GB2370281A

GB2370281A - Iron-based sintered alloy for valve seats

Info

Publication number: GB2370281A
Application number: GB0125293A
Authority: GB
Inventors: Teruo Takahashi; Arata Kakiuchi; Kenichi Sato
Original assignee: Nippon Piston Ring Co Ltd
Current assignee: Nippon Piston Ring Co Ltd
Priority date: 2000-10-27
Filing date: 2001-10-22
Publication date: 2002-06-26
Also published as: GB0125293D0; US20020084004A1; JP2002129296A

Abstract

An iron-based sintered alloy comprises 10-30 volume % of particles (H) having a diameter of 10-150 m and a hardness of Hv 600-1300, 5-40 volume % of pearlite (P), 10-40 volume % of a phase (R) formed by diffusion of elements from the hard particles, optionally 0.1-10.0 volume % of solid lubricant (ST) (e.g. manganese, molybdenum or tungsten sulphide, calcium or lithium fluoride or graphite) and up 10 volume % of porosity. The pores may be infiltrated with copper, a copper alloy, lead, a lead alloy or a phenol-based resin. The hard particles (H) are preferably one or more of the following: Mo-Ni-Cr-Si-Co intermatallics, Cr-Mo-Co intermetallics, Fe-Mo alloys or carbide precipitated particles (e.g. SKH 51, SKH 57 OR SKD 11). The alloy may be used for valve seats.

Description

237028 1

IRON-BASED SINTERE1) ALLOY MATERIAL

FY)R VALVE SEATAND

VALVE SEAT.MADE OF IRON-BASED SINTEREDAILOY

Background of the Invention

Field of the Invention

The present invention relates to a Rintered alloy material and 9peciScally to an iron-based metered alloy material suitable for a valve seat used in an internal combustion engine.

Deception of prior Art

A aintered alloy produced by a method including the steps of blending and mmng alloy powder; filling the blended alloy powder in a mold and compression the alloy powder Or molding; and Anteing the molding in art atmosphere at a predetermined temperature. By this method, according to a metered alloy, a metal or an alloy which difficult to obtain by an o y melting and casting method can be easily produced. In addidon, as the various factions can be easily imparted to the product in a combed manner, a member having unique Smctions can be produced according to this method. Further, a Rintered alloy is suitable fir producing a porous material, a hard-machining material or a mechanical member had a complicated shape. Due to Bush reasons, a metered alloy has recently been applied to a valve seat of an internal combustion engine which must have high wear resistance. In recent years, in the field of automobile engine, a demand for

improvement, such as prolonging the product life, rea g the power, pumping exhaustion and enhancing fuel consumption thereof has been increasing. As a result, a valve seat for an automobile engine is now required to have a more excellent durability than is required in the conventional model so that the valve seat can bear a harsher application environment.

Accordingly, there has increasingly been a demerit far furler improvement of the heat resistance property and the wear resistance properly of a valve seat.

As the sintered alloy material Ibr a valve seat, for examples, JP-B 51-

13093 Laid Open discloses an iron-based sintered alloy materja1 for a valve seat, which mnultaneously exhibits excellent wear resistance, heat reactance and corrosion resistance even when lead-lice gasoline is used. JP-B 51-13093 Laid-Open rli rloses a Entered alloy containing C, Nit Cr. Mo, Co and W by relatively large amounts, in which Specific alloy panicles comprised of C-Cr-

W-Co and ferromolybden un particles are dispersed the pear.lite base matrix, and Co and Hi are diffused around these particles. In other words, in the sintered alloy described in JP-B B1-13093 Laid-Open, specifically He amounts of W and Co must be added in order to pronde the metered alloy with excellent heat resiatance, wear reeista, corrosion radiance and the like. As a result, the valve seat made of such a Rmtered alloy quite expensive and problematic in terms of production costs Farther, JP-A 53158 Laid-Open discloses an iron-based Catered alloy of the hard-phase dispersion- pe. The iron-based Rmtered alloy described in JP-A 63168 Laid Open has an iron-based matrix which conning: 3 to lB wt % of Ni; 3 to l5 wt 56 of Mo; 0.5 to 5 wt % of Cr.; 0.6 to l.2 wt hi of C; and Fe as the reminder. Hard phase parses are dispersed by the amount of 3 to 20 wt % in the iron-based math As the hard phase parables, at least one type of hard phase particles selected from the group consisting of hard phase particles contn rur g 50 to 57 wt A of Cr. 18 to 22 art % of Mo, 8 to 12 wt % of Co, 0.1 to 1.4 wt % of C, 0.8 to 1.3 At % of Sit and Fe as the remainder; hard phase particles containing 27 to 33 wt % of Cr. 22 to 28 wt % of W. 8 to 12 At % of Co, 1.7 to 2.3 wt % of C, 1.0 to 2.0 wt % of Sit and Fe as the re nder; hard phase parddles containing 60 to 70 wt % of Mo, no more than 0.01 wt % of C, and Fe as the reminder, are used.

