Note: Descriptions are shown in the official language in which they were submitted.
BACKGROU~ OF T~E INVEN~ION
;~ ~his invention relates to a valve seat material for
an internal combustion engine. Of late, the characteristics
required ~or valve seat materials tend to become increasingly
severe with the size reduction o~ an internal combustion en-
gine, with the rising of the output thereof and wi~h the in-
crease o~ kinds of fuels used~ Generally a valve seat materi-
al ~or an internal combustion engine should have the followins
characteristics: -
1) Sufficient strength for an impact load at a hightemperature such as b~ beating o~ a valve 7
2) ~xcellent wear resistance at a high temperature,
in particular, in the case of the exhaust side exposed to an
exhaust g?S at a high temperature,
3) Excellent heat resistln~ strength and
4) Cheapness.
Up to the present time, ordinary c,ast irons, low alloy cast
. irons 3 ch~omium alloys and stainless cast steels have been
~ 9
1 used as a valve seat material for an internal combustion en-
gine, but these materials have problems on the ability in an
internal oombustion engine using a lead-free gasoline or liquid
propane gas~ ~he valve seat on the exhaust side is always ex-
posed ~o a combustion gas at a high temperature during the ope-
ration of an internal combustion engine and subjected to an
impact load by the beating of a valve and to a sliding action
due to an irregular rotation of valve~ In an internal combus-
tion engine using the ordinary lead-containing gasoline~ the
.
lead contained in gasoline is converted into lead oxide and
lead sulfate and sulfur~ phosphorus, calcium and sodium con-
tained in lubricating oil or gasoline are converted into
other combustion products such as calcium oxide, sodium oxide,
phosphorus oxide and calcium sulfate, which may possibly form
a lubricating film pla~ing a role as an antioxidant or anti-
friction material between the contact surfaces of the valve
and valve seat. In another internal combustion engine using
a lead-~ree gasoline~ on the contra:r~, such lubricating pro-
; ducts are not sufficientl~ formed and the valve and valve
seat are brought into direct contact at a high temperature,
resulting in rapid wearing of the valve seat and, sometimes,
the valve itself due to adhesive wearing. Consequentl~, the
englne cannot be opera~ed normally, since there is no tappet
; clearance due to such abnormal wearing~
.
SUMM~RY OF ~HE IN~ENTIOM
It is an object of the invention to provide an improv-
ed valve seat material for an internal combustion engine, which
overcomes the above described difficulties and which is resist-
ant -to oxidation and wearing at high temperatures.
It is another object of the invention to provide a
valve seat material for an internal combustion engine~ which
is suitable for u.se of lead-free gasolines.
~ 73~
1 I-t is a further object of the invention to pro~ide
a valve seat material for an internal combustion engine, which
is capable of satisfying the severe requirements for internal
combustion engines and which can be produced by the mass pro-
duction system.
~hese objects can be accomplished by a valve seat
for an internal combustion engine, which comprises a sintered
ferrous alloy having the composition: 3-15 ~ by weight moly-
bdenum, ~-12 % cobalt, 0~1-2.0 % carbon, 0-15 % lead, prefer-
ably 2-15 ~ lead, and 0-8 ~ glass, preferably 0.5-8 ~ glass
and the remainder being iron ex¢ept for usual impurities and
trace elements.
DE~AI~ED DESCRIP~IO~ OF ~HE INVEN~ION
he above mentioned alloy has particular application
to a valve seat insert for a reciprocating internal combustïon
l~ ~ engine and can be produced preferably by mixing the correspond-
I ing powders in the required proporl;ions, pressing the mixture
to form a compact and sintering the compact.
~he features of the alloy according to the invention
are as follows:
1 1) ~he base matrix is a sintered ferrous alloy con-
taining Co 9 Mo and C as alloy elements.
` ~ 2) A phase of Mo-containing hard compounds such as
FeMo, ~e3Mo2, FeMo3 and (FeMo)6C is dispersed in the base matri~.
3) At least one of lead and a low melting glass are
optionally incorporated in this alloy, which are capable of
meltin~ and forming a lubricating film on the surface of a
; valve seat during the operation o~ an internal combustion en-
gine.
3o ~he alloy of the invention has generally the composi-
tion by weight: 3-15 % molybdenum~ 2-12 % cobalt, 0.1-2 ~ carbon
and the remainder being ixon except ~or usual impurities and
~a~3s~
1 trace elementsO In a case where it is desirable to raise the
self-lubrica-ting propert~ further, in particular7 at least one
of 2-15 % lead and 0.5-8 % glass can, in addition, be inco~po-
rated therein.
In the above mentioned composition of the valve seat
material according to the invention~ molybdenum dissolves in
iron with other alloy elements to form solid solutions which
strengthen the matrix and raise the heat resistance, and to
..
form a phase of hard compounds containing iron and carbon
and having a hardness mHv (Micro Vickers Hardness) of 800 to
1500~ which assures of the wear resistance. ~he range of
quantity of the molybdenum to be added is limited to 3 to 15
~7 since if less than ~ %, the quantity of the foxmed hard
phase is too little to raise the wear resistance and if more
than 15 %, the machinability is lowered and the ~uality become~
; brittle~
Cobalt enters partly the molybdenum hard phase also,
but the most part of cobalt dissolves in tke iron matrix to
~orm solid solutions, thus contributing to the improvement of
the heat resistance of the matrix. ~he range of quantity of
the cobalt to be added is limited to 2 to 12 ~ since if less
than 2 %, the effect of increasing the heat resistance of the
matrix i~ little and even if more than 12 %, this effect is
~ot so increased~
Carbon combines with molybdenum and iro~ to form
their carbide~, thus improving the strength of the matri~
~he carbon is added in a ~uantity range of 0~1 to 2 ~, since
if less than 0.1 %, this effect is little and if more than 2
%, the quality becomes brittle.
~ead plays a role of forming a lubricating film on
the ~urface of a valve seat and preventing the valve and valve
~eat from the adhesion of metal during the running of the en-
gine~ A preferred range of quantity of the lead to be added
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~ 73~
1 is from 2 to 15 ~, since if less than 2 ~, this effect is lit-
tle and if moxe than 15 ~, the strength of the alloy is lowered~
~ ow melting point glass plays also a xole of forming
a lubricating film on the surface o~ a valve seat and prevent-
ing the valve and valve seat from the adhesion of metal, and,
in paxticular, forms a strong film at a high temperature of at
¦ least 400 C to thus raise -the wear resistance. As such a low
melting point glass there can be used those containing B203,
~ P205, ZnO and PbO as main components and melting at a temper-
ature of lower than 500 a, for example, 30 % B203 - 30 % P205
- 30 % PbO and 50 ~ PbO - 30 % ZnO - 20 ~ B203. A preferred
- range of quantity of the low melting glass is 0.5 to 8 %,
since if less than 0.5 %, the lubricating effect is little
and if more than 8 ~, the strength of the alloy is lowered.
In one preferred embodiment of the valve seat mate-
rial according to the present invention~ tungqten is further
incorporated in the above described alloy composition in a
j
proportion of 0.5 to 10 %. In this case, the sintered ferrous
allo~ has generally the composition by weight: 3-15 % molybde-
num, 2--12 % cobalt, 0.5-10 % W, 0.1-2 ~ carbon and the remain-
der ~eing iron except ~or usual impurities and trace elements.
In cases where it is desirable to raise the self-lubricating
,
property, in particular, at least one of 2-15 % lead and 0.5-8
% glass can, in addition, be incorporated in the matrix.
~ungsten having the similar effect to molybdenum dissolves in
iron to form solid solutions, thus stren~thening the matrix
and raising the heat resistance. ~he range of quantity of the
tungsten to be added is limited to 0.5 to 10 %, since if less
than 0~5 ~, this effect is little and if more than 10 ~ the
machinability is markedly deterioxated~
In another preferred embodiment of the valve seat
material according to the inventio~, tungsten in a proportion
of 0.5 to 10 ~ and nickel in a proportion of 0~5 to 8 % are
6~73~
1 further incorporated in the above described allo~ composition.
~hat is to sa~, the sintered ~errous alloy has generall~ the
composition b~ weight: 3~15 ~ mol~bdenum, 2-12 % cobalt, 0.5-
10 ~ tungsten, 0.5-8 % nickel~ 0.1 2 % carbon and the remain-
der being iron except for usual impurities and trace elements.
In cases where it is desirable to raise further the self-lubri-
cating property~ in particular9 at least one oP 2-15 % lead and
0.5-8 ~o glass ~-an, in addition, be incorporated in the matrix.
. . .
Nickel serves to stxengthen the ferrite and to raise the tough-
ness of the matrix~ ~he range of quantity of the nickel to be
added is limited to 0~5 to 8 ~, since if less than 0.5 %, this
e~ect is little, while if more than 8 ~, precipitation of cax-
bides is suppressed too much.
~ he present invention will be further illustrated in
greater detail in the following examples and comparative exam-
ples. It will be self-evident to those skilled in the art that
the ratios? ingredients in the following formulations and the
order of operations can be modified within the scope o~ the
present invention. ~herefoxe~ the prese~t invention is not
~20 to be interp~eted as being limited to the following examples.
All percents are by weight unless otherwise indicated.
EXAMPLE 1
.
A reduced iron powder of -100 mesh (~yler standard
sieve), ~erromolybde~um (50 % Mo, 0.06 % C, 1.26 % Si) powder
o~ -200 me~h, cobalt powder of -325 mesh, lead powder of -?50
me~h and low melting point glass powder o~ 30~oB203-30~P2S~ bO
were mixed so as to give each o~ the following compositions,
formea in a densit~ of 90 % and sintered at 1130 C for 30 min- -
utes ln a reducing atmosphere:
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473~
1 Sample ~ Chemical Composition Density ~ardness
No. (by wei~ht- ~e remainder) (y) fHRB*~
. _ ,
1 Fe-3%Mo-0.1%C (for comparison) 90 60
2 ~e-5,~Mo-1%C (for comparison) 90 61
~e-1o%Mo-1%a (for comparison) 90 . 65
4 Fe-15~Mo-1%C (for comparison) 90 68
Fe-15~Mo-2ya (for comparison 90 73
6 ~e-10%Mo-1%C-4%Pb-2%G**
(for comparison) 90 64
7 Fe-3%Mo-2%Co-0.1~C 90 G2
~e-5%Mo-8~Co-1%C 90 73
; 9 . ~e-10YMo-8%Co-1yC 90 74
~e-15%Mo-8%Co-1%C 90 78
e-10yMo-4~Co-1%C 90 74
12 ~e-105~Mo~11%Co-1%C 90 79
Fe-15%Mo-12%Co-2~oC 9 78
14 Fe-10~Mo-8YCo-1%C-4YPb 90 72
Fe-10~Mo-8%Co-1%C-2%G 9 72
16 Fe-10%Mo-8~Co-1YC-4~Pb-2%G 90 73
Note: * Rockwell Hardnes~ B Scale
** Glass
: EXAMPIE 2 :
A reduced iron powder of -100 mesh, ferromolybdenum
(50 % Mo, 0.06 ~o C, 1~26 % Si~ powder o~ -200 mesh, tungsten
,
powder sf 325 mesh~ cobalt powder of -325 mesh, lead powder
of -250 mesh and low melting point glass powder of 30YOB2O~-
30%P205-30~oPbO were mixed so as to gi~e each of the following
compositions, formed in a density of 90 % and sintered at 1130
: a for 30 minutes in-a reducing atmosphere:
73~ ~
Sample Chemical Composition DensityHardness
No~ ~ (%) ~HRB)
A 17 Fe-3%Mo-2~-2%W-0~190C 90 71
. 18 Fe-5%Mo-8%Co-8,6W-1%C 9 76
19 Fe-'10%Mo-5%Co 0.5%W-1.5;qÇa 9 85
Fe-1 0~6Mo-8,6Co~3%W-1~C 90 77
21 Fe-15%Mo-8%Co-3%W~ 1%C 90 81
22 Fe-10~Mo-4%Co-5yW-1,6C 90 77
23 Fe-10~Mo-11%Go-550~W-1%C 90 82
24 Fe-15,~Mo-12%Co-1090W-2%C 90 83
~t 25 Fe-10%Mo-8%Co-5%W-1%C-4,6Pb 90 75
26 Fe-10,bMo-8%Co 5%W-1%C-2%G 90 75
27 Fe-10%Mo~8~6Co-5%W~1~6C-4%Pb-2%G 9 76
:EXAMPIE 3
A reduced iron powder of -100 mesh, ~erromolybdenum
(50 % Mo, 0 06 % C, 1.26 % Si) powder of -200 rnesh, tungsterl
powder of -325 mesh? cobalt powder of -325 mesh, nickel car-
~; ~ bonyl powder of -325 mesh, lead powder of -250 mesh and low
melting point glass powder of 30%B203-30~oP205-3090PbO were
20 mixed so as to give each o~ the ~ollowing compositions, îormed
in a density of 90 % and then sintered at 1130 C for 30 min-
ute~3 in a reducing atmosphere:
: Sample Chemical Composition Densi-ty3~ardne.ss
: No. (by weight. :Ee remainder) _ _ (%)_(BRB~
28 Fe-3,6Mo-2~Co--2%W-296Ni-0.l%a 90 73
- ~ ~ 29 Fe-5%Mo-89o'Co-8%W-3%Ni-1%C 90 79
Fe~ 6Mo-5%ao-3,~W-0.5/Ni-1%C 90 . 86
31 Fe~ oMo-8%ao~3%W-3%Ni-1%a 90 80
32 Fe-10%Mo-4%Co-5%W-6~6Ni~ a 90 78
33 Fe-15%Mo-12%Co-10%W-8/6Ni-2%a 90 84
34 Fe-10~oMo-8%Co-5%W-3%Ni-1%a-4%Pb 9 78
Fe~ Mo-8%Co-5%W-3~oNi- 1%C-2%G 90 79
36 Fe-10%Mo-8%Co-5%W-3%Ni-1~C-4%Pb-2%G 90 79
.
4~73se
1 ~he so obtained Samples 1 to 36 (~xampies 1-3) were worked or
fini~hed in a predetermined size and then subjected to the
~ollowing durability test:
Test of Durabilit~
Using a 360 cc~ water-cooling, two c~linder- a~d two
caburetterengine at 7500 rpm with ~ull throttle and full load~
the tappet gap was first adjusted to 0.1 m/m and a period of
time was measured irre~pective of the right and left c~linders
when the gap became zero. ~he life of a ring for the valve
seat was de~ined by the measured period of time. A gasoline
was used having an octane number of 87 and containing lead in
a quar.tit~ of 0.002 g/gallon.
~he measured results are tabulated below:
~able 1 Durability_(hrs)
Sample No~irst ~estSecond ~est
1 23 20
2 24 28
` 3 51 60
4 71 68
~ 5 65 64
6 122 134
7 56 61
:
8 76 69
9 86 92
105 101
; - 11 89 82
12 101 109
13 96 104
14 130 118
3 15 113 119
16 186 , 178
17 84 78
_ 9 _
-
~ii9L73~
1 18 85 - 92
19 92 87
91 95
21 109 125
22 113 101
23 120 129
24 122 131
. 148 151
26 1~7 131
.
27 192 205
28 82 88
29 96 g5
'. ~ . 30 96 . g8
31 ~5 101
32 120 115
:: . 33 126 132
.34 156 162
148 153
I~ ~ 36 206 211
:~; 2~ As is evident from these results, the sintered ferrous alloys
~ having bhe composition according to the present i~vention can
: : :: ~
fa~ouxabl~ be compared i~ darability with the ~imilar Fe Mo
alloys we had~proposed. I
.
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