JP3535253B2 - Method for producing cast slab for R-Fe-B permanent magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an R--Fe--B based permanent magnet slab having a fine homogeneous structure.
-After the molten Fe-B alloy is melted in a melting furnace, the molten metal is poured from a nozzle at the tip of the tundish onto a quenched piece roll arranged at a specific gap length and at a specific angle, and rapidly solidified. To obtain a quenched slab of a specific thickness having a homogeneous structure in which the R-rich phase is finely dispersed.
The present invention relates to a method for producing a cast piece for an e-B permanent magnet.

[0002]

2. Description of the Related Art A typical R-Fe as a high performance permanent magnet
-B-based permanent magnets (JP-A-59-46008) provide high magnet properties in a structure having a main phase and an R-rich phase of a ternary tetragonal compound, and can be used for various household electrical appliances and large computers. Used in a wide range of fields, including peripheral devices,
R-Fe-B permanent magnets of various compositions have been proposed so as to exhibit various magnet characteristics according to the application.

In order to increase the residual magnetic flux density (Br) of the R—Fe—B based sintered magnet, 1) increasing the abundance of the main phase, R ₂ Fe ₁₄ B phase, which is a ferromagnetic phase; 2) increasing the density of the sintered body to the theoretical density of the main phase, 3)
It is required to increase the degree of orientation of the main phase crystal grains in the easy axis direction.

That is, in order to achieve the above item 1),
It is important that the composition of the magnet be close to the stoichiometric composition of the above R ₂ Fe ₁₄ B, but an alloy lump obtained by melting an alloy having the above composition and casting in a mold is used as an R-Fe-B-based starting material. When trying to make a sintered magnet, the α-
Since Fe and the R-rich phase are locally ubiquitous, there is a problem that pulverization becomes difficult particularly during fine pulverization and a composition deviation occurs.

Recently, in order to prevent coarsening of crystal grains, residual α-Fe, and segregation, which are disadvantages of the R-Fe-B alloy powder by the ingot grinding method, a molten R-Fe-B alloy is used. A method has been proposed in which a slab having a specific thickness is formed by a roll method and a sintered magnet is manufactured from the slab according to a usual powder metallurgy method (Japanese Patent Application Laid-Open No. 63-317643).

A method of manufacturing a quenched cast for a permanent magnet by a horizontal casting strip casting method using a single roll of a molten R-Fe-B alloy has been proposed by using a nozzle having a required width in the horizontal direction at the tip of a tundish. Is provided adjacent to the nozzle, and a single roll is horizontally supported and placed in a tundish after melting the molten metal in the high-frequency melting furnace, and then the molten metal is horizontally disposed from the nozzle and continuously rotates. And quenched and solidified to produce quenched cast slabs (JP-A-5-222488, JP-A-6-846).
No. 24).

[0007]

Generally, in the case of the horizontal casting strip casting method, the gap is made of a refractory material such as alumina or silica in order to prevent the molten metal from leaking out from the gap between the nozzle and the one roll. The nozzle portion was pressed against a single roll with a cushion material interposed, and used. However, since the cushion material is in contact with the molten metal, the solidified slab adheres to the cushion material, and the slab is cast while gradually tearing the cushion material, so that the cushion material is mixed into the slab. The mixed refractory is reduced by the liquid phase of the magnet alloy during sintering. For example, when the refractory is alumina, an abnormal structure in which rare earth oxides are accumulated around Al formed by reducing Al ₂ O _3. Thus, there is a problem that the corrosion resistance of the sintered magnet is deteriorated.

In the case of the horizontal casting strip casting method, if the temperature of the molten metal and the heat transfer coefficient between the molten metal and the single roll are constant, the level of the molten metal in the nozzle portion and the peripheral speed of the roll, ie, the contact between the molten metal and the single roll, The thickness and crystal structure of the slab are determined by the length and the peripheral speed of the roll, but it is difficult to keep the molten metal level constant during operation, and the crystal structure varies from large to small due to the fluctuation of the plate thickness. There is. Since the size and the variation of the crystal grain size in the minor axis direction of the crystal structure fluctuate the magnet characteristics, particularly the coercive force, there is a problem that it is difficult to obtain stable magnet characteristics. Furthermore, if the contact time between the slab and the single roll is short, the cooling of the slab is insufficient, and the slab temperature when the slab leaves the single roll is high, so that the crystal grains grow and become coarse. Therefore, there has been a problem that magnet properties, particularly coercive force, are reduced.

The present invention solves the problem of the molten metal and the single roll in the horizontal casting strip casting method, and
A method for producing a cast piece for an R-Fe-B permanent magnet, which can prevent deterioration of the corrosion resistance of the -B permanent magnet, stably refine the crystal structure, and have excellent and stable magnet properties such as coercive force. The purpose is to provide.

[0010]

SUMMARY OF THE INVENTION The present invention provides
To eliminate lateral pour cushion strip casting problems, to eliminate the cushioning material between the nozzle and the rolls
A result of various studies and this to the purpose, the air gap length between the nozzle and the roll is changed by the roll peripheral speed, as the peripheral speed is higher,
Since the gap length can be increased, and the gap length changes due to the thermal expansion of the quenched piece roll during casting, it is necessary to adjust the gap length to the required length in advance according to the material, peripheral speed, etc. of the quenched piece roll. And the gap length is set to 0.01 to 3.0 m
It has been found that setting m is important.

Further, the inventor has set the thickness of the slab to 0.03 mm.
As a result of various investigations on the positional relationship between the nozzle and the roll to make the structure finer, the angle between the line connecting the uppermost portion and the center point of the quenched piece roll and the nozzle is 30 ° to 90 °. , The thickness of the slab cast by the quenched slab roll is reduced to 0.03 to 1
With the required thickness of 0 mm, it was found that the structure could be refined, and the present invention was completed.

That is, the present invention provides a quenched cast slab in which the main phase is made of R ₂ Fe ₁₄ B crystal by pouring a molten R-Fe-B alloy from a nozzle into a quenched roll in a vacuum or an inert atmosphere. Get RF
In the method for producing a cast piece for an eB permanent magnet, the nozzle at the tip of the tundish containing the molten alloy is set at 45 ° to 80 ° with respect to a line connecting the top and the center point of the quenched piece roll.
Placed facing the angle range position, and providing a gap length of 0.01 mm to 3.0 mm between the quenching piece roll surface and the nozzle end
Pouring, 0.03mm to 10mm thick and short axis direction of the main phase
Is a method for producing a slab for R-Fe-B-based permanent magnets, characterized in that a quenched slab having a dimension of 0.1 mm to 50 mm is obtained .

The preferred alloy composition of the alloy slab for producing the R-Fe-B permanent magnet in the present invention will be described below. Rare earth element R contained in the permanent magnet slab of the present invention
Is a rare earth element containing yttrium (Y) and including light rare earth elements and heavy rare earth elements. As R, a light rare earth element is sufficient, and Nd and Pr are particularly preferable. Usually, one kind of R is sufficient, but in practice, a mixture of two or more kinds (mish metal, dymium, etc.) can be used for reasons such as convenience in obtaining, and Sm, Y, La, Ce, Gd
Etc. can be used as a mixture with other R, especially Nd, Pr and the like. Note that this R may not be a pure rare earth element, and may contain impurities that are unavoidable in production within the industrially available range.

R is an essential element of alloy slabs for producing R—Fe—B permanent magnets. If it is less than 10 atomic%, high magnetic properties, especially high coercive force, cannot be obtained. The residual magnetic flux density (Br) decreases, and a permanent magnet with excellent characteristics cannot be obtained. Therefore, R is in the range of 10 at% to 30 at%.

B is an essential element of the alloy slab for producing the R—Fe—B permanent magnet. If it is less than 2 atomic%, a high coercive force (iHc) cannot be obtained. Since the magnetic flux density (Br) decreases, an excellent permanent magnet cannot be obtained. Therefore, B is set in the range of 2 to 28 atomic%.

Fe is an essential element of alloy slabs for producing R—Fe—B permanent magnets. When the content is less than 42 atomic%, the residual magnetic flux density (Br) decreases. Since magnetic force cannot be obtained, Fe is limited to 42 to 88 atomic%. Further, a part of Fe can be replaced by one or two of Co and Ni. This is because the effect of improving the temperature characteristics of the permanent magnet and the effect of improving the corrosion resistance can be obtained. Is one or two of Fe5
If it exceeds 0%, a high coercive force cannot be obtained, and an excellent permanent magnet cannot be obtained. Therefore, the upper limit of the substitution amount of one or two of Co and Ni is 50% of Fe.

