To provide a cold rolled steel sheet excellent in both deep drawability and fatigue characteristic, and to provide its manufacturing method.
A steel containing, by mass%, C:0.015 to 0.15%; Si:2.0% to less; Mn:0.1 to 3.0%; P:0.05% or less; S:0.05% or less; sol.Al:0.001 to 0.1%; N:0.001 to 0.01%; and O:0.01% or less is subjected to multisteps pass hot rolling with conditions of time of rolling passes between just before a final rolling pass and the final rolling pass of 0.3 to 4.0 seconds, a finish temperature of the final rolling pass of Ar3 point to 780°C, a cooling time by 720°C after completion of rolling within 0.4 seconds, then cold rolling with a rolling reduction of 40 to 90%, and then annealed. The obtained cold rolled steel sheet has TSave [=(TS0+2×TS45+TS90)/4] of 300 MPa or more, YRave [=(YR0+2×YR45+YR90)/4] of 0.67 or more, |Δr| of 0.20 or less, rave/|Δr| of 4.7 or less, where [Δr=(r0-2×r45+r90)/2, rave=(r0+2×r45+r90)/4]. Subscripts 0, 45 and 90 mean a rolling direction, a 45° direction to the rolling direction and a 90° direction to the rolling direction respectively.
IMAI NORIO
TOMITA TOSHIRO
| JP2001335888A | 2001-12-04 | |||
| JPH05339640A | 1993-12-21 | |||
| JP2005120471A | 2005-05-12 | |||
| JP2001073077A | 2001-03-21 | |||
| JP2004137565A | 2004-05-13 | |||
| JPS59166651A | 1984-09-20 | |||
| JP2008189958A | 2008-08-21 | |||
| JP2001335888A | 2001-12-04 | |||
| JPH05339640A | 1993-12-21 | |||
| JP2005120471A | 2005-05-12 | |||
| JP2001073077A | 2001-03-21 | |||
| JP2004137565A | 2004-05-13 | |||
| JPS59166651A | 1984-09-20 | |||
| JP2008189958A | 2008-08-21 |
Hideki