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Austenitic stainless steel

The austenitic family of stainless steels with its large number of grades and favorable fabrication properties is by far the most widely used group of stainless steels. Austenitic grades are commonly used in all industry sectors and are the primary alloys used for consumer products and building and construction applications. Their overwhelming popularity is due to several factors:

  • Readily available in all sizes and product forms
  • Highly formable, making very tight crisp bends possible
  • Excellent toughness providing superior impact, blast, and seismic performance
  • Easy to weld and repair
  • Widest range of aeshetic finishes

The Austenitic family of stainless steels can be further divided into subgroups depending on their alloying content.

AISI 300 Series: The most widely used of all stainless steels are the AISI 300 Series austenitic grades, which include standard grades such as 304 (S30400), 304L (S30403), 316 (S31600), and 316L (S31603). 

AISI 200 Series: The 200 Series stainless steels contain a lower level of nickel and higher levels of manganese and nitrogen than the 300 Series stainless steels. This subgroup of stainless steels tends to have higher strength levels and larger strain hardening coefficients than the 300 Series grades. Because of the lower nickel contents the 200 Series grades are often considered a lower cost alternative to the 300 Series stainless steels. The following table lists the composition and PREN for some common 200 and 3000 Series stainless steels.

Table 1: Chemical composition* (weight %) and PREN of some common standard wrought 300 and 200 series austenitic stainless steels**.
Grade No. UNS EN No. C N Cr Ni Mo Cu Other PREN***
Representative standard grades – 300 series
304 S30400 1.4301 0.07 2.00 0.10 17.5 19.5 8.0 10.5 18–20
304L S30403 1.4307 0.03 2.00 0.10 17.5 19.5 8.0 12.0 18–21
321 S32100 1.4541 0.08 2.00 0.10 17.0 19.0 9.0 12.0 Ti 5x(C+N)min., 0.70 max. 18–21
347 S34700 1.4550 0.08 2.00 0.10 17.0 19.0 9.0 13.0 Nb 10xC min., 1.00 max 18–21
316 S31600 1.4401 0.08 2.00 0.10 16.0 18.0 10.0 14.0 2.00 3.00 24–26
316L S31603 1.4404 0.03 2.00 0.10 16.0 18.0 10.0 14.0 2.00 3.00 24–26
1.4435 0.03 2.00 0.11 17.0 19.0 12.5 15.0 2.50 3.00 27–29
317L S31703 1.4438 0.03 2.00 0.10 18.0 20.0 11.0 15.0 3.00 4.00 29–30
Representative standard grades – 200 series
201 S20100 1.4372 0.15 5.5 7.5 0.25 16.0 18.0 3.5 5.5 17–20
201L S20103 0.03 5.5 7.5 0.25 16.0 18.0 3.5 5.5 17–20
201LN S20153 0.03 6.4 7.5 0.10 0.25 16.0 17.5 4.0 5.0 1.0 17–20

Notes:

* Taken from ASTM specifications for plate, sheet and strip when available or from company data sheets. For complete compositional requirements consult these sources.
** Chemistry maximum, unless range or minimum is indicated, EN chemistry does not correspond exactly to ASTM chemistry
*** Pitting Resistance Equivalent Number calculated from the expression PREN = %Cr + 3.3(%Mo + 0.5%W) + 16(%N) and expected nominal chemical compositions for the grade

High-Performance austenitic stainless steels: The more highly alloyed austenitic grades are often termed High-Performance austenitic stainless steels. These steels have increased levels of chromium, nickel, molybdenum, and occasionally nitrogen and are designed to provide increased resistance to aggressive environments such as stronger acids, bases, and higher chloride-bearing environments including seawater, brackish water and brines.  A copper addition used in the 904L (N08904) and alloy 20 (N08020) stainless steels provides improved resistance to reducing acids.  As a group, the High-Performance grades also tend to have higher strength levels and improved resistance to stress corrosion cracking compared to the 300 and 200 Series stainless steels.

The 6% Mo super austenitic stainless steels, which include the grades UNS N08367, S31254, and N08926, contain approximately 20% chromium, 6% molybdenum, and 0.20% nitrogen. These grades show very good resistance to various chemical environments and can resist long-term exposures to seawater.  In many environments, 6% Mo grades have a corrosion resistance that is just below that of the Ni/Cr/Mo alloys such as 625 (N06625) and C276 (N10276). 

The most corrosion resistant austenitic stainless steels are the 7% Mo grades UNS S32654, S31277 and N08354, which have a resistance in many environments that approaches the C276 (N10276) alloy.

