Iron-based sintered alloy valve seat and its manufacturing method

Abstract

This invention provides an iron-based sintered alloy valve seat with excellent radial compressive strength. The functional component side layer and the support component side layer are integrally sintered to form a double-layer sintered body. The mixed powders for the functional component side layer and the support component side layer are sequentially filled into a mold and stamped to form a pressed powder body. This pressed powder body is then sintered to form the double-layer iron-based sintered alloy valve seat. In the mixed powders for the functional component side layer, an iron-based powder with a hardness of 170–220 HV is used as the iron-based powder for matrix phase formation, forming a matrix phase in the form of fine carbide precipitates. Within this matrix phase, 20–40% of Si-Cr-Mo based Co-based intermetallic compound particles or Si-Cr-Mo-Ni based Co-based intermetallic compound particles are dispersed by area, and 0–5% of solid lubricant particles are also dispersed by area.

Description

Technical Field

[0001] This invention relates to valve seats for internal combustion engines and methods for manufacturing the same, and particularly to improving radial crushing strength. Background Art

[0002] Valve seats are typically pressed into the cylinder head of an internal combustion engine, serving to seal the combustion gases and cool the valve. Because valve seats are subjected to valve impacts, sliding wear, heating from combustion gases, and corrosion from combustion products, they have always been required to have excellent heat resistance and wear resistance.

[0003] For example, Patent Document 1 describes a "steel-based sintered alloy valve seat for internal combustion engines with excellent wear resistance." In the technology described in Patent Document 1, an iron-based sintered alloy valve seat is manufactured, which has the following microstructure: the matrix phase is formed with precipitates of 10... m The matrix phase consists of fine carbides with a hardness of 550 HV or higher, forming a hard single-phase structure. Within this matrix phase, 20–40% (by area) of hard particles with a hardness of 650–1200 HV are dispersed. Around these hard particles, 0.5–5% (by area) of a diffused phase is formed, or less than 5% (by area) of solid lubricant particles are also dispersed. Therefore, in internal combustion engines operating under harsh abrasive environments, such as those using special fuels like gaseous fuels, even with valves possessing high surface hardness, valve seat wear is minimal, enabling a valve and seat combination with excellent wear resistance.

[0004] Existing technical documents

[0005] Patent Literature

[0006] Patent document 1: Japanese Patent No. 6736227. Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] However, the iron-based sintered alloy valve seat described in Patent Document 1 has the following problems: low radial compressive strength, which easily causes cracks when pressed into the cylinder head; in addition, particles are easily shed when in contact with the valve, reducing wear resistance; furthermore, it also has problems such as low Young's modulus leading to easy deformation, decreased sealing performance, and combustion gas leakage.

[0009] The purpose of this invention is to solve the aforementioned technical problems and provide an iron-based sintered alloy valve seat with excellent radial compressive strength. It should be noted that "excellent radial compressive strength" here refers to a radial compressive strength of 470 MPa or higher obtained according to JIS Z 2507.

[0010] Methods for solving problems

[0011] To achieve the above objectives, the inventors conducted in-depth research on various factors affecting radial compressive strength. As a result, they concluded that the low radial compressive strength was due to the low compressibility of the iron-based powder used. In the technology described in Patent Document 1, although an iron-based powder capable of precipitating fine carbides was used as the iron-based powder, carbide precipitation already occurred in the powder, leading to increased powder particle hardness. This resulted in insufficient plastic deformation (compression) of the powder particles during powder pressing, making it difficult to promote element diffusion during sintering, and consequently, a decrease in interparticle bonding strength.

[0012] Therefore, in this invention, it was conceived to use iron-based powder with low carbon content as the iron-based powder for matrix phase formation, so that sufficient pressing and forming can be performed during powder pressing, and sufficient plastic deformation can be applied to the powder particles. However, if the carbon content of the iron-based powder is reduced excessively, the amount of carbides decreases, and the wear resistance of the sintered body decreases. Therefore, it was considered to increase the amount of graphite powder mixed in, so as not to reduce the carbon content of the sintered body. As a result, it was found that the amount of fine carbide precipitation in the sintered body is significantly increased compared with the past, and the wear resistance and radial compressive strength are significantly improved.

[0013] This invention was completed based on further research into the aforementioned insights. Specifically, the key points of this invention are as follows.

[0014] [1] An iron-based sintered alloy valve seat, which is an iron-based sintered alloy valve seat having a single-layer structure composed of functional component side layers, characterized in that:

[0015] The aforementioned functional component side layer is formed by dispersing hard particles and solid lubricant particles in a matrix phase, and has the following structure:

[0016] The matrix phase described above is a fine carbide precipitate phase, wherein the particle size is 10. m Micro-carbides below μm with 150 particles / (30) m m×30 m The precipitate has a density of m or higher and a hardness of 550 HV or higher according to the Vickers hardness tester.

[0017] The aforementioned hard particles are Si-Cr-Mo based Co-based intermetallic compound particles and powders, exhibiting a Vickers hardness of 650–1200 HV, and comprising, by mass%, 2.20–2.70% Si, 7.5–9.5% Cr, and 27.0–30.0% Mo, with the balance being Co and unavoidable impurities; or Si-Cr-Mo-Ni based Co-based intermetallic compound particles, exhibiting a Vickers hardness of 650–1200 HV, and comprising, by mass%, 1.5–2.5% Si, 24.0–26.0% Cr, 23.0–26.0% Mo, and 9.5–11.0% Ni, with the balance being Co. In the aforementioned matrix phase, 20–40% of these hard particles are dispersed by area.

[0018] The mixture also contains 0-5% of the aforementioned solid lubricant particles, based on area ratio.

[0019] The density is 6.65 g / cm³. 3 The radial compressive strength is excellent.

[0020] [2] [1] The iron-based sintered alloy valve seat is characterized in that the matrix portion comprising the above-mentioned matrix phase, the above-mentioned hard particles and the above-mentioned solid lubricant particles has the following composition: comprising, by mass%, 1.0 to 2.0% C, 0.5 to 1.5% Si, less than 2.0% Mn, 2.0 to 10.0% Cr, 5.0 to 15.0% Mo, 0.5 to 10.0% W, 0.5 to 5.0% V, 10.0 to 35.0% Co, 0 to 5.0% Ni, 0 to 2.0% S, with the balance consisting of Fe and unavoidable impurities.

[0021] [3] An iron-based sintered alloy valve seat, which is an iron-based sintered alloy valve seat with a double-layer structure having a functional component side layer and a support component side layer integrally sintered together, characterized in that:

[0022] The aforementioned functional component side layer is formed from a matrix phase and hard particles and solid lubricant particles dispersed within that matrix phase, and has the following structure: the matrix phase is a fine carbide precipitate phase, wherein the particle size is 10 mm. m Micro-carbides below μm with 150 particles / (30) m m×30 mThe precipitate has a density of m or higher and a hardness of 550 HV or higher on a Vickers hardness tester. The aforementioned hard particles are Si-Cr-Mo based Co-based intermetallic compound particles, with a hardness of 650–1200 HV on a Vickers hardness tester. They contain 2.20–2.70% Si, 7.5–9.5% Cr, and 27.0–30.0% Mo by mass, with the balance consisting of Co and unavoidable impurities; or Si-Cr-Mo-N i-series Co-based intermetallic compound particles, having a Vickers hardness of 650–1200 HV, contain, by mass percent, 1.5–2.5% Si, 24.0–26.0% Cr, 23.0–26.0% Mo, and 9.5–11.0% Ni, with the balance being Co. In the aforementioned matrix phase, 20–40% of these hard particles are dispersed by area percentage, and 0–5% of the aforementioned solid lubricant particles are also dispersed by area percentage.

