Welding of Ferritic Stainless Steels

Ferritic steel is a commonly used stainless steel in welding. It belongs to the stainless steel family which also includes austenitic, duplex, martensitic and precipitation hardening steels.  It is a type of stainless steel alloy and contains more than 12% chromium. The proportion of chromium may go up to 30%. However, the carbon content is less than 0.10%. It may or may not have nickel. 

Ferritic steel is available in different grades, depending on ferritic stainless steel composition. It can be classified into 1 to 5 grades as per the American Iron and Steel Institute (AISI). The grades 1 to 3 are referred to as standard grades while the grades 4 and 5 are referred to as speciality grades because they are used only in special cases.

The ferritic materials have a wide range of applications in the following industries:

• Industrial equipment

• Kitchenware

• Coldwater tanks

• Chemical and food processing

• Electrical cabinets

• Water treatment plan

• Automotive production

• Induction cookers

• Magnetic fasteners

• Dishwashers

• Kitchen sinks

• Coins

• Nuclear reactors

• Heat transfer applications

Development of Ferritic Stainless Steels

The history of ferritic steel can be traced to 1912 when Canada-born engineer Frederick Mark Becket discovered a ferrous alloy containing 25-27% chromium. It was the first high-chromium alloy which became heat-resisting stainless steel. However, it was not until the 1980s that ferritic steel became commercially popular.

Ferritic Stainless Steel Properties

The characteristic of ferritic steel is defined by its Body-Centred Cubic (BCC) crystal structure. This means that the crystal structure has a cubic atom cell with an atom in the centre. It is similar to pure iron at room temperature. It is also made up of microstructures called ferrite. Ferrite is a ceramic compound which is a mixture of iron oxide and one or more other metals with ferrimagnetic properties.

Ferritic steel has the following properties:

• Magnetic

• Non-hardenable by heat treatment

• Slightly hardenable by cold rolling

• Corrosion-resistant

• Good ductility and formability

• Low coefficient of thermal expansion

• High thermal conductivity

• High oxidation resistance

Weldability of Ferritic Steel

Though ferritic steel has low weldability, it is suitable for most arc welding processes. When it comes to Shielded Metal Arc Welding - SMAW electrodes, ferritic steel can offer superior performance. However, welders should limit the heat input to minimise grain growth which otherwise could result in joint cracking.

Conventional Welding

It refers to the process of joining ferritic metal through the application of heat with or without applying pressure or filter. 

Reclamation Welding

It refers to the repair of a badly worn out component of ferritic metal and bringing it to its original condition.

If you are looking for flux or wires to weld ferritic steel, you can consider buying them from D&H Secheron.