JPH01290704A - Kneaded matter of magnetic powder for sintering - Google Patents

Abstract

PURPOSE:To improve flowability and formability and to allow easier diffusion and alloying by kneading a specified ratio of water sprayed alloy steel powder which contains carbonyl Fe or Ni powder and Fe and Si and is specified in grain size together with an org. binder. CONSTITUTION:The kneaded matter of the magnetic powder for sintering is prepd. by mixing 10-30wt.% water sprayed alloy steel powder with the carbonyl Fe powder or Ni powder and further, incorporating the org. binder therein. The water sprayed alloy steel powder which contains >=30% Fe and 10-25% Si and is adjusted in the average grain size to the range of 1-6 times the average grain size of the carbonyl Fe or Ni powder is used. The diffusion and alloying of the alloy components are accelerated at the time of sintering after forming and the high-density sintered body is obtd. if this kneaded matter is used. In addition, the sintered body having excellent magnetic characteristics such as saturation magnetic flux density and max. magnetic permeability is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magnetic powder kneaded material for sintering that has excellent formability, is easily formed into a diffusion alloy during sintering, and has good magnetic properties.

(Prior Art) Powder metallurgy is widely known as a method for manufacturing final products or mechanical structural parts, magnetic material parts, etc. in shapes similar to final products, along with melting methods such as casting and forging.

The magnetic properties of magnetic material parts manufactured using this powder metallurgy method, such as saturation magnetic flux density and maximum magnetic permeability, are easily affected by the metal structure. It is desirable that the powder be able to produce a dense sintered body.

For example, Fe-3i silicon steel (Si steel) soft magnetic powder is made by mixing small amounts of elemental powders such as Si, Cr, and Mo with iron powder. In addition to the manufacturing method, a master alloy mixing method is known in which elemental powders of predetermined components are added and mixed with iron powder.

However, according to the molten metal spraying method, since the alloying elements in the magnetic powder are solid solution hardened, the good compressibility inherent to the iron powder is not exhibited during molding, and a high-density sintered body cannot be obtained. Also according to the master alloy mixing method.

Compressibility is relatively good because the elemental powder just adheres to the surroundings of the iron powder. The metal structure cannot be made uniform.

Therefore, in order to improve this master alloy mixing method, one of the inventors of the present invention proposed that the alloying elements to be added to the iron powder be attached to the iron powder in advance in the form of fine-grained iron alloy powder, thereby forming a diffusion alloy during sintering. Based on this knowledge, the applicant filed a patent application (Japanese Patent Application No. 61-2585).
No. 83, Japanese Patent Application No. 62-234797).

A sintered body of Fe-3i silicon steel is disclosed in Japanese Patent Application No. 62-294] No. 442 by the present applicant.
No. 94143, respectively.

(Problems to be Solved by the Invention) According to recent powder metallurgy, it has become possible to directly produce sintered magnetic powder crystals in a final product or a specific three-dimensional shape similar to the final product by injection molding.

Here, the metal powder used in the injection molding method has a particle size that is larger than the particle size of the raw material powder for powder metallurgy when making conventional two-dimensional shaped sintered crystals, in order to ensure fluidity during q-th 11 molding. Using fine metal powder with an order of magnitude smaller particle size, for example, fine carbonyl 170 powder or carbonyl Ni powder (average particle size 5 μm
(below) is used.

However, the metal powder used in conventional injection molding methods is 6R alloy steel manufactured by molten metal spraying methods such as high-pressure gas spraying or high-pressure water spraying, and the powder particle size is 10 μm due to equipment limitations. This is the limit for grain refinement, and it is difficult to produce alloy steel powder with a grain size finer than this. In other words, in the case of magnetic alloy steel powder manufactured by the molten metal spraying method, there is a limit to the fineness of the particles due to a type of mechanical pulverization, and in terms of shape, the carbonyl Fc and Ni powders are spherical and have uniform particle size. It's hard to get something like that. Therefore, when q = is extruded using alloyed steel powder produced by the molten metal spraying method, the powder is coarse and the particle size is uneven, resulting in poor fluidity and formability, resulting in an increase in the density of the sintered body. The problem is that it cannot be measured.

In particular, when using magnetic alloy copper powder produced by high-pressure water spraying, the particle shape becomes irregular, so when mixed with an organic binder, a large amount of organic binder is required to ensure a certain level of fluidity. However, when the amount of this organic binder is increased, the problem arises that degreasing treatment and dimensional control of sintered parts become difficult.

Therefore, the present inventors applied the above-mentioned master alloy mixing method,
Generally, Fe-3i alloy steel powder produced by high-pressure water spraying method is added to carbonyl Fe and Ni powder, which are fine particles, and
If this mixed powder mixed with an organic binder is used as a raw material, it will have good fluidity during injection molding, and will be relatively easily diffused and alloyed during sintering, resulting in silicon steel powder sintered with good magnetic properties. I found out that the body can be obtained.

An object of the present invention is to provide a magnetic powder kneaded material for sintering that has excellent fluidity and formability during injection molding, and has good magnetic properties that facilitate diffusion alloying during sintering.

(Means for Solving the Problems) For this purpose, the magnetic powder kneaded material for sintering of the present invention is prepared by mixing 10 to 30% by weight of water spray alloy steel powder with carbonyl Fe or Ni powder, and adding an organic binder to this mixed powder. The water-sprayed alloy steel powder is composed of a kneaded material mixed with an appropriate amount of Fe30.
Euffi% or more and 10 to 25% by weight of 5i, and the average grain size of the water spray alloy steel is the carbonyl F
It is characterized by being in the range of 1 to 6 times the average particle size of the e or N1 powder.

Carbonyl Fe powder was used because it is relatively easy to obtain fine, uniform, spherical, and highly pure powder with a particle size of 5 μm or less using a special manufacturing method called thermal decomposition of metal carbonyl. .

Water-sprayed alloyed steel powder was used because this alloyed steel powder can be produced at relatively low cost. The water-sprayed alloy powder containing 30 weight% or more of Fe was 3
If the weight is less than 1%, alloying elements such as Sl will not diffuse into the carbonyl Fe or Ni powder during sintering.
In particular, alloy elements such as Si and AQ are easily oxidized during sintering and produce stable oxides. In addition, as alloying elements other than Fe and Si contained in the water spray alloyed steel powder, various property improving elements such as octaβ, Ni, Cr, MO, and co can be mentioned, but it is limited to these elements. Of course, this is not something that can be done. .

The reason why the Si content in the water-sprayed alloy steel powder is set to 1.0 to 25% by weight is that within this range the melting point is the upper limit of the normal sintering temperature.
For example, if the Si content is 21% by weight, a melt will be generated at 1200°C, which will result in relatively low temperature caking in this region, resulting in high density and uniform structure. is measured.

The average particle size of the water-sprayed alloy steel powder is set to 1 to 6 times the average particle size of the carbonyl Fe or N1 powder. This means that when the carbonyl Fe or Ni powder has an average particle size of 5 μm or less, the water spray alloy steel powder has an average particle size of 30 μm or less. Within this range, the fluidity of the kneaded product can be improved by diluting the water-sprayed alloy steel powder with carbonyl Fe or Ni powder. When the average particle size of the iron alloy steel powder exceeds 6 times the average particle size of the carbonyl Fe or Ni powder,
At the mixing ratio (mixing ratio) of the iron alloy steel powder and the carbonyl Fe powder described later, injection molding becomes difficult and the density of the sintered body decreases unless an excessive amount of organic binder is added.

10-30% by weight of water-sprayed alloy steel powder into carbonyl powder
If the amount of the mixture is less than 10% by weight, the concentrated alloying elements in the water spray alloyed steel powder will not fully diffuse into the carbonyl Fe or Ni powder during sintering, making it difficult to homogenize the alloying elements. This is because micro-segregation remains and impairs the good magnetic properties inherent to silicon iron.

Further, when liquid phase sintering is used, 10% by volume or more of water-sprayed alloy steel powder is required to generate a melt during sintering. On the contrary, the water spray alloy steel powder was made less than 30% by weight,
Characteristics inherent to carbonyl Fe or Ni powder (≦5μ
This is because, in order to ensure sufficient fluidity of the kneaded material due to the spherical shape (m, spherical shape), the blending ratio of the water-sprayed alloy steel powder should be small, and the upper limit thereof is preferably 30% by weight.

(Example) Examples of the present invention will be described.

Mitate ■1 Carbonyl Fe powder with an average particle size of 5 μm was mixed with 14% by weight of silicon iron powder Fe-20,731 having a predetermined average particle size, and further 8% by weight of an organic binder was added and kneaded at 160°C or less. , sufficiently homogenized.

In order to test the moldability of this kneaded product, the melt index (Ml) value was measured. The tests were conducted on silicon (iron powder) having various average particle sizes (Test Examples 1 to 3, Comparative Example 4).

FIG. 1 is a graph showing how the melt index value (Ml value) of the kneaded material changes in relation to the injection molding temperature depending on the average particle size of the silicon-iron powder.

