JPH0518895B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD This invention relates to a method for producing a sintered permanent magnet material mainly composed of R (R is at least one rare earth element including Y) B, Fe, and in particular, hot isostatic pressing. The present invention relates to a method of manufacturing a sintered permanent magnet material in which the permanent magnet material is densified through processing to improve magnetic properties and mechanical strength. BACKGROUND OF THE INVENTION Current typical permanent magnet materials are alnico, hard ferrite and rare earth cobalt magnets. Among these, rare earth cobalt magnets have exceptionally excellent magnetic properties and are used for a variety of purposes, but the main components, Sm and Co, are both scarce and expensive, and will continue to be used for a long time. Therefore, it is difficult to stably supply it in large quantities. Therefore, there has been a strong desire for a permanent magnet material that has excellent magnetic properties, is inexpensive, and is composed of constituent elements that are abundant in resources and can be stably supplied in the future. The applicant has previously proposed a new high-performance permanent magnet that does not contain expensive Sm or Co.
proposed a permanent magnet (at least one rare earth element containing Y) (Japanese Patent Application Laid-Open No. 59-46008,
No. 59-64733, JP-A No. 59-89401 1 JP-A-59-
No. 132104). This permanent magnet is an excellent permanent magnet that uses resource-rich light rare earths such as Nd and Pr as R, and has Fe as its main component and exhibits an extremely high energy product of 25 MGOe or more. Problems to be Solved by the Invention This Fe-BR-based anisotropic permanent magnet material is
Since the density is about 96% of the theoretical density and it is a porous material, there is a limit to the improvement of magnetic and mechanical properties.In addition, this type of permanent magnet alloy does not contain a large amount of Nd or Pr, which is very easily oxidized. Therefore, in practice, it is necessary to apply an oxidation-resistant coating such as a plating layer to the magnet surface to improve oxidation resistance. 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. . For this reason, the inventor first densified the Fe-BR-based permanent magnet material by hot isostatic pressing to improve its magnetic properties and mechanical strength, and then Manufacturing method of sintered permanent magnet material with improved oxidation resistance through treatment (Patent application 1983-
259761). However, in the above manufacturing method, Fe-B-
Depending on the composition of the R-based permanent magnet material, particularly the composition of R, there has been a problem in that even if hot isostatic pressing is performed, the sintered body cannot be densified. The purpose of this invention is to provide a method for manufacturing a sintered permanent magnet material, which improves magnetic properties and mechanical strength by increasing the density of the permanent magnet material, and improves oxidation resistance through surface treatment in the subsequent process. In particular, a method for producing a high-performance sintered permanent magnet material that can increase the density of a sintered magnet body by hot isostatic pressing regardless of the R composition of the Fe-B-R permanent magnet material. It is an object. Means for Solving the Problems As a result of various studies aimed at increasing the density of Fe-B-R permanent magnet materials, the present invention has been made by primary sintering to obtain a sintered body having a specific density, and then under specific conditions. By hot isostatic pressing and aging, the density can be made almost 100% of the theoretical density, improving magnetic properties and mechanical properties, and making the magnetic material highly dense and non-porous. It was found that the oxidation-resistant surface treatment functions effectively and is effective in improving oxidation resistance. It was discovered that a decrease in density occurs, such as the generation of pores inside the sintered body, without isostatic pressing, and the temperature was lower than that of hot isostatic pressing under the above specific conditions. When subjected to hot isostatic pressing under these conditions, even if the composition has a large R-rich liquid phase, the sintered body can be uniformly hot isostatically pressed, achieving a high density of almost 100% of the theoretical density. I found out what I can do. That is, in this invention, R is 10 atomic % to 30 atomic % (R is Nd, Pr, Dy,
At least one of Ho, Tb or further,
La, Ce, Sm, Gd, Er, Eu, Tm, Yb, Lu, Y
(consisting of at least one of the following), B2 at % to 28 at %, and Fe65 at % to 80 at %, the primary sintered body is sintered as necessary. After aging the aggregate at 700°C to 1000°C, the temperature is increased using an inert gas as a pressure medium in a sealed container embedded in an antioxidant such as metallic titanium powder.
This is a method for producing a high-performance sintered permanent magnet material, which is characterized by subjecting it to hot isostatic pressing at 400°C to 700°C and a pressure of 500 to 1300 atmospheres, and subjecting it to aging treatment if necessary. In the primary sintering process performed before the hot isostatic pressing process of this invention, the density of the primary sintered body obtained is 90% or more of the theoretical density in order to improve magnetic properties, mechanical strength, and oxidation resistance. It is preferable to do so. This is because if the density of the primary sintered body is less than 90% of the theoretical density, the density cannot be increased to 98.5% or more of the theoretical density by hot isostatic pressing. In addition, the temperature conditions for the hot isostatic pressing treatment were set at 400°C to 700°C, because if the temperature is below 400°C, even if hot isostatic pressing is performed at high pressure, high density cannot be obtained, and if the temperature exceeds 700°C, This is not preferable because a R-rich liquid phase is formed, and depending on the composition, the hot isostatic pressing process cannot be applied. 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. In this invention, as a pre-process performed before hot isostatic pressing, necessary steps are taken to improve the residual magnetic flux density, coercive force, and squareness of the demagnetization curve of the magnet after hot isostatic pressing. Depending on the condition, aging treatment is performed, but if the treatment temperature is less than 700℃, the coercive force will decrease, and if it exceeds 1000℃, the coercive force will similarly decrease, so the aging treatment temperature is preferably in the range of 700℃ to 1000℃, and The aging treatment time is preferably 30 minutes to 6 hours. If it is less than 30 minutes, the effect of aging treatment will be small;
Variations in the magnetic properties of the obtained magnet material become large, and if the time exceeds 6 hours, the effect will be saturated, making it impractical. In this invention, in order to improve the coercive force and the squareness of the demagnetization curve, aging treatment may be performed after hot isostatic pressing, and the aging treatment temperature is preferably in the range of 450°C to 700°C. Moreover, the aging treatment time is preferably 5 minutes to 40 hours. If the aging treatment is carried out for less than 5 minutes, the effect of the aging treatment will be small and the magnetic properties of the obtained magnet material will vary widely, and if it exceeds 40 hours, it will take too long for industrial use to be practical. From the viewpoint of desirable development of magnetic properties and practical aspects, the aging treatment time is preferably 30 minutes to 8 hours. In addition, the aging process is 2
