HIGH-STRENGTH H-BEAM STEEL EXHIBITING EXCELLENT LOW-TEMPERATURE TOUGHNESS AND METHOD OF MANUFACTURING SAME
First Claim
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1. An H-beam steel with a composition comprising, in mass %:
- C;
0.011 to 0.040%;
Si;
0.06 to 0.50%;
Mn;
0.80 to 1.98%;
Al;
0.006 to 0.040%;
Ti;
0.006 to 0.025%;
N;
0.001 to 0.009%;
O;
0.0003 to 0.0035%;
Nb;
0.020 to 0.070%;
B;
0.0003 to 0.0010%;
P;
limited to not more than 0.010%; and
S;
limited to not more than 0.005%,with a balance including Fe and inevitable impurities, whereinan amount of Nb and an amount of B satisfy, in mass %, Equation 1 described below,the H-beam steel has a metal structure in which, in a microstructure, an area fraction of bainite is not less than 70%, a total of an area fraction of pearlite and an area fraction of cementite is not more than 15%, and the remainder consists of at least one of ferrite and island martensite,an effective crystalline-grain size of the bainite is not more than 40 μ
m, anda thickness of a flange falls in a range of 12 to 40 mm.
0.070≦
Nb+125B≦
0.155
Equation 1
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Abstract
This H-beam steel contains, in mass %, C, Si, Mn, Al, Ti, N, O, Nb, and B. The H-beam steel has composition in which the amount of Nb and the amount of B satisfy, in mass %, 0.070≦Nb+125B≦0.155, and has a metal structure in which, in a microstructure, an area fraction of bainite is not less than 70%, a total of an area fraction of pearlite and an area fraction of cementite is not more than 15%, and the remainder is at least one of ferrite and island martensite. The effective crystalline-grain size of the bainite is not more than 40 μm, and the thickness of a flange falls in a range of 12 to 40 mm.
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Citations
7 Claims
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1. An H-beam steel with a composition comprising, in mass %:
-
C;
0.011 to 0.040%;Si;
0.06 to 0.50%;Mn;
0.80 to 1.98%;Al;
0.006 to 0.040%;Ti;
0.006 to 0.025%;N;
0.001 to 0.009%;O;
0.0003 to 0.0035%;Nb;
0.020 to 0.070%;B;
0.0003 to 0.0010%;P;
limited to not more than 0.010%; andS;
limited to not more than 0.005%,with a balance including Fe and inevitable impurities, wherein an amount of Nb and an amount of B satisfy, in mass %, Equation 1 described below, the H-beam steel has a metal structure in which, in a microstructure, an area fraction of bainite is not less than 70%, a total of an area fraction of pearlite and an area fraction of cementite is not more than 15%, and the remainder consists of at least one of ferrite and island martensite, an effective crystalline-grain size of the bainite is not more than 40 μ
m, anda thickness of a flange falls in a range of 12 to 40 mm.
0.070≦
Nb+125B≦
0.155
Equation 1 - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification