Stainless steel

High-alloyed iron based alloys with an extended ?-phase are called austenitic. Unlike other steels, austenitics do not have transformations when are heated or cooled, so heat treatment for strengthening austenitic steels is not used. In austenitic steels, chromium provides heat resistance and corrosion resistance, nickel stabilizes austenitic structure and increases heat resistance, plasticity and porosity, also at high and low temperatures. The typical composition of austenitic steel contains 18% chromium and 8% nickel.

Ferritic steels are created at low carbon content and a large number of alloying elements. As a rule they contain not more than 30% of chromium and 0,12% of carbon. Ferritic steels have good strength, good plasticity, excellent corrosion resistance, are characterized by moderate ability to undergo pressure treatment and are relatively inexpensive. The range of use of ferritic steels is very wide – from living conditions to exploitation in aggressive environments and high temperatures.

In duplex steels there are both austenitic and ferritic phases. As a result, duplex steel combines a lot of quality properties of both. Due to the high content of chromium and nitrogen, and more often of molybdenum, these steels show good resistance to continuous and local corrosion. Duplex microstructure ensures high strength and resistance to corrosion cracking under stress. Duplex steel has good welding ability and is easily machined.

Martensitic steels, like ferritic, contain on average 12% to 17% of chromium, but have a higher carbon content. The features of martensitic steels that can be emphasized, are: high level of corrosion resistance in alkaline solutions and some acid solutions, in conditions of high humidity; high heat resistance, self-calcining ability, low plasticity for high hardness, high resistance to hydrogen, complexity of cutting.