JP2583113B2 - Rare earth magnet manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a rare earth permanent magnet containing rare earth (R), iron (Fe), and boron (B) as main components, in particular, isotropic in a plane perpendicular to the axis. The present invention relates to a method for producing a plane-anisotropic rare earth magnet in which the easy axis of magnetization is oriented.

[Conventional technology]

Conventionally, a method for producing an R-Fe-B-based anisotropic magnet as a rare earth magnet includes a sintered body obtained by compacting a powder mainly composed of a tetragonal phase of an R-Fe-B-based alloy in a magnetic field and sintering the powder. (Japanese Unexamined Patent Publication No. Sho 59-46008), or a molded article obtained by subjecting a quenched powder of an amorphous or microcrystalline phase to high-temperature molding and plastic working (Japanese Patent Unexamined Publication No. 60-100402). In recent years, uniaxial anisotropic magnets mainly by the former method have been marketed and put to practical use,
Also in the latter method, a uniaxial anisotropic magnet is produced by a method of high-temperature compression working at high temperature.

[Problems to be solved by the invention]

However, according to any of the above methods, the magnet obtained by this method is mainly a uniaxial anisotropic magnet, which has excellent properties in the radial direction all around, and is suitable for a magnet for motors and the like. It was difficult to obtain a magnet.

That is, in the former method of sintering, the material is formed by the orientation of the radial anisotropic magnet in the magnetic field, and the anisotropic material oriented in the magnetic field is sintered to crack during sintering. There was a problem that it was easy to enter and lacked reliability in mechanical strength.

Further, in the latter method of plastic working, it is advantageous in terms of mechanical strength, and although the above-mentioned Japanese Patent Application Laid-Open No. 60-100402 discloses various plastic working methods, A magnet having excellent characteristics has not yet been obtained. Moreover, according to the method described in the above-mentioned publication, the molten metal quenched powder is preformed at room temperature, or is formed at a high temperature, to produce an isotropic magnet body for the time being, and then with respect to this isotropic magnet body. Since compression and backward extrusion are performed, there is a problem in that the plastic working process is performed in two steps and cannot cope with various magnet products requiring various shapes and dimensions.

The present invention provides a method of plastic working at a high temperature using a quenched powder of a molten metal, which is suitable for motors and the like, and is a permanent magnet having excellent properties in the radial direction over the entire circumference, that is, isotropically in a uniaxial vertical plane. It is an object of the present invention to provide a method for manufacturing a plane anisotropic magnet in which the easy axis of magnetization is oriented.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a permanent magnet by subjecting a magnetic alloy powder comprising a rare earth, iron, an amorphous phase containing boron as a main component or a fine resultant phase or a mixed phase thereof to high temperature. The manufacturing method is characterized in that the magnet alloy powder is extruded at an extrusion ratio of 2.4 or more.

[Action]

By extruding the melt quenched powder having the above composition at an extrusion ratio of 2.4 or more, it is possible to produce a plane anisotropic magnet in which the axis of easy magnetization is isotropically oriented in a plane perpendicular to the extrusion axis. The magnet body thus obtained becomes a nearly 100% filled alloy by the composition processing at a high temperature, so that the mechanical strength is high.

Also, according to the method of the present invention by this extrusion process,
If only a metal of appropriate strength is pushed in as a pre-press, there is no place other than the upper opening in the mold, so the molten metal quenched powder is put in from the opening and the punch is pushed in. As a result, the inside of the mold is sealed. In this mold, the powder is subjected to plastic working while being pressed, and a texture in which the axis of easy magnetization is gradually oriented isotropically in a plane perpendicular to the extrusion direction is formed. When the value of the extrusion ratio as the processing amount is 2.4 or more, the orientation reaches a substantially saturated state. Therefore, in the method of the present invention, room-temperature molding or high-temperature molding as preliminary processing becomes unnecessary.

〔Example〕

Hereinafter, examples of the present invention will be described in detail. First, the present inventors have developed an anisotropic magnet having excellent characteristics in the radial direction over the entire circumference and suitable for use as a motor magnet or the like,
Extrusion was selected as a plastic working method capable of producing an anisotropic magnet having a texture in which the axis of easy magnetization was oriented in the plane perpendicular to the axis of a cylindrical body made of an Fe-B alloy material. Was.

Generally, a plastically processed material forms a texture unique to the material according to its crystal structure.

Regarding this point, Japanese Patent Application Laid-Open No. SHO 60-100402 has already disclosed that the easy axis of magnetization is oriented in the compression direction by the compression processing, and a uniaxial anisotropic magnet can be obtained. By applying this extrusion method to apply a compressive force in the radial direction of the columnar material, there is a possibility that a texture having characteristics suitable for a motor can be realized.

However, it is widely known that the content of texture and the degree of organization of the material differ due to the difference in the amount of plastic working, and the setting of the amount of plastic working determines the success or failure of the initial texture. Things.

Therefore, the present inventors have adopted the extrusion ratio, that is, the cross-sectional area ratio before and after the extrusion processing, as a numerical value representing the amount of plastic working, and decided to study.

For this study, R-Fe prepared by the molten metal quenching method was used.
-An experiment was conducted in which the flakes made of a B-based alloy material were crushed and processed into powder having a particle size of about 1 mm or less and the extrusion ratio was changed, and a square pillar measurement sample was obtained from the sample mass obtained by this. Was cut out, and the magnetic characteristics were measured in a total of three directions, that is, two directions, an axial direction and a radial direction. This measurement test was performed in an Ar gas atmosphere under the conditions of an extrusion processing temperature of 700 ° C.

FIG. 1 and FIG. 2 show the results of the magnetic measurement in the measurement test.

FIG. 1 is a diagram showing the relationship between the maximum energy product (BH) max and the extrusion ratio, and FIG. 2 is a diagram showing the relationship between the coercive force BHC and the extrusion ratio with the residual magnetization Br. As shown in these figures, as the extrusion ratio increases, the magnetic properties in the axial direction gradually decrease in the residual magnetization Br and the maximum energy product (BH) max, and become substantially constant when the extrusion ratio exceeds 2.4. On the other hand, the electric characteristics in the radial direction are opposite to the magnetic characteristics in the axial direction, and the remanent magnetization Br and the maximum energy product (BH) max gradually increase at substantially the same value in the two directions. The magnetic properties of these are almost constant at an extrusion ratio of 2.4 or more.

As is clear from the above test results, as the extrusion process proceeds, the axis of easy magnetization is oriented in the radial direction, that is, the orientation in the plane perpendicular to the extrusion axis proceeds, and the extrusion ratio is increased.
When it exceeds 2.4, the magnetic properties become almost constant. Considering this point, when the extrusion ratio is 2.4 or more, the previously oriented structure is destroyed by the extrusion process, and the broken part and the insufficiently oriented part are newly oriented. This phenomenon is considered to occur, and the magnetic characteristics are considered to be constant as a whole.

The coercive force BHC decreased in the axial direction within the range of the extrusion ratio in this experiment, but was substantially constant in the radial direction with little change.

Also, in the above experiment, the pressure applied to the mold and the like increased with the increase of the extrusion ratio. In particular, when the extrusion ratio was 6, a pressure close to the limit strength was applied to the mold and punch used. There was found. Therefore, in consideration of the mass production system, it is difficult to employ a particularly large extrusion ratio in view of the relationship with the mold life and the like, and the smaller the processing force, the more preferable. It is desirable that the extrusion ratio be 2.4 or more and be close to a value close to 2.4.

Further, in the above experiment, the molten metal quenched powder was put into an extrusion die in a powder state without being preformed, and extrusion was performed. As a result, at the time of the first extrusion, it is necessary to use a molded body of the R-Fe-B alloy material or a cylindrical body made of another metal material having a similar deformation resistance, but the powder is injected after the second time. I was able to extrude. As described above, since it is not necessary to preliminarily mold a molded body corresponding to the inner diameter of the extrusion die, a dedicated molding die can be omitted.

Further, in the method of the present invention in which the material powder is directly injected into the mold, an extrusion ratio of 2.4 or more is required to obtain the mechanical strength of the extruded magnet body. At an extrusion ratio of 2.4 or less, although the processing force is small, the obtained magnet body has a somewhat low mechanical strength, and there is anxiety about using it as a rotor magnet for high-speed rotation.

 Hereinafter, specific examples of the present invention will be described.

Example After blending and dissolving Nd metal, electrolytic iron and boron, using a cast ingot, a flake was prepared by a single roll type molten metal quenching method, and the flake was further subjected to a particle size of about 1 mm or less. Into powder. The composition of this flake was analyzed.
As a result, a small amount of impurities of 13.0 atomic% of Nd, 0.8 atomic% of Pr, 4.8 atomic% of B, and 81.3% of Fe was obtained.

Next, in a vacuum hot press furnace, the inner diameter is 30mm to 19mm.
Hold the extrusion die continuously changing to
^After evacuating to ^-4 Torr, Ar gas was injected to return to atmospheric pressure, and the temperature of the extrusion mold was raised to 700 ° C.

As the first extruded material, a MnAlC alloy material sufficiently coated with a graphite-based lubricant is used, and this material is pushed into a mold, and then the punch is lifted to obtain a graphite-based powder lubricant. And by pushing in using a punch with an outer diameter about 1 mm smaller than the inner diameter of the extrusion mold, and further pushing up the lubricant into the gap between the inner surface of the mold and the punch,
After the lubricant was adhered to the inner surface of the mold, the punch was raised and the molten metal quenched powder was injected, and the molten metal quenched powder was pushed in instead of the first punch. Thereafter, the same operation was repeated to prepare an extruded material of the quenched powder of the molten metal.

The processing pressure during this extrusion was 40 kgf / mm, and a square prism of 5 mm square was cut out from the cylindrical body having an outer diameter of 19 mm obtained by the above-mentioned method, and the magnetic properties were measured.
As a result, in the extrusion direction, residual Br = 3.2KG, holding force BHC =
2.5KOe, maximum energy product (BH) max = 1.8MGOe,
The radial characteristics are almost the same in both directions and the residual magnetization Br =
8.8KG, holding power BHC = 6.8KOe, maximum energy product (BH) ma
x = 16.6MG · Oe. The density was 7.5 g / cc and the filling rate was almost 100%. Furthermore, a disk parallel to the extrusion axis perpendicular to the extrusion axis and a disk parallel to the extrusion axis were cut out from this extruded material, and the magnetic torque curve was measured. Indicates a hard magnetization axis, and it was confirmed that the magnet was a plane anisotropic magnet.

Example Using an extrusion die having an inner diameter continuously changing from 18 mm to 10 mm, extrusion was performed using the same material powder as in the example. The resulting cylindrical body with an outer diameter of 10 mm has a length
At 10 cm, there was little variation in the magnetic properties in the longitudinal direction, and it was found to be an advantageous method for producing a small-diameter long magnet having high radial properties.

Further, when the powder was examined under magnification with an optical microscope, the powder was completely bulky due to plastic deformation at a high temperature, and no crack was found at the grain boundary.

〔The invention's effect〕

As described above, when the method for manufacturing a rare-earth magnet of the present invention is used, the quenched molten powder is extruded at an extrusion ratio of 2.4 or more, so that the R-Fe-B-based alloy material which has not been obtained conventionally can be used for motors. A suitable plane anisotropic magnet can be obtained. In this plane anisotropic magnet, the axis of easy magnetization is isotropically oriented in the plane perpendicular to the axis, so that the radial characteristics are uniform over the entire circumference, and when the outer circumference is magnetized, the user must The number of magnetizations and the width of magnetization can be freely selected.

Also, since the melt quenched powder can be directly extruded, there is no need for conventional preforming, and there is no need to prepare a preforming die in response to the user's request for various dimensions and shapes. Only one set of mold and punch is required, and by setting the extrusion ratio to a value close to 2.4 or higher, the working pressure can be reduced and the life of the mold can be prolonged. Is what you do.

Furthermore, when molding directly from powder material, the extrusion ratio is 2.4.
By the above, it is possible to form a complete bulk body by high-temperature extrusion, and because of its high mechanical strength, there is no restriction on use as in the case of a sintered body, and an excellent magnet with a large use range can be obtained. The effect was excellent.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the maximum energy product (BH) max and the extrusion ratio, and FIG. 2 is a diagram showing the relationship between the coercive force BHC and the residual magnetization Br and the extrusion ratio.

Claims (1)

(57) [Claims] 1. A method for producing a permanent magnet by subjecting a magnetic alloy powder comprising an amorphous phase or a fine crystalline phase containing rare earth, iron and boron as main components or a mixed phase thereof to a high temperature, to produce a permanent magnet. A method for producing a rare earth magnet, comprising extruding an alloy powder at an extrusion ratio of 2.4 or more.