Seamless Super Duplex Steel UNS S32950 Pipe
Designed for superior reliability in chloride-rich media, our S32950 super duplex pipes offer an optimized Pitting Resistance Equivalent Number (PREN), ensuring exceptional resistance to pitting, crevice corrosion, and stress corrosion cracking (SCC). With a yield strength nearly double that of standard austenitic stainless steels, these pipes allow for thinner wall designs and enhanced pressure ratings in heat exchangers, chemical processing, and maritime infrastructure. Through advanced cold-drawing and specialized solution annealing, GZH ensures every pipe maintains optimal phase balance and precise dimensional tolerances for mission-critical industrial applications.
"Our S32950 pipes offer an optimized PREN value tailored for brackish water and industrial chemical media, providing extreme durability at a competitive cost."
What Is a Seamless Super Duplex Steel UNS S32950 Pipe?
Seamless Super Duplex Steel UNS S32950 Pipe is a high-grade, pressure-resistant cylindrical conductor manufactured from a solid billet of a super duplex stainless steel alloy. Distinguished by the complete absence of a weld seam, this pipe offers uncompromised structural integrity, superior uniformity, and enhanced resistance to cyclic loading and stress fatigue, making it highly reliable for demanding piping systems.
The"UNS S32950" designation refers to a specific, high-strength super duplex grade characterized by a balanced chemical composition, including high levels of Chromium (Cr), Molybdenum (Mo), and Nitrogen (N). This carefully controlled balance results in a two-phase microstructure of approximately 40−60% ferrite and 60−40% austenite. This structure delivers a powerful combination of exceptionally high mechanical strength (significantly higher than standard duplex grades) and excellent resistance to various forms of corrosion, particularly stress corrosion cracking (SCC) and pitting in chloride-rich environments.
Key Features and Advantages
S32950 Seamless Pipe deliver a specialized set of properties that make them an economical yet high-performing material choice for challenging applications:
Excellent Corrosion Resistance: Provides superior resistance to pitting and crevice corrosion compared to conventional duplex stainless steels (like 2205). Its PREN (Pitting Resistance Equivalent Number) value is typically ≥38, suitable for moderately severe chloride environments.
Very High Strength: The duplex microstructure provides a yield strength roughly 2.5 times that of austenitic stainless steels (e.g., 316L), allowing for reduced wall thickness and lower material usage in high-pressure systems.
Good Weldability and Formability: Despite its high strength, UNS S32950 exhibits better cold-forming and welding characteristics than some higher-alloyed super duplex grades, simplifying fabrication.
Cost-Effective Solution: It offers a significant performance upgrade over standard duplex stainless steels without the extreme cost associated with nickel-based alloys, providing an excellent strength-to-cost ratio.
Resistance to SCC: It performs very well in environments prone to chloride stress corrosion cracking, a common failure mechanism for standard austenitic stainless steels.
Product Specifications and Data
To provide a comprehensive overview of this high-performance material, here are the detailed technical specifications and performance data for Super Duplex UNS S32950.
Table 1: Chemical Composition of UNS S32950
The composition of UNS S32950 is optimized for strength and corrosion resistance within the super duplex family.
| 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 | … |
Table 2: Typical Mechanical Properties of S32950
S32950 is specifically designed to maintain its strength and shape in high-stress, corrosive environments.
| Property | Value |
| Tensile Strength | ≥795 MPa |
| Yield Strength | ≥550 MPa |
| Elongation | ≥25% |
| Hardness | ≤290 HBW |
Table 3: Typical Physical Properties of S32950
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 | 1400−1440 ∘C approx. |
| Thermal Expansion | 13.0 μm/m⋅∘C (20−100∘C) |
| Thermal Conductivity | 15 W/m⋅K (20∘C) |
| Modulus of Elasticity | 200 GPa |
| Electrical Resistivity | 0.80×10−6 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% |
Length Tolerance
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.
Common Applications
The combination of high strength and excellent corrosion resistance makes Seamless Super Duplex Steel UNS S32950 Pipe ideal for specific industrial sectors:
Pulp and Paper Industry: Primarily used in digester components and piping for the brownstock washing and bleaching sections.
Fertilizer Production: Piping and heat exchanger applications where resistance to nitric acid and other corrosive reagents is required.
Offshore and Marine: Suitable for seawater cooling, firewater systems, and moderate-chloride piping where its strength is beneficial.
Chemical Processing: Used in various plant equipment, including reactors, condensers, and process piping handling corrosive chemical mixtures.
Hydropower: Used for penstocks and piping components where high strength combined with exposure to mildly corrosive water is present.
Manufacturing Process
The production of a Seamless Super Duplex Steel Pipe adheres to stringent quality controls to ensure the optimal final microstructure:
- Billet Preparation and Heating: A solid, precisely-alloyed billet of UNS S32950 is meticulously prepared and heated to the required hot-working temperature.
- Piercing: The heated billet is then passed through a piercing mill, where a mandrel is forced through the center, generating the hollow seamless shell.
- Hot Extrusion/Rolling: The shell is further dimensioned by hot rolling or extrusion, reducing its diameter and wall thickness to match the required pipe specifications.
- Solution Annealing and Quenching: The pipe is subjected to a critical heat treatment: solution annealing at a high temperature (typically 1080∘C to 1120∘C) to homogenize the structure, immediately followed by rapid water quenching. This step is crucial for achieving the correct ≈50/50 ferrite-austenite phase balance and maximizing corrosion resistance.
- Finishing and Inspection: After cooling, the pipe undergoes straightening, end finishing (e.g., beveling), and rigorous non-destructive testing, including eddy current, hydrostatic, and ultrasonic inspections, to guarantee dimensional accuracy and internal soundness.
