KR20220057588A - Alloy steel powder for powder metallurgy, iron-based mixed powder for powder metallurgy, and sintered compact - Google Patents

Abstract

Provided is an alloy steel powder for powder metallurgy which is excellent in compressibility and capable of obtaining a sintered body having improved strength while being sintered. Cu: 1.0 mass% or more and 8.0 mass% or less, Mo: more than 0.50 mass% and 2.00 mass% or less, and V: 0.05 mass% or more and 0.50 mass% or less, Nb: 0.02 mass% or more and 0.40 mass% or less, and Ti: 0.02 mass% It is an alloy steel powder for powder metallurgy comprising at least one selected from the group consisting of not less than 0.40 mass% and the remainder being Fe and unavoidable impurities.

Description

Alloy steel powder for powder metallurgy, iron-based mixed powder for powder metallurgy, and sintered compact

The present invention relates to alloy steel powder for powder metallurgy, iron-based mixed powder for powder metallurgy, and a sintered body.

According to the powder metallurgy technology, parts with complex shapes can be manufactured in a shape very close to the product shape (so-called near-net shape), and can be manufactured with high dimensional accuracy, and a significant reduction in cutting cost in the manufacturing of parts can be achieved. can Therefore, powder metallurgy products are used in various fields as parts for various machines. In addition, in order to cope with the miniaturization, weight reduction and complexity of parts, the demand for powder metallurgy technology is increasing.

Against the background of the above, the demand for alloy steel powder used in powder metallurgy is also increasing. In addition, there is a strong demand for reduction in manufacturing cost, and from this point of view, it is required that alloy steel powder can be manufactured by a conventional metallurgical powder manufacturing process without requiring an additional process, and It is required not to require expensive alloying components.

Regarding the improvement of the strength of the sintered body, a method of mixing a specific metal powder with steel powder to obtain a mixed powder, a method of diffusing and adhering a specific metal powder to the surface of the steel powder, a method of further combining graphite powder, an alloy steel powder alloyed with a specific metal element A method of using , etc., has been proposed.

For example, in patent document 1, the steel powder which alloyed V and Mn is proposed, and it is said that Cu powder and Ni powder may be mixed.

Patent Document 2 proposes an alloy steel powder for powder metallurgy in which Cu powder is diffused and adhered to the surface of the steel powder alloyed with Cu.

Patent Document 3 proposes a powder metallurgy mixed powder in which at least one of Cu powder and Ni powder is mixed with a steel powder obtained by alloying Mo.

In Patent Document 4, an alloy steel powder obtained by alloying Ni, Mo and Mn is proposed.

Patent Document 5 proposes a method of bonding graphite powder to iron-based powder with a binder, and it is said that the iron-based powder may be alloyed with an alloying element such as Ni, Cr, Mo, and Mn.

In patent document 6, the method of combining reduced amount of C with alloy elements, such as Cr, Mo, and Cu, is proposed.

Japanese Patent Publication No. 2012-520942 International Publication No. 2016/092827 Japanese Patent Publication No. 2003-500538 Japanese Patent Publication No. 2010-529302 Japanese Patent Publication No. 2013-508558 Japanese Patent Laid-Open No. 2013-204112

However, in Patent Document 1, even if Cu powder or the like is used together, the effect of improving the strength of the sintered body by precipitation strengthening of V is limited, and since it contains Mn, a decrease in the strength of the sintered body due to oxidation may also occur. , further enhancement of strength is required.

About patent document 2, when Cu alone is used, the strength improvement effect of a sintered compact is limited, and the improvement of the further strength is calculated|required.

About patent document 3, even if it uses Cu powder etc. together, the intensity|strength improvement effect of the sintered compact by Mo alloying is limited, and the further improvement of intensity|strength is calculated|required.

About patent document 4, since it contains Ni, it is high cost, and since it contains Mn, the intensity|strength fall resulting from oxidation may also generate|occur|produce.

About patent document 5, in order to improve the mechanical characteristic of a sintered compact, it is required to perform heat processing, such as carburizing, quenching, tempering, after sintering.

Regarding Patent Document 6, by reducing the amount of C (graphite powder, etc.) mixed with the alloy steel powder to the last, the compressibility of the mixed powder is only improved, and the compressibility of the alloy steel powder itself cannot be improved. Moreover, in order to ensure the hardness and tensile strength of a sintered compact, it is required to make the cooling rate in quenching after sintering into 2 degreeC/s or more. In order to control such a cooling rate, modification of a manufacturing facility is required, and manufacturing cost increases.

The present invention has been made in view of the above, and it is an object of the present invention to provide an alloy steel powder for powder metallurgy that is excellent in compressibility and can obtain a sintered body having improved strength in a sintered state (without additional heat treatment). do. Here, the compressibility refers to the density (compression density) of a molded article obtained when it is molded under a given molding pressure, and the larger this value is, the better.

Another object of the present invention is to provide an iron-based mixed powder for powder metallurgy comprising the alloy steel powder for powder metallurgy.

Another object of the present invention is to provide a sintered body using the alloy steel powder for powder metallurgy or the iron-based mixed powder for powder metallurgy.

As a result of repeated intensive studies, the present inventors have found that alloy steel powder using at least any of Cu, Mo, V, Nb, and Ti in specific amounts, respectively, as an alloying element has excellent compressibility and improved strength while sintered It found out that the sintered compact which has had can be provided, and this invention was completed. The alloy steel powder of the present invention can make the distribution of Cu and Mo uniform, and furthermore can make the distribution of Cu and Mo in the sintered body uniform. In addition, since it contains at least any of V, Nb and Ti, it is assumed that it is possible to refine the precipitate in the sintered compact, and furthermore, the structure can be refined, and these can work together to obtain a sintered compact having improved strength. do.

The configuration of the gist of the present invention is as follows.

[1] Cu: 1.0 mass% or more and 8.0 mass% or less;

Mo: more than 0.50 mass % and 2.00 mass % or less, and

V: 0.05 mass% or more and 0.50 mass% or less, Nb: 0.02 mass% or more and 0.40 mass% or less, and Ti: at least one selected from the group consisting of 0.02 mass% or more and 0.40 mass% or less,

Alloy steel powder for powder metallurgy, with the balance consisting of Fe and unavoidable impurities.

[2] V: The alloy steel powder for powder metallurgy according to [1], containing 0.05 mass% or more and 0.50 mass% or less.

[3] The alloy steel powder for powder metallurgy according to [1] or [2], comprising Nb: 0.02 mass% or more and 0.40 mass% or less.

[4] The alloy steel powder for powder metallurgy according to any one of [1] to [3], comprising Ti: 0.02 mass% or more and 0.40 mass% or less.

[5] An iron-based mixed powder for powder metallurgy comprising the alloy steel powder for powder metallurgy according to any one of [1] to [4] and metal powder,

For powder metallurgy, wherein the metal powder is any one or both of Cu powder of more than 0 mass% and 4 mass% or less and Mo powder of more than 0 mass% and 4 mass% or less with respect to 100 mass% of the iron-based mixed powder for powder metallurgy. iron mixture.

[6] A sintered body using the alloy steel powder for powder metallurgy according to any one of [1] to [4] or the iron-based mixture powder for powder metallurgy according to [5].

The alloy steel powder for powder metallurgy of the present invention can obtain a sintered body having excellent compressibility and improved strength while still being sintered.

Further, since the alloy steel powder for powder metallurgy of the present invention does not contain easily oxidized alloying elements such as Cr or Mn, it is advantageous in that the strength of the sintered body due to oxidation of the alloying elements does not decrease.

In addition, the alloy steel powder for powder metallurgy of the present invention does not contain Ni, which is expensive for alloying, Cr, which requires annealing in a special atmosphere, etc. It is convenient also in that it can manufacture by the conventional powder manufacturing process for metallurgy.

In addition, the iron-based mixed powder for powder metallurgy of the present invention can provide a sintered body which is similarly excellent in compressibility and has improved strength while being sintered.

By using the alloy steel powder for powder metallurgy or the iron-based mixed powder for powder metallurgy of the present invention, a sintered body having improved strength can be manufactured at low cost.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail.

[Alloy steel powder for powder metallurgy]

The alloy steel powder for powder metallurgy of the present invention (hereinafter also referred to as "alloy steel powder") consists of an iron-based alloy containing Cu, Mo, and at least any one of V, Nb, and Ti as essential components. Here, an "iron group" means containing 50 mass % or more of Fe. "%" regarding a component composition shall mean "mass %" unless otherwise stated. The component composition of the alloy steel powder for powder metallurgy is based on 100% by mass of the alloy steel powder for powder metallurgy.

Cu: 1.0% or more and 8.0% or less

Cu is an element which improves hardenability, and is excellent in that it is hard to oxidize than elements, such as Si, Cr, and Mn. Moreover, compared with Ni, Cu is advantageous also at a point cheap. When Cu content is less than 1.0 %, the improvement effect of the hardening property by Cu becomes inadequate. Therefore, Cu content shall be 1.0 % or more. On the other hand, although manufacture of a sintered compact is generally performed at about 1130 degreeC, from the Fe-Cu system phase diagram, when Cu content exceeds 8.0 %, Cu will precipitate in an austenite phase. Cu precipitated at the time of sintering does not function effectively to improve the quenching property, but rather remains as a soft phase in the structure, which may lead to a decrease in mechanical properties. Therefore, Cu content shall be 8.0 % or less. If it is the said range, improvement of tensile strength can fully be aimed at, suppressing the fall of a density by addition of Cu. In order to effectively obtain higher strength, the Cu content is preferably 2.0% or more, and preferably 6.0% or less.

Mo: more than 0.50% and less than 2.00%

Mo is an element which improves hardenability, and is excellent in that it is hard to oxidize than elements, such as Si, Cr, and Mn. Mo has a characteristic that sufficient quenching property improvement effect is acquired by addition in a small amount compared with Ni. When Mo content is 0.50 % or less, the strength improvement effect by Mo becomes inadequate. Therefore, Mo content shall be more than 0.50 %. On the other hand, when the Mo content exceeds 2.00%, the compressibility of the alloy steel powder decreases and the mold for molding is easily worn, and the effect of improving the strength of the sintered body by containing Mo is saturated. Therefore, Mo content shall be 2.00 % or less. In order to effectively obtain higher strength, the Mo content is preferably 1.00% or more, and preferably 1.50% or less.

The alloy steel powder of the present invention contains at least any one of V, Nb and Ti. Alloy steel powder may contain only 1 type of V, Nb, and Ti, may contain 2 types, and may contain all 3 types. When 2 types are contained, any combination of V and Nb, V and Ti, and Nb and Ti may be sufficient. Each content of V, Nb, and Ti is as follows.

V: 0.05% or more and 0.50% or less

V is an element which acts very effectively for the improvement of strength by precipitating as a carbide|carbonized_material in the solid part of a sintered compact. When the V content is less than 0.05%, the amount of carbide produced becomes insufficient, and sufficient strength improvement of the sintered body cannot be achieved. Therefore, when V is contained, V content is made into 0.05 % or more. On the other hand, when the V content exceeds 0.50%, the carbide is coarsened and the effect of improving the strength is lowered, and each grain of the alloy steel powder is hardened, which not only causes a decrease in compressibility, but is also disadvantageous from an economical point of view. Therefore, the V content is made 0.50% or less. In order to effectively obtain higher strength, the V content is preferably 0.10% or more, and preferably 0.40% or less.

Nb: 0.02% or more and 0.40% or less

Nb is an element which not only significantly improves quenching property, but also acts effectively on the improvement of strength by precipitating as a carbide in the solid part of a sintered compact. When the Nb content is less than 0.02%, the amount of carbide produced becomes insufficient, and sufficient strength improvement of the sintered body cannot be achieved. Therefore, when containing Nb, Nb content shall be 0.02 % or more. On the other hand, when the Nb content exceeds 0.40%, the carbide is coarsened and the effect of improving the strength is lowered, and each grain of the alloy steel powder is hardened, which not only causes a decrease in compressibility, but also disadvantages from an economic point of view. Therefore, when containing Nb, Nb content shall be 0.40 % or less. In the case of containing Nb, in order to effectively obtain higher strength, the Nb content is preferably 0.05% or more, and preferably 0.20% or less.

Ti: 0.02% or more and 0.40% or less

Ti is an element which acts effectively on the improvement of strength by precipitating as a carbide|carbonized_material in the solid part of a sintered compact. When the Ti content is less than 0.02%, the amount of carbide produced becomes insufficient, and sufficient strength improvement of the sintered body cannot be achieved. Therefore, when containing Ti, Ti content shall be 0.02 % or more. On the other hand, when the Ti content exceeds 0.40%, the carbide is coarsened and the effect of improving the strength is lowered, and each grain of the alloy steel powder becomes hard to cause a decrease in compressibility, and it is disadvantageous from an economic point of view. Therefore, when containing Ti, Ti content shall be 0.40 % or less. In the case of containing Ti, in order to effectively obtain higher strength, the Ti content is preferably 0.05% or more, and preferably 0.20% or less.

The remainder of the alloy steel powder other than the above components consists of Fe and unavoidable impurities. The amount of the unavoidable impurities is not particularly limited as long as it is an amount to be unavoidably mixed, but it is preferable to control so as not to contain substantially. Since Ni causes an increase in alloy cost, it is preferable to suppress the Ni content to 0.1% or less. Since Cr is easily oxidized and an annealing atmosphere control is required, it is preferable to suppress the Cr content to 0.1% or less. Also about Si, from the same reason as Cr, it is preferable to suppress Si content to 0.1 % or less. C: 0.01% or less, O: 0.20% or less, Mn: 0.15% or less, P: 0.025% or less, S: 0.025% or less, N: 0.05% or less, and other elements: It is preferable to suppress to 0.01% or less.

The alloy steel powder of the present invention includes the following aspects.

Cu: 1.0 mass% or more and 8.0 mass% or less, Mo: more than 0.50 mass% and 2.00 mass% or less, V: 0.05 mass% or more and 0.50 mass% or less, and the balance is Fe and unavoidable impurities. .

Cu: 1.0 mass% or more and 8.0 mass% or less, Mo: more than 0.50 mass% and 2.00 mass% or less, Nb: 0.02 mass% or more and 0.40 mass% or less, and the balance is Fe and unavoidable impurities. .

