Highly wear-resistant valve seat for use in internal combustion engine

Abstract

A highly wear-resistant valve seat insert for an internal combustion engine, having a material composition in which hard-particles are uniformly and finely dispersed in the matrix phase, and which is excellent in wear-resistance and radial crushing strength, based on a blended fine powder and a matrix forming powder with a particle size approximately equal to that of the hard-particles so as to prevent the hard-particles from aggregating and thus coarsely dispersing as a hard-particle phase.

Claims

1. A wear-resistant valve seat insert for an internal combustion engine, comprising: two integrated layers, made by a sintered body, wherein a first layer of said two integrated layers, on the valve-contacting face side of the valve seat insert, has a matrix part composition that contains C: 0.3 to 2.0% by mass, one or more selected from the group consisting of Co, Si, Ni, Mo, Cr, Mn, S, W, and V at 70% by mass or less in total, and the balance being Fe and unavoidable impurities, and a matrix part structure which contains hard-particles at from 10 to 65% by mass with respect to a total amount of the layer on the valve-contacting face side and disperses the hard-particles at 1000 particles/mm.sup.2 or more, wherein the hard-particles are Co-based intermetallic compound particles having a Vickers hardness HV.sub.0.1 of from 500 to 1200 HV, and wherein a second layer of said two integrated layers, on the seating face side of the valve seat insert, has a matrix part composition that contains C: 0.3 to 2.0% by mass, one or more selected from the group consisting of Mo, Si, Ni, Cr, Mn, S, W and V, at 10% by mass or less in total, and the balance being Fe and unavoidable impurities.

2. The valve seat insert for an internal combustion engine according to claim 1, wherein solid lubricant particles are contained in the matrix part structure at from 0.5 to 2.0% by mass with respect to a total amount of the first layer.

3. The valve seat insert for an internal combustion engine according to claim 1, wherein solid lubricant particles are contained in a matrix phase of the second layer at from 0.5 to 2.0% by mass with respect to a total amount of the second layer.

4. The valve seat insert for an internal combustion engine according to claim 1, wherein the Co-based intermetallic compound particles are MoFeCrSi type Co-based intermetallic compound particles.

5. The valve seat insert for an internal combustion engine according to claim 4, wherein solid lubricant particles are contained in the matrix part structure at from 0.5 to 2.0% by mass with respect to a total amount of the first layer.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIGS. 1(a) and 1(b) illustrate the structures observed by an optical microscope (b) of the cross section of the sintered body (valve seat insert) and schematic diagrams thereof (a).

(2) FIG. 2 is a schematic diagram illustrating the overview of a single rig testing machine.

DESCRIPTION OF EMBODIMENTS

(3) In the invention, an iron-based powder, a graphite powder as an alloy element powder, a hard-particle powder, or further an alloy element powder other than the graphite powder, or further a solid lubricant particle powder, or further a lubricant particle powder are blended as raw material powders and mixed to obtain a mixed powder. Thereafter, the mixed powder thus obtained is putted into a mold and compression-molded to form a green compact having a predetermined shape and a predetermined density. Subsequently, the green compact is sintered to obtain a valve seat insert which is made of an iron-matrix sintered body and consists of one layer or integrated two layers.

(4) An iron-based powder, a graphite powder as an alloy element powder, a hard-particle powder, or further an alloy element powder other than the graphite powder, or further a solid lubricant particle powder, or further a lubricant particle powder are blended as raw material powders in the mixed powder.

(5) The valve-contacting face side layer of the valve seat insert in the invention is made of an iron-based sintered alloy which has a matrix part in which the hard-particles are dispersed in the matrix phase. The wear-resistance of the valve seat insert is remarkably improved as the hard-particles are dispersed in the matrix phase. For this reason, the hard-particle powder to be blended is preferably a powder having the Vickers hardness HV.sub.0.1 of from 500 to 1200 HV. Examples of such a powder may include a Co-based intermetallic compound powder or an Fe-based intermetallic compound powder, or an FeMo-type hard-particle powder. Among them, the Co-based intermetallic compound particles are particles in which an intermetallic compound having a high hardness is dispersed in a relatively soft Co matrix and which have a characteristic exhibiting low aggressiveness to mated material, and thus are preferable. In addition, examples of the Co-based intermetallic compound powder may include a SiCrMo-type Co-based intermetallic compound, a SiNiCrMo-type Co-based intermetallic compound, and a MoFeCrSi-type Co-based intermetallic compound powder, and examples of the Fe-based intermetallic compound powder may include a CoNiCrMo-type Fe-based intermetallic compound. Meanwhile, it is preferable that the hardness of the Co-based intermetallic compound particles and the Fe-based intermetallic compound particles be from 500 to 1200 HV.sub.0.1.

(6) Among the Co-based intermetallic compound particles, the MoFeCrSi-type Co-based intermetallic compound particles exhibit remarkable acting to improve wear-resistance particularly as the hard-particles. The composition of the MoFeCrSi-type Co-based intermetallic compound particles is preferably composed of Mo: 35 to 47%, Fe: 3 to 15%, Cr: 3 to 10%, Si: 2 to 5% by mass, and the balance being Co and unavoidable impurities.

(7) In addition, in the invention, the hard-particles are blended in the layer on the valve-contacting face side such that the matrix part structure after sintering is a structure which contains hard-particles at from 10 to 65% by mass with respect to the total amount of the valve-contacting face side layer and in which the hard-particles are dispersed at 1000 particles/mm.sup.2 or more.

(8) It is impossible to secure the desired wear-resistance when the amount of the hard-particles dispersed is less than 10%. On the other hand, the effect is saturated when the dispersion exceeds 65%, and thus it is impossible to expect the effect to meet the amount added. For this reason, the amount of the hard-particles dispersed in the valve-contacting face side layer is limited in the range of from 10 to 65% by mass with respect to the total amount of the valve-contacting face side layer. In addition, it is more preferably from 30 to 40%.

(9) In the invention, the number of the hard-particles dispersed is an index of the fine and uniform dispersion of the hard-particles. In the invention, the hard-particles are limited to the content described above and the dispersed number of 1000 particles/mm.sup.2 or more in the valve-contacting face side layer. The aggregation of the hard-particles is significant when the number of the hard-particles dispersed is less than 1000 particles/mm.sup.2, and thus it is impossible to expect a remarkable improvement in wear-resistance. For this reason, the number of hard-particles dispersed is limited to 1000 particles/mm.sup.2 or more. In addition, the number is preferably from 1200 to 2000 particles/mm.sup.2.

(10) Meanwhile, the number of hard-particles dispersed is determined as follows. The heavy metals contained in the hard-particles are analyzed using a scanning electron microscope with an analyzer, the image (COMP image) thereof is taken, the independent hard-particle is identified from the distributed situation thereof, and the number of per unit area is measured. Meanwhile, it is preferable to perform the measurement of the number by binarizing into the COMP image of the heavy metal elements contained in the hard-particles and the COMP image of the elements other than those heavy elements in order to facilitate the measurement.

(11) In addition, the solid lubricant may be further contained in the valve-contacting face side layer at from 0.5 to 2.0% by mass with respect the total amount of the layer on the valve-contacting face side in addition to the hard-particles described above. The desired lubrication effect cannot be expected and the machinability also deteriorates when the content is less than 0.5%. On the other hand, the machinability improving effect is saturated and a decrease in strength is also caused when the content exceeds 2.0%. For this reason, it is preferable that the solid lubricant is limited in the range of from 0.5 to 2.0% in the case of being contained. Examples of the solid lubricant may include MnS and CaF.sub.2.

(12) In addition, in the invention, for formation of the layer in the case of one layer or for formation of the layer on the valve-contacting face side in the case of integrated two layers, the raw material powders are blended in the mixed powder such that the matrix part composition after sintering has a composition which contains the matrix phase, the hard-particles as described above or further the solid lubricant particles, contains C: 0.3 to 2.0% by mass, further contains one kind or two or more kinds selected from among Co, Si, Ni, Mo, Cr, Mn, S, W, and V at 70% by mass or less in total, and the balance being Fe and unavoidable impurities.

(13) The reason to limit the composition of the matrix part will be described. Here, the % means % by mass unless otherwise specified.

(14) C: 0.3 to 2.0%

(15) C is an element which increases the strength and hardness of the sintered body and facilitates the diffusion of metal atoms at the time of sintering, and it is preferable to contain C at 0.3% or more in the invention. On the other hand, there is a problem that a liquid phase is easily generated at the time of sintering and the dimensional accuracy decreases as well as cementite is easily produced in the matrix when the content exceeds 2.0%. For this reason, C is limited in the range of from 0.3 to 2.0%. In addition, it is preferably from 0.9 to 1.1%.

(16) One kind or two or more kinds selected from among Co, Si, Ni, Mo, Cr, Mn, S, W, and V: 70% or less in total

(17) All of Co, Si, Ni, Mo, Cr, Mn, S, W, and V are elements which increase the strength and hardness of the sintered body and further to improve the wear-resistance, and it is desirable to select at least one kind among them to be contained at 25% or more in total including the element originating in the hard-particles in order to obtain such an effect. On the other hand, the compactibility deteriorates and the strength also decreases when the content of these elements exceeds 70% in total. For this reason, the content of one kind or two or more kinds selected from among Co, Si, Ni, Mo, Cr, Mn, S, W, and V is limited to 70% or less in total. In addition, it is preferably 60% or less in total and even more preferably 40% or less.

(18) The balance of the valve-contacting face side layer other than the components described above is composed of Fe and unavoidable impurities.

