JPS63286511A - Manufacture of permanent magnet - Google Patents

Abstract

PURPOSE:To manufacture an inexpensive permanent magnet having sufficient coercive force and high efficiency, by subjecting an alloy containing rare-earth elements, transition metals, and boron as principal components to melting, to cooling at a specific cooling rate, and then to heat treatment. CONSTITUTION:An alloy containing rare-earth elements (including Y), transition metals, and boron as principal components is melted, heated at 10<-1>-10<6> deg.C/sec cooling rate by a double roll method, etc., and then heat-treated at >=250 deg.C to undergo magnetic hardening, or, after the above-mentioned cooling, this alloy is subjected to hot working at >=500 deg.C so as to orient a crystal axis in a crystalline state in a specific direction and make the magnet magnetically anisotropic or is subjected to hot working at >=500 deg.C and then to heat treatment at >=500 deg.C to undergo magnetic hardening. In this way, the high-efficiency permanent magnet can be manufactured by means of low-temp. and short-time treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a permanent magnet whose main components are rare earth elements, transition gold dust, and boron, and a method for manufacturing the same.

[Conventional technology]

Permanent magnets are important electrical and electronic materials that are used in a wide range of fields, from various household appliances to peripheral terminal equipment for large computers.

With the recent demand for smaller and more efficient electrical products,
Permanent magnets are also required to have increasingly higher performance. Representative permanent magnets currently in use are alnico hard ferrite and earthwork i-transition metal magnets. In particular, rare earth-transition metal magnets such as R-C, permanent magnets, and R
Since -Fe-B permanent magnets provide high magnetic performance, much research and development has been carried out on them.

Conventionally, there are methods for manufacturing these R-Pe-B permanent magnets as shown in the following literature regarding the amount of sand.

(1) Based on powder metallurgy (sintering method).

(References 1 and 2) ■ A quenched thin strip manufacturing device used to manufacture amorphous alloys produces quenched thin flakes with a thickness of about 30 μm, and the quenched thin flakes are made into magnets using a resin bonding method using the melt spinning method. resin bonding method. (References 3, 4) (3) A method of mechanically aligning the rapidly cooled flakes used in the above method (■) using a two-step hot press method (References 4, 6) Here, Reference 1: JP-A-59-46008; Document 2: M,
Sagawa, S., Fujimura, N.
, Togawa, H. Yamam.

to, and Y, Matsuura;J
, App 1 , Phys ,
V o 1, 5 5 (6) 1 5 M
a r c h1984, p 2083゜Reference 3: JP-A-59-2TX549; Reference 4: R
,W,Lee:APPI, Phys,Lett,
Vol, 46(8), 15 April 11985,
P2O3 Document 5: Japanese Unexamined Patent Publication No. 80-100402 Next, the above conventional method will be explained.

First, in the sintering method, an alloy ingot is produced by melting and casting, and then pulverized to obtain magnet powder with transparent grains I! (several μm).The magnet powder is kneaded with a binder, which is a forming aid, and
The molded body is completed by press molding in a magnetic field. The compact is sintered in argon at a temperature around 1100° C. for 1 hour and then rapidly cooled to room temperature. After sintering, the coercive force is improved by heat treatment at a temperature of around 600°C.

In the resin bonding method using quenched thin strips by the melt spinning method, first, the quenched ribbon manufacturing equipment is rotated at the optimal rotation speed.
A quenched ribbon of R-Fe-B alloy is made. Obtained thickness 30
A μm ribbon-like thin strip is an aggregate of crystals with a diameter of 400λ or less, is brittle and easily broken, and since the crystal grains are distributed isotropically, it is also magnetically isotropic. The thin ribbon is crushed to an appropriate particle size, kneaded with resin, and press-molded.

In the manufacturing method (3), the R-Fe- This is to obtain a B magnet.

In this pressing process, a uniform pressure is applied, the axis of easy magnetization is oriented parallel to the pressing direction, and the alloy becomes anisotropic.

In addition, the crystal grains of the ribbon-like thin strip produced by the initial melt spinning method are made smaller than the grain size at which they exhibit the maximum coercive force, to avoid coarsening of the crystal grains during the subsequent hot pressing. Allow the particles to grow to the optimum particle size.

[Problem that the invention seeks to solve]

Permanent magnets containing rare earth elements, iron, and boron as main components can be manufactured using the following conventional techniques, but these manufacturing methods have the following drawbacks.

In the sintering method (1), it is essential to turn the alloy into powder, but since R-re-B alloys are very active against oxygen, turning them into powder will make the oxidation even more stale and cause sintering. The oxygen concentration in the compact is unavoidably high.Also, when the powder is compacted, a compacting aid such as zinc stearate must be used; However, the enemy in the forming aid remains in the form of carbon inside the magnet, and this carbon has a significant R-
This is undesirable because it lowers the magnetic performance of the Fe-B alloy.

