JPH0362507A - Manufacture of anisotropic rare earth magnet - Google Patents

Abstract

PURPOSE:To obtain an anisotropic rare earth magnet of a high magnetic characteristic by shaping an anisotropic super quench magnet with a sleeve-shaped or ring-shaped cross section by one heating. CONSTITUTION:A preformed material 1 of an Nd-Fe-B magnet shaped by cold dust shaping is prepared. The same material is compressed with a double-action punch 5 having a core punch 3 and a sleeve punch 4. That is, as shown in Figures (a) and (b), the material at 650-900 deg.C is pressurized and compressed uniformly with the integrated punches 3 and 4 in the first step to obtain a raw material 9 made by dust shaping and composed of a magnetically isotropic solid or solid shaped body having theoretical density of 99% or higher. In the second step, extrusion molding in the same die is performed only with the core punch 3 without re-heating to obtain an anisotropic rare earth magnet raw material 10 with a sleeve-shaped or ring-shaped cross section.

Description

[Detailed description of the invention] [Purpose of the invention]

(Industrial Application Field) The present invention relates to a method for manufacturing an anisotropic rare earth magnet, and more specifically, the present invention relates to a method for manufacturing an anisotropic rare earth magnet, and more specifically, the present invention relates to a method for manufacturing an anisotropic rare earth magnet.
e-B series (R is a La-based rare earth metal, Fe is representative of a transition metal, B is representative of other property-improving metals,
) relates to a method of manufacturing an anisotropic permanent magnet. (Conventional technology) R-Fe-B permanent magnets are made by (a) melting a base alloy, casting it into a mold to form an ingot, pulverizing it into ultrafine powder, and placing this powder in a magnetic field. (b) A sintered magnet that is compacted using a mold and sintered to make it anisotropic; (b) The molten base alloy is ultra-quenched into a thin ribbon, and the coarsely ground powder is used as it is or, for example, As shown in FIG. 4(a), once cold compaction is performed (forming pressure:
on/cm2) and a preformed body 5 with a theoretical density ratio of 80%
1, and using this preformed body 51, wS4 figure (b)
The die 52 and upper punch 53 shown in Fig.
Hot press at ℃ (press pressure e.g. 1 ton/Cm
2) to make an isotropic magnetic material 54, and this material 54 is
The anisotropic superstructure is made by plastic deformation processing (extrusion pressure, e.g., 4 ton/Cm2) with an area reduction rate of 40% or more at a temperature of 900°C or less using another die 55 shown in Figure (C) and an upper bunch 56. There is an ultra-quenched magnet using a rapidly cooled magnet material 5. (Problems to be Solved by the Invention) Although these magnets with high magnetic properties are extremely useful in reducing the size and weight of motors, especially if they can be applied to small motors for OA and FA equipment. However, at present, there are problems in practical application technology, and the actual situation is that it has not been fully applied to motors. To apply the above rare earth magnets to these motors,
It is most desirable to use a thin sleeve-shaped or ring-shaped magnet with magnetic anisotropy in the radial direction, but in the case of the former sintered magnet, it is best to apply a radial magnetic field when molding the powder in a magnetic field. Therefore, the degree of anisotropy is about 50 to 60% lower than that of plate magnets, and those that have become anisotropic will crack due to anisotropy of thermal expansion during heating and cooling during sintering. The problem is that it is easy for this to occur. On the other hand, the latter super-quenched magnet does not require forming in a magnetic field, and anisotropy is achieved through plastic deformation, so even if the sleeve-shaped or ring-shaped magnet is used, the anisotropy can be maximized. However, due to the isotropy of the die 52 and the upper punch 53 shown in FIG. 4(b), the theoretical density ratio is 9.
9% or more of the material 54, and plastic deformation processing using the die 55 and upper punch 56 shown in FIG. 4(C) to make it anisotropic, two heats are required. The problem is that its magnetism is sensitive to crystal grains, and if the crystal grains become coarse due to long-term heating, the magnetism decreases. Additionally, this material is extremely brittle, so the material is extruded into a sleeve. When molding into a ring shape, large molding cracks 58 as shown in FIG. 4(C) occur. (Object of the Invention) The present invention aims to obtain an anisotropic magnet with high magnetism by one heat heating when forming the latter super-quenched magnet into a sleeve-like or ring-like cross-sectional annular shape. The aim is to reduce mold costs and prevent mold cracks by using a set of molds.

