Iron-based sintered alloy valve seat for internal combustion engine and method for manufacturing the same

Abstract

Provided is an iron-based sintered alloy valve seat that has excellent wear resistance and peeling resistance. The valve seat is produced as a double-layer structure in which a functional component side layer and a support component side layer are integrated by sintering. The functional component side layer is an iron-based sintered alloy material in which a structure having fine carbide precipitates of 20.0% or less, an annealed martensite phase, and further a high alloy phase around the fine carbide precipitates is dispersed with hard particles or further dispersed with solid lubricant particles, and which has a base portion composition containing, by mass%, C: 0.5 to 2.0%, and further one or two or more of Si, Mn, Ni, Cr, Mo, Co, W, V, or further S, and contains pores filled with Cu by melt impregnation. Thus, the wear resistance and peeling resistance are improved, and sufficient durability is maintained even when used in a cast iron cylinder head of an internal combustion engine.

Description

Technical Field

[0001] This invention relates to iron-based sintered alloy valve seats for internal combustion engines and methods for manufacturing the same, and particularly to improvements in the wear resistance and resistance to detachment from the cylinder head of valve seats used in press-fitted cast iron cylinder heads. Background Technology

[0002] The valve seat serves as a seal and cooling valve for combustion gases, and is pressed into the engine cylinder head for use. In addition to requiring sufficient wear resistance, heat resistance, and corrosion resistance to withstand repeated contact with the valve, the valve seat also requires low mating aggression to prevent wear on the valve itself, which is the mating material.

[0003] In recent years, with the increasing efficiency and load of engines, the temperature around the combustion chamber has tended to rise. As a result, the thermal load on the valve seat has become higher, requiring it to withstand harsh operating environments.

[0004] For example, Patent Document 1 proposes a sintered alloy valve seat suitable for use in cast iron cylinder heads. The sintered alloy valve seat described in Patent Document 1 is a sintered alloy valve seat in which a surface layer and a base layer are sintered together, with the surface layer having a porosity of 5-20% and the base layer having a porosity of less than 5%. The sintered alloy valve seat described in Patent Document 1 is manufactured by cold rotary forging of the sintered body from the base layer side after forming the two-layer sintered body, followed by re-sintering.

[0005] Furthermore, Patent Document 2 describes an iron-based sintered alloy valve seat for internal combustion engines. The valve seat described in Patent Document 2 has a single-layer structure. The matrix phase consists of an annealed martensite phase containing fine carbides with a major diameter of 30 μm or less, comprising 27% or less of the precipitate by area. Furthermore, the matrix phase contains 31% to 80% by area of ​​one or more hard particles selected from Cr-Mo-Si-Co, Cr-Mo-Ni-Si-Co, and Mo-based hard particles, with a density of 7.3 to 8.2 g / cm³. 3 The radial crushing strength is above 400 MPa, exhibiting excellent wear resistance and detachment resistance. For the valve seat described in Patent Document 2, the process includes a mixing step of blending raw material powders to form a mixed powder in a prescribed manner; a molding step of compressing and shaping the mixed powder to form a pressed powder body; and a sintering step of heating and sintering the pressed powder body to form a valve seat-shaped sintered body. Subsequently, a hot forging hot working step is performed on the valve seat-shaped sintered body, followed by a heat treatment step of imparting prescribed properties to the valve seat-shaped sintered body. According to the technology described in Patent Document 2, valve seats exhibiting excellent durability even under harsh conditions can be easily manufactured.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Publication No. 61-10644,

[0009] Patent Document 2: Japanese Patent Application Publication No. 2018-178208. Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, in the technology described in Patent Document 1, to reduce the porosity of the base layer of the valve seat, a compression forging process based on cold rotary forging and then re-sintering is required for the sintered body. Therefore, the technology described in Patent Document 1 suffers from complex processes. Furthermore, the technology described in Patent Document 2 also requires a process with a valve seat density of 7.3 g / cm³. 3 The above methods of hot forging involve complex processes.

[0012] The purpose of this invention is to solve the problems of the prior art described above, and to provide a high-strength iron-based sintered alloy valve seat that is cheaper than the prior art and has excellent wear resistance and detachment resistance, suitable for use as a valve seat in cylinder heads of press-fit internal combustion engines, especially cast iron cylinder heads.

[0013] Methods for solving problems

[0014] To achieve the above objectives, the inventors first conducted an in-depth study of various factors affecting the resistance to detachment of the pressed-in valve seat. As a result, they conceived of first performing a Cu impregnation treatment on the valve seat, allowing Cu to be impregnated in the pores to achieve high strength, followed by quenching and annealing (heat treatment) to stabilize the matrix phase. Then, in addition to resistance to detachment, to also achieve wear resistance, they considered making the hard particles dispersed in the matrix phase high-hardness and low-aggression Ni-Cr-Mo-Co intermetallic compound particles or Cr-Mo-Co intermetallic compound particles.

[0015] This invention was completed based on such insights and further research.

[0016] In other words, the key points of this invention are as follows.

[0017] [1] An iron-based sintered alloy valve seat for internal combustion engines, which is a valve seat pressed into the cylinder head of an internal combustion engine, characterized in that,

[0018] The valve seat has a single-layer structure consisting of functional component side layers.

[0019] The functional component side layer comprises a matrix portion in which hard particles or solid lubricant particles are dispersed in the matrix phase, and pores filled with Cu by melt impregnation.

[0020] The matrix phase consists of a fine carbide precipitate phase and an annealed martensite phase, comprising less than 20.0% of the total area percentage relative to the total area of ​​the functional component side layers.

[0021] The matrix portion is composed of an iron-based sintered alloy material, which has a matrix structure in which 10.0% to 40.0% of the hard particles or 0.3% to 3.0% of the solid lubricant particles are dispersed in the matrix phase relative to the total area percentage of the functional component side layer, and further has 25.0% or less of a high-alloy phase around the hard particles, and contains C: 0.5% to 2.0% relative to the total mass percentage of the matrix portion, and further contains Si: 0.1% to 1.0%. The matrix consists of one or more of the following: Mn: 0.1–2.5%, Ni: 1.0–7.0%, Cr: 1.0–12.0%, Mo: 2.0–12.0%, Co: 2.0–20.0%, W: 0.1–2.0%, V: 0.01–1.0%, and further contains S: 0–1.5%, with the balance being a matrix composed of Fe and unavoidable impurities, and further contains Cu, which is filled into the pores by melt infiltration at an area percentage of 1.0–20.0% relative to the total area percentage of the functional component side layer.

