HIGH-STRENGTH, HIGH-TOUGHNESS STEEL PLATE AND METHOD FOR PRODUCING THE SAME
First Claim
1. A high-strength, high-toughness steel plate having a composition containing, by mass %,C:
- 0.03% or more and 0.08% or less,Si;
0.01% or more and 0.50% or less,Mn;
1.5% or more and 2.5% or less,P;
0.001% or more and 0.010% or less,S;
0.0030% or less,Al;
0.01% or more and 0.08% or less,Nb;
0.010% or more and 0.080% or less,Ti;
0.005% or more and 0.025% or less,N;
0.001% or more and 0.006% or less,and further containing at least one selected fromCu;
0.01% or more and 1.00% or less,Ni;
0.01% or more and 1.00% or less,Cr;
0.01% or more and 1.00% or less,Mo;
0.01% or more and 1.00% or less,V;
0.01% or more and 0.10% or less, andB;
0.0005% or more and 0.0030% or less,with the balance being Fe and unavoidable impurities,wherein the steel plate has a microstructure in which an area fraction of Martensite-Austenite constituent in each of a surface portion and a central portion in a thickness direction is less than 3%, an area fraction of bainite in each of the surface portion and the central portion in the thickness direction is 90% or more, and an average particle size of cementite present in the bainite in the central portion in the thickness direction is 0.5 μ
m or less, andthe steel plate has a Vickers hardness difference (Δ
HV) between the surface portion and the central portion in the thickness direction of 20 or less.
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Accused Products
Abstract
A high-strength, high-toughness steel plate having excellent surface properties and a high absorbed energy includes, by mass %, C: 0.03% to 0.08%, Si: 0.01% to 0.50%, Mn: 1.5% to 2.5%, P: 0.001% to 0.010%, S: 0.0030% or less, Al: 0.01% to 0.08%, Nb: 0.010% to 0.080%, Ti: 0.005% to 0.025%, and N: 0.001% to 0.006%, and further includes at least one selected from Cu: 0.01% to 1.00%, Ni: 0.01% to 1.00%, Cr: 0.01% to 1.00%, Mo: 0.01% to 1.00%, V: 0.01% to 0.10%, and B: 0.0005% to 0.0030%, with the balance being Fe and unavoidable impurities. In a surface portion and a central portion in the thickness direction, the area fraction of Martensite-Austenite constituent is less than 3% and the area fraction of bainite is 90% or more, and in the central portion in the thickness direction, the average particle size of cementite in bainite is 0.5 μm or less.
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Citations
4 Claims
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1. A high-strength, high-toughness steel plate having a composition containing, by mass %,
C: - 0.03% or more and 0.08% or less,
Si;
0.01% or more and 0.50% or less,Mn;
1.5% or more and 2.5% or less,P;
0.001% or more and 0.010% or less,S;
0.0030% or less,Al;
0.01% or more and 0.08% or less,Nb;
0.010% or more and 0.080% or less,Ti;
0.005% or more and 0.025% or less,N;
0.001% or more and 0.006% or less,and further containing at least one selected from Cu;
0.01% or more and 1.00% or less,Ni;
0.01% or more and 1.00% or less,Cr;
0.01% or more and 1.00% or less,Mo;
0.01% or more and 1.00% or less,V;
0.01% or more and 0.10% or less, andB;
0.0005% or more and 0.0030% or less,with the balance being Fe and unavoidable impurities, wherein the steel plate has a microstructure in which an area fraction of Martensite-Austenite constituent in each of a surface portion and a central portion in a thickness direction is less than 3%, an area fraction of bainite in each of the surface portion and the central portion in the thickness direction is 90% or more, and an average particle size of cementite present in the bainite in the central portion in the thickness direction is 0.5 μ
m or less, andthe steel plate has a Vickers hardness difference (Δ
HV) between the surface portion and the central portion in the thickness direction of 20 or less. - View Dependent Claims (2, 3, 4)
- 0.03% or more and 0.08% or less,
Specification