JPH06163295A - Manufacture of rare earth permanent magnet - Google Patents

Abstract

PURPOSE:To make an R-Fe-B based magnet of high performance, by casting and hot rolling. CONSTITUTION:In a process wherein R-Fe-B based casting alloy is put in a capsule and rolled, the capsule form and the total draft are so optimized that T/D becomes 0.05 to 0.1 for the final plate thickness T and the roll diameter D. Thereby magnetic characteristics are improved and irregularity is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a rare earth permanent magnet, and more particularly to a method for manufacturing an R-Fe-B type rare earth permanent magnet in which a cast alloy is subjected to hot plastic working to make it magnetically anisotropic. It is about.

[0002]

2. Description of the Related Art Typical permanent magnets currently in use are alnico type cast magnets, ferrite magnets and rare earth-transition metal type magnets. In particular, R-Co based permanent magnets and R-Fe-B based permanent magnets, which are rare earth-transition metal based magnets, have high magnetic performance as permanent magnets having an extremely high coercive force and energy product. Much research and development has been done.

Conventionally, there are the following methods for manufacturing these rare earth-iron (transition metal) high-performance permanent magnets.

(1) First, Japanese Patent Laid-Open No. 59-46008 and M.K. Sagawa, S .; Fujimura, N .; T
Ogawa, H .; Yamamoto and Y. Ma
tsuura; J. Appl, Phys, Vol, 55
(6) 15March 1984, p2083, etc., a magnetic anisotropy consisting of 8 to 30% R (where R is at least one rare earth element including Y), 2 to 28% B and the balance Fe in atomic percentage. It is disclosed that the permanent magnet is a isotropic sintered body, and that the permanent magnet is manufactured by sintering based on a powder metallurgy method.

(2) In addition, JP-A-59-211549 and R.I. W. Lee; Appl, Phys, Let
t. Vol, 46 (8), 15 April 198
5, p790 is a resin using melt-spinning quenching flakes produced by a quenching ribbon manufacturing apparatus used for manufacturing an amorphous alloy to form quenching flakes with a thickness of about 30 μm and using the flakes as magnets by a resin bonding method. Rare earth-
It is disclosed that iron magnets are manufactured.

(3) Further, JP-A-60-100402
Gazette and the aforementioned R. W. Lee's article describes a method of making anisotropic permanent magnets by high temperature treatment, wherein the permanent magnets are iron-rare earth metals, and the method is amorphous or fine crystalline containing iron, neodymium and / or praseodymium and boron. Solid material with high temperature is treated at high temperature to make a plastically deformed body with a fine structure of fine particles, and the body is cooled, and the obtained body is magnetically anisotropic and exhibits permanent magnet characteristics. Disclosed is a method of manufacturing a permanent magnet, which is characterized by comprising the steps shown below.

In this magnet manufacturing method, the ribbon-like quenched ribbon or strip of ribbon in (2) above is hot-pressed at about 700 ° C. in a vacuum or in an inert atmosphere to densify it. By performing upsetting (die up set) until it becomes 1/2 of the thickness of
The alloy is oriented parallel to the pressing direction and becomes anisotropic.

(4) Further, in JP-A-62-276803, R (provided that R is at least one of rare earth elements including Y) is 8 atom% to 30 atom% and B 2 atom% to
28 atomic%, Co 50 atomic% or less, Al 15 atomic%
Below, and after the alloy consisting of iron and other unavoidable impurities in manufacturing is melted and cast, the cast alloy is
At a temperature of 00 ° C or higher, extrusion processing for charging into a die of a hydraulic press, rolling processing for rolling with rolls, and hot processing such as stamping for placing on a substrate and stamping are performed to obtain crystal grains. A rare earth-iron based permanent magnet, characterized in that the cast alloy is magnetically anisotropy by refining the alloy and orienting the crystal axis in a specific direction.

[0009]

[Problems to be Solved by the Invention] (1) to (4) above
The conventional method for manufacturing an R-Fe-B system permanent magnet has the following drawbacks.

In the method of manufacturing a permanent magnet of (1), it is essential to make the alloy into powder, but R-Fe-B
Since the system alloys are very active with respect to oxygen, if they are pulverized, excessive oxidation will occur, and the oxygen concentration in the sintered body will inevitably increase.

When molding the powder, it is necessary to use a molding aid such as zinc stearate, which is removed beforehand in the sintering process, but a few percent of the molding aid is However, it remains in the form of carbon in the magnet body, and this carbon remarkably deteriorates the magnetic performance of R-Fe-B, which is not preferable.

