| 摘要 |
<p>The present invention relates to a cold rolled steel sheet having a yield ratio of 60% or higher, superior dent resistance and durability, superior drawability having an r-value of 1.4 or higher, and a superior tensile strength of 490 MPa or higher, to a galvanized steel sheet using same, to an alloyed galvanized steel sheet, and to a method for manufacturing same. More particularly, the present invention relates to a high-strength cold rolled steel sheet having superior deep drawability and a high yield ratio, comprising, by weight, C: 0.02-0.05%, Mn: 1.0-3.0%, Si: 0.5-2.0%, P: 0.05% or less, N: 0.006% or less, Al: 0.01-0.1%, S: 0.012% or less, and Nb: 0.04-0.15%, and one or more components selected from a group consisting of Ti, B, and Zr, wherein said components satisfy the condition in which the following Eq_N value is 0.001 or less and the following Eq_C value is 0.03 or less.; The residuals consist of Fe and inevitable impurities, and the fraction of the retained austenite is 5%or less. The present invention also relates to a galvanized steel sheet using same, to an alloyed galvanized steel sheet, and to a method for manufacturing same. Eq_N = N - 14 (Ti/47.9 + Zr/91.2 + B/10.8) Eq_C = C - 12/92.9 Nb <Ti, Zr not added> Eq_C = C - 12 (Nb/92.9 + (Ti - 47.9/14 N)/47.9+ (Zr - 91.2/14 N)/91.2) <Ti, Zr added> (wherein, if Ti - 47.9/14 N < 0, Ti - 47.9/14 N is regarded as 0, and if Zr - 91.2/14 N < 0, Zr - 91.2/14 N is regarded as 0).</p> |