[0023] The aforementioned support member side layer has a structure consisting of a matrix phase composed of pearlite and hard particles and solid lubricant particles dispersed in the matrix phase at a ratio of 0 to 5% by area.

[0024] The density is 6.65 g / cm³. 3 The radial compressive strength is excellent.

[0025] [4] [3] The iron-based sintered alloy valve seat is characterized in that: the matrix portion of the side layer of the above-mentioned functional component, which includes the above-mentioned matrix phase, the above-mentioned hard particles and the above-mentioned solid lubricant particles, has the following composition: by mass % comprising 1.0 to 2.0% C, 0.5 to 1.5% Si, less than 2.0% Mn, 2.0 to 10.0% Cr, 5.0 to 15.0% Mo, 0.5 to 10.0% W, 0.5 to 5.0% V, 10.0 to 35.0% Co, 0 to 5.0% Ni, 0 to 2.0% S, with the balance consisting of Fe and unavoidable impurities.

[0026] The matrix portion of the side layer of the aforementioned support member, which contains the aforementioned matrix phase, the aforementioned hard particles, and the aforementioned solid lubricant particles, has the following composition: it contains 0.9 to 2.0% C by mass, or it also contains one or more of the following: less than 0.5% Ni, less than 0.8% Mo, less than 5.0% Cu, less than 5.0% Mn, less than 2.0% S, with the balance consisting of Fe and unavoidable impurities.

[0027] [5] A method for manufacturing an iron-based sintered alloy valve seat, which is a method for manufacturing a single-layer iron-based sintered alloy valve seat as described in [1] or [2], characterized in that:

[0028] The mixture is prepared by mixing and kneading a specified amount of iron-based powder, graphite powder, alloy element powder, hard particle powder, or solid lubricant powder to form a mixed powder.

[0029] The above-mentioned mixed powder is filled into a mold of a specified shape, and then stamped to form pressed powder.

[0030] After the above-mentioned pressed powder is sintered in a protective environment to form a sintered body, it is then machined or further ground to manufacture a valve seat of a specified shape.

[0031] The aforementioned iron-based powder is configured as follows: it contains, by mass % 0.05 to 0.70% C, less than 0.70% Si, less than 0.50% Mn, less than 4.5% Cr, less than 10.0% Mo, less than 4.5% V, less than 10.0% W, with the balance being Fe and unavoidable impurities; it has a particle hardness of 170 to 220 HV according to a Vickers hardness tester; and 40 to 70% of this iron-based powder is incorporated relative to the total mass of the aforementioned mixed powder.

[0032] The aforementioned hard particle powder is configured as follows: Si-Cr-Mo based Co-based intermetallic compound particle powder, having a Vickers hardness of 650–1200 HV, comprising 2.20–2.70% Si, 7.5–9.5% Cr, and 27.0–30.0% Mo by mass%, with the balance being Co and unavoidable impurities; or Si-Cr-Mo-Ni based Co-based intermetallic compound particles, having a Vickers hardness of 650–1200 HV, comprising 1.5–2.5% Si, 24.0–26.0% Cr, 23.0–26.0% Mo, and 9.5–11.0% Ni by mass%, with the balance being Co. 20–40% of this hard particle powder is incorporated relative to the total mass of the aforementioned mixed powder.

[0033] The graphite powder is mixed in at 0.5% to 2.0% by mass relative to the total mass of the above-mentioned mixed powder.

[0034] The total amount of the above-mentioned alloying element powder, calculated as a percentage by mass relative to the total amount of the above-mentioned mixed powder, is 0 to 5.0%.

[0035] The above-mentioned solid lubricant powder is also mixed in at 0-5% by mass relative to the total mass of the above-mentioned mixed powder.

[0036] The above-mentioned stamping process is performed to make the density of the pressed powder 6.6 g / cm³. 3 The above densities,

[0037] The above sintering treatment was carried out at a sintering temperature of 1100-1200℃ to obtain the above sintered body.

[0038] [6] [5] The method for manufacturing the iron-based sintered alloy valve seat is characterized in that: the sintered body has a particle size of 10 m Micro-carbides below μm with 150 particles / (30) m m×30 m The matrix phase, consisting of fine carbide precipitates with a density of m or higher and a hardness of 550 HV or higher on a Vickers hardness scale, has the following structure and composition: the structure comprises 20-40% hard particles dispersed in terms of area ratio, and 0-5% solid lubricant particles dispersed in terms of area ratio; and the composition comprises, in the matrix portion containing the matrix phase, the diffused phase, the hard particles, and the solid lubricant particles, 1.0-2.0% C, 0.5-1.5% Si, less than 2.0% Mn, 2.0-10.0% Cr, 5.0-15.0% Mo, 0.5-10.0% W, 0.5-5.0% V, 10.0-35.0% Co, 0-5.0% Ni, and 0-2.0% S, with the balance being Fe and unavoidable impurities.

[0039] [7] A method for manufacturing an iron-based sintered alloy valve seat, which is a method for manufacturing a double-layer iron-based sintered alloy valve seat as described in [3] or [4], characterized in that:

[0040] A mixture of specified amounts of iron-based powder, graphite powder, alloy element powder, hard particle powder, and possibly solid lubricant powder is blended and kneaded to produce a mixed powder for the side layer of functional components.

[0041] A mixture of iron-based powder, graphite powder, or alloying element powder, hard particle powder, and solid lubricant powder is blended and kneaded to produce a mixed powder for the side layer of the support component.

[0042] The mixed powder for the side layer of the aforementioned functional components and the mixed powder for the side layer of the aforementioned support components are sequentially filled into a mold of a specified shape, and then stamped to form a pressed powder body. Next, the pressed powder body is sintered in a protective environment to form a sintered body with a double-layer structure. Finally, it is machined or further ground to manufacture a valve seat with a specified double-layer structure.

[0043] In the mixed powder for the side layer of the aforementioned functional component, the iron-based powder is configured as follows: it contains, by mass % 0.05 to 0.70% C, less than 0.70% Si, less than 0.50% Mn, less than 4.5% Cr, less than 10.0% Mo, less than 4.5% V, less than 10.0% W, and the balance being Fe and unavoidable impurities; and has a particle hardness of 170 to 220 HV using a Vickers hardness tester. The iron-based powder is blended at 40 to 70% by mass relative to the total amount of the aforementioned mixed powder.

[0044] The aforementioned hard particle powder is configured as follows: Si-Cr-Mo based Co-based intermetallic compound particle powder, having a Vickers hardness of 650–1200 HV, comprising 2.20–2.70% Si, 7.5–9.5% Cr, and 27.0–30.0% Mo by mass%, with the balance being Co and unavoidable impurities; or Si-Cr-Mo-Ni based Co-based intermetallic compound particles, having a Vickers hardness of 650–1200 HV, comprising 1.5–2.5% Si, 24.0–26.0% Cr, 23.0–26.0% Mo, and 9.5–11.0% Ni by mass%, with the balance being Co. 20–40% of this hard particle powder is incorporated relative to the total mass of the aforementioned mixed powder.

[0045] The graphite powder is mixed in at a rate of 0.5% to 2.0% by mass relative to the total mass of the mixed powder used in the side layer of the above-mentioned functional components.

[0046] The total amount of the above-mentioned alloying element powder, calculated as a percentage by mass relative to the total amount of the above-mentioned mixed powder, is 0 to 5.0%.

[0047] The above-mentioned solid lubricant powder is also mixed in at 0-5% by mass relative to the total mass of the above-mentioned mixed powder.

[0048] The above-mentioned stamping process is performed to make the density of the pressed powder 6.6 g / cm³. 3 The above densities,

[0049] In the aforementioned mixed powder for the side layer of the support member, the iron-based powder is pure iron powder, and 0.5 to 2.0% of the aforementioned graphite powder is mixed in according to the mass percentage of the total amount of the mixed powder for the side layer of the support member; 0 to 5.0% of the aforementioned alloying element powder is mixed in according to the mass percentage of the total amount of the mixed powder for the side layer of the support member; the aforementioned hard particle powder is Fe-Mo alloy powder, and 0 to 5% of the hard particle powder is mixed in according to the mass percentage of the total amount of the mixed powder for the side layer of the support member; and 0 to 5% of the aforementioned solid lubricant powder is mixed in according to the mass percentage of the total amount of the mixed powder for the side layer of the support member.

[0050] The above-mentioned stamping process is performed to make the density of the pressed powder 6.6 g / cm³. 3 The above densities,

[0051] The above sintering treatment was carried out at a sintering temperature of 1100–1200℃.

[0052] The above sintered body is made into a double-layer sintered body.

[0053] [8] [7] The method for manufacturing the iron-based sintered alloy valve seat is characterized in that the sintered body with the above-mentioned double-layer structure is a sintered body with the following double-layer structure, wherein the side layer of the above-mentioned functional component has: a particle size of 10 m Micro-carbides below μm with 150 particles / (30) m m×30 m The matrix phase consists of a fine carbide precipitate phase with a density of m or higher and a hardness of 550 HV or higher on a Vickers hardness scale; a matrix phase containing 20-40% hard particles and 0-5% solid lubricant particles dispersed in terms of area ratio; and a matrix portion comprising the matrix phase, the hard particles, and the solid lubricant particles containing, by mass%, 1.0-2.0% C, 0.5-1.5% Si, less than 2.0% Mn, 2.0-10.0% Cr, 5.0-15.0% Mo, 0.5-10.0% W, 0.5-5.0% V, 10.0-35.0% Co, 0-5.0% Ni, 0-2.0% S, with the balance being Fe and unavoidable impurities.

[0054] The aforementioned support member side layer comprises: a matrix phase composed of pearlite; a structure formed by dispersing 0 to 5% hard particles and 0 to 5% solid lubricant particles in the matrix phase by area; and a composition comprising, by mass, 0.9 to 2.0% C, or further comprising one or more selected from 0.5% or less Ni, 0.8% or less Mo, 5.0% or less Cu, 5.0% or less Mn, and 2.0% or less S, with the balance being Fe and unavoidable impurities.

[0055] Invention Effects

[0056] According to the present invention, iron-based sintered alloy valve seats with excellent wear resistance and radial compressive strength can be manufactured, which has significant industrial benefits. Attached Figure Description

[0057] [ Figure 1 [This is an explanatory diagram showing an overview of the drilling (rig) testing machine.] Detailed Implementation

[0058] The valve seat of the present invention is a single-layer iron-based sintered alloy valve seat with only the functional component side layer, or a double-layer iron-based sintered alloy valve seat formed by integrally sintering the functional component side layer and the support component side layer.

[0059] First, the functional component side layer will be explained.

[0060] The functional component side layer has a matrix phase and a structure in which hard particles and solid lubricant particles are dispersed.

[0061] The matrix phase is a single phase composed of fine carbide precipitates, which exhibit a hardness of over 550 HV using a Vickers hardness tester, with a particle size of 10 mm. m Micro-carbides below μm with 150 particles / (30) m m×30 m Precipitates with a density of m or higher. Here, "single phase" refers to a phase comprising 95% or more by area ratio. It should be noted that if the area ratio is less than 5%, even if a phase with a hardness less than 550 HV remains in the matrix phase, the impact on wear resistance is minimal and acceptable. When the hardness of the matrix phase is less than 550 HV, it tends to solidify upon contact with the valve, reducing wear resistance. On the other hand, if it hardens to over 700 HV, the toughness of the sintered body decreases. Therefore, the hardness of the matrix phase, measured by Vickers hardness, is set to 550 HV or higher, preferably 700 HV or lower. It should be noted that 560–660 HV is preferred.

[0062] If the particle size of the carbides precipitated in the matrix phase exceeds 10... m As m increases, the hardness and toughness of the matrix phase decrease, its aggressiveness increases, and its radial compressive strength decreases. In this invention, carbides in the matrix phase are arranged at a ratio of 150 per (30) m m×30 m Precipitates with a density greater than 150 (m). Precipitates with a density less than 150 (m / (30)) precipitates. m m×30 m When the density is too low (m), the desired radial compressive strength or wear resistance cannot be guaranteed. Therefore, the matrix phase is set as a fine carbide precipitate phase with a hardness of over 550 HV on a Vickers hardness tester, wherein the particle size is 10. m Micro-carbides below μm with 150 particles / (30) m m×30 m Precipitates with a density of m or higher.

[0063] The matrix phase having the above-mentioned hardness and structure preferably has the following composition: containing 0.05 to 0.70% C, less than 0.70% Si, less than 0.50% Mn, less than 4.5% Cr, less than 10.0% Mo, less than 4.5% V, less than 10.0% W, or also containing less than 5.0% Co, with the balance consisting of Fe and unavoidable impurities.

[0064] The functional component side layer of the valve seat of the present invention has a structure in which hard particles, or solid lubricant particles, are dispersed in a matrix phase having the aforementioned hardness, structure, and composition. The dispersed hard particles are hard particles with a Vickers hardness of 650–1200 HV. When the hardness of the hard particles is less than 650 HV, the improvement in wear resistance is minimal. On the other hand, if the hardness exceeds 1200 HV, it leads to a decrease in machinability. Therefore, the hardness of the hard particles dispersed in the matrix phase is limited to the range of 650–1200 HV using a Vickers hardness tester.

[0065] It should be noted that the hard particles dispersed in the matrix phase are preferably set with an average particle size of 10–150 mm. m Particles with an average diameter of less than 10 μm. m At a temperature of m, diffusion is likely during sintering, making it impossible to ensure the desired improvement in wear resistance. On the other hand, if the temperature exceeds 150... m As the particle size (m) increases, the binding force with the matrix decreases. Therefore, the average particle size of the hard particles dispersed in the matrix phase is preferably set to 10–150 μm. m m. The "average particle size" mentioned here refers to the particle size D50, which represents the 50% cumulative distribution, as determined by laser scattering.

[0066] Furthermore, in the functional component side layer of the valve seat of the present invention, 20-40% of the aforementioned hard particles of the aforementioned hardness are dispersed in the matrix phase by area. When the dispersion amount of hard particles is less than 20%, the desired wear resistance cannot be ensured. On the other hand, if it exceeds 40%, the bonding force between the matrix phase and the hard particles decreases, and the wear resistance is reduced.

