US2025297347A1PendingUtilityA1
Low-yield-ratio, easy-to-weld and weather-resistant bridge steel and manufacturing method therefor
Est. expiryMay 6, 2042(~15.8 yrs left)· nominal 20-yr term from priority
Inventors:Ying-Bo YangTianzi LinZhe ZhangYubo WangRuogang WangXinling LiTao ZhangWenbo JiYiqing ChenHuaxing Hou
C21D 8/02C21D 2211/009C21D 1/84C21D 8/0242C21D 8/021C21D 1/60C21D 1/25C21D 1/26C21D 1/20C21D 2211/002C21D 9/46C21D 2211/005C22C 38/50C22C 38/48C22C 38/46C22C 38/44C22C 38/42C22C 38/06C22C 38/04C22C 38/02C22C 38/002C21D 8/0263C21D 8/0226B22D 11/18B22D 11/001B21B 37/58B21B 37/74B21B 1/463C21D 8/0247C22C 33/04
55
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Claims
Abstract
A low-yield-ratio, easy-to-weld and weather-proof bridge steel and a manufacturing method therefor. The present invention comprises the following components in percentages by mass: C: 0.051-0.080%, Si: 0.20-0.50%, Mn: 1.20-1.50%, P≤0.010%, S≤0.003%, Cr: 0.30-0.60%, Ni: 0.20-0.50%, Cu: 0.20-0.50%, Mo: 0-0.20%, Nb: 0.02-0.06%, V: 0-0.070%, Ti: 0.005-0.025%, Al: 0.010-0.040%, CEV≤0.46%, Pcm≤0.20% and the balance of iron and inevitable impurities. The production method comprises the process steps of molten iron pretreatment, converter smelting, external refining, continuous casting, rolling, cooling, straightening and heat treatment, and the steel and the corresponding production process solve matching problems of technical indexes, such as high strength, low yield ratio, weather resistance and welding performance, of the bridge steel.
Claims
exact text as granted — not AI-modified1 . A low-yield-ratio, easy-to-weld and weather-resistant bridge steel, comprising the following components in percentages by mass: C: 0.051%-0.080%, Si: 0.20%-0.50%, Mn: 1.20%-1.50%, P≤0.010%, S≤0.003%, Cr: 0.30%-0.60%, Ni: 0.20%-0.50%, Cu: 0.20%-0.50%, Mo: 0%-0.20%, Nb: 0.02%-0.06%, V: 0%-0.070%, Ti: 0.005%-0.025%, Al: 0.010%-0.040%, and a balance of iron and inevitable impurities,
CEV≤0.46%, Pcm≤0.20%, and an atmospheric corrosion resistance index I≥6.2,
wherein,
CEV
%
=
C
+
Mn
/
6
+
(
Cr
+
Mo
+
V
)
/
5
+
(
Ni
+
Cu
)
/
15
;
Pcm
%
=
C
+
Si
/
30
+
Mn
/
20
+
Cu
/
20
+
Ni
/
60
+
Cr
/
20
+
Mo
/
15
+
V
/
10
+
5
B
;
and
I
=
26.01
(
%
Cu
)
+
3.88
(
%
Ni
)
+
1.2
(
%
Cr
)
+
1.49
(
%
Si
)
+
17.28
(
%
P
)
-
7.29
(
%
Cu
)
(
%
Ni
)
-
9.1
(
%
Ni
)
(
%
P
)
-
33.39
(
%
Cu
)
2
.
2 . The low-yield-ratio, easy-to-weld and weather-resistant bridge steel according to claim 1 , wherein a maximum thickness of the steel plate is 100 mm, a yield strength thereof is ≥345 MPa, a tensile strength thereof is ≥500 MPa, an elongation after fracture thereof is ≥22%, a yield ratio thereof is ≤0.80, a Z-direction area reduction thereof in a thickness direction is ≥60%, and an impact energy of a base material of the steel plate at −40° C. is ≥200 J.
3 . The low-yield-ratio, easy-to-weld and weather-resistant bridge steel according to claim 1 , wherein in a preset atmospheric corrosion environment, a thickness corrosion rate in a 168 h alternate immersion corrosion test is 0.74-1.20 g/m 2 ·h.
4 . The low-yield-ratio, easy-to-weld and weather-resistant bridge steel according to claim 1 , wherein an impact energy of a heat affected zone in welding of the steel plate at −40° C. is ≥100 J.
5 . A method for preparing the low-yield-ratio, easy-to-weld and weather-resistant bridge steel according to claim 1 , comprising process steps of continuous casting, rolling, cooling, straightening and heat treatment, wherein the process steps are as follows:
1) the continuous casting process: a casting superheat temperature of a continuous casting billet is 10-25° C.; 2) the rolling process: heating of the continuous casting billet: a heating zone temperature of the continuous casting billet is 1210-1250° C., a soaking zone temperature is 1190-1230° C., and a soaking time is not less than 60 min; the rolling process comprises rough rolling and finish rolling; wherein, an initial rolling temperature of the rough rolling is 1070-1120° C., a finishing rolling temperature of the rough rolling is 1020-1070° C., it should be ensured that each deformation rate of at least the last two passes is greater than 15% and a pass interval does not exceed 15 s in the rough rolling, and a cumulative deformation rate in the rough rolling is ≥50%; a thickness of an intermediate billet at holding temperature is 2.5 t-3.5 t, wherein t is a thickness of the finished steel plate; an initial rolling temperature of the finish rolling is 830-900° C., and a finishing rolling temperature of the finish rolling is 770-830° C.; 3) the cooling process: a rolled steel plate is subjected to accelerated water cooling, wherein the steel plate is subjected to temperature holding after completion of the rolling, an initial temperature of water cooling is 680-740° C., a self-tempering temperature is 400-600° C., and a water cooling rate is 10-25° C./s; subsequently, the water-cooled steel plate is subjected to thermal straightening and air cooling; 4) the heat treatment: the rolled steel plate is subjected to high-temperature tempering, wherein a heating temperature is 580-690° C., a total holding time is 2.5-4.5 min/mm, and the steel plate is air-cooled to room temperature after taken out of a furnace.
6 . The method according to claim 5 , wherein a deformation rate of each pass is not less than 10% in the finish rolling.
7 . The method according to claim 5 , wherein the rolled steel plate is stacked for slow cooling after finish rolling, wherein a stacking temperature is ≥300° C., and a stacking time is ≥24 h.
8 . The method according to claim 5 , wherein a final microstructure of the steel plate is one of composite structures of ferrite+pearlite, ferrite+bainite, ferrite+pearlite+bainite, wherein a volume percentage of the ferrite is 20-70%.Join the waitlist — get patent alerts
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