JPH04183840A - Production of sintered compact of fe-co-si alloy soft-magnetic material - Google Patents

Abstract

PURPOSE:To easily obtain a sintered compact having high magnetic flux density, low coercive force, and high magnetic permeability by preparing a green compact which consists of powder of prescribed grain size consisting of specific percentages of Co, Si, and Fe and binder, sintering this green compact, and then cooling the resulting sintered compact at the prescribed cooling velocity. CONSTITUTION:Powdered Co, powdered Si, and powdered Fe or a powder consisting of an alloy of these metals is blended and formed into a powder consisting of, by weight, 40-60% Co, 0.5-3% Si, and the balance Fe and having <=45/mum average grain size. A composition consisting of this powder and a binder is subjected to injection molding to form a green compact. Subsequently, this green compact is subjected to binder removal treatment, sintered, and cooled slowly at 2-50 deg.C/min cooling rate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a sintered Fe-Co-Si alloy soft magnetic material having excellent soft magnetic properties.

・[Prior art] Fe-Co alloy soft magnetic material is an alloy material that has ordered-disorder transformation and forms a C5Cjl type ordered lattice phase at the transformation temperature, and is the best among the currently known alloys. Since it exhibits a saturation magnetic flux density, it is widely used as a magnetic material for yokes such as pulse motors and printer heads, and as a diaphragm for telephone receivers.

Conventionally, when this alloy consists only of Fe and Co, no amount of heat treatment can suppress the transformation from an irregular lattice to a regular lattice, and therefore cold working of the compact is not necessary. It was possible.

Therefore, in order to improve this situation, expensive V
It was necessary to improve the workability of the molded body by adding Cr or Cr.

However, this is still not sufficient to suppress the transformation into a regular lattice, and attempts have been made to manufacture products such as parts, particularly products with complex shapes, by powder metallurgy.

On the other hand, in the normal powder metallurgy method, raw material powder is inserted into a mold,
It is obtained by compression molding using a press, and because the Co powder and Fe-Co alloy powder used in magnet manufacturing are hard, it cannot be molded even if large pressure is applied during compression molding of the product. This has become a problem as it is difficult and cracks are likely to occur.

In addition, normal powder metallurgy uses raw material powder with a relatively large average particle size, and Fe and Co are difficult to diffuse into each other, so it is necessary to increase the density to obtain advanced magnetic properties. This was difficult, and in order to increase the density of the product, it was necessary to use expensive fine powder, sinter for a long time, and introduce HIP processing.

Furthermore, after sintering the compact, it was always necessary to perform heat treatment to improve magnetic properties.

Furthermore, when used as a soft magnetic material under alternating current,
Electrical resistance is high and iron loss must be reduced,
Fe--Co alloys had the disadvantage of low electrical resistance.

[Problems to be Solved by the Invention] The present invention provides a method for easily manufacturing a Fe-Co-Si alloy material sintered body having excellent soft magnetic properties by eliminating the conventional drawbacks as described above. Our goal is to provide the following.

[Means for Solving the Problems] As a result of intensive research to achieve the above problems, the present inventors have discovered that
Fe-Co-S, i alloy powder with a specific particle size blended in a specific ratio is injection molded, and the resulting molded body is subjected to binder removal treatment and further sintering treatment,
The inventors have discovered that by slow cooling at a specific cooling rate, it is possible to suppress the occurrence of lattice strain that occurs during cooling and achieve the above-mentioned problems without deteriorating the magnetic properties of the product.

The details will be described below.

That is, in the present invention, the Co content is 40 to 60% by weight and 5i
ijSO, Fe powder, Co powder, and Si powder are blended so that the balance is substantially Fe at 5 to 3% by weight, and if necessary, Fe-Co alloy powder and Fe-Si alloy powder are added. A composition consisting of a blended powder and a binder in which the average particle size of each raw material powder is 45 μm or less was injection molded, the obtained molded body was subjected to a binder removal treatment, and further, this molded body was subjected to a sintering treatment. After, 26C/min or more, 50'
Fe-C by slow cooling at a cooling rate of C/min or less.

This is a method for producing a -8t alloy soft magnetic material sintered body.

[Function] The Co content of the blended powder and the sintered body after sintering is 40
~60% by weight is required.

When the Co content is less than 40% by weight, the magnetic flux density does not decrease that much, but the maximum magnetic permeability decreases so much that it cannot be used as a soft magnetic material.When the Co content exceeds 60% by weight, the magnetic flux density decreases by that much. Although it does not decrease, the maximum magnetic permeability decreases significantly and it cannot be used as a soft magnetic material.

Further, the content of Sl needs to be 0.5 to 3% by weight.

When the Si content is less than 0.5% by weight, the final relative density of the product after sintering is hardly improved, and as a result, not only excellent soft magnetic properties are not exhibited, but also electrical resistance is not improved.

When the Si content exceeds 3% by weight, the magnetic flux density decreases rapidly and the material cannot be used as a soft magnetic material.

It is preferable that elements other than Fe, Co, and St are not included, but they may be included as long as the magnetic flux density of the soft magnetic properties of the sintered body does not become less than 83S = 19,0OOG. I can't use it again.

Further, it is necessary that the average particle size of this powder is 45 μm or less.

If the average particle size exceeds 45 μm, the fluidity of the composition consisting of the powder and the binder will decrease, making injection molding almost impossible, and even if injection molding is possible, it will be difficult to sinter the molded product. The progress of the tying process is slow.

Therefore, the final density of the sintered body is difficult to increase, and the magnetic properties are also significantly reduced.

The binder used in the present invention can be a binder known for injection molding powder metallurgy, such as polyethylene or wax, but residual carbon is generated when these binders are removed. If carbon easily enters the Fe-Co-Si alloy, the magnetic properties will deteriorate, so it is preferable to use a binder in which carbon does not easily remain, for example, a binder mainly composed of wax.

Methods for removing the binder from the molded product include heat degreasing, solvent degreasing, and solvent degreasing, depending on the type of binder used.
Although other known methods can be used, thermal degreasing is preferably carried out in a nitrogen or hydrogen atmosphere or in a vacuum during mass production because a thermal degreasing apparatus is simpler than apparatus for other methods.

When sintering the binder-removed molded body, 1
3 in hydrogen atmosphere or vacuum at 200-1450℃
This is carried out by holding for 0 to 180 minutes.

The sintered crystals that have been sintered in this way are then
It is necessary to perform slow cooling at a cooling rate of 21'C/min or more and 50°C/min or less.

Slow cooling at a cooling rate of less than 2°C/min not only fails to improve the effect of the present invention on removing lattice strain, but is also economically unfavorable, and furthermore, it seems to significantly reduce productivity. It's coming.

Furthermore, if the cooling rate exceeds 50° C./min, lattice distortion occurs during cooling, and this remains as it is until room temperature, resulting in a decrease in the soft magnetic properties of the magnet.

[Example] Example 1 Fe-50 heavy flying spark Co alloy powder with an average particle size of 9 μm and Fe-44 heavy flying spark 5ifIJ with an average particle size of 40 μm as raw material powder
: Alloy powder and carbonyl F with an average particle size of 5 μm if necessary
Table 1 using E powder and reduced Co powder with an average particle size of 4.5 μm.
The mixtures were mixed at the compounding ratio shown in , and a wax-based binder was added thereto so that the binder content was 40 to 50% by volume. After kneading at 150° C., the mixture was granulated into pellets. This pellet was molded using an injection molding machine at an injection pressure of 1200
It was injection molded into a mold under conditions of 9/cm''.

The wax-based binder was removed while the obtained molded body was maintained at 300°C.

After that, the binder-removed molded product was treated with 1400
A sintering process was carried out for 2 hours at a temperature of 10°C.
It was cooled at a cooling rate of 8 C/min to reach room temperature.

The sintered body thus obtained was wound with both an excitation coil and a surge coil for 50 turns, and a DC recording magnetometer measured 8
11 Draw a hysteresis curve and calculate the magnetic flux density (Bis), coercive force (Hc), and maximum permeability (
μ,,X) was determined. The results are shown in Table 1.

In this case, the obtained product has excellent magnetic properties, with a sintered density of 93%, electrical resistance of 16μΩCm, magnetic flux density of 20,500G, coercive force of 2.80e, and maximum permeability of 3500G/Oe. It was showing.

Examples 2 to 5 All of them were subjected to the same treatment as in Example 1, and when they had the compositions listed in Table 1 and the raw material formulations listed in Table 1, in any case, The results showed almost the same results as in Example 1.

Example 6 The cooling rate was set to 50°C/min, but if there was no change in other processing conditions, the composition shown in Table 1 and the raw material combination shown in Table 1 were good. A product with excellent magnetic properties was obtained.

-〇- Comparative Examples 1 to 8 were manufactured using the same process as the example of the present invention, but were manufactured by changing the composition, particle size of raw material powder, cooling rate, etc.

Comparative Example I This is an example in which the Si content is 0.09% by weight and the composition is 0.5% by weight or less, which is the lower limit of the Si content in Claim 1, and the electrical resistance is poor.

Comparative Example 2 This is an example in which the Si content is 3.96% by weight and the composition is more than 3%, which is the upper limit of the Si content in claim 1, and the maximum magnetic permeability is degraded to 2000G/○e. 6 Comparative Example 3 An example in which the Co content is 35% by weight and the composition is 40% by weight or less, which is the lower limit of the Co content in claim 1,
The maximum magnetic permeability has deteriorated to 1900G10e.

Comparative Example 4 An example in which the Co content is set to 65 layers, and the composition is set to 60 layers or more, which is the upper limit of the Co content in claim 1,
The maximum magnetic permeability has deteriorated to 1200G10e.

Comparative Example 5 This is an example in which the cooling rate after sintering was oil-cooled, which exceeded the upper limit of claim 1 of 50°C/min, and the maximum magnetic permeability deteriorated to 850 G/Oe. At the same time, the magnetic flux density is 11,500G, 50% of the example.
It has decreased to a certain extent.

Comparative Example 6 This is an example in which the cooling rate exceeded the upper limit of claim 1 of 50°C/min because the cooling after sintering was performed using 25°C tap water, and the maximum magnetic permeability deteriorated to 690 G10e. At the same time, the magnetic flux density is 9°300G, compared to Example 4.
It has decreased to around 5%.

Comparative Example 7 This is an example in which the cooling rate after sintering was 0°C cold water, so the cooling rate exceeded the upper limit of claim 1, 50°C/min, and the maximum magnetic permeability was 420 G/Oe. In addition to deteriorating, the magnetic flux density is also 6700G, which is 30% in the example.
It has decreased to about %.

Comparative Example 8 Particle size of Fe'-50 superimposed Co alloy powder was 48 to 58 μm
45 μm, which is the limit of the raw material powder of claim 1.
An example made with coarser powder, with a sintered density of 79%
has deteriorated significantly.

From the above results, it is confirmed that the soft magnetic properties of the sintered body produced according to the present invention are high magnetic flux density, low coercive force, and high magnetic permeability, and it is also found that the electrical resistance is improved.

(Margins below this page) [Effects of the Invention] The present invention has excellent soft magnetic properties, has higher density compared to conventional Fe-Co alloys, has improved electrical resistance, and is suitable for injection molding. By using this technology, it becomes possible to stably supply soft magnetic sintered bodies with complex shapes and high performance soft magnetic properties, and contribute to the industry by providing industrially useful products. There is something big.

Claims (1)

[Claims] 1. 40-60% by weight of Co, 0.5-3% by weight of Si
, injection molding a composition consisting of powder with an average particle size of 45 μm or less and a binder, the remainder of which is blended so that the remainder substantially consists of Fe, and the resulting molded body is subjected to a binder removal treatment,
Furthermore, after performing the sintering treatment, the sintered body is slowly cooled at a cooling rate of 2°C/min or more and 50°C/min or less. manufacturing method.