[0022] [2] An iron-based sintered alloy valve seat for an internal combustion engine, which is a valve seat pressed into the cylinder head of the internal combustion engine, characterized in that,

[0023] The valve seat has a two-layer structure in which the functional component side layer and the support component side layer are integrally sintered.

[0024] The functional component side layer comprises a matrix portion in which hard particles or solid lubricant particles are dispersed in a matrix phase, and pores filled with Cu by melt impregnation. The matrix phase consists of a fine carbide precipitate phase and an annealed martensite phase, comprising less than 20.0% of the total area percentage relative to the total amount of the functional component side layer.

[0025] The matrix portion is composed of an iron-based sintered alloy material, which has a matrix structure in which 10.0% to 40.0% of the hard particles or 0.3% to 3.0% of the solid lubricant particles are dispersed in the matrix phase relative to the total area percentage of the functional component side layer, and further has 25.0% or less of a high-alloy phase around the hard particles, and contains C: 0.5% to 2.0% relative to the total mass percentage of the matrix portion, and further contains Si: 0.1% to 1.0%. The composition comprises one or more of the following: Mn: 0.1–2.5%, Ni: 1.0–7.0%, Cr: 1.0–12.0%, Mo: 2.0–12.0%, Co: 2.0–20.0%, W: 0.1–2.0%, V: 0.01–1.0%, and further contains S: 0–1.5%, with the balance being a matrix composed of Fe and unavoidable impurities. It also contains Cu, which is melt-filled into the pores at a rate of 1.0–20.0% per square meter of area relative to the total area of ​​the functional component side layer.

[0026] The support component side layer comprises a matrix portion in which solid lubricant particles are dispersed in a matrix phase, and pores filled with Cu by melt infiltration. The matrix phase is composed of an annealed martensitic phase, and the matrix portion is composed of an iron-based sintered alloy material. The iron-based sintered alloy material has a matrix portion structure in which 0 to 3.0% of the solid lubricant particles are dispersed in the matrix phase in terms of area % relative to the total amount of the support component side layer, and a matrix portion containing, in terms of mass % relative to the total amount of the matrix portion, C: 0.1 to 1.5%, further containing one or more of Cr: 1.0 to 10.0%, Mo: 0.1 to 3.0%, Ni: 0.1 to 2.0%, further containing Mn: 0 to 1.0% and S: 0 to 1.0%, with the balance being Fe and unavoidable impurities, and further containing 1.0 to 20.0% Cu filled in the pores by melt infiltration in terms of area % relative to the total amount of the support component side layer.

[0027] The iron-based sintered alloy valve seat for internal combustion engines described in [3][1] or [2] is characterized in that the cylinder head is a cast iron cylinder head.

[0028] [4][1] or [2] the iron-based sintered alloy valve seat for internal combustion engines, characterized in that the hard particles are intermetallic compound particles having a composition of Ni: 5.0-15.0%, Cr: 20.0-30.0%, Mo: 20.0-30.0%, Si: 1.0-5.0%, with the balance being Co, and having a hardness of 900-1300 HV on a Vickers hardness scale, or having a composition of Cr: 5.0-15.0%, Mo: 25.0-35.0%, Si: 1.0-5.0%, with the balance being Co, and having a hardness of 600-900 HV on a Vickers hardness scale.

[0029] The iron-based sintered alloy valve seat for internal combustion engines described in [5][1] or [2] is characterized in that the solid lubricant particles are MnS particles.

[0030] [6] A method for manufacturing an iron-based sintered alloy valve seat for an internal combustion engine, which is the method for manufacturing a single-layer iron-based sintered alloy valve seat for an internal combustion engine as described in [1], characterized in that,

[0031] When a mixed powder is prepared by mixing and kneading a specified amount of iron-based powder, graphite powder, alloy element powder, hard particle powder, or further mixing a specified amount of solid lubricant particle powder in a manner that forms the matrix composition and matrix structure of the functional component side layer of the single-layer structure, it becomes a mixed powder.

[0032] The iron-based powder is selected from one or more of pure iron powder, alloy iron powder, and alloy steel powder, expressed as a percentage by mass relative to the total amount of the mixed powder.

[0033] The graphite powder is mixed with 0.5-2.0% of the graphite powder, 0-5.0% of the alloying element powder, and 10.0-40.0% of the hard particle powder, respectively.

[0034] 0-3.0% of the solid lubricant particle powder is mixed and kneaded to form a mixed powder, which has the following properties:

[0035] In the molding process, the mixed powder is filled into a mold of a specified shape, compressed, and molded to obtain pressed powder.

[0036] The sintering process involves sintering the obtained pressed powder in a reducing atmosphere at a heating temperature of 1100–1200°C to obtain a sintered body.

[0037] The Cu melting process involves subjecting the obtained sintered body to Cu melting treatment to fill the pores of the sintered body with Cu; and

[0038] The heat treatment process includes a quenching and annealing process in which the sintered body with Cu impregnated in the pores is reheated to a quenching temperature of 800-1000℃, then rapidly cooled, and then reheated to an annealing temperature of 500-700℃ before cooling.

[0039] [7] A method for manufacturing an iron-based sintered alloy valve seat for an internal combustion engine, which is the method for manufacturing a double-layer structure iron-based sintered alloy valve seat for an internal combustion engine described in [2], characterized in that,

[0040] When a mixed powder is prepared by mixing and kneading a specified amount of iron-based powder, graphite powder, alloy element powder, hard particle powder, or further mixing a specified amount of solid lubricant particle powder in a manner that constitutes the matrix composition and matrix structure of the aforementioned double-layer structure, the mixed powder is prepared.

