JPH076025B2 - Method of manufacturing permanent magnet material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a Fe—BR permanent magnet material, and in particular, a raw material powder is a powder having excellent powder characteristics such as fluidity and transportability. The present invention relates to a manufacturing method in which a Fe-BR permanent magnet material having excellent magnet characteristics and having no variation is stably obtained by molding and sintering the material.

BACKGROUND ART At present, there is a demand for a permanent magnet material that has high magnetic properties and is inexpensive, and there is a strong demand for a permanent magnet material that is rich in resources and that can be stably supplied in the future with a composition element. In addition, as a new high-performance permanent magnet containing no expensive Sm or Co, an Fe-BR type permanent magnet (R is at least one of rare earth elements including Y) is proposed (JP-A-59-46).
008, JP-A-59-64733, JP-A-59-89401, JP-A-59-132104). This permanent magnet is an excellent permanent magnet that uses a resource-rich light rare earth centering on Nd and Pr as R and has an extremely high energy product of 20 MGOe or more with Fe as a main component.

The rare earth metal as a starting material for producing the above novel Fe-B-R type and Fe-Co-B-R type permanent magnet materials is generally produced by a Ca reduction method or an electrolytic method. It is manufactured by the process.

As a starting material, a rare earth metal, electrolytic iron, ferroboron alloy, or electrolytic Co is further high-frequency melted to cast an ingot.

The ingot is roughly crushed by a stamp mill and then wet crushed by a ball mill to obtain a fine powder raw material powder having a size of 1.5 μm to 10 μm.

Mold in an oriented magnetic field.

Sinter in vacuum and allow to cool.

Aging treatment in Ar atmosphere.

Alternatively, at least one kind of rare earth oxide, iron powder and pure boron powder, at least one kind of ferroboron powder and boron oxide, or an alloy powder or a mixed oxide of the above constituent elements is added to a mixed powder in a required composition, Metal Ca and CaCl ₂ are mixed, and the reaction product obtained by reducing and diffusing in an inert gas atmosphere is slurried and treated with water.

The treated product is made into a fine powder of 0.5 μm to 5 μm by a ball mill and used as a raw material powder.

Mold in an oriented magnetic field.

Sinter in vacuum and allow to cool.

Aging treatment in Ar atmosphere.

As described above, since both the ingot crushed raw material powder and the Ca reducing raw material powder are fine powders having a powder particle size of about several μm, the raw material powder to the molding die space portion is not subjected to the magnetization middle orientation molding in the above step. Poor powder feedability, reduced press efficiency, and low fluidity tend to cause variations in weight per press unit, which tends to cause dimensional variations in the sintered body and cracks and cracks. Has a problem in that the powder is not easily conveyed and it is difficult to automate the powder feeding, which hinders improvement in press productivity and labor saving.

Therefore, in order to solve such a problem, the applicant first
The pulverized fine powder is pressed in a magnetic field, and the pressed body is crushed and sized to a required powder particle size, and then the sized powder is shaped into a required shape and dimension in a magnetic field, and then sintered and aged. A manufacturing method has been proposed (JP-A-60-19050).

The raw material powder obtained by the above-mentioned manufacturing method has excellent powder characteristics, the powder feeding property to the die space at the time of pressing is improved, and it has a great effect on the improvement of the pressing efficiency. Since the powder is crushed and sized to a specific particle size, there is a problem that the magnetic properties of the obtained permanent magnet are likely to vary due to the disorder of the orientation of the raw material powder.

OBJECT OF THE INVENTION The present invention, in the production of the permanent magnet material of the present applicant mainly composed of rare earth, boron, iron, based on the powder characteristics of the raw material powder, it is possible to eliminate the deterioration of press efficiency and product quality, Fe with uniform and excellent magnet characteristics
An object of the present invention is to provide a manufacturing method capable of stably obtaining a BR permanent magnet material.

