JPS589144B2 - Manganese-Aluminum-Tansokeigokinjiyakuno Seizouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a manganese (Mn)-aluminum (Al)-carbon C alloy magnet.

Although conventional Mn-Al-C alloy magnets were excellent as isotropic magnets, their improvement in magnetic properties had reached a limit.

Under these circumstances, the inventors invented an anisotropic Mn-Al-C alloy magnet that has dramatically improved magnetic properties, mechanical properties, and machinability.

The details are described in, for example, Japanese Patent Application No. 48-87391 and Japanese Patent Application No. 106311-1982.

That is, 68.0 to 73.0% by weight (hereinafter simply referred to as % and -2
2.2) A Mn-Al-C alloy whose basic composition is %C (Mn in the formula indicates manganese component %) and the remainder Al is subjected to warm plastic working in a temperature range of 530° to 830°. As a result, an anisotropic magnet having excellent magnetic properties, mechanical properties, and machinability can be obtained.

In manufacturing this anisotropic Mn-Al-C alloy magnet,
The material obtained by melting and casting is made into a uniform high-temperature phase at high temperature, and then subjected to appropriate heat treatment before being subjected to mixed plastic working. If this heat treatment is performed at a slow cooling rate, transformation to a stable β-Mn phase or a non-magnetic phase called MnAl(r) will occur, and even if warm plastic working is performed, only a magnet with poor characteristics will be obtained. I can't do it.

In other words, in order to obtain a magnet with excellent magnetic properties,
Cooling is necessary to prevent such transformation. On the other hand, as the cooling rate increases, cracks are more likely to occur. These cracks are small cracks, such as those formed on the surface layer of the material, that stick together during mixed plastic working and do not affect the processing or properties, but large cracks progress during processing and the material deteriorates. It may fall apart, the magnetic properties may be poor because it cannot be processed smoothly, or the die may be damaged, which has a large negative impact on processing and properties.

Therefore, there is a limit to the size of the material in order to avoid cracks in the heat treatment required to obtain excellent magnetic properties.

That is, there is a critical diameter.

Here is an example of an experiment.

Approximately 1450℃ by appropriately blending the raw materials of Mn, Al, and C.
The mixture was melted for 30 minutes to produce cast bodies with diameters of 60 mm (hereinafter mm is omitted), 80, 100, and 120.

The composition of this lot is 69.05%Mn,3 as determined by chemical analysis.
It was 0.43% Al and 0.52% C.

6 from the obtained cast body so that the ratio of length to diameter is 1.
Cylindrical bodies with lengths of 0 mm, 80 mm, 100 mm, and 120 mm were cut out, and each was heated to 1150 °C for 2
The mixture was held for a period of time, and then cooled from 1150°C to 500°C at a cooling rate of 100°C/min, and allowed to cool from 500°C to room temperature.

As a result of investigating the occurrence of cracks in the obtained samples, the 60φ and 80φ samples had no cracks at all, and the 10
For 0φ, only one thin crack was observed,
A large crack occurred with respect to 120φ.

After tempering these samples at 600°C for 30 minutes, the processing temperature was 700°C and the pressure was 40k in the atmosphere.
As a result of extrusion processing with g/mm2 and area reduction rate of 75%,
The samples of 60φ, 80φ, and 100φ were processed well, but the sample of 120φ broke in the middle and could not be processed.

As a result of magnetic measurements for 60φ, 80φ, and 100φ, the dominant direction of magnetization is in the axial direction, and the magnetic properties in the axial direction are Br≧6200G, BHC≧25000e, (BH
) max≧6.3×106G·Oe.

In addition, metallurgical microscope observation revealed that 60φ and 80φ
had a nearly uniform and dense structure, but for 100φ, black striped patterns, which were thought to be traces of cracks, were observed.

The critical diameter of this composition at a cooling rate of 100° C./min is 80φ to 100φ; increasing the cooling rate decreases this critical diameter, and decreasing the cooling rate increases the critical diameter.

It has been desired to develop a method for preventing the occurrence of cracks and applying appropriate heat treatment to materials having a size larger than this critical diameter.

As a result of research into a manufacturing method for Mn-Al-C alloy magnets that solves the above-mentioned problems, the inventors have found that the following manufacturing method is effective and that this method is a manufacturing method for magnets with new characteristics. It was found to be effective as

That is, by providing a hole in the material so that the wall thickness of the material is equal to or less than the critical diameter, appropriate heat treatment can be performed without causing cracks.

By fitting the rod-shaped material into the hole of the perforated material thus obtained and performing warm plastic working in the atmosphere, an Mn--Al--C based anisotropic magnet can be obtained as an integrated object.

Here, the number of holes is not limited to one, but may be multiple. For example, for large materials, by drilling two or more holes and making the wall thickness of the material less than the critical diameter, it is possible to prevent cracks from occurring. Appropriate heat treatment can be performed.

In addition, the shape of the material and the hole may be cylindrical or cylindrical, or may have a rectangular or elliptical cross section.

Further, it is desirable that the hole penetrates in the axial direction, but it is also possible to use a hole that is closed at one end.

In this manufacturing method, the internal magnetic property distribution of the resulting alloy magnet is controlled by using different compositions and pre-treatments for the perforated material and the rod-shaped material inserted into the hole. It can be changed.

Furthermore, by using a rod-shaped material that has been subjected to warm plastic processing once to be inserted into the hole, it is possible to improve the overall magnetic properties or change the internal magnetic properties.

Even if a material other than the Mn-Al-C alloy is used as the rod-shaped material to be inserted into the hole, it has similar warm plastic workability to the Mn-Al-C alloy and is oxidation resistant. If it has properties, it can be processed and unique magnets can be created.

Possible processing methods include extrusion, rolling, and forging.

Examples of the present invention will be described below.

Example 1 Mn, Al, and C raw materials were mixed appropriately and heated to about 1450°C.
The mixture was melted for 30 minutes, and several cylindrical cast bodies with an outer diameter of 180φ and an inner diameter of 72φ, and several rod-shaped cast bodies with an 80φ diameter were produced.

The composition of this lot is 69.53%Mn, as determined by chemical analysis.
It was 29.77% Al and 0.70% C.

Each of these cast bodies was cut out to a length of 250 mm, heated to 1150°C and held for 2 hours, and heated to 1150°C.
The sample was cooled from 0.degree. C. to 500.degree. C. at a cooling rate of 100.degree. C./min or more, and then tempered at 600.degree. C. for 30 minutes.

Examination of the obtained cast body revealed that there were no large cracks at all, and only a few small cracks were observed only in the surface layer.

By cutting these cast bodies, the perforated cast body has an outer diameter of 176φ and an inner diameter of (76.0+0.05-0)φ, while the rod-shaped cast body of 80φ has an outer diameter of (76.0+0-0.05). ) φ and fitted the two together.

This sample was extruded in the atmosphere without any oxidation prevention at a processing temperature of 720° C., a pressure of 40 kg/mm 2 , and an area reduction rate of 70%.

The processing was carried out well, and when a test piece was cut out from the center of the obtained sample and the magnetic properties were measured, it was found to be an excellent magnetic alloy with a dominant magnetization direction in the axial direction.

The magnetic properties in the magnetization dominant direction are Br=6000G, BHC
=2350Oe, (BH)max=5.5×106G・
It was Oe.

Further, when observed under a metallurgical microscope, the structure was dense and almost uniform, but a ring-shaped black streak pattern was observed, which was thought to be a trace of the bonding surface.

Example 2 The perforated material cast in Example 1 was subjected to the same heat treatment and cutting process as in Example 1, and was finished into the same shape.

A rod-shaped material to be fitted was cut out from the sample processed in Example 1.

Warm plastic working was carried out under the same conditions as in Example 1, and was carried out satisfactorily.

When the cross-section of the obtained sample was observed under a metallurgical microscope, a nearly ring-shaped black striped pattern, which appeared to be traces of the bonded surface, was observed.

As a sample for magnetic measurement, 10 mm x 10 mm from the center surrounded by the striped pattern and from the outer periphery.
A sample piece of 10 mm in size was cut out and magnetically measured, and it was found that both were anisotropic magnets with a dominant magnetization direction in the axial direction.

Its magnetic properties are Br=6500G, BHc at the center.
=2600Oe, (BH)max=6.7×106G・
Oe, and in the surrounding area Br=6100G, BHC=23
00Oe(BH)max=5.6×106G·Oe, and the characteristics of the center part were better than those of the peripheral part.

As a result of magnetizing the obtained cylindrical magnet and the cylindrical magnet obtained in Example 1 and measuring the magnetic flux distribution on their end faces, it was found that in Example 1, the magnetic flux was high in the peripheral part, and the magnetic flux was high in the central part. Although the magnetic flux distribution was approximately 20% lower than that of the surrounding area, the magnetic flux distribution in this example was almost uniform.

In this way, a magnet with substantially uniform magnetic flux distribution on the end face could be obtained.

Example 3 Approximately 1450
The mixture was melted at ℃ for 30 minutes to create a rod-shaped cast body of 80φ.

The composition of this lot is 72.40%Mn,2 as determined by chemical analysis.
It was 6.36% Al and 1.24% C.

A cylindrical body with a length of 250 mm was cut out from this cast body,
Homogenized at 1150℃ for 2 hours, then heated from 1150℃ to 8℃.
Cool down to 30℃ at a rate of 10-15℃/min, and then cool to 830℃
After that, it was quenched from 830°C to 500°C at a rate of 100°C/min, and then tempered at 600°C for 1 hour.

There were no cracks in the obtained material.

Also, using the perforated material cast in Example 1,
The same heat treatment as in Example 1 was performed and the occurrence of cracks was examined, but only small cracks were observed in the surface layer.

These two materials were cut in the same manner as in Example 1, and then fitted together in the atmosphere at a processing temperature of 680°C and a pressure of 40k.
Extrusion processing was performed at g/mm2 and area reduction rate of 70%.

The processing was carried out well, and when sample pieces were cut out from the center and the periphery as samples for magnetic measurement and magnetic measurements were performed, they were found to be an anisotropic magnet with a dominant magnetization direction in the axial direction.

The characteristic in the axial direction is that at the center, Br=520
0G, BHC=2250Oe, (BH)max=4.4
×106G・Oe, and in the surrounding area, Br=6150G
, BHC=2350Oe, (BH)max=6.0×1
06G・Oe, the peripheral part is better than the center part,
It was excellent in Br and (BH)max.

After the obtained cylindrical magnet was magnetized, the magnetic flux distribution at the end face was measured. As a result, the magnetic flux was about 30% higher in the peripheral part than in the central part.

In Mn-Al-C alloy magnets, the magnetic properties after mixed plastic working change greatly depending on the composition and pretreatment heat treatment. Therefore, as is clear from Examples 2 and 3, by changing the composition of the perforated material and the rod-shaped material to be fitted into the holes and the pretreatment heat treatment, the magnetic properties inside the resulting magnet can be freely adjusted. For example, the magnetic flux distribution shape on the end face of the obtained cylindrical magnet can be varied in various ways.

In addition, in this manufacturing method, even though the joint surface of the perforated material and the rod-shaped material was subjected to mixed plastic working in the atmosphere, there were slight black streaks, as is clear from the metallurgical microscope observation in the example. Only traces of this pattern can be observed, and the bonding performance is extremely good.

This is thought to be due to the fact that Mn-Al-C alloy magnets have excellent weather resistance, corrosion resistance, and oxidation resistance.

In other words, thick scale forms on the surface of general materials such as structural steel in high-temperature atmosphere.

With Mn-Al-C alloys, only a thin oxide film is formed.

It is thought that this thin oxide film greatly contributes to the good bondability of the Mn-Al-C alloy.

In other words, at the beginning of processing, these thin oxide films are in close contact with each other, but as processing progresses, the contact surface is stretched as the processing rate increases, so the thin oxide film is separated and new surfaces are exposed. They are in close contact with each other at close interatomic distances,
At this time, the new surface does not come into contact with the atmosphere, so
Will not be oxidized and can withstand pressure from processing and 530°~8
It is believed that at a high temperature of 30° C., mutual diffusion progresses and metallic bonding occurs, resulting in a strong bond.

In the production of cladding materials, most of the process must be carried out in an inert gas atmosphere or an anti-oxidation treatment must be performed to prevent oxidation, but in the present invention, there is no such need at all, and Mn-Al - This thin oxide film of C-based alloy fits the perforated material and rod-shaped material, and
It is believed that the present invention, which is an anisotropic magnet as a single piece, is made possible by performing warm plastic working in the mixed light region of 830° C. and in the atmosphere.

As described above, the present invention is characterized in that the same or different materials are fitted into the holes of a perforated material and subjected to warm plastic working to form the anisotropic magnet as an integral body.

According to the present invention, it is possible to manufacture large magnets with excellent magnetic properties, which have hitherto been impossible to manufacture due to cracks occurring during pretreatment.

Further, according to the present invention, by making the composition and pretreatment conditions of the perforated material and the material fitted therein different, it is possible to impart an unprecedented distribution of magnetic properties inside the obtained magnet.

As a result, for example, what used to obtain a uniform magnetic field using a pole piece, etc., can be replaced with the Mn magnetic field obtained by the present invention.
-By using Al-C alloy magnets, it is possible to obtain a uniform magnetic field without the need for pole beads, so it has a wide range of uses, not just as a large magnet material, and has extremely high industrial value. .

Claims (1)

[Claims] 1 After heat treatment is applied to a manganese-aluminum-carbon-based magnet alloy material in which a hole is provided so that the wall thickness is less than the critical diameter during heat treatment and cooling, a manganese-aluminum-aluminum material separately prepared is placed in the hole of this material. A method for producing a manganese-aluminum-carbon alloy magnet, which comprises fitting together solid materials of a carbon-based magnet alloy and simultaneously subjecting these materials to wet plastic working to form an anisotropic magnet as an integrated object.