JPH08199201A - Production of partially alloyed steel powder for powder metallurgy - Google Patents

Abstract

PURPOSE: To produce a partially alloyed steel powder with which high-strength sintered parts are obtainable by low-temp. sintering at a low cost by uniformly mixing Ni powder with and sticking to a base iron powder uniformly mixed with a binder, then mixing and sticking Cu powder and MoO3 powder with and to this powder mixture and heating the mixture in a reducing atmosphere. CONSTITUTION: A binder is previously mixed uniformly with a base iron powder and 1.5 to 5wt.% Ni powder is added to this mixture and the mixture is uniformly mixed by a stationary vessel and rotary vane type high-speed mixing machine, by which the powder mixture is adhered to the base iron powder. On or more kinds of <=2wt.% Cu powder and 0.4 to 1.5wt.%, in terms of Mo, MoO3 powder are added to the mixture and the mixture is mixed to adhere these powders to the mixture and thereafter, the mixture is heated in the reducing atmosphere. The base iron powder is high-purity iron powder consisting of <=0.04wt.% Mn, <=0.003wt.% P and the balance iron with inevitable impurities. The Ni powder is preferably carbonyl Ni powder having the max. particle of <45μm and the average Fischer grain size of 3 to 5μm. As a result, the partially alloyed iron powder for powder metallurgy which yields the high-strength sintered parts by the low-temp. sintering at about 1130 to 1150 deg.C is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a partially alloyed steel powder for powder metallurgy, and particularly for powder metallurgy in which a high-strength sintered part can be obtained even at a low temperature of about 1130 to 1150 ° C. The present invention relates to a method for producing partially alloyed steel powder.

[0002]

2. Description of the Related Art In powder metallurgical processes, conventionally, sintered parts made of pure iron powder as a main raw material have been generally manufactured, but this type of sintered part has a low strength level and its use is limited. Was there. Therefore, recently, as a raw material for powder metallurgy for high-strength sintered parts, a technique of using various alloy steel powders instead of pure iron powders has been developed.

By the way, there are three types of alloying methods. First, a method of obtaining alloy steel powder (hereinafter referred to as pre-alloyed steel powder) by containing a certain amount or more of alloy components at the molten steel stage and then atomizing The obtained alloy steel powder has low compressibility, and the molded body and the sintered body thereof have a problem that the strength is low because the sintered density does not increase. On the other hand, the pure iron powder and the alloy element powder are compressed and molded in a mixed state,
There is also a method of reacting the alloy element powder with pure iron powder to form a solid solution when the compact is sintered (hereinafter referred to as premixing). However, in this method, although the compressibility of the mixed steel powder is ensured to some extent, the formability is lowered, the powder is segregated during transportation after mixing, during storage or during molding, and further, the alloying elements during sintering are There is a problem that the structure of the sintered body becomes non-uniform due to insufficient solid solution and diffusion.

Therefore, as disclosed in, for example, Japanese Patent Publication No. 45-9649, it has been proposed to overcome the above problems by diffusing and depositing alloy powder on pure iron powder. A specific method described in the publication is iron powder and 1.5
Carbonyl Ni powder of 0 to 2.00% and Mo in terms of Mo.
40-1.00% MoO ₃ powder and 0.5-Cu conversion
A 2.00% copper oxide powder or a mixture with copper powder is heated to 704 to 1010 ° C. under a reducing atmosphere to partially diffuse and adhere these alloy element powders to the iron powder to form aggregated particles. After milling, strain relief annealing is performed again at about 732 ° C. When this alloy steel powder is molded and sintered, it is possible to further diffuse the alloy elements.

However, when the above partial diffusion adhesion type alloy steel powder is sintered at a low temperature of about 1130 to 1150 ° C., there is a problem that high strength cannot be obtained after carburizing and quenching the sintered body. This is N, which is a strength improving element.
This is because the melting points of i and Mo are high and the diffusion speed into the iron powder is slow, and it is considered that high temperature and long-time sintering treatment is required to obtain sufficient diffusion. Also, with iron powder,
It is also considered that the mixture of the alloy element or the oxide powder thereof causes separation and segregation of the powder of the alloy element or the oxide due to the difference in specific gravity between mixing and diffusion and adhesion.

