JPH04214803A - Method for molding alloy powder for rare earth-iron-boron based permanent magnet - Google Patents

Abstract

PURPOSE:To offer a novel method for molding alloy powder suitable for the industrial production of a rare earth-iron-boron based permanent magnet. CONSTITUTION:The powder of an alloy consisting essentially of, by atom, 10 to 30% R (where R denotes at least one kind among rare earth elements including Y), 2 to 28% B and 65 to 82% Fe is mixed with at least one kind among stearic acid, zinc stearate and bisamid as a lubricant, and this mixture is thereafter molded. Its moldability is remarkably improved, its draft can be reduced and an advantage can be given from the viewpoint of industrial production.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to R (where R is at least one rare earth element including Y), B, Fe,
The method for molding a new alloy powder for permanent magnets based on rare earths, iron, and boron, which is mainly composed of This invention relates to a method for molding alloy powder for rare earth, iron, and boron permanent magnets that is suitable for production.

0002

2. Description of the Related Art Permanent magnetic materials are one of the extremely important electrical and electronic materials used in a wide range of fields, from various household electrical appliances to peripheral terminal equipment for large computers. In recent years, with the demand for smaller size and higher efficiency of electrical and electronic equipment, permanent magnet materials are required to have increasingly higher performance.

Current typical permanent magnet materials are alnico, hard ferrite, and rare earth cobalt magnets. As the raw material situation for cobalt has become unstable in recent years, demand for alnico magnets containing 20 to 30 wt% cobalt has decreased.
Inexpensive hard ferrite, whose main component is iron oxide, has come to dominate magnet materials.

On the other hand, rare earth cobalt magnets contain 5 cobalt.
It is very expensive because it contains 0 to 60 wt% and uses Sm, which is not included in rare earth ores, but it has much higher magnetic properties than other magnets, so it is mainly small and has high added value. It has come to be widely used in magnetic circuits. Therefore, the present inventor first developed Fe-B-R as a new high-performance permanent magnet that does not necessarily contain expensive Sm or Co.
proposed a permanent magnet (R is at least one rare earth element including Y) (Japanese Patent Application No. 145072/1982).

Furthermore, in order to improve the temperature characteristics of permanent magnets made of Fe-B-R based magnetically anisotropic sintered bodies, some of the Fe is replaced with Co, thereby increasing the Curie of the produced alloy. Fe-Co with improved temperature characteristics by raising the point
-We proposed a permanent magnet made of B-R anisotropic sintered body (
(Special Application No. 166663/1982).

[0006] The above novel Fe-B-R system, Fe-Co
- The rare earth metal that is the starting material for manufacturing the B-R system (R is at least one rare earth element including Y) permanent magnet is generally a metal lump manufactured by a Ca reduction method or an electrolytic method, Using this rare earth metal lump, for example, in the case of a sintered magnet, the above-mentioned novel permanent magnet is manufactured through the following steps.

■ As a starting material, electrolytic iron with a purity of 99.9%, containing 19.4% B, the balance being Fe, Al, Si,
Ferroboron alloy consisting of impurities such as C, purity 99.7
% or more of rare earth metals, or even with a purity of 99.9%
of electrolytic Co is high-frequency melted and then cast into a water-cooled copper mold. ■ Coarsely pulverize to 35 mesh through using a stamp mill, then use a ball mill to coarsely pulverize, e.g.
g was wet-pulverized for 6 hours to form a fine powder of 3 to 10 μm. ■Oriented in a magnetic field (10kOe) and molded (1.5t/
Pressurize at cm2). ■Sintering, 1000℃~1200℃
C. for 1 hour in Ar and then allowed to cool. ■Aging processing,
500°C to 1000°C in Ar.

[0008]

[Problems to be Solved by the Invention] As mentioned above, this new alloy powder for permanent magnets can be obtained by coarsely and finely pulverizing an ingot of the desired composition, but the formability of the pulverized powder is extremely poor. During molding, friction with the die wall surface, etc., tends to cause scratches, peeling, cracks, etc. on the die surface and the surface of the molded product, which poses a major problem in terms of quality and product yield.

The purpose of the present invention is to provide an excellent method for molding alloy powder for rare earth/iron/boron based permanent magnets, which have industrially stable formability and sufficient magnetic properties. Provided is a method for molding rare earth/iron/boron alloy powder for permanent magnets using a lubricant that reduces friction between the die surface and the molded body, improves moldability, and causes less deterioration of the magnetic properties of the magnet. It is an object.

0010

[Means for Solving the Problems] This invention provides R10 at% to 30 at% (wherein R is at least one kind of rare earth elements including Y), B2 at% to 28 at%, Fe65 at% to For use in rare earth/iron/boron based permanent magnets, which is characterized in that alloy powder containing 82 atomic % as a main component is mixed with at least one of stearic acid, zinc stearate, and bisamide as a lubricant, and then molded. This is a method for molding alloy powder.

[0011] As a result of various studies on lubricants that can be used for molding alloy powder for permanent magnets containing R, B, and Fe as main components, the present invention has revealed that at least a specific amount of stearic acid, zinc stearate, and bisamide. It was found that type 1 is suitable, and it has excellent lubricity, reduces friction between the die surface and the compact, improves moldability, and has the advantage of less deterioration of the magnetic properties of the sintered magnet. In particular, the ejection pressure of the molded body during molding can be lowered, which is extremely advantageous in industrial production.

0012

[Function] In this invention, the amount of lubricant added may be appropriately selected depending on the particle size of the raw alloy powder, die, shape and dimensions of the compact, friction area, press conditions, etc. The improvement effect is large, and as the amount added increases, the moldability such as ejection pressure improves, but the preferable addition amount is 0 to 100 parts by weight of alloy powder for both individual and combined additions.
．． It is 2 parts by weight or less.

Furthermore, in the present invention, the lubricant may be added to the alloy powder by either dry mixing or wet mixing using a solvent. Therefore, it is preferable to carry out the process in a wet manner, and the solvent used is preferably an inert solvent such as hexane, toluene, trichloroethylene, or a fluorine-based solvent. The mixing state may be either a dry state or a slurry state, and for example, mixing may be carried out as appropriate during or before or after the wet pulverization process, or during or before or after the drying process.

[0014] In the present invention, the alloy powder can be molded in the same manner as a normal powder metallurgy method, and an anisotropic magnet or an isotropic magnet can be obtained depending on whether or not 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 explained below. The rare earth element R contained in the raw material alloy powder for permanent magnets of this invention is a rare earth element that includes yttrium (Y) and includes light rare earths and heavy rare earths. As R,
Light rare earth elements are sufficient, and Nd and Pr are particularly preferred. Generally, one type of R is sufficient, but in practice, a mixture of two or more types (mischmetal, dididium, etc.) can be used for reasons such as convenience of acquisition, Sm, Y, La,
Ce, Gd, etc. can be used as a mixture with other R, especially Nd, Pr, etc. Note that this R does not have to be a pure rare earth element, and may contain impurities that are unavoidable in production within an industrially available range.

[0016] R (at least one rare earth element including Y) is an essential element as an alloy powder for manufacturing the new above-mentioned permanent magnet, and if it is less than 10 atomic %, high magnetic properties, especially high coercive force can be obtained. If it exceeds 30 at %, the residual magnetic flux density (Br) decreases, making it impossible to obtain a permanent magnet with excellent characteristics. Therefore, R is set in the range of 10 atomic % to 30 atomic %.

[0017] B is an essential element as an alloy powder for producing the above-mentioned novel permanent magnet, and if it is less than 2 atomic %, high coercive force (iHc) cannot be obtained, and if it exceeds 28 atomic %, the residual magnetic flux density ( Br) decreases, making it impossible to obtain an excellent permanent magnet. Therefore, B is in the range of 2 atomic % to 28 atomic %.

[0018] Fe is an essential element in the alloy powder for manufacturing the new permanent magnet of the above system, but if it is less than 65 atomic %, the residual magnetic flux density (Br) decreases, and if it exceeds 82 atomic %, a high coercive force cannot be obtained. Therefore, Fe is 65 at% to 82
Limited to atomic percent. In addition, the reason why a part of Fe is replaced with Co is that it has the effect of improving the temperature characteristics of the permanent magnet, and if Co exceeds 50% of Fe, high coercive force cannot be obtained. I can't get a magnet. Therefore, the upper limit of Co is 50%.

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

[0020] Furthermore, the alloy powder according to the present invention has R, B
, In addition to Fe, the presence of unavoidable impurities in industrial production can be tolerated, but a part of B can be replaced with 4.0 atomic % or less of C, 3.5 atomic % or less of P, 2.5
By substituting at least one of S at % or less and Cu at 3.5 atomic% or less in a total amount of 4.0 atomic% or less, it is possible to improve the manufacturability and lower the price of the magnetic alloy.

