1. Rationale
The chemical composition of the super duplex grade UNS S32750 allows rather wide ranges of the alloying elements in order to comprise many different product forms. however, especially for tubes and pipe the best possible corrosion resistance is required in many applications. Therefore a minimum PRE* = 41 should be specified in all ASTM specifications for tube and pipe. With the minimum allowed contents of Cr, Mo and N the PRE can be less than 38. This means an increased risk of corrosion, in particular the critical pitting temperature could drop with nearly 10%, compared to common specified temperatures for the grade. With PRE min 41 the low end composition can be avoided. The PRE number is also helpful for material specialists for comparison and selection of the proper grade. *) PRE (Pitting Resitance Equivalent)= %Cr + 3.3x%Mo + 16x%N
Keywords
duplex stainless steel; ferritic/austenitic stainless steel; seamless steel tube; stainless steel tube; steel tube; welded steel tube; Austenitic stainless steel tube--specifications; Corrosion-resistant steel--specifications; Corrosive service applications--tube (steel); Duplex stainless steel--specifications; Ferritic steel tube--specifications; Seamless steel tube--specifications; Stainless steel tube--specifications; Structural steel (SS) tube--specifications; Welded steel tube--specifications ;
Citing ASTM Standards
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