As is clear from Fig. 1, the larger the average particle size of the silicon iron powder mixed with the carbonyl Fe powder, that is, the larger the average particle size is 9.16.27.35 μm, the smaller the Ml value of the kneaded product. It can be seen that the fluidity decreases.

From this test result, the average particle size of silicon iron powder is 30 μm.
Before and after, that is, the average particle size of the silicon iron powder is carbonyl Fe
If it is 1 to 6 times the particle size of the powder, as shown in Test Examples 1 to 3, the Ml value up to the normal injection molding temperature of 190°C is relatively higher than Comparative Example 4, so it is difficult to mold the kneaded product. The properties were judged to be good.

5) Mix an appropriate amount of various silicon steel powders with a predetermined average particle size of 15-20 ALm with carbonyl Fe or Ni powder with an average particle size of 3-5 μm, and add an organic binder to this mixed powder in the same manner as in Example 1. The mixture was sufficiently kneaded at a temperature of 160°C or lower.

The composition of the mixed powder in the kneaded material and the Si content in the silicon steel powder in this case are as shown in Table 1.

After measuring the Ml value of this kneaded product at 190°C, the kneaded product was heated at a temperature of 170 to 190°C and a pressure of 1 ton.
/ cm 2 injection molding was performed to produce an annular molded body. The obtained annular molded body was degreased and sintered in a pressurized atmosphere. The sintering temperature was set at a temperature 30° C. lower than the melting point of the silicon steel powder. however.

For those marked with this mark in Table 1, liquid phase sintering was performed at a temperature of about 1230°C, which is 30°C higher than the melting point of silicon steel powder.

The results of measuring the sintered density, saturation magnetic flux density, and maximum magnetic permeability μm of the obtained sintered body are shown in Table 1.

In general, a feature of Fe-3i magnetic materials is silicon-containing M.
As the number increases, the true density and saturation magnetic flux density tend to decrease, the maximum magnetic permeability increases, and the magnetostriction tends to decrease.

As is clear from Table 1, Test Examples 5.6.8 to 11.
14 and 16 are relatively M compared to Comparative Example 12.15.
The l value was large and the fluidity was good, so the moldability during injection molding was good, the sintered density was high, and the magnetic properties such as saturation magnetic flux density and maximum magnetic permeability were good.

On the other hand, in Comparative Examples 7 and 13, the silicon content in the silicon steel powder mixed into the carbonyl Fe powder was 2.
This is an example in which the mixing ratio of silicon steel powder to carbonyl Fe powder is smaller than 5% by weight, but in Comparative Examples 7 and 13, the MI value is large and the fluidity of the kneaded product is good. Although the sintered density is relatively high, the maximum magnetic permeability is low, making it unsuitable as a soft magnetic material. This is presumed to be due to the fact that diffusion alloying does not proceed during sintering and the influence of micro-segregation is large.

Furthermore, in Comparative Example 12, the mixing ratio of silicon steel powder was too high to allow injection molding under standard conditions, and the sintered density and magnetic properties could not be measured.

Comparative Example 15 had a high mixing ratio of silicon steel powder, but injection molding was possible. However, perhaps due to the internal heterogeneity of the structure, microcracks occurred after sintering, and although there was a suitable amount of silicon-containing total rings, the maximum magnetic permeability was much lower than expected.

In addition, as for the magnetic powder kneaded material for sintering of the present invention, those with good judgment are marked with ○ in Table 1, those with poor judgment are shown with X in Table 1, and the criteria for poor judgment are MI The value was 20 or less, and the maximum magnetic permeability μm was 3000 or less.

(Effects of the Invention) As explained above, when the magnetic powder kneaded material for sintering of the present invention is used, molded products with a specific three-dimensional shape can be easily produced during injection molding because of good fluidity or moldability. is possible,
When this molded product is sintered, the diffusion alloying of the alloy components is promoted, so a high-density sintered body is obtained, and the saturation magnetic flux density is
This has the effect that a sintered body with excellent magnetic properties such as maximum magnetic permeability can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the melt index value and the injection molding temperature of various kneaded water-sprayed alloy steels having different average particle sizes in Examples of the present invention. Temperature (0C) Figure 1

Claims (1)

[Claims] (1) It consists of a kneaded product in which carbonyl Fe or Ni powder is mixed with 10 to 30% by weight of water-sprayed alloy steel powder, and an appropriate amount of an organic binder is mixed into this mixed powder, and the water-sprayed alloy steel powder contains 30% by weight or more of Fe and Si10-25% by weight
and the average particle size of the water-sprayed alloy steel powder is the carbonyl Fe
Or a magnetic powder kneaded material for sintering, characterized in that the average particle diameter is in a range of 1 to 6 times the average particle diameter of Ni powder.