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

Abstract

To provide a valve seat formed of an iron sintered alloy which is excellent in wear resistance and falling resistance.SOLUTION: There is provided, a two layer structure valve seat 1 which is obtained by integrating by sintering, a function member layer 11 and a support member layer 12. The function member layer includes in a matrix phase mainly formed of an annealing martensite phase: dispersed hard particles or solid lubricant particles; and a matrix part tissue having a high alloy phase around the hard particles. The valve seat has a matrix part composition which includes in mass%, one or two or more kinds selected from: 0.3-2.0% of C; 0.1-1.5% of Si; 0.1-2.5% of Mn; 0.1-2.0% of S; 1.0-6.0% of Ni; 1.0-20.0% of Cr; 2.0-15.0% of Mo; 10.0-30.0% of Co, or the valve seat further includes 0.1-2.0% of S, and a balance Fe and inevitable impurities, and a layer including holes in which Cu is filled by infiltration.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an iron-based sintered alloy valve seat for internal combustion engines and a method for manufacturing the same, and particularly relates to improvement of wear resistance of a valve seat that is used by being press-fitted into a cast iron cylinder head, and improvement of falling resistance from the cylinder head.

Background Art

[0002] A valve seat plays the roles of sealing combustion gas and cooling the valve, and is used by being press-fitted into the cylinder head of an engine. In addition to sufficient wear resistance to withstand wear caused by repeated abutment of the valve, heat resistance, corrosion resistance and the like, a valve seat is also required to have low aggressiveness to the counterpart material so as not to wear the valve which is the counterpart material.

[0003] In recent years, along with the promotion of higher efficiency and higher load of engines, the temperature around the combustion chamber tends to rise. As a result, the thermal load on the valve seat becomes further higher, and the valve seat is required to withstand harsh usage environments.

[0004] In response to such requirements, 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 integrally sintered in two layers of a surface layer portion and a base layer portion, wherein the porosity of the surface layer portion is 5 to 20%, and the porosity of the base layer portion is 5% or less. The sintered alloy valve seat described in Patent Document 1 is manufactured by forming a two-layer integrated sintered body, then subjecting the sintered body to cold rotary forging from the base layer side, and then performing a resintering step.

[0005] Furthermore, Patent Document 2 describes a valve seat made of iron-based sintered alloy for internal combustion engines. The valve seat described in Patent Document 2 has a single-layer structure, and the matrix phase consists of a tempered martensite phase in which fine carbides with a major axis of 30 μm or less are precipitated at an area ratio of 27% or less. In addition, the matrix phase has a structure in which one or more types of hard particles selected from Cr-Mo-Si-Co hard particles, Cr-Mo-Ni-Si-Co hard particles, and Mo hard particles are dispersed at an area ratio of 31-80%, and has a density of 7.3-8.2 g / cm³. 3 The valve seat has a compression ring strength of 400 MPa or more and is said to have excellent wear resistance and resistance to detachment. The valve seat described in Patent Document 2 is said to involve a mixing step in which raw material powders are blended to form a mixed powder with a predetermined composition, a molding step in which the mixed powder is compressed and molded to form a compact, a sintering step in which the compact is heated and sintered to form a valve seat-shaped sintered body, a hot working step in which hot forging is performed on the valve seat-shaped sintered body, and a heat treatment step in which heat treatment is performed thereafter to impart predetermined properties to the valve seat-shaped sintered body. According to the technology described in Patent Document 2, it is possible to easily manufacture a valve seat that exhibits excellent durability even under harsh conditions. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Special Publication No. 61-10644 [Patent Document 2] Japanese Patent Publication No. 2018-178208 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the technology described in Patent Document 1 requires a process of compression forging by cold rotary forging of the sintered body and then re-sintering in order to reduce the porosity of the base layer of the valve seat. Therefore, the technology described in Patent Document 1 has the problem of being complex and having high manufacturing costs. In addition, the technology described in Patent Document 2 also has the problem of the valve seat density being 7.3 g / cm³. 3 As described above, the process required a hot working step involving hot forging, which resulted in a complex manufacturing process.

[0008] The present invention aims to solve the problems of the prior art described above and to provide a high-strength iron-based sintered alloy valve seat that is inexpensive compared to the prior art, has excellent wear resistance and resistance to detachment, and is suitable as a valve seat for press-fitting into the cylinder head of an internal combustion engine, particularly a cast iron cylinder head. [Means for solving the problem]

[0009] To achieve the above objective, the inventors first diligently investigated various factors affecting the resistance of press-fitted valve seats to falling off.

[0010] As a result, we first decided to apply a Cu fusion treatment to the sintered body (valve seat) to impregnate the pores with Cu and increase the strength of the valve seat, and then to perform a quenching and tempering treatment (heat treatment) to stabilize the base phase. Furthermore, in order to provide both resistance to detachment and wear resistance, we came up with the idea of ​​dispersing Ni-Cr-Mo-Co intermetallic compound particles or Cr-Mo-Co intermetallic compound particles, which have high hardness and low aggressiveness towards other materials, as hard particles in the base phase.

[0011] This invention was completed based on these findings and further investigations.

