JPH03175602A - Manufacture of permanent magnet - Google Patents

Abstract

PURPOSE:To obtain a permanent magnet characterized by high magnetic flux density, excellent square-shapedness and excellent oxidation resistance furthermore without necessarily requiring rare earth metal and B by heat-treating an alloy comprising Zr of specified atomic % and the substantial amount of Co for the remaining part. CONSTITUTION:An alloy comprising Zr of 20atom.% and the substantial amount of Co for the remaining part is heat-treated at 300-1,000 deg.C. For example, at first Zr and Co are compounded at the rare of 15% Zr and 85% Co in atomic fraction. Arc melting is performed by using a water-cooled copper boat in an Ar atmosphere. Then, the obtained alloy is cooled at a super quench speed by a single-roll method using a copper roll having the diameter of 300mm at a speed of 40m/sec in the Ar atmosphere. Thus the ribbon-shaped alloy which has the average grain diameter of 0.07mum in main phase and is cooled at the super quick speed is manufactured. Then the super quench ribbon-shaped alloy described above is heat-treated in vacuum at 700 deg.C for 10 minutes, and the ribbon-shaped permanent magnet is manufactured. Or the alloy is crushed and the alloy powder is obtained. Epoxy resin is added and mixed. Thereafter, the powder is compressed and molded, and curing is performed. Thus the bond magnet is manufactured.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for manufacturing a permanent magnet.

(Prior Art) Rare earth metal-iron based magnets have been known as high-performance magnets. Manufacturing methods for this type of magnet include the powder metallurgy method (Japanese Patent Application Laid-Open No. 59-48008), the ultra-fast metal method (Japanese Patent Application Laid-Open No. 59-64739), and mechanical alloying a.
(L, 5chultz et al, J, Appl, P
hys, (10) (198g) p5302, etc.). However, since the permanent magnets of this type mainly consist of light rare earth metals and iron, there are problems in that they have poor corrosion resistance and require the use of large amounts of relatively expensive rare earth metals.

On the other hand, recently, Mitra Ghemawat et al.
989 rod with IEEE Trans, on Magn, M
CogoZ r 16 in AG-225p3312
It has been reported that ultra-quenched alloys with compositions of B4 and C011Oz r 1gB2 can obtain coercive forces of about 3 kOe. However, these super-quenched alloys have the disadvantage that their magnetic properties change greatly depending on the manufacturing conditions if they are left super-quenched, and their squareness is poor, making it impossible to obtain stable permanent magnets.

(Problems to be Solved by the Invention) The present invention has been made to solve the above-mentioned conventional problems, and does not necessarily require rare earth metals or B, has high magnetic flux density, good squareness, and The purpose is to provide a permanent magnet with excellent oxidation resistance.

[Configuration of the Invention (Means for Solving the Problems) The method for manufacturing a permanent magnet according to the present invention is as follows: 20, “n(
% or less of Zr and the remainder is substantially Co':r:i
”.

It is characterized by heat treating the alloy at 300 to 1000°C.

The above alloy can be obtained by the following method.

(2) It is obtained by ultra-quenching an alloy material consisting of 20 atomic % or less of Zr and the balance substantially of Co. Examples of this ultra-quenching method include, for example, a single roll method, a twin roll method, etc., a gas atomization method, and RDP (Rotating Dlsk P), which injects a molten alloy onto a rotating disk.
rocess) method etc. may be adopted.

In such ultra-rapid cooling, the average grain size of the main phase is set to 0.0.
The processing conditions are controlled so that the thickness is within the range of 1 to 20 μm. Furthermore, if the alloy after super-quenching contains an amorphous state or is entirely amorphous, it is desirable to control the average grain size by heat treatment at a temperature higher than the crystallization temperature. Furthermore, during ultra-quenching, A r SHe is used from the viewpoint of preventing oxidation and improving magnetic properties.
It is preferable to carry out in an inert gas atmosphere such as SN 2 or in a flow.

