Austenitic-ferritic stainless steel

An austenitic-ferritic stainless steel having excellent deep drawability, the stainless steel having austenite and ferrite two-phase structure, and comprising about 0.2% or less C, about 4% or less Si, about 10% or less Mn, about 0.1% or less P, about 0.03% or less S, about 15 to about 35% Cr, about 1 to about 3% Ni, about 0.05 to about 0.6% N, by mass, and balance of Fe and inevitable impurities, the amount of (C+N) in the austenite phase being in a range from about 0.16 to about 2% by mass, and the volume percentage of the austenite phase being in a range from about 10 to about 85%.

An austenitic-ferritic stainless steel having excellent punch-stretchability and crevice corrosion resistance, comprising about 0.2% or less C, about 1.2% or less Si, about 2% or less Mn, about 0.1% or less P, about 0.03% or less S, about 15 to about 35% Cr, about 1% or less Ni, about 0.05 to about 0.6% N, by mass, and balance of Fe and inevitable impurities, the percentage of the austenite phase in the metal structure being in a range from about 10 to about 85% by volume.

An austenitic-ferritic stainless steel having excellent corrosion resistance at welded part, comprising about 0.2% or less C, about 1.2% or less Si, about 4 to about 12% Mn, about 0.1% or less P, about 0.03% or less S, about 15 to about 35% Cr, about 1% or less Ni, about 0.05 to about 0.6% N, by mass, and balance of Fe and inevitable impurities, the percentage of the austenite phase being in a range from about 10 to about 85% by volume.

An austenitic-ferritic stainless steel having excellent resistance to intergranular corrosion, comprising about 0.2% or less C, about 0.4% or less Si, about 2 to about 4% Mn, about 0.1% or less P, about 0.03% or less S, about 15 to about 35% Cr, about 1% or less Ni, about 0.05 to about 0.6% N, by mass, and balance of Fe and inevitable impurities, the percentage of the austenitic phase being in a range from about 10 to about 85% by volume.