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

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

[0001] The present disclosure relates to a method for producing an iron-based sintered sliding member, an iron-based sintered sliding member, and a sliding part.

[0002] Powder metallurgy, which involves compressing raw material powders in a mold and sintering the resulting green compact, is an economical method that can produce near-net shapes. This minimizes material loss due to subsequent machining and allows for mass production of identically shaped products once the mold is made. Powder metallurgy also offers a wide range of alloy design possibilities, as it can produce special alloys that cannot be obtained using alloys produced by conventional melting. For these reasons, powder metallurgy is widely used in the production of automotive and other mechanical parts.

[0003] Among mechanical components, it is important for sliding members to have both 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 bodies 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. Furthermore, lead bronze-based sintered bodies can improve their wear resistance by having the lead phase contained in the matrix exert a solid lubricating effect.

[0004] Patent Document 1 proposes an iron-based sintered sliding member having excellent sliding properties and mechanical strength, which 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 at 15 to 30 volume % relative to the matrix. Patent Document 1 describes that the 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 with a maximum particle size of 10 μm or more preferably occupies 30% or more of the area of ​​the entire sulfide particles.

[0005] JP 2014-181381 A

[0006] Because lead-bronze sintered bodies contain a large amount of lead, there is a need to reduce the amount of lead and develop alternative materials to address environmental issues. Various materials have been 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. In addition, copper-based sintered bodies have the problem of high costs due to the large amount of copper used.

[0007] Iron-based sintered sliding members are also being considered as an alternative material to lead-bronze sintered bodies. Patent Document 1 describes that in an iron-based sintered sliding member, the particle size of sulfide particles in the matrix is ​​preferably as large as 10 μm or more from the viewpoint 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 also coarsening the sulfide particles.

[0008] From the viewpoint of improving sliding performance, it is desirable to have the matrix contain many fine metal sulfide particles, but if the matrix contains many fine metal sulfide particles, the strength of the sintered body may decrease during sintering.

[0009] The present disclosure has been made in view 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 a sintered body, an iron-based sintered sliding member in which a decrease in strength is suppressed, and a sliding part including the same.

[0010] 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, so that the sulfur content of a sintered body is 1% by mass to 10% by mass, compressing the obtained mixed powder, and sintering the obtained compact in a temperature range of 900°C to 1200°C. <2> A 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 3% by mass or more. <3> A 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> A 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 size of 45 μm or less accounts for 50% or more. <5> An iron-based sintered sliding member comprising: 1 mass % to 10 mass % S; one or more elements selected from the group consisting of Cr, Ca, V, Ti, and Mg: a total amount of 0.2 mass % to 6 mass %; and the balance: Fe and inevitable impurities, 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, wherein the average value of the maximum diameter of the pores when measurements are made at five locations is 70 μm or less. <6> An iron-based sintered sliding member according to <5>, wherein the average value of the number of pores when measurements are made at five locations is 1,200 or more. <7> An iron-based sintered sliding member according to <5> or <6>, wherein the following calculated value, calculated from the average value (Ave) of the proportion of the pores when measurements are made 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> An iron-based sintered sliding member according to any one of <5> to <7>, wherein the content of Ni is 0% to 10%. <9> An iron-based sintered sliding member according to any one of <5> to <8>, wherein the content of Mo is 0% to 10%. <10> An 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>.

[0011] According to the present disclosure, there are provided a method for producing an iron-based sintered sliding member capable of suppressing a decrease in strength of a sintered body, an iron-based sintered sliding member in which a decrease in strength is suppressed, and a sliding part including the same.

[0012] Fig. 1 shows a cross-sectional image of the sintered member of Example 1. Fig. 2 shows a cross-sectional image of the sintered member 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.

[0013] Hereinafter, embodiments for carrying out the present disclosure will be described in detail. However, the present disclosure is not limited to the following embodiments. In the following embodiments, 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.

