Manufacturing method for iron-based sintered alloy valve seat for internal combustion engine

Abstract

To provide a valve seat made of an iron sintered alloy 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 including mainly, 20.0% of a fine carbide precipitation phase, and an annealing martensite phase: dispersed hard particles or solid lubricant particles; and a high allow phase around the hard particles. The iron sintered alloy material includes in mass%, one or two or more kinds selected from: 0.5-2.0% of C; 0.1-1.0% of Si; 0.1-2.5% of Mn; 1.0-7.0% of Ni; 1.0-12.0% of Cr; 2.0-12.0% of Mo; 2.0-20.0% of Co; 0.1-2.0% of W; 0.01-1.0% of V, and further has a matrix part composition including 0-1.5% of S, and includes 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 an internal combustion engine and a manufacturing method thereof, and more particularly to improving the wear resistance and resistance to falling off of a valve seat that is press-fitted into a cast iron cylinder head. [Background technology]

[0002] Valve seats are press-fitted into the cylinder head of an engine to seal combustion gases and cool the valves. Valve seats are required to have sufficient wear resistance to withstand wear caused by repeated contact with the valve, as well as heat resistance and corrosion resistance, and also low aggressiveness to the mating material, the valve, so as not to wear it.

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

[0004] In response to such demands, 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 two layers, a surface layer and a base layer, are sintered together, with the surface layer having a porosity of 5 to 20% and the base layer having a porosity of 5% or less. The sintered alloy valve seat described in Patent Document 1 is manufactured by forming a two-layer sintered body, then subjecting the sintered body to cold rotary forging from the base layer side, and further subjecting it to a re-sintering process.

[0005] Patent Document 2 describes a valve seat made of an iron-based sintered alloy for an internal combustion engine. The valve seat described in Patent Document 2 has a single-layer structure, and the base phase is made of a tempered martensite phase in which fine carbides with a major axis of 30 μm or less are precipitated in an area ratio of 27% or less, and further has a structure in which one or more types selected from Cr-Mo-Si-Co-based hard particles, Cr-Mo-Ni-Si-Co-based hard particles, and Mo-based hard particles are dispersed as hard particles in the base phase in an area ratio of 31 to 80%, and has a density of 7.3 to 8.2 g / cm 3 and a radial crushing strength of 400 MPa or more, and is said to have excellent wear resistance and resistance to shedding. The valve seat described in Patent Document 2 is produced by sequentially carrying out a mixing process in which raw material powders are blended to form a mixed powder to achieve a predetermined composition, a molding process in which the mixed powder is compressed and molded to form a green compact, and a sintering process in which the green compact is heated and sintered to form a sintered valve seat-shaped body, followed by a hot working process in which the sintered valve seat-shaped body is hot forged, and a heat treatment process in which the sintered valve seat-shaped body is heat treated to impart predetermined properties to the sintered valve seat-shaped body. The technology described in Patent Document 2 is said to make it easy to produce 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 Application Publication No. 2018-178208 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the technology described in Patent Document 1 requires a process in which the sintered body is subjected to cold rotary forging to reduce the porosity of the base layer of the valve seat, followed by a process of re-sintering. Therefore, the technology described in Patent Document 1 has the problem of complicated processes. Also, the technology described in Patent Document 2 also requires a process in which the density of the valve seat is 7.3 g / cm 3 As described above, it is necessary to perform hot working by hot forging, which makes the process complicated.

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

[0009] In order to achieve the above-mentioned object, the present inventors first conducted extensive research into various factors that affect the detachment resistance of a press-fitted valve seat. As a result, they came up with the idea of ​​first subjecting the valve seat to Cu infiltration treatment to impregnate Cu into the pores, thereby increasing the strength of the valve seat, and then subjecting it to quenching and tempering treatment (heat treatment) to stabilize the matrix phase. They then came up with the idea of ​​using Ni-Cr-Mo-Co-based intermetallic compound particles or Cr-Mo-Co-based intermetallic compound particles, which have high hardness and low aggressiveness against mating members, as hard particles to be dispersed in the matrix phase in order to further impart wear resistance in addition to detachment resistance.

[0010] The present invention was completed based on these findings and further investigations.

[0011] That is, the gist of the present invention is as follows. [1] A valve seat press-fitted into a cylinder head of an internal combustion engine, the valve seat has a single-layer structure made of a functional component-side layer, the functional component side layer includes a matrix portion in which hard particles or solid lubricant particles are dispersed in a matrix phase, and pores filled with Cu by infiltration; the base phase is composed of a fine carbide precipitate phase and a tempered martensite phase, the area percentage of which is 20.0% or less relative to the total amount of the functional component side layer; The matrix has a matrix structure in which, in area % relative to the total amount of the functional component side layer, 10.0 to 40.0% of the hard particles are dispersed in the matrix phase, or further 0.3 to 3.0% of the solid lubricant particles are dispersed, and further has a high alloy phase of 25.0% or less around the hard particles; and further contains, in mass % relative to the total amount of the matrix, 0.5 to 2.0% of C, 0.1 to 1.0% of Si, 0.1 to 2.5% of Mn, 1.0 to 7.0% of Ni, 1.0 to 12.0% of Cr, and An iron-based sintered alloy valve seat for an internal combustion engine, characterized in that it comprises an iron-based sintered alloy material having a matrix composition containing one or more selected from O: 2.0 to 12.0%, Co: 2.0 to 20.0%, W: 0.1 to 2.0%, and V: 0.01 to 1.0%, further containing S: 0 to 1.5%, with the balance being Fe and unavoidable impurities, and further containing Cu filled into said pores by infiltration in an amount of 1.0 to 20.0% by area relative to the total amount of the functional component-side layer. [2] A valve seat press-fitted into a cylinder head of an internal combustion engine, the valve seat has a two-layer structure formed by integrally sintering a functional member-side layer and a support member-side layer, the functional component-side layer includes a matrix portion in which hard particles or further solid lubricant particles are dispersed in a matrix phase, and pores filled with Cu by infiltration, the matrix phase comprising a fine carbide precipitate phase occupying 20.0% or less of an area percentage relative to the total amount of the functional component-side layer, and a tempered martensite phase; The matrix has a matrix structure in which, in area % relative to the total amount of the functional component side layer, 10.0 to 40.0% of the hard particles are dispersed in the matrix phase, or further 0.3 to 3.0% of the solid lubricant particles are dispersed, and further has 25.0% or less of a high alloy phase around the hard particles; and further contains, in mass % relative to the total amount of the matrix, 0.5 to 2.0% of C, 0.1 to 1.0% of Si, 0.1 to 2.5% of Mn, and 1.0 to 7.0% of Ni, an iron-based sintered alloy material having a matrix composition containing one or more selected from Cr: 1.0 to 12.0%, Mo: 2.0 to 12.0%, Co: 2.0 to 20.0%, W: 0.1 to 2.0%, and V: 0.01 to 1.0%, further containing S: 0 to 1.5%, with the balance being Fe and unavoidable impurities, and further containing Cu filled into said pores by infiltration in an amount of 1.0 to 20.0% by area with respect to the total amount of the functional component-side layer; 1. An iron-based sintered alloy valve seat for an internal combustion engine, comprising an iron-based sintered alloy material, wherein the support member-side layer includes a matrix having solid lubricant particles dispersed in the matrix phase and pores filled with Cu by infiltration, the matrix phase being made of a tempered martensite phase, the matrix having a matrix structure in which the solid lubricant particles are dispersed in the matrix phase at 0 to 3.0% by area % relative to the total amount of the support member-side layer, and a matrix composition containing, in mass % relative to the total amount of the matrix, 0.1 to 1.5% C, and one or more elements selected from 1.0 to 10.0% Cr, 0.1 to 3.0% Mo, and 0.1 to 2.0% Ni, and further containing 0 to 1.0% Mn and 0 to 1.0% S, with the balance being Fe and unavoidable impurities, and further including 1.0 to 20.0% Cu, in mass %, relative to the total amount of the support member-side layer, filled into the pores by infiltration. [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 iron-based sintered alloy valve seat for an internal combustion engine according to [1] or [2], characterized in that the hard particles are intermetallic compound particles having a composition consisting of, by mass%, Ni: 5.0 to 15.0%, Cr: 20.0 to 30.0%, Mo: 20.0 to 30.0%, Si: 1.0 to 5.0%, and the balance Co, and having a Vickers hardness of 900 to 1300 HV, or intermetallic compound particles having a composition consisting of, by mass%, Cr: 5.0 to 15.0%, Mo: 25.0 to 35.0%, Si: 1.0 to 5.0%, and the balance Co, and having a Vickers hardness of 600 to 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. [6] A method for manufacturing a valve seat made of an iron-based sintered alloy with a single layer structure for an internal combustion engine according to [1], In order to obtain the matrix composition and matrix structure of the functional component side layer having the single-layer structure, predetermined amounts of iron-based powder, graphite powder, alloying element powder, hard particle powder, and / or solid lubricant particle powder are blended, mixed, and kneaded to obtain a mixed powder, The iron-based powder is one or more types selected from the group consisting of pure iron powder, alloy iron powder, and alloy steel powder, and the iron-based powder contains, in mass % relative to the total amount of the mixed powder, The graphite powder is 0.5 to 2.0%, the alloy element powder is 0 to 5.0%, and the hard particle powder is 10.0 to 40.0%, The solid lubricant particle powder is blended in an amount of 0 to 3.0%, mixed and kneaded to form a mixed powder, and then a molding step of filling the mixed powder into a mold of a predetermined shape and compressing and molding it to obtain a green compact; a sintering step of sintering the obtained powder compact in a reducing atmosphere at a heating temperature of 1100 to 1200°C to obtain a sintered body; a Cu infiltration step of subjecting the obtained sintered body to a Cu infiltration treatment to fill pores of the sintered body with Cu; A method for manufacturing an iron-based sintered alloy valve seat for an internal combustion engine, comprising: a heat treatment step in which the sintered body, in which the pores have been infiltrated with Cu, is subjected to a quenching and tempering treatment in which the sintered body is heated to a quenching temperature of 800 to 1000°C, followed by rapid cooling, and then heated to a tempering temperature of 500 to 700°C, followed by cooling. [7] A method for manufacturing a two-layer structure iron-based sintered alloy valve seat for an internal combustion engine according to [2], In order to obtain the two-layered matrix composition and matrix structure, predetermined amounts of iron-based powder, graphite powder, alloying element powder, hard particle powder, and / or solid lubricant particle powder are blended, mixed, and kneaded to obtain a mixed powder, The iron-based powder is one or more types selected from the group consisting of pure iron powder, alloy iron powder, and alloy steel powder, and the iron-based powder contains, in mass % relative to the total amount of the mixed powder, The graphite powder is 0.5 to 2.0%, the alloy element powder is 0 to 5.0%, and the hard particle powder is 10.0 to 40.0%, The solid lubricant particle powder is mixed in an amount of 0 to 3.0%, and then mixed and kneaded to obtain a mixed powder for a functional component side layer. The iron-based powder is one or two selected from the group consisting of pure iron powder and alloy iron powder, In mass% with respect to the total amount of the mixed powder, The graphite powder is blended in an amount of 0.5 to 2.0%, the alloying element powder is blended in an amount of 0 to 5.0%, and the solid lubricant particle powder is blended in an amount of 0 to 3.0%, and then mixed and kneaded to obtain a mixed powder for a support member side layer. a molding step of filling predetermined amounts of the mixed powder for the support member side layer and the mixed powder for the functional member side layer in this order into a mold, and compressing and molding them as a single unit to obtain a green compact; a sintering step of sintering the obtained powder compact in a reducing atmosphere at a heating temperature of 1100 to 1200°C to obtain a sintered body; a Cu infiltration step of subjecting the obtained sintered body to a Cu infiltration treatment to fill pores of the sintered body with Cu; A method for manufacturing an iron-based sintered alloy valve seat for an internal combustion engine, comprising: a heat treatment step in which the sintered body, in which the pores have been infiltrated with Cu, is subjected to a quenching and tempering treatment in which the sintered body is heated to a quenching temperature of 800 to 1000°C, followed by rapid cooling, and then heated to a tempering temperature of 500 to 700°C, followed by cooling. [8] The method of manufacturing a valve seat made of an iron-based sintered alloy for an internal combustion engine according to [6] or [7], characterized in that the sintering step includes the Cu infiltration step. [Effects of the Invention]

