JPH0226006A - Manufacture of anisotropic permanent magnet - Google Patents

Abstract

PURPOSE:To obtain sufficient magnetic anisotropy with a small compression force by a method wherein an upper punch having a pressing plane which is inclined from its center to circumference is pressed against a molded unit and the molded unit is compressed by the pressing plane. CONSTITUTION:A molded unit 2 of magnetic powder is put on the top surface of a lower punch 1 and an upper punch 3 is pressed against the top of the molded unit 2. The pressing plane 3a of the upper punch 3 is so formed as to be inclined along all the radial directions from its center to circumference. In this state, the center axis (a) of the punch 3 is rotated around a vertical axis (b) with the center axis (a) as a fulcrum, i.e., the precession of the upper punch 3 is performed, the molded unit 2 is compressed and metal flow is induced and plastic deformation is made to progress. With this constitution, excellent magnetic anisotropy can be obtained with a small compression force.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing magnetically anisotropic permanent magnets by plastic deformation processing, and more specifically, to a method for producing magnetically anisotropic permanent magnets using plastic deformation processing. The present invention relates to a method for manufacturing an anisotropic permanent magnet that provides a high degree of anisotropy and that does not cause barreling or cracking on the side surface during processing.

(Prior art) A method of plastically deforming a magnetic material to make its material structure anisotropic and exhibit excellent magnetic properties in a specific direction is well known as the formation of aggregated tIIi weave in silicon steel sheets by rolling. ing.

The above effect has also been confirmed in permanent magnets, for example, in extrusion processing for Mn-A11-C-based materials, upset processing for Nd-Fe-B-based materials, and the like.

Such plastic deformation processing utilizes the property that the direction of stress or strain during processing and the axis of easy magnetization of the crystal form a specific orientation relationship.

By the way, during this plastic deformation process, especially during upsetting,
A molded body or an ingot of magnetic powder is placed on a lower punch of a press, and the molded body is pressed by an upper punch to plastically deform the molded body without restraining the peripheral edge of the molded body.

In this case, the press surface of the upper punch that presses the compact is formed as a smooth horizontal surface, and therefore the press surface is usually in contact with the compact over its entire surface. Then, due to the processing pressure from the upper punch, the molded body undergoes metal flow toward its periphery and is plastically deformed.

(Problem to be solved by the invention) However, when using the above-described upper punch,
Since the entire press surface is in contact with the compact, the frictional resistance between the two becomes large. Therefore, the metal flow of the compact will also be resisted. As a result, in order to sufficiently plastically deform the molded body, a correspondingly large pressing force is required.

Generally, in order to obtain excellent magnetic anisotropy, it is sufficient to strongly work the molded body to increase the processing rate and increase the plastic deformation of the material structure. It is not possible to increase the processing rate indefinitely due to problems such as the ability of the material or the deformability of the material.

In addition, plastic deformation can often be increased by increasing the processing temperature.However, as with Nd-Fe-B permanent magnets, the fineness of the crystal grains increases the holding force. In the case of materials that define magnetic properties such as, if the temperature during plastic deformation processing is increased, crystal grains will become coarser and the magnetic properties will deteriorate. Therefore, when manufacturing such magnets, it is not possible to set a high processing temperature.

As a result, it is necessary for such magnets to undergo plastic deformation under high pressure at low temperatures.
It is necessary to use a press machine with a large capacity.

However, since the temperature is low, the deformability of the material is small.

As a result, the tensile stress generated at the periphery of the molded body causes barreling, cracking, etc. to occur in the periphery in the pressurizing direction, resulting in a significant decrease in product yield.

In addition, when plastic deformation is performed using a conventional upper punch, the pressure applied to the molded body shows a pressure distribution such that it is large at the center and small at the periphery. Variations in magnetic properties tend to occur between the center and periphery of the processed product, making it unsatisfactory in terms of producing permanent magnets with uniform properties.

