JPH06302451A - Manufacture of rare-earth permanent magnet - Google Patents

Abstract

PURPOSE:To enhance the mechanical strength of a rare-earth permanent magnet which is manufactured by a forging and hot-working method and to enhance the bonding strength of the magnet to a yoke. CONSTITUTION:An alloy whose raw-material basic components are R (where R represents at least one kind out of rare-earth elements including Y), Fe and B is melted and cast. Then, a plurality of arc-shaped magnets 1 manufactured by a process in which a cast ingot is hot-worked so as to give anisotropy and hot-bent and worked are combined at the inside of a ring composed of a material whose coefficient of thermal expansion is lower than that of the material of the magnets, they are held at a temperature of 450 to 1100 deg.C in a nonoxidizing atmosphere and they are formed to be a ring shape. In addition, pure iron, low-carbon steel or an Invar alloy is used as the material of the ring. Thereby, it is possible to obtain a magnet whose mechanical strength and bonding strength are extremely high. In addition, a yoke-integrated magnet can be manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rare earth permanent magnet, and more particularly to a ring-shaped R-Fe-B rare earth permanent magnet magnetically anisotropy obtained by subjecting a casting alloy to hot plastic working. The present invention relates to a manufacturing method of.

[0002]

2. Description of the Related Art Permanent magnets are one of the 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 electrical products,
Permanent magnets are also required to have higher performance.

Typical permanent magnets currently in use are alnico type cast magnets, ferrite magnets and rare earth-transition metal type magnets. In particular, R-Fe-B system permanent magnets have been extensively researched and developed as permanent magnets having extremely high coercive force and energy product.

Conventionally, there are the following methods for manufacturing these R—Fe—B type high-performance permanent magnets.

(1) Sintering method (JP-A-59-46008)
Publication and M.I. Sagawa, S .; Fujimura,
N. Togawa, H .; Yamamoto and
Y. Matsuura; J. Appl, Phys, Vo
1, 55 (6) 15 March 1984, p2083) (2) Die-up set (Japanese Patent Laid-Open No. 59-2111549)
Gazette and R. W. Lee; Appl, Phys, Let
t. Vol, 46 (8), 15 April 1985.
p790, JP-A-60-100402) (3) Casting / hot working method (JP-A-62-276803)
All of these production methods can be applied to the production of ring-shaped magnets.

In the sintering method, when radial anisotropy is imparted, a magnet having radial anisotropy is obtained by press-molding while applying a magnetic field radially in the radial direction of the molded body when molding in a magnetic field. That it can be produced
3109 and Japanese Patent Laid-Open No. 62-117305.

In the method related to the die upset method,
A method for producing a ring-shaped magnet having radial anisotropy by extruding a material obtained by subjecting a quenched ribbon to hot pressing to consolidate is disclosed in JP-A-60-10.
No. 0402 and Japanese Patent Application Laid-Open No. 1-248503.

In the casting / hot working method, a plate magnet having anisotropy in the plate thickness direction is rolled by rolling to form an arc shape, and a plurality of the magnets are bonded to form a ring. Japanese Patent Application No. 2-3153
No. 97.

[0009]

However, the above-mentioned conventional method for manufacturing an R-Fe-B system ring-shaped permanent magnet is as follows.
It has the following drawbacks.

In the manufacturing method by the sintering method, it is indispensable to make the alloy into a powder, but in the manufacturing method, it is unavoidable that the contained oxygen concentration and the carbon concentration become high. This significantly reduces the corrosion resistance and mechanical strength of the magnet. Also,
Dimensional accuracy is poor due to shrinkage during sintering, height /
There is a shape restriction that one with a large diameter ratio cannot be used. Further, there is a problem that yield is poor because cracks are likely to occur on the side surface. Generally, the manufacturing process of an R-Fe-B system sintered magnet has a problem that the manufacturing process is complicated, expensive equipment is required, the production efficiency is poor, and the manufacturing cost of the magnet is eventually increased.

Next, the manufacturing method by the die-upset method uses a vacuum melt spinning apparatus, but this apparatus has very poor productivity and is expensive. In addition, the magnet produced by this method has a problem that the magnetic characteristics vary widely and the mechanical strength is low.

The magnet produced by the casting / hot working method has excellent mechanical strength and corrosion resistance, and it is possible to manufacture a large-sized magnet which is impossible by the above two methods, but a ring-shaped magnet is integrally formed. Since it is difficult to do so, there was a problem that the arc-shaped magnet had to be formed into a ring shape by adhesion.

An object of the present invention is to solve the problems associated with the ring-shaped magnet produced by this casting / hot working method.
It is an object of the invention to provide a method for producing a high-performance and low-cost rare earth permanent magnet.

[0014]

The present invention uses an arc-shaped magnet formed by hot bending a plate-shaped permanent magnet manufactured by a method of casting and hot working, A method of making a ring-shaped magnet is provided.

