JPH0561340B2 - - Google Patents

Description

[Detailed description of the invention]

[0001]

[Industrial Application Field] This invention is based on R (however,
R is at least one rare earth element including Y
A new rare earth, iron,
Regarding the method of molding alloy powder for boron-based permanent magnets,
By mixing the required lubricant with the alloy powder,
This invention relates to a method for molding alloy powder for rare earth, iron, and boron permanent magnets that is suitable for industrial production by lowering the ejection pressure of the molded body during molding.

[0002]

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

[0003] Current typical permanent magnet materials are alnico, hard ferrite, and rare earth cobalt magnets. As the cobalt raw material situation has become unstable in recent years, the demand for alnico magnets containing 20 to 30 wt% cobalt has decreased, and inexpensive hard ferrite, whose main component is iron oxide, has become the mainstream magnet material. Summer.

[0004] On the other hand, rare earth cobalt magnets contain 50 to 60 wt% of cobalt and are very expensive because they use Sm, which is not contained in rare earth ores. Because of its high cost, it has come to be used mainly for small, high-value-added magnetic circuits. Therefore, the present inventor first developed Fe as a new high-performance permanent magnet that does not necessarily contain expensive Sm or Co.
-B-R system permanent magnet (R is at least one rare earth element including Y) was proposed (Patent application 1983-
No. 145072).

[0005] Furthermore, in order to improve the temperature characteristics of a permanent magnet made of a magnetically anisotropic sintered body of the Fe-B-R system, by replacing a part of Fe with Co, the Curie of the produced alloy is improved. We have proposed a permanent magnet made of an anisotropic sintered body of Fe-Co-BR system which has improved temperature characteristics by increasing the temperature characteristics (Japanese Patent Application No. 166663/1982).

[0006] The above novel Fe-BR system, Fe-Co
- The rare earth metal that is the starting material for producing a B-R system (R is at least one rare earth element including Y) permanent magnet is a metal lump that is generally produced 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.

[0007] As a starting material, electrolytic iron with a purity of 99.9%, containing 19.4% B, the remainder being Fe, Al, Si, and C.
Ferroboron alloy consisting of impurities such as, purity 99.7
% or more rare earth metals, or even purity 99.9
% electrolytic Co is radio-frequency melted and then cast into a water-cooled copper mold. Coarsely pulverize to 35 mesh through using a stamp mill, and then wet-pulverize, for example, 300 g of coarsely pulverized powder for 6 hours using a ball mill to form a fine powder of 3 to 10 μm. Oriented in a magnetic field (10kOe) and molded (1.5t/cm ²
pressurize). Sintering: 1000°C to 1200°C for 1 hour. After sintering in Ar, allow to cool. Aging treatment, 500℃~1000℃, in Ar.

[0008]

[Problem to be solved by the invention] As mentioned above,
This new alloy powder for permanent magnets can be obtained by coarsely pulverizing and finely pulverizing an ingot of the desired composition, but the formability of the pulverized powder is very poor, and it is difficult to form the powder due to friction with the die wall surface etc. during forming. , scratches, peeling, cracking, etc. are likely to occur on the die surface and the molded body surface, which poses a big problem in terms of quality and product yield.

[0009] This invention has industrially stable formability and sufficient magnetic properties.
The purpose is to create a method for molding alloy powder for boron-based permanent magnets, which uses excellent lubricity to reduce friction between the die surface and the compact, improves moldability, and prevents deterioration of the magnet's magnetic properties. The purpose of this invention is to provide a method for molding rare earth/iron/boron alloy powder for permanent magnets using a small amount of lubricant.

[0010]

[Means for Solving the Problems] This invention provides R10 atomic% to 30 atomic% (wherein R is at least one kind of rare earth elements including Y), B2 atomic% to 28 atomic%, Fe65 atomic% 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 discovered 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 amount added is 0.2 parts by weight or less per 100 parts by weight of the alloy powder, both alone and in combination.

[0013] Furthermore, in the present invention, the lubricant may be added to the alloy powder by either dry mixing or wet mixing using a solvent, but if the alloy powder is easily reactive with oxygen or moisture and is active, 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 in 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 this 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.

[0015] Below, rare earths and
The reason for limiting the composition of the raw material alloy powder for iron/boron permanent magnets will be explained. 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, a light rare earth element is sufficient, especially Nd,
Pr is preferred. In addition, it is usually sufficient to have one type of R, but in practice, a mixture of two or more types (Mitsushimetal, didymium, 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 producing the new above-mentioned permanent magnet, and if it is less than 10 atomic %, high magnetic properties, especially high coercive force, cannot be obtained. If it exceeds 30 atom%, the residual magnetic flux density (Br) decreases,
Permanent magnets with excellent characteristics cannot be obtained. Then,
R is in the range of 10 atomic % to 30 atomic %.