JP-A 2000199040 Laid-Open discloses an iron-based metered alloy ibr a valve seat, in which 3 to 20 % of hard particles are dispersed rn a base

J matrix phase, the base me c phase being comprised of 5 to 40 % of the pearlite. phase; 20 to 60 % of the carbide dispersed phase including fine carbides dispersed therein; and 5 to 20 % of the high-alloy do phase.

Object and Summary of 1 he Invention

However, in the iron-based wintered alloy described in dP-A 9 53158 LaidOpen, Cr. Mo, Ni, Co and W must be added by relatively large amounts, in order to provide the Amtered alloy with excellent heat resistance pmperl y, wear resistance property, corrosion reactance property and the like. AB a result, the valve Beat made of such a sintered alloy is quite e penswe and came a problem terms of production cost Further, in producing 1 hit' iron-based amtered alloy, the influence of 1 and Co powder on human body remains as a problem to be solved.

As the iron-based Entered alley described in JP-A 200 199040 Laid-

Open mcludea the carbide dispersed phase having relatively high hardness therein by a high proportion, the iron-based aintezed alloy is quite hard and cause a problem when the sintered alloy is utilized an application in which excellent toughness is required.

An object of the present invention is to propose all iron-based sintered alloy material ibr a valve seat, as well as a valve seat made of the ironbased sintered ahoy for the use in an internal combustion engine, which solves the aibrementioned problems in an advantageous manner, does not contain the alloy elements by large amounts and thus is inexpensive, and exhibits excellent toughness and wear rematance The inventors at the present invention, as a result of tile keen study tar achieving the aforementioned object, have discovered that, by oonstituting the base matrix phase of the iron-based Bantered alloy material with the pearlite phase and the bigh-aUoy diffused phase and dispersing hard parties in the base matrix phase, the wear rems e of the resulting sistered alloy can be si - firmly increased ant toughness thereof can be exhorted without

adding a large amount of alloy elements. The present invention has been completed on the bum of this discovery. In the present invention, "a high-

alloy diffused phase" represents a phase which is characteristically Formed around hard particles due to the diffusion of the alloy elements of the hard particles, contributes to the excellent heat renounce, wear resistance and corrosion resistance of the amtered alloy and has hardness of Hv 350 to 600.

Specificity, the gut of the present invention is as follows (1) An ironbased Entered alloy material for a valve seat, in Sleigh hard parables are dispersed in a base matrix phase and whith is characterized in that the base matrix phase is comprised of 5 to 40 voL % of a pearlite phase and 10 to 40 voL % of a high-alloy diffused phase and parties having hardness of Hv 600 to 1300 and parve dieter of 10 to 150 Am are dispersed as lihe hard particles, by the amount of 10 to 30 voL %, the base mstaX phase (2) An iron-based sistered alloy material for a valve seat' in whirls hard parables are dispersed in a base matrix phase, characterized in Mat a base metric portion which includes the hard particles has a composition composed oLO.2to2.0wt%ofC; 1.0 to9.0vrt%ofCr; l.Oto9.0wt%ofMo; O.Ito1.0 wt % of Si; 1.0 to 3.0 wt % of W; 0.1 tO 1.0 wt % oúV; 3.0 to 15. 0 wt %, as the sum, of at least one t ype of element selected firm tlte group consisting of Cu.

Co and Ni; and the remainder which is substantially Fe, the base matrix phase is oomprmed of 5 to 40 voL % of a pearlite phase and 10 to 40 vol. % of a high alloy diffused phase and particles having hardness of Hv 600 to 1300 and particle d;: meter of 10 to 150 Am are dispersed as the hard particles, by the amount of 10 to 30 voL %, in the base matr phase.

(3) An iron-based sintered alloy material for a valve seat described in the aforementioned (1) or (2), wherein the hard particles are at lesat one type of parses selected from the group consisting of intermetallic compound particles of Mo-Ni-Cr-Si-Co; mtennetallic compound particles of Cr-Mo-Co; F+Mo alloy parddles; and carbide-precipitated particles.

(4) An iron-based sistered alloy material for a valve seat described in the aibrementioned (3), wherein the carbide-precipitated partiblea have a composition which is comprised of: 0.2 to 2.0 wt % of C; no to 10.0 wt % of Cr; 0 to 10.0 wt % of Mo; 2.0 to 10.0 wt % of V; 0.2 to 5.0 wt 56 of V; Id Fe and inevitable impurities as the remainder.

(5) An iron-based metered alloy material for a valve seat dewed the aforementioned (4), wherein the content of the carbide-precipitated particles, as is expressed as the proportion by volume thereof present in the base matrix phase, leas than 20 volt %.