Structure and Effect of the Invention The inventors have conducted various studies on a method for obtaining a permanent magnet material having stable magnet characteristics along with powder characteristics such as fluidity and transportability of raw material powder, and as a result, the ingot crushing method or Ca reduction described above. The finely pulverized powder obtained by the method is pressed in a specific magnetic field, and the pressure-molded body is crushed and sized into a specific particle size range to form a raw material powder, which is housed in a sealed container such as a die. By crushing in an alternating magnetic field, and crushing this crushed powder in the conventional process described above in a magnetic field, sintering, and magnetizing, it has the same or better characteristics as the permanent magnet material obtained in the conventional process. Since the permanent magnet material can be obtained stably and the crushed raw material powder has excellent powder characteristics, the press efficiency is improved, and the magnet characteristics, shape, and dimensional variation in manufacturing are reduced, and the product yield is improved. We found that it had a great effect on improvement

That is, the present invention provides R (R is at least one of Nd, Pr, Dy, Ho, and Tb or at least one of La, Ce, Sm, Gd, Er, Eu, Tm, Yb, Lu, and Y). (Comprising seeds) 10 atom% to 30 atom%, B 2 atom% to 28 atom%, Fe 65 atom% to 80 atom% as the main components, and pulverized fine powder is pressurized in a magnetic field to After crushing and sizing to a powder particle size of 0.1 to 3 mm, the above sizing powder is housed in a sealed container such as a die and crushed in an alternating magnetic field, and then the crushed powder is molded into a required shape and dimension in a magnetic field, After that, it is sintered to obtain a permanent magnet, which is a method for producing a permanent magnet material.

The permanent magnet material obtained by the above-mentioned production method according to the present invention has a compound having a tetragonal crystal structure having an average crystal grain size in the range of 1 to 80 μm as a main phase and a volume ratio of 1% to 50%.
% Non-magnetic phase (excluding oxide phase) is included, mainly Rd is used as a resource rich light rare earth mainly as Nd or Pr, and Fe, B, R as main components By doing, extremely high energy product of 20MGOe or more,
It is possible to inexpensively obtain an Fe-BR system permanent magnet material having a high residual magnetic flux density and a high coercive force.

Preferred Embodiment of the Invention The production method according to the present invention is as follows: First, as a starting material, a rare earth metal, electrolytic iron, ferroboron alloy or further electrolytic Co is high frequency melted to cast an ingot, and the ingot is roughly crushed by a stamp mill. Then, it is wet pulverized by a ball mill to obtain a finely pulverized powder.

Alternatively, at least one kind of rare earth oxide, iron powder and pure boron powder, at least one kind of ferroboron powder and boron oxide, or an alloy powder or a mixed oxide of the above constituent elements in a mixed powder having a required composition, Metal Ca and CaCl
₂ , the reaction product obtained by reducing and diffusion in an inert gas atmosphere is slurried, treated with water,
A finely pulverized powder is obtained from this treated product by a ball mill.

Using the above-mentioned finely pulverized powder as a raw material, in order to align the crystal grains in the granulated powder in a specific direction, in a magnetic field of 8 kOe to 20 kOe, press pressure
At ^{0.5t / cm 2 ~3.0t / cm 2} , e.g., pressurized by a pair of rolls, or molded using conventional magnetic field during pressing device at after which the molded-type body crusher, crushing Sizing,
Make the powder particle size within the range of 0.1 mm to 3 mm.

Then, the sized powder is stored in a sealed container such as a die, and the sized powder is crushed in an alternating magnetic field of 1000 Oe to 10000 Oe.

The obtained crushed powder is subjected to the powder metallurgical manufacturing process described above, for example, after being shaped into a required shape and dimensions by orientation in a magnetic field, sintered in a vacuum and then allowed to cool, and further in an Ar atmosphere. A permanent magnet material is obtained through a step of aging treatment.

In the present invention, the magnetic field under the pressure condition in the magnetic field before crushing and sizing is less than 8 kOe, the orientation of the powder is not sufficient,
It is not preferable because the magnet characteristics are deteriorated, and when it exceeds 20 kOe, there is a problem that the manufacturing equipment cost increases.

