Ferritic stainless steel is a type of chromium alloy that has ferritic, body-centered cubic crystal structures. These alloys are typically made up of no more than 30 percent chromium but contain no nickel, unlike other types of stainless steel. They are also ferromagnetic, meaning that they attract other electrically uncharged materials. Stainless steel is classified by a numerical system. One common form of ferritic stainless steel is Grade 430.
Like other types of stainless steel, ferritic steel resists corrosion. This is because the chromium in the alloy binds with oxygen particles in the air, creating a chromium oxide barrier between the metal and the atmosphere. Ferritic stainless steel is particularly resistant to corrosion from acids. Generally, the higher the chromium content, the stronger the chromium oxide barrier and the less likely a steel alloy will corrode.
Ferritic stainless steel resists oxidation but may become brittle at room temperature following prolonged heating at 400 to 600 degrees Celsius. Annealing, a type of heat treatment commonly applied to steel, can eliminate this effect, according to The A to Z of Materials’ online database. While annealing can soften ferritic metals, they cannot be hardened by or strengthened with heat treatment, notes Stainless Processing, Inc. on its website.
Ferritic steels are most commonly used in applications where cracking over time may be a concern, such as car trims and exhaust systems, and sinks and stoves. That’s because this type of metal is particularly resistant to stress-related cracking.
This type of steel is ductile in its annealed condition, meaning that it can be manipulated extensively without fracturing. It can also be formed using roll-forming or mild stretch-bending techniques, according to Action Stainless’ website. However, ferritic stainless steel has limited weldability, so it’s not easily welded and is not very strong in its welded condition.
The lack of nickel or molybdenum in ferritic steel make it relatively cheap when compared to other types of stainless steels, according to Action Stainless. For this reason, if ferritic steel is a good choice for applications that require large quantities of this metal, as long as it meets all other mechanical requirements.