JPH0445573B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field The present invention relates to a method for producing 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. The present invention relates to a method for producing a high-performance sintered permanent magnet material that has a high density composition and further improves magnetic properties, mechanical strength, and corrosion resistance. 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 form 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. Problem to be solved by the invention Fe-B- obtained by the above manufacturing method
The R-based anisotropic permanent magnet material has a density of 96, which is the theoretical density.
%, 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. . The present invention provides a method for producing high-performance sintered permanent magnet material, which improves magnetic properties and mechanical strength by increasing the density of permanent magnet material, and improves oxidation resistance through surface treatment in subsequent steps. It is an object. Means for Solving the Problems This invention was developed as a result of various studies on densification for the purpose of improving the magnetic properties, mechanical strength, and corrosion resistance of Fe-BR permanent magnet materials. By hot isostatic pressing the primary sintered body consisting of the composition under specific conditions, the density can be made almost 100% of the theoretical density, improving magnetic properties and mechanical properties. This invention was completed based on the finding that oxidation resistance is improved by making the magnetic material highly dense and non-porous. That is, this invention mainly consists of R (wherein R is at least one kind of rare earth elements including Y) 11 atomic % to 16 atomic %, B4 atomic % to 15 atomic %, and Fe 70 atomic % to 85 atomic %. In the method for manufacturing sintered permanent magnet materials, the primary sintered body is placed in a sealed container using an inert gas as a pressure medium at a temperature of 700°C to 1100°C and a pressure of 500 atm to
This is a method for producing a high-performance sintered permanent magnet material, which is characterized by hot isostatic pressing at 1300 atmospheres. More specifically, the present invention provides a method for forming a molded body having the specific composition into a primary sintered body by sintering the molded body having the specific composition, for example, at 900°C to 1200°C in a vacuum,
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. Hot isostatic pressing treatment conditions The method for producing alloy powder for permanent magnet material until obtaining a primary sintered body, the method for obtaining a compact, the primary sintering method, etc. 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 hot isostatic pressing treatment are such that if the temperature is less than 700℃, high pressure and hot isostatic pressure treatment cannot increase the density, and if the temperature exceeds 1100℃, the temperature will be close to the melting point of the sintered body. As a result, the deformation of the sintered body is extremely undesirable, so the temperature is set in the range of 700°C to 1100°C. 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, a sintered body sintered at 1060°C is subjected to hot isostatic pressing at a temperature of 900°C and a pressure of 900 atm, and then, as the first stage, it is heated at 750°C to 1000°C for 30 minutes to 6 hours. By performing the first stage aging treatment and then performing one or more stages of aging treatment at 450°C to 700°C for 2 to 30 hours, the residual magnetic flux density, coercive force, and squareness of the demagnetization curve can be improved. It is also possible to obtain a magnetic material having extremely excellent magnetic properties. 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 at least one of Nd, Pr, Ho, and Tb in an amount of 11 atomic % to 16 atomic %, or in addition, La,
Sm, Ce, Gd, Er, Eu, Pm, Tm, Yb, Lu,
Those containing at least one type of 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 11 atomic %, the crystal structure becomes cubic, which is the same structure as α-iron, so it has high magnetic properties,
Particularly high coercive force cannot be obtained, and if it exceeds 16 atomic%, R
The rich nonmagnetic phase increases, and the residual magnetic flux density Br
decreases, making it impossible to obtain a permanent magnet with excellent characteristics. Therefore, R should be in the range of 11 atomic % to 16 atomic %. B is an essential element in the above-mentioned new permanent magnet materials.If it is less than 4 at%, a rhombohedral structure will result and a high coercive force iHc cannot be obtained, and if it exceeds 15 at%, a B-rich nonmagnetic phase will form. As a result, 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, and if it is less than 70 at%, the residual magnetic flux density
If Br decreases and exceeds 85 atom%, a high coercive force cannot be obtained, so Fe is contained in a range of 70 atom% to 85 atom%. 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 it deteriorates the magnetic properties. In the permanent magnet material of this invention, in order to obtain high residual magnetic flux density and high coercive force, R12 atomic % ~
15 atomic%, B6 atomic% ~ 14 atomic%, Fe71 atomic% ~
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 4.0 atom% or less of C, 3.5 atom% or less of P, 2.5 atom% or less of S, 3.5
By substituting at least one type of Cu in a total amount of 4.0 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 R-B-Fe or R-B-Co-Fe permanent magnets because it is effective in improving the coercive force, etc., improving manufacturability, and reducing costs. However, due to the addition to improve coercive force, the residual magnetic flux density
Since it causes a decrease in Br, it is desirable to add it in the following range. Al less than 5.0 atom%, Ti less than 3.0 atom%, V less than 5.5 atom%, Cr less than 4.5 atom%, Mn less than 5.0 atom%, Bi less than 5 atom%, Nb less than 9.0 atom%, 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, 5.0 atomic % or less Si, and 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 less than atomic % of the above, it becomes possible to increase the coercive force of the permanent magnet. The crystalline phase of the alloy powder in this invention is tetragonal with a main phase of at least 50 vol% or more, and at least 1 vol.
