Key properties

Abstract

Nitrogen as an alloying element in steel causes non-trivial and even extraordinary changes in properties. In particular this statement relates to an unusual combination of the yield strength and fracture toughness. For the first time perhaps, mechanical properties of nitrogen steels were tested by Andrew (1912) who constructed a furnace for melting under high pressure, obtained Fe-N samples and revealed the nitrogen-caused increase in yield strength as well as an austenitizing nitrogen effect. Frehser and Kubisch (1963) were the first to discover that, with increasing nitrogen content, an increase in the yield strength of austenitic steels is not accompanied by the expected deterioration of toughness. In fact, this result meant that nitrogen steels represent a new promising class of engineering materials. It was also shown later in a number of studies that nitrogen in steel can improve fatigue life, strength at low and elevated temperatures, cold work hardening, wear resistance etc.