Table 2: Chemical composition* (weight %) and PREN of common high performance austenitic stainless steels**.
Grade No. UNS EN No. C N Cr Ni Mo Cu Other PREN***
Alloy 20 N08020 2.4660 0.07 2.00 19.0 21.0 32.0 38.0 2.00 3.00 3.00 4.00 (Nb+Ta): 8xC min., 1.00 max. 25–27
317LM S31725 0.03 2.00 0.20 18.0 20.0 13.2 17.5 4.00 5.00 30–32
317LMN S31726 1.4439 0.03 2.00 0.10 0.20 17.0 20.0 13.5 17.5 4.00 5.00 31–33
904L N08904 1.4539 0.02 2.00 0.10 19.0 23.0 23.0 28.0 4.00 5.00 1.00 2.00 33–35
S31727 0.03 1.00 0.15 0.21 17.5 19.0 14.5 16.5 3.80 4.50 2.80 4.00 33–35
N08028 1.4563 0.02 2.00 0.15 0.25 26.0 28.0 30.0 34.0 3.00 4.00 38–40
S34565 1.4565 0.03 5.00 7.00 0.40 0.60 23.0 25.0 16.0 18.0 4.00 5.00 45–47
N08026 0.03 1.00 0.10 0.16 22.0 26.0 33.0 37.2 5.00 6.70 2.00 4.00 41–43
S32053 0.03 1.00 0.17 0.22 22.0 24.0 24.0 26.0 5.00 6.00 41–43
N08926 1.4529 0.02 2.00 0.15 0.25 19.0 21.0 24.0 26.0 6.00 7.00 0.50 1.50 41–43
S31254 1.4547 0.02 1.00 0.18 0.22 19.5 20.5 17.5 18.5 6.00 6.50 41–43
N08367 0.03 2.00 0.18 0.25 20.0 22.0 23.5 25.5 6.00 7.00 0.75 43–45
S31266 1.4659 0.03 2.00 4.00 0.35 0.60 23.0 25.0 21.0 24.0 5.20 6.20 1.00 2.50 W: 1.5–2.5 48–59
S31277 0.02 3.00 0.30 0.40 20.5 23.0 26.0 28.0 6.50 8.00 0.50 1.50 47–49
N08031 1.4562 0.02 2.00 0.15 0.25 26.0 28.0 30.0 32.0 6.00 7.00 1.00 1.40 48–50
N08354 0.03 1.00 0.17 0.24 22.0 24.0 34.0 36.0 7.00 8.00 48–50
N08935 0.03 1.20 0.25 0.36 26.0 28.0 34.0 36.0 6.10 7.10 0.4 50–53
S32654 1.4652 0.02 2.00 4.00 0.45 0.55 24.0 26.0 21.0 23.0 7.00 8.00 0.30 0.60 54–56

Notes:

* Taken from ASTM specifications for plate, sheet and strip when available or from company data sheets. For complete compositional requirements consult these sources.
** Chemistry maximum, unless range or minimum is indicated, EN chemistry does not correspond exactly to ASTM chemistry
*** Pitting Resistance Equivalent Number calculated from the expression PREN = %Cr + 3.3(%Mo + 0.5%W) + 16(%N) and expected nominal chemical compositions for the grade

Additional resources

There are many resources available on IMOA’s website to assist in the selection, design, and fabrication of austenitic stainless steels.  These include the following:

Practical Guidelines for the Fabrication of Austenitic Stainless Steels
Linee Guida Pratiche per la Lavorazione di Acciai Inossidabili Austenitici ad Elevate Prestazioni

There is also a library of resources from IMOA and the Nickel Institute, specifically for the building and construction industry that includes a large number of documents:

Building & Construction Stainless Steel Library
This is the 2018 version of the International Molybdenum Association and Nickel Institute's comprehensive stainless steel library for the architecture, building and construction industry. It contains over 550 PDFs, which is about 50% increase over the 2015 version.  The information is categorized into seven primary topic areas:

  • Applications
  • Finishes & Nickel Plating
  • Alloy Selection & Specification
  • Fabrication/Cleaning
  • Structural Design
  • Sustainability, Resilience, Health & Safety
  • Educational Programs

Subfiles are used to further categorize the information by topic. Information has been provided to assist with design, engineering, sustainability assessment, fabrication, installation and maintenance cleaning.  The application examples are diverse and include elaborate facades and roofs, structural stainless and glass, pedestrian bridges, infrastructure, restoration, ductwork, memorials, swimming pools, transit structures, interiors, industrial buildings, alternative energy, water and other subjects.