Valve seat made of iron-based sintered alloy and its manufacturing method

Abstract

To provide an iron-based sintered alloy valve seat excellent in radial crushing strength.SOLUTION: A functional member-side layer and a support member-side layer are integrally sintered to form a sintered body having a two-layer structure. A mixed powder for the functional member-side layer and a mixed powder for the supporting member-side layer are charged in this order in a mold, pressed to form a compact, and the compact is sintered to form a two-layer structured iron-based sintered alloy valve seat. In the mixed powder for the functional member-side layer, an iron-based powder having a hardness of 170 to 220 HV is used as an iron-based powder for forming a base phase, and the base phase is composed of 150 particles / (30 μm×30 μm) or more of fine carbides with a particle size of 10 μm or less having a Vickers hardness of 550 HV or more, in the base phase, Si-Cr-Mo based Co-based intermetallic compound particles or Si-Cr-Mo-Ni based Co-based intermetallic compound particles having a Vickers hardness of 650 to 1200HV are dispersed in an area ratio of 20 to 40%, and solid lubricant particles are dispersed in an area ratio of 0 to 5%. As a result, a valve seat can have superior radial crushing strength and superior wear resistance. It should be noted that a single-layer structure may be employed in which only the layer on the functional member-side is used.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a valve seat for an internal combustion engine and a manufacturing method thereof, and particularly to an improvement in radial crushing strength. [Background technology]

[0002] Valve seats are typically press-fit into the cylinder head of an internal combustion engine, sealing against combustion gases and cooling the valves. Valve seats are subject to various types of damage, including being struck by the valve, wear due to sliding, heating by combustion gases, and corrosion by combustion products, and therefore have traditionally been required to have excellent heat resistance and wear resistance.

[0003] In response to such demands, for example, Patent Document 1 describes a "valve seat made of an iron-based sintered alloy for an internal combustion engine with excellent wear resistance." The technology described in Patent Document 1 describes a valve seat made of an iron-based sintered alloy with a structure in which the base phase is a hard single-phase structure in which fine carbides of 10 μm or less are precipitated and have a hardness of 550 HV or more. Hard particles with a hardness of 650 to 1200 HV are dispersed in the base phase at an area ratio of 20 to 40%, and a diffusion phase is formed around the hard particles at an area ratio of 0.5 to 5%. Alternatively, solid lubricant particles are dispersed at an area ratio of 5% or less. This results in a valve seat with excellent wear resistance, even when a valve with a high face hardness is used in an internal combustion engine using special fuels such as gas fuel, which is a severe wear environment. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6736227 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the iron-based sintered alloy valve seat described in Patent Document 1 has problems such as low radial crushing strength, which makes it prone to cracking when press-fitted into a cylinder head, and particles easily falling off when it comes into contact with the valve, which reduces wear resistance, etc. Also, the valve seat has a low Young's modulus, which makes it prone to deformation, which reduces sealing performance and causes combustion gas leakage.

[0006] The present invention aims to solve the problems of the prior art and to provide a valve seat made of an iron-based sintered alloy that has excellent radial crushing strength. Note that "excellent radial crushing strength" here refers to a radial crushing strength of 470 MPa or more obtained in accordance with the provisions of JIS Z 2507. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the present inventors have conducted extensive research into various factors that affect radial crushing strength. As a result, they have discovered that low "radial crushing strength" is caused by the low compressibility of the iron-based powder used. In the technology described in Patent Document 1, an iron-based powder capable of precipitating fine carbides is used as the iron-based powder, but the carbides are already precipitated in the powder, increasing the hardness of the powder particles, which leads to insufficient plastic deformation (compression) of the powder particles during compaction. This makes it difficult to promote element diffusion during sintering, resulting in a decrease in interparticle bonding strength.

[0008] Therefore, in the present invention, we have conceived the idea of ​​using an iron-based powder with a low carbon content as the iron-based powder for forming the matrix phase, so that sufficient compaction can be achieved during compaction and sufficient plastic deformation can be imparted to the powder particles. However, if the carbon content of the iron-based powder is reduced too much, the amount of carbide decreases and the wear resistance of the sintered body decreases. Therefore, we decided to increase the amount of graphite powder blended so as not to reduce the carbon content of the sintered body. We have found that this significantly increases the amount of fine carbide precipitated in the sintered body compared to conventional methods, significantly improving the wear resistance and radial crushing strength.

[0009] The present invention was completed based on these findings and further investigations. That is, the gist of the present invention is as follows. [1] A valve seat made of an iron-based sintered alloy having a single-layer structure consisting of a functional component side layer, the functional component-side layer is formed by dispersing hard particles and solid lubricant particles in a matrix phase, the matrix phase is a fine carbide precipitate phase in which fine carbides having a particle size of 10 μm or less are precipitated at a density of 150 particles / (30 μm×30 μm) or more and have a Vickers hardness of 550 HV or more, the hard particles are Si-Cr-Mo-based Co-based intermetallic compound particles having a Vickers hardness of 650 to 1200 HV and consisting of, by mass, 2.20 to 2.70% Si, 7.5 to 9.5% Cr, and 27.0 to 30.0% Mo, 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 to 1200 HV and consisting, by mass, of 1.5 to 2.5% Si, 24.0 to 26.0% Cr, 23.0 to 26.0% Mo, and 9.5 to 11.0% Ni, with the balance being Co, and are dispersed in the matrix phase at an area ratio of 20 to 40%, and further The solid lubricant particles have a dispersed structure of 0 to 5% by area, Density is 6.65g / cm 3 The above provides an iron-based sintered alloy valve seat characterized by excellent radial crushing strength. [2] The iron-based sintered alloy valve seat according to [1], characterized in that the matrix portion including the matrix phase, the hard particles, and the solid lubricant particles has a composition, in mass%, of C: 1.0 to 2.0%, Si: 0.5 to 1.5%, Mn: less than 2.0%, Cr: 2.0 to 10.0%, Mo: 5.0 to 15.0%, W: 0.5 to 10.0%, V: 0.5 to 5.0%, Co: 10.0 to 35.0%, Ni: 0 to 5.0%, S: 0 to 2.0%, with the remainder being Fe and unavoidable impurities. [3] A valve seat made of an iron-based sintered alloy having a two-layer structure in which a functional member-side layer and a support member-side layer are sintered together, The functional component side layer comprises a matrix phase and hard particles and solid lubricant particles dispersed in the matrix phase, the matrix phase being a fine carbide precipitate phase in which fine carbides having a particle size of 10 μm or less are precipitated at a density of 150 particles / (30 μm×30 μm) or more and having a Vickers hardness of 550 HV or more, the hard particles having a Vickers hardness of 650 to 1200 HV, and containing, by mass%, Si: 2.20 to 2.70%, Cr: 7.5 to 9.5%, Mo: 27.0 to 30.0%, and the balance a powder of Si-Cr-Mo-based Co-based intermetallic compound particles comprising Co and inevitable impurities, or Si-Cr-Mo-Ni-based Co-based intermetallic compound particles having a Vickers hardness of 650 to 1200 HV and consisting of, by mass%, 1.5 to 2.5% Si, 24.0 to 26.0% Cr, 23.0 to 26.0% Mo, 9.5 to 11.0% Ni, and the balance Co, the powder having a structure in which the solid lubricant particles are dispersed in the matrix phase at an area ratio of 20 to 40% and the solid lubricant particles are further dispersed at an area ratio of 0 to 5%, the support member side layer has a structure in which a matrix phase made of pearlite and hard particles and solid lubricant particles are dispersed in the matrix phase at an area ratio of 0 to 5% and 0 to 5%, respectively; Density is 6.65g / cm 3 The above provides an iron-based sintered alloy valve seat characterized by excellent radial crushing strength. [4] The matrix portion including the matrix phase, the hard particles, and the solid lubricant particles in the functional component-side layer has a composition, by mass%, of C: 1.0 to 2.0%, Si: 0.5 to 1.5%, Mn: less than 2.0%, Cr: 2.0 to 10.0%, Mo: 5.0 to 15.0%, W: 0.5 to 10.0%, V: 0.5 to 5.0%, Co: 10.0 to 35.0%, Ni: 0 to 5.0%, S: 0 to 2.0%, with the remainder being Fe and unavoidable impurities; The iron-based sintered alloy valve seat according to [3], characterized in that the matrix portion in the support member side layer, which includes the matrix phase, the hard particles, and the solid lubricant particles, contains, in mass %, C: 0.9 to 2.0%, or further contains one or more selected from Ni: 0.5% or less, Mo: 0.8% or less, Cu: 5.0% or less, Mn: 5.0% or less, and S: 2.0% or less, with the remainder being Fe and unavoidable impurities. [5] A method for manufacturing a valve seat made of a single-layer iron-based sintered alloy according to [1] or [2], Predetermined amounts of iron-based powder, graphite powder, alloying element powder, hard particle powder, and / or solid lubricant powder are blended, mixed, and kneaded to obtain a mixed powder, and then The mixed powder is filled into a mold of a predetermined shape and pressed to form a green compact, and then The green compact is sintered in a protective atmosphere to form a sintered body, and then the sintered body is subjected to cutting or further grinding to manufacture a valve seat having a predetermined shape. The iron-based powder has a composition containing, by mass%, C: 0.05 to 0.70%, Si: 0.70% or less, Mn: 0.50% or less, Cr: 4.5% or less, Mo: 10.0% or less, V: 4.5% or less, W: 10.0% or less, with the remainder being Fe and unavoidable impurities, and has a particle hardness of 170 to 220 HV in Vickers hardness, and the iron-based powder is blended in an amount of 40 to 70% by mass with respect to the total amount of the mixed powder, the hard particle powder is Si-Cr-Mo-based Co-based intermetallic compound particles having a Vickers hardness of 650 to 1200 HV and consisting of, by mass, 2.20 to 2.70% Si, 7.5 to 9.5% Cr, and 27.0 to 30.0% Mo, 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 to 1200 HV and consisting, by mass, of 1.5 to 2.5% Si, 24.0 to 26.0% Cr, 23.0 to 26.0% Mo, and 9.5 to 11.0% Ni, with the balance being Co; and the hard particle powder is blended in an amount of 20 to 40% by mass with respect to the total amount of the mixed powder; The graphite powder is blended in an amount of 0.5 to 2.0% by mass relative to the total amount of the mixed powder, The alloy element powder is blended in a total amount of 0 to 5.0% by mass relative to the total amount of the mixed powder, and further The solid lubricant powder is blended in an amount of 0 to 5% by mass relative to the total amount of the mixed powder, The density of the powder compact obtained by the press processing is 6.6 g / cm 3 The above will be implemented. The method for producing an iron-based sintered alloy valve seat is characterized in that the sintering treatment is carried out at a sintering temperature of 1100 to 1200°C to obtain the sintered body. [6] The sintered body has a structure in which hard particles are dispersed in an area ratio of 20 to 40% in a matrix phase, which is a fine carbide precipitate phase having a particle size of 10 μm or less, precipitated at a density of 150 particles / (30 μm×30 μm) or more and having a Vickers hardness of 550 HV or more, and further in which solid lubricant particles are dispersed in an area ratio of 0 to 5%, and the matrix portion includes the matrix phase, the diffusion phase, the hard particles, and the solid lubricant particles, [5] A method for producing a valve seat made of an iron-based sintered alloy according to [5], characterized in that the alloy has a composition containing, in mass %, C: 1.0 to 2.0%, Si: 0.5 to 1.5%, Mn: less than 2.0%, Cr: 2.0 to 10.0%, Mo: 5.0 to 15.0%, W: 0.5 to 10.0%, V: 0.5 to 5.0%, Co: 10.0 to 35.0%, Ni: 0 to 5.0%, S: 0 to 2.0%, with the remainder being Fe and unavoidable impurities. [7] A method for manufacturing a valve seat made of a two-layered iron-based sintered alloy according to [3] or [4], Predetermined amounts of iron-based powder, graphite powder, alloying element powder, hard particle powder, and / or solid lubricant powder are blended, mixed, and kneaded to obtain a mixed powder for a functional component-side layer; Predetermined amounts of iron-based powder, graphite powder, or alloy element powder, hard particle powder, and solid lubricant powder are blended, mixed, and kneaded to obtain a mixed powder for a support member side layer; The mixed powder for the functional component side layer and the mixed powder for the support component side layer are filled in this order into a mold of a predetermined shape, and pressed to form a green compact. The green compact is then sintered in a protective atmosphere to form a two-layered sintered body, which is then subjected to cutting or further grinding to produce a two-layered valve seat of a predetermined shape. The mixed powder for the functional component side layer contains, by mass%, C: 0.05 to 0.70%, Si: 0.70% or less, Mn: 0.50% or less, Cr: 4.5% or less, Mo: 10.0% or less, V: 4.5% or less, W: 10.0% or less, with the remainder being Fe and unavoidable impurities, and has a particle hardness of 170 to 220 HV in Vickers hardness, and the iron-based powder is blended in an amount of 40 to 70% by mass with respect to the total amount of the mixed powder, the hard particle powder is Si-Cr-Mo-based Co-based intermetallic compound particles having a Vickers hardness of 650 to 1200 HV and consisting of, by mass, 2.20 to 2.70% Si, 7.5 to 9.5% Cr, and 27.0 to 30.0% Mo, 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 to 1200 HV and consisting, by mass, of 1.5 to 2.5% Si, 24.0 to 26.0% Cr, 23.0 to 26.0% Mo, and 9.5 to 11.0% Ni, with the balance being Co; and the hard particle powder is blended in an amount of 20 to 40% by mass with respect to the total amount of the mixed powder; The graphite powder is blended in an amount of 0.5 to 2.0% by mass relative to the total amount of the mixed powder for the functional component side layer, The alloy element powder is blended in a total amount of 0 to 5.0% by mass relative to the total amount of the mixed powder, and further The solid lubricant powder is blended in an amount of 0 to 5% by mass relative to the total amount of the mixed powder, The density of the powder compact obtained by the press processing is 6.6 g / cm 3 The above will be implemented. In the mixed powder for the support member side layer, the iron-based powder is pure iron powder, the graphite powder is blended in an amount of 0.5 to 2.0% by mass relative to the total amount of the mixed powder for the support member side layer, the alloy element powder is blended in a total amount of 0 to 5.0% by mass relative to the total amount of the mixed powder for the support member side layer, the hard particle powder is Fe-Mo alloy powder, the hard particle powder is blended in an amount of 0 to 5% by mass relative to the total amount of the mixed powder for the support member side layer, and the solid lubricant powder is blended in an amount of 0 to 5% by mass relative to the total amount of the mixed powder for the support member side layer, The density of the powder compact obtained by the press processing is 6.6 g / cm 3The above will be implemented. The sintering process is carried out at a sintering temperature of 1100 to 1200°C, A method for manufacturing an iron-based sintered alloy valve seat, characterized in that the sintered body is a two-layer structure sintered body. [8] The two-layered sintered body is characterized in that the functional component side layer comprises a matrix phase in which fine carbides of 10 μm or less are precipitated at a density of 150 particles / (30 μm×30 μm) or more and have a Vickers hardness of 550 HV or more, and hard particles are dispersed in the matrix phase at an area ratio of 20 to 40% and solid lubricant particles are dispersed at an area ratio of 0 to 5%. a matrix containing the solid lubricant particles and the solid lubricant particles, the matrix having a composition, in mass %, of C: 1.0 to 2.0%, Si: 0.5 to 1.5%, Mn: less than 2.0%, Cr: 2.0 to 10.0%, Mo: 5.0 to 15.0%, W: 0.5 to 10.0%, V: 0.5 to 5.0%, Co: 10.0 to 35.0%, Ni: 0 to 5.0%, S: 0 to 2.0%, with the balance being Fe and unavoidable impurities; The method for manufacturing a valve seat made of an iron-based sintered alloy according to [7], characterized in that the support member side layer is a sintered body with a two-layer structure, which has a matrix phase made of pearlite, a structure in which hard particles are dispersed in the matrix phase at an area ratio of 0 to 5%, and solid lubricant particles are dispersed in the matrix phase at an area ratio of 0 to 5%, and a composition in which the matrix portion containing the matrix phase, the hard particles, and the solid lubricant particles contains, by mass%, C: 0.9 to 2.0%, or further contains one or more selected from Ni: 0.5% or less, Mo: 0.8% or less, Cu: 5.0% or less, Mn: 5.0% or less, and S: 2.0% or less, with the remainder being Fe and unavoidable impurities. [Effects of the Invention]