The molded body after press molding with the addition of a molding aid is called a green body, which is extremely brittle and difficult to handle.

Therefore, a major drawback is that it takes a considerable amount of effort to arrange them neatly in the sintering furnace. Because of these drawbacks, generally speaking, the production of R-Fe-B permanent magnets not only requires expensive equipment, but also has poor production efficiency1. turn into.

Therefore, it cannot be said that this is a method that can take advantage of the advantages of R-Fe-B magnets, which have relatively low raw material costs.

Furthermore, although methods (2) and (3) are interesting and change the concept of conventional permanent magnet manufacturing, they require a cooling rate of about 10"C/sec, and variations in the cooling rate greatly affect performance. do.

■ The structure contains not only a crystalline phase (but also an amorphous phase, which is highly dependent on the magnetic properties. Therefore, it has poor stability at high temperatures where the amorphous phase crystallizes. .

■ Hot processing for anisotropy needs to be done in a short time to avoid crystallization, making manufacturing technology difficult ■ The coercive force mechanism has pinning, and it has a high coercive force to compensate for poor temperature characteristics. There are many problems caused by productivity, such as the difficulty in attaching and detaching magnets.

The present invention solves the above-mentioned drawbacks of the prior art, and its purpose is to provide a high-performance, low-cost rare earth-iron permanent magnet and a method for manufacturing the same.

[Means for solving problems]

fJl in the permanent magnet manufacturing method of the present invention is a rare earth element (
However, in the manufacturing method of a permanent magnet whose basic components are Y), a transition metal, and boron, after melting 10"-' to 10
''' After cooling the alloy at a cooling rate of C/sec,
This is a method for producing a permanent magnet, characterized by subjecting it to heat treatment at a temperature of 250° C. or higher and magnetically hardening it.
A method for producing a permanent magnet, characterized in that the magnet is made magnetically anisotropic by cooling the alloy at a cooling rate of sec and then hot working at a temperature of 500"C or higher, and further comprising: The third method is a method for producing a permanent magnet, which is characterized in that the permanent magnet is magnetically hardened by heat treatment at a temperature of 250" or more after hot working in the second production method. After the first, second, and third manufacturing methods, a pulverization step and a kneading step with a resin may be added, and bonding may be performed with the resin.

[Effect]

As mentioned above, the sintering method and the quenching method, which are methods for producing rare earth-iron magnets, each have major drawbacks such as difficulty in powder control through pulverization and poor productivity.

In order to improve these shortcomings, the present inventors started research on magnetization using bulk materials, and first, melting in the composition range of magnets whose basic components are rare earth elements, transition metals, and porous metals. It has been found that a sufficient coercive force can be obtained by controlling the subsequent cooling rate and heat-treating the black structure to make it finer. We also discovered that this magnet can be made anisotropic by hot working. This point will be explained below.

Classifying conventional R-Fe-B magnets based on the coercive force mechanism, the sintering method (1) in the above conventional technology is the nucleage 2-in type, and the quenching method (2) and (3) is the pinning type. It is. These two divisions can be easily made by examining the rise of the truncation curve. In other words, in the nucleated tan type, the rise of the rupture curve is abrupt, and in the pinning type, the rupture curve is difficult to rise while the magnetization is pinned by the precipitate, and suddenly rises when the value exceeds the pinning four pattern. It takes the form of standing up. Generally, in R-Fe-B magnets, residual magnetic density [fB
Since the temperature coefficients of r and coercive force iHc are large, iHc is made thick to cover this.

However, when fHc is increased, it becomes extremely difficult to attach and detach the magnet. In particular, in rotating machines, etc., which are the mainstream in which rare earth magnets are used these days, multiple magnetizations are often required (this problem is becoming increasingly important. In the case of the pinning type, the rise of the cutting curve is steep, so some degree of magnetization can be achieved even without a sufficient magnetic field, but in the case of the pinning type, magnetization is hardly possible if the magnetic field is within the pinning force. Creation type is an advantage.

However, the sintering method has disadvantages in that it is difficult to control the powder because it involves the steps of crushing and sintering as described above, and the oxygen and carbon concentration increases. In order to solve these problems, the coercive force mechanism should be a Nucleage 3 model, as long as it can be made into a magnet without going through the process of crushing and sintering.

In general, in the New Clinicon model, the main phase (Rs Feta B phase in the case of rare earth-iron-boron system, R is the rare earth element) approaches the critical radius of a single magnetic domain, so that it cannot easily generate a reverse magnetic domain. This is said to be the cause of coercive force generation. However, although the critical radius of the R1F e , a B phase is on the submicron order, the grain size of the sintered magnet is about 10 μm. This is because in the case of the sintering method, the casting input goes through the process of being pulverized, and at that stage the surface area increases significantly and the oxygen concentration increases, so in reality, sintered bodies with a particle size close to the critical radius are This means that it cannot be created.

