What is the Difference Between Austenitic & Ferritic Stainless Steel

I bet like most people you might have thought stainless steel was all the same. In fact, there are 5 types of stainless steel each with slightly different chemical compositions which changes its properties and thus its application.

The 5 types of stainless are as follows;

  • Austenitic
  • Duplex
  • Ferritic
  • Martensitic
  • PH (Precipitation Hardening)

The most widely used are austenitic and ferritic and it’s those that we compare in our latest infographic.

What Are Their Chemical Compositions & Properties?

Austenitic

This is by far the most common type. In fact, of all the stainless steel produced globally, 70-80% of it is austenitic. Its main chemical composition is made up of carbon, chromium, nickel and molybdenum. Molybdenum is added to primarily increase corrosion resistance and nickel is added to give strength, ductility, toughness and tensile strength, even at cryogenic temperatures.

Ferritic

Despite not being as common as austenitic, it is the second most used of all the stainless steel types, making up almost 20% of the worlds production. Its chemical composition includes chromium but very little nickel. As nickel is one of the most expensive elements, it makes ferritic stainless much more cost-effective in applications where the need for aesthetics, easy cleaning and corrosion resistance in non-extreme conditions is suffice.

Where Are They Used?

Due to its performance, even under extreme temperatures, austenitic stainless steel is widely used in commercial settings such as chemical plants, food processing and water or dairy processing.

Austenitic

Ferritic

Largely driven by its lower cost, ferritic stainless steel is most commonly used in domestic settings, commercial kitchens, hospitals and the automotive sector.

Can you Tell The Difference?

To the naked eye it would be difficult to tell the difference between these two types, however there is an easy way to tell the difference and that is with a magnet!

For stainless steel to be magnetic a couple of requirements need to be met:

  1. The stainless steel must have iron in it
  2. The stainless steel crystal structure must be arranged in a ferritic or martensitic structure

Since stainless steels are a type of steel, it must contain iron in their chemical composition. So that’s the first requirement taken care of. The second requirement is that stainless steel must have its crystal structure arranged in a ferrite or martensite structure. Therefore, if a stainless steel has an austenite structure it will not be magnetic.

Conclusion

These two classifications of stainless steel are the most widely used and both have pros and cons when considering which to use. Where and how the material is used, together with cost will ultimately dictate which type will be chosen.

Infographic:

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