Duplex & Super Duplex Stainless Steel Fabrication

Large-Scale Duplex & Super Duplex Fabrication

When extreme environments demand superior strength and uncompromising localized corrosion resistance, engineers turn to Duplex and Super Duplex stainless steels. Featuring a dual microstructure of austenite and ferrite, these advanced alloys provide up to twice the yield strength of standard 304/316 stainless steels while offering exceptional resistance to chloride stress corrosion cracking (SCC).

However, Duplex alloys are notoriously difficult to process. They require incredibly rigid CNC machining setups, precise heat input control during welding, and strict material handling protocols. With decades of heavy fabrication experience, Openex has the specialized equipment and metallurgical expertise required to successfully fabricate massive Duplex components to ASME, API, and ISO standards.

Why Choose Openex for Duplex Fabrication?

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Strict Material Segregation Dedicated stainless processing areas to completely eliminate carbon steel cross-contamination.
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Advanced Heat Input Control Strictly monitored interpass temperatures during welding to maintain the critical 50/50 phase balance.
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Rigid Heavy Machining Massive gantry mills and VTLs with high-torque spindles capable of handling the high work-hardening rate of Super Duplex.
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Comprehensive NDT & Pickling In-house penetrant testing (PT), ultrasonic testing (UT), and full passivation/pickling services.

Common Duplex Grades We Process

We source and process fully traceable materials with complete Material Test Reports (MTRs). We regularly work with plates, heavy forgings, and thick-walled pipes in the following grades:

Material Category	Common UNS Grades	Key Characteristics
Standard Duplex	UNS S31803 / S32205 (Alloy 2205)	Excellent general corrosion resistance; PREN usually 34-35. The workhorse of the oil & gas industry.
Super Duplex	UNS S32750 (Alloy 2507) UNS S32760 (Zeron 100)	Higher Mo and Ni content; PREN > 40. Built for highly aggressive chloride environments and offshore platforms.
Lean Duplex	UNS S32304 / S32101	Cost-effective alternative to 316L with higher yield strength; ideal for structural tank farms and bridges.

Typical Duplex Fabrications

Because of our massive 250-ton lifting capacity, Openex is the premier choice for manufacturing heavy, oversized components from Duplex alloys:

Pressure Vessels & Heat Exchangers: Heavy-wall shells and precision-drilled large tube sheets.
Desalination & Water Treatment: Massive evaporation chambers and high-pressure piping manifolds.
Offshore & Marine: Topside platform structural nodes, subsea manifolds, and heavy winch bases.
Chemical Processing: Reactor shells, storage tanks, and high-pressure centrifuges.

💡 Engineer FAQ: Duplex Fabrication

What is the main advantage of Duplex steel over 316L stainless steel? ▾

The primary advantage of Duplex stainless steel (like 2205) over 316L austenitic stainless is its superior strength—often double the yield strength—and its significantly higher resistance to chloride stress corrosion cracking (SCC). This makes Duplex the preferred choice for demanding environments like offshore platforms, subsea equipment, and chemical processing plants where saltwater and corrosive chemicals are present.

Why is heat control so critical when welding Duplex and Super Duplex steels? ▾

Duplex steel gets its desirable properties from a balanced microstructure of roughly 50% austenite and 50% ferrite. If too much heat is applied during welding (a high heat input), or if the material does not cool quickly enough, this balance can be disrupted, leading to the formation of undesirable intermetallic phases. These phases can severely reduce the material's corrosion resistance and toughness. At Openex, we strictly control interpass temperatures and use specific welding procedures to maintain the critical phase balance.

Is Super Duplex always better than standard Duplex? ▾

Not necessarily; it depends on the application. Super Duplex (like 2507) has higher chromium, molybdenum, and nitrogen content, giving it a higher Pitting Resistance Equivalent number (PREN > 40). This makes it exceptionally resistant to highly corrosive environments, such as warm, high-chloride seawater. However, it is also more expensive and even more challenging to machine. For many applications where the corrosion risk is high but not extreme, standard Duplex (2205) provides an excellent and more cost-effective solution.