JPH0617491B2 - Permanent magnet material processing method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for processing an Fe-BR permanent magnet material, and relates to a black skin remaining on at least one main surface of a sintered permanent magnet surface, or grinding of the magnet surface. The present invention relates to a method for processing a Fe-BR permanent magnet material in which deterioration of magnet characteristics due to processing and the like is improved.

BACKGROUND ART Currently, typical permanent magnet materials are alnico, hard ferrite and rare earth cobalt magnets. Since this rare earth cobalt magnet has remarkably excellent magnetic characteristics, it is used for various purposes. However, the main components Sm and Co are both resource-deficient and expensive.
It is difficult to stably supply a large amount.

Therefore, there has been a strong demand for a permanent magnet material which has excellent magnetic properties, is inexpensive, is abundant in resources, and can be stably supplied in the future from a composition element.

The present applicant has previously proposed a Fe-BR type 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 Sm or Co (Japanese Patent Laid-Open No. 2006-242242).
59-46008, JP-A-59-64733, JP-A-59-89401, JP-A-59-132104). This permanent magnet uses Nd or Pr as R.
It is an excellent permanent magnet that uses light rare earths, which are abundant in terms of resources, and has an extremely high energy product of 25 MGOe or more, and at most 45 MGOe or more, with B and Fe as the main components.

Recently, as the performance and size of magnetic circuits have increased, Fe-B-
R-based permanent magnet materials have been receiving more and more attention. In order to manufacture a permanent magnet material for such an application, the magnet body is used to remove irregularities and distortions on the surface of the sintered magnet body that has been molded and sintered, to remove the surface oxide layer, or to be incorporated in a magnetic circuit. It is necessary to cut the entire surface or required surface of the machine, and an outer peripheral blade cutting machine, an inner peripheral blade cutting machine, a surface grinder, a centerless grinder, a lapping machine, etc. are used for the processing.

However, when the Fe-BR permanent magnet material is ground by the above apparatus, the Fe-BR permanent magnet material, as a main component, is extremely easily oxidized in air and immediately forms a stable oxide. Because it contains rare earth elements and iron, it generates heat and generates an oxide layer due to contact between the atmosphere and the processed surface,
There is a problem that the deterioration of magnetic characteristics is caused.

An object of the present invention is to provide a method for processing a permanent magnet material, which is a novel permanent magnet material mainly containing rare earth, boron and iron, which can improve the deterioration of the magnetic properties due to the oxidation of the sintered magnet body and the cutting work. It is an object.

Structure and Effect of the Invention The present invention is based on R (R is at least one of Nd, Pr, Dy, Ho and Tb, or further, La, Ce, Sm, Gd, Er, Eu, Tm, Yb, Lu and Y). (At least one of them) 10 atom% to 30 atom%, B
Hard powder with a Mohs hardness of 5 or more is inertized or dehumidified on the surface of a sintered permanent magnet body containing 2 atom% to 28 atom% and Fe 65 atom% to 80 atom% as a main component and a tetragonal main phase. The method for processing a permanent magnet material is characterized in that the permanent magnet material is sprayed with a pressurized gas consisting of air to remove the oxide layer and the work strain layer on the surface of the magnet body.

More specifically, the present invention is to inject a hard powder having the required properties together with a pressurized gas onto a surface of a sintered magnet body to form a black skin black skin of the sintered magnet body, an oxide layer or a work strain layer. By removing the surface layer, it is intended to improve the deterioration of the magnet characteristics due to oxidation and cutting, further, for example, by depositing an Al thin film layer on the cleaned magnet body surface, It is also good to improve the adhesion between the material and the surface thin film layer and the corrosion resistance of the magnet material.

The permanent magnet material of the present invention has an average crystal grain size of 1 to 80.
A compound having a tetragonal crystal structure in the range of μm is used as a main phase, and a volume ratio of 1% to 50% of a nonmagnetic phase (excluding an oxide phase) is included.

In the processing method of the present invention, R is a light rare earth resource rich in Nd and Pr, and B and Fe are the main components.
Exhibits extremely high energy product reaching MGOe or higher, and reaching 45 MGOe or higher at the highest, high residual magnetic flux density, and high coercive force
It is possible to inexpensively obtain an Fe-BR permanent magnet material which is an excellent permanent magnet and which is improved in deterioration of magnetic properties due to grinding processing and an oxide layer.

