Title:
COLD ROLLED STEEL SHEET AND PRODUCTION METHOD THEREOF
Document Type and Number:
Japanese Patent JP2014141717
Kind Code:
A
Abstract:
PROBLEM TO BE SOLVED: To provide a cold rolled steel sheet which is produced by utilizing precipitation strengthening of fine carbide, instead of solid-solution strengthening of Si, Mn, or the like and has a tensile strength of 590 MPa or higher and good workability.SOLUTION: A cold rolled steel sheet comprises, by mass%, C:0.07-0.12%, Si+Al:0.05-0.10%, Mn:0.15-0.45%, P:0.01-0.05%, S:0.004% or less, N:0.0045% or less, Ti:0.09-0.14% and remaining Fe and unavoidable impurities and meets the condition 2.4≤4C/Ti≤4.5, where Tiis expressed by Ti=Ti-(3.43 N+1.5S). The cold rolled steel sheet contains a ferrite phase in a volume fraction of 90-95% and cementite in a volume fraction of 5-10%. The ferrite phase consists of a recovery structure of a recrystallization ratio of 15-30%. In the ferrite phase, Ti carbide of an average length of smaller than 10 nm is precipitated in a precipitation ratio of Ti of 85% or higher.
Inventors:
YAMADA KATSUMI
TAKASAKA NORIAKI
TANAKA YUJI
TAKASAKA NORIAKI
TANAKA YUJI
Application Number:
JP2013011757A
Publication Date:
August 07, 2014
Filing Date:
January 25, 2013
Export Citation:
Assignee:
JFE STEEL CORP
International Classes:
C22C38/00; C21D9/46; C22C38/14
Attorney, Agent or Firm:
Shigeru Inoue
Kazuhiro Mori
Kazuhiro Mori