(6) An iron-based Rmtered alloy material for a valve seat described in the aforementioned (4) or (5), wherein fine carbides having particle diameter of 1 to 10 Am have been precipitated on said carbide- precipitated particles.

(7) An iron-based Rintered alloy material for a valve seat described in any one of the aforementioned (0 to (6), wherein the base matrix phase contains solid lubricant partiblea by the mnount of 0.1 to 10.0 vol. %.

(8) An iron-based Entered alloy material for a valve seat described ill the aforementioned (7), wherein the solid lubricant particles made of are at least one type of compound selected from the group coasting of a sulfide, a fluoride and graphite.

(9) An iron-based wintered alloy material for a valve seat described in alar one of the albrementioned (1) to (8), wherein sauntered pores are infiltrated with one of the material selected from the group consisting. of Cu. Cu alloy, Pb and Pb alloy or with a phenol-based In.

(10) A valve seat made of an iron-based sintered alloy, characterized in that the valve seat is made of the iron based sintered allay material tar a valve seat of any one of the aforementioned (1) to (9).

Brief Description of the Drawl

Pig. l(a) is a optical micrograph of a shntered alloy material (the sintered body No. 3) of an ample of the present mventiom Fig. 1(b) a

sketch of Fig. l(a).

- Fig. 2(a) is a optical micrograph of a Watered allay material (the Rintered may No 6) of an example of the present invention Pig. (2b) is a sketch of Fig 2(a).

fig 3(a) is a optical micrograph of a metered alloy material (the wintered body No. 10) of a comparative example ofthe present invention. Fig. 3(b) is a sketch of Fig. 3(a).

Fig 4(a) a optical micro aph of a Enntered alloy material (the sintered body No. 12) of a comparators example of the present invention. Fig. 4(b) in a sketch of rig. 4(a).

Fig. 5 is a graph which shows t he result of the ale piece wear test on rig of the examples.

fig 6 is a schematic view of a tester of the angle piece wear test on ng. Detailed Option of the Preferred Embodiments The iron-based metered alleger material of the present invention is comp g of a base math phase, hard particles diverged in the base matrix phase, and optionally a solid lubricant parables dispersed in the hard motam The base matrix phase has a sty which mbludes a pearlite phase and a high-alloy diffused phase. The high-alloy diffused phase is Armed of the alloy elements which have been dimmed Tom the hard particles to the surrounding of the hard particles In the structure of the base matnx, We pearlite phase occupies to 40 vol. % and the high-alloy diffused phase occupies 10 to 40 voL % of the sistered alloy material as a whole.

When the proportion by volume of the pearlite phase is led 5 56, hardness of the bane matrix phase increases and the machinability thereof may be deteriorated On the other hand, when the proportion by volume of the pearlite phase exceeds 40 %, hardness of the base matrix phase is

decreased, whereby the wear Once and the heat resistance may deteriorate. The high-alloy diffi - ed phase contributes to enhancing the heat resistanoe, the wear resistance and the corrosion resistance properties, whereby the properties of the iron-based metered alloy material as a whole are improved When the proportion by volume of the high-allay Red phase less than 10 %, improvement of the aforementioned properties of the iron-

based sintered alloy material is reduced. On the other hand, when the proportion by volume of tile high-alloy diffused phase exceeds 40 if, hardens of the base matrix phase increases and the machinability 1 hereof may be disturbed. Dine hard particles dispersed in the base matrix phase are particles having Madness in a range of Hv 600 to 1300 and particle diameter in a range of 10 to 150 m.

When hardness of the hard parties is lower then Hv 600, the wear resistance deteriorates. On the other hand, when hardness of the hard particles exceeds Hv 1300, toughness ofthe resulting sintered alloy material is reduced and the generation rate of chip and crack thereof increases. When the particle dieter of the hard particles is smaller than 10 m, the components of the hard particles tend to be diffused We base matrix phase in an excessive manner at the time of sintering, whereby hardness of the particles is lowered. On the other hand, when the parse di eter of the hard particles exceed 150 m, the machinability of the Rintered body may be deteriorated and the aggrea - Pness to mated materials increases.

The hard particles are preferably at least one type of particles selected Tom the group courting of intermetallic compound part icles of Mo-M-Cr i-

Co; intermetallic compound parolee of Cr-Mo-Co; Fe-Mo alloy particles; and carbide-precipitated particles. By dispersing particles having the aforementioned composition, as the hard particles, in the base matrix phase, the diffusion property during sistering is increased, whereby the strength, the toughness and the wear resistance of the Entered alloy material are

enhanced. The mtennetallic compound particles of M+Ni-Cr-Si-Co are made of an mtermet llic compound which conning: 20 to 30 wt % of Mo; to 20 wt 96 of Ni; 10 to 35 wt % of Cr; 1 to 5 wt % of Si; and the reminder which is substantially comprised of Co. Ibe intermetallic compound parddles of Cr-

Mo-Co are made of an intermetallic compound whicl1 contains: 6.0 to 15.0 wt % of Cr; solo to 40.0 wt % of Mo; and t he remainder which substantially comprised of Co. The Fe-Mo allay particles are particles which contain 50 to 70 wt 96 of Mo and the redder which is Bta:rlti, compused of Fe.

The a rb de-pre itated particles are particles which have a composition comprised of 0.2 to 2.0 wt % of C; 2.0 to Leo wt % of C'r; 2.0 to 10.0 wt % of Mo; 2.0 to 10.0 wt % of W; 0.2 to 6.0 wt % of V; and Fe and m vitable impurities as the reminder and on which fine carbides, preferably having the partible Meter of 1 to 10 m, have been precipitated. When the Parke diameter of the precipitated carbide smaller than 1 m, the carbide particles Nil to make significant contribution to the increase hardness and the wear resistance of the sintered alloy material deteriorates. On the other hand, when the particle diameter of the precipitated Abide exceeds 10 An, the aggre enesa to mated materials increases. Preferable Rumples of the carbide-prempitated particles include SKH 61 powder which con a large amount of carbide foxing elements such as V, W. Mo and the like (the t apical composition thereof: 0.9 wt % of C, 4 wt % of Cr. wt % of Mo, 6 wt % of W. 2 wt % of V and Fe as the reminder), SARI 57 powder and SIN 11 powder.

In a case in which the carbide-prec pitated particles are used as the hard particles, the content of the carbide-prec itated parses, as is expressed as the proportion by volume thereof present the base matrix phase, is prefierabIy less than 20 voL %. When the content of the carbide-

prec pitated particles iB no less than 20 voL %, hardness of the sintered alloy material increases, whereby toughness of the parlidea deteriorates, the machinability thereof may be disturbed, and the opposite aggressienesa to

mated materials.

In the present invention, at least one type of the aforementioned hard particles is dispersed in the base matrix phase such that the total amount thereoúis 10 to 30 voL %. When the total content of the hard particles is less than 10 voL %, the content of the hard parses is too small and the wear resistance thereof will deteriorate On the other hand, when the total content of the hard particles exceeds 30 vol. %, the strength of the metered alloy material lowered, the aggresmeness to mated materials increases, and the ma hinahility of the Rintered allay material may be deteriorated.

The compom on of the base matnX port ion including the base matrix phase and the hard particles dispersed in the base matrix phase is preferably comprised of. 0.2 to 2.0 wt % of C; 1.0 to 9.0 wt of Cr; 1.0 to 9.0 wt % of Mo; 0.1 to l.Owt 56 of Si; 1.O to 3.0 wt % of W; O.l to l.0wt % of V; 3.0 to 15.0 wt %, as Me e''m, of at least one Me of element selected from the group consisting of Cu. Co and Ni; and the remember which subatan lly Fe.

Next, the preferable oo.ntents of the respective alloy elements of the base matrix port ion will be described hereafter.

C: 0.2 to 2.0 At % Carbon is an element which is s d-eolved in the base matrix phase, thereby leasing hardness of the base mstnx phase. In addition, carbon is reacted tenth other alloy elements and Anna a carbide, thereby increasing hardness of the base matrix phase and improving the wear resistance thereof When the content of carbon is less than 0.2 At %, the base matrix phase cannot have the predetermined hardness and the wear resistance thereof deteriorates. When the content of carbon exceeds 2.0 wt %, not only the resulting carbide becomes gross and the toughness thereof deteriorates, but also the diffusion of the components of the hard parses proceeds excesaively and hardness of the particles is lowered Accordingly, the content of C is preferably restricted to 0.2 to 2.0 wt Hi.

Cr: l.Oto9.0wt%

Cr. is an element which is cantoned in the bow matrix phase and the hard panicles and contributes to increa ring hardness, the wear resistance and the corrosion resistance of the sistered alloy material. When the content of Cr exceeds 9.0 It %, tile content of the hard particles becomes too} or the hardness of the base matrix phase increases too high, whereby the aggre eness to mated materials of the metered alloy mote qalA increases.

On the other hand, when the content of Cr is lees than 1.0 wt %, the content of the hard particles is not him enough and the wear Stance of the Sabered alloy material deteriorates. Acoordindy, the content of Cr is preferably in a range of 1.0 to 9.0 wt %.