Specifically, R (provided that R is at least one of rare earth elements including Y), Fe, and B are the basic components of the raw materials, the alloy having the basic components is melted and cast, and then a cast ingot is formed. After the hot working to give anisotropy, the arc-shaped magnet manufactured by the step of hot bending,
A plurality of magnets are combined inside a ring made of a material having a thermal expansion coefficient lower than that of the magnet material, and 450 to 11 in a non-oxidizing atmosphere.
It is characterized in that it is made into a ring shape by holding it at a temperature of 00 ° C, and that pure iron / low carbon steel or Invar alloy is used as the material of the ring.

The magnet alloy produced by the casting / hot working method of the present invention has a low-melting grain boundary phase in addition to the main phase R ₂ Fe _{1 4} B intermetallic compound, and the grain boundary phase melts. When the temperature is maintained at a certain temperature, the magnet alloys can be integrated by adhesion, or when the ring can be used as a yoke, the magnet and the yoke can be integrated by adhesion.

Since the bonding step is carried out by utilizing the melting of the grain boundary phase at a high temperature, a temperature higher than the melting point of the grain boundary phase is required. The addition of Cu, Ag, Au, Pd, Ga, etc. has the effect of lowering the melting point of the grain boundary phase. Cu
In the case of the Pr-Fe-B based magnet added with, the grain boundary phase melting point is about 450 ° C. Therefore, the adhesion temperature is 45
A temperature of 0 ° C. or higher is necessary, and at a temperature of higher than 1100 ° C., the R ₂ Fe ₁₄ B phase rapidly grows to lose coercive force, so a temperature of 450 to 1100 is preferable.

The ring for holding the shape of the magnet causes thermal expansion as the temperature rises. The R-Fe-B magnet alloy has almost no volume change up to the Curie temperature as a characteristic of a ferromagnetic material, but the expansion coefficient becomes remarkably high when the grain boundary phase melting point is exceeded. If the thermal expansion of the ring for maintaining the shape is smaller than the thermal expansion of the magnet, pressure is generated at the contact interface of the magnet segments, and the liquid phase adhesion is effectively performed. As a ring material, heat-resistant steel,
Mo alloy, W alloy, ceramics, etc. are preferable. The lower the coefficient of thermal expansion of the ring material, the greater the force generated on the contact surface and the greater the effect of pressure welding. However, there is a problem that such a material is industrially expensive.

Low carbon steel is effective as an inexpensive material. It is known that iron undergoes α-γ transformation at 910 ° C, and the coefficient of thermal expansion sharply decreases at 910 ° C or higher. By utilizing this, it is possible to generate a large pressure on the contact surface of the magnet.

Further, the use of the Invar alloy ring has the effect of increasing the dimensional accuracy. That is, the Curie point of Nd (Pr) ₂ Fe ₁₄ B is about 300.
C, melting point of grain boundary phase is 450 to 550 when Cu is added
Since it is ℃, the coefficient of thermal expansion of this magnet is very small at a temperature below the grain boundary phase melting point. Since the Invar alloy has a very small thermal expansion at 400 ° C. or less, the dimensional accuracy of the magnet is improved and the ring and the magnet can be easily removed. Further, the cracks generated during cooling are eliminated and the yield is improved.

Next, examples of the present invention will be described.

[0022]

【Example】

(Example 1) Using an induction heating furnace in an argon atmosphere,
Melting an alloy of composition Pr ₁₆ Fe _77.4 B _5.1 Cu _1.5 ,
Cast. This cast ingot was placed in a low carbon steel capsule, degassed, sealed, and hot rolled at a processing temperature of 950 ° C. At this time, the reduction amount of height in one rolling is 30
% Rolling was performed for 4 passes so that the total processing amount became 76%.

Width 10 mm from the rolled magnet thus obtained
A sample having a length of 25 mm and a thickness of 2 mm was cut out and heated to 1000 ° C. in an inert gas, and then an outer diameter of 24 mm,
Molded into an arc-shaped magnet with an inner diameter of 20 mm, the center angle after cooling is 1
The end face was molded so as to form an angle of 20 °. Further, as shown in FIG. 1, the arc-shaped magnet 1 is provided with an outer diameter of 32 mm × an inner diameter of 24 mm ×
Inside of various bonding rings (yoke) 2 having a height of 10 mm, three pieces are combined to form a ring, and 100 rings in argon gas are used.
Hold at 0 ° C for 30 minutes. As a result, the ring-shaped magnet 3 was adhered and had radial anisotropy. The results are shown below.

[0024]

[Table 1]

Example 2 An alloy having a composition of Pr ₁₆ Fe _77.4 B _5.1 Cu _1.5 was melted and cast in an argon atmosphere using an induction heating furnace. This cast ingot was placed in a low carbon steel capsule, degassed, sealed and processed at a processing temperature of 950.
Hot rolling was performed at ℃. At this time, rolling with a height reduction amount of 30% in one rolling is performed for 4 passes, and the total processing amount is 76%.
I tried to become.