[0012] According to the present invention, a valve seat made of an iron-based sintered alloy that is high in strength and has excellent wear resistance and shedding resistance can be manufactured at low cost, which is of great industrial benefit. According to the present invention, a valve seat that is particularly excellent in wear resistance and shedding resistance compared to conventional valve seats is obtained, and is therefore of great benefit when used for a cast iron cylinder head. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view schematically showing an example of the cross-sectional structure of a valve seat according to the present invention. [Figure 2] FIG. 1 is a schematic diagram of a single rig wear tester. [Figure 3] FIG. 1 is a schematic explanatory diagram of a dropout tester. DETAILED DESCRIPTION OF THE INVENTION

[0014] As shown in FIG. 1, the valve seat 1 of the present invention has a two-layer structure in which the side on which the valve sits (functional member side) 11 and the side on which the head sits (support member side) 12 are made of different materials and sintered together, or a single-layer structure (not shown) consisting of only the functional member side layer 11.

[0015] First, the functional component side layer will be described. The functional component side layer is made of an iron-based sintered alloy material including a matrix portion in which hard particles or solid lubricant particles are dispersed in a matrix phase, and an infiltrated portion in which pores are filled with Cu.

[0016] In the valve seat of the present invention, the pores are filled with Cu by infiltration, thereby improving the strength of the valve seat. The functional component side layer of the valve seat of the present invention has a porosity of 1.0 to 20.0% by area before infiltration. If the porosity is less than 1.0%, the process for increasing density becomes complicated, resulting in a significant increase in manufacturing costs. On the other hand, if the porosity exceeds 20.0%, the wear resistance decreases.

[0017] In the functional component side layer, the matrix phase is composed of a fine carbide precipitate phase and a tempered martensite phase, the area percentage of which is 20.0% or less relative to the functional component side layer.

[0018] In the functional component-side layer of the valve seat of the present invention, a predetermined amount (20.0% or less) of fine carbide precipitate phase is present in the matrix phase. The presence of the fine carbide precipitate phase in the matrix phase improves the wear resistance of the functional component-side layer (valve seat) in which pores are filled with Cu. To achieve this effect, the fine carbide precipitate phase must preferably be present in an area percentage of 20.0% or less, preferably 1.0% to 20.0%, relative to the functional component-side layer. If the fine carbide precipitate phase is present in a large amount exceeding 20.0%, the number of pores increases, resulting in a decrease in wear resistance. Here, the "fine carbide precipitate phase" refers to a phase in which fine carbides, such as Cr-Mo-WV carbides, are precipitated in tempered martensite.

[0019] Furthermore, in the functional component side layer of the valve seat of the present invention, the matrix phase other than the fine carbide precipitate phase is a tempered martensite phase. By making the remainder (main phase) of the matrix phase a tempered martensite phase, the strength and toughness are improved, and the valve seat can be made to be able to sufficiently maintain the specified functions even in a severe operating environment where the combustion temperature of the engine is high.

[0020] In the functional component-side layer of the valve seat of the present invention, the matrix has a matrix structure in which, in terms of area % relative to the total amount of the functional component-side layer, 10.0 to 40.0% of hard particles, or 0.3 to 3.0% of solid lubricant particles, are dispersed in the matrix phase, and further the matrix structure has 25.0% or less of a high alloy phase around the hard particles.

[0021] The hard particles dispersed in the matrix phase contribute to improving wear resistance, and the amount of dispersion is set to 10.0 to 40.0% by area. If the amount of dispersion of the hard particles is less than 10.0%, the desired wear resistance cannot be maintained. On the other hand, if the amount of dispersion exceeds 40.0%, the attacking tendency of the mating member increases.

[0022] The hard particles dispersed in the matrix phase are preferably intermetallic compound particles having a composition consisting of, by mass%, Ni: 5.0 to 15.0%, Cr: 20.0 to 30.0%, Mo: 20.0 to 30.0%, Si: 1.0 to 5.0%, and the balance Co, and having a Vickers hardness of 900 to 1300 HV, or intermetallic compound particles having a composition consisting of, by mass%, Cr: 5.0 to 15.0%, Mo: 25.0 to 35.0%, Si: 1.0 to 5.0%, and the balance Co, and having a Vickers hardness of 600 to 900 HV. The Ni-Cr-Mo-Co based intermetallic compound particles and Cr-Mo-Co based intermetallic compound particles are hard particles that have high hardness and low attacking properties against mating members.

[0023] Furthermore, the solid lubricant particles dispersed in the matrix phase contribute to improving formability and machinability, and when dispersed, the amount of dispersion is preferably 0.3 to 3.0% in area % relative to the total amount of the functional component-side layer. If the amount of dispersed solid lubricant particles is less than 0.3%, the desired lubricating effect cannot be expected. On the other hand, if the amount exceeds 3.0%, the desired effect saturates. Therefore, when dispersed, the amount of dispersed solid lubricant particles is preferably limited to the range of 0.3 to 3.0% in area % relative to the total amount of the functional component-side layer. MnS particles are preferably used as the solid lubricant particles.

[0024] Furthermore, in the functional component-side layer of the valve seat of the present invention, the matrix further contains a high alloy phase, the area percentage of which is 25.0% or less relative to the total amount of the functional component-side layer. The high alloy phase is formed when alloying elements diffuse from the hard particles during sintering, forming a stable high alloy phase, which contributes to preventing the hard particles from falling off and improving interparticle bonding. Note that if the area percentage of the high alloy phase is less than 1.0%, the above-mentioned effects cannot be expected.

[0025] Furthermore, in the functional component side layer of the valve seat of the present invention, the matrix contains, in mass % relative to the total amount of the matrix, 0.5 to 2.0% C, and one or more selected from 0.1 to 1.0% Si, 0.1 to 2.5% Mn, 1.0 to 7.0% Ni, 1.0 to 12.0% Cr, 2.0 to 12.0% Mo, 2.0 to 20.0% Co, 0.1 to 2.0% W, and 0.01 to 1.0% V, and further contains 0 to 1.5% S, with the remainder being Fe and unavoidable impurities, making up the matrix composition.

[0026] The reasons for limiting each component in the matrix composition of the functional component side layer will be explained below, where mass % in the composition is simply indicated as %.

[0027] C: 0.5 to 2.0% C is an element contained in the matrix phase that strengthens the matrix phase and contributes to improving wear resistance, and a content of 0.5% or more is required. On the other hand, if the content exceeds 2.0%, wear resistance decreases. For this reason, the C content is limited to the range of 0.5 to 2.0%.

[0028] One or more selected from the following: Si: 0.1-1.0%, Mn: 0.1-2.5%, Ni: 1.0-7.0%, Cr: 1.0-12.0%, Mo: 2.0-12.0%, Co: 2.0-20.0%, W: 0.1-2.0%, V: 0.01-1.0% Si: 0.1 to 1.0% Si is an element contained in the matrix phase and contributes to increasing the strength and wear resistance of the matrix phase. If the content is less than 0.1%, the above-mentioned effects are not observed. If the content exceeds 1.0%, attacking of mating members increases. Therefore, if Si is contained, it is preferable to limit the Si content to the range of 0.1 to 0.7%.

[0029] Mn: 0.1 to 2.5% Mn is an element contained in the matrix phase that contributes to strengthening the matrix phase and improving its wear resistance. A portion of Mn disperses in the matrix phase as solid lubricant particles MnS, contributing to improvements in formability, machinability, and wear resistance. If the Mn content is less than 0.1%, the above-mentioned effects are not observed. On the other hand, if the Mn content exceeds 2.5%, aggressiveness to mating members increases. Therefore, if Mn is contained, it is preferable to limit the Mn content to the range of 0.1 to 2.5%.

[0030] Ni: 1.0 to 7.0% Ni is contained in the matrix phase and hard particles and is an element that improves strength (hardness) and heat resistance in addition to improving wear resistance. If the content is less than 1.0%, the above-mentioned effects are small, so it is preferable to contain 1.0% or more. On the other hand, if the content exceeds 7.0%, wear resistance decreases. Therefore, if Ni is contained, it is preferable to limit the Ni content to the range of 1.0 to 7.0%.

[0031] Cr: 1.0 to 12.0% Cr is contained in the matrix phase and hard particles and is an element that improves strength (hardness) and heat resistance in addition to improving wear resistance. If the content is less than 1.0%, the above-mentioned effects are small, so it is preferable to contain 1.0% or more. On the other hand, if the content exceeds 12.0%, aggressiveness to mating members increases. Therefore, if Cr is contained, it is preferable to limit the Cr content to the range of 1.0 to 12.0%.

[0032] Mo: 2.0 to 12.0% Like Ni and Cr, Mo is contained in the matrix phase and hard particles and is an element that improves not only wear resistance but also strength (hardness) and heat resistance, and is preferably contained in an amount of 2.0% or more. On the other hand, a content exceeding 12.0% increases the attacking tendency of mating members. Therefore, when Mo is contained, it is preferable to limit the Mo content to the range of 2.0 to 12.0%.

[0033] Co: 2.0 to 20.0% Like Ni and Cr, Co is contained in the matrix phase and hard particles, and is an element that not only improves wear resistance but also improves strength (hardness) and heat resistance, and strengthens the bond between the hard particles and the matrix phase. It is preferable that Co be contained in an amount of 2.0% or more. On the other hand, if it is contained in an amount exceeding 20.0%, aggressiveness to mating members increases. Therefore, if Co is contained, it is preferable that the Co content be limited to the range of 2.0 to 20.0%.

[0034] W: 0.1 to 2.0% W is an element that precipitates as fine carbides to strengthen the matrix phase and contribute to improving wear resistance, and is preferably contained in an amount of 0.1% or more. On the other hand, a content exceeding 2.0% reduces wear resistance. Therefore, when W is contained, it is preferable to limit the W content to the range of 0.1 to 2.0%.

[0035] V: 0.01 to 1.0% V is an element that strengthens the matrix phase and improves wear resistance, and is preferably contained in an amount of 0.01% or more. On the other hand, if it is contained in an amount exceeding 1.0%, attack on mating members increases. Therefore, when it is contained, it is preferably limited to the range of 0.01 to 1.0%.

[0036] In addition to the above components, S: 0 to 1.5% may be contained. S: 0 to 1.5% S is an element that disperses mainly as solid lubricant particles MnS in the matrix, contributing to improvements in formability, machinability, and wear resistance. When contained, it is preferable that it be contained in an amount of 0.1% or more. On the other hand, if it is contained in an amount exceeding 1.5%, wear resistance decreases. For this reason, the S content is limited to the range of 0 to 1.5%.

[0037] The balance other than the above components consists of Fe and unavoidable impurities. The infiltrated portion (Cu infiltration amount) in which Cu fills the pores in the functional component side layer of the valve seat of the present invention is limited to 1.0 to 20.0% by area relative to the total amount of the functional component side layer. If the infiltrated portion (Cu infiltration amount) is less than 1.0%, the desired strength of the valve seat cannot be ensured. On the other hand, if it exceeds 20.0%, the wear resistance decreases. For this reason, the infiltrated portion (Cu infiltration amount) in the functional component side layer is limited to a range of 1.0 to 20.0% by area relative to the total amount of the functional component side layer. Preferably, it is 15.0% or less.

[0038] The support member side layer of the valve seat of the present invention is made of an iron-based sintered alloy material including a matrix portion in which solid lubricant particles are dispersed in a matrix phase and an infiltrated portion in which pores are filled with Cu. The porosity of the support member side layer before infiltration is set to a range of 1.0 to 20.0% by area. If the porosity is less than 1.0%, the process for increasing density becomes complicated, resulting in a significant increase in manufacturing costs. On the other hand, if the porosity exceeds 20.0%, the desired strength cannot be ensured.

[0039] The base phase in the support member side layer of the valve seat of the present invention is a tempered martensite phase. By making the base phase a tempered martensite phase, the strength and shedding resistance of the support member side layer are improved, and the desired function (shedding resistance) can be sufficiently maintained even in a severe operating environment where the combustion temperature of the engine is high.

[0040] The matrix portion of the support member side layer of the valve seat of the present invention contains solid lubricant particles in an amount of 0 to 100% by area relative to the total amount of the support member side layer. 3.0 % dispersed in the matrix structure. 3.0 %, the effect of improving formability and machinability is saturated. Therefore, the dispersed solid lubricant particles should be in the range of 0 to 100% by area based on the total amount of the support member side layer. 3.0 It is preferable to limit the range of the solid lubricant particles to MnS particles.

[0041] The matrix in the support member side layer has the above-mentioned matrix structure and a matrix composition that contains, in mass % relative to the total amount of the matrix, 0.1 to 1.5% C, one or more selected from 1.0 to 10.0% Cr, 0.1 to 3.0% Mo, and 0.1 to 2.0% Ni, 0 to 1.0% Mn, and 0 to 1.0% S, with the balance being Fe and unavoidable impurities.

[0042] Next, the reasons for limiting the components in the matrix composition of the support member side layer will be explained. C: 0.1 to 1.5% C is an element contained in the matrix phase and contributes to strengthening the matrix phase, and a content of 0.1% or more is required. On the other hand, if the content exceeds 1.5%, the hardness decreases. For this reason, the C content is limited to the range of 0.1 to 1.5%.

[0043] Cr: 1.0 to 10.0% Cr is an element contained in the matrix phase that improves strength (hardness) and shedding resistance, and can be contained as needed. When Cr is contained, it is preferable that it be 1.0% or more. On the other hand, if it is contained in excess of 10.0%, machinability decreases. Therefore, it is preferable to limit Cr to the range of 1.0 to 10.0%.

[0044] Mo: 0.1 to 3.0% Like Cr, Mo is an element contained in the matrix phase that improves strength (hardness) and shedding resistance, and can be contained as needed. When Mo is contained, it is preferable that it be 0.1% or more. On the other hand, if it is contained in an amount exceeding 3.0%, machinability decreases. Therefore, it is preferable to limit Mo to the range of 0.1 to 3.0%.

[0045] Ni: 0.1 to 2.0% Ni is contained in the matrix phase and hard particles and is an element that improves strength (hardness) and heat resistance in addition to wear resistance. It can be contained as needed. When contained, it is preferable that it be 0.1% or more. On the other hand, if it is contained in excess of 2.0%, austenite is formed, reducing wear resistance. For this reason, it is preferable to limit Ni to 0.1 to 2.0%.

[0046] Mn: 0 to 1.0% Mn is an element contained in the matrix phase and contributes to strengthening the matrix phase. Some of it disperses in the matrix phase as solid lubricant particles MnS, contributing to improved formability. It can be contained as needed. When Mn is contained, it is preferable that it be contained in an amount of 0.1% or more. On the other hand, a content exceeding 1.0% reduces formability. Therefore, it is preferable to limit the Mn content to the range of 0 to 1.0%.

[0047] S: 0 to 1.0% S is an element that disperses mainly as solid lubricant particles in the matrix, contributing to improved formability and machinability, and can be contained as needed. When contained, it is preferable to contain 0.1% or more. On the other hand, if it is contained in excess of 1.0%, the number of solid lubricant particles becomes too large, resulting in a decrease in strength (hardness). For this reason, it is preferable to limit S to the range of 0 to 1.0%.

