JPH01175705A - Manufacture of rare earth magnet - Google Patents

Abstract

PURPOSE:To obtain a method for producing rare earth magnet which is superb in density, magnetic properties, and machinability in a short time by applying discharge energy to alloy powder for rare earth magnet and by performing compression molding for improved denseness. CONSTITUTION:Discharge energy is applied to alloy powder for rare earth magnet for performing compression molding for improved denseness. For example, an ingot, where an alloy consisting of Nd 33weight%, B 1.3weight%, and the remainder Fe is fused and cast, is ground by a ball mill to obtain an alloy powder whose grain diameter is approximately 3mum. The alloy powder 5a is filled into a molding cavity 5 of the device show in figure and alloy powder is orientated by applying a magnetic field of 50kOe from an electromagnetic ball piece 1. Then, upper and lower punches 3 and 4 are operated to apply a primary pressure of 10kg/m<2> to the alloy powder and arc discharge is executed between the upper and lower punches 3 and 4 while maintaining that status and by applying current between electrodes 6a and 6b. Then, after the alloy powder reaches 1100 deg.C, pressure is increased to 1tonf/cm<2> as the secondary pressure and conduction of current is stopped simultaneously for performing cooling.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing rare earth magnets, and more specifically,
This invention relates to a method for quickly manufacturing rare earth permanent magnets that are dense and have good magnetic properties, as well as excellent toughness and workability.

(Prior Art) Methods for producing rare earth permanent magnets can be broadly classified into the following two types. The first method is to melt an alloy with a predetermined composition, which is the raw material for the target rare earth magnet, and grind it into an ingot.The alloy powder with the target particle size is then molded into a predetermined shape in a magnetic field. This is a sintering method in which a molded body is sintered under normal pressure and then subjected to heat treatment.

The second method is called a quenching method, and the process proceeds roughly as follows.

First, an alloy of a predetermined composition is melted. The obtained melt is rapidly cooled, for example, by a melt quenching method to form a thin ribbon or flake of the alloy, which is then pulverized. Next, the alloy powder with a predetermined particle size is cold-opened to form a green compact, and then this green compact is warm-formed to form a compact into a predetermined shape. Furthermore, if necessary, this molded body is subjected to warm plastic deformation treatment.

The sintering process in the former sintering method and the hot-opening process in the latter quenching method involve filling alloy powder for rare earth magnets into a predetermined mold and then press-forming while heating. is applied. As a heating method at this time, resistance heating or induction heating is generally adopted.

In addition, in the case of the latter quenching method, it has been proposed to add a predetermined amount of various metal powders as a binder component to the above-mentioned magnetic powder in order to make the final magnet dense and improve workability. (See Japanese Patent Application No. 62-230855).

(Problems to be Solved by the Invention) By the way, in the heating method described above, the time required to heat the alloy powder at a predetermined temperature after filling the mold is limited to the temperature rise of the mold. Including time, it usually takes several hours.

Therefore, each component element in the alloy powder will be exposed to high temperature for a long time until the predetermined temperature is reached.

As a result, active elements such as rare earth elements are oxidized or evaporated during this process, which not only impedes densification but also deviates from the desired magnet composition. A situation occurs where this occurs. Furthermore, by staying at high temperatures for a long time, the crystal grains of the alloy become coarse, resulting in a disadvantage that the coercive force (iHc), which is the most important characteristic for a permanent magnet, decreases.

In particular, this problem is more likely to occur in the latter rapid cooling method than in the sintering method.

In addition, if a binder component is added in the latter method, the alloy powder and various metal powders that are the binder components react with each other during the above-mentioned warm forming process, resulting in iHc.
This may lead to a significant decrease in residual magnetic flux density (Br).

The present invention aims to solve the above-mentioned problems and provide a method for manufacturing rare earth magnets in a short time that have high density, excellent magnetic properties, and improved workability.

(Means for Solving the Problems) In order to achieve the above object, the method for manufacturing a rare earth magnet of the present invention is such that the structure is compacted by compression molding while applying discharge energy to alloy powder for rare earth magnets. Another method is characterized in that the composition is 80 to 99% by volume of alloy powder for rare earth magnets, Pb, Zn, Bi, Sn,
Cd, In.

At least one low melting point metal selected from the group of Ga, Tl or an alloy thereof; Al, Co, Nb.

At least one metal selected from the group of Ti, Cu, Cr, Mn, Zr, and V; or DytOs.