[0067] The hard particulate powder used as the side layer of the functional component of the valve seat in this invention is preferably Si-Cr-Mo based Co-based intermetallic compound particulate powder or Si-Cr-Mo-Ni based Co-based intermetallic compound particulate powder. The Si-Cr-Mo based Co-based intermetallic compound particulate powder has the following composition: comprising 2.20–2.70% Si, 7.5–9.5% Cr, 27.0–30.0% Mo by mass, with the balance being Co and unavoidable impurities; and has a hardness of 650–1200 HV using a Vickers hardness tester. The Si-Cr-Mo-Ni based Co-based intermetallic compound particulate powder has the following composition: comprising 1.5–2.5% Si, 24.0–26.0% Cr, 23.0–26.0% Mo, 9.5–11.0% Ni by mass, with the balance being Co; and has a hardness of 650–1200 HV using a Vickers hardness tester.

[0068] In the functional component side layer of the valve seat of the present invention, a diffuse phase is sometimes formed around the hard particles, but its amount is small, at most less than 0.5% in terms of area ratio. This diffuse phase is formed by alloying elements diffusing from the hard particles into the matrix phase during sintering, but in the functional component side layer of the valve seat of the present invention, the amount of diffuse phase formed is small due to carbide stabilization.

[0069] In the functional component side layer of the valve seat of the present invention, 0 to 5% of solid lubricant particles are dispersed in the matrix phase by area. Dispersing solid lubricant particles in the matrix phase improves machinability, processability, and lubricity. However, if the concentration exceeds 5%, it hinders the sintering reaction and leads to a decrease in mechanical properties. Therefore, the solid lubricant particles are limited to a range of 0 to 5% by area. Examples of solid lubricants include manganese sulfide (MnS) and molybdenum disulfide (MoS2).

[0070] In the functional component side layer of the valve seat of the present invention, the matrix portion comprising a matrix phase, hard particles, and solid lubricant particles has the following composition by mass%: 1.0 to 2.0% C, 0.5 to 1.5% Si, less than 2.0% Mn, 2.0 to 10.0% Cr, 5.0 to 15.0% Mo, 0.5 to 10.0% W, 0.5 to 5.0% V, 10.0 to 35.0% Co, 0 to 5.0% Ni, and 0 to 2.0% S, with the balance consisting of Fe and unavoidable impurities.

[0071] The following explains the rationale for defining the composition of the matrix portion in the side layer of the functional component. It should be noted that, in the following description, mass percentages in the composition are expressed as percentages only.

[0072] C: 1.0~2.0%

[0073] Carbon (C) is an essential element for adjusting the matrix phase to a specified hardness and microstructure and forming specified fine carbides, and is contained in the matrix at a concentration of 1.0% or more. On the other hand, if the concentration exceeds 2.0%, liquid-phase sintering occurs during sintering, resulting in excessive carbide precipitation, increased porosity, and decreased dimensional accuracy. Therefore, C is preferably limited to the range of 1.0% to 2.0%. It should be noted that 1.0% to 1.5% is more preferred.

[0074] Si: 0.5%–1.5%

[0075] Si is an element that increases hardness, and it is preferable to contain 0.5% or more. On the other hand, a content exceeding 1.5% will lead to a decrease in toughness. Therefore, the Si content is preferably limited to the range of 0.5% to 1.5%. It should be noted that 0.5% to 1.3% is more preferred.

[0076] Mn: less than 2.0%

[0077] Mn is an element that increases the hardness of the matrix phase. Furthermore, Mn contains solid lubricant particles within the matrix, which helps improve machinability. This effect becomes significant when the content is 0.05% or more, but a content of 2.0% or more leads to a decrease in the hardness, toughness, and ductility of the matrix phase. Therefore, Mn is preferably limited to less than 2.0%. It should be noted that 0.05% to 1.5% is more preferred.

[0078] Cr: 2.0~10.0%

[0079] Cr is an element that dissolves in the matrix phase, forms carbides to increase the hardness of the matrix phase, increases the hardness of hard particles, and improves heat resistance and wear resistance. It is preferable to contain 2.0% or more Cr. On the other hand, if the content exceeds 10.0%, excessive Cr carbides are formed, making it difficult to form fine carbides, and the hardness of the hard particles becomes excessively high. Therefore, the Cr content is preferably limited to the range of 2.0% to 10.0%. It should be noted that 4.0% to 6.0% is more preferred.

[0080] Mo: 5.0–15.0%

[0081] Mo is an element that dissolves in the matrix phase and forms fine carbides, thereby increasing the hardness of the matrix phase and contributing to improved wear resistance. Furthermore, it increases the hardness of hard particles. This effect becomes significant when the content is 5.0% or more, but if the content exceeds 15.0%, the formability decreases. Therefore, the content of Mo is preferably limited to 5.0% to 15.0%. It should be noted that 10.0% to 14.0% is more preferred.

[0082] W: 0.5–10.0%

[0083] W is an element that forms fine carbides, increases the hardness of the matrix phase, and improves wear resistance. This effect becomes significant when the content is 0.5% or more, but the formability decreases if the content exceeds 10.0%. Therefore, W is preferably limited to 0.5% to 10.0%. It should be noted that 2.0% to 5.0% is more preferred.

[0084] V: 0.5~5.0%

[0085] V is an element that forms fine carbides, increases the hardness of the matrix phase, and improves wear resistance. This effect becomes significant when the content is 0.5% or more, but if the content exceeds 5.0%, the formability decreases. Therefore, V is preferably limited to the range of 0.5% to 5.0%. It should be noted that 0.5% to 2.0% is more preferred.

[0086] Co: 10.0%–35.0%

[0087] Co increases the strength of the matrix phase, especially its high-temperature strength, and improves its wear resistance. It also increases the toughness of the matrix phase and the hardness of hard particles. This effect becomes significant when the content is 10.0% or more. On the other hand, if the content exceeds 35.0%, it reduces the hardness of the matrix phase. Therefore, the content of Co is preferably limited to the range of 10.0% to 35.0%. It should be noted that it is more preferably 10.0% to 25.0% or less.

[0088] Ni: 0~5.0%

[0089] Ni is an element that helps improve the hardness and toughness of the matrix phase, and also helps increase the hardness of hard particles; it can be included as needed. When Ni is present, it is preferably 0.3% or more; if it exceeds 5.0%, it will lead to a decrease in the formability of the matrix phase. Therefore, when Ni is present, it is preferably limited to 5.0% or less. It should be noted that it is more preferably 1.0% or less.

[0090] S: 0~2.0%

[0091] S is an element contained in the matrix due to the presence of solid lubricant particles, which helps improve machinability, and can be included as needed. However, if the content of S exceeds 2.0%, it will lead to a decrease in toughness and ductility. Therefore, when S is present, it is preferable to limit S to 2.0% or less.

[0092] The balance other than the above components consists of Fe and unavoidable impurities. As an unavoidable impurity, less than 0.03% P is permissible.

[0093] Next, the support member side layer in the case where the valve seat of the present invention is made into a double-layer structure will be described. It should be noted that the functional member side layer of the double-layer structure is the same as the functional member side layer of the single-layer structure described above.

[0094] The matrix phase of the support member side layer of the valve seat of the present invention is mainly composed of pearlite. The support member side layer has a matrix phase with the above-mentioned structure and a structure formed by dispersing hard particles and solid lubricant particles with an area ratio of 0 to 5% in the matrix phase.

