ULTRA HIGH STRENGTH HOT ROLLED STEEL SHEET HAVING EXCELLENT SHAPE AND BENDABILITY PROPERTIES AND METHOD OF MANUFACTURING THE SAME

摘要

The present invention relates to an ultra-high strength hot-rolled steel sheet having excellent shape quality and bendability, and a method of manufacturing the same. One embodiment of the present invention is by weight, C: 0.16 to 0.26%, Mn: 0.75 to 1.50%, B: 0.0009 to 0.0050%, Ti: 0.009 to 0.070%, N: 0.001 to 0.010%, balance Fe and others Containing inevitable impurities, satisfying the following relational equations 1 to 3, and including a microstructure in which the sum of martensite and tempered martensite is 93% or more, and ferrite is 7% or less (including 0%) by area fraction. It provides an ultra-high-strength hot-rolled steel sheet with excellent shape quality and bendability, and a manufacturing method thereof. [Relationship 1] 0.32 ≤ (C+0.2Mn) ≤ 0.53 [Relationship 2] 130 ≤ (C+0.2Mn)/B ≤ 450 [Relationship 3] 5 ≤ (C+0.2Mn)/Ti ≤ 45 (However, the contents of C, Mn, B, and Ti in the relational formulas 1 to 3 are weight %.)