[0010] According to the present invention, it is possible to manufacture a valve seat made of an iron-based sintered alloy that is excellent in wear resistance and radial crushing strength, and this brings about significant industrial effects. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is an explanatory diagram showing an overview of a rig testing machine. DETAILED DESCRIPTION OF THE INVENTION

[0012] The valve seat of the present invention is either a valve seat made of an iron-based sintered alloy with a single-layer structure consisting of only a functional component-side layer, or a valve seat made of an iron-based sintered alloy with a two-layer structure in which a functional component-side layer and a support component-side layer are sintered together.

[0013] First, the functional component side layer will be described.

[0014] The functional component side layer has a structure in which a matrix phase and hard particles and solid lubricant particles are dispersed in the matrix phase.

[0015] The matrix phase is a single phase consisting of a fine carbide precipitate phase in which fine carbides with a particle size of 10 μm or less are precipitated at a density of 150 particles / (30 μm × 30 μm) or more and have a Vickers hardness of 550 HV or more. Here, "single phase" refers to a case in which the phase occupies 95% or more in area ratio. Note that even if a phase with a hardness of less than 550 HV remains in the matrix phase, as long as the area ratio is less than 5%, the impact on wear resistance is minimal and acceptable. If the matrix phase hardness is less than 550 HV, adhesion is likely to occur upon contact with the valve, reducing wear resistance. On the other hand, if the hardness exceeds 700 HV, the toughness of the sintered body decreases. Therefore, the Vickers hardness of the matrix phase is set to 550 HV or more, preferably 700 HV or less. Note that a Vickers hardness of 560 to 660 HV is preferred.

[0016] If the particle size of the carbides precipitated in the matrix phase exceeds 10 μm, the hardness and toughness of the matrix phase decrease, the aggressiveness to mating members increases, and the radial crushing strength decreases. In the present invention, carbides are precipitated in the matrix phase at a density of 150 particles / (30 μm×30 μm) or more. If the precipitation density is less than 150 particles / (30 μm×30 μm), the precipitation density is too low to ensure the desired radial crushing strength and wear resistance. For this reason, the matrix phase is a fine carbide precipitate phase in which fine carbides with a particle size of 10 μm or less are precipitated at a density of 150 particles / (30 μm×30 μm) or more, and which has a Vickers hardness of 550 HV or more.

[0017] The matrix phase having the above-described hardness and structure preferably contains, by mass%, C: 0.05 to 0.70%, Si: 0.70% or less, Mn: 0.50% or less, Cr: 4.5% or less, Mo: 10.0% or less, V: 4.5% or less, and W: 10.0% or less, or may further contain Co: 5.0% or less, with the balance being Fe and unavoidable impurities.

[0018] The functional component-side layer of the valve seat of the present invention has a structure in which hard particles, or further solid lubricant particles, are dispersed in a matrix phase having the above-mentioned hardness, structure, and composition. The dispersed hard particles have a Vickers hardness of 650 to 1200 HV. If the hardness of the hard particles is less than 650 HV, the effect of improving wear resistance is small. On the other hand, if the hardness exceeds 1200 HV, machinability is reduced. For this reason, the hardness of the hard particles dispersed in the matrix phase is limited to a range of 650 to 1200 HV Vickers hardness.

[0019] The hard particles dispersed in the matrix phase preferably have an average particle size of 10 to 150 μm. If the average particle size is less than 10 μm, they tend to diffuse during sintering, making it impossible to ensure the desired effect of improving wear resistance. On the other hand, if the particle size exceeds 150 μm, the bonding strength with the matrix decreases. For this reason, the average particle size of the hard particles dispersed in the matrix phase is preferably 10 to 150 μm. Here, "average particle size" refers to the particle size D50 at which the cumulative distribution measured by laser scattering method becomes 50%.

[0020] In the functional component-side layer of the valve seat of the present invention, the hard particles having the above-mentioned hardness are dispersed in the matrix phase at an area ratio of 20 to 40%. If the amount of dispersed hard particles is less than 20%, the desired wear resistance cannot be ensured. On the other hand, if it exceeds 40%, the bonding strength between the matrix phase and the hard particles decreases, resulting in a decrease in wear resistance.

