JPS61186402A - Ferrous powder for sintered magnetic material - Google Patents

Abstract

PURPOSE:To provide ferrous powder for a sintered magnetic material having excellent magnetic characteristics by incorporating P- and O-contg. materials such as phosphorus oxide, iron phosphate and iron hydrogenphosphate at a specific ratio into iron powder. CONSTITUTION:1 or >=2 kinds of phosphorus oxide such as phosphorus pentaoxide, iron phosphate such as ferrous phosphate or ferric phosphate or iron hydrogenphosphate such as ferrous hydrogen phosphate or ferric hydrogenphosphate are incorporated into the iron powder as the raw material for the sintered material for an iron core of an electric apparatus such as motor so as to be incorporated therein at 0.02-2.5wt% P, 0.10-2.0wt% O2. The iron powder contg. <0.1% C, <0.2% Si, <0.5% Mn and <0.02% N or further 0.1-10% Sn is used. Such P- and O-contg. iron powder is molded and sintered, by which the iron powder for the sintered ferrous material having the magnetic characteristics equiv. to the magnetic characteristics of the conventional electrical steel sheet and silicon steel sheet is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a raw material powder for iron-based sintered materials used in soft magnetic materials.

Generally, electric iron plates and silicon steel plates have been widely used as soft magnetic parts such as iron cores of electric equipment such as motors, but recently, sintered magnetic materials obtained by compacting and sintering iron powder have been widely used. is beginning to be used in place of electric iron plates, silicon steel plates, etc. Such sintered magnetic materials have advantages unique to powder metallurgy, such as high raw material yield, low processing cost, and large degree of freedom in shape.However, since pores remain in the material, magnetic flux density is low and storage The current situation is that its magnetic properties are inferior to those of electric iron plates and silicon steel plates, such as a large magnetic force, and improvements are still desired.

(Prior art) Regarding the above-mentioned iron-based powder for sintered magnetic materials, conventional methods have been used to increase the purity of iron powder (Japanese Patent Laid-Open No. 51-20703).
, adding phosphorus (P) and tin (Sn)
-21803 and Japanese Patent Application Laid-Open No. 102008/1983), and it has been reported that it is effective in improving magnetic properties. However, in order to industrially achieve these excellent properties, there remain the following major problems that must be solved.

That is, there is a problem in that carbon (C) is trapped in the sintered body during sintering, resulting in deterioration of magnetic properties. Possible carbon sources that can be considered are firstly C contained in iron powder, additives, lubricants, etc., and secondly carbon contained in the sintering atmosphere gas. In this regard, experimentally, sintering is performed using high-purity hydrogen (H2) gas that does not contain carbon oxide (CO), ammonia decomposition (AX) gas, a vacuum atmosphere, etc. It is possible to prevent C capture from the atmosphere, and to promote decarburization by sintering with a gas having a high dew point as disclosed in Japanese Patent Application Laid-Open No. 58-34442. However, such a method is not easy to use industrially.Specific problems in industrial sintering are as follows.

(1) When the sintering furnace for magnetic material parts and the sintering furnace for mechanical material parts are used together, the sintering machine parts usually use a compact formed by mixing graphite powder as a C source. CO gas is generated during the curing process, and graphite adheres to the inside of the furnace. Therefore, during sintering of magnetic parts, carburization of the sintered body occurs.

(2) The material of the tray used for sintering is generally graphite. In this case, CO gas is generated from the graphite in the tray during sintering, causing carburization of the sintered body.

That is, in industrial sintering, the carbon potential of the atmosphere tends to be high, and therefore carburization tends to occur in the sintered powder. To prevent this, it is possible to raise the dew point of the atmospheric gas, but this is not a general-purpose method because it has problems such as dew condensation occurring inside the gas piping and pipes.

After all, industrial sintering involves sintering in an atmosphere with a high carbon potential, so even if you use high-purity iron powder or add useful elements, the coercive force will increase. The adverse effects result in unsatisfactory final magnetic properties. Also, P! Sn has the effect of improving sinterability and increasing sintered density by causing the alpha phase of iron to appear during sintering, but in a carburizing atmosphere, the alpha phase is less likely to appear, so the sintered density ultimately decreases. does not increase, and the effect of improving magnetic flux density is not fully demonstrated.

(Problems to be Solved by the Invention) In view of the above-mentioned problems, particularly the problems in industrial sintering, the present invention has been developed to solve the following problems: The purpose of this invention is to propose an iron-based powder for sintered magnetic materials that exhibits suppressed and excellent magnetic properties.

(Means for Solving the Problems) The basic idea of the present invention is to pre-contain an oxygen source such as an oxide in the iron-based powder to be used for sintering, and to mix this oxygen with carbon from the atmosphere etc. The aim is to suppress carburization of the sintered body by causing a reaction. The type and amount of the oxides, etc. to be applied should be such that (11) the compressibility of the powder is not extremely inhibited, (2) the reduction proceeds during sintering, and (3) the reduction is sufficiently completed after sintering. (4)
) Selection is made from the viewpoints of leaving no harmful elements or leaving useful elements in the sintered body.

Examples of the sintered powder according to the present invention manufactured to meet the above-mentioned demands include the following.

1. One or more types of phosphorus/oxygen containing substances selected from phosphorus oxide, iron phosphate, and iron hydrogen phosphate, with a P content of 0.02 to 2.5% by weight and a 0 content of 0. .10～
An iron-based powder for sintered magnetic materials, which contains Fe in an amount of 2.0% by weight, with the remainder containing unavoidable contaminants.

2. One or more phosphorus/oxygen containing substances selected from phosphorus oxide, iron phosphate, and iron hydrogen phosphate with a P content of 0.02 to 2.5% by weight and an O content of 0.02 to 2.5% by weight. 10-2
．． Contains so as to be 0% by weight, C: 0.1% by weight or less,
St: 0.2% by weight or less, Mn: 0.5% by weight or less,
An iron-based powder for sintered magnetic materials containing N: 0.02% by weight or less, with the remainder consisting of Fe and unavoidable impurities.

3. One or more types of phosphorus/oxygen-containing substances selected from phosphorus oxides, iron phosphates, and iron hydrogen phosphates with a P content of 0.02 to 2.5% by weight and a 0 content of 0.02 to 2.5% by weight. 10-2
．． Contains 0% by weight and 0.1 to 1% Sn
Contains 0% by weight, further C: 0.1% by weight or less, Si: 0
．． 2% by weight or less, Mn: 0.5% by weight or less, N: 0.0
An iron-based powder for sintered magnetic materials containing 2% by weight or less, with the remainder consisting of Fe and unavoidable impurities.

(Function) The feature of the present invention is that the sintered powder contains phosphorus and oxygen-containing substances such as phosphorous oxide, iron phosphate, and iron hydrogen phosphate (hereinafter these are simply referred to as "P-0 containing substances"). The purpose is to contain the following: Under normal sintering conditions, these P-0-containing substances undergo little or no reduction during temperature rise, and they "absorb" C during sintering, causing it to be absorbed into the sintered body. It has the effect of suppressing carburization. Furthermore, phosphorus (P) and iron (Fe) remain in the sintered body after sintering, and these are elements that do not have an adverse effect on the magnetic properties of the sintered body, or are rather harmful.

The amount of these po-containing substances added is such that the residual components (so-called P content, 0 content) in the iron-based powder after addition, including the P and 0 contained before addition, are is 0.02 ~
2.5% by weight, and 0 is selected to be 0.10 to 2.0% by weight.

As will be discussed in detail later, p- progresses during sintering.

In order to prevent carburization of the sintered body due to the reduction reaction of the contained substances, P in the iron-based powder should be 0.02% by weight or more, and 0 should be 0.1% by weight.
0% by weight or more is required. On the other hand, if P exceeds 2.0% by weight, the compressibility of the powder will be significantly deteriorated, and the magnetic properties of the final sintered body will be adversely affected.
If it exceeds % by weight, the compressibility and thus the magnetic properties are similarly adversely affected, and precipitates harmful to the magnetic properties appear in the sintered body. Therefore, 0 is 0.10 to 2.
0% by weight, P is preferably in the range of 0.02 to 2.5% by weight.

