JPS6329908A - Manufacture of r-fe-b rare earth magnet - Google Patents

Abstract

PURPOSE:To increase coercive force to a permanent magnet manufactured, and to display a large effect for improving heat stability by bringing a specific alloy, mean crystal grain size of which extends over 0.01-0.5mum, to an anisotropic state through warm processing and thereafter executing specific heat treatment. CONSTITUTION:An R-Fe-B group alloy, mean crystal grain size of which extends over 0.01-0.5mum, is brought to an anisotropic state through warm working, and thermally treated. R in the alloy represents one kind or more of rare earth elements containing Y, and the alloy includes an R-Fe-Co-B group alloy, one part of Fe of which is replaced with Co, and an R-Fe-B-M group alloy or an R-Fe-Co-B-M group alloy using the combination of one kind or more of Si, Al, Nb, Zr, Hf, Mo, Ga, P, C as additional elements (M). Heat treatment consists of processes in which the alloy is heated at a temperature to 900 deg.C from 600 deg.C, held for the time to 240 min from 0 min, and cooled at a cooling rate of 1 deg.C/sec or more. Accordingly, a permanent magnet thus manufactured has coercive force larger than conventional devices, and has a large effect for improving heat stability.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides R-Fe-B rare earth 6n using an ultra-quenching method.
The present invention relates to a method for producing stone (R represents one type or a combination of two or more types of rare earth elements including Y).

[Conventional technology]

The manufacturing process of R-Fe-B rare earth magnets having a high energy product can be roughly divided into two types.

The first method is the R-F
This is a powder metallurgy process similar to the method used to manufacture Sm, Co-based rare earth magnets, in which an ingot of e-B alloy is crushed, molded in a magnetic field, and then sintered.

This method is a practical method because it has the advantage of being able to manufacture magnets of various shapes. However, there is a drawback that in order to satisfy thermal stability, it is necessary to add Dy, which is a rare resource and is expensive.

The second method is, for example, as described in Japanese Patent Application Laid-Open No. 100402/1982, after compacting alloy powder produced by an ultra-quenching method by hot pressing at 600 to 750°C, swaging is performed. This is a method of obtaining an anisotropic magnet with anisotropy in the compression direction.

Magnets made by this method have the advantage of having better thermal stability than sintered bodies when compared at the same coercive force level.

However, in order to further improve thermal stability, a magnet with a larger coercive force has been desired.

An object of the present invention is to provide a manufacturing method for increasing the coercive force of an anisotropic magnet using an ultra-quenching method and warm working.

[Means for solving the problem] In the present invention, the following technical means are used to achieve the above-mentioned agreement.

That is, R-F with an average crystal grain size of 0.01 to 0.5 μm
e-B alloy (R is one or more rare earth elements including Y, or R-Fe-Co- in which a part of Fe is replaced with Co)
Contains B-based alloy, and further contains Si as an additional element (M),
AI! , Nb, Zr, Hf, Mo, Ga, P.

R-Fe- using one type or a combination of two or more types of C
The above object was achieved by heat-treating a material (including B-M alloy and R-Fe-Co-B-M alloy) by warm working to make it anisotropic.

The above alloy preferably has R: 11 to 18atχ, B: 4
-1at%, Co: 30atX or less, balance Fe and unavoidable impurities, more preferably R: 11-18atX, B: 4-11atχ
, co=30atx or less, additives: 0.001-3a
tχ (Additive M is Sl, A I! + Nb +
One or a combination of two or more of Zr, Hf+Mo, Ga, P, and C); the balance is Fe and unavoidable impurities.

The above heat treatment is applied to the R-Fe-B alloy at temperatures above 600°C and 90°C.
Preferably, the process includes heating to a temperature of 0° C. or lower, holding the temperature for 0 to 240 minutes, and cooling at a cooling rate of 1° C./sec or higher.

In the present invention, the average grain size of the R-Fe-B alloy is 0.
．． If it exceeds 5 μm, it is disadvantageous because the IHc decreases and the irreversible demagnetization rate at 160° C. becomes 10% or more, resulting in a significant decrease in thermal stability. Also, the average particle size is 0.01μm
If it is less than 1. Hc is low, making it impossible to obtain desired permanent magnet characteristics. Therefore, the average crystal grain size was limited to 0.01 μm or more and 0.5 μm or less.

