WO2025224841A1 - Method for producing iron-based sintered sliding member, iron-based sintered sliding member, and sliding component - Google Patents

Abstract

This method for producing an iron-based sintered sliding member comprises: adding a sulfur alloy powder B having an oxygen content of 5 mass% or less to an iron alloy powder A that contains a total of 1 mass% or more of at least one element selected from the group consisting of Cr, Ca, V, Ti and Mg, so that the sulfur content in a sintered body will be 1 mass% to 10 mass%; compression molding the obtained mixed powder; and sintering the obtained molded body at a temperature within the range of 900ºC to 1200ºC.

Description

Manufacturing method of iron-based sintered sliding member, iron-based sintered sliding member and sliding part

This disclosure relates to a method for manufacturing an iron-based sintered sliding member, an iron-based sintered sliding member, and a sliding component.

The so-called powder metallurgy method, in which raw material powder is compressed and molded in a mold and the resulting green compact is sintered, allows for near-net shapes to be created, resulting in minimal material loss due to subsequent machining, and is highly economical for reasons such as the ability to mass-produce products of the same shape once the mold is made. Powder metallurgy also allows for a wide range of alloy design possibilities, as it can produce special alloys that cannot be obtained using alloys produced by conventional melting. For this reason, it is widely used in automotive and other mechanical parts.

Among mechanical parts, it is important for sliding members to have a low coefficient of friction and wear resistance. In particular, for applications where high surface pressure is applied, sliding members formed from copper-based sintered bodies such as bronze-based and lead bronze-based materials are preferably used.
Conventional copper-based sintered bodies can improve their wear resistance by retaining lubricating oil in the pores contained in the sintered body, while lead bronze-based sintered bodies can improve their wear resistance by having the lead phase contained in the matrix exert a solid lubricating effect.

Patent Document 1 proposes an iron-based sintered sliding member that has excellent sliding properties and mechanical strength, and has a metal structure consisting of a ferrite matrix in which sulfide particles are dispersed and pores, and in which the sulfide particles are dispersed in an amount of 15 to 30% by volume relative to the matrix.
Patent Document 1 describes that sulfides precipitated in the matrix preferably have a predetermined size in order to exert a solid lubricating effect. Specifically, Patent Document 1 proposes that the area of sulfide particles having a maximum particle size of 10 μm or more preferably occupies 30% or more of the area of the entire sulfide particles.

JP 2014-181381 A

Because lead-bronze sintered bodies contain a large amount of lead, there is a need to reduce the amount of lead used and develop alternative materials to address environmental issues. Various materials are being considered as alternatives to lead-bronze sintered bodies, but further improvements in the friction coefficient and wear resistance of copper-based sintered bodies are desired. Furthermore, copper-based sintered bodies have the problem of high costs due to the large amount of copper used.

Iron-based sintered sliding components are also being considered as an alternative material to lead-bronze sintered bodies. Patent Document 1 states that in iron-based sintered sliding components, the particle size of the sulfide particles in the matrix is preferably large, at 10 μm or larger, from the perspective of sliding performance. In Patent Document 1, iron sulfide is added to iron powder containing 0.03 to 0.9 mass% Mn as an unavoidable impurity, thereby achieving a predetermined volume ratio of sulfide particles in the sintered body and coarsening the sulfide particles.

From the perspective of improving sliding performance, it is desirable for the matrix to contain many fine metal sulfide particles. However, if the matrix contains many fine metal sulfide particles, the strength of the sintered body may decrease during sintering.

The present disclosure has been made in light of the above, and aims to provide a method for manufacturing an iron-based sintered sliding member that can suppress a decrease in strength of the sintered body, an iron-based sintered sliding member in which a decrease in strength is suppressed, and a sliding part including the same.

Specific means for achieving the above object are as follows.
<1> A method for producing an iron-based sintered sliding member, comprising: adding a sulfur alloy powder B having an oxygen content of 5% by mass or less to an iron alloy powder A containing at least one kind selected from the group consisting of Cr, Ca, V, Ti, and Mg in a total amount of 1% by mass or more; adding the sulfur alloy powder B having an oxygen content of 5% by mass or less to an iron alloy powder A such that the sulfur content of a sintered body is 1% by mass to 10% by mass; compressing and molding the resulting mixed powder; and sintering the resulting molded body at a temperature in the range of 900°C to 1200°C.
<2> The method for producing an iron-based sintered sliding member according to <1>, wherein the mixed powder further contains at least one kind selected from the group consisting of nickel powder and nickel-iron alloy powder in an amount of at least 3 mass %.
<3> The method for producing an iron-based sintered sliding member according to <1> or <2>, wherein the mixed powder has a graphite content of 0% by mass to 1% by mass.
<4> The method for producing an iron-based sintered sliding member according to any one of <1> to <3>, wherein the number of particles in the sulfur alloy powder B having a particle diameter of 45 μm or less is 50% or more.
<5> An iron matrix containing 1 mass% to 10 mass% of S, 0.2 mass% to 6 mass% in total of one or more elements selected from the group consisting of Cr, Ca, V, Ti, and Mg, and the balance being Fe and unavoidable impurities, and containing dispersed sulfide particles having one or more elements selected from the group consisting of Cr, Ca, V, Ti, and Mg, and pores,
An iron-based sintered sliding member, wherein the average value of the maximum diameter of the pores measured at five locations is 70 μm or less.
<6> The iron-based sintered sliding member according to <5>, wherein the average number of pores measured at five locations is 1,200 or more.
<7> The iron-based sintered sliding member according to <5> or <6>, wherein the following calculated value calculated from the average value (Ave) of the proportions of pores when measurements are carried out at five locations and the density (d) of the iron-based sintered sliding member is 8.0 to 15.0:
Calculated value = Ave (%) - 10 x (7 - d (g/cm ³ ))
<8> The iron-based sintered sliding member according to any one of <5> to <7>, wherein the Ni content is 0% to 10%.
<9> The iron-based sintered sliding member according to any one of <5> to <8>, wherein the content of Mo is 0% to 10%.
<10> The iron-based sintered sliding member according to any one of <5> to <9>, wherein the content of graphite is 0% to 1%.
<11> A sliding part comprising the iron-based sintered sliding member according to any one of <5> to <10>.

The present disclosure provides a method for manufacturing an iron-based sintered sliding member that can suppress a decrease in strength of the sintered body, an iron-based sintered sliding member in which a decrease in strength is suppressed, and a sliding part including the same.

FIG. 1 shows a cross-sectional image of the sintered member of Example 1. FIG. 2 shows a cross-sectional image of the sintered part of Example 2. FIG. 3 shows a cross-sectional image of the sintered member of Comparative Example 1. FIG. 4 shows a cross-sectional image of the sintered member of Comparative Example 2.

Below, modes for implementing the present disclosure are described in detail. However, the present disclosure is not limited to the following embodiments. In the following embodiments, the components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values and their ranges, and do not limit the present disclosure.

In the present disclosure, numerical ranges indicated using "to" include the numerical values before and after "to" as the minimum and maximum values, respectively.
In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples.
In the present disclosure, each component may contain multiple substances corresponding to the component. When multiple substances corresponding to each component are present in the composition, the content or amount of each component means the total content or amount of the multiple substances present in the composition, unless otherwise specified.
In the present disclosure, the particles corresponding to each component may contain multiple types of particles. When multiple types of particles corresponding to each component are present in the composition, the particle size of each component means the value for a mixture of the multiple types of particles present in the composition, unless otherwise specified.

<Method for manufacturing iron-based sintered sliding member>
The method for producing an iron-based sintered sliding member of the present disclosure is a method in which sulfur alloy powder B, which has an oxygen content of 5 mass% or less, is added to iron alloy powder A, which contains at least one kind selected from the group consisting of Cr, Ca, V, Ti, and Mg in a total amount of 1 mass% or more, so that the sulfur content of a sintered body is 1 mass% to 10 mass%, the mixed powder obtained is compression-molded, and the resulting molded body is sintered at a temperature range of 900°C to 1200°C.

In the manufacturing method for an iron-based sintered sliding member disclosed herein, sulfur alloy powder B, which has a low oxygen content, is added to iron alloy powder A so that the sulfur content of the sintered body falls within a specific range. The resulting mixed powder is then compression-molded to produce a green body, which is sintered at a temperature range of 900°C to 1200°C. The low oxygen content of sulfur alloy powder B suppresses the effect of inhibiting sintering, which tends to suppress the maximum diameter of pores contained in the iron-based sintered sliding member, making it possible to suppress a decrease in the strength of the sintered body.

Iron alloy powder A contains one or more components selected from the group consisting of Cr, Ca, V, Ti, and Mg (hereinafter referred to as "specific components") in a total amount of 1 mass% or more. Iron alloy powder A is an alloy powder containing the specific components and whose main component is iron. Iron alloy powder A may be an alloy powder consisting of the specific components and iron, an alloy powder consisting of the specific components, iron, and unavoidable impurities, or an alloy powder containing the specific components and components other than iron.

When iron alloy powder A contains Cr, Ca, V, Ti, or Mg, the content of Cr, Ca, V, Ti, or Mg contained in iron alloy powder A is preferably 0.1% to 8% by mass, more preferably 0.5% to 6% by mass, and even more preferably 1% to 5% by mass, based on the total amount of iron alloy powder.

When iron alloy powder A contains specific components and components other than iron, such components include, for example, C, Ni, Cu, Mo, and combinations thereof. The total content of the specific components and components other than iron contained in iron alloy powder A may be 3% by mass or less, 2% by mass or less, or 1% by mass or less.

The sulfur alloy powder B is an alloy powder containing sulfur and having an oxygen content of 5% by mass or less. The oxygen content may be 3% by mass or less, or may be 2% by mass or less. Examples of the sulfur alloy powder B include iron sulfide powder and molybdenum disulfide powder.
The lower limit of the oxygen content is not particularly limited as long as it is 0% by mass or more, and may be, for example, 0.5% by mass or more, or 1% by mass or more.

When sulfur alloy powder B is iron sulfide powder, it preferably contains 30% by mass or more of S, and more preferably 35% by mass or more. The S content may also be 50% by mass or less.

Sulfur alloy powder B is added to iron alloy powder A so that the sulfur content of the sintered body is 1% to 10% by mass. The elemental component amounts of each material, such as the sulfur content of the sintered body, can be measured using, for example, scanning electron microscope energy dispersive X-ray spectroscopy (SEM-EDS).

In the sulfur alloy powder B, the number of particles having a particle size of 45 μm or less is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. In the sulfur alloy powder B, the number of particles having a particle size of 45 μm or less may be 100% or less, with no particular upper limit.
The number of particles having a particle diameter of 45 μm or less can be determined from the number-based particle size distribution measured by, for example, a laser diffraction scattering method.

In the manufacturing method disclosed herein, iron alloy powder A and sulfur alloy powder B, which serves as a source of S, are added separately as raw material powders. During sintering, sulfur alloy powder B decomposes and releases S, which combines with one or more elements selected from the group consisting of Cr, Ca, V, Ti, and Mg in the iron matrix, thereby precipitating MnS, CrS, VS, or a combination thereof. This manufacturing method allows MnS, CrS, VS, or a combination thereof to precipitate in the form of fine particles within the crystal grains.

A mixed powder of at least iron alloy powder A and sulfur alloy powder B is compression molded into a compact. The shape of the compacted product is not particularly limited, but it is preferably a shape corresponding to the iron-based sintered sliding component. Furthermore, the pressure applied during compaction is not particularly limited as long as it is capable of molding the mixed powder, and may be, for example, 300 MPa to 1000 MPa.

When mixing iron alloy powder A and sulfur alloy powder B, other raw material powders may also be mixed in. Examples of other raw material powders include raw material powders containing C, Ni, Mo, or combinations thereof. When other raw material powders are mixed in, the amount of the other raw material powders added may be 1 to 20 parts by mass, or 2 to 10 parts by mass, per 100 parts by mass of the total of iron alloy powder A and sulfur alloy powder B.

