ALLOYS

The most common alloy elements in stainless steel are chromium, nickel, molybdenum, titanium, niobium, vanadium and cobalt. From a minimum content of 12% chromium, stainless steel becomes resistant. On the surface, a thin layer of chromium oxide forms due to the influence of oxygen. This protects the steel beneath it from other chemical influences.

FERRITIC STEELS

There are two types of ferritic steels. Their chrome content is either between 11 and 13% or around 17%. The former are only referred to as “corrosion-inert” due to their lower chrome content. They are used whenever a long service life and safety are important, while the optical appearance is less significant. Examples include container, wagon and vehicle construction.

FERRITIC AUSTENITIC STEELS (DUPLEX STEEL)

Due to having both ferrite and austenite structure components, these stainless steels are often also called duplex steels. They combine two particularly good properties: increased strength as rust-free chrome-nickel steel and increased ductility and formability as rust-free chromium steel. Due to its high resistance to surface corrosion, duplex steel is mainly used in the chemical and petrochemical industry, as well as in offshore projects.

MARTENSITIC STEELS

These stainless steels have a chrome content of 12–18% and a carbon content of over 0.1%. They can be tempered by heating and quickly cooling, and have a high strength that increases as the carbon content rises. They are used, for example, in the production of razor blades, knives and scissors. However, they are less corrosion resistant than other stainless steels.