Therefore, in recent years, solutions to the above partial diffusion adhesion problem have been actively studied, and the following methods have been proposed and put into practical use. (1) A high-purity iron powder is preliminarily alloyed by a method of diffusing and adhering an alloy powder in which two or more kinds of elements among Ni, Cu, and Mo are preliminarily alloyed.
It facilitates alloying (see, for example, Japanese Patent Laid-Open No. 63-
297502 and JP-A-2-145702).

(2) In the above method (1), Ni;
6-8 wt%, Cu; 2 wt% or less, Mo; 0.5-
The target is 1.0 wt% to diffuse and adhere, which is more Ni than the technique disclosed in Japanese Patent Publication No. 45-9649.
It is intended to improve the strength by remarkably increasing the compounding amount of (No. 2-145702). (3) High-purity iron powder, fine powder of a single element of Ni, Cu, Mo, or alloy fine powder in which two or more kinds of these elements are alloyed in advance, and one or more kinds of these fine powders are average. The particle size is 1 to 5 μm and the specific surface area is 0.45 to 0.
This is a method for diffusing and adhering 80 m ² / g of fine powder for alloys. By using ultrafine powder with an average particle size of 1 to 5 μm, the fine powder is well dispersed between the iron powder particles, and the structure becomes non-uniform. In addition to preventing the above, by specifying the specific surface area within the above range, while preventing the formation of agglomerates due to the entanglement of the fine powder, improve the entanglement of the iron powder and the alloy powder, to increase the contact area To promote diffusion (Japanese Patent Laid-Open No. 2-145703).

(4) In addition to the above methods (1) to (3), a method of wet mixing using an organic solvent or a solution obtained by adding a binder such as a resin to an organic solvent, iron powder, and others At least one selected from the group consisting of polyvinyl acetate, nitrocellulose, polyacrylic acid ester and polymethacrylic acid ester.
There is a method of uniformly mixing with a binder containing seeds as a main component, drying, and then heating at a temperature of 750 to 1000 ° C. in a reducing atmosphere to diffuse and adhere. It is intended to prevent the segregation after the mixing and to the diffusion and adhesion so that the diffusion and adhesion can be performed uniformly and sufficiently (the above-mentioned publication and JP-A-3-97801).

[0009]

However, the above-mentioned improved technology still has the following problems.
That is, (A) In the method of diffusing and depositing the alloy powder in which two or more kinds of elements among Ni, Cu, and Mo are alloyed in advance, the manufacturing cost of the alloy powder in which alloying is performed beforehand is high, and the target alloy element is In the case of various compounding, various alloy powders must be prepared. Further, the above-mentioned Japanese Patent Laid-Open No. 2-14
As in No. 5702, when the amount of Ni powder blended is increased, the manufacturing cost is further increased.

(B) In the case of using fine powder of a single element of Ni, Cu, Mo, if the methods (3) and (4) are adopted, the strength of the sintered body is improved as compared with the conventional one, but at high temperature,
Sufficient strength cannot be obtained as compared with the case where the sintering process is performed for a long time. And, in the structure of the low temperature sintered body, many coarse austenite regions having low strength were observed, which was a cause of insufficient strength.

In view of such circumstances, the present invention is a powder which can be manufactured at a low cost and can significantly improve the strength of the sintered carburized heat-treated body even in the low temperature sintering of about 1130 to 1150 ° C. as compared with the conventional powder. An object of the present invention is to provide a method for producing a partially alloyed steel powder for metallurgy.

[0012]

[Means for Solving the Problems] The inventors of the present invention have conducted extensive studies to achieve the above-mentioned object, and observed many coarse austenite regions in the structure of a sintered body using a conventional partial diffusion adhesion type alloy steel powder as a raw material. As a result, he found that the low-strength coarse austenite region was made as small as possible and the martensite structure region was made large.

As a result, among the alloy elements Ni, Cu and Mo, Ni and Cu are auteneite forming elements, and Ni has a stronger action than Cu, and Ni is the most elemental Fe among these three elements. Since the diffusion rate is low, it was found necessary to distribute Ni as uniformly as possible during sintering. Furthermore, as a result of detailed research, the uniform diffusion and adhesion of the Ni powder particles around the iron powder particles is greatly influenced by the mixing method of the iron powder and the powders for each additive alloy before the partial alloying heat treatment. found. That is, it has been found that it is important that the Ni powder is first adhered uniformly around the iron powder particles during the mixing, and that state is maintained during the diffusion adhesion treatment, that is, until heating in the reducing atmosphere.

