Steel sheet

A steel sheet having a chemical composition comprising, by mass %,

• C:
• 0.040 to 0.100%,
• Mn:
• 1.00 to 2.50%,
• Si:
• 0.005 to 1.500%,
• P:
• 0.100% or less,
• S:
• 0.0200% or less,
• Al:
• 0.005 to 0.700%,
• N:
• 0.0150% or less,
• O:
• 0.0100% or less,
• Cr:
• 0 to 0.80%,
• Mo:
• 0 to 0.50%,
• B:
• 0 to 0.0100%,
• Ti:
• 0 to 0.100%,
• Nb:
• 0 to 0.060%,
• V:
• 0 to 0.50%,
• Ni:
• 0 to 1.00%,
• Cu:
• 0 to 1.00%,
• W:
• 0 to 1.00%,
• Sn:
• 0 to 1.00%,
• Sb:
• 0 to 0.200%,
• Ca:
• 0 to 0.0100%,
• Mg:
• 0 to 0.0100%,
• Zr:
• 0 to 0.0100%,
• REM:
• 0 to 0.0100%, and
• balance:
• Fe and impurities, wherein
• an index A represented by following formula 1 is 1.10% or less, and
• a microstructure comprising, by area %,
• ferrite:
• 70 to 95%, and
• a hard phase:
• 5 to 30%, wherein
• a maximum connected length of the hard phase in a rolling direction at a sheet thickness ½ position is 80 μm or less, and
• a maximum connected length of the hard phase in a rolling direction at a sheet thickness ¼ position is 40 μm or less:
• A=10[C]+0.3[Mn]−0.2[Si]−0.6[Al]−0.05[Cr]−0.2[Mo] formula 1
• where [C], [Mn], [Si], [Al], [Cr], and [Mo] are the contents of the elements [mass %], and when the elements are not contained, the contents are 0%.