JPH0625793A - Fe-cu-ni compound powder for powder metallurgy and its manufacture as well as sintered body using the same powder - Google Patents

Abstract

PURPOSE:To obtain Fe-Cu-Ni compound powder for powder metallurgy capable of obtaining a homogeneous sintered body having high density and high strength by applying Ni electroless plating to the surface of iron powder and thereafter applying Cu-Ni electroless plating thereto to regulate its compsn. into a specified one. CONSTITUTION:The Fe-Cu-Ni compound powder for powder metallurgy is one which the surface of the iron powder is applied with the Cu-Ni plated layer, and its compsn. is constituted of, by weight, 0.1 to 10% Cu and 1 to 20% Ni, and the balance Fe with inevitable impurities. By subjecting it to compacting and sintering, a sintered body having high density and dimensional stability as well as high strength can be obtd. This compound powder can inexpensively and efficiently be manufactured by previously applying the Ni electroless plating to the surface of the iron powder and thereafter applying the Cu-Ni electroless plating thereto to uniformly stick the Cu-Ni alloy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Fe-Cu-Ni composite powder for powder metallurgy and a method for producing the same, which is capable of providing a sintered body having high density and high strength and less variation in dimensional accuracy during sintering. Furthermore, the present invention relates to a sintered body as described above.

[0002]

2. Description of the Related Art The powder metallurgy method is a method in which a conventional manufacturing process including rolling, forging, casting, etc. is largely rewritten, and a metal powder as a raw material is compression molded and then sintered to obtain a product. Therefore, according to the powder metallurgy method, it is difficult to manufacture by the conventional melting method such as high melting point metal materials such as W and Mo, porous materials such as oil-impregnated bearings and filters, cemented carbide and cermet. Can be manufactured. Not only that, but in the case of ingots such as the advantage in manufacturing such as improvement of material yield due to non-cutting, high dimensional accuracy, and the fact that segregation and anisotropy, which are likely to occur in ingots, are small. Since there are various advantages that cannot be obtained, various members conventionally manufactured by the melting method are replaced with the powder metallurgy method and manufactured.

Most of the sintered bodies currently manufactured by the powder metallurgy method are used as parts for automobiles, and in particular, iron sintered members are widely used. Various types of such iron sintered members are known. For example, with the purpose of improving strength, weather resistance, wear resistance, etc., graphite, copper, etc. are added to iron powder as the main component. It is known that the fine powders of 1. are mixed and sintered. Further, from the viewpoint of expanding the range of application of sintered members, higher toughness and strength are required for sintered members, and alloying elements such as Ni and Mo are added to form alloys as a means for achieving the toughness and strength. It is also known how to do it. By the way, as a typical method for obtaining a high-strength iron sintered body by the powder metallurgy method, a premix method and a prealloy method are known.

In the premix method, iron powder and metal powder or alloy powder (hereinafter sometimes referred to as additive metal powder) are uniformly mixed, and this is compacted and then heated and sintered to solidify the additive element. It is a method of melting. This method has the advantage that the forming process is relatively simple, but the additive metal powder in the iron powder is separated / segregated due to the difference in specific gravity during the step up to powder compacting, or it is added during sintering. There is a problem in that the diffusion of the metal powder does not proceed sufficiently, and there is a problem in quality that the strength and dimensions of the sintered body vary.

On the other hand, the pre-array method uses Ni, Cu,
Since alloy steel powder in which an alloying element such as Mo is dissolved in iron in advance is used, the problem as pointed out in the premix method does not occur. However, in this method, the alloy steel powder obtained by pre-alloying is extremely hard as compared with iron, so it is not possible to sufficiently enhance the consolidation during powder compaction,
It is difficult to obtain a high-density sintered body. Therefore, the physical properties of the alloy steel cannot be fully utilized. Furthermore, the process is more complicated than the premix method, and there is a problem that composition adjustment and molding are difficult.

[0006]

Cu is an element that melts during sintering to accelerate sintering and improve strength, while Ni is used.
Is an element that improves the strength of the sintered member. Further, addition of any of these elements is said to have an effect of improving hardenability. For this reason, the demand for the Fe-Cu-Ni sintered member is great, but in the prior art, since each of the above-mentioned problems exists, a homogeneous sintered body having excellent mechanical properties has not been obtained.