The present invention solves the above-mentioned problems, makes it possible to provide sufficient magnetic anisotropy even with a small pressing force, and does not cause barreling or cracking at the periphery. The purpose of the present invention is to provide a method for manufacturing an anisotropic permanent magnet with small variations in characteristics.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a method for manufacturing an anisotropic permanent magnet in which a molded body of magnetic powder or an ingot is subjected to plastic deformation. is an anisotropic permanent magnet characterized in that the molded body is contacted with an upper punch having a press surface that is inclined from the center point toward the periphery, and the molded body is pressurized by the press surface. A manufacturing method is provided.

The molded body of magnetic powder or ingot to be subjected to plastic deformation according to the present invention is manufactured as follows.

First, the magnetic powder to be used is rare earth l1(R)-iron (F
e) alloy powder, especially R-Fe-B alloy powder, Mn
-A11-C alloy powder, Fe-Cr-Co alloy powder, A
Examples include l-N1-Co alloy powder.

In particular, in the case of R-Fe-B alloy powder, R of a predetermined composition is
-By applying a common molten metal quenching method to a -Fe'-B alloy to prepare a ribbon or flake consisting of an amorphous material or a mixture of amorphous and crystalline material having the alloy composition, 20 ribbons or flakes are prepared. Manufactured by crushing.

Fill such magnetic powder into a predetermined mold and perform hot pressing or isostatic hot pressing at a temperature of 500 to 800°C in a vacuum or non-oxidizing atmosphere to obtain a compact compression molded product. . Furthermore, anisotropy is imparted not only to the molded body of magnetic powder but also to an ingot of the above-mentioned alloy cast under appropriate conditions through plastic working, which will be described later.

In the method of the present invention, the molded body thus produced is subjected to plastic deformation processing as described below.

The outline of the press machine used for plastic deformation processing of the present invention is explained in the first part.
In Figure 0 shown in the figure, the upper surface of the lower punch 1 is a smooth horizontal surface, on which the molded body 2 of magnetic powder described above is placed. An upper punch 3 is brought into contact with the molded body 2.

The upper punch 3 has a pressing surface 3a that is inclined in all directions from the center to the periphery.

Therefore, when the press surface 3a and the molded body 3 come into contact at a certain location, the central axis a of the upper punch 3 is inclined by an angle T in the figure with respect to the overall vertical axis.

In this state, if the center axis of the upper bunch 3 is rotated around the vertical axis using the center axis a as a fulcrum, that is, if the upper bunch 3 is caused to precess, the pressing surface 3a of the upper bunch 3 and the formed object The contact surface (the shaded area in the figure) rotates sequentially over the molded body, and in the process, the molded body 2
is pressurized, metal flow occurs, and plastic deformation progresses.

Note that the movement of the upper bunch 3 is not limited to the above-mentioned precession movement with the center axis a as a fulcrum, but may also perform spiral movement, linear pivot movement, daisy pattern movement, etc. with the center axis a above the formed body. It may be an exercise that makes you feel better.

As described above, in the method of the present invention, the contact surface between the pressing surface 3a of the upper punch and the molded body 2 is a part of the surface of the molded body 2, and is smaller than that in the conventional method.

Therefore, during the precession of the upper punch 3, the frictional resistance between the pressing surface 3a of the upper punch and the compact 2 is significantly reduced. As a result, the metal flow of the molded body 2 can be promoted with a small pressing force, so that the plastic deformation of the molded body 2 can be increased by appropriately selecting the pressing force.

In addition, since the contact surface with the upper punch 3 is a part of the surface of the compact, the metal flow of the compact material progresses relatively freely, so during conventional upset, the side surface of the compact 2 Barreling and cracking, which occur frequently, almost no longer occur. Note that this compositional modification processing is performed at a temperature of 500 to 800° C. in a vacuum or a non-oxidizing atmosphere.

In the method of the present invention, the above-mentioned compact or magnetic powder itself is encapsulated in a can made of an oxidation-resistant material, such as stainless steel, Ni alloy, copper, or titanium, and the above operations are carried out. You can also do it. In this way, it is possible to omit the densification treatment such as hot pressing or isostatic hot pressing that was conventionally performed for manufacturing molded objects (when magnetic powder is enclosed in the can body), and the overall Plastic deformation can also be carried out in the atmosphere.

In addition, this can body is made of a material with high saturation magnetization and high magnetic permeability, such as pure iron, silicon iron, and permendur, and the can body (after deformation) is not removed even after plastic deformation processing. If so, this product can be used as it is as a rotor or stator for a motor, with the yoke material being integrally molded.

Furthermore, if an oxidation-resistant coating such as Ni plating is formed on the surface of the molded body of magnetic powder, the plastic deformation process of the present invention can be performed as it is even in the atmosphere.

Furthermore, by applying a lubricant such as BN or water glass to the surface, plastic deformation of the layer can proceed smoothly.

In addition, as shown in FIG. 2-A and FIG. 2-B, the molded body 2 is extruded forward (FIG. 2-A) or backward as shown by the arrow with the upper punch 1. In the former case, it is possible to obtain an in-plane anisotropic permanent magnet with the axis of easy magnetization randomly in the plane perpendicular to the extrusion axis, and in the latter case, the radial direction It is possible to obtain a radially anisotropic permanent magnet in which the axis of easy magnetization is aligned.

(Example of the invention) Nd: 30% by weight, Fe561% by weight, B: 1% by weight,
A molten metal quenching method was applied to an alloy consisting of Co: 2% by weight, and the obtained flakes were crushed to obtain an average crystal grain size of 0.03. um
Magnetic powder was obtained.

This magnetic powder was vacuum hot pressed at 700°C, and the density was 7.
A molded article having a diameter of 20 mm and a thickness of 20 m was obtained at 5 g/c-.

This molded body was set in the press machine shown in FIG. 1, and upset processing was performed at a temperature of 700' C1 in a vacuum until the processing rate reached 80. Note that the angle T formed between the central axis a of the upper punch and the vertical axis was 2 degrees.

For comparison, upset processing was performed under the same conditions as in the example, except that the upper punch of the press had a conventional structure.

Regarding the obtained magnet (diameter 44.7×thickness 4m), the state of cracks on the side surface and the residual magnetic flux density (Br) in the compression direction
, holding force (Mu Hc), maximum energy product ((B H)
wax) and other magnetic properties were measured. Note that the magnetic properties were measured by cutting samples from two locations, the center and the ends. Also, from the Br value, B r/// (
Table 1 shows the results of the anisotropy rate (%) calculated as 0 or more as Br//+Br soil). The maximum pressure required for processing is also listed in the table.

4゜ (Effects of the Invention) As is clear from the above explanation, the method of the present invention requires less pressing force than the conventional method even when performing plastic deformation processing at the same processing rate. Good plastic deformation can be performed with a small pressing force. Moreover,
Since the metal flow is free, there are fewer cracks on the sides during processing, resulting in a higher overall yield, and the variation in magnetic properties depending on the location is also small.The method of the present invention can be used at lower temperatures than conventional methods. Because it can perform heavy machining! The anisotropy rate can be increased within a range in which the decrease in Hc is small, and as a result, a permanent magnet with increased (BH)wax can be manufactured, and its industrial value is great.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a press machine used in the present invention, FIG. 2-A is a diagram showing forward extrusion using an upper punch according to the present invention, and FIG. 2-B is a diagram similarly showing backward extrusion. ! ...Lower punch, 2...Molded body of magnetic powder, 3...
Upper punch, 3a...Press surface of upper bunch.

Claims (4)

[Claims] (1) In a method for manufacturing an anisotropic permanent magnet in which a molded body of magnetic powder or an ingot of magnetic material is subjected to plastic deformation processing,
A method characterized in that the plastic deformation process is a method in which an upper punch having a press surface that slopes from the center point toward the periphery is brought into contact with the molded body, and the molded body is pressurized by the press surface. Method for manufacturing oriented permanent magnets. (2) The method for manufacturing an anisotropic permanent magnet according to claim (1), wherein the magnetic powder or ingot is a rare earth-iron alloy. (3) Claim (
The method for producing an anisotropic permanent magnet according to 1) or (2). (4) The method for manufacturing an anisotropic permanent magnet according to claim (3), wherein the can body is made of a material having high saturation magnetization, high magnetic permeability, and oxidation resistance.