The green body after press-molding by adding a molding aid is called a green body, which is very fragile and difficult to handle. Therefore, it takes a great deal of time to neatly put them side by side in the sintering furnace, which is a big drawback.

Due to these drawbacks, generally speaking, not only expensive equipment is required for producing an R--Fe--B system sintered magnet, but also the production method thereof has poor production efficiency, Eventually, the manufacturing cost of the magnet increases. Therefore, it is not possible to take advantage of the advantages of the R-Fe-B magnets, which have relatively low raw material costs.

Next, in the manufacturing method of the permanent magnets of (2) and (3), a vacuum melt spinning device is used, but this device is currently very poor in productivity and expensive.
Since the permanent magnet of (2) is isotropic in principle and has a low energy product, and the squareness of the hysteresis loop is not good, it is disadvantageous in terms of temperature characteristics and use.

The method of manufacturing a permanent magnet of (3) is a unique method of using hot pressing in two steps, but it cannot be denied that it is inefficient in terms of mass production. Further, in this method, the crystal grains are remarkably coarsened at a high temperature, for example, 800 ° C. or higher, which causes the coercive force iH
c is extremely reduced, and it does not become a practical permanent magnet.

In the method of manufacturing a permanent magnet of (4), since the magnet alloy is sealed in a capsule and hot-worked, it can be processed in the atmosphere, and therefore atmosphere control during processing is unnecessary and expensive equipment is not required. . Since the entire manufacturing process is simple, the manufacturing cost is low. Further, since the powder process is not included, the oxygen content is low and the corrosion resistance is good. Furthermore, it has many advantages such as high mechanical strength and the ability to manufacture large magnets. Especially by using rolling as a means of hot working, mass productivity is improved. In terms of the characteristics of rolling, the problem is the effect of shear strain generated by the friction between the material and the roll.
In order to control this, there is a method of changing the rolling reduction and the sheath thickness. Regarding the reduction rate, Japanese Patent Application No. 2-257650
Indicates that a pass having a rolling reduction of more than 20% is included, and that a high degree of orientation can be obtained by performing a plurality of passes having a rolling reduction of 30% or more. Japanese Patent Application No. 3-09
It is shown in 5698 that a high degree of orientation can be obtained by performing a pass with a reduction ratio of 20% or more once or more in a workability range of 40 to 70% by hot rolling.
Japanese Patent Application No. 1-072276 discloses that the sheath thickness needs to be 20% or more of the alloy plate thickness. However, until now, regardless of the rolling reduction and the sheath thickness, if the rolling material is repeatedly thinned and the rolled material becomes too thin, the magnetic properties may rather deteriorate. Further, when the roll diameter is small, high magnetic properties may not be obtained even if the roll diameter is reduced by 75% or more.

[0017]

[Means for Solving the Problems] As a result of research on the above problems, it was found that by optimizing the ratio of the plate thickness to the roll diameter, higher magnetic properties can be stably obtained. It was That is, the method for producing a rare earth permanent magnet according to the present invention includes R (where R is at least one of rare earth elements including Y), Fe (iron), and B (boron).
In the manufacturing process of the rare earth permanent magnet, in which the alloy containing the as a raw material basic component is melted and cast, put in a metal sheath and hot-rolled, and then heat-treated, especially in the hot-rolling process,
The relationship is 0.05 <T / D <0.1 with respect to the final plate thickness T including the sheath and the roll diameter D.

That is, in the above-mentioned method for producing a rare earth permanent magnet, in the process in which the orientation degree of the R-Fe-B system cast alloy is improved by hot rolling, the efficiency of the orientation degree improvement by the plate thickness and the roll diameter is improved. The difference is taken into consideration.
In order to obtain a high degree of orientation, that is, high magnetic characteristics, by hot rolling, it is desirable that the rolling reduction of each pass is sufficiently large. Specifically, at least 1 pass has a reduction rate of 30% or more.
It will be necessary more than once. The total workability is required to be 50 to 85%. Further, the sheath thickness needs to be 20% or more of the thickness of the magnet alloy. If it is thinner than this, not only the magnet will crack more, but also the degree of orientation will be low. A large roll diameter is desirable to keep shear strain low, but
If it is too large or the plate thickness is too thin, the magnetic properties will rather deteriorate.

Specifically, the highest degree of orientation is obtained when the ratio T / D of the final plate thickness T and the roll diameter D is in the range of 0.05 to 0.1. If the roll diameter is too small, that is, if T / D is considerably larger than 0.1, a sufficient degree of orientation cannot be obtained. Further, when rolling is carried out until T <0.05, the shear strain becomes large and the magnetic properties are deteriorated.

