Super Duplex Stainless Steel: A Key Material for Industrial Structures

In modern industries where extreme pressure, aggressive environments, and structural strength are daily challenges, Super Duplex Stainless Steel stands out as an essential material. Combining superior corrosion resistance, mechanical strength, and ease of maintenance, super duplex stainless steel is the go-to solution for industrial applications like offshore platforms, chemical plants, desalination, and high-pressure piping systems.

If you’re sourcing super duplex stainless steel sheets, plates, super duplex flanges, or looking for easy-to-maintain super duplex pipe options, this guide dives deep into its properties, applications, grades, and buying insights.

What Is Super Duplex Stainless Steel?

Super Duplex Stainless Steel, a high-alloy material, comprises approximately 50% austenite and 50% ferrite in its microstructure, which enhances its performance characteristics. This duplex structure provides excellent corrosion resistance against chloride pitting and crevice corrosion, particularly in corrosive environments.

Common Designations:

UNS S32750
UNS S32760
EN 1.4410
ASTM A240 (for plates/sheets)
ASTM A182 (for flanges)

Its popularity stems from outperforming both austenitic (like 316L) and super duplex materials in critical operations.

Super Duplex Chemical Composition (UNS S32750/S32760)

Element	Typical Range (%)
Chromium (Cr)	24 – 26
Nickel (Ni)	6 – 8
Molybdenum (Mo)	3 – 5
Nitrogen (N)	0.24 – 0.32
Manganese (Mn)	≤ 1.2
Carbon (C)	≤ 0.030
Iron (Fe)	Balance

The high levels of chromium, molybdenum, and nitrogen in super duplex materials contribute to its high pitting resistance equivalent number (PREN), often exceeding 40.

Mechanical Properties of Super Duplex Steel

Property	Value
Density	7.8 g/cm³
Tensile Strength	770–850 MPa
Yield Strength	≥ 550 MPa
Elongation	≥ 15%
Hardness	≤ 32 HRC
Impact Toughness	Excellent (even at -50°C)

These properties make super duplex materials suitable for high-stress and highly corrosive environments.

Where Is Super Duplex Stainless Steel Used?

Industry	Applications
Oil & Gas	Subsea pipelines, heat exchangers, separators
Petrochemical	Pressure vessels, scrubbers, heat exchangers
Desalination	Evaporator tubes, brine heaters
Marine	Propeller shafts, hull reinforcements
Pulp & Paper	Digesters, bleach washers
Power Plants	Superheaters, water treatment lines

Due to its excellent corrosion resistance and superior strength, super duplex materials are widely adopted in aggressive environments.

Common Product Forms of Super Duplex Steel

Form	Standard/Spec	Application
Super Duplex Stainless Steel Sheets and Plates	ASTM A240	Structural panels, tanks, pressure vessels
Super Duplex Flanges	ASTM A182 F53/F55	Piping connections in high-pressure systems
Super Duplex Pipes	ASTM A790 / A928	Oil & gas piping, marine exhaust
Super Duplex Fittings	ASTM A815	Pipe couplings, reducers, elbows
Super Duplex Round Bars	ASTM A479	Shafts, valve stems, fasteners

These super duplex materials are often sourced with certifications like NACE MR0175, PED, and ISO 9001 for global compatibility.

Super Duplex Grades Overview

Grade	UNS Number	PREN	Common Use
S32750	UNS S32750	>41	Oil & gas pipelines
S32760	UNS S32760	>42	Desalination & marine
S39274	UNS S39274	>45	Aggressive sour service
F53	ASTM A182	>40	High-pressure flanges
F55	ASTM A182	>42	Offshore and chemical plants

A PREN (Pitting Resistance Equivalent Number) >40 indicates excellent corrosion resistance for super duplex materials in seawater.

Why Choose Super Duplex for Industrial Use?

1. Strength and Durability:

Up to twice the yield strength of austenitic stainless steels (like 304 or 316), reducing wall thickness in pressure vessels and piping.

2. Corrosion Resistance:

Outstanding resistance to chloride-induced stress corrosion cracking, pitting, and general corrosion.

3. Cost-Effective Over Life Cycle:

Though more expensive upfront than 316L, its long service life, lower maintenance, and reduced downtime result in lower total cost of ownership.

4. Easy to Maintain:

Super duplex pipes and fittings require minimal maintenance due to their high resistance to scaling, corrosion, and erosion.

Super Duplex vs Other Stainless Steels

Property	316L	Duplex 2205	Super Duplex S32750
Yield Strength (MPa)	290	450	550–600
PREN	~24	~35	>41
Chloride SCC Resistance	Moderate	Good	Excellent
Cost	Low	Medium	High (but value-rich)
Lifespan in Aggressive Environments	Short	Medium	Long

Installation & Maintenance Tips

Use matching filler metals (ER2594 or ENiCrMo-3) for welding.
Avoid prolonged exposure above 250°C to prevent embrittlement.
Post-weld heat treatment is not always required—it reduces fabrication costs.
Use pickling and passivation for surface protection post-installation.

Need Super Duplex Stainless Steel Products?

Looking for certified super duplex stainless steel sheets, plates, flanges, or pipes?

Connect with verified Indian suppliers offering:

ASTM and ASME standard-compliant materials
Custom fabrication and cut-to-length services
Export-ready packaging and logistics support
Third-party inspection approvals

Enhance your industrial infrastructure with materials engineered for extreme environments and lasting performance.

Final Thoughts

Super Duplex Stainless Steel is not just another alloy—it’s an industrial workhorse designed for extreme environments where strength, corrosion resistance, and long-term value matter most. Whether you’re sourcing super duplex flanges for a petrochemical pipeline or easy to maintain super duplex pipe for a desalination plant, the material’s reliability pays dividends in performance and durability.

Always choose reputed super duplex stainless steel suppliers with certifications for your project compliance.

FAQs

What makes super duplex steel different from duplex steel?

Super duplex has higher alloy content, giving it better mechanical strength and corrosion resistance, especially in seawater or acidic conditions.

Are super duplex flanges resistant to seawater corrosion?

Yes, they are highly resistant to chloride stress corrosion and pitting, making them ideal for marine and desalination industries.

Is super duplex stainless steel easy to maintain?

Yes, due to its high resistance to erosion, pitting, and stress corrosion, it requires minimal maintenance compared to carbon steel or even austenitic stainless steels.

What are the main grades of super duplex stainless steel?

UNS S32750 and S32760 are the most widely used grades, with F53 and F55 designations for forged products.

Can super duplex steel be welded easily?

Yes, but it requires proper procedures to avoid intermetallic phase formation. Use appropriate filler metals and inert shielding gases.