Note: Descriptions are shown in the official language in which they were submitted.
~3~7~
REF~RENCE TO PATENTS, APPLICATIONS AND PUBI,ICATIONS
PERTINENT TO THE INVENTION
. . _ . .
As far as we know, there are available the
following prior art documents pertinent to the present
invention:
(1) Japanese Patent Provisional Publication No. 62-142,726
dated June 26, 1937;
(2) Japanese Patent Provisional Publication No. 63-169,359
dated July 13, 1988; and
10(3) Japanese Patent Provisional Publication No. 1-142,023
dated June 2, 1989.
The contents of the p.r1or art disclosed in the
above-mentioned prior art documents wi.ll be discussed
hereafter under the heading of the "BACKGROUND OF THE
INVENTION."
:
FIELD OF_THE INVENTION ;~
The present inventLon relates to a wear-resistant : : :
steel having a high hardness in an intermediate tempera-
ture region ancl a room-temperature region.
BACKGROUND OF THE INVENTION
,
,
,.
:: : :
:
` : - 2 - ~ :
::
:
,
. . - : : ,
2~3~
A wear-resistant steel is used as a material ~or
portions exposed to serious wea~ in an indu.strial machine
and a transportation machine such as a power shovel, a
bulldozer, a hopper or a bucket and parts thereof. Wear
resistance of steel can be improved by increasing
hardness of the steel. A steel having a high hardness
which contains carbon, silicon and manganese in prescribed
amounts and is additionally added with elements to
increase hardness, is therefore used as the wear-resistant
steel mentioned above.
.
The following wear-resistant steels have so far
been proposed as steels excellen~ in wear resistance and
satlsfactory in weldabllity, toughness and workabillty~
(1) A wear-resistant steel sheet having an~excellent
weldability, disclosed in Japanese Patent Provisional ` ;
Publicatlon No. 62-142,726 dated June~26j 1987, whlch
consists essentially o~
carbon : from 0.10 to O.l9 wt.%,
silicon : : from O . 05 to O. 55 wt.
manganese : from 0.90 to 1.60 wt.%,
and
the balance being iron an~ incidental impuri~.ies;
where, a carbon;eguivalent (C + 1/24 Si~ T
- 1/6 Mn +~l/40 Ni + :1/5 Cr ~ 1/4~ Mo * 1/14 V)~
~ - 3
:. : - . ,, , . : . :. , ,
- :: :: :
being within a range of from 0.35 to 0.44
wt.%
(hereinafter eierred to as ~he "prior art 1").
The above-mentioned wear-resistant steel sheet
of the prior art 1 may additionally contain at least one
of vanadium and niobium in an amount of up to 0.10 wt.%.
(2) A wear-resistant steel sheet having a high
toughness, disclosed in Japanese Patent Provisional
Publication No. 63-169,359 dated July 13, 1988, which
consists essentially of: ~
carbon ~ : from 0.~10 to 0.20 wt.%,
sillcon ~ - from~0.03 to 0.75 wt.%,
manganese~ from C. 4 to 1.8~wt.~,
phosphorus ~ ~: up to 0.015 wt.%,
sulfur ~ : up to~0.002 wt.
nitrogen ~ ;up to 0~0025 wt.%~
sol. Al ~ ~: from~;0~.001 ~to 0.080 wt.%,
oxygen ~ up to 0~.0020 wt.
and
the balance belng~iron~and lnclden~tal l~purlties
(hereinafter referred to~as the "prior art"). ~
The above-mentioned we.r-resistant steel sheet
af the prior art Z may~additionally contain Rt least~one
elemen~ selected;~rom the~group~consisting o~
:
. ., . : : ~ . . :
7 ~
copper : from 0.05 to 0.75 wt.%,
nickel : from 0.05 to 1.50 wt.%,
c~romium : from 0.05 to 1.50 wt.%,
molybdenum : from 0.01 to 0.75 wt.%
and
boron : from 0.0001 to 0.0025 wt.%.
(3) A wear-resistant steel sheet having an excellent
bending workability, disclosed in Japa~ese Patent Provi-
sional Publication No. 1-142,023 dated June 2, 1989,
which consists essentially of:
carbon : from 0.07 to 0.17 wt.%,
~, . .
silicon from 0.05~ to 0.55 wt.%,
manganese : from 0.70 to 1.80 wt.%,
vanadium ~ : from 0.02 to 0.10 wt.~%,
boron ~ :~from 0 0003 to 0.0050;wt.%~
aluminum :~from 0.01~ ~to O.lO~wt.%, ~ i-
and
the balance being iron and~lncidental impurities
;hareinafter referred~to as the~"prlor~art 3")~
~: : , : ~
The above-mentioned wear-resistant ste~.l sheet ~
~ ; , : : :
of the prior art 3 may additionally contain at least one
element selected;from the~grou~ consi~stlng of:~
:
copper ~ from 0.05 to 0.30 wt.%,
nichel~ : from O.OS~to 0.45 wt.%,
`
- 5 ~ ~ ~
,
: ~ . : : . , : ~ .
~0~87~
chromium : from 0.05 to 0.20 wt.%,
and
molybdenum : fro~n 0.03 to 0.20 wt.~.
According to the above-ment.ioned prior arts 1
to 3, a wear-resistant steel having a high room-tempera-
ture hardness is available in all cases. However, the
prior arts 1 to 3 have the following problems: ~ wear-
resistant steel is used also as a material for a machine
and parts thereof for treatlng slag at a temperature
within an intermediate temperature region of from about
300 to about 400C in a slag yArd. A wear-resistant
steel used as such a material should preferably have a
Brinell hardness(HB) at a room-temperature~of at~least:
250, a Brinell hardness~at:a~temperature of~ about 300C~ -
of at least 90% of its room-tempèrature Brinel~l hardness,~
and a Brinell hardness at a temperature~ of about:400C ::
of at least 70% of its:room-:temperature Brinel~l;hardness.
However, according to the wear-reslstant~steels
of the prior arts l~to 3, whl1e it ls possible~to~lmprove
wear resista7lce at a temperature within a room~temperature
region, it: lS lmpossible to lmprove~ear~reslstance~at
a temperature with:;n an intermedLal'e:temperature:~region
of from about 300 to~ahout~400C.~ The wear-resis~tant~
ste~ls of the prior~arts l to ~a~re not satisfactory i~n
:: : : .
terms of wear~reslstance:when used~as~a:material~for a
- 6 -~
:
::
. -
;, - : , :
~3~7~
machine and parts thereof employel at a temperature within
an intermediate temperature region.
With a view to improving wear resistance at a
temperature within an intermediate temperature region,
a conceivable measure is to largely increase a room-
temperature hardness of steel, kaking account of the
decrease in hardness at a temperature within an interme-
diate temperature region. When a room-temperature hardness
of steel is increased excessively, however, ductility,
toughness, workability and weldability o~ the steel are
deteriorated. --
Under such circumstances, there is a strong demand
for the development of a wear-resistant steel for the
intermediate and room temperature service, which has a
Brinell hardness at a room-temperature of at least 250~ ~
and has a Brinell hardness at a temperature of about 300C
of at least 90% of its room temperature Brinell hardness,
and a Brinell hardness at a temperature of about 400C
of at least 70% of its room-temperature Brinell hardness,
the last two Brinell hardnesses being available without
largely lnCreaSing its room-temperature Brinell hardness, ~ ~ -
but SUC_l ~a wear-resistant ~:teel eor the intermediate and
room temperature~service has not as yet been proposed.
:: : : ::
SUM~RY OF~THE INVENTION ~ ~ ~
_ 7 _ ~ -
. : . : : : : , . ::~ : . :
,
~J3~ 7
An object of the present invention is therefore
to provide a wear-resistant steel for the intermediate
and room temperature service, which has a Brinell hardness
at a room-temperature of at least 250, and has a Brinell
hardness at a temperature of 300C of at least 90% of
its room-temperature Brinell hardness and a Brinell
hardness at a temperature of 400C of at least 70% of
its room-temperature Brinell hardness, the last two
Brinell hardnesses being available without largely
increasing its room-temperature Brinell hardness.
