JPS6345303A - Composite iron powder for soft magnetic sintering material - Google Patents

Abstract

PURPOSE:To obtain composite iron powder for a soft magnetic sintering material by which a sintered body having good dimensional stability and magnetic characteristics is obtainable by specifying the compsn. consisting of P, Sn and Fe of the composite iron powder diffused and bonded with Fe-P alloy powder and Sn powder on the surface of iron powder particles. CONSTITUTION:This composite iron powder for the soft magnetic sintering material consists of the composite iron powder diffused and bonded with the Fe-P alloy powder and Sn powder on the surface of the iron powder particles and the chemical compsn. thereof consists of 0.3-1.0wt% P, 1-4% Sn and the balance substantially Fe. The segregation of the P and Sn components into a molding at the time of molding is obviated and the dispersion in the dimensional accuracy and magnetic characteristics is surely prevented. The above-mentioned composite iron powder is obtd. by mixing atomized iron powder and fine powder of the Fe-P alloy contg. about 14-17wt% P at a prescribed ratio, diffusing and bonding the Fe-P alloy powder to the surface of the Fe powder particles in a reducing or nonoxidizing atmosphere, then mixing the fine Sn powder therewith at a prescribed ratio and diffusing the bonding the same at about 250-300 deg.C in the nonoxidizing atmosphere except H2 atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a metal powder used as a raw material metal powder for iron-based soft magnetic sintered materials such as iron cores of electrical equipment.

(Prior Art) Among the iron cores of electrical equipment, small ones or those with complicated shapes are manufactured by precision casting methods such as the lost wax method or sintering methods.

The sintering method is a method in which magnetic metal powder is compressed into a desired shape and then sintered to metallurgically integrate the powder. As the magnetic metal powder, Fe-Al alloy powder, F
Although e-5i alloy powders are widely used, these iron-based soft magnetic alloy powders have the drawback of poor compression moldability and sinterability.

Therefore, in order to eliminate the above-mentioned drawbacks, a method is used in which a mixture of iron powder, Sn powder, and P powder at a predetermined ratio of υ1 is used as the sintering raw material powder, and this is compressed and then sintered (hereinafter, mixed ) was proposed in Japanese Patent Publication No. 51-43008.

(Problems to be Solved by the Invention) However, in the above method, the powder tends to segregate after mixing and before compression molding, which tends to cause distortion in the sintered body and unstable dimensional accuracy. There was a problem. Furthermore, when the Sn powder segregates, the magnetic flux density decreases, resulting in a problem that required magnetic properties cannot be obtained.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a raw material powder for soft magnetic sintered material that can easily produce a sintered body with excellent dimensional stability and good magnetic properties. With the goal.

(Means for Solving the Problems) The present invention is characterized by the fact that Fe-2 is added to the surface of iron powder particles as raw material powder.
A composite iron powder in which alloy powder and Sn powder are diffusion bonded is used, and the content of P and Sn in the composite iron powder is determined in weight%: p: 0.3 to 1.0% Sn: 1 to 4% The balance is real The point is that it is Fe.

(Example) The composite iron powder according to the present invention has Fe-2 alloy powder and Sn powder diffusion bonded to the surface of iron powder particles.

As the iron powder that becomes the base powder of the composite iron powder, pure iron powder is preferable. This is because pure iron powder has excellent magnetic properties and compression moldability. As for the pure iron powder, atomized iron powder is more preferable than reduced iron powder because it is easier to obtain high purity iron powder.

The reason why the Fe-2 alloy powder is diffused and bonded to the surface of the iron powder particles is to add P to the iron powder in terms of wood quality.

However, if P powder is directly diffused and bonded, P will be easily diffused into the iron powder, resulting in an increase in the hardness of the iron powder and a decrease in compressibility. Therefore, Fe-2 alloy powder is used to add P to the iron powder while suppressing the diffusion of P.

The purpose of adding P to the iron powder is to increase the shrinkage of the iron powder during sintering, improve the density of the sintered body, and thereby improve the magnetic properties, particularly the magnetic flux density and electrical resistance.

The content of P in the composite iron powder is 0.3 to 1% by weight.
It is assumed to be 0%. If it is less than 0.3%, it does not contribute to contraction, and as a result, a large magnetic flux density cannot be obtained. On the other hand, if it exceeds 1.0%, it tends to aggregate during sintering, making it difficult to stabilize the shrinkage rate.

In addition, the diffusion bonding of Sn powder to iron powder particles improves the formability of the composite iron powder by adding Sn to the iron powder, which in turn contributes to reducing the forming pressure. It's for a reason. Although iron powder itself has good compression moldability, the diffusion of P impairs the moldability. Sn is added to compensate for this. Furthermore, the provision of Sn has the effect of suppressing dimensional variations due to shrinkage during sintering due to P.

The content of Sn in the composite iron powder is 1 to 4% by weight. If it is less than 1%, it does not contribute to improving moldability and dimensional stability. On the other hand, if it exceeds 4%, Sn tends to aggregate during sintering, degrading dimensional stability and degrading magnetic properties due to aggregation of Sn, which is a non-magnetic metal.

Next, a method for producing composite iron powder of the present invention will be explained.

First, iron powder and Fe-2 alloy powder are mixed, and the Fe-2 alloy powder is diffusion bonded to the surface of the iron powder particles in a reducing or non-oxidizing atmosphere.

As the iron powder, as described above, atomized iron powder is preferable because pure iron powder can be easily obtained. The size of the iron powder particles is usually 60 mesh or less, which is used as a raw material for powder metallurgy.

As Fe-2 alloy powder, the P content is 14 to 17% by weight.
For example, Fe3P (P content about 16%
) can be exemplified. The smaller the particle size of the Fe-2 alloy powder, the better the diffusion bonding properties, dimensional stability, and magnetic properties, but it is preferably 10 μm or less as it allows for easy diffusion bonding. The Fe3P is supplied on the market up to a size of about 4 μm and is easy to handle. However, it goes without saying that other Fe-P alloys may be used after being ground.

The diffusion bonding temperature of the Fe-2 alloy powder is preferably 750 to 900°C. Diffusion bonding is difficult at temperatures below 750°C, while at temperatures above 900°C, the diffusion of P in the alloy into the iron powder is promoted, even though Fe-2 alloy powder is used. increases the hardness of the material and deteriorates compression moldability. A sufficient diffusion bonding state can be obtained with a holding time of about 60 to 15 minutes in the above temperature range.

The cake obtained by the above heat treatment is pulverized to 60 mesunyu or less, and then mixed with Sn powder to diffusely bond the Sn powder to the surface of the iron powder particles.

The size of the Sn powder can be as small as the Fe-2 alloy powder, but it is set to 45 μm in consideration of dimensional stability and economical efficiency.
Use the following (those passed through a 350 mesh sieve). Sn has a lower melting point than Fe-P and is easier to bond by diffusion, so even if the diameter is larger than that of Fe-P powder, there is no problem with diffusion bonding, but if it is too large, there will be problems with dimensional stability and agglomeration. The magnetic properties of the magnetic material deteriorate.

The diffusion bonding temperature of the Sn powder is preferably 250 to 300°C. The melting point of Sn is about 230°C, and below 250°C it becomes difficult for Sn to diffuse onto the surface of the iron powder.
If the temperature exceeds .degree. C., Sn agglomeration occurs, impairing dimensional stability and magnetic properties. The holding time at the above temperature is 60 to 1
A sufficient diffusion bonding state can be obtained in about 5 minutes.

In addition, when performing diffusion bonding of Sn, heating in a reducing hydrogen atmosphere poses a risk of explosion, so such an atmosphere must be removed (it must be performed in a non-oxidizing atmosphere).

Next, specific examples will be listed and explained.

(1) Manufacture of composite powder■ After mixing high-purity atomized iron powder of 60 mf or less and Fe3P powder with an average particle size of about 4 μm so as to have the composition shown in Table 1, this mixed powder is Diffusion bonding was carried out at 880° C. for 30 minutes in an ammonia decomposition gas (mixed gas of N2 and 82, hereinafter referred to as AX gas) atmosphere.

The composition in Table 1 is pure iron powder, Fe3P powder, and Sn.
The ratio of each powder (weight %) to the total amount of powder is shown.

■ After disintegrating the cake with diffusion bonded Fe3P powder to 60 mesh or less, add and mix Sn powder of 350 mesh or less to have the composition shown in the table, and diffusion bond at 280°C for 30 minutes in a N2 gas atmosphere. , a composite iron powder having the composition shown in Table 1 was obtained.

Table 1 Note: Unit Weight % Remaining f+, l Fe (2) Production of sintered body (Composite iron powder manufactured in 11 (Th1~7.11~
16), 0.75% zinc stearate was added to it as a lubricant based on the weight of composite iron $5),
n/cIIl, outer diameter 45 x inner diameter 33 x thickness 6 (unit: m
After compression molding into the ring body of s), 1150°C x 30 minutes,
Sintering was carried out in an AX gas atmosphere. 20 ring-shaped sintered body samples were produced each.

(2) For comparison, 20 ring-shaped sintered bodies having the same composition as shown in Table 1 were manufactured using the mixing method. The amount of lubricant added, molding pressure, and sintering conditions were set in the same manner as in ①.

(3) Results The compact density, sintered compact density, outer diameter shrinkage rate due to sintering, and standard deviation (total number of samples n = 20) of each sample were organized by Sn content and P content. Shown in Figures 1 to 4. In addition, the ring-shaped molded body and the sintered body are tla (b) to 7a (bl, lla (bl
~16a (b) and are numbered to distinguish them and shown in the same figure. A shows the one using composite iron (a), and b shows the one using the mixing method.

(4) Evaluation■ Figure 1 shows the relationship between Sn content, compact density, and sintered compact density, and Figure 2 shows the relationship between Sn content, outer diameter dimensional shrinkage rate, and standard deviation of the shrinkage rate. It is a graph diagram showing the relationship.

