Seamless Super Duplex Steel UNS S32750 Pipe
Designed for the most aggressive environments, our S32750 pipes are optimized to achieve a high Pitting Resistance Equivalent Number (PREN ≥ 41). This superior threshold ensures exceptional resistance to pitting, crevice corrosion, and stress corrosion cracking (SCC) in hot seawater and sour gas services. With a yield strength significantly higher than conventional austenitic stainless steels, these pipes enable lighter wall designs and enhanced pressure ratings for mission-critical reliability. Through advanced cold-drawing and specialized solution annealing, GZH ensures every pipe maintains optimal phase balance and a high-integrity surface finish.
Technical Note: Our S32750 ensures PREN = %Cr + 3.3X%Mo + 16 X%N ≥41
Product Overview: Seamless Super Duplex Steel UNS S32750 Pipe
Seamless Super Duplex Steel UNS S32750 Pipe(also called Seamless 1.4410 duplex steel pipe too) belong to the duplex stainless steel family and feature a balanced austenite and ferrite microstructure. This unique structure offers excellent strength and corrosion resistance along with durability in demanding environments. The alloy is composed of key elements like chromium, nickel, molybdenum and nitrogen, enhancing resistance to pitting, crevice corrosion and stress corrosion cracking. Key properties include high tensile and yield strength, good elongation and reliable hardness. Dimensional ranges cover various outer diameters, wall thicknesses, lengths and standard schedules. Available surface finishes include annealed, pickled and polished. These non-magnetic pipes are produced with precise manufacturing tolerances for consistent quality.
Super Duplex Steel UNS S32750 represents a next-generation stainless steel alloy specifically engineered for applications that demand an unparalleled combination of mechanical strength and corrosion resistance. Defined by its balanced ferritic/austenitic microstructure and enriched with significant levels of chromium, molybdenum, and nitrogen, this material transcends the capabilities of conventional austenitic and standard duplex grades.
The choice of seamless pipe and tube as a product form is not merely a matter of convenience; it is a critical engineering decision that enhances the inherent benefits of the UNS S32750 alloy. By eliminating the longitudinal weld seam, the finished product is free from the primary metallurgical weak points that can arise from welding, such as the formation of undesirable intermetallic phases in the heat-affected zone (HAZ). This ensures a uniform, pure microstructure and superior pressure integrity throughout the entire length of the pipe or tube.
Positioning UNS S32750 seamless pipes and tubes as a strategic investment, the initial higher cost is justified by the significant long-term savings they offer. The material’s exceptional durability and resistance to degradation in harsh environments, such as those found in offshore oil and gas or water desalination, lead to a reduced need for maintenance and replacement, minimizing downtime and lowering total lifecycle costs.This makes UNS S32750 not just a material but a robust, long-term solution for mission-critical applications where reliability and longevity are paramount.
Detailed Chemical Composition
The exceptional performance of UNS S32750 is a direct result of its precisely controlled chemical composition. The key alloying elements and their typical weight percentages are as follows:
- Chromium (Cr): Ranging from 24% to 26%, chromium is the foundational element that provides exceptional resistance to uniform corrosion in both organic and inorganic acids, particularly those containing chlorides.
- Molybdenum (Mo): At 3% to 5%, molybdenum is crucial for enhancing the alloy's resistance to localized corrosion, such as pitting and crevice corrosion, which are common failure modes in saline or chloride-rich environments.
- Nickel (Ni): With a content between 6% and 8%, nickel is essential for stabilizing the austenitic phase, contributing to the material's ductility and overall toughness.
- Nitrogen (N): The inclusion of nitrogen at 0.24% to 0.32% is a highly potent addition. Nitrogen significantly improves resistance to pitting and crevice corrosion while simultaneously strengthening the alloy and helping to maintain the critical dual-phase balance.
- Copper (Cu): A maximum of 0.5% copper is often present, which is known to further enhance the alloy's resistance to corrosion in certain acidic media.
- Other Elements: The alloy also contains minor percentages of Carbon (max 0.03%), Manganese (max 1.2%), Silicon (max 0.8%), Phosphorus (max 0.035%), and Sulfur (max 0.020%), with the remainder being Iron (Fe).
The balanced microstructure of approximately 50% ferrite (δ) and 50% austenite (γ) is the cornerstone of UNS S32750's performance.A more detailed examination of this structure reveals that its strength is not merely due to the presence of two phases but is rooted in the strategic partitioning of alloying elements between them. Research using SEM-EDS techniques has shown that chromium, molybdenum, and silicon preferentially concentrate within the ferritic phase, while nickel and copper are enriched in the austenitic phase.
This elemental segregation is a master key to the alloy's functional excellence. The ferritic phase, made hard and strong by its high chromium and molybdenum content, is the primary source of the material's exceptional mechanical strength and its potent resistance to localized corrosion. Simultaneously, the softer, more ductile austenitic phase, enriched with nickel, provides the crucial toughness and outstanding resistance to stress corrosion cracking (SCC), a common failure mechanism for other grades in corrosive environments.The resulting material is not a simple compromise; rather, it is a sophisticated combination of the greatest strengths of two different metallurgical structures.
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 S32750 / 1.4410.
Table 1: Chemical Composition of UNS S32750 / 1.4410
The composition of UNS S32750 / 1.4410 is carefully balanced to achieve its superior 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 | … |
NOTE: PREN:Cr+3.3*Mo+16*N≥41 |
UNS S32750 / 1.4410 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 | ≤ 290 HBW |
Table 3: Typical Physical Properties of UNS S32750 / 1.4410
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% |
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.
Special Points: NACE MR0175/ISO 15156 is an internationally recognized standard that specifies the requirements for materials used in sour oilfield environments, where the presence of hydrogen sulfide gas can lead to sulfide stress cracking. UNS S32750 is listed in this standard for sour service applications, making it a preferred choice for the oil and gas industry.
A crucial distinction within the standard relates to the material's condition and the specific application. Although UNS S32750 is generally compliant, some cold-drawn products, which are common in tube manufacturing, may have specific limitations. For instance, a product that is cold-drawn may be NACE compliant for external exposure to sour gas, but not for internal exposure where the surface is wetted by the fluid and under tensile stress. This is because the standard states that a tensile stress component is required to enable cracking modes, and cold-drawing can increase the residual tensile stress in the material. This distinction underscores that compliance is not a simple binary classification but is dependent on the specific product form and the conditions of its intended service.
The Seamless Manufacturing Process
Seamless pipes and tubes are manufactured from a solid steel billet.This billet is heated to a specified temperature and then pierced with a mandrel to create a hollow cylinder.The resulting hollow shell is then further rolled, drawn, or extruded to achieve the final dimensions of the pipe or tube. The defining characteristic of this process is the absence of any welding, resulting in a product with a completely uniform wall thickness and no longitudinal or spiral weld seam.
Applications of Seamless Super Duplex Steel Pipe
1 Oil & Gas
The oil and gas industry is a primary consumer of UNS S32750, particularly for its offshore and subsea operations.The material’s high strength allows for lighter-weight designs, which is a major advantage for structural components and deep-sea installations. Its exceptional resistance to chloride SCC and sour gas cracking makes it ideal for use in hydraulic and process piping, connectors, and manifolds that operate in demanding, high-pressure environments.
2 Water Desalination and Treatment
UNS S32750 is extensively used in the water desalination industry. The process of removing salt and minerals from seawater to produce potable water is highly corrosive, with high concentrations of chlorides.The alloy's superior resistance to pitting and crevice corrosion in these high-salinity environments makes it the perfect material for seawater intake and discharge pipelines, reverse osmosis (RO) membrane systems, evaporators, and heat exchangers.
3 Chemical, Petrochemical, and Pulp & Paper
The alloy's robust resistance to aggressive acids and other corrosive media makes it a preferred choice in the chemical, petrochemical, and pulp and paper industries.Applications include use in process piping, chemical tankers, and heat exchangers where exposure to harsh chemicals is routine.
4 Other Applications
UNS S32750 is also widely employed in a variety of other critical applications, including pumps, valves, chokes, and fire-fighting systems.3 Its combination of high strength and durability makes it suitable for structural components where both mechanical load and corrosive resistance are required.
The Core Comparison: UNS S32750 vs. Duplex 2205 (S31803)
Duplex 2205 is a widely used stainless steel grade, but UNS S32750 is a clear step up in performance.The primary difference lies in their chemical composition. UNS S32750 has higher chromium, molybdenum, and nitrogen content than Duplex 2205 (25% vs. 22% chromium and 4% vs. 3% molybdenum). This compositional difference results in a higher PREN value for UNS S32750 (typically >40 vs. 34-36 for 2205).7 This translates to superior resistance to pitting and crevice corrosion. Additionally, UNS S32750 provides higher yield and tensile strengths, allowing for more robust designs or the use of thinner materials.
Outshining the Austenite: UNS S32750 vs. 316L (S31603)
Comparing UNS S32750 to a conventional austenitic grade like 316L highlights the dramatic performance advantages of the super duplex alloy. As shown in the comparative data, UNS S32750 has a significantly higher yield strength (590 MPa vs. 190 MPa), allowing it to bear much greater loads. Furthermore, its thermal properties are superior, with a higher maximum corrosion temperature (450°C vs. 410°C) and a much higher mechanical temperature limit (1100°C vs. 870°C). The lower thermal expansion coefficient of UNS S32750 also makes it a more dimensionally stable material.
Conclusion: A Strategic Investment for Reliability and Longevity
UNS S32750 is a sophisticated engineering material whose unique dual-phase microstructure and high alloy content provide a powerful combination of high mechanical strength and exceptional corrosion resistance. When fabricated as a seamless pipe or tube, this material's benefits are maximized, as the product is free from the inherent metallurgical weaknesses of a weld seam, ensuring optimal integrity and reliability.
The choice to utilize UNS S32750 seamless pipes and tubes is not simply a procurement decision; it is a strategic investment in the long-term reliability and longevity of a system. While the initial capital outlay may be higher than for conventional stainless steels, the material’s superior performance in aggressive environments leads to a significant reduction in operational costs. This is achieved by minimizing the risk of catastrophic failure, extending service life, and dramatically reducing the need for costly maintenance and replacement.7 Ultimately, for mission-critical applications in industries such as oil and gas, water desalination, and chemical processing, UNS S32750 seamless pipes and tubes represent the most economically sound and technically robust solution available, providing a foundation for engineering excellence that endures under the most challenging conditions.
