JPS63317643A - Production of rare earth-iron permanent magnetic material - Google Patents

Abstract

PURPOSE:To obtain the titled material which shows high magnetic characteristics by grinding a thin plate obtd. by quench casting an Fe alloy molten metal contg. specific amounts of Y contg. one or two kinds of Nd and Pr, rare earth elements and B, forming said late and sintering it. CONSTITUTION:The molten metal of the Fe alloy (e.g. Nd12.3Fe79.7B8) expressed by general formula is quench cast to the thick plate having 0.05-3mm more preferably 0.5-2.5mm plate thickness, 3-20mum more preferably 10-15mum crystal grain size and the homogenizing structure by a double rolling method. Said thin plate is successively ground and the desired rare earth-iron permanent magnetic material is obtd. by a powder metallurgy method, i.e., by executing pressing, sintering and heat treatment thereto. The capacity, particularly the coercive force of a permanent magnet can drastically be increased by using said permanent magnetic material.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides a sintered magnet whose main components are R (where R is Y containing at least one of Nd or Pr and a rare earth element), Fe, and B. In the material manufacturing method, R-Fe-B, which improves the structure of slabs and provides high magnetic properties, is used.
The present invention relates to a method for producing a sintered magnet material.

(Prior Art) Permanent magnetic materials are one of the extremely important electrical and electronic materials used in a wide range of fields, from general home appliances to peripheral terminals for large computers. In recent years, as electrical and electronic equipment becomes smaller, lighter, and more efficient, permanent magnets are required to have even higher performance.

Recently, R-Fe-B alloys have been attracting attention as new high-performance permanent magnets. Its component is Fe. . -a-1kR
11BI+ +(Fe+-xCox) 100-m-b
RaBb (where,
~20 at%, b: 4~10 at%)
No. 4242, IEEE Trans.

Magn, MAG-20, 1584 (1984)]
It has been known.

There are two known manufacturing methods: powder metallurgy and melt spin. In the powder metallurgy method, the starting material is an ingot made by casting molten metal into a mold, and the ingot is coarsely crushed using a stamp mill, show crusher, etc., and then crushed to an average particle size using a disc mill, ball mill, attritor mill, jet mill, etc. After finely pulverizing the powder into a powder of 3 to 5 μm, a molded body is created by pressing in a magnetic field,
After sintering it at a temperature range of 1000-1150℃,
This is a method for producing a permanent magnet that is aged in a temperature range of 400 to 900°C.

In order to improve the magnetic properties, especially the residual magnetic flux density, it is necessary to reduce the content of Nd or B in the sintered magnet of this system. However, at least stoichiometrically, NdzFe
N that forms +J and does not contain excess Fe.
d or B is necessary. However, if Nd or B is decreased, Nd≦15at% or B≦8a
In the range of t%, γFe precipitates as primary crystals during the cooling process of the ingot, and after cooling, it segregates in the ingot as αFe.

This residual αFe is a phase that deteriorates the magnetic properties of the sintered magnet of this system. Therefore, the ingot was heated to 1000-1150℃.
By homogenizing annealing in the range of
There are ways to reduce this. However, this annealing causes the main phase (Nd, Fe+J) to become coarse, which causes deterioration of the magnetic properties. Metallographically, it is possible to reduce the proportion of residual αFe by increasing the cooling rate of the ingot and allowing it to rapidly pass through the γFe formation temperature range, but the currently used water-cooled copper mold ( Special Public Service 1986
The cooling rate at which the ingot is cast into the ingot (No. 34242) is insufficient, and the residual αFe is not suppressed, resulting in coarse grains and a non-uniform ingot. Nd>15at% or B>
In the range of 8 at%, there is almost no residual αFe, but in the method of casting into a water-cooled copper mold, the crystal grains become coarse and there is a lot of segregation, which causes a decrease in magnetic properties.

On the other hand, there is a method of rapidly cooling molten metal and directly forming it into a thin ribbon (Japanese Patent Application Laid-open No. 1983-
15943, Japanese Patent Application Laid-Open No. 15944/1983), but these are characterized by being used as permanent magnets in the form of thin strips, and cannot be used as materials manufactured using powder metallurgy. I don't get it.

(Problems to be Solved by the Invention) As mentioned above, according to conventional knowledge, when a sintered magnet ingot manufactured using a powder metallurgy method is manufactured using a water-cooled copper mold, coarsening of crystal grains occurs. There were problems such as residual αFe and segregation.

The present invention aims to solve the above-mentioned problems by rapid cooling casting into a thin plate shape with a controlled cooling rate, and to provide a slab for powder metallurgy with improved magnetic properties.

