UNS S32760 (Zeron 100): A Super Duplex Stainless Steel (SDSS)
1. Introduction
UNS S32760 (Zeron 100) is a super duplex stainless steel (SDSS) with a mixed microstructure of austenite and ferrite, giving it superior strength and corrosion resistance. It contains significant amounts of chromium, molybdenum, and nitrogen, providing excellent resistance to chloride-induced pitting, crevice corrosion, and stress-corrosion cracking (SCC). Its high strength-to-weight ratio makes it a preferred choice for various industries, offering substantial cost savings in design and fabrication. In this blog post, we will explore UNS S32760 in detail, covering its specifications, applications, corrosion resistance, and more to clearly understand why this alloy is highly valued in critical industries.
Key Features:
- High Strength: Superior tensile and yield strength compared to standard austenitic stainless steels.
- Corrosion Resistance: Exceptional performance in chloride-rich environments.
- Cost-Effective: Lower material costs compared to more expensive nickel-based alloys.
2. UNS S32760 (Zeron 100) Product Forms and Specifications
- UNS Number: S32760
- Common Name: Super Duplex Stainless Steel, Zeron 100
- W.Nr.: 1.4501
- ASTM/ASME Standards: A240, A182, A276, A789, A790, B649
Available Product Forms:
- Pipe
- Tube
- Plate
- Sheet
- Strip
- Bar
- Rod
- Wire
- Forging Stock
These product forms provide versatility, making UNS S32760 suitable for various industrial applications requiring mechanical and corrosive stress resistance.
UNS S32760 ZERON 100
3. Applications of UNS S32760 (Zeron 100)
Due to its exceptional corrosion resistance and high strength, UNS S32760 is widely used in the following industries:
- Chemical Processing: Ideal for processing equipment that handles aggressive chemicals like sulfuric and phosphoric acids.
- Oil and Gas: Used extensively in subsea pipelines, pumps, valves, and manifolds due to its resistance to chloride and hydrogen sulfide environments.
- Marine and Offshore: These are excellent for seawater applications such as heat exchangers, seawater cooling systems, and marine hardware.
- Pulp and Paper: Resistant to the corrosive chemicals used in pulp bleaching processes.
- Air Pollution Control: Suitable for scrubbers, flue gas desulfurization (FGD) systems, and other pollution control systems that handle acidic gases.
- Power Generation: Used in systems that deal with brackish water and steam, such as condensers and feedwater heaters.
4. Corrosion Resistance Properties of UNS S32760 (Zeron 100)
UNS S32760 offers outstanding corrosion resistance in various environments, making it ideal for harsh industrial applications. Its corrosion resistance properties include:
- Pitting and Crevice Corrosion Resistance: With high chromium (25%) and molybdenum (3.5%) content, S32760 provides superior resistance to localized corrosion in chloride-rich environments.
- Stress Corrosion Cracking (SCC) Resistance: Its duplex structure offers significant resistance to SCC, a common issue in austenitic steels when exposed to chloride and high-temperature environments.
- General Corrosion Resistance: Excellent performance in acidic and alkaline environments, including exposure to seawater, acids, and harsh industrial chemicals.
5. Physical and Thermal Properties of UNS S32760 (Zeron 100)
UNS S32760 maintains its mechanical and corrosion-resistant properties over a wide range of temperatures:
- Density: 7.8 g/cm³
- Thermal Conductivity: 14 W/m·K (at 100°C)
- Thermal Expansion: 13 × 10⁻⁶/°C (at 100°C)
- Melting Range: 1350°C to 1450°C (2462°F to 2642°F)
These properties make S32760 suitable for applications requiring thermal stability and resistance to temperature fluctuations.
6. UNS S32760 (Zeron 100) Chemical Composition
The chemical composition of UNS S32760 is carefully balanced to enhance both its corrosion resistance and mechanical strength:
- Chromium (Cr): 24.0 – 26.0%
- Nickel (Ni): 6.0 – 8.0%
- Molybdenum (Mo): 3.0 – 4.0%
- Copper (Cu): 0.5 – 1.0%
- Tungsten (W): 0.5 – 1.0%
- Nitrogen (N): 0.2 – 0.3%
- Iron (Fe): Balance
- Others: Trace elements such as carbon, silicon, and manganese are kept at minimal levels to prevent precipitation of secondary phases that can reduce corrosion resistance.
7. UNS S32760 (Zeron 100) Mechanical Properties
UNS S32760 offers excellent mechanical strength, making it suitable for high-stress environments:
- Tensile Strength: 750 MPa (109 ksi)
- Yield Strength: 550 MPa (80 ksi)
- Elongation: 25%
- Hardness: 28 HRC (Rockwell)
This high tensile and yield strength combination makes S32760 ideal for applications where mechanical stress and corrosion are simultaneous concerns.
8. Heat Treatment
To achieve optimal mechanical and corrosion-resistant properties, UNS S32760 undergoes a solution annealing process:
- Solution Annealing Temperature: 1100°C to 1150°C (2012°F to 2102°F), followed by rapid quenching.
This heat treatment prevents the formation of detrimental secondary phases and ensures the alloy maintains its duplex microstructure.
9. Forming
UNS S32760 can be hot or cold-formed using standard techniques:
- Cold Forming: Suitable for cold-forming applications due to its good ductility.
- Hot Forming: Hot-working should be done at temperatures between 1000°C and 1100°C (1832°F to 2012°F) and followed by a solution anneal to restore corrosion resistance.
It is important to note that heat treatment may be necessary after significant cold work to restore the alloy’s balance of strength and corrosion resistance.
10. Welding
UNS S32760 offers excellent weldability using standard welding techniques, including TIG, MIG, and SMAW. Key considerations for welding include:
- Preheat: Not required.
- Post-Weld Heat Treatment: In certain applications, solution annealing may be necessary to restore full corrosion resistance.
- Filler Metal: Use over-matching filler metals like ER2594 or E2594 for optimal weld performance.
Proper welding procedures ensure the alloy’s duplex microstructure remains intact and prevents the formation of unwanted phases that could compromise corrosion resistance.
11. Corrosion of Welds
Welds are often more susceptible to corrosion if not properly treated. However, UNS S32760’s low carbon and high nitrogen content reduce the risk of carbide precipitation, which can lead to intergranular corrosion. Proper heat input control and post-weld cleaning, including pickling and passivation, are crucial for maintaining weld integrity.
12. Descaling, Pickling, and Cleaning
Post-weld cleaning is essential to ensure maximum corrosion resistance. Descaling and pickling can be done using a nitric-hydrofluoric acid solution followed by thorough rinsing. This process removes oxides and surface contamination that could otherwise initiate localized corrosion.
13. Surface Hardening
Surface hardening processes like nitriding are generally not recommended for UNS S32760 as they can negatively affect the alloy’s corrosion resistance. The high inherent strength of the alloy usually eliminates the need for additional hardening treatments.
Conclusion
UNS S32760 (Zeron 100) is a highly versatile and cost-effective super duplex stainless steel that excels in extreme environments where both corrosion and mechanical stress are prevalent. Its excellent corrosion resistance, high strength, and weldability make it a preferred choice across various industries, including chemical processing, oil and gas, marine, and power generation. For industries looking for a reliable material with long service life and low maintenance, UNS S32760 is a top-tier option.
For more information or assistance in selecting UNS S32760 for your application, feel free to contact our expert team at [email protected]. We are here to provide the best material solutions tailored to your needs.