Width 10 mm from the rolled magnet thus obtained
A sample having a length of 25 mm and a thickness of 2 mm was cut out and heated to 1000 ° C. in an inert gas, and then an outer diameter of 24 mm,
Molded into an arc-shaped magnet with an inner diameter of 20 mm, the center angle after cooling is 1
The end face was molded so as to form an angle of 20 °. Further, as shown in FIG. 1, the arc-shaped magnet 1 is provided with an outer diameter of 28 mm × an inner diameter of 24 mm ×
Three pieces are combined inside the pure iron yoke 2 with a height of 10 mm to form a ring, and the temperature is 500 to 1000 ° C. in argon gas.
Hold for 30 minutes. Thus, the ring-shaped magnet 3 having the radial anisotropy of the yoke was obtained. As a result, as shown below, a sample with the best adhesion state was obtained at 1000 ° C. This indicates that the iron contracted due to the α → γ transformation of iron at 910 ° C., and pressure welding was performed between the magnet and the yoke.

[0027]

[Table 2]

Example 3 An alloy having a composition of Pr ₁₆ Fe _77.4 B _5.1 Cu _1.5 was melted and cast in an argon atmosphere using an induction heating furnace. This cast ingot was placed in a low carbon steel capsule, degassed, sealed and processed at a processing temperature of 950.
Hot rolling was performed at ℃. At this time, rolling with a height reduction amount of 30% in one rolling is performed for 4 passes, and the total processing amount is 76%.
I tried to become.

Width 10 mm from the rolled magnet thus obtained
A sample having a length of 25 mm and a thickness of 2 mm was cut out and heated to 1000 ° C. in an inert gas, and then an outer diameter of 24 mm,
Molded into an arc-shaped magnet with an inner diameter of 20 mm, the center angle after cooling is 1
The end face was molded so as to form an angle of 20 °. Further, as shown in FIG. 1, the arc-shaped magnet 1 is provided with an outer diameter of 32 mm × an inner diameter of 24 mm ×
Inside of various bonding rings (yoke) 2 having a height of 10 mm, three pieces are combined to form a ring, and 100 rings in argon gas are used.
Hold at 0 ° C for 30 minutes. After cooling, the ring was removed.
For the ring-shaped magnet 3 having radial anisotropy thus obtained, the dimensional accuracy of the outer diameter was measured by an appearance inspection and a tool microscope. The results are shown below.

When the Invar alloy (36Ni-Fe) is used, a magnet having a high dimensional accuracy and a good appearance is obtained.

[0031]

[Table 3]

[0032]

As described above, according to the method for producing a rare earth permanent magnet of the present invention, a radial anisotropic ring magnet having excellent mechanical strength and high dimensional accuracy can be produced at low cost. In addition, the magnet and the yoke can be easily integrally molded, and at the same time, the reliability of a large motor or the like requiring high-speed rotation is improved due to the large adhesive strength.

[Brief description of drawings]

FIG. 1A is a schematic view showing a state in which a plurality of arc-shaped magnets and a yoke are combined to be integrated in Embodiments 1 and 2 of the present invention. (B) is an external view of the ring-shaped magnet obtained by the present invention.

[Explanation of symbols]

 1 arc-shaped magnet 2 adhesive ring or yoke 3 ring-shaped magnet

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Akioka 3-3-5 Yamato, Suwa, Nagano Seiko Epson Corporation

Claims (3)

[Claims] 1. R (where R is at least one of rare earth elements including Y), Fe and B as raw material basic components, an alloy having the basic components is melted and cast, and then the cast ingot is hot worked. A plurality of arc-shaped magnets produced by the process of hot bending after applying anisotropy to the inside of a ring made of a material having a smaller coefficient of thermal expansion than the magnet material, and a non-oxidizing atmosphere In 450-1100 ℃
A method for producing a rare earth permanent magnet, which is characterized by forming a ring-shaped magnet by maintaining the temperature at. 2. R (where R is at least one of rare earth elements including Y), Fe and B as raw material basic components, an alloy having the basic components is melted and cast, and then the cast ingot is hot worked. Then, a plurality of arc-shaped magnets produced by a process of performing hot bending after imparting anisotropy are combined inside a ring made of pure iron or low carbon steel, and heated in a non-oxidizing atmosphere at 910 to 1100. A method for producing a rare earth permanent magnet, which comprises forming a ring-shaped magnet by maintaining the temperature at ℃. 3. R (where R is at least one of rare earth elements including Y), Fe and B as raw material basic components, an alloy having the basic components is melted and cast, and then the cast ingot is hot worked. After applying the anisotropy, a plurality of arc-shaped magnets manufactured by the process of hot bending is combined inside the ring made of Invar alloy and heated to a temperature of 450 to 1100 ° C in a non-oxidizing atmosphere. A method for producing a rare earth permanent magnet, characterized by forming a ring-shaped magnet by holding it.