Product Introduction
Seamless Austenitic Steel 316LN Pipe is a premium nitrogen-enhanced, low-carbon variant of the 316 stainless steel family, engineered to combine superior corrosion resistance with elevated mechanical strength. As an austenitic alloy, it features a microstructure that balances ductility, formability, and durability, making it ideal for demanding environments where conventional stainless steels may fall short. The alloy’s defining characteristics—low carbon content (≤0.035%) and intentional nitrogen addition (0.10-0.16%)—address critical limitations of standard 316L, such as intergranular corrosion risk and lower yield strength.
The nitrogen in TP316LN acts as a solid solution strengthener, boosting yield strength by up to 20% compared to 316L, while maintaining excellent weldability without sensitization. This makes it particularly suitable for welded components in corrosive media. The addition of 2-3% molybdenum enhances resistance to pitting and crevice corrosion in chloride-rich environments, while 16-18% chromium and 10-14% nickel form a protective oxide layer against general corrosion.
Manufactured via seamless extrusion, TP316LN pipes exhibit uniform grain structure and precise dimensional control, eliminating weld lines that could compromise integrity. Post-production treatments like pickling, annealing, and polishing further optimize surface quality and corrosion resistance. The result is a material that excels in harsh chemical, marine, and high-purity applications, balancing performance with cost-effectiveness.
Key Product Parameters
Material Grades & Specifications
ASTM A312: Seamless/welded austenitic stainless steel pipes for high-pressure systems.
ASTM A213: Boiler, superheater, and heat-exchanger tubes.
EN 10216-5: European standard for seamless steel tubes in pressure applications.
JIS G3459: Japanese standard for stainless steel pipes.
Chemical Composition (wt.%)
| Grade | C | Mn | P | S | Si | Cr | Ni | Mo | N |
| 316LN | ≤0.035 | ≤2.00 | ≤0.045 | ≤0.03 | ≤1.00 | 16.0-18.0 | 10.0-14.0 | 2.0-3.0 | 0.10-0.16 |
| 316L | ≤0.035 | ≤2.00 | ≤0.045 | ≤0.03 | ≤1.00 | 16.0-18.0 | 10.0-14.0 | 2.0-3.0 | – |
| 316N | ≤0.08 | ≤2.00 | ≤0.045 | ≤0.03 | ≤1.00 | 16.0-18.0 | 10.0-14.0 | 2.0-3.0 | 0.10-0.16 |
Mechanical Properties
| Property | 316LN | 316L | 316N |
| Tensile Strength | ≥75 ksi (515 MPa) | ≥70 ksi (485 MPa) | ≥75 ksi (515 MPa) |
| Yield Strength | ≥30 ksi (205 MPa) | ≥25 ksi (170 MPa) | ≥30 ksi (205 MPa) |
| Elongation | ≥35% | ≥35% | ≥35% |
| Hardness (HRB) | ≤95 | ≤90 | ≤95 |
| Impact Toughness | ≥100 J/cm² at 20°C | ≥100 J/cm² at 20°C | ≥100 J/cm² at 20°C |
Dimension Range
Outer Diameter (OD): 6 mm to 1016 mm (0.24" to 40")
Wall Thickness: 1 mm to 65 mm (0.04" to 2.56")
Length: Customizable up to 12 meters (standard: 6 meters)
Corrosion Resistance
Media Resistance:
Chloride solutions (up to 1000 ppm Cl⁻)
Mild acids (sulfuric, hydrochloric at low concentrations)
Alkaline solutions (NaOH, KOH)
Seawater and marine atmospheres
Limitations:
Poor resistance to concentrated reducing acids
Susceptible to stress corrosion cracking in high-Cl⁻, high-temperature environments
Surface & Testing
Surface Treatments:
Pickled & Annealed: Removes scale, ideal for general corrosion resistance (Ra ≤1.6μm).
Polished: Ra ≤0.8μm for hygienic applications (food, pharmaceuticals).
Electropolished: Ra ≤0.2μm for ultra-clean surfaces (medical, semiconductor).
Quality Control:
100% Eddy Current Testing (ET) for surface defects.
Hydrostatic Pressure Testing (1.5x design pressure).
Intergranular Corrosion (IGC) Testing per ASTM A262 Practice E.
Application Scenarios
Chemical Processing
Acid Handling: Transport of sulfuric, phosphoric, and acetic acids in chemical plants.
Reactors & Vessels: Components exposed to corrosive reactants in pharmaceutical synthesis.
Waste Treatment: Pipes and tanks for acidic/alkaline wastewater neutralization.
Marine & Offshore
Offshore Platforms: Deck structures, seawater cooling systems, and subsea pipelines.
Shipbuilding: Hull components, ballast water systems, and marine exhausts.
Desalination Plants: Heat exchangers and brine transport lines in RO systems.
Food & Beverage
Processing Equipment: Milk pasteurizers, brewery tanks, and juice extraction lines.
Packaging Machinery: Hygienic pipes for edible oil and beverage distribution.
Commercial Kitchens: Sanitary tubing for food-grade fluid transport.
Medical & Biotechnology
Surgical Instruments: Scalpels, forceps, and endoscope components.
Pharmaceutical Manufacturing: WFI (Water for Injection) systems and API transfer lines.
Dental Equipment: Sterilizable tools and implantable device components.
Oil & Gas
Sour Gas Processing: Pipes and valves in H₂S/CO₂-rich environments.
Refinery Equipment: Catalytic cracking units and corrosion-resistant internals.
Downhole Tubing: High-pressure applications in oil well completions.
FAQ (Frequently Asked Questions)
Q: How does TP316LN differ from TP316L?
A: TP316LN contains 0.10-0.16% nitrogen, boosting yield strength by ~20% (205 MPa vs. 170 MPa) and improving resistance to pitting in chloride environments. Its low carbon (≤0.035%) also prevents intergranular corrosion better than 316L.
Q: Can TP316LN be used in seawater applications?
A: Yes, TP316LN resists seawater corrosion better than 304/316L, but for prolonged submerged use, consider duplex steels (e.g., 2205) or nickel alloys for superior chloride resistance.
Q: What welding procedures are recommended for TP316LN?
A: Use low-heat-input TIG welding with 316L or 316LN filler wire. Maintain interpass temperatures ≤150°C to avoid nitrogen loss, and post-weld annealing is typically unnecessary.
Q: How to prevent pitting corrosion in TP316LN?
A: Avoid stagnant chloride solutions (>1000 ppm Cl⁻). For aggressive environments, specify electropolished surfaces or use corrosion inhibitors to reduce Cl⁻ concentration.
Q: Is TP316LN magnetic?
A: No, TP316LN is austenitic and non-magnetic in its as-annealed state. Cold working may induce slight magnetism, but it can be eliminated via annealing.
Q: What is the lead time for custom TP316LN orders?
A: Standard sizes are available within 1–2 weeks. Custom dimensions or special finishes (e.g., electropolishing) require 3–4 weeks, including testing and documentation.