In addition, as a phosphorus oxide, diphosphorus pentoxide (pzos,
phosphoric anhydride) and phosphoric acid reacted with water (pzo
s・nHzo) etc. are used. As the iron phosphate, ferrous phosphate (Fe3 (PO9)!.nH,o) and ferric phosphate (PePO4.nHzO) can be used. As iron hydrogen phosphate, ferrous hydrogen phosphate (FeHPO
Hlo.

Fe(HzPO#)t'nHzO) and ferric hydrogen phosphate(FeHz(Pot)t''nHzO,Pe(
ToPO*) 3 ・nHzo+ Fe(HtPO*)
There is z).

Furthermore, composite compounds or mixtures of the above-mentioned po-containing substances are also included in the po-containing substances referred to in the present invention.

Various methods can be considered for adding the po-containing substance. The simplest method is to mix the po-containing material in powder form with the iron-based powder. In order to achieve uniform mixing, it is also possible to use various binders or to dissolve the po-containing substance in water or other solvents to form a solution or suspension. In addition, by mixing and adding a part or all of red phosphorus or iron phosphide, or by partially oxidizing an iron-based powder containing P, it is substantially the same as adding a P-O containing substance. This effect can be achieved. Furthermore, by mixing the powdered po-containing substance with the iron-based powder and then heat-treating it to partially react and bond the po-containing substance and the iron-based powder particles, the iron-based powder can be transported. It is also an effective means to prevent P-0 containing substances from segregation. In this case, the heating conditions are as follows: ■ The iron-based powder is not excessively oxidized; ■ The P-O-containing substance is not completely reduced; and ■ The reactive bond between the P-O-containing substance and the iron-based powder particles is partially However, it is determined taking into consideration that elements such as P do not excessively diffuse into the iron-based powder particles and impair the compressibility of the powder. For example, heat treatment at 300 to 900° C. in decomposed ammonia gas or nitrogen gas can be cited.

Next, regarding the type of iron-based powder to which the po-containing substance is added, one example is pure iron-based powder. These include atomized iron powder, reduced iron powder, electrolytic iron powder, etc., and are known as raw materials for pure iron-based sintered magnetic materials. However, in order to exhibit the effect of the present invention method of improving magnetic properties, the content of impurity elements is limited.

The basic Si and Mn contained in the iron-based powder are easily oxidized, and once oxidized, they are difficult to reduce during annealing, so oxides remain during sintering and deteriorate the magnetic properties. Furthermore, if large amounts of St and Mn are contained, the iron powder particles become hard and have poor compressibility, resulting in a decrease in sintered density and, as a result, deterioration in magnetic properties. These adverse effects become noticeable when the content exceeds 0.2% by weight for Si and 0.5% by weight for Mn. % or less.

Note that these contents are values for the entire iron-based powder after adding the po-containing substance, and the same applies to the following description.

Next, N and C harden the iron powder particles, but each has 0
．． A content of 0.02% by weight or less, 0.1% by weight or less is acceptable.

Now, among iron-based powders other than pure iron powder, the additive substances that are particularly effective in the present invention are Sn and/or P.

FIG. 1 and FIG. 2 show equilibrium diagrams of Pe-Sn and Fe-P, respectively. Figure 3 shows the low P of the Fe-P equilibrium phase diagram.
It is an enlarged view of the side. By adding both Sn and P,
The α phase of Fe appears at the sintering temperature (usually 950 to 1300°C), and the self-diffusion of Fe and the diffusion of Sn and P in Fe are much faster in the α phase than in the γ phase.
As sintering progresses and the sintered density increases, crystal grains grow, and as a result, the magnetic properties of the sintered body improve. 1st
As is clear from the figure and FIG. 2, this effect appears when Sn is 1% by weight or more, and when P is 0.1% by weight or more. On the other hand, Sn also has the effect of binding the additive powder to the iron powder particles. That is, when iron powder, powder of a po-containing substance, powder of a P-containing substance, etc. is mixed with Sn powder or Sn oxide powder, etc. and then heated, molten Sn appears, wets the surface of the iron powder particles, and removes the additive. Combines with powder and becomes a binder,
This prevents segregation of the added powder. This binder effect appears when Sn 2 O is 1% by weight or more. Regarding P, P O,0
As mentioned above, the effect appears when the amount is 2% by weight or more. For the above reasons, the limits of Sn and P are each 0.
．． 1% by weight and 0.02% by weight.

Further, the upper limits of Sn and P are determined by the following reasons.

As shown in Figures 1 and 2, Sn is 10% by weight, and P is 2.5% by weight even in metastable equilibrium.
If the content exceeds FeSn and Fe during cooling after sintering,
3P precipitates and deteriorates magnetic properties. Therefore, S
The upper limits of n and P are set as 10% by weight and 2.5% by weight, respectively.

There are many possible ways to add Sn and P, including a method in which a homogeneous alloy is made and it is included in iron powder, a method in which powder containing Sn and P is mixed into iron powder, and a method in which Sn and P are added by heating after mixing as described above. A method of making a so-called composite powder can be arbitrarily adopted.

Note that the present invention also includes iron-based powders to which a po-containing substance is added and zinc stearate as a lubricant.

(Example) (1) - 80 mesh water atomized pure iron powder, -
250 meshes of PtOs, each 0.01% by weight
(hereinafter simply expressed as %), 0.2χ, 1.0χ, 2.
5x and 4.0x were added and mixed to create an iron-based powder containing a po-containing substance. For comparison, 1% zinc stearate was added to each iron-based powder, including iron powder without addition of P, O, and molding pressure cuff t/cd was 381 in outer diameter and 2 in inner diameter.
It was made into a ring-shaped molded body with a diameter of 5 mm and a height of 6.5+wm. Next, the molded body was sintered at 1200° C. for 60 minutes in a mixed gas with a dew point of 0° C. in which 5% CO gas was added to ammonia decomposition gas. The obtained sintered body was wound with a wire, and the DC magnetic characteristics Bzs (magnetic flux density in a magnetic field of 250e) were determined.
Hc (coercive force) and μmax (maximum magnetic permeability) were measured.

As a result of chemical analysis of all iron-based powders, Si: 0.02~
0.03%, Mn: 0.08-0.09%, N: 0
．． 002-0.003χ.

C: Contained 0.003 to 0-005χ. 1st
The table shows the p, o analysis values, green density, sintered density, and C, O analysis values and magnetic properties of the sintered body for each powder.

As can be seen from Table 1 above, the sintered body using powder without PtOs contains 0.06% C, and has magnetic properties such as low magnetic flux density, high coercive force, and low maximum magnetic permeability. However, the PzOs-added powder produced by the method of the present invention prevents carburization and achieves good magnetic properties, especially high maximum magnetic permeability. When the amount of 0% Pt added is 1% or more, the sintered density increases and the magnetic properties are further improved, and this is due to the effect of P. However, if too much P2O is added, as in the case of 4% addition, the green powder density will be extremely reduced, and the sintered density will not increase sufficiently, leading to deterioration of the magnetic properties. This was the result.

(2) The same water atom ÷ is pure iron powder as in Example 1, -25
0 mesh Fe5P powder, -250 mesh Sn powder,
-250 mesh iron phosphate (Fes (PO)!・8
A predetermined amount of HtO) was added to prepare iron-based powders as shown in Table 2.

These powders were molded and sintered in the same manner as in Example 1, and tested for green density, sintered density, and magnetic properties, and the results shown in Table 3 were obtained.