By optimizing the ratio of the roll diameter to the plate thickness in this way, it is possible to select the shape of the rolled material that is most easily oriented with respect to the rolling roll used, and as a result, it is possible to obtain high magnetic characteristics. .

[0021]

【Example】

Example 1 First, an induction heating furnace was used in an argon atmosphere to melt an alloy having a composition of Pr _16.5 Fe _77.2 B _5.1 Cu _1.2 , and then cast to have an average grain size of columnar crystal structure of 15
μm length 150 mm x height 140 mm x thickness 20 mm
A casting sample of was obtained. This cast sample was processed into the shape shown in Table 1. This is the SS with the dimensions shown in the table.
The sheath made of No. 41 was sealed by welding and heated in a furnace at 950 ° C. for 1 hour, and rolled using a rolling machine with a roll diameter of 300 mm at a rolling reduction of 10 to 30% in each pass.
As a result, a rolled material having a final workability of 75% was obtained.

[0022]

[Table 1]

After cooling, the sheath is removed and the temperature is adjusted to 1 at 1025 ° C.
After heat treatment for 2 hours at 500 ° C. for 6 hours, a sample of 7 mm × 7 mm × height 8 mm was prepared by machining, and the magnetic characteristics were measured by a BH tracer. For the final plate thickness T and roll diameter D (= 300mm), the value of T / D and (BH) ma
Table 2 shows the relationship between x and iHc.

[0024]

[Table 2]

From these results, high magnetic properties were obtained when the T / D value was in the range of 0.05 to 0.1.

(Example 2) As in Example 1, first, using an induction heating furnace in an argon atmosphere, Pr _16.5 Fe _77.2
B _5.1 Cu _1.2 alloy is melted, then cast,
150 mm long with an average grain size of 15 μm consisting of a columnar crystal structure
A cast sample having a height of 140 mm and a thickness of 20 mm was obtained. This cast sample is 18 mm wide x 125 mm high x
It was processed into a billet having a length of 150 mm. Arrange 7 of them, put them in SS41 sheath of width 320mm x height 250mm x length 400mm, seal by welding, and 950 ° C.
Heated for 2 hours in a furnace with a roll diameter of φ500, φ
Rolling was performed using a 900 rolling mill. The rolling reduction in one pass was 10 to 30%, and the final workability was 75% or more. Remove the sheath after cooling and remove at 1225 ° C for 12
After heat treatment at 500 ° C. for 6 hours, a sample having a size of 7 mm × 7 mm × height of 8 mm was prepared by machining, and the magnetic characteristics were measured with a BH tracer.

Table 3 shows the final plate thickness T, roll diameter D, T / D value, workability and magnetic properties of each sample.

[0028]

[Table 3]

Although the magnetic properties are improved as the plate thickness is reduced by rolling, particularly high magnetic properties are obtained when T / D is in the range of 0.05 to 0.1. The variation is also small. Therefore, in order to obtain high magnetic properties, the final plate thickness T after rolling has T / D of 0.0.
It can be seen that it is desirable to fall within the range of 5 to 0.1.

[0030]

INDUSTRIAL APPLICABILITY As described above, the method for producing rare earth permanent magnet powder of the present invention has the following effects.

(1) Since it is manufactured by the steps of casting, hot rolling and heat treatment, a large-sized and low-cost magnet having high mechanical strength can be obtained.

(2) Since the orientation efficiency by rolling increases,
Magnetic properties are improved and variations are reduced.

(3) Even if the rolling mill or roll diameter changes, the optimum rolled material shape can be easily designed.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number in the agency FI Technical indication H01F 1/053 1/08 A (72) Inventor Seiji Ihara 3-3-5 Yamato, Suwa City, Nagano Prefecture No. Seiko Epson Corporation (72) Inventor Koji Akioka 3-3-5 Yamato, Suwa City, Nagano Seiko Epson Corporation

Claims (1)

[Claims] 1. An alloy containing R (where R is at least one of rare earth elements including Y), Fe (iron), and B (boron) as basic raw materials is melted and cast into a metal sheath. In the manufacturing process of a rare earth permanent magnet in which heat treatment is performed after hot rolling, particularly in the hot rolling process thereof, 0.05 <T / D <0 with respect to the final plate thickness T including the sheath and the roll diameter D. 1. A method for manufacturing a rare earth permanent magnet, characterized in that the relationship 1 is satisfied.