JPS6148570B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improved method for manufacturing rare earth-containing permanent magnets. Generally, RM _Z (R is a rare earth element such as Sm or Ce,
M is Co or Co and Fe and Cu or Co, Fe,
Represents Ni and Cu. Many research reports have been made so far regarding alloy systems represented by 5≦Z≦8.5), among which alloy systems whose main components are rare earth elements and Co, specifically RCo ₅ and R ₂ Co _17.
These days, magnets are attracting attention as permanent magnet materials, and their industrialization is progressing. All of these elemental metal systems have sufficiently high saturation magnetization strength (4πIs) and extremely large crystal anisotropy constants, and therefore have excellent coercivity and maximum magnetic energy product. It is known to be a permanent magnetic material. In addition, the maximum magnetic energy product (BH) _nax , which is a typical characteristic of permanent magnets, has a theoretical upper limit of (4πIs/2) ² if a sufficiently high coercive force is obtained.
It can be calculated as Regarding rare earth magnets having RM ₅ , particularly RCo ₅ alloy compositions, magnetic materials with (BH) _nax values close to the upper limit have already been obtained industrially. Therefore, in order to further improve the properties, it is necessary to increase the amount of M, that is, the molar ratio of M to the rare earth element.
R ₂ Co ₁₇ -based rare earth magnets have started to attract attention. However, if the amount of M is simply increased, the coercive force, which is one of the basic characteristics of a magnet, will drop significantly, and sufficient characteristics as a practical permanent magnet cannot be obtained. In order to overcome these difficulties, conventionally, Sm (samarium), which is a type of rare earth element, has been used as the R component, and the optimal composition has been found by changing the combinations and proportions of each component of M. It was being tried. For example, Japanese Patent Application No. 14453/1983 proposes an R ₂ Co ₁₇ rare earth permanent magnet characterized by containing Ni, but the obtained characteristic values are limited to about 20MGO, and values higher than that are not possible. It was not easy to obtain. In addition, in this case, a so-called aging treatment step of 1 to 10 hours at a temperature of 800° C. was always required after sintering. In order to improve the above points, the present invention aims to improve R
_{( Ni _ _ _}
The present invention also provides an improved manufacturing method for a new, low-cost, high-performance, Ni-containing R ₂ Co ₁₇ rare earth magnet that can omit an aging treatment step. According to the findings of the present inventors, the magnet alloy of the present invention generally has a
By cooling to a temperature below 500℃ at a cooling rate of ~500℃/min, aging treatment can be omitted and 20MGO
A high-performance permanent magnet having the above characteristics can be manufactured. At this time, the optimum cooling rate largely depends on the Ni content. Although the mechanism of magnetic hardening related to the improvement of magnetic properties associated with an increase in coercive force is not clear, as the Ni content increases, the optimum cooling rate becomes slower and the obtained coercive force increases. On the other hand, however, it has been found that the maximum magnetic energy product obtained tends to become smaller as a result. Therefore, the present invention provides general formula: R
_{( Ni _ _ _} ) 0.1≦X≦0.15 0.01≦Y≦0.3 0.02≦Z≦0.3 6.5≦A≦7.5 After pulverizing the alloy having the composition, arranging the obtained finely pulverized powder in a magnetic field and press-molding it. , 1180
Sintered at a temperature of ~1250℃, then 10~200℃/m
By cooling the magnet to a temperature of 500° C. or less at a cooling rate of 500° C., this method can omit the aging treatment step and produce a high-performance permanent magnet with properties of 20 MGO or higher. In the magnetic alloy having the composition range according to the present invention, when cooling is performed at a cooling rate within the above range, the characteristics can be obtained by performing a rapid cooling treatment immediately after sintering and then adding an aging treatment, as is conventionally said. However, it was found that the characteristics of the present magnet alloy were not fully exhibited in the sintering-quenching-aging process. In addition, in this alloy, Fe addition has the effect of improving Br, but if the addition is less than 0.01, no effect appears, while if it exceeds 0.3, although Br improves, the coercive force decreases significantly, making it impractical for practical use. It is no longer a permanent magnetic material. Addition of Cu has the effect of improving coercive force, but if the amount added is less than 0.02, it has no effect, and if it exceeds 0.3, although the coercive force is improved, Br decreases significantly, making it impossible to put it into practical use. Furthermore, when magnetization occurs in the region where the molar ratio A of the rare earth element R and the transition element including Cu is 6.5<A<7.5, the magnetic properties deteriorate due to a decrease in the strength of residual magnetization Br and the coercive force iHc. A permanent magnet material of 20 MGO or higher can be obtained without deterioration of thermal stability due to a decrease in the Kyrie point. In addition, in the present invention, the sintering temperature is 1180 to 1250°C.
The reason why the sintering temperature is limited to this range is that if the sintering is outside this range, the sintering will not be performed sufficiently, or even if it is performed, it will take a long time. In addition, the reason why the upper limit temperature of controlled cooling is limited to 500℃ or less is that at 500℃ or higher, the precipitation reaction, which is closely related to the generation of coercive force in this system control, is promoted too much, and the precipitated phase becomes coarse, resulting in significant damage. This is not preferable because it causes deterioration of coercive force. Hereinafter, the present invention will be further explained with reference to Examples, but these Examples are shown merely to illustrate the present invention, and are not intended to limit the present invention thereby. Example 1 An alloy having _a composition represented _{by the chemical formula Sm(Ni0.11Fe0.19Co0.6Cu0.1)6.9 was high - frequency melted} in _{an argon} gas atmosphere and coarsely ground in _an iron mortar. The coarsely ground powder was further ground into a fine powder with an average particle size of 2 to 10 μm by ball milling in a hexane solvent. The obtained fine powder was compression molded using a mold at a pressure of 5 Tons/cm ² in a magnetic field of 12 KOe. The compacted body thus obtained was sintered at a temperature of 1210° C. for 2 hours in an inert gas atmosphere and subsequently cooled to below 500° C. at a cooling rate of 60° C./min. The obtained magnetic properties are summarized in Table 1.