[Structure of the invention]

(Means for Solving the Problems) A method for manufacturing an anisotropic rare earth magnet according to the present invention, as described in claim (1), involves ultra-quenching a molten metal of a base alloy of a rare earth magnet to form a thin ribbon. A preform obtained by cold compacting the powder obtained by pulverizing the ribbon is heated to 650 to 900° C., and is uniformly compressed by 7111 pressure using a double-acting punch having a core punch and a sleeve punch to form a green powder. It is characterized by a structure in which an anisotropic rare earth magnet with an annular cross section is manufactured in one heat processing by increasing the theoretical density of the molding material to 99% or more, then retracting the sleeve punch and extruding it with a core punch. . Furthermore, in the invention described in claim (2), in the method described in claim (1), instead of using a cold compacted preform,
It is characterized by a structure in which the powder is directly heated and uniformly compressed under pressure using a double-acting punch having a core punch and a sleeve punch. Furthermore, in the invention described in claim (3), in the method described in claim (1) or (2), instead of retracting the sleeve punch, the sleeve punch is used to apply a slight constant pressure. It is characterized by a structure in which extrusion molding is performed using a core punch while compressive stress is applied to the end face of the processed material. Furthermore, in the invention described in claim (4), in the method described in claim (1), (2), or (3),
It is characterized by a structure in which pressure compression and extrusion molding are performed under a vacuum or an inert gas atmosphere at a pressure lower than that of ITorr. Furthermore, in the invention described in claim (5), in the method described in claim (1), (3), or (4), the material powder is cold compacted. In order to improve the lubrication ability between the mold and the powder grains, we used a preform whose green density was improved by mixing 2% by weight or less of a lubricant such as lithium stearate. It is characterized by In the method for manufacturing an anisotropic rare earth magnet according to the present invention, as described above, a cold compacted pre-formed body (in the case of claim (1)) or a raw material powder (in the case of claim (2)) is used.
), using a two-action double-acting punch having a core punch and a sleeve punch, at 650 to 950°C.
In the first step, the material heated to After obtaining a compacted material consisting of an oriented solid or hollow compact, it is extruded in the same mold as a second step using only a core punch without reheating to form a transverse sleeve-like or ring-like material. An anisotropic rare earth magnet material having a ring-shaped surface is obtained, and then it is suitably magnetized to become an anisotropic rare earth permanent magnet. Note that in this second step, the sleeve punch may be completely retreated from the end surface of the workpiece, but as stated in claim (3), it is preferable to press the end surface of the workpiece with a constant low pressure. By maintaining this condition, mold cracks can be more reliably prevented from occurring. Further, as described in claim (4), it is more desirable that these moldings be performed under a vacuum at a pressure lower than that of ITorr or under heating at 650 to 900° C. in an inert gas atmosphere. In the R-Fe-B magnet to which the present invention is applied, R is a La-based rare earth element represented by Nd, and this magnet contains a small amount of Co, Dy2O3, Ga, etc. to improve the magnetic properties. It goes without saying that it is possible to contain substances for improving corrosion resistance, heat resistance, and workability, such as Ni, Zn, Pb, and aluminum. In the method for manufacturing an anisotropic rare earth magnet according to the present invention, a compacting material made of a magnetically isotropic solid or hollow material is produced using a raw material powder or a preformed body obtained by cold compacting the material powder. This is then extruded to form a magnet material with an annular cross section such as a sleeve or ring shape.The extrusion