JPH0475303B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field The present invention relates to a method for manufacturing a sintered permanent magnet material whose main components are R (R is at least one rare earth element including Y), B, and Fe, and is intended for high performance. We aim to improve the orientation of the magnet alloy by preventing the deterioration of magnetic properties due to component segregation during production of alloy ingots, and by increasing the density of the permanent magnet material, further improving magnetic properties, mechanical strength, and corrosion resistance. The present invention relates to a method for producing high-performance sintered permanent magnet material that aims to improve the performance. BACKGROUND OF THE INVENTION Current typical permanent magnet materials are alnico, hard ferrite and rare earth cobalt magnets. As the cobalt raw material situation has become unstable in recent years, the demand for alnico magnets containing 20 to 35 wt% cobalt has decreased, and inexpensive hard ferrite, whose main component is iron oxide, has become the mainstream magnet material. Summer. On the other hand, rare earth cobalt magnets contain cobalt from 50 to
It is very expensive because it contains 60wt% and uses Sm, which is not included in rare earth ores.
Compared to other magnets, the magnetic properties are much higher,
It has come to be used mainly for small, high value-added magnetic circuits. Therefore, the present inventor first developed Fe-B- as a new high-performance permanent magnet that does not contain expensive Sm or Co.
An R-based permanent magnet (R is at least one rare earth element including Y) was proposed (Japanese Patent Application No. 145072/1982). Furthermore, in order to improve the temperature characteristics of permanent magnets made of Fe-BR-based magnetically anisotropic sintered bodies,
By replacing a portion of Fe with Co, we raised the Curie point of the resulting alloy and improved its temperature characteristics.
We proposed a permanent magnet made of Fe-Co-B-R magnetically anisotropic sintered body (Japanese Patent Application No. 166663/1983). These permanent magnets use resource-rich light rare earths such as Nd and Pr as R, and are excellent permanent magnets that have Fe as their main component and exhibit an extremely high energy product of 25 MGOe or more. The above novel Fe-BR system, Fe-Co-BR
Rare earth metals as starting materials for producing permanent magnets are generally produced by a Ca reduction method or an electrolytic method, for example, by the following steps. As starting materials, the rare earth metals, electrolytic iron,
An ingot is cast by high-frequency melting of ferroboron alloy or electrolytic Co. The ingot is coarsely pulverized using a stamp mill, and then wet pulverized using a ball mill to obtain a fine powder of 1.5 μm to 10 μm. Molding with orientation in a magnetic field. After sintering in vacuum, let it cool. Aging treatment is performed in an Ar atmosphere. Problems to be Solved by the Invention As mentioned above, this alloy powder for permanent magnets can be obtained by mechanically crushing and finely crushing an ingot having a desired composition. In this case, compositional segregation is likely to occur during solidification, and Fe and
When such an ingot is crushed and oriented in a magnetic field, these precipitated phases interfere with the orientation, and the part of the ingot that was in contact with the mold is cooled. Due to the high speed, fine crystal grains are likely to be formed, and the crystal growth direction of Fe-Nd-B tetragonal crystals does not match the direction of easy magnetization. Therefore, when the cast alloy is crushed and oriented in a magnetic field, the orientation direction is inconsistent. There was a problem that the degree of orientation decreased because the powder contained a plurality of regular crystal grains. In addition, Fe obtained by the above manufacturing method
-B-R permanent magnet material has a theoretical density of 96
%, and since it is a porous material, there is a limit to the improvement of magnetic and mechanical properties.Also, this type of permanent magnet alloy contains a large amount of Nd or Pr, which is very easily oxidized, so it is not practical. In order to improve oxidation resistance, it is necessary to apply an oxidation-resistant coating such as a plating layer to the magnet surface. However, as mentioned above, this type of magnet is a porous material, and there have been problems such as moisture or acidic or alkaline solutions for surface treatment remaining in the micropores, which can cause rust over time. . This invention aims to improve the orientation of the magnetic alloy by preventing the deterioration of magnetic properties due to component segregation during the production of alloy ingots, and further improves the magnetic properties and mechanical strength by increasing the density of the permanent magnet material. The aim is to develop a method for manufacturing high-performance sintered permanent magnet materials that can improve oxidation resistance through surface treatment in subsequent processes. Means for Solving the Problems