:
In accordance with one o~f the features of the
present invention, there is provided a wear-resistant
steel for the intermediate and room temperature service,
which has a Brinell hardness at a~room-temperature of ~
,
at least 250, a Brinell hardness at~a temperature~of;
300C of at least 90% of its room-temperature Brinell
hardness/and a Brinell hardness at a temperature of 430C
of at least 70~ of its room-temperature Brinell hardness,
characterized hy consisting essentially of:
carbon ~: from 0.08;~to~0.40~wt~%, ;
silicon : from;0.8 to~2.S ~wt.%,~
manganese : from~0.1 to ~.O wt.
and
- ~
the bal~ance being iron and inciden~al impu~ities.
The wear-reslstant~ste~l~for the intermedi~te
.
~.~3~7~
and room temperature service of the present invention may
additionally contain at least one element selected from
the group (A) consistinc of:
(A)
copper : from 0.1 to 2.0 wt.~,
nickel : from 0.1 to 10.0 wt.~, i
chromium : from 0~1 to 3.0 wt.~,
molybdenum : from 0.1 to 3.0 wt.~,
and
boron : from 0.0003 to 0.0100 wt.~.
The wear-resistant steel for the 1ntermediate and
: .
room temperature service of the~present invention`may
additionally contain at least one element selected from
the group (B) consisting of:
:
(B)
niobium : from O.OOS to O.lOO`wt.~,
vanadium : from 0.01 to 0.~10 wt.~,
and
titanium : from O~OO5 to 0~.100 wt.
Furthermore, the wear-resistant~stee1~for the~
intermediate and -room temperature service of the~present
invention may addLtion~lly~contain at least~one element~
selected from the above-mentioned group~ (A)~and~at~least
one~element selected from the above-mentioned group (B).
:
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~3~7~
BRIEF DESCRIPTION OF THE DRAWING
Fig. 1 is a graph illustrating the relationship
between a silicon content and a Brinell hardness (HB) in
a wear-resistant steel.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
From the above-mentioned point of view, extensive
studies were carried out to develop a wear-resistant
steel for the intermediate and room temperature service
having an excellent wear resistance in an intermediate
temperature region without largely incxeasing its room-
temperature hardness. As a result, findlngs were
obtained that silicon contained in steel had a function
of increasing, for a certain range of the content thereof,
hardness of steeI ln an intermedlate temperature region
without increasing a room-temperature hardness thereof.
The present invention was made on the basis of
the above-mentioned findings, and the wear-resistant
st~el for the intermediate and room temperature service
of tne present invention consists essentially of:
~0 carbon : from 0.08 to 0~40 wt.~,
silicon ~ : fxom 0. 8 to 2 . 5 wt. ~o;,
manganese ~ ~: from 0.1 to 2.0 wt.~,
and
the balance~ being iron and~incidental impurities.
-- 1 0 -- ~
3-~87~
The wear-resistant steel for the intermediate
and room temperature service of ~he presen~ invention may
additionally contain at least one e'ement selected from
the group (A) consisting of:
(A)
copper : from 0.1 to 2.0 wt.~,
nickel : from 0.1 to 10.0 wt.%,
chromium : from 0.1 to 3.0 wt.%,
molybdenum : from 0.1 to 3.0 wt.%,
and boron : from 0.000~3 to O~.OlOO wt.~.
The wear-resistant steel for the~intermediate~and
room temperature service of the present~invention may
additionally contain at least one element~selected from
the group (B) consisting of~
niobium : from 0.005 to~0.;100 wt.%,~
vanadium : from O.0~1 to~O.lO~ wt.%,;
and ;~
titanium : from O.OO5~to O~.~lOO~wt.
Purthermore, the wear-res1stant steel~ for the~
intermediate and room tem~erature~service~o~the~present
iDVentlon may additionally contain~at~least one~elemQnt
selected from the above-mentloned group~(Aj and at~least
onè element selected from the~above-men~tioned group tB).
.~ .. ,: ~ ,, , . . . : ,
~3~7~
The chemical composition of the wear-resistant
steel for ~he intermediate and room temperature service
of the p~esent invention is limited within a range as
described above for the following reasons.
(1) Carbon:
Carbon is an element which exerts an important
effect on hardness of steel. ~owever, with a carbon
content of under 0~08 wt.%, a Brinell hardness (HB) a~
a room-temperature of at least 250 is not availab1e.
With a carbon content of over 0.40 wt.%, on the other
~ ~
hand, a room-temperature Brinell hardness becomes
excessively high to result in deteriorati~on of ductility,
toughness, workability~and weldability of s~teel.~The
carbon content should therefore be limited wi~hin a~
range of from 0.08 to 0.40 wt.
~2) Silicon~
Silicon has a function of increasing`~hardness of
steel in an intermedlate~temperature re~lon without~
increaslng its room-temperature hardne3s.~ owever,~with~
a silicon content of under 0.8 wt.~,~a~desired~effect~as~
mentione~;abo-ve 13 ~not av~1lable.
The relationship between a silicon content and
a Brinall hardness (HB) in a Wear-reSlStant steel was
nvestigated. More particularly, for test pieces~o
~ - 12 -~
: ~
-, :-; , ~ ~ , : .
: ~ , . .. . .
2~87~
hardened wear-resistant steel haviny a thickness of 20 mm,
which containec 0.3 wt.~ carbon, 0.7 wt.% manganese, 0.9
wt.~ chromium and silicon in a certain amount, a Brinell
hardness (HB) was measured for each test piece at a
S room-temperature, 300C, 400C and 500C with the silicon
content varying within a range of from about 0.4 to about
2.0 wt.~. The results are shown in Fig. 1.
In Fig. 1, the mark "o" represents a Brinell
hardness at a room-temperature of the test piece; the
mark "e" represents a Brinell hardness at a temperature
of 300C of the test piece; the mark ~"~" represents a
Brinell hardness at a temperature of~400C of the test
piece; and the mark "~" represents a Bri~nell hardness
at a temperature of 500C of the test piece. As shown in
Fig. 1, the test pieces showed a Brinell hardness~at~a
room-temperature of about 500 almost constantly irrespec-
,
tive of the increase in the silicon content. The test
~ .
pieces showed a Brinell~hardness at a~temperature of~
300C of at least 450, i.e., about 90% of lts room-
~0 tr~mperature Brinell hardness by increasing the silic~n
content to at least 0.8 wt.~. The test~pLeoes~showed a
Brir.ell hardness at a temperature of 400C of at least
350, i.e.j about 70% of~lts room-temperature~Brlnell~
har~ness by increasing the siliCQn~content ~o at least
:: :
25 0.8 wt.~. The test pieces showed a;Brinell~hardness at ~ `
~ ~ :
~:
~ - 13 -
:
~;7~ 7
a temperature of 500~C also increased, though on a rela-
tively low level~ by increasing the silicon content to
at least 0.8 wt.~.
With a silicon content of over 2.5 wt.%, on the
other hand, ~-ferrite is produced in the steel structure,
and this may cause degradation of a room-temperature
hardness o~ steel, and the manufacturing cost of steel
becomes higher. The silicon content should therefore be
limited within a range of from 0.8 to 2.5 wto~.
~3) Manganese: ~ ~
Manganese has a function of~improvlng hardenability
of steel. However, with a manganese content of under~0.~
wt.%, a desired effect as mentioned above ;l~s not~available.
With a manganese content of over 2.0 wt.~ on the~other `
handr weldability of steel is degraded,; and the~manufactur~
ing Fost of steel becomes hlgher.~ The manganese content
should therefore be limited within a range~of;from 0.1 to
2.0 wt.%.
(4) Copper~
Copper has a fun~tlon~of lmproving~hardenabillt~
of steel. In the wear-resistant steeI of the present
invention, therefore, copper is additionally ad~ed as
required.; However, wlth a copper con~ent of under~0.1
wt.%, a desired efLec~; as ~wentioned~above;is~not ava~lable.
2)~3~7~
With a copper content of o~er 2.0 wt.~, on the other hand,
hot workability of steel is degraded. The copper content
should therefore be limited within a range of from O.l to
2.0 wt.~.