[0048] The balance other than the above components consists of Fe and unavoidable impurities. The support member side layer is made of an iron-based sintered alloy material that has the above-mentioned matrix structure and matrix composition, and further includes an infiltrated portion (Cu infiltration amount) in which pores are filled with Cu, in an area percentage of 1.0 to 20.0% relative to the total amount of the support member side layer.

[0049] The infiltrated portion (Cu infiltration amount) in which Cu fills the pores in the support member side layer is limited to 1.0 to 20.0% by area relative to the total amount of the support member side layer. If the infiltrated portion (Cu infiltration amount) is less than 1.0%, the desired strength of the valve seat cannot be ensured. On the other hand, if it exceeds 20.0%, the wear resistance decreases. For this reason, the Cu infiltration amount in the support member side layer is limited to a range of 1.0 to 20.0% by area relative to the total amount of the support member side layer. Preferably, it is 15.0% or less, and more preferably 10.0% or less.

[0050] Next, a preferred method for manufacturing the valve seat of the present invention will be described. First, raw material powders are blended and mixed to obtain the matrix composition of the functional component side layer and the matrix composition of the support component side layer, respectively, to prepare a mixed powder for the functional component side layer and a mixed powder for the support component side layer.

[0051] The mixed powder for the functional component side layer is prepared by blending and mixing the raw material powders of an iron-based powder, graphite powder, alloying element powder, hard particle powder, and / or solid lubricant particle powder so as to achieve the matrix composition of the functional component side layer. Examples of the iron-based powder for forming the matrix phase blended into the mixed powder for the functional component side layer include pure iron powder, iron alloy powder, and alloy steel powder. Examples of the pure iron powder include atomized pure iron powder. Examples of the alloy powder include Cr-Mo-based iron alloy powder containing predetermined amounts of Cr and Mo, or iron alloy powder containing a predetermined amount of Ni in addition to Cr and Mo. Examples of the alloy steel powder include high-speed tool steel powder, such as that specified in JIS G 4403, containing predetermined amounts of C, Si, Mn, Cr, Mo, V, W, and / or Co.

[0052] The mixed powder for the support member side layer is prepared by blending and mixing the raw material powders of iron-based powder, graphite powder, alloying element powder, and solid lubricant particle powder to form the matrix composition of the support member side layer. Examples of iron-based powders for forming the matrix phase include pure iron powder and iron alloy powder. Examples of pure iron powder include atomized pure iron powder, and examples of iron alloy powder include Cr-Mo-based iron alloy powder containing predetermined amounts of Cr and Mo. The iron alloy powder may also be an iron alloy powder containing a predetermined amount of Ni in addition to Cr and Mo. Examples of alloying element powder include Cr powder, Mo powder, Ni powder, Mn powder, etc.

[0053] Next, the manufacturing method of the valve seat of the present invention includes a molding step, a sintering step, a Cu infiltration step, and a heat treatment step. In the molding step, the obtained mixed powder is filled into a mold and compressed and molded in a press molding machine to obtain a green compact. When a valve seat with a two-layer structure is to be obtained, the mixed powder for the support member side layer and the mixed powder for the functional component side layer are sequentially filled into the mold so as to obtain a two-layer structure. When a valve seat with a single-layer structure is to be obtained, only the mixed powder for the functional component side layer is filled into the mold. Needless to say, in the molding step, the compression pressure is adjusted so as to obtain a green compact with the desired porosity (density).

[0054] Next, in the sintering step, the obtained green compact is sintered to form a sintered compact. The sintering step is preferably performed by heating to a temperature range of 1000 to 1200°C in a reducing atmosphere such as ammonia decomposition gas and maintaining the temperature for 10 to 30 minutes. Note that a 2P2S process in which the compacting step and the sintering step are repeated may also be used.

[0055] Next, in the Cu infiltration step, Cu is infiltrated to fill the pores in the sintered body with Cu. The Cu infiltration treatment may be carried out during the sintering treatment or may be carried out separately from the sintering treatment.

[0056] Next, in the heat treatment step, the sintered body with the pores filled with Cu is subjected to a heat treatment (quenching and tempering) to impart the desired strength and matrix stabilization. The quenching treatment is preferably performed by heating to a quenching temperature in the range of 800 to 1000°C, maintaining the temperature, and then quenching (N2 gas quenching or oil quenching). After the quenching treatment, a tempering treatment is further performed. The tempering treatment is preferably performed by heating to a temperature in the range of 500 to 700°C, maintaining the temperature, and then quenching (N2 gas quenching or air quenching).

[0057] The heat-treated sintered body is then processed by cutting, grinding, etc. to form a valve seat (product) of a predetermined shape.

[0058] The present invention will now be further described with reference to examples. [Example]

[0059] 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 and mixed in the amounts shown in Table 1 to prepare various mixed powders for the functional component side layers. The raw material powders shown in Table 2 (iron-based powder, graphite powder, alloying element powder, solid lubricant particle powder) were blended and mixed in the amounts shown in Table 2 to prepare various mixed powders for the support component side layers. 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.

[0060] [Table 1]

[0061] [Table 2]

[0062] [Table 3]

[0063] [Table 4]

[0064] Next, these mixed powders were integrally pressure-molded in a press molding machine to obtain a two-layered green compact for a valve seat, although a portion of the green compact was made into a single-layered green compact for a valve seat.

