H-SECTION STEEL AND METHOD OF PRODUCING THE SAME

• US 20150361664A1
• Filed: 04/15/2014
• Published: 12/17/2015
• Est. Priority Date: 04/26/2013
• Status: Abandoned Application

• Current Assignee: Nippon Steel & Sumitomo Metal Corporation (Nippon Steel Corporation)
• Original Assignee: Nippon Steel & Sumitomo Metal Corporation (Nippon Steel Corporation)
• Inventors: ICHIKAWA, Kazutoshi, ITO, Hidetoshi, ONODERA, Noriaki, MITSUYASU, Kazuaki, YAMAMOTO, Kohichi
• Application Number:
  US14/763,344
• Publication Number:
  US 20150361664A1
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B21B 1/026 Rolling
• CPC Class Codes: C21D 2211/002 Bainite
• CPC Class Codes: C21D 2211/005 Ferrite
• CPC Class Codes: C21D 2211/009 Pearlite
• CPC Class Codes: C21D 6/001 containing Ni C21D6/004 takes precedence
• CPC Class Codes: C21D 6/004 containing Cr and Ni
• CPC Class Codes: C21D 6/005 containing Mn
• CPC Class Codes: C21D 6/008 containing Si
• CPC Class Codes: C21D 8/005 of ferrous alloys C21D8/02 - C21D8/12 take precedence
• CPC Class Codes: C21D 8/1222 Hot rolling
• CPC Class Codes: C21D 9/0068 for particular articles not mentioned below
• CPC Class Codes: C21D 9/46 for sheet metals
• CPC Class Codes: C22C 38/00 Ferrous alloys, e.g. steel alloys cast-iron alloys C22C37/00
• 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 38/42 : with copper
• CPC Class Codes: C22C 38/48 : with niobium or tantalum
• CPC Class Codes: C22C 38/50 : with titanium or zirconium
• CPC Class Codes: C22C 38/54 : with boron
• CPC Class Codes: C22C 38/58 : with more than 1.5% by weight of manganese
• CPC Class Codes: E04C 2003/0421 : comprising one single unitary part
• CPC Class Codes: E04C 2003/0452 : H- or I-shaped
• CPC Class Codes: E04C 3/06 : with substantially solid, i.e. unapertured, web E04C3/10, E04C3/11 take precedence honeycomb girders E04C3/083

Abstract

An H-section steel has a predetermined chemical composition, an Nb content and a B content satisfy Nb+125×B≧0.075%, a thickness of a flange is 12 mm to 40 mm, and in a thickness center portion and ¼ flange width portion of the flange, a metallographic structure of a cross-section perpendicular to a rolling direction contains pearlite having a distribution density of 3.2×10⁻³ units/μm² or lower and the remainder is formed of ferrite and bainite.

Claims

1. An H-section steel, wherein

a chemical composition thereof includes, in terms of mass %:

C;

0.010% to 0.014%;

Si;

0.05% to 0.50%;

Mn;

0.8% to 2.0%;

Cu;

0.01% or more and less than 0.60%;

Ni;

0.01% or more and less than 0.50%;

Al;

more than 0.005% and 0.040% or less;

Ti;

0.001% to 0.025%;

Nb;

0.010% to 0.070%;

N;

0.001% to 0.009%;

O;

0.0005% to 0.0035%;

B;

more than 0.0003% and 0.0015% or less;

V;

0% to 0.10%;

Mo;

0% to 0.10%;

Cr;

0% or more and less than 0.20%;

Zr;

0 to 0.030%;

Hf;

0 to 0.010%;

REM;

0 to 0.010%;

Ca;

0 to 0.0050%; and

a remainder including Fe and an impurity,

wherein an Nb content and a B content satisfy Expression 1,

a thickness of a flange is 12 mm to 40 mm, and

in a thickness center portion and ¼

flange width portion of the flange, a metallographic structure of a cross-section perpendicular to a rolling direction contains a pearlite having a distribution density of 3.2×

10<sup>−

3</sup> units/μ

m² or lower and the remainder consists of a ferrite and a bainite,

Nb+125×

B≧

0.075% 

 

(Expression

     1),

wherein Nb and B in Expression 1 are amounts of the elements in terms of mass %.

2. The H-section steel according to claim 1,

wherein a tensile strength is 460 MPa to 550 MPa.

3. The H-section steel according to claim 1 or 2,

wherein the chemical composition includes, in terms of mass %, at least one of:

V;

0.01% to 0.10%;

Mo;

0.01% to 0.10%; and

or

Cr;

0.01% or more and less than 0.20%.

4. The H-section steel according to claim 1 or 2,

wherein the chemical composition includes, in terms of mass %, at least one of:

Zr;

0.001% to 0.030%;

or

Hf;

0.001% to 0.010%.

5. The H-section steel according to claim 1 or 2,

wherein the chemical composition includes, in terms of mass %, at least one of:

REM;

0.0001% to 0.010%;

or

Ca;

0.0001% to 0.0050%.

6. A method of producing an H-section steel, the method comprising:

a heating process of heating a steel slab having the chemical composition according to claim 1 or 2 to 1100°

C. to 1350°

C.;

a hot rolling process of performing a hot rolling on the steel slab into an H-section steel; and

an air cooling process of performing an air cooling on the H-section steel,

wherein the hot rolling process includes a rough rolling process of rolling the steel slab by using a roughing mill, an intermediate rolling process of performing a reverse rolling by using an intermediate rolling mill, and a finish rolling process of performing a rolling by using a finishing mill,

wherein during the reverse rolling of the intermediate rolling process, a controlled rolling in which a rolling is performed while the H-section steel is cooled by using a water cooling apparatus provided on a front surface and a rear surface of the intermediate rolling mill is performed, and

in the finish rolling process, the rolling is performed in one or more passes while a surface temperature of a flange is in a range of 770°

C. to 870°

C., and

a thickness of the flange is 12 mm to 40 mm.