(5) Nickel:
Nickel has a function of improving hardenability
and low-temperature ~oughness of steel. In the wear-
resistant steel of the present invention, therefore,
nickel lS additionally added as required. However, ~ith a
nickel content of under O.l wt.%, a~desired effect as
mentioned above is not avaL1ab1e. With~a nickel content
of over lO.0 wt.%, on the other handi the~manufacturing
cost of steel becomes higher. The nickel content~should~
:~ .
therefore be limited within a-range of from O.l to lO.0
wt.%.
.
(6) Chromium:
::
Chro~ium has a function of 1mprov1ng hardenab1lity ~;
of steel. In the wear-resistant steel of the present
invention, therefore,~chromium lS ~additionally added as~
required. However~ with a chromium content of under~0~
;tt.~, a desired ~3ffect ~as~ ment1~oned~above~;is~not~av-9-1ab1e.
With a chrom1um content~of over ~.O~wt.~, on the~other
hand, weldàbility of steel~is degraded~, and the manufactur- `
ing cost~of ste~l becomes higher.~The chromium content ;
showld therefore be limited withi~ a range of from 0.1 to
~ - 15 - ~
.
8 7 ~
3.n wt.%.
(7) Moly-bdenum:
Similarly to chromium, molybdenum has a function
of improving hardenability of steel. In the wear-resistant
steel of the present invention, therefore, molybdenum is
additionally added as required. However, with a molybdenum
content of under O.l wt.~, a desired effect as mentioned
above is no~ available. With a molybdenum content of
over 3.0 wt.%, on the other hand, weldability of steel is
degraded and the manufacturing cost o~ steel becomes
higher. The molybdenum content should therefore be
limited within a range of from O.l to 3.0 wt.%.
(8) Boron:
Boron has a Eunction of improving~hardenability o~
steel with a slight content. In;the~wear-resl$tant~steel
of the present invention, thereore,~boron;is additionally
added as required. However, with a boron content of
under 0.0003 wt.~, a desired effect as mentioned above
is not available. With a boron;content~of over O.O100
~O wt.~, on the other hand, weldability and hardenability of~
steel are degraded. ~The boron~;-ontent should~therefore be
limi.ted within a range~of ~rom 0.00~03~to 0.OlOU wt.%;.
~9) Niobium~
~iobium has a iunc-ion Gf impro-i~n~ bardnes6 of ~ ;
16~
,, ,: . : ~: . ~:
:, . .
7 ~
steel through precipitation hardening. In the wear-
resistant steel of the present invention, therefore,
niobium is additionally a~ded as rPquired. ~owever, with
a niobium content of under 0.005 wt.%, a desired effect
as mentioned above is not available. With a niobium
content of over 0.100 wt.~, on the other hand, weldability
of steel is degraded. The niobium content should therefore
be limited within a range of from 0.005 to 0.100 wt.%.
(10) Vanadium
Similarly to niobium, vanadium has a function of
improving hardness of steel through precipitation hardening.
In the wear-resistant steel of the present invention,
therefore, vanadium is additionally added as required.
However, with a vanadium coDtent of under 0.01 wt.%,
a desired effect as mentioned above is not available.
With a vanadium content of over 0.10 wt.~, on the other
hand, weldability of steel is degraded. The vanadium
content should therefore be limited within a range of
~xom 0.01 to O.lQ wt.~.
: ~
(11) Titanium~ ~
Similai-ly to n~obium, itanium has a function
of improving ha~dness Or steel through precipi~atlon
hardening. In the wear-resistant steel of the present
:
invention, therefore, titaniw,l is additionally added as
required. Howeve~^, with a titanium content of under
~ - 17 -
7 ~
0.005 wt.~, a desired effect as mentioned above is not
available. With a titanium content of over 0~100 wt.%,
weldability of steel i5 degraded. The titanium content
should therefore be lim.ited within a range of from 0.005
to 0.100 wt.%.
In the present invention, for example, a slab of
a wear-resistant steel having the above-mentioned chemical
composition may be hot-rolled to prepare a steel sheet,
and the thus prepared steel sheet may be subjected to
heat treatments including a hardening treatment,~ a
tempering treatment, an ageing treatment and a s~ress
relieving treatment. Hardness~ and toughness of the steel
sheet can further be improved by the~application of these
heat treatments thereto. ;~
Now, the wear-reslstant steel of the present
invention is described more in~detail by means of examples
while comparing with a wear-resistant steel for comparison
outside the scope of the present l~nVentlon.
EXA~SPLES
Ingots of the wear-resistant steel of the present
invention havlng the chemical compositions withln the ~
scop~ of the present ir.ventlon as shown in Table l, an~d
ingots of a wear-resistant steel for comparison having
the chemical composltions outslde the s~ope of ~he
:- 18 ~
:
: ~: .
~3~87~
present invention as shown also in Table 1, were melted
in a melting .l`urnace, and then cast into slabs. The
resultant slabs were then hot-rolled to prepare samples of
the wear-resistant steel of the present invention (herein-
after referred to as the "samples of the invention")
Nos. 1 to 13 having a thickness of 15 mm, and samples of
the wear-resistant steel for comparison outside the scope
of the present invention (hereinafter referred to as the
"samples for comparison") Nos. 1 to 4 also having a
thickness of 15 mm.
The samples of the invention Nos. 1 to 4 and
6 to 13, and the samples for comparison Nos~ 1 to 3 were
subjected to any one of the following heat treatments as
shown in the column of "heat treatment" in Table l.~ The
sample of the invention No. 5;and~the sample for comparison
No. 4 were maintained in~the~as-rolled state without being
subjected to any heat treatment. ~ ~
(1) A sample is hardened by heating the sample to a
temperature of 900C and then water-quenching the heated
sample from the above-mentioned temperature (hereinafter,
this heat treatm~nt being referred to as the "RQ")i
(j) A sample is subjected:to the~above-mentio4ed RQ,
and then tempered at a temperature as shown in the
parentheses in the column of "heat t.reatment" in Table 1
,
(hereinafter, thls heat~treatment being referred to as
19 -; ~
-- - . : . ,
~ - ' ~ , :,: ,
8~
the "RQT");
t3) A sample is directly hardened by immediately
water-quenching the samp~e from the hot-rolling finishing
temperature (hereinafter, this heat treatment being
referred to as the "nQ"); and
(4) A sample is subjected to the above-mentioned DQ,
and then tempered at a temperature as shown in the paren-
theses in the column of "heat treatment" in Table l
(hereinafter, this heat treatment being referred to as
the "DQT").
Then, for each of the samples of the invention
Nos. l to 13 and the samples for comparison Nos, l to 4,
a Brinell hardness (HB) at a room-temperature, a Brinell
hardness at a temperature of 300C and a Br1ne11 hardness
at a temperature of 400C were investigated. ~ThP results
are shown in ~able 2. In the column of "Brinell hardness
(HB)" in Table 2, the values of Brinell hardness shown
in the subcolumns oE "at 300C" and "at 400-C" were~
obtain~d by converting the values measured in the tensile
2Q test, although the values of Brinell hardness showr. In
the subcolumn of "at room-temperature" were obtained by
means of the Brinell test. Each va1ue of percentages
shown in~the parentheses in the subcolumns of "at 300C"
~ and "at 400~C"~presents a ratio of each value of Brinell
hardnesses ~at temperatures of 300C and 400C to a value
of its Brinell hardness at a room-temperature.
- 20 -
'
.
8 7
.J ~ ~ ~ ~ a _ u o ~ a o ~1~ a a ~ _
~ ~ _ _ _ _ ~ E~ ._ C~ _ _ _ _ _ _
Ql Ql a) Ql ~1) Q) C) Ql 5) a) Ql a) (U IU a~ a) ~1)
r r-l r I r-l r1 r1 r-l r1 r~ r1 r-J r-l r-l r-l r l r~ r-l rl
r _ _ _ J __ _ . O O O O O _ __ _ r _
~ l l l l l l ~ O l l O O l l l c l
_ _ _ _ _ _ _ _ N U~ _ O O ~ _ _ O _
,~0 ~ ~ ~
r t.l _ _ _ _ O O O _ _ _ O O _ _ _ O _
~LI~ t~t~ i
O~ 1~1 O r-l ~ ~ O r-l O O O ~1 O rl ~ rl
~ 1~ CO CO I~ I_ ~_ 1~ ~ G ~r 1~ U~ It~ 1~ 1~ 1~ t--
_ O O O O O O O ~ r-l O r-l _ O O O O
N ~ ~ ~1 ~ C~ N N C O ~) ~1 CO ~D ~ r l N r 1
r O r: N r~ r~ r-l r-l r-l O~ O O r; O N O O r1
_ ~ _ --- - -1- - -- -- - ~
~ ,.o~ o ~r ~ ~ 1 O O O u~
r1 N l r ¦ N r-l r1 ¦ N ¦ (`'1 ~¦
L~ uo~uaJ~u~ a~ 30 aldwes uosl~edwo
-- 21 -- .
.
8 ~ ~
Table 2
_ ~
Brinell hardness (HB)
~o . . . ~ __ . __ ._ _ _
At room- At 300CAt 400C
m~ _. _ . __ _
1518 477 (92%)383 (74%)
_ ._ _.
. 2481 ~ 441 (92%)361 (75%)
3510 477 ~94%)448 (88%)
,
o 449g 461 (92%)388 (78~)
.~ _
5304 280 (92%)221 (73%3
~ _ :
.~ 6522 495 -(g5%)~395 ~76%)
_ . . ____ . . .. . . . _ _
7 378 3S6 (94%):~ ~295 (78~)
o 8 ~04 ~ 375~(93%)~:~ ~ 297 (74%j
~ 9 429 406~(95%~ ~333 ~78%): ~:
. ~ _ _ ~ _ ____ __
~ 10 412 ~ ~378~ (92%)~ ~ 302 (~73%~):
u~ . ~ - :: - :
ll 522 478 (9~%): ~ :~;374 (72%) ~ ~ ~
2 339 ~ 317~(94%) ~ 250 ~(74~ : ~ ~ :
13 352 326 (9~3%) ~ ~260~(74~)
1 518 432 ~(~83~%):~:~~:~341~(66%) :
o o . ~ ~ -.
2 522 : 4~4 (85%): ~ :~-339~(65%)
a) ~ - .,.
3 510 426 (84%) ~ ~ 34~6~(68~) ` ~
o 4 : 150 ~ 139~(93%)~ ~ :121;(81%)~ :: :
_ _ _ _ n~ . _
: : ,
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As is clear from Tables 1 and 2, each of the
samples for comparison Nos. 1 to 3, which have a low
silicoll content outside the scope of the present invention,
has a Brinell hardness at a temperature of 300C within
a range of from 83 to 85% of its room-temperature Brinell
hardness, and a Brinell hardness at a temperature of
400C within a range of from 65 to 68% of its room-
temperature Brinell hardness, both of which are lower
than the target values in the present invention. The
sample for comparison No. 4, which has a low carbon
content outside the scope of the present invention, has
a room-temperature Brinell hardness of 150, which is
far lower than the target value in the present lnvention.
Each of the samples of the invention Nos. 1 to
:
13 has, in contrast, a Brinell hardness at a room-
temperature withln a range~of from 304 to 522, which lS
higher than the target value in the present invention,
and has a Brinell ha~rdness at a temperature of 300C of
at least 90% of its room-temperature Brinell hardness,
which is the target ~alue in the present invention, and
has a Brinell hardnèss at a temperature 400~C of at
least ?~ of its room temperature Brinell hardness,
which is the tar~et value in the present invention. ~
Thus, each~of the sampies of the invention Nos. 1 to 13
has an~exceller.t w~ar~ resistance in the intermediate
tempernture rec.lon without largely increasing its room-
. .
.
- .
.. . . . . . .
~3~87~
temperature hardness.
According to the present invention, as described
abc.ve in detail, ~.t is possible to obtain a wear-resistant
steel for the intermediate and room temperature service,
which has a Brinell hardness at a room-temperature of
at least 250, and has a srinell hardness at a temperature
of 300C of at least 90% of its room-temperature Brinell
hardness, and a Brinell hardness at a temperature of
400C of at least 70~ of its room-temperature Brinell
hardness, the last two Brinell hardnesses being available
without largely increasing its room-temperature Brinell
hardness, thus providing lndustrially useful effects.
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