Duplex stainless steel sheet having excellent corrosion resistance and method for manufacturing the same

Abstract

Provided are a duplex stainless steel sheet having high surface quality and high corrosion resistance manufactured through a twin roll strip casting process, and a method for manufacturing the duplex stainless steel sheet.

What is claimed is: 
     
         1 . A method for manufacturing a duplex stainless steel sheet having high corrosion resistance, the method comprising:
 supplying molten steel having a stainless steel composition comprising, by wt %, carbon (C): 0.1% or less (excluding 0%), silicon (Si): 0.2% to 1.0%, manganese (Mn): 1.0% to 4.0%, chromium (Cr): 19.0% to 23.0%, nickel (Ni): 1.0% to 3.0%, nitrogen (N): 0.1% to 0.3%, molybdenum (Mo): 0.5% to 3.0%, and a balance of iron (Fe) and inevitable impurities; and   casting the supplied molten steel as a strip by discharging the molten steel through a gap between a pair of rotating casting rolls while solidifying the molten steel,   wherein each of the casting rolls comprises fine grooves in a surface thereof, and the fine grooves have a sum of a ridge width and a furrow width within a range of 600 μm to 1200 μm, a depth of 100 μm to 200 μm, and a ridge area fraction of 10% to 40% in a widthwise center region and 40% to 70% in a widthwise edge region.   
     
     
         2 . The method of  claim 1 , wherein the ridge area fraction gradually increases from the widthwise center region to the widthwise edge region. 
     
     
         3 . The method of  claim 1 , wherein a transition region between the widthwise center region to the widthwise edge region has a width of 50 mm to 200 mm. 
     
     
         4 . The method of  claim 1 , wherein after the casting of the supplied molten steel, the method further comprises hot rolling at a reduction ratio of 20% to 50%. 
     
     
         5 . The method of  claim 4 , wherein after the hot rolling, the method further comprises coiling, cold rolling, and annealing. 
     
     
         6 . A duplex stainless steel sheet having high corrosion resistance, the duplex stainless steel sheet comprising, by wt %, carbon (C): 0.1% or less (excluding 0%), silicon (Si): 0.2% to 1.0%, manganese (Mn): 1.0% to 4.0%, chromium (Cr): 19.0% to 23.0%, nickel (Ni): 1.0% to 3.0%, nitrogen (N): 0.1% to 0.3%, molybdenum (Mo): 0.5% to 3.0%, and a balance of iron (Fe) and inevitable impurities,
 wherein the duplex stainless steel sheet has a microstructure comprising ferrite and austenite,   wherein the duplex stainless steel sheet has a pitting potential of 600 mV to 720 mV.   
     
     
         7 . The duplex stainless steel sheet of  claim 6 , wherein the duplex stainless steel sheet comprises ferrite in an area fraction of 40% to 60% and austenite in an area fraction of 40% to 60%. 
     
     
         8 . The duplex stainless steel sheet of  claim 6 , wherein the duplex stainless steel sheet has the following PREN index within a range of 25 or greater,
 PREN index=Cr+3.3Mo+30N where each element symbol refers to a content of each element in wt %.   
     
     
         9 . The duplex stainless steel sheet of  claim 6 , wherein the duplex stainless steel sheet is manufactured by the method of  claim 1 .