JPH08264310A - Manufacture of rare earth-iron-boron permanent magnet - Google Patents

Abstract

PURPOSE: To provide a manufacturing method of a rare earth-iron-boron permanent magnet with which the deterioration in magnetic characteristics, owing to the formation of an anti-corrosion film on the surface of a sintered magnet body, can be prevented and the close contact between the anti-corrosion film and the sintered body can be improved. CONSTITUTION: After an anti-corrosion film has been formed on the surface of a sintered magnet body consisting of R (R indicates one or two or more kinds of rare earth element cont aining Y) of 20 to 45wt.%, Fe of 50 to 80wt.%, Co of 0.1 to 15wt.% and B of 0.5 to 6wt.%, a heat treatment is conducted at 500 to 600 deg.C in an inert gas atmosphere, a non-oxidizing atmosphere or in a vacuum atmosphere in the rare earth-iron-boron permanent magnet manufacturing method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cutting process or electrolytic plating by forming a corrosion resistant coating on a rare earth-iron-boron permanent magnet having improved temperature coefficient of residual magnetic flux density and corrosion resistance, and then performing heat treatment. The present invention relates to a method for manufacturing a rare earth-iron-boron-based permanent magnet, which improves the deterioration of magnetic properties due to the above, and also improves the adhesion between the coating and the magnet body.

[0002]

2. Description of the Related Art In recent years, along with the market trend toward smaller and lighter electronic equipment and precision equipment, rare earth magnets have been used in many fields in permanent magnets instead of conventional alnico and ferrite magnets. . Among rare earth permanent magnets, there is an increasing demand for rare earth-iron-boron-based permanent magnets that can obtain a high energy product, and there is a tendency for higher energy products and higher coercive force to be required than ever. However, this rare earth-iron-boron-based permanent magnet has a drawback that the temperature coefficient of residual magnetic flux density is large and demagnetization occurs at high temperature because of its low Curie temperature. In addition, it has a defect that it is easily rusted because it contains a rare earth element that is easily oxidized and iron as main components. In order to overcome these low Curie temperature and low corrosion resistance, various methods of adding elements such as Co, Ga, Ni and Sn have been proposed, and the Curie temperature and the corrosion resistance are improved more than ever before. .

[0003]

However, even a rare earth-iron-boron-based permanent magnet containing these elements cannot provide complete corrosion resistance. Therefore, when a rare earth-iron-boron-based permanent magnet having no corrosion resistant coating is incorporated into a magnetic circuit of an electronic device or the like, oxidation occurs from the surface of the magnet body and progresses inside the magnet body. As a result, the magnetic characteristics are deteriorated and the performance of electronic devices and the like is deteriorated, and oxides on the surface of the magnet body fall off, so that the peripheral devices are contaminated with the magnetic substance. For this reason, various surface treatment methods have been proposed in order to prevent oxidation of the surface of the rare earth-iron-boron-based permanent magnet body. For example, resin coating by spraying or electrodeposition coating, vacuum deposition, ion sputtering, vapor phase plating method by ion plating, Cr,
There are an electrolytic plating method and an electroless plating method for plating a metal or alloy such as Ni. Among these, in the electrolytic plating method or the electroless plating method, in order to perform degreasing or activation treatment with an alkali or an acid as a pretreatment for plating, the grain boundary phase responsible for the coercive force from the magnet body surface portion during the pretreatment is It elutes, and as a result, a layer having deteriorated magnetic characteristics is generated on the surface of the magnet body, and the magnetic characteristics of the magnet body deteriorate. In particular, a thin magnet has a problem that the rate of deterioration in magnetic characteristics is large.

Further, in order to incorporate a rare earth-iron-boron permanent magnet body into an electronic device, it is necessary to cut the entire surface of the magnet body or a required surface before coating.
At this time as well, the surface of the magnet body is roughened and a processing deterioration layer is generated to deteriorate the magnetic characteristics. When a coating is applied on the processing-deteriorated layer, coating peeling easily occurs at the processing-deteriorated layer portion, and the adhesion of the coating deteriorates. In order to improve the deterioration of magnetic properties due to such cutting work, an alloy thin film layer of a metal element such as Ti and W and a rare earth element such as Ce, La, and Nd is formed by vapor deposition such as vacuum deposition or ion sputtering. After forming by plating method, 400 to 9 in vacuum or inert atmosphere
It has been proposed to perform heat treatment at 00 ° C for 1 minute to 3 hours (Japanese Patent Laid-Open No. 62-192566). However,
Active rare earth element at 50 at. %, The corrosion resistance is poor and the cost is high. Also, the inner hole,
There is also a problem that the groove cannot be coated.
Further, in Japanese Patent Laid-Open No. 63-211703, in order to improve corrosion resistance, adhesion, and abrasion resistance, a Ni-P alloy layer is formed by an electroplating method or an electroless plating method.
A method of performing heat treatment at a temperature of 0 to 500 ° C. for 10 minutes to several hours has been proposed, and the examples also show a method of performing heat treatment at a temperature of 150 to 180 ° C. after forming a Ni—P plating layer. . However, the heat treatment at the temperature shown in this example is a heat treatment for removing hydrogen occluded by plating as is generally known. Also, 500
Since the temperature is lower than ℃, the liquid phase is not sufficiently generated in the rare earth-iron-boron permanent magnet, and the deterioration of the magnetic properties due to cutting, etc. is recovered, and the adhesion between the magnet body and the plating layer is improved. There is a problem that it is impossible to improve the sex. In JP-A-1-139705, in order to improve the adhesion between the oxidation resistant film and the magnet body, P is formed on the surface of the magnet body.
It has been proposed that a noble metal layer such as d or Pt and a base metal layer such as Ni be stacked and subjected to diffusion heat treatment at 400 to 700 ° C. However, 10 to 10 precious metals such as Pd and Pt
In the vapor-phase plating method or the method of adsorbing the noble metal colloid, which is formed on the surface of the magnet with a film thickness of 100 angstrom, the noble metal layer is apt to be thin and porous, which causes pinholes in the base metal layer to be attached thereon. It becomes easier and corrosion resistance decreases. In addition, there is a problem in that the cost of precious metals is high. Therefore, the present invention is a method for producing a rare earth-iron-boron-based permanent magnet capable of preventing the deterioration of magnetic properties due to the formation of a corrosion resistant coating on the surface of a sintered magnet body and improving the adhesion between the corrosion resistant coating and the sintered magnet body. The purpose is to provide.

[0005]

A method for manufacturing a permanent magnet according to the present invention for solving the above-mentioned problems includes a rare earth element R (R is at least one kind or a combination of two or more kinds of rare earth elements including Y) of 20 to 20%. 45 wt. %, Fe 50 to 80 wt.
%, Co 0.1 to 15 wt. %, B is 0.5-6w
t. %, A heat-resistant film is formed on the surface of a sintered magnet body containing 100% and then heat-treated at a temperature of 500 to 600 ° C. in an inert gas atmosphere, a non-oxidizing atmosphere or a vacuum.
Boron-based permanent magnet manufacturing method or rare earth element R
(R is at least one kind or a combination of two or more kinds of rare earth elements including Y) is 20 to 45 wt. %, Fe is 50
~ 80 wt. %, Co 0.1 to 15 wt. %, B is 0.5 to 6 wt. % And M (M is Al, Si, Nb,
Mo, V, Mn, Sn, Ni, Zn, Ti, Cr, T
a, W, Ge, Zr, Hf, and Ga) of 10 wt. % Or less, a corrosion-resistant coating is formed on the surface of the sintered magnet body, and then 500 to 6 in an inert gas atmosphere, a non-oxidizing atmosphere or a vacuum.
A method of manufacturing a rare earth-iron-boron-based permanent magnet in which heat treatment is performed at a temperature of 00 ° C., wherein the corrosion-resistant coating is Zn, Cr, N.
i, Cu, Sn, Pb, Cd, Ti, W, Co, Al,
A single-layer film or a multi-layer film composed of at least one element or two or more elements of Ta, or the corrosion-resistant film is C,
Zn, Cr, Ni, Cu, Sn, Pb, Cd, T and at least one or more elements of P, S, O, B and H
It is preferable to use a single-layer film or a multi-layer film made of at least one element or two or more elements out of i, W, Co, Al, and Ta. In the present invention, the corrosion resistant film may be either a single layer film or a multilayer film. In the case of a single layer film, the thickness of the film is 10 μm or more. In the case of a multilayer film, it is preferable that the thickness of the coating in contact with the magnet body is 0.1 μm or more, and the thickness of the entire corrosion resistant coating is 10 μm or more. Further, in the present invention, in order to improve the adhesion between the magnet body and the corrosion resistant coating, it is preferable to perform pretreatment such as degreasing and activation treatment on the surface of the magnet body before forming the corrosion resistant coating.

