strength of vapor phase plating is dramatically improved. This prevents the thin film from peeling off and rusting. Furthermore, by forming a stable oxide passivity on the vapor phase plating surface, it becomes possible to use the product for a long period of time under extremely harsh environmental conditions.

Further, the permanent magnet according to the present invention having vapor phase plating and its diffusion coating on the surface has the advantage that its coercive force is improved for the following reason.

In other words, the FEI-B-R permanent magnet has a main phase of Nd2.
FEl14 B crystal grains with a diameter of about 10 m and surrounding <bCC phase, NdrICh phase, and a small amount of B ric
h phase. Among these, the main phase Nd2Fl
The presence of 1148 and bcc phase is largely involved in the generation of coercive force, but in FeBR permanent magnets, the bcc phase is the same as the Ncirich phase and the square Nd2Fe12B
It is formed only when a phase exists, and only the Nd + Fe114 B tetragonal compound exists on the surface of the permanent magnet, and this bcC phase is not present, so the coercive force of the magnet surface layer decreases. Processing has caused deterioration in the magnetic properties of the permanent magnets, which have been made small or thin.

However, the diffusion layer between the vapor-phase plating layer and the permanent magnet body of the present invention improves the magnetic anisotropy of the crystal in the above-mentioned portion, prevents the coercive force from decreasing on the stone surface, and improves the magnetic properties. This brings about an improvement effect.

In addition, as mentioned above, the mr at the grain boundaries of the permanent magnet body
Due to the presence of the ich phase, the formation of a thin film did not progress and was a cause of rust, but this problem was resolved by the formation of the diffusion layer.

Preferred Embodiments of the Invention The method of forming the corrosion-resistant vapor phase plating layer on the surface of the magnet material in this invention includes vacuum evaporation method, ion sputtering method, ion blating method, ion evaporation thin film forming method (I
VD) or plasma vapor deposition thin film formation method (CVD)
etc. can be adopted.

In this invention, the thickness of the corrosion-resistant thin film formed on the surface of the permanent magnet by the above-mentioned vapor phase plating layer forming means is 3.
A thickness of 0i or less can be obtained.

In this invention, the formation of a diffusion layer between the vapor phase plating and the permanent magnet is obtained by heat treatment in the air or vacuum, but when heat treatment is performed after vapor phase plating is applied to the aged permanent magnet body, The temperature conditions are preferably from 250°C to the aging treatment temperature.

This is because if the temperature is lower than 250'C, sufficient diffusion between the vapor phase plating and the permanent magnet will not take place, and if it exceeds the aging treatment temperature, the effect of the aging treatment applied in advance will be lost, which is not preferable.

When vapor-phase plating is applied to a permanent magnet that has not been subjected to aging treatment, and then heat-treated, the temperature condition is preferably between 250℃ and below the melting point of the vapor-phase plated metal. processing, and the subsequent aging processing can be omitted.

Further, the aging treatment temperature of the permanent V7i stone body according to the present invention is preferably from 350'C to below the sintering temperature (900°C to 1200'C) when performing one-stage aging treatment, and when performing two-stage aging treatment, Preferably, the conditions are 750'C to 1000C in the first stage and 480'C to 700'C in the second stage.

If the aging treatment is one-stage aging treatment, the heat treatment temperature should be set to 250℃.
It is preferable to set the temperature to not less than °C and not more than the aging treatment temperature, and if the aging treatment is a two-stage aging treatment, the temperature should be not less than 250'C,
Temperature conditions below the first-stage aging treatment temperature are preferred.

Even if heat treatment is performed at 250'C to below the melting point of the vapor-phase plated metal without aging treatment, it is desirable to carry out aging treatment after the heat treatment in terms of magnetic properties.

Furthermore, if the heat treatment conditions after the aging treatment are higher than the pre-aging temperature, it is necessary to perform the aging treatment again from the viewpoint of magnetic properties.

In addition, the heat treatment time can be selected as appropriate to obtain the required diffusion rate depending on the type of metal to be vapor-phase plated, the amount of treatment, and the temperature conditions.
time is preferable.

In this invention, the thickness of the diffusion layer formed between the vapor-phase plating layer and the permanent magnet by heat treatment is preferably 0.01 to 10 μm in consideration of corrosion resistance and adhesion to the base magnet.

