What Is A182 F55?

Quick Answer

ASTM A182 F55 (UNS S32760) is a forged super duplex stainless steel with copper and tungsten additions that enhance resistance to reducing acids (sulfuric, phosphoric) and further improve pitting resistance. F55 is often specified under the trade name Zeron 100. It matches F53 (2507) in PREN and strength but offers broader corrosion resistance in mixed-acid environments.

Chemical Composition and Properties

Property	F55 (S32760)	F53 (S32750)
UNS	S32760	S32750
Common name	Zeron 100 type	Super Duplex 2507
Carbon	0.030% max	0.030% max
Chromium	24.0-26.0%	24.0-26.0%
Nickel	6.0-8.0%	6.0-8.0%
Molybdenum	3.0-4.0%	3.0-5.0%
Nitrogen	0.20-0.30%	0.24-0.32%
Copper	0.50-1.00%	-
Tungsten	0.50-1.00%	-
Tensile (min)	750 MPa (109 ksi)	795 MPa (116 ksi)
Yield (min)	550 MPa (80 ksi)	550 MPa (80 ksi)
Elongation (min)	25%	15%
Hardness	310 HBW max	310 HBW max
PREN	41-43	41-43
PREN_W	42-45	41-43
Ferrite	40-60%	40-60%
Cast equivalent	A995 6A	A995 5A

F55 vs F53: Practical Differences

Both grades achieve a standard PREN above 40 and share the same yield strength minimum. The key differences:

Copper (0.50-1.00%): Improves resistance to sulfuric acid and phosphoric acid at moderate concentrations and temperatures. In reducing acid environments, F55 outperforms F53.

Tungsten (0.50-1.00%): Enhances pitting resistance when calculated using the modified PREN formula (PREN_W = %Cr + 3.3(%Mo + 0.5%W) + 16%N). Tungsten also improves resistance to crevice corrosion in hot chloride environments.

Elongation: F55 specifies 25% minimum elongation vs 15% for F53, offering better ductility for cold-working and forming operations.

Applications

• Chemical processing: sulfuric acid, phosphoric acid, and mixed acid environments
• Offshore oil and gas: subsea manifold flanges, wellhead components, and production valves
• Flue gas desulfurization: scrubber outlet piping flanges and fittings
• Mining and mineral processing: leach circuit piping in acidic chloride slurries
• Sour gas: flanges and fittings per NACE MR0175 (hardness below 32 HRC)

F55 pairs with A995 6A cast valve bodies, A790 S32760 seamless pipe, and A815 S32760 buttweld fittings.

Testing

ASTM A182 F55 requires solution annealing (1100-1140°C), rapid water quench, ferrite verification, and corrosion testing per ASTM A923 Method C. Mill test certificates per EN 10204 3.1 or 3.2 must document chemistry (including Cu and W), mechanical properties, ferrite content, and pitting test results. NDT and hydrostatic testing follow the same requirements as other super duplex grades.

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