Also, pressing pressure, 0.5 t / cm without sizing powder having sufficient strength can be obtained in less than ² is not preferable because it can not improve the powder properties, also exceeds 3.0 t / cm ² rolls It is not preferable because the abrasion of dies, dies and punches is severe and continuous work becomes difficult.

In this invention, the particle size of the crushed and sized powder is less than 0.1 mm, which is not preferable because of the problem of reduced fluidity, and 3 m
When it exceeds m, it is not preferable because the weight per press unit at the time of powder feeding varies in the pressing of small articles, and the particle size of the sized powder is 0.1 mm to 3.0 mm, preferably 0.3 mm to 0.8 mm. is there.

In the crushing of the sized powder, which is a feature of the present invention, the sized powder contained in a sealed container such as a die repeatedly moves and rotates in an alternating magnetic field, and repeats friction and collision. As a result, it is crushed without disturbing its orientation.

If the AC magnetic field during crushing is less than 1000 Oe, it takes a long time to crush to the required particle size, which is not preferable, and if it exceeds 1000 Oe, the magnetic field generator becomes large and the facility requires a large amount of cost. Therefore, the range of 1000 to 10000 Oe is preferable, and the crushing time is desirably 1 minute or less.

Further, in the present invention, the magnetic field conditions for molding the crushed raw material powder in a magnetic field into required shapes and dimensions are 7 kOe to 20 kO.
e is preferably, pressing ^{conditions, 0.5t / cm 2 ~8t / cm} 2 is preferred.

The temperature condition in sintering is preferably 900 ° C to 1200 ° C, more preferably 1000 ° C to 1100 ° C, and the time is preferably 30 minutes to 8 hours. If the temperature is lower than 900 ° C, sufficient strength cannot be obtained as a sintered magnet body, and if the temperature exceeds 1200 ° C, the sintered body is deformed, orientation is disturbed, magnetic flux density is lowered, and squareness is lowered. Further, the coarsening of the crystal grains proceeds and the coercive force decreases, which is not preferable.

Further, in this invention, in order to improve and improve the residual magnetic flux density, coercive force, and squareness of the demagnetization curve of the magnet material,
~ Aging treatment at a sintering temperature is preferable. If the aging temperature is lower than 350 ° C, there is no effect because the diffusion rate decreases, and if it exceeds the sintering temperature, re-sintering occurs and oversintering occurs.

Furthermore, the aging treatment temperature is preferably in the range of 450 ° C. to 800 ° C., and the aging treatment temperature is preferably 5 minutes to 40 hours.
If it is less than 5 minutes, the effect of aging treatment is small, and the variation of the magnetic properties of the obtained magnet material becomes large. If it exceeds 40 hours, it takes a long industrial time and is not practical. Aging treatment time is 30 minutes to 8 from the viewpoint of favorable expression of magnet characteristics and practical use.
Time is preferred. Further, as the aging treatment, a multi-step aging treatment having two or more steps can be used.

Further, instead of the multi-step aging treatment, a cooling method such as air cooling or water cooling from the aging temperature of 400 ℃ ~ 1000 ℃ to room temperature, by a method of cooling at a cooling rate of 0.2 ℃ / min ~ 20 ℃ / min, It is possible to obtain a permanent magnet material having the same magnetic characteristics as those of the aging treatment.

Reasons for Limiting Components of Raw Material Powder for Permanent Magnet Material The rare earth element R used in the raw material powder for permanent magnet material of the present invention occupies 10 atom% to 24 atom% of the composition, but Nd, Pr, D
At least one of y, Ho, Tb, or even La, C
Those containing at least one of e, Sm, Gd, Er, Eu, Tm, Yb, Lu and Y are preferable.

Also, one of R is usually used (preferably Nd, Pr, Dy, Ho, Tb
Etc.) is sufficient, but in practice, a mixture of two or more kinds (Misch metal, didymium, etc.) can be used for reasons such as convenience of availability.