While applying discharge energy to a mixed powder consisting of at least one heavy rare earth metal oxide selected from the group of TbzOs, Hog's, and Era's, and 1 to 20% by volume of a binder component of any one of It is characterized by compression molding and densification.

First, the alloy powder to which the method of the present invention is applied may be any powder that can be used as a raw material powder for rare earth magnets, and is not particularly limited.

Among such alloy powders, those having the compositions described below are suitable. That is, one of them is that the crystal structure is Rt
Fe+ a is of the type known as type B (wherein R is a rare earth element), for example, with the following formula: R(Pe
, X) -M (where R, M.

Each of X is at least one rare earth element; B.

At least one metalloid element selected from the group of C, Si, P; Co, AI, Ga, Pb, Zn, Ti, Zr,
represents at least II metal element selected from the group of Nb, Ni, Cr, Mn, Cu, Sn, and
The composition ratio of R, M, and X is 20 to 40% by weight, respectively.
, 0.1 to 2.0% by weight, and 20% by weight or less).

In the above alloy composition, if R is less than 20% by weight, sufficient iHc cannot be obtained, and if it is more than 40% by weight, the proportion of R, Fe, and B phases decreases, and 'B
This results in a decrease in r.

When M is 0.1 ffl amount% ungrooved, the amount of R, Fe, and B phases produced decreases, and the RzFe+ phase with a low Chieri point increases, B' decreases at room temperature or higher, and 2, When the overlapping percentage exceeds 0%, the R@Fe Ia B phase similarly decreases, the nonmagnetic RFeJn phase increases, and B'' decreases.

Furthermore, if X is present in an amount exceeding 20% by weight, it not only reduces Br but also causes the formation of a new phase that inhibits iHc (
Sometimes.

In particular, it is preferable that R be a component element such as Nd, M be B, and X be a component element such as CO, and R is 27 to 3.
5% by weight, M is preferably 0.5 to 1.4% by weight, and X is preferably 5 to 15% by weight.

Other alloys whose crystal structure is RzCO+ type (R
is a type known as a rare earth element), for example, the following formula: R-(Co, Fe, Cu, Zr, X) (wherein, R
, X are at least one rare earth element, Ti,
Represents at least one element selected from the group of Hf, Nb, Nl, and B, and R, Fe.

The composition ratio of Cu, Zr, and I can give you powder.

In the above alloy composition, if R is less than 22% by weight, sufficient iHc cannot be obtained, and if it exceeds 27% by weight, both iHc and Br decrease.

If pe is less than 10% by weight, saturation magnetization cannot be increased and Br decreases, and if it exceeds 25% by weight, iHc decreases and the squareness of the demagnetization curve deteriorates. becomes unavoidable. If the amount of Cu is less than 2% by weight, there will be problems such as a decrease in iHc and deterioration of squareness, and if the amount is more than 10 times, the saturation magnetization will be low. Furthermore, if Zr is less than 0.3% by weight, sufficient iHc cannot be obtained, and if it exceeds 4% by weight, both iHc and Br will decrease, which is disadvantageous. Finally, if X is more than 2% by weight, both iHc and Br decrease, which is disadvantageous.

In particular, it is preferable that R is Sm and %, X is 0
．． Alloys with compositions between 5 and 1% by weight are preferred.

In the case of the sintering method, these alloy powders have an average particle size of 2
．． It is suitable to use the particles after sizing them to 5 μm.

Moreover, in the case of the rapid cooling method, it is preferable to size the particles to 80 to 250 mesh sizes using a sieve specified in JIS Z8801.

In the method of the present invention, it is useful to add a predetermined amount of a binder as described below to the alloy powder as described above, since it can improve the toughness and workability of the obtained magnet.

Such binder components include Pb and Zn.

1 of low melting point metals such as Bi, Sn, Cd, In, Ga, Tl or alloys prepared by appropriately combining these
Species or species i A I , Co, N b .

1 of metals such as Ti, Cu, Cr, Mn, Zr, VO)
species or two or more species; furthermore, DVsOs, TbO 0°,
Hog's, Er! One or more types of oxides of heavy rare earth elements such as 's can be mentioned.

Among these binder components, for example, Pb and Zn are effective components for reducing the hardness of the obtained magnet and improving machinability such as machinability and polishability, but on the other hand, they also reduce iHc. Also, A
I, Co, and DyzOs are effective in suppressing the decrease in iHc of the magnet, but their contribution to improving the workability of the magnet is small. Therefore, it is necessary to appropriately select the binder components in consideration of the effects of each component described above.

