Title:
HOT-ROLLED STEEL SHEET WITH HIGH TENSILE STRENGTH AND SUPERIOR PROCESSABILITY AND METHOD FOR PRODUCING SAME
Document Type and Number:
WIPO Patent Application WO/2011/122031
Kind Code:
A1
Abstract:
Disclosed is a hot-rolled steel sheet with high tensile strength that is provided with both strength and processability (elongation and stretch flangeability) and a method for producing the same. Specifically disclosed is a hot-rolled steel sheet with high tensile strength that has tensile strength of 980 MPa or greater and superior processability. This hot-rolled steel sheet has a composition containing 0.07 - 0.13% C, 0.3% or less Si, 0.5 - 2.0% Mn, 0.025% or less P, 0.005% or less S, 0.0060% or less N, 0.06% or less Al, 0.08 - 0.14% Ti, and 0.15 - 0.30% V (% by mass) such that C, Ti, V, S and N satisfy Ti ≥ 0.08 + (N/14 × 48 + S/32 × 48) and 0.8 ≤ (Ti/48 + V/51)/(C/12) ≤ 1.2 (wherein C, Ti, V, S and N are the content for each element in % by mass). The composition further contains 0.04 - 0.1% V in solid solution and 0.05% or less Ti in solid solution, and the remainder is Fe and unavoidable impurities. The hot-rolled steel sheet has a matrix that is 97% or more in areal proportion of the overall structure of the ferrite phase, and fine carbide that has an average particle diameter of less than 10 nm and contains Ti and V is dispersed and precipitated, with a structure forming 0.007 or more in areal proportion of the overall structure of that fine carbide. Moreover, the bending characteristics are improved further by making the total of (solid solution V + solid solution Ti) 0.07% or greater.
Inventors:
ARIGA TAMAKO (JP)
NAKAJIMA KATSUMI (JP)
MEGA TETSUYA (JP)
NAKAJIMA KATSUMI (JP)
MEGA TETSUYA (JP)
Application Number:
PCT/JP2011/001931
Publication Date:
October 06, 2011
Filing Date:
March 30, 2011
Export Citation:
Assignee:
JFE STEEL CORP (JP)
ARIGA TAMAKO (JP)
NAKAJIMA KATSUMI (JP)
MEGA TETSUYA (JP)
ARIGA TAMAKO (JP)
NAKAJIMA KATSUMI (JP)
MEGA TETSUYA (JP)
International Classes:
C22C38/14; C21D8/02; C21D9/46; C22C38/38
Foreign References:
| JP2009052139A | 2009-03-12 | |||
| JP2007063668A | 2007-03-15 | |||
| JP2006161112A | 2006-06-22 | |||
| JP2004143518A | 2004-05-20 | |||
| JP2005002406A | 2005-01-06 | |||
| JP2009084643A | 2009-04-23 | |||
| JP3591502B2 | 2004-11-24 | |||
| JP2006161112A | 2006-06-22 | |||
| JP3821036B2 | 2006-09-13 | |||
| JP2009052139A | 2009-03-12 |
Other References:
See also references of EP 2554706A4
Attorney, Agent or Firm:
SUGIMURA, KENJI (JP)
Kenji Sugimura (JP)
Kenji Sugimura (JP)
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Claims: