Super Duplex

Heat treatment of duplex stainless steel is usually restricted to their initial production, in the form of solution annealing.

Ferrite content is a measure of the amount of ferrite in a steel. Ferrite is one form of microstructure that may exist within a steel.

Ferrite content in duplex stainless steels should be close to 50%, and within the range of 35-60%, in order to optimise their properties.

ASTM is the American Society for Testing and Materials, and A473 is the ‘Standard Specification for Stainless Steel Forgings’.

ASTM A240 is the ‘Standard Spec for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet and Strip for Pressure Vessels and General Use’.

A790 is the ‘Standard Specification for Seamless and Welded Ferritic/Austenitic Stainless Steel Pipe’.

ASTM A479 is the ‘Standard Specification for Stainless Steel Bars and Shapes for use in Boilers and Other Pressure Vessels’.

ASTM is the American Society for Testing and Materials, and A276 is the ‘Standard Specification for Stainless Steel Bars and Shapes’.

Super duplex stainless steel is 3-4x higher yield strength, 2x the resistance to pitting corrosion, yet less than twice the cost than 316.

Super duplex stainless steels have been used to substitute 904L (UNS N08904, 1.4539) austenitic stainless steels for many applications.

254SMO (UNS S31254, ASTM F44, 1.4547) is a super austenitic stainless steel, that can be substituted by super duplex for many applications.

The nearest equivalent cast specifications to UNS S32750 are ASTM A890, ASTM A995 and ASME SA351/995 grade CE3Mn or 5A.