[0017] B is an essential element as an alloy powder for manufacturing the new above-mentioned permanent magnet, and if it is less than 2 atomic %, high coercive force (iHc) cannot be obtained;
As the residual magnetic flux density (Br) decreases when exceeding
An excellent permanent magnet cannot be obtained. Therefore, B is 2
The range is from atomic% to 28 atomic%.

[0018] Fe is an essential element as an alloy powder for manufacturing the new above-mentioned permanent magnet, but 65 at%
Fe
is limited to 65 at% to 82 at%. In addition, the reason why part of Fe is replaced with Co is that it has the effect of improving the temperature characteristics of permanent magnets, and if Co exceeds 50% of Fe, high coercive force cannot be obtained, so I can't get a magnet. Therefore, the upper limit for Co is 50%.

[0019] In the alloy powder of this invention, in order to obtain an excellent permanent magnet having both a high residual magnetic flux density and a high coercive force, R10 atomic % to 25 atomic %,
B4 atomic% to 26 atomic% and Fe65 atomic% to 82 atomic% are preferable.

[0020] Furthermore, the alloy powder according to the present invention is
In addition to R, B, and Fe, the presence of unavoidable impurities in industrial production is acceptable, but some of the B must be replaced by 4.0 atom% or less of C, 3.5 atom% or less of P, 2.5 atom% or less of S, 3.5 Improved manufacturability of magnetic alloys by replacing at least one type of Cu with a total amount of 4.0 atomic % or less,
It is possible to lower the price.

[0021] Furthermore, in the R, B, Fe alloy or R, B, Fe alloy containing Co, Al of 9.5 atomic % or less, Ti of 4.5 atomic % or less, V of 9.5 atomic % or less, 8.5 atomic % or less Cr, 8.0 atom% or less Mn, 5 atom% or less Bi, 12.5 atom% or less Nb, 10.5 atom% or less Ta, 9.5 atom% or less Mo, 9.5 atom% or less W, 2.5 atom% or less It is possible to increase the coercive force of a permanent magnet alloy by adding at least one of Sb, Ge at 7 at % or less, Sn at 3.5 at % or less, Zr at 5.5 at % or less, and Hf at 5.5 at % or less. become.

[0022] In the R-B-Fe permanent magnet of the present invention, it is essential that the main crystal phase is tetragonal, and in particular, to obtain a fine and uniform alloy powder,
It is effective for producing sintered permanent magnets with excellent magnetic properties.

[0023] The particle size of the alloy fine powder according to this invention is
If the average grain size exceeds 10 μm, excellent magnetic properties, especially high coercive force, cannot be obtained during the production of permanent magnets, and if the average grain size is less than 1 μm, the manufacturing process of permanent magnets, that is, press forming, sintering, and aging treatment steps will be difficult. Since the oxidation of the alloy is significant and excellent magnetic properties cannot be obtained, a fine alloy powder with an average particle size of 1 to 10 μm is most desirable.

[0024] The magnetically anisotropic permanent magnet alloy obtained using the alloy fine powder for permanent magnets according to the present invention is
It shows coercive force iHc≧1kOe, residual magnetic flux density Br>4kG, and the maximum energy product (BH)max is equal to or higher than hard ferrite.In the most preferable composition range, (BH)max≧10MGOe, and the maximum value is
Reach over 25MGOe. Further, the composition of the alloy fine powder according to the present invention is R10
atomic% ~ 30 atomic%, B2 atomic% ~ 28 atomic%, Co45
When Fe is 65 atomic % to 82 atomic %, the obtained magnetically anisotropic permanent magnet alloy exhibits magnetic properties equivalent to those of the above magnetic alloys, and has an excellent temperature coefficient of residual magnetic flux density of 0.1%/°C or less. characteristics can be obtained. In addition, when the main component of R in the alloy powder is 50% or more of light rare earth metals, R12 at% to 20 at%, B4 at% to 24 at%, Fe65 at% to 82 at%, or Furthermore, Co5 atomic% to 45 atomic%
In particular, when the light rare earth metal is Nd, the maximum value of (BH)max reaches 33MGOe or more.

【0025】

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

[0026] Using this dry alloy powder and alloy powder without adding a lubricant, it is oriented in a magnetic field of 12 kOe, pressure molded at 2t/cm ² , and a width of 15 mm x length of 16 mm is obtained.
Ten molded bodies with a height of 10 mm were obtained. During this molding process, the ejection pressure, green density, and green strength of the molded body were measured.
The results are shown in Table 1. 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] ■■■ Turtle shell [0039] ■■■

【0028】

Effects of the Invention As is clear from Table 1, the method of the present invention, in which stearic acid, zinc stearate, and bisamide are mixed as lubricants and then molded, results in low extraction pressure, high green density, and improved lubricity. Also, there are fewer scratches and cracks in the appearance of the molded product, and moldability is greatly 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
After mixing an alloy powder whose main components are B2 atomic% to 28 atomic% and Fe65 atomic% to 82 atomic% with at least one of stearic acid, zinc stearate, and bisamide as a lubricant, the mixture is molded. A method for molding rare earth/iron/boron alloy powder for permanent magnets.