[0012] In other words, the gist of the present invention is as follows: [1] A valve seat that is press-fitted into the cylinder head of an internal combustion engine, The valve seat has a single-layer structure consisting of a functional member side layer, The functional member side layer comprises a base portion in which hard particles or solid lubricant particles are dispersed in the base phase, and voids filled with Cu by dissolution. The aforementioned base phase consists of a tempered martensite phase. The aforementioned matrix has a structure in which, by area % of the total amount of the functional member side layer, 10.0 to 50.0% of the hard particles, or further 0.3 to 3.0% of the solid lubricant particles, are dispersed in the matrix phase, and 60.0% or less of the high alloy phase surrounds the hard particles. The matrix also contains, by mass % of the total amount of the matrix, C: 0.3 to 2.0%, and further Si: 0.1 to 1.5%, Mn: 0.1 to 2.5%, Ni: 1.0 to 6.0%, and Cr: 1.0 to 2%. A valve seat made of an iron-based sintered alloy for internal combustion engines, characterized by comprising one or more elements selected from 0.0%, Mo: 2.0-15.0%, and Co: 10.0-30.0%, or further comprising S: 0.1-2.0%, with the remainder being Fe and unavoidable impurities, and further containing Cu (dissolved) dissolved in the voids at an area percentage of 1.0-20.0% relative to the total amount of the functional member side layer. [2] A valve seat that is press-fitted into the cylinder head of an internal combustion engine, The valve seat has a two-layer structure in which a functional member side layer and a support member side layer are sintered together as a single unit. The functional member side layer comprises a base portion in which hard particles or solid lubricant particles are dispersed in the base phase, and voids filled with Cu by dissolution. The aforementioned base phase consists of a tempered martensite phase. The aforementioned matrix has a structure in which, in terms of area % of the total amount of the functional member side layer, 10.0 to 50.0% of the hard particles, or further 0.3 to 3.0% of the solid lubricant particles, are dispersed in the matrix phase, and 60.0% or less of the high alloy phase surrounds the hard particles. The matrix also contains, in terms of mass % of the total amount of the matrix, C: 0.3 to 2.0%, and further Si: 0.1 to 1.5%, Mn: 0.1 to 2.5%, Ni: 1 The material is an iron-based sintered alloy material having a matrix composition consisting of one or more elements selected from 0.0-6.0%, Cr: 1.0-20.0%, Mo: 2.0-15.0%, Co: 10.0-30.0%, further containing S: 0-2.0%, with the remainder being Fe and unavoidable impurities, and further containing Cu (dissolved) dissolved in the voids at an area percentage of 1.0-20.0% relative to the total amount of the functional member side layer. The support member side layer comprises a matrix in which solid lubricant particles are dispersed in a matrix phase, and voids filled with Cu by dissolution, the matrix phase being a tempered martensite phase, the matrix structure comprising a matrix in which the solid lubricant particles are dispersed at an area % of the total amount of the support member side layer, and containing C: 0.1-1.5% by mass % of the total amount of the matrix, and further comprising Cr: 1.0-10.0%, Mo: 0.1%. A valve seat made of iron-based sintered alloy for internal combustion engines, characterized by having a matrix composition consisting of one or more elements selected from ~3.0% and Ni:0.1~2.0%, further containing Mn:0~1.0% and S:0~1.0%, with the remainder being Fe and unavoidable impurities, and further containing Cu (dissolved) dissolved in the voids at an area percentage of 1.0~20.0% relative to the total amount of the support member side layer. [3] The iron-based sintered alloy valve seat for an internal combustion engine according to [1] or [2], characterized in that the cylinder head is a cast iron cylinder head. [4] The valve seat made of iron-based sintered alloy for internal combustion engines according to [1] or [2], characterized in that the hard particles are intermetallic compound particles having a composition by mass% of Ni: 5.0-15.0%, Cr: 20.0-30.0%, Mo: 20.0-30.0%, Si: 1.0-5.0%, with the remainder being Co, and having a Vickers hardness of 900-1300 HV, or intermetallic compound particles having a composition by mass% of Cr: 5.0-15.0%, Mo: 25.0-35.0%, Si: 1.0-5.0%, with the remainder being Co, and having a Vickers hardness of 600-900 HV. [5] The iron-based sintered alloy valve seat for an internal combustion engine according to [1] or [2], characterized in that the solid lubricant particles are MnS particles. A method for manufacturing a single-layer iron-based sintered alloy valve seat for an internal combustion engine as described in [6][1], In order to obtain a mixed powder by blending, mixing, and kneading iron-based powder, graphite powder, alloying element powder, hard particle powder, or further solid lubricant particle powder in predetermined amounts, so as to obtain the matrix composition and matrix structure of the side layer of the functional member of the single-layer structure, The aforementioned iron-based powder is one or two types selected from pure iron powder and iron alloy powder. In mass % relative to the total amount of the aforementioned mixed powder, The aforementioned graphite powder is 0.5-2.0%, the aforementioned alloying element powder is 0-5.0%, and the aforementioned hard particle powder is 10.0-50.0%. The aforementioned solid lubricant particle powders are added in amounts of 0 to 3.0%, mixed, kneaded, and then obtained as a mixed powder. A molding step in which the mixed powder is filled into a mold of a predetermined shape, compressed and molded to obtain a compacted powder body, The obtained compacted powder is subjected to a sintering process in a reducing atmosphere at a heating temperature of 1100-1200°C to obtain a sintered body. The obtained sintered body is subjected to a Cu immersion treatment to fill the voids in the sintered body with Cu in a Cu immersion step, A method for manufacturing an iron-based sintered alloy valve seat for an internal combustion engine, comprising: a heat treatment step of subjecting a sintered body with Cu infiltrated into pores to quenching and tempering treatment, wherein the sintered body is further heated to a quenching heating temperature of 800 to 1000°C and then rapidly cooled, and further heated to a tempering heating temperature of 500 to 700°C and then cooled. A method for manufacturing a two-layer-structured iron-based sintered alloy valve seat for an internal combustion engine according to [7][2], wherein In order to obtain the matrix composition and matrix structure of the two-layer structure, when a predetermined amount of iron-based powder, graphite powder, alloying element powder, hard particle powder, or optionally further solid lubricant particle powder are blended, mixed and kneaded to obtain a mixed powder, the iron-based powder is one or two selected from the group consisting of pure iron powder and alloyed iron powder, and in mass% based on the total mass of the mixed powder, 0.5 to 2.0 mass% of the graphite powder, 0 to 5.0 mass% of the alloying element powder, 10.0 to 50.0 mass% of the hard particle powder, 0 to 3.0 mass% of the solid lubricant particle powder are blended respectively, mixed and kneaded to obtain mixed powder for a functional member side layer; meanwhile, the iron-based powder is one or two selected from the group consisting of pure iron powder and alloyed iron powder, and in mass% based on the total mass of the mixed powder, 0.5 to 2.0 mass% of the graphite powder, 0 to 5.0 mass% of the alloying element powder, and 0 to 3.0 mass% of the solid lubricant particle powder are blended respectively, mixed and kneaded to obtain mixed powder for a supporting member side layer, and then a forming step of filling a predetermined amount of the mixed powder for the supporting member side layer and the mixed powder for the functional member side layer into a mold in this order, and performing compression molding as an integrated body to obtain a green compact; a sintering step of subjecting the obtained green compact to sintering treatment at a heating temperature of 1100 to 1200°C in a reducing atmosphere to obtain a sintered body; a Cu infiltration step of subjecting the obtained sintered body to Cu infiltration treatment to fill Cu into the pores of the sintered body; and a heat treatment step of subjecting the sintered body with Cu infiltrated into pores to quenching and tempering treatment, wherein the sintered body is further heated to a quenching heating temperature of 800 to 1000°C and then rapidly cooled, and further heated to a tempering heating temperature of 500 to 700°C and then cooled. The method is characterized by comprising the above steps. [8] The method for manufacturing an iron-based sintered alloy valve seat for an internal combustion engine according to [6] or [7], wherein the sintering step includes the Cu infiltration step. Effects of the Invention