(19) In addition, the hard-particles to be blended in the mixed powder as a raw material powder are dispersed in the matrix phase in the sintered body and contribute to the wear-resistance improvement. The powder tends to be finely dispersed in the matrix as the powder to be blended as the hard-particles is fine, and thus it is preferable to use a powder which is as fine as possible in order to improve the wear-resistance. For this reason, in the invention, the hard-particle powder is a powder having an average particle size of from 15 to 50 m (about #350) of a fine hard-particle powder from the viewpoint of manufacturability, particularly fluidity. Meanwhile, with regard to the measurement of the average particle size of the powder, for example, a value measured using a laser diffraction method is adopted.

(20) In the invention, the iron-based powder which is blended in the mixed powder as one of the raw material powders and constitutes the matrix is preferably a powder having an average particle size which is substantially the same as or smaller than the average particle size of the hard-particle powder. The hard-particle powder is prone to aggregate when the iron-based powder that forms the matrix is greater than the average particle size of the hard-particle powder, and thus it is difficult to uniformly and finely disperse the hard-particle powder. For this reason, in the invention, the iron-based powder to be blended is a powder having an average particle size of from 15 to 50 lam, which has substantially the same average particle size as the hard-particles. Meanwhile, the average particle size is preferably from 25 to 35 m.

(21) Meanwhile, examples of the iron-based powder to be blended may include an atomized pure iron powder, an alloy steel powder having a total amount of the alloy elements of 5% by mass or less, and a high-speed tool steel powder. These powders are preferably blended singly or compositely so as to meet the matrix part composition after sintering.

(22) A powder to be blended in the mixed powder other than the hard-particle powder, the solid lubricant powder, the iron-based powder, for example, an alloy element powder such as a Ni powder, a Co powder, and a graphite powder is also preferably a powder having an average particle size of from 15 to 50 m from the viewpoint of finely dispersing the hard-particles. It is impossible to finely disperse the hard-particles when using a powder greater than the average particle size described above.

(23) On the other hand, in a case where the valve seat insert has the layer on the seating face side (seating face side layer) which is integrated with the valve-contacting face side layer, the seating face side layer is integrated with the valve-contacting face side layer via the boundary face by sintering and is made of the iron-based sintered alloy in the same manner as the valve-contacting face side layer. The seating face side layer is not in contact with the valve but supports the valve-contacting face side layer and thus preferably has a composition which can simply secure the desired strength as the valve seat insert.

(24) For formation of the layer on the seating face side, it is preferable to use a mixed powder obtained by blending and mixing the iron-based powder and the graphite powder or further the alloy element powder, or further the solid lubricant particle powder as the raw material powders. Meanwhile, in this case, as the iron-based powder to be blended as the raw material powder, any of the same powders as those for the valve-contacting face side layer is suitable, an atomized iron powder is preferable and moreover a powder having an average particle size of from 60 to 80 m is preferable.

(25) In addition, the solid lubricant particle powder may be contained in the seating face side layer at from 0.5 to 2.0% by mass with respect to the total amount of the seating face side layer. It is impossible to expect the desired lubrication effect and the machinability also deteriorates when the content is less than 0.5%. On the other hand, the machinability improving effect is saturated and a decrease in strength is also caused when the content exceeds 2.0%. For this reason, it is preferable that the solid lubricant be limited in the range of from 0.5 to 2.0% in the case of being contained. Examples of the solid lubricant may include MnS and CaF.sub.2.

(26) It is preferable to blend the raw material powders in the mixed powder for formation of the layer on the seating face side such that the matrix phase composition after sintering (meanwhile, matrix part composition including the solid lubricant particles in a case where the solid lubricant particles are dispersed) is a composition which contains C: 0.3 to 2.0% by mass, or further contains one kind or two or more kinds selected from among Mo, Si, Ni, Cr, Mn, S, W, and V at 10% by mass or less in total, and the balance being Fe and unavoidable impurities.

(27) Meanwhile, the reason to limit the matrix phase composition of the seating face side layer after sintering (meanwhile, matrix part composition including the solid lubricant particles in a case where the solid lubricant particles are dispersed) is as follows.

(28) C: 0.3 to 2.0%

(29) C is an element which increases the strength and hardness of the sintered body, and in the invention, it is desirable to contain C of 0.3% or more in the seating face side layer in order to secure the desired strength and the hardness as the valve seat insert. However, there is a problem that a liquid phase is easily generated at the time of sintering and the dimensional accuracy decreases as well as cementite is easily produced in the matrix when the content exceeds 2.0%. For this reason, it is preferable to limit C in the range of from 0.3 to 2.0%. In addition, it is more preferably from 0.9 to 1.1%.

(30) The component described above is the basic component of the seating face side layer, and further one kind or two or more kinds selected from among Co, Si, Ni, Mo, Cr, Mn, S, W, and V may be contained at 10% or less in total as the selective element in addition to this basic composition.

(31) One kind or two or more kinds selected from among Co, Si, Ni, Mo, Cr, Mn, S, W, and V: 10% or less in total.

