Duplex stainless steel is divided into 4 grades.
1: Low alloy type: S31500, S32001, S32003, S32304
1) S31500 duplex stainless steel chemical 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.
2) S32001 duplex stainless steel chemical 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.
3) S32003 duplex stainless steel chemical 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.
4) S32304 duplex stainless steel chemical 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,
1) S31803 duplex stainless steel alloy 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.
2) S32205 duplex stainless steel alloy 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 alloy 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,
1) S32750 duplex stainless steel chemical 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.
2) S32760 duplex stainless steel chemical composition: Carbon: ≤0.03, Chromium: 24.0~26.0, Nickel: 6.0~8.0 , Mo: 3.0~4.0, Copper: 0.5~1.0, Nitrogen: 0.20~0.30, Tensile strength ≥750, Yield strength ≥550, Elongation: ≥25.
(Super) Duplex Stainless Steel Pipe
Duplex stainless steel has an α+Y dual-phase structure, so its performance is similar to that of austenitic stainless steel and ferritic stainless steel. It is a type of stainless steel with the best high strength and corrosion resistance. Usually, when the C content is low, the Cr content is 18%~28%, and the Ni content is 3%~10%. Some steels also contain alloying elements such as Mo, Cu, Nb, Ti, and N. Compared with ferrite, it has higher plasticity and toughness, no room temperature brittleness, and significantly higher intergranular corrosion resistance and welding performance. At the same time, it also maintains the 475℃ brittleness of ferritic stainless steel and high thermal conductivity and has the characteristics of superplasticity.
Compared with austenitic stainless steel, the yield strength is significantly higher, and the resistance to intergranular corrosion, stress corrosion, corrosion fatigue, and abrasion is significantly improved.
Common standards for duplex stainless steel pipes:
ASTM A789 (ASME SA789) General purpose seamless and welded ferritic/austenitic stainless steel pipes,
ASTM A790 (ASME SA790) Seamless and welded ferritic/austenitic stainless steel nominal pipes,
ASTM A928 (ASME SA928) Standard specification for ferritic/austenitic (duplex) stainless steel pipes with filler metal,
GB/T 21832-2008 Austenitic-ferritic duplex stainless steel welded steel pipes,
GB/T 21833-2008 Austenitic-ferritic duplex stainless steel seamless steel pipes,
Performance characteristics of duplex stainless steel pipes:
1. Excellent resistance to overall corrosion and local corrosion, especially stress corrosion, pitting corrosion, crevice corrosion, corrosion fatigue, and abrasion
2. Good weldability
3. Good comprehensive mechanical properties
4. Good resistance to intergranular corrosion
Post time: May-09-2025