(2) A mixed powder consisting of 15 atomic % or less of Zr powder and the remainder being substantially Co powder is alloyed by solid phase reaction. As this solid phase reaction means, for example, a method of mechanical alloying using a planetary ball mill, a rotary ball mill, an attritor, a vibrating ball mill, a screw ball mill, etc. can be adopted. In such a solid phase reaction, treatment conditions are controlled so that the average crystal grain size of the main phase is in the range of 0.01 to 20 μm. Further, if the alloy after the solid phase reaction contains an amorphous state or is entirely amorphous, it is desirable to control the average grain size by heat treatment at a temperature higher than the crystallization temperature.

Furthermore, from the viewpoint of preventing oxidation and improving magnetic properties, the solid phase reaction is preferably carried out in an atmosphere of an inert gas such as Ar5He or N2 or an atmosphere such as an organic solvent that does not come into contact with the atmosphere.

The reason for limiting the amount of Zr in the above alloy is that the amount of Zr is 20
This is because the magnetic flux density decreases when the amount exceeds atomic %. From the perspective of increasing coercive force, the lower limit of Zr is as follows:
It is desirable to set it to 6 atom%. In addition, from the viewpoint of improving coercive force, part of Zr is replaced with Hf % T and rare earth metal, and part of Co is replaced with CSB, P, Ge, S.
i, AN, V.

Cr s M n % N 1 , Cu SZ n S
G a % N b % MoSAg, Ta, W, P t
You may replace it with

It is desirable that the amount of substitution of these elements be kept at a few atomic percent or less. In addition, although Fe is effective in improving magnetic flux density,
Excessive Fe content causes deterioration of coercive force, so Co8
It is desirable to substitute 0% or less of both. In addition, as starting materials Co2B%Co2P, Fe3BS
Intermetallic compounds such as Fe3C may also be used.

The reason for limiting the above heat treatment temperature is to set the temperature to 300°C.
If the temperature is less than 1,000° C., the magnetic properties such as coercive force cannot be improved, whereas if the temperature exceeds 1000° C., the crystal grains become coarse and the magnetic properties such as coercive force deteriorate. A more preferable heat treatment temperature is
It is in the range of 400 to 900°C.

The heat treatment time is preferably 0.1 to 100 hours. Such heat treatment may be performed by hot pressing. Also during this hot pressing, Ar and He are used from the viewpoint of preventing oxidation and improving magnetic properties.

It is preferable to perform this in an inert gas atmosphere such as N2. By carrying out the heat treatment by hot pressing, there is an advantage that the alloy obtained by the ultra-quenching method (2) above and the alloy obtained by the solid phase reaction (2) above can be integrated. Note that, after hot pressing, heat treatment may be further performed at the above temperature in order to improve magnetic properties.

Moreover, magnetic orientation can be obtained by applying pressure and performing plastic working.

In order to manufacture a bonded magnet from the heat-treated alloy, a method is employed in which a powdered alloy is mixed with an epoxy resin, a nylon resin, or the like, and then molded. When the resin is an epoxy-based thermosetting resin, it is cured at a temperature of 100 to 2 (10°C) after compression molding, and when the resin is a nylon-based thermoplastic resin, injection molding is used. good.

(Function) According to the present invention, an alloy consisting of 20 atomic % or less of Zr and the balance substantially of Co, particularly an alloy having an average crystal grain size of the main phase of 0.
By heat-treating the 01-20 μm alloy at a specific temperature range, rare earth metals, metals, and B are not necessarily required.
It is possible to produce a permanent magnet that has excellent magnetic properties such as increased coercive force and improved squareness, and also has excellent oxidation resistance.

(Example) Examples of the present invention will be described in detail below.

Example 1 First, Zr and Co were mixed so that the atomic fractions were 15% for Zr and 85% for CO, and arc melted using a water-cooled copper boat in an Ar atmosphere. The obtained alloy was super-quenched in an Ar atmosphere at a speed of 40 m/see by a single roll method using a copper roll with a diameter of 300 II 1 ml to produce an ultra-quenched ribbon-like alloy. When this alloy was observed by TEM and SEM, the average grain size of the main right eye was 00
．． It was confirmed that it was 7 μm.

Next, the ultra-quenched ribbon-like alloy was heated at 700°C in vacuum.
A ribbon-shaped permanent magnet was manufactured by performing heat treatment for 10 minutes.

The coercive force of the permanent magnet of Example 1 and the permanent magnet made of the ultra-quenched ribbon-shaped alloy (Comparative Example 1) was measured using a vibrating sample magnetometer.

As a result, the permanent magnet of Example 1 was 2.2k Oe.

The permanent magnet of Comparative Example 1 showed a value of 0.8 kOe, and it was confirmed that the permanent magnet of Example 1 had a high coercive force.

Example 2 First, Zr, Co and B were mixed in atomic fractions such that Zr was 15% and C
The alloy was arranged so that O was 81% and B was 4%, and arc melted using a water-cooled copper boat in an atmosphere of A.
An ultra-quenched ribbon-like alloy was produced by super-quenching by a single roll method using a brass roll of 100 nm. This alloy is TE
When observed with M and SEM, it was confirmed that the average particle size of the main phase was 0.1 μm.

Next, the ultra-quenched ribbon-like alloy was heated at 500°C in vacuum.
A ribbon-shaped permanent magnet was manufactured by performing heat treatment for 10 minutes.

The magnetic properties of the permanent magnet of Example 2 and the permanent magnet made of the ultra-quenched ribbon-like alloy (Comparative Example 2) were measured using a vibrating sample magnetometer. the result,
Shown in Figure 1.

As is clear from FIG. 1, the permanent magnet of Example 2 has significantly improved squareness and coercive force compared to the permanent magnet of Comparative Example 2.

Examples 3-1 to 3-8 Ultra-quenching method similar to Example 1, 500 to 700 in vacuum
Ribbon-shaped alloys having the compositions shown in Table 1 below were prepared by heat treatment at .degree. C. for 10 minutes, and these alloys were ground to an average particle size of 60 .mu.m to obtain alloy powder. Next, 2.5% by weight of each of these alloy powders was added to the epoxy resin, mixed, compression molded, and further heated to 1.5% by weight at 120°C.
Eight types of bonded magnets were manufactured by subjecting them to time curing treatment.

Regarding the bonded magnets of Examples 3-1 to 3-8, the average crystal grain size of the main phase of the alloy powder and the residual magnetic flux density [Br]
, Coercive force [IHc] Maximum energy product [(BH)I
Ilax] was measured. The results are also listed in Table 1.

Example 4 First, Zr and Co were mixed so that the atomic fractions were 15% for Zr and 85% for Co, and arc melted using a water-cooled steel boat in an Ar atmosphere. The obtained alloy was ultra-quenched in an Ar atmosphere at a speed of 40 m/see by a single roll method using a copper roll with a diameter of 300 am to produce an ultra-quenched ribbon-like alloy. Next, this ribbon-shaped alloy is
After pulverizing the powder to about 00 μm, it was hot pressed in an Ar atmosphere at 800° C. and 1.2 ton/cω2 to form a permanent magnet.

Regarding the permanent magnet of Example 4, the residual magnetic flux density [Brl
, coercive force [IHc, maximum energy product ((3H)ma
w was measured using an automatic self-magnetometer. As a result, B
r is l1lkGSiHc is 2.7k Oe, (BH
) maw obtained a value of 10.2 M G Oe. Also, T
When observed by EM and SEM, the average particle size of the main phase was 0.
．． It was confirmed that the thickness was 0.06 μm.

Examples 5-1 to 5-9 Super rapid cooling similar to Example 4, 800°C in Ar atmosphere,
Nine types of permanent magnets having the compositions shown in Table 2 below were manufactured by hot pressing under the conditions of 1.2 ton/a112.