[0014] 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 numerical ranges described in stages in the present disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another staged numerical range. Furthermore, in numerical ranges described in the present 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 corresponding substances. 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, particles corresponding to each component may include 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.

[0015] <Method for Manufacturing Iron-Based Sintered Sliding Member> The method for manufacturing 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.

[0016] In the method for producing an iron-based sintered sliding member of the present disclosure, sulfur alloy powder B having 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 obtain a green body, which is then 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, and as a result, it is possible to suppress a decrease in the strength of the sintered body.

[0017] Iron alloy powder A contains one or more components selected from the group consisting of Cr, Ca, V, Ti, and Mg (hereinafter, "specific components") in a total amount of 1 mass% or more. Iron alloy powder A is an alloy powder containing the specific components and having iron as the main component. 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.

[0018] 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 mass % to 8 mass %, more preferably 0.5 mass % to 6 mass %, and even more preferably 1 mass % to 5 mass %, based on the total amount of the iron alloy powder.

[0019] When the iron alloy powder A contains the specific component and a component other than iron, the components include, for example, C, Ni, Cu, Mo, and combinations thereof. The total content of the specific component and the components other than iron contained in the iron alloy powder A may be 3% by mass or less, 2% by mass or less, or 1% by mass or less.

[0020] 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.

[0021] When the sulfur alloy powder B is an iron sulfide powder, it preferably contains 30% by mass or more of S, more preferably 35% by mass or more, and may contain 50% by mass or less of S.

[0022] The sulfur alloy powder B is added to the iron alloy powder A so that the sulfur content of the sintered body is 1 mass % to 10 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).

[0023] In sulfur alloy powder B, the number of particles having a particle diameter of 45 μm or less is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. In sulfur alloy powder B, the number of particles having a particle diameter of 45 μm or less may be 100% or less, and there is no particular upper limit. The number of particles having a particle diameter of 45 μm or less can be determined, for example, from a number-based particle size distribution measured by a laser diffraction scattering method.

[0024] In the manufacturing method of the present disclosure, iron alloy powder A and sulfur alloy powder B, which serves as a source of S, are added separately as raw material powders, and S released upon decomposition of sulfur alloy powder B during sintering 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. According to this manufacturing method, MnS, CrS, VS, or a combination thereof can be precipitated in the form of fine particles within crystal grains.

[0025] 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 member. The pressure during compaction is not particularly limited as long as it is possible to mold the mixed powder, and may be, for example, 300 MPa to 1000 MPa.

[0026] When mixing the iron alloy powder A and the sulfur alloy powder B, other raw material powders may be further mixed. Examples of the other raw material powders include raw material powders containing C, Ni, Mo, or a combination thereof. When the other raw material powders are further mixed, the amount of the other raw material powders added may be 1 to 20 parts by mass, or 2 to 10 parts by mass, relative to 100 parts by mass of the total of the iron alloy powder A and the sulfur alloy powder B.

[0027] For example, nickel powder, nickel-iron alloy powder, or a combination thereof may be used as the other raw material powder. 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 alone 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, based on the total amount of the mixed powder.

[0028] For example, the mixed powder may further contain at least one selected from the group consisting of nickel powder and nickel-iron alloy powder in an amount of at least 3 mass%, or may further contain at least 5 mass% to 10 mass%.

[0029] The mixed powder may have a graphite content of 0% to 1% by mass. That is, the mixed powder may not contain graphite, or if it contains graphite, the graphite content may be more than 0% by mass and 1% by mass or less.

[0030] When the iron alloy powder A and the sulfur alloy powder B are mixed, an optional component such as a die lubricant may be further added to the mixed powder.

[0031] A compact obtained by compression molding a mixed powder comprising 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, and the like into Fe, producing a metal structure with high matrix hardness and further increasing the tensile strength of the sintered body.