Mo: 1.0 to 9.0 IS So iB contained in the base mata'C phase and the hard particles and contributes to enh g hardness and the wear resistance of the altered alloy material. However, when the content of Mo exceeds 9.0 wt %, the content of the hard parses becomes too high or the hardness of the base matrix phase increases too him whereby the ag essiene" to meted materials increased On the other hand, when the content of Mo is 1eBS than 1.0 wt %, the content of the hard parses is not high enough and the hardness of the base portion is lowered' whereby the wear re e of the metered alloy material iB liltely to be deteriorate. Accordingly, the content of Mo is preferably in a range of 1.0 to 9.0 wt %.

Si: 0.1 to 1.0 wt % Si iB an element which contauted mainly in the hard parties and contributes to enhancing the wear resistance of the arntered alloy material.

When the content of Si is led than 0.1 wt %, the content of the hard particles is not high enough and the edict of improving the wear re e is not clearb observed. On the other hand, when the content of Si exceeds 1. 0 %, the mutent of the hard particles becomes too high or the hardness of the base matrix phase increases too high, whereby the aggressieness to mated materials increases. Accordingly, the content of Si is preferably restricted to

a range of O.l to l.0 wt % W: 1.0 to 3.0 wt % W is an element which contained the base matrix phase and/or the hard particles and Contributes to strengthening the base matrix phase and enhancing hardness and the wear remstanoe of the Entered alloy material When the content of W is less than 1.0 wt %, the content of the hard parables is not high enough and the effect of improving the wear resistance not clearly observed. On the other hand, when the content of W exceeds 3.0 6, the content of the hard pales becomes too high or the hardness of the base matte phase increases too high, whereby the ag essieness to mated materials increases. Ac rdin y, the content of W is preibrably restricted to a range al 1.0 to 3.0 wt %.

V: O.l to 1.0 wt % V is an element which is contained in the base metro phase and/or the hard parses and contributes to strengthen the base mat phase and enhancing hardness and the wear resistance of the Entered alloy material When the content of V is less than Q2 wt %, the effect of unproving the wear reactance is not clearly observed On the other hand, when the content of V exceeds 1.0 96, the content of the hard parses becomes too high or the hardness of the base matrix phase mereases too high, whereby the aggresmeneas to mated materials increases. Aooordingly, the content of V preferably restricted to a range of 0.1 to l.O wt %.

At least one type of elements selected loom the group orating of Cu.

Co and Ni: the total content 1hereofbeing 3.0 to 16.0 wt % Cu. Co and Ni are all contained in the base matrix phase and the hard parses and contributes to strengthening the base mates phase and enhRnring hardness and the wear resistance of the sintered alloy material However, when the total content of Cu. Co and Ni is less than 3.0 wt %, the enact thereof is not clearly observed. On the other hand, when the total content of added Cu' Co and At is too large, the hardness of the base mAtnx

phase increases too high and the aggresmeness to mated materials Creases.

Acoordin y, the total content of Cu. Co and M is preferably in a range of 3 0 to 15.0 wt %.

In the base matrix portion which includes the base matrix phase ma the hard parses, the remainder other than the aforementioned components is subatan y Fe.

the iron-base sintered alloy material of the present invention, the solidlubricant particles may optionally be dispersed in the base matrix phase.

The solid lubricant particles are preferably at least one type of compo Ed selected Mom 1 he group consisting of sulfide, fluoride and graphite.

R.snmples of Me sulfide include MhS, MoS2 and WAS. Examples of the fluoride include CaFz and liF. By dispel the solid lubzi t parables in the base matrix phase, the machinability of the Intend alloy material facilitated, I he wear resistance of the sauntered alloy material is enhanced and the aggre ene" to mated materials decreases It is preferable that the solid lust particles is dispersed in the base matrix phase, by the total amount thereof of 0.1 to 10.0 wt %, with respect to the total amount of the base matrix phase, the hard parddlea and the solid lubricant parables. When the content of the solid lubricant particles is IRSS than 0.1 wt %, the content of the solid lubricant particles is not} sigh enough, whereby the sliding lubricity of the sintered alloy material deteriorates and the machinability of the sintered alloy material may be decreased Further, when the content of the solid lubricant particles less than 0.1 wt 56, occurrence of adhesion is accelerated and the wear regimen- of the Catered alloy material deteriorates. On the other hand, when the content of the solid lubn t particles exceeds 10.0 wt %, the powder compression property(compactibility), the Lion property dunug stinted and the strength of the sintered alloy material deteriorate.

The particle diameter of the solid lubn ntpsrtibles is preferably is in a range of 2 to So m. a case in which the particle diameter of the solid

lubricant particles smaller than 2 m, the aibrementioned effect at the solid lambent parses cannot be Red. On the other hand, in a case in which the particle diameter of the solid lubricant particles exceeds 50 run, the aintering and powder-compreasion properties(compactibility) will be adversely affected The iron-based Entered allay material of the present invention may contain pores by the proportion by volume of no higher than 10.0 %. When the content of pores exceeds 10.0 vat. %, the strength at a high temperature sold the heat conductivity are lowered and dropout resistance of the sintered alloy material deteriorates.

In order to obtain the iron based sistered alloy material of the present invention, first, at least one 1 ype of powder selected Mom the Coup consisting of pure iron powder, alloy iron powder and alloy elements powder iB blended with powder of the hard particles (and optionally with powder of the solid lubricant powder) such that the aforementioned composition of the base matrix Ron iB satisfied, to prepare raw material powder as the mixture of the components powders.

Preferable examples of combmabon of at least one type of powder selected Mom the group conR'sl;ing of pure iron powder, alloy iron powder and alloy elements powder include the follow 1) to 5). In each of 1) to 5),. %" represents At %" with respect to the total amount of pure iron powder, alloy An powder, alley elements powder, powder of the hard particles and powder of the solid lubricant.

1) 40.0 to 85.0 % of pure iron powder and 8.0 to 35.0 % of alloy elements powder which continua at least one type of element selected from the group conBi3hng of C, Cr. Mo, SO W. V, Cu. Co and Ni (i.e., the total content of C, Cr.

Mo, Si, W. Cu. Co and Nils in a range of 8.0 to 3fi.0 %) 2) At least one type of alloy iron powder, each type of alloy iron powder containing at least one type of elements selected hom C, Cr. Mo, SO W. V, Cu.

Co and Ni by the amount of 20 % or led each, as well as Fe and inevitable

impurities as the remainder, the content of each type of alloy iron powder being adjusted such that the total content thereof is within a range of 70.0 to 95.0 %

3) 20.0 to 70.0 % of pure iron powder and at least one type of alloy iron powder, each type of alloy iron powder contR=mg at least one type of elements selected from C, Cr. Mo, Si, W. V, Cu. Co and N1 by the amount of 20 % or less each, as well as Fe and inevitable impurities as the reminder, the content of each type of alloy iron powder being adjusted such that the total content thereofis within a range of 5.0 to 70.0 % 4) At least one type of alloy iron powder, each lype of allay iron powder containing at least one type of elements selected from C, Cr. Mo, Si W. Cu.

Co and Ni by the amount of 20 % or less each, as well as Fe and inevitable imp eB as the reminder, and allay elements powder which contains at least one t ype of element selected Mom the group oonR'Rting of Cr. Mo, Si W. V, Cu. Co and Ni the total content of the alloy iron powder(s) teeing m a range of 45.0 to 90.0 % and the content of the alloy elements powder, Be., Me total content of the alloy elements being in a range of 5.0 to 30.0 6 5) 15.0 to 65.0 % of pure iron powder, at least one lope of alloy iron powder, each type of alloy iron powder containing at least one 1 ype of element seed from C, Cr. Mo, SO W. V, Cu. Co and Ni by the amount of 20 % or less each, as well as Fe and inevitable impurities as the remainder, alloy elements powder which contains at least one type of element selected hom the group coneis g of Cr. Mo, Si W. V, Cu. Co and Ni the total content of the alloy iron powder(s) being in a range of 5.0 to 65.0 6 and the content of the alloy elements powder, be., the total content of Me alloy elements being in a range of 5.0 to 25. 0 % The Id powder as the raw material powder is preferably prepared by blending and at lesat one 1 ype of powder selected Mom the group con isting of the pure iron powder, the alloy In powder and the alloy.

elements powder, with the hard parses ( d optionally with the solid lubricant powder), sum that the content of the added hard panicles is in a

range of 3 to 20 wt % and the content of the added Mid lubricant powder a range of 0.1 to 10 wt % evil h respect to the total mount of 1 he pure iron powder, the alloy iron powder, the alloy elements powder, the hard esand the solid lubricant powder. AS the lubricant, Ann stearate and the like -may further be added.

The hard parses powder is preferably at least one 1 ype of powder selected from the group oonsisdug of intenne ic compound parses of MA Nit Si- Co; intermetallic compound p articles of Cram Co; Fe-Mo alps parses; and carbide-pre pitated partidea. The solid lubricant powder preferably at least ne type of powder Selected fmm the group conniving of a sulfide, a fluoride and graphite.

Me mired powder as the raw material powder prepared as deacril ed above is filled in a mold and subjected to compreaston and molding by a molding press, whereby a compr ed powder body is obtained (the molding process), aIld the compressed powder body is healed to a temperature in a range of 1,000 to 1,200 C in a protective atmosphere and aintered, whereby a metered body obtained (the amtering process). The Rintered body may be farther aubj to infiltration or impregnation (the infiltrationimpregnalion.

process). AB a result, an iron-based Catered alloy material far a valve seat is produced When the temperature at the aintenug process is below 1, 000 C, the Don during ainter g does not occur in a sufficient manner and the formation of the base is mRuflicient. On the other had, when tlte temperature at the Entering process exceeds 1.Z00. C, Eve Dickson Occurs at the hard particles and the base matrix, whereby the wear resistance of the Ed alloy material d4tez ora s. It is preferable that the nter g at nosphere is protective atmosphere and specificity NH; gea, a mixture of In;, and gases or the like.

The infiltradon-impregnation process optionalb tamed out in order to seal 1 he Mitered pores (air pores). The pore sealing process may be cameo

out by setting a low melting priest metal such as Cu. Cu a -, Pb or Pb alloy on the sighted body, heating the metal and allow the metal to infiltrate the sintered body. Alternatively, the pore sealing promos may be camed out by allowing a phenol-based resin to imprecate the Inn body.

The produced Rmtered body is then subjected deco cutting and grinding, 80 that a valve seat having a desired dimenawn and shape obtained Examples

At least one type of powder selected Tom the group consiating of the iron powder, the alloy iron powder and t}te allay elements powder was blended and kneaded with powder of t he hard particles (and optionalb with Me solid }ubucant powder) as Mown in Bible 1, whereby the nutted powder was obtained. The blended amount of each component powder was mdi ted as At 6 with respect to the total amount aft he mixed powder.

T.ne Apes of the alloy iron powder whim was used are: ail" stem powder oDnt 'ning 1.0 % of Cr. 0.5 % of Mn, 0.3 % of Mo and Fe as the "mainder; (B) alloy steel powder containing 3.0 % of Cr. 0.2 % of Mo and Fe as the redder; (C;) allay steel powder containing4.0 % of NO 1.5 % of Cu. 0.5 % of Mo and Fe as the re nder. Here, 6" represents It % T'ne types of the hard parried which were used are: (a) powder of carbide-precipitated particles (the average parve diameter being 80 m, the average particle Riveter of carbide bed 3 m) of SKD 11 (1.5 % of C, 12 % of Cr. 0.8 % of V, 1 % of Mo and Fe as the reminder); (b) powder of carbide-

preapitabed parses (the average particle diameter being 80 m, the average pate dinmeter of carbide being 3 m) of SKH 51 (0.8 % of C, 4 56 of Cr. 5 % of Mo, 2 % of U 6 % of W and Fe as the reminder); (c) powder of carbide preapita1 d particles (the average particle diameter being 80 m, the average particle diameter of carbide being 4 m) of SKH 57 (1.2 % of C, 4 % of Cr. 3 56 of Mo, 10 % of W. 3 96 old, 10 % of Co and lie as the reminder); (d) powder of inbermetallic compound particles oontaining 9 % of Cr. 30 % of Mo and Co as

the reminder (the average particle diameter being 100 fun); (e) powder of intennetallic compound particles confining 24 % of Mo, 10 % of Ni, 24 % of Cr.

2 % of Si and Co as the reminder (the average particle diameter being 100 m); (f' powder of alloy particles containing 60 % of Mo and Fe as the remainder (the average particle diameter being 100,um). "%" represents nwt %".

The types of the solid lubricant powder which was used are MbS CaF2 (Y) and Graphite(Z).

The mined powder as described above was filled in a mold and subjected to compression and molding by a molding press, whereby a compressed powder body was obtained. Each compressed powder body was subjected to ainter g in a reducing atmosphere (NH3 gas) at a temperature of 1,000 to 1,200 C for 15 to 45 minutes, whereby a sintered body was obtained.

Some of the sintered body samples were subjected to the infiltration process in which each sample was heated with an infiltration agent Dead) at 500 C.

The compoa t on of the base matrix portion, as well as the structural proportions, of each of the obtained R,ntered body Rumples are shown in Table 2. Fig. l(a), Fig. 2(a), Fig. 3(a) and Pig. 4(a) show the optical micrograplls of the metered body No. 3, the wintered body No. 6, the sintered body No. 10 and the aintered body No. 12, respectively. Figs. 1GD) to 4(b) are sketches of Figs. l(a) to 4(a), respectively. "P" represents the pearlite phase, "R" represents the high-alloy diffused phase, "H" represents the hard parses (other than the carbide-prempitated parties), "HC" represents the carbide-

premp tated particles (the hard particles), "ST' represents the solid lubricant panacea. Next, each smtered body was processed to form a valve seat (having a dimension of 41.4 x 3B.8 x 7.0 mm), whereby a He piece wear test on Dig was carried out as described below.

V A singe piece wear test on rig wear test (an wear resistance test)

Lane wear resistance was inve bed by wing a Angle piece wear test on rig shown Fig. 6. The single piece wear test on rig was carried out by: pressingly inserting 1 he valve seat 1 into a fig 2 which simulated a cylinder head; moving upldown the valve 4 in the vertical direction with heating the valve 4 and the valve seat 1 by mug a heat source BERG Ar) 3 provided in the testing device; and measuring the amount of wear as the amount of sinking of the valve. The conditions at the test were as follows.