Further, it is preferable that Sm and La in R constituting the main phase are as small as possible, for example, Sm is 1 atom% or less, more preferably 0.5 atom% or less.

In addition, in order to improve the temperature characteristics, as an R mixed system, N
Desirably, d, Pr, or a combination of 0.005 atom% to 5 atom%, preferably 0.2 atom% to 3 atom% of Dy, Ho, Tb, etc., is added.

Furthermore, from the viewpoint of characteristics, cost and resources, R is as follows:
Nd and Pr are preferably 50% or more, more preferably 80% or more of the total R.

It should be noted that this R does not have to be a pure rare earth element, and may contain an impurity that is unavoidable in manufacturing within the industrially available range.

R is the raw material powder for the above new permanent magnet material,
It is an essential element, and if it is less than 10 atomic%, the crystal structure is α-
Since a cubic crystal structure having the same structure as iron is deposited, high magnetic properties, especially high coercive force, cannot be obtained.
The rich non-magnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet with excellent characteristics cannot be obtained. Therefore, the rare earth element content is in the range of 10 atom% to 30 atom%.

B is an essential element in the raw material powder for a permanent magnet material according to the present invention, and if it is less than 2 atomic%, the rhombohedral structure becomes the main phase and a high coercive force (iHc) cannot be obtained and exceeds 28 atomic%. Then, the B-rich non-magnetic phase increases and the residual magnetic flux density (Br) decreases, so that an excellent permanent magnet cannot be obtained. Therefore, B is in the range of 2 at% to 28 at%.

Fe is an essential element in the new raw material powder for permanent magnet materials, and if the content is less than 65 atom%, the residual magnetic flux density (Br) is reduced, and if it exceeds 80 atom%, a high coercive force cannot be obtained. Fe is contained at 65 atom% to 80 atom%.

Further, in the raw material powder for a permanent magnet material according to the present invention, substituting a part of Fe with Co can improve the temperature characteristics without impairing the magnetic characteristics of the obtained magnet. Is more than 20% of Fe, the magnetic properties are deteriorated, which is not preferable. When the atomic ratio of Co is 5% to 15% in terms of the total amount of Fe and Co, (Br) is increased as compared with the case where no substitution is made, which is preferable for obtaining a high magnetic flux density.

Further, the permanent magnet material according to the present invention can tolerate the presence of impurities unavoidable in industrial production in addition to R, B and Fe, but a part of B is 4.0 atomic% or less of C and 2.0 atomic% or less of P. , S of 2.0 atomic% or less, Cu of 2.0 atomic% or less, at least 1
It is possible to improve the manufacturability of the permanent magnet and reduce the cost by substituting the total amount of the seeds by 2.0 at% or less.

Further, at least one of the following additional elements is RB-
It can be added to the Fe-based permanent magnet material because it is effective in improving the coercive force and the squareness of the demagnetization curve, improving the manufacturability, and lowering the cost.

5.0 atomic% or less Al, 3.0 atomic% or less Ti, 5.5 atomic% or less V, 4.5 atomic% or less Cr, 5.0 atomic% or less Mn, 5.0 atomic% or less Bi, 9.0 atomic% or less Nb, 7.0 Ta less than atomic%, Mo less than 5.2 atomic%, W less than 5.0 atomic%, Sb less than 1.0 atomic%, Ge less than 3.5 atomic%, Sn less than 1.5 atomic%, Zr less than 3.3 atomic%, 6.0 atomic % Or less Ni, 5.0 atomic% or less Si, 1.1 atomic% or less Zn, 3.3 atomic% or less Hf, at least one type is added. However, when two or more types are contained, the maximum content is By containing at most atomic% of the additive element having the maximum value,
It is possible to increase the coercive force of the permanent magnet. In addition, the upper limit of the addition amount is to set the (BH) max of the magnet material to 20 MGOe or more,
Since (Br) is required to be at least 9 kG or more, the range was set to satisfy the condition.

