UNS S31653 AISI 316LN Stainless Steel Data Sheet

UNS S31653, commonly called AISI 316LN, represents a grade of austenitic stainless steel that combines the excellent corrosion resistance of standard 316L with enhanced mechanical properties.

This low-carbon, nitrogen-strengthened stainless steel is specifically engineered for applications requiring superior strength, improved resistance to sensitization, and outstanding performance in aggressive environments.

This data sheet provides a comprehensive technical overview of UNS S31653/316LN stainless steel, covering its chemical composition, physical and mechanical properties, corrosion behavior, fabrication characteristics, and industrial applications.

SS 316LN Chemical Composition

The specific chemical composition of 316LN stainless steel is carefully balanced to achieve its performance characteristics. The table below details the composition ranges according to major international standards:

The addition of nitrogen is particularly significant, as it provides solid solution strengthening that substantially increases the yield and tensile strengths without compromising ductility or toughness.

Meanwhile, the strictly controlled low carbon content (≤0.03%) effectively minimizes chromium carbide precipitation during welding or high-temperature exposure, thereby enhancing resistance to inter granular corrosion.

316LN Stainless Steel Physical Properties

The physical properties of 316LN stainless steel make it suitable for various applications across different temperatures:

These physical properties make 316LN maintain remarkable toughness even at temperatures as low as -196°C. The relatively low thermal conductivity and specific heat capacity are important considerations for heat transfer applications, while the non-magnetic characteristic is valuable in electronic and medical applications where magnetic interference must be avoided.

316LN Steel Mechanical Properties

316LN stainless steel exhibits enhanced mechanical properties compared to standard 316L, primarily due to the solid solution strengthening effect of nitrogen. The typical mechanical properties at room temperature are as follows:

The 40% higher yield strength compared to standard 316L represents one of the most significant advantages of 316LN. The material maintains excellent elongation, demonstrating its ability to undergo significant plastic deformation before fracture.

At elevated temperatures, 316LN offers improved creep and stress-rupture properties compared to standard 316L, while at cryogenic temperatures, it exhibits exceptional impact toughness, making it suitable for LNG applications, liquid nitrogen containers, and other cryogenic services.

316LN Stainless Steel Corrosion Resistance

316LN stainless steel offers excellent corrosion resistance:

The alloy demonstrates outstanding resistance to general corrosion in a wide range of environments, including atmospheric conditions, fresh waters, and various chemical media. The combination of chromium (16-18.5%) and molybdenum (2-3%) provides a robust passive film that protects against uniform attack.

The molybdenum content significantly enhances resistance to localized corrosion phenomena. 316LN shows good performance in chloride-containing environments, though for severely aggressive conditions, more highly alloyed steels may be required.

The low carbon content, combined with nitrogen, provides excellent resistance to sensitization and subsequent intergranular corrosion. This is particularly valuable for welded components where the heat-affected zone might be exposed to corrosive environments during service.

While austenitic stainless steels are generally susceptible to chloride stress corrosion cracking, 316LN offers performance comparable to other 316 grades.

Heat Treatment and Fabrication

Heat Treatment

316LN stainless steel is typically supplied in the solution-annealed condition, which involves heating to 1040-1175°C followed by rapid cooling to dissolve carbides and ensure maximum corrosion resistance. This heat treatment cannot harden the material through phase transformation, as 316LN is an austenitic stainless steel.

Welding

The alloy exhibits excellent weld ability using common fusion welding techniques. Recommended practices include:

Preferred Methods: TIG/GTAW for critical applications; GMAW/MIG for less critical joints.

Filler Metals: ER316LN for matching composition; ENiCrMo-3 for dissimilar joints.

Shielding Gas: High-purity argon with possible nitrogen addition (1-2%) to maintain austenite balance.

Heat Input Control: Moderate levels to avoid excessive micro structural changes.

Post-Weld Treatment: Generally not required for thin sections; stress relief may be beneficial for thick components.

Forming and Machining

316LN can be formed using standard equipment, though its higher strength and work hardening rate compared to carbon steels require greater power during forming operations.

Machining requires techniques appropriate for austenitic stainless steels, including positive rake angles, rigid setups, and appropriate cutting fluids.

316LN Steel Applications

316LN stainless steel is used in applications across numerous industries:

Nuclear Industry

Nuclear reactor components and piping systems.

Fuel handling equipment.

Structural components requiring radiation resistance.

The non-magnetic properties and controlled composition make 316LN suitable for nuclear environments, with specific grades meeting RCC-M and ASME nuclear standards.

Chemical and Petrochemical Processing

Pressure vessels and reactors.

Heat exchangers and condensers.

Piping systems for corrosive media.

Storage tanks for chemicals.

The enhanced strength allows for thinner vessel walls, while the improved inter granular corrosion resistance benefits welded construction.

Cryogenic Applications

LNG storage and transportation systems.

Liquid nitrogen containers (-196°C service).

Cryogenic processing equipment.

The exceptional toughness at low temperatures makes 316LN particularly valuable for cryogenic services.

Specialized Industries

Pharmaceutical and Biotechnology: High-purity systems requiring clean ability and corrosion resistance.

Semiconductor Manufacturing: Ultra-clean gas delivery systems.

Marine Engineering: Components requiring a combination of strength and seawater resistance.

Medical Devices: Surgical instruments and implants.

316LN Comparison with Similar Grades

The table below compares 316LN with related stainless steels to highlight its distinctive position: