Super Duplex F55 Plate

Q: Does NACE Approve?

Sim ,Super Duplex F55 is fully approved under NACE MR0175 / ISO 15156 for use in sour gas applications.To maintain compliance,the material must be supplied in the solution-annealed condition and exhibit a maximum hardness of 28 HRC (290 HBW).

UMA super duplex F55 plate is a high-performance flat-rolled metal sheet made from a highly alloyed ferritic-austenitic stainless steel.This specific grade-also designated as UNS S32760, EN 1.4501 or Zeron 100-is explicitly engineered to provide extreme mechanical strength and exceptional corrosion resistance in harsh,chloride-rich,and acidic environments.

Core Technical Properties

High Pitting Resistance:
It achieves a PREN of >40, guaranteeing outstanding durability in seawater.
Alta resistência mecânica:
F55 yields double the strength of standard austenitic 316L stainless steel,allowing engineers to design thinner,lighter walls for pressure-rated systems.
SCC Resistance:
Excellent resistance to cracking in high-chloride,sour,and marine environments.
Temperature Limitations:
It maintains high impact strength at sub-zero temperatures,but is prone to embrittlement if subjected to prolonged use above 300°C (approx. 570°F).

Applications of Super Duplex F55 Plate

We offer super duplex F55 plates and sheets in thicknesses of 2.0, 3.0, 4.0, 5.4, and 6.0.We offer not only placas de aço inoxidável and sheets but also plates made of Hastelloy,Incoloy,Inconel,Monel,and other alloys.Our products comply with ASTM A240,EN 10204,ISO 9001,PED 2014/68/EU ,CE,and other standards.With over a decade of experience in manufacturing and import/export,we are your best wholesaler in China.

Chemical Composition of Super Duplex F55 Plate

Cr	Ni	Mo	C	Cu	N	Mn	Si	C	P	S	Fe
24,0 – 26,0	6,0 – 8,0	3,0 – 4,0	0.50 – 1.0	0.50 – 1.0	0.20 - 0.30	≤ 1,0	≤ 1,0	≤ 0.03	≤ 0.035	≤ 0,015	Equilíbrio

Core Metallurgy: Why F55 is Unique

The Dual-Phase Microstructure

F55 plates consist of a precisely balanced 50:50 matrix of Austenite and Ferrite.

The Ferrite phase provides excellent resistance to chloride-induced SCC and offers high mechanical strength.
The Austenite phase ensures high ductility,structural toughness,and clean weldability.

The Tungsten & Copper Distinction

The definitive difference between Grade F55 and other common super duplex grades like Grade F53 is the deliberate addition of Tungsten and Copper.

This combination makes F55 much more reliable in handling highly concentrated sour gas and industrial organic/mineral acids like sulfuric and hydrochloric acids.

PREN

The composition ensures a high pitting index,calculated using the standard formula:
PREN = %Cr + 3.3 (%Mo + 0.5%W) + 16 (%N)
Due to high Cr, Mo, W, and N levels,F55 guarantees a PREN ≥ 40.Any steel with a PREN over 40 is classified as a “Super” Duplex and is theoretically immune to ambient seawater corrosion.

Critical Fabrication Considerations

Temperature Limitations

High-Temperature Embrittlement:
F55 plates must not be used for extended periods at temperatures exceeding 300℃(572℉).Exposure to high temperatures causes the rapid precipitation of brittle intermetallic phases,resulting in a dramatic loss of toughness.
Low-Temperature Toughness:
It retains good impact strength and ductility down to sub-zero service applications,often tested down to -46℃ or -50℃.

Welding Specifications

F55 plates can be successfully welded using common processes like GTAW/TIG,SMAW,and SAW.

Over-alloyed Filler Metals:
Welding must utilize a filler wire over-alloyed with Nickel to ensure the weld pool solidifies with the proper 50:50 phase balance.
Controle de entrada de calor:
Strict limits on interpass temperatures are required to prevent sigma phase formation.No PWHT is required unless a full solution anneal is performed.

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Mechanical Properties of Super Duplex F55 Plate

The mechanical behavior of a Super Duplex F55 plate is defined by its balanced 50:50 austenitic-ferritic microstructure.This dual-phase matrix provides double the yield strength of standard austenitic stainless steels alongside high ductility,toughness,and fatigue resistance.

Room-Temperature Mechanical Properties

Propriedade	Metric Units	Imperial Units
Resistência à tracção	730 – 930 MPa	106 – 135 ksi
0,2% Resistência ao escoamento	≥ 530 MPa	≥ 77 ksi
1.0% Yield Strength	≥ 550 MPa	≥ 80 ksi
Alongamento	≥ 25 %	≥ 25 %
Dureza Brinell	≤ 290 HBW	≤ 290 HBW
Rockwell C Hardness	≤ 30 HRC	≤ 30 HRC
Charpy V-Notch Impact Energy	≥ 80 Joules (-40°C)	≥ 59 ft-lbf (-40°F)

Modulus and Physical Strength

Modulus of Elasticity (Young’s Modulus):
Approximately 200 GPa (29 × 10⁶ psi) at room temperature.
Shear Modulus:
Approximately 75 GPa.
Poissons Ratio:0.3.

Impact Toughness and Sub-Zero Behavior

Traditional ferritic stainless steels are highly brittle at low temperatures.However,because F55 contains a significant amount of the tough Austenite phase,it retains remarkable impact strength at sub-zero temperatures.

Low-Temperature Testing:
According to NORSOK M-630 (MDS D55) standards for petroleum offshore piping,plates are regularly tested for impact toughness at -46°C or -50°C.
Charpy V-Notch Requirements:
The material must consistently achieve a minimum average impact energy of 80J (transverse) or 100J (longitudinal) at these freezing thresholds,proving it safe against catastrophic brittle fracturing.

Elevated Temperature Limitations & Strength De-rating

While F55 plates maintain strong structural integrity up to moderate temperatures,their design strength drops as heat increases.The material is also constrained by metallurgical limitations:

Allowable Design Strength De-rating

At 50°C (122°F):
Tensile properties remain relatively stable near nominal room-temp baselines.
At 150°C (302°F):
Yield strength decreases to roughly 430 MPa.
At 250°C (482°F):
Yield strength drops further to around 380 MPa.

The 475°C (885°F) Embrittlement Hazard

Between 300°C and 525°C,a phenomenon known as 475°C embrittlement occurs.
Microscopic separation within the chromium-rich ferrite phase creates a spinodal decomposition (α’ phase).
While this dramatically increases the hardness of the plate,it completely destroys the material’s impact toughness and ductility,rendering it as brittle as glass.

Influence of Heat Treatment on Mechanical Integrity

Heating:
The plate is heated to a temperature between 1040°C and 1120°C (1900°F to 2050°F).This high heat dissolves any harmful secondary precipitates back into the metal matrix.
Resfriamento:
The plate is then rapidly cooled via water quenching or forced air cooling.

If the cooling process is too slow through the 600°C to 1000°C range,dangerous intermetallic phases like Sigma (σ) and Chi (χ) will form. Even a 1% presence of sigma phase will cut the material’s impact toughness in half and degrade its corrosion thresholds.

Our Advantages in Manufacturing Super Duplex F55 Plate

Manufacturing Super Duplex F55 plates requires exceptional metallurgical expertise.Because the alloy is heavily balanced with Chromium,Molybdenum,Tungsten,and Copper,a minor mistake in temperature control can trigger brittle intermetallic phases,ruining the plate’s structural and corrosion-resistant integrity.

Our facility has optimized the manufacturing process to deliver 4 main competitive advantages in the production of high-quality Super Duplex F55 plates:

Controlled Phase Balance

We employ advanced Thermomechanical Control Processing combined with automated rolling mills.We precisely manage the deformation energy and finish-rolling temperatures.
This process creates a highly refined,uniform grain structure.It guarantees that the 50:50 phase ratio is consistent from the surface to the core of the plate,preventing localized structural weakness and ensuring predictable mechanical properties.

Sigma Free Quenching

Our solution-annealing line is integrated with a high-volume,high-pressure water quenching system capable of rapid cooling rates that far exceed standard commercial limits.
We freeze the high-temperature microstructural matrix instantly.This ensures a 100% sigma-free microstructure,allowing our plates to comfortably surpass the strict corrosion and microstructure requirements of NORSOK M-650 (MDS D55) and ASTM A923 Method C.

Elevated Pitting Resistance

Using Argon Oxygen Decarburization and refining processes,we keep tramp impurities (like sulfur and phosphorus) to ultra-low levels,while keeping Chromium,Molybdenum,and Nitrogen near the top of their specification limits.
We consistently deliver F55 plates with an actual heat analysis PREN ≥ 42.This provides an extra margin of safety against pitting and crevice corrosion in hot,chlorinated seawater and aggressive sour oilfield environments.

Severe Service Qualification

We feature an in-house, third-party accredited laboratory that subjects every production batch to rigorous NDT,including high-frequency UT and liquid penetrant inspection,alongside destructive tests (like Charpy V-Notch impact testing at -50°C).
Our plates ship with comprehensive EN 10204 3.1 material test certificates that are fully compliant with NACE MR0175/ISO 15156,ASME Section VIII Div 1,and prestigious oil and gas approvals like NORSOK.

FAQs About Super Duplex F55 Plate

F53 Versus F55?

While both are super duplex grades with a PREN ≥ 40,F55 contains deliberate additions of Tungsten and Copper.F53 does not.These additions give F55 superior corrosion resistance in hot,aggressive mineral acids and sour oilfield environments.

Can It Weld?

Yes,F55 features good weldability using standard methods like TIG,MIG,and SMAW.However,fabricators must use an over-alloyed filler metal to ensure the weld pool cools into the proper 50:50 austenite-ferrite phase balance.

What Is Sigma?

Sigma (σ) phase is a hard,brittle intermetallic compound that forms if F55 is cooled too slowly between 600°C and 1000°C during welding or heat treatment.Even a 1% presence of sigma phase can cut the material’s impact toughness in half and degrade its corrosion properties.

Does NACE Approve?

Sim,Super Duplex F55 is fully approved under NACE MR0175 / ISO 15156 for use in sour gas applications.To maintain compliance,the material must be supplied in the solution-annealed condition and exhibit a maximum hardness of 28 HRC (290 HBW).

Sub Zero Behavior?

Unlike standard ferritic steels that become highly brittle in cold climates,F55 retains outstanding impact toughness at sub-zero temperatures.It is regularly tested and certified down to -46°C or -50°C for arctic or deep-water offshore installations.

Super Duplex F55 Plate