WHAT IS STAINLESS STEEL?
In metallurgy, the term stainless steel refers to an iron-carbon alloy containing a minimum of 10.5% chromium (Cr) by chemical composition. The chromium element provides corrosion resistance to the alloy. Stainless steel is frequently preferred in modern applications, especially for materials expected to operate under harsh environmental conditions. Stainless steel is used in cutlery such as forks and knives, pots and other kitchen utensils, durable consumer goods like white goods, pumps, valves, and many other contemporary applications. Steels are highly susceptible to oxidation and corrosion. The development of stainless steels was primarily driven by the need to prevent corrosion of these materials over time.
Corrosion Resistance Mechanism and Classification
The basic principle is based on the formation of a passive layer of Cr₂O₃ due to the reaction of chromium (Cr) with oxygen present in the air. This passive layer protects the base metal from other corrosive substances in contact. Other elements contributing to passivation include nickel (Ni), molybdenum (Mo), and titanium (Ti). Although there are over 200 stainless steel grades in total, only about 10% are commonly used in applications. Stainless steels, which can offer highly attractive aesthetic results, are available in various forms such as coils, sheets/plates, wire, bars, hexagons, flat bars (lama), and angle profiles. Microstructure is especially important today for metallurgists and materials engineers in project design, process planning, and material development. Stainless steels are classified according to their microstructure:
Austenitic Stainless Steels
Ferritic Stainless Steels
Martensitic Stainless Steels
Duplex Stainless Steels
Precipitation-Hardened Stainless Steels