JPS6263617A - Manufacture of fe-co soft magnetic material - Google Patents

Abstract

PURPOSE:To manufacture soft magnetic material superior in magnetic property, by reheating Fe-Co sintered alloy to a specified temp., then rapidly cooling it to apply heat treatment. CONSTITUTION:Electrolytic iron fines of <=200 mesh, <=400 mesh Co fines and atomized powder of Fe-50% Co alloy are mixed to 1 Fe/Co atomic ratio substantially. Stearic acid as lubricant is added by 0.75wt% to the mixed powder, mixed therewith and compacted to the desired shape, then heated to 400 deg.C to remove zinc stearate as lubricant. This is heated to 750-850 deg.C and previously sintered in hydrogen atmosphere, then compacted again, and sintered in 1,300-1,400 deg.C hydrogen atmosphere furnace. Sintered material is cooled to room temp., then reheated to 750-900 deg.C, held for 1hr, then rapidly cooled. Fe-Co soft magnetic sintered material having superior magnetic characteristic such as high flux density, low coercive force, high permeability and 90-96% relative density is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] Soft magnetic properties such as coercive force, magnetic flux density, and magnetic permeability are improved by heat-treating a Fe--Co sintered material with rapid cooling after sintering.

[Industrial application field]

The present invention relates to a soft magnetic material, and more specifically, to a method for manufacturing a Fe--Co based sintered soft magnetic material.

[Conventional technology]

Conventional soft magnetic materials include iron, silicon steel, permalloy,
Sendust, permendur, etc. are widely used. Among these, permendur exhibits the highest density (51), but its ingot material has the disadvantage of poor cold workability.

Therefore, 2■-bar and Mendur are known, which have improved cold workability by adding 2% vanadium, but their workability is still not sufficient. Powder metallurgy is an effective manufacturing method for molding difficult-to-process materials, but when Fe-Co alloys are manufactured using powder metallurgy, soft magnetic properties comparable to those of molten materials cannot be obtained. . In order to solve this problem, the effects of various additives have been investigated, but the soft magnetic properties have not been fundamentally solved.

[Problem that the invention seeks to solve]

Conventionally, attempts have been made to improve the soft magnetic properties of Fe--Co based soft magnetic alloys by increasing their relative density during sintering. However, because the diffusion coefficient of iron to cobalt is larger than that of cobalt to iron, Kagendall poids occur in the iron phase, and the crystal structure of Fe-Co alloys during high-temperature sintering ( There was a limit to the density improvement of the sintered body due to two reasons: slow diffusion during sintering due to the FCC phase). Furthermore, the density of the sintered body was not fundamentally improved by the addition of elements.

The object of the present invention is to find a method for providing a Fe--Co based sintered soft magnetic material having practical magnetic properties.

[Means for solving problems]

The present invention improves the magnetic properties of a Fe--Co sintered soft magnetic material by performing heat treatment involving rapid cooling after sintering an Fe--Co alloy.

In the present invention, sintering refers to ordinary powder mixing 1. Refers to a series of steps in powder metallurgy that involve compaction and sintering. There are no particular restrictions on the conditions for each step in this sintering method, but the sintered body obtained by a normal sintering method that achieves a relative density of 90 to 96%, that is, not using a special method such as HIP. The method of the present invention can also be applied. In the present invention,
"After sintering" means after the density and uniform composition of a normal sintered body have been obtained. A feature of the present invention is that after such a sintered body is obtained, it is subjected to heat treatment again to improve its soft magnetic properties. Normally, sintering is completed by heating to a high temperature and then cooling to room temperature, so heat treatment is performed by reheating from room temperature to a predetermined temperature. In this case, it is natural that the desired effect can be obtained even if the user who receives the sintered body performs heat treatment, and the timing of the heat treatment does not matter.

Alternatively, heat treatment may be performed immediately after cooling to a predetermined heat treatment temperature after sintering. The reason why quenching is performed during heat treatment in the present invention is that quenching is one of the conditions for improving magnetic properties. For rapid cooling, various methods such as oil cooling, air cooling, water cooling, fan cooling, gas jet cooling, and immersion in a low-temperature bath, which have a substantially faster cooling rate than furnace cooling, or a combination of these methods can be employed. By the way, since it is likely that the effect of the heat treatment in the present invention is to release the Fe-Co ordered lattice as described below, it is considered necessary to perform the rapid cooling in the heat treatment within the temperature range for forming an ordered lattice. . Although it is not possible to clearly determine the temperature at which the sintered Fe-Co alloy forms an ordered lattice, it is safe to rapidly cool the high temperature range. Rapid cooling in a low temperature range or a high temperature range where the risk of forming an ordered lattice is low is not essential.

The present inventors investigated the relationship between thermal treatment temperature and magnetic improvement and found that a sufficient effect was observed at 750 to 900°C.

The composition of the Fe-Co sintered soft magnetic material of the present invention may be a known one, and the Fe:Co atomic ratio = 1:1 and the Fe-Co alloy, which is the remaining impurity, can also be used as an excellent soft magnetic material according to the present invention. modified.

[For production]

The FeCo ordered lattice has a high saturation magnetic flux density but a low magnetic permeability. In general Fe-Co magnetic materials, such Fe-C
o The properties of a regular lattice are utilized.

It is thought that the heat treatment accompanied by rapid cooling in the present invention has the effect of canceling regularization, increasing magnetic permeability, and lowering coercive force. In addition, the magnetic flux density can be increased to 84 by heat treatment accompanied by rapid cooling.

The present invention will be explained in detail below.

〔Example〕

Example 1 As raw material powder, 200mesh electrolytic Fe powder, 400mesh
Mesoyu reduced Co powder and atomized Fe, -50
%Co alloy powder was prepared, raw material powder was mixed so that Fe/Co=1, and 0.75% of zinc stearate was added as a lubricant and mixed. 3 of these mixed powders
φ4 at a molding pressure of 92MPa (4t/ct&)
It was compacted into a shape of 5 cranes x φ35 x 7 ni (t). Thereafter, the aforementioned lubricant was removed from the green compact at 400°C, and pre-sintering was carried out at 750-850°C for 1 hour in a hydrogen atmosphere, followed by further sintering at 588 MPa (6t/
Re-compression molding was performed at a pressure of c+J). Sintering was performed at 1300 to 1400° C. for 1 hour in a Busha type hydrogen atmosphere furnace. After this, in a tubular atmosphere furnace, 8 hours were heated in a hydrogen atmosphere.
The temperature was maintained at 00 to 900°C for 1 hour, and then rapidly cooled with oil.

[Magnetic properties] Both an excitation coil and a search coil are wound with 42 turns around the obtained sintered alloy, and the maximum applied magnetic field is 4KA.
/m (500e), draw a BH hysteresis curve with a DC self-recording magnetometer, and calculate the magnetic flux density (134K).

Coercive force (Hc) and maximum magnetic permeability (μm) were determined.

As is clear from Figure 1, which shows these results, the post-sintering heat treatment results in favorable magnetic properties as a soft magnetic material (
We were able to improve the properties (high magnetic flux density, low coercive force, high magnetic permeability).

[Relative specific gravity] The relative specific gravity of the sintered body was 90 to 96%.

Comparative Example 1 Oil cooling after heat treatment in Example I was changed to furnace cooling [Effects of the invention] According to the present invention, a Fe-Co alloy having practical magnetic properties can be obtained by simply performing heat treatment after sintering. be able to.

[Brief explanation of the drawing]

1 and 2 are graphs showing the influence of heat treatment on magnetic properties, the former showing the results of Example 1 and the latter showing the results of Comparative Example 1.

Claims (1)

[Claims] 1. A method for producing a Fe-Co soft magnetic material, which comprises performing a heat treatment involving rapid cooling after sintering the Fe-Co alloy. 2. Claim 1, wherein the Fe-Co soft magnetic material has an Fe/Co atomic ratio of substantially 1.
Manufacturing method described in section. 3. The method according to claim 1 or 2, wherein the heat treatment is performed at a temperature lower than the sintering temperature. 4. The method according to claim 3, wherein the heat treatment temperature is 750 to 900°C. 5. The method according to claim 2, wherein components other than Fe and Co in the Fe--Co soft magnetic material are impurities. 6. The method according to any one of claims 1 to 5, wherein the sintering is performed by a sintering method that obtains a sintered body with a relative density of 90 to 96%.