|Melting point -210 °C
This element can occur both as a steel parasite and as an alloying element. Parasitic because of the reduction in toughness through precipitation processes, causing susceptibility to ageing and blue brittleness (deformation in the blue heat range of 300-350 °C) and on account of the possibility of initiation of intercrystalline stress cracks in unalloyed and low alloy steels. As an alloying element, N extends the γ-phase and stabilizes the austenitic structure. In austenitic steels increases strength and above all the yield point plus mechanical properties in heat. As a result of nitride formation during nitriding, N permits high surface hardness to be achieved (nitriding).