Qualification of Super 13Cr UNS S41426 According to NORSOK M-650

Abstract 13Cr super martensitic stainless steel grades (SMSS-13Cr) show a good compromise between corrosion resistance, high strength and excellent toughness and are widely used in oil and gas applications. SMSS-13Cr that exhibits minimum yield strength of 110 ksi (759 MPa) was investigated in the past leading to different results concerning resistance against sulfide stress corrosion cracking (SSC). This contribution summarizes the qualification procedure for hot-rolled and forged 13Cr super martensitic stainless steel in 110 ksi condition according to NORSOK M-650, and the posterior requalification procedure. The qualification was carried out on UNS S41426. An optimized production route was defined to successfully meet a minimum yield strength of 110 ksi (759 MPa) in combination with an impact energy higher than 50 ft-lbs (68 J) at 14°F (-10°C). Resistance to sulphide stress corrosion cracking (SSC) per NACE TM0177 Method A and B was investigated in different conditions. A working window with respect to pH, pH2S, and chloride concentration at room temperature has been determined. The results of all investigations together with a verified manufacturing route led to a Super 13Cr material that is in conformance to NACE MR0175, Annex B.2.3, and the production route is qualified per NORSOK M-650. Since then, hot-rolled and forged bars of UNS S41426 110 ksi have been produced without degradation in performance compared with the qualified material.