[0095] In the matrix phase of the side layer of the support member, solid lubricant particles that improve machinability can be dispersed as needed. Examples of solid lubricant particles include MnS and MoS2. When dispersed, the solid lubricant particle content is preferably set to 0.3% or more in terms of area ratio. If it is less than 0.3%, it is difficult to achieve the purpose of improving machinability. On the other hand, even if the dispersion exceeds 5%, the effect will saturate, and an effect commensurate with the dispersion amount cannot be expected. Therefore, when dispersed, the solid lubricant particle content is preferably limited to 5% or less.

[0096] In addition, to increase the strength of the matrix phase, 0 to 5% hard particles can be dispersed in the side layer of the support member. For example, iron-molybdenum (Fe-Mo) alloy iron can be used as the hard particles dispersed in the side layer of the support member. Even if more than 5% of hard particles are dispersed in terms of area, the effect will saturate; therefore, 5% is set as the upper limit.

[0097] Furthermore, the matrix portion of the support member side layer of the valve seat of the present invention, which includes a matrix phase, hard particles and solid lubricant particles, has the following composition: it contains 0.9 to 2.0% C by mass, or it also contains one or more of Ni (less than 0.5%), Mo (less than 0.8%), Cu (less than 5.0%), Mn (less than 5.0%), and S (less than 2.0%), with the balance consisting of Fe and unavoidable impurities.

[0098] C, Ni, Mo, and Cu are elements that increase the strength (hardness) of the matrix phase in the side layer of the support member. To ensure the desired strength, C is contained at least 0.9%. On the other hand, if the content exceeds 2.0%, the strength is too high and the toughness is reduced. Therefore, C is limited to the range of 0.9% to 2.0%. Furthermore, although Ni, Mo, and Cu are contained according to the desired strength, if Ni exceeds 0.5%, Mo exceeds 0.8%, and Cu exceeds 5.0%, the strength becomes too high. Therefore, it is preferable to limit the content to less than 0.5% Ni, less than 0.8% Mo, and less than 5.0% Cu. Additionally, Mn, S, and Mo are partially included due to the dispersion of solid lubricant particles; even if a large amount of solid lubricant particles are dispersed, the effect will saturate. Therefore, Mn is limited to less than 5.0%, and S to less than 2.0%.

[0099] Next, the manufacturing method of the iron-based sintered alloy valve seat of the present invention will be described.

[0100] In the manufacturing method of the single-layer iron-based sintered alloy valve seat of the present invention, firstly, a specified amount of iron-based powder, graphite powder, alloy element powder, hard particle powder, or solid lubricant powder is mixed and kneaded to form the above-mentioned matrix composition, and then mixed and kneaded to produce a mixed powder (mixed powder for the side layer of functional components).

[0101] The iron-based powder mixed in the mixed powder (mixed powder for the side layer of functional components) is a powder mixed in to form a matrix phase. In this invention, it is set as an alloy steel powder that can make the matrix phase a fine carbide precipitate phase. As such an alloy steel powder, an example is a powder with a composition based on the high-speed tool steel composition specified in JIS G 4403, but it is not limited thereto.

[0102] The blended iron-based powder is defined as follows: It contains, by mass % 0.05–0.70% C, 0.70% or less Si, 0.50% or less Mn, 4.5% or less Cr, 10.0% or less Mo, 4.5% or less V, 10.0% or less W, with the balance being Fe and unavoidable impurities, and has a particle hardness of 170–220 HV using a Vickers hardness tester. The rationale for limiting the composition of the iron-based powder will be explained below. Hereinafter, the mass % in the composition is abbreviated as %.

[0103] The reasons for limiting the composition of the blended iron-based powders are explained below.

[0104] C: 0.05~0.70%

[0105] The iron-based powder incorporated in this invention is a powder composed of high-speed steel with reduced carbon content. When the carbon content is less than 0.05%, no decrease in hardness of the powder particles is observed. On the other hand, if the carbon content exceeds 0.70%, the hardness of the powder particles becomes excessively high, and the compressibility of the powder particles decreases. Therefore, the carbon content of the iron-based powder is preferably limited to the range of 0.05% to 0.70%. It should be noted that 0.3% to 0.6% is more preferred.

[0106] Si: below 0.70%

[0107] Si acts as a deoxidizer, and this effect becomes significant when the content is 0.05% or more. On the other hand, if the content exceeds 0.70%, compressibility decreases. Therefore, Si is preferably limited to 0.70% or less. It should be noted that 0.40% or less is more preferred.

[0108] Mn: below 0.50%

[0109] Mn acts as a deoxidizer and also helps increase strength (hardness). This effect becomes significant when the content is above 0.10%. On the other hand, if the content exceeds 0.50%, the hardness increases and the compressibility decreases. Therefore, Mn is preferably limited to 0.50% or less.

[0110] Cr: below 4.5%

[0111] Cr is an element that forms carbides and improves wear resistance. This effect becomes significant when the content is above 2.0%, but toughness decreases if the content exceeds 4.5%. Therefore, Cr is preferably limited to 4.5% or less.

[0112] Mo: 10.0% or less

[0113] Mo is an element that forms fine carbides and improves wear resistance. This effect becomes significant when the content is 3.0% or more, but if the content exceeds 10.0%, the formability decreases. Therefore, the content of Mo is preferably limited to 10.0% or less. It should be noted that 4.0% to 6.0% is more preferred.

[0114] V: Below 4.5%

[0115] V is an element that forms fine carbides and improves wear resistance. This effect becomes significant when the content is above 1.5%, but the formability decreases if the content exceeds 4.5%. Therefore, V is preferably limited to 4.5% or less.

[0116] W: Below 10.0%

[0117] W is an element that forms fine carbides and improves wear resistance. This effect becomes significant when the content is 5.0% or more, but the formability decreases if the content exceeds 10.0%. Therefore, W is preferably limited to 10.0% or less.

[0118] The balance other than the above-mentioned components consists of Fe and unavoidable impurities. As unavoidable impurities, P of 0.03% or less and S of 0.02% or less are permissible. Since P segregates at austenite grain boundaries and promotes grain boundary brittleness, it is preferable to minimize P as much as possible. It should be noted that 0.010% or less is more preferred. Furthermore, S exists in steel as sulfide inclusions, hindering hot workability; therefore, it is desirable to minimize S as much as possible. It should be noted that 0.005% or less is more preferred.

[0119] Particle hardness: 170~220HV

[0120] The iron-based powder used in this invention has a particle hardness of 170–220 HV. When the particle hardness is less than 170 HV, the iron-based powder has too low a hardness, resulting in reduced wear resistance as a sintered body. On the other hand, if the particle hardness exceeds 220 HV and increases, the compressibility decreases, leading to a decrease in the radial compressive strength of the sintered body. Therefore, the particle hardness of the blended iron-based powder is limited to 170–220 HV.

[0121] Furthermore, the hard particle powder to be blended is preferably Si-Cr-Mo based Co-based intermetallic compound particle powder or Si-Cr-Mo-Ni based Co-based intermetallic compound particle powder having the aforementioned hardness and composition. In this invention, 20 to 40% of the hard particle powder having this hardness is blended in relative to the total mass percentage of the mixed powder.

