Patent ID: 8685181

Claim:
A carbon steel sheet having excellent formability, wherein: the carbon steel sheet comprises, in the unit of wt %, C at 0.2-0.5%, Mn at 0.1-1.2%, Si at less than or equal to 0.4%, Cr at less than or equal to 0.5%, Al at 0.01-0.1%, S at less than or equal to 0.012%, Ti at less than 0.5Ã—48/14Ã—[N]%, B at 0.0005-0.0080%, N at less than or equal to 0.006%, Fe, and extra inevitable impurities, wherein the condition of B(atomic %)/N(atomic %)>1 is satisfied; an average particle size of carbide in the carbon steel sheet is less than or equal to 1 Î¼m; an average grain size of ferrite in the carbon steel sheet is less than or equal to 5 Î¼m; and fractions of free ferrite and pearlite having a lamellar carbide structure are respectively less than or equal to 5%, and that of bainite is greater than or equal to 90%.