Temperature: 400 C (at the seat surface) log time: 9.0 hr Number of cam rotation: 3000 Pm Number of valve mtation 20 tom Load of spring 35 kgf (at the time of setting) Valve material: SUH3 The result of the single piece wear test on rig are shown in Moles 2 and ESg. 5.

liable 1 ladle 2 The amount of wear ofthe valve seat in each ofthe Watered bodies No. 1 to No. 9, No.14 to No.17 of the present examples was in a range of 11 to 19 m. In these examples, the amount of wear of the mated material was in a range of 4 to 11 m. The amount of wear of the valve seat in each of the smtered bows No. 10 to No. 13 of the comparative examples, which were beyond the scope of the present invention, was in a range of 29 to 48 these comparative examples, the amount of wear of the mated material was a range of IS to 47 m. Accordingly, it is understood that the amount of wear is deceased, the wear resistance Is improved and the aggressieness to meted materials lowered the present examples, as compared with the comparative examples.

As deacclbed above, according to the present invention, a sintered alloy material which is inexpensive and excellent in toughness and wear

resistance can be obtained This metered alloy material exhibits excellent durability a harsh operation when used as a valve seat fur an automobile and achieves a significantly excellent effect the industrial terms.

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Claims

What is Claimed is:

1. An unabused sintered alloy material for a valve seat, which hard particles are dispersed in a base matrix phase, characterized that the base matrix phase is compound of 5 to 40 wl. % of a penalize phase and 10 to 40 vol. % of a high-alloy do phase and particles having hardness of Hv 600 to 1300 and parve diameter of 10 to 150,um are dispersed as the hard particles, by the amount of 10 to 30 vol. %, in the base matrix phase.

2. An iron-based sintered alloy material for a valve seat, in which hard particles are dispersed in a base math phase, c cterized in that a base portion which includes the hard particles has a composition composed of 0. 2 to 2.0 wt 6 of C; 1.0 to 9.0 wt % of Cr; 1.0 to 9.0 wt % of Mo; O.l to l.O wt % of Si; 1.0 to 3.0 wt % of W; 0.1 to 1.0 wt % of V; 3.0 to 16. 0 art %, as the total, of at least one type of element selected fiom the group consisting of Cu. Co and A;; and the rem mder which substantially Fe, the base matrix phase is comprised of 5 to 40 voL % of a pearlite phase and 10 to 40 vol. % of a high-

alloy diffused phase and particles haven Fess of Hv 600 to 1300 and particle diameter of 10 to 150 Am are diapered as the hard particles, by the amount of 10 to 30 voL %, in the base matrix phase.

3. An iron-ba ed Rintered alloy material for a valve seat according to claim 1 or 2, wherein the hard particles are at least one type of parties selected fiom the group consisting of intermetallic compound particles of Mo-Ni-Cr-Si-Co; mtermetallic compound particles of Cr-M Co; Fe-Mo alloy particles; and carbide-prempitated particles.

4. An iron-based aintered alloy material for a valve seat according to Him 3, wherein the carbide-p itated particles have a composition which is composed of 0.2 to 2.0 At % of C; 2.0 to 10.0 wt % of Cr.; 2.0 to 10.0 At % of 2 2

Mo; 2.0 to 10.0 wt % of W; 0.2 to 5.0 wt % of V; and Fe and inevitable impunity as the remainder.

5 An iron-based sintered alloy material for a valve seat awarding to Aim ú wherein the content of the carbide-prempitated parks, as is expressed as the proportion by volume thereof present in the base matrix phase, lem than 20 vo1. %.

6. An iron based Catered alloy material for a valve seat according to Aim 4 or 5, wherein fine carbides having particle diameter of 1 to 10 Em have been precipitated on said carbide-prec pitated particles.

7. An iron-based sdntered alloy material fir a valve seat according to any one of maims 1 to 6, wherein the base matrix phase fronts solid lubricant parses by the amount of Q1 to 1().0 voL 56.

8. An iron-based sintered alloy material for a valve seat according to 1Alm 7, wherem the solid luhucant particles made of are at least one type of compound selected Tom the group consisting of a sulfide, a iluonde and graphite.

9. An iron-based metered alloy materis1 for a valve seat ac rd g to any one of claims 1 to 8, wherein sintered pores are infiltrated with one of the material selected from the group consisting of Cu. Cu alloy, Pb and Pb alloy or vnth a phenol-based rem.

10. A valve seat made of an iron-based entered alloy, characterized in that the valve seat is He of the iron-based sdntered ally material for a valve seat of any one of rdnims 1 to 9.

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