JPS63285909A - Permanent magnet and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve performance, and to reduce cost by specifying the crystal mean grain size of a magnet and specifying each concentration of carbon and oxygen contents in the magnet using a rare earth element, iron and boron as basic ingredients. CONSTITUTION:In a permanent magnet employing a rare earth element (where including Y), iron and boron as basic ingredients, the crystal mean grain size of the permanent magnet ranges from 0.04mum to 100mum, carbon and oxygen contents respectively range from 400ppm to 1000ppm, and the rise of an initial magnetization curve is made steep. For shape such a permanent magnet, these basic ingredients are casted so that the crystal mean grain size ranges from 0.04mum to 100mum, and thermally treated at 250 deg.C or higher. The basic ingredients are casted, and hot-worked at a temperature of 500 deg.C or higher, thus changing the basic ingredients into anisotropy. Or the basic ingredients are hot-worked, and thermally treated at 250 deg.C or higher, thus acquiring the permanent magnet. The permanent magnet is also obtained in such a manner that the basic ingredients are cooled so that the crystal mean grain size ranges from 0.04mum to 130mum, thermally treated at a temperature of 250 deg.C or higher, crushed, and kneaded and bonded with a resin.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a permanent magnet whose basic components are earthworks and boron of iron, and a method for manufacturing the same.

[Conventional technology]

Permanent magnets are one of the 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 and more efficient electrical products,
Permanent magnets are also required to have increasingly higher performance. Typical permanent magnets currently in use are alnico, hard ferrite, and rare earth-transition metal magnets. In particular, R-Co permanent magnets, which are rare earth-transition metal 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-Fe-B permanent magnets as shown in the following literature.

(1) Sintering method based on powder metallurgy.

(Reference 1, Reference 2) ■ Create a quenched thin piece with a thickness of about 30 μm using the quenched ribbon manufacturing equipment used to manufacture amorphous alloys, and then make the thin piece! 4.Resin bonding method using quenched flakes by melt spinning method to make magnets using sushi stuffing method (Reference 3, Reference 4) (3) The quenched flakes used in method (2) above are
A method that performs mechanical alignment treatment using a two-step hot press method.

(Reference 4, Reference 5) Here, Reference 1: JP-A-59-46008; Reference 2: M
, Sagawa, S., Fuji imura, N., T.
ogawa, H, Yamamo to, and Y.
Matsuura; J, Appl, Phys, Vo 1
, 55 (6) 15 Mar.

h 1984. P2O83° Document 3: JP-A-59-211549: Document 4: R,
W, Lee; Al) pI, Phys, Lett, V
ol, 46 (8), 15APrif 1985.
p790; Document 5: Japanese Unexamined Patent Publication No. 80-100402 Next, the above conventional method will be explained.

First, in the sintering method (1), an alloy ingot is produced by melting and casting, and this ingot is crushed to a particle size of about 3 μm, kneaded with a binder, and press-formed in a magnetic field to complete a compact.

This compact is sintered in argon gas at a temperature of around 1100°C for 1 hour, and then heat treated at a temperature of around 600°C to improve its coercive force.

In the resin bonding method using quenched thin flakes by the melt spinning method, first, the rotation speed of the quenched ribbon manufacturing equipment is optimized, and R-Fe- A ribbon-shaped thin piece of B alloy with a thickness of 30 μm is produced. The crystal axes of the crystal grains in this flake are isotropically distributed and magnetically isotropic. If the particles are crushed to an appropriate particle size, kneaded with resin, and press-molded, an isotropic magnet can be obtained. It will be done.

The two-step hot press manufacturing method (3) is as follows: (2)
) The ribbon-shaped quenched flakes used in
”.Next, press at 700℃ and 0.7ton.
/cm' for a few seconds to reduce its thickness to 1/2 of the original thickness, the alloy becomes anisotropic, forming a dense and anisotropic R-
Fe-B magnets can be manufactured.

Also, Liquid dynamic compac
An alloy having a coercive force is also produced in a bulk state by the ion method (hereinafter referred to as LDC method). (Reference 6) Reference 6: T, S, Chin et al., J, AppI.

Phys, 59 (4), 15 February 198
B, p1297 [Disadvantages that the invention seeks to solve] Permanent magnets whose basic components are rare earth elements, iron, and boron can be manufactured using the conventional techniques described above, but these manufacturing methods have the following drawbacks. I'm growing up.

