JPH064882B2 - Permanent magnet material processing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a permanent magnet processing method that prevents deterioration of magnet characteristics associated with grinding of a Fe—B—R based sintered permanent magnet, etc. Relates to a method for processing a small or thin permanent magnet material having a thickness of 2.5 cm ³ or less or a thickness of 5.0 mm or less.

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, Sm and Co as main components are both resource-deficient and expensive, and are expected to be long-term in the future.
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 abundant resource-rich light rare earths, mainly Fe, and has an extremely high energy product of 25 MGO _e or more with Fe as the main component.

Recently, as the performance and size of magnetic circuits have increased, Fe-B-
R-based permanent magnet materials are receiving more and more attention, and the volume is 2.5c.
F for small or thin objects of m ³ or less or thickness of 5.0 mm or less
There has been a demand for e-B-R permanent magnet materials.

In order to manufacture a permanent magnet material for such an application, a molded or sintered small or ultra-thin sintered magnet body is used to remove surface irregularities or distortion, or to remove a surface oxide layer, In order to be incorporated into a circuit, it is necessary to cut the entire surface of the magnet body or a required surface, and an outer peripheral blade cutting machine, an inner peripheral blade cutting machine, a surface grinding machine, 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-mentioned apparatus, the magnetic characteristics are deteriorated, and particularly in the Fe-BR permanent magnet material for small or thin objects, the magnetic characteristics are significantly deteriorated. There was a problem to do.

OBJECT OF THE INVENTION The present invention is a novel permanent magnet material containing rare earths, boron and iron as main components, and in particular, the deterioration of magnetic properties due to cutting or grinding of a sintered magnet body for small or ultra-thin materials. The purpose is to prevent the permanent magnet material from being processed.

Composition and Effects of the Invention The Fe-BR permanent magnet material contains as a main component a rare earth element and iron which are extremely easily oxidized in the air and immediately generate a stable oxide, so that they generate heat or are exposed to the atmosphere. An oxide layer is generated by contact with the processed surface, and particularly in a small or ultra-thin sintered magnet body, the influence of this oxide layer is remarkable, resulting in a serious deterioration of magnetic characteristics.
Therefore, by processing in a non-oxidizing fluid, the formation of this oxide layer was prevented, and the deterioration of the magnetic characteristics due to the processing was prevented.

That is, the present invention provides R (R is at least one of Nd, Pr, Dy, Ho, Tb, or at least one of La, Ce, Sm, Gd, Er, Eu, Tm, Yb, Lu, Y). (Comprising seeds) 10 atomic% to 30 atomic%, B2 atomic% to 28 atomic%, Fe65 atomic% to 80 atomic% as main components, and the main phase is a tetragonal sintered magnet body in a non-oxidizing fluid. Is a method of processing a permanent magnet material, which is characterized by cutting or grinding.

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.

Therefore, the permanent magnet material of the present invention mainly uses light rare earths rich in resources centering on Nd or further Pr as R and has Fe, B and R as the main components.
An Fe-BR permanent magnet material having an extremely high energy product of MGOe or more, a high residual magnetic flux density and a high coercive force, and preventing deterioration of magnetic characteristics due to grinding can be obtained at low cost.

In the present invention, the non-oxidizing fluid may be any mineral oil such as vegetable oil or light oil, as long as it is a non-oxidizing oil containing almost no water, and the above mixed oil may be used. For prevention, the water content is preferably 0.1 wt% or less.

The non-oxidizing gas may be an inert gas such as Ar gas or N ₂ gas, but a purity of 99% or more is desirable for preventing oxidation.

As the processing method in the present invention, an outer peripheral blade cutting method, an inner peripheral blade cutting method, a wire cutting method, a surface grinding method, a double-sided grinding method,
All the usual magnet processing methods such as the centerless grinder method and the lapping method can be applied.

Further, regarding the magnet in the processing method, the diamond grindstone and the porazon grindstone are effective in preventing deterioration of the magnetic characteristics, and the lap rotation speed is improved from the viewpoint of improvement of the magnet characteristics and processing efficiency.
A range of 900 rpm to 3600 rpm is desirable.

Reasons for Limiting Components of Permanent Magnet The rare earth element R used in the permanent magnet of the present invention has a composition of 10
Occupies at least 30 at%, but at least one of Nd, Pr, Dy, Ho, Tb, or even La, Ce, Sm, Gd, Er, Eu, T
Those containing at least one of m, 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 impurities that are 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 it exceeds 30 at%, the R-rich non-magnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet with excellent characteristics cannot be obtained. Therefore, the rare earth element is 10
The range is from atomic% to 30 atomic%.

