The Different Types of Stainless Steel

Stainless steel is one of the most worked materials in our workshop. After talking about its discovery (partly thanks to research, part by chance), we'll look more in detail at the different types of steel we treat.

With many respects, welding stainless steel is not different from other metallic materials. However, due to its non-corrosive quality, it requires special care during the heating and cooling phase, and in the choice of the filler metal.

If we consider all the possible combinations of the alloys, the complete list of the types of stainless steels would be very long. However, they can be divided into five different categories.

Austenitic

Thanks to its weldability and resistance, it’s the most widespread type of stainless steel, and they're used in several applications such as consumer products, chemical plants or food processing. They are made of alloys of chrome and nickel, or chrome, nickel, manganese and nitrogen.

Ferritic

Ferritic stainless steel contains a lower percentage of carbon (less than 0.1%) and it's composed mainly by an alloy of iron and chrome in different proportions. Compared to austenitic steels, ferritic steels are less resistant to high temperatures and cannot be welded with the same high standards. For this reason, they are mainly used for consumer products, such as exhaust systems or kitchen sinks.

Martensitic

They're similar to ferritic steel in composition, but they contain a higher part of carbon (up to 1%). They're usually used for precision tools such as medical instruments, but they have to be tempered to be truly resistant.

Austenitic-ferritic

Although still in the development phase, this type of steel is growing in popularity. It's also called duplex, because it has a mixed austenitic-ferritic structure that makes it more resistant to mechanic and corrosive stress and, at the same time, with the same level of weldability of austenitic steel.

Precipitation hardening stainless steel

This type of steel is made very resistant by the addition of elements like aluminium, copper and niobium, which allow it to undergo a hardening process.

Furthermore, it can be modelled in different shapes without compromising the structure, offering the same resistance to corrosion of austenitic steels.