Table 3*As is clear from Table 3 of the iron-based powder of the present invention, A and C to which no po-containing substance was added were carburized by sintering and had deteriorated magnetic properties. In A and C, the effect of adding P and Sn is hardly utilized, but this is because the α phase of Fe is difficult to appear even if P and Sn are included due to carburization, and the P and Sn in Fe are difficult to appear. This is because the diffusion of Sn and the self-diffusion of Pe are hindered, resulting in insufficient sintering.The products using powders B and D, which are used in the products of the present invention, have successfully solved this problem, and P , the effect of Sn addition is fully utilized.

(3) The same water atomized pure iron powder as in Example 1 was added to -25
After adding and mixing 1.8% of FeOP powder of 0 mesh, 0.4% of Sn powder of -250 mesh, and 0.3% of iron hydrogen phosphate (Fe(HtPO*)s) powder of 1,250 mesh, The mixed powder was heated at 450℃ in ammonia decomposition gas for 6 hours.
Heated for 0 minutes. When the powder was examined by X-ray diffraction after heating, PtOs, Fe(HzPO*) l Fe+
P, P8tP.

A diffraction peak of PeSn was observed. In addition, the chemical analysis values of the powder are P: (1,52%, Sn: 0.38%, 0
:0.25%.

Si: 0.03%, Mn: 0.07%, N: 0.00
1%, and C: 0.009%. For comparison, the same iron powder, the same Pe and P powder was used at 2.0χ, and the same Sn powder was added at 0.4χ.
When the mixed powder was examined, X-ray diffraction revealed that Fe
3P+FeP+β-5n was identified, but no diffraction peak of po-containing material was observed. Chemical analysis value: P: 0.55%.

Sn: 0.40%, O: 0.091%, 3i: 0.0
3%, Fln: 0.07%.

N: 0.003%, C: 0.010%.

The same molding and sintering tests as in Example 1 were conducted, and the green density, sintered density, and magnetic properties were tested, and the results shown in Table 4 were obtained.・In this case as well, Examples 1 and 2
Similarly, significant improvements in magnetic properties can be seen.

(Effects of the Invention) As explained above, according to the iron-based powder for sintered magnetic materials according to the present invention, carburization of the sintered body is suppressed even when sintered in a sintering atmosphere with a high carbon potential. Therefore, a soft magnetic component exhibiting excellent magnetic properties can be obtained.

[Brief explanation of the drawing]

Figure 1 is an equilibrium state diagram of Fe-Sn, and Figure 2 is a Fe-Sn equilibrium diagram.
-P equilibrium state diagram. FIG. 3 is a partially enlarged view of the Fe-P equilibrium state diagram. Fig. 1 Sn amount (Wt %) Fig. 2 P amount (Wt bow) Fig. 3 P amount twt%)

Claims (1)

[Claims] 1. One or more phosphorus/oxygen-containing substances selected from phosphorus oxide, iron phosphate, and iron hydrogen phosphate, with a P content of 0.02 to 2.5% by weight. , O content is 0.10-2
．． An iron-based powder for sintered magnetic materials, which contains Fe in an amount of 0% by weight, with the remainder containing unavoidable contaminants. 2. One or more phosphorus/oxygen-containing substances selected from phosphorus oxide, iron phosphate, and iron hydrogen phosphate with a P content of 0.02 to 2.5% by weight and an O content of 0.2% by weight. 10-2.
Contains 0% by weight, C: 0.1% by weight or less, S
i: 0.2% by weight or less, Mn: 0.5% by weight or less, N:
An iron-based powder for sintered magnetic materials containing 0.02% by weight or less, with the remainder consisting of Fe and unavoidable impurities. 3. One or more phosphorus/oxygen containing substances selected from phosphorus oxides, iron phosphates, and iron hydrogen phosphates with a P content of 0.02 to 2.5% by weight and an O content of 0. 10-2.
Contains 0% by weight and 0.1 to 10% Sn
% by weight, C: 0.1% by weight or less, Si: 0.
2% by weight or less, Mn: 0.5% by weight or less, N: 0.02
An iron-based powder for sintered magnetic materials containing less than % by weight and the remainder consisting of Fe and unavoidable impurities.