Ultra-high strength hot-rolled steel sheet having excellent bending processability and method for manufacturing same

Abstract

An aspect of the present invention relates to an ultra-high strength hot-rolled steel sheet having excellent bending processability, the steel sheet comprising, in terms of weight%, 0.18-0.28% of C, 1.2-2.2% of Mn, 0.1-0.5% of Si, 0.005-0.05% of P, 0.01% or less of S, 0.01-0.05% of Al, 0.01-0.10% of Ti, 0.001-0.0045% of B, 0.001-0.01% of N, and the remainder Fe and unavoidable impurities, whereina microstructure comprises, by area fraction, 90% or more of martensite, 4-10% of auto-tempered martensite, and 5% or less of residual austenite.

Description

technical field [0001] The present invention relates to an ultrahigh-strength hot-rolled steel sheet excellent in bending workability and a manufacturing method thereof. Background technique [0002] According to the body and passenger crash stability and CO 2 Strict requirements such as environmental regulations require ultra-high-strength and ultra-lightweight car bodies around the world. Therefore, ultra-high-strength steel sheets of 1.0 Gpa or higher are actively being developed. [0003] Most ultra-high-strength hot-rolled steel sheets used for bumper reinforcement materials and door impact beams, which are most vehicle body reinforcement materials, need to have high strength and excellent bending for roll forming (Roll Forming) quality and shape. [0004] In order to satisfy this physical property, steel plates for vehicle structural parts are basically composed of ferrite (Ferrite), bainite (Baintie), martensite (Martensite) and tempered martensite (Tempered Martens...

AI Technical Summary

Problems solved by technology

[0013] According to Patent Document 5, although an ultra-high tensile strength of 1.8 GPa can be ensured, the cold-rolled st

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