JPS62260305A - Permananent magnet - Google Patents

Abstract

PURPOSE:To prevent crystal grains from becoming large and control a distribution of final grain diameters after a sintering process, by reducing a mean diameter and distribution of the grains in permanent magnet minute powder. CONSTITUTION:A R-Fe-B group sintered permanent magnet, whose sintered crystal grains are all made to be essentially within the range of 3-30mum in their final grain diameters (n) by using minute powder obtained by moreover powdering minute powdered grains so as to have a uniform granular degree, is provided with excellent magnetic characteristics. The sintered permanent magnet, containing crystal grains of less than 3mum in their final grain diameters (n) after the sintering process, is remarkably deteriorated in the magnetic characteristics, caused by oxidation during the manufacturing process. On the other hand, a sintered permanent magnet, containing crystal grains in excess of 30mum in their final grain diameters (n) after the sintering process, is also deteriorated in their magnetic characteristics, caused by inferior orientation. Constituents of the sintered permanent magnet are permitted to be ones as known, without special limitation, and generally with R=5-20atom% and B=2-15atom%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an R-Fe-B permanent magnet (R represents a rare earth element containing Y). More specifically, the present invention relates to an R-Fe-B based sintered permanent magnet that has good magnetic properties such as residual magnetic flux density, coercive force, and maximum energy product.

[Conventional technology]

Research on permanent magnets having R-Fe-B as a basic component has been actively conducted in recent years, and the results have been published in published patent publications and the like.

According to JP-A-57-141901, a composition consisting of a combination of a transition group metal (T), a metalloid metal (M), Y, and a lanthanide element is made amorphous, and then the amorphous composition is crystallized by heat treatment. A method for manufacturing permanent magnet powder is described in which coercive force is generated by According to this publication, T is Ti.

V, Cr, Mn, Fe, Co, Ni, Cu, Zr.

One or a combination of two or more selected from Nb, Mo, Hf, Ta, and W, and M is B.

one or more combinations selected from si, p, and c; R is one or more combinations selected from Y and lanthanide elements;
xMX)2R+-z (however, 0≦X≦063
A patent is claimed for a permanent magnet powder containing a powder with a content of 5.0.35≦2≦0.90).

According to JP-A-58-123853, a material containing La and Pr has been proposed, and its composition is (Fe
xB +-x)y(L at P r wR+-z
-w) +-y, where R is a rare earth metal other than l, a, and pr, x = 0.75 to 0.85, y = 0.85
~0.95.2 = 0.40~0.75, W=0, 2
5 to 0.60, and z+w≦1.0. This bulletin includes
In order to appropriately increase the coercive force when annealing and crystallizing the R-Fe-B-containing alloy that has been made amorphous by the liquid quenching method, the types and proportions of the rare earth elements are adjusted according to the above (L a z
A method for adjusting the composition of P r wRl-11-W) is described.

JP-A No. 59-46008 discloses that 8 to 30 atomic % of R (wherein R is at least one rare earth element), 2 to 2
It is described that a magnetically anisotropic sintered body consisting of 8 atomic % of B and the balance of Fe is produced by a pulverization process to obtain fine powder in a stamp mill and a ball mill, a molding process in a magnetic field, and a sintering process.

According to the examples in the publication, a fine powder of 3 to 10 pm is obtained in the pulverization process.

Generally, in the sintering method, an alloy is melted, an ingot is pulverized, and the permanent magnet material is cleaved by force q. Fine pulverization methods include a ball mill method and a jet mill method, and a fine powder having an average particle size of about 2 to about 10 μm is usually obtained.

This fine powder is press-molded in a magnetic field to obtain an anisotropic magnet, or in no magnetic field to obtain an isotropic magnet, and then sintered or sintered and heat treated to obtain a permanent magnet.

(Problems to be Solved by the Invention) Conventional finely pulverized powder has an average particle diameter of about 2 to about 10 μm, but the particle size distribution has an average value of about 3 μm.

When powder with such a particle size distribution is sintered, the particle size distribution will be about 2 to about 1 due to grain growth and aggregation of particles during sintering.
It further expands from 0 μm to about 2 to 60 μm. The presence of polycrystalline particles in the coarse powder during pulverization reduces the degree of orientation of the sintered body, thereby degrading the residual magnetic flux density, coercive force, and squareness ratio of the anisotropic sintered magnet. Furthermore, fine powder with a small particle size is very easily oxidized and forms a non-magnetic phase in the sintered body, causing deterioration of the magnetic properties of the magnet regardless of whether it is anisotropic or isotropic.

