JPH05214406A - Method for compacting alloy powder for rare-earth element-iron-boron permanent magnet - Google Patents

Abstract

PURPOSE:To obtain the compact of an alloy powder suitable for the industrial production of a novel rare-earth element-iron-boron group permanent magnet. CONSTITUTION:At least one kind between solid paraffin and camphor is mixed as a lubricant into an alloy powder consisting essentially of 10-30 atomic % of R (R is at least one kind among the rare-earth elements including Y), 2-28 atomic % of B and 65-82 atomic % of Fe, and the mixture is compacted. The compatibility is drastically improved, especially a thin compact is produced, and the releasing pressure is reduced which is advantageous in industrial production.

Description

Detailed Description of the Invention

[0001]

This invention relates to R (where R is at least one of rare earth elements including Y), B and Fe.
A new rare earth / iron / boron-based alloy powder for permanent magnets, whose main component is, is manufactured by mixing the alloy powder with the required lubricant to reduce the drawing pressure of the molded product during molding. The present invention relates to a molding method of rare earth / iron / boron alloy powder for permanent magnets suitable for production.

[0002]

2. Description of the Related Art Permanent magnet materials are one of the extremely important electric and electronic materials used in a wide range of fields from various household electric appliances to peripheral terminals for large computers. With the recent demand for miniaturization and high efficiency of electric and electronic devices, permanent magnet materials are required to have higher performance.

The typical current permanent magnet materials are alnico, hard ferrite and rare earth cobalt magnets. With the destabilization of the situation of cobalt raw materials in recent years, the demand for alnico magnets containing 20 to 30 wt% of cobalt has decreased, and inexpensive hard ferrite containing iron oxide as a main component has become the mainstream of magnet materials. became.

On the other hand, rare earth cobalt magnets contain cobalt 5
It is very expensive because it contains 0 to 60 wt% and uses Sm that is rarely contained in rare earth ores, but its magnetic properties are significantly higher than other magnets, so it is mainly small and has high added value. It has become widely used in magnetic circuits. Therefore, the present inventor has previously proposed Fe-B- as a new high-performance permanent magnet that does not necessarily contain expensive Sm or Co.
R type (R is at least one of rare earth elements including Y,
Fe-BR ternary compounds exist regardless of the type of R)
Proposed a permanent magnet (Japanese Patent Application No. 57-145072).

Further, in order to improve the temperature characteristics of the permanent magnet made of an Fe—BR system magnetically anisotropic sintered body, a part of Fe is replaced with Co to form a Curie alloy. Fe-C whose temperature characteristics are improved by raising the temperature
A permanent magnet composed of an o-B-R anisotropic sintered body has been proposed (Japanese Patent Application No. 57-166663).

The above-mentioned novel Fe-BR system, Fe-Co
A rare earth metal as a starting material for producing a —B—R type (R is at least one of rare earth elements including Y) permanent magnet is a metal block generally produced by a Ca reduction method or an electrolytic method, Using this rare earth metal block, for example, in the case of a sintered magnet, the above new permanent magnet is manufactured by the following steps.

As starting materials, electrolytic iron having a purity of 99.9% and B19.4% are contained, and the balance is Fe and Al, Si,
Ferroboron alloy consisting of impurities such as C, purity 99.7
% Or more rare earth metal, or further, purity 99.9%
Electrolytic Co is melted by high frequency and then cast in a water-cooled copper mold. Coarsely pulverized by a stamp mill to a size of 35 mesh through, and then by a ball mill, for example, 300 g of coarsely pulverized powder is wet finely pulverized for 6 hours to form fine powder of 3 to 10 μm. Oriented in a magnetic field (10 kOe) and molded (1.5 t / c
(pressurize at m ² ). Sintering, 1000 ° C. to 1200 ° C., 1 hour, sintering in Ar, and then allowed to cool. Aging treatment, 500 ° C to 1000 ° C, in Ar.

[0008]

As described above, this new alloy powder for permanent magnets can be obtained by coarsely pulverizing and finely pulverizing an ingot of the required composition. Unfavorably, due to friction with the die wall surface during molding,
Scratches, peeling, cracks and the like are likely to occur on the die surface and the surface of the molded product, which has been a serious problem in terms of quality and product yield.

The present invention has an object of a method for molding an alloy powder for a rare earth / iron / boron permanent magnet having industrially stable moldability and having sufficient magnetic properties, which is excellent. Provides a method for forming alloy powder for rare earth / iron / boron permanent magnets that uses a lubricant that reduces friction between the die surface and the formed body by improved lubricity and improves formability, and that does not deteriorate the magnetic properties of the magnet. It is an object.

[0010]

According to the present invention, R is 10 atom% to 30 atom% (provided that R is at least one of rare earth elements including Y), B2 atom% to 28 atom%, and Fe.
For rare earth / iron / boron-based permanent magnets, characterized by mixing alloy powder containing 65 atomic% to 82 atomic% as a main component with at least one of solid paraffin and camphor as a lubricant, and then molding the mixture. This is a method for molding alloy powder.