In order to obtain an excellent permanent magnet having both a high residual magnetic flux density and a high coercive force in the alloy slab according to the present invention, R12 atomic% to 16 atomic%, B4 atomic% to 12 atomic%, and Fe 72 atomic%. % To 84 at%. Further, the alloy slab according to the present invention comprises R, B, Fe
In addition, the presence of unavoidable impurities such as oxygen, C, Ca, and Mg in industrial production can be tolerated, but a part of B is converted to 4.0 atomic% or less of C, 3.5 atomic% or less of P, At least one of S at most 3.5 at.%, Cu at most 3.5 at.%,
By replacing the total amount by 4.0 atomic% or less, it is possible to improve the productivity of the magnet alloy and reduce the price.

Further, the R, B, Fe alloy or C
In an R-Fe-B alloy containing o, 9.5 atomic% or less of Al, 4.5 atomic% or less of Ti, V of 9.5 atomic% or less, Cr of 8.5 atomic% or less, M of 0 atomic% or less
n, Bi at 5 atomic% or less, Nb at 12.5 atomic% or less,
10.5 atomic% or less of Ta, 9.5 atomic% or less of Mo,
9.5 at% or less W, 2.5 at% or less Sb, 7 at% or less Ge, 35 at% or less Sn, 5.5 at%
By adding at least one of the following Zr and 5.5 atomic% or less of Hf, a high coercive force of the permanent magnet alloy becomes possible. In the R-Fe-B-based permanent magnet of the present invention, it is essential that the main phase of the crystal phase is tetragonal, and in particular, a sintered permanent magnet having excellent magnetic properties is obtained by obtaining a fine and uniform alloy powder. It is effective for producing a magnet.

In the present invention, the thickness of the slab of the magnet material having a structure in which the R-rich phase is finely dispersed is set to 0.03 mm to 10 mm.
The reason for limiting to mm is that if it is less than 0.03 mm , the quenching effect will be large, the crystal grain size will be smaller than 3 mm, and it will be easy to oxidize when powdered, leading to deterioration of magnetic properties and after fine grinding. Undesirably, since the grains become polycrystalline, the degree of orientation decreases and Br decreases, and if it exceeds 10 mm, the cooling rate decreases, α-Fe tends to crystallize, the crystal grain size increases, and the Nd-rich phase This is not preferable because magnetic properties, especially coercive force, are reduced because of the presence of the magnetic flux. More preferably, the thickness is 0.05 mm to 3 mm.

The cross-sectional structure of the R—Fe—B alloy having a specific composition obtained by the strip casting method according to the present invention is an ingot obtained by casting a main phase R ₂ Fe ₁₄ B crystal in a conventional mold. Is about 1/10 or more finer than that of, for example, its short axis dimension is 0.1 μm to 50 μm.
m, the long axis direction is a fine crystal of 5 μm to 200 μm,
In addition, the R-rich phase is finely dispersed so as to surround the main phase crystal grains, and the size thereof is 20 μm or less even in a locally ubiquitous region.

[0021]

The operation of the manufacturing method according to the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory view schematically showing an apparatus used for the strip casting method of the present invention. A tundish 3 having a high-frequency melting furnace 2 and a nozzle 4 at a tip thereof is placed in a closed chamber 1 in a vacuum or an inert atmosphere.
A quenching piece roll 5 disposed adjacent thereto, a scraper 6 provided in contact with the surface of the quenching piece roll 5, and a slab collection container 7 are arranged and accommodated therein. The quenching piece roll 5 has a configuration in which the quenching piece roll 5 is axially arranged in a horizontal direction and horizontally rotates at a predetermined rotation speed by a rotation driving device (not shown), and is cooled by a water cooling device (not shown).