Cu: 1.0 mass% or more and 8.0 mass% or less, Mo: more than 0.50 mass% and 2.00 mass% or less, Ti: 0.02 mass% or more and 0.40 mass% or less, and the balance is Fe and unavoidable impurities. .

Cu: 1.0 mass% or more and 8.0 mass% or less, Mo: more than 0.50 mass% and 2.00 mass% or less, V: 0.05 mass% or more and 0.50 mass% or less, and Nb: 0.02 mass% or more and 0.40 mass% or less, the balance being Fe and Alloy steel powder for powder metallurgy composed of unavoidable impurities.

Cu: 1.0 mass% or more and 8.0 mass% or less, Mo: more than 0.50 mass% and 2.00 mass% or less, V: 0.05 mass% or more and 0.50 mass% or less, and Ti: 0.02 mass% or more and 0.40 mass% or less, the balance being Fe and alloy steel powder for powder metallurgy composed of unavoidable impurities.

Cu: 1.0 mass% or more and 8.0 mass% or less, Mo: more than 0.50 mass% and 2.00 mass% or less, Nb: 0.02 mass% or more and 0.40 mass% or less, and Ti: 0.02 mass% or more and 0.40 mass% or less, the balance being Fe and alloy steel powder for powder metallurgy composed of unavoidable impurities.

Cu: 1.0 mass% or more and 8.0 mass% or less, Mo: more than 0.50 mass% and 2.00 mass% or less, V: 0.05 mass% or more and 0.50 mass% or less, Nb: 0.02 mass% or more and 0.40 mass% or less, and Ti: 0.02 mass% or more An alloy steel powder for powder metallurgy containing 0.40 mass% or less, the balance being Fe and unavoidable impurities.

The manufacturing method of alloy steel powder is not specifically limited, It can manufacture by arbitrary methods. For example, the alloy steel powder may be atomized powder produced by the atomization method, and among them, water atomization produced by the water atomization method, which has a low manufacturing cost and is easy to mass-produce. It is preferable that it is an izubun. In the case of manufacturing alloy steel powder by the atomization method, for example, molten steel adjusted to have a predetermined component composition is atomized to obtain a powder, and, if necessary, reduced and/or classified to obtain alloy steel powder.

The particle size of the alloy steel powder is not particularly limited, and can be any particle size. From a viewpoint of manufacturing easiness, it is preferable that an average particle diameter is 30 micrometers or more and 150 micrometers or less. By the water atomization method, alloy steel powder having an average particle diameter in the above range can be industrially manufactured at low cost. Here, the average particle diameter refers to the median diameter (D50) on a mass basis. The average particle size can calculate the mass-based integrated particle size distribution from the particle size distribution measured by the dry sieve classification method described in JISZ2510, and the particle size from which the value will be 50% can be calculated|required by the interpolation method.

[Mixed iron powder for powder metallurgy]

The alloy steel powder can be used as it is for powder metallurgy, but it can also be used as an iron-based mixed powder for powder metallurgy (hereinafter also referred to as “mixed powder”) comprising alloy steel powder and metal powder. The metal powder in the mixed powder of the present invention is either one or both of Cu content: more than 0% and 4% or less and Mo content: more than 0% and 4% or less. The component composition of the iron-base mixed powder for powder metallurgy is based on 100 mass% of the iron-based mixed powder for powder metallurgy.

Cu min: more than 0% and not more than 4%

When Cu powder is added to alloy steel powder, sintering can be promoted and strength can be improved, but when it exceeds 4%, the amount of liquid phase generated during sintering increases, resulting in a decrease in density of the sintered body due to expansion. , lower the strength. Therefore, the addition amount of Cu powder shall be 4 % or less. When adding Cu powder, in order to improve intensity|strength efficiently, 0.5 % or more is preferable.

Mo min: more than 0% and not more than 4%

When Mo powder is added to the alloy steel powder, sintering can be promoted and strength can be improved. However, when it exceeds 4%, the alloy steel powder becomes hard and the compression density is lowered, thereby reducing the strength. Therefore, the addition amount of Mo powder shall be 4 % or less. When adding Mo powder, in order to improve intensity|strength efficiently, 0.5 % or more is preferable.

The manufacturing method of the mixed powder is not specifically limited, It can manufacture by arbitrary methods. For example, with respect to the said alloy steel powder, it can manufacture by mixing one or both of Cu powder and Mo powder so that it may become the said content. Mixing can be performed by arbitrary methods. For example, the method of mixing using a V-type mixer, a double cone-type mixer, a Henschel mixer, a Nauta mixer, etc. is mentioned. At the time of mixing, in order to prevent segregation of one or both of Cu powder and Mo powder, you may add binders, such as machine oil. Alternatively, one or both of the alloy steel powder, Cu powder, and Mo powder may be filled in a mold for pressure molding so as to have the above content to be mixed powder.

