High-strength H-beam steel exhibiting excellent low-temperature toughness and method of manufacturing same

Patent metadata

Field	Value
Publication number	US-9644372-B2
Application number	US-201214359620-A
Country	US
Kind code	B2
Filing date	Dec 12, 2012
Priority date	Dec 15, 2011
Publication date	May 9, 2017
Grant date	May 9, 2017

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.

First claim

The invention claimed is:

1. An H-beam steel with a composition comprising, in mass %:
C: 0.011 to 0.020%;
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 %, the following Equation (1):
0.070≦Nb+125B≦0.155,

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 or island martensite,
an effective crystalline-grain size, which represents an equivalent circle diameter of an area surrounded by a large-angle grain boundary having an orientation difference not less than 15°, of the bainite is 21 to 40 μM, and

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

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%; or
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%; or
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%; or
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%; or
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 %, the following Equation (2):
0.070≦Nb+125B≦0.115.

Assignees

• Nippon Steel & Sumitomo Metal Corp

Inventors

• Ichikawa Kazutoshi
• Wakatsuki Teruyuki
• Onodera Noriaki
• Yamamoto Kohichi

Classifications

• C21D8/02

  during manufacturing of plates or strips (C21D8/12 takes precedence) · CPC title

• C22C38/58

  with more than 1.5% by weight of manganese · CPC title

• C21D2211/005

  Ferrite · CPC title

• C22C38/32

  with boron · CPC title

• C22C38/26

  with niobium or tantalum · CPC title