When the vapor phase plating metal is a metal such as M, Cr, or TL, during heat treatment, an oxide layer is generated on the surface of the vapor phase plating layer, which becomes passivated and the corrosion resistance is further improved. Can be used for long periods of time under harsh conditions.

Reason for Limiting Components of Permanent Magnet Material The rare earth element R used in the permanent magnet material of the present invention accounts for 8 to 30 at% of the composition, and M.

At least one of Yen, u, Ho, Th, Orui, La, Ce, Sm, (a, Er,
Eu, Tm, Yb, Lu.

Those containing at least one type of Y are preferred.

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 new above-mentioned permanent magnet material, and when it is less than 8 atomic %, the crystal structure becomes a cubic structure that is the same as α-iron, so high magnetic properties, especially high coercive force, can be obtained. If it exceeds 30 at %, the R-rich nonmagnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet with excellent properties cannot be obtained. Therefore, the rare earth element is in the range of 8 atomic % to 30 atomic %.

B is an essential element in the permanent magnet material according to the present invention, and when it is less than 2 atomic %, the rhombohedral structure becomes the main phase, and the high coercive force (iHC) is not q, and when it exceeds 28 atomic %, Since the B-rich nonmagnetic phase increases and the residual magnetic flux density (Sr) decreases, an excellent permanent magnet cannot be obtained.Therefore, B is set in a range of 2 atomic % to 28 atomic %.

Fe is an essential element in the new above-mentioned permanent magnet.If it is less than 42 at%, the residual magnetic flux density (Br) decreases, and if it exceeds 90 at%, high coercive force cannot be obtained. The content is from atomic % to 90 atomic %.

In addition, in the permanent magnet material according to the present invention, replacing a part of Fe with iron can improve the temperature characteristics without impairing the magnetic properties of the resulting magnet.
If the amount of substitution exceeds 20% of Fe, the magnetic properties will deteriorate, which is not preferable. When the amount of G substitution is 5 atomic % to 15 atomic % in total of Fe and G, (Br) increases compared to the case where no substitution is made, which is preferable in order to obtain a high magnetic flux density.

Further, the permanent magnet material according to the present invention includes R, B.

In addition to Fe, the presence of unavoidable impurities in industrial production can be tolerated, but a portion of B may be 4.0 atomic % or less of C13, 5 atomic % or less of P, 2.5 atomic % or less of S, 3. By substituting at least one of the 5 atomic % or less of the marrow with a total amount of 4.0 atomic % or less, it is possible to improve the manufacturability and reduce the cost of permanent magnets.

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

A1 of 9.5 atom % or less; publication of 4.5 atom % or less; 9.
V at 5 atomic % or less, Cr at 8.5 atomic % or less.

8.0 atom% or less of H, 5.0 atom% or less of Bi, 9
．． Nb of 5 atomic % or less, Ta of 9.5 atomic % or less, 9.
5 atomic % or less of No, 9.5 atomic % or less of glue, 2.5 atomic % or less of Sb, 7 atomic % or less of Ge.

Sn of 3.5 atomic% or less, Zr of 5.5 atomic% or less
, 9.0 atom% or less of Ni, 9.0 atom% or less of 8
1.1.1 atomic% or less Zn15.5 atomic% or less Hf
.

At least one of these elements is added and contained; however, when two or more types are contained, the maximum content is less than or equal to the atomic percent of the element having the maximum value among the added elements.
It becomes possible to increase the coercive force of permanent magnets.

It is essential that the main phase of the crystalline phase is a tetragonal one in order to produce a sintered permanent magnet having superior magnetic properties than a fine and uniform alloy powder.

Further, the permanent magnet of the present invention can be press-molded in a magnetic field to obtain a magnetically anisotropic magnet, and can be press-molded in a non-magnetic field to obtain a magnetically isotropic magnet.

The permanent magnet material according to the present invention has a coercive force iHc≧1 k
oa, the residual magnetic flux density Br > 4 kG, and the maximum energy product (BH) max is (BH) max ≧ 108
GOe, and the maximum value reaches 25) IGOs or more.

Further, the main component of R of the permanent magnet according to the present invention is 5
In the case where 0% or more is occupied by light rare earth metals mainly composed of metals, and when the main components are R12 to 20 atom%, B44 to 24 atom%, and F874 to 80 atom%, ( BH) max 35) It exhibits excellent magnetic properties of IGOe or higher, and especially when the light rare earth metal is Nd, its maximum value is delayed to 45HGOa or higher.

Further, the alloy for permanent magnets of this invention has a crystal grain size of 1 to 1.
At least 50 vol 1% or more of a compound having a tetragonal crystal structure in the range of 100A1, and 1% by volume
It is desirable to include ~50% non-magnetic phase (excluding oxide phase).

Example: As a starting material, electrolytic iron with a purity of 99.9%, B19°4
A ferroboron alloy with a purity of 99.7% or more is used, and the balance is FB and impurities such as M, SL, and C. After blending, the alloy is high-frequency melted, and then cast in a water-cooled copper mold. .0f11 to 17.0B77, OF
An ingot having a composition of e (atomic %) was obtained.

The one-flame ingot is coarsely crushed by a stamp mill,
Next, it was pulverized using a ball mill to obtain a fine powder with a particle size of 2.8AITn.

This fine powder was inserted into a mold, oriented in a magnetic field of 15 kOa, and molded at a pressure of 1.2 t, J in a direction perpendicular to the magnetic field.

The obtained compact was sintered at 100°C for 1 hour in an Ar atmosphere, then allowed to cool, and roughly aged in Ar at 600°C for 2 hours to produce a permanent magnet. did.

The obtained permanent magnet has an outer diameter of 20 m1r + x inner diameter of 10 mm.
Seven test pieces were cut out to a size of 1.5 mm in thickness.

Next, the above test piece was placed in a vacuum container with a vacuum degree of lXl0-5 Torr, and placed in Ar gas of 0.8 Torr.
After performing reverse sputtering for 1 minute at a voltage of 00V, as a pretreatment, it was heated at 350℃ for 30 minutes and heated to 300℃.
The temperature dropped to 'C.

Furthermore, the coating material 10mmφX10mm
An N piece with a dimensional purity of 99.99% or more was irradiated with an electron beam of 0.6 Δ, 8 x ■ for 30 minutes, heated and evaporated to vacuum deposit an M thin film on the test piece. The thickness of the Afha film formed on the surface of the permanent magnet is 10. It was am.

The test piece provided with the M thin film was subjected to the following temperature conditions as shown in Table 1.
Heat treatment was performed for 1.5 hours.

This test piece was subjected to a corrosion resistance test and an adhesion strength test of the MH film after the corrosion resistance test. In addition, the rate of decrease in magnetic flux after the corrosion resistance test was measured. The test results and measurement results are shown in Table 1.

In addition, in the case of samples positive 4 and 5, after heat treatment, the temperature was increased to 600℃ again.
, each test after 2 hours of aging treatment.

Measurements were made.

For comparison, the same test specimens were also used, including a test piece manufactured under exactly the same conditions except for no heat treatment (positive 6), and a test piece as cut without a thin film (positive 7). The test results and measurement results are shown in Table 1.

The corrosion resistance test was evaluated based on the appearance of the test piece when it was left in an atmosphere of 80° C. and 90% humidity for 175 hours.

In addition, in the adhesion strength test, the above test piece after the corrosion resistance test was
Folds spaced at 1 mm intervals were pulled with an adhesive tape, and whether or not the thin film layer peeled was evaluated based on the number of folds without peeling/number of squares.

The diffusion layer thickness was measured using an X-ray microanalyzer.

As is clear from the test and measurement results in Table 1 below, the corrosion-resistant vapor phase plating layer according to the present invention has a diffusion effect caused by heat treatment, so oxidation of the permanent magnet body is reliably prevented.
It can be seen that there is no deterioration in magnetic properties, and the magnetic properties are significantly improved compared to the comparative example.

Claims (1)

[Claims] R (R is Nd, Pr, Dy, Ho), at least one of Tb, or furthermore, La, Ce, Sm, Cd,
At least one of Er, Eu, Tm, Yb, Lu, Y
(consisting of seeds) 8 atom% to 30 atom%, B2 atom% to 28 atom%
%, Fe42 atomic % to 90 atomic % is the main component, and the main phase is a tetragonal phase, and has a vapor phase plating layer on the surface of the permanent magnet body, and is diffused between the vapor phase plating layer and the permanent magnet body. A permanent magnet with excellent corrosion resistance, characterized by the fact that it has layers.