[Table] Comparative example For comparison, only the cooling rate after sintering in Example 1 was set to 1000°C/min, and then 800°C x 4
Optimum aging treatment was performed. The magnetic properties obtained were as shown in Table 2.

[Table] Example 2 In the same manner as in Example 1, after sintering at 1210°C for 2 hours, immediately after sintering at 10°C/min, 20°C/min, and 40°C, respectively.
Six types of permanent magnets were obtained by cooling to a temperature of 500°C or less at cooling rates of ℃/min, 60°C/min, 100°C/min, and 150°C/min. The magnetic properties for these controls are summarized in Table 3. Also, the cooling rate and coercive force after sintering
The relationship with iHc is shown graphically in the attached drawing.

[Table] It can also be seen from the illustrated graph that in the present invention, satisfactory magnetic properties can be obtained when the cooling rate is 10 to 200°C/min. As shown in the above embodiments, according to the present invention, in the R ₂ Co ₁₇ -based rare earth permanent magnet alloy characterized by containing Ni, the cooling rate is reduced to 10% immediately after sintering.
By selecting the temperature within the range of ~200° C./min, a high performance magnet of 20 MGO or higher can be easily obtained without performing an aging treatment step, so the present invention is an industrially very effective manufacturing method.

[Brief explanation of the drawing]

The attached drawing is a graph showing the relationship between the cooling rate after sintering and the holding force iHc.

Claims (1)

_{[ Claims} ] 1 General formula _{: R} ( _Ni (Y, Z, and A are each in the following ranges) 0.1≦X≦0.15 0.01≦Y≦0.3 0.02≦Z≦0.3 6.5<A<7.5 An alloy having a composition expressed as follows is ground, and the obtained powder is placed in a magnetic field. After pressure molding with
A method for manufacturing a rare earth-containing permanent magnet, which is characterized by cooling to a temperature of 500°C or less.