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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.