As a result of various studies on a lubricant that can be used for molding a new alloy powder for permanent magnets containing R, B and Fe as main components, the present invention shows that at least one of solid paraffin and camphor of a specific amount. It has been found that is suitable for the production of thin-walled molded products by improving the bondability of the powder and reducing the friction between the die surface and the molded product by adding a small amount to improve the lubricity. It is possible, and further, there is an advantage that the magnetic characteristics of the sintered magnet are less deteriorated. Particularly, the drawing pressure of the molded body at the time of molding can be lowered, which is extremely advantageous in industrial production.

[0012]

In the present invention, as the solid paraffin, general commercially available products can be used, and in order to improve the strength of the molded product, a waxy or waxy or solid form is preferable at around room temperature. At this time, it is preferable that the molecular weight thereof is not so large in view of solubility in a solvent, and that having a carbon number of 50 or less is preferable. There are natural and synthetic camphor, also called English camphor, and general commercial products can be used.

In the present invention, the amount of lubricant added is such that the grain size and die of the raw material alloy powder, the shape and size of the compact,
It may be appropriately selected according to the friction area, press conditions, etc.,
Addition of a small amount has the effect of improving formability, and with an increase in the amount added, the formability such as drawing pressure improves. In the binding step, carbon remains in the sintered body and deteriorates the magnetic characteristics. The preferable addition amount is 0.5 parts by weight or less with respect to 100 parts by weight of the alloy powder in both single addition and composite addition.

In the present invention, the lubricant may be added to the alloy powder by either dry mixing or wet mixing using a solvent. However, the alloy powder easily reacts with oxygen or moisture and is active. Therefore, it is preferably carried out by a wet method, and the solvent used is preferably an inert solvent such as hexane, toluene, trichloroethylene, or a fluorine-based solvent. The state of mixing may be either in a dry state or a slurry state, and for example, they can be appropriately mixed during or before or after the wet pulverization step, or during or before or after the drying step.

In the present invention, the alloy powder can be molded in the same manner as in the ordinary powder metallurgy method, and an anisotropic magnet or an isotropic magnet can be obtained depending on whether a magnetic field is applied during pressure molding.

The reasons for limiting the composition of the raw material alloy powder for rare earth / iron / boron permanent magnets in the present invention will be described below. The rare earth element R contained in the raw material alloy powder for a permanent magnet of the present invention is a rare earth element including yttrium (Y) and including light rare earths and heavy rare earths.
Nd, Pr, La, Ce, Tb, Dy, Ho, Er, E
u, Sm, Gd, Pm, Tm, Yb, Lu and Y are included. For R, light rare earths are sufficient, especially N
d and Pr are preferred. Usually, one of R is sufficient, but in practice, a mixture of two or more (Misch metal,
Didymium, etc.) can be used for reasons of availability, and Sm, Y, La, Ce, Gd, etc. can be used as a mixture with other R, especially Nd, Pr, etc. 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 a range that is industrially available.

R (at least one of rare earth elements including Y) is an essential element as an alloy powder for producing the novel permanent magnet, and if it is less than 10 atomic%, high magnetic properties, particularly high coercive force can be obtained. If it exceeds 30 atomic%, the residual magnetic flux density (Br) is lowered, and a permanent magnet having excellent characteristics cannot be obtained. Therefore, R is 10 atom% to 30 atom%.
The range is.

B is an essential element as an alloy powder for producing the above-mentioned new permanent magnet. When it is less than 2 atomic%, a high coercive force (iHc) cannot be obtained, and when it exceeds 28 atomic%, the residual magnetic flux density ( Since Br) decreases, an excellent permanent magnet cannot be obtained. Therefore, B is in the range of 2 at% to 28 at%.

Fe is an essential element as an alloy powder for producing the above new permanent magnet, but if it is less than 65 atom%, the residual magnetic flux density (Br) is lowered, and if it exceeds 82 atom%, a high coercive force is obtained. Therefore, the Fe content is 65 atomic% to 82.
Limit to atomic%. Further, the reason for substituting a part of Fe with Co is that the effect of improving the temperature characteristics of the permanent magnet can be obtained, and when Co exceeds 50% of Fe, a high coercive force cannot be obtained, which is an excellent permanent magnet. I can't get a magnet. Therefore, Co has an upper limit of 50%.

In order to obtain an excellent permanent magnet having both a high residual magnetic flux density and a high coercive force in the alloy powder of the present invention, R10 atomic% to 25 atomic% and B4 atomic% to
26 at% and Fe at 65 to 82 at% are preferable.

The alloy powder according to the present invention contains R,
In addition to B and Fe, the presence of impurities that are unavoidable in industrial production can be tolerated, but a part of B is 4.0 atomic% or less of C, 3.
Manufacturability of a magnet alloy by substituting at least one of P at 5 atomic% or less, S at 2.5 atomic% or less, and Cu at 3.5 atomic% or less by a total amount of 4.0 atomic% or less. Improvements and lower prices are possible.