This invention was developed as a result of various studies aimed at preventing component segregation in an alloy ingot for Fe-B-R permanent magnets and increasing the density of magnet materials. By annealing the alloy ingot to prevent component segregation and coarsening the crystal grains, and by subjecting the primary sintered body produced using the alloy powder obtained from the alloy ingot to hot isostatic pressing under specific conditions. We found that the density can be almost 100% of the theoretical density, improving magnetic properties and mechanical properties, and that oxidation resistance is improved by making the magnetic material denser and non-porous. , this invention has been completed. That is, this invention has R (where R is at least one kind of rare earth elements including Y) 12 atomic % to 16 atomic %, B4 atomic % to 15 atomic %, and Fe 70 atomic % to 85 atomic % as main components. In the method for producing a sintered permanent magnet material, an alloy ingot having the above composition is annealed at 1000°C to 1150°C, and then the primary sintered body produced by pulverizing this is heated in a sealed container with an inert gas. as pressure medium, temperature 700
This is a method for producing a high-performance sintered permanent magnet material, characterized by hot isostatic pressing at a temperature of 1100°C to 1100°C and a pressure of 500 to 1300 atmospheres. More specifically, the present invention provides a method for forming a molded body having the above characteristic composition into a primary sintered body by sintering it at 900°C to 1200°C in a vacuum, for example,
For example, this primary sintered body is placed in a sealed container embedded in an antioxidant such as metal titanium powder at a temperature of 700°C to 1100°C and a pressure of 500°C using an inert gas as a pressure medium.
This is a manufacturing method for obtaining a high-performance sintered permanent magnet material with improved magnetic properties, mechanical strength, and corrosion resistance by hot isostatic pressing at a pressure of 1,300 to 1,300 atmospheres and further aging treatment. Annealing treatment conditions for alloy ingot In this invention, the annealing treatment temperature for alloy ingot is
The reason for setting the range from 1000℃ to 1150℃ is that below 1000℃, the diffusion rate becomes very slow, and it takes a long time to coarsen the crystal grains and eliminate segregation. This is because it is impossible to prevent Fe or Nd from dissolving and segregation. Furthermore, if the annealing treatment time is less than 0.5 hours, the effect of coarsening the crystal grains and eliminating segregation will not be sufficiently obtained, and if the annealing treatment time exceeds 50 hours, it is effective in preventing segregation and coarsening the crystal grains, but it is not suitable for mass production. Therefore, 0.5 to 50 hours is preferable. Generally, in the production of rare earth cobalt magnet alloys, solution treatment of ingots has been proposed (Japanese Patent Laid-Open No. 126944/1983).
However, _the effect _of solution treatment of rare earth cobalt magnet alloy ingots is remarkable for R ₂ T ₁₇ type compounds (R: rare earth element, T: transition metal). The purpose of solution treatment of permanent magnet ingots is to form an unstable phase (RT ₇ type structure) at room temperature, and after solution treatment, rapid cooling is required, for example by oil quenching or immersion in liquid nitrogen. . However, the annealing treatment of the ingot in this invention is
Unlike the case of the rare earth cobalt magnet described above, the objective is to obtain a single-phase state of the R ₂ Fe ₁₄ B compound, which is a compound stable at low temperatures, and there is no need for rapid cooling after the above-mentioned annealing treatment. In the manufacturing method according to the present invention, starting materials are blended in required amounts, melted and alloyed in a vacuum or inert gas atmosphere to form an ingot, and then subjected to an annealing treatment, which is a feature of the present invention, and then pulverized. is preferred. Coarse pulverization is carried out by mechanical pulverization such as a stamp mill or geocrusher, and further finely pulverized by a jet mill or ball mill. Preferably, this is carried out by wet milling using a solvent. The average particle size of the alloy powder obtained by fine grinding is
In order to obtain excellent magnetic properties, a fine powder with an average particle size of 1 to 40 μm is preferable, and a fine powder with an average particle size of 2 to 2 μm is most preferable. Sintering is performed at a temperature of 900°C to 1200°C in an inert or reducing atmosphere of at least non-oxidizing or 99.9% purity, such as a vacuum of 10 ^-2 Torr or less or a pressure atmosphere of 1 to 760 Torr. ~
It is preferable to perform the primary sintering for 4 hours. Hot isostatic pressing treatment conditions As mentioned above, the Fe-B-R permanent Magnet materials and conventionally known permanent magnet manufacturing methods can be appropriately selected and employed. The density of the primary sintered body is preferably 90% or more of the theoretical density in order to make the density by hot isostatic pressing almost 100% of the theoretical density and to achieve improvements in magnetic properties, mechanical strength, and corrosion resistance. In addition, the temperature conditions for the hot isostatic pressing treatment were set at 700°C to 1100°C, because at temperatures below 700°C, high density cannot be achieved even with hot isostatic pressing at high pressure, and at temperatures exceeding 1100°C. This is because the temperature is close to the melting point of the sintered body, and deformation of the sintered body is extremely undesirable. Furthermore, if the processing pressure is less than 500 atm, it is difficult to increase the density of the sintered compact, and if it exceeds 1300 atm, it is possible to increase the density, but it is not desirable in terms of the durability and cost of the processing equipment. , 500 atm~
The pressure shall be 1300 atm. Performing the aging treatment after the hot isostatic pressing treatment in the present invention is effective in suppressing excessive growth of crystal grains in the magnet body and developing excellent magnetic properties. The aging treatment temperature is preferably in the range of 450°C to 700°C, and the aging treatment time is preferably 5 minutes to 40 hours. The aging treatment time is closely related to the aging treatment temperature, but if it is less than 5 minutes, the aging treatment effect will be small and the magnetic properties of the obtained magnet material will vary widely, and if it exceeds 40 hours, it will take a long time for industrial purposes. Too impractical. From the viewpoint of desirable development of magnetic properties and practical aspects, the aging treatment time is preferably 30 minutes to 8 hours. Moreover, multi-stage aging treatment of two or more stages can also be used for the aging treatment. For example, after hot isostatic pressing a sintered body sintered at 1060℃ at a temperature of 900℃ and a pressure of 900 atm,
By performing an initial aging treatment at ℃ for 30 minutes to 6 hours, and then performing one or more aging treatments at 450℃ to 750℃ for 2 to 30 hours, the residual magnetic flux density, coercive force, and It is possible to obtain a magnetic material having extremely excellent magnetic properties in all squareness of magnetic curves. In addition, instead of multi-stage aging treatment, a method of cooling from the aging treatment temperature of 450°C to 700°C to room temperature using a cooling method such as air cooling or water cooling at a cooling rate of 0.2°C/min to 20°C/min is used. Also, it is possible to obtain a permanent magnet material having magnetic properties equivalent to those obtained by the above-mentioned aging treatment. Reason for limiting the composition of the permanent magnet material Rare earth element R used in the permanent magnet material of this invention
is 12 at% to 16 at% Nd, Pr, Dy, Ho,
At least one of Tb, or in addition,
La, Ce, Sm, Gd, Er, Eu, Pm, Tm, Yb,
Those containing at least one of Lu and Y are preferred. Further, although it is usually sufficient to use one type of R, in practice, a mixture of two or more types (Mitsushimetal, didymium, etc.) can be used for reasons such as convenience of availability. Note that this R may not be a pure rare earth element,
It may contain impurities that are unavoidable during production within an industrially available range. R (at least one rare earth element including Y)
is an essential element in the new above-mentioned permanent magnet materials, and if it is less than 12 atomic %, the crystal structure becomes a cubic structure, which is the same as α-iron, so it has high magnetic properties,
Particularly high retention force cannot be obtained, and if it exceeds 16 atom%, R
The rich nonmagnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet with excellent characteristics cannot be obtained. Therefore, R should be in the range of 12 at.% to 16 at.%. B is an essential element in the new above-mentioned permanent magnet materials. If it is less than 4 atomic %, it will form a rhombohedral structure and high coercive force (iHc) will not be obtained, and if it exceeds 15 atomic %, a B-rich nonmagnetic phase will occur. increases, and the residual magnetic flux density (Br) decreases, making it impossible to obtain an excellent permanent magnet. Therefore, B should be in the range of 4 at.% to 15 at.%. Fe is an essential element in the new above-mentioned permanent magnet materials.If it is less than 70 atom%, the residual magnetic flux density (Br) decreases, and if it exceeds 85 atom%, high coercive force cannot be obtained. % to 85 atomic %. Further, in the permanent magnet material according to the present invention,
Substituting a portion of Fe with Co can improve the temperature characteristics of the resulting magnet without impairing its magnetic properties, but if the amount of Co substitution exceeds 50% of Fe,
On the contrary, it is not preferable because the magnetic properties deteriorate. In the permanent magnet material of this invention, in order to obtain high residual magnetic flux density and high coercive force, R12.5 atomic% is required.
~15 at%, B6 at% ~14 at%, Fe71 at%
~82 atom % is preferred. Further, the permanent magnet material according to the present invention has R,
In addition to B and Fe, the presence of unavoidable impurities in industrial production can be tolerated, but a part of B can be replaced by 20 atom% or less of C, 2.0 atom% or less of P, 2.0 atom% or less of S, 2.0
By substituting at least one type of Cu in a total amount of 2.0 atomic % or less, it is possible to improve the manufacturability and lower the price of permanent magnets. In addition, at least one of the following additional elements is
It is added to Fe-BR-based or Fe-Co--BR-based permanent magnets because it is effective in improving the holding force, etc., improving manufacturability, and reducing costs. However, addition to improve coercive force causes a decrease in residual magnetic flux density (Br), so it is desirable to add in the following range. Al up to 5.0 at%, Ti up to 3.0 at%, 5.5
V at % or less, Cr at 4.5 atomic% or less, 5.0 atomic%
Mn below 5 atomic%, Bi below 9.0 atomic%
Nb, Ta below 7.0 atomic%, Mo below 5.2 atomic%,
5.0 atomic% or less W, 1.0 atomic% or less Sb, 3.5 atomic% or less Ge, 1.5 atomic% or less Sn, 3.3 atomic% or less Zr, 6.0 atomic% or less Ni, 5.0 atomic% or less Si,
Addition of at least one type of Hf of 3.3 atomic % or less; however, if two or more types are contained, the maximum content can be permanently maintained by containing atomic % or less of the one with the maximum value among the added elements. It becomes possible to increase the coercive force of the magnet. The crystalline phase of the alloy powder in this invention is tetragonal with a main phase of at least 50 vol%, at least lvol
% or more of non-magnetic intermetallic compounds is essential for producing sintered permanent magnets with excellent magnetic properties. Further, the permanent magnet material according to the present invention can be press-molded in a magnetic field to obtain a magnetically anisotropic magnet, and can be press-molded in a no-magnetic field to obtain a magnetically isotropic magnet. . The permanent magnet material according to this invention has a residual magnetic flux density
Br＞10.5kG, maximum energy product (BH)
Indicates max≧25MGOe, and the maximum value reaches 40MGOe or more. Further, the composition of the permanent magnet material according to the present invention is
R12 atomic% ~ 16 atomic%, B4 atomic% ~ 15 atomic%,
In the case of Co45 atomic% or less and the balance Fe, the resulting magnetically anisotropic permanent magnet alloy exhibits magnetic properties equivalent to the above magnet alloy, and the temperature coefficient of residual magnetic flux density is 0.1
%/℃ or less, and excellent characteristics can be obtained. Moreover, the R of the alloy powder for permanent magnets according to the present invention is
When the main component is 50% or more of light rare earth metals, R12.5 atomic% to 15 atomic%, B6 atomic% to 14 atomic%
Magnetically anisotropic sintered magnets exhibit the best magnetic properties when the main component is Fe71 to 82 at%, or even Co5 to 45 at%. When the rare earth metal is Nd, the maximum value of (BH)max reaches 40MGOe or more. Effect This invention prevents component segregation by subjecting an alloy ingot of a specific composition to annealing treatment at 1000°C to 1150°C for the purpose of improving the magnetic properties of Fe-BR permanent magnet materials. It is possible to measure the coarsening of crystal grains, and by subjecting the primary sintered body produced by powdering it to hot isostatic pressing under the above-mentioned specific conditions, the density can be made almost 100% of the theoretical density. It has improved magnetic properties and improved mechanical properties, and since the magnet material is made dense and non-porous, the oxidation-resistant surface treatment functions effectively, resulting in excellent oxidation resistance. High performance sintered permanent magnet material can be obtained. Examples Example 1 A 1 kg alloy ingot having a composition of 79.6Fe6.7B13.7Nd in atomic percentage was obtained by high-frequency melting of the starting material in Ar gas and subsequent water-cooled copper casting. This alloy ingot was annealed at 1070° C. for 40 hours, then coarsely crushed to a size of 40 mesh through or less using a geocrusher, and further finely crushed using a ball mill. The obtained alloy powder with an average particle size of 1 to 20 μm,
After pressure molding at a pressure of 2 ton/cm ² in a magnetic field of 10 kOe, it was molded at 1050°C in a vacuum of 1 × 10 ^-4 Torr.
After time sintering, a primary sintered body having a density of 96% of the theoretical density was obtained. Furthermore, this primary sintered body was embedded in metal titanium powder in a sealed container, and Ar gas was used as a pressure medium.
Hot isostatic pressing was performed at a temperature of 880°C and a pressure of 900 atm. Then, after aging treatment at 600°C for 1 hour, magnetic properties and mechanical properties were measured. The results are shown in Table 1. For comparison, a comparative magnet material (Comparison 1) manufactured using the above manufacturing method except that the ingot was not annealed, and a comparative magnet material (Comparison 1) manufactured using the above manufacturing method except that the primary sintered body was not subjected to hot isostatic pressing treatment. A comparative magnet material (Comparison 2) was produced, and its magnetic properties and mechanical properties were similarly measured, and the results are shown in Table 1. Example 2 A 1 kg alloy ingot having a composition of 79Fe7B0.5Dy13.5Nd in atomic percentage was obtained by high frequency melting of the starting material in Ar gas and subsequent water-cooled copper casting. This alloy ingot was annealed at 1080° C. for 20 hours, then coarsely crushed to a size of 40 mesh through or less using a geocrusher, and further finely crushed using a ball mill. The obtained alloy powder with an average particle size of 1 to 20 μm,
After pressure molding at a pressure of 1.8 ton/cm ² in a magnetic field of 10 kOe, it was molded at 1040°C in a vacuum of 1 × 10 ^-4 Torr.
After sintering for 2 hours, a primary sintered body having a density of 95% of the theoretical density was obtained. This primary sintered body was embedded in metal titanium powder in a sealed container, and heated to a temperature of 900°C using Ar gas as a pressure medium.
It was subjected to hot isostatic pressing at a temperature of 900 atm. Then, after aging treatment at 620°C for 2 hours, magnetic properties and mechanical properties were measured. The results are shown in Table 2. For comparison, a comparative magnet material (Comparison 3) manufactured using the above manufacturing method except that the ingot was not annealed, and a comparative magnet material (Comparison 3) manufactured using the above manufacturing method except that the primary sintered body was not subjected to hot isostatic pressing treatment. A comparative magnet material (Comparison 4) was produced, and its magnetic properties and mechanical properties were similarly measured, and the results are shown in Table 2.

【table】

[Table] Effects of the Invention As is clear from the results in Tables 1 and 2 of Examples, the permanent magnet material manufactured by the manufacturing method of the present invention can be manufactured without undergoing annealing treatment and hot isostatic pressing treatment at the time of alloy ingot. It can be seen that the magnetic properties and mechanical properties are improved compared to the comparative magnet material that is not coated.

Claims (1)

[Claims] 1 R (where R is at least one rare earth element including Y) 12 atomic % to 16 atomic %, B4 atomic % to
In a method for producing a sintered permanent magnet material whose main components are 15 at% Fe and 70 at% to 85 at% Fe, an alloy ingot having the above composition is annealed at 1000°C to 1150°C, and then pulverized. A high-performance product characterized by hot isostatic pressing of the primary sintered body produced by the process in a sealed container at a temperature of 700°C to 1100°C and a pressure of 500 atm to 1300 atm using an inert gas as a pressure medium. Method for manufacturing sintered permanent magnet material.