[0006]

The present invention provides a magnetic property by cutting or electrolytic plating by forming a corrosion resistant film on a rare earth-iron-boron permanent magnet with improved temperature coefficient of residual magnetic flux density and corrosion resistance, and then performing heat treatment. Improve the deterioration of
The present invention relates to a method for producing a rare earth-iron-boron-based permanent magnet having improved adhesion between a coating film and a magnet body. That is, since the coercive force mechanism of the rare earth-iron-boron permanent magnet belongs to the nucleation type, the magnitude of the coercive force is the main phase R2F14B, which is a bud of the reverse magnetic domain.
It is determined by the number of lattice defects and dislocations inside, or the crystal structure and amount of the grain boundary phase surrounding the main phase R2F14B which is considered to pin the reverse magnetic domain buds. Therefore, if cracks or strains are generated in the main phase due to cutting, or if the main phase that does not have a grain boundary phase is exposed, buds in the reverse magnetic domain are likely to occur and the domain wall becomes easy to move and the coercive force is reduced. To do.
In addition, in the pretreatment with acid or alkali that is performed at the time of coating the corrosion resistant film, the coercive force of the magnet body surface portion decreases because the grain boundary phase of the magnet body surface portion elutes, and as a result, The magnetic properties are also reduced. In particular, in the case of a thin magnet body, the deterioration of the magnetic characteristics due to these cutting or pretreatments for plating becomes large.

Therefore, the present invention makes use of the rare earth-rich phase, the B-rich phase, and the like, which are excessively present in the grain boundary phase, and after the corrosion-resistant film is formed, the inert gas, the non-oxidizing atmosphere, or the vacuum is used for 500 to It is characterized by heat treatment at 600 ° C. The heat treatment temperature is particularly preferably 500 to 550 ° C. The present invention improves the temperature characteristics and corrosion resistance of a sintered magnet body by containing Co, and a temperature of 500 to 600 ° C. at which a liquid phase appears after forming an oxidation resistant or corrosion resistant film and the coercive force is improved. Part of the rare earth-rich phase existing at the grain boundaries was discharged to the interface between the surface of the magnet body and the corrosion-resistant coating by heat treatment at, and it was eluted by the processing-deteriorated layer portion generated by cutting or pretreatment with acid or alkali. This is a method of manufacturing a permanent magnet that restores the grain boundary phase portion and restores the magnetic properties. In the present invention, the thickness of the corrosion-resistant coating is set to 10 μm or more because when the thickness of the corrosion-resistant coating is less than 10 μm, pinholes are easily formed, and the rare earth-rich phase is exuded from the pinholes by heat treatment to provide sufficient corrosion resistance. Because I can't get it. Further, if the thickness exceeds 50 μm, the smoothness of the corrosion-resistant coating deteriorates, so the thickness of the corrosion-resistant coating is preferably 50 μm or less. The corrosion resistant film may be a single layer film,
It is preferable that the film is a multilayer film and the thickness of the film in contact with the magnet body is 0.1 μm or more. By forming the multilayer film, the number of pinholes penetrating from the surface of the corrosion resistant film to the surface of the magnet body is reduced, and the corrosion from the pinholes can be prevented. If the thickness of the coating in contact with the magnet body is less than 0.1 μm, the coating tends to be thin and porous, which easily causes pinholes in the coating to be applied on top of it, so that the coating in contact with the magnet body The thickness is preferably 0.1 μm or more.

The reasons for limitation of the present invention will be described below. The rare earth element R used in the permanent magnet of the present invention is 20 to 45w.
t. %, But one or two rare earth elements including Y
20 wt. If less than%, α-F
e was generated and a high coercive force could not be obtained. %, The amount of the rare earth-rich phase that is a non-magnetic phase increases, the residual magnetic flux density decreases, and a permanent magnet having excellent characteristics cannot be obtained. Therefore, R is 20 to 45 wt. % Range is preferred. B
Is an essential element in the above permanent magnet, and is 0.5 w
t. %, The rhombohedral structure becomes the main phase and a high coercive force cannot be obtained. %, The B-rich nonmagnetic phase increases and the residual magnetic flux density decreases, so that an excellent permanent magnet cannot be obtained. Therefore, B is 0.5 to 6 wt. % Range is preferred. Fe is also an essential element in the permanent magnet, and is 50 wt. If it is less than 80%, the residual magnetic flux density decreases,
wt. %, A high coercive force cannot be obtained, so that Fe is 50 to 80 wt. % Range is preferred. Co is necessary to improve temperature characteristics and corrosion resistance, and the amount of Co added is 0.1 wt. % Or less, a sufficient effect cannot be obtained,
15 wt. If it exceeds%, the coercive force will decrease. Therefore, C
The addition amount of o is 0.1 to 15 wt. % Range is preferred.
Further, in order to improve the magnetic characteristics or physical characteristics of the permanent magnet body, Ni, Nb, Ta, W, Al, Ti, Z
r, Si, Ga, Mo, V, Sn, Cr, Mn, Zn,
One or more elements of Ge and Hf of 10 wt. %
The permanent magnet of the present invention may be added in the following ranges, and the permanent magnet of the present invention is a sintered anisotropic permanent magnet obtained by anisotroping crystalline alloy powder by magnetic field molding and then sintering the average crystal. Particle size is 1-5
A compound having a tetragonal crystal structure in the range of 0 μm is used as a main phase, and the maximum energy product reaches 20 MGOe or more. The rare earth-iron-boron-based permanent magnet body thus obtained is subjected to pretreatment with an acid or alkaline solution such as phosphoric acid or sodium hydroxide, and then the corrosion resistant coating is subjected to electrolytic plating, electroless plating, vapor phase plating, etc. It is produced by a generally known method. After that, heat treatment is performed at 500 to 600 ° C. in an inert atmosphere, a non-oxidizing atmosphere, or a vacuum.
As a method for forming the corrosion resistant coating, electrolytic plating and electroless plating are desirable from the viewpoint of cost and uniformity of coating thickness.
Further, after forming the corrosion resistant film, heat treatment can be performed to further form the corrosion resistant film. Since the corrosion resistant film is crystallized and becomes brittle by heat treatment, the strength can be supplemented by further forming the corrosion resistant film after the heat treatment. When forming a corrosion resistant film after heat treatment, after performing pretreatment with an acid or alkaline solution such as phosphoric acid, sodium hydroxide, etc., the corrosion resistant film is generally known for electrolytic plating, electroless plating, vapor phase plating, etc. Can be manufactured by the method described above. Further, a film such as a resin coat may be formed.

[0009]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

(Example 1) Nd18.1 wt. %, Pr
5.2 wt. %, Dy 9.0 wt. %, Al 0.3w
t. %, Nb 1.0 wt. %, B1.03 wt. %, C
o 4.0 wt. %, Ga 0.15 wt. %, And the balance Fe was used to produce a cast ingot by high-frequency melting in an inert atmosphere. After breaking this ingot to 50 mm square or less, the broken mass was inserted into a closed container and Ar gas was added to 20
It is allowed to flow for a minute to replace air, treated with hydrogen gas of 1 kgf / cm 2 for 2 hours, and mechanically crushed to obtain an average particle size of 500.
It was made into a powder of μm. This coarse powder was finely pulverized into a powder having an average particle diameter of 5.0 μm using a jet mill. Fill this molding powder into the molding space formed by the die and lower punch, and
2 ton / cm2 while orienting in a magnetic field of 0 kOe
And pressure-molded to obtain a molded body. This molded body is 1080
Sintering was performed under the conditions of 2 ° C. for 2 hours, and heat treatment was performed for 1 hour at 530 ° C. to produce a permanent magnet. 10x11 from this magnet
A sample of x8 mm (magnetization direction: 8 mm) was cut out, and after surface polishing, pretreatment with phosphoric acid was performed and electrolytic Ni plating with an average thickness of 20 μm was performed using a Watts bath. The sample coated with this Ni plating film was heated at 530 ° C. in an Ar gas atmosphere.
After heat treatment for 1 hour, magnetic properties, change in irreversible demagnetization rate with respect to heating temperature and adhesion strength of coating film (SEVASTIAN 5 manufactured by QUAD GROUP)
Was measured. The irreversible demagnetization rate was measured by the method shown below.
First, measure the magnetic flux φ0 of the magnetized sample at room temperature, then
After heating and holding at each temperature of 100 to 260 ° C. for 1 hour, the temperature was returned to room temperature and left for 1 hour or more, and the magnetic flux φ was measured and calculated by the following definition formula. Irreversible demagnetization rate = {(φ-φ0) / φ0} × 100% In addition, after heating at 100 ° C., cumulative heating was performed at 120 ° C. Table 1 shows the magnetic characteristics, and Fig. 1 shows 4πI-
H curve, FIG. 2 shows the change of the irreversible demagnetization rate with respect to the heating temperature, and Table 2 shows the adhesion strength.