Further, the R, B, Fe alloy or C
7. O-containing R, B, Fe alloys with 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. Mn of 0 atomic% or less, Bi of 5 atomic% or less, Nb of 12.5 atomic% or less, T of 10.5 atomic% or less
a, Mo at 9.5 atomic% or less, W at 9.5 atomic% or less, Sb at 2.5 atomic% or less, Ge at 7 atomic% or less, Sn at 3.5 atomic% or less, 5.5 atomic% By adding at least one of the following Zr and Hf of 5.5 atomic% or less, it becomes possible to increase the coercive force of the permanent magnet alloy.

In the RB-Fe system permanent magnet of the present invention, it is essential that the main phase of the crystal phase is a tetragonal crystal,
In particular, it is effective for obtaining a fine and uniform alloy powder and producing a sintered permanent magnet having excellent magnetic properties.

With respect to the particle size of the alloy fine powder according to the present invention, when the average particle size exceeds 10 μm, excellent magnetic properties, particularly high coercive force, cannot be obtained at the time of producing a permanent magnet. Oxidation in the manufacturing process, that is, press molding, sintering, and aging treatment is remarkable,
Average particle size 1 to 10 because excellent magnetic properties cannot be obtained
A micron alloy fine powder is most desirable.

The magnetic anisotropic permanent magnet alloy obtained by using the alloy fine powder for permanent magnet according to the present invention has a coercive force iH.
c ≧ 1 kOe, residual magnetic flux density Br> 4 kG, the maximum energy product (BH) max is equal to or greater than that of hard ferrite, and in the most preferable composition range, (BH) ma
x ≧ 10 MGOe, and the maximum value reaches 25 MGOe or more. The composition of the alloy fine powder according to the present invention is R
10 atom% to 30 atom%, B2 atom% to 28 atom%, C
When the content is 45 atomic% or less and Fe is 65 atomic% to 82 atomic%, the obtained magnetic anisotropic permanent magnet alloy exhibits magnetic characteristics equivalent to those of the above magnetic alloy, and the residual magnetic flux density has a temperature coefficient of 0.
It is 1% / ° C or less, and excellent characteristics are obtained. Also,
When the main component of R of the alloy powder occupies 50% or more of the light rare earth metal, and when R12 atomic% to 20 atomic%, B4 atomic% to 24 atomic%, and Fe65 atomic% to 82 atomic%,
Further, when it further contains Co 5 at% to 45 at%, it exhibits the best magnetic characteristics, and in particular, the light rare earth metal is N
In the case of d, the maximum value of (BH) max is 33 MG.
Reach more than Oe.

[0026]

[Example] As a starting material, electrolytic iron having a purity of 99.9%,
Ferroborone alloy containing B19.4% with the balance being Fe and C and other impurities, Nd having a purity of 99.7% or more was blended in a predetermined amount and high-frequency melted, and then cast in a water-cooled copper mold to obtain 15Nd8B77Fe (at% ) Was obtained. This ingot was coarsely pulverized by mechanical pulverization to a 35 mesh through. Then, fine pulverization was performed with a ball mill to obtain an alloy powder having an average particle size of 3.3 μm. To this alloy powder, 0.5 parts by weight of solid paraffin and camphor, each dissolved in or dispersed in trichlorotrifluoroethane, were wet mixed with 100 parts by weight of the alloy powder, and then dried.

Using this dry alloy powder and the alloy powder without addition of a lubricant, orientation was performed in a magnetic field of 12 kOe and 2 t
Pressurizing and pressure molded at / cm ^2, width 15 mm × length 16 mm ×
A molded body having a height of 10 mm was obtained. The drawing pressure, the green compact density and the green strength of the molded product during this molding were measured, and the results are shown in Table 1. The green strength index is represented by the residual weight% after the molded body was rotated 100 times with a Ratler tester.

[0028]

[Table 1]

[0029]

As is clear from Table 1, according to the method of the present invention in which solid paraffin and camphor are mixed as a lubricant and then molded, the drawing pressure is small, the green compact density and the green strength are high, and the lubricity is improved. There are few flaws and cracks, and the formability is greatly improved. In particular, since it is possible to manufacture a thin-walled molded product with good powder binding properties and further reduce the drawing pressure, it is possible to reduce the load on the molding die and prolong the life of the mold. An alloy powder molding method suitable for industrial production of iron-boron permanent magnets can be provided.

Claims (1)

[Claims] 1. R10 atomic% to 30 atomic% (provided that R is at least one of rare earth elements including Y), B2 atomic% to 28 atomic%, Fe65 atomic% to 82 atomic% as main components. A method for forming an alloy powder for a rare earth / iron / boron permanent magnet, which comprises mixing at least one of solid paraffin and camphor as a lubricant with an alloy powder and then forming the mixture.