Excellent-strength and excellent-toughness steel and the method of manufacturing the same
Abstract
A steel with excellent-strength and excellent-toughness comprises, by weight percent, C: 0.02 to less than 0.15%; Si: not greater than 1%; Mn: 0.3 to 2.5%; P: not greater than 0.05%; S: less than 0.004%; sol. Al: 0.001 to 0.1%; Ti: not greater than 0.02%; N: not greater than 0.009%; wherein, the metal structure of the steel contains either or both of martensite and bainite, or the tempered structure thereof; an aspect ratio of prior austenite grains is not greater than 1.5, the average short diameter of the prior austenite grains is within a range of 60 to 700 μm; and the contents of Ti, N, S and the short diameter dr of the prior austenite grains satisfy the following expression (1) and (2): when Ti/N<3.4, Ti + 8.1 S ≦ 0.315 d γ - 30 - 0.011 ( 1 ) when Ti/N≧3.4, 3.4 N + 8.1 S ≦ 0.315 d γ - 30 - 0.011 ( 2 ) The high-strength and excellent-toughness steel can be obtained with less alloy elements addition and produced with continuously high productivity.
Claims
exact text as granted — not AI-modified1 . An excellent-strength and excellent-toughness steel comprising, by weight percent, C: 0.02 to less than 0.15%; Si: not greater than 1%; Mn: 0.3 to 2.5%;
P: not greater than 0.05%; S: less than 0.004%; sol. Al: 0.001 to 0.1%; Ti: not greater than 0.02%; N: not greater than 0.009%; wherein, the metal structure of the steel contains either or both of martensite and bainite, or the tempered structure thereof; an aspect ratio of prior austenite grains is not greater than 1.5, the average short diameter of the prior austenite grains is within a range of 60 to 700 μm; and the contents of Ti, N, S and the short diameter dr of the prior austenite grains satisfy the following expression (1) and (2):
when Ti/N<3.4,
Ti
+
8.1
S
≦
0.315
d
γ
-
30
-
0.011
(
1
)
when Ti/N≧3.4,
3.4
N
+
8.1
S
≦
0.315
d
γ
-
30
-
0.011
(
2
)
in which each symbol of element represents the content by weight percent of its corresponding element, and the unit of dr is μm.
2 . An excellent-strength and excellent-toughness steel with large heat input for welding comprising, by weight percent, C: 0.02 to less than 0.15%; Si: not greater than 1%; Mn: 0.3 to 2.5%; P: not greater than 0.05%; S: less than 0.004%; sol. Al: 0.001 to 0.1%; Ti: 0.004 to 0.02%; N: 0.001 to 0.009%; Ti/N: 0.4 to 4, wherein, the metal structure of the contains either or both of martensite and bainite, or the tempered structure thereof; the aspect ratio of the prior austenite grains is not greater than 1.5, the average short diameter of the prior austenite grains is within a range of 60 to 700 μm; and the contents of Ti, N, S and the short diameter dr of prior austenite grains satisfy the following expression (3) and (4):
Ti
+
8.1
S
≦
0.315
d
γ
-
30
-
0.011
(
3
)
3.4
N
+
8.1
S
≦
0.315
d
γ
-
30
-
0.011
(
4
)
in which each symbol of element represents the content by weight percent of its corresponding element, and the unit of dr is μm.
3 . A method of manufacturing an excellent-strength and excellent-toughness steel, wherein, hot processing subjected to the steel having the chemical composition defined in claim 1 is terminated at a temperature of 950° C. or higher for making the short diameter of the prior austenite grains be 60 to 700 μm, and quenching process is carried out directly.
4 . A method of manufacturing an excellent-strength and excellent-toughness steel, wherein, hot processing subjected to the steel having the chemical composition defined in claim 2 is terminated at a temperature of 950° C. or higher for making the short diameter of the prior austenite grains be 60 to 700 μm, and quenching process is carried out directly.Join the waitlist — get patent alerts
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