[Sintered body]

The present invention also relates to a sintered body formed by sintering a molded body containing the alloy steel powder or mixed powder.

The sintered body can be manufactured using the above alloy steel powder or mixed powder (hereinafter, also referred to as “raw material”) as a raw material. The manufacturing method of a sintered compact is not specifically limited, It can manufacture by arbitrary manufacturing methods. For example, it can manufacture by adding arbitrary components to the said raw material as needed, press-molding these, and sintering.

(optional ingredient)

As a raw material of a sintered compact, although the said raw material can be used as it is, you may use together auxiliary raw materials, such as carbon powder.

The carbon powder is not particularly limited, and graphite powder (natural graphite powder, artificial graphite powder, etc.) and carbon black are preferable. By adding carbon powder, the intensity|strength of a sintered compact can be improved further. When adding carbon powder, 0.2 mass part or more is preferable with respect to 100 mass parts of said raw materials from the point of a strength improvement effect, and 1.2 mass part or less is preferable.

You may add a lubricant to the said raw material. By containing the lubricant, it is possible to facilitate extraction of the molded article from the mold. The lubricant is not particularly limited, and metal soaps (zinc stearate, lithium stearate, etc.), amide waxes (ethylenebisstearic acid amide, etc.), etc. are mentioned. The lubricant is preferably in the form of a powder. When using a lubricant, 0.3 mass part or more and 1.0 mass part or less of a lubricant are preferable with respect to 100 mass parts of said raw materials.

You may add the powder for machinability improvement with respect to the said raw material. The powder for machinability improvement is not specifically limited, MnS powder, oxide powder, etc. are mentioned. When using the powder for machinability improvement, 0.1 mass part or more and 0.7 mass part or less of the powder for machinability improvement are preferable with respect to 100 mass parts of said raw materials.

(Pressure molding)

With respect to the above raw materials, optional ingredients such as auxiliary materials, lubricants, and powder for machinability improvement are blended according to the case, and then press-molded into a desired shape to obtain a molded body. The method of pressure molding is not specifically limited, Arbitrary methods can be used, For example, the method of filling a metal mold|die etc. with a raw material, and carrying out pressure molding is mentioned. A lubricant may be applied or adhered to the mold, and the amount of the lubricant at that time is preferably 0.3 parts by mass or more and 1.0 parts by mass or less with respect to 100 parts by mass of the raw material.

The pressure at the time of setting it as a molded object by pressure molding can be 400 Mpa or more and 1000 Mpa or less. If it is this range, the density of a molded object becomes low, and it can avoid that the density of a sintered compact falls, and becomes a lack of intensity|strength, and the burden on a metal mold|die can also be suppressed. The raw material of the present invention can, for example, have a density (compression density) of a molded body of 6.75 Mg/m 3 or more under a molding pressure of 588 MPa. The density (compressed density) of the molded article is preferably 6.80 Mg/m 3 or more.

(sintering)

Next, the obtained molded body is sintered. The method of sintering is not specifically limited, It can implement by arbitrary methods. The sintering temperature can be set to 1100°C or higher, preferably 1120°C or higher, from the viewpoint of sufficiently advancing sintering. On the other hand, since the distribution of Cu and Mo in the sintered body becomes uniform as the sintering temperature is higher, the upper limit of the sintering temperature is not particularly limited. is more preferable. Since the raw material uses an alloy steel powder alloyed with Cu, Mo, and at least any of V, Nb and Ti, even at a sintering temperature in the above range, the distribution of Cu and Mo can be uniformed, and as a result, The strength of the sintered body can be effectively improved.

Sintering time can be made into 15 minutes or more and 50 minutes or less. If it is this range, sintering becomes insufficient and it can avoid becoming insufficient in intensity|strength, and manufacturing cost can also be suppressed. The cooling rate at the time of cooling after sintering can be made into 20 degrees C/min or more and 40 degrees C/min or less. At a cooling rate of less than 20°C/min, quenching cannot be sufficiently performed, and the tensile strength may decrease. At a cooling rate of 40°C/min or higher, ancillary equipment for accelerating the cooling rate is required, increasing the manufacturing cost.

When using a lubricant, before sintering, in order to decompose and remove the lubricant, a degreasing step of holding the lubricant in a temperature range of 400°C or higher and 700°C or lower for a certain period of time may be added.

Manufacturing conditions, equipment, etc. of the sintered compact other than the above are not specifically limited, For example, a well-known thing is applicable.

The obtained sintered compact may be processed, such as carburizing quenching and tempering.

Example

Next, the present invention will be described more specifically based on Examples. The following examples show preferred examples of the present invention, and the present invention is not limited thereto.

Manufacture of the alloy steel powder in the Example and manufacture of the sintered compact using the alloy steel powder were performed in the following procedure.

· Manufacture of alloy steel powder

Molten steels having the component compositions shown in Tables 1 to 4 were prepared, and alloy steel powder was manufactured by the water atomization method. The amounts of Si, Mn, P, S and Cr contained as unavoidable impurities in the alloy steel powder are: Si: less than 0.05 mass%, Mn: less than 0.15 mass%, P: less than 0.025 mass%, S: less than 0.025 mass%, Cr : It was less than 0.03 mass %.

The obtained alloy steel powder was hold|maintained at 920 degreeC for 30 minutes in hydrogen atmosphere, and finish reduction was performed. After the final reduction, the heat-treated body in which the particles were sintered to form a lump was pulverized using a hammer mill, classified through a sieve having a mesh of 180 μm, and the fraction passed through the sieve was collected to obtain alloy steel powder. The amounts of C, O and N contained as unavoidable impurities in the alloy steel powder were C: less than 0.01 mass%, O: less than 0.20 mass%, and N: less than 0.05 mass%. The component composition of the alloy steel powder was equivalent to the component composition of the molten steel.

· Production of diffusion-attached alloy steel powder

The content of Cu or Mo in the alloy steel powder with diffusion is the amount shown in Tables 1 to 3, and the Cu content (D50 is about 30 µm) or Mo oxide content (D50 is about 3 µm) relative to the alloy steel powder. ) was added, mixed with a V-type mixer for 15 minutes, and then, in a hydrogen atmosphere, at 920°C for 30 minutes, final reduction was performed. After the final reduction, the reduced treated body in which the particles are sintered to form a lump is pulverized using a hammer mill, classified through a sieve having a mesh of 180 μm, and the fraction passing through the sieve is collected, and Cu or Mo is diffused and adhered It was set as the alloy steel powder with diffusion adhesion. The amounts of C, O and N contained as unavoidable impurities in the diffusion-attached alloy steel powder were C: less than 0.01 mass%, O: less than 0.20 mass%, and N: less than 0.05 mass%.

· Manufacturing of sintered body

With respect to 100 parts by mass of alloy steel powder or alloy steel powder with diffusion, 0.8 parts by mass of graphite powder, 0.6 parts by mass of lubricant (zinc stearate), Cu powder (D50 of about 45 µm) or Mo in the amount shown in Tables 1 to 3 or 5 Flour (D50 of about 25 µm) was added and mixed using a double cone mixer to obtain an iron-based mixture. The iron-based powder was molded into a rectangular parallelepiped shape of 10 mm × 10 mm × 55 mm at a molding pressure of 588 MPa to obtain a molded body. The density of the compact was calculated by dividing the volume of the rectangular parallelepiped with respect to the weight of the compact.

The compact was hold|maintained for 20 minutes at 1130 degreeC in ₁₀ % _H2-90 %N2 atmosphere, and it was set as the sintered compact. A test piece of length: 50 mm × diameter: 3 mm was cut out from the sintered compact, and the maximum stress (tensile strength) before fracture was measured.

(Example 1)

This is an example regarding the alloy steel powder to which Cu, Mo and V are added. Table 1 shows the component composition and evaluation results. "-" in the component composition is a component that is not added, and the same applies to the following.

As a comparative example, iron-based powder prepared under the following 4 conditions was also evaluated. In No. 1-10, Cu was diffused and adhered to the surface of the alloy steel powder containing Mo and V as alloying elements, and graphite powder and a lubricant were mixed. In No. 1-11, Cu powder, graphite powder and a lubricant were mixed with alloy steel powder containing Mo and V as alloying elements. In No. 1-12, Mo was diffused and adhered to the surface of the alloy steel powder containing Cu and V as alloying elements, and graphite powder and a lubricant were mixed. In No. 1-13, Mo powder, graphite powder and a lubricant were mixed with alloy steel powder containing Cu and V as alloying elements. Table 1 shows the adhesion amount, the addition amount, and the evaluation result.

As shown in Table 1, in No.1-2 containing Cu, Mo, and V, the tensile strength was remarkably improved compared with No.1-1 containing Cu and V only. With respect to No.1-2, the tensile strength of No.1-3 in which V was made no addition and Cu was increased did not reach No.1-2. With respect to No. 1-4 containing Cu and V only, and No. 1-5 containing only Mo and V, No. 1-6 containing Cu, Mo and V had remarkably improved tensile strength. With respect to No. 1-6, also in No. 1-7 in which Cu was increased, No. 1-8 in which Mo was increased, and No. 1-9 in which V was increased, high tensile strength was maintained.

With respect to compressibility, it turns out that all of No. 1-2 and 1-6 - 1-9 which are invention examples have a sufficiently high density and are excellent in compressibility. From the results of Nos. 1-5 to 1-7, it is understood that Cu can improve the tensile strength by increasing the addition amount while maintaining the high density.

