Most people are unsure whether stainless steel is a magnetic or a non-magnetic metal. Some believe it could be magnetic because it has traces of iron, but in a real sense, the answer is neither a yes or a no. Some stainless steel varieties are magnetic while others aren’t.
For stainless steel to be magnetic, it has to meet certain requirements:
· The alloy must have iron in it.
· The crystal structure of the alloy must be arranged in a martensitic or ferritic structure.
All stainless steel metals are a type of steel. That means their chemical composition contains iron. In most cases, stainless steel varieties with iron in their composition are magnetic. If the alloy has an austenitic crystal structure, then it’s not magnetic.
Whether a type of stainless steel is magnetic or not, it can be grouped depending on the type of stainless steel. Some of the typical magnetic stainless steels include:
· Stainless steel grades 410, 420 and 440 – martensitic stainless steels.
Ferritic stainless steels
This type of stainless steel is magnetic primarily because it contains large quantities of ferrite in its chemical composition, which is a compound of iron and other elements.
The crystal structure of ferrite and iron is what makes these types of stainless steel magnetic. However, some of the stainless steels with ferrite have a weak magnetic pull.
Martensitic stainless steels
Most of the stainless steels in this category are magnetic. If iron is present, the crystal structure of martensitic stainless steel can be ferromagnetic. Because iron is the primary material in stainless steel, martensitic steels have magnetic properties.
Austenitic Stainless Steels
Most stainless steels falling under this category are non-magnetic because they contain high amounts of austenite. Even though some of the metals like grade 304 and 316 have iron in their chemical composition, they are austenite, meaning they are non-ferromagnetic.
They can be made partially magnetic through special thermal treatment or work-hardening which can form ferrite in some locations. This is why, austenitic grades display vary slight magnetism on any edge that has been mechanically worked, such as the edge of a sheet.
Why Does Magnetism In Stainless Steels Matter?
Magnetism affects the performance and intended use of the material during application. Throughout fabrications and other processes like welding, magnetic materials can complicate the processes being carried out. Magnetic materials can also cause electric currents to behave differently.