JPH0777178B2 - Method for manufacturing R-TM-B type radial anisotropic magnet - Google Patents

Description

The present invention relates to a method for producing a rare earth / transition metal / boron (hereinafter abbreviated as “R-TM-B”)-based radial anisotropic magnet,
In particular, it relates to those having a good circularity and roundness.

[Conventional technology]

In stepping motors, linear actuators, magnetic couplings, etc., so-called radial anisotropic cylindrical magnets whose magnetization anisotropic directions are radial are often used. This is because the magnetic flux density on the surface can be made higher than that of the conventional isotropic permanent magnet. Therefore, the radial anisotropic permanent magnet is greatly demanded as one that can meet the needs of the above-mentioned electronic devices that are light, thin, short and small.

By the way, the conventional radial anisotropic permanent magnet has been manufactured by a method of molding magnetic particles in a magnetic field. (JP-A-61-15411
8, JP-A-61-284907, JP-A-62-117305).

When the radial anisotropic permanent magnet is used as a rotor or a stator in the above-mentioned electronic device, the circularity of the inner diameter of the cylinder, the straightness of the cylinder, etc. are reduced due to the decreasing tendency of the gap size due to the miniaturization. Dimensional accuracy is highly demanded, and in order to ensure the roundness of the inner diameter of the cylinder when incorporating it into the product, a cylinder was inserted into the inner diameter during sintering to improve the roundness and straightness.
(Refer to Japanese Patent Application No. 62-273905) [Problems to be solved by the invention] However, during sintering, after the sintering due to the reaction between the R-TM-B material and the metal inserted into the inner diameter and shrinkage during cooling, There has been a problem that it is difficult to separate the body and the cylinder on the inner diameter side.

[Means for solving problems]

The present invention is an R-TM-B-based radial anisotropic permanent magnet, characterized in that a cylindrical metal or oxide sintered body having an oxide sprayed thereon is sintered in a state of being inserted into the inner diameter. -A method for producing a B-system radial anisotropic permanent magnet. As the columnar metal or oxide sintered body, one having a larger coefficient of thermal expansion than that of the R-TM-B material is used.

The present inventor, when sintering a radial anisotropic magnet in a restrained state, as a columnar material used for restraint, a cylindrical metal or oxide sintered body having a thermal expansion coefficient larger than that of the R-TM-B material. It has been found that, by using, there is no reaction or sticking after sintering, the cylinder on the inner diameter side can be easily separated from the sintered body, and the roundness is at the same level as in the past.

The raw material powder used in the present invention may be one obtained by crushing an R-TM-B-based casting alloy (see, for example, Japanese Patent Laid-Open No. 59-46008) or by ultra-quenching (for example, Japanese Patent Laid-Open No. 59-59). No. 64739)), or a material obtained by super-quenching and consolidating with a hot press or the like to cause a plastic flow to impart magnetic anisotropy (see JP-A-60-100402) is re-ground. Anything is fine.

〔Example〕

(Example 1) A magnetic alloy having a composition of Nd _0.9 Dy _0.1 (Fe _baL B _0.08 Nb _0.015 ) _5.7 was prepared by arc melting, cast in a water-cooled copper mold, and coarsely pulverized with a stamp mill to pass 35 mesh, Then, the mixture was finely pulverized with a ball mill for 3 hours to have an average particle size of 5 μm. The powder was filled in a mold having an outer diameter of 26.2 x an inner diameter of 20.8 x a length of 25 (mm), and a lateral magnetic field of 2230 (G) (the magnetic field applying direction was perpendicular to the molding direction) was molded. A 25 ton mechanical press was used as the molding machine. Molding pressure is 0.7 ton / cm ² Magnetic field strength is 10.700 (Oe)
Is.

The cylinder used during sintering was a 17.55 mm diameter (material: SUS304) cylinder with an oxide sprayed on its outer periphery with a film thickness of 200 μm, and BN (boron nitride) was applied as a mold release material to the SUS304 outer diameter side with a diameter of 17.95 mm. I used one.

Here, an insert was made in which the above-mentioned two types of cylinders were inserted on the peripheral side of the molded body.

The obtained molded body was sintered at 1100 ° C. for 2 hours with the cylinder inserted. Sintered body at 900 ℃ × 2 hours and 600 ℃ × 1
Heat treatment was applied for an hour.

Fig. 1 shows the dimensional change of the inserted column after sintering.

Conventional BN coating has a dimensional change of about 0.2 mm due to seizure after 3 times of sintering, whereas dimensional change of 10 or more times of sintering
Being within 5/100 mm is a surprising effect.

The inner diameter roundness is about 0.06 mm, and the magnetic characteristics are Hk11.6KOe.
(BH) _max 18.6MGOe, which was the same as the conventional one.

(Example 2) The powder produced by the same method as in Example 1 was filled in a mold having an outer diameter of φ121.5 and an inner diameter of φ106.5, and molded in a transverse magnetic field of 4 KG. The molding pressure is 0.7 ton / cm ² .

The cylinder used during sintering is a MgO sintered body with a diameter of φ90.3 × 30 mm (coefficient of thermal expansion 15 × 10 ⁻⁶ ) and a SUS304 columnar body with a diameter of φ90.3 × 30 mm coated with BN.

Here, an insert was made in which the above-mentioned two types of cylinders were inserted on the peripheral side of the molded body.

The obtained molded body was sintered and heat treated in the same manner as in Example 1.

The change in inner diameter of the obtained sintered body is shown in FIG. Conventional SUS304
The inner diameter of the sintered body is approx.
It can be seen that the MgO sintered body falls within a substantially constant dimensional range while the increase by 0.2 mm.

〔The invention's effect〕

According to the present invention, it is possible to dramatically extend the life of a cylinder used for restraint during sintering, which has not been predicted in the past, and there is no reaction or sticking between the sintered body and the cylinder.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the number of times of sintering and the outer diameter of a cylinder,
FIG. 2 is a diagram showing the relationship between the number of times of sintering and the inner diameter of the sintered body.

Claims (1)

[Claims] 1. R-TM for obtaining a rare earth (R), transition metal (TM), boron (B) based radial anisotropic magnet by sintering in a restrained state.
-B type radial anisotropic magnet manufacturing method, which is a columnar metal or columnar oxide sintered with a larger coefficient of thermal expansion than the R-TM-B material in which the oxide is sprayed on the inner diameter of the constraint. A method for producing an R-TM-B-based radial anisotropic magnet, which is characterized in that it is performed with the body inserted.