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. A valve seat is produced that has 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 a layer in which a hard particle or a solid lubricant particle is dispersed in a matrix phase mainly composed of an annealed martensite phase, and further, a high alloy phase is present around the hard particle, and further, a matrix portion composition containing C: 0.3 to 2.0% by mass, and further, one or two or more selected from Si, Mn, Ni, Cr, Mo, Co, or further, S, and a layer in which pores are filled with Cu by melting and impregnation. Thus, the wear resistance and peeling resistance are improved, and even when used in a cast iron cylinder head of an internal combustion engine, sufficient durability can be maintained.

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, as the aforementioned hard particles, one or more types of hard particles selected from Cr-Mo-Si-Co, Cr-Mo-Ni-Si-Co, and Mo-based hard particles, comprising 31% to 80% of the precipitate by area, 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 is required, followed by re-sintering. Therefore, the technology described in Patent Document 1 suffers from complex processes and high manufacturing costs. 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 for hot forging involve complex hot processing steps.

[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] In order to achieve the above objectives, the inventors first conducted an in-depth study on various factors affecting the resistance to detachment of the pressed-in valve seat.

[0015] The following approach was considered: First, Cu impregnation treatment was applied to the sintered body (valve seat) to impregnate Cu within the pores, thereby increasing the strength of the valve seat. Then, quenching and annealing (heat treatment) was performed to stabilize the matrix phase. Next, in addition to improving resistance to shedding, to also enhance wear resistance, it was further considered to disperse high-hardness, low-aggression Ni-Cr-Mo-Co intermetallic compound particles or Cr-Mo-Co intermetallic compound particles as hard particles within the matrix phase.

[0016] This invention was completed based on such insights and further research.

[0017] In other words, the key points of this invention are as follows.

[0018] [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,

[0019] The valve seat has a single-layer structure consisting of functional component side layers.

[0020] 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.

[0021] The matrix phase is composed of annealed martensite.

[0022] The matrix is ​​composed of an iron-based sintered alloy material, which has a matrix structure in which 10.0% to 50.0% 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 less than 60.0% of a high-alloy phase is surrounding the hard particles. It also contains 0.3% to 2.0% C relative to the total mass percentage of the matrix, and further contains components selected from Si. The composition consists of one or more of the following: 0.1-1.5% Mn, 0.1-2.5% Ni, 1.0-6.0% Cr, 1.0-20.0% Mo, 2.0-15.0% Co, and 10.0-30.0% S, with the balance being a matrix composed of Fe and unavoidable impurities, and further containing 1.0-20.0% Cu (melt-impregnated) melt-impregnated into the pores relative to the total area % of the functional component side layer.

[0023] [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,

[0024] The valve seat has a two-layer structure in which the functional component side layer and the support component side layer are integrally sintered.

[0025] 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.

[0026] The matrix phase is composed of annealed martensite.

[0027] The matrix is ​​composed of an iron-based sintered alloy material, which has a matrix structure in which 10.0% to 50.0% 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 less than 60.0% of a high-alloy phase is surrounding the hard particles. It also contains 0.3% to 2.0% C relative to the total mass percentage of the matrix, and further contains components selected from Si. The composition comprises one or more of the following: 0.1–1.5% Mn, 0.1–2.5% Ni, 1.0–6.0% Cr, 1.0–20.0% Mo, 2.0–15.0% Co, and 10.0–30.0% S, with the balance consisting of a matrix composed of Fe and unavoidable impurities, and further containing 1.0–20.0% Cu (melt-impregnated) melt-impregnated into the pores relative to the total area percentage of the functional component side layer.

[0028] 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 having 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 comprising, relative to the total mass percentage of the matrix portion, C: 0.1 to 1.5%, further comprising one or more of Cr: 1.0 to 10.0%, Mo: 0.1 to 3.0%, Ni: 0.1 to 2.0%, further comprising Mn: 0 to 1.0% and S: 0 to 1.0%, with the balance being Fe and unavoidable impurities, and further comprising 1.0 to 20.0% Cu melt-infiltrated into the pores relative to the total area percentage of the support component side layer.

[0029] 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.

[0030] [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.

[0031] 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.

[0032] [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,

[0033] 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.

[0034] The iron-based powder is selected from one or two types of pure iron powder and alloy iron powder.

[0035] In terms of mass % relative to the total amount of the mixed powder,

[0036] The graphite powder is mixed with 0.5-2.0% of the graphite powder, 0-5.0% of the alloying element powder, and 10.0-50.0% of the hard particle powder, respectively.

[0037] 0-3.0% of the solid lubricant particle powder is mixed and kneaded to form a mixed powder, which has the following properties:

[0038] In the molding process, the mixed powder is filled into a mold of a specified shape, compressed, and molded to obtain pressed powder.

[0039] 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.

[0040] 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

[0041] 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.

[0042] [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,

[0043] 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.

[0044] The iron-based powder is selected from one or two types of pure iron powder and alloy iron powder, expressed as a percentage by mass relative to the total amount of the mixed powder.

[0045] The graphite powder is mixed with 0.5-2.0% of the graphite powder, 0-5.0% of the alloying element powder, and 10.0-50.0% of the hard particle powder, respectively.

[0046] 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,

[0047] The iron-based powder is selected from one or two types of pure iron powder and alloy iron powder, expressed as a percentage by mass relative to the total amount of the mixed powder.

[0048] 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:

[0049] 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.

[0050] 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.

[0051] 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

[0052] 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.

[0053] 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.

[0054] The effects of the invention

[0055] According to the present invention, high-strength iron-based sintered alloy valve seats with excellent wear resistance and detachment resistance can be manufactured inexpensively for use in cast iron cylinder heads, which has a significant effect on industry. Attached Figure Description

[0056] [ Figure 1 A cross-sectional view schematically illustrating an example of the cross-sectional structure of the valve seat of the present invention.

[0057] [ Figure 2 A schematic diagram illustrating a single-bench wear testing machine.

[0058] [ Figure 3 A schematic diagram illustrating the shedding test machine. Detailed Implementation

[0059] like Figure 1 As shown, the valve seat 1 of the present invention is a double-layer valve seat 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 it can be made into a single-layer valve seat with only the functional component side layer 11 as shown in the figure.

[0060] First, the functional component side layer will be explained.

[0061] 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 pores are filled with Cu.

[0062] In the valve seat of this invention, Cu is filled into the pores through a melt-dip treatment, 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-dip treatment 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 wear resistance cannot be ensured.

[0063] In the functional component side layer, the matrix phase consists of annealed martensite.

[0064] By making the matrix phase an annealed martensitic phase, the strength and toughness of the valve seat are improved, and a valve seat that can maintain high performance even in harsh operating environments with high engine combustion temperatures can be manufactured.

[0065] 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 50.0% 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 the matrix portion has a high alloy phase of less than 60.0% around the hard particles.

[0066] Hard particles dispersed in the matrix phase contribute to improved wear resistance, with a dispersion amount ranging from 10.0% to 50.0% 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 50.0%, pairing aggression increases.

[0067] 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% by mass, 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% by mass, with the balance being Co, and having a hardness of 600–900 HV on a Vickers hardness scale. These Ni-Cr-Mo-Co intermetallic compound particles and Cr-Mo-Co intermetallic compound particles are hard particles with high hardness and low pairing aggression.

[0068] Furthermore, solid lubricant particles dispersed in the matrix phase contribute to improved machinability, and should be dispersed as needed. During dispersion, the amount of dispersed particles is preferably 0.3 to 3.0% of the area relative to the total area of ​​the functional component side layer. If the amount of dispersed 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 amount of solid lubricant particles is preferably limited to the range of 0.3 to 3.0% of the area relative to the total area of ​​the functional component side layer. MnS particles are preferred as the solid lubricant particles.

[0069] In the functional component side layer of the valve seat of the present invention, a high-alloy phase, comprising 60.0% or less of the area percentage relative to the total area of ​​the functional component side layer, is present around the aforementioned hard particles. The high-alloy phase is formed by the diffusion of alloying elements from the hard particles during sintering, resulting in a stable phase that helps prevent the shedding or bonding of hard particles. It should be noted that if the high-alloy phase content is less than 1.0% in area percentage, the aforementioned effect cannot be expected; therefore, 1.0% or more is preferred.