For the sintering method (1), it is essential to turn the alloy into powder, but in the case of R-Fe-B magnet alloys, the powder is highly active against oxygen, so it is used in the sintering method. Powder must be strictly controlled, and expensive equipment such as an inert gas atmosphere is required.

In addition, in the sintering method, there are problems such as the carbon in the binder having a negative effect on magnetic performance and the difficulty in handling the green body, which reduces production efficiency. It is difficult to say that this is a method that can fully take advantage of low raw material costs.

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/see, and variations in the cooling rate can greatly affect performance. Affect.

■ The structure contains not only crystalline phases but also amorphous phases, and the magnetic properties are highly dependent on these phases. Therefore, it has poor stability at high temperatures where the amorphous phase crystallizes.

■ Hot working for anisotropy also needs to be done in a short time to prevent crystallization, and requires advanced manufacturing technology, resulting in high manufacturing costs.

■ Since the coercive force mechanism has pinning and has a high coercive force to compensate for poor temperature characteristics, it is extremely difficult to attach and detach the magnet.

There are many problems caused by productivity.

The LDC method also has problems such as expensive equipment and poor production efficiency.

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]

The permanent magnet of the present invention is a magnet whose basic components are a rare earth element (including Y), iron, and boron, and the average crystal grain size of the magnet is 0.04 μm or more and 100 μm or less,
Containing carbon and oxygen are each 400 ppm or less, 11000
It is a permanent magnet characterized by a pp or less.

However, the first method for manufacturing permanent magnets is a method for manufacturing magnets whose basic components are rare earth elements (including Y), iron, and boron, in which the average crystal grain size is 0.04 μm or more and 100 μm or less. Then cast at 250°C.
This is a method for manufacturing a permanent magnet, which is characterized by performing the above heat treatment.

A second method for manufacturing a permanent magnet is characterized in that after casting in the first manufacturing method, the magnet is hot worked at a temperature of 500° C. or higher to make the magnet anisotropic. It's a method.

The third method for manufacturing a permanent magnet is a method for manufacturing a permanent magnet, which is characterized in that, after the hot working in the second manufacturing method, heat treatment is performed at 250° C. or higher.

The fourth method of manufacturing the permanent magnet is to further speed up the cooling in the first manufacturing method to obtain a magnet with a diameter of 30 μm or less, and then
This method of producing a permanent magnet is characterized in that the magnet is heat-treated at a temperature of 50° C. or higher, then pulverized, kneaded with a resin, and bonded.

[For use]

A preferred composition of the permanent magnet used in the present invention, which has rare earth elements, iron, and boron as basic components, is 8 to 30 at. % of rare earth elements, 2 to 28 at. % of boron, and the balance is iron.

Rare earth elements include Y s L a s C8% P
r 1Nds PmlSmt Eus Gdt Tb
s DY% HotEr, T m s Y b 1L
u is used, but N d 1P r is particularly preferred. Also, these rare earth elements are 2! ! The above may be included. In addition to the basic components mentioned above, impurities unavoidable in the manufacturing process may be included, such as cobalt to improve the Curie temperature and temperature characteristics, and A1, C to improve the coercive force.
r, Mos WlNblTalZrs Hft Ti, etc.

When R-Fe-B magnets are classified based on their coercive force mechanism,
In the prior art, the sintering method (1) is a nu-creation type, and the quenching methods (2) and (3) are a vinyl/vinyl sintering method.
Getaibu. These two divisions can be easily made by examining the rise of the truncation curve. In other words, in the nucleation type, the initial magnetization curve rises steeply, and in the pinning type, the initial magnetization curve is difficult to rise while the magnetization is pinned by precipitates, and rises suddenly when the pinning force is exceeded. becomes. Generally, in R-Fe-B magnets, the residual magnetic flux density Br
Since the temperature coefficient of coercive force iHc is large, iHc is made large to cover this.

However, if iHc is increased, it becomes very difficult to attach and detach the magnet. In particular, in rotating machines, etc., which are the mainstream of recent rare earth magnets, multi-pole magnetization is often required, and this problem is becoming increasingly important. Considering this point, the Nucleage Desired type has a steep initial magnetization curve, so it can be magnetized to some extent even without a sufficient magnetic field, but the pinning type can hardly be magnetized if the magnetic field is within the pinning force. This means that it cannot be magnetized. In this respect, the New Creation type is advantageous.

