What are stainless steels?

Stainless steels are alloys of iron, chromium, and carbon, which are sometimes complemented with other elements, mainly nickel.

It is the addition of chromium that gives these steels their stainless characteristic. In oxidizing environments like air, chromium forms a very thin and compact oxide layer that insulates the material from corrosive attacks. Stainless steels are classified based on the different elements and the relative quantities of each one involved in their composition.

In general, there are four basic families of stainless steels: martensitic, ferritic, austenitic, duplex, and precipitation-hardened (PH).

Austenitic

These are alloys of iron, chromium, nickel, and carbon. The addition of nickel modifies the structure of these materials. It is the group of stainless steels with the highest performance from the point of view of component and equipment manufacturing, as well as service behavior. They have excellent formability properties, good weldability, and high resistance to various types of corrosion. As an example, alloys 201, 301, 304, and 316L are included.

Ferritic

Ferritic steels are also alloys of iron, chromium, and carbon, with a higher chromium content and less carbon than martensitic ones. The typical values of these elements are: C<0.12%; Cr 16-18% (types 409L, 430, 441 steels).

Martensitic

These stainless steels are alloys of iron, chromium, and carbon with typical contents of C: 0.15% and Cr: 12-15%.

These steels undergo structural modifications with temperature, so they are usually subjected to quenching and tempering heat treatments.

After these processes, they achieve good mechanical properties and have sufficient corrosion resistance. Their main application is for surgical instruments and cutlery (type 410, 420, 440A steels).

Duplex

Stainless steels duplex are microstructurally composed of two phases: ferrite and austenite. They contain as alloying elements, iron, chromium, carbon, and nickel, this last element in a smaller percentage than in the austenitic ones.

As a general rule, they have higher mechanical properties and corrosion resistance than ferritic and austenitic steels (for example, steels 2001, 2304, 2205).

Precipitation Hardened (PH)

This type of steel offers an alternative to austenitic stainless steels when high mechanical strength and machinability are desired. They are Fe-Cr-Ni alloys characterized by mechanical resistance, which is obtained from hardening by aging heat treatment, for example, 17-4PH, 17-7PH).

At Ulbrinox we offer you the best quality Stainless Steel tailored to your needs, in flat, sheet, roll, or strip presentations, and with a wide range of alloys: