Seamless Super Duplex Steel UNS S32760 Pipe
Designed for the most aggressive environments, our S32760 pipes feature an exceptionally high Pitting Resistance Equivalent Number (PREN ≥ 41). This ensures unmatched resistance to pitting and crevice corrosion in hot seawater and sour gas (H2S) services. The addition of tungsten and copper provides critical stability in both organic and inorganic acids, making it the optimal choice for desalination, offshore oil & gas, and subsea infrastructure. Through advanced cold-drawing and precise solution annealing, GZH guarantees optimal phase balance and maximum mechanical strength for mission-critical industrial applications.
PREN =%Cr + 3.3X(%Mo + 0.5X%W) + 16X%N≥ 41
Seamless Super Duplex Steel UNS S32760 Pipe – High-Performance Corrosion-Resistant Solution
What is Seamless Super Duplex Steel UNS S32760 Pipe?
Seamless Super Duplex Steel S32760 Pipe (also known as EN 1.4501 or F55) is a premium, high-alloy stainless steel piping solution engineered for the most aggressive industrial environments. Manufactured from a single solid billet via seamless hot extrusion, it delivers homogenous microstructure, superior burst strength, and exceptional reliability under high-pressure and corrosive conditions.
As a Super Duplex grade, S32760 features a carefully balanced 50:50 austenite-ferrite microstructure, enriched with Chromium (Cr), Molybdenum (Mo), Nitrogen (N), Tungsten (W), and Copper (Cu). This unique composition provides a Pitting Resistance Equivalent Number (PREN) ≥ 41, placing it among the highest corrosion-resistant stainless steels available.
Key Advantages of Super Duplex S32760 Pipes
Exceptional Localized Corrosion Resistance
Engineered to resist pitting and crevice corrosioninhot, high-chloride environments, such as seawater, brine, and chemical processing fluids.
High Mechanical Strength
With a yield strength ≥ 550 MPa (over twice that of 316L austenitic stainless steel), S32760 pipes allow for thinner wall designs and significant weight reduction without compromising structural integrity.
Stress Corrosion Cracking (SCC) Immunity
The ferritic phase provides outstanding resistance to chloride-induced SCC, critical for oil & gas, marine, and chemical applications.
Cryogenic Toughness
Maintainsexcellent impact resistance and structural performance at temperatures down to -50°C, making it suitable for subsea and cold-environment installations.
Erosion-Corrosion Protection
The addition of Tungsten (W) enhances hardness and wear resistance, ideal for high-velocity fluid systems carrying sand or abrasive particles.
Technical Specifications of UNS S32760 / F55
Table 1: Chemical Composition of UNS S32760
The composition of UNS S32760 is precisely controlled to maximize its duplex properties and corrosion resistance.
| Grade | C | Mn | P | S | Si | Ni | Cr | Mo | N | Cu | Ohters |
| 31803 | ≤0.03 | ≤2.00 | ≤0.03 | ≤0.02 | ≤1.00 | 4.50-6.50 | 21.00-23.00 | 2.50-3.50 | 0.08-0.20 | … | … |
| 32205 | ≤0.03 | ≤2.00 | ≤0.03 | ≤0.02 | ≤1.00 | 4.50-6.50 | 22.00-23.00 | 3.00-3.50 | 0.14-0.20 | … | … |
| 31500 | ≤0.03 | 1.20-2.00 | ≤0.03 | ≤0.03 | 1.40-2.00 | 4.20-5.20 | 18.00-19.00 | 2.50-3.00 | 0.15-0.10 | 1.50-2.50 | … |
| 32550 | ≤0.04 | ≤1.50 | ≤0.04 | ≤0.03 | ≤1.00 | 4.50-6.50 | 24.00-27.00 | 2.90-3.90 | 0.10-0.25 | … | … |
| 32750 | ≤0.03 | ≤1.20 | ≤0.035 | ≤0.02 | ≤0.80 | 6.00-8.00 | 24.00-26.00 | 3.00-5.00 | 0.24-0.32 | ≤0.50 | … |
| 32760 | ≤0.05 | ≤1.00 | ≤0.030 | ≤0.01 | ≤1.00 | 6.00-8.00 | 24.00-26.00 | 3.00-4.00 | 0.20-0.30 | 0.50-1.00 | W 0.50 -1.00 |
| 32950 | ≤0.08 | ≤2.00 | ≤0.035 | ≤0.01 | ≤0.60 | 3.50-5.20 | 26.00-29.00 | 1.00-2.50 | 0.15-0.35 | … | … |
| 32906 | ≤0.03 | 0.80-1.50 | ≤0.030 | ≤0.03 | ≤0.50 | 5.80-7.50 | 28.00-30.00 | 1.50-2.60 | 0.30-0.40 | ≤0.80 | … |
NOTE: PREN:Cr+3.3*(Mo+0.5*W)+16*N≥41 |
Table 2: Typical Mechanical Properties of UNS S32760
UNS S32760 is specifically designed to maintain its strength and shape in high-stress, corrosive environments.
