Standard duplex and superduplex stainless steels (SDSS) are increasingly used due to their favorable combination of corrosion and mechanical properties. However, for some specific applications – e.g. in the chemical and offshore industry – SDSS available on the market do not fulfil all the requirements with respect to corrosion resistance, strength and toughness.

Therefore a SDSS grade with a PREN value (% Cr + 3.3% Mo + 16% N) of more than 44 has recently been developed at Böhler (A920). On basis of thermodynamically calculations the chemical composition was balanced in order to obtain an austenite volume fraction of about 60% by increasing the nitrogen content to a level above 0.35 weight per cent.

Corrosion tests, especially SCC in chloride environment, display an outstanding resistance of this new steel grade which might allow extended application in highly aggressive environments. The pitting and crevice corrosion behavior was found to be evidently superior in comparison to commercial superduplex grades.

The desired mechanical properties (0.2% yield strength level > 600 MPa and high toughness values) have also been achieved. The only drawback is a slightly decreased phase stability, i.e. a slightly higher tendency to sigma-phase formation.

The parameters of an industrial scale production are similar to that of superduplex grades, the manufacture of forged and rolled bar material and medium size forgings with excellent properties will be shown in examples.