[0032] If the temperature exceeds 988°C during the temperature rise 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 form coarse pores. Therefore, from the viewpoint of suppressing an increase in the maximum pore size, it is preferable to sufficiently decompose the sulfur alloy when S diffuses at a temperature lower than 988°C, for example, 800°C to 900°C, and then reduce the amount of sulfur alloy when the temperature exceeds 988°C. For example, it is preferable to hold the material at 800°C to 900°C for 30 to 100 minutes, and then sinter at a temperature higher than 900°C.

[0033] The molded body is preferably held at the maximum holding temperature for 10 to 90 minutes.

[0034] The sintering atmosphere is preferably a vacuum atmosphere or a non-oxidizing atmosphere, which tends to suppress decomposition of the metal sulfide by oxygen during sintering. Examples of non-oxidizing atmospheres include atmospheres of decomposed ammonia gas, nitrogen gas, hydrogen gas, argon gas, etc., with a dew point of −10° C. or less.

[0035] After sintering is completed, the sintered body is cooled at a rate of preferably 1°C / min to 150°C / min, more preferably 5°C / min to 150°C / min. At this cooling rate, it is preferable to cool the sintered body from the maximum holding temperature to a temperature range of 900 to 200°C.

[0036] <Iron-based sintered sliding member> The iron-based sintered sliding member of the present disclosure comprises S: 1% by mass to 10% by mass, one or more elements selected from the group consisting of Cr, Ca, V, Ti, and Mg: a total amount of 0.2% by mass to 6% by mass, and the balance: Fe and inevitable impurities, and 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 value of the maximum diameter of the pores when measurements are made at five locations is 70 μm or less.

[0037] 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 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, for example, by the production method described above.

[0038] In the iron-based sintered sliding member of the present disclosure, the maximum pore diameter 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 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.

[0039] In the present disclosure, the maximum pore diameter can be measured as follows. First, an 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.

[0040] In the iron-based sintered sliding member of the present disclosure, the average value of the pore ratio 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 the pores to the measurement area.

[0041] In the present disclosure, the average value of the porosity can be measured as follows. First, an 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 × 1.2 mm) is binarized using QuickGrain to identify the pore portion, and the total area of ​​the pores relative to the measurement area is calculated, and this value is taken as the porosity (%). This operation is performed at four other locations, and the average value of the porosity when measurements are taken at a total of five locations is calculated.

[0042] 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.

[0043] 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 portion and determine the number of pores in the image. This operation is performed at four other locations, and the average number of pores is determined when measurements are taken at a total of five locations.

[0044] The density of the iron-based sintered sliding member of the present disclosure is not particularly limited, and is 5.0 g / cm ３ ~8.0 g / cm ３ 6.0 g / cm ３ ~7.0 g / cm ３ may be.

[0045] In the iron-based sintered sliding member, the proportion of the pores described above tends to decrease as the density of the iron-based sintered sliding member increases, and the proportion of the pores described above tends to increase as the density of the iron-based sintered sliding member decreases.

[0046] In the iron-based sintered sliding member of the present disclosure, the following calculated value calculated from the average value (Ave) of the pore ratios when measurements are made 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 ))

[0047] The aforementioned calculated value of the iron-based sintered sliding member of the present disclosure may be 8.0 to 12.0, or may be 8.5 to 10.5.

[0048] The iron-based sintered sliding member contains 1 mass % to 10 mass % of S. By including S in the iron-based sintered sliding member, it is possible to include metal sulfides in the matrix. This allows an appropriate amount of metal sulfides to be exposed on the sliding surface of the sliding member, thereby further improving the sliding performance.

[0049] The amount of S may be 1.5% by mass or more, or 2% by mass or more. The amount of S may be 8% by mass or less, 6% by mass or less, 5% by mass or less, or 4% by mass or less. When the amount of S contained in the iron-based sintered sliding member is small, coarse sulfides are suppressed, and the strength of the sintered body can also be improved.

[0050] 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 1,000 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 sliding performance.