This binder component is blended with the above-mentioned alloy powder to form raw material powder for a magnet to be sintered or warm-formed. At this time, the blending amount of the binder component is 1 to 2 in the above raw material powder.
The amount is set so that it occupies 0% by volume. If the blending amount is less than 1% by volume, the blending effect will not be exhibited and the density and workability of the obtained magnet will not improve.
If the blending amount exceeds % by volume, the chance of reaction with the alloy powder tends to increase, resulting in a decrease in iHc and Br, which is disadvantageous. Preferably it is 2 to 10% by volume. In addition, it is preferable to use these binder components after sizing the particle size to 330 mesh or less.

The method of the present invention is carried out as follows.

First, an alloy powder having the composition described above or a mixed powder of the alloy powder and a binder component is prepared as a raw material powder.

Next, this raw material powder is compression molded using a molding apparatus schematically shown in FIG.

In the figure, a die 2 surrounded by an excitation electromagnetic pole piece 1 has a through hole 2a of a predetermined diameter formed in its center. A lower punch 3 and an upper punch 4 are slidably inserted from below and above the through hole 2a, respectively, and a molding cavity 5 is formed in the opposing portion of both punches 3.4.

The upper bunch 3 and the lower punch 4 each have a pair of electrodes 6a,
6b is attached, from which electric power can be supplied to form an arc discharge within the molding cavity 5.

Using this device, first, the above-described raw material powder 5a is filled into the molding cavity 5. When filling, it is preferable to make the filling state as coarse as possible. Next, the electromagnetic pole piece 1 is operated to apply a magnetic field to the raw material powder 5a to orient the alloy powder. The magnitude of the magnetic field at this time varies depending on the type of raw material powder, etc., but is usually about 10 kOe.

Thereafter, the upper punch 4 and the lower punch 3 are slid to compress the raw material powder 5a. The pressure at this time should not be too high and is usually about 10 kg/cm''.

This is because if the pressure is increased, the raw material powder is shaped and the efficiency of generating arc discharge within the molding cavity 5 is reduced.

At the same time as this compression molding, the electrodes 6a and 6b are energized and the upper punch 4. Arc discharge is generated between the lower bunches 3, that is, between each particle of the raw material powder in the molding cavity 5.

The raw material powder is heated to a high temperature in a short period of time due to heat generation due to arc discharge and resistance heat generation. When it is confirmed that the temperature has risen to a predetermined temperature, the power supply is stopped and at the same time, the upper punch 4 and the lower punch 3 are further slid.
After compressing and molding the raw material powder 5a by increasing the molding pressure to about "nf/cm", the entire raw material powder 5a is cooled.
transforms into a compact magnet.

Finally, if the obtained molded body is subjected to appropriate heat treatment or plastic deformation treatment as necessary, the desired glaze top W
4 magnets can be obtained.

(Embodiments of the Invention) Example I After melting and casting an alloy consisting of 33% by weight Nd, 1.3% by weight B, and the balance Fe, the resulting ingot was ground in a ball mill to give an average particle size of 3 μm. - grade alloy powder was obtained. This alloy powder was filled into the molding cavity 5 of the apparatus shown in FIG.
After applying a magnetic field of e to orient the alloy powder, operate the upper and lower punches 3.4 to give the alloy powder a
While applying a primary pressure of , and maintaining this state, the electrodes 6a,
6b (DC 800 A and 2 kHz high frequency were superimposed) to eliminate arc discharge between the upper and lower punches 3.4.

The temperature of the alloy powder rose to 1100°C 20 seconds after the start of current application. Then, the secondary pressure was increased to 1 tonf/Cm'', and at the same time, the supply of electricity was stopped to perform cooling.

The obtained molded body was subjected to aging treatment at 650°C for 1 hour, and its density and surface hardness (Vickers hardness: 1v
), residual magnetic flux density, coercive force, and maximum energy product were measured. The results are shown in Table 1.

Comparative Example 1 The alloy powder used in Example 1 was first subjected to an applied magnetic field of 15 ko
The molded body was molded in a magnetic field under the conditions of e and pressure of 1 tonf/cm''.Then, this molded body was subjected to pressureless sintering at a temperature of 1100°C for 1 hour in an Ar atmosphere.The obtained sintered The solids were heated at 650°C as in Example 1.
After being subjected to aging treatment for 1 hour, its various properties were measured. The results are shown in Table 1.

Example 2 A commonly used molten metal quenching method (single roll method) was applied to an alloy consisting of Nd: 30% by weight, B: ], O% by weight, and the balance being Fe.
A thin strip having a thickness of several tens of microns was obtained. Crush this ribbon and J
An alloy powder having a sieve size of 80 sieves as defined in IS28801 was obtained.

The obtained alloy powder was filled into the molding cavity 5 of the apparatus shown in FIG. Without operating the electromagnetic pole piece l, slide the upper and lower bunches 3.4 to apply a primary pressure of 10 kg/cm, and in this state, the electrode 6 a
, 6b was energized to blow an arc discharge between the upper and lower punches 3° and 4°.

The temperature was raised to 700° C. about 15 seconds after the start of electricity supply.

At this point, a secondary pressure of 1 tonf was applied to Hashira 1, electricity supply was stopped, and cooling was performed. A magnetically isotropic molded body was obtained. Each of these characteristics was measured and the results are shown in Table 1.

This isotropic molded body was then subjected to a conventional gouy upsetting process at 700°C until its height was reduced to 1/4. An anisotropic magnet having an axis of easy magnetization in the upset pressure direction was obtained. Its properties are shown in Table 1.

Comparative Example 2 The alloy powder used in Example 2 was filled into a mold with an inner diameter of 10 mm, and under a vacuum of 1X10-' Torr, a pressure of 1
．． 5 tonf/cs+", a temperature of 700° C., and a time of 2 minutes. A magnetically isotropic magnet was obtained. The characteristics were measured and the results are shown in Table 1.

Next, this isotropic magnet was subjected to a guiamp set process under the same conditions as in Example 2 to produce a magnetically anisotropic magnet. Its properties are shown in Table 1.

(The following is a blank space) As is clear from the results shown, when a magnet manufactured by the conventional method is subjected to die-up setting processing to become an anisotropic magnet, its iHc decreases significantly. On the contrary, in the case of the magnet manufactured by the method of the present invention, such a problem does not occur, and a high degree of stability of magnetic properties is recognized.

Example 3 The binder components shown in Table 2 were added to the alloy powder used in Example 2 at the indicated ratios (volume %), and mixed for 4 hours using a V-type mixer.

The obtained mixed powder was treated in the same manner as in Example 2 to produce an isotropic magnet and an anisotropic magnet. These characteristics are the second
Shown in the table.

Comparative Example 3 The binder components shown in Table 2 were added to the alloy powder used in Example 2 at the indicated ratios (volume %), and mixed for 4 hours using a ■-type mixer.

The obtained mixed powder was treated in the same manner as in Comparative Example 2 to produce an isotropic magnet and an anisotropic magnet. Their properties are shown in Table 2.

As is clear from the results shown, in both Examples and Comparative Examples, when Pb and Zn are added, the hardness of the obtained magnet decreases. This means improved workability such as machinability and polishability.

However, in the case of the comparative example, the iHc is also at a significantly low level, reducing its value as a magnet, whereas in the case of the example, the decrease in iHc is small and the usefulness as a magnet is maintained. This proves that since the examples were manufactured by the method of the present invention, no reaction between Pb, Zn and the alloy powder occurred, and no coarsening of crystal grains occurred.

Incidentally, when the fracture surfaces of each of the isotropic magnets of Example 2 and Comparative Example 2 were observed using Scan 1iiB, the crystal grain size of Example 2 was as fine as about 0.1μ on average; ,
The particles of Comparative Example 2 were coarse grains with an average size of about 0.4μ.

Example 4 An alloy consisting of Sm: 25% by weight, Fe: 20% by weight, Cu: 4% by weight, Zr: 2% by weight, and the remainder Go was melted and cast, and the obtained ingot was crushed to obtain an average grain size. Diameter 3
An alloy powder of μ■ was obtained.

This alloy powder was molded under the same conditions as in Example 1. The obtained compact was subjected to solution treatment under vacuum at a temperature of 1170°C for 2 hours, and further subjected to aging treatment at 800°C for 5 hours to obtain a magnet. The cooling rate at this time is 0 up to 400℃.
．． The temperature was controlled at 5°C/win. The characteristics of the obtained magnet are
Shown in the table.

Comparative Example 4 A mold was filled with the alloy powder used in Example 4, and an applied magnetic field of 1
A molded body was formed under the conditions of 5 kOe and a pressure of 1 tonf/cm''.Then, this molded body was sequentially subjected to the same sintering/containing treatment and aging treatment as in Example 1 to form a magnet.The properties are shown in Table 3. It was shown to.