R-F with average crystal grain size of 0.01 μm or more and 0.5 μm or less
The e-B alloy is produced by the following process.

First, an alloy with a predetermined composition is created by high-frequency melting arc melting or the like, and the alloy is turned into flakes or powder by an ultra-quenching method. Ultra-quenching is carried out by methods such as a single roll method, a twin roll method, an ultrasonic gas atomization method, a high pressure water atomization method, and a high pressure oil atomization method. R produced by these methods
-Fe-B alloys are usually amorphous, a mixture of amorphous and crystalline, or a microcrystalline aggregate, so the average grain size can be reduced by heating it as is or by heating it to a temperature of 500°C to 800°C. Adjust to 0.01 μm or more and 0.5 μm or less. Generally, the residual magnetic flux density of an isotropic R-Fe-B alloy is 7.5 kG or less. It can be said that an R-Fe-B alloy having a residual magnetic flux density of 8 kG or more is anisotropic.

Examples of the warm working method used in the present invention for anisotropy include hot pressing, swaging, rolling, and extrusion. In these processes, the processing temperature is 600 to 75
If the temperature is 0° C. and the strain rate variation is 10 −4 to 10°, anisotropy can be achieved.

The crystal grains of the R-Fe-B alloy that have become anisotropic due to plastic working are crushed in the C-axis direction.

If the average value of the ratio c/a of the average diameter (c) in the direction perpendicular to the C-axis of the crystal grains and the average diameter (a) in the C-axis direction is 2 or more,
This is desirable because a residual magnetic flux density of 8 kG or more can be obtained.

High magnetic properties can sometimes be obtained when the means of plastic deformation is warm swaging.

R-Fe-B alloy means an alloy having RzFe+4B or Rz(Fe, Co)+4B as a main phase. The reason for determining the desirable range of components for a permanent magnet is as follows.

If R (Y is one type of rare earth element or a combination of two or more types) is less than 1 latχ, sufficient Hc cannot be obtained, and 18
Exceeding atχ causes a decrease in Br.

Therefore, the R amount was set to 11 to 18 atχ.

When the amount of B is less than 4atχ, Rz, which is the main phase of the magnet of this system,
Formation of Fe+aB phase is insufficient, and both Br and 1Hc are low. Furthermore, when the amount of B exceeds 1 latχ, Br decreases due to the appearance of phases that are unfavorable in terms of magnetic properties.

Therefore, the amount of B was set to 4 to 1 latχ.

When Col exceeds 30 atχ, the Curie point improves, but the anisotropy constant of the main phase decreases, making it impossible to obtain high Hc.

Therefore, the amount of co was set to 30 at% or less.

Moreover, the reason for determining the elements that may be added as additive elements is as follows.

Si raises the Curie point and A6. Nb, G
a.

P has the effect of increasing coercive force.

C is an element that is likely to be mixed in during the electrolysis of rare earth elements, but if it is in a small amount, it will not adversely affect the magnetic properties (5). N
b, Zr + Hf + Nb, and Mo improve corrosion resistance.

If the amount of these elements added is less than O,0O1atZ, the effect of the additive is insufficient, and if it exceeds 3at%, B
This is not preferable because it causes a large decrease in r. Therefore, the amount of additive is 0
．． 001 to 3atχ.

Note that impurities contained in ferroboron, reducing agents mixed in during reduction of Nd and other rare earth elements, and impurities may be present in the alloy of the present invention.

By applying heat treatment to an R-Fe-B magnet that has been made anisotropic through warm working, the coercive force of the IF stone can be increased.

The heat treatment temperature is preferably 600°C or higher and 900°C or lower. The reason for this is that when the heat treatment temperature is less than 600°C, no increase in coercive force is observed, and when it is higher than 900°C, the coercive force is lower than before the heat treatment.

The holding time may be a time during which the temperature of the sample becomes uniform. Therefore, in consideration of industrial productivity, the duration was set to 240 minutes or less.

The cooling rate must be 1° C./sec or more. If the cooling rate is less than 1° C./sec, the coercive force will be lower than before the heat treatment. Note that the cooling rate here means the average cooling rate until the heat treatment is completed.

〔Example〕

The present invention will be explained in more detail with reference to Examples below.

Example I Nd+7Fe+sBe alloy was produced by arc melting,
A flake-like thin piece of this alloy was produced by a single roll method in an Ar atmosphere. The thin piece obtained at a roll circumferential speed of 30 m/sec was amorphous with a thickness of about 30 μm, and was found to be a mixture of amorphous and crystalline as a result of X-ray diffraction.

This flake was coarsely ground to 32 meshes or less, and molded into a molded body. Molding pressure is 5 tons
/ca, and no magnetic field was applied. The density of the molded body is 5-8 g/cc. The obtained molded body was heated to 700℃
Hot pressed. The temperature of the hot press is 700"C
The pressure is 2 ton/cI11. The density obtained by hot pressing was 7.30 g/cc, and the density was sufficiently increased by real pressing. The densified bulk body was further processed at 700°C. The height of the sample was adjusted so that the compression ratio was 3 before and after swaging. (If the height before swaging is ho and the height after swaging is h, then h o / h = 3) The swaged sample was heated to 750°C in an Ar atmosphere, and 6
After holding for 0 minutes, it was cooled with water. The cooling rate at this time is 7℃/
It was sec.

Table 1 shows the 6P1 characteristics before and after heat treatment. It can be seen that the coercive force is improved by heat treatment.

Table 1 Example 2 An R-Fe-B permanent magnet was produced in the same manner as in Example 1 except for the compression ratio. The results are shown in Table 2.

It can be seen that the coercive force increases after heat treatment regardless of the compression ratio.

Table 2 Example 3 An R-Fe-B permanent magnet was produced by the same method as in Example 1 except for the holding time in the heat treatment.

The results are shown in Table 3.

Table 3 Example 4 An R-Fe-B permanent magnet was produced in the same manner as in Example 1 except that the heat treatment temperature was changed and the holding time was changed to 10 minutes. The results are shown in Table 4.

Table 4 Example 5 An R-Fe-B permanent Eu stone was produced by the same method as in Example 1 except that the holding time was 10 minutes and the cooling method was changed. The results are shown in Table 5.

Table 5 Example 6 R-Fe was prepared in the same manner as in Example 1 except for changing the composition.
-B series permanent magnets were produced. The results are shown in Table 0.

Table 6 Example 7 An anisotropic bonded magnet was produced in the same manner as in Example 1 except that the crystal grain size was changed by changing the swaging temperature. The results are shown in Table 7.

It can be seen that an average crystal grain size of 0.001 μm or more and 0.5 μm or less has good magnetic properties.

Table 7 [Effects] As described above, the R-Fe-B permanent magnet according to the present invention has a larger coercive force than the conventional magnet, and has a great effect on improving thermal stability.

Claims (4)

[Claims] (1) R- with an average crystal grain size of 0.01 to 0.5 μm
Fe-B alloy (R is one or more rare earth elements including Y, or R-Fe-Co in which a part of Fe is replaced with Co)
- Contains B-based alloy, and further includes Si and A as additional elements (M)
R-Fe-B-M alloy using one or a combination of two or more of L, Nb, Zr, Hf, Mo, Ga, P, and C, R
- Fe-Co-B-M alloy) is made anisotropic by warm working, and then subjected to heat treatment.
A method for manufacturing an e-B permanent magnet. (2) After heating the R-Fe-B alloy that has been made anisotropic by warm working to a temperature of 600°C or more and 900°C or less, hold it for 0 minutes or more and 240 minutes or less, and cool it at a cooling rate of 1°C/sec or more. Claim 1, characterized in that the process comprises a cooling process.
A method for producing an R-Fe-B permanent magnet as described in 2. (3) R-Fe-B alloy has R: 11 to 18 at%, B
4 to 11 at%, Co: 30 at% or less, and the remainder Fe and unavoidable impurities. (4) R-F according to claim 1, characterized in that the amount of the additional element added is 0.001 to 3 at%.
A method for manufacturing an e-B permanent magnet.