[0021] The hard particle powder used in the functional component-side layer of the valve seat of the present invention is preferably a Si-Cr-Mo-based Co-based intermetallic compound powder or a Si-Cr-Mo-Ni-based Co-based intermetallic compound powder. The Si-Cr-Mo-based Co-based intermetallic compound powder has a composition, by mass%, of 2.20-2.70% Si, 7.5-9.5% Cr, and 27.0-30.0% Mo, with the balance being Co and unavoidable impurities, and has a Vickers hardness of 650-1200 HV. The Si-Cr-Mo-Ni-based Co-based intermetallic compound has a composition, by mass%, of 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, and has a Vickers hardness of 650-1200 HV.

[0022] In the functional component-side layer of the valve seat of the present invention, a diffusion phase may be formed around the hard particles, but the amount is small, at most about 0.5% in area ratio. This diffusion phase is formed when alloy elements diffuse 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 carbides are stabilized, so the amount of diffusion phase formed is small.

[0023] In the functional component-side layer of the valve seat of the present invention, solid lubricant particles may be dispersed in the matrix phase at an area ratio of 0 to 5%. Dispersing solid lubricant particles in the matrix phase improves machinability, processability, and lubrication. However, if the dispersion exceeds 5%, it hinders the progress of the sintering reaction, resulting in a decrease in mechanical properties. For this reason, the area ratio of the solid lubricant particles is limited to the range of 0 to 5%. Examples of solid lubricants include manganese sulfide (MnS) and molybdenum disulfide (MoS2).

[0024] In the functional component side layer of the valve seat of the present invention, the matrix portion including the matrix phase, hard particles, and solid lubricant particles has a composition, by mass%, of C: 1.0 to 2.0%, Si: 0.5 to 1.5%, Mn: less than 2.0%, Cr: 2.0 to 10.0%, Mo: 5.0 to 15.0%, W: 0.5 to 10.0%, V: 0.5 to 5.0%, Co: 10.0 to 35.0%, Ni: 0 to 5.0%, S: 0 to 2.0%, with the remainder being Fe and unavoidable impurities.

[0025] The reasons for limiting the composition of the matrix in the functional component side layer will be explained below, where % by mass in the composition will be simply expressed as %.

[0026] C: 1.0 to 2.0% C is an element necessary for adjusting the matrix phase to a predetermined hardness and structure and for forming predetermined fine carbides, and is contained in an amount of 1.0% or more. On the other hand, if the C content exceeds 2.0%, liquid phase sintering occurs during sintering, the amount of precipitated carbides becomes excessive, the number of voids increases, and dimensional accuracy decreases. For this reason, C is preferably limited to the range of 1.0 to 2.0%, and more preferably 1.0 to 1.5%.

[0027] Si: 0.5 to 1.5% Si is an element that increases hardness, and a content of 0.5% or more is preferable. On the other hand, a content of more than 1.5% leads to a decrease in toughness. Therefore, the Si content is preferably limited to the range of 0.5 to 1.5%, and more preferably 0.5 to 1.3%.

[0028] Mn: Less than 2.0% Mn is an element that increases the hardness of the matrix phase. Furthermore, Mn is included in the matrix due to the inclusion of solid lubricant particles, contributing to improved machinability. This effect is significant at a content of 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, it is preferable to limit the Mn content to less than 2.0%. A more preferable range is 0.05 to 1.5%.

[0029] Cr: 2.0 to 10.0% Cr is an element that dissolves in the matrix phase and forms carbides to increase the hardness of the matrix phase and further increase the hardness of the hard particles, improving heat resistance and wear resistance. It is preferable to include 2.0% or more of 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 too high. Therefore, the Cr content is preferably limited to the range of 2.0 to 10.0%. It is more preferably 4.0 to 6.0%.

[0030] Mo: 5.0 to 15.0% Mo is an element that dissolves in the matrix phase and forms fine carbides to increase the hardness of the matrix phase, thereby contributing to improved wear resistance. It also increases the hardness of the hard particles. This effect is significant at a content of 5.0% or more, but if it exceeds 15.0%, formability decreases. For this reason, Mo is preferably limited to 5.0 to 15.0%, and more preferably 10.0 to 14.0%.

[0031] W: 0.5 to 10.0% W is an element that forms fine carbides, increases the hardness of the matrix phase, and improves wear resistance. This effect is significant when the content is 0.5% or more, but when the content exceeds 10.0%, formability decreases. For this reason, it is preferable to limit W to 0.5 to 10.0%, and more preferably 2.0 to 5.0%.

[0032] V: 0.5 to 5.0% V is an element that forms fine carbides, increases the hardness of the matrix phase, and improves wear resistance. This effect is significant when the content is 0.5% or more, but when the content exceeds 5.0%, formability decreases. For this reason, it is preferable to limit the V content to the range of 0.5 to 5.0%, and more preferably 0.5 to 2.0%.

[0033] Co: 10.0 to 35.0% Co is an element that increases the strength of the matrix phase, particularly its high-temperature strength, and improves its wear resistance. It also improves the toughness of the matrix phase and increases the hardness of the hard particles. These effects become significant when the Co content is 10.0% or more. On the other hand, a Co content exceeding 35.0% reduces the hardness of the matrix phase. For this reason, the Co content is preferably limited to the range of 10.0 to 35.0%. More preferably, it is 10.0 to 25.0% or less.

[0034] Ni: 0 to 5.0% Ni is an element that contributes to improving the hardness and toughness of the matrix phase and also contributes to increasing the hardness of the hard particles, and can be contained as needed. When Ni is contained, it is preferably 0.3% or more, but if it is contained in excess of 5.0%, it will cause a decrease in the formability of the matrix phase. Therefore, when Ni is contained, it is preferably limited to 5.0% or less, and more preferably 1.0% or less.

[0035] S: 0-2.0% S is an element contained in the matrix due to the inclusion of solid lubricant particles and contributes to improving machinability, and can be contained as needed. However, if the S content exceeds 2.0%, it will lead to a decrease in toughness and ductility. Therefore, if S is contained, it is preferable to limit the S content to 2.0% or less.

[0036] The balance other than the above components consists of Fe and unavoidable impurities. As unavoidable impurities, P: 0.03% or less is allowable.

[0037] Next, the support member side layer in the case where the valve seat of the present invention has a two-layer structure will be described. Note that the functional member side layer in the two-layer structure is the same as the functional member side layer in the case of the single-layer structure described above.

[0038] The matrix phase of the support member side layer of the valve seat of the present invention has a structure mainly composed of pearlite, and the support member side layer has a matrix phase with the above-mentioned structure and a structure in which hard particles are dispersed in an area ratio of 0 to 5% and solid lubricant particles are dispersed in an area ratio of 0 to 5% in the matrix phase.

[0039] Solid lubricant particles for improving machinability may be dispersed in the matrix phase of the support member-side layer as needed. Examples of solid lubricant particles include MnS and MoS2. When dispersed, the solid lubricant particles are preferably at an area ratio of 0.3% or more. If the area ratio is less than 0.3%, it is difficult to achieve the objective of improving machinability. On the other hand, if the area ratio exceeds 5%, the effect saturates and it is no longer possible to expect an effect commensurate with the amount dispersed. Therefore, when dispersed, it is preferable to limit the solid lubricant particles to 5% or less.

[0040] Furthermore, hard particles may be dispersed in the matrix phase of the support member side layer at an area ratio of 0 to 5% to increase the strength of the matrix phase. Ferro-molybdenum (Fe-Mo) alloys are an example of hard particles dispersed in the support member side layer. Dispersing the hard particles at an area ratio of more than 5% saturates the effect, so 5% is set as the upper limit.

[0041] Furthermore, the support member side layer of the valve seat of the present invention has a composition in which the matrix portion including the matrix phase, hard particles, and solid lubricant particles contains, by mass%, 0.9 to 2.0% C, or further contains one or more elements 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 remainder being Fe and unavoidable impurities.

[0042] C, Ni, Mo, and Cu are elements that increase the matrix strength (hardness) of the support member-side layer. C is contained in an amount of 0.9% or more to ensure the desired strength. On the other hand, if the C content exceeds 2.0%, the strength becomes too high and the toughness decreases. For this reason, the C content is limited to a range of 0.9 to 2.0%. Ni, Mo, and Cu are contained according to the desired strength, but if the Ni, Mo, and Cu content exceeds 0.5%, 0.8%, and 5.0%, the strength becomes too high. Therefore, it is preferable to limit the Ni content to 0.5% or less, Mo content to 0.8% or less, and Cu content to 5.0% or less. Furthermore, some of Mn, S, and Mo are contained due to the dispersion of solid lubricant particles, but even if the solid lubricant particles are dispersed in large amounts, the effect saturates. For this reason, the Mn content is limited to 5.0% or less and the S content to 2.0% or less.

[0043] Next, a method for manufacturing a valve seat made of an iron-based sintered alloy according to the present invention will be explained.

[0044] In the manufacturing method of the single-layer structured iron-based sintered alloy valve seat of the present invention, first, iron-based powder, graphite powder, alloying element powder, hard particle powder, and / or solid lubricant powder are blended in predetermined amounts so as to obtain the above-mentioned matrix composition, and then mixed and kneaded to obtain a mixed powder (mixed powder for functional component-side layer).

[0045] The iron-based powder to be blended in the mixed powder (mixed powder for the functional component-side layer) is a powder blended to form a matrix phase, and in the present invention, an alloy steel powder capable of forming a fine carbide precipitate phase as the matrix phase is used. Examples of such alloy steel powder include, but are not limited to, powders having a composition conforming to the high-speed tool steel composition specified in JIS G 4403.

[0046] The iron-based powder to be blended contains, by mass%, C: 0.05 to 0.70%, Si: 0.70% or less, Mn: 0.50% or less, Cr: 4.5% or less, Mo: 10.0% or less, V: 4.5% or less, W: 10.0% or less, with the remainder being Fe and unavoidable impurities, and has a particle hardness of 170 to 220 HV in Vickers hardness. The reasons for limiting the composition of the iron-based powder will be explained below. Hereinafter, mass% in the composition will be simply referred to as %.

[0047] The reasons for limiting the composition of the iron-based powder to be blended will be explained below.

[0048] C: 0.05 to 0.70% The iron-based powder blended in the present invention is a powder with a high-speed steel composition with reduced C. If the C content is less than 0.05%, no further reduction in the hardness of the powder particles is observed. On the other hand, if the C content exceeds 0.70%, the hardness of the powder particles becomes too high, resulting in a decrease in the compressibility of the powder particles. For this reason, the C content of the iron-based powder is preferably limited to the range of 0.05 to 0.70%, and more preferably 0.3 to 0.6%.

[0049] Si:0.70% or less Si is an element that acts as a deoxidizer, and this effect is most pronounced when the content is 0.05% or more. On the other hand, if the content exceeds 0.70%, compressibility decreases. Therefore, it is preferable to limit the Si content to 0.70% or less, and more preferably to 0.40% or less.

[0050] Mn: 0.50% or less Mn acts as a deoxidizer and contributes to increasing strength (hardness). This effect is significant when the content is 0.10% or more. On the other hand, when the content exceeds 0.50%, the hardness increases and the compressibility decreases. Therefore, it is preferable to limit the Mn content to 0.50% or less.

[0051] Cr:4.5% or less Cr is an element that forms carbides and has the effect of improving wear resistance. This effect is significant when the content is 2.0% or more, but if the content exceeds 4.5%, toughness decreases. For this reason, it is preferable to limit the Cr content to 4.5% or less.

[0052] Mo: 10.0% or less Mo is an element that forms fine carbides and has the effect of improving wear resistance. This effect is significant when the content is 3.0% or more, but if the content exceeds 10.0%, formability decreases. For this reason, it is preferable to limit Mo to 10.0% or less. Furthermore, it is more preferable to limit it to 4.0 to 6.0%.

[0053] V:4.5% or less V is an element that forms fine carbides and has the effect of improving wear resistance. This effect is significant when the V content is 1.5% or more, but when the V content exceeds 4.5%, formability decreases. For this reason, it is preferable to limit the V content to 4.5% or less.

[0054] W: 10.0% or less W is an element that forms fine carbides and has the effect of improving wear resistance. This effect is significant when the content is 5.0% or more, but when the content exceeds 10.0%, formability decreases. For this reason, it is preferable to limit the W content to 10.0% or less.

[0055] The remainder other than the above-mentioned components consists of Fe and unavoidable impurities. As unavoidable impurities, P: 0.03% or less and S: 0.02% or less are permissible. Since P segregates at austenite grain boundaries and promotes intergranular embrittlement, it is preferable to reduce it as much as possible. More preferably, it is 0.010% or less. Furthermore, S exists in the steel as sulfide-based inclusions and impairs hot workability, so it is desirable to reduce it as much as possible. More preferably, it is 0.005% or less.

[0056] Particle hardness: 170~220HV The iron-based powder used in the present invention has a particle hardness of 170 to 220 HV. If the particle hardness is less than 170 HV, the hardness of the iron-based powder is too low, resulting in a decrease in the wear resistance of the sintered body. On the other hand, if the particle hardness exceeds 220 HV, the compressibility decreases, resulting in a decrease in the radial crushing strength of the sintered body. For this reason, the particle hardness of the iron-based powder to be blended is limited to 170 to 220 HV.

[0057] The hard particle powder to be blended is preferably a Si-Cr-Mo-based Co-based intermetallic compound particle powder or a Si-Cr-Mo-Ni-based Co-based intermetallic compound particle powder having the above-mentioned hardness and composition. In the present invention, the hard particle powder having such hardness is blended in an amount of 20 to 40% by mass based on the total amount of the mixed powder.

