Request a quote

How Is Duplex Stainless Steel Processed for Heavy Applications?

In this comprehensive guide, we’ll explore how duplex stainless steel is processed, its grades, physical properties, and applications.
Book A Consultation

Duplex stainless steel is a high-performance material widely used in demanding environments like oil & gas, chemical processing, marine, and structural engineering. Known for its excellent combination of mechanical strength and corrosion resistance, duplex stainless steel is specially processed and fabricated to meet the rigorous requirements of heavy-duty industrial applications.

What Is Duplex Stainless Steel?

Duplex stainless steel is a family of stainless steels that features a dual-phase microstructure—approximately equal parts austenite and ferrite. This balanced structure gives duplex steel its superior strength, corrosion resistance, and weldability compared to standard austenitic grades like 304 and 316.
2 What Is Duplex Stainless Steel

Duplex Stainless Steel Composition

The composition of duplex stainless steel is carefully controlled to achieve its desirable properties. Here is the typical chemical composition:

Element

Typical Range (%)

Chromium (Cr)

21–25

Nickel (Ni)

4.5–7

Molybdenum (Mo)

2.5–4

Nitrogen (N)

0.1–0.3

Manganese (Mn)

≤ 2

Carbon (C)

≤ 0.03

Iron (Fe)

Balance

 

Key Properties of Duplex Stainless Steel

Property

Value

Tensile Strength

600–900 MPa

Yield Strength

450–650 MPa

Elongation

25–30%

Hardness (Brinell)

170–290 HB

Density

~7.8 g/cm³

Pitting Resistance Equivalent (PREN)

>35 (high resistance to pitting)

These values make duplex stainless steel twice as strong as austenitic grades and highly suitable for heavy structural components and pipelines.

How Duplex Stainless Steel Is Processed?

Melting & Casting

Duplex steel begins its life in an electric arc furnace, where it’s melted and refined to the precise composition. Molten duplex is then cast into slabs or billets for further processing.

Hot Working

Billets are hot rolled or forged into duplex stainless steel round bars, sheets, plates, and pipes. Controlled heat and pressure are applied to maintain uniform grain structure and eliminate impurities.

Heat Treatment

Post-rolling, duplex steel is annealed to:

  • Relieve internal stresses

  • Optimize its austenite-ferrite balance

  • Improve corrosion resistance
The standard annealing temperature ranges from 1040–1100°C, followed by rapid water or air cooling.

Cold Working & Finishing

For precision components or structural profiles, cold working (drawing, bending, machining) enhances strength and surface finish. Duplex stainless steel sheets and plates are then polished or surface-treated as needed.

Duplex Stainless Steel Forms & Grades

Product Type

Common Grades

Applications

Duplex Round Bar

UNS S31803 / S32205

Shafts, fasteners and structural supports

Duplex Steel Pipes

UNS S32205, S32750

Offshore platforms, chemical plants

Duplex Sheets & Plates

UNS S32304, S32760

Pressure vessels, tanks and marine components

Popular Grades of Duplex Stainless Steel:

  • UNS S31803 / S32205 (Standard Duplex)
  • UNS S32750 (Super Duplex)
  • UNS S32760 (Super Duplex)
  • UNS S32101 (Lean Duplex)
Each grade is selected based on its mechanical strength, corrosion resistance, and weldability for a given application.

Applications of Duplex Stainless Steel in Heavy Industries

Industry

Applications

Oil & Gas

Subsea pipelines, valves, pressure vessels

Marine & Shipbuilding

Propeller shafts, hull components, seawater cooling systems

Chemical Processing

Heat exchangers, reactors, caustic solution tanks

Structural Engineering

Load-bearing beams, bridges, heavy frames

Power Generation

Boiler components, cooling tower parts

 

Due to its resistance to chloride stress corrosion, duplex is often the material of choice for offshore and marine environments.

Duplex vs Austenitic Stainless Steel

Feature

Duplex Stainless Steel

Austenitic (304/316)

Strength

2x stronger

Moderate

Corrosion Resistance

Excellent (especially to pitting & SCC)

Good

Weldability

Requires expertise

Easier to weld

Cost

Slightly higher

Lower initial cost

Density

~7.8 g/cm³

~7.9 g/cm³

 

Looking for high-quality Duplex Stainless Products?

Steelco Metal is a leading Duplex Stainless Steel supplier in high-quality products, including:

  • Duplex round bars

  • Duplex stainless steel pipes

  • Sheets and plates for structural, industrial, and marine-grade applications.

We supply a wide range of duplex stainless steel grades and provide custom processing and cutting services to suit your project needs.

 

FAQ

Duplex is a stainless steel alloy with both austenitic and ferritic phases, offering superior strength and corrosion resistance, especially in chloride-rich environments.
The typical density of duplex stainless steel is approximately 7.8 g/cm³, slightly lower than that of austenitic grades.
The most widely used grades are UNS S31803 (standard duplex) and UNS S32750/S32760 (super duplex).
Yes, but it requires controlled heat input and expert welders to maintain the correct austenite-ferrite balance in the heat-affected zone.
Vector 2

Need Help?
We're Here for You!

Feel free to contact us any time. we will get back to you as soon as we can!
Download Our Brochure
Our Company Details
Scroll to Top
Call Now Button