For the permanent magnets of Examples 5-1 to 5-9, the residual magnetic flux density [Brl, coercive force [iHc], and maximum energy product [(BH)maxl] were measured using an automatic self-magnetometer.

The results are also listed in Table 2.

Example 6 First, a Zr powder with a purity of 99.8% and a particle size of 45 μm or less and a CO powder with a purity of 99.9% and a particle size of 100 μm or less were prepared. is 85
%, and milling was performed for 70 hours using a planetary ball mill. In this step, a stainless steel container and a ball were used, and the atmosphere was Ar gas.

Subsequently, the obtained alloy powder was heated at 700°C for 20
A permanent magnet was produced by heat treatment for 1 minute.

The coercive force of the permanent magnet of Example 6 and the permanent magnet (Comparative Example 3) made of the alloy powder after the solid phase reaction was measured using a vibrating sample magnetometer.

As a result, the permanent magnet of Example 6 showed a value of 2.5 kOe, and the permanent magnet of Comparative Example 3 showed a value of 0.1 kOeO.
It was confirmed that this permanent magnet has a high coercive force. In addition, the permanent magnet of Example 6 was T E M and S E
When observed with M, the average grain size of the main) eyes was 0.15μ
It was confirmed that it was m.

Example 7-(~7-11 Solid phase reaction similar to Example 1, 700'Co2 in vacuo
Alloy powders having the composition shown in Table 3 below were prepared by a method of heat treatment for 0 minutes, and 2.5% by weight of each of these alloy powders was added to epoxy resin, mixed, compression molded, and further heated at 120°C. A curing treatment was performed for 1.5 hours to produce 11 types of bonded magnets.

For the bonded magnets of Examples 7-1 to 7-11, residual magnetic flux density [B11, coercive force [jHcl], and maximum energy product [(BH)maxl] were measured. The results are shown in the same third column.
Also listed in the table.

Example 8 First, a Zr powder with a purity of 99.8% and a particle size of 45 μm or less and a Co powder with a purity of 99.9% and a particle size of 10 μm or less were prepared, and these powders had an atomic fraction of Zr of 15%, CO is 8
The mixture was blended at a concentration of 5% and milled for 70 hours using a planetary ball mill. In this step, a stainless steel container and a ball were used, and the atmosphere was Ar gas. Subsequently, the obtained alloy powder was heated to 800°C in an Ar atmosphere.
C. and 1.2 ton/cm2 to produce a permanent magnet.

Regarding the permanent magnet of Example 8, the residual magnetic flux density [B'']
Coercive force [jHcl Maximum energy product [(BH)
maxl was measured using an automatic self-magnetometer.

As a result, Br is 7.8kG, iHc is 2.8k
Oe.

(BH) wax obtained a value of 9.8 MGOe. Also,
When observed by TEM and SEM, it was confirmed that the average particle size of the main particles was 0.07 μm.

Examples 9-1 to 9-11 Solid phase reaction similar to Example 4, 800°C in Ar atmosphere,
Eleven types of permanent magnets having the compositions shown in Table 4 below were manufactured by hot pressing under the conditions of 1.2 ton/cll12.

For the permanent magnets of Examples 9-1 to 9-11, the residual magnetic flux density [B11], coercive force [1tlc], and maximum energy product [(B)l)maxl were measured using an automatic self-magnetometer.

The results are also listed in Table 4.

[Effects of the Invention] As detailed above, according to the present invention, Z of 20 atomic % or less
By heat treating an alloy in which the main phase has an average crystal grain size of 0.01 to 20 μm in a specific temperature range, it is possible to remove rare earth metals and B.
It is possible to provide a method for producing a permanent magnet that does not require a magnet, has excellent magnetic properties such as increased coercive force and improved squareness, and has excellent oxidation resistance.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the magnetic characteristics of the permanent magnets of Example 2 and Comparative Example 2.

Claims (1)

[Claims] A method for producing a permanent magnet, which comprises heat treating an alloy consisting of 20 atomic % or less of Zr and the remainder substantially of Co at 300 to 1000°C.