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Super Duplex Stainless Steel UNS S39274: Key Insights

Super Duplex Stainless Steel UNS S39274 has become a material of choice across industries requiring exceptional strength, corrosion resistance, and performance under extreme conditions.

Developed to outperform standard duplex grades,
UNS S39274 is a high-alloyed super duplex stainless steel combining chromium, molybdenum, and nitrogen in precise ratios.

With enhanced pitting resistance and high mechanical strength, this grade is extensively used in offshore, chemical processing, and desalination applications. If you’re exploring the ideal material for critical environments, understanding the key properties of Super Duplex Stainless Steel UNS S39274 is essential.

What is Super Duplex Stainless Steel?

Super duplex stainless steel is a type of stainless alloy that features a mixed microstructure of austenite and ferrite, typically in a 50:50 ratio. This dual-phase structure offers a unique combination of high tensile strength and superior resistance to stress corrosion cracking, outperforming standard austenitic and duplex stainless steels.

While conventional duplex grades are suitable for many uses, super duplex stainless steel grades like UNS S39274 and UNS S32760 provide even greater corrosion resistance and mechanical performance in aggressive media such as seawater, acidic slurries, and chloride-rich environments.

UNS S39274 Chemical Composition

UNS S39274 contains a high percentage of chromium (25–27%), molybdenum (3.5–4.5%), and nitrogen (0.3%) to improve its corrosion and pitting resistance. Below is the typical composition chart:

ElementContent (%)
Chromium 25.0 – 27.0
Nickel6.0 – 8.0
Molybdenum3.5 – 4.5
Nitrogen 0.3 max
Carbon0.03 max
Manganese1.0 max
Silicon0.8 max
Iron Balance

This precise blend delivers an excellent pitting resistance equivalent number (PREN) typically >40, which is considered very high for stainless steels.

Mechanical Properties of UNS S39274

PropertyValue
Tensile Strength 750 MPa min
Yield Strength (0.2% offset)550 MPa min
Elongation 25% min
Hardness (Brinell) ≤ 290 HB
Impact Toughness > 100 J at -50°C

These mechanical properties ensure structural stability and toughness even in cryogenic and high-pressure applications.

Grades Comparable to UNS S39274

UNS S39274 is often compared with UNS S32760, another widely used super duplex stainless steel grade. While both are designed for high resistance to corrosion, S39274 typically offers slightly better mechanical performance and higher pitting resistance due to its precise alloy composition.

GradePREN ValueCorrosion ResistanceStrength
S39274 >42 Very HighVery High
S32760 41–42High High

Key Features of Super Duplex UNS S39274

  • High resistance to pitting and crevice corrosion in chloride-containing environments
  • Excellent stress corrosion cracking resistance
  • Outstanding mechanical strength, double that of standard austenitic stainless steels
  • High resistance to erosion and fatigue
  • Reliable performance in seawater, brine, and acidic conditions
  • Long service life with minimal maintenance

Applications of UNS S39274

Because of its corrosion resistance and mechanical properties, super duplex stainless steel UNS S39274 is used in:

  • Offshore oil & gas platforms
  • Seawater desalination plants
  • Heat exchangers and pressure vessels
  • Pulp and paper digesters
  • Marine and shipbuilding components
  • Chemical processing pipelines
  • Water injection and riser systems

Trusted Super Duplex Stainless Steel Suppliers

When sourcing super duplex stainless steel, it’s vital to choose suppliers who provide traceable material certification and consistent quality. Look for suppliers who offer:

  • Mill test certificates (EN 10204 3.1 or 3.2)
  • Stock in various forms – sheets, plates, pipes, bars, and flanges
  • Fast delivery for critical projects
  • Custom machining and fabrication services

FAQs

What is super duplex stainless steel?

Super duplex stainless steel is a high-alloy stainless steel with a mixed microstructure of austenite and ferrite, offering enhanced strength and corrosion resistance compared to standard stainless grades.

How does UNS S39274 differ from UNS S32760?

While both are super duplex alloys, UNS S39274 generally provides slightly improved mechanical strength and pitting resistance due to its precise chemical makeup.

Where is UNS S39274 commonly used?

It’s used in offshore oil rigs, desalination plants, and chemical processing units where extreme corrosion resistance and strength are required.

Can super duplex stainless steel be welded easily?

Yes, but it requires expertise to avoid phase imbalance or intermetallic phase formation. Using low heat input and controlled cooling is recommended.

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