[0051] 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 84.4 μm × 60.5 μm area of ​​the polished surface. For image analysis, for example, general-purpose image processing software (QuickGrain manufactured by Innotek Co., Ltd.) can be used. The number of metal sulfide particles within the 84.4 μm × 60.5 μm area may be the average value of measurements taken at multiple locations (e.g., 10 locations).

[0052] The metal sulfide is preferably finely dispersed. In the sintered body, the number of metal sulfide particles per unit area is preferably 1.0×10 １０ pieces / m ２ More than 1.0 x 0 is preferable. １１ pieces / m ２ This is more preferable. As a result, a larger number of fine metal sulfide particles are contained in the iron matrix of the sintered body, and a large number of fine particles can be exposed on the sliding surface of the sliding member, thereby further improving the sliding performance.

[0053] The sintered body has a metal sulfide particle count of 1.0 × 10 per unit area. １２ pieces / m ２ The following is preferable. This reduces the possibility that multiple metal sulfides will combine to generate larger particles, allowing for a more appropriate inclusion of many fine particles. The number of metal sulfide particles per unit area may be an average value of measurements taken at multiple locations (e.g., 10 locations).

[0054] 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 predetermined 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.

[0055] The iron-based sintered sliding member 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 mass %.

[0056] 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 imparting a hardened structure to 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 can facilitate the formation of high-strength bainite or martensite at a normal cooling rate during sintering. Furthermore, Ni can bring about solid-solution strengthening by diffusing into the iron matrix. Ni can be added as Ni powder, Ni alloy powder, etc.

[0057] From the viewpoint 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, and may be 8 mass % or less.

[0058] 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 as Mo powder, Mo alloy powder, etc.

[0059] From the viewpoint 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, and may be 8 mass % or less.

[0060] The graphite content in the iron-based sintered sliding member may be 0% by mass to 1% by mass. A part of C dissolves in Fe to improve the strength of the sintered body. The graphite content may be 0.001% by mass or more.

[0061] The iron matrix is ​​composed of the balance of the above-mentioned components, 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. Examples of these additives include MgO, SiO２ , TiN, CaAlSiO ３ , CrB ２ etc., or a combination thereof.

[0062] The iron matrix preferably contains, as a metal structure, one or more types selected from the group consisting of ferrite, pearlite, and martensite, and more preferably contains ferrite.

[0063] <Sliding component> The sliding component of the present disclosure includes the iron-based sintered sliding member of the present disclosure. The sliding component may be integrally formed of a sintered body. Furthermore, when the sliding component is configured by combining a sintered body with other members, it is preferable that at least a portion including a sliding surface is formed of the iron-based sintered sliding member.

[0064] Hereinafter, the present disclosure will be described based on examples, but the present disclosure is not limited to the following examples.

[0065] Example 1: Raw Powder A: Iron alloy powder containing 3% by mass of Cr, 0.5% by mass of Mo, 0.006% by mass of C, and the remainder being iron. Raw Powder B: Iron sulfide containing 35.5% by mass of S (oxygen content: 1.6% by mass). Raw Powder C: Ni powder. Raw Powder D: 95.5% by mass of C, 4.5% by mass of others. Lubricant E: Organic molding lubricant (component that decomposes during sintering). A mixed powder was obtained by mixing 95 parts by mass of Raw Powder A, 5.7 parts by mass of Raw Powder B, 6 parts by mass of Raw Powder C, 0.3 parts by mass of Raw Powder D, and 0.6 parts by mass of Lubricant E. The mixed powder was then molded at a molding pressure of 600 MPa to produce a ring-shaped compact. The mixture was then sintered at 1,130°C in a non-oxidizing gas atmosphere to produce the sintered member of Example 1. In Example 1, the component ratios of each element 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%

[0066] <Example 2> The sintered member 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 member were changed to a lower pressure of 400 MPa to produce a low-density sintered member.

