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Discussing the Classes of Different Stainless Steel Alloys

by Mar 8, 2019News

There is no shortage of stainless steel alloys. In fact, there are well over 100 of them, each of which falls into an overarching class. These classes include ferritic, austenitic, martensitic, precipitation hardened, and duplex.

Wondering what types of alloys belong to which classes? This blog post should contain all the information you’ll need to know. Read below!


Possessing only scarce amounts of carbon (less than .1%), ferritic stainless steels are high in chromium, and generally contain a variety of other metal additives. Magnetic and strong, these types of steels are also highly resistant to corrosion. For this reason, they are often used in situations where corrosive chemicals are present.

Ferritic stainless steels are defined by the 400 class of alloys. Popular examples of these include alloy 405, alloy 430, and alloy 446.


The most common types of stainless steels in existence, austenitic stainless steels contain a great deal of nickel compared to other types of stainless steels. In addition to nickel, they also contain fairly high levels of chromium, molybdenum, and nitrogen.

Renowned for their strength, their malleability, and their weldability, austenitic stainless steels are used in a variety of functions. They’re also fairly resistant to corrosion, allowing them to hold up well in chemically abrasive environments.

Austenitic stainless steels are defined by the 300 class of alloys. Some of the most popular examples of austenitic stainless steel include alloy 304, alloy 309, alloy 310, alloy 316 and N08904 (904L).


In terms of construction, martensitic and ferritic stainless steels are very similar. However, there is one big difference between the two: martensitic stainless steels contain much more carbon. In fact, while the carbon consistency of ferritic stainless steels stays below 0.1%, the carbon consistency of martensitic stainless steels stays around 1%.

What difference does this increase in carbon make? It allows martensitic stainless steels to be hardened, but also makes them fairly vulnerable to corrosion.

While there are quite a few martensitic stainless steels, the most popular are alloy 410, alloy 420S45 and alloy 431.

Precipitation Hardened

Precipitation hardened stainless steels contain a great deal of chromium and nickel. They are essentially hybrids of austenitic and martensitic stainless steels. As such, they contain two of the greatest characteristics of those stainless steel classes: corrosion resistance and hardening capability.

From the martensitic side, they gain an ability to be heat-treated and hardened. From the austenitic side, they gain a high corrosion resistance.

Some of the most prominent examples of precipitation hardened stainless steel alloys include 17-4 PH and 15-5 PH.


Duplex stainless steels are unique in that they are hybrids of two different stainless steel classes: austenitic stainless steels and ferritic stainless steels. While they behave in very similar ways to both of these stainless steels, they differ substantially from austenitic stainless steels in their nickel content.

These stainless steels thrive on a number of different levels. Not only are they strong, malleable, and tough, but they’re also highly resistant to corrosion.

There are a few different types of duplex stainless steel, but perhaps the most popular are S32205 stainless steel and S31803 (2205) stainless steel.

In Need of Stainless Steel Components?

If you are reading this article, you might very well be on the search for stainless steel items. If so, there’s no need to search any longer—Great Plains Stainless has you covered.

We sell a wide variety of stainless steel products made from wide variety of stainless steel alloys. Regardless of whether you need duplex, martensitic, austenitic, ferritic, or precipitation hardened steel, we can accommodate you.

Contact us today to discuss your stainless steel needs!