[0013] According to the present invention, an iron-based sintered alloy valve seat having high strength and excellent wear resistance and drop-out resistance can be manufactured at low cost, and produces a remarkable industrial effect when used for cast iron cylinder heads. Brief Description of the Drawings

[0014] [Figure 1] FIG. 1 is a cross-sectional view schematically showing an example of the cross-sectional structure of the valve seat of the present invention. [Figure 2] FIG. 2 is a schematic explanatory view of a single-body rig wear tester. [Figure 3] FIG. 3 is a schematic explanatory view of a drop-out resistance tester. Mode for Carrying Out the Invention

[0015] As shown in FIG. 1, the valve seat 1 of the present invention is a valve seat having a two-layer structure in which a valve seating side (functional member side) 11 and a head seating side (support member side) 12 are formed of different materials and integrally sintered, or although not illustrated, may be a valve seat having a single-layer structure including only the functional member side layer 11.

[0016] First, the functional member side layer will be described. The functional member side layer is formed of an iron-based sintered alloy material including: a base portion in which hard particles or further solid lubricant particles are dispersed in a matrix phase; and an infiltration portion in which pores are filled with Cu.

[0017] In the valve seat of the present invention, the strength of the valve seat is improved by filling the voids with Cu through a melting process. The porosity of the functional member side layer of the valve seat of the present invention before melting is set to a range of 1.0 to 20.0% by area. If the porosity is less than 1.0%, the process for improving density becomes complex, leading to a significant increase in manufacturing costs. On the other hand, if it exceeds 20.0%, it becomes impossible to ensure the desired wear resistance.

[0018] In the functional member side layer, the base phase consists of a tempered martensite phase. By using a tempered martensite phase as the base phase, the strength and toughness of the valve seat are improved, making it possible to create a valve seat that can maintain sufficiently high performance even in harsh operating environments where the engine combustion temperature is high.

[0019] In the functional member side layer of the valve seat of the present invention, the base portion has a structure in which, in terms of area % of the total functional member side layer, hard particles are dispersed in the base phase at a concentration of 10.0 to 50.0%, or further solid lubricant particles at a concentration of 0.3 to 3.0%, and a high-alloy phase of 60.0% or less surrounds the hard particles.

[0020] Hard particles dispersed in the base phase contribute to improved wear resistance, and their dispersion amount should be between 10.0% and 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 amount exceeds 50.0%, the aggressiveness towards the target material increases.

[0021] Preferably, the hard particles dispersed in the matrix phase 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% by mass, with the remainder being Co, and having a Vickers hardness of 900-1300 HV, or intermetallic compound particles having a composition of Cr: 5.0-15.0%, Mo: 25.0-35.0%, Si: 1.0-5.0% by mass, with the remainder being Co, and having a Vickers hardness of 600-900 HV. These Ni-Cr-Mo-Co intermetallic compound particles and Cr-Mo-Co intermetallic compound particles are hard particles with high hardness and low aggressiveness towards other materials.