[0070] Furthermore, in the functional component side layer of the valve seat of the present invention, the matrix portion contains C: 0.3 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 1.5%, Mn: 0.1 to 2.5%, Ni: 1.0 to 6.0%, Cr: 1.0 to 20.0%, Mo: 2.0 to 15.0%, Co: 10.0 to 30.0%, and further contains S: 0 to 2.0%, with the balance being Fe and unavoidable impurities.

[0071] 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.

[0072] C: 0.3–2.0%

[0073] Carbon (C) is included in the matrix phase and is an element that contributes to the strengthening of the matrix phase and improves its wear resistance. In this invention, it is necessary to contain 0.3% or more. On the other hand, if it exceeds 2.0%, the matrix hardness decreases. Therefore, C is limited to the range of 0.3% to 2.0%.

[0074] Selected from one or more of the following: Si: 0.1–1.5%, Mn: 0.1–2.5%, Ni: 1.0–6.0%, Cr: 1.0–20.0%, Mo: 2.0–15.0%, and Co: 10.0–30.0%.

[0075] Si: 0.1–1.5%

[0076] Si, when included in the matrix phase, contributes to increased strength and improved wear resistance of the matrix phase. These effects are not observed below 0.1%. On the other hand, a content exceeding 1.5% increases pairing aggression. Therefore, when present, Si is preferably limited to the range of 0.1% to 1.5%.

[0077] Mn: 0.1–2.5%

[0078] Mn, contained in the matrix phase, contributes to the strengthening of the matrix phase and improves its wear resistance. Additionally, some MnS particles, dispersed in the matrix phase as solid lubricant, contribute to improved formability and machinability. 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%.

[0079] Ni: 1.0–6.0%

[0080] Ni, contained in both the matrix phase and hard particles, is an element that improves not only wear resistance but also strength and heat resistance. If the content is below 1.0%, these effects are minimal. Conversely, if the content exceeds 6.0%, wear resistance decreases. Therefore, when present, Ni is preferably limited to the range of 1.0% to 6.0%.

[0081] Cr: 1.0–20.0%

[0082] Cr, contained in the matrix phase and hard particles, is an element that improves not only wear resistance but also strength and heat resistance, and is preferably present at 1.0% or more. On the other hand, a content exceeding 20.0% increases pairing aggression. Therefore, when present, Cr is preferably limited to the range of 1.0% to 20.0%.

[0083] Mo: 2.0–15.0%

[0084] Like Ni and Cr, Mo is contained in the matrix phase and hard particles. It is an element that improves not only wear resistance but also strength and heat resistance, and is preferably present at 2.0% or more. On the other hand, a content exceeding 15.0% increases pairing aggression. Therefore, when present, Mo is preferably limited to the range of 2.0% to 15.0%.

[0085] Co: 10.0%–30.0%

[0086] Like Ni and Cr, Co is contained in the matrix phase and hard particles. Besides improving wear resistance, it enhances strength and heat resistance while strengthening the bond between hard particles and the matrix phase. It is preferable to contain 10.0% or more of Co. On the other hand, if the content exceeds 30.0%, pairing aggression increases. Therefore, when Co is present, it is preferably limited to the range of 10.0% to 30.0%.

[0087] In addition to the above-mentioned components, it may also contain S: 0-2.0%.

[0088] S: 0~2.0%

[0089] S, primarily dispersed as solid lubricant particles (MnS) in the matrix, is an element that contributes to improved formability and machinability. To achieve this effect, a content of 0.1% or more is preferred. On the other hand, if the content exceeds 2.0%, wear resistance decreases. Therefore, S is limited to a range of 0% to 2.0%.

[0090] The balance other than the above components consists of Fe and unavoidable impurities.

[0091] The amount of Cu impregnated into the pores in the functional component side layer of the valve seat of the present invention (Cu impregnation amount) is limited to 1.0% to 20.0% in area percentage relative to the total area of ​​the functional component side layer. If the Cu impregnation amount is less than 1.0%, the desired strength of the valve seat cannot be ensured. On the other hand, if the impregnation amount increases to more than 20.0%, the wear resistance decreases. Therefore, the Cu impregnation amount in the functional component side layer is limited to a range of 1.0% to 20.0% in area percentage relative to the total area of ​​the functional component side layer.

[0092] Furthermore, the support component side layer of the valve seat of the present invention is made of an iron-based sintered alloy material. This iron-based sintered alloy material has a matrix portion in which solid lubricant particles, with an area ratio of 0 to 1.0%, are dispersed in the matrix phase, and includes pores filled with Cu through melt impregnation. It should be noted that the porosity of the support component side layer before melt impregnation ranges from 1.0% to 20.0% in area percentage. 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.

[0093] The matrix phase in the side layer of the valve seat support component of this invention is annealed martensite. By making the matrix phase annealed martensite, the strength and toughness of the side layer of the support component are improved, as is its resistance to shedding. Even in harsh operating environments with high engine temperatures, the desired high performance can be fully maintained.

[0094] Furthermore, the matrix portion of the support member side layer of the valve seat of the present invention has a matrix portion 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. When solid lubricant particles are dispersed, it is preferable to disperse 0.1% or more. On the other hand, if the amount of solid lubricant particles exceeds 3.0%, the effect of improving formability and machinability becomes saturated. Therefore, the amount of solid lubricant particles is preferably limited to 0 to 1.0% based on the area percentage relative to the total area of ​​the support member side layer. MnS particles are preferred as the solid lubricant particles.

[0095] 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.

[0096] Next, the reasons for defining each component in the matrix of the side layer of the support member will be explained.

[0097] C: 0.1-1.5%

[0098] 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%.

[0099] In addition to C mentioned above, the matrix portion of the side layer of the support component also contains one or more of the following: Cr: 1.0 to 10.0%, Mo: 0.1 to 3.0%, Ni: 0.1 to 2.0%.

[0100] Cr: 1.0–10.0%

[0101] 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, when included, Cr is preferably limited to the range of 1.0% to 10.0%.

[0102] Mo: 0.1–3.0%

[0103] 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, when included, Mo is preferably limited to 0.1% to 3.0%.

[0104] Ni: 0.1–2.0%

[0105] 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, and can be included as needed. When present, 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, when present, Ni is preferably limited to 0.1% to 2.0%.

[0106] In addition to the above-mentioned components, it may also contain Mn: 0-1.0% and S: 0-1.0%.

[0107] Mn: 0~1.0%

[0108] Mn is contained in the matrix phase and contributes to its strengthening. Additionally, a portion of MnS particles, acting as solid lubricant particles dispersed in the matrix phase, contributes to improved machinability and can be included as needed. When present, it is preferable to contain 0.1% or more. On the other hand, a content exceeding 1.0% will reduce formability. Therefore, Mn is preferably limited to 0–1.0%.

[0109] S: 0~1.0%

[0110] S, primarily dispersed as solid lubricant particles in the matrix, is an element that contributes to improved formability and machinability, and 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, resulting in reduced strength (hardness). Therefore, S is preferably limited to 0–1.0%.

[0111] It should be noted that the Cu (melted impregnation) in the pores of the side layer of the support component is limited to 1.0% to 20.0% relative to the total area of ​​the side layer of the support component. If the Cu (melted impregnation) is less than 1.0%, the desired strength of the valve seat cannot be ensured. If the Cu (melted impregnation) increases to more than 20.0%, the resistance to detachment decreases. Therefore, the Cu (melted impregnation) in the side layer of the support component is limited to a range of 1.0% to 20.0% relative to the total area of ​​the side layer of the support component.

[0112] Next, a preferred manufacturing method for the valve seat of the present invention will be described.

[0113] 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.

[0114] The mixed powder for the side layer of the functional component 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 component. It should be noted that the iron-based powder mixed in the mixed powder for the side layer of the functional component to form the matrix phase can be, for example, pure iron powder or alloy iron powder. Examples of alloy iron powder include Cr-Mo alloy iron powder containing a specified amount of Cr and Mo, or Cr-Mo-Ni alloy iron powder containing a specified amount of Ni in addition to Cr and Mo.

[0115] 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 support component. It should be noted that the iron-based powder used as the matrix phase for forming the side layer of the support component can be pure iron powder or alloy iron powder. As alloy iron powder, examples include Cr-Mo alloy iron powder containing a specified amount of Cr and Mo, or Cr-Mo-Ni alloy iron powder containing a specified amount of Ni in addition to Cr and Mo.

[0116] Next, the manufacturing method of the valve seat of the present invention includes a forming process, a sintering process, a Cu melting and impregnation process, and a heat treatment process.

