Nickel (Ni) in stainless steels has no direct influence on corrosion resistance. Thanks to nickel austenitic stainless steels exhibit a wide range of ideal mechanical properties, like excellent ductility and toughness, even at high strength levels. These properties are retained up to cryogenic temperatures.

Carbon (C) is an important alloying element in all-ferrous metal based materials. Carbon is a very strong austenitizer and increases the strength of steel. By increasing its content we raise hardness and toughness and make the steel heat treatable by quenching and tempering to develop the martensite phase. However, resistance to fracture, ductility and weldability are reduced with higher carbon content.

Nitrogen (N) raises the strength and the resistance of steel, while at the same time it reduces its ductility. More specifically, it improves the mechanical properties of austenitic and duplex stainless steels, increasing at the same time their resistance to localized corrosion like pitting or intergranular.

Manganese (Mn) is essential to steel making because of two key properties: its ability to combine with sulphur and its powerful deoxidation capacity. Manganese will combine preferentially with sulphur to form manganese sulphide (Mn S) which favour workability and weldability of steel. Moreover, its presence increases the hardenability of the steel. Its ability to stabilize the austenite in steel is used to substitute nickel in some austenitic stainless steels.

Copper (Cu) improves resistance to corrosion from sulphuric acid.

Neutral elements
Sulphur (S) και Phosphorous (P) are undesired impurities. They act on reducing ductility, weldability. At the same time they reduce resistance to corrosion and increase steel’s inclination to cracking.