The present invention has been made based on the above-mentioned findings. A base iron powder is uniformly mixed with a binder in advance, and then Ni powder is uniformly mixed and adhered to the base iron powder. A method for producing a partially alloyed steel powder for powder metallurgy, which comprises mixing and adhering one or more kinds of easily reducing metal oxide powders, and heating the mixture in a reducing atmosphere. Further, in the present invention, the base iron powder is uniformly mixed with a binder in advance, and then 1.5 to 5 wt% of Ni powder is uniformly mixed and adhered to the base iron powder.
Partial alloy for powder metallurgy, characterized in that 2% by weight or less of Cu powder and 0.4 to 1.5% by weight of MoO ₃ powder in terms of Mo are mixed and adhered and heated in a reducing atmosphere. It is a method of producing a chemical steel powder. Furthermore, in the present invention, the above-mentioned base iron powder is Mn: 0.04 wt% or less, P: 0.003
High-purity iron powder consisting of less than wt%, balance iron and unavoidable impurities, or the above Ni powder has an average particle size of less than 45 μm and an average fisher (Fisher: person name) particle size of 3 to 5 μm.
m is a carbonyl Ni powder, or the above mixing is carried out by a fixed vessel rotary vane type high speed mixer, which is also a method for producing a partially alloyed steel powder for powder metallurgy.

The base iron powder does not necessarily mean pure iron but may be so-called alloy steel powder containing other alloy components.

[0016]

In the present invention, the base iron powder is uniformly mixed with the binder in advance, and then the Ni powder is uniformly mixed and adhered to the base iron powder.
Since at least one kind of non-oxidizing metal powder and / or easily reducing metal oxide powder is mixed and adhered and heated in a reducing atmosphere, Ni powder is first mixed with iron powder when mixing iron powder and alloy powder. The particles can be uniformly attached around the particles, and the state can be maintained until after heating during the diffusion attachment process. As a result, the alloy steel powder obtained was mixed with Ni and M during sintering as a compact.
One or more of the alloying elements that do not oxidize during the diffusion adhesion treatment such as o and Cu are diffused in the iron powder, and the subsequent carburizing heat treatment reduces the retained austenite phase having a large Ni content in the sintered body structure, The martensite phase will increase.

In the present invention, the base iron powder is uniformly mixed with a binder in advance, and then 1.5 to 5 wt% of Ni is mixed.
After uniformly mixing and adhering the powders, at least 2% by weight of Cu powder and 0.4 to 1.5% by weight of MoO ₃ powder in terms of Mo are mixed and adhered, and heated in a reducing atmosphere. Therefore, the above effect can be achieved more reliably.

Further, in the present invention, the base iron powder is
Mn: 0.04 wt% or less, P: 0.003 wt% or less, high-purity iron powder composed of the balance iron and unavoidable impurities, or the Ni powder has a maximum particle size of less than 45 μm and an average Fisher particle size of 3 Carbonyl Ni powder having a particle size of up to 5 μm, or the above mixing was carried out in a fixed vessel rotary vane type high-speed mixer, so that it is possible to easily achieve a predetermined purpose without increasing manufacturing costs with relatively easily available raw materials and equipment. Can be achieved. The supplementary content of the present invention and the reasons for limiting the alloy components will be described below.

First, in the process of actual mass production, it is difficult to simply mix the iron powder and the Ni powder with a mixer, and it is better to keep the cost increase as low as possible. Therefore, the present invention eliminates the use of a mixer having a special function by using a binder. Also,
At that time, it is more effective to uniformly mix the binder with the base iron powder in advance than to simultaneously add and mix with the alloy powder such as Ni powder to achieve uniform mixing and uniform adhesion. further,
By using the binder, the Ni powder and other alloy powders that have been once uniformly adhered do not separate and segregate until the diffusion adhesion treatment, and the uniform adhesion during the diffusion adhesion is guaranteed.