% or more of non-magnetic intermetallic compounds is essential for producing sintered permanent magnets with excellent magnetic properties. 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 anisotropic magnet. The permanent magnet material according to this invention has a residual magnetic flux density
Shows 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 of this invention is R11
atomic% ~ 16 atomic%, B4 atomic% ~ 15 atomic%, Co45
In the case of atomic% or less and Fe balance, the resulting magnetically anisotropic permanent magnet alloy exhibits magnetic properties equivalent to the above magnet alloys, and the temperature coefficient of residual magnetic flux density is 0.1%/℃ or less, providing excellent properties. . In addition, when the main component of R in the permanent magnet material of the present invention is a light rare earth metal that accounts for 50% or more,
R12 atomic% to 15 atomic%, B6 atomic% to 14 atomic%,
For Fe71 atomic% to 82 atomic%, or even
Magnetic anisotropic sintered magnets exhibit the best magnetic properties when the main component is Co5 atomic% to 45 atomic%, and especially when the light rare earth metal is Nd, (BH)
The maximum value reaches 40MGOe or more. Function This invention is capable of increasing the density by hot isostatic pressing a primary sintered body having a characteristic composition for the purpose of improving the magnetic properties of Fe-B-R based permanent magnet materials under the above-mentioned specific conditions. 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. Examples Example 1 An alloy powder having a composition of 79Fe7B14Nd in atomic percentage and having an average particle size of 4 μm was heated in a magnetic field of 10 kOe.
After pressure molding at a pressure of 2ton/ ^cm2 , 1×10 ^-7
A primary sintered body having a density of 96% of the theoretical density was obtained by sintering in a Torr vacuum at 1060°C for 2 hours. 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 600°C for 1 hour, magnetic properties and mechanical properties were measured. The results are shown in Table 1. In addition, for comparison, a comparative magnet material was manufactured using the above manufacturing method except that the primary sintered body was not subjected to hot isostatic pressing treatment, and its magnetic properties and mechanical properties were similarly measured. The results are shown below. Example 2 An alloy powder having a composition of 71.5Fe8B6Co14.5Nd in atomic percentage and having an average particle size of 5 μm was press-molded in a magnetic field of 10 kOe at a pressure of 2 ton/cm ² and then 1×
A primary sintered body having a density of 95% of the theoretical density was obtained by sintering at 1040°C for 2 hours in a vacuum of 10 ^-4 Torr. This primary sintered body was embedded in metal titanium powder in a sealed container, and heated to a temperature of 800°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 600°C for 1 hour, magnetic properties and mechanical properties were measured. The results are shown in Table 2. In addition, for comparison, a comparative magnet material was manufactured using the above manufacturing method except that the primary sintered body was not subjected to hot isostatic pressing treatment, and its magnetic properties and mechanical properties were similarly measured. The results are shown below.

【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 (R is at least one rare earth element including Y) 11 atomic% to 16 atomic%, B4 atomic% to
In a method for manufacturing a sintered permanent magnet material whose main components are 15 at% Fe and 70 at% to 85 at% Fe, the primary sintered body is heated in a sealed container at a temperature of 700°C to 1100°C using an inert gas as a pressure medium. A method for producing a high-performance sintered permanent magnet material, characterized by hot isostatic pressing at a pressure of 500 atm to 1300 atm.