JPS6140738B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing rare earth permanent magnet materials, such as samarium cobalt magnets, which are intermetallic compounds of yttrium, rare earth metals (R), and _transition metals ₍ T). The present invention relates to a manufacturing method capable of improving the squareness ratio of rare earth permanent magnets. Among the intermetallic compounds of R and T, RT ₅ and
It is well known that two types of R ₂ T ₁₇ are useful as magnets. The former is a single-phase rare earth magnet represented by SmCo ₅ , and is the most commonly used rare earth magnet. The latter is _Sm2 in which Co is partially replaced with other metals.
(Co-Fe-Cu) ₁₇ is a two-phase separation type magnet, which has recently been expected to be used as a high-energy product magnet. Rare earth magnets are generally manufactured through the steps of melting raw materials, pulverization, orientation in a magnetic field and compression molding, sintering solution treatment, and aging heat treatment. Here, the dissolution is
The process is carried out using a predetermined amount of raw metal in a furnace such as a high frequency furnace in an inert atmosphere. In the grinding step, the alloy obtained after melting is coarsely ground and finely ground to obtain alloy particles of 1 to 10 microns. Orientation in a magnetic field and compression molding are usually performed simultaneously when a mold is used. The magnetic field strength required for orientation is 8 to 20 KOe
The compression pressure is about 0.3 to 10 ton/cm ² . Sintering is performed in an inert atmosphere such as Ar or He or in vacuum at a temperature range of about 1150 to 1250°C. Since solution treatment usually proceeds at the same time as sintering, there is no need to perform a separate solution treatment step, but of course, solution treatment may be performed separately after sintering. The aging heat treatment is performed by maintaining the temperature within a range of about 750 to 900°C. obtained by the conventional manufacturing method described above.
R ₂ T ₁₇ -based rare earth magnets have a poor squareness ratio of the magnetic hysteresis curve, and therefore have a high energy product ((BH)
There was a drawback that it was not possible to obtain a magnet of max. In the conventional technology, as mentioned above, after solution treatment,
Aging heat treatment is performed, but this is because the aging heat treatment after solution treatment creates an appropriate amount of heat in the R ₂ T ₁₇ phase.
This is to precipitate the RT ₅ phase. like this
The formation of the cell structure of the R ₂ T ₁₇ phase and the RT ₅ phase is due to the coercive force ( _I
Hc) is advantageous for improving. However, if the heat treatment time is extended for a long time, the residual magnetic flux density (Br) and the squareness ratio will decrease, and the energy product will decrease. The reason for this is that a different phase with a low 4πI ₅ (RT ₅ phase) grows, and the easy magnetization direction (C axis) of the R ₂ T ₁₇ phase is not exactly the same as that of the RT ₅ phase, and the orientation as a magnet is This is thought to be due to sexual disturbance. The present invention improves the drawbacks of such conventional manufacturing methods, improves the squareness ratio of hysteresis characteristics,
The purpose of the present invention is to provide a method for manufacturing an R ₂ T ₁₇ rare earth permanent magnet with a high (BH) max. The present invention provides a method for producing an R ₂ T ₁₇ -based magnetic alloy (where R represents yttrium and a rare earth element, and T represents a transition element) by a powder metallurgy method, after sintering and solution treatment. It is characterized by performing aging heat treatment at a temperature of 600°C to 950°C while applying pressure in a direction parallel to the axis of easy magnetization so as to deform in a direction perpendicular to the axis of easy magnetization at low temperatures. That is, the present invention is characterized by applying pressure in a direction parallel to the axis of easy magnetization and deforming it in a direction perpendicular to the pressing direction when performing a step corresponding to the conventional aging heat treatment. Due to such pressurized deformation, alignment of the C-planes of crystal grains present in the sintered body progresses, and as a result, anisotropy progresses and high magnetic properties are obtained. If the direction of pressure deformation is different, the C-plane alignment will not progress, so
The direction of pressure deformation is limited to the above. Further, even if the deformation rate is minute, effects such as improvement in the squareness of the demagnetization curve are recognized, and the higher the deformation rate, the more anisotropy progresses. However, if the deformation rate is too high, defects such as cracks will occur in the sintered body, so the deformation amount is preferably about 10% or less. Examples of the present invention will be described below. Example 1 Sm is 25.8wt%, Ca is 5.2wt%, Fe is 20wt%Zr
The alloy was melted by high-frequency heating in an argon atmosphere so that Co was 2.8 wt%, Ti was 0.1 wt%, and the balance was Co. Next, this alloy was coarsely ground, and then finely ground to an average particle size of about 4 μm using a ball mill.
This alloy was molded at a pressure of 1 ton/cm ² in a magnetic field of 10 KOe. After degassing the molded product in vacuum, it was sintered at 1210°C for 1 hour in an Ar atmosphere, and then solution treated at 1180°C for 1 hour. This sintered body was held at a temperature of 900℃ for 10 hours while being pressed at 2 tons/cm ² so that it deformed by about 5% in a direction perpendicular to the direction of pressure applied during compression molding, and then it was deformed at a rate of 5℃/min or less. with a cooling rate of
Cooled to 300°C. Table 1 shows the magnetic properties of this sample and a sample that was not pressurized during aging.

[Table] Example 2 _{An alloy} of Sm ( _{Co 0} . ₈ Fe ₀ . ₀₅ Cu ₀ . ₁₄₅ Al ₀ . The resulting fine powder was packed into a rubber tube, oriented in a magnetic field of 15 KOe, and press-molded at a pressure of 2 tons/cm ² . This molded body was sintered at 1200° C. for 1 hour in Ar gas, and then rapidly cooled to room temperature in Ar gas. After this, the magnet was aged at 800℃ for 3 hours in an Ar gas atmosphere, and then rapidly cooled to room temperature in Ar.
Table 2 summarizes the magnet properties when the magnet was deformed by about 0.5% in a direction perpendicular to the direction of pressure while being pressurized at 3 ton/cm ² during this aging.

[Table] As is clear from these examples, Br, _B Hc
By using the method of the present invention, there is also a slight improvement in
It is clear that (BH)max is significantly improved, that is, the squareness ratio is significantly improved.

Claims (1)

[Claims] 1 In a method for producing R ₂ T ₁₇ -based magnetic alloy (where R represents yttrium and a rare earth element, and T represents a transition element) by a powder metallurgy method, after sintering and solution treatment, the temperature is lower than 600°C. A method for producing a rare earth permanent magnet, characterized by performing aging heat treatment at a temperature of 950°C while applying pressure in a direction parallel to the axis of easy magnetization so as to deform the magnet in a direction perpendicular to the axis of easy magnetization at low temperatures.