[0022] Furthermore, solid lubricant particles dispersed in the base phase contribute to improved machinability and are dispersed as needed. When dispersed, the amount dispersed is preferably 0.3 to 3.0% of the total area of ​​the functional member 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 it exceeds 3.0%, the desired effect will saturate. For this reason, when dispersed, it is preferable to limit the amount of solid lubricant particles to the range of 0.3 to 3.0% of the total area of ​​the functional member side layer. MnS particles are preferred as the solid lubricant particles.

[0023] In the functional member side layer of the valve seat of the present invention, a high-alloy phase is present around the hard particles, with an area percentage of 60.0% or less relative to the total amount of the functional member side layer. The high-alloy phase is formed during sintering when alloying elements diffuse from the hard particles, creating a stable phase that contributes to preventing the hard particles from falling off and to interparticle bonding. It is preferable that the high-alloy phase be 1.0% or more, as the above-mentioned effects cannot be expected if it is less than 1.0% by area percentage.

[0024] Furthermore, in the functional member side layer of the valve seat of the present invention, the matrix portion has a matrix composition consisting of C: 0.3-2.0% by mass relative to the total amount of the matrix portion, and further comprising one or more selected from 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%, and further containing S: 0-2.0%, with the remainder being Fe and unavoidable impurities.

[0025] The following explains the reasons for the limitations on each component in the base composition of the functional member side layer. Note that mass percentages in the composition are simply expressed as percentages.

[0026] C: 0.3~2.0% Carbon (C) is an element present in the matrix phase that contributes to strengthening the matrix phase and improving wear resistance. In this invention, a content of 0.3% or more is required. On the other hand, if it exceeds 2.0%, the hardness of the matrix decreases. For this reason, the amount of C is limited to the range of 0.3% to 2.0%.

[0027] One or more elements selected from 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%, Co: 10.0-30.0%. Si: 0.1~1.5% Si is an element present in the matrix phase that contributes to increasing the strength and improving the wear resistance of the matrix phase. Below 0.1%, the above-mentioned effects are not observed. On the other hand, a content exceeding 1.5% increases the aggressiveness towards other elements. Therefore, when including Si, it is preferable to limit the Si content to the range of 0.1 to 1.5%.

[0028] Mn: 0.1~2.5% Mn is an element present in the matrix phase that contributes to strengthening the matrix phase and improving wear resistance. Furthermore, a portion of it is dispersed in the matrix phase as solid lubricant particles (MnS), contributing to improved formability and machinability. Below 0.1% content, the above effects are not observed. On the other hand, above 2.5% content, the aggressiveness towards the target material increases. Therefore, when Mn is included, it is preferable to limit its content to the range of 0.1-2.5%.

[0029] Ni: 1.0~6.0% Ni is an element found in the matrix phase and hard particles that improves strength and heat resistance in addition to wear resistance. Below 1.0% content, the above effects are minimal. On the other hand, above 6.0% content, wear resistance decreases. Therefore, when including Ni, it is preferable to limit its content to the range of 1.0-6.0%.

[0030] Cr: 1.0~20.0% Cr is an element found in the matrix phase and hard particles that improves strength and heat resistance in addition to wear resistance, and it is preferable to have a content of 1.0% or more. On the other hand, a content exceeding 20.0% increases the aggressiveness towards other materials. Therefore, when including Cr, it is preferable to limit the Cr content to the range of 1.0 to 20.0%.

[0031] Mo: 2.0~15.0% Mo, like Ni and Cr, is an element found in the matrix phase and hard particles that improves strength and heat resistance in addition to wear resistance, and it is preferable to have a content of 2.0% or more. On the other hand, a content exceeding 15.0% increases the aggressiveness towards other materials. Therefore, when Mo is included, it is preferable to limit the Mo content to the range of 2.0 to 15.0%.

[0032] Co: 10.0~30.0% Co, like Ni and Cr, is an element found in the matrix phase and hard particles that improves wear resistance, strength, and heat resistance, as well as strengthening the bond between the hard particles and the matrix phase. It is preferable to include 10.0% or more. On the other hand, if the content exceeds 30.0%, the aggressiveness towards other materials increases. Therefore, when including Co, it is preferable to limit the amount to the range of 10.0 to 30.0%.

[0033] In addition to the above-mentioned components, it may also contain S:0-2.0%. S: 0~2.0% S is an element that primarily disperses in the matrix as solid lubricant particles (MnS) and contributes to improved moldability and machinability. To obtain these effects, it is preferable to contain 0.1% or more. On the other hand, if the content exceeds 2.0%, wear resistance decreases. For this reason, the amount of S was limited to the range of 0 to 2.0%.

[0034] The remainder of the material, other than the components mentioned above, consists of Fe and unavoidable impurities. The amount of Cu dissolved into the voids in the functional member side layer of the valve seat of the present invention (Cu dissolution amount) is limited to 1.0 to 20.0% of the total area of ​​the functional member side layer. If the Cu dissolution amount is less than 1.0%, the desired strength of the valve seat cannot be secured. On the other hand, if the dissolution amount exceeds 20.0%, the wear resistance decreases. For this reason, the Cu dissolution amount in the functional member side layer is limited to the range of 1.0 to 20.0% of the total area of ​​the functional member side layer.

[0035] Furthermore, the side layer of the support member of the valve seat of the present invention is made of an iron-based sintered alloy material having a base phase in which solid lubricant particles are dispersed at an area ratio of 0 to 1.0%, and which contains voids filled with Cu by melting. The porosity of the support member side layer before melting is in the range of 1.0 to 20.0% by area. If the porosity is less than 1.0%, the process for improving density becomes complicated, leading to a significant increase in manufacturing costs. On the other hand, if it exceeds 20.0%, it becomes impossible to secure the desired strength.

[0036] The base phase in the support member side layer of the valve seat of the present invention is a tempered martensite phase. By using a tempered martensite phase as the base phase, the strength and toughness of the support member side layer are improved, the resistance to detachment is improved, and the desired high performance can be maintained even in harsh operating environments where the engine temperature is high.

[0037] Furthermore, the base portion of the support member side layer of the valve seat of the present invention has a base structure in which solid lubricant particles are dispersed in the base phase at an area percentage of the total amount of the support member side layer, from 0 to 3.0%. When dispersed, it is preferable to disperse the solid lubricant particles at a concentration of 0.1% or more. On the other hand, if the amount of solid lubricant particles exceeds 3.0%, the effect of improving moldability and machinability saturates. For this reason, it is preferable to limit the amount of solid lubricant particles to 0 to 1.0% at an area percentage of the total amount of the support member side layer. MnS particles are preferred as the solid lubricant particles.

[0038] Furthermore, the matrix in the side layer of the support member has the above-described matrix structure and a matrix composition consisting of C: 0.1-1.5% by mass relative to the total amount of the matrix, further containing one or more selected from Cr: 1.0-10.0%, Mo: 0.1-3.0%, and Ni: 0.1-2.0%, further containing Mn: 0-1.0% and S: 0-1.0%, with the remainder being Fe and unavoidable impurities.

[0039] Next, we will explain the reasons for limiting each component in the base composition of the support member side layer. C: 0.1~1.5% Carbon (C) is an element present in the base phase that contributes to strengthening it, and its content must be at least 0.1%. On the other hand, exceeding 1.5% reduces hardness. Therefore, the amount of carbon was limited to the range of 0.1 to 1.5%.

[0040] In addition to the above-mentioned C, the base portion of the support member side layer further contains one or more elements selected from Cr: 1.0-10.0%, Mo: 0.1-3.0%, and Ni: 0.1-2.0%.

[0041] Cr: 1.0~10.0% Cr is an element present in the matrix phase that improves strength (hardness) and resistance to shedding, and can be included as needed. When included, it is preferable to include 1.0% or more. On the other hand, including more than 10.0% reduces machinability. Therefore, when included, it is preferable to limit the amount of Cr to the range of 1.0 to 10.0%.

[0042] Mo: 0.1~3.0% Mo, like Cr, is an element found in the matrix phase that improves strength (hardness) and resistance to shedding, and can be included as needed. When included, it is preferable to include 0.1% or more. On the other hand, including more than 3.0% reduces machinability. Therefore, when included, it is preferable to limit the amount of Mo to 0.1-3.0%.

[0043] Ni: 0.1~2.0% Ni is an element found in the matrix phase and hard particles that improves strength (hardness) and heat resistance in addition to wear resistance, and can be included as needed. When included, it is preferable to include 0.1% or more. On the other hand, if included in amounts exceeding 2.0%, austenite is formed, and wear resistance decreases. For this reason, when included, it is preferable to limit the amount of Ni to 0.1 to 2.0%.

[0044] In addition to the components mentioned above, it may also contain Mn: 0-1.0% and S: 0-1.0%. Mn: 0~1.0% Mn is an element that is present in the matrix phase and contributes to strengthening it. A portion of it is also dispersed in the matrix phase as solid lubricant particles (MnS), contributing to improved machinability. It can be included as needed. If included, it is preferable to include 0.1% or more. On the other hand, including more than 1.0% reduces moldability. Therefore, it is preferable to limit the Mn content to 0-1.0%.

[0045] S: 0~1.0% S is an element that primarily contributes to improved moldability and machinability by being dispersed in the substrate as solid lubricant particles, and can be included as needed. When included, it is preferable to include 0.1% or more. On the other hand, if the amount exceeds 1.0%, the amount of solid lubricant particles becomes too high, reducing the strength (hardness). For this reason, it is preferable to limit the amount of S to 0-1.0%.

[0046] Furthermore, the amount of Cu (infused) in the voids of the support member side layer is limited to 1.0-20.0% of the total area of ​​the support member side layer. If the amount of Cu (infused) is less than 1.0%, the desired strength of the valve seat cannot be secured. If the amount of Cu (infused) exceeds 20.0%, the resistance to detachment decreases. For this reason, the amount of Cu (infused) in the support member side layer is limited to the range of 1.0-20.0% of the total area of ​​the support member side layer.

[0047] Next, a preferred method for manufacturing the valve seat of the present invention will be described. First, the raw material powders are blended and mixed to obtain the base composition for the functional member side layer and the base composition for the support member side layer as described above, thereby preparing the mixed powder for the functional member side layer and the mixed powder for the support member side layer.

[0048] The mixed powder for the functional member side layer is prepared by blending and mixing raw material powders, such as iron-based powder, graphite powder, alloying element powder, hard particle powder, or further solid lubricant particle powder, in order to obtain the base composition of the functional member side layer described above. Examples of iron-based powder for forming the base phase to be blended into the mixed powder for the functional member side layer include pure iron powder or iron alloy powder. Examples of iron alloy powder include Cr-Mo iron alloy powder containing a predetermined amount of Cr and Mo, or Cr-Mo-Ni iron alloy powder containing a predetermined amount of Ni in addition to Cr and Mo.