No. 1-10 using diffusion-attached alloy steel powder in which Cu is diffused and deposited on the surface of alloy steel powder containing Mo and V as alloying elements and No. 1-11 using a mixture of Cu powder mixed with the same alloy steel powder The sintered compact was inferior in tensile strength with respect to the sintered compact of No. 1-6 in spite of the amount of Cu, Mo, and V being equal. No. 1-12 using diffusion-attached alloy steel powder in which Mo is diffusion-attached to the surface of alloy steel powder containing Cu and V as alloying elements and No. 1-13 using mixed powder mixed with Mo powder in the same alloy steel powder The sintered compact was inferior in tensile strength with respect to the sintered compact of No. 1-6 in spite of the content of Cu, Mo, and V being equal.

(Example 2)

This is an example regarding the alloy steel powder to which Cu, Mo and Nb are added. Table 2 shows the component composition and evaluation results.

As a comparative example, iron-based powder prepared under the following 4 conditions was also evaluated. In No. 2-11, Cu was diffused and adhered to the surface of the alloy steel powder containing Mo and Nb as alloying elements, and graphite powder and a lubricant were mixed. In No. 2-12, Cu powder, graphite powder and a lubricant were mixed with alloy steel powder containing Mo and Nb as alloying elements. In No. 2-13, Mo was diffused and adhered to the surface of the alloy steel powder containing Cu and Nb as alloying elements, and graphite powder and a lubricant were mixed. In No. 2-14, Mo powder, graphite powder and a lubricant were mixed with alloy steel powder containing Cu and Nb as alloying elements. Table 2 shows the adhesion amount, the addition amount, and the evaluation result.

As shown in Table 2, in No. 2-2 containing Cu, Mo, and Nb, the tensile strength was remarkably improved compared with No. 2-1 containing only Cu and Nb. With respect to No.2-2, the tensile strength of No.2-3 in which Nb was not added and Cu was increased did not reach No.2-2. With respect to No.2-4 containing only Cu and Nb and No.2-5 containing only Mo and Nb, the tensile strength of No.2-6 containing Cu, Mo and Nb was remarkably improved. With respect to No.2-6, high tensile strength was maintained also in No.2-7 which increased Cu, No.2-8 which increased Mo, and No.2-9 which increased Nb. On the other hand, in No. 2-10 in which each quantity of Cu, Mo, and Nb was outside the range of this invention, the density was falling and the tensile strength was also inferior.

With respect to compressibility, it turns out that all of No. 2-2 and 2-6 - 2-9 which are invention examples have a sufficiently high density and are excellent in compressibility. From the results of Nos. 2-5 to 2-7, it is understood that Cu can improve the tensile strength by increasing the addition amount while maintaining high density.

No. 2-11 using diffusion-attached alloy steel powder in which Cu is diffused and deposited on the surface of alloy steel powder containing Mo and Nb as alloying elements, and No. 2-12 using a mixture of Cu powder mixed with the same alloy steel powder The sintered compact was inferior in tensile strength with respect to the sintered compact of No. 2-6 in spite of the amount of Cu, Mo, and Nb being equal. No. 2-13 using diffusion-attached alloy steel powder in which Mo is diffusion-attached to the surface of alloy steel powder containing Cu and Nb as alloying elements and No. 2-14 using a mixture of Mo powder mixed with the same alloy steel powder The sintered compact was inferior in tensile strength with respect to the sintered compact of No. 2-6 in spite of the content of Cu, Mo, and Nb being equal.

(Example 3)

This is an example regarding the alloy steel powder to which Cu, Mo and Ti are added. Table 3 shows the component composition and evaluation results.

As a comparative example, iron-based powder prepared under the following 4 conditions was also evaluated. In No. 3-11, Cu was diffused and adhered to the surface of the alloy steel powder containing Mo and Ti as alloying elements, and graphite powder and a lubricant were mixed. In No. 3-12, Cu powder, graphite powder and a lubricant were mixed with alloy steel powder containing Mo and Ti as alloying elements. In No. 3-13, Mo was diffused and adhered to the surface of the alloy steel powder containing Cu and Ti as alloying elements, and graphite powder and a lubricant were mixed. In No. 3-14, Mo powder, graphite powder and a lubricant were mixed with alloy steel powder containing Cu and Ti as alloying elements. Table 1 shows the adhesion amount, the addition amount, and the evaluation result.

As shown in Table 3, the tensile strength of No. 3-2 containing Cu, Mo, and Ti was remarkably improved compared with No. 3-1 containing only Cu and Ti. With respect to No.3-2, the tensile strength of No.3-3 in which Ti was not added and Cu was increased did not reach No.3-2. With respect to No.3-4 containing Cu and Ti only and No.3-5 containing only Mo and Ti, No.3-6 containing Cu, Mo and Ti had remarkably improved tensile strength. With respect to No.3-6, the high tensile strength was maintained also in No.3-7 which increased Cu, No.3-8 which increased Mo, and No.3-9 which increased Ti. On the other hand, in No. 3-10 in which each quantity of Cu, Mo, and Ti was outside the range of this invention, the density was falling and the tensile strength was also inferior.

