JPH0444404B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention provides a permanent magnet made of an R ₂ T ₁₇ magnet alloy (where R is at least one rare earth element and T is at least one transition metal) by powder metallurgy. It relates to a manufacturing method. Of course, rare earth elements include yttrium. [Prior art] Among rare earth cobalt magnets, those that are widely used industrially are RCo 5 magnets, typified by SmCo ₅ , which has _a high coercive force _IHC , and RCo ₅ magnets, which have a high residual magnetization ( This is the above-mentioned R ₂ T _17- based magnet represented by Sm ₂ Co ₁₇ , which is characterized by Br). In the R ₂ T ₁₇ series magnet, R is Sm, T is Co, and a part of Co is Fe, Ni,
Magnets with high energy product (BH) _nax have been realized with alloys substituted with transition metals such as Cu, Ti, Zr, and Hf. These magnets are generally manufactured by powder metallurgy. When manufacturing R ₂ T ₁₇ series permanent magnets by powder metallurgy, they are generally obtained by molding powder.
It is manufactured by liquid-phase sintering a powder compact made of an R ₂ T ₁₇ magnet alloy, followed by solution treatment and aging treatment. The R ₂ T ₁₇ -based magnet can obtain high magnetic properties by improving the coercive force ( _I H _C , _B H _C ) and the squareness of the demagnetization curve, that is, 4·(BA) _nax /Br ² . H _C
Regarding the squareness, composition and solution treatment have a large contribution. When R ₂ T ₁₇ magnets are manufactured by powder metallurgy, generally the solid and liquid phases of the alloy coexist at the sintering temperature, and sintering progresses. This liquid phase is also related to the composition of the alloy, and disappears below a certain temperature. Furthermore, when the temperature is lowered further, two types of solid phases exist: Th ₂ Zn ₁₇ type phase and CaCu ₅ type phase, and conventional solution treatment requires keeping the temperature at a constant temperature several tens of degrees Celsius lower than the sintering temperature. Only one step was carried out. [Problems to be solved by the invention] As described above, in the conventional manufacturing method of permanent magnets, the solution treatment after sintering is carried out in only one step while being held at a constant temperature, so that the coercive force _I H _C , _{BHC ,}
Energy product (BH) _nax , squareness 4・(BH) _nax /
Only a relatively low value of Br ² was obtained, and high magnetic properties could not be obtained. The object of the present invention is to reduce the solution treatment temperature in sequence within the temperature range in which the liquid phase generated during sintering disappears, instead of the conventional one-step solution treatment after sintering. By performing solution treatment in multiple stages, _I H _C and _B
An object of the present invention is to provide a method for producing a permanent magnet, which makes it possible to obtain an R ₂ T ₁₇ -based permanent magnet with improved H _C , (BH) _nax , and squareness. [Means for solving the problem] According to the present invention, the powder obtained by molding the powder
A powder compact made of an R ₂ T ₁₇ magnet alloy (where R is at least one rare earth element including yttrium, and T is at least one transition metal) is subjected to liquid phase sintering, followed by solution treatment and aging treatment. Particularly, in the method for manufacturing a permanent magnet, the solution treatment is performed in multiple steps by successively lowering the solution treatment temperature within a temperature range in which a liquid phase generated during the sintering disappears. A method for manufacturing a permanent magnet is obtained. [Example] Next, an example of the present invention will be described with reference to the drawings. Example 1 Sm is 25.5wt%, Fe is 19.0wt%, Cu is 4.8wt%,
The alloy was melted by high frequency heating in an argon atmosphere so that Zr was 2.5 wt% and Co was the balance. Next, this alloy was coarsely ground, and then finely ground to an average particle size of about 4 μm using a ball mill. This powder was compacted at a pressure of 1 ton/cm ² in a magnetic field of approximately 30 KOe.
This powder compact was sintered at 1215° C. for 1 hour in an Ar atmosphere. This sintered body is subjected to a first solution treatment at a temperature below the sintering temperature, held at a temperature higher than 1180℃ and lower than 1205℃ for 1 hour, and then subjected to a second solution treatment. The test was carried out by holding at 1180°C for 2 hours. Prior to this, we investigated the disappearance temperature of the liquid phase contained in the sintered body of the lever, and found that the liquid phase disappeared at around 1200°C based on metallographic observation. This sintered sample was aged at 800°C for 7 hours, slowly cooled, and then its magnetic properties were measured. FIG. 1 shows the relationship between the first stage solution treatment temperature and magnet properties. By performing the first stage solution treatment at a temperature between 1200℃, where the liquid phase disappears, and the second stage solution treatment,
Magnetism is significantly improved. Example 2 Sm is 25.0wt%, Fe is 22wt%, Cu is 4.3wt%,
Example 1 so that Zr was 2.1wt% and Co was the balance.
A powder compact was created in the same manner as above. After sintering this compact at 1220℃ for 1 hour in an Ar atmosphere,
A first stage solution treatment was carried out for 1 hour at 1185°C where the liquid phase had disappeared, followed by a second stage solution treatment at 1170°C for 3 hours. This sample was heated to 800℃.
After aging for 30 hours and slow cooling, the magnetic properties were measured. Table 1 shows a comparison between this two-stage treated sample and a sample that was solution-treated at 1170°C for 4 hours without solution treatment at 1185°C (single-stage treatment). The two-step solution treatment showed significantly better magnetic properties. Example 3 Sm _0.5 Ce _0.5 is 24.5wt%, Fe is 16wt%, Cu is
A powder compact was prepared in the same manner as in Example 1 so that Zr was 4.9 wt%, Zr was 2.6 wt%, and Co was the balance.
After sintering this compact at 1180°C for 1 hour in an Ar atmosphere, a first solution treatment at 1170°C for 30 minutes, where the liquid phase has disappeared, followed by a second solution treatment at 1165°C for 30 minutes. Then, the third stage solution treatment was carried out at 1160
The reaction was carried out for 2 hours at ℃. This sample was aged at 800°C for 30 hours, and after slow cooling, the magnetic properties were measured. Table 2 shows a comparison between a sample that was solution-treated at 1160° C. for 3 hours without multi-stage solution treatment (single-stage treatment) and a sample that was subjected to the three-stage treatment described above. It shows that the magnetic properties are better when the solution treatment is performed in three stages.