The nozzle 4 at the tip of the tundish 3
It is arranged so as to face an angle range of θ = 30 ° to 90 ° with respect to a line connecting the uppermost portion 5a and the center point 5b of the quenching piece roll 5, and a gap is formed from the surface of the quenching piece roll 5 The length T is set to 0.01 mm to 3.0 mm. After the molten alloy 8 of the R—Fe—B magnet composition melted in the melting furnace 2 is poured into the tundish 3, the molten metal 8 in the tundish 3 is set in a predetermined angle range with respect to the quenching single roll 5. The molten metal is poured from the nozzle 4 disposed at a predetermined gap length to the surface of the quenching piece roll 5 rotating in the direction of the arrow, and quenched and solidified on the cooled roll surface to obtain a plate thickness of 0.03 m.
The slab is formed into a slab of m to 10 mm, then scraped off by the scraper 6 and stored in the slab recovery container 7.

In the present invention, the position of the nozzle is set to 30 ° to 90 ° with respect to a line connecting the uppermost portion of the quenching piece roll and the center line.
The reason for limiting to °° is that if it is less than 30 °, the contact time between the slab and the roll is short, the slab is not sufficiently cooled, and the thickness of the slab varies due to the variation in the level of the nozzle surface. The structure in the slab changes greatly, and the required structure cannot be obtained. If the angle exceeds 90 °, the molten metal easily slides on the roll surface, and the nozzle is liable to be clogged by solidification of the molten metal in the nozzle portion. It is not good. A more preferable angle range is 45 ° to 80 °.

In the present invention, the gap length between the tip of the tundish nozzle and the roll surface is set to 0.01 mm or less.
The reason for limiting to 3.0 mm is that if it is less than 0.01 mm, the quenching roll and the nozzle come into contact with each other and flaws may be formed on the roll surface, or the tip of the nozzle may be chipped, which is not preferable. It is not preferable because the molten metal leaks from between the roll surface and the nozzle. The preferred void length is 0.1
mm to 0.5 mm.

[0025]

【Example】

Example 1 A closed chamber containing a melting furnace, a tundish having a nozzle and a quenching piece roll shown in FIG.
0Nd-1.0Dy-1.1B-3.0Co-63.9
It was melted in a melting furnace so as to become a Fe (wt%) magnet.
The quenched piece roll has a diameter of 300 mm and a rotation speed of 130 rpm.
Using a water-cooled Cu roll, the nozzle at the tip of the tundish is arranged at an angle of 60 ° and a gap of 0.3 mm with respect to a line connecting the top of the water-cooled Cu roll and the center point,
After the atmosphere was Ar 300 Torr, the molten metal was housed in a tundish, and then poured on a water-cooled Cu roll from the nozzle at a nozzle height of 20 mm and a width of 10 mm.
A quenched slab of 0 mm and a length of 10 to 300 mm was obtained.

As a result of arbitrarily selecting 300 slabs and measuring the slab thickness, the plate thickness was 0.23 to 0.35 mm, and the average value was 0.3 mm.
It was 31 mm. The crystal grain size of the slab is 0.5 μm to 15 μm in the minor axis direction and 10 μm to 2 μm in the major axis direction.
50 μm, and the R-rich phase is 1 μm so as to surround the main phase.
It was confirmed that the particles were finely dispersed below m.

The slab is coarsely and finely pulverized by a known method to obtain an alloy powder having an average particle size of 3.5 μm.
It was molded in 5 kOe at a pressure of 1.0 T /, sintered at 1060 ° C. for 3 hours, and then subjected to an aging treatment at 600 ° C. for 1 hour to obtain a permanent magnet. Table 1 shows the magnet properties and the corrosion resistance test results of the obtained permanent magnet. The corrosion resistance test was performed after processing the sintered magnet into a size of 15 mm x 15 mm x 8 mm.
After applying a 25 μm-thick epoxy resin coating, 10 magnets were kept in an environment of 80 ° C. × 90% RH for 200 hours.
It was performed by a method of inspecting its appearance.

Comparative Example 1 The same casting conditions and production as in Example 1 were carried out except that a 3 mm-thick alumina cushion material was interposed between the melt having the same magnet composition as in Example 1 and the tumbling nozzle and the quenching roll. A magnet was obtained under the conditions. The crystal grain size of the obtained slab was almost the same as that of the example. Table 1 shows the magnet properties of the obtained permanent magnet and the same corrosion resistance test results as in Example 1. As shown in the table, the corrosion resistance test results
Swelling having a diameter of 0.5 to 2 mm was observed in three coating films out of ten magnets.

After removing the coating film on the blisters, EPMA
As a result, it was confirmed that Nd oxide was accumulated around Al. The cushion material made of Al ₂ O ₃ mixed in the slab is reduced by the Nd-rich liquid phase during sintering, and the Nd oxide in which Nd oxide accumulates around Al has extremely poor corrosion resistance and reacts with moisture. Since it changed to Nd (OH) ₃ , it was confirmed that the coating film was swollen.

COMPARATIVE EXAMPLE 2 A molten metal having the same magnet composition as in Example 1 was placed at an angle of 2 with respect to a line connecting the nozzle, the top of the water-cooled Cu roll, and the center point.
A magnet was obtained at 0 ° at a molten metal height of 11 mm under the same casting conditions and magnetizing production conditions as in Example 1. The dimensions of the obtained slab are 100 mm in width and 10 to 300 mm in length.
00 sheets were arbitrarily selected and the thickness was measured.
It was 8-0.42 mm and the average value was 0.32 mm. Also,
The crystal grain diameter of the slab of this comparative example is 3 μm to 3 in the minor axis direction.
0 μm, and the major axis dimension was 30 μm to 200 μm. Table 1 shows the magnet properties and the corrosion resistance test results of the obtained permanent magnets.

COMPARATIVE EXAMPLE 3 A molten metal having the same magnet composition as in Example 1 was placed at an angle of 1 with respect to a line connecting the nozzle, the top of the water-cooled Cu roll, and the center point.
The molten metal was poured from the nozzle under the same casting conditions as in Example 1 except that the molten metal surface height was 18 mm at 00 °. Twelve seconds after the start of casting, the molten metal solidified in the nozzle portion, clogging of the nozzle occurred, and casting became impossible.

[0032]

[Table 1]

[0033]

The present invention solves the problem of the molten metal and the single roll in the horizontal casting strip casting method.
By eliminating the cushion material between the nozzle and the roll, and specifying and optimizing the gap length between the nozzle and the roll and the positional relationship between the nozzle and the roll, the R-Fe It is possible to prevent the corrosion resistance of the -B permanent magnet from deteriorating, stably refine the crystal structure, and obtain an R-Fe-B permanent magnet having excellent coercive force and stable magnet properties. It is possible to stably produce casts for similar magnets.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing an apparatus used for a strip casting method of the present invention.

[Explanation of symbols]

1 closed room 2 High frequency melting furnace 3 Tundish 4 nozzles 5 Roll for rapid cooling 5a Top 5b Center point 6 scraper 7 Slab collection container 8 molten alloy

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masami Ueda 2-191-1, Minami Suita, Suita-shi, Osaka Sumitomo Special Metals Co., Ltd. In Suita Works (72) Inventor Takashi Kojima 2-chome, Minami Suita, Suita-shi, Osaka No. 19-1, Sumitomo Special Metals Co., Ltd., Suita Works (72) Inventor Yukiyoshi Watanabe 2-9-1, Minami Suita, Suita-shi, Osaka Sumitomo Special Metals Co., Ltd., Suita Works (56) References JP-A-6 -297114 (JP, A) Special table 63-63,1062 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 11/06 360

Claims (1)

(57) [Claims] 1. An R-Fe-B alloy melt is poured from a nozzle into a quenched roll in a vacuum or in an inert atmosphere, and the main phase is R ₂ Fe _14.
In the method of manufacturing a slab for an R-Fe-B-based permanent magnet to obtain a quenched slab made of a B crystal, a nozzle at the tip of a tundish containing the molten alloy is connected to the top of the quenched slab roll and a center point. to the line, so as to face an angular range position of 45 ° to 80 ° are arranged, and a quench piece roll surface between the nozzle end
Pouring with a gap length of 0.01mm to 3.0mm , thickness 0.03mm
Is 0.1 mm ~ 50 mm minor axis dimension of ~ 10 mm and and said main phase
A method for producing a slab for an R-Fe-B-based permanent magnet, characterized by obtaining a quenched slab .