[0041] The iron-based powder is selected from one or more of pure iron powder, alloy iron powder, and alloy steel powder, expressed as a percentage by mass relative to the total amount of the mixed powder.

[0042] The graphite powder is mixed with 0.5-2.0% of the graphite powder, 0-5.0% of the alloying element powder, and 10.0-40.0% of the hard particle powder, respectively.

[0043] 0-3.0% of the aforementioned solid lubricant particle powder is mixed and kneaded to prepare a mixed powder for the side layer of functional components. On the other hand,

[0044] The iron-based powder is selected from one or two types of pure iron powder and alloy iron powder.

[0045] In terms of mass % relative to the total amount of the mixed powder,

[0046] The graphite powder, alloy element powder, and solid lubricant particle powder are respectively mixed and kneaded to form a mixed powder for the side layer of the support component, which has the following properties:

[0047] In the molding process, a specified amount of the mixed powder for the side layer of the support component and the mixed powder for the side layer of the functional component are sequentially filled into a mold, and compressed and molded as a whole to obtain a pressed powder body.

[0048] The sintering process involves sintering the obtained pressed powder in a reducing atmosphere at a heating temperature of 1100–1200°C to obtain a sintered body.

[0049] The Cu melting process involves subjecting the obtained sintered body to Cu melting treatment to fill the pores of the sintered body with Cu; and

[0050] The heat treatment process includes a quenching and annealing process in which the sintered body with Cu impregnated in the pores is reheated to a quenching temperature of 800-1000℃, then rapidly cooled, and then reheated to an annealing temperature of 500-700℃ before cooling.

[0051] The method for manufacturing iron-based sintered alloy valve seats for internal combustion engines as described in [8][6] or [7] is characterized in that the Cu melting and impregnation process is included in the sintering process.

[0052] The effects of the invention

[0053] According to the present invention, high-strength iron-based sintered alloy valve seats with excellent wear resistance and anti-slip properties can be manufactured inexpensively, resulting in significant industrial benefits. According to the present invention, valve seats with particularly superior wear resistance and anti-slip properties are used in cast iron cylinder heads, providing excellent performance compared to conventional valve seats. Attached Figure Description

[0054] [ Figure 1 A cross-sectional view schematically illustrating an example of the cross-sectional structure of the valve seat of the present invention.

[0055] [ Figure 2 A schematic diagram illustrating a single-bench wear testing machine.

[0056] [ Figure 3 A schematic diagram illustrating the shedding test machine. Detailed Implementation

[0057] like Figure 1 As shown, the valve seat 1 of the present invention is a double-layer structure in which the side where the valve sits (functional component side) 11 and the side where it sits on the cover (support component side) 12 are made of different materials and are integrally sintered together, or a single-layer structure (not shown) with only the functional component side layer 11.

[0058] First, the functional component side layer will be explained.

[0059] The functional component side layer is made of an iron-based sintered alloy material, which includes a matrix portion in which hard particles or solid lubricant particles are dispersed in the matrix phase, and a molten portion in which Cu is filled in the pores.

[0060] In the valve seat of this invention, Cu is filled into the pores through melt impregnation, thereby improving the strength of the valve seat. It should be noted that the porosity of the functional component side layer of the valve seat before melt impregnation ranges from 1.0% to 20.0% in area percent. If the porosity is less than 1.0%, the process for increasing density becomes complex, leading to a significant increase in manufacturing costs. On the other hand, if it exceeds 20.0%, the wear resistance decreases.

[0061] In the functional component side layer, the matrix phase consists of a fine carbide precipitate phase and an annealed martensite phase, which together constitute less than 20.0% of the area of ​​the functional component side layer.

[0062] In the functional component side layer of the valve seat of the present invention, a specified amount (20.0% or less) of fine carbide precipitates is present in the matrix phase. The presence of fine carbide precipitates in the matrix phase improves the wear resistance of the functional component side layer (valve seat) with Cu-filled pores. To achieve this effect, it is preferable that the presence of fine carbide precipitates is 20.0% or less, preferably 1.0% or more and 20.0% or less, relative to the area percentage of the functional component side layer. If the fine carbide precipitates exceed 20.0% and are present in large quantities, porosity increases and wear resistance decreases. It should be noted that, here, "fine carbide precipitates" refers to a phase in which fine carbides such as Cr-Mo-WV carbides precipitate in annealed martensite.

[0063] Furthermore, in the functional component side layer of the valve seat of the present invention, the matrix phase other than the aforementioned fine carbide precipitate phase is an annealed martensite phase. By making the remainder of the matrix phase (the main phase) an annealed martensite phase, the strength and toughness are improved, and a valve seat that can adequately maintain its intended function even in harsh operating environments where the combustion temperature of the engine is high can be manufactured.

[0064] In the functional component side layer of the valve seat of the present invention, the matrix portion has a matrix structure in which 10.0 to 40.0% of hard particles or 0.3 to 3.0% of solid lubricant particles are dispersed in the matrix phase relative to the total area percentage of the functional component side layer, and further, 25.0% or less of high alloy phase is dispersed around the hard particles.

[0065] Hard particles dispersed in the matrix phase contribute to improved wear resistance, with a dispersion amount ranging from 10.0% to 40.0% by area. If the dispersion amount of hard particles is less than 10.0%, the desired wear resistance cannot be maintained. On the other hand, if the dispersion exceeds 40.0%, pairing aggression increases.

[0066] As hard particles dispersed in the matrix phase, preferably intermetallic compound particles having a composition of Ni: 5.0–15.0%, Cr: 20.0–30.0%, Mo: 20.0–30.0%, Si: 1.0–5.0%, with the balance being Co, and having a hardness of 900–1300 HV on a Vickers hardness scale; or intermetallic compound particles having a composition of Cr: 5.0–15.0%, Mo: 25.0–35.0%, Si: 1.0–5.0%, with the balance being Co, and having a hardness of 600–900 HV on a Vickers hardness scale. Ni-Cr-Mo-Co intermetallic compound particles and Cr-Mo-Co intermetallic compound particles are hard particles with high hardness and low pairing aggression.

