Seamless UNS S31500 Duplex Steel Pipe
Our S31500 duplex pipes are specifically designed to provide a strategic combination of high mechanical strength and exceptional resistance to chloride-induced stress corrosion cracking (SCC). With a yield strength nearly double that of conventional 300-series stainless steels, these pipes allow for thinner wall designs and increased pressure ratings in heat exchangers and chemical processing systems. Through advanced cold-drawing and precise solution annealing, GZH ensures every pipe maintains optimal phase balance and a high-integrity surface finish for the most demanding industrial environments.
"Our S31500 pipes offer a PREN value that ensures durability in brackish water and mildly corrosive chemical media."
What Is a Seamless UNS S31500 Duplex Steel Pipe?
Seamless UNS S31500 Duplex Steel pipe is a high-performance, corrosion-resistant pipe crafted from a single, solid billet of a lean duplex stainless steel. It is manufactured without a weld joint, ensuring superior structural integrity and reliability, especially under high-stress and moderately corrosive conditions. The"UNS S31500"designation is its specific Unified Numbering System identifier. This grade is known as a"lean"duplex because it has a lower alloy content, particularly less nickel and molybdenum, than standard duplex grades like S31803. Its unique microstructure, a balanced mix of austenitic and ferritic stainless steel phases, gives it a combination of good toughness and stress-corrosion cracking resistance, making it an excellent alternative to standard austenitic stainless steels like 304 and 316.
Key Features and Advantages
Seamless S31500 Duplex Steel pipes offer a unique combination of benefits that make them invaluable in various industries:
Good Corrosion Resistance: It provides good resistance to chloride-ion stress-corrosion cracking, pitting, and crevice corrosion, outperforming standard austenitic grades like 304 and 316 in many applications.
High Strength: It offers significantly higher tensile and yield strength than standard austenitic stainless steels, allowing for the use of thinner wall thicknesses and reduced material costs.
High Pressure and Temperature Tolerance: The seamless construction and robust material allow the pipe to safely handle high internal pressures and a wide range of operating temperatures.
Cost-Effective: Its high strength-to-weight ratio and lean alloy content often make it a more economical choice than higher-alloy duplex or austenitic grades.
Good Weldability: The alloy can be welded using standard methods, and its balanced composition minimizes the risk of harmful phase precipitation.
Product Specifications and Data
To provide a comprehensive overview of this high-performance material, here are the detailed technical specifications and performance data for UNS S31500 Duplex Steel.
Table 1: Chemical Composition of UNS S31500 Duplex Steel
The composition of UNS S31500 is carefully balanced to achieve its good corrosion resistance and high strength.
| 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 UNS S31500 Duplex Steel
UNS S31500 Duplex Steel is specifically designed to maintain its strength and shape in high-stress, corrosive environments.
| Property | Value (Annealed) |
| Tensile Strength | ≥ 590 MPa |
| Yield Strength | ≥ 400 MPa |
| Elongation | ≥ 30% |
| Hardness | ≤ 290 HBW |
Table 3: Typical Physical Properties of UNS S31500 Duplex Steel
These physical properties highlight the material's ability to perform reliably under a wide range of conditions.
| Property | Value |
| Density | 7.7 g/cm³ |
| Melting Point | 1450 - 1510 °C approx. |
| Thermal Expansion | 13.0 µm/m·°C (20-100°C) |
| Thermal Conductivity | 18.0 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% |
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 good corrosion resistance of seamless UNS S31500 Duplex Steel pipes makes them a preferred choice for:
Oil and Gas Industry: For piping, risers, and manifolds in mildly corrosive environments.
Chemical Processing: In heat exchangers and piping for handling mildly corrosive chemicals.
Marine Engineering: In seawater applications and structural components of ships.
Construction: In structural applications where both strength and corrosion resistance are required.
Manufacturing Process
The manufacturing of a SeamlessDuplex Steel pipes is a precise, multi-step process:
- Heating: A solid billet of UNS S31500 Duplex Steel is heated to a high temperature.
- Piercing: A piercing mill pushes a mandrel through the center of the heated billet to form a hollow shell.
- Drawing and Sizing: The hollow shell is then rolled and drawn to reduce its diameter and wall thickness to the desired dimensions.
- Heat Treatment: The pipe is solution annealed to achieve its specified metallurgical properties and to ensure optimal performance.
- Finishing: The pipe is cut to length, straightened, and subjected to rigorous non-destructive testing to verify its integrity before final inspection and packaging. This meticulous process ensures that every seamless UNS S31500 Duplex Steel pipe is built to withstand the most demanding applications.