In this invention, the Mohs hardness of 5 or more hard powder, Al ₂ O ₃ system, silicon carbide Motokei, ZrO ₂ system, boron carbide-based, there are powders of garnet, etc., high hardness Al ₂ O ₃ system powder Is preferable, and an irregular shape is preferable as the powder shape.

If the Mohs hardness of the hard powder is less than 5, the grinding force is too small and the grinding process takes a long time, which is not preferable.

In this invention, the average particle size of the hard powder is 20 μm to 350 μm.
If it is less than 20 μm, the grinding force is too small and it takes a long time to grind, and if it exceeds 350 μm, the surface roughness of the sintered magnet body surface becomes too rough and the grinding amount becomes uneven, Not preferable.

As for the injection conditions of hard powder, if the pressure is less than 1.0 kg / cm ^2, it takes a long time for the grinding process, and if the pressure exceeds 6.0 kg / cm ² , the amount of grinding on the surface of the magnet becomes non-uniform, resulting in a rough surface. The pressure of pressurized gas is 1.0 kg / cm ^{2 to}
A range of g / cm ² is preferred.

Further, if the injection time is less than 0.5 minutes, the grinding amount is small and non-uniform, and if it exceeds 60 minutes, the grinding amount on the surface of the magnet body is large and the surface roughness deteriorates.
Minute injection times are preferred.

Further, as the pressurized fluid for injecting the hard powder, air or an inert gas such as Ar or N ₂ gas can be used, but an inert gas is preferable for preventing the oxidation of the magnet body. When used, dehumidified air is desirable.

Reasons for Limiting Components of Permanent Magnet Material The rare earth element R used in the permanent magnet material of the present invention occupies 10 atom% to 30 atom% of the composition, and at least one of Nd, Pr, Dy, Ho and Tb, or further , La, Ce, Sm, Gd, Er, E
Those containing at least one of u, Tm, Yb, Lu and Y are preferable.

Also, one type of R is usually sufficient, but it is practically 2
Mixtures of more than one species (Misch metal, didymium, etc.) can be used for reasons of availability.

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

R is an essential element in the novel permanent magnet material described above, and if it is less than 10 atomic%, the crystal structure becomes a cubic structure having the same structure as α-iron, so that high magnetic properties, especially high coercive force can be obtained. If the content exceeds 30 at%, the R-rich nonmagnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet with excellent characteristics cannot be obtained. Therefore, the rare earth element content is in the range of 10 atom% to 30 atom%.

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

Fe is an essential element in the novel permanent magnets, and the residual magnetic flux density (Br) decreases if it is less than 65 atom%, and a high coercive force cannot be obtained if it exceeds 80 atom%.
The content is 65 atom% to 80 atom%.

Further, in the permanent magnet material according to the present invention, substituting a part of Fe with Co can improve the temperature characteristics without deteriorating the magnetic characteristics of the obtained magnet. If it exceeds 20%, on the contrary, the magnetic properties deteriorate, which is not preferable. When the substitution amount of Co is 5 atom% to 15 atom% as the total amount of Fe and Co, (Br) is increased as compared with the case of not substituting, which is preferable for obtaining a high magnetic flux density.

Further, the permanent magnet material according to the present invention can tolerate the presence of impurities unavoidable in industrial production in addition to R, B and Fe, but a part of B is 4.0 atomic% or less of C and 3.5 atomic% or less of P. , S of 2.5 atomic% or less, and Cu of 3.5 atomic% or less, by substituting at least one kind with a total amount of 4.0 atomic% or less, it is possible to improve the productivity of the permanent magnet material and reduce the cost.

Further, at least one of the following additional elements is RB-
It can be added to the Fe-based permanent magnet material because it is effective in improving the coercive force and the squareness of the demagnetization curve, improving the manufacturability, and lowering the cost. However, since the residual magnetic flux density (Br) is lowered with the addition for improving the coercive force, it is desirable to add the residual magnetic flux within the range equal to or more than the residual magnetic flux density of the conventional hard ferrite magnet.