[0067] Furthermore, the solid lubricant particles dispersed in the matrix phase contribute to improved formability and machinability. During dispersion, the dispersion amount, in terms of area % relative to the total amount of the functional component side layer, is preferably 0.3% to 3.0%. If the dispersion amount of solid lubricant particles is less than 0.3%, the desired lubrication effect cannot be expected. On the other hand, if the amount exceeds 3.0%, the desired effect saturates. Therefore, during dispersion, the solid lubricant particles are preferably limited to a range of 0.3% to 3.0% in terms of area % relative to the total amount of the functional component side layer. MnS particles are preferred as the solid lubricant particles.

[0068] Furthermore, in the functional component side layer of the valve seat of the present invention, the matrix portion further comprises a high-alloy phase comprising 25.0% or less of the area percentage relative to the total area of ​​the functional component side layer. The high-alloy phase is formed by the diffusion of alloying elements from hard particles during sintering, resulting in a stable phase that helps prevent the shedding of hard particles or interparticle bonding. It should be noted that if the high-alloy phase comprises less than 1.0% of the area percentage, the aforementioned effects cannot be expected.

[0069] Furthermore, in the functional component side layer of the valve seat of the present invention, the matrix portion contains C: 0.5 to 2.0% by mass percentage relative to the total amount of the matrix portion, and further contains one or more of Si: 0.1 to 1.0%, Mn: 0.1 to 2.5%, Ni: 1.0 to 7.0%, Cr: 1.0 to 12.0%, Mo: 2.0 to 12.0%, Co: 2.0 to 20.0%, W: 0.1 to 2.0%, V: 0.01 to 1.0%, and further contains S: 0 to 1.5%, with the balance being a matrix portion composed of Fe and unavoidable impurities.

[0070] The following explains the rationale for defining each component in the matrix composition of the functional component side layer. It should be noted that the mass percentage in the composition is expressed as a percentage only.

[0071] C: 0.5–2.0%

[0072] Carbon (C) is included in the matrix phase and is an element that helps strengthen the matrix phase and improve its wear resistance; it needs to be present at a level of 0.5% or more. On the other hand, if it exceeds 2.0%, the wear resistance decreases. Therefore, the content of C is limited to the range of 0.5% to 2.0%.

[0073] Selected from one or more of the following: Si: 0.1–1.0%, Mn: 0.1–2.5%, Ni: 1.0–7.0%, Cr: 1.0–12.0%, Mo: 2.0–12.0%, Co: 2.0–20.0%, W: 0.1–2.0%, and V: 0.01–1.0%.

[0074] Si: 0.1–1.0%

[0075] Si, when included in the matrix phase, contributes to increased strength and improved wear resistance of the matrix phase. Below 0.1%, these effects are not observed. Content exceeding 1.0% increases pairing aggression. Therefore, when present, Si is preferably limited to the range of 0.1% to 0.7%.

[0076] Mn: 0.1–2.5%

[0077] Mn, contained in the matrix phase, contributes to the strengthening of the matrix phase and improves its wear resistance. Additionally, a portion of MnS particles, dispersed in the matrix phase as solid lubricant, contributes to improved formability, machinability, and wear resistance. If the content is below 0.1%, these effects are not observed. On the other hand, a content exceeding 2.5% increases pairing aggression. Therefore, when present, Mn is preferably limited to the range of 0.1% to 2.5%.

[0078] Ni: 1.0–7.0%

[0079] Ni, contained in both the matrix phase and hard particles, is an element that improves not only wear resistance but also strength (hardness) and heat resistance. If the content is less than 1.0%, these effects are minimal; therefore, a content of 1.0% or more is preferred. On the other hand, if the content exceeds 7.0%, wear resistance decreases. Therefore, when present, Ni is preferably limited to the range of 1.0% to 7.0%.

[0080] Cr: 1.0–12.0%

[0081] Cr, contained in the matrix phase and hard particles, is an element that improves not only wear resistance but also strength (hardness) and heat resistance. If the content is below 1.0%, these effects are minimal; therefore, a content of 1.0% or more is preferred. On the other hand, a content exceeding 12.0% increases pairing aggression. Therefore, when present, Cr is preferably limited to the range of 1.0% to 12.0%.

[0082] Mo: 2.0–12.0%

[0083] Like Ni and Cr, Mo is contained in the matrix phase and hard particles. It is an element that, in addition to improving wear resistance, also enhances strength (hardness) and heat resistance, and is preferably present at 2.0% or more. On the other hand, a content exceeding 12.0% increases pairing aggression. Therefore, when present, Mo is preferably limited to the range of 2.0% to 12.0%.

[0084] Co: 2.0~20.0%

[0085] Like Ni and Cr, Co is contained in the matrix phase and hard particles. Besides improving wear resistance, it enhances strength (hardness) and heat resistance while strengthening the bond between hard particles and the matrix phase. It is preferable to contain 2.0% or more of Co. On the other hand, if the content exceeds 20.0%, pairing aggression increases. Therefore, when Co is present, it is preferably limited to the range of 2.0% to 20.0%.

[0086] W: 0.1–2.0%

[0087] W, as a fine carbide precipitate that strengthens the matrix phase, is an element that contributes to improved wear resistance, and is preferably contained at 0.1% or more. On the other hand, a content exceeding 2.0% will reduce wear resistance. Therefore, when contained, W is preferably limited to the range of 0.1% to 2.0%.

[0088] V: 0.01~1.0%

[0089] V is an element that strengthens the matrix phase and improves wear resistance, and it is preferable to contain 0.01% or more. On the other hand, if it contains more than 1.0%, pairing aggression increases. Therefore, when it is contained, it is preferable to limit it to the range of 0.01% to 1.0%.

[0090] In addition to the above-mentioned components, it may also contain S: 0-1.5%.

[0091] S: 0-1.5%

[0092] S, primarily dispersed as solid lubricant particles (MnS) in the matrix, is an element that contributes to improved formability, machinability, and wear resistance. When present, it is preferable to contain 0.1% or more. On the other hand, if the content exceeds 1.5%, wear resistance decreases. Therefore, S is limited to a range of 0–1.5%.

[0093] The balance other than the above components consists of Fe and unavoidable impurities.

[0094] The amount of Cu impregnated in the pores of the functional component side layer of the valve seat in this invention, which is filled with Cu, is limited to 1.0% to 20.0% of the area relative to the total area of ​​the functional component side layer. If the amount of Cu impregnated is less than 1.0%, the desired strength of the valve seat cannot be ensured. On the other hand, if it increases to more than 20.0%, the wear resistance decreases. Therefore, the amount of Cu impregnated in the functional component side layer is limited to 1.0% to 20.0% of the area relative to the total area of ​​the functional component side layer. It should be noted that it is preferably 15.0% or less.

[0095] Furthermore, the support component side layer of the valve seat of the present invention is made of an iron-based sintered alloy material, which comprises a matrix portion in which solid lubricant particles are dispersed in a matrix phase, and a melt-infiltrated portion in which Cu is filled in the pores. It should be noted that the porosity of the support component side layer before melt-infiltration ranges from 1.0% to 20.0% in area percent. If the porosity is less than 1.0%, the process for increasing density becomes complex, leading to a significant increase in manufacturing costs. On the other hand, if it exceeds 20.0%, the desired strength cannot be ensured.

[0096] The matrix phase in the support component side layer of the valve seat of the present invention is annealed martensite. By making the matrix phase annealed martensite, the strength and resistance to shedding of the support component side layer are improved, and the desired function (resistance to shedding) can be fully maintained even in the harsh operating environment where the combustion temperature of the engine is high.

[0097] Furthermore, the matrix portion of the support member side layer of the valve seat of the present invention has a matrix structure in which 0 to 3.0% of solid lubricant particles are dispersed in the matrix phase, based on the area percentage relative to the total area of ​​the support member side layer. If the amount of solid lubricant particles dispersed in the matrix phase exceeds 3.0%, the effect of improving formability and machinability becomes saturated. Therefore, the amount of dispersed solid lubricant particles is preferably limited to the range of 0 to 3.0% based on the area percentage relative to the total area of ​​the support member side layer. MnS particles are preferred as solid lubricant particles.

[0098] In addition, the matrix portion in the side layer of the support member has the above-mentioned matrix portion structure, and is composed of a matrix portion containing, by mass% relative to the total amount of matrix portion, C: 0.1 to 1.5%, further containing one or more of Cr: 1.0 to 10.0%, Mo: 0.1 to 3.0%, Ni: 0.1 to 2.0%, further containing Mn: 0 to 1.0% and S: 0 to 1.0%, with the balance being Fe and unavoidable impurities.

[0099] Next, the reasons for defining each component in the matrix of the side layer of the support member will be explained.

[0100] C: 0.1-1.5%

[0101] Carbon (C) is included in the matrix phase and is an element that helps strengthen the matrix phase; it needs to be present at a level of 0.1% or higher. On the other hand, if it exceeds 1.5%, the hardness decreases. Therefore, the content of C is limited to the range of 0.1% to 1.5%.

[0102] Cr: 1.0–10.0%

[0103] Cr, contained in the matrix phase, is an element that improves strength (hardness) and resistance to peeling, and can be included as needed. When included, it is preferable to contain 1.0% or more. On the other hand, a content exceeding 10.0% will reduce machinability. Therefore, Cr is preferably limited to the range of 1.0% to 10.0%.

[0104] Mo: 0.1–3.0%

[0105] Like Cr, Mo is contained in the matrix phase and is an element that improves strength (hardness) and resistance to chipping. It can be included as needed. When included, it is preferable to contain 0.1% or more. On the other hand, a content exceeding 3.0% will reduce machinability. Therefore, Mo is preferably limited to the range of 0.1% to 3.0%.

[0106] Ni: 0.1–2.0%

[0107] Ni, contained in both the matrix phase and hard particles, is an element that improves not only wear resistance but also strength (hardness) and heat resistance. It can be included as needed. When included, it is preferable to contain 0.1% or more. On the other hand, if the content exceeds 2.0%, austenite is formed, reducing wear resistance. Therefore, Ni is preferably limited to 0.1% to 2.0%.

[0108] Mn: 0~1.0%

[0109] Mn is contained in the matrix phase and is an element that helps strengthen the matrix phase. Additionally, a portion of MnS particles, acting as solid lubricant particles, are dispersed in the matrix phase and contribute to improved formability; these can be included as needed. When included, it is preferable to contain 0.1% or more. On the other hand, containing more than 1.0% will reduce formability. Therefore, Mn is preferably limited to the range of 0 to 1.0%.

[0110] S: 0~1.0%

[0111] S is mainly dispersed in the matrix as solid lubricant particles and is an element that helps improve formability and machinability. It can be included as needed. When included, it is preferable to contain 0.1% or more. On the other hand, if the content exceeds 1.0%, there are too many solid lubricant particles, which reduces strength (hardness). Therefore, S is preferably limited to the range of 0 to 1.0%.

[0112] The balance other than the above components consists of Fe and unavoidable impurities.

[0113] The side layer of the support component is made of an iron-based sintered alloy material, which has the above-mentioned matrix structure and matrix composition, and further contains a molten portion (Cu molten amount) filled with Cu in the pores, which is 1.0 to 20.0% of the area percentage relative to the total area of ​​the side layer of the support component.

[0114] It should be noted that the amount of Cu impregnated in the pores of the support member side layer, which is filled with Cu (Cu impregnation amount), is limited to 1.0% to 20.0% of the total area of ​​the support member side layer. If the amount of Cu impregnation is less than 1.0%, the desired strength of the valve seat cannot be ensured. On the other hand, if it increases to more than 20.0%, the wear resistance decreases. Therefore, the amount of Cu impregnated in the support member side layer is limited to a range of 1.0% to 20.0% of the total area of ​​the support member side layer. It should be noted that it is preferably 15.0% or less, and more preferably 10.0% or less.

[0115] Next, a preferred manufacturing method for the valve seat of the present invention will be described.

[0116] First, raw material powders are mixed and blended to form the matrix composition of the functional component side layer and the matrix composition of the support component side layer, respectively, to prepare mixed powder for the functional component side layer and mixed powder for the support component side layer.

[0117] The mixed powder for the side layer of functional components is prepared by mixing iron-based powder, graphite powder, alloying element powder, and hard particle powder as raw material powders, or by further mixing solid lubricant particle powder, in a manner that constitutes the matrix portion of the side layer of the aforementioned functional components. It should be noted that the iron-based powder mixed in the mixed powder for the side layer of functional components to form the matrix phase can include, for example, pure iron powder, alloy iron powder, and alloy steel powder. Examples of pure iron powder include atomized pure iron powder; examples of alloy iron powder include Cr-Mo alloy iron powder containing a specified amount of Cr and Mo, or alloy iron powder containing a specified amount of Ni in addition to Cr and Mo; and examples of alloy steel powder include high-speed tool steel powder as specified in JIS G 4403, containing specified amounts of C, Si, Mn, Cr, Mo, V, W, or further containing a specified amount of Co.

[0118] Furthermore, the mixed powder for the side layer of the support component is prepared by mixing iron-based powder, graphite powder, alloying element powder, and solid lubricant particle powder as raw material powders in a manner that constitutes the matrix portion of the side layer of the aforementioned support component. It should be noted that the iron-based powder used to form the matrix phase can be pure iron powder or alloy iron powder. Atomized pure iron powder can be an example of pure iron powder, and Cr-Mo alloy iron powder containing a specified amount of Cr and Mo can be an example of alloy iron powder. It should also be noted that the alloy iron powder can be alloy iron powder containing a specified amount of Ni in addition to Cr and Mo. Furthermore, Cr powder, Mo powder, Ni powder, Mn powder, etc., can be examples of alloying element powders.

[0119] Next, the manufacturing method of the valve seat of the present invention includes a molding process, a sintering process, a Cu melting and impregnation process, and a heat treatment process. In the molding process, the obtained mixed powder is filled into a mold, and compressed and molded using a stamping molding machine to obtain a pressed powder body. It should be noted that when making a double-layer valve seat, the mixed powder for the support component side layer and the mixed powder for the functional component side layer are sequentially filled into the mold to form a double-layer structure. In the case of a single-layer structure, only the mixed powder for the functional component side layer is filled into the mold. It should be noted that in the molding process, the compression pressure is adjusted in order to form a pressed powder body with the desired porosity (density).

[0120] Next, in the sintering process, the obtained pressed powder is sintered to form a sintered body. The sintering process is preferably carried out in a reducing atmosphere such as ammonia decomposition gas, heating to a temperature range of 1000–1200°C and holding for 10–30 minutes. It should be noted that a 2P2S process, which involves repeating the molding and sintering processes, is also possible.

[0121] Next, in the Cu melting process, Cu melting treatment is performed to fill the pores of the sintered body with Cu.

[0122] It should be noted that Cu melt infiltration treatment can be performed during sintering or separately from sintering.

[0123] Next, in the heat treatment process, to impart the desired strength and matrix stabilization, the sintered body filled with Cu in the pores is further heat-treated (quenching and annealing). It should be noted that the quenching treatment is preferably performed by heating to a quenching temperature range of 800–1000°C and holding it before rapid cooling (using N2 gas or oil cooling). After quenching, annealing is then performed. The annealing treatment is preferably performed by heating to 500–700°C and holding it before cooling (using N2 gas or gas cooling).

[0124] The sintered body that has undergone heat treatment is processed into valve seats (products) of a specified shape through cutting, grinding, and other processes.

[0125] The present invention will be further described below based on embodiments.

[0126] Example

[0127] Various functional component side layer mixed powders were prepared by mixing the raw material powders (iron-based powder, graphite powder, alloy element powder, hard particle powder, and solid lubricant particle powder) shown in Table 1 with the mixing amounts shown in Table 1. Additionally, various support component side layer mixed powders were prepared by mixing the raw material powders (iron-based powder, graphite powder, alloy element powder, and solid lubricant particle powder) shown in Table 2 with the mixing amounts shown in Table 2. It should be noted that the composition of the iron-based powders used is shown in Table 3, and the composition of the hard particle powders used is shown in Table 4.

[0128] [Table 1]

[0129]

[0130] * Refer to Table 3

[0131] **Refer to Table 4

[0132] ***)SL1:MnS

[0133] [Table 2]

[0134]

[0135] * Refer to Table 3

[0136] **Refer to Table 4

[0137] ***)SL1:MnS

[0138] [Table 3]

[0139]

[0140] [Table 4]

[0141]

[0142] Next, these mixed powders are integrally pressed and molded using a stamping machine to obtain a double-layer structured pressed powder for valve seats. It should be noted that a portion is made into a single-layer structured pressed powder for valve seats.

[0143] The obtained compressed powder is further subjected to sintering to form a sintered body. The sintering process is carried out at a heating temperature of 1000–1200°C in an atmosphere of ammonia decomposition gas. It should be noted that during sintering, a Cu infiltration treatment is performed to fill the pores with Cu. It should be noted that sintered body No. 2 (existing example) undergoes forging (cold rotary forging) and then re-sintering. It should be noted that no Cu infiltration treatment is performed.

[0144] Next, the obtained sintered body is heat-treated, and then machined and ground to produce a valve seat (product) with an outer diameter of 37.7 mm × an inner diameter of 31.2 mm × a thickness of 6.0 mm. It should be noted that the heat treatment is a quenching and annealing process. Quenching involves heating to a temperature of 870°C followed by oil cooling, while annealing involves heating to a temperature of 640°C followed by air cooling.

[0145] Test pieces are collected from the valve seat (product), and the content (mass%) of each component in each layer is analyzed by luminescence analysis to determine the composition of each layer.

[0146] The results are shown in Table 5.

[0147]

[0148] In addition, the cross-section of the polished valve seat (product) was etched with a nitric acid-alcohol solution to expose the microstructure of each layer, which was then observed and photographed using a scanning electron microscope (or optical microscope) (magnification: 200x). The microstructure fraction in each layer was calculated through image analysis from the obtained microstructure photographs. The results are shown in Table 6. It should be noted that the microstructure shown in the table is pores (Cu leaching).

[0149]

[0150]

[0151] Next, the obtained valve seat (product) was used as a test piece and installed on... Figure 2 Abrasion resistance tests were conducted on the single-bench abrasion testing machine shown. The test conditions are as follows.

[0152] Test temperature: 300℃ (seat surface)

[0153] Test duration: 4 hours

[0154] Cam speed: 2500 rpm

[0155] Valve speed: 10 rpm

[0156] Valve material: SUH35 with nitride film

[0157] Heat source: LPG

[0158] After pressing valve seat 1 into clamp 2, which is equivalent to a cylinder head, valve 4 and valve seat 1 are heated using heat source 3 mounted on the testing machine, while valve 4 is raised and lowered using a crank mechanism to conduct the test. The wear of valve seat is calculated from the shape change before and after the test. The wear of valve 4 is calculated by measuring the indentation of the seat contact surface based on the shape measurement after the test.

[0159] The results are shown in Table 7.

[0160] In addition, the obtained valve seat (product) was used as a test piece. Figure 3 The drop resistance tester shown was used to conduct the drop resistance test. The test conditions are as follows.

[0161] Test temperature: 500℃

[0162] Duration: 1 hour

[0163] Initial tightening allowance: 90μm

[0164] Thermal cycling conditions: Repeated heating for 10 cycles at 500°C for 1 hour, followed by air cooling to below 100°C.

[0165] At room temperature, valve seat 1 is pressed into an article (test fixture 5) equivalent to a cylinder head. Then, while pressed in, valve seat 1 is subjected to a prescribed thermal cycle using a cylindrical heater 7 in a heat-resistant and water-resistant container 6 maintained in cooling water 9 at a certain temperature. After the prescribed thermal cycle, valve seat 1 is pushed using a push-press fixture (universal testing machine), and the load (pull-out load) and residual tightness when pulled out from the article (test fixture 5) equivalent to a cylinder head are measured. The results are shown in Table 7.

[0166] In addition, for the obtained valve seat (product), the radial crushing strength is calculated in accordance with the provisions of JIS Z 2507.

[0167] The results are recorded in Table 7.

[0168]

[0169] Compared to sintered body No. 1 (a prior art example), the wear rate of this invention is less than 29%, the wear resistance is improved, the pull-out load is more than 356%, the residual fastening allowance is more than 165% (functional component side layer), and the resistance to detachment is improved. Therefore, it can be seen that by manufacturing the valve seat of this invention, the wear resistance and resistance to detachment are significantly improved compared to the past. Furthermore, compared to sintered body No. 2 (a prior art example) subjected to rotary forging, this invention example has equal or higher wear resistance, substantially equal resistance to detachment, and equal or higher radial crushing strength.

[0170] Therefore, the valve seat (sintered body) of the present invention, with its excellent resistance to spalling and wear, is suitable for use in cast iron cylinder heads. On the other hand, comparative examples outside the scope of the present invention show less improvement in wear resistance and spalling resistance, and less increase in radial crush strength compared to existing examples.

[0171] Marker description

[0172] 1 valve seat,

[0173] 2 clamps,

[0174] 3 heat sources

[0175] 4 valves

[0176] 5. Test fixtures

[0177] 6. Heat- and water-resistant containers

[0178] 7-cylinder heater,

[0179] 8 simulated test pieces,

[0180] 9. Cooling water,

[0181] 11. Functional component side layer,

[0182] 12. Side layer of support component.

Claims

1. A sintered iron-based alloy valve seat for an internal combustion engine, which is a valve seat pressed into a cast iron cylinder head of an internal combustion engine, characterized in that, The valve seat has a single-layer structure consisting of functional component side layers. The functional component side layer comprises a matrix portion in which hard particles or solid lubricant particles are dispersed in the matrix phase, and pores filled with Cu by melt impregnation. The matrix phase consists of a fine carbide precipitate phase comprising less than 5.87% of the total area percentage relative to the total area of ​​the functional component side layers, and an annealed martensite phase. The matrix portion is composed of an iron-based sintered alloy material, which has a matrix structure in which 10.0% to 40.0% of the hard particles or 0.3% to 3.0% of the solid lubricant particles are dispersed in the matrix phase relative to the total area percentage of the functional component side layer, and further has 25.0% or less of a high-alloy phase around the hard particles, and contains C: 0.5% to 2.0% and further contains Si: 0.1% to 1.0% relative to the total mass percentage of the matrix portion. The matrix consists of one or more of the following: Mn: 0.1~2.5%, Ni: 1.0~7.0%, Cr: 1.0~12.0%, Mo: 2.0~12.0%, Co: 2.0~20.0%, W: 0.1~2.0%, V: 0.01~1.0%, and further contains S: 0~1.5%, with the balance being a matrix composed of Fe and unavoidable impurities, and further contains Cu, which is filled into the pores by melt infiltration at a rate of 1.0~20.0% relative to the area percentage of the total amount of the functional component side layer.

2. A sintered alloy valve seat based on iron for internal combustion engines, which is a valve seat pressed into a cast iron cylinder head of an internal combustion engine, characterized in that... The valve seat has a two-layer structure in which the functional component side layer and the support component side layer are integrally sintered. The functional component side layer comprises a matrix portion in which hard particles or solid lubricant particles are dispersed in a matrix phase, and pores filled with Cu by melt impregnation. The matrix phase consists of a fine carbide precipitate phase and an annealed martensite phase, comprising less than 5.87% of the total area percentage relative to the total amount of the functional component side layer. The matrix portion is composed of an iron-based sintered alloy material, which has a matrix structure in which 10.0% to 40.0% of the hard particles or 0.3% to 3.0% of the solid lubricant particles are dispersed in the matrix phase relative to the total area percentage of the functional component side layer, and further has 25.0% or less of a high-alloy phase around the hard particles, and contains C: 0.5% to 2.0% and further contains Si: 0.1% to 1.0% relative to the total mass percentage of the matrix portion. The matrix consists of one or more of the following: Mn: 0.1~2.5%, Ni: 1.0~7.0%, Cr: 1.0~12.0%, Mo: 2.0~12.0%, Co: 2.0~20.0%, W: 0.1~2.0%, V: 0.01~1.0%, and further contains S: 0~1.5%, with the balance being a matrix composed of Fe and unavoidable impurities. It also contains Cu, which is melt-filled into the pores at a rate of 1.0~20.0% per square meter of area relative to the total area of ​​the functional component side layer. The support component side layer comprises a matrix portion in which solid lubricant particles are dispersed in a matrix phase, and pores filled with Cu by melt infiltration. The matrix phase is composed of an annealed martensitic phase, and the matrix portion is composed of an iron-based sintered alloy material. The iron-based sintered alloy material has a matrix portion structure in which 0 to 3.0% of the solid lubricant particles are dispersed in the matrix phase relative to the total area percentage of the support component side layer, and a matrix portion containing, relative to the total mass percentage of the matrix portion, C: 0.1 to 1.5%, further containing one or more of Cr: 1.0 to 10.0%, Mo: 0.1 to 3.0%, Ni: 0.1 to 2.0%, further containing Mn: 0 to 1.0% and S: 0 to 1.0%, with the balance being Fe and unavoidable impurities. The matrix portion further contains 1.0 to 20.0% Cu filled in the pores by melt infiltration relative to the total area percentage of the support component side layer.

3. The iron-based sintered alloy valve seat for internal combustion engines as described in claim 1 or 2, characterized in that, The hard particles are intermetallic compound particles having a composition of Ni: 5.0~15.0%, Cr: 20.0~30.0%, Mo: 20.0~30.0%, Si: 1.0~5.0%, with the balance being Co, and having a hardness of 900~1300 HV on a Vickers hardness scale; or intermetallic compound particles having a composition of Cr: 5.0~15.0%, Mo: 25.0~35.0%, Si: 1.0~5.0%, with the balance being Co, and having a hardness of 600~900 HV on a Vickers hardness scale.

4. The iron-based sintered alloy valve seat for internal combustion engines as described in claim 1 or 2, characterized in that, The solid lubricant particles are MnS particles.

5. A method for manufacturing an iron-based sintered alloy valve seat for an internal combustion engine, wherein the method for manufacturing a single-layer iron-based sintered alloy valve seat for an internal combustion engine as described in claim 1, is characterized in that... When a mixed powder is prepared by mixing and kneading a specified amount of iron-based powder, graphite powder, alloy element powder, hard particle powder, or further mixing a specified amount of solid lubricant particle powder in a manner that forms the matrix composition and matrix structure of the functional component side layer of the single-layer structure, it becomes a mixed powder. The iron-based powder is selected from one or more of pure iron powder, alloy iron powder, and alloy steel powder, expressed as a percentage by mass relative to the total amount of the mixed powder. The graphite powder, alloy element powder, hard particle powder, and solid lubricant particle powder are respectively mixed and kneaded to form a mixed powder, which has the following properties: In the molding process, the mixed powder is filled into a mold of a specified shape, compressed, and molded to obtain pressed powder. The sintering process involves sintering the obtained pressed powder in a reducing atmosphere at a heating temperature of 1100~1200℃ to obtain a sintered body. The Cu melting process involves subjecting the obtained sintered body to Cu melting treatment to fill the pores of the sintered body with Cu; and The heat treatment process includes a quenching and annealing process in which the sintered body with Cu impregnated in the pores is reheated to a quenching temperature of 800~1000℃ and then rapidly cooled, and then reheated to an annealing temperature of 500~700℃ and then cooled.

6. A method for manufacturing an iron-based sintered alloy valve seat for an internal combustion engine, comprising the method for manufacturing a double-layered iron-based sintered alloy valve seat for an internal combustion engine as described in claim 2, characterized in that... When a mixed powder is prepared by mixing and kneading a specified amount of iron-based powder, graphite powder, alloy element powder, hard particle powder, or further mixing a specified amount of solid lubricant particle powder in a manner that constitutes the matrix composition and matrix structure of the aforementioned double-layer structure, the mixed powder is prepared. The iron-based powder is selected from one or more of pure iron powder, alloy iron powder, and alloy steel powder, expressed as a percentage by mass relative to the total amount of the mixed powder. The graphite powder (0.5-2.0%), alloy element powder (0-5.0%), hard particle powder (10.0-40.0%), and solid lubricant particle powder (0-3.0%) are respectively mixed and kneaded to produce a mixed powder for the side layer of functional components. On the other hand, The iron-based powder is selected from one or two types of pure iron powder and alloy iron powder. In terms of mass percentage relative to the total amount of the mixed powder, The graphite powder, alloy element powder, and solid lubricant particle powder are respectively mixed and kneaded to form a mixed powder for the side layer of the support component, which has the following properties: In the molding process, a specified amount of the mixed powder for the side layer of the support component and the mixed powder for the side layer of the functional component are sequentially filled into a mold, and compressed and molded as a whole to obtain a pressed powder body. The sintering process involves sintering the obtained pressed powder in a reducing atmosphere at a heating temperature of 1100~1200℃ to obtain a sintered body. The Cu melting process involves subjecting the obtained sintered body to Cu melting treatment to fill the pores of the sintered body with Cu; and The heat treatment process includes a quenching and annealing process in which the sintered body with Cu impregnated in the pores is reheated to a quenching temperature of 800~1000℃ and then rapidly cooled, and then reheated to an annealing temperature of 500~700℃ and then cooled.

7. The method for manufacturing an iron-based sintered alloy valve seat for an internal combustion engine as described in claim 5 or 6, characterized in that, Instead of the sintering process and the Cu melting process, The sintering process includes a Cu melting process, which involves sintering the pressed powder in a reducing atmosphere at a heating temperature of 1100-1200°C, and performing a Cu melting process during the sintering process to obtain a sintered body with Cu melt-impregnated in the pores.

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