Steel plate having superior toughness in weld heat-affected zone and welded structure made therefrom
First Claim
1. A welding structural steel product exhibiting a superior heat affected zone toughness. comprising, in terms of percent by weight, 0.03 to 0.17% C, 0.01 to 0.5% Si, 0.4 to 2.0% Mn, 0.005 to 0.2% Ti, 0.0005 to 0.1% Al, 0.008 to 0.030% N, 0.0003 to 0.01% B, 0.001 to 0.2% W, at most 0.03% P, at most 0.03% 5, at most 0.005% O, and balance Fe and incidental impurities while satisfying conditions of 1.2≦
- Ti/N≦
2.5, 10≦
N/B≦
40, 2.5 Al/N≦
7, and 6.5≦
(Ti 2Al 4B)/N≦
14, and having a microstructure essentially consisting of a complex structure of ferrite and pearlite having a grain size of 20 μ
m or less.
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Accused Products
Abstract
A welding structural steel product exhibiting a superior heat affected zone toughness, comprising, in terms of percent by weight, 0.03 to 0.17% C, 0.01 to 0.5% Si, 0.4 to 2.0% Mn, 0.005 to 0.2% Ti, 0.0005 to 0.1% Al, 0.008 to 0.030% N, 0.0003 to 0.01% 0.00 1 to 0.2% W, at most 0.03% P, at most 0.03% S, at most 0.005% 0, and balance Fe and incidental impurities while satisfying conditions of 1.2≦Ti/N≦2.5, 10≦N/B≦40, 2.5≦Al/N≦7, and 6.5≦(Ti 2Al 4B)/N≦14, and having a microstructure essentially consisting of a complex structure of ferrite and pearlite having a grain size of 20 μm or less. The method includes the steps of preparing a slab of the above-described composition, heating the slab to 1,100° C. to 1,250° C. for 60-180 minutes, hot rolling the heated slab in an austenite recrystallization range at a 40% or more rolling reduction followed by controlled cooling.
89 Citations
7 Claims
-
1. A welding structural steel product exhibiting a superior heat affected zone toughness. comprising, in terms of percent by weight, 0.03 to 0.17% C, 0.01 to 0.5% Si, 0.4 to 2.0% Mn, 0.005 to 0.2% Ti, 0.0005 to 0.1% Al, 0.008 to 0.030% N, 0.0003 to 0.01% B, 0.001 to 0.2% W, at most 0.03% P, at most 0.03% 5, at most 0.005% O, and balance Fe and incidental impurities while satisfying conditions of 1.2≦
- Ti/N≦
2.5, 10≦
N/B≦
40, 2.5 Al/N≦
7, and 6.5≦
(Ti 2Al 4B)/N≦
14, and having a microstructure essentially consisting of a complex structure of ferrite and pearlite having a grain size of 20 μ
m or less.
- Ti/N≦
-
2. The welding structural steel product according to claim 1, further comprising 0.01 to 0.2% V while satisfying conditions of 0.3≦
- V/N≦
9, and 7≦
(Ti 2Al 4B V)/N≦
17.
- V/N≦
-
3. The welding structural steel product according to claim 1, further comprising one or more selected from a group consisting of Ni:
- 0.1 to 3.0%, Cu;
0.1 to 1.5%, Nb;
0.01 to 0.1%, Mo;
0.05 to 1.0%, and Cr;
0.05 to 1.0%.
- 0.1 to 3.0%, Cu;
-
4. The welding structural steel product according to claim 1, further comprising one or both of Ca:
- 0.0005 to 0.005% and REM;
0.005 to 0.05%.
- 0.0005 to 0.005% and REM;
-
5. The welding structural steel product according to claim 1, wherein TiN prebipitates having a grain size of 0.01 to 0.1 μ
- m are dispersed at a density of 1.0×
107/mm2 or more and a spacing of 0.5 μ
m or less.
- m are dispersed at a density of 1.0×
-
6. The welding structural steel product according to claim 1, wherein a toughness difference between a matrix and a heat treated zone is within a range of ±
- 30 J when the steel product is heated to a temperature of 1,400°
C. or more, and then cooled within 60 seconds over a cooling range of from 800°
C. to 500°
C.;is within a range of ±
70 J when the steel product is heated to a temperature of 1,400°
C. or more, and then cooled within 60 to 120 seconds over a cooling range of from 800°
C. to 500°
C.; and
is within a range of 0 to 100 J when the steel product is heated to a temperature of 1,400°
C. or more, and then cooled within 120 to 180 seconds over a cooling range of from 800°
C. to 500°
C.
- 30 J when the steel product is heated to a temperature of 1,400°
-
7. A welded structure having a superior heat affected zone toughness, manufactured using a welding structural steel product according to claim 1.
Specification