Austenitic stainless steel is one of the most common stainless steels. It is known for its fantastic corrosion resistance, temperature resistance, high ductility, and strength. Due to its ease of fabrication, it is vital in several industries, from aerospace to food processing.
In this blog post, we will examine what austenitic stainless steel is and why it is so crucial in manufacturing today. We will note its properties and applications.
What makes up austenitic stainless steel?
Austenitic stainless steel is made up of a crystal structure, face-centered cubic (FCC), the arrangement of the atoms forms when alloying iron with adequate levels of chromium and nickel.. It is one of the primary categories in the stainless steel family. “Austenite” refers to the addition of nickel or nitrogen to steel.
More specifically, on the alloy makeup, austenitic stainless steels have high levels of chromium content (16 – 26%), and the addition of nickel stabilizes the austenitic structure (6 – 22%). When annealed, most grades are nonmagnetic or only mildly magnetic. When dealing with acids, chlorides, and other harsh substances, it displays excellent corrosion resistance.
What elements form austenitic stainless steel?
The elements that form austenitic stainless steel comprise a combination of several elements.
- The primary element is Iron (Fe)
- Chromium is the primary alloying agent (16 – 26%)
- Nickel is another significant alloying material (6 – 22%)
- Manganese is often added (2 – 6%)
- Carbon content is low (0.08%)
- Secondary alloying elements are present in smaller quantities, such as molybdenum, nitrogen, silicon, phosphorus, and sulfur (< 0.08%).
What are the most common grades of austenitic stainless steels?
304 Stainless Steel
Otherwise known as “18-8,” it includes 18% chromium and 8% nickel. It offers outstanding corrosion resistance and hygienic properties. Typical applications are storage tanks, sinks, cookware, piping, surgical instruments, and implant components.
316 Stainless Steel
This alloy possesses 16 – 18% chromium, 10 – 14% nickel, and 2 – 3% molybdenum. These elements enhance the corrosion resistance and are a fantastic choice for marine components. It has nonmagnetic properties, is strong at low temperatures, and is easy to clean. Uses include marine hardware, medical instruments, and offshore drilling structural components.
303 Stainless Steel
Featuring 17 – 19% chromium and 8-10% nickel, the addition of sulfur to this alloy improves its machinability. This specific combination, while enhancing machinability, reduces corrosion resistance. Typical applications for this alloy include screw machining, shafts, valves, and other components where ease of machining is necessary.
321 Stainless Steel
Titanium (0.4 – 0.7%) stabilizes this alloy and gives it excellent weldability. Its resistance to sensitization and intergranular corrosion at high temperatures makes it an excellent choice for aircraft exhaust systems, jet engine parts, heat exchangers, and oil and gas components.
310 Stainless Steel
Exceptional for high-temperature applications with 24 – 26% chromium and 19 – 22% nickel, it also offers outstanding oxidation resistance and strength under heat. Ideal for applications such as furnace components, gas turbines, and boiler parts.
904L Stainless Steel
With the high chromium (19 – 23%), nickel (23 – 28%), and molybdenum (4 – 5%) content, this alloy offers incredible corrosion resistance against sulfuric acid and chlorides. It has high strength, good ductility and weldability, and is nonmagnetic. Typical applications are equipment exposed to corrosive chemicals, offshore platforms, heat exchangers, marine components, and pharmaceutical processing equipment.
347L Stainless Steel
Stabilized with niobium and tantalum (0.06%) to enhance sensitization and intergranular corrosion resistance at high temperatures. It includes 17 – 19% chromium and 9 – 13% nickel, offering excellent mechanical properties, ductility, and weldability. Typical applications include heat exchangers, oil refining tubing, aircraft components, and equipment in corrosive environments.
Why is austenitic stainless steel essential in manufacturing?
There are several reasons austenitic stainless steel is a standard in manufacturing.
Corrosion Resistance
Due to the high chromium content, a passive, self-healing oxide layer forms on the surface. This protective layer deters rust from forming and stops chemicals from permeating it. These features enable its use in harsh environments where exposure to acids, moisture, and salts is everyday. It is an ideal option for chemical factories, food processing facilities, and marine applications.
Formability & Weldability
Even at very low temperatures, the austenitic structure remains ductile, allowing shaping, bending, and drawing into wires or sheets easily.
Austenitic stainless steel components are excellent candidates for welding without losing strength or corrosion resistance.
High Strength
Suitable for cryogenic and high-heat applications, austenitic stainless steel retains its strength across an extensive temperature range. The high strength means parts made with this material have longer lifespans and require less maintenance.
Cleanability & Hygienic Qualities
Due to its smooth, non-porous surface, it is easy to clean, making it a great choice for food processing, pharmaceutical, and medical device manufacturing. It also does not foster bacterial growth, which is a significant advantage for these industries.
Aesthetic Appeal
Austenitic stainless steel has a bright, reflective sheen, making it widespread for several uses from architectural to consumer applications. Examples of these are kitchen appliances and public transportation interiors.
Common Applications
The following are typical applications for austenitic stainless steel:
- Food & Beverage: From takes to pipes and surfaces like countertops, austenitic stainless steel is a fantastic choice. It is crucial for these applications due to its outstanding safety, corrosion resistance, and contamination resistance. These alloys can also withstand extreme cleaning agents and sanitization processes, along with extended exposure to acids and moisture.
- Chemical & Petrochemical: Reactors, heat exchangers, and piping systems are critical components in these industries. These components need to resist aggressive chemicals, as well as high pressure and temperatures. Its capacity to resist corrosion while retaining structural integrity guarantees efficiency and safety in chemical reactions.
- Medical Devices & Surgical Instruments: From tools to implants and equipment, they must be of the highest quality. Austenitic stainless steel exhibits biocompatibility and is acceptable by the human body. These components must be able to undergo sterilization to prevent infections and provide safety during medical procedures.
- Automotive & Aerospace: Components in these industries must have the ability to withstand corrosive environments, extreme temperatures, and vibrations. Components in exhaust systems, structural elements, and fasteners use this material due to its lightweight yet strong and reliable under severe conditions.
- Consumer Goods: Everyday items like cutlery, cookware, and appliances utilize austenitic stainless steel for its aesthetic charm and its ability to resist regular use and deviations in moisture and temperature.
In Review
A cornerstone material in modern everyday life, austenitic stainless steel has exceptional strength, corrosion resistance, and sterilization capabilities. It can rise to the occasion, meeting demanding requirements in diverse industries.
FAQs
The definition of austenitic stainless steel is a corrosion-resistant alloy with high nickel and chromium content.
Common grades of austenitic stainless steel include 304, 316, and 321, each offering unique properties for various applications.
Austenitic stainless steel alloys are generally non-magnetic.