【table】

〔Effect of the invention〕

As described above, in the present invention, when producing an R ₂ T ₁₇ -based magnet alloy by powder metallurgy, after sintering a powder compact, the temperature range within which the liquid phase produced during sintering disappears. By sequentially lowering the solution treatment temperature and performing solution treatment in multiple stages, significantly higher _B H _C , _I H _C , and
(BH) _Nax and squareness can be obtained, and an extremely excellent permanent magnet alloy can be realized. Further, by performing solution treatment at a temperature at which the liquid phase disappears as in the present invention, diffusion is promoted and a single R ₂ T ₁₇ phase is formed, thereby improving magnetic properties. Furthermore, according to the present invention, the magnetic properties can be improved in a relatively short time compared to the conventional method where the magnetic properties were not improved unless the solution treatment time was extremely long at a temperature lower than the vanishing temperature. , It is also industrially advantageous from this point of view.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the first stage solution treatment temperature after sintering and magnet characteristics in Example 1 of the present invention.

Claims (1)

[Claims] 1. After liquid-phase sintering of a powder compact made of an R ₂ T _17- based alloy (where R is at least one rare earth element including yttrium and T is at least one transition metal) obtained by compacting the powder, In the method of manufacturing a permanent magnet by solution treatment and aging treatment, the solution treatment includes sequentially lowering the solution treatment temperature within a temperature range in which a liquid phase generated during the sintering disappears. A method for producing a permanent magnet, characterized in that the process is carried out in multiple steps.