Development of Commercial Nitrogen-Rich Stainless Steels

Abstract

This paper reviews the development of nitrogen alloyed stainless steels. Nitrogen alloying of austenitie stainless steels started at an early stage and was to a large extent caused by nickel shortage However, direct technical advantages such as increased strength of the nitrogen alloyed steels made them attractive alternatives to the current steels It was not until the advent of the AOD (Argon Oxygen Decarburisation) process in the late 1960s that nitrogen alloying could be controlled to such accuracy that it became successful commercially on a broader scale. The paper describes production aspects and how nitrogen addition influences microstructure and the resulting properties of austenitie and duplex stainless steels. For austenitie steels there are several reasons for nitrogen alloying. Apart from increasing strength nitrogen also improves structural stability, work hardenmg and corrosion resistance. For duplex steels nitrogen also has a decisive effect in controlling the microstructure during thermal cycles such as welding.