The present invention has been made by paying attention to the problems of the prior art as described above, and its purpose is for powder metallurgy capable of obtaining a sintered body having high density, high strength and homogeneity. An object of the present invention is to provide an Fe-Cu-Ni composite powder, a method for producing the same, and a sintered body having such characteristics.

[0008]

The present invention, which has been able to solve the above-mentioned problems, is an Fe-Cu-Ni composite powder for powder metallurgy, in which a Cu-Ni alloy plating layer is formed on the surface of iron powder. And the composition of the composite powder is Cu: 0.
It has a gist that it is composed of 1 to 10% by weight, Ni: 1 to 20% by weight, and the balance Fe and unavoidable impurities. The Fe-Cu-Ni composite powder thus obtained is sintered to obtain a high-density, high-strength and homogeneous sintered body. The Fe-Cu-Ni composite powder of the present invention can be easily obtained by performing Ni electroless plating on the iron powder surface in advance and then performing Cu-Ni electroless plating.

[0009]

The present inventors have made various studies on the structure of the powder for powder metallurgy so that a sintered body having excellent characteristics can be obtained, and as a result, the Fe powder obtained by previously plating the surface of the iron powder with the Cu--Ni alloy was used.
It has been found that a -Cu-Ni composite powder (hereinafter sometimes referred to as "composite powder") may be used. Since Cu-Ni alloy is plated on the surface of this composite powder,
It solves the problems of segregation of alloy elements and diffusivity of the conventional premix method. Further, since the Cu-Ni alloy layer exists in the vicinity of the surface of the composite powder in the form of plating,
Compared with the powder of the conventional pre-alloying method in which the entire powder is alloyed, the compaction during powder compaction can be sufficiently enhanced, and a high-density sintered body can be obtained.

Conventionally, it has been attempted to plate the surface of iron powder with Cu alone or Ni alone (Lu Tatsun:
Anticorrosion plating and chemical plating, February 1964, P416
Nikkan Kogyo Shimbun etc.). However, in this case, for example, C
When the amount of u added increases, an abnormal expansion phenomenon called Cu-Growth occurs, which causes a large dimensional change. Therefore, as a result of various studies, the present inventors have found that when Cu—Ni is alloyed in advance and plated on iron powder, the expansion coefficient is different even if the weight ratio is the same as that of powder plated with Cu and Ni plain metal. I found it.

The cause of such a phenomenon is considered as follows. That is, the melting point (or liquid phase generation point) of the pure Cu metal is 1083 ° C., and the normal sintering conditions (11
At 20 to 1130 ° C x 30 minutes), Cu melts and penetrates between iron powder particles to form an alloy, thereby Cu-Grow.
However, the melting point (or liquid phase generation point) is higher than the sintering temperature in the Ni-Cu alloy (1310).
It is believed that these alloys do not melt and expansion does not occur due to alloying by solid phase diffusion.

Next, the reasons for limiting the composition of the Fe-Cu-Ni composite powder of the present invention will be described. First, Cu is contained from the viewpoint of lowering the melting point and improving the strength, but the content thereof is preferably in the range of 0.1 to 10% by weight with respect to the entire composite powder. If the content is less than 0.1% by weight, the effect of improving the strength of the sintered body is insufficient. On the other hand, if the content exceeds 10% by weight, the toughness deteriorates and Cu-Growt.
This is because there is a possibility that variations in the size of the sintered body due to h may occur.

Ni is contained in order to improve toughness and hardenability, but the content is preferably in the range of 1 to 20% by weight based on the whole composite powder. If the content is less than 1% by weight, the effect of improving the toughness of the sintered body is insufficient.
This is because if the content exceeds 10% by weight, not only the effect of improving toughness is further improved but also the cost is increased.

Next, a method for producing the composite powder of the present invention will be described. Examples of the method for plating the Cu-Ni alloy on iron include electrolytic plating, electroless plating, vapor-phase plating, and the like. In the present invention, the object of plating is usually an average particle size of about 3
Since the iron powder has a particle size of 00 μm or less, the electroless plating method is particularly recommended. This is because it is easy to control the composition of the Cu-Ni alloy plating by changing the plating bath and plating conditions, the plating process is simple, and the equipment is inexpensive and economical.