[0058] The hard particle powder blended into the mixed powder preferably has the above-mentioned hardness and an average particle size of 10 to 150 μm. If the average particle size is less than 10 μm, the particles tend to diffuse during sintering, making it impossible to ensure the desired wear resistance. On the other hand, if it exceeds 150 μm, the bonding strength with the matrix decreases. For this reason, the average particle size of the hard particle powder is preferably 10 to 150 μm. The "average particle size" refers to the particle size D50 at which the cumulative distribution measured by the laser scattering method is 50%.

[0059] Furthermore, solid lubricant particles are dispersed in the matrix phase to improve machinability, processability, and lubricity. The solid lubricant particles are preferably MnS, MoS2, or the like. The amount of solid lubricant particles blended is preferably 0 to 5% by mass relative to the total amount of the mixed powder.

[0060] It goes without saying that the mixed powder contains the above-mentioned iron-based powder, hard particle powder, or solid lubricant powder in a predetermined amount, and further contains graphite powder and alloy element powder so as to have the above-mentioned matrix phase composition and matrix composition. The mixed powder may also contain a lubricant such as zinc stearate.

[0061] As described above, the iron-based powder is further blended with predetermined amounts of graphite powder, alloying element powder, hard particle powder, and / or solid lubricant powder, and then mixed and kneaded to form a mixed powder.

[0062] The resulting mixed powder is then filled into a mold having a predetermined valve seat shape.

[0063] After filling the mixed powder into a mold, it is pressed with a press machine or the like to form a green compact in the shape of a valve seat. Note that the pressing process is carried out so that the density of the green compact is 6.6 g / cm 3 It is preferable to adjust the temperature so that the temperature is equal to or higher than this.

[0064] The obtained green compact is then subjected to a sintering treatment to form a sintered body.

[0065] The sintering process is preferably carried out in a protective atmosphere at a heating temperature in the range of 1100 to 1200°C. If the heating temperature is less than 1100°C, sintering diffusion will be insufficient, while if it exceeds 1200°C, excessive diffusion will occur, resulting in reduced wear resistance. The pressing P-sintering S process may be repeated multiple times (e.g., 2P2S).

[0066] The obtained sintered body is subjected to processing such as grinding and cutting to form a valve seat of desired dimensions and shape.

[0067] Next, in the method of manufacturing the two-layered iron-based sintered alloy valve seat of the present invention, in addition to the mixed powder (mixed powder for the functional component-side layer) described above, a mixed powder for the support component-side layer is also prepared.

[0068] The powder mixture for the support member side layer is prepared by blending, mixing, and kneading predetermined amounts of iron-based powder, graphite powder, and / or alloying element powder, hard particle powder, and solid lubricant powder. The iron-based powder is pure iron powder, the graphite powder is blended in an amount of 0.5 to 2.0% by mass relative to the total amount of the powder mixture for the support member side layer, the alloying element powder is blended in an amount of 0 to 5.0% by mass relative to the total amount of the powder mixture for the support member side layer, the hard particle powder is ferro-molybdenum (Fe-Mo) alloy powder, and the solid lubricant powder is blended in an amount of 0 to 5% by mass relative to the total amount of the powder mixture for the support member side layer.

[0069] Then, the mixed powder for the functional component side layer and the mixed powder for the support component side layer are filled in this order and at a desired ratio into a mold of a predetermined shape.

[0070] After filling the mold, the mixture is pressed to form a green compact in the same manner as in the case of the single-layer structure described above, and then the green compact is sintered to obtain a sintered body with a two-layer structure in the same manner as in the case of the single-layer structure described above.

[0071] The obtained two-layered sintered body is subjected to processing such as grinding and cutting to form a two-layered valve seat having the desired dimensions and shape.

[0072] The present invention will be further described below with reference to examples. [Example]

[0073] First, a mixed powder for the functional member side layer and a mixed powder for the support member side layer were prepared.

[0074] The mixed powder for the functional component side layer was prepared by mixing and kneading an iron-based powder for forming the matrix phase with graphite powder, alloying element powder, hard particle powder, and solid lubricant powder (MnS powder) in the amounts shown in Table 1 to obtain mixed powders (No. A to No. K). The iron-based powder used was a high-speed tool steel-based powder (No. a to No. d) with the composition and hardness shown in Table 2. The hard particle powder used was a particle powder (No. h1 to No. h2) with the composition, hardness, and average particle size shown in Table 3.

[0075] The mixed powder for the support member side layer was prepared by mixing and kneading iron-based powder for forming the matrix phase, graphite powder, or alloying element powder, hard particle powder, and solid lubricant particle powder in the amounts shown in Table 1 to obtain mixed powders (No. 1A to No. 1B). The iron-based powder used was powder (No. e) with the composition and hardness shown in Table 2. Iron-based powder No. e is pure iron powder. The hard particle powder used was particle powder (No. h3) with the composition, hardness, and average particle size shown in Table 3. Hard particle powder No. h3 is a ferro-molybdenum alloy. The mixed powder contained 1 part by mass of zinc stearate per 100 parts by mass of the mixed powder as a lubricant. Some valve seats had a single-layer structure consisting of only the functional component side layer.

[0076] [Table 1]

[0077] [Table 2]

[0078] [Table 3]

[0079] The resulting mixed powder was filled into a mold and pressed into a green compact having a predetermined valve seat shape using a press machine. The density of the green compact was measured by the Archimedes method.

[0080] The obtained green compact was then subjected to a sintering treatment, in which the compact was charged into a sintering furnace in a protective atmosphere at a heating temperature of 1150°C (holding time: 6 hours) to produce a sintered compact.

[0081] The obtained sintered body was further subjected to processing such as cutting and polishing to obtain an iron-based sintered alloy valve seat of a predetermined shape (outer diameter: 27 mmΦ x inner diameter: 22 mmΦ x thickness: 6 mm).

[0082] The obtained valve seats were subjected to chemical analysis, structure observation, hardness test, density test, wear test, and radial crushing strength test. The test methods were as follows. (1)Chemical analysis Analytical samples were taken from each portion of the obtained valve seat, and the content of each component in each portion was analyzed by optical emission spectrometry to determine the composition of the sintered body matrix. (2) Microstructure observation The cross section of the obtained valve seat perpendicular to the axial direction was polished and etched (etchant: nital solution) to reveal the structure. The structure was observed under an optical microscope (magnification: 200x) to identify the type of matrix structure. Furthermore, using a scanning electron microscope (magnification: 2000x), the grain size of the carbides precipitated in the matrix was measured. When it was confirmed that the maximum carbide grain size was 10 μm or less, the matrix was deemed to be a fine carbide precipitate phase. When the maximum diameter of the carbide grain size (long side length) exceeded 10 μm, it was simply deemed to be a carbide precipitate phase. Furthermore, using a scanning electron microscope (magnification: 2000x), the number of carbides precipitated in the matrix within an observation field (30 μm × 30 μm) was counted, and the carbide precipitation density (number / (30 μm × 30 μm)) was calculated. (3) Hardness test The cross section of the obtained valve seat perpendicular to the axial direction was polished and etched (etching solution: nital solution) to reveal the structure, and the Vickers hardness HV of the matrix phase was measured using a Vickers hardness tester (test force: 0.98 N (100 gf)). (4) Density test The density (sintered body density) of the obtained valve seat was measured using the Archimedes method. (5) Abrasion test The obtained valve seats were subjected to a wear test using a rig tester shown in FIG. 1 under the following test conditions. Test temperature: 300°C (seat face) Test time: 12 hours Cam rotation speed: 3000 rpm Valve rotation speed: 20 rpm Impact load: 700N Valve material: Heat-resistant steel with nitride coating (SUH35 surface hardness 1150HV) After the test, the wear amount of the test piece (valve seat) was measured. From the measured wear amount, the wear ratio of the valve seat was calculated, with the valve seat No. 1 (conventional example) set as the reference (1.00). (6) Radial crushing strength test The radial crushing strength of the obtained valve seat was measured in accordance with the provisions of JIS Z 2507. From the measured radial crushing strength, the radial crushing strength ratio of the valve seat was calculated, with Valve Seat No. 1 (Conventional Example) set as the reference (1.00). The radial crushing strength of Valve Seat No. 1 (Conventional Example) was 470 MPa.