[0117] In the molding process, the obtained mixed powder is filled into a mold and compressed and molded using a stamping machine to obtain a pressed powder body. It should be noted that when making a double-layer valve seat, the mixed powder for the functional component side layer and the mixed powder for the support 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 also be noted that in the molding process, the compression pressure is adjusted to produce a pressed powder body with the desired porosity.

[0118] 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, in which the forming and sintering processes are repeated twice, is also possible.

[0119] In the Cu melting process, Cu is melt-infiltrated to fill the pores of the resulting sintered body. It should be noted that a Cu melting process can also be included in the sintering process, and the Cu melting process can be performed during the sintering process.

[0120] In the heat treatment process, in order to impart the desired strength and to stabilize the matrix, the sintered body filled with Cu in the pores is further heat-treated (quenched and annealed).

[0121] It should be noted that the quenching treatment is preferably performed by heating in a vacuum to a quenching temperature range of 800–1000°C and holding it, followed by 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, followed by cooling (using N2 gas or air cooling).

[0122] The sintered body that has undergone heat treatment is processed into valve seats (products) of a specified shape through cutting, grinding, and other processes.

[0123] The present invention will be further described below based on embodiments.

[0124] Example

[0125] 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.

[0126] [Table 1]

[0127]

[0128] * Refer to Table 3

[0129] **Refer to Table 4

[0130] ***)SL1:MnS

[0131] [Table 2]

[0132]

[0133] * Refer to Table 3

[0134] **Refer to Table 4

[0135] ***)SL1:MnS

[0136] [Table 3]

[0137]

[0138] [Table 4]

[0139]

[0140] Next, these mixed powders are integrally pressed and molded using a stamping machine to obtain a double-layered valve seat pressed powder. It should be noted that a portion is made into a single-layered valve seat pressed powder with only the functional component side layer.

[0141] The obtained pressed powder is further subjected to sintering treatment to form a sintered body. The sintering treatment is carried out at a heating temperature of 1000-1200℃ in an ammonia decomposition gas atmosphere (reducing atmosphere). It should be noted that during sintering, Cu melting treatment is performed to fill the pores of the sintered body with Cu.

[0142] It should be noted that for sintered body No.2 (existing example), Cu melting treatment was not performed. Sintered body No.2 (existing example) was subjected to cold rotary forging and then re-sintered.

[0143] Next, the obtained sintered bodies (except for sintered body No. 2) were subjected to heat treatment, and then machined and ground to produce valve seats (products) 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 was quenching and annealing. Quenching involved heating to a temperature of 870°C followed by oil cooling, while annealing involved heating to a temperature of 600°C followed by air cooling.

[0144] 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.

[0145] The results are shown in Table 5.

[0146]

[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 an optical microscope (magnification: 200x). From the obtained microstructure photographs, the microstructure fraction (area ratio) in each layer was calculated through image analysis. The results are shown in Table 6. It should be noted that the microstructure shown in the table is pores (Cu leaching).

[0149] 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.

[0150] Test temperature: 300℃ (seat surface)

[0151] Test duration: 4 hours

[0152] Cam speed: 2500 rpm

[0153] Valve speed: 10 rpm

[0154] Valve material: SUH35 residual nitride film

[0155] Heat source: LPG

[0156] After pressing the valve seat 1 into the clamp 2, which corresponds to the cylinder head, the valve 4 and valve seat 1 are heated using a heat source 3 mounted on the testing machine, while the valve 4 is raised and lowered using a crank mechanism to conduct the test. The wear amount of the valve seat is determined by comparing its shape before the test with its shape after the test. Furthermore, the wear amount of valve 1 is obtained by measuring the shape after the test and determining the amount of indentation on the valve seat contact surface.

[0157] The results are shown in Table 7.

[0158] In addition, the obtained valve seat (product) was used as a test piece. Figure 3 The test machine shown was used to conduct a shedding resistance test. The test conditions are as follows.

[0159] Test temperature: 500℃

[0160] Duration: 1 hour

[0161] Initial tightening allowance: 90μm

[0162] Thermal cycling conditions: Repeated heating for 10 cycles at 500°C for 1 hour, followed by air cooling to below 100°C.

