What is the Duplex Steel Grades?
ASTM A815 UNS S31803 Buttweld Fittings
People described 31803 as a duplex stainless steel with a microstructure of 50:50 austenite and ferrite. The steel combines good mechanical strength (typically up to over 480 MPa yield strength) and ductility with moderate to good corrosion resistance in a variety of environments.

ASTM A815 UNS S32205 Buttweld Fittings
2205 is a duplex stainless steel, with a chemical composition of nearly equal proportions of austenite and ferrite. This combination allows the alloy to be stronger and tougher than standard austenitic steels.

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