method used at this time is either backward extrusion or forward extrusion. is also possible. Conventionally, in these molding processes, in the first step, the powder or its preform is heated and compressed to form a magnetically isotropic compacted material, and in the second step, it is reheated and subjected to another molding process. It is extruded in a mold to form a magnetically anisotropic sleeve-like or ring-like cross-sectional annular shape. However, in the conventional case, when this material is heated for a long time, crystal grains grow and its magnetic properties deteriorate. Therefore, in the present invention, f of the core punch and sleeve punch is
By using a double action punch, a magnetically anisotropic sleeve- or ring-shaped permanent magnet having an annular cross section can be obtained with one heat and one set of molds. Furthermore, in the second step of extrusion molding, the occurrence of mold cracks can be more effectively prevented by applying and maintaining a constant pressure compression to the free surface of the end face of the workpiece using a sleeve punch. FIG. 1 shows an embodiment of the method for manufacturing an anisotropic rare earth magnet according to the present invention, in which a molten base alloy of a rare earth magnet is ultra-quenched into a thin ribbon, and the thin ribbon is pulverized into powder. A preform is provided which is molded and cold formed using conventional powder compacting techniques. The density of this preform is 70 to 8 in terms of theoretical density ratio.
0%, and about 80% according to a general molding method. This pre-lil molded body is heated to a temperature of 650 to 900°C, more preferably 700 to 8°C, by a heating method (not shown).
Next, as shown in FIG.
and a double-acting punch 5 having a sleeve punch 4, and a facing punch 6.
At this time, the mold 7 is also heated to 600 to 900
℃, preferably preheated to 700-800℃,
Further, if the preform 1 is small, only the mold 7 may be preheated, and the preform 1 may be heated by heat transfer from the mold 7, or if the preform 1 is large, the preform 1 may be heated by heat transfer from the mold 7. Hayo @ precept form 1
In some cases, the mold 7 can be molded while remaining at room temperature by preheating the mold. Furthermore, instead of the pre-lil molded body 1, it is also possible to set the raw material powder in the molding space 7a of the molding die 7 as it is. Also, if necessary, keep all of these in a sealed tank and make the tank atmosphere a vacuum with a pressure lower than ITorr, or fill it with an inert gas such as argon gas to create an oxidation-preventing atmosphere. preferable. Next, the core bunch 3 of the double-acting punch 5 and the sleeve punch 4
By compressing the preform 1 uniformly by compressing the preform 1 integrally so that their tip surfaces 3a and 4a are on the same plane, a compacted powder material 9 is obtained as shown in FIG. 1(b). . The pressurizing pressure at this time is 0, 5 to 2, Ot
on/cm2, more preferably 1 to 1,5
It is preferable to give ton/cm2, thereby obtaining a compacted material (cylindrical isotropic magnet material) 9 having a theoretical density ratio of 99% or more. Next, as shown in FIG. 1(e), only the core bunch 3 of the double-acting punch 5 is pressed down to perform backward extrusion, and the first
The compacted material 9 shown in Figure (b) is formed into an anisotropic rare earth magnet material 10 having a sleeve-like annular cross section. The extrusion pressure at this time is 2 to 5 tons/cm2 in terms of punch surface pressure. More preferably 3 to 4 tb. Since it cannot be said that molding cracks will not occur on the inner surface during this backward extrusion, the upper end surface 10b is punched in the direction shown by the arrow in FIG. 1(C) using the sleeve punch 4. By applying compressive stress, this cracking can be more reliably prevented from occurring. The compressive force at that time is 0.2 to 1.0 ton/c in pressure.
