JP2002100524A - METHOD OF MANUFACTURING HOT-PLASTIC WORKING ND-Fe-B MAGNET - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that a large amount of discard mateial such as spent disposal material is generated in a step of manufacturing a hot-plastic working Nd-Fe-B magnet, thus reducing a product yield rate and increasing a manufacturing cost. SOLUTION: Disposal material of a hot-plastic worked Nd-Fe-B magnet is once ground to obtain its powder, the powder is mixed with virgin raw powder obtained by grinding an ultra-quench thin band to obtain a mixture raw powder for a magnet, the mixture powder is subjected to hot-plastic working to obtain an Nd-Fe-B magnet. At this time, the powder of the disposal material is mixed in 40 weight % or less with the weight of powder after being mixed as a reference. Oxygen and carbon amounts in the disposal material powder are restricted to 0.5 weight % or less and to 0.2 weight % or less respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to hot plastic working Nd
The present invention relates to a method for producing a Fe-B magnet.

[0002]

2. Description of the Related Art Conventionally, hot plastically processed Nd-Fe-B based magnet materials have conventionally been used for ultra-quenched Nd-Fe-B magnet materials.
The powder of the d-Fe-B-based ribbon is manufactured through three press workings of cold press forming, hot press forming, and hot plastic working. Here, the cold press forming is a step for first forming the powder, and in this cold press forming, the powder is once formed into a shape such as a column or a ring. Hot press forming is a processing step for increasing the density of the molded product obtained by the cold press forming, and hot plastic working is a processing step for imparting magnetic anisotropy.

[0003] A molded product to which magnetic anisotropy is imparted by hot plastic working is thereafter subjected to machining, rust prevention treatment (epoxy electrodeposition, Ni plating, or the like), and a defective product is removed in an inspection process. Then, the non-defective product is subjected to a magnetizing treatment to obtain a magnet product.

Heretofore, a large amount of discarded material has been generated in the manufacturing process of this hot-worked Nd-Fe-B magnet. Specifically, first, in the step of machining a molded product after hot plastic working, cut off material (material for disposal) is generated.

[0005] For example, if a ring-shaped molded product as shown in FIG. 2 described later is formed by hot plastic working, the opening side end shown in FIG. Further, since the bottom portion 22 has a different direction of magnetic anisotropy from that of the product 18, the bottom portion 22 is cut and removed.
At this time, the cut-out opening side end 20 and the bottom 22 are generated as end materials.

[0006] These scraps are inevitably generated every time one product is produced, and the amount thereof is large. In addition, in the pressing and inspection processes, defective products due to defective materials (cracks, chips, etc.), defective dimensions, and the like are generated, which also become waste materials.

Conventionally, the amount of this waste material generated has reached 40%, and it contains a large amount of expensive Nd. Therefore, it is of course not only to dispose of this as it is, but also to produce industrial waste.

As described above, Nd is an expensive metal, and as a method of recovering the same, a method of melting the same with other metals to produce an alloy, or a method of chemically extracting only Nd is considered. However, in the former method, it is difficult to adjust the components. In the latter method, the amount of Nd contained in the waste material is 30%, which is smaller than Fe, and the substantial balance of Fe is limited by cost. Therefore, even if the latter method is implemented, the cost will be rather high as a whole.

[0009]

Means for Solving the Problems The hot plastic working N of the present invention
A method for producing a d-Fe-B-based magnet has been devised to solve such a problem. A virgin raw material obtained by pulverizing a material for disposing of Nd-Fe-B-based magnets once hot-plastically worked and then pulverizing the resulting powder into a super-quenched ribbon It is characterized in that it is mixed with powder to form a mixed raw material powder for a magnet, and is subjected to hot plastic working to obtain an Nd-Fe-B-based magnet.

According to a second aspect of the present invention, in the first aspect, the waste material powder is mixed with the powder based on the weight of the powder after mixing.
It is characterized by being mixed in an amount of 0% by weight or less.

According to a third aspect of the present invention, in the method of any one of the first and second aspects, the amount of oxygen in the waste material powder is 0.5% by weight.
And the carbon content is 0.2% by weight or less.