[0083] The results obtained are shown in Tables 4 and 5.

[0084] [Table 4]

[0085] [Table 5]

[0086] In all of the examples of the present invention, the carbide precipitation density in the matrix phase is significantly higher than in the conventional example (valve sheet No. 1), and the carbides are more finely dispersed than in the conventional example. As a result, all of the examples of the present invention have a higher sintered body density, a higher radial crushing strength ratio, improved radial crushing strength, a lower wear ratio, and improved wear resistance. [Explanation of symbols]

[0087] 1 Valve seat 2 Cylinder block equivalent material 3 Heating means 4 valves

Claims

1. A valve seat made of an iron-based sintered alloy having a single-layer structure consisting of a functional component-side layer, the functional component-side layer is formed by dispersing hard particles and solid lubricant particles in a matrix phase, the matrix phase is a fine carbide precipitate phase in which fine carbides having a particle size of 10 μm or less are precipitated at a density of 150 particles / (30 μm×30 μm) or more and have a Vickers hardness of 550 HV or more, the hard particles are Si-Cr-Mo-based Co-based intermetallic compound particles having a Vickers hardness of 650 to 1200 HV and consisting of, by mass, 2.20 to 2.70% Si, 7.5 to 9.5% Cr, and 27.0 to 30.0% Mo, 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 to 1200 HV and consisting, by mass, of 1.5 to 2.5% Si, 24.0 to 26.0% Cr, 23.0 to 26.0% Mo, and 9.5 to 11.0% Ni, with the balance being Co, and are dispersed in the matrix phase at an area ratio of 20 to 40%, and further The solid lubricant particles have a dispersed structure of 1.0 to 5% by area, Density is 6.65g / cm 3 The above provides an iron-based sintered alloy valve seat characterized by excellent radial crushing strength.

2. 2. The iron-based sintered alloy valve seat according to claim 1, wherein the matrix portion including the matrix phase, the hard particles, and the solid lubricant particles has a composition that contains, in mass %, C: 1.0 to 2.0%, Si: 0.5 to 1.5%, Mn: less than 2.0%, Cr: 2.0 to 10.0%, Mo: 5.0 to 15.0%, W: 0.5 to 10.0%, V: 0.5 to 5.0%, Co: 10.0 to 35.0%, Ni: 0 to 5.0%, S: 0 to 2.0%, with the remainder being Fe and unavoidable impurities.

3. A valve seat made of an iron-based sintered alloy having a two-layer structure in which a functional member-side layer and a support member-side layer are sintered together, the functional component side layer comprises a matrix phase and hard particles and solid lubricant particles dispersed in the matrix phase; the matrix phase is a fine carbide precipitate phase in which fine carbides having a particle size of 10 μm or less are precipitated at a density of 150 particles / (30 μm×30 μm) or more and have a Vickers hardness of 550 HV or more, the hard particles are Si-Cr-Mo-based Co-based intermetallic compound particles having a Vickers hardness of 650 to 1200 HV and consisting of, by mass, 2.20 to 2.70% Si, 7.5 to 9.5% Cr, and 27.0 to 30.0% Mo, 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 to 1200 HV and consisting, by mass, of 1.5 to 2.5% Si, 24.0 to 26.0% Cr, 23.0 to 26.0% Mo, and 9.5 to 11.0% Ni, with the balance being Co, and are dispersed in the matrix phase at an area ratio of 20 to 40%, and further The solid lubricant particles have a dispersed structure of 1.0 to 5% by area, the support member side layer has a structure in which a matrix phase made of pearlite and hard particles and solid lubricant particles are dispersed in the matrix phase at an area ratio of 0 to 5% and 0 to 5%, respectively; Density is 6.65g / cm 3 The above provides an iron-based sintered alloy valve seat characterized by excellent radial crushing strength.

4. the matrix portion including the matrix phase, the hard particles, and the solid lubricant particles in the functional component-side layer has a composition, in mass %, of C: 1.0 to 2.0%, Si: 0.5 to 1.5%, Mn: less than 2.0%, Cr: 2.0 to 10.0%, Mo: 5.0 to 15.0%, W: 0.5 to 10.0%, V: 0.5 to 5.0%, Co: 10.0 to 35.0%, Ni: 0 to 5.0%, S: 0 to 2.0%, with the balance being Fe and unavoidable impurities; 4. The iron-based sintered alloy valve seat according to claim 3, wherein the matrix portion in the support member-side layer, which includes the matrix phase, the hard particles, and the solid lubricant particles, contains, in mass %, C: 0.9 to 2.0%, or further contains one or more selected from Ni: 0.5% or less, Mo: 0.4 to 0.8%, Cu: 5.0% or less, Mn: 5.0% or less, and S: 2.0% or less, with the remainder being Fe and unavoidable impurities.