It is also possible to use a multi-stage aging treatment. 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 limitation of permanent magnet material Rare earth element R in rare earth alloy powder of this invention
accounts for 12 to 20 at% of the composition, but at least one of Nd, Pr, Dy, Ho, and Tb
Species, or even La, Ce, Sm, Gd, Er,
Contains at least one of Eu, Tm, Yb, Lu, and Y. Furthermore, although it is usually sufficient to use one type of R, in practice, a mixture of two or more types (mitsumetal, dididium, etc.) may be used depending on the availability of the material. Note that R does not need to be a pure rare earth element, and may contain impurities that are unavoidable in production within an industrially available range. R is an essential element in new Fe-B-R permanent magnets, and if it is less than 10 atomic %, the crystal structure becomes cubic, which is the same structure as α-iron, so it has high magnetic properties, especially high coercive force. If it is not obtained and exceeds 30 atom%, the R-rich nonmagnetic phase increases and the coercive force decreases.
Although it is 10 kOe or more, 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 10 atomic % to 30 atomic %. B is an essential element in Fe-B-R permanent magnets, and if it is less than 2 atom%, the rhombohedral crystal structure will be the main phase, and high coercive force iHc will not be obtained, and the coercive force will be less than 10 kOe, and if it exceeds 28 atom%. and B-rich nonmagnetic phase increases, the residual magnetic flux density Br decreases, and (BH)
max is less than 20MGOe, making it impossible to obtain an excellent permanent magnet. Therefore, B is 2 atom% to 28 atom%
The range shall be . Fe is an essential element in the new above-mentioned permanent magnets.If it is less than 65 at%, the residual magnetic flux density Br decreases, and if it exceeds 80 at%, high coercive force cannot be obtained. The content is atomic%. Further, in the permanent magnet material according to the present invention,
Replacing 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 30% of Fe, the magnetic properties will be adversely affected. is undesirable because it deteriorates
Further, the preferred amount of substitution is 20% or less. Further, the permanent magnet according to the present invention has R, B,
In addition to Fe, the presence of unavoidable impurities in industrial production can be tolerated, but a portion of B can be replaced with 4.0 atomic % or less of C,
Production of permanent magnets by substituting at least one of 3.5 atomic % or less P, 2.5 atomic % or less S, 1.5 atomic % or less Cu, and 5 atomic % or less Si, in a total amount of 5.0 atomic % or less. It is possible to improve performance and reduce costs. In addition, at least one of the following additional elements is
It can be added to Fe-BR-based permanent magnets because it has the effect of improving the coercive force and squareness of the demagnetization curve, 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 a range that is equal to or higher than the residual magnetic flux density of conventional hard ferrite magnets. 5.0 atomic% or less Al3.0 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 5.2 atom%, Mo less than 5.0 atom%, W less than 5.0 atom%, Sb less than 1.0 atom%, Ge less than 3.5 atom%, Sn less than 1.5 atom%, Zr less than 3.3 atom%, 6.0 atom % or less Ni, 1.1 atomic % or less Zn, 3.3 atomic % or less Hf. However, if two or more types are contained, the maximum content is the maximum value of the added elements. By containing atomic percent or less of a material having the following, it becomes possible to increase the coercive force of the permanent magnet. Particularly preferable additive elements include V,
Nb, Ta, Mo, W, Cr, Al, the content is preferably a small amount, 3 at% or less is effective, and Al
is 0.1 to 3 atomic %, preferably 0.2 to 2 atomic %. It is essential that the main crystalline phase (80% or more of a specific phase) be tetragonal in order for the magnet to exhibit high magnetic properties. This magnetic phase is composed of FeBR tetragonal compound crystals, and the grain boundaries are surrounded by a nonmagnetic phase. The non-magnetic phase mainly consists of an R-rich phase, and if there is a large amount of B, a B-rich phase may also be partially present. The presence of non-magnetic phase grain boundary regions is thought to contribute to high coercive force, and is an important structural feature of the alloy of the present invention, and even a small amount is effective; for example, 1 vol% or more is a sufficient amount. be. Further, the permanent magnet of the present invention can be press-molded in a magnetic field to obtain a magnetically anisotropic magnet, and can be press-molded in a non-magnetic field to obtain a magnetically isotropic magnet. In the raw material powder, TiB ₂ , BN, ZrB ₂ , ZrB ₁₂ ,
HfB ₂ , VB ₂ , NbB, NbB ₂ , TaB, TaB ₂ ,
At least one of borides such as CrB ₂ , MoB, MoB ₂ , Mo ₂ B, WB, W ₂ B, etc. in an amount of 0.05 at % to 3.0
By containing atomic percent, growth of crystal grains during sintering of the magnet body can be suppressed. The permanent magnet according to the present invention exhibits a coercive force iHc≧10kOe, a residual magnetic flux density Br>9kG,
The maximum energy product (BH)max shows (BH)max≧25MGOe in the most preferred composition range,
The maximum value reaches over 50MGOe. Further, the composition of the permanent magnet material of this invention is R11
atomic% ~ 16 atomic%, B2 atomic% ~ 15 atomic%, Co45
In the case of atomic% or less Fe balance, the obtained 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. In addition, when the main component of R in the alloy powder for permanent magnets of this invention is light rare earth metals mainly consisting of Nb and Pr, R12 atomic % to 15 atomic %,
B5.5 atomic% to 10 atomic%, when Fe is the main component,
Alternatively, when some of the Fe is replaced with 20% or less Co, magnetically anisotropic sintered magnets exhibit the best magnetic properties, especially when the light rare earth metal is Nd
In this case, the maximum value reaches 50MGOe or more. Function This invention is capable of increasing the density by subjecting a primary sintered body of a specific composition to hot isostatic pressing under the aforementioned specific conditions to improve the magnetic properties of Fe-B-R permanent magnet materials. It is possible to achieve almost 100% of the theoretical density, resulting in improved magnetic and mechanical properties.Furthermore, because the magnet material is made highly dense and non-porous, the oxidation-resistant surface treatment works effectively. As a result, a high-performance sintered permanent magnet material having excellent oxidation resistance can be obtained. Example In terms of atomic percentage, alloy powders (invention Nos. 1 to 4) with an average particle size of 4 μm consisting of the composition shown in Table 1,
After pressure molding at a pressure of 2 ton/cm ² in a magnetic field of 10 kOe, it was molded at 1060°C in a vacuum of 1 × 10 ^-7 Torr.
A primary sintered body having a density of 96% of the theoretical density was obtained by sintering for a period of time, and this primary sintered body was embedded in metal titanium powder in a closed container, and Ar gas was used as a pressure medium.
Hot isostatic pressing was performed at a temperature of 600°C and a pressure of 900 atm. After aging at 660° C. for 1 hour, magnetic properties and mechanical properties were measured. The results are shown in Table 2. For comparison, the temperature of the primary sintered body was 800℃.
Hot isostatic pressing treatment at a pressure of 900 atm and 600℃, 1
Comparative magnet materials (Nos. 5 to 8) were manufactured using the above manufacturing method except that they were subjected to a time aging treatment, and their magnetic properties and mechanical properties were similarly measured, and the results are shown in Table 2.

【table】

【table】

[Table] Effects of the Invention As is clear from the results in Tables 1 and 2 of Examples, the permanent magnet material produced by the manufacturing method of the present invention has a higher It can be seen that the magnetic properties and mechanical properties are improved.

Claims (1)

[Claims] 1 R 10 atomic % to 30 atomic % (R is Nd, Pr, Dy,
At least one of Ho, Tb or further,
La, Ce, Sm, Gd, Er, Eu, Tm, Yb, Lu, Y
), B2 atomic% ~ 28
In a method for producing a sintered permanent magnet material whose main component is Fe65 to 80 atom%, the primary sintered body is placed in a sealed container at a temperature of 400℃ to 700℃ using an inert gas as a pressure medium. Pressure 500 atm ~
A method for producing a high-performance sintered permanent magnet material, which is characterized by hot isostatic pressing at 1300 atm. 2 R10 atomic% to 30 atomic% (R is Nd, Pr, Dy,
At least one of Ho, Tb or further,
La, Ce, Sm, Gd, Er, Eu, Tm, Yb, Lu, Y
), B2 atomic% ~ 28
In the method for manufacturing sintered permanent magnet materials whose main components are Fe65 to 80 at%, the primary sintered body is aged at 700 to 1000 degrees Celsius, and then an inert gas is blown in a sealed container. As a pressure medium,
A method for producing a high-performance sintered permanent magnet material, characterized by performing hot isostatic pressing at a temperature of 400°C to 700°C and a pressure of 500 to 1300 atmospheres.