Conversely, as long as the magnet complies with the coercive force of the New Clinic model, it is possible to increase the cooling speed and grow coarse columnar crystals or equiaxed products without having to go through the process of crushing and sintering the cast ingot. By suppressing this, it is possible to control the Rs Few a B phase to a particle size that is possible to obtain a sufficient coercive force. This method makes it possible to obtain coercive force with a bulk decoy, and is freed from productivity problems such as the difficulty in powder management as described above.

Here, the reason for specifying the cooling rate will be explained. The cooling rate specified in the present invention basically does not include an amorphous phase,
Moreover, the cooling rate is within a range that does not cause the grains to become so coarse that they cannot obtain coercive force. If the cooling rate is faster than specified in the present invention, an amorphous phase tends to form (and the coercive force mechanism becomes like the pinning described above.) If the cooling rate is slower than specified in the present invention, the crystal grains become coarse and the coercive force becomes insufficient. In addition, within this cooling rate range, the thickness of the cast ingot or flake can be from several mm to several centimeters, which significantly improves productivity compared to the conventional example (2), which has a thickness of several tens of micrometers. becomes more sexual.

Furthermore, the present invention provides a new R-F that is not based on the prior art (2).
Application to e-B resin bonded magnets is also possible. The breaking curve of the permanent magnet of the present invention is of the nucleation type, but when a sintered magnet with a similar type of breaking curve was crushed, the coercive force was drastically reduced, and it could not be made into a resin-bonded magnet. . This is due to mechanical strain caused by crushing and the crystals being too large. However, by using the present invention to increase the cooling rate and refine the crystal grains within a range that does not precipitate the amorphous phase, it is possible to obtain a powder that maintains coercive force even when the particle size of the powder for resin-bonded magnets is (several to several μm). Unlike conventional technology (2), it becomes possible to create a Nucleage mushroom-type resin bonded magnet.

The preferred composition range of the permanent magnet according to the present invention will be explained below.

Rare earths include N Y, La, Ce, Pr, Nd, Sm
, Eu, Gd, Tb, Dy-Ho, Er, Tm, Yb,
Lu is listed as a candidate, and among these, 1!1 or 28 [or more] may be used in combination. The highest magnetic performance is obtained with Pr.

Therefore, Pr, Pr-Nd alloy, Ce-Pr-
Nd alloy or the like is used. In addition, small amounts of additive elements, such as heavy rare earth elements such as D y s T b, A1, MOIS
i etc. are effective in improving coercive force.

The main phase of the R-Fe-B magnet is R1FetaB. Therefore, if R is less than 8 at %, the above compound is no longer formed and a cubic crystal structure having the same structure as α-iron is formed, so that high magnetic properties cannot be obtained.

On the other hand, when R exceeds 30 atoms, the nonmagnetic R-rich phase increases and the magnetic properties deteriorate significantly. Therefore, the range of R is 8 to 3
0 atomic % is appropriate. However, in order to form a magnet according to the present invention, preferably R8 to R25 atoms are suitable.

B is an essential element for forming the Rs Feta B phase, and if it is less than 2 atomic %, it becomes a rhombohedral R-Fe system, so a high coercive force cannot be expected. Moreover, if it exceeds 28 at%, there will be a large amount of B-rich non-magnetic phase, and the residual magnetic flux density will drop significantly. However, for the magnet according to the present invention, it is preferable that the B content is 88 atoms or less, and if it is more than that, fine R* Fe
+a It is difficult to obtain the B phase, and the coercive force becomes small.

Co is an element that is effective in increasing the Curie point of this magnet, and basically replaces the Fe site to create R* Co,
a B is formed, but this compound has a small crystal anisotropy magnetic field, and as the amount increases, the coercive force of the magnet as a whole decreases. Therefore, I can be considered as a permanent magnet.
In order to provide a coercive force of KOe or more, the content is preferably within 50 atomic %.

AI has the effect of increasing coercive force. (Reference 7: Zha
ng Maocai et al., Proceedings
of the 8th International
al Workshop on Rare-Ea
rth Magnets, 1985, p.
541) This document 7 shows the effect on a sintered magnet, but the effect also exists in the magnet according to the present invention.

However, since AI is a non-magnetic element, increasing the amount added will lower the residual magnetic flux density, and if it exceeds 15 at %, the residual magnetic flux density will be lower than that of hard ferrite, so it cannot fulfill its purpose as a rare earth magnet. . Therefore, the amount of A1 added is preferably 15 atomic % or less.