The binder used must be a component that is removed by the diffusion deposition process. In that sense, spindle oil that is cheap, low in viscosity, and easy to handle is excellent,
Other oils such as oleic acid may be used. The amount of addition may be the minimum necessary amount for adhering the Ni powder or other alloy powder to the base iron powder, and if it is too large, it becomes difficult for Ni to diffuse to the iron powder surface during the diffusion adhesion treatment. Since the optimum amount of the binder changes depending on the added amount of the Ni powder or other alloy powder and the particle size of the iron powder, the required minimum amount is not particularly limited in the present invention. Since a binder is used, a container rotating type such as a double cone type mixer or a V type blender which is widely used in such a case as the mixer may be used, but a container fixed rotating blade type having a rotating blade inside. The use of a high speed mixer, such as a Henschel mixer, is most preferred from a homogenous mixing perspective.

Next, in the order of admixing the deposited alloy elements, Ni powder having the highest austenite forming ability and slow diffusion in Fe is first mixed, and thereafter, for other alloys such as Mo and Cu. To mix powder, it is possible to mix the base iron powder with Ni.
It was convenient to evenly attach the powder. In addition, Ni
The powder has a Fisher average particle size of 3
It is preferable to use carbonyl Ni of ~ 5 μm, but since coarse powder and pseudo particles are mixed in as it is, using carbonyl Ni that has removed them with a sieve of 45 μm opening is effective for uniform mixing and uniform adhesion. In addition to this, since it promotes the diffusion of Ni into iron, it is very effective when used in combination with the above method for uniform deposition. If coarse Ni particles or pseudo particles are mixed, they do not sufficiently diffuse during sintering and stabilize austenite, so it is better to remove them with a sieve beforehand as described above. Sieving with a sieve also has the effect of facilitating uniform mixing and uniform adhesion because the entangled Ni powder particles are easily disentangled and dispersed. If the average particle size of the Ni powder is less than 3 μm in terms of Fisher particle size, the alloy yield will decrease due to the scattering of fine powder, and
When it exceeds m, the fine powder particles are not well dispersed between the iron powder particles, and it is difficult for the fine powder particles to diffuse at the time of sintering, so that the structure of the sintered body tends to be nonuniform. Therefore, in the present invention,
It is preferred to use carbonyl Ni with an average Fisher grain size of 3-5 μm.

Increasing the purity of the base iron powder is also effective as a means for promoting the diffusion of Ni into the iron powder, but in combination with the above-mentioned method for uniformly depositing the Ni powder, M
n: 0.04 wt% or less, P: O. The use of high-purity iron powder composed of OO 3% or less, other iron, and unavoidable impurities was particularly effective for uniform diffusion of Ni. Finally, the alloy element to be diffused and adhered to the base iron powder is Ni: 1.5 to 5 wt
% Is essential, MoO ₃ is 0.4 to 1.5 in terms of Mo.
The reason for using one or more of wt% and Cu: 2% or less is as follows.

Ni: Ni that diffuses into the sintered body improves the hardenability of the sintered body to improve its strength and toughness. Ni is an element that promotes shrinkage, and is an important element for adjusting the dimensional change during sintering. And N
If the addition amount of i exceeds 5 wt%, the compressibility of the alloy steel powder decreases, which is not preferable in practice, so the content is set to 5 wt% or less.
Further, when Ni is less than 1.5 wt%, dimensional shrinkage during sintering is small and the sintered density is lowered, which is not preferable in practical use.

Mo: Improves the hardenability of the sintered body and prevents softening during quenching and tempering. If the Mo content is less than 0.4 wt%, the strength is low, and if it exceeds 1.5 wt%, the hardness of the sintered body becomes too high and the workability of the sintered body becomes problematic. The range is%. Cu; Cu has the smallest hardenability improving effect as compared with Mo and Ni, but its addition causes a liquid phase to appear at a normal sintering temperature, promotes the progress of sintering, and contributes to the improvement of strength.
In addition, due to the action called Cu expansion, the dimensional change during sintering is likely to expand. Therefore, it may be added selectively in consideration of the dimensional change within the range that does not affect the compressibility.
% Or less.

[0025]

【Example】

(Example-1) First, spindle oil as a binder was added to the base iron powder of 1.5 tons in the range of 0 to 200 cc. This base iron powder has (A) Mn; 0
7% by weight, P; 0.004 to 0.010% by weight, the balance iron and inevitable impurities, and (B) Mn;
Two types of high-purity iron powder are used: 04 wt% or less, P: 0.003 wt% or less, the balance iron and inevitable impurities. On the other hand, Ni powder as an alloy element source is also (a) Carbonyl Ni having a Fisher average particle size of 3 to 5 μm.
Powder commercial product, and (b) the commercial product is sieved with a sieve having an opening of 45 μm to prepare two types of carbonyl Ni powder from which coarse particles of 45 μm or more and pseudo particles have been removed. We decided to adopt two types of mixer, a fixed-rotating blade Henschel mixer.

Next, as a mixing method, (a) simultaneous mixing of base iron powder, binder, and additive powder for alloy (comparative example),
(A) Simultaneous mixing of the additive powder for alloy after pre-mixing the iron powder and the binder (comparative example), (c) Mixing Ni powder after pre-mixing the iron powder and the binder, and then mixing of the additive powder for other alloys ( (Corresponding to the present invention), iron powder, Ni powder, MoO ₃
Powder, Cu powder 4 wt% Ni-1.5 wt% Cu-
Dry or wet mixing was carried out so that the composition was 0.5 wt% Mo-remaining Fe, and the resulting mixed powder was mixed in a hydrogen atmosphere for 8 hours.
Various partially alloyed steel powders were obtained by a process of crushing and classifying after diffusion annealing at a temperature of 50 to 900 ° C. for 30 to 60 minutes.

In order to investigate the use results of these partially alloyed steel powders, graphite powder 0.5 was added to each of the partially alloyed steel powders.
wt% and zinc stearate as a lubricant 0.8 wt%
35m outside diameter to make the density 7Mg / m ³
m, an inner diameter of 14 mm, and a height of 10 mm were molded into a hollow cylindrical body, and sintered at 1130 ° C. for 20 minutes in an RX gas atmosphere. Then, the sintered body was carburized at 900 ° C. for 60 minutes at a carbon potential of 0.9%, quenched with oil at a temperature of 60 ° C., and tempered at 200 ° C. for 60 minutes to obtain a hollow cylinder. The sample was subjected to a compression test in the length direction of the cylinder to measure the radial crushing strength of each sample.

Table 1 shows the above mixing conditions and the measured radial crushing strength.

[0029]

[Table 1]

According to Table 1, iron powder, Ni powder, MoO ₃
Powder, Cu powder 4 wt% Ni-1.5 wt% Cu-
In a method for producing a partially alloyed steel powder diffusion-adhered to have a composition of 0.5 wt% Mo-remaining Fe, in a mixing step before diffusion-adhesion, an appropriate amount of base iron powder and a binder are pre-mixed, and then Ni By mixing the powders and then mixing the other additive powders for alloys (method (c) above), it is possible to obtain high sintered body strength in low-temperature sintering at 1130 ° C and carburizing / quenching. Recognize. However, Comparative Example 2
3 and Comparative Examples 4 and 5, respectively, and Invention Examples 1 and 2, as is clear, when the binder amount is too large, the mutual diffusion of Fe and Ni is hindered during the partial alloying heat treatment.
On the contrary, the strength of the sintered body was low, and it was also found that there was an optimum amount of binder added.

From the steel powder obtained by the manufacturing method according to the present invention, in which the binder is premixed with the base iron powder, and then the Ni powder is mixed prior to the mixing with other alloy additive powder, the high purity of the base iron powder is obtained. And removing coarse particles of 45 μm or more and pseudo particles with a sieve 3
By using a fine carbonyl Ni powder of ˜5 μm, using a container fixed rotary vane type high-speed mixer, etc., a synergistic effect is exerted to obtain a sintered body of higher strength.

High-purity base iron powder, spindle oil 100
cc premixed in a double cone mixer, then 4
3 to 5 μm after removing coarse particles and pseudo particles of 5 μm or more with a sieve
The crush strength of the sintered compact of Inventive Example 5 in which the fine carbonyl Ni powder of No. 1 was mixed, and then the other additive powder for alloy was mixed was 1494.
MPa, non-high purity base iron powder, spindle oil 1
00cc, coarse particles of 45 μm or more, commercial carbonyl Ni powder of 3 to 5 μm in which pseudo particles are not removed by a sieve, and other alloy additive powders are simultaneously mixed in a double cone mixer, and the radial crushing strength of a sintered body of Comparative Example 2 A strength improvement of about 12% was obtained over 1338 MPa. Further, the radial crushing strength of the sintered body of Inventive Example 9 using a Henschel mixer in place of the double cone type of Inventive Example 5 was 1525 MPa, which was about 14% higher than that of Comparative Example 2. . (Example-2) First, 200 cc of spindle oil was added as a binder to 1.5 tons of iron powder. This base iron powder has a Mn of 0.05 to O. 07 wt%, P; 0.00
4 to 0.010 wt%, the balance consisting of iron and unavoidable impurities, and Ni powder is a commercially available carbonyl Ni powder having a Fisher average particle size of 3 to 5 μm.
A sieve in which coarse particles of 45 μm or more and pseudo particles were removed was prepared, and a rotating container type double cone mixer was used as a mixer.