m2. More preferably, it is 0.4 to 0.6 ton/Cm2. After extrusion molding is completed, the opposed punch 6 is raised to knock out the sleeve-shaped anisotropic rare earth magnet material 10 from the mold 7, and the bottom portion 10a is separately cut and removed, and then magnetized in the radial direction. An anisotropic rare earth magnet is obtained. In the method of manufacturing an anisotropic rare earth magnet according to the present invention, in addition to the above-described backward extrusion, a forward extrusion molding method can also be used, and an example of molding by this forward extrusion will be explained based on FIG. In the mold 7 shown in FIG. 2, the sleeve punch 4 of the double-acting punch 5 is slidably fitted to the core bunch 3, and as shown in FIG. While keeping the surface 3a and the tip surface 4a of the sleeve punch 4 aligned, the pre-IiI shaped body is set in the molding space 7a with the die 2, and then pressurized and compressed by the opposing punch 6 to achieve a theoretical density ratio of 99. % or more of the compacted material 9. Next, as shown in FIG. 2(b), the core punch 3 is
While keeping it fixed, the facing punch 6 is pressed down, and the compacted material 9 is forwardly extruded into a sleeve-shaped anisotropic rare earth magnet material 10. In this case, by applying a constant compressive force to the lower end surface 10b of the anisotropic rare earth magnet material 10 by the sleeve punch 4, the occurrence of mold cracks can be more reliably prevented. By the way, in order to produce sufficient magnetic anisotropy in the radial direction in molding the anisotropic rare earth magnet material 10, which is the sleeve-shaped molded product, the extrusion area reduction ratio must be 40 to 40.
80%, more preferably 55-65% is required. Therefore, in order to obtain a thin sleeve, if a material consisting of a cylindrical pre-shaped body 1 as shown in Figs. 1 and 2 is used as the magnet material, the extrusion area reduction rate may become too large. There is. Therefore, in such a case, it is better to use a thick-walled cylindrical preform 1 as the raw material, as shown in FIG. 3. In other words, as shown in FIG. A thick-walled cylindrical cold compacted preform 1 is set in a molding space 7a of a mold 7 equipped with a double-acting punch 5 having a sleeve punch 3 and a sleeve punch 4, and an opposing punch 6. As shown in FIG. 3(b), the core punch 3 and sleeve punch 4 of the double-acting punch 5 are simultaneously pressed down to form a compacted powder material 9 which is an isotropic magnetic material with a theoretical density ratio of 99% or more.
get. At this time, the core punch 3 is equipped with a small diameter part 3b that enters into the hollow part 1b of the thick-walled cylindrical preformed body 1, and as shown in FIG. The small diameter portion 3b of the core punch 3 is inserted into the hole 9. Further, the opposing punch 6 is provided with a hollow portion 6b for receiving the small diameter portion 3b of the core punch 3.
Next, as shown in FIG. 3(C), only the core punch 3 of the double-acting punch 5 is pressed down and extruded into an anisotropic rare earth magnet material 10 which is a thin sleeve-shaped molded product. During this time, if a certain compression force is applied to the end surface 10b of the anisotropic rare earth magnet material 10 using the sleeve punch 4, the occurrence of molding cracks can be more reliably prevented, but molding can be performed without applying pressure. It is. (Function of the Invention) Since the method for manufacturing an anisotropic rare earth magnet according to the present invention has the above-described configuration, anisotropy is performed by plastic deformation without requiring forming in a magnetic field. When forming an anisotropic ultra-quenched magnet that is later magnetized into a sleeve-like or ring-like cross-section,
An anisotropic rare earth magnet with high magnetic properties can be manufactured by one heat heating. (Example) Thickness 20ILm obtained by ultra-quenching a molten base alloy of a rare earth magnet having a composition of Nd13.5Fe80.5B8.0
