Properties and applications of duplex stainless steel ASTM A240 UNS S31803

What is duplex stainless steel S31803?

Duplex stainless steel ASTM A240 UNS S31803 is a widely used duplex alloy that combines the best properties of austenitic and ferritic stainless steels. It has a two-phase microstructure consisting of approximately equal parts of ferrite and austenite, offering excellent mechanical strength and superior corrosion resistance compared to standard stainless steels like 304 and 316.

S31803 is commonly used in industries requiring high strength, excellent toughness, and outstanding corrosion resistance, such as oil and gas, marine, chemical processing, and offshore structures.

ASME B16.11 concentric reducer swage nipples ASTM A815 UNS S31803

Corrosion resistance of S31803 (How PREN ≥ 35 improves pitting resistance?)

One of the key advantages of S31803 is its high resistance to localized corrosion, such as pitting and crevice corrosion, which are common in aggressive environments containing chlorides.

The pitting resistance equivalent Number (PREN) is a crucial indicator of a stainless steel alloy’s ability to resist pitting corrosion. S31803 has a PREN value of ≥ 35, meaning it provides superior protection against pitting corrosion, especially in seawater and other chloride-rich environments.

S31803 seamless pipes

The formula to calculate PREN is:

PREN = %Cr + 3.3(%Mo) + 16(%N)

With its high chromium (21-23%), molybdenum (2.5-3.5%), and nitrogen (0.08-0.2%) content, S31803 is more resistant to localized corrosion than standard austenitic stainless steels such as 316L.

Why is S31803 suitable for harsh environments like marine, oil & gas, and chemical processing?

S31803 is widely used in demanding industrial applications due to its:

Superior corrosion resistance – Excellent resistance to stress corrosion cracking, pitting, and crevice corrosion in chloride-containing environments.

High strength and toughness – Higher mechanical strength than 316L, reducing material thickness and weight.

Good weldability – Suitable for welding with minimal risk of intergranular corrosion.

Excellent performance in low and high temperatures – Retains mechanical properties in extreme conditions.

Common Applications of S31803:

Oil & Gas Pipelines – Withstands high pressures and corrosive fluids.

Marine & Offshore Structures – Ideal for seawater environments with high salinity.

Chemical Processing Plants – Resistant to acidic and corrosive substances.

LNG & Cryogenic Applications – Maintains strength at low temperatures.

ASME B16.9 A815 Gr.S31803 seamless concentric reducer

How Haihao Group Ensures the Quality of S31803 Materials?

At Haihao Group, we follow strict quality control measures to ensure our ASTM A240 UNS S31803 products meet international standards and customer requirements:

Chemical Composition Analysis – Spectrometric testing ensures precise alloy composition (Cr, Mo, N, etc.).

Mechanical Property Testing – Tensile strength, yield strength, and elongation tests verify performance.

Corrosion Testing – PREN verification and pitting resistance tests ensure durability in harsh environments.

Non-Destructive Testing (NDT) – Ultrasonic, radiographic, and magnetic particle inspections detect internal defects.

Heat Treatment & Microstructure Examination – Optimized ferrite-austenite balance for maximum strength and corrosion resistance.

Impact Testing (-46°C) – Ensures toughness in low-temperature applications.

Duplex stainless steel ASTM A240 UNS S31803 offers outstanding corrosion resistance, superior strength, and excellent performance in challenging environments. Its PREN ≥ 35 ensures high resistance to pitting and crevice corrosion, making it a preferred material for oil and gas, marine, and chemical industries.

Haihao Group is committed to delivering high-quality duplex stainless steel components with stringent quality control and international certification, ensuring reliable performance for our global customers.

Contact us today to learn more about our S31803 duplex stainless steel products! Email:sales@haihaogroup.com