Ferritic stainless steel having reduced carbon sludge adsorption for exhaust system heat exchanger and method of manufacturing same

A ferritic stainless steel for an exhaust system heat exchanger, the ferritic stainless steel comprising, in percent (%) by weight of the entire composition, 0.003 to 0.1% of carbon (C), 0.01 to 2.0% of silicon (Si), 0.01 to 1.5% of manganese (Mn), 0.05% or less of phosphorus (P), 0.005% or less of sulfur (S), 10 to 30% of chromium (Cr), 0.02 to 0.10% of titanium (Ti), 0.001 to 0.15% of aluminum (Al), 0.008 to 0.03% of nitrogen (N), 0.3 to 0.6% of niobium (Nb), 0.01 to 2.5% of molybdenum (Mo), and the remainder of iron (Fe) and other inevitable impurities,

• wherein:
• TiN precipitates having a size of 0.1 μm or more are distributed in a surface layer of a ferrite matrix at a concentration of 2.5*104 ea/mm2 or less and TiN precipitates, TiN·NbC complex precipitates, and NbC precipitates having a size of 0.1 μm or more respectively are distributed in the surface layer of the ferrite matrix and satisfy Expression 1:
• {Z/(X+Y)}≥20 Expression 1
• where X is the number of the TiN precipitates per unit area, ea/mm2, Y is the number of the TiN·NbC complex precipitates per unit area, ea/mm2, and Z is the number of the NbC precipitates per unit area, ea/mm2.