[0049] Furthermore, the mixed powder for the support member side layer is prepared by blending and mixing raw material powders—iron-based powder, graphite powder, alloying element powder, and solid lubricant particle powder—to obtain the base composition of the support member side layer as described above. Examples of iron-based powder for forming the base phase of the support member side layer include pure iron powder or iron alloy powder. Examples of iron alloy powder include Cr-Mo iron alloy powder containing a predetermined amount of Cr and Mo, or Cr-Mo-Ni iron alloy powder containing a predetermined amount of Ni in addition to Cr and Mo.

[0050] Furthermore, the valve seat manufacturing method of the present invention comprises a molding step, a sintering step, a Cu immersion step, and a heat treatment step.

[0051] In the molding process, the obtained mixed powder is filled into a mold and compressed and molded in a press molding machine to obtain a compacted powder. When a two-layer valve seat is to be formed, the mixed powder for the functional member side layer and the mixed powder for the support member side layer are sequentially filled into the mold to create a two-layer structure. For a single-layer structure, only the mixed powder for the functional member side layer is filled into the mold. Needless to say, in the molding process, the compression pressure is adjusted to obtain a compacted powder with the desired porosity.

[0052] Next, in the sintering process, the obtained compacted powder is subjected to a sintering treatment to form a sintered body. The sintering treatment is preferably carried out by heating to a temperature range of 1000 to 1200°C in a reducing atmosphere such as ammonia decomposition gas and holding for 10 to 30 minutes. Alternatively, the molding process and the sintering process may be repeated twice, forming a 2P2S process.

[0053] In the Cu immersion process, a Cu immersion treatment is performed to fill the voids in the resulting sintered body with Cu. Alternatively, the Cu immersion process can be incorporated into the sintering process, allowing the Cu immersion treatment to be performed during the sintering process.

[0054] In the heat treatment process, the sintered body, in which the voids are filled with Cu, is subjected to further heat treatment (quenching and tempering) in order to impart the desired strength and stabilize the base material.

[0055] Furthermore, the quenching treatment is preferably carried out by heating and holding the material in a vacuum to a quenching temperature in the range of 800 to 1000°C, followed by rapid cooling (rapid cooling with nitrogen gas or oil cooling). After the quenching treatment, a tempering treatment is further performed. The tempering treatment is preferably carried out by heating and holding the material to 500 to 700°C, followed by cooling (rapid cooling with nitrogen gas or air cooling).

[0056] The heat-treated sintered body is then processed by cutting, grinding, and other methods to form a valve seat (product) of a predetermined shape.

[0057] The present invention will be further described below based on the following examples. [Examples]

[0058] The raw material powders shown in Table 1 (iron-based powder, graphite powder, alloying element powder, hard particle powder, solid lubricant particle powder) were blended in the proportions shown in Table 1 and mixed to produce mixed powders for the side layers of various functional members. Similarly, the raw material powders shown in Table 2 (iron-based powder, graphite powder, alloying element powder, solid lubricant particle powder) were blended in the proportions shown in Table 2 and mixed to produce mixed powders for the side layers of various support members. The composition of the iron-based powder used is shown in Table 3, and the composition of the hard particle powder used is shown in Table 4.

[0059] [Table 1]

[0060] [Table 2]

[0061] [Table 3]

[0062] [Table 4]

[0063] Next, these mixed powders were integrally pressure-molded in a press molding machine to obtain a two-layer compact for valve seats. In some cases, a single-layer compact for valve seats consisting only of the functional member side layer was used.

[0064] The obtained compacted powder was further subjected to a sintering process to form a sintered body. The sintering process was carried out at a heating temperature of 1000 to 1200°C in an ammonia decomposition gas atmosphere (reducing atmosphere). In addition, a Cu immersion treatment was performed during sintering to fill the voids in the sintered body with Cu.

[0065] In addition, sintered body No. 2 (conventional example) was not subjected to Cu immersion treatment. Sintered body No. 2 (conventional example) was subjected to cold rotary forging and then re-sintering treatment.

[0066] Next, the obtained sintered bodies (excluding sintered body No. 2) were heat-treated, and then cut and ground to form valve seats (products) with an outer diameter of 37.7 mmΦ, an inner diameter of 31.2 mmΦ, and a thickness of 6.0 mm. The heat treatment consisted of quenching and tempering. The quenching process involved heating to a temperature of 870°C followed by oil cooling, and the tempering process involved heating to a temperature of 600°C followed by air cooling.

[0067] Test specimens were taken from the valve seat (product), and the content (mass %) of each component in each layer was analyzed by emission spectrometry to determine the composition of each layer.

[0068] The results obtained are shown in Table 5.

[0069] [Table 5]

[0070] Furthermore, the cross-section of the valve seat (product) was polished, and the microstructure of each layer was exposed by Nital corrosion. This was then observed and imaged using an optical microscope (magnification: 200x). From the obtained microscopic images, the microstructure fraction (area fraction) of each layer was calculated through image analysis. The results are shown in Table 6. Note that any microstructure other than those shown in the table represents voids (Cu fusion).

[0071] Next, the obtained valve seats (products) were mounted as test specimens on the single-rig abrasion testing machine shown in Figure 2, and an abrasion resistance test was conducted. The test conditions were as follows. Test temperature: 300℃ (seat surface) Exam duration: 4 hours Cam rotation speed: 2500 rpm Valve rotation speed: 10 rpm Valve material: SUH35 with residual nitride coating Heat source: LPG After pressing the valve seat 1 into a jig 2 equivalent to a cylinder head, the valve 4 and valve seat 1 were heated by a heat source 3 attached to the testing machine, and the valve 4 was moved up and down by a crank mechanism during the test. The amount of wear on the valve seat was measured by matching the shape after the test to the shape before the test. The amount of wear on the valve 1 was obtained by measuring the shape after the test and measuring the amount of indentation on the valve seat contact surface.

[0072] The results obtained are shown in Table 7.

[0073] Furthermore, the obtained valve seats (products) were used as test specimens, and a detachment resistance test was conducted using the testing machine shown in Figure 3. The test conditions were as follows.

[0074] Test temperature: 500℃ Holding time: 1hr Initial clamping force: 90 μm Thermal cycling conditions: Heat at 500°C for 1 hour, then air cool to below 100°C. This process is repeated 10 times.

[0075] At room temperature, the valve seat 1 is press-fitted into a cylinder head equivalent (test fixture 5). While still press-fitted, the valve seat 1 is subjected to a predetermined thermal cycle using a cartridge heater 7 in a heat-resistant and water-resistant container 6 held in cooling water 9 maintained at a constant temperature. After the predetermined thermal cycle, the valve seat 1 is pressed using a pressing fixture (universal testing machine), and the load (pull-out load) and residual compression when it is removed from the cylinder head equivalent were measured. The results are shown in Table 7.

[0076] Furthermore, the compression strength of the obtained valve seats (products) was determined in accordance with the provisions of JIS Z 2507.

[0077] The results obtained are shown in Table 7.

[0078] [Table 6]

[0079] [Table 7]

[0080] In all of the examples of the present invention, the amount of wear is 30% or less, and the amount of wear is 366% or more, and the amount of pull-out load is 185% or more (functional member side layer), showing improved abrasion resistance and resistance to detachment compared to sintered body No. 1 (conventional example). From this, it can be seen that by using a valve seat having the structure and composition of the present invention, abrasion resistance and resistance to detachment are significantly improved compared to conventional products. Furthermore, in all of the examples of the present invention, the abrasion resistance is equivalent to or better than that of sintered body No. 2 (conventional example) with rotary forging added, and the resistance to detachment is almost the same, and moreover, the compression ring strength is equivalent to or better.

[0081] On the other hand, comparative examples that fall outside the scope of the present invention show less improvement in wear resistance and detachment resistance, and less increase in compression ring strength compared to sintered body No. 1 and sintered body No. 2 (conventional examples).

[0082] For these reasons, the valve boot of the present invention is particularly suitable as a valve seat for press-fitting into a cast iron cylinder head. [Explanation of Symbols]

[0083] 1 Valve seat 2. Jig 3 Heat source 4 valves 5. Test fixtures 6. Heat-resistant and water-resistant containers 7. Cartridge heater 8 Dummy test specimens 9 Cooling water 11. Side layer of functional component 12 Support member side layer

Claims

1. A valve seat that is press-fitted into the cylinder head of an internal combustion engine, The valve seat has a single-layer structure consisting of a functional member side layer, The functional member side layer comprises a base portion in which hard particles or solid lubricant particles are dispersed in the base phase, and voids filled with Cu by dissolution. The aforementioned base phase consists of a tempered martensite phase. The aforementioned matrix has a structure in which, in area % of the total area of ​​the functional member side layer, 10.0 to 50.0% of the hard particles, or further 0.3 to 3.0% of the solid lubricant particles, are dispersed in the matrix phase, and 60.0% or less of the high-alloy phase surrounds the hard particles. The composition of the matrix, in mass % of the total amount of the matrix, includes C: 0.3 to 2.0%, and further includes Si: 0.1 to 1.5%, Cr: 1.0 to 20.0%, Mo: 2.0 to 15.0%, and Co:

10. A valve seat made of an iron-based sintered alloy for internal combustion engines, characterized by having a matrix composition consisting of 0-30.0% of iron, further comprising one or two selected from Ni: 1.0-6.0% and Mn: 0.1-2.5%, further containing S: 0-2.0%, with the remainder being Fe and unavoidable impurities, and further comprising 1.0-20.0% of Cu (dissolved) in the voids, in terms of area % relative to the total amount of the functional member side layer, made of an iron-based sintered alloy material.

2. A valve seat that is press-fitted into the cylinder head of an internal combustion engine, The valve seat has a two-layer structure in which a functional member side layer and a support member side layer are sintered together as a single unit. The functional member side layer comprises a base portion in which hard particles or solid lubricant particles are dispersed in the base phase, and voids filled with Cu by dissolution. The aforementioned base phase consists of a tempered martensite phase. The aforementioned matrix has a structure in which, in area % of the total amount of the functional member side layer, 10.0 to 50.0% of the hard particles, or further 0.3 to 3.0% of the solid lubricant particles, are dispersed in the matrix phase, and 60.0% or less of the high alloy phase surrounds the hard particles. The matrix also contains, in mass % of the total amount of the matrix, C: 0.3 to 2.0%, further Si: 0.1 to 1.5%, Cr: 1.0 to 20.0%, and Mo: 2.0%. The material is an iron-based sintered alloy material having a matrix composition consisting of ~15.0%, Co: 10.0-30.0%, further containing one or two selected from Ni: 1.0-6.0% and Mn: 0.1-2.5%, further containing S: 0-2.0%, with the remainder being Fe and unavoidable impurities, and further containing Cu (dissolved) dissolved in the voids at an area percentage of 1.0-20.0% relative to the total amount of the functional member side layer. The support member side layer comprises a base portion in which solid lubricant particles are dispersed in a base phase, and voids filled with Cu by dissolution, the base phase being a tempered martensite phase, the base portion having a structure in which the solid lubricant particles are dispersed in the base phase at an area % of the total amount of the support member side layer, and containing C: 0.1 to 1.5% by mass % of the total amount of the base portion, and further containing Cr: 1.0 to 10.0%. An iron-based sintered alloy valve seat for an internal combustion engine, characterized by having a matrix composition comprising Mo: 0.1-3.0%, Mn: 0.1-1.0%, S: 0.1-1.0%, or further comprising Ni: 0.1-2.0%, with the remainder being Fe and unavoidable impurities, and further containing Cu (dissolved) dissolved in the voids in an area percentage of 1.0-20.0% relative to the total amount of the support member side layer, wherein the material is an iron-based sintered alloy material.

