19.09 / 2019

How many types of stainless steel are there?

How to understand what type is suitable for the manufacture of stainless steel products?

Today we will analyze 3 main types:

Ferritic steels

These steels are used for the manufacture of products operating in oxidizing environments (for example, in nitric acid solutions), for household appliances, in the food and light industry, and for heat exchange equipment in power engineering. Ferritic chromium steels have high corrosion resistance in nitric acid, aqueous solutions of ammonia, in ammonium nitrate, a mixture of nitric, phosphoric and hydrofluoric acids, as well as in other aggressive environments.

Austenitic steels

The main advantage of austenitic steels is their high service characteristics (strength, ductility, corrosion resistance in most working environments) and good processability. Therefore, austenitic corrosion-resistant steels are widely used as a structural material in various engineering industries. Theoretically, products made of austenitic stainless steels under normal conditions are non-magnetic, but after cold deformation (any machining) they can exhibit some magnetic properties (part of the austenite turns into ferrite).

Duplex stainless steels

Duplex stainless steels must be selected as extremely corrosion resistant material. Duplex stainless steels have a mixed microstructure of ferrite and austenite.

For this reason, their properties are similar to both ferritic and austenitic steels. They are extremely resistant to corrosion - both pitting and crevice. Their disadvantage is the difficulty of welding. There are two types of duplex steels known as “first generation” and “second generation”. The improved second generation steels contain more nitrogen and are significantly more resistant to pitting corrosion. Their difference from super duplex stainless steels is that their numerical equivalent of pitting resistance (PREN) is less than 40, while super duplex steels have a PREN of more than 40.