Duplex & Super-Duplex
When strength and corrosion resistance alone are not enough, the choice is Duplex.
Strengths of Duplex
-
The dual strength of Duplex combines the best properties of ferritic and austenitic structures. It offers excellent mechanical strength and corrosion resistance for demanding process applications.
-
Super Duplex withstands high pressure and chloride-rich environments where standard steel fails to maintain its strength. It is especially suitable for high-pressure piping and critical structures in seawater treatment.
-
At PreOne, Duplex and Super Duplex welding is performed using qualified WPS procedures across a wide range of material thicknesses. This ensures joint strength, dimensional accuracy, and long-term operational reliability.
Duplex 2205 / Super-Duplex 2507
Duplex & SDX vs. other materials
Duplex & SDX vs. other materials
Duplex & SDX vs. others
- Duplex & SDX
- Titanium
- Tantalum
- Zirconium
- Hastelloy
- Nickel alloys
- Stainless steels
- Aluminium
- Duplex & SDX
- Titanium
- Tantalum
- Zirconium
- Hastelloy
- Nickel alloys
- Stainless steels
- Aluminium
- Duplex & SDX
- Titanium
- Tantalum
- Zirconium
- Hastelloy
- Nickel alloys
- Stainless steels
- Aluminium
- Duplex & SDX
- Titanium
- Tantalum
- Zirconium
- Hastelloy
- Nickel alloys
- Stainless steels
- Aluminium
- Duplex & SDX
- Titanium
- Tantalum
- Zirconium
- Hastelloy
- Nickel alloys
- Stainless steels
- Aluminium
Typical applications for Duplex
Processes where Duplex’s strength and corrosion resistance are crucial.
AQ about Duplex & Super Duplex
When is Duplex a better choice than stainless steel?
Duplex is used when the process involves chlorides, seawater, high pressure, or risks of stress corrosion cracking. These conditions rapidly degrade standard stainless steel, but Duplex’s dual-phase structure (containing both austenite and ferrite) offers double the strength and excellent corrosion resistance. This often also allows for the use of thinner wall thicknesses, saving weight and costs.
Does Duplex require special procedures in welding?
Yes, absolutely. Duplex is sensitive to heat input during welding: if it cools too fast or too slow, the material’s phase balance is disturbed, and corrosion resistance collapses.
- Heat input: Must be kept within strictly calculated limits.
- Filler materials: We always use “over-alloyed” filler materials to ensure the corrosion properties of the weld seam.
- Gas shielding: The use of backing gas is critical to prevent nitrogen loss from the weld pool (which would degrade quality).
Which Duplex and Super Duplex grades does PreOne use?
We most commonly use so-called “Standard Duplex” (2205 / EN 1.4462), which is the industry workhorse. For more demanding applications, such as offshore conditions or highly corrosive processes, we use Super Duplex (2507 / EN 1.4410), which has a significantly higher PREN value (Pitting Resistance Equivalent Number). We source materials from reliable suppliers with complete traceability.
Strength and corrosion resistance in a single structure
Duplex and Super Duplex perform in processes where mechanical loads and chloride-rich environments challenge the limits of steel.
Duplex and Super Duplex are the material choices when the environment is simultaneously mechanically demanding and chemically challenging. Their dual-phase structure combines the strength of ferrite and the toughness of austenite in a way that offers significantly better resistance to stress corrosion cracking and pitting than standard stainless steel. This makes Duplex a reliable option for seawater, pulp, and paper industry applications, as well as other processes where chlorides and pressure are constantly present.
Super Duplex takes these properties a step further. Its extremely high strength and corrosion resistance enable structures that function amidst strong pressure fluctuations, seawater exposure, and chemical reactions without performance degradation. Super Duplex is chosen when other materials no longer offer a sufficient safety factor.
Duplex and Super Duplex solutions require a strictly controlled welding process to maintain the correct ferrite-austenite balance of the material. At PreOne, we handle these tasks using qualified WPS procedures for all thicknesses. This ensures the mechanical properties, dimensional accuracy, and long service life of the joints, even in rapidly fluctuating conditions.
Duplex is not just strong steel — it is the material for processes where strength and corrosion resistance must go hand in hand.