(32) All of Co, Si, Ni, Mo, Cr, Mn, S, W, and V are elements which increase the strength and hardness of the sintered body, and it is possible to select one kind or two or more kinds among them to be contained if necessary. It is desirable to contain these elements at 1% or more in total in order to obtain such an effect, but the effect is saturated when the content of these elements is more than 10% in total, thus it is impossible to expect the effect to meet the amount added, and it is economically disadvantageous as a result. For this reason, it is preferable to limit the content of these elements to 10% or less in total in the case of being contained. In addition, it is more preferably from 5 to 6%.

(33) Meanwhile, the balance of the seating face layer other than those described above is composed of Fe and unavoidable impurities.

(34) Next, the preferred method of forming the valve seat insert will be described.

(35) In the invention, it is preferable to use a press compacting machine having a die, a core rod, an upper punch, a lower punch, and two kinds of feeder capable of being independently driven from each other. Hereinafter, the method of forming a valve seat insert consisting of two layers of the valve-contacting face side layer and the seating face side layer will be described as an example.

(36) First, the lower punch is relatively lowered to form a filling space for the seating face side layer by the lower punch, the die, and core rod, and the filling space is filled with the mixed powder for the seating face side layer by moving the first feeder. Subsequently, the die and the core rod are relatively raised with respect to the lower punch to form a filling space for the valve-contacting face side layer, and the filling space is filled with the mixed powder for the valve-contacting face side layer by moving the second feeder. Thereafter, the upper punch is lowered, and the mixed powder for the valve-contacting face side layer and the mixed powder for the seating face side layer are integrally pressed to form a green compact. Meanwhile, the pressing conditions may be appropriately determined according to the desire and are not particularly required to limit. It is preferable to adjust the (pressing) conditions so as to have a green compact density in the range of from 5.0 to 7.5 g/cm.sup.3 with regard to the desired characteristics of the valve seat insert.

(37) Thereafter, the green compact thus obtained is subjected to the sintering treatment so as to obtain a sintered body having a two-layer structure of the upper and the lower. The conditions for the sintering treatment may be appropriately determined according to the desired properties except performing in a reducing atmosphere and are not particularly required to limit. Meanwhile, the sintering temperature is preferably from 1100 to 1200 C. from the viewpoint of the sintering diffusion.

(38) Meanwhile, the so-called 2P2S process in which the press compacting and the sintering treatment are repeated at least two times is preferable from the viewpoint of securing strength. In the 2P2S process, it is preferable that the first sintering treatment be a provisional sintering and the sintered body having the desired density be obtained by the second sintering treatment. By virtue of this, a further improvement in density is expected. In addition, the forging-sintering process, FS process in which the sintering treatment is performed after the forging may be adopted instead of the 2P2S process.

(39) Hereinafter, the invention will be further described based on Examples.

Examples

(40) The raw material powders shown in Table 2 were blended in the blending amounts shown in Table 2 and mixed using a V-type mixing machine, thereby preparing various mixed powders for the valve-contacting face side layers and various mixed powders for the seating face side. Meanwhile, the kind and the average particle size of the iron-based powders and the hard-particle powders used are collectively shown in Table 3. Meanwhile, the mixed powder No. A1 is a blending example of the related art (Conventional Example).

(41) These mixed powders were made into green compacts having two layers of the upper and the lower using a press compacting machine which had a die, a core rod, an upper punch, a lower punch, and two kinds of feeder capable of being independently driven from each other.

(42) First, the lower punch was relatively lowered to form a filling space for the seating face side layer by the lower punch, the die, and core rod, and the filling space was filled with the mixed powder for the seating face side layer by moving the first feeder. Subsequently, the die and the core rod were relatively raised with respect to the lower punch to form a filling space for the valve-contacting face side layer, and the filling space was filled with the mixed powder for the valve-contacting face side layer by moving the second feeder. Thereafter, the upper punch was lowered, and the mixed powder for the valve-contacting face side layer and the mixed powder for the seating face side layer were integrally pressed to form a green compact having two layers of the upper and the lower. Meanwhile, a green compact having one layer was formed in some cases. In those cases, the first feeder was not used.

(43) The green compact thus obtained was subjected to the 2P2S process in which the provisional sintering was performed, further the press compacting (face pressure: 6 to 10 ton/cm.sup.2) by a powder compacting machine was performed, and then the sintering treatment (1100 to 1200 C. in a reducing atmosphere) was performed so as to obtain a sintered body. Meanwhile, the 1P1S process in which compacting and sintering were performed one time was adopted for some sintered bodies. In addition, the FS process in which the forging-sintering process was performed was adopted instead of the 2P2S process for some sintered bodies. Meanwhile, the thickness of the sintered body was 8 mm, and the ratio of the upper layer to lower layer was 1:1 in the case of having two layers.

(44) The analytical sample was taken from each layer of the sintered body thus obtained, and the content of each element was determined by the emission spectrochemical analysis. The cross-section on the inner side than the boundary face of the two layers was subjected to the measurement.

(45) Moreover, the density of the sintered body thus obtained was measured using the Archimedes method.

