| 摘要 |
PROBLEM TO BE SOLVED: To provide a cold rolled steel sheet excellent in bulging moldability in addition to deep drawability.SOLUTION: Provided is a ferritic thin steel sheet having a composition containing, by mass, C:0.0060% or lower, S: 0.010% or lower, Al: 0.00050 to 0.10%, N: 0.0040% or lower, Ti: 0.0010 to 0.10% and Nb: 0.0010 to 0.10%, and the balance is Fe with impurities, in which the value of F1 defined by formula (1) is above 0.7 to 1.2, and further, in the range from the surface of the steel sheet to a depth of 1/16 of the sheet thickness, at least either condition of the following (a) and (b) is satisfied: (a) the condition that the area fraction of the crystals having a crystal orientation from the {001} face parallel to the steel sheet surface within ±15° is 0.25 or lower; and (b) the condition that the average crystal grain size of the crystals having a crystal orientation from the {001} face parallel to the steel sheet surface within ±15° is 25 μm or lower: F1=(C/12+N/14+S/32)/(Ti/48+Nb/93)(1)SELECTED DRAWING: Figure 1 |