For example, other raw material powders may be nickel powder, nickel-iron alloy powder, or a combination thereof.
Nickel is preferably used because it dissolves as Ni in the iron matrix of the sintered body and acts to increase the strength of the iron matrix. Nickel may be added as a single element or as an alloy. Nickel may be added so that it is 3% by mass or more, or 5% by mass to 10% by mass, of the total amount of the mixed powder.

For example, the mixed powder may further contain at least 3% by mass, or 5% to 10% by mass, of one or more types selected from the group consisting of nickel powder and nickel-iron alloy powder.

The graphite content in the mixed powder may be between 0% and 1% by mass. In other words, the mixed powder may not contain graphite, or if it contains graphite, the graphite content may be greater than 0% by mass and less than or equal to 1% by mass.

When mixing iron alloy powder A and sulfur alloy powder B, optional components such as a die lubricant may be added to the mixed powder.

A compact made by compression molding a mixed powder of at least iron alloy powder A and sulfur alloy powder B is sintered at a maximum holding temperature of 900°C to 1200°C. This temperature range allows the sulfur alloy powder to decompose, bonding S with specific components in the iron matrix to form fine metal sulfides. It also promotes the diffusion of C, Ni, Mn, Cr, Cu, Mo, V, etc. into Fe, creating a metal structure with high matrix hardness and further increasing the tensile strength of the sintered body.

If the temperature exceeds 988°C during the heating process during sintering, a eutectic liquid phase of the sulfur alloy will be generated, and the expansion of the eutectic liquid phase will tend to result in the formation of large coarse pores. Therefore, from the perspective of suppressing an increase in the maximum pore size, it is preferable to use a temperature lower than 988°C, for example, 800°C to 900°C, so that the sulfur alloy fully decomposes when S diffuses, and then reduce the amount of sulfur alloy when the temperature exceeds 988°C. For example, it is preferable to hold the temperature at 800°C to 900°C for 30 to 100 minutes, and then sinter at a temperature higher than 900°C.

It is preferable that the molded body be held at the maximum holding temperature for 10 to 90 minutes.

The sintering atmosphere is preferably a vacuum atmosphere or a non-oxidizing atmosphere. This tends to prevent the metal sulfide from being decomposed by oxygen during sintering. Examples of non-oxidizing atmospheres include atmospheres with a dew point of -10°C or below, such as decomposed ammonia gas, nitrogen gas, hydrogen gas, and argon gas.

After sintering is complete, the sintered body is preferably cooled at a rate of 1°C/min to 150°C/min, and more preferably at a rate of 5°C/min to 150°C/min. It is preferable to cool the body at this cooling rate from the maximum holding temperature to a temperature range of 900 to 200°C.

<Iron-based sintered sliding member>
The iron-based sintered sliding member of the present disclosure comprises 1% by mass to 10% by mass of S, 0.2% by mass to 6% by mass in total of one or more elements selected from the group consisting of Cr, Ca, V, Ti, and Mg, and the balance being Fe and unavoidable impurities. The iron-based sintered sliding member comprises an iron matrix in which sulfide particles having one or more elements selected from the group consisting of Cr, Ca, V, Ti, and Mg are dispersed, and pores, and the average of the maximum diameters of the pores when measurements are made at five locations is 70 μm or less.

The iron-based sintered sliding member of the present disclosure includes the iron matrix and pores, and the average value of the maximum diameters of the pores (also referred to as the maximum pore diameter) measured at five locations is 70 μm or less. The reduction in the maximum pore diameter makes it possible to suppress a decrease in the strength of the sintered body.
The method for producing the iron-based sintered sliding member of the present disclosure is not particularly limited, and it can be produced by, for example, the above-mentioned production method.

In the iron-based sintered sliding member of the present disclosure, the maximum pore size is preferably 68 μm or less, more preferably 65 μm or less, and even more preferably 62 μm or less.
By making the maximum pore diameter 70 μm or less, it is possible to more suitably suppress a decrease in the strength of the sintered body.
The lower limit of the maximum pore diameter is not particularly limited, and may be, for example, 50 μm or more.