From FIG. 1 (lower diagram), it was confirmed that the inclusion of Sn contributed to improving the density of the compact, that is, improving the moldability.

In particular, in m2a to 5a using composite iron powder, Sn1
% or more, this tendency is remarkable.

From Figure 2 (above), lTh1a~7 using composite iron powder
a is for mlb ~ 7b obtained by the mixed method,
In all Sn ranges, the standard deviation of the shrinkage rate of outer diameter is small. This means that dimensional stability can be improved by using composite iron powder. In particular, m2a to 5a within the range of the present invention and ff16a outside the range have excellent dimensional stability. Furthermore, as the Sn content increased, the sintered body density and the outer diameter shrinkage rate decreased, which confirmed that the dimensional shrinkage during sintering was alleviated by the Sn content.

■ Figure 3 shows the relationship between P content and compact density and sintered body density, and Figure 4 is a graph showing the relationship between P content, outer diameter dimensional shrinkage rate, and standard deviation of the shrinkage rate. It is.

From Fig. 3 (lower figure), the formability decreases as P content increases, while from Fig. 4 (lower figure) it shrinks during sintering.
It was confirmed that this increases the density of the sintered body.

From FIG. 4 (lower figure), it was confirmed that large shrinkage was obtained when P was 0.3% or more. In addition, from Figure 4 (upper figure), when P is 0.3% or more and composite iron powder is used, N3a and Nn13a to 16a are m3b and Th by the mixing method.
The standard deviation of shrinkage rate is all smaller than 13b to 16b,
In particular, it was confirmed that the dimensions 3a and 1Th1a to 7a within the scope of the present invention had small standard deviations and good dimensional stability.

(5) Evaluation of magnetic properties■ From Figure 2 (top) and Figure 4 (top), among the sintered bodies using composite iron powder, those with a small standard deviation of dimensional shrinkage rate (Ex 2a to 6a, 13a to 15a) were selected and their DC magnetic properties were measured. At this time, for comparison, sintered bodies (lTh2b to 6b, 13b -1
5b) and those manufactured using pure iron powder were also subjected to similar measurements.

■ The results are shown in Table 2. Among the magnetic properties, the magnetic flux density in particular greatly depends on the sintered body density, so the sintered body density is also shown in the same table. In the same table, B. indicates the magnetic flux density (unit: T: terrace) at a magnetic field strength of 5000 A/m.

Table 2 Crocodile] i According to Table 2, the sintered body density is different for each sample (1) It is not possible to compare the density.

Therefore, as shown in the following formula, the difference ΔB between the sample and B5° of a pure iron powder sintered body having the same density. I decided to investigate and evaluate.

ΔB,. =A-α A: Sample B.

α: B5°ΔB of pure iron powder sintered body with the same density as the sample. The closer to zero, the more equivalent the magnetic properties are to a pure iron powder sintered body, indicating that the influence of mixtures other than iron powder in the sample is small.

The relationship between the density and magnetic flux density of the pure iron powder sintered body is B based on research by the present inventor. = 0.508 x sintered body density - 2.23, so the value of α was given by this value.

(4)　ΔB,. Table 3 shows the calculation results.

Table 3 Note: Unit: T (terrace) ■ From Tables 2 and 3, all of the sintered bodies using composite iron powder excluding 6a (corresponding to the examples of the present invention) are B,. is 1.52T or more, ΔB,.

GTli LH was also found to have a magnetic flux density of O~-0.01, which is extremely superior to that obtained by the mixing method.

Among the magnetic properties, regarding coercive force, both those using composite iron powder and those manufactured by the mixing method have obtained better results than pure iron powder sintered bodies.

The reason why the magnetic properties of k6a are inferior is considered to be that when the amount of Sn increases, Sn aggregates during sintering.

(Effects of the Invention) As explained above, the composite iron powder for soft magnetic sintered materials of the present invention has Fe-P alloy powder and Sn powder diffusion bonded to the surface of the iron powder particles, so P to Sn There is no risk that the components will be unevenly distributed in the molded article, and variations in dimensional accuracy and magnetic properties caused by such uneven distribution can be completely prevented.

Furthermore, since the content ranges of P and Sn are limited to a specific range, a sintered body with good dimensional stability and magnetic properties can be reliably obtained.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between Sn content, compact density, and sintered body density, and Figure 2 is a graph showing the relationship between Sn content, outer diameter dimensional shrinkage rate, and standard deviation of the shrinkage rate. Figure 3 is a graph showing the relationship between P content and compact density and sintered body density, and Figure 4 is a graph showing the relationship between P content, outer diameter shrinkage rate, and standard deviation of the shrinkage rate. FIG.

Claims (1)

[Claims] (1) A composite iron powder in which Fe-P alloy powder and Sn powder are diffusion bonded to the surface of iron powder particles, the chemical composition is in weight%,
A composite iron powder for a soft magnetic sintered material, characterized in that P: 0.3 to 1.0% Sn: 1 to 4%, the balance being substantially Fe.