Furthermore, the R, B, Fe alloy or C
9.5 atomic % or less of Al, 4.5 atomic % or less of Ti, 9
．． 5 at% or less V, 8.5 at% or less Cr, 8.0
Mn below 5 atomic %, Bi below 5 atomic %, Nb below 12.5 atomic %, Ta below 10.5 atomic %, Mo below 9.5 atomic %, W below 9.5 atomic %, 2 ．．
5 at% or less Sb, 7 at% or less Ge, 3.5 at% or less Sn, 5.5 at% or less Zr, 5.5 at%
By adding and containing at least one of the following Hf types, it is possible to increase the coercive force of the permanent magnet alloy.

In the R-B-Fe permanent magnet of the present invention, it is essential that the main crystal phase is tetragonal,
In particular, it is effective in obtaining fine and uniform alloy powder and producing sintered permanent magnets with excellent magnetic properties.

Regarding the particle size of the alloy fine powder according to the present invention, if the average particle size exceeds 10 μm, excellent magnetic properties, especially high coercive force, cannot be obtained when producing a permanent magnet, and if the average particle size is less than 1 μm, the permanent magnet will not be able to produce a permanent magnet. There is significant oxidation during the manufacturing process, that is, press forming, sintering, and aging treatment.
Because excellent magnetic properties cannot be obtained, the average particle size is 1 to 10.
Micron alloy powder is most desirable.

The magnetically anisotropic permanent magnet alloy obtained using the alloy fine powder for permanent magnets according to the present invention has a coercive force iH
c≧1kOe, residual magnetic flux density Br>4kG, maximum energy product (BH)max is equal to or higher than hard ferrite, and in the most preferable composition range, (BH)max
x≧10MGOe, and the maximum value reaches 25MGOe or more. Further, 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 O is 45 atomic % or less and Fe is 65 atomic % to 82 atomic %, the resulting magnetically anisotropic permanent magnet alloy exhibits magnetic properties equivalent to those of the above magnet alloy, and the temperature coefficient of residual magnetic flux density is 0.1.
%/℃ or less, and excellent characteristics can be obtained. In addition, when the main component of R in the alloy powder is a light rare earth metal that accounts for 50% or more, R12 at % to 20 at %, B4 at %
The best magnetic properties are exhibited when the content of Fe is 65 at % to 82 at %, or when Co is 5 at % to 45 at %, especially when the light rare earth metal is Nd.
In the case of (BH)max, its maximum value is 33MGO
Reach more than e.

[0025]

[Example] As a starting material, electrolytic iron with a purity of 99.9%,
A ferroboron alloy containing 19.4% B and the remainder consisting of impurities such as Fe and C is blended with a predetermined amount of Nd with a purity of 99.7% or higher, high-frequency melted, and then cast in a water-cooled copper mold to produce 15Nd8B77Fe (at% ) was obtained. This ingot was mechanically crushed to a size of 35 mesh. Then, fine pulverization was performed using a ball mill to obtain an alloy powder with an average particle size of 3.3 μm. Stearic acid, zinc stearate, and bisamide, each dissolved or dispersed in trichlorotrifluoroethane in an amount of 0.2 parts by weight per 100 parts by weight of the alloy powder, were wet-mixed with this alloy powder, and then dried. I let it happen.

Using this dry alloy powder and the alloy powder to which no lubricant is added, it is oriented in a magnetic field of 12 kOe, and a 2t
Pressure molded at /cm2, width 15mm x length 16mm x
Ten molded bodies each having a height of 10 mm were obtained. The ejection pressure, green density, and green strength of the molded body during this molding were measured, and the results are shown in Table 1. Note that the green strength index is expressed as the weight remaining after the molded body is rotated 100 times using a Rattler tester.

[0027]

[Table 1]

[0028]

[Effect of the invention] As is clear from Table 1, stearic acid,
This invention method, in which zinc stearate and bisamide are mixed as lubricants and then molded, results in low ejection pressure, high green density, improved lubricity, and fewer scratches and cracks on the appearance of the molded product. performance is significantly improved. In particular, since the extraction pressure can be reduced, the load on the molding die can be reduced and its life can be extended, and the alloy powder can be molded with good workability and is suitable for the industrial production of new rare earth, iron, and boron permanent magnets. I can provide a method.

Claims (1)

[Claims] Claim 1: R10 atomic% to 30 atomic% (however, R
is at least one rare earth element including Y), B
An alloy powder mainly composed of 2 atomic % to 28 atomic % and Fe 65 atomic % to 82 atomic % is mixed with at least one of stearic acid, zinc stearate, and bisamide as a lubricant, and then molded. Characteristic method for forming alloy powder for rare earth, iron, and boron permanent magnets.