5. A method for manufacturing the single-layer structure iron-based sintered alloy valve seat according to claim 1 or 2, comprising the steps of: Predetermined amounts of iron-based powder, graphite powder, alloying element powder, hard particle powder, and solid lubricant powder are blended, mixed, and kneaded to obtain a mixed powder, and then The mixed powder is filled into a mold of a predetermined shape and pressed to form a green compact, and then The green compact is sintered in a protective atmosphere to form a sintered body, which is then subjected to cutting or further grinding to produce a valve seat having a predetermined shape. the iron-based powder contains, by mass%, C: 0.05 to 0.70%, Si: 0.70% or less, Mn: 0.50% or less, Cr: 4.5% or less, Mo: 10.0% or less, V: 4.5% or less, W: 10.0% or less, with the balance being Fe and unavoidable impurities, and has a particle hardness of 170 to 220 HV in Vickers hardness; the iron-based powder is blended in an amount of 40 to 70% by mass with respect to the total amount of the mixed powder; the hard particle powder is selected from Si-Cr-Mo system Co-based intermetallic compound particles having a Vickers hardness of 650 to 1200 HV and consisting of, by mass, 2.20 to 2.70% Si, 7.5 to 9.5% Cr, and 27.0 to 30.0% Mo, with the balance being Co and unavoidable impurities; or Si-Cr-Mo-Ni system Co-based intermetallic compound particles having a Vickers hardness of 650 to 1200 HV and consisting, by mass, of 1.5 to 2.5% Si, 24.0 to 26.0% Cr, 23.0 to 26.0% Mo, and 9.5 to 11.0% Ni, with the balance being Co; and the hard particle powder is blended in an amount of 20 to 40% by mass with respect to the total amount of the mixed powder; The graphite powder is blended in an amount of 0.5 to 2.0% by mass relative to the total amount of the mixed powder, The alloy element powder is blended in a total amount of 1.0 to 5.0% by mass relative to the total amount of the mixed powder, and further The solid lubricant powder is blended in an amount of 1.0 to 5% by mass relative to the total amount of the mixed powder, The density of the powder compact obtained by the press processing is 6.6 g / cm 3 The above will be implemented. The method for producing an iron-based sintered alloy valve seat is characterized in that the sintering treatment is carried out at a sintering temperature of 1100 to 1200°C to obtain the sintered body.

6. The sintered body has a matrix phase in which fine carbides having a particle size of 10 μm or less are precipitated at a density of 150 particles / (30 μm×30 μm) or more and have a Vickers hardness of 550 HV or more. A structure in which hard particles are dispersed at an area ratio of 20 to 40% and solid lubricant particles are dispersed at an area ratio of 1.0 to 5%, and the matrix portion containing the hard particles and the solid lubricant particles has a composition, in mass %, of C: 1.0 to 2.0%, Si: 0.5 to 1.5%, Mn: less than 2.0%, Cr: 2.0 to 10.0%, Mo: 5.0 to 15.0%, W: 0.5 to 10.0%, V: 0.5 to 5.0%, Co: 10.0 to 35.0%, Ni: 0 to 5.0%, S: 0 to 2.0%, with the balance being Fe and unavoidable impurities.

6. The method for manufacturing an iron-based sintered alloy valve seat according to claim 5.

7. A method for manufacturing the two-layered iron-based sintered alloy valve seat according to claim 3 or 4, comprising the steps of: Predetermined amounts of iron-based powder, graphite powder, alloying element powder, hard particle powder, and solid lubricant powder are blended, mixed, and kneaded to obtain a mixed powder for a functional component side layer; Predetermined amounts of iron-based powder, graphite powder, or alloy element powder, hard particle powder, and solid lubricant powder are blended, mixed, and kneaded to obtain a mixed powder for a support member side layer; The mixed powder for the functional component side layer and the mixed powder for the support component side layer are filled in this order into a mold of a predetermined shape, and pressed to form a green compact. The green compact is then sintered in a protective atmosphere to form a two-layered sintered body, which is then subjected to cutting or further grinding to produce a two-layered valve seat of a predetermined shape. The mixed powder for the functional component side layer contains, by mass%, C: 0.05 to 0.70%, Si: 0.70% or less, Mn: 0.50% or less, Cr: 4.5% or less, Mo: 10.0% or less, V: 4.5% or less, W: 10.0% or less, with the remainder being Fe and unavoidable impurities, and has a particle hardness of 170 to 220 HV in Vickers hardness, and the iron-based powder is blended in an amount of 40 to 70% by mass with respect to the total amount of the mixed powder for the functional component side layer, the hard particle powder is selected from Si-Cr-Mo-based Co-based intermetallic compound particles having a Vickers hardness of 650 to 1200 HV and consisting of, by mass, 2.20 to 2.70% Si, 7.5 to 9.5% Cr, and 27.0 to 30.0% Mo, 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 to 1200 HV and consisting, by mass, of 1.5 to 2.5% Si, 24.0 to 26.0% Cr, 23.0 to 26.0% Mo, and 9.5 to 11.0% Ni, with the balance being Co; and the hard particle powder is blended in an amount of 20 to 40% by mass with respect to the total amount of the mixed powder for the functional component side layer; The graphite powder is blended in an amount of 0.5 to 2.0% by mass relative to the total amount of the mixed powder for the functional component side layer, The alloy element powder is blended in a total amount of 1.0 to 5.0% by mass with respect to the total amount of the mixed powder for the functional component side layer, and further The solid lubricant powder is blended in an amount of 1.0 to 5% by mass relative to the total amount of the mixed powder for the functional component side layer, The density of the powder compact obtained by the press processing is 6.6 g / cm 3 The above will be implemented. In the mixed powder for the support member side layer, the iron-based powder is pure iron powder, the graphite powder is blended in an amount of 0.5 to 2.0% by mass relative to the total amount of the mixed powder for the support member side layer, the alloy element powder is blended in a total amount of 0 to 5.0% by mass relative to the total amount of the mixed powder for the support member side layer, the hard particle powder is Fe—Mo alloy powder, the hard particle powder is blended in an amount of 0 to 5% by mass relative to the total amount of the mixed powder for the support member side layer, and the solid lubricant powder is blended in an amount of 0 to 5% by mass relative to the total amount of the mixed powder for the support member side layer, The density of the powder compact obtained by the press processing is 6.6 g / cm 3 The above will be implemented. The sintering process is carried out at a sintering temperature of 1100 to 1200°C, A method for manufacturing an iron-based sintered alloy valve seat, characterized in that the sintered body is a two-layer structure sintered body.

8. The two-layered sintered body has a structure in which the functional component side layer comprises a matrix phase in which fine carbides of 10 μm or less in particle size are precipitated at a density of 150 particles / (30 μm×30 μm) or more and have a Vickers hardness of 550 HV or more, and in which hard particles are dispersed in the matrix phase at an area ratio of 20 to 40% and solid lubricant particles are dispersed at an area ratio of 1.0 to 5%. a matrix containing the solid lubricant particles and the solid lubricant particles, the matrix containing, in mass %, C: 1.0 to 2.0%, Si: 0.5 to 1.5%, Mn: less than 2.0%, Cr: 2.0 to 10.0%, Mo: 5.0 to 15.0%, W: 0.5 to 10.0%, V: 0.5 to 5.0%, Co: 10.0 to 35.0%, Ni: 0 to 5.0%, S: 0 to 2.0%, with the balance being Fe and unavoidable impurities; 8. A method for producing an iron-based sintered alloy valve seat according to claim 7, wherein the support member-side layer is a two-layered sintered body having a matrix phase made of pearlite, a structure in which hard particles are dispersed in the matrix phase at an area ratio of 0 to 5%, and solid lubricant particles are dispersed in the matrix phase at an area ratio of 0 to 5%, and a matrix portion containing the matrix phase, the hard particles, and the solid lubricant particles contains, in mass%, C: 0.9 to 2.0%, or further contains one or more selected from Ni: 0.5% or less, Mo: 0.8% or less, Cu: 5.0% or less, Mn: 5.0% or less, and S: 2.0% or less, with the balance being Fe and unavoidable impurities.

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