With respect to compressibility, it turns out that all of No. 3-2 and 3-6 - 3-9 which are invention examples have a sufficiently high density and are excellent in compressibility. From the results of Nos. 3-5 to 3-7, it turns out that the tensile strength can be improved by increasing the addition amount of Cu, maintaining high density.

No.3-11 using diffusion-attached alloy steel powder in which Cu is diffused and deposited on the surface of alloy steel powder containing Mo and Ti as alloying elements and No.3-12 using a mixture of Cu powder mixed with the same alloy steel powder The sintered compact was inferior in tensile strength with respect to the sintered compact of No. 3-6 in spite of the amount of Cu, Mo, and Ti being equal. No. 3-13 using diffusion-attached alloy steel powder in which Mo is diffusion-attached to the surface of alloy steel powder containing Cu and Ti as alloying elements and No. 3-14 using a mixture of Mo powder mixed with the same alloy steel powder The sintered compact was inferior in tensile strength with respect to the sintered compact of No. 3-6 in spite of the content of Cu, Mo, and Ti being equal.

(Example 4)

This is an example regarding an alloy steel powder in which Cu, Mo, and 2 or 3 types selected from V, Nb and Ti are added as alloy components. Table 4 shows the component composition and evaluation results.

As shown in No. 4-1 to 4-3, 4-5 to 4-7, 4-9 to 4-11, 4-13 to 4-15, 2 or 3 selected from V, Ni and Ti It can be seen that the tensile strength is further improved by using the alloy steel powder to which the species is added in a specific amount. Moreover, it turns out that all of these examples have a sufficiently high density and are excellent in compressibility. On the other hand, for Nos. 4-4, 4-8, 4-12, and 4-16 in which the addition amount did not satisfy the predetermined condition, the tensile strength was rather decreased.

(Example 5)

This is an example regarding a mixed powder in which Cu powder and/or Mo powder are added to alloy steel powder. Table 5 shows the addition amounts of alloy steel powder, Cu powder and Mo powder used, and evaluation results.

Contrast No.1-6 and No.5-1, 5-3 to 5-4, 5-6, and No.2-6 and No.5-8, 5-10 to 5-11, 5- Contrast of 13, No.3-6 and No.5-15, 5-17 to 5-18, 5-20 contrast, No.4-10 and No.5-22, 5-24 to 5-25, From the contrast of 5-27, No.4-14 and No.5-29, 5-31 to 5-32, and 5-34, by mixing Cu powder and/or Mo powder in specific amounts, tensile strength is increased It can be seen that the improvement is further improved. Moreover, it turns out that all of these examples have a sufficiently high density and are excellent in compressibility. On the other hand, No. 5-2, 5-5, 5-7, 5-9, 5-12, 5-14, 5-16, 5 in which the mixing amount of Cu powder and/or Mo powder does not satisfy predetermined conditions -19, 5-21, 5-23, 5-26, 5-28, 5-30, 5-33, and 5-35 resulted in a decrease in tensile strength on the contrary.

Claims (6)

Cu: 1.0 mass% or more and 8.0 mass% or less;
Mo: more than 0.50 mass % and 2.00 mass % or less, and
V: 0.05 mass% or more and 0.50 mass% or less, Nb: 0.02 mass% or more and 0.40 mass% or less, and Ti: at least one selected from the group consisting of 0.02 mass% or more and 0.40 mass% or less,
Alloy steel powder for powder metallurgy, with the balance consisting of Fe and unavoidable impurities. The method of claim 1,
V: The alloy steel powder for powder metallurgy containing 0.05 mass % or more and 0.50 mass % or less. 3. The method of claim 1 or 2,
Nb: The alloy steel powder for powder metallurgy containing 0.02 mass % or more and 0.40 mass % or less. 4. The method according to any one of claims 1 to 3,
Ti: The alloy steel powder for powder metallurgy containing 0.02 mass % or more and 0.40 mass % or less. An iron-based mixed powder for powder metallurgy comprising the alloy steel powder for powder metallurgy according to any one of claims 1 to 4 and metal powder,
For powder metallurgy, the metal powder is any one or both of Cu powder of more than 0 mass% and 4 mass% or less and Mo powder of more than 0 mass% and 4 mass% or less with respect to 100 mass% of the iron-based mixed powder for powder metallurgy iron mixture. A sintered body using the alloy steel powder for powder metallurgy according to any one of claims 1 to 4 or the iron-based mixed powder for powder metallurgy according to claim 5.