STEEL MATERIAL HAVING EXCELLENT CORROSION RESISTANCE IN DEW CONDENSATION ENVIRONMENT CONTAINING SULFIDE AND METHOD FOR PRODUCING SAME
The present invention relates to a steel material having excellent corrosion resistance for use in an oil tanker, a crude oil tank, and the like and, particularly to a steel material having excellent corrosion resistance in a dew condensation environment containing a sulfide gas and a method for producing the same.
1 . A steel material, having excellent corrosion resistance in a dew condensation environment containing a sulfide gas, comprising, by weight percent (wt %), 0.02 to 0.2% of carbon (C), 0.1 to 1.0% of silicon (Si), 0.2 to 2.0% of manganese (Mn), 0.03% or less of phosphorus (P), 0.03% or less of sulfur (S), 0.05 to 0.5% of copper (Cu), 0.05 to 0.5% of nickel (Ni), 0.02 to 0.5% of molybdenum (Mo), 0.1% or less of aluminum (Al), 0.05 to 0.5% of chromium (Cr), 0.001 to 0.01% of calcium (Ca), and the balance of iron (Fe) and inevitable impurities,
wherein a sensitivity index of sulfide dew point corrosion, given by Relational Expression 1, is 1.7 or more to 2.5 or less
Sensitivity Index of Sulfide Dew point corrosion=0.4Ca/S+5Cr+6Mo+2Cu+Ni−0.5Mn (Relational Expression 1)
where Ca, S, Cr, Mo, Cu, Ni, and Mn denote contents (wt %) of corresponding elements.
2 . The steel material of claim 1 , wherein a content of the Ni is greater than or equal to a content of the Cu, and is 1.5 times or less the content of the Cu.
3 . The steel material of claim 1 , wherein the Cu is 0.002 to 0.01%.
4 . A method for producing a steel material, having excellent corrosion resistance in a dew condensation environment containing a sulfide gas, by hot-rolling and cooling a slab comprising, by weight percent (wt %), 0.02 to 0.2% of carbon (C), 0.1 to 1.0% of silicon (Si), 0.2 to 2.0% of manganese (Mn), 0.03% or less of phosphorus (P), 0.03% or less of sulfur (S), 0.05 to 0.5% of copper (Cu), 0.05 to 0.5% of nickel (Ni), 0.02 to 0.5% of molybdenum (Mo), 0.1% or less of aluminum (Al), 0.05 to 0.5% of chromium (Cr), 0.001 to 0.01% of calcium (Ca), and the balance of iron (Fe) and inevitable impurities,
wherein a sensitivity index of sulfide dew point corrosion, given by Relational Expression 1, is 1.7 or more to 2.5 or less
Sensitivity Index of Sulfide Dew point corrosion=0.4Ca/S+5Cr+6Mo+2Cu+Ni−0.5Mn (Relational Expression 1)
where Ca, S, Cr, Mo, Cu, Ni, and Mn denote contents (wt %) of corresponding elements, and
wherein the cooling is performed at a cooling rate of 10° C./s or higher between cooling start temperature, higher than or equal to Ar3 temperature, and cooling stop temperature of (Ae1−30° C.) to 600° C.
5 . The method of claim 4 , wherein a content of the Ni is greater than or equal to a content of the Cu, and is 1.5 times or less the content of the Cu.
6 . The method of claim 4 , wherein the Cu is 0.002 to 0.01%.