9.5 atomic% or less Al, 4.5 atomic% or less Ti, 9.5 atomic% or less V, 8.5 atomic% or less Cr, 8.0 atomic% or less Mn, 5.0 atomic% or less Bi, 9.5 atomic% or less Nb, 9.5 Ta less than atomic%, Mo less than 9.5 atomic%, W less than 9.5 atomic%, Sb less than 2.5 atomic%, Ge less than 7 atomic%, Sn less than 3.5 atomic%, Zr less than 5.5 atomic%, 9.0 atomic % Or less Ni, 9.0 atom% or less Si, 1.1 atom% or less Zn, and 5.5 atom% or less Hf, at least one kind is added, but when two or more kinds are contained, the maximum content is By containing atomic% or less of the additional element having the maximum value,
It is possible to increase the coercive force of the permanent magnet material.

The fact that the main phase of the crystal phase is a tetragonal crystal is indispensable for producing a sintered permanent magnet having excellent magnetic properties from a fine and uniform alloy powder.

In addition, the permanent magnet material of the present invention can be magnetically anisotropic magnet by press molding in a magnetic field, and can be magnetically isotropic magnet by press molding in a non-magnetic field. .

The permanent magnet material according to the present invention exhibits a coercive force iHc ≧ 1 kOe, a residual magnetic flux density Br> 4 kG, and a maximum energy product (BH).
In the most preferable composition range, max indicates (BH) max ≧ 10 MGOe, and the maximum value reaches 25 MGOe or more.

Further, the main component of R in the permanent magnet material of the present invention is 50%
When the above is occupied by a light rare earth metal mainly composed of Nd and Pr, R12 atom% to 20 atom%, B4 atom% to 24 atom%, Fe
When 74 atomic% to 80 atomic% is the main component, (BH) max35M
It shows excellent magnetic properties over GOe, and its maximum value reaches over 45MGOe especially when the light rare earth metal is Nd.

Examples Example 1 As starting materials, electrolytic iron having a purity of 99.9%, ferroboron alloy, and Nd having a purity of 99.7% or more were used, and these were blended and then high-frequency melted, and then cast in a water-cooled copper mold to obtain 16.0Nd7.0B77. 0
An ingot having a composition of Fe was obtained.

After that, this ingot was roughly crushed with a stamp mill and then finely crushed with a ball mill to obtain an average particle size of 2.8 μm.
Of fine powder was obtained.

Insert this fine powder into the mold, orient in a magnetic field of 15 kOe,
It was molded in a direction parallel to the magnetic field at a pressure of 1.2 t / cm ² .

The obtained molded body was sintered at 1100 ° C. for 1 hour in an Ar atmosphere to obtain a sintered body having dimensions of length 25 mm × width 40 mm × thickness 30 mm.

Furthermore, a two-step aging treatment was performed in Ar at 800 ° C for 1 hour and 630 ° C for 1.5 hours.

Length of the above permanent magnet body was 2400 rpm at a feed rate of 5 mm / min in the atmosphere with diamond # 200 as a grindstone.
Cut out to a size of 5 mm × width 10 mm × thickness 3 mm.

Furthermore, glass beads (comparative example) and Al ₂ O ₃ powder (present invention) as sprayed powder shown in Table 1 were added to the cut sample.
Was blasted with 4 kg / cm ² of pressurized air for 7 to 10 minutes to remove the surface layer of the magnet body.

The magnetic properties of each sample before and after blasting were measured. Table 1 shows the processing conditions and the measurement results.

As is clear from the results shown in Table 1, according to the present invention, the residual black scale of the sintered magnet body and the deterioration of the magnetic properties associated with the oxide layer and the strained layer due to the cutting process for commercialization are improved. I know that

Claims (1)

[Claims] 1. R (R is at least one of Nd, Pr, Dy, Ho and Tb, or further La, Ce, Sm, Gd, Er, Eu, Tm, Yb, Lu, Y.
Of 10 to 30 at%, B 2 to 28 at%, Fe 65 to 80 at% as main components, and the main phase is a tetragonal crystal surface of a sintered permanent magnet body To
A method for processing a permanent magnet material, characterized in that a hard powder having a Mohs hardness of 5 or more is jetted together with a pressurized gas consisting of an inert gas or dehumidified air to remove the oxide layer and the work strain layer on the surface of the magnet body. .