F55 (UNS S32760, EN 1.4501, Zeron 100) is a high-performance super duplex stainless steel with a balanced 50:50 austenitic-ferritic microstructure. Compared with standard duplex and ordinary austenitic stainless steel, F55 adds copper and tungsten alloy elements on the basis of high chromium, high molybdenum and high nitrogen. It features extremely high mechanical strength, excellent pitting resistance, crevice corrosion resistance and stress corrosion cracking resistance. Its comprehensive corrosion resistance is far superior to 316L and standard 2205 duplex steel. F55 round bar is widely recognized as the preferred material for extreme chloride, seawater, acid and alkali harsh industrial environments, commonly used in marine engineering, petrochemical, desalination and high-pressure equipment manufacturing.

2. International Equivalent Grade Standard

ASTM/USA: A182 F55 / UNS S32760

European Standard: EN 1.4501 / X2CrNiMoCuWN25-7-4

British Brand: Zeron 100

Chinese Standard: 022Cr25Ni7Mo4WCuN

Feature: PREN ≥ 40, top-level anti-corrosion grade in commercial duplex stainless steel

3. Chemical Composition (Weight % / ASTM A182 Standard)

Strict alloy proportion ensures ultra-high strength and extreme corrosion resistance for harsh medium service.

Carbon (C): ≤ 0.03% (Ultra-low carbon, prevent intergranular corrosion)

Silicon (Si): ≤ 1.00%

Manganese (Mn): ≤ 1.00%

Phosphorus (P): ≤ 0.030%

Sulfur (S): ≤ 0.010% (Ultra-low sulfur, excellent weldability)

Chromium (Cr): 24.00 – 26.00% (Core anti-corrosion element)

Nickel (Ni): 6.00 – 8.00% (Stabilize duplex microstructure)

Molybdenum (Mo): 3.00 – 4.00% (Greatly improve pitting & crevice corrosion resistance)

Nitrogen (N): 0.20 – 0.30% (Strengthen mechanical strength & structure stability)

Tungsten (W): 0.50 – 1.00% (Auxiliary anti-corrosion, improve high-temperature stability)

Copper (Cu): 0.50 – 1.00% (Enhance resistance to reducing acid corrosion)

Iron (Fe): Balance

4. Physical & Mechanical Properties

4.1 Basic Physical Properties

Density: 7.81 g/cm³

Modulus of Elasticity: 199 GPa

Thermal Conductivity: 14.5 W/m·K

Thermal Expansion Coefficient: 15.5 × 10⁻⁶ /°C

Magnetism: Magnetic (ferritic-austenitic duplex structure)

Max Working Temperature: 300°C

Low-temperature Toughness: Excellent, no brittle fracture at low temperature

4.2 Mechanical Properties (Solution Annealed Condition)

F55 strength is nearly double that of 316L and far higher than ordinary 304/2205 stainless steel

Tensile Strength: ≥ 750 MPa

0.2% Offset Yield Strength: ≥ 550 MPa

Elongation: ≥ 25%

Hardness: ≤ 290 HB / 31 HRC

4.3 High-strength Cold Drawn Condition (Optional)

Tensile Strength: ≥ 860 MPa

Yield Strength: ≥ 720 MPa

Elongation: ≥ 16%

Hardness: ≤ 335 HB / 36 HRC

5. Round Bar Diameter Tolerance Classification & Range

F55 round bars are divided into hot rolled, cold drawn and ground polished grades with strict industrial tolerance standards for different processing scenarios.

5.1 Size Range

Hot Rolled Round Bar: Φ16mm – Φ300mm

Cold Drawn Round Bar: Φ3mm – Φ120mm

Precision Ground Bar: Φ2mm – Φ80mm

Standard Length: 3000mm / 6000mm / customized fixed length

5.2 Tolerance Classification (Standard Grade)

Hot Rolled Tolerance (Normal Grade): ±0.3mm ~ ±0.8mm (for rough machining, structural parts)

Cold Drawn Tolerance (Medium Precision): ±0.05mm ~ ±0.15mm (for conventional finishing parts)

Ground Polished Tolerance (High Precision): h8 / h9 / h10 tolerance (±0.01mm~±0.03mm), smooth surface, no oxide layer, for precision mechanical and hydraulic parts

6. Surface Finishes

Black Hot Rolled Surface: Original rolling surface, suitable for rough processing and welding structural parts

Pickled Matte Surface: Uniform silver-gray finish, no oxide scale, standard industrial finished surface

Bright Cold Drawn Surface: Smooth bright surface, consistent diameter, directly usable for machining

Mirror Ground Surface: High-precision polishing, ultra-smooth surface, for high-end precision equipment parts

7. Core Product Advantages

●Extreme Corrosion Resistance: Resists seawater chloride corrosion, salt spray, pitting, crevice corrosion and stress corrosion cracking; suitable for marine and coastal high-salt environments
●Super High Mechanical Strength: Yield strength more than twice of 304/316L, effectively reduce equipment wall thickness, save material cost
●Excellent Acid Resistance: Unique Cu and W alloy elements greatly improve resistance to sulfuric acid and reducing acid medium corrosion
●Good Weldability & Processability: Ultra-low sulfur & carbon design, stable welding performance, no post-weld cracking, supports cutting, turning, forging and drilling
●High Wear & Erosion Resistance: Higher hardness than ordinary stainless steel, excellent anti-erosion performance for fluid scouring working conditions
●Long Service Life: Stable duplex structure, anti-aging, anti-fatigue, far longer service life than austenitic stainless steel in harsh environments

8. Main Applications

Marine & Offshore Engineering: Seawater desalination equipment, offshore platform fasteners, subsea pipeline parts, ship propeller shafts, seawater pump shafts and valves

Petrochemical & Oilfield: Acid medium pipeline parts, oilfield downhole tools, high-pressure corrosion-resistant bolts, chemical reactor accessories

Desalination & Environmental Protection: Seawater desalination heat exchanger tubes, brine treatment equipment, sewage corrosion-resistant structural parts

Energy Industry: Thermal power flue gas desulfurization equipment, wind power corrosion-resistant fasteners, new energy high-pressure fluid parts

Mechanical Precision Manufacturing: High-strength corrosion-resistant shafts, valve cores, hydraulic parts, precision corrosion-resistant fasteners

Paper & Pulp Industry: Corrosion-resistant roller shafts and equipment parts in pulp bleaching process

9.Production & Quality Inspection Standard

9.1 Executive Standards

ASTM A182, ASTM A479, EN 10263, GB/T 20878

9.2 Full Inspection Items

Spectroscopic chemical composition test

Tensile, yield and elongation mechanical test

Hardness test

Ultrasonic flaw detection (no internal crack & inclusion)

Dimensional tolerance full inspection

Salt spray corrosion resistance test

Metallographic microstructure detection (strict 50:50 duplex phase ratio)

10. Export Packaging

Round bars are bundled and fixed with steel strips, covered with waterproof and moisture-proof woven bags and plastic films. Both ends are protected to avoid collision deformation and surface scratch. Custom labeling, logo and export packaging requirements are supported, suitable for long-term sea transportation.