Duplex stainless steel is divided into 4 grades.
1: Low alloy type: S31500, S32001, S32003, S32304
S31500 duplex stainless steel composition: carbon: ≤0.03, chromium: 18.0~19.0, nickel: 4.5~5.25, molybdenum: 2.5~3.0, nitrogen: 0.05~0.10, tensile strength ≥630, yield strength ≥440, elongation: ≥30.
S32001 duplex stainless steel composition: carbon: ≤0.03, chromium: 19.5~21.5, nickel: 1.0~3.0, molybdenum: ≤0.60, copper: ≤1.0, nitrogen: 0.05~0.17, tensile strength ≥620, yield strength ≥450 , Elongation: ≥25.
S32003 duplex stainless steel composition: carbon: ≤0.03, chromium: 19.5~22.5, nickel: 3.0~4.0, molybdenum: 1.5~2.0, nitrogen: 0.14~0.20, tensile strength ≥620, yield strength ≥450, elongation: ≥25.
S32304 duplex stainless steel composition: carbon: ≤0.03, chromium: 21.5~24.5, nickel: 3.0~5.5, molybdenum: 0.05~0.60, copper: 0.05~0.60, nitrogen: 0.05~0.20, tensile strength ≥600, yield strength ≥450, elongation: ≥25.
2: Medium alloy type: S31803, S32205,
S31803 duplex stainless steel composition: carbon: ≤0.03, chromium: 21.0~23.0, nickel: 4.5~6.5, molybdenum: 2.5~3.5, nitrogen: 0.08~0.20, tensile strength ≥620, yield strength ≥400, elongation: ≥25.
S32205 duplex stainless steel composition: carbon: ≤0.03, chromium: 22.0~23.0, nickel: 4.5~6.5, molybdenum: 3.0~3.5, nitrogen: 0.14~0.20, tensile strength ≥655, yield strength ≥450, elongation: ≥25.
3: High alloy type: S32550,
S32550 duplex stainless steel composition: carbon: ≤0.04, chromium: 24.0~27.0, nickel: 4.5~6.5, molybdenum: 2.9~3.9, copper: 1.5~0.25, nitrogen: 0.10~0.25, tensile strength ≥760, yield strength ≥485, elongation: ≥15.
4: Super DSS: S32750, S32760,
S32750 duplex stainless steel composition: carbon: ≤0.03, chromium: 24.0~26.0, nickel: 6.0~8.0, molybdenum: 3.0~5.0, copper: ≤0.5, nitrogen: 0.24~0.32, tensile strength ≥800, yield strength ≥ 550, elongation: ≥15.
S32760 duplex stainless steel composition: carbon: ≤0.03, chromium: 24.0~26.0, nickel: 6.0~8.0, molybdenum: 3.0~4.0, copper: 0.5~1.0, nitrogen: 0.20~0.30, tensile strength ≥750, yield strength ≥550, elongation: ≥25.
Common standards for duplex stainless steel pipes:
ASTM A789 (ASME SA789) general purpose seamless and welded ferritic/austenitic stainless steel pipe,
ASTM A790 (ASME SA790) seamless and welded ferritic/austenitic stainless steel nominal pipes,
ASTM A928 (ASME SA928) Standard specification for filler metal electrofusion welded ferritic/austenitic (duplex) stainless steel tubing,
GB/T 21832-2008 Austenitic-ferritic duplex stainless steel welded steel pipe,
GB/T 21833-2008 Austenitic-ferritic duplex stainless steel seamless steel pipe,