Further, as a result of various studies by the present inventors, when the composite powder of the present invention is produced by using the electroless plating method,
After performing the electroless plating of Ni on the iron powder surface in advance, Cu-
It has been found that it is necessary to perform electroless plating of Ni alloy.

The conventional electroless plating technique may be applied to the method of independently plating Cu or Ni on the surface of the iron powder. However, when plating these alloys, Cu and N are used.
Due to the difference in the ionization tendency of i, both plating baths are basically different, and it is difficult to manufacture them by the combination of the conventional techniques. For example, when the surface of iron powder is solely plated with Cu, plating can be easily performed by adding a predetermined amount of iron powder while stirring with an aqueous solution of copper sulfate. In addition, in order to plate Ni alone on the surface of iron powder, the so-called "chemical plating method" in which hydrazine is added to an aqueous solution of nickel chloride + sodium citrate to reduce the amount of Ni can be easily controlled. Can be done. However,
In order to produce the composite powder of the present invention, a method of simply combining the two is not appropriate, and it is necessary to first perform Ni electroless plating on the iron powder surface and then perform Cu-Ni alloy electroless plating. Is found.

The particle size of the Fe-Cu-Ni composite powder of the present invention is not particularly limited, but for the purpose of obtaining a dense and homogeneous sintered body, the average particle size is preferably 300 μm or less. This is because if the average particle size becomes too large, alloying during sintering deteriorates, it becomes difficult to obtain a uniform structure, and variations in properties such as strength and hardness occur.

By sintering the Fe-Cu-Ni composite powder thus obtained according to a conventional method, it is possible to obtain a sintered body having a high density and high strength and less variation in dimensional accuracy during sintering. Incidentally, it is of course effective to further improve the quality of the sintered body by adding various additives such as a lubricant during the sintering.

[0019]

The present invention will be described in more detail with reference to the following examples, but the following examples are not intended to limit the present invention, and all modifications can be made without departing from the spirit of the preceding and the following. It is included in the technical scope of the present invention. Example 1 A predetermined amount of iron powder was added while stirring an aqueous solution of NiCl ₂ + ammonium citrate + hydrazine to cause a plating reaction in advance to form a Ni plating layer, and then a predetermined amount of Cu was added.
SO ₄ aqueous solution was added and stirred, and Cu: 1.35 wt%, Ni: 3.78 wt%, balance Fe: Fe—Cu—N
i composite powder was obtained. It was confirmed that the surface of the obtained composite powder had a metallic luster and that the surface of the iron powder was almost uniformly plated with the Cu—Ni alloy.

Comparative Example 1 NiCl ₂ which is an electroless plating bath for chemical plating of Ni
After adding CuSO _{4 in the} same amount as in Example 1 to an aqueous solution of + ammonium citrate + hydrazine, iron powder was added while stirring to perform plating. As a result, Ni was plated on the surface of the iron powder, but Cu was a mass of metallic Cu in a state of being separated from these, and Cu—Ni alloy-plated iron powder could not be obtained. The amount of each reagent and raw material added was in accordance with Example 1.

Comparative Example 2 CuSO was added to an aqueous solution of NiCl ₂ + ammonium citrate.
After adding ₄ aqueous solutions, iron powder and hydrazine were simultaneously administered with stirring. As a result, iron powder and metallic Ni and metallic C
u was present in each separated lump, and Cu-Ni plated iron powder was not obtained.

Example 2 High-purity pure iron powder (C <0.01% (% by weight, hereinafter the same),
Mn <0.10%, P <0.01%, S <0.01%,
O <0.15%) was used as the base powder, and Cu—Ni alloy electroless plating was performed by the method according to Example 1 to prepare Fe—Cu—Ni composite powder having the composition shown in Table 1. Incidentally, a composite powder produced by the conventional premix method is given as a comparative example (No. 1). Produced No. 5 (inventive example) composite powder and N
FIG. 1 shows the results of standard deviation of the analytical values obtained by sampling 30 pieces each from the composite powder of o.1 (Comparative Example) and analyzing Cu and Ni. Composite powder No. 5 of the present invention
Has much less variation in components than Comparative Example No.1. This shows that the examples of the present invention are excellent in adhesion to iron powder and uniformity.