(Example 2) Nd18.1 wt. %, Pr
5.2 wt. %, Dy 9.0 wt. %, Al 0.3w
t. %, Nb 1.0 wt. %, B1.03 wt. %, C
o 4.0 wt. %, Ga 0.15 wt. %, And the balance Fe was heat-treated at 530 ° C. for 1 hour.
10x11x8mm from this magnet (magnetization direction: 8m
m) sample was cut out and surface-polished, followed by pretreatment with phosphoric acid and using a Watts bath, electrolytic Ni having an average thickness of 20 μm
Plated. The sample coated with this Ni plating film is Ar
After performing heat treatment at 510 ° C. for 1 hour in a gas atmosphere, changes in magnetic properties and irreversible demagnetization rate with respect to heating temperature were measured. Table 1 shows the magnetic characteristics, FIG. 1 shows the 4πI-H curve, and FIG. 2 shows the change in the irreversible demagnetization rate with respect to the heating temperature.

(Example 3) Nd18.1 wt. %, Pr
5.2 wt. %, Dy 9.0 wt. %, Al 0.3w
t. %, Nb 1.0 wt. %, B1.03 wt. %, C
o 4.0 wt. %, Ga 0.15 wt. %, And the balance Fe was heat-treated at 530 ° C. for 1 hour.
10x11x8mm from this magnet (magnetization direction: 8m
The sample m) was cut out and the surface was polished, and then pretreatment for plating was performed with nitric acid, hydrogen peroxide solution, and acetic acid. Next, using a Watt bath, an electrolytic Ni plating layer of 2 μm as a base layer, an electrolytic Cu plating layer of 14 μm with a Cu pyrophosphate bath, and an electrolytic Ni plating layer of 4 μm with a Watt bath were applied to give a total film thickness of 20 μm.
A Ni-Cu-Ni plated film of m was prepared. This sample was heat-treated at 530 ° C. for 1 hour in an Ar gas atmosphere, and then the changes in magnetic properties and irreversible demagnetization rate with respect to heating temperature were measured. Table 1 shows the magnetic characteristics, FIG. 1 shows the 4πI-H curve, and FIG. 2 shows the change in the irreversible demagnetization rate with respect to the heating temperature.

(Comparative Example 1) Nd 18.1 wt. %, Pr
5.2 wt. %, Dy 9.0 wt. %, Al 0.3w
t. %, Nb 1.0 wt. %, B1.03 wt. %, C
o 4.0 wt. %, Ga 0.15 wt. %, And the balance Fe was heat-treated at 530 ° C. for 1 hour.
10x11x8mm from this magnet (magnetization direction: 8m
m) sample was cut out and surface-polished, followed by pretreatment with phosphoric acid and using a Watts bath, electrolytic Ni having an average thickness of 20 μm
Plated. The sample coated with this Ni plating film is Ar
After performing heat treatment at 200 ° C. for 1 hour in a gas atmosphere, magnetic properties, changes in irreversible demagnetization rate with heating temperature, and adhesion strength of coating film (QUAD GROUP
SEVASTIAN 5) manufactured by the company was measured. Table 1 shows the magnetic characteristics, FIG. 1 shows the 4πI-H curve, FIG. 2 shows the change of the irreversible demagnetization rate with respect to the heating temperature, and Table 2 shows the adhesion strength. The squareness of the demagnetization curve is worse than in Examples 1 and 2, and the adhesion is also lower.

(Comparative Example 2) Nd18.1 wt. %, Pr
5.2 wt. %, Dy 9.0 wt. %, Al 0.3w
t. %, Nb 1.0 wt. %, B1.03 wt. %, C
o 4.0 wt. %, Ga 0.15 wt. %, And the balance Fe was heat-treated at 530 ° C. for 1 hour.
10x11x8mm from this magnet (magnetization direction: 8m
m) sample was cut out and surface-polished, followed by pretreatment with phosphoric acid and using a Watts bath, electrolytic Ni having an average thickness of 20 μm
Plated. The sample coated with this Ni plating film is Ar
After performing heat treatment at 400 ° C. for 1 hour in a gas atmosphere, changes in magnetic properties and irreversible demagnetization ratio with respect to heating temperature were measured. Table 1 shows the magnetic characteristics, FIG. 1 shows the 4πI-H curve, and FIG. 2 shows the change in the irreversible demagnetization rate with respect to the heating temperature. The squareness of the demagnetization curve is lower than in Examples 1 and 2.

(Comparative Example 3) Nd18.1 wt. %, Pr
5.2 wt. %, Dy 9.0 wt. %, Al 0.3w
t. %, Nb 1.0 wt. %, B1.03 wt. %, C
o 4.0 wt. %, Ga 0.15 wt. %, And the balance Fe was heat-treated at 530 ° C. for 1 hour.
10x11x8mm from this magnet (magnetization direction: 8m
m) sample was cut out and surface-polished, followed by pretreatment with phosphoric acid and using a Watts bath, electrolytic Ni having an average thickness of 20 μm
Plated. The sample coated with this Ni plating film is Ar
After performing heat treatment at 650 ° C. for 1 hour in a gas atmosphere, changes in magnetic properties and irreversible demagnetization factor with respect to heating temperature were measured. Table 1 shows the magnetic characteristics, FIG. 1 shows the 4πI-H curve, and FIG. 2 shows the change in the irreversible demagnetization rate with respect to the heating temperature. The squareness of the demagnetization curve and the coercive force are lower than in Examples 1 and 2.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

According to the present invention, a corrosion resistant film is formed on an R-Fe-B system permanent magnet having improved temperature characteristics and corrosion resistance, and the R-Fe-B system permanent magnet is subjected to an inert atmosphere, a non-oxidizing atmosphere or a vacuum,
By heat treatment at 500 to 600 ° C., the crystal structure portion deteriorated by cutting or electrolytic plating is repaired,
It is possible to improve the deterioration of the magnetic properties and the secular change of the magnetic properties, and also to improve the adhesion between the coating film and the magnet body, and its industrial utility value is extremely high.

[Brief description of drawings]

FIG. 1 is a 4πI-H of Examples 1 to 3 and Comparative Examples 1 to 3.
It is a figure which shows a curve.

FIG. 2 is a diagram comparing changes in irreversible demagnetization rates with respect to heating temperatures in Examples 1 to 3 and Comparative Examples 1 to 3.

Claims (7)

[Claims] 1. R (wherein R is one or more of rare earth elements including Y) is 20 to 45 wt. %, Fe 50 to
80 wt. %, Co 0.1 to 15 wt. %, B is 0.
5-6 wt. %, A rare earth-iron-boron system characterized by being heat-treated at a temperature of 500 to 600 ° C. in an inert gas atmosphere, a non-oxidizing atmosphere or a vacuum after forming a corrosion resistant film on the surface of the sintered magnet body of Manufacturing method of permanent magnet. 2. R (wherein R is one or more of rare earth elements including Y) is 20 to 45 wt. %, Fe 50 to
80 wt. %, Co 0.1 to 15 wt. %, B is 0.
5-6 wt. % And M (M is Al, Si, Nb, M
o, V, Mn, Sn, Ni, Zn, Ti, Cr, Ta,
W, Ge, Zr, Hf, and Ga) of 10 wt. % On the surface of the sintered magnet body having a thickness of 10 μm or more, and then 500 to 60 in an inert gas atmosphere, a non-oxidizing atmosphere or a vacuum.
Rare earth-iron-characterized by heat treatment at a temperature of 0 ° C
Method for manufacturing boron permanent magnet. 3. The corrosion resistant coating is Zn, Cr, Ni, Cu,
The method for producing a rare earth-iron-boron-based permanent magnet according to claim 1 or 2, comprising one or more elements selected from Sn, Pb, Cd, Ti, W, Co, Al, and Ta. 4. The corrosion-resistant coating comprises at least one element selected from C, P, S, O, B and H, or two or more elements, and Zn, Cr,
Ni, Cu, Sn, Pb, Cd, Ti, W, Co, A
The method for producing a rare earth-iron-boron-based permanent magnet according to claim 1 or 2, comprising at least one element or two or more elements of 1 and Ta. 5. The method for producing a rare earth-iron-boron-based permanent magnet according to claim 1, wherein the corrosion-resistant coating is a single-layer coating having a thickness of 10 μm or more. 6. The rare earth-iron- according to claim 1, wherein the corrosion-resistant coating is a multi-layered coating and the coating in contact with the magnet body has a thickness of 0.1 μm or more.
Method for manufacturing boron permanent magnet. 7. The method for producing a rare earth-iron-boron-based permanent magnet according to claim 1, further comprising forming a corrosion resistant film after the heat treatment.