3. The iron-based sintered alloy valve seat for an internal combustion engine according to claim 1 or 2, characterized in that the cylinder head is a cast iron cylinder head.

4. The valve seat made of iron-based sintered alloy for internal combustion engines according to 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% by mass, with the remainder being Co, and having a Vickers hardness of 900-1300 HV, or intermetallic compound particles having a composition of Cr: 5.0-15.0%, Mo: 25.0-35.0%, Si: 1.0-5.0% by mass, with the remainder being Co, and having a Vickers hardness of 600-900 HV.

5. The valve seat made of iron-based sintered alloy for an internal combustion engine according to claim 1 or 2, characterized in that the solid lubricant particles are MnS particles.

6. A method for manufacturing a single-layer iron-based sintered alloy valve seat for an internal combustion engine according to claim 1, In order to obtain a mixed powder by blending, mixing, and kneading iron-based powder, graphite powder, alloying element powder, hard particle powder, or further solid lubricant particle powder in predetermined amounts, so as to obtain the matrix composition and matrix structure of the side layer of the functional member of the single-layer structure, The aforementioned iron-based powder is one or two types selected from pure iron powder and iron alloy powder. In mass % of the total amount of the aforementioned mixed powder, The aforementioned graphite powder is 0.5 to 2.0%, the aforementioned alloying element powder is 0 to 5.0%, and the aforementioned hard particle powder is 10.0 to 50.0%. The aforementioned solid lubricant particle powders are added in amounts of 0 to 3.0%, mixed, kneaded, and then obtained as a mixed powder. A molding step in which the mixed powder is filled into a mold of a predetermined shape, compressed and molded to obtain a compacted powder body, The obtained compacted powder is subjected to a sintering process in a reducing atmosphere at a heating temperature of 1100 to 1200°C to obtain a sintered body. The obtained sintered body is subjected to a Cu immersion treatment to fill the voids in the sintered body with Cu in a Cu immersion step, A method for manufacturing an iron-based sintered alloy valve seat for an internal combustion engine, characterized by comprising a heat treatment step of further heating a sintered body in which Cu is dissolved into the pores to a quenching temperature of 800 to 1000°C, followed by rapid cooling, and then further heating to a tempering temperature of 500 to 700°C, followed by cooling.

7. A method for manufacturing a two-layered iron-based sintered alloy valve seat for an internal combustion engine according to claim 2, In order to obtain the aforementioned two-layer structure and base structure, a predetermined amount of iron base powder, graphite powder, alloying element powder, hard particle powder, or further solid lubricant particle powder is blended, mixed, and kneaded to form a mixed powder, The aforementioned iron-based powder is one or two types selected from pure iron powder and iron alloy powder, and is expressed in mass % of the total amount of the mixed powder. The aforementioned graphite powder is 0.5 to 2.0%, the aforementioned alloying element powder is 0 to 5.0%, and the aforementioned hard particle powder is 10.0 to 50.0%. The aforementioned solid lubricant particle powder is blended in amounts of 0 to 3.0%, mixed, and kneaded to obtain a mixed powder for the side layer of the functional member, while, The aforementioned iron-based powder is one or two types selected from pure iron powder and iron alloy powder, and is expressed in mass % of the total amount of the mixed powder. The graphite powder is blended in an amount of 0.5 to 2.0%, the alloying element powder in an amount of 0 to 5.0%, and the solid lubricant particle powder in an amount of 0 to 3.0%, and then mixed and kneaded to obtain a mixed powder for the side layer of the support member. A molding step in which a predetermined amount of the mixed powder for the side layer of the support member and the mixed powder for the side layer of the functional member are filled into a mold in this order, and compressed and molded as a whole to obtain a compacted powder body, The obtained compacted powder is subjected to a sintering process in a reducing atmosphere at a heating temperature of 1100 to 1200°C to obtain a sintered body, and the obtained sintered body is subjected to a Cu immersion process to fill the voids in the sintered body with Cu, A method for manufacturing an iron-based sintered alloy valve seat for an internal combustion engine, characterized by comprising a heat treatment step of further heating a sintered body in which Cu is dissolved into the pores to a quenching temperature of 800 to 1000°C, followed by rapid cooling, and then further heating to a tempering temperature of 500 to 700°C, followed by cooling.

8. Instead of the sintering step and the Cu immersion step, A method for manufacturing an iron-based sintered alloy valve seat for an internal combustion engine according to claim 6 or 7, characterized in that the sintering step comprises the Cu immersion step, wherein the compacted powder is subjected to a sintering treatment in a reducing atmosphere at a heating temperature of 1100 to 1200°C, and a Cu immersion treatment is performed during the sintering treatment to obtain a sintered body in which Cu is dissolved into the pores.

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