However, the sintering method involves the steps of pulverization and sintering as described above, making powder control difficult and having the drawbacks of high oxygen and carbon concentrations. In order to solve these problems, the coercive force mechanism should be a Nuclinisicon model and be able to be magnetized without going through the steps of crushing and sintering.

Generally, in the nucleation model, the main phase (R*Fc, aB phase, R is the rare earth element in the case of rare earth-iron-boron system) approaches the critical radius of a single magnetic domain, so that a reverse magnetic domain cannot easily be generated. This is said to be the cause of coercive force generation. However, although the critical radius of the Ra'F'e Ia''B phase is on the submicron order, the grain size of the sintered magnet is about 10 μm. Since it goes through a process of pulverization, the surface area increases significantly and the oxygen concentration increases at that stage, so in reality, it is impossible to create a sintered body with a particle size close to the critical radius.

Conversely, as long as the magnet complies with the coercive force of the Nucleage 9 model, you can obtain sufficient coercive force by increasing the cooling rate during casting than usual, without having to go through the process of crushing and sintering the casting ingot. R* to the possible particle size
Fes a B phase can be controlled. With this method, it is possible to obtain coercive force with a bulk die, and productivity problems such as difficulty in powder management are freed. Furthermore, even though the cooling rate is faster than usual, there is no need to form an amorphous phase as in the conventional rapid cooling method, and the structure consists only of crystalline materials, so hot working for anisotropy can also be done at high temperatures. It can be performed stably and with high productivity.

With magnets produced using conventional sintering methods, it was not possible to crush the finished magnets into resin-bonded magnets. This is due to mechanical strain caused by crushing and too large crystal grains. However, if the particle size is controlled by changing the cooling rate using the present invention, the particle size of resin-bonded magnet powder (several to several tens of μm) can be reduced.
Even with m), it is possible to create powder that increases coercive force,
It becomes possible to create a resin bonded magnet according to the Nucleage 9 model.

As mentioned above, R- according to the nucleagin model
In order to obtain coercive force in a bulk mill in a Fe-B based magnet, its crystal grains must be appropriate. That is,
Even after hot working with an average grain size of over 100 μm upon cooling, the coercive force is still not sufficient for a rare earth magnet.
, 0.04 μm or less is less than the critical radius of a single magnetic domain, and the initial magnetization curve including the amorphous phase becomes a pinning type, so the average grain size must be 0.04 or more and 100 μm or less. These particle size controls can be accomplished by adjusting the mold material and heat capacity of the mold, or by using cooling rolls at low speeds that do not form an amorphous phase.

Heat treatment after cooling is necessary to diffuse the Fe phase that exists as a primary crystal in the alloy and eliminate the magnetically soft phase, and of course it is important to perform the same heat treatment after hot working. It has the effect of improving magnetic properties.

Hot working at a temperature of 500°C or higher has the effect of orienting the crystal axes of the crystal grains to make them anisotropic, and also has the effect of making the crystal grains finer, significantly improving magnetic performance. . Setting the upper limit of the particle size to 30 μm or less by further increasing the cooling rate is effective in producing powder having coercive force when producing a resin-bonded magnet by pulverization.

Oxygen and carbon'e4 degrees are within the claimed range because, as mentioned above, the present invention does not require a pulverizing step unlike the sintering method, and also does not require nurturing binder as a molding aid during molding. can be easily accommodated.

Next, examples of the present invention will be described.

〔Example〕

(Example 1) Table 1 shows the composition of the permanent magnet alloy whose basic components are various rare earth elements and iron boron used in this example.

First, an alloy having a desired composition was melted in an Ar atmosphere using a low frequency melting furnace, and cast into various molds at 1000°C. After 20 minutes, the cast alloy was taken out. At this time, the rare earth metal used was one with a purity of 95% (impurities were mainly other rare earth metals), the transition metal used was one with a purity of 99.9% or more, and the boron used was Ferroboro 7 alloy. .

These cast alloys are then heat treated at 250°C or higher (1
000°C for 24 hours), cutting and grinding were performed to obtain a permanent magnet.

Table 2 shows the magnetic performance and average grain size of each composition when cast using an iron mold.

Further, FIG. 1 shows the relationship between the average grain size (μm) during casting and the coercive force iHc after hot pressing for samples using compositions No. 3, No. 4, and No. 4 in Table 1. At this time, the grain size was controlled using various molds such as water-cooled copper molds, iron molds, and ceramic molds, and by applying vibration to the molds. This result shows that a permanent magnet with high coercive force can be obtained by casting with controlled particle size.

