HIGH STRENGTH AND LOW TOUGHNESS COLD-ROLLED STEEL SHEET HAVING GOOD FRACTURE CHARACTERISTICS METHOD FOR MANUFACTURING SAME

摘要

Provided are a cold-rolled steel sheet with a high strength, low toughness, and excellent fracture characteristics, and a manufacturing method thereof. According to the present invention, the cold-rolled steel sheet comprises: 0.30-0.70 wt% of C; 0.2-1.0 wt% of Mn; 0.005-0.5 wt% of Si; 0.005-0.02 wt% of P; 0.01 wt% or less of S; 0.01-0.1 wt% of Al; 0.005-0.1 wt% of Cr; and residual Fe and other unavoidable impurities. A steel refined structure comprises: 50-95% of perlite; and residual ferrite. An average size of crystalline particle of the ferrite structure is 10-50 μm. An average size of perlite colony is 10-50 μm. The thickness is 1.5-3.0 mmt. A Charpy absorbed energy at a room temperature satisfies 1.0-5.0 J (0.05-0.35 J/cm2).