Next, 0.75% of zinc stearate powder as a lubricant was added to the obtained composite powder and mixed, and then the pressure was 6 ton / cm ² using a mold, and the width was 10 mm and the height was 10 mm. A rectangular rod having a length of 55 mm and an inner diameter of 24 mm, an outer diameter of 64 mm, and a height of 17 mm were pressed and molded into a donut shape, and then sintered in a nitrogen gas atmosphere at 1300 ° C. for 50 minutes to obtain a sintered body.

From the obtained rectangular rod-shaped sintered body, the diameter of the parallel portion was 6
The tensile strength was examined by cutting out a tensile test piece of mm, and the Charpy impact value was examined at room temperature without notch using a rectangular rod-shaped sintered body, and the results shown in Table 1 were obtained. Regarding No. 1 and No. 5 of the donut-shaped sintered body, the dimensions before and after sintering were measured (n = 30), and the standard deviation of the dimensional change rate was calculated by the following formula, and the results shown in FIG. 2 were obtained. . Dimensional change rate (%) = (outer diameter of test piece after sintering-outer diameter of test piece before sintering) x 100 / outer diameter of test piece before sintering

[0025]

[Table 1]

As is clear from Table 1 and FIG. 2, the comparative examples (No. 4 to 13) satisfy the requirements of the present invention.
The variation in dimensional change is smaller and the mechanical strength is stronger than those in 1 to 3). This shows that in the Fe-Cu-Ni composite powder according to the present invention, the Cu-Ni alloy is uniformly attached to the iron powder surface, and further, the diffusivity of Cu and Ni during sintering is excellent. There is.

[0027]

The present invention is configured as described above,
Fe for powder metallurgy in which the Cu-Ni alloy is uniformly attached to the iron powder by applying Cu-Ni alloy plating to the surface of the iron powder
The -Cu-Ni composite powder can be manufactured inexpensively and efficiently. The composite powder thus obtained is also excellent in compressibility, and since the Cu-Ni alloy diffuses mutually with Fe into a uniform alloy by sintering, it has a high density, high dimensional stability, and high dimensional stability. It gives a strong sintered body.

[Brief description of drawings]

FIG. 1 is Cu of an Fe—Cu—Ni composite powder obtained in an example.
5 is a graph showing the standard deviations of the analysis values of Ni and Ni in contrast.

FIG. 2 is a graph showing, in comparison, standard deviations of dimensional change rates during sintering of a sintered body using the Fe—Cu—Ni composite powder obtained in the example.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor, Hitoshi Sakuma, 2 Nadahamahigashi-cho, Nada-ku, Kobe-shi, Hyogo Stock Company Kobe Steel Works, Kobe Steel Works (72) Inventor, Hiroshi Iso 2 Nadahama-higashi, Nada-ku, Kobe-shi, Hyogo Address Stock Company Kobe Steel Works Kobe Steel Works (72) Inventor Kazuo Fujiwara 3-4-6 Matsugaeda-cho, Kita-ku, Kobe-shi, Hyogo Prefecture (72) Akio Oyashiki 453-1-13 Nakamura, Inami-cho, Kako-gun

Claims (3)

[Claims] 1. An Fe-Cu-Ni composite powder for powder metallurgy, wherein a Cu-Ni alloy plating layer is formed on the surface of iron powder, and the composition of the composite powder is Cu: 0.1-0.1.
Fe-C for powder metallurgy characterized by comprising 10% by weight, Ni: 1 to 20% by weight, the balance Fe and unavoidable impurities.
u-Ni composite powder. 2. A method for producing an Fe—Cu—Ni composite powder for powder metallurgy, which comprises performing electroless plating of Ni on the surface of the iron powder in advance and then electroless plating of a Cu—Ni alloy. 3. A sintered body obtained by sintering using the composite powder according to claim 1.