[0012]

Operation and Effect of the Invention As described above, the present invention provides Nd-
A material for producing Nd-Fe-B magnets by pulverizing a material for disposing of Fe-B magnets, mixing the resulting powder with virgin raw powder to form a mixed raw powder, and performing hot plastic working. By doing so, it is possible to effectively utilize the scraps and the like that had to be disposed of conventionally, thereby reducing the manufacturing cost of the Nd-Fe-B magnet, and It can contribute to the reduction of industrial waste.

By the way, the powder obtained by grinding the offcuts and the like naturally has a different particle form and chemical composition from those of the virgin raw material powder. In particular, the crushed powder such as offcuts has a higher oxygen content and carbon content than the virgin raw material powder.

Here, the reason why the oxygen content is increased in the case of powder such as offcuts is that oxygen is absorbed in the process of performing hot working twice and further in the process of grinding. In addition, the reason why the carbon content is increased is that carbon applied during press working is not sufficiently removed in the process of pulverizing to obtain a powder and remains in the powder. Therefore, when a magnet is manufactured using a mixture of powder such as offcuts and virgin raw material powder, molding properties and magnet properties generally deteriorate.

However, the specific properties, specifically, the residual magnetic properties and the seizure resistance between the material and the mold during hot plastic working may be rather increased by adding a small amount of powder such as scrap material. It has been found by the study of the present inventor.

[0016] As described above, when powders such as scraps are mixed, molding properties and magnet properties are generally deteriorated. Therefore, in the present invention, the amount of addition is limited to 40% by weight or less based on the powder weight of the mixed powder. Is desirable (claim 2). By restricting the amount of addition to 40% by weight or less as described above, it is possible to suppress the reduction in molding characteristics and magnet characteristics to a certain level or less. In addition, the amount of the powder of the offcuts is desirably 10% by weight or more in order to effectively use the offcuts and the like.

In the present invention, the amount of oxygen in the powder of waste material such as offcuts is 0.5% by weight or less and the carbon amount is 0.2% by weight.
It is desirable to regulate as follows (claim 3). It has been confirmed that better results can be obtained by regulating the amounts of oxygen and carbon in this way.

[0018]

Next, embodiments of the present invention will be described in detail. Nd: 26.5% by weight, Dy: 4.0% by weight, Fe: balance, Co: 6
An ultra-quenched ribbon powder having a composition of 0.6% by weight, Ga: 0.6% by weight and B: 0.9% by weight was cold-pressed.

After applying a carbon lubricant to the cold press-formed body, hot press forming was performed at 800 ° C. Then, after cooling the hot press-formed body to room temperature, a carbon lubricant was applied again, and hot extrusion (plastic working) was performed at 800 ° C. to produce a magnet material.

Here, the hot extrusion was performed as shown in FIG. That is, a hot press molded body was extruded by the dies 12 and 14 inside the dies 10. FIG. 2 specifically shows the shape of the magnet material 16 thus obtained.

Next, the obtained magnet material 16 is machined,
The opening side end 20 having low magnetic properties and the bottom 22 having a different direction of magnetic anisotropy are cut off, and φ30 mm × φ25 mm ×
A 30 mm ring-shaped product 18 was obtained. Next, the cut off material was pulverized and carbon-removed under various conditions to obtain the offcut material powder shown in Table 1.

In Table 1, the amount of oxygen and the amount of carbon contained in the powder are shown together with the particle size of the powder. still,
In the case of virgin raw material powder, the oxygen content is about 0.06% and the carbon content is about 0.02%. That is, in the case of powder obtained by pulverizing offcuts, both the amount of oxygen and the amount of carbon are higher than that of virgin material.

[0023]

[Table 1]

The powders of A, B, C and D shown in Table 1 are added to the virgin raw material powder obtained by pulverizing the ultra-quenched ribbon in various amounts and mixed, and the mixed powder is mixed for a magnet. Press molding and extrusion were performed on the raw material powder in the same process as above, and the extrusion characteristics and magnetic characteristics at that time were evaluated. The results are shown in FIG.

FIG. 3 (a) shows the mixing amount of the powder on the horizontal axis, and the time required for extrusion molding into a predetermined shape on the vertical axis, showing the moldability of each mixed powder. As shown in (a), for powder A having a high content of both oxygen and carbon, it is difficult to extrude it into a predetermined shape if mixed in more than 15%, and powder having a low carbon content but a high oxygen content If B is mixed in more than 20%, it becomes difficult to extrude it into a predetermined shape. However, powders C and D having an oxygen content of less than 0.5% and a carbon content of less than 0.2% are 40%. It can be seen that extrusion molding can be favorably performed under the following mixing amounts.

