JP2010255069A5

JP2010255069A5 -

Info

Publication number: JP2010255069A5
Application number: JP2009108820A
Authority: JP
Filing date: 2009-04-28
Publication date: 2012-03-15
Anticipated expiration: 2029-04-28

Claims

In mass%, C: 0.030 to 0.060%, Si: 0.05% or less, Mn: 0.1 to 0.3%, P: 0.05% or less, S: 0.02% or less, Al: 0.02 to 0.10%, N: 0.005% or less, The balance is iron and inevitable impurities, the average yield strength (YS _m ) shown by the following formula (a) is 230 MPa or less, and the average elongation (El _m ) shown by the following formula (b) is 40% or more, the r value in the rolling direction and the direction perpendicular to the rolling is 0.7 to 1.4, the in-plane anisotropy (Δr) of the r value represented by the following formula (c) is −0.2 ≦ Δr ≦ 0.2, A cold-rolled steel sheet having a yield elongation of 2% or less after being held at 170 ° C. for 60 minutes in all directions of rolling, rolling 45 °, and perpendicular to rolling.
Average yield strength YS _m = (YS _L + 2YS _D + YS _C ) / 4 (a)
Average elongation El _m = (El _L + 2El _D + El _C ) / 4 (b)
In-plane anisotropy of r value Δr = (r _L −2r _D + r _C ) / 2 (c)
Where YS _L : Yield strength in rolling direction
YS _D : Yield strength in 45 ° direction of rolling
YS _C : Yield strength in the direction perpendicular to rolling
El _L : Elongation in rolling direction
El _D : Rolling 45 ° direction elongation
El _C : elongation in the direction perpendicular to the rolling r _L : r value in the rolling direction r _D : r value in the rolling 45 ° direction r _C : r value in the rolling perpendicular direction

When the steel slab having the composition of claim 1 is hot-rolled, the steel slab is heated at a heating temperature of 1200 ° C or higher and then finished at (A1 transformation point -50 ° C) to (A1 transformation point + 100 ° C). Perform hot rolling to finish rolling, wind up at 550 to 680 ° C, pickle, then cold-roll at 50 to 85% reduction, and then anneal at 600 ° C A cold-rolled steel sheet characterized by heating at an annealing temperature of 700 ° C. or higher at an average heating rate of 1-30 ° C./s, and then cooling at an average cooling rate of up to 600 ° C. at 3 ° C./s or higher. Manufacturing method.