[0065] The obtained green compact was further subjected to a sintering process to obtain a sintered body. The sintering process was carried out at a heating temperature of 1000 to 1200°C in an ammonia decomposition gas atmosphere. During sintering, a Cu infiltration process was carried out to fill the pores with Cu. For sintered body No. 2 (conventional example), the sintered body was subjected to a forging process (cold rotary forging) and then a re-sintering process. However, the Cu infiltration process was not carried out.

[0066] The sintered body was then heat treated, and then cut and ground to produce a valve seat (product) with an outer diameter of 37.7 mm, an inner diameter of 31.2 mm, and a thickness of 6.0 mm. The heat treatment consisted of quenching and tempering, with the quenching treatment involving heating to a temperature of 870°C followed by oil cooling, and the tempering treatment involving heating to a temperature of 640°C followed by air cooling.

[0067] A test piece was taken from the valve seat (product), and the content (mass %) of each component in each layer was analyzed by optical emission spectrometry to measure the composition of each layer.

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

[0069] [Table 5]

[0070] In addition, the cross section of the valve seat (product) was polished and etched with nital solution to reveal the structure of each layer, which was then observed and photographed using a scanning electron microscope (or optical microscope) (magnification: 200x). From the obtained structural photographs, the structure fraction in each layer was calculated by image analysis. The results are shown in Table 6. Note that structures other than those shown in the table are voids (Cu infiltration).

[0071] [Table 6]

[0072] Next, the obtained valve seat (product) was used as a test piece and attached to a single rig wear tester shown in Figure 2, and a wear resistance test was carried out. The test conditions were as follows. Test temperature: 300°C (seating surface) Test time: 4 hours Cam rotation speed: 2500 rpm Valve rotation speed: 10 rpm Valve material: SUH35 with nitride coating Heat source: LPG After the valve seat 1 was press-fitted into a jig 2 equivalent to a cylinder head, the test was performed by moving the valve 4 up and down using a crank mechanism while heating the valve 4 and valve seat 1 with a heat source 3 attached to the testing machine. The amount of wear on the valve seat was calculated from the change in shape before and after the test. The amount of wear on the valve 4 was calculated by measuring the amount of concavity on the seat contact surface from shape measurements after the test.

[0073] The results obtained are shown in Table 7.

[0074] Furthermore, a falling-off resistance test was carried out using the obtained valve seat (product) as a test piece using a falling-off resistance tester shown in Fig. 3. The test conditions were as follows. Test temperature: 500℃ Holding time: 1hr Initial tightening: 90 μm Heat cycle conditions: After heating and holding at 500°C for 1 hour, the sample was air-cooled to 100°C or below, and this cycle was repeated 10 times.

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

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

[0077] The results are shown in Table 7.

[0078] [Table 7]

[0079] Compared to sintered body No. 1 (conventional example), all of the inventive examples have improved wear resistance, with a wear amount of 29% or less, and a punching load of 356% or more and a residual interference of 165% or more (functional component side layer), improving resistance to shedding. This demonstrates that the structure and composition of the valve seat of the present invention significantly improves wear resistance and resistance to shedding compared to conventional examples. Furthermore, all of the inventive examples have the same or better wear resistance, nearly the same resistance to shedding, and the same or better radial crushing strength compared to sintered body No. 2 (conventional example), which was rotary forged.

[0080] From these findings, it can be seen that the valbut (sintered body) of the present invention, which has excellent resistance to shedding and wear, is suitable for use in cast iron cylinder heads. On the other hand, the comparative examples, which fall outside the scope of the present invention, show less improvement in wear resistance and resistance to shedding, and less increase in radial crushing strength, compared to the conventional examples. [Explanation of symbols]

[0081] 1 Valve seat 2 Jig 3 Heat source 4 valves 5 Test fixture 6. Heat-resistant and water-resistant container 7 Cartridge heater 8 Dummy test specimens 9 Cooling water 11 Functional component side layer 12 Support member side layer

Claims

1. A valve seat press-fitted into a cylinder head of an internal combustion engine, the valve seat has a single-layer structure made of a functional component-side layer, the functional component side layer includes a matrix portion in which hard particles or solid lubricant particles are dispersed in a matrix phase, and pores filled with Cu by infiltration; the base phase is composed of a fine carbide precipitate phase and a tempered martensite phase, the area percentage of which is 20.0% or less relative to the total amount of the functional component side layer; The matrix has, in area % relative to the total amount of the functional component side layer, 10.0 to 40.0% of the hard particles, or further 0.3 to 3.0% of the solid lubricant particles, dispersed in the matrix phase, and further has a matrix structure having 25.0% or less of a high alloy phase around the hard particles, and further contains, in mass % relative to the total amount of the matrix, 0.5 to 2.0% of C, 0.1 to 1.0% of Si, 0.1 to 2.5% of Mn, 1.0 to 7.0% of Ni, 1.0 to 7.0% of Cr, and a base composition containing 0 to 12.0%, Mo: 2.0 to 12.0%, Co: 2.0 to 20.0%, W: 0.1 to 2.0%, V: 0.01 to 1.0%, and further containing S: 0 to 1.5%, with the balance being Fe and unavoidable impurities, and further containing Cu in an area of ​​1.0 to 20.0% with respect to the total amount of the functional component-side layer, the method comprising: In order to obtain the matrix composition and matrix structure of the functional component side layer having the single-layer structure, predetermined amounts of iron-based powder, graphite powder, alloying element powder, hard particle powder, and / or solid lubricant particle powder are blended, mixed, and kneaded to obtain a mixed powder, The iron-based powder is one or more types selected from the group consisting of pure iron powder, alloy iron powder, and alloy steel powder, and the iron-based powder contains, in mass % relative to the total amount of the mixed powder, The graphite powder is 0.5 to 2.0%, the alloy element powder is 0 to 5.0%, and the hard particle powder is 10.0 to 40.0%, The solid lubricant particle powder is blended in an amount of 0 to 3.0%, mixed and kneaded to form a mixed powder, and then a molding step of filling the mixed powder into a mold of a predetermined shape and compressing and molding it to obtain a green compact; a sintering step of sintering the obtained powder compact in a reducing atmosphere at a heating temperature of 1100 to 1200°C to obtain a sintered body; a Cu infiltration step of subjecting the obtained sintered body to a Cu infiltration treatment to fill pores of the sintered body with Cu; a heat treatment step in which the sintered body, in which the pores have been infiltrated with Cu, is subjected to a quenching and tempering treatment in which the sintered body is heated to a quenching temperature of 800 to 1000°C, followed by rapid cooling, and then heated to a tempering temperature of 500 to 700°C, followed by cooling.