In the present disclosure, the maximum pore diameter can be measured as follows.
First, the iron-based sintered sliding member is cut, the cross section is mirror-polished, and a metallographic image of the polished surface is observed. The metallographic image (for example, an image of an area of 0.9 mm x 1.2 mm) is binarized using QuickGrain to identify the pore portion, and the maximum diameter of the multiple pores present is determined. This operation is performed at four other locations, and the average value of the maximum pore diameters when measurements are taken at a total of five locations is calculated.

In the iron-based sintered sliding member of the present disclosure, the average value of the proportion of pores when measurements are carried out at five locations may be 10% to 20%, or may be 12% to 18%.
The pore ratio means the area ratio (%) of pores to the measurement area.

In the present disclosure, the average porosity can be measured as follows.
First, the iron-based sintered sliding member is cut, the cross section is mirror-polished, and a metallographic image of the polished surface is observed. The metallographic image (for example, an image of an area of 0.9 mm x 1.2 mm) is binarized using QuickGrain to determine the pore portion, and the total area of the pores relative to the measurement area is calculated, and this value is the pore ratio (%). This operation is performed at four other locations, and the average value of the pore ratios when measurements are taken at a total of five locations is calculated.

In the iron-based sintered sliding member of the present disclosure, the average number of pores measured at five locations may be 1200 or more, 1250 or more, or 1300 or more. Moreover, the average number of pores may be 2000 or less, or 1500 or less.
Even if the average number of pores is 1200 or more, if the maximum pore diameter is small, it is possible to more suitably suppress a decrease in strength of the sintered body.

In the present disclosure, the average number of pores can be measured as follows.
First, the iron-based sintered sliding member is cut, the cross section is mirror-polished, and a metallographic image of the polished surface is observed. The metallographic image (for example, an image of an area of 0.9 mm x 1.2 mm) is binarized using QuickGrain to identify the pore areas and calculate the number of pores in the image. This operation is performed at four other locations, and the average number of pores measured at a total of five locations is calculated.

The density of the iron-based sintered sliding member of the present disclosure is not particularly limited, and may be 5.0 g/cm ³ to 8.0 g/cm ³ , or may be 6.0 g/cm ³ to 7.0 g/cm ³ .

In iron-based sintered sliding components, the proportion of the aforementioned pores tends to decrease as the density of the iron-based sintered sliding component increases, and the proportion of the aforementioned pores tends to increase as the density of the iron-based sintered sliding component decreases.

In the iron-based sintered sliding member of the present disclosure, the following calculated value calculated from the average value (Ave) of the proportions of pores when measurements are carried out at five locations and the density (d) of the iron-based sintered sliding member may be 8.0 to 15.0.
Calculated value = Ave (%) - 10 x (7 - d (g/cm ³ ))

The aforementioned calculated value for the iron-based sintered sliding component of the present disclosure may be 8.0 to 12.0, or 8.5 to 10.5.

The iron-based sintered sliding member contains S: 1% by mass to 10% by mass.
By including S in the iron-based sintered sliding member, it is possible to include metal sulfides in the matrix, which allows an appropriate amount of metal sulfides to be exposed on the sliding surface of the sliding member, thereby further improving the sliding performance.

The S content may be 1.5% by mass or more, or may be 2% by mass or more.
S may be 8% by mass or less, 6% by mass or less, 5% by mass or less, or 4% by mass or less.
The iron-based sintered sliding member contains a small amount of S, which suppresses the formation of coarse sulfides and improves the strength of the sintered body.

The sintered body preferably has 200 or more metal sulfide particles within an area of 84.4 μm×60.5 μm. The number of metal sulfide particles may be 1000 or less.
This allows the iron matrix of the sintered body to contain a larger number of fine metal sulfide particles, allowing a large number of fine particles to be exposed on the sliding surface of the sliding member, thereby further improving the sliding performance.

Here, the number of metal sulfide particles can be determined, for example, by cutting the sintered body, mirror-polishing the cross section, observing an image of the polished surface, and measuring the number of metal sulfide particles contained in an area of 84.4 μm × 60.5 μm on the polished surface. For image analysis, for example, general-purpose image processing software (QuickGrain manufactured by Innotec Co., Ltd.) can be used.
The number of metal sulfide particles within the 84.4 μm×60.5 μm region may be the average value of measurements taken at multiple locations (for example, 10 locations).

The metal sulfide is preferably finely dispersed. The number of metal sulfide particles per unit area of the sintered body is preferably 1.0 × 10 ¹⁰ particles/m ² or more, and more preferably 1.0 × 10 ¹¹ particles/m ² or more.
This allows the iron matrix of the sintered body to contain a larger number of fine metal sulfide particles, allowing a large number of fine particles to be exposed on the sliding surface of the sliding member, thereby further improving the sliding performance.

The sintered body preferably has a number of metal sulfide particles per unit area of 1.0 × 10 ¹² particles/m ² or less.
This reduces the possibility that multiple metal sulfides will combine to generate larger particles, and allows the mixture to contain a larger number of finer particles more appropriately.
The number of metal sulfide particles per unit area may be an average value of measurements taken at multiple locations (for example, 10 locations).

Here, the number of metal sulfide particles per unit area can be determined, for example, by cutting the sintered body, mirror-polishing the cross section, observing an image of the polished surface, and measuring the number of metal sulfide particles contained in a specified measurement area of the polished surface. For image analysis, for example, general-purpose image processing software (QuickGrain, manufactured by Innotec Co., Ltd.) can be used.

The iron-based sintered sliding component contains one or more elements selected from the group consisting of Cr, Ca, V, Ti, and Mg: a total amount of 0.2% to 6% by mass.

The content of Ni in the iron-based sintered sliding member may be 0% by mass to 10% by mass. Ni improves the hardenability of the sintered body, and after sintering and cooling, Ni has the effect of including a hardened structure in the sintered body and remaining as austenite. Furthermore, due to the relationship of electronegativity, Ni does not inhibit the formation of metal sulfides mainly composed of iron sulfide. When used in combination with C, Ni improves the hardenability of the iron matrix, refines pearlite to increase strength, and makes it easier to obtain high-strength bainite or martensite at a normal cooling rate during sintering. Furthermore, diffusing Ni into the iron matrix can bring about solid-solution strengthening.
Ni can be added as Ni powder, Ni alloy powder, or the like.

From the standpoint of material strength and sliding properties, the Ni content may be 0.1 mass% or more, 0.5 mass% or more, or 1 mass% or more. The Ni content may be 8 mass% or less.

The content of Mo in the iron-based sintered sliding member may be 0% by mass to 10% by mass. Mo has the effect of promoting sintering, stabilizing the metal structure, particularly the ferrite phase, and obtaining a sintered body with high strength. Furthermore, diffusing Mo into the iron matrix can bring about solid solution strengthening.
Mo can be added in the form of Mo powder, Mo alloy powder, or the like.

From the standpoint of material strength and sliding properties, the Mo content may be 0.1 mass% or more, 0.5 mass% or more, or 1 mass% or more. The Mo content may be 8 mass% or less.

The content of graphite in the iron-based sintered sliding member may be 0% by mass to 1% by mass. A part of C dissolves in Fe, and the strength of the sintered body can be improved.
The graphite content may be 0.001% by mass or more.

The iron matrix contains the above-mentioned components, with the balance being Fe and unavoidable impurities.
The iron matrix may further contain one or more additives selected from the group consisting of minerals, oxides, nitrides, and borides that do not diffuse into the matrix, such as MgO, _SiO2 , TiN, _CaAlSiO3 , _CrB2 , and the like, or combinations thereof.

The iron matrix preferably contains one or more metal structures selected from the group consisting of ferrite, pearlite, and martensite, and more preferably contains ferrite.

<Sliding parts>
The sliding component of the present disclosure includes the iron-based sintered sliding member of the present disclosure described above.
The sliding component may be integrally formed of a sintered body. When the sliding component is formed by combining a sintered body with other members, it is preferable that at least a portion including the sliding surface is formed of an iron-based sintered sliding component.

The present disclosure will be explained below based on examples, but the present disclosure is not limited to the following examples.