The fact that the main phase of the crystal phase is a tetragonal crystal is indispensable for producing a sintered permanent magnet having excellent magnetic properties from a fine and uniform alloy powder.

In addition, the permanent magnet material of the present invention can be magnetically anisotropic magnet by press molding in a magnetic field, and can be magnetically isotropic magnet by press molding in a non-magnetic field. .

The permanent magnet material according to the present invention exhibits a coercive force iHc ≧ 1 kOe, a residual magnetic flux density Br> 4 kG, and a maximum energy product (BH) m
ax indicates 20 MGOe or more, and the maximum value reaches 25 MGOe or more in the preferable composition range.

Further, when the main component of R of the raw material powder for permanent magnet material of the present invention is 50% or more of the light rare earth metal mainly composed of Nd and Pr, R 12 atom% to 15 atom%, B 6 atom% In the composition range of ~ 9 atomic% and Fe 78 atomic% -80 atomic%, (B
H) shows excellent magnetic properties of more than 35MGOe, especially when the light rare earth metal is Nd, the maximum value reaches more than 45MGOe.

Example 1 As a starting material, electrolytic iron having a purity of 99.9%, ferroboron alloy, Nd and Dy having a purity of 99.7% or more were used, and after mixing these, high-frequency melting was performed, and then cast in a water-cooled copper mold, and 14.5Nd 7
An ingot having a composition of B 0.5 Dy78Fe was obtained.

After that, this ingot was roughly crushed with a stamp mill and then finely crushed with a ball mill to obtain an average particle size of 3.0 μm.
Of fine powder was obtained.

This fine powder is oriented in a magnetic field of 10 kOe in a magnetic field press machine and pressure-molded at a pressure of 1.5 t / cm ² to obtain 100 mm x 60 mm.
It was made into a molded body with a size of 50 mm.

The obtained pressurized body was sized by a particle sizer to give a powder particle size of 0.4 mm to 0.6 mm.
It was crushed and sized so that the particle size became mm.

After charging the above-mentioned sized powder into a die with dimensions of 15 mm × 20 mm × 20 mm, close the space inside the die with the upper and lower punches,
An alternating magnetic field of 00 Oe was applied for 5 seconds to crush the sized powder.

This crushed powder was charged into the same mold, oriented in a magnetic field of 12 kOe, and horizontally molded in a magnetic field at a pressure of ² t / cm ² ,
It is a molded body with dimensions of 15 mm × 20 mm × 12 mm.

The obtained compact is sintered under the conditions of 1080 ° C, 1.5 hours in Ar atmosphere, and further, in Ar atmosphere, 800 ° C, 1 hour and 630
Two-stage aging treatment was performed at ℃ for 1.5 hours.

The magnetic properties of the obtained permanent magnet material were measured, and the results are shown in Table 1 together with the press efficiency.

In the comparative example of Table 1, powder obtained by sizing the above-mentioned pressed body in a magnetic field to a specific particle size is used as a raw material powder, which is directly placed in a die, molded in a magnetic field, and subjected to an aging treatment after sintering. It is a permanent magnet material, and other manufacturing conditions are the same as those of the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C22C 38/00 303 DH 01F 1/08

Claims (1)

[Claims] 1. R (R is at least one of Nd, Pr, Dy, Ho, Tb or at least one of La, Ce, Sm, Gd, Er, Eu, Tm, Yb, Lu, Y. 10 atom% to 30 atom%, B 2 atom% to 28 atom%, Fe 65 atom% to 80 atom%, as a main component, pulverized fine powder is pressed in a magnetic field to powder the pressed body. After crushing and sizing to a particle size of 0.1 to 3 mm, the above sizing powder is stored in a sealed container and crushed in an alternating magnetic field, and then the crushed powder is molded into the required shape and size in a magnetic field and then sintered. A method for producing a permanent magnet material, comprising: