Steel sheet having excellent hydrogen induced cracking resistance and longitudinal strength uniformity, and manufacturing method therefor

Abstract

The present invention relates to a steel sheet used for a line pipe or the like, and particularly, to a steel sheet having excellent hydrogen induced cracking resistance, and longitudinal strength uniformity, and a method for manufacturing the same.

1 . A method for manufacturing a steel sheet having excellent hydrogen induced cracking resistance and longitudinal strength uniformity, comprising operations of:
 reheating a steel slab including 0.02 wt % to 0.06 wt % of carbon (C), 0.1 wt % to 0.5 wt % of silicon (Si), 0.8 wt % to 1.8 wt % of manganese (Mn), 0.03 wt % or less of phosphorus (P), 0.003 wt % or less of sulfur (S), 0.06 wt % or less of aluminum (Al), 0.01 wt % or less of nitrogen (N), 0.01 wt % to 0.08 wt % of niobium (Nb), 0.005 wt % to 0.05 wt % of titanium (Ti), and 0.0005 wt % to 0.005 wt % of calcium (Ca), one or more selected from a group consisting of 0.05 wt % to 0.3 wt % of nickel (Ni), 0.05 wt % to 0.3 wt % of chromium (Cr), 0.02 wt % to 0.2 wt % of molybdenum (Mo), and 0.005 wt % to 0.1 wt % of vanadium (V), and a balance of iron (Fe) and other inevitable impurities;   finish hot rolling the reheated steel slab in a temperature range of Ar3+50° C. to Ar3+150° C.; and   cooling a steel sheet at a cooling rate of 30° C. to 100° C./sec after the hot rolling operation, and performing inclined cooling to satisfy the following [cooling conditions] based on a temperature of the cooling point,   [Cooling conditions]   Cooling start temperature: 650° C. to 850° C.   Cooling end temperature: 400° C. to 700° C.   Cooling start temperature-cooling end temperature: 100° C. to 350° C.   
     
     
         2 . The method for manufacturing a steel sheet having excellent hydrogen induced cracking resistance and longitudinal strength uniformity of  claim 1 , wherein the steel slab is reheated to 1100° C. to 1300° C. 
     
     
         3 . The method for manufacturing a steel sheet having excellent hydrogen induced cracking resistance and longitudinal strength uniformity of  claim 1 , wherein a cumulative rolling reduction ratio is 50% or more during the hot finish rolling.