Your Guide to Austenitic Stainless Steels

Classes of stainless steel are organized by their crystalline structure, which describes how their atoms are arranged. Of the five classes of stainless steel—martensitic, ferritic, austenitic, duplex, and precipitation-hardening—austenitic is the most common. The grades in this group contain high chromium and nickel content which provides good corrosion resistance and desirable mechanical properties. Read on to learn everything you need to know about austenitic stainless steels.

What Does It Mean to Be Austenitic?

Austenitic stainless steels possess an austenitic microstructure, meaning their cells are in the shape of a cube with one atom at the corner of each cube and one in the middle. In crystallography, this is known as a face-centered crystal structure.

Stainless steel becomes austenitic by alloying steel with enough nickel, nitrogen, and/or manganese to keep the microstructure at all temperature ranges, from very low to the melting point. Since they possess the same microstructures at all temperatures, they are not hardenable by heat treatment. However, they can be hardened through cold-working. In addition, grades in this class are non-magnetic.

Key Features of Austenitic Stainless Steels

Some of the major advantages of austenitic stainless steels include:

• Hygienic and easily cleaned
• High weldability
• Performs well at high temperatures
• Excellent corrosion resistance

The Different Series of Austenitic Stainless Steel

They are divided into two subgroups: the 200 and 300 series. In 300 series stainless steel, nickel is the most prominent alloying element. In 200 series stainless steel, manganese and nitrogen are the leading alloying elements, though it does still contain some nickel.

Applications of the 200 vs 300 Series 

The 300 series is more common because it has a wider range of applications. The high content of nickel it has gives 300 series of austenitic stainless steel superior corrosion resistance. Although 200 series stainless steels have a narrower range of applications, it is still utilized in various items due to its high impact resistance and toughness. Some uses for 200 series stainless steel include:

• Cookware
• Architecture (decorative)
• In-house water tanks
• Automobiles (structural & decorative)

Common Grades of Austenitic Stainless Steels

300 series stainless steel is the larger subgroup and has a much wider range of applications than the 200 series. The most common austenitic stainless-steel grades are from the 300 series.

Type 304

Not only is it the most popular type of austenitic stainless steel, 304 is the most common type of stainless steel. With high content of nickel and chromium, this grade possesses a desirable combination of strength, corrosion resistance, and fabricability.

Type 316

As the second most used grade of stainless steel, 316 is very similar to 304. However, the addition of Molybdenum gives it an increased resistance to corrosion and higher heat resistance.

Type 310

This grade has a high chromium and medium nickel content that makes it highly resistant to oxidation and corrosion. It is used for high temperature applications.

Type 321

Titanium is added to this grade as well as a large amount of carbon, which gives it an increased amount corrosion resistance when exposed to chemicals at high temperatures.

Low and High Carbon Grades of Austenitic Stainless Steel

Another differing characteristic of austenitic stainless steel is their carbon content. The standard grades of austenitic stainless steel have no minimum carbon requirement, although they do have a maximum requirement of .08% carbon. Some grades of austenitic stainless steel such as 304 and 316 is offered in a high carbon grade or low carbon grade depending on the added capabilities you seek.

L Grades 

Low carbon grades also known as L grades are used to provide extra corrosion resistance. The carbon levels are kept at 0.03% or below to reduce corrosion after welding, which is caused by carbide precipitation.

H Grades

High carbon grades contain a maximum of 0.10% carbon and a minimum of 0.04% carbon to help the stainless steel retain strength at higher temperatures. H grades can be used as standard grades as long as their carbon contents are 0.08% max. These grades are commonly used for applications that expose them to extreme temperature environments.

Compositional Differences Between Common Grades

                                              Chemical Composition % of Common Grades

Mechanical Differences Between Typical Grades

                                                                  Mechanical Properties

What Industries Are Austenitic Stainless Steels Appropriate For?

They are the most popular class of stainless steel because of the key properties they possess. Their superior corrosion resistance, formability, strength, and heat resistance make them a staple in transport, industrial, and architectural products. In addition, austenitic stainless steel is used to the pharmaceutical, chemical, and food industries because its corrosion resistance provides high cleanability, low maintenance, and durability.

Different Applications of Common Grades of Austenitic Stainless Steel

304 Stainless Steel

• Kitchen equipment
• Architecture
• Medical Equipment
• Food preparation

316 Stainless Steel

• Water heaters
• Marine Parts
• Medical equipment
• Chemical processing equipment

310 Stainless Steel

• Kilns
• Steam boilers
• Combustion Chambers
• Thermowells

321 Stainless Steel

• Heat exchangers
• Aircraft engine manifolds
• Furnace parts
• Refinery Equipment

Choose Austenitic Stainless Steel

Known as the workhorse of steel for its durability and versatility, austenitic stainless steel is a staple in the metal industry. It has high formability, corrosion resistance, and heat resistance which makes it a good choice for many products.