(Means for solving the problem) That is, in order to solve the above problem, in the present invention, F
eloo-m-bRmBb, (Fe+-xco
x) 100-m-bRmBb (however, X≦20at%
and R is Y containing at least one of Nd or Pr.
and rare earth elements, a and b are content rates of a: 10 to 20 at% and b: 4 to 1 Oat%, respectively) from molten metal to a plate thickness of 0.05 to 3 u+ by twin roll method.
It is characterized in that a thin piece with a homogeneous structure with a crystal grain size of 3 to 20 μm is obtained by rapid cooling casting into a thin plate at a rapid cooling rate of 10” to 104° C./S.

The composition of the alloy used in the present invention is based on Fe, and R
is a rare earth element essential for obtaining the high-performance magnet of the present invention, and usually one kind is sufficient, but in practice, a mixture of two or more kinds can be used.

In the present invention, at least one of mainly Nd or Pr
Seeds are used because they have particularly excellent magnetic properties. However, if R is less than 10 at%, sufficient coercive force cannot be obtained, while if it is added in excess of 20 at%, the residual magnetic flux density decreases and the magnetic properties deteriorate. For the above reasons, R was set in the range of 10 to 20 at%.

B stabilizes the formation of the NdzFelJ phase, which is the main phase, but if it is less than 4 at%, the formation is unstable, and if it exceeds 10 at%, the residual magnetic flux density decreases, so it was set in the range of 4 to 10 at%.

Co increases the Curie temperature and improves the temperature resistance characteristics, so it may be substituted up to 20 at % with respect to Fe, but if it is substituted more than that, the magnetic properties will deteriorate.

Next, a method for rapidly cooling a molten alloy having the above-mentioned components, which is the key point of the present invention, will be explained.

In the present invention, it is desirable and practical to use a twin roll method as a method for rapid cooling.

Next, we will discuss the reasons for limiting the plate thickness. Plate thickness is 0,05
If it becomes thinner than 3 mm, the quenching effect becomes excessive and the crystal grain size becomes 3 mm.
The plate thickness was set to 0.05 nm or more because the probability of the thickness becoming smaller than μm increases and the magnetic properties deteriorate.

On the other hand, if the plate thickness is thicker than 3 x m, the cooling rate will be slow and αFe will remain, and the crystal grain size will exceed 20 μm and the magnetic properties will deteriorate, so the plate thickness was set to 3 x m or less. In other words, when the crystal grain size becomes smaller than 3 μm, when grinding it to a single crystal (in order to increase the degree of magnetic field orientation by pressing in a magnetic field, it is necessary to grind the slab to a single crystal size smaller than the crystal grain size), oxidation becomes very large and the magnetic properties deteriorate. On the other hand, if the crystal grain size is larger than 20 μm, the grain size distribution of the crystals becomes non-uniform, and the particle size distribution of the particles after pulverizing them also becomes non-uniform, resulting in a decrease in magnetic properties.

Therefore, the crystal grain size was set in the range of 3 to 20 μm. Set the plate thickness to 0
．． If the cooling rate is controlled to a negative value of 5 to 2.5 m to obtain a homogeneous structure with a crystal grain size of 10 to 15 μm, the particle size distribution of the powder particles after pulverization becomes narrower, and the magnetic properties are further improved.

The holding power of the permanent magnet manufactured by crushing the slab of plate thickness 0.05 to 3 fins manufactured according to the present invention, pressing, sintering, and heat treatment is the same as that of the ingot cast in a water-cooled copper mold. The holding force is significantly increased compared to that of permanent magnets manufactured by This is because the crystal grain size is made finer by the present invention.
This is thought to be due to the fact that residual αFe was particularly suppressed and the structure of the slab was homogenized.

Examples are shown below.

(Example 1) As a starting material, electrolytic iron with a purity of 99.9 wt%, 99.9 wt%.
9wt% Nd and 99.9wt% B Nd,
□, A predetermined amount of 3FE179.7B8 was mixed and melted by high-frequency induction heating, and a thin plate casting material with a plate thickness of 1.1 ** was produced using a twin-roll thin plate manufacturing equipment equipped with two copper rolls with a diameter of 300 mm. I got it. However, all A
The casting was carried out in an r atmosphere. This cast piece was coarsely ground to 48 mesos. or less. At this stage, in order to improve the sinterability of this magnet, the coarsely ground powder was pre-cast in a water-cooled copper mold.
d-Fe-8 ternary eutectic component (Nd69.5Fezs,
4.8w of coarsely ground powder of SB6.7) of 48 mesoyu or less
t% was added and thoroughly mixed. Further, this mixed powder was finely pulverized using a jet mill to obtain an alloy powder with an average particle size of 3.5 μm. This alloy powder was oriented in a magnetic field of 16 kOe and pressurized with a pressure of 1.5 tons/- to form a powder with a width of 10 mm x height of 1 mm.
A molded body having a length of Q m and a length of 20 dragons was obtained. This molded body is 1
Sintering in vacuum at 080℃xlh, followed by 600℃xl
A permanent magnet was obtained by aging in hAr. A photograph of the structure of the twin-roll cast slab according to the present invention is shown in FIG. 1, and magnetic property values are shown in Table 1 (a). In Figure 1, no residual αFe was observed in the structure of the slab, and the grain size was 3 to 20μ.
It has a homogeneous structure within the range of m.