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 magnet materials described above, and if the content is less than 65 atomic%, the residual magnetic flux density (Br) decreases, and
If the atomic percentage is exceeded, high coercive force cannot be obtained, so Fe is
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 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 atom% or less of C, 3.5 atom% or less of P, At least one of 2.5 atomic% or less S and 3.5 atomic% or less Cu
It is possible to improve the manufacturability of permanent magnets and reduce the cost by substituting the total amount of seeds by 4.0 at% or less.

Further, at least one of the following additional elements is RB-
It can be added to the Fe-based permanent magnet because it is effective in improving the coercive force and squareness of the demagnetization curve, improving the manufacturability, and lowering the cost. However, since the residual magnetic flux density (Br) is reduced with the addition for improving the coercive force, it is desirable to add the residual magnetic flux density in 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 type is added, provided that the maximum content is 2 or more types. By containing at most atomic% of the additive element having the maximum value,
It is possible to increase the coercive force of the permanent magnet.

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.

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

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

Further, the main component of R of the alloy powder for permanent magnets of the present invention is
When 50% or more is occupied by a light rare earth metal mainly composed of Nd and Pr, and R ₁₂ atom% to 20 atom%, B 4 atom% to 24 atom%, and Fe 74 atom% to 80 atom% are the main components. , (BH)
It has excellent magnetic properties of more than max35MGOe, and its maximum value reaches more than 42MGOe especially when the light rare earth metal is Nd.

Examples Example 1 As a starting material, 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 16.0Nd7.0B77Fe.
An ingot having the following composition was obtained.

After that, this ingot was crushed by a stamp mill and then finely crushed by 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, permanent magnets were manufactured by performing a two-step aging treatment at 800 ° C for 1 hour and 630 ° C for 2 hours in Ar.

Length of the above-mentioned permanent magnets in the air at a rotational speed of 2400 rpm, feed speed of 5 mm / min, using diamond # 200 as a grindstone.
Cut out to a size of 1.5 mm × width 2.5 mm × thickness 1.0 mm.

Also, it is immersed in a mixed oil of 50% vegetable oil containing 50% oil-soluble surfactant and 50% mineral oil with a water content of 0.05 wt% and diamond # 200 is used as a grindstone to rotate at 2400 rpm and feed speed at 5 m.
Cut out at a length of 1.5 mm × width of 2.5 mm × thickness of 1.0 mm at m / min.

Fig. 1 shows the demagnetization curves of each permanent magnet material obtained before and after grinding, and the values of Br, iHc and (BH) max were measured using a vibrating sample magnetometer (VSM). The results are shown in Table 1. In FIG. 1, a curve a is a permanent magnet before grinding, a curve b is a case of grinding in the atmosphere, and a curve c is a case of the present invention ground in a non-oxidizing oil.

Example 2 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 16.5Nd6.5B77.
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 under the conditions of 1100 ° C. for 1 hour in an Ar atmosphere to obtain a sintered body having dimensions of 50 mm in length × 20 mm in width × 12.0 mm in thickness.

Furthermore, permanent magnets were manufactured by performing a two-step aging treatment at 800 ° C for 1 hour and 630 ° C for 2 hours in Ar.

The above permanent magnet, in the atmosphere, using borazon # 300 as a grindstone, rotation speed 2400 rpm, feed speed 2 mm / min, length 8 mm ×
Cut out to a width of 10 mm and a thickness of 1.5 mm.

Also, in Ar gas with a purity of 99.5%, borazon # 300 as a grindstone, rotation speed 2400 rpm, feed speed 2 mm / min, length 8 m
It was cut into a size of m x width 10 mm x thickness 1.5 mm.

Fig. 2 shows the demagnetization curves of each permanent magnet material obtained before and after grinding, and the values of Br, iHc and (BH) max were measured using a vibrating sample magnetometer (VSM). The results are shown in Table 2. In FIG. 2, curve a is the permanent magnet before grinding, curve b is the case of grinding in air, and curve c is the case of the present invention ground in Ar gas.

As is clear from the results shown in FIGS. 1 and 1 and FIGS. 2 and 2, the processing in the non-oxidizing fluid is extremely effective in preventing the deterioration of the magnetic characteristics of the magnet.

[Brief description of drawings]

1 and 2 are diagrams showing demagnetization curves of permanent magnet materials. Curve a is the permanent magnet before grinding, curve b is the case of grinding in air, and curve c is the case of the present invention ground in a non-oxidizing fluid.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yutaka Matsuura, 2-15, Egawa, Shimamoto-cho, Mishima-gun, Osaka Pref. 15-17 17 Sumitomo Special Metals Co., Ltd. Yamazaki Works

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%, B2 to 28 at%, Fe at 65 to 80 at% as the main component, and a sintered magnet body whose main phase is a tetragonal phase. A method for processing a permanent magnet material, which comprises cutting or grinding in an oxidizing fluid.