Alloying Elements

THE INFLUENCE OF ALLOYING ELEMENTS ON THE PROPERTIES OF STAINLESS STEEL

ELEMENT	EFFECT ON STAINLESS STEEL
Chromium	Forms a passive film with oxygen that prevent the further diffusion of oxygen into the surface Composition needs to contain at least 10.5% to be a stainless steel.
Nickel	Increases ductility and toughness. Increase corrosion resistance to acids Addition creates non-magnetic structure.
Molybdenum	Increases pitting and crevice corrosion resistance. Increase resistance to chlorides.
Copper	Increase corrosion resistance to sulfuric acid.
Titianium/Niobium	Ties up carbon and prevents inter-granular corrosion in welded zone of ferritic grades.
Nitrogen	Increase strength and corrosion resistance in austenitic and duplex grades.
Silicon	Improves resistance to high temperature scaling.
Sulfur	Usually kept low except for “free-machining” grades.
Carbon	Usually kept low. Used in martensitic grades to increase strength and hardness.

REFERENCE: “Alloying Elements in Stainless Steel” Pierre-Jean Cunat Published by the International Chromium Development Association.