3 (b), 3 (c) and 3 (d) each show the mixing amount on the horizontal axis and Br (residual magnetic flux density) and iHc on the vertical axis.
(Coercive force) and (BH) max (maximum magnetic energy) are shown, respectively. As is clear from these figures, powders A and B having a high oxygen content and / or high carbon content are clearly shown. It can be seen that although the magnetic properties decrease as the mixing amount increases, the powders C and D having small amounts of oxygen and carbon retain good magnetic properties within a mixing amount of 40%. That is, it can be seen that even when the powder of the offcuts is added, a hot plastically processed Nd-Fe-B-based magnet satisfying the required characteristics can be manufactured.

According to the results shown in FIG. 3, when the powder of the scrap material is mixed, the magnetic characteristics generally tend to decrease.
As shown in (b), for powders C and D having a small amount of oxygen and carbon, when the amount of addition and mixing is relatively small, specifically, about 10%, Br is rather high. ing. The reason is not clear at this time. However, this result is a reproducible result.

It has been confirmed by the present inventor's research that the mixing of the powder of other offcuts suppresses seizure during extrusion molding. FIG. 4 shows this concretely. The results in FIG. 4 show the relationship between the cumulative number of shots and the burn-in amount when the powder D was added to the 20% virgin raw material powder and the mixture was extruded by the method shown in FIG.

Pressing (extrusion) by the method shown in FIG.
Is performed, seizure 24 occurs on the surface of the mold 14 as shown in FIG. The amount of seizure increases cumulatively as the number of presses (the number of shots) increases. When such seizure occurs, the inner diameter of the extruded product gradually increases.

The baking amount on the vertical axis in FIG. 4 represents this cumulative baking amount. As shown in FIG. 4, the cumulative number of shots increases for those without mixing the powder of the offcuts. As a result, the amount of seizure increases, but the amount of seizure does not increase so much even if the number of shots is increased in the case of mixing 20% of the powder of the offcuts. That is, by mixing the powder of the offcuts, the productivity is rather improved.

The reason why the seizure resistance is improved by mixing the powder of the offcuts is not clearly understood. However, it is presumed that carbon contained in the powder of the offcuts functions as a lubricant or a release agent during extrusion molding, thereby improving seizure resistance.

Although the embodiment of the present invention has been described in detail, this is merely an example, and the present invention can be implemented in variously modified forms without departing from the gist of the invention.

[Brief description of the drawings]

FIG. 1 is a view showing a process of hot plastic working in one embodiment of the present invention.

FIG. 2 is a view showing a magnet material obtained by hot plastic working of FIG. 1;

FIG. 3 is a diagram showing the relationship between the mixing amount of the offcuts powder obtained in an example of the present invention and the extrusion characteristics and magnetic characteristics.

FIG. 4 is a view showing the amount of seizure in the case where the offcut powder is mixed, in comparison with the case where no offcut powder is mixed.

FIG. 5 is an explanatory diagram illustrating seizure caused by hot plastic working.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01F 1/08 H01F 1/08 A // C22C 38/00 303 C22C 38/00 303D F-term (Reference) 4K001 AA10 AA39 BA22 CA01 CA18 CA22 4K018 AA27 BA18 BB08 EA31 KA45 5E040 AA04 AA19 BD01 CA01 HB07 HB15 NN01 5E062 CC02 CD04 CE01 CE03 CE04 CE05 CG01

Claims (3)

[Claims] A crushed material for disposing of Nd-Fe-B-based magnet once subjected to hot plastic working, and the resulting powder is mixed with virgin raw material powder obtained by crushing a super-quenched ribbon. Nd-Fe-B after hot plastic working with mixed raw material powder for magnet
Hot working Nd-Fe-
A method for producing a B-based magnet. 2. The hot plastic working Nd-Fe-B according to claim 1, wherein the waste material powder is mixed in an amount of 40% by weight or less based on the weight of the mixed powder.
Method of manufacturing system magnet. 3. The hot working method according to claim 1, wherein the amount of oxygen in the powder of the waste material is 0.5% by weight or less and the carbon amount is 0.2% by weight or less. A method for producing a plastically processed Nd-Fe-B magnet.