2. A valve seat press-fitted into a cylinder head of an internal combustion engine, the valve seat has a two-layer structure formed by integrally sintering a functional member-side layer and a support member-side layer, the functional component-side layer includes a matrix portion in which hard particles or solid lubricant particles are dispersed, and pores filled with Cu by infiltration, the matrix phase comprising a fine carbide precipitate phase occupying 20.0% or less of the total area of ​​the functional component-side layer, and a tempered martensite phase; The matrix has a matrix structure in which the hard particles are dispersed in an amount of 10.0 to 40.0%, or further the solid lubricant particles are dispersed in an amount of 0.3 to 3.0%, in terms of area % relative to the total amount of the functional component side layer, and further has a high alloy phase of 25.0% or less around the hard particles, and further contains, in mass % relative to the total amount of the matrix, C: 0.5 to 2.0%, Si: 0.1 to 1.0%, Mn: 0.1 to 2.5%, Ni: a matrix composition comprising 1.0 to 7.0%, Cr: 1.0 to 12.0%, Mo: 2.0 to 12.0%, Co: 2.0 to 20.0%, W: 0.1 to 2.0%, V: 0.01 to 1.0%, and further containing S: 0 to 1.5%, with the balance being Fe and unavoidable impurities, and further comprising Cu filled into said pores by infiltration in an amount of 1.0 to 20.0% by area with respect to the total amount of the functional component-side layer; a method for producing an iron-based sintered alloy valve seat for an internal combustion engine, the method comprising: an iron-based sintered alloy material in which the support member-side layer includes a matrix having solid lubricant particles dispersed in a matrix phase and pores filled with Cu by infiltration, the matrix phase being made of a tempered martensite phase, the matrix having a matrix structure in which the solid lubricant particles are dispersed in the matrix phase at an area % of 0 to 3.0% relative to the total amount of the support member-side layer, and a matrix composition containing, in mass % relative to the total amount of the matrix, C: 0.1 to 1.5%, further containing Cr: 1.0 to 10.0%, Mo: 0.1 to 3.0%, or further containing Ni: 0.1 to 2.0%, further containing Mn: 0 to 1.0%, and S: 0 to 1.0%, with the balance being Fe and unavoidable impurities; and further containing Cu filled in the pores by infiltration at an area % of 1.0 to 20.0% relative to the total amount of the support member-side layer, In order to obtain the two-layered matrix composition and matrix structure, predetermined amounts of iron-based powder, graphite powder, alloying element powder, hard particle powder, and / or solid lubricant particle powder are blended, mixed, and kneaded to obtain a mixed powder, The iron-based powder is one or more types selected from the group consisting of pure iron powder, alloy iron powder, and alloy steel powder, and the iron-based powder contains, in mass % relative to the total amount of the mixed powder, The graphite powder is 0.5 to 2.0%, the alloy element powder is 0 to 5.0%, and the hard particle powder is 10.0 to 40.0%, The solid lubricant particle powder is blended in an amount of 0 to 3.0%, mixed and kneaded to obtain a mixed powder for a functional component side layer, The iron-based powder is one or two selected from the group consisting of pure iron powder and iron alloy powder, In mass% with respect to the total amount of the mixed powder, The graphite powder is blended in an amount of 0.5 to 2.0%, the alloying element powder is blended in an amount of 0 to 5.0%, and the solid lubricant particle powder is blended in an amount of 0 to 3.0%, and then mixed and kneaded to obtain a mixed powder for a support member side layer. a molding step of filling a mold with predetermined amounts of the mixed powder for the support member side layer and the mixed powder for the functional component side layer in this order, and compressing and molding them as a single unit to obtain a green compact; a sintering step of sintering the obtained powder compact in a reducing atmosphere at a heating temperature of 1100 to 1200°C to obtain a sintered body; a Cu infiltration step of subjecting the obtained sintered body to a Cu infiltration treatment to fill pores of the sintered body with Cu; a heat treatment step in which the sintered body, in which the pores have been infiltrated with Cu, is subjected to a quenching and tempering treatment in which the sintered body is heated to a quenching temperature of 800 to 1000°C, followed by rapid cooling, and then heated to a tempering temperature of 500 to 700°C, followed by cooling.

3. Instead of the sintering step and the Cu infiltration step, the sintering step includes the Cu infiltration step, and is a step of performing Cu infiltration during the sintering process to obtain a sintered body in which Cu is infiltrated into pores, 3. The method for manufacturing an iron-based sintered alloy valve seat for an internal combustion engine according to claim 1, further comprising the step of heat treating the valve seat after the step of forming the valve seat.

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