HIGH-STRENGTH H-BEAM STEEL EXHIBITING EXCELLENT LOW-TEMPERATURE TOUGHNESS AND METHOD OF MANUFACTURING SAME

• US 20140301888A1
• Filed: 12/12/2012
• Published: 10/09/2014
• Est. Priority Date: 12/15/2011
• Status: Active Grant

• Current Assignee: Nippon Steel Corporation
• Original Assignee: Nippon Steel & Sumitomo Metal Corporation (Nippon Steel Corporation)
• Inventors: Ichikawa, Kazutoshi, Wakatsuki, Teruyuki, Onodera, Noriaki, Yamamoto, Kohichi
• Granted Patent: US 9,644,372 B2
• Time in Patent Office: Days
• US Class Current: 420/83
• CPC Class Codes: B21B 1/088 H- or I-sections
• CPC Class Codes: C21D 2211/002 Bainite
• CPC Class Codes: C21D 2211/005 Ferrite
• CPC Class Codes: C21D 2211/008 Martensite
• CPC Class Codes: C21D 8/00 Modifying the physical properties by deformation combined with, or followed by, heat treatment hardening articles or materials formed by forging or rolling with no further heating beyond that required for the formation C21D1/02
• CPC Class Codes: C21D 8/0205 of ferrous alloys
• CPC Class Codes: C22C 38/001 containing N
• CPC Class Codes: C22C 38/002 containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
• CPC Class Codes: C22C 38/005 containing rare earths, i.e. Sc, Y, Lanthanides
• CPC Class Codes: C22C 38/02 containing silicon
• CPC Class Codes: C22C 38/04 containing manganese
• CPC Class Codes: C22C 38/06 containing aluminium
• CPC Class Codes: C22C 38/08 containing nickel C22C38/105 takes precedence
• CPC Class Codes: C22C 38/12 containing tungsten, tantalum, molybdenum, vanadium, or niobium
• CPC Class Codes: C22C 38/14 containing titanium or zirconium
• CPC Class Codes: C22C 38/16 containing copper
• CPC Class Codes: C22C 38/26 with niobium or tantalum
• CPC Class Codes: C22C 38/28 with titanium or zirconium
• CPC Class Codes: C22C 38/32 with boron
• CPC Class Codes: C22C 38/38 with more than 1.5% by weight of manganese
• CPC Class Codes: C22C 38/58 : with more than 1.5% by weight of manganese
• CPC Class Codes: E04C 2003/0404 : beams, girders, or joists characterised by cross-sectional aspects
• CPC Class Codes: E04C 3/32 : of metal E04C3/36 takes precedence

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.

Claims

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, 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, and

a thickness of a flange falls in a range of 12 to 40 mm.

0.070≦

Nb+125B≦

0.155 

 

Equation 1

2. The H-beam steel according to claim 1, wherein

the composition further comprises, in mass % at least one of:

V;

not more than 0.10%;

Cu;

not more than 0.60%;

Ni;

not more than 0.55%;

Mo;

not more than 0.15%; and

Cr;

not more than 0.20%.

3. The H-beam steel according to claim 1, wherein

the composition further comprises, in mass %, at least one of:

Zr;

not more than 0.01%; and

Hf;

not more than 0.01%.

4. The H-beam steel according to claim 1, wherein

the composition further comprises, in mass %, at least one of:

REM;

not more than 0.01%;

Ca;

not more than 0.005%; and

Mg;

not more than 0.005%.

5. The H-beam steel according to claim 1, wherein

the composition further comprises, in mass %, at least one of:

V;

not more than 0.10%;

Cu;

not more than 0.60%;

Ni;

not more than 0.55%;

Mo;

not more than 0.15%;

Cr;

not more than 0.20%;

Zr;

not more than 0.01%;

Hf;

not more than 0.01%;

REM;

not more than 0.01%;

Ca;

not more than 0.005%; and

Mg;

not more than 0.005%.

6. The H-beam steel according to claim 1, wherein

the amount of Nb and the amount of B satisfy, in mass %, Equation 2 described below.

0.070≦

Nb+125B≦

0.115 

 

Equation 2

7. A method of manufacturing, an H-beam steel, wherein

when a steel with the composition according to any one of claims 1 to 6 is rolled, finishing rolling includes rolling performed for one or more passes at a surface temperature of a flange in a range of 770 to 870°

C.