[0122] It should be noted that the hard particulate powder mixed in the mixed powder is preferably configured to have the above-mentioned hardness and an average particle size of 10 to 150. m Particles with an average diameter of less than 10 μm. m At m, diffusion is prone to occur during sintering, making it impossible to ensure the desired wear resistance. On the other hand, above 150... m When the particle size is m, the bonding force with the matrix decreases. Therefore, the average particle size of the hard granular powder is preferably 10–150 μm. m m. It should be noted that "average particle size" refers to the particle size D50 with a cumulative distribution of 50% as determined by laser scattering.

[0123] Furthermore, dispersing solid lubricant particles in the matrix phase improves machinability, processability, and lubricity. MnS, MoS2, etc., are preferably used as solid lubricant particles. The amount of solid lubricant particle powder mixed in is preferably 0 to 5% by mass relative to the total mass of the mixed powder.

[0124] It should be noted that the mixed powder may contain a specified amount of the aforementioned iron-based powder, hard particle powder, or solid lubricant powder. Graphite powder and alloying element powder may also be added to achieve the aforementioned matrix phase composition and matrix component composition. It should also be noted that lubricants such as zinc stearate may be added to the mixed powder.

[0125] As described above, a specified amount of graphite powder, alloy element powder, hard particle powder, or solid lubricant powder are also mixed and kneaded in the iron-based powder to produce a mixed powder.

[0126] Next, the resulting mixed powder is filled into a mold of a specified valve seat shape.

[0127] After the mixed powder is filled into the mold, it is stamped using a stamping machine or similar tool to form a pressed powder body in the shape of a valve seat. It should be noted that the stamping process is preferably performed when the density of the pressed powder body is 6.6 g / cm³. 3 The above methods will be adjusted accordingly.

[0128] Next, the obtained pressed powder is subjected to sintering treatment to produce a sintered body.

[0129] The sintering process is preferably performed in a protective environment at a temperature range of 1100–1200°C. Below 1100°C, sintering diffusion is insufficient; conversely, above 1200°C, excessive diffusion occurs, reducing wear resistance. It should be noted that the stamping process (P-sintering process S) can be repeated multiple times (e.g., 2P2S).

[0130] The obtained sintered body is subjected to grinding / cutting and other processing to produce a valve seat of the desired size and shape.

[0131] Next, in the manufacturing method of the double-layer iron-based sintered alloy valve seat of the present invention, in addition to preparing the above-mentioned mixed powder (mixed powder for the functional component side layer), mixed powder for the support component side layer is also prepared.

[0132] The mixed powder for the side layer of the support component is prepared by mixing and kneading a specified amount of iron-based powder, graphite powder, or alloy element powder, hard particle powder, and solid lubricant powder. In the mixed powder for the side layer of the support component, the iron-based powder is pure iron powder, and 0.5 to 2.0% of graphite powder is mixed in by mass relative to the total mass of the mixed powder for the side layer of the support component; a total of 0 to 5.0% of alloy element powder is mixed in by mass relative to the total mass of the mixed powder for the side layer of the support component; the hard particle powder is iron-molybdenum (Fe-Mo) alloy powder, and 0 to 5% of this hard particle powder is mixed in by mass relative to the total mass of the mixed powder for the side layer of the support component; and 0 to 5% of solid lubricant powder is mixed in by mass relative to the total mass of the mixed powder for the side layer of the support component.

[0133] Then, the mixed powder for the side layer of the functional component and the mixed powder for the side layer of the support component are sequentially filled into the mold of the specified shape at the desired ratio.

[0134] After being filled into the mold, the powder is stamped in the same manner as the single-layer structure described above to form a pressed powder. Then, the pressed powder is sintered in the same manner as the single-layer structure described above to obtain a sintered body with a double-layer structure.

[0135] The obtained sintered double-layer structure is subjected to grinding / cutting and other processing to produce a valve seat of the desired size and shape.

[0136] The present invention will be further described below with reference to embodiments. Example

[0137] First, mixed powder for the side layer of functional components and mixed powder for the side layer of support components were prepared.

[0138] The mixed powder for the side layer of functional components is prepared by adjusting the blending amounts of graphite powder, alloying element powder, hard particle powder, and solid lubricant powder (MnS powder) in the iron-based powder used for matrix phase formation to achieve the blending amounts shown in Table 1, followed by mixing and kneading to produce mixed powders (No. A to No. K). It should be noted that the iron-based powder used is the high-speed tool steel powder (No. a to No. d) with the composition and hardness shown in Table 2. Furthermore, the hard particle powder used is the particulate powder (No. h1 to No. h2) with the composition, hardness, and average particle size shown in Table 3.

[0139] The mixed powder used for the side layer of the support component is a mixture of iron-based powder, graphite powder, or alloying element powder, hard particle powder, and solid lubricant particle powder used to adjust the matrix phase formation, to achieve the blending amounts shown in Table 1. This mixture is then blended and kneaded to produce mixed powders (No. 1A to No. 1B). It should be noted that the iron-based powder used is the powder with the composition and hardness shown in Table 2 (No. e). Iron-based powder No. e is pure iron powder. Additionally, the hard particle powder used is the particle powder with the composition, hardness, and average particle size shown in Table 3 (No. h3). Hard particle powder No. h3 is an iron-molybdenum alloy iron. It should be noted that in the mixed powder, 1 part by mass of zinc stearate is added as a lubricant per 100 parts by mass of the mixed powder. In some valve seats, a single-layer structure consisting only of the functional component side layer is produced.

[0140] [Table 1]

[0141]

[0142] [Table 2]

[0143]

[0144] [Table 3]

[0145]

[0146] The obtained mixed powder was filled into a mold and pressed into a powder body with a specified valve seat shape using a stamping mechanism. The density of the obtained powder body was determined by Archimedes' method.

[0147] Next, the obtained pressed powder was subjected to sintering treatment. The sintering treatment was carried out by placing it in a sintering furnace at a heating temperature of 1150°C in a protective environment (holding time: 6 hours) to produce a sintered body.

[0148] The obtained sintered body was further processed by cutting, grinding and other processes to produce an iron-based sintered alloy valve seat with a specified shape (outer diameter: 27mmϕ × inner diameter: 22mmϕ × thickness: 6mm).

[0149] The obtained valve seat underwent chemical analysis, microstructure observation, hardness testing, density testing, wear testing, and radial compressive strength testing. The test methods are as follows.

[0150] (1) Chemical analysis

[0151] Samples were collected from various parts of the obtained valve seat for analysis. The content of each component in each part was analyzed by luminescence analysis, and the composition of the matrix of the sintered body was determined.

[0152] (2) Organizational observation

[0153] The obtained valve seat was ground with a section perpendicular to the axis and etched (using nitric acid ethanol solution) to reveal the microstructure. The matrix phase microstructure was determined by observation under an optical microscope (magnification: 200x). Furthermore, the particle size of the carbides precipitated in the matrix phase was measured using a scanning electron microscope (magnification: 2000x), confirming a maximum carbide particle size of 10 mm. m Below μm, the matrix phase consists of fine carbide precipitates. When the maximum diameter of the carbide particles (long side length) exceeds 10 μm... m In the case of m, only carbide precipitates formed. Furthermore, using a scanning electron microscope (magnification: 2000x), the carbides precipitated in the matrix phase were measured within a 30-meter field of view. m m×30 m The number of carbides within m was calculated, and the carbide precipitation density (numbers / (30)) was determined. m m×30 m m)).

[0154] (3) Hardness test

[0155] The obtained valve seat was ground with a section perpendicular to the axis and etched (etching solution: nitric acid ethanol solution) to reveal the microstructure. The Vickers hardness HV of the matrix phase was determined using a Vickers hardness tester (test force: 0.98 N (100 gf)).

[0156] (4) Density test

[0157] The density (density of sintered body) of the obtained valve seat was determined using the Archimedes method.

[0158] (5) Wear test

[0159] For the obtained valve seat, use Figure 1 The drilling test machine shown was subjected to a wear test under the test conditions shown below.

[0160] Test temperature: 300℃ (valve seat surface);

[0161] Test duration: 12 hours;

[0162] Cam speed: 3000 rpm;

[0163] Valve rotation speed: 20 rpm;

[0164] Impact load: 700N.

[0165] Valve material: Heat-resistant steel with nitrided film (SUH35 surface hardness is 1150HV).

[0166] After the test, the wear of the test piece (valve seat) was measured. Using valve seat No.1 (existing example) as the benchmark (1.00), the wear ratio of the valve seat was calculated from the obtained wear amount.

[0167] (6) Radial compressive strength test

[0168] For the obtained valve seat, the radial compressive strength was calculated according to JIS Z 2507. Using valve seat No. 1 (existing example) as a reference (1.00), the radial compressive strength ratio of the valve seat was calculated from the obtained radial compressive strength. It should be noted that the radial compressive strength of valve seat No. 1 (existing example) is 470 MPa.

[0169] The results are shown in Tables 4 and 5.

[0170]

[0171]

[0172] In the examples of this invention, compared with the prior art (valve seat No. 1), the precipitation density of carbides in the matrix phase is significantly increased, and the carbides are more finely dispersed compared with the prior art. As a result, the sintered body of the examples of this invention has a higher density, resulting in a higher radial compressive strength ratio, improved radial compressive strength, lower wear ratio, and improved wear resistance.

[0173] Symbol Explanation

[0174] 1: Valve seat;

[0175] 2: Cylinder block equivalent material;

[0176] 3: Heating device;

[0177] 4: Valves.

Claims

1. An iron-based sintered alloy valve seat, which is a single-layer iron-based sintered alloy valve seat having a structure composed of functional component side layers, characterized in that: The aforementioned functional component side layer is formed by dispersing hard particles and solid lubricant particles in a matrix phase, and has the following structure: The aforementioned matrix phase is a fine carbide precipitate phase, wherein the fine carbides with a particle size of less than 10 μm precipitate at a density of more than 150 particles / (30 μm × 30 μm), and have a hardness of more than 550 HV according to the Vickers hardness tester. The aforementioned hard particles are Si-Cr-Mo based Co-based intermetallic compound particles and powders, exhibiting a Vickers hardness of 650–1200 HV, and comprising, by mass % 2.20–2.70% Si, 7.5–9.5% Cr, and 27.0–30.0% Mo, with the balance being Co and unavoidable impurities; or Si-Cr-Mo-Ni based Co-based intermetallic compound particles, exhibiting a Vickers hardness of 650–1200 HV, and comprising, by mass % 1.5–2.5% Si, 24.0–26.0% Cr, 23.0–26.0% Mo, and 9.5–11.0% Ni, with the balance being Co. In the aforementioned matrix phase, 20–40% of these hard particles are dispersed by area. The above-mentioned solid lubricant particles are dispersed at 0-5% by area ratio. The matrix portion comprising the above-mentioned matrix phase, the above-mentioned hard particles, and the above-mentioned solid lubricant particles has the following composition by mass: 1.0–2.0% C, 0.5–1.5% Si, less than 2.0% Mn, 2.0–10.0% Cr, 5.0–15.0% Mo, 2.0–10.0% W, 0.5–5.0% V, 10.0–35.0% Co, 0–5.0% Ni, and 0–2.0% S, with the balance consisting of Fe and unavoidable impurities. The density is 6.65 g / cm³. 3 The radial compressive strength is above 470 MPa.

2. An iron-based sintered alloy valve seat, characterized in that it has a double-layer structure in which the functional component side layer and the support component side layer are integrally sintered, and is characterized in that: The aforementioned functional component side layer is formed from a matrix phase and hard particles and solid lubricant particles dispersed in the matrix phase, and has the following structure: The aforementioned matrix phase is a fine carbide precipitate phase, wherein the fine carbides with a particle size of less than 10 μm precipitate at a density of more than 150 particles / (30 μm × 30 μm), and have a hardness of more than 550 HV according to the Vickers hardness tester. The aforementioned hard particles are Si-Cr-Mo based Co-based intermetallic compound particles and powders, exhibiting a Vickers hardness of 650–1200 HV, and containing, by mass % 2.20–2.70% Si, 7.5–9.5% Cr, and 27.0–30.0% Mo, with the balance consisting of Co and unavoidable impurities; or Si-Cr-Mo-Ni based Co-based intermetallic compound particles, exhibiting a Vickers hardness of 650–1200 HV, and containing, by mass % 1.5–2.5% Si, 24.0–26.0% Cr, 23.0–26.0% Mo, and 9.5–11.0% Ni, with the balance consisting of Co. The matrix phase contains 20-40% of the hard particles by area percentage and 0-5% of the solid lubricant particles by area percentage. The matrix portion comprising the matrix phase, the hard particles, and the solid lubricant particles in the side layer of the functional component has the following composition by mass percentage: 1.0-2.0% C, 0.5-1.5% Si, less than 2.0% Mn, 2.0-10.0% Cr, 5.0-15.0% Mo, 2.0-10.0% W, 0.5-5.0% V, 10.0-35.0% Co, 0-5.0% Ni, and 0-2.0% S, with the balance consisting of Fe and unavoidable impurities. The aforementioned support member side layer has a structure consisting of a matrix phase composed of pearlite and hard particles and solid lubricant particles dispersed in the matrix phase at an area ratio of 0-5%. The matrix portion of the side layer of the aforementioned support member, comprising the aforementioned matrix phase, the aforementioned hard particles, and the aforementioned solid lubricant particles, has the following composition: containing 0.9 to 2.0% C by mass, or further containing one or more selected from Ni (less than 0.5%), Mo (less than 0.4 to 0.8%), Cu (less than 5.0%), Mn (less than 5.0%), and S (less than 2.0%), with the balance consisting of Fe and unavoidable impurities. The density is 6.65 g / cm³. 3 The radial compressive strength is above 470 MPa.

3. A method for manufacturing an iron-based sintered alloy valve seat, which is the method for manufacturing a single-layer iron-based sintered alloy valve seat as described in claim 1, characterized in that: The mixture is prepared by blending and kneading a specified amount of iron-based powder, graphite powder, alloy element powder, hard particle powder, or solid lubricant powder to form a mixed powder. The above-mentioned mixed powder is filled into a mold of a specified shape, and then stamped to form pressed powder. After the above-mentioned pressed powder is sintered in a protective environment to form a sintered body, it is then machined or further ground to manufacture a valve seat of a specified shape. The aforementioned iron-based powder is configured as follows: it contains, by mass % 0.05 to 0.70% C, less than 0.70% Si, less than 0.50% Mn, less than 4.5% Cr, less than 10.0% Mo, less than 4.5% V, less than 10.0% W, and the balance being Fe and unavoidable impurities; it has a particle hardness of 170 to 220 HV according to a Vickers hardness tester; and 40 to 70% of this iron-based powder is incorporated relative to the total mass of the aforementioned mixed powder. The aforementioned hard particle powder is configured as follows: Si-Cr-Mo based Co-based intermetallic compound particle powder, having a Vickers hardness of 650–1200 HV, comprising 2.20–2.70% Si, 7.5–9.5% Cr, and 27.0–30.0% Mo by mass, with the balance being Co and unavoidable impurities; or Si-Cr-Mo-Ni based Co-based intermetallic compound particles, having a Vickers hardness of 650–1200 HV, comprising 1.5–2.5% Si, 24.0–26.0% Cr, 23.0–26.0% Mo, and 9.5–11.0% Ni by mass, with the balance being Co. 20–40% of this hard particle powder is incorporated relative to the total mass of the aforementioned mixed powder. The graphite powder is mixed in at 0.5 to 2.0% by mass relative to the total mass of the above-mentioned mixed powder. The total amount of the above-mentioned alloying element powder, calculated as a percentage by mass relative to the total amount of the above-mentioned mixed powder, is 0 to 5.0%. The above-mentioned solid lubricant powder is also mixed in at 0-5% by mass relative to the total mass of the above-mentioned mixed powder. The above-mentioned stamping process is performed to make the density of the pressed powder 6.6 g / cm³. 3 The above densities, The above sintering treatment was carried out at a sintering temperature of 1100–1200℃ to obtain the above sintered body. The above-mentioned sintered body has the following structure and composition in the fine carbide precipitate phase (matrix phase) with a particle size of less than 10 μm, a density of more than 150 particles / (30 μm × 30 μm), and a hardness of more than 550 HV on a Vickers hardness scale: The structure comprises: 20-40% hard particles dispersed in area ratio, and 0-5% solid lubricant particles dispersed in area ratio; and the composition comprises, in the matrix portion containing the matrix phase, the hard particles and the solid lubricant particles, 1.0-2.0% C, 0.5-1.5% Si, less than 2.0% Mn, 2.0-10.0% Cr, 5.0-15.0% Mo, 2.0-10.0% W, 0.5-5.0% V, 10.0-35.0% Co, 0-5.0% Ni, 0-2.0% S, with the balance consisting of Fe and unavoidable impurities.

4. A method for manufacturing an iron-based sintered alloy valve seat, which is the method for manufacturing a double-layer iron-based sintered alloy valve seat as described in claim 2, characterized in that: A mixture of specified amounts of iron-based powder, graphite powder, alloy element powder, hard particle powder, and possibly solid lubricant powder is blended and kneaded to produce a mixed powder for the side layer of functional components. A mixture of iron-based powder, graphite powder, or alloying element powder, hard particle powder, and solid lubricant powder is blended and kneaded to produce a mixed powder for the side layer of the support component. The mixed powder for the side layer of the aforementioned functional components and the mixed powder for the side layer of the aforementioned support components are sequentially filled into a mold of a specified shape, and then stamped to form a pressed powder body. Next, the pressed powder body is sintered in a protective environment to form a sintered body with a double-layer structure. Finally, it is machined or further ground to manufacture a valve seat with a specified double-layer structure. In the mixed powder for the side layer of the aforementioned functional component, the iron-based powder is configured as follows: it contains, by mass %, 0.05-0.70% C, less than 0.70% Si, less than 0.50% Mn, less than 4.5% Cr, less than 10.0% Mo, less than 4.5% V, less than 10.0% W, with the balance being Fe and unavoidable impurities, and has a particle hardness of 170-220 HV using a Vickers hardness tester. This iron-based powder is blended at 40-70% by mass % relative to the total mass of the mixed powder for the side layer of the aforementioned functional component. The aforementioned hard particle powder is configured as follows: Si-Cr-Mo based Co-based intermetallic compound particle powder, having a Vickers hardness of 650–1200 HV, comprising 2.20–2.70% Si, 7.5–9.5% Cr, and 27.0–30.0% Mo by mass, with the balance being Co and unavoidable impurities; or Si-Cr-Mo-Ni based Co-based intermetallic compound particles, having a Vickers hardness of 650–1200 HV, comprising 1.5–2.5% Si, 24.0–26.0% Cr, 23.0–26.0% Mo, and 9.5–11.0% Ni by mass, with the balance being Co. 20–40% of this hard particle powder is incorporated relative to the total mass percentage of the mixed powder used in the side layer of the aforementioned functional component. The graphite powder is mixed in at 0.5 to 2.0% by mass relative to the total mass of the mixed powder used in the side layer of the above-mentioned functional components. The total amount of the above-mentioned alloying element powder, calculated as 0% to 5.0% by mass relative to the total amount of the mixed powder used in the side layer of the above-mentioned functional components, is incorporated. The above-mentioned solid lubricant powder is also mixed in at 0-5% by mass relative to the total mass percentage of the mixed powder for the side layer of the functional component. In the mixed powder for the side layer of the support component, the iron-based powder is pure iron powder, 0.5-2.0% of the above-mentioned graphite powder is mixed in at 0.5-2.0% by mass relative to the total mass percentage of the mixed powder for the side layer of the support component, and a total of 0-5.0% of the above-mentioned alloying element powder is mixed in at 0%-5% by mass relative to the total mass percentage of the mixed powder for the side layer of the support component. The hard particle powder is Fe-Mo alloy powder, and 0-5% of this hard particle powder is mixed in at 0%-5% by mass relative to the total mass percentage of the mixed powder for the side layer of the support component, and 0-5% of the above-mentioned solid lubricant powder is mixed in at 0%-5% by mass relative to the total mass percentage of the mixed powder for the side layer of the support component. The above-mentioned stamping process is performed to make the density of the pressed powder 6.6 g / cm³. 3 The above densities, The above sintering treatment was carried out at a sintering temperature of 1100–1200℃. The above sintered body is made into a sintered body with a double-layer structure, wherein, The aforementioned functional component side layer comprises: a matrix phase consisting of fine carbide precipitates with a particle size of 10 μm or less, precipitated at a density of 150 particles / (30 μm × 30 μm) or more, and having a hardness of 550 HV or more on a Vickers hardness tester; a matrix phase in which 20-40% hard particles are dispersed by area ratio and 0-5% solid lubricant particles are also dispersed by area ratio; and a structure comprising the aforementioned matrix phase, the aforementioned hard particles, and the aforementioned... The matrix portion of the solid lubricant particles contains, by mass%, 1.0–2.0% C, 0.5–1.5% Si, less than 2.0% Mn, 2.0–10.0% Cr, 5.0–15.0% Mo, 2.0–10.0% W, 0.5–5.0% V, 10.0–35.0% Co, 0–5.0% Ni, 0–2.0% S, and the balance being Fe and unavoidable impurities. The aforementioned support member side layer comprises: a matrix phase composed of pearlite; a structure formed by dispersing 0 to 5% hard particles and 0 to 5% solid lubricant particles in the matrix phase by area; and a composition comprising 0.9 to 2.0% C by mass in the matrix portion containing the matrix phase, the hard particles and the solid lubricant particles, or further comprising one or more of Ni (less than 0.5%), Mo (less than 0.8%), Cu (less than 5.0%), Mn (less than 5.0%), and S (less than 2.0%), with the balance being Fe and unavoidable impurities.

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