304LN/316LN Nitrogen-Alloyed Cryogenic Stainless Steel Coil Tube
Product Overview
The 304LN/316LN cryogenic stainless steel coil tube, manufactured by Wenzhou Jixing Metal Materials Co., Ltd, represents the pinnacle of austenitic stainless steel engineering for ultra-low-temperature service. These nitrogen-alloyed coil tubes are purpose-designed to maintain superior mechanical integrity and ductility at temperatures as low as −196 °C (liquid nitrogen temperature), making them an indispensable solution for the liquefied natural gas (LNG), cryogenic gas handling, and extreme cold-process industries.
Unlike conventional austenitic grades such as 304L or 316L, the deliberate addition of nitrogen (N) as a solid-solution strengthening element provides a significant enhancement in yield strength without compromising the inherent toughness and corrosion resistance of the austenitic microstructure. This unique metallurgical advantage positions 304LN and 316LN coil tubes as the preferred material selection for cryogenic pressure vessels, cryogenic piping systems, and LNG infrastructure worldwide.
Material & Properties
The nitrogen alloying technology employed in these coil tubes delivers a combination of properties that cannot be replicated by conventional low-carbon austenitic stainless steels:
- Exceptional Cryogenic Toughness: Retains outstanding impact energy and ductility at −196 °C, eliminating the risk of brittle fracture under extreme thermal cycling conditions.
- Enhanced Yield Strength: Nitrogen solid-solution strengthening provides approximately 20–30% higher yield strength compared to 304L/316L equivalents, enabling thinner wall designs and reduced material weight.
- Superior Corrosion Resistance: The 316LN variant, with its molybdenum and nitrogen content, offers outstanding resistance to pitting and crevice corrosion in chloride-containing environments, making it ideal for marine and chemical applications.
- Excellent Weldability: The low-carbon composition (≤0.03% C) combined with controlled nitrogen levels ensures minimal sensitization during welding, preserving full mechanical properties in the heat-affected zone.
- Non-magnetic: Fully austenitic microstructure ensures non-magnetic properties throughout the cryogenic temperature range.
- Widened Temperature Envelope: Maintains functional mechanical properties from cryogenic temperatures up to 600 °C in oxidizing atmospheres.
Specifications
| Parameter | 304LN | 316LN |
|---|---|---|
| Standard Designation | ASTM A790 / EN 10088-1 / GB/T 20878 | ASTM A790 / EN 10088-1 / GB/T 20878 |
| Carbon (C) Max | 0.030% | 0.030% |
| Nitrogen (N) | 0.030 – 0.10% | 0.030 – 0.10% |
| Chromium (Cr) | 17.5 – 19.5% | 16.5 – 18.5% |
| Nickel (Ni) | 18.0 – 21.0% | 10.0 – 14.0% |
| Molybdenum (Mo) | — | 2.0 – 3.0% |
| Yield Strength (≥) | 290 MPa | 290 MPa |
| Tensile Strength (≥) | 515 MPa | 515 MPa |
| Elongation (%) | ≥ 35% | ≥ 35% |
| Cryogenic Impact (−196 °C) | ≥ 300 J (Charpy V) | ≥ 300 J (Charpy V) |
| Operating Temperature Range | −196 °C to +600 °C | −196 °C to +600 °C |
| Available Outer Diameters | Φ6.0 mm – Φ355.6 mm | Φ6.0 mm – Φ355.6 mm |
| Available Wall Thickness | 0.5 mm – 20.0 mm | 0.5 mm – 20.0 mm |
| Coil Length | Continuous coil (custom lengths available) | Continuous coil (custom lengths available) |
| Surface Finish | Bright annealed / Pickled & passivated / Custom | Bright annealed / Pickled & passivated / Custom |
Manufacturing Process
The production of 304LN/316LN cryogenic coil tubes at Wenzhou Jixing Metal Materials Co., Ltd follows a rigorously controlled process chain designed to ensure metallurgical homogeneity and dimensional precision:
- Raw Material Selection & Ingot Casting: High-purity ferroalloys with precisely controlled nitrogen levels are melted in vacuum induction or AOD furnaces. The nitrogen content is carefully managed to achieve optimal solid-solution strengthening without exceeding the solubility limit.
- Hot Rolling & Annealing: Slabs are hot-rolled to coil blank dimensions and subsequently annealed in a controlled-atmosphere furnace to ensure a fully austenitic, strain-free microstructure.
- Precision Cold Drawing: The coil blanks are cold-drawn through calibrated dies to achieve the required outer diameter and wall thickness with tight tolerances (typically ±0.1 mm or better).
- Intermediate Annealing: At strategic intervals during cold working, the material is annealed to relieve accumulated work-hardening and restore ductility for continued forming.
- Final Bright Annealing: A final continuous annealing cycle in a protective atmosphere (H₂ or vacuum) produces a clean, oxide-free surface with a stable austenitic grain structure.
- Pickling & Passivation: The annealed coil is pickled to remove any residual scale and passivated to form a stable chromium oxide protective layer.
- Non-Destructive Testing (NDT):strong>
- 100% eddy current inspection for surface and near-surface defect detection
- Hydrostatic pressure testing to verify wall integrity
- Visual inspection and dimensional verification per ASTM E1444 and EN 10204 standards
- Coiling & Packaging: Finished coils are wound onto precision mandrels, protected with moisture-barrier wrap, and packaged for international shipment.
Applications
The 304LN/316LN cryogenic coil tubes find critical application in industries where ultra-low-temperature performance, corrosion resistance, and structural reliability are non-negotiable:
Liquefied Natural Gas (LNG) Infrastructure
- LNG storage tank inner linings and cryogenic piping
- LNG vaporization systems and heat exchanger coils
- LNG transport ship containment systems and manifold assemblies
- LNG regasification terminal piping and valves
Cryogenic Gas Handling Systems
- Liquid nitrogen (LN₂) distribution and transfer pipelines
- Liquid oxygen (LOX) storage vessels and transfer lines
- Liquid argon and helium handling equipment
- Cryogenic air separation unit (ASU) interconnect piping
Additional Industrial Applications
- Spacecraft fuel systems and cryogenic propulsion components
- Superconducting magnet cooling circuits (MRI, particle accelerators)
- Food and beverage cryogenic freezing and flash-freezing equipment
- Medical cryosurgery and biological sample storage systems
- Chemical processing equipment requiring cryogenic service with chloride resistance (316LN)
- Offshore and marine cryogenic systems
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system aligned with international standards to ensure every coil tube meets the most demanding specifications:
- ISO 9001:2015 — Quality Management System Certification
- EN 10204 3.1/3.2 — Material Test Certificates with independent third-party verification
- ASME Stamp Certification — For pressure vessel and piping component applications
- API Monogram License — For oil and gas industry supply qualification
- CE Marking — Compliance with European Pressure Equipment Directive (PED 2014/68/EU)
- Material Standards Compliance: ASTM A790/A790M, EN 10088-1, GB/T 20878, JIS G4305
- Cryogenic Testing: All products undergo Charpy V-notch impact testing at −196 °C with results exceeding 300 J, verified by accredited laboratories
- Traceability: Full heat-to-coil traceability from raw material through final dispatch, with digital material passport documentation
Why Choose Wenzhou Jixing Metal Materials Co., Ltd
Wenzhou Jixing Metal Materials Co., Ltd brings decades of metallurgical expertise and precision manufacturing capability to the cryogenic stainless steel coil tube market. Their nitrogen-alloyed 304LN/316LN products are engineered to deliver:
- Uncompromised safety in the most demanding cryogenic environments
- Weight and cost optimization through enhanced strength-to-weight ratios
- Full compliance with global regulatory and industry standards
- Customized specifications tailored to project-specific engineering requirements
- Reliable, repeatable quality backed by rigorous NDT protocols and full traceability
For projects requiring absolute confidence in cryogenic material performance, the 304LN/316LN stainless steel coil tubes from Wenzhou Jixing Metal Materials Co., Ltd represent the gold standard in austenitic cryogenic engineering.