Table 1 Table 2 (Example 2) The composition of the permanent magnet alloy shown in Table 3 was cast using a water-cooled copper mold in the same manner as in Example 1, and then hot pressed at 1000°C to obtain an anisotropic It became sexualized.

Table 4 shows the average grain size and magnetic performance when heat treated at the casting stage and the average grain size and magnetic performance after hot pressing.

Also, No. 11 and No. 13. Table 5 shows the magnetic properties of samples No. 14 when they were further heat-treated at 1000° C. for 24 hours after hot pressing.

Table 3 Table 4 Table 5 As is clear from the results, it can be seen that hot working reduces the grain size and significantly improves the magnetic performance.

It is also seen that heat treatment improves magnetic performance.

(Example 3) P r s tF with the highest performance in Example 2
The circumferential speed of twin rolls (chrome-plated copper rolls) with a radius of 30 mm is 10 m/s.
A molten metal having the above composition was poured with Ar gas and rapidly cooled to form a ribbon. At this time, the ribbon thickness was 50 μm. This was annealed at 700°C for 0°5 hours, pulverized to an average particle size of 20 μm, and kneaded with 2 wt% of epoxy resin.
After molding in a magnetic field of 15 KOe, a resin-bonded magnet was prepared at a temperature of 150°C.

As a comparative example, using conventional technology (2), Nd.

*20 single rolls of FettBa composition with a radius of 60 mm
It was rotated at m/s, the molten metal was injected in the same way, and the ribbon was rapidly cooled to create a ribbon.The ribbon thickness at this time was 25 μm. Grind this in the same way as above.

As a resin bonded magnet by kneading. Table 6 shows the magnetic properties at each measurement magnetic field. However, the saturation value when pulse magnetized at 40KOe is (BH)ram x =8.
5 (MGOe), 1Hc = 12.9K Oe s Conventional technology product (BH) max = 8.9 (MGOc) iH
c = 18.7 KOe.

Table 6 It can be seen that when the present invention is used, high characteristics can be obtained even in a low magnetic field. As mentioned above, this is very advantageous for applications such as rotating machines.

〔Effect of the invention〕

As described above, according to the permanent magnet and its manufacturing method of the present invention, sufficient coercive force can be obtained in the bulk state without going through the steps of crushing and sintering, and the manufacturing process can be simplified and costs can be reduced. In addition, it becomes possible to manufacture high-performance permanent magnets. Furthermore, by adjusting the particle size, it is possible to manufacture a resin-bonded magnet that has a steep initial magnetization curve and is easy to use.

[Brief explanation of the drawing]

? Figure g1 is a graph showing the relationship between coercive force iHc after hot pressing and average grain size after casting in Examples of the present invention. Above Figure 1

Claims (5)

[Claims] (1) In a permanent magnet whose basic components are rare earth elements (including Y), iron, and boron, the average crystal grain size of the permanent magnet is 0.04 μm or more and 100 μm or less, and the carbon and oxygen content is 400 PPM or less, respectively. , 1000 PPM or less, and the initial magnetization curve rises rapidly. (2) Rare earth elements (including Y), iron and boron,
A method for producing a permanent magnet as a basic component, which comprises cooling the permanent magnet so that its average crystal grain size becomes 0.04 μm or more and 100 μm or less, and then heat-treating it at 250° C. or more. (3) In a method for manufacturing a permanent magnet whose basic components are rare earth elements (including Y), iron, and boron, the magnet is cast so that the average crystal grain size is 0.4 μm or more and 100 μm or less, and then heated at 500°C. A method for producing a permanent magnet, comprising making the magnet anisotropic by hot working at a temperature above. (4) In a method for manufacturing permanent magnets whose basic components are rare earth elements (including Y), iron, and boron, they are cast so that the average crystal grain size is 0.4 μm or more and 100 μm or less, and then heated at 500°C or higher. A method for producing a permanent magnet, which comprises making the permanent magnet anisotropic by hot working at a temperature of 250° C. or higher, and then subjecting the permanent magnet to heat treatment at a temperature of 250° C. or higher. (5) In a method for manufacturing a magnet whose basic components are rare earth elements (including Y), iron, and boron, the magnet is cooled to have an average crystal grain size of 0.04 μm or more and 130 μm or less, and then cooled to 250° C. or more. A method for producing a permanent magnet, which comprises heat-treating the magnet at a temperature of , followed by pulverization, kneading with resin, and bonding.