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UNS N08904 904L PIPEGSM

UNS N08904 (904L): A Comprehensive Guide

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Introduction

UNS N08904, commonly referred to by its trade name 904L, is a high-performance stainless steel alloy known for its superior resistance to various corrosive environments. Unlike typical stainless steels, 904L contains higher levels of nickel, chromium, and molybdenum, which give it exceptional durability and resistance to corrosion. This makes it suitable for applications in industries such as oil and gas, chemical processing, marine environments, power generation, and pharmaceuticals.

904L is considered an austenitic stainless steel, which means it has a non-magnetic structure and excellent formability. Its high resistance to stress corrosion cracking, pitting, and crevice corrosion under extreme conditions makes it a versatile and reliable material choice for various demanding applications.

UNS N08904 (904L) Product Forms and Specifications

Equivalent Grades

  • Common Name: 904L
  • UNS No.: N08904
  • DIN: 1.4539
  • EN: 1.4539
  • ISO: 904L
  • JIS: No direct equivalent
  • W.Nr.: 1.4539

Related Product Standards

  • ISO: ISO 3506
  • JIS: JIS G 4305
  • EN: EN 10088-2
  • ASTM: ASTM A240, ASTM B625
  • ASME: ASME SA240, ASME SA312

Available Product Forms

UNS N08904 (904L) is available in multiple forms to cater to various industries and manufacturing processes:

  • Pipe and Tube: Suitable for high-pressure environments and chemical processing applications.
  • Plate and Sheet: Used for structural applications requiring corrosion resistance.
  • Bar and Rod: Machined into specific components for mechanical and structural purposes.
  • Wire and Strip: Often used for specialized applications such as spring manufacturing or as reinforcing materials.
  • Forging Stock: Ideal for custom shapes and complex geometries in demanding applications.
UNS N08904 (904L) Seamless Stainless Steel Pipe

UNS N08904 (904L) Seamless Stainless Steel Pipe

Applications

The superior properties of UNS N08904 (904L) make it an ideal material for several challenging applications:

  • Chemical Processing: Used in equipment such as reactors, heat exchangers, and tanks where resistance to aggressive chemicals like sulfuric acid, phosphoric acid, and acetic acid is required.
  • Oil and Gas Industry: Employed in pipelines, offshore platforms, and other equipment exposed to high levels of chloride and other corrosive substances.
  • Marine and Offshore: Excellent resistance to seawater and chloride stress corrosion makes it a go-to choice for marine piping systems, desalination plants, and offshore platforms.
  • Power Generation: Used in heat exchangers, cooling systems, and condensers where both corrosion and temperature resistance are crucial.
  • Pharmaceuticals and Food Processing: Because of its high purity and resistance to contamination, UNS N08904 (904L) is also used in pharmaceutical equipment, tanks, and pipelines in the food and beverage industries.

Corrosion Resistance Properties of UNS N08904 (904L)

One of the key advantages of UNS N08904 (904L) is its outstanding corrosion resistance. It offers the following corrosion-related benefits:

  • Pitting and Crevice Corrosion Resistance: 904L is highly resistant to pitting and crevice corrosion in chloride environments, including seawater and coastal areas.
  • Stress Corrosion Cracking (SCC): Unlike many other stainless steels, 904L excels in environments with chloride ions, preventing stress corrosion cracking in highly corrosive media.
  • Oxidation Resistance: Its high content of chromium and molybdenum provides excellent oxidation resistance at elevated temperatures, making it suitable for high-temperature applications where other stainless steels would degrade.

Physical and Thermal Properties of UNS N08904 (904L)

Understanding the physical and thermal properties of UNS N08904 (904L) is essential for determining its performance in various conditions:

  • Density: 8.0 g/cm³
  • Melting Point: 1375–1400°C
  • Thermal Conductivity: 14 W/m·K
  • Specific Heat: 500 J/kg·K at 25°C
  • Modulus of Elasticity: 200 GPa

These properties show that 904L can perform well under both thermal and mechanical stresses in harsh environments.

UNS N08904 (904L) Chemical Composition

The chemical composition of UNS N08904 (904L) is crucial in giving it its unique corrosion resistance and mechanical properties. Typical composition includes:

  • Nickel (Ni): 23–28%
  • Chromium (Cr): 19–23%
  • Molybdenum (Mo): 4–5%
  • Iron (Fe): Balance
  • Copper (Cu): 1–2%
  • Carbon (C): Max 0.020%
  • Manganese (Mn): 2–2.5%
  • Silicon (Si): 1.0%
  • Sulfur (S): Max 0.005%

This alloy composition provides excellent resistance to various corrosive environments, including sulfuric acid, phosphoric acid, and chlorides.

UNS N08904 (904L) Mechanical Properties

The mechanical properties of UNS N08904 (904L) make it suitable for demanding applications where both strength and corrosion resistance are necessary:

  • Tensile Strength: 530 MPa (min)
  • Yield Strength: 240 MPa (min)
  • Elongation: 40% (min)
  • Hardness: 220 HB (max)

These properties provide the necessary balance of strength and ductility, allowing the alloy to be used in both structural and pressure-containing applications.

Heat Treatment

UNS N08904 (904L) is typically used in an annealed condition, which ensures good formability and corrosion resistance. Annealing is performed by heating the material to a temperature range of 1050–1150°C and then cooling it rapidly. This treatment helps relieve internal stresses and improves the alloy’s ductility and corrosion resistance.

Forming

The alloy is easily formed using conventional techniques such as hot rolling, cold rolling, and forging. When hot working, 904L should be heated to temperatures between 1100°C and 1200°C, and rapid cooling should be applied afterward to ensure optimal performance.

Welding

Welding of UNS N08904 (904L) can be carried out using typical methods such as TIG, MIG, and SMAW. It is essential to use a compatible filler material to ensure that the welds retain the same level of corrosion resistance as the base material. Preheating is not required, but post-weld heat treatment may be recommended for thick sections to relieve stresses and enhance weld integrity.

Corrosion of Welds

While 904L exhibits excellent corrosion resistance, welding can sometimes lead to localized corrosion, such as weld decay. To mitigate this risk, proper post-weld treatment is essential. Descaling, pickling, or passivating the weld area can prevent the formation of chromium carbides and restore the material’s resistance to corrosion.

Descaling, Pickling, and Cleaning

To enhance the surface quality and corrosion resistance, UNS N08904 (904L) should undergo descaling or pickling processes. This removes oxide layers formed during manufacturing processes. Pickling typically involves using a mixture of nitric acid and hydrofluoric acid, followed by thorough rinsing and passivation to prevent future corrosion.

Surface Hardening

For specific applications requiring enhanced surface properties, surface hardening techniques such as nitriding or shot peening can be applied. These processes improve wear resistance without compromising the alloy’s corrosion resistance, making it suitable for parts exposed to high mechanical stress.

Conclusion

UNS N08904 (904L) is an ideal material for highly corrosive environments, offering exceptional resistance to pitting, crevice corrosion, and stress corrosion cracking. Its high strength, combined with good formability, makes it suitable for a wide range of applications in industries such as chemical processing, marine, oil and gas, and pharmaceuticals.

By understanding the properties, fabrication processes, and maintenance practices associated with UNS N08904 (904L), engineers and professionals can confidently use this material in demanding environments, ensuring long-term performance and reliability in the most challenging conditions.

UNS S32760 ZERON® 100

UNS S32760 (Zeron 100): A Super Duplex Stainless Steel (SDSS)

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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

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.