Next, embodiments of the present invention will be described.

〔Example〕

(Example 1) An alloy having a composition as shown in Table 1 was melted in an induction furnace and poured into a twin-roll thin plate continuous casting machine consisting of steel rolls with a diameter of 150 mm and a width of 200 mm. At this time, the roll rotation speed was 40 RPM. The thickness of the thin plate was approximately 3 mm (the cooling rate at this time was approximately lθ''
"C/5ec) This was annealed at 800°C for 4 hours and its magnetic properties were measured. As a comparative example, the same composition was used in a ceramic mold with a heating element (cooling rate 10-s"C/5ec).
The following are the measurement results of a 10009CX 24-hour annealed ingot (thickness: 10 mm) that was cast and roughened and turned into an ingot. The results are shown in Table 2.

It can be seen that by using the present invention and specifying the cooling rate, high magnetic properties can be obtained with low temperature and short time annealing.

Table 1 Table 2 (Example 2) No. 11 composition P that had the highest performance in Table 1 of Example 1
Using r+s Dye Fes t Ba, a plate with a thickness of about 10 mm was produced by lowering the roll rotation speed to IORPM. This was molded to a thickness of 3 mm (processing [70%)] at 1000° C. using a hot press (using graphite as the mold), and then heat treated at 1000° C. for 4 hours to measure the magnetic period characteristics.

As a comparative example, the ingot used in Example 1 was molded and heat treated under the same conditions. The results are shown in Table 3.

Table 3 shows that anisotropic magnets can also be produced with higher performance according to the present invention.

(Example 3) Same as Example 2 <Prs a Dye Fes v
Using Ba, set the rotation speed to 1100RP this time and set it to 0.
．． A thin plate with a thickness of 5 mm was prepared, and then annealed at 800° C. for 4 hours. This was mechanically crushed to an average particle size of 20μm, and after kneading with 2wt% of epoxy resin, 20KO
It was molded into a block shape in a magnetic field of e, and cured at 150°C to obtain a resin-bonded magnet. Magnetic properties were measured in two directions: the direction of magnetic field application and the direction perpendicular to that direction.

The results are shown in Table 4.

Table 4 It can be seen that according to the present invention, it is possible to create an anisotropic resin-bonded magnet.

(Example 4) Same as Example 2.3 <Prt s DY* Fee 1
B4 was used to cool the molten metal at various cooling rates. The cooling rate was adjusted by adjusting the rotational speed of the twin rolls used in Example 1.2.3 and the mold material for normal casting (water-cooled shell, iron, ceramic, controlled cooling ceramic mold with heating element). All finished slabs were heated at 1000℃ for 12 hours.
Heat treatment was performed and coercive force was measured. The results are shown in Figure 1.

It can be seen that the coercive force iHc increases as the cooling rate increases. This is because the grains have become finer. 10
Even at a cooling rate of 6″C/sec, iHc is obtained, but the squareness of the hysteresis curve deteriorates and the coercive force mechanism becomes pinning (the appearance of an amorphous phase), so the cooling rate of 10″C/s
ec is the limit for a magnet that has the truncation curve of the nucleage layer model.

〔Effect of the invention〕

As described above, according to the method of manufacturing a permanent magnet of the present invention, sufficient coercive force can be obtained without going through the steps of crushing and sintering (with only a short heat treatment at a low temperature), and anisotropic resin bonding can be achieved. The effect is that it is also possible to manufacture magnets.

[Brief explanation of drawings]

Figure 1 shows the cooling rate and coercive force i in an embodiment of the present invention.
Graph showing the relationship between Hc. Applicant: Seiko Epson Corporation, -f.

Claims (3)

[Claims] (1) In a method for manufacturing a permanent magnet whose basic components are rare earth elements (including Y), transition metals, and boron, the alloy is melted at a cooling rate of 10^-^1 to 10^6°C/sec. After cooling, heat treatment is performed at a temperature of 250°C or higher,
A method for manufacturing a permanent magnet characterized by magnetically hardening it. (2) After melting in the method for manufacturing permanent magnets whose basic components are rare stone elements (including Y), transition metals, and boron.
After cooling the alloy at a cold pouring rate of 0^-^1 to 10^6°C/sec, the crystal axes of the crystal are oriented in a specific direction by hot working at a temperature of 500°C or higher. A method for producing a permanent magnet, comprising making the magnet magnetically anisotropic. (3) After melting in the method for manufacturing permanent magnets whose basic components are rare earth elements (including Y), transition metals, and boron,
After cooling the alloy at a cooling rate of 10^-^1 to 10^6°C/sec, it is then hot worked at a temperature of 500°C or higher, and then heat treated at a temperature of 250°C or higher to magnetically Method for producing a permanent magnet characterized by being hardened