What is 1.4565 Stainless Steel?

1.4565 stainless steel, commonly known as Alloy 31 or UNS N08926, is a high-performance, nitrogen-enhanced austenitic stainless steel. It is designed to provide exceptional resistance to both oxidizing and reducing acids, particularly sulfuric and phosphoric acids, as well as excellent resistance to chloride-induced pitting and crevice corrosion. This makes it suitable for demanding chemical processing, pollution control, and offshore applications.

 

This high-performance grade is standardized under key international designations.

Standard	Equivalent Grade
EN (Europe)	1.4565
ASTM/AISI (USA)	Alloy 31, UNS N08926
Common Name	Alloy 31

Its high alloy content, including nickel, chromium, molybdenum, nitrogen, and copper, provides outstanding corrosion resistance.

Element	C	Si	Mn	P	S	Cr	Ni	Mo	N	Cu
Content (%)	≤ 0.02	≤ 0.50	≤ 2.0	≤ 0.03	≤ 0.01	26.0 - 28.0	30.0 - 33.0	6.0 - 7.0	0.15 - 0.25	1.0 - 1.4

It offers good mechanical properties combined with superior corrosion resistance.

Property	Yield Strength (Rp0.2)	Tensile Strength (Rm)	Elongation (A)	Hardness (HB)
Typical Value	≥ 300 MPa	650 - 850 MPa	≥ 35%	≤ 250

 

Key Characteristics and Applications of 1.4565 / Alloy 31

Exceptional Acid Resistance: Provides excellent resistance to sulfuric, phosphoric, and nitric acids across a wide range of concentrations and temperatures.

High Pitting and Crevice Corrosion Resistance: With a PREN (Pitting Resistance Equivalent Number) > 40, it performs well in chloride-containing environments, including seawater and brine solutions.

Good Weldability and Formability: Can be welded using common techniques and exhibits good ductility for forming operations.

 

Primary Applications:

Chemical Processing: Reactors, heat exchangers, and piping for aggressive acid services.

Pollution Control: Scrubbers, ducting, and chimney liners in flue gas desulfurization (FGD) systems.

Offshore & Marine: Seawater piping, pumps, and valves in desalination plants.

Pharmaceutical: Equipment handling corrosive cleaning agents and process chemicals.

 

How does Alloy 31 (1.4565) compare to 904L (1.4539)?
Both are high-alloy austenitic grades, but Alloy 31 contains higher levels of chromium, nickel, and molybdenum, and includes nitrogen, giving it a higher PREN and superior resistance to pitting and crevice corrosion. Alloy 31 also offers better performance in mixed acid environments, especially those containing sulfuric and phosphoric acids. It is generally considered an upgrade from 904L for more severe corrosive conditions.

 

What are the welding recommendations for Alloy 31 stainless steel?
Welding Alloy 31 requires matching or over-alloyed filler metals, such as Alloy 625 or a higher-grade austenitic filler, to maintain corrosion resistance in the weld zone. Controlled heat input and proper shielding gas (typically argon-based) are important to avoid excessive grain growth and precipitation of detrimental phases. Post-weld cleaning is recommended to restore corrosion resistance.

 

Looking for a Reliable Supplier of 1.4565 / Alloy 31 Stainless Steel?
GNEE Steel supplies premium Alloy 31 (1.4565) stainless steel in plate, pipe, fitting, and bar forms for the most demanding corrosive applications. We provide full material traceability and certification to ensure optimal performance. If you have any requirements, please feel free to contact us.