Why Is Stainless Steel Not Magnetic?

 

 

When we think of stainless steel, many of us immediately think of stainless steel—anything from kitchen appliances, medical devices, renewable energy technology components, to building structures may come to mind. If you think about it, you'll probably find something made of stainless steel almost everywhere.

 

While stainless steel is known for being corrosion-resistant, strong, and beautiful, one quality that is often questioned is its magnetism.

Why is stainless steel not magnetic?

You can also ask, is stainless steel magnetic? The fact is that some stainless steel is magnetic while others are not. You see, stainless steel is often thought of as a single type of material, but in metallurgy, stainless steel is actually a group of metals with varying qualities and chemical compositions. In fact, it might be helpful to think of stainless steel as a general term based on the chemical composition of steel.

How is steel classified as stainless steel?

Steel alloys with a chromium content of at least 10.5% belong to the stainless steel category.

 

The chromium content gives steel special qualities, including excellent corrosion resistance. This quality gives stainless steel its rust-free status. It also allows the steel to repair itself after being scratched or damaged – unlike galvanized steel, which is often scratched, and these scratches can cause the steel to eventually corrode.

 

What makes something magnetic?

But back to magnetism. In the case of steel, whether it is magnetic or not depends on the microstructure of the steel. Basic stainless steels have what is called a "ferrite" structure, which makes them magnetic. Remember the chromium content? It is the addition of chromium that creates the ferritic structure. This, along with the addition of carbon, hardens the steel and makes it a martensitic steel. Stainless steel cutting tools are usually martensitic.

 

Martensitic steels differ from the most common stainless steels, called austenitic steels. In austenitic steels, the chromium content is higher and nickel is also present. In terms of magnetism, it is the addition of nickel that makes steel non-magnetic.

 

Is stainless steel magnetic?

As I mentioned above, this is not an all or nothing answer. Some stainless steels are magnetic and some are not. The decisive factor for magnetism depends on the microstructure of the steel. Martensitic stainless steels (having a ferritic microstructure) are magnetic. Austenitic stainless steel contains nickel and is non-magnetic.