[0163] 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 constant 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 equivalent to a cylinder head are measured. The results are shown in Table 7.

[0164] In addition, for the obtained valve seat (product), the radial crushing strength is calculated in accordance with the provisions of JIS Z 2507.

[0165] The results are recorded in Table 7.

[0166]

[0167]

[0168]

[0169] Compared to sintered body No. 1 (a prior art example), the wear rate of the present invention is less than 30%, the wear resistance is improved, the pull-out load is greater than 366%, the residual fastening allowance is greater than 185% (functional component side layer), and the resistance to detachment is improved. Therefore, it can be seen that by manufacturing a valve seat with the structure and composition of the present 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, the present invention examples have equal or higher wear resistance, substantially equal resistance to detachment, and equal or higher radial crushing strength.

[0170] On the other hand, the comparative examples, which are outside the scope of the present invention, show less improvement in wear resistance and detachment resistance, and less increase in radial crush strength compared to sintered bodies No. 1 and No. 2 (existing examples).

[0171] Therefore, it can be said that the valve seat of the present invention is particularly suitable as a valve seat that is pressed into a cast iron cylinder head.

[0172] Marker description

[0173] 1. Valve seat,

[0174] 2. Fixtures

[0175] 3. Heat source

[0176] 4 valves

[0177] 5. Test fixtures,

[0178] 6. Heat- and water-resistant containers,

[0179] 7. Cylindrical heater,

[0180] 8. Simulated test pieces,

[0181] 9. Cooling water,

[0182] 11. Functional component side layer,

[0183] 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 is composed of annealed martensite. The matrix is ​​composed of an iron-based sintered alloy material, which has a matrix structure in which 10.0% to 50.0% 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 less than 60.0% of a high-alloy phase is surrounding the hard particles. It also contains 0.3% to 2.0% C relative to the total mass percentage of the matrix, and further contains components selected from Si. The composition consists of one or more of the following: 0.1-1.5% Mn, 0.1-2.5% Ni, 1.0-6.0% Cr, 1.0-20.0% Mo, 2.0-15.0% Co, and 10.0-30.0% S, with the balance being a matrix composed of Fe and unavoidable impurities, and further containing 1.0-20.0% Cu (melt-impregnated) melt-impregnated into the pores relative to the total area % 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 the matrix phase, and pores filled with Cu by melt impregnation. The matrix phase is composed of annealed martensite. The matrix is ​​composed of an iron-based sintered alloy material, which has a matrix structure in which 10.0% to 50.0% 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 less than 60.0% of a high-alloy phase is surrounding the hard particles. It also contains 0.3% to 2.0% C relative to the total mass percentage of the matrix, and further contains components selected from Si. The composition comprises one or more of the following: 0.1–1.5% Mn, 0.1–2.5% Ni, 1.0–6.0% Cr, 1.0–20.0% Mo, 2.0–15.0% Co, and 10.0–30.0% S, with the balance consisting of a matrix composed of Fe and unavoidable impurities, and further containing 1.0–20.0% Cu (melt-impregnated) melt-impregnated into the pores relative to the total area percentage 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 having 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 comprising, relative to the total mass percentage of the matrix portion, C: 0.1 to 1.5%, further comprising one or more of Cr: 1.0 to 10.0%, Mo: 0.1 to 3.0%, Ni: 0.1 to 2.0%, further comprising Mn: 0 to 1.0% and S: 0 to 1.0%, with the balance being Fe and unavoidable impurities, and further comprising 1.0 to 20.0% Cu melt-infiltrated into the pores 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 two types of pure iron powder and alloy iron powder. In terms of 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°C 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℃, then rapidly cooled, and then reheated to an annealing temperature of 500-700℃ before cooling.

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 two types of pure iron powder and alloy iron 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 (10.0–50.0%), and solid lubricant particle powder (0–3.0%) are respectively mixed and kneaded to prepare 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, expressed as a percentage by mass 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°C 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℃, then rapidly cooled, and then reheated to an annealing temperature of 500-700℃ before cooling.

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 the Cu melting and impregnation process, which involves sintering the pressed powder in a reducing atmosphere at a heating temperature of 1100-1200°C, and performing Cu melting and impregnation during the sintering process to obtain a sintered body with Cu melt-impregnated in the pores.

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