Holding force (iHc) 11.0 koe, residual magnetic flux density (Br) 12.8kG, maximum energy product (BH)
A magnetic property value of □, 37.0 MGOe was obtained.

Next, for comparison, an alloy with the same composition was cast into a water-cooled copper mold, and a permanent magnet was obtained by the same method. A photograph of the structure of the ingot is shown in FIG. 2, and the magnetic property values are shown in Table 1 (b). In Figure 2, a large amount of residual αFe is observed in the area not in contact with the water-cooled copper mold, and the crystal grain size is 50%.
It has a heterogeneous structure exceeding μm in size. Retention cuff, 3
Magnetic property values of kOe, residual magnetic flux density of 12.8 kG, and maximum energy product of 36.0 MGOe were obtained.

Table 1 Comparing the twin-roll cast material and the comparative material, the coercive force was significantly increased when the twin-roll cast material was used.

(Example 2) A twin-roll cast material of Nd I 5.5FeT&, :+fla, 2 was produced in the same manner as in Example 1. This cast material was coarsely ground to 48 meshes or less, and then finely ground using a jet mill to obtain an alloy powder with an average particle size of 3.5 μm. This alloy powder was oriented in a magnetic field of 16 kOe, pressed at a pressure of 1.5 ton/crl, and made into a material with a width of 10 mm.
A molded body measuring 10 m in height and 20 m in length was obtained. This molded body was sintered at 1080°Cxlh in vacuum, and then at 600°C
A permanent magnet was obtained by aging in ℃×1hAr. The magnetic property values at this time are shown in Table 2 (a). Holding force 13.5koe
, residual magnetic flux density 12.2kG, maximum energy product 34
．． 'Magnetic property values of OMGOe can be obtained. Next, for comparison, an alloy with the same composition was cast into a water-cooled copper mold, and a permanent magnet was obtained using the same method. The magnetic property values at this time are shown in Table 2 (b
)It was shown to. Holding force 9.5kOe, residual magnetic flux density 12.
Magnetic property values of 2 kG and a maximum energy product of 33.0 MGOe were obtained. When comparing the twin-roll cast material and the comparative material, although no residual αFe was observed in either material,
The grain size of the twin-roll cast material was smaller, and as a result, the holding force was significantly increased.

(Example 3) The plate thickness is 2. 3. Four crane twin-roll cast materials were produced in the same manner as in Example 1, and permanent magnets were obtained from these cast materials in the same manner as in Example 1. Table 3 shows the relationship between plate thickness, grain size, and holding force.

From Table 3, the holding force of a permanent magnet obtained using slabs whose plate thicknesses are controlled to 2 m (crystal grain size 13 μm) and 3 m (crystal grain size 18 μm) is the same as when the plate thickness is 4 m (crystal grain size 40 μm). The holding force was significantly increased compared to that of permanent magnets obtained using slabs.

(Effects of the Invention) As described above, the use of a cast material rapidly cast into a thin plate using twin rolls according to the present invention improves the performance of permanent magnets.
In particular, it is of high industrial value because it makes it possible to significantly increase the holding power.

[Brief explanation of the drawing]

FIG. 1 is a metallographic micrograph showing the structure of a twin-roll cast slab according to the present invention taken with a metallographic microscope, and FIG. 2 is a metallographic micrograph showing the structure of an ingot material as a comparative material.

Claims (1)

[Claims] (1) Fe_1_0_0_-_a_-_bR_aB_b
(However, R is a component consisting of Y containing at least one of Nd or Pr, and a rare earth element, and a and b are content rates of a: 10 to 20 at% and b: 4 to 10 at%, respectively). It is characterized by being rapidly cast by a roll method into a thin plate having a homogeneous structure with a thickness of 0.05 to 3 mm and a crystal grain size of 3 to 20 μm, followed by crushing the thin plate and then manufacturing it by a normal powder metallurgy method. A method for producing a rare earth-iron permanent magnet material. 2, (Fe_1_-_xCo_x)_1_0_0_-_
a_-_bR_aB_b (where, ~10 at%) is rapidly cooled and cast into a thin plate having a homogeneous structure with a thickness of 0.05 to 3 mm and a crystal grain size of 3 to 20 μm using a twin roll method, and then the thin plate is crushed and then cast into a conventional 1. A method for producing a rare earth-iron permanent magnet material, characterized in that it is produced by a powder metallurgy method. (3) The method for manufacturing a permanent magnet material according to claim 1 or 2, wherein the plate thickness is 0.5 to 2.5 mm. (4) The method for producing a permanent magnet material according to claim 1 or 2, wherein the crystal grain size is 10 to 15 μm.