Low carbon steel sheet excellent in cold formability and toughness after heat treatment and manufacturing method

摘要

PROBLEM TO BE SOLVED: To enhance cold moldability and toughness after a heat treatment in a low carbon steel sheet.SOLUTION: There is provided a low carbon steel sheet excellent in cold moldability and toughness after a heat treatment containing, by mass%, C:0.10 to 0.40%, Si:0.01 to 0.30%, Mn:0.30 to 1.00%, Al:over 0.10 to 1.00%, P:0.0001 to 0.02%, S:0.0001 to 0.01% and the balance Fe with impurities, and having (x) a ratio of the number of carbides of a ferrite grain boundary:B to the number of carbides in a ferrite particle:A, B/A, of over 1, (y) a ferrite particle diameter of 5 μm to 50 μm inclusive and (z) a Vickers hardness of 100 HV to 150 HV inclusive.SELECTED DRAWING: None