#1 Ferritic Stainless Steel

Based on Chromium with small quantities of Carbon, ferritic stainless steel has a similar microstructure to both carbon and low alloy steels. Compared to other types of stainless steel, it is usually limited to the use of relatively thin sections, due to a lack of toughness in welds. Although, contractors use ferritic stainless steel for a wide range of applications that do not require welding. Additionally, you cannot harden ferritic steel with heat treatment. But you can use it in seawater or other aggressive conditions when you include the addition of Molybdenum. Ferritic stainless steel is also magnetic, but not as formable as austenitic stainless steel for example. On the other hand, steelworkers often choose ferritic stainless steel because of its resistance to stress corrosion cracking.

#2 Austenitic Stainless Steel

Austenitic stainless steel is one of the most common types of stainless steel on this list. It has a microstructure that includes an addition of Nitrogen, Nickel, and Manganese. The structure of austenitic stainless steel is the same as what you would find in regular steel. But only in a much higher temperature giving it formability and weldability. Furthermore, you can make austenitic stainless steel corrosion-resistant by adding Nitrogen, Chromium, and Molybdenum. While you cannot harden it with heat, austenitic stainless steel has the useful property of retaining a helpful level of toughness and ductility when hardened to high strength. Typical austenitic stainless steel is susceptible to stress corrosion cracking, but austenitic stainless steel with higher nickel content has increased resistance to stress corrosion cracking. Nominally non-magnetic, austenitic stainless steel shows some magnetic response depending on its composition.

#3 Martensitic Stainless Steel

Similar to ferritic stainless steel, martensitic stainless steel bases on Chromium with higher Carbon levels. You can temper and harden martensitic stainless steel much like carbon and low-alloy steels. We use martensitic stainless steel where a moderate level of corrosion resistance and high strength is needed. As it is counted among the magnetic types of stainless steel, it has low formability and weldability. Companies use martensitic stainless steel mostly in long products that require sheet and plate form.

#4 Duplex Stainless Steel

With a microstructure that is half austenitic and half ferritic, duplex stainless steel has a higher strength than these types of stainless steel. It is also resistant to stress corrosion cracking. “Lean” duplex stainless steel is designed to have similar corrosion resistance to regular austenitic stainless steel. But it includes enhanced resistance and strength to stress corrosion cracking. “Super duplex” stainless steel also has enhanced resistance and strength to corrosion in comparison to regular austenitic stainless steel. Furthermore, they are weldable as long as you take care to use the right heat input and welding consumables. Duplex stainless steel is also magnetic with moderate formability.