[Means for solving problems]

The present inventors used fine powder with uniform particle size obtained by further classifying conventional finely pulverized powder. It has been found that R-Fe-B based sintered permanent magnets within this range can provide excellent magnetic properties. Final particle size (n) after sintering is 3μ
In sintered permanent magnets containing crystal grains of less than 30 μm, the magnetic properties deteriorate significantly due to oxidation during the manufacturing process, and in sintered permanent magnets containing crystal grains with a final grain size (n) of more than 30 μm after sintering, Defects in magnetic properties occur due to orientation deterioration. Therefore, in the present invention, the final particle size (n) after sintering is set to 3 to 3.
It was set to 30 μm. Preferably (n) is 3 to 20 μm.

In order to obtain a sintered permanent magnet with a final particle size (n) of 3 to 30 μm after sintering, the fine powder obtained by a known pulverization method is coarsened by using a classifier such as a centrifuge. Grain powder and fine powder are separated to obtain classified fine powder having a desired particle size (N) ±2 μm, preferably (N) ±1 μm. This classified fine powder is sequentially processed by conventional pressing, sintering and, if necessary, heat treatment. Sintering conditions are usually 1050-1150"
C, argon or vacuum atmosphere.

The composition of the sintered permanent magnet according to the present invention may be a known one, and is not particularly limited, but generally R = 5 to 20 atomic %.
, B atom -15 atom %. Furthermore, Ce and L related to Japanese Patent Application No. 59-280125 assigned to the present applicant.
Composition in which a is the main component of rare earth element: ((Ce XL a +-x)yR+-y) z(F
e l-11Bv) I-2, provided that R is at least one rare earth metal (including Y), 0.4≦X≦0.9.0.
2 < y≦1.0.0.05≦2≦0, 3.0.01
≦V≦0,03, and R is also for at least one rare earth element other than Ce and La, the final particle size (n) =
Magnetic properties are improved by setting the thickness to 3 to 30 μm.

[For production]

As described above, by reducing the average particle size and particle size distribution of the fine powder for permanent magnets, coarsening of crystal grains is prevented and the final particle size distribution after sintering is controlled.

Such particle size distribution control reduces the presence of non-magnetic phases and improves orientation, thereby improving the magnetic properties of the sintered magnet.

The present invention will be explained in detail below.

〔Example〕

Example I Nd IsB? Fe? I! After melting an alloy having the following composition, the ingot obtained by agglomeration was coarsely pulverized, and then finely pulverized to an average particle size of about 4 μm using a jet mill.

Next, a classified fine powder with a particle size (N) distribution of 4±2 μm and a classified fine powder with a particle size (N) distribution of 4±1 μm were produced using a centrifugal classifier. Each classified fine powder and the fine powder obtained by the jet mill were compacted at a pressure of 1.5 tons/cI11 in a magnetic field of 10 kOe, and then heated at 1100°C for 2 hours.
Sintering was performed in an argon atmosphere, followed by aging treatment at 600° C. for 1 hour.

The particle size (n) after sintering of the permanent magnet produced using the 4±1 μm classified fine powder was 4 to 18 μm (Invention A).

The particle size (n) after sintering of the permanent magnet produced using the 4±2 μm classified fine powder was 3 to 27 μm (Invention B).

The particle size (n) of the permanent magnet after sintering produced using fine powder with an average particle size of 4 μm (particle size (N) distribution = 1 to 10 μm) obtained with a jet mill was 1 to 39 μm (comparative example )
.

The grain size after sintering was measured using a microscope, excluding the outermost surface of the sintered body from the measurement target.

Squareness ratio (Hk/1Hc), maximum energy product ((BH)□, l), residual magnetic flux density (Br), coercive force (i
The results of measuring Hc) are shown in FIG.

From FIG. 1, examples of inventions A and B, in which the particle size (n) after sintering is within the range of 3 to 30 μm, have a particle size (n) of 3 to 30 μm after sintering.
It can be seen that the magnetic properties are superior to those of the comparative example outside the 30 μm range.

〔Effect of the invention〕

According to the present invention, a sintered permanent magnet with high residual magnetic flux density, high coercive force, and high maximum energy product is manufactured.

[Brief explanation of drawings]

FIG. 1 is a graph showing squareness ratio, maximum energy product, residual magnetic flux density, and coercive force for examples and examples of the present invention.

Claims (1)

[Scope of Claims] 1. An R (rare earth element containing Y)-Fe-B based sintered permanent magnet, characterized in that the particle size (n) is within the range of 3 to 30 μm. 2. The sintered permanent magnet according to claim 1, wherein the R content is 5 to 20 at % and the B content is 2 to 15 at %.