The mixing method is as follows: (I) Base iron powder and binder are pre-mixed and then alloy additive powder is simultaneously mixed (comparative example),
(II) After mixing the base iron powder and the binder in advance, the Ni powder was mixed, and thereafter, two levels of mixing of other alloy additive powder (corresponding to the present invention) were performed. And base iron powder and Ni powder,
MoO ₃ powder was wet mixed so as to have a composition of 2 wt% Ni-1.0 wt% Mo-remaining Fe, and the obtained mixed powder was subjected to diffusion annealing in a hydrogen atmosphere at a temperature of 850 to 900 ° C. for 30 to 60 minutes. Partially alloyed steel powder was obtained by the steps of crushing and classifying.

Graphite powder 0.3% was added to these partially alloyed steel powders.
wt% and zinc stearate as a lubricant 0.8 wt%
After the addition, it is molded into a hollow cylinder at a molding pressure of 686 MPa,
Sintering was performed in an RX gas atmosphere at 1150 ° C. for 60 minutes.
Then, the sintered body was carburized at 920 ° C. and a carbon potential of 0.9% for 150 minutes, quenched with oil at a temperature of 60 ° C., and tempered under the conditions of 180 ° C. × 60 minutes to obtain a tensile sample. A test was conducted to measure the tensile strength of each.

The tensile strength of the sample using the partially alloyed steel powder obtained by premixing the base iron powder and the binder with the alloy additive powder was 1150 N / mm ² , whereas
The tensile strength of the sample using the partially alloyed steel powder (corresponding to the present invention) in which the Ni powder was first mixed after the base iron powder and the binder were premixed and then the MoO ₃ powder was mixed was 1260.
An improvement of about 6% in strength of the sintered body was observed at N / mm ² .

[0036]

As described above, the method for producing a partially alloyed steel powder for powder metallurgy according to the present invention enables the Ni powder to be uniformly mixed and adhered to the iron powder. As a result, if the partially alloyed powder produced by this method is used, it is not necessary to use a fine alloy powder that has been completely alloyed in advance, which is high in manufacturing cost, or to increase the amount of expensive Ni powder compounded. In the production of sintered parts by, the high strength can be obtained even in the low temperature sintering of 1130 ~ 1150 ° C, which is easy to compress / mold and is widely used, and it can greatly contribute to the high strength of mass produced sintered parts. .

Claims (5)

[Claims] 1. A base iron powder is uniformly mixed with a binder in advance, and then Ni powder is uniformly mixed and adhered thereto. Then, at least one of non-oxidizable metal powder and / or easily reducible metal oxide powder is added. A method for producing a partially alloyed steel powder for powder metallurgy, which comprises mixing, adhering, and heating in a reducing atmosphere. 2. A base iron powder is uniformly mixed with a binder in advance, then 1.5 to 5 wt% of Ni powder is uniformly mixed and adhered thereto, and then 2 wt% or less of Cu powder and 0.4 in Mo conversion.
A method for producing a partially alloyed steel powder for powder metallurgy, which comprises mixing and adhering one or more kinds of MoO ₃ powder of up to 1.5% by weight and heating the mixture in a reducing atmosphere. 3. The base iron powder is Mn; 0.04 wt.
% Or less, P: 0.003 wt% or less, and a high-purity iron powder consisting of the balance iron and inevitable impurities, The method for producing a partially alloyed steel powder for powder metallurgy according to claim 1 or 2. 4. The partial alloying for powder metallurgy according to claim 1, wherein the Ni powder is carbonyl Ni powder having a maximum particle size of less than 45 μm and an average Fisher particle size of 3 to 5 μm. Steel powder manufacturing method. 5. The method for producing a partially alloyed steel powder for powder metallurgy according to claim 1 or 2, wherein the mixing is performed by a fixed vessel rotary blade type high speed mixer.