(The following is a blank space) (Effects of the invention) As is clear from the above explanation, the method of the present invention has a unique configuration. [Characterized by compression molding and densification while applying electric discharge energy to alloy powder for magnet, and further contains 80 to 99 volume % of alloy powder for rare earth magnet, Pb, Zn
, Bi, Sn, Cd.

At least one low melting point metal selected from the group of In, Ga, Tl or an alloy thereof HAI, Co.

A metal selected from the group of Ga, Nb, Ti, Cu, Cr, Mn, Zr, V; or D V ! Os + Tb
tO3.

A mixed powder consisting of a binder component of 1 to 20% by volume of at least one heavy rare earth metal oxide selected from the group of Ho1Oz and Era's is compacted by compression molding while applying electrical discharge energy. Because it is characterized by the ability to create precise images in an extremely short period of time, from a few seconds to over 10 minutes, compared to conventional methods! ! Magnets can be manufactured.

In addition, heating time is shortened, preventing oxidation and explosion of ingredients.
Furthermore, the occurrence of an inconvenient situation such as coarsening of crystal grains can be suppressed, and as a result, a magnet with excellent magnetic properties can be manufactured.

Furthermore, as is clear from the results in Table 2, in the conventional method, even though the binder components are Pb and Zn, which significantly reduce the hardness and magnetic properties (especially iHc) of the magnet, according to the method of the present invention, , Pb.

This negative effect of Zn can be suppressed, and as a result, P
b. It is possible to reduce hardness, which is a positive effect of Zn blending, or to improve workability.

In addition, in the method of the present invention, when discharge energy is supplied to the alloy powder, it has the effect of cleaning the particle surface of the powder, and since it is heated in a short time, the oxidation of the powder particles is less than the conventional method. This is advantageous in terms of equipment, etc., since compression molding can be carried out in the atmosphere.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an apparatus used in carrying out the method of the present invention. 1... Electromagnetic pole piece, 2... Dice, 2a.
...Through hole, 3...Lower punch, 4...Upper punch, 5.
... Molding cavity, 5a... Raw material powder, 6a, 6b.
··electrode.

Claims (6)

[Claims] (1) A method for manufacturing rare earth magnets, which comprises compressing and compacting alloy powder for rare earth magnets while applying discharge energy. (2) The alloy powder has the following formula: R-(Fe,X)-M(
In the formula, R, M, and X are each at least one rare earth element; at least one selected from the group of B, C, Si, and P.
Seed metalloid elements; Co, Al, Ga, Pb, Zn, Ti
, Zr, Nb, Ni, Cr, Mn, Cu, and Sn, and R,
The composition ratios of M and X are 20 to 40% by weight and 0% by weight, respectively.
．． 1 to 2.0% by weight and 20% by weight or less). (3) The alloy powder has the following formula: R-(Co, Fe, Cu
, Zr,
, Cu, Zr, and X are 22 to 27% by weight, 10 to 25% by weight, 2 to 10% by weight, and 0.3 to 4% by weight, respectively.
2. The method for producing a rare earth magnet according to claim 1, wherein the rare earth magnet is powder of an alloy represented by 2% by weight or less. (4) 80-99% by volume of alloy powder for rare earth magnets and P
b, at least one low melting point metal or alloy thereof selected from the group of Zn, Bi, Sn, Cd, In, Ga, Tl; Al, Co, Nb, Ti, Cu, Cr, Mn,
At least one metal selected from the group of Zr, V; or Dy_2O_3, Tb_2O_3, Ho_2O_3, E
Any one binder component 1 to 20 of at least one heavy rare earth metal oxide selected from the group r_2O_3;
1. A method for producing a rare earth magnet, which comprises compressing and densifying a mixed powder consisting of % by volume while applying electric discharge energy. (5) The alloy powder has the following formula: R-(Fe,X)-M(
In the formula, R, M, and X are each at least one rare earth element; at least one selected from the group of B, C, Si, and P.
Seed metalloid elements; Co, Al, Ga, Pb, Zn, Ti
, Zr, Nb, Ni, Cr, Mn, Cu, and Sn, and R,
The composition ratios of M and X are 20 to 40% by weight and 0% by weight, respectively.
．． 1 to 2.0% by weight and 20% by weight or less). (6) The alloy powder has the following formula: R-(Co, Fe, Cu
, Zr,
, Cu, Zr, and X are 22 to 27% by weight, 10 to 25% by weight, 2 to 10% by weight, and 0.3 to 4% by weight, respectively.
2. The method for producing a rare earth magnet according to claim 1, wherein the rare earth magnet is powder of an alloy represented by 2% by weight or less.