Example 1
Raw material powder A: Iron alloy powder containing 3 mass% Cr, 0.5 mass% Mo, 0.006 mass% C, and the balance being iron. Raw material powder B: Iron sulfide containing 35.5 mass% S (oxygen content: 1.6 mass%).
Raw material powder C: Ni powder Raw material powder D: 95.5% by mass C, 4.5% by mass others Lubricant E: Organic molding lubricant (component that decomposes during sintering)
95 parts by mass of raw material powder A, 5.7 parts by mass of raw material powder B, 6 parts by mass of raw material powder C, 0.3 parts by mass of raw material powder D, and 0.6 parts by mass of lubricant E were mixed to obtain a mixed powder.
The mixed powder was then compacted under a compacting pressure of 600 MPa to produce a ring-shaped compact, which was then sintered at 1130° C. in a non-oxidizing gas atmosphere to produce the sintered member of Example 1.
In Example 1, the component ratios of the elements in the mixed powder were as follows:
Fe: 89.0 mass%, C: 0.3 mass%, Cr: 2.7 mass%, Mo: 0.4 mass%, Ni: 5.6 mass%, S: 1.9 mass%, others: 0.1 mass%

Example 2
The sintered part of Example 2 was produced in the same manner as in Example 1, except that the mixed powder produced in Example 1 was used and the production conditions for the sintered part were changed to a lower pressure of 400 MPa to produce a low-density sintered part.

<Comparative Example 1>
Raw material powder F: iron alloy powder containing 3 mass% Cr, 0.3 mass% Mo, 0.3 mass% V, 0.006 mass% C, and the balance being iron. Raw material powder C: Ni powder. Raw material powder G: iron sulfide containing 50 mass% S (oxygen content: 7.0 mass%).
Lubricant H: Organic molding lubricant (component that decomposes during sintering)
95 parts by mass of raw material powder F, 5 parts by mass of raw material powder C, 10 parts by mass of raw material powder G, and 0.5 parts by mass of lubricant H were mixed together to obtain a mixed powder.
The sintered member of Comparative Example 1 was produced in the same manner as in Example 1, except that the mixed powder of Comparative Example 1 was used and the production conditions for the sintered member were changed to a higher pressure of 810 MPa.
In Comparative Example 1, the component ratios of the elements in the mixed powder were as follows:
Fe: 87.2 mass%, Cr: 2.6 mass%, Mo: 0.3 mass%, Ni: 4.5 mass%, S: 4.5 mass%, V: 0.3 mass%, others 0.6 mass%

<Comparative Example 2>
The sintered part of Comparative Example 2 was produced in the same manner as Comparative Example 1, except that the mixed powder produced in Comparative Example 1 was used and the production conditions for the sintered part were changed to a lower pressure of 500 MPa to produce a low-density sintered part.

The average number of pores, average pore area ratio, and maximum pore diameter of the sintered components were measured using the methods described above. The results are shown in Table 1.

<Ring crushing strength>
The radial crushing strength of the ring-shaped sintered member was measured in accordance with JIS Z 2507: 2000. The results are shown in Table 1.

<Hardness>
The Rockwell hardness (HRB) of the sintered parts was measured in accordance with JIS Z2245: 2016. The results are shown in Table 1.

<Impact Value>
The sintered parts were subjected to a Charpy impact test in accordance with JIS Z2242:2018 to determine the impact value (J/cm ² ). The results are shown in Table 1.

Figures 1 to 4 show a comparison of the metal structures (mirror polished) of the sintered parts of Examples 1 and 2 and Comparative Examples 1 and 2. The iron matrix is the white part, the metal sulfide particles are the gray part, and the pores are the black part.

<Coefficient of friction>
In each of the examples and comparative examples, a ring-shaped sintered member having an outer diameter of 16 mm, an inner diameter of 10 mm, and a thickness of 10 mm was prepared.
Furthermore, a shaft made of S45C having a diameter of 9.980 mm and a length of 184 mm was prepared.
A radial compression test was carried out under the following conditions to measure the coefficient of friction.
Circumferential speed: 1.57m/min
Surface pressure: 40 MPa
Time: 5 min
Oil type: Oil VG460 (impregnation)

<Number of metal sulfide particles>
The number of metal sulfide particles contained within an area of 84.4 μm × 60.5 μm and the number of metal sulfide particles per unit area (1 m × 1 m) were measured by the above-described method for Example 1. General-purpose image processing software (QuickGrain manufactured by Innotec Corporation) was used for image analysis.
The number of metal sulfide particles contained within an area of 84.4 μm × 60.5 μm (number of particles (1) in Table 2) and the number of metal sulfide particles per unit area (1 m × 1 m) (number of particles (2) in Table 2) were measured at 10 locations, and the average values were calculated.
The results are shown in Table 2. In Table 2, AE+B (A and B are positive numbers) means A×10 8 ^B.

As shown in Table 1, the sintered member of Example 1 was superior in strength to the sintered member of Comparative Example 1.
When comparing Example 2 and Comparative Example 2, which are low-density sintered parts in which the manufacturing conditions for the sintered parts were changed to lower pressure, the sintered part of Example 2 was found to have superior strength to the sintered part of Comparative Example 2.
As shown in Table 2, the average number of metal sulfide particles contained within an area of 84.4 μm × 60.5 μm (number of particles (1) in Table 2) was 200 or more, and the average number of metal sulfide particles per unit area (1 m × 1 m) (number of particles (2) in Table 2) was 1.0 × 10 ¹⁰ particles/m ² or more. This is thought to enable a large number of fine particles to be exposed on the sliding surface of the sliding member, thereby further improving sliding performance.

All publications, patent applications, and technical standards mentioned in this specification are incorporated by reference into this specification to the same extent as if each individual publication, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims (11)

A method for manufacturing an iron-based sintered sliding component, comprising: adding sulfur alloy powder B, which has an oxygen content of 5% or less by mass, to iron alloy powder A, which contains at least 1% by mass of one or more elements selected from the group consisting of Cr, Ca, V, Ti, and Mg, so that the sulfur content of the sintered body is 1% to 10% by mass; compressing and molding the resulting mixed powder; and sintering the resulting compact at a temperature ranging from 900°C to 1200°C. The method for producing an iron-based sintered sliding member according to claim 1, wherein the mixed powder further contains at least 3 mass% of one or more selected from the group consisting of nickel powder and nickel-iron alloy powder. The method for producing an iron-based sintered sliding member according to claim 1 or 2, wherein the graphite content in the mixed powder is 0% by mass to 1% by mass. The method for manufacturing an iron-based sintered sliding member according to any one of claims 1 to 3, wherein the number of particles in the sulfur alloy powder B having a particle diameter of 45 μm or less is 50% or more. the iron matrix is composed of 1 mass% to 10 mass% of S, 0.2 mass% to 6 mass% in total of one or more elements selected from the group consisting of Cr, Ca, V, Ti, and Mg, and the balance is composed of Fe and inevitable impurities, and the iron matrix has dispersed therein sulfide particles having one or more elements selected from the group consisting of Cr, Ca, V, Ti, and Mg, and the iron matrix has pores;
An iron-based sintered sliding member, wherein the average value of the maximum diameter of the pores measured at five locations is 70 μm or less. The iron-based sintered sliding component according to claim 5, wherein the average number of pores measured at five locations is 1,200 or more. The iron-based sintered sliding member according to claim 5 or 6, wherein the following calculated value calculated from the average value (Ave) of the proportions of pores when measurements are carried out at five locations and the density (d) of the iron-based sintered sliding member is 8.0 to 15.0:
Calculated value = Ave (%) - 10 x (7 - d (g/cm ³ )) The iron-based sintered sliding component according to any one of claims 5 to 7, wherein the Ni content is 0% to 10%. The iron-based sintered sliding component according to any one of claims 5 to 8, wherein the Mo content is 0% to 10%. The iron-based sintered sliding component according to any one of claims 5 to 9, wherein the graphite content is 0% to 1%. A sliding part comprising the iron-based sintered sliding member according to any one of claims 5 to 10.