ThePipingMart Blog Grades Duplex Stainless Steel (UNS S31500) – Composition, Properties, and Uses

Duplex Stainless Steel (UNS S31500) – Composition, Properties, and Uses

Duplex Steel UNS S31500

Duplex steel UNS S31500 is a high-strength alloy with excellent corrosion resistance and mechanical properties. This alloy comprises austenite and ferrite microstructures, making it two times stronger than standard austenitic steels. It also has superior resistance to stress corrosion cracking, pitting, crevice corrosion, and erosion. This article will discuss the composition, chemical properties, mechanical properties, physical properties, uses corrosion resistance, heat resistance, heat treatment, machining and welding of duplex steel UNS S31500.


The primary elements in the composition of duplex steel UNS S31500 are chromium (Cr), nickel (Ni), molybdenum (Mo) and nitrogen (N). It has a balanced combination of these elements, which gives it excellent strength and good corrosion resistance. The exact percentage of each component varies depending on the product grade used.

Element Content (%)
Iron, Fe 71.2
Chromium, Cr 18.5
Nickel, Ni 4.50
Molybdenum, Mo 2.60
Silicon, Si 1.60
Manganese, Mn 1.50
Nitrogen, N 0.070
Carbon, C ≤0.030
Phosphorous, P ≤ 0.030
Sulfur, S ≤ 0.015

Chemical Properties

Regarding its chemical properties, DSS UNS S31500 contains a higher percentage of chromium than other stainless steels, giving it excellent corrosion resistance. It also has more nickel than austenitic stainless steel, which improves its strength at elevated temperatures. Additionally, it contains higher amounts of molybdenum than other grades, which helps improve its pitting resistance and general wear resistance. Lastly, the addition of nitrogen further enhances this alloy’s strength and corrosion resistance properties compared to other grades.

Mechanical Properties

It has a high yield strength due to its dual microstructure combined with an increased amount of nitrogen in its composition compared to other grades. Its tensile strength is also high, which helps make it suitable for many applications requiring high stress or pressure levels, such as pumps or valves. Additionally, it has good fatigue strength, which means that it can withstand cyclic loading without failure over time. Furthermore, it exhibits good ductility, making it easier to form complex shapes if required by an application.

Properties Metric Imperial
Tensile strength 700-880 MPa 102000-128000 psi
Yield strength (at strain 0.200 %) ≥ 450 MPa ≥ 65300 psi
Elastic modulus 200 GPa 29000 ksi
Elongation at break ≥30% ≥ 30%
Charpy Impact ( at -100°C/-148°F) 30.0 J 22.1
Hardness, Rockwell C ≤ 28 ≤ 28

Physical Properties

The physical properties of duplex ss uns s 31500 are quite impressive as well; not only does this material have very good electrical and thermal conductivity, but it also exhibits very low magnetic permeability, making it ideal for use in applications requiring non-magnetic components such as electrical motors or transformers for example. Additionally, it has a relatively low coefficient of thermal expansion, meaning that components made from this material will not expand or contract significantly when exposed to changing temperatures. This property makes duplex steel uns s 31500 ideal for use in applications where temperature variations, such as cryogenic storage vessels or piping systems, need to be kept minimal.

Properties Metric Imperial
Density 7.80 g/cm3 0.282 lb/in3

Thermal Properties

Properties Metric Imperial
Thermal expansion co-efficient (at 30-100°C/86-212°F) 13.0 µm/m°C 7.22 µin/in°F


  • ASTMA789
  • ASTMA790
  • DIN1.4417


Duplex Steel UNS S31500 is a popular choice for many industries due to its high strength, corrosion resistance, and excellent weldability. It is often used in the marine and offshore oil and gas industries as it can withstand harsh conditions encountered in those environments. This type of steel is also commonly used in the petrochemical industry because it is highly resistant to chloride stress-corrosion cracking. Its strength makes it popular for applications such as valves, pumps, fittings, heat exchangers, pressure vessels, and other components requiring superior strength. In addition, Duplex Steel UNS S31500 boasts durability that makes it suitable for any mechanical application involving high wear and tear, such as transport vehicles. With its numerous benefits, this type of steel is ideal for use in industrial and commercial enterprises across various industries.

Corrosion Resistance

Duplex steel UNS S31500 has impressive properties, making it a sought-after material among multiple industries. It is known for its corrosion resistance and high strength, and toughness. This makes the alloy suitable for projects that require superior corrosion resistance, like sea water piping or marine use, chemical industry and food processing equipment. The combination of good strength, excellent corrosion resistance and high toughness, even at low temperatures, make duplex steel UNS S31500 an ideal choice for demanding applications since it provides more cost-effective solutions than other alloys.

Heat Resistance

Duplex steel UNS S31500 is known for its superior heat resistance properties compared to conventional stainless steel alloys. Due to its two-phase microstructure, the alloy shows excellent oxidation and corrosion resistance – even in harsh environments. In addition, it has a higher chromium content which helps it withstand elevated temperatures without losing ductility or toughness. This makes Duplex steel UNS S31500 an ideal choice for applications such as wall panels and linings in chemical processing units, marine equipment and pressure vessels operating at extreme temperatures.

Heat Treatment

If you’re looking for an alloy with excellent corrosion resistance and high-temperature strength, duplex steel UNS S31500 is the answer. This alloy is resistant to pitting and crevice corrosion and retains its strength when exposed to temperatures up to 600°C. To achieve these amazing performance levels, S31500 must be heat treated carefully to maintain the balance between its ferrite and austenitic structures. During heat treatment, the alloy may undergo several cycles of heating and cooling to reach the desired level of toughness and corrosion resistance. Once it has been heat treated, duplex steel UNS S31500 can be used for components that require long-term exposure to corrosive environments or extreme temperature fluctuations.


Duplex steel UNS S31500 is a type of steel with a unique composition, which makes it highly effective for many complex machining operations. This steel exhibits excellent durability and wear resistance during machining, even under difficult conditions, allowing for high production rates. Duplex S31500 also boasts great heat-treatability, making it well-suited for custom manufacturing intricate components. In addition to its specialized machinability properties, this duplex steel also offers superior corrosion resistance and weldability. As such, UNS S31500 can be used in various applications while maintaining its top-tier performance.


Welding duplex steel UNS S31500 offers numerous benefits for engineers and production staff. Its distinct composition, which utilizes ferrite and austenite components, allows for strength and formability that is otherwise difficult to achieve with other steels. This combination also creates higher corrosion resistance, allowing it to be utilized in challenging applications without additional protective coatings that could reduce or complicate its effectiveness. Welding this alloy requires knowledge of its specific heat treatments, as these can affect how difficult the process is and how accurately it should be implemented for an optimal result. Nonetheless, when done correctly, it provides an incredibly durable welding solution across various projects.


Duplex steel uns s 31500 is an incredibly versatile material with numerous advantages over other grades thanks to its unique dual microstructure combined with specific elemental additions such as nitrogen and molybdenum. This grade offers excellent mechanical properties, but its ability to resist certain types of corrosive environments makes it suitable for many industries, including oil & gas, petrochemical, marine, nuclear energy, medical, food processing & pharmaceuticals. Furthermore, its suitability for machining and welding makes duplex steel uns s 31500 an excellent choice for many demanding applications. Therefore, few materials on the market today can match the performance offered by duplex steel uns s 31500.​ Intended Audience: Engineers and product designers looking for information about Duplex Steel UNS S31500

Related Post