[0067] Comparative Example 1: Raw Powder F: Iron alloy powder containing 3% by mass of Cr, 0.3% by mass of Mo, 0.3% by mass of V, 0.006% by mass of C, and the remainder being iron. Raw Powder C: Ni powder. Raw Powder G: Iron sulfide containing 50% by mass of S (oxygen content: 7.0% by mass). Lubricant H: Organic molding lubricant (component that decomposes during sintering). A mixed powder was obtained by mixing 95 parts by mass of Raw Powder F, 5 parts by mass of Raw Powder C, 10 parts by mass of Raw Powder G, and 0.5 parts by mass of Lubricant H. The mixed powder of Comparative Example 1 was used to prepare a sintered member in the same manner as in Example 1, except that the preparation conditions for the sintered member were changed to a higher pressure of 810 MPa. In Comparative Example 1, the component ratios of each element 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%

[0068] <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.

[0069] The average number of pores, the average pore area ratio, and the maximum pore diameter of the sintered member were measured by the methods described above. The results are shown in Table 1.

[0070] <Radial 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.

[0071] <Hardness> The Rockwell hardness (HRB) of the sintered member was determined in accordance with JIS Z2245: 2016. The results are shown in Table 1.

[0072] <Impact Value> A Charpy impact test was performed on the sintered component in accordance with JIS Z2242:2018, and the impact value (J / cm ２ The results are shown in Table 1.

[0073] 1 to 4 show a comparison of the metal structures (mirror polished) of the sintered members 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.

[0074] <Friction Coefficient> For each example and comparative example, 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 crushing test was performed under the following conditions to measure the friction coefficient: Circumferential speed: 1.57 m / min, Surface pressure: 40 MPa, Time: 5 min, Oil type: Oil VG460 (impregnation)

[0075] <Number of Metal Sulfide Particles> For Example 1, 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 using the method described above. For image analysis, general-purpose image processing software (QuickGrain manufactured by Innotek Co., Ltd.) was used. 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 averaged. The results are shown in Table 2. AE + B (A and B are positive numbers) in Table 2 is calculated by multiplying A × 10 Ｂ means.

[0076]

[0077]

[0078] As shown in Table 1, the sintered member of Example 1 had superior strength to the sintered member of Comparative Example 1. When comparing Example 2 and Comparative Example 2, which are low-density sintered members in which the manufacturing conditions for the sintered member were changed to lower pressure, the sintered member of Example 2 had superior strength to the sintered member 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 pieces / m ２ It is presumed that this allows a large number of fine particles to be exposed on the sliding surface of the sliding member, thereby further improving the sliding performance.

[0079] 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, or technical standard was specifically and individually indicated to be incorporated by reference.

Claims

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 element 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 the sintered body is 1% by mass to 10% by mass; compressing the resulting mixed powder; and sintering the resulting compact 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 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.

3. The method for producing an iron-based sintered sliding member according to claim 1 or 2, wherein the content of graphite in the mixed powder is 0% by mass to 1% by mass.

4. The method for producing an iron-based sintered sliding member according to any one of claims 1 to 3, wherein the number of particles in said sulfur alloy powder B having a particle diameter of 45 μm or less accounts for 50% or more.

5. An iron-based sintered sliding component comprising: 1% by mass to 10% by mass of S; 0.2% by mass to 6% by mass 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 component comprising 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, wherein the average maximum diameter of the pores when measured at five locations is 70 μm or less.

6. The iron-based sintered sliding member according to claim 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 claim 5 or 6, wherein the following calculated value calculated from the average value (Ave) of the proportion of pores when measurements are made 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. An iron-based sintered sliding member according to any one of claims 5 to 7, wherein the Ni content is 0% to 10%.

9. An iron-based sintered sliding member according to any one of claims 5 to 8, wherein the content of Mo is 0% to 10%.

10. An iron-based sintered sliding member according to any one of claims 5 to 9, wherein the graphite content is 0% to 1%.

11. A sliding part comprising the iron-based sintered sliding member according to any one of claims 5 to 10.

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