API TR 938-C

Description

This report covers many of the “lean,” “standard,” “super,” and “hyper” grades of duplex stainless steels (DSSs) most commonly used within refineries. These terms have not been firmly established by the industry, and their use may vary between literature references and suppliers. The ISO document ISO 17781 Petroleum, Petrochemical and Natural Gas Industries—Test Methods for Quality Control of Microstructure of Ferritic/Austenitic (Duplex) Stainless Steels provides a fairly consistent and inclusive classification of these materials based on their chemical composition and corrosion resistance.

In an attempt to facilitate future cross reference, this document adopted materials classifications consistent with ISO 17781. The following list summarizes the classification group (refer to Table 1 for a complete list of grades):
— Type 20 Cr Duplex, Group A (Lean DSSs): S32001, S32101, S32202, S82011, S82031, and S82441;
— Type 20 Cr Duplex, Group B (Lean DSSs): S32003, S32304, S31500, S81921;