Stainless steel has been a cornerstone of various industries, providing durability, corrosion resistance, and strength. Among the different stainless steel grades, UNS S31803 Duplex Stainless Steel stands out as a versatile and high-performance material. In this blog, we will delve into the world of UNS S31803, exploring its properties, applications, and the difference between UNS S31803 and UNS S32205.

Understanding UNS S31803

UNS S31803/2205 belongs to the duplex stainless steel family, characterized by its unique ferritic-austenitic microstructure. In the annealed condition, it contains approximately 40-50% ferrite, combining the robust mechanical strength of ferritic grades with the corrosion resistance of austenitic ones.

Corrosion Resistance

One of UNS S31803’s remarkable features is its superior resistance to chloride pitting and crevice corrosion compared to 317L stainless steel. It also exhibits outstanding corrosion resistance to seawater and various concentrations of sulfuric acid, making it a top choice for applications in challenging environments, including the oil and gas industry and chemical tankers.

High-Quality Composition

The exceptional performance of UNS S31803 can be attributed to its composition, which includes high levels of chromium, nitrogen, and molybdenum. These elements play a pivotal role in enhancing the material’s corrosion resistance and mechanical strength.

Manufacturing Options

UNS S31803 can be processed using various manufacturing methods, allowing for versatility in its applications:

Smelting Options:

Electric Arc Furnace (EAF)

Refined-smelting and vacuum degassing (EAF+LF+VD)

Electro Slag Remelting (EAF+ESR)

Protective atmosphere Electro Slag Remelting (EAF+PESR)

Vacuum induction melting (VIM+PESR)

Forming Options:

Hot rolling process

Hot Forging (Electro-hydraulic, High-speed-hydraulic, Oil-hydraulic, Precision-forging)

Heat-treatment Options:

Annealed (full/soft/spheroidizing) – +A

Normalized – +N

Normalized and tempered – +NT

Quenched and tempered (water/oil) – +QT

Solution annealed – +AT

Precipitation hardened – +P

Surface Options:

Black Surface

Grounded (Bright but rough; Not precision)

Machining for plate (Bright and precision; Little turning scar)

Peeled/Turned (Bright and precision; Little turning scar)

Polished (Very Bright and precision size; Not turning scar)

Other Services

UNS S31803 offers additional services like cutting into small pieces, CNC machining based on your drawings, various packaging options (Bare/Nylon/Canvas/Wooden), flexible payment methods (T/T, L/C, O/A upon request), and versatile transport options (FOB/CFR/CIF/DDU/DDP by train, ship, or air).

UNS S31803 vs. UNS S32205

Duplex stainless steels, like UNS S31803 and UNS S32205, offer impressive strength and corrosion resistance compared to austenitic stainless steels like 304/316. The difference between these two grades lies in their composition. UNS S32205 includes higher levels of chromium, molybdenum, and nitrogen, resulting in improved corrosion performance. In fact, S32205 fully meets the S31803 specification, but the reverse is not true. Therefore, S32205 can be dual-certified as S31803.

Mechanical and Physical Properties

Mechanical Properties of UNS S31803:

Tensile Strength, min.: 620 MPa

Yield Strength, min.: 450 MPa

Elongation, min.: 25%

Hardness Brinell, max: 290 HB

Physical Properties of UNS S31803:

Density: 7.805 g/cm³

Thermal Expansion: 13.7 x 10^-6 K

Modulus of Elasticity: 200 GPa

Thermal Conductivity: 19.0 W/m·K

Electrical Resistivity: 0.085 x 10^-6 Ω·m

Applications and Benefits

UNS S31803 finds extensive use in various industries, including oil and gas, hydro power, pressure vessels, pulp and paper, structural components, and chemical tankers. Its benefits include:

Good weldability in thick plates.

Good low-temperature toughness.

Resistance to stress corrosion cracking is crucial in applications like hot water tanks, process plants, brewing tanks, and desalination plants.

Higher strength, approximately twice that of Type 304 austenitic stainless steel, leads to reduced plate thickness and weight in fabrications.


UNS S31803 Duplex Stainless Steel, with its remarkable combination of strength and corrosion resistance, is a valuable material for numerous industries. Its versatile manufacturing options, superior properties, and cost-effectiveness make it a preferred choice for various applications. Whether in challenging environments or everyday use, UNS S31803 continues to play a vital role in advancing industries worldwide.