A flaky powder with a size of about 2001 Lm was obtained by pulverizing the ribbon.Next, 0.5% by weight of lithium stearate was mixed uniformly into this powder, and then it was extruded using a conventional powder molding press. A cylindrical preform with a diameter of 29.5 mm and a height of 25 mm was obtained. Subsequently, this preform was heated in a conventional vacuum degreasing furnace at a vacuum level of 10-2 Torr and a temperature of 450°C. Degreasing was carried out for a holding time of 30 ml to remove lithium stearate by evaporation. This forecast! The density of the a-shaped body was measured, and the theoretical density ratio was 77%. Next, after applying graphite powder as a lubricant to the surface of this preform and drying it, it was heated for 2 ml in an argon gas atmosphere to raise the temperature to 750°C, and immediately after that, the die 2 shown in FIG. It was charged into the molding space 7a of the molding die 7 having an inner diameter of 30 mm. In this case, the mold 7 is
The core punch 3 and sleeve punch 4 were preheated to 50° C. in an argon gas atmosphere, and the core punch 3 and the sleeve punch 4 were first pressed down at the same time to uniformly compress the material at a pressure of 1 ton/cm 2 to obtain a compacted powder material 9 . Although it is not necessary to take out the 7 molds in the manufacturing process, for reference purposes, the compacted material 9 was taken out from the mold 7 in this state, cooled, and its dimensions and density were measured. As a result, the diameter was 30.1 mm. , height 18.5mm,
The theoretical density ratio was 99.6% ◆ Next, after obtaining a uniformly compressed powder molding material 9 by the same molding process as above, as shown in FIG.
The anisotropic rare earth magnet material 10, which is a sleeve-shaped molded product, was obtained by pressing down only the core punch 3 having a diameter of 1 mm and performing backward extrusion molding. In this case, the pressing force by the core punch 3 is 4.0t
on/cm2, and the sleeve punch 4 has a pressing force of 0.6.
A pressure of ton/cm 2 was applied so as to follow the positional change of the end face 10b of the anisotropic rare earth magnet material 10, which is a molded product. After cooling this anisotropic rare earth magnet material 10, it was taken out from the argon atmosphere chamber and its dimensions were measured. As a result, the outer diameter was 30.1.
mm, inner diameter 24.1mm, height 45mm, bottom thickness 3.5m
m, and there were no molding cracks on its inner and outer surfaces. Next, after cutting and removing the bottom part 10a of this sleeve-shaped anisotropic rare earth magnet material 10, it was magnetized in the radial direction to form an anisotropic rare earth magnet, and the maximum magnetic energy in the radial direction was measured. However, we were able to obtain a material with excellent magnetic properties of 31 MG·Oe. Example 2 Using the same flaky powder as above, 100 g of it was weighed and placed in the molding space 7a of the mold 7 shown in FIG. 1, which was preheated to 800° C. in an argon atmosphere. It was charged without heating. The inner diameter of the die 2 of this mold 7 was 30 mm. Then, as shown in FIG. 1(b), the core punch 3 and sleeve punch 4 are simultaneously pressed down to a pressurizing pressure of 1 ton/ton.
The powder was heated by heat transfer from the molding die 7 while being kept under pressure of 2 m1n at am', and at the same time, the density was improved. Next, by pressing down only the core punch (diameter 24 mm) 3 and performing backward extrusion molding, an anisotropic rare earth magnet material 10 as a sleeve-shaped molded product was obtained. In this case, the pressure of the core punch 3 was set to 3.5 ton/cm<2>, and the sleeve punch 4 was moved backward so that no pressing force was applied. Next, after cooling the anisotropic rare earth magnet material 10,
As a result of taking it out of the argon atmosphere chamber and measuring its dimensions, the outer diameter was 30.1 mm, the inner diameter was 24.1 mm, the height was 45.5 mm,
The bottom thickness was 3.4 mm. However, molding cracks with a depth of about 1.2 mm had occurred on the inner surface. Next, the bottom part 10a of the anisotropic rare earth magnet material 10, which is the sleeve-shaped molded product, was cut and removed, and the inner diameter part was ground to remove the molding cracks and the inner diameter was set to 26.5 mm. . This was magnetized in the radial direction to form an anisotropic rare earth permanent magnet, and as a result of measuring the maximum magnetic energy in the radial direction, it was possible to obtain excellent magnetic properties of 28 MG·Oe.

【Effect of the invention】

In the method for manufacturing an anisotropic rare earth magnet according to the present invention, a molten metal of a base alloy of a rare earth magnet is ultra-quenched into a thin ribbon, and a powder obtained by pulverizing the thin ribbon is cold-pressed into a preform (one molded body). 65
After heating to 0 to 900°C and uniformly pressurizing and compressing with a double-acting punch having a core punch and a sleeve punch to increase the theoretical density of the compacted material to 99% or more, the sleeve punch is retreated to form a core punch. By extrusion molding, an anisotropic rare earth magnet with an annular cross section is manufactured in one heat process. It is heated and compressed uniformly by a double-acting punch having a core punch and a sleeve punch.Furthermore, in the above manufacturing method, instead of retracting the sleeve punch, the sleeve punch applies a slight compressive stress at a constant pressure. is applied to the end surface of the workpiece, and extrusion molding is performed using a core punch.Furthermore, in the above manufacturing method, pressure compression and extrusion molding are performed under vacuum or an inert gas atmosphere at a pressure lower than ITorr. Furthermore, in the above manufacturing method, when cold compacting the raw material powder, 2% by weight or less of a lubricant such as lithium stearate is mixed in order to improve the lubrication ability between the molding die and the powder particles. Since we used a preform with improved compaction density, we did not need to form it in a magnetic field, but instead created anisotropy through plastic deformation and then magnetized it. When forming a quenched permanent magnet into a sleeve-like or ring-like cross-sectional annular shape, it is possible to make an anisotropic permanent magnet with high magnetic properties by one heat heating, and it is also possible to make it into an anisotropic permanent magnet with high magnetic properties by compressing it under pressure. Pressure compression to increase the density to over 99% and extrusion molding to form a sleeve or ring shape are performed in the same mold, making it possible to significantly reduce mold costs. A remarkable effect is brought about in that it is possible to prevent cracks from occurring on the inner surface of the ring-shaped or ring-shaped inner surface. and. As in conventional methods, where pressure compression and plastic working with a theoretical density ratio of 99% or more are performed in separate molds and heating is performed in two heats, the crystal grains become coarser due to long-term heating. This brings about an extremely excellent effect in that there is no deterioration in magnetic properties due to this.

[Brief explanation of drawings]

FIGS. 1(a), (b), and (c) are cross-sectional explanatory diagrams showing the manufacturing method of an anisotropic rare earth magnet according to an embodiment of the present invention in the order of steps, and FIGS. 3(a), (b), and (c) are cross-sectional explanatory diagrams illustrating a method for manufacturing an anisotropic rare earth magnet in another embodiment in the order of steps, and FIGS. FIGS. 4(a), 4(b), and 4(c) are cross-sectional explanatory views showing the conventional method for manufacturing an anisotropic rare earth magnet in order of steps. 1...Pre-order form, 2...Dice, 3...Core punch, 4...Sleeve punch, 5...Double acting punch, 7...Forming mold. 9...Powder molding material, 10...Anisotropic rare earth magnet material. Figure 1 (G) Figure 1 (b) @ Figure 2 (0) Figure 2 (b) Figure 3 (()) Figure 3 (b) 3rd “Ma<c>

Claims (5)

[Claims] (1) The molten base alloy of rare earth magnets is ultra-quenched into a thin ribbon, the thin ribbon is pulverized and the powder is cold compacted to form a preform, which is then heated to 650 to 900°C to form a core punch and a sleeve punch. After increasing the theoretical density of the compacted material to 99% or more by uniformly pressurizing and compressing it with a double-acting punch having A method for manufacturing an anisotropic rare earth magnet, characterized by manufacturing a rare earth magnet by one heat processing. (2) In the method according to claim (1), instead of using a cold compacted preform, the powder is directly heated and uniformly formed by a double-acting punch having a core punch and a sleeve punch. A method for manufacturing an anisotropic rare earth magnet characterized by compressing it under pressure. (3) In the method according to claim (1) or (2), instead of retracting the sleeve punch, the sleeve punch applies a slight compressive stress of a constant pressure to the end surface of the workpiece, and then the core punch is used. A method for producing an anisotropic rare earth magnet, characterized by extrusion molding. (4) In the method according to claim (1), (2) or (3), pressure compression and extrusion molding are carried out in one step.
A method for manufacturing an anisotropic rare earth magnet, characterized in that the manufacturing method is carried out under a vacuum at a pressure lower than Torr or under an inert gas atmosphere. (5) In the method described in claim (1), (3), or (4), when cold compacting the raw material powder, the mutual lubrication ability of the forming mold and the powder particles is 2% by weight of lubricants such as lithium stearate to improve
A method for producing an anisotropic rare earth magnet, characterized by using a preform whose green density has been improved by mixing the following: