Stainless steel

Stainless steels have very good corrosion resistance compared to carbon steels, coupled with impressive mechanical properties. This combination is the result of the addition of a relatively high proportion of alloys, in particular chromium (Cr). They tend to be more expensive, and so reserved for applications that demand their superior properties.

Based on their crystalline structure, they are grouped in five families: ferritic, austenitic, martensitic, precipitation-hardening (PH) and duplex. Ferritic stainless steel is not seen much outside industrial applications, automotive and white goods, for which it is well suited. The lower alloy content makes it less expensive than the more common austenitic types.

Austenitic stainless steel, which includes the very popular 300 series, is a good all-rounder with high resistance to corrosion. It is non-magnetic (which makes it easy to distinguish from other steels), with excellent formability, machining properties and weldability.

Martensitic stainless steel has high hardness and strength, good for industrial applications, household appliances and some knife blades, with moderate resistance to corrosion. Its high hardness makes it relatively more difficult to form, cut and weld.

Duplex types are a modification on austenitic grades, designed to provide higher strength with comparable or improved corrosion resistance. PH stainless steels are a family of corrosion resistant alloys, which can be heat treated to tensile strength several times greater than austenitic types. They are used in very demanding applications in aerospace, off-shore and nuclear energy, for example.