HIGH PROCESSING HIGH STRENGTH COLD ROLLED STEEL SHEET HAVING SUPERIOR PROCESSING PROPERTY AND BENT RESISTANCE AND METHOD FOR MANUFACTURING THE SAME

摘要

PURPOSE: A high processing high strength cold rolled steel sheet and a method for manufacturing the same are provided which is easily processed using a press due to superior processing property, and is applied to the outer panel and the inner panel of impact absorbing area of an automobile due to superior bent resistance in final products by increasing the strength in press, coating and drying processes during manufacturing of the automobile components. CONSTITUTION: The high strength cold rolled steel sheet having superior processing property and bent resistance comprises 0.005 wt.% or less of carbon, 0.005 wt.% or less of nitrogen, 0.02 wt.% or less of sulphur, 0.2 to 2.0 wt.% of manganese, 0.02 to 0.08 wt.% of aluminum, 0.02 to 0.10 wt.% of phosphorus, 0.005 to 0.03 wt.% of titanium and other Fe and inevitable impurities, wherein a ratio of manganese/titanium is 25 or more. The method for manufacturing the high processing high strength cold rolled steel sheet comprises the steps of homogenizing annealing an ultra-low carbon aluminum killed steel comprising the above compositions in the temperature range of 1050 to 1300 deg.C; final hot rolling the homogenizing annealed steel in the temperature range of 850 to 950 deg.C which is directly above the Ar3 transformation point; hot coiling the final hot rolled steel in the temperature range of 450 to 650 deg.C; rolling the hot coiled steel to a cold reduction ratio of 40 to 80%; and continuous annealing the cold rolled steel in the temperature ranging from 750 to 900 deg.C.