JPS5854486B2 - permanent magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in permanent magnets by sintering Fe-Cr-Co alloys.

According to the present invention, a high-density sintered body can be obtained, and a permanent magnet with excellent magnetic properties can be manufactured.

Fe-Cr-Co magnets have almost the same magnetic properties as Alnico 5 magnets, and can be subjected to plastic working and machining that cannot be done with Alnico magnets, so they are finding a wide variety of uses.

There are two methods for manufacturing this alloy-based magnet: casting and sintering.

In the case of the former, the alloy is melted, cast, hot-worked, and processed into raw materials such as rods, wires, and plates, or casts close to the shape of the product are made and polished. The following steps are generally taken.

The more complex the shape required for the final product, the more machining such as cutting and drilling will be required after casting.

Although it can be machined, it is difficult to machine compared to materials such as carbon steel, and cracks can easily occur if care is not taken during plastic working.

Therefore, an effective means is to prepare a powder of a Fe-Co-Cr alloy and use powder metallurgy to obtain a final product, or to finish it into a shape similar to the final product.

Generally, in magnetic materials manufactured by sintering, there is a close relationship between magnetic density and magnetic properties; for example, residual magnetic flux density Br is proportional to density.

Therefore, in order to achieve excellent magnetic properties in a sintered magnet, it is important to bring the sintered density as close to the theoretical density as possible.

Until now, attempts to obtain high-density sintered bodies using powder metallurgy of Fe-Cr-Co alloys have required sintering at high temperatures of 1350°C or higher, and there is a limit to the density that can be achieved. there were.

The present inventor pursued a means to bring the density of the sintered body closer to the theoretical density in the production of permanent magnets using powder metallurgy of Fe-Cr-Co alloys, and this time, we added an appropriate amount of S to the alloy. The present invention was achieved by discovering that by spraying and pulverizing, a finer powder than before can be obtained, which results in higher sintered density.

Since S is generally considered to be an unfavorable component for magnetic properties, efforts have been made to reduce its content as much as possible, and no attempts have been made to actively utilize it.

According to the inventor's experience, the benefit of increased sintered density brought about by finer grain size of the powder more than compensates for the slight effect that the presence of S has on the magnetic properties.

The permanent magnet of the present invention basically has Cr: 15 to 40%.
S
: A molten metal containing 0.01-1.0% is prepared, and the powder obtained by spraying the molten metal is sintered.

Spray & L Water spraying and gas spraying techniques have been established, and may be carried out in accordance with them.

The above Cr and Co in the Fe-Cr-Co alloy
The amounts of the components are generally those employed in alloys of this type.

If the Cr content is less than 15%, the desired magnetic properties cannot be obtained;
On the other hand, if it exceeds 40%, the value of saturation magnetization becomes small, resulting in poor magnetic properties.

When the CO content is less than 10%, the coercive force is low, and when it exceeds 30%, the temperature required for solution treatment becomes high and the price increases, making it impractical.

If the amount of S added is at least 0.01%, the effect of making the particles finer during spraying will be insufficient, and if it is more than 1.0%, the negative effects on the magnetic properties will be significant.

Usually amounts lower than 0.2-0.4% are suitable.

The present inventor also found that by adding an appropriate amount of Si to this alloy, the particle shape of the powder obtained by spraying becomes irregular, and the benefit of fine graining due to the addition of S is further enhanced. I found it.

Therefore, in a preferred embodiment of the present invention, S: 0.01 to 1
．． It is made by sintering a powder obtained by spraying a molten metal containing 0.05 to 3.0% Si to the Fe-Cr-Co alloy containing 0% Si.

Since Si is an α-phase forming element, it has been added in the past for the purpose of facilitating solution treatment, but it was not known that it has the effect of making the shape of alloy powder irregular.

If the amount added is less than 0.01%, this effect is small; on the other hand, 3.
If the amount is more than 0%, the magnetic properties may be impaired.

A more preferred embodiment of the present invention is one in which Ti: 0.05 to 1.5% is added to the above two types of alloys.

It is believed that Ti combines with S to form TiS and alleviates the adverse effects of S on magnetic properties.

The above range was selected from this point of view.

As another aspect of the present invention, B: 0.03 to 0.5% can be added to the above three types of alloys.

B causes liquid phase sintering and improves the sintered density.

This effect can be obtained by adding at least 0.03%, but if more than 0.5% is added, the presence of B itself poses a negative effect on magnetic properties.

In the present invention, if desired, the above-mentioned various Fe-C
C, Nb for r-Co alloy.

Appropriate amounts of one or more of Al, VlMO and W can be added.

The subsequent steps for manufacturing the permanent magnet of the present invention may be carried out according to conventional techniques.

That is, the above alloy powder is press-molded and sintered in vacuum.

Sintering may be carried out at a commonly employed temperature of about 1200° to 1300°C, and there is no need to sinter at a high temperature of 1350°C or higher.

Techniques known to those skilled in the art can also be used for the series of subsequent steps necessary to produce a permanent magnet product, such as solution treatment, heat treatment in a magnetic field, and aging treatment.

Example Cr: 28.0%, Co: 12.0%, s,
A molten metal containing Si, B, and Ti at various values shown in the table was powdered by a water spray method.

Particles passing through 100 meshes were classified, and the proportion (weight %) of fine powders of 350 meshes or less was further measured.

Using a press, apply a pressure of 5 tons/cWL, diameter 11 m
A cylindrical green compact with a length of 15 m was molded.

The compact was sintered in vacuum at 1300°C for 2 hours, and then sintered for 1 hour.
After solution treatment at 200°C, at 650°C for 1 hour, 3
Heat treatment was performed in a magnetic field of 00000e, followed by multistage aging treatment from 620°C to 540°C at 20C intervals.

The sintered density and magnetic properties of the obtained permanent magnet were measured.

The above results are summarized in the table.

From the table, it can be seen that as the S content increases, the proportion of fine particles increases and the sintered density improves accordingly.
.

The effect of adding Ti can also be seen.

Claims (1)

[Claims] I Fe-Cr-C containing 15 to 40% Cr and co=10 to 30φ, with the remainder being Fe and impurities
In a permanent magnet made by sintering an o-based alloy, S:0 is added to the alloy.
．． A permanent magnet characterized by being made by sintering a powder obtained by adding and spraying 01 to 1.0%. 2. The permanent magnet according to claim 1, wherein Si: 0.05 to 3.0φ is further added to the alloy. 3. The permanent magnet according to claim 1 or 2, in which Ti:o, 5 to 3.0% is further added to the alloy. 4. The permanent magnet according to any one of claims 1 to 3, wherein 0.03 to 0.5% of B is further added to the alloy.