(46) In addition, the valve seat insert (sintered body) thus obtained was introduced into a single rig wear testing machine illustrated in FIG. 2, the machine was operated under the following testing conditions to measure the depth of the depression on the specimen (valve seat insert) after the test, and the wear amount (m) was calculated. The ratio of the wear amounts of the sintered bodies was calculated by taking the wear amount of the sintered body No. 1 as the reference (1.00). The wear-resistance was evaluated by granting in a case where the wear amount is less than the reference and X in other cases.

(47) Test temperature: 300 C. (seat surface)

(48) Test time: 6 hr

(49) Rotation number of cam: 3000 rpm

(50) Rotation number of valve: 20 rpm

(51) Spring load: 2940 kgf (300 N) (at the time of setting)

(52) Lifted quantity: 9 mm

(53) Valve material: T400 hardfacing material

(54) Meanwhile, the amount of LPG+ Air and the amount of cooling water were constant.

(55) In addition, a valve seat insert (dimensions: 28226.5 mm) was formed from the iron-matrix sintered body thus obtained by cutting and grinding, and the radial crushing strength was measured in conformity with JIS Z 2507. The ratio of the radial crushing strengths of the sintered bodies was calculated by taking the radial crushing strength of the sintered body No. 1 as the reference (1.00). The radial crushing strength was evaluated by granting in a case where the radial crushing strength is higher than the reference and X in other cases.

(56) The results thus obtained are shown in Table 4 and Table 5.

(57) TABLE-US-00002 TABLE 2 Blending ratio Lubricant Iron-based Alloy element particle powder Graphite powder Hard-particle Solid lubricant powder Kind*: powder Kind: powder particle powder Kind***: blending Blending blending Kind*: blending Kind**: blending blending Mixed powder amount (% by amount (% by amount (% by amount (% by amount (% by amount (part No. mass) mass) mass) mass) mass) by mass) Remarks A1 a: 50.0, 1.0 Ni: 2.0 A: 10.0, B: 25.0 SR1: 2.0 P1: 1.0 For b: 10.0 valve-contacting B1 a: 50.0, 1.0 Ni: 2.0 A: 35.0 SR1: 2.0 P1: 1.0 face side layer b: 10.0 C1 c: 50.0, 1.0 Ni: 2.0 A: 35.0 SR1: 2.0 P1: 1.0 d: 10.0 D1 c: 50.0, 1.0 Ni: 2.0 A: 10.0, B: 25.0 SR1: 2.0 P1: 1.0 d: 10.0 E1 c: 45.0, 1.0 Ni: 2.0 A: 40.0 SR1: 2.0 P1: 1.0 d: 10.0 F1 c: 35.0, 1.0 Ni: 2.0 A: 50.0 SR1: 2.0 P1: 1.0 d: 10.0 G1 c: 51.5, 1.0 Ni: 2.0 A: 35.0 SR1: 0.5 P1: 1.0 d: 10.0 H1 c: 55.0, d: 5.0 1.0 Ni: 2.0 A: 35.0 SR1: 2.0 P1: 1.0 I1 c: 40.0, 1.0 Ni: 2.0 A: 35.0 SR1: 2.0 P1: 1.0 d: 20.0 J1 c: 48.0, 1.0 Ni: 4.0 A: 35.0 SR1: 2.0 P1: 1.0 d: 10.0 K1 c: 49.8, 1.2 Ni: 2.0 A: 35.0 SR1: 2.0 P1: 1.0 d: 10.0 L1 c: 50.2, 0.8 Ni: 2.0 A: 35.0 SR1: 2.0 P1: 1.0 d: 10.0 M1 b: 10.0, 1.0 Ni: 2.0 A: 35.0 SR1: 2.0 P1: 1.0 e: 50.0 N1 d: 10.0, 1.0 Ni: 2.0 A: 10.0, B: 25.0 SR1: 2.0 P1: 1.0 f: 50.0 O1 c: 50.0, 1.0 Ni: 2.0 C: 15.0. D: 20.0 SR1: 2.0 P1: 1.0 d: 10.0 P1 c: 50.0, 1.0 Ni: 2.0 D: 35.0 SR1: 2.0 P1: 1.0 d: 10.0 Q1 c: 60.0, 1.0 Ni: 2.0 A: 15.0 SR1: 2.0 P1: 1.0 d: 10.0 R1 c: 29.7, 1.3 Ni: 2.0 A: 20.0, E: 35.0 SR1: 2.0 P1: 1.0 d: 10.0 R2 c: 30.0, 1.0 Ni: 2.0 A: 35.0, E: 20.0 SR1: 2.0 P1: 1.0 d: 10.0 S1 c: 31.0, 1.0 Ni: 2.0 A: 20.0, E: 35.0 SR1: 1.0 P1: 1.0 d: 10.0 T1 c: 30.0, 1.0 Ni: 2.0 A: 20.0, E: 35.0 SR1: 2.0 P1: 1.0 d: 10.0 U1 c: 31.0, 1.0 Ni: 2.0 A: 20.0, E: 35.0 SR1: 1.0 P1: 1.0 d: 10.0 V1 c: 31.0, 1.0 Ni: 2.0 A: 20.0, F: 35.0 SR1: 1.0 P1: 1.0 d: 10.0 W1 c: 31.0, 1.0 Ni: 2.0 A: 20.0, G: 35.0 SR1: 1.0 P1: 1.0 d: 10.0 X1 c: 31.0, 1.0 Ni: 2.0 A: 20.0, H: 35.0 SR1: 1.0 P1: 1.0 d: 10.0 Y1 c: 31.0, 1.0 Ni: 2.0 A: 20.0, I: 35.0 SR1: 1.0 P1: 1.0 d: 10.0 Z1 c: 31.0, 1.0 Ni: 2.0 A: 20.0, J: 35.0 SR1: 1.0 P1: 1.0 d: 10.0 Z2 c: 21.0, 1.0 Ni: 2.0 B: 20.0, E: 45.0 SR1: 1.0 d: 10.0 1A c: 98.5 1.0 SR1: 0.5 P1: 1.0 For seating face 1B c: 96.5 1.0 C: 2.0 SR1: 0.5 P1: 1.0 side layer *see Table 3 **SR1: MnS ***P1: zinc stearate Blending amount (part by mass): part by mass with respect to 100 parts by mass of the total amount of (iron-based powder + graphite powder + alloy element powder + hard-particle powder + solid lubricant particle powder)

(58) TABLE-US-00003 TABLE 3 Kind Kind No. Kind: average particle size Iron-based a Atomized pure iron powder: average particle size 80 m powder b High-speed tool steel powder*: average particle size 60 m c Atomized pure iron powder: average particle size 35 m (#325) d High-speed tool steel powder*: average particle size 35 m (#325) e 3Cr alloy steel powder**: average particle size 80 m f 3Cr alloy steel powder**: average particle size 35 m (#325) Hard-particle A Co-based intermetallic compound powder***: average particle powder size 25 m (#325), 700 HV.sub.0.1 B Co-based intermetallic compound powder***: average particle size 60 m (#100), 700 HV.sub.0.1 C FeMo-type hard-particle powder: average particle size 60 m (#100), 1200 HV.sub.0.1 D FeMo-type hard-particle powder: average particle size 25 m (#350), 1200 HV.sub.0.1 E Co-based hard-particle powder****: average particle size 60 m (#100), 1000 HV.sub.0.1 F Co-based hard-particle powder*****: average particle size 60 m (#100), 1000 HV.sub.0.1 G Co-based hard-particle powder******: average particle size 60 m (#100), 1000 HV.sub.0.1 H Co-based hard-particle powder*******: average particle size 60 m (#100), 1000 HV.sub.0.1 I Co-based hard-particle powder********: average particle size 60 m (#100), 1000 HV.sub.0.1 J Co-based hard-particle powder*********: average particle size 60 m (#100), 1000 HV.sub.0.1 *high-speed tool steel powder: 0.9% C0.3% Si0.2% Mn4.0% Cr5.0% Mo6.0% W2.0% VFe (balance) **3Cr alloy steel powder: 3.0% Cr0.3% Mo0.3% VFe (balance) ***Co-based intermetallic compound powder: 9% Cr28% Mo3% SiCo (balance) ****Co-based intermetallic compound powder: 45% Mo10% Fe4% Cr3% SiCo (balance) *****Co-based intermetallic compound powder: 35% Mo10% Fe4% Cr3% SiCo (balance) ******Co-based intermetallic compound powder: 47% Mo10% Fe4% Cr3% SiCo (balance) *******Co-based intermetallic compound powder: 45% Mo3% Fe4% Cr3.5% SiCo (balance) ********Co-based intermetallic compound powder: 40% Mo15% Fe4% Cr2.7% SiCo (balance) *********Co-based intermetallic compound powder: 20% Mo10% Ni24% Cr2% SiCo (balance)