| Property | Value |
| Tensile Strength | ≥750 MPa |
| Yield Strength | ≥550 MPa |
| Elongation | ≥25% |
| Hardness | ≤270 HBW |
Table 3: Typical Physical Properties of UNS S32760
These physical properties highlight the material's ability to perform reliably under a wide range of conditions.
| Property | Value |
| Density | 7.8 g/cm³ |
| Melting Point | 1450 °C approx. |
| Thermal Expansion | 13.5 µm/m·°C (20-100°C) |
| Thermal Conductivity | 15.0 W/m·K (20°C) |
| Modulus of Elasticity | 200 GPa |
| Electrical Resistivity | 0.85 x 10⁻⁶ Ω·m (20°C) |
Table 4: The Standard of ASTM A790 Size Tolerance Size Chart :
| NPS Designator (Inches) | Permissible Variations in Outside Diameter (Inches) |
| 1⁄8 to 1 1⁄2, inclusive | Over: 1⁄64 in. (0.015 in.) |
| Under: 1⁄32 in. (0.031 in.) | |
| Over 1 1⁄2 to 4, inclusive | Over: 1⁄32 in. (0.031 in.) |
| Under: 1⁄32 in. (0.031 in.) | |
| Over 4 to 8, inclusive | Over: 1⁄16 in. (0.062 in.) |
| Under: 1⁄32 in. (0.031 in.) | |
| Over 8 to 18, inclusive | Over: 3⁄32 in. (0.093 in.) |
| Under: 1⁄32 in. (0.031 in.) | |
| Over 18 to 26, inclusive | Over: 1⁄8 in. (0.125 in.) |
| Under: 1⁄32 in. (0.031 in.) | |
| Over 26 to 34, inclusive | Over: 5⁄32 in. (0.156 in.) |
| Under: 1⁄32 in. (0.031 in.) | |
| Over 34 to 48, inclusive | Over: 3⁄16 in. (0.187 in.) |
| Under: 1⁄32 in. (0.031 in.) |
Wall Thickness (WT) Tolerance
The wall thickness tolerances are defined by the nominal wall thickness (t) and the outside diameter (D).
1. Minimum Wall Thickness
The minimum wall thickness at any point on the pipe shall not be more than {12.5%} under the nominal (specified) wall thickness.
2. Maximum Wall Thickness (Percentage Over Nominal)
The maximum allowable wall thickness variation depends on the size and the t/D ratio (ratio of nominal wall thickness to ordered outside diameter):
| NPS Designator (Inches) | t/D Ratio | Permissible Variation (Over Nominal WT) |
| 1/8 to 2, inclusive | All ratios | +20.0% |
| 3 to 18, inclusive | t/D ≤ 5% | +22.5% |
| 3 to 18, inclusive | t/D >5% | +15.0% |
| 20 and larger (Seamless) | t/D ≤ 5% | +22.5% |
| 20 and larger (Seamless) | t/D >5% | +15.0% |
| 20 and larger (Welded) | All ratios | +17.5% |
For pipe ordered to a Specific Cut Length, the standard tolerance is +1⁄8 in. [3.2 mm], -0 in. [0 mm].
Pipe is typically supplied in Single Random Lengths (17 to 24 ft) or Double Random Lengths (38 to 40 ft), unless otherwise specified.
Disclaimer: These tolerances are based on the common requirements found in ASTM A790, primarily through its reference to ASTM A999. The full and most current specification document must always be consulted for official design and procurement purposes.
High-End Industrial Applications
Thehigh-performance characteristics of UNS S32760 make it ideal for critical, zero-failure applications:
- Deepwater Oil & Gas – Subsea manifolds, risers, and flowlines handling sour (H₂S-rich) fluids
- Desalination Plants – High-pressure Reverse Osmosis (RO) piping and brine concentrators
- Chemical Processing – Production of organic/fatty acids, flue gas desulfurization (FGD) scrubbers
- Marine & Naval – Fire-main systems, propeller shafts, and seawater cooling systems
Quality Assurance & Certified Testing
AllSeamless Super Duplex S32760 pipesare100% tested and certified to meet EN 10204 3.1 / 3.2standards.
Corrosion Testing
- ASTM G48 Method A – Pitting corrosion
- Intergranular corrosion tests
Non-Destructive Testing (NDT)
- Ultrasonic Testing (UT)
- Eddy Current Testing (ET)
- Hydrostatic Pressure Testing
Mechanical Verification
- Impact Testing at -50°C
- Flattening, Flare, and Hardness Tests
Material Verification
- 100% Positive Material Identification (PMI)
- Third-Party Inspection (TPI)
Product Selection Guide: Duplex vs. Super Duplex
Selecting the right grade involves balancing corrosion resistance (PREN),mechanical strength, and project budget.
Table 1: Comparative Technical Overview
Feature | Duplex S31803 (2205) | Super Duplex S32750 (2507) | Super Duplex S32760 (F55) |
Alloy Type | Standard Duplex | Super Duplex | Super Duplex (+W/Cu) |
PREN Value | 31 - 35 | ≥ 41 | ≥ 41 |
Yield Strength | ≥450MPa | ≥550$MPa | ≥550$MPa |
Main Chemistry | 22Cr, 5Ni, 3Mo | 25Cr, 7Ni, 4Mo | 25Cr, 7Ni, 3.5Mo, 0.7W |
Critical Pitting Temp (CPT) | ~35°C | ~50°C | ~50°C+ |
Understanding the Differences
1. UNS S31803 (Standard Duplex 2205)
This is the most widely used duplex grade. It is the"all-rounder"for general industrial use where standard 316L stainless steel fails due to stress corrosion cracking.
- Best For: General chemical processing, oil and gas gathering lines, and brewery equipment.
- Limitation: Not recommended for service temperatures above 300°C or highly concentrated hot chlorides.5
2. UNS S32750 (Super Duplex 2507)
Designed for highly corrosive conditions, S32750 has higher Chromium and Molybdenum content than 2205.
- Best For: Desalination, subsea piping, and marine environments.
- Performance: Exceptional resistance to pitting in seawater. It is stronger than S31803, allowing for thinner walls.
3. UNS S32760 (Super Duplex F55 / Zeron 100)
Technically similar to S32750, but with the specific addition of Tungsten (W)andCopper (Cu).
- The Tungsten Advantage: Tungsten improves pitting resistance in very low pH environments and enhances the material's resistance to erosion-corrosion.
- Best For: Aggressive"sour"oil and gas wells, flue gas desulfurization (FGD), and complex chemical mining processes.
Selection Logic: Which one should you choose?
- Is the environment high in chlorides (seawater)?
- IfYes, move to Super Duplex (S32750orS32760).
- Does the fluid contain abrasives or very low pH (acidic) chemicals?
- IfYes,S32760 is the superior choice due to the Tungsten addition.
- Is weight a critical factor for offshore platforms?
- S32750/S32760 allow for the thinnest pipe walls due to their high yield strength.
- Is cost the primary driver for a non-extreme environment?
- S31803 offers the best value-to-performance ratio for standard corrosive service.
Quality Assurance for All Grades
Regardless of the grade selected, all our seamless pipes are supplied with:
- ASTM A790Compliance.
- 100% PMI (Positive Material Identification) to ensure no grade mixing.
- Microstructure Analysis to verify the 50/50 phase balance.