(59) TABLE-US-00004 TABLE 4 Mixed powder No. Chemical components of sintered body (% by mass) Sintered Seating Valve-contacting face side layer (matrix part) body Face side face side Others Total of No. layer layer C Co Si Ni Mo Cr Mn S W V others Balance 1 A1 1A 1.1 21.1 0.9 2.0 10.5 3.4 1.2 0.8 0.6 0.2 41.8 Fe 2 B1 1A 1.1 21.1 0.9 2.0 10.5 3.4 1.2 0.8 0.6 0.2 41.8 Fe 3 C1 1A 1.1 21.1 0.9 2.0 10.5 3.4 1.2 0.8 0.6 0.2 41.8 Fe 4 C1 1A 1.1 21.1 0.9 2.0 10.5 3.4 1.2 0.8 0.6 0.2 41.8 Fe 5 D1 1A 1.1 21.1 0.9 2.0 10.5 3.4 1.2 0.8 0.6 0.2 41.8 Fe 6 E1 1A 1.1 24.2 1.1 2.0 11.9 3.6 1.2 0.8 0.6 0.2 46.8 Fe 7 F1 1A 1.1 30.2 1.3 2.0 14.7 4.7 1.2 0.8 0.6 0.2 56.8 Fe 8 G1 1A 1.1 21.1 0.9 2.0 10.5 3.4 0.3 0.2 0.6 0.2 41.8 Fe 9 H1 1A 1.0 21.1 0.9 2.0 10.2 3.2 1.2 0.8 0.3 0.1 40.9 Fe 10 I1 1A 1.2 21.1 1.0 2.0 11.0 3.8 1.2 0.8 1.2 0.4 43.7 Fe 11 J1 1A 1.1 21.1 0.9 4.0 10.5 3.4 1.2 0.8 0.6 0.2 43.8 Fe 12 K1 1A 1.3 21.1 0.9 2.0 10.5 3.4 1.2 0.8 0.6 0.2 42.0 Fe 13 L1 1A 0.9 21.1 0.9 2.0 10.5 3.4 1.2 0.8 0.6 0.2 41.6 Fe 14 M1 1A 1.1 21.1 0.9 2.0 10.6 4.9 1.2 0.8 0.6 0.2 43.4 Fe 15 N1 1A 1.1 21.1 0.9 2.0 10.6 4.9 1.2 0.8 0.6 0.2 43.4 Fe 16 O1 1A 1.1 2.0 21.5 0.4 1.2 0.8 0.6 0.2 27.8 Fe 17 P1 1A 1.1 2.0 21.5 0.4 1.2 0.8 0.6 0.2 27.8 Fe 18 Q1 1A 1.1 9.1 0.4 2.0 4.8 1.7 1.2 0.8 0.6 0.2 21.9 Fe 19 R1 1A 1.4 33.2 1.6 2.0 21.9 3.5 1.2 0.8 0.6 0.2 66.4 Fe 20 C1 1B 1.1 21.1 0.9 2.0 10.5 3.4 1.2 0.8 0.6 0.2 41.8 Fe 21 C1 1.1 21.1 0.9 2.0 10.5 3.4 1.2 0.8 0.6 0.2 41.8 Fe 22 R2 1A 1.1 28.7 1.5 2.0 19.5 4.2 1.2 0.8 0.6 0.2 58.7 Fe 23 S1 1A 1.1 25.4 1.6 2.0 21.9 3.5 0.6 0.4 0.6 0.2 56.2 Fe 24 T1 1A 1.1 25.4 1.6 2.0 21.9 3.5 1.2 0.8 0.6 0.2 57.2 Fe 25 U1 1A 1.1 25.4 1.6 2.0 21.9 3.5 0.6 0.4 0.6 0.2 56.2 Fe 26 V1 1A 1.1 28.9 1.6 2.0 18.4 3.5 0.6 0.4 0.6 0.2 56.2 Fe 27 W1 1A 1.1 24.7 1.6 2.0 22.6 3.5 0.6 0.4 0.6 0.2 56.2 Fe 28 X1 1A 1.1 27.7 1.8 2.0 21.9 3.5 0.6 0.4 0.6 0.2 58.7 Fe 29 Y1 1A 1.1 25.5 1.5 2.0 20.2 3.5 0.6 0.4 0.6 0.2 54.5 Fe 30 Z1 1A 1.1 27.5 1.3 5.5 13.2 10.5 0.6 0.4 0.6 0.2 56.0 Fe 31 Z2 1A 1.1 29.2 1.9 2.0 26.4 3.9 0.6 0.4 0.6 0.2 65.2 Fe Structure of sintered body Chemical components of Valve - sintered body (% by mass) contacting face Seating face side layer (matrix part) side layer Sintered Others Number of hard - body Mo, Si, Cr, Mn, Total of particles No. C W, V, Ni, S others Balance (particles/mm.sup.2) Remarks 1 1.0 Mn: 0.3, 0.5 Fe 700 Conventional S: 0.2 Example 2 1.0 Mn: 0.3, 0.5 Fe 740 Comparative S: 0.2 Example 3 1.0 Mn: 0.3, 0.5 Fe 1867 Example of the S: 0.2 invention 4 1.0 Mn: 0.3, 0.5 Fe 1733 Example of the S: 0.2 invention 5 1.0 Mn: 0.3, 0.5 Fe 1333 Example of the S: 0.2 invention 6 1.0 Mn: 0.3, 0.5 Fe 1600 Example of the S: 0.2 invention 7 1.0 Mn: 0.3, 0.5 Fe 1600 Example of the S: 0.2 invention 8 1.0 Mn: 0.3, 0.5 Fe 2100 Example of the S: 0.2 invention 9 1.0 Mn: 0.3, 0.5 Fe 1733 Example of the S: 0.2 invention 10 1.0 Mn: 0.3, 0.5 Fe 1933 Example of the S: 0.2 invention 11 1.0 Mn: 0.3, 0.5 Fe 1867 Comparative S: 0.2 Example 12 1.0 Mn: 0.3, 0.5 Fe 1867 Example of the S: 0.2 invention 13 1.0 Mn: 0.3, 0.5 Fe 1867 Example of the S: 0.2 invention 14 1.0 Mn: 0.3, 0.5 Fe 730 Comparative S: 0.2 Example 15 1.0 Mn: 0.3, 0.5 Fe 1733 Example of the S: 0.2 invention 16 1.0 Mn: 0.3, 0.5 Fe 1733 Example of the S: 0.2 invention 17 1.0 Mn: 0.3, 0.5 Fe 1867 Example of the S: 0.2 invention 18 1.0 Mn: 0.3, 0.5 Fe 1000 Example of the S: 0.2 invention 19 1.0 Mn: 0.3, 0.5 Fe 1200 Example of the S: 0.2 invention 20 1.0 Mo: 1.2, 1.7 Fe 1867 Example of the Mn: 0.3, invention S: 0.2 21 1867 Example of the invention 22 1.0 Mn: 0.3, 0.5 Fe 1333 Example of the S: 0.2 invention 23 1.0 Mn: 0.3, 0.5 Fe 1200 Example of the S: 0.2 invention 24 1.0 Mn: 0.3, 0.5 Fe 1200 Example of the S: 0.2 invention 25 1.0 Mn: 0.3, 0.5 Fe 1767 Example of the S: 0.2 invention 26 1.0 Mn: 0.3, 0.5 Fe 1200 Example of the S: 0.2 invention 27 1.0 Mn: 0.3, 0.5 Fe 1200 Example of the S: 0.2 invention 28 1.0 Mn: 0.3, 0.5 Fe 1200 Example of the S: 0.2 invention 29 1.0 Mn: 0.3, 0.5 Fe 1200 Conventional S: 0.2 Example 30 1.0 Mn: 0.3, 0.5 Fe 1200 Comparative S: 0.2 Example 31 1.0 Mn: 0.3, 0.5 Fe 1833 Example of the S: 0.2 invention

(60) TABLE-US-00005 TABLE 5 Radial crushing strength Wear-resistance Ratio of radial Density of Ratio of wear crushing sintered amount strength Sintered body (reference: (reference: body No. Process (g/cm.sup.2) 1.00) Evaluation 1.00) Evaluation Remarks 1 2P2S 7.2 1.00 1.00 Conventional Example 2 2P2S 7.2 1.50 x 0.80 x Comparative Example 3 2P2S 7.2 0.60 1.40 Example of the invention 4 1P1S 6.8 0.80 1.20 Example of the invention 5 2P2S 7.2 0.90 1.10 Example of the invention 6 2P2S 7.2 0.58 1.40 Example of the invention 7 2P2S 7.2 0.58 1.40 Example of the invention 8 2P2S 7.2 0.65 1.50 Example of the invention 9 2P2S 7.2 0.80 1.40 Example of the invention 10 2P2S 7.2 0.58 1.40 Example of the invention 11 2P2S 7.2 0.59 1.40 Example of the invention 12 2P2S 7.2 0.60 1.50 Example of the invention 13 2P2S 7.2 0.65 1.30 Example of the invention 14 2P2S 7.2 1.01 x 0.90 x Comparative Example 15 2P2S 7.2 0.55 1.20 Example of the invention 16 2P2S 7.2 1.50 x 1.20 Example of the invention 17 2P2S 7.2 1.50 x 1.30 Example of the invention 18 2P2S 7.2 0.98 1.40 Example of the invention 19 2P2S 7.2 0.45 1.00 Example of the invention 20 2P2S 7.2 0.60 1.40 Example of the invention 21 2P2S 7.2 0.60 1.40 Example of the invention 22 2P2S 7.2 0.30 1.10 Example of the invention 23 2P2S 7.2 0.20 1.05 Example of the invention 24 2P2S 7.2 0.20 1.10 Example of the invention 25 2P2S 7.2 0.10 1.50 Example of the invention 26 2P2S 7.2 0.25 1.20 Example of the invention 27 2P2S 7.2 0.15 1.02 Example of the invention 28 2P2S 7.2 0.14 1.02 Example of the invention 29 2P2S 7.2 0.21 1.10 Example of the invention 30 2P2S 7.2 0.60 1.50 Example of the invention 31 FS 7.4 0.05 1.05 Example of the invention

(61) All of Examples of the invention are a valve seat insert (iron-matrix sintered body) which exhibits superior wear-resistance and a higher radial crushing strength compared to the Conventional Example (sintered body No. 1). On the other hand, Comparative Examples out of the range of the invention have a decreased wear-resistance, a decreased radial crushing strength, or both of them.

REFERENCE SIGNS LIST

(62) 1 valve seat insert 2 setting plate 3 heat source (LPG+ Air) 4 valve