316L Austenitic Stainless Steel Coil Tube
Product Overview
The 316L Austenitic Stainless Steel Coil Tube (Catalog No. 5) is a premium-grade seamless or welded coil tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd, engineered specifically for demanding environments requiring exceptional resistance to pitting corrosion and intergranular corrosion. As a member of the austenitic corrosion-resistant stainless steel family, the 316L grade incorporates the strategic combination of low carbon content (≤0.03%) and molybdenum (Mo, 2.0–3.0%), which synergistically enhances the material's overall corrosion resistance profile beyond that of standard 304L austenitic stainless steel.
This coil tube product is supplied in continuous coil form, offering superior material utilization, reduced cutting waste, and enhanced downstream fabrication efficiency. It represents the first-choice material for critical process piping in pharmaceutical, food and beverage, seawater desalination, and high-purity water distribution systems worldwide.
Material & Properties
Chemical Composition (ASTM A270 / EN 10217-7)
| Element | Specification (%) | Remarks |
|---|---|---|
| Carbon (C) | ≤ 0.03 | Ultra-low carbon for intergranular corrosion resistance |
| Chromium (Cr) | 16.5 – 18.5 | Primary passive film former |
| Nickel (Ni) | 10.0 – 14.0 | Austenite stabilizer |
| Molybdenum (Mo) | 2.0 – 3.0 | Enhances pitting and crevice corrosion resistance |
| Silicon (Si) | ≤ 0.75 | Deoxidizer |
| Manganese (Mn) | ≤ 2.0 | — |
| Phosphorus (P) | ≤ 0.035 | Impurity limit |
| Sulfur (S) | ≤ 0.030 | Impurity limit |
| Nitrogen (N) | ≤ 0.10 | — |
Mechanical Properties (Annealed Condition)
| Property | Value | Standard Reference |
|---|---|---|
| Tensile Strength (UTS) | ≥ 485 MPa (70,000 psi) | ASTM A270 |
| Yield Strength (0.2% Offset) | ≥ 170 MPa (25,000 psi) | ASTM A270 |
| Elongation (in 50 mm / 2 in) | ≥ 40% | ASTM A270 |
| Hardness (Brinell) | ≤ 217 HB | ASTM A270 |
| Density | 8.0 g/cm³ | — |
| Thermal Conductivity (at 20°C) | 16.3 W/(m·K) | — |
| Modulus of Elasticity | 193 GPa | — |
| Maximum Service Temperature | 870°C (1600°F) [oxidation] | — |
Corrosion Resistance Characteristics
- Pitting Corrosion Resistance: The 2.0–3.0% molybdenum content significantly elevates the pitting resistance equivalent number (PREN = %Cr + 3.3×%Mo + 16×%N ≈ 24–26), providing superior resistance to chloride-induced pitting compared to 304L (PREN ≈ 19).
- Intergranular Corrosion (IGC) Resistance: The ultra-low carbon content (≤0.03%) eliminates chromium carbide precipitation at grain boundaries during welding or heat exposure (450–850°C), ensuring the material passes the ASTM A262 Practice 1A acid solution test without sensitization.
- Crevice Corrosion Resistance: Effective in dilute sulfuric and phosphoric acid solutions at ambient temperatures.
- Stress Corrosion Cracking (SCC): Excellent resistance to chloride SCC under typical process conditions, outperforming duplex and ferritic grades in many aqueous environments.
Specifications
| Parameter | Specification / Range |
|---|---|
| Product Form | Coil Tube (Continuous Coil) |
| Manufacturing Method | Seamless (Cold Drawn) / Welded (ERW / Autoclaved Welded) |
| Outer Diameter (OD) | 6.0 mm – 168.3 mm (1/4" – 6") |
| Wall Thickness (WT) | 0.5 mm – 12.7 mm (0.020" – 0.500") |
| Coil Length | 15 m – 60 m (customizable) |
| Coil ID (Inner Diameter of Coil) | 150 mm – 300 mm (standard) |
| Surface Finish | No. 4 Brushed / 2B / Electropolished / Mirror (Ra ≤ 0.4 μm) |
| Dimensional Tolerance | ±0.1 mm (OD) / ±10% (WT) |
| Applicable Standards | ASTM A269, ASTM A270, EN 10217-7, ISO 3506, GB/T 12771 |
| Deliverable Condition | Annealed (Solution Heat Treated) — Soft, Fully Austenitic |
| Packaging | Export-grade wooden crate / steel strapping / VCI paper wrapping |
| Traceability | Heat number stamped on coil end; full mill certificate available |
Manufacturing Process
The 316L coil tube is produced through a rigorously controlled multi-stage manufacturing process designed to ensure metallurgical integrity, dimensional precision, and surface quality:
- Raw Material Selection: High-purity 316L billet or strip is sourced from certified steel mills with strict chemical composition control. Incoming material is verified via Optical Emission Spectroscopy (OES) and Inductively Coupled Plasma (ICP) analysis.
- Pierling & Extrusion / Cold Rolling: Seamless tubes are produced via hot piercing and extrusion followed by cold drawing. Welded tubes are manufactured through precision cold rolling of 316L strip with continuous resistance welding (ERW).
- Seam Annealing & Pickling: Welded tubes undergo protective atmosphere annealing (950–1100°C) followed by acid pickling and passivation to restore the full corrosion-resistant properties at the weld zone.
- Cold Drawing / Sizing: Tubes pass through precision drawing dies to achieve final OD and wall thickness tolerances, improving grain structure and mechanical properties.
- Solution Heat Treatment: Final annealing at 1050–1150°C with rapid water quenching to ensure a fully austenitic microstructure free of carbide precipitation.
- Surface Finishing: Electropolishing or mechanical polishing to achieve the required surface roughness (Ra) for hygienic applications.
- Coiling & Packaging: Tubes are wound onto precision coil cores with protective packaging to prevent mechanical damage and contamination during transit.
- Final Inspection: 100% ultrasonic testing (UT), hydrostatic pressure testing, dimensional verification, and surface inspection per applicable standards.
Applications
The 316L coil tube is the industry-preferred material for the following critical applications:
Pharmaceutical & Biotechnology
- CIP/SIP (Clean-in-Place / Sterilize-in-Place) process piping
- Bioreactor and fermenter connections
- Pharmaceutical fluid transfer and purification systems
- Compliant with FDA 21 CFR Part 117 and EU GMP Annex 1 requirements
Food & Beverage Processing
- Dairy processing equipment and piping
- Beverage transfer lines (including acidic and carbonated products)
- Hygienic process connections meeting 3-A Sanitary Standards
- Wine and brewery process systems
Seawater Desalination (RO / MED / MSF)
- Seawater intake and pre-treatment piping
- Reverse osmosis (RO) high-pressure transfer lines
- Concentrate discharge lines
- Resistance to high-chloride marine environments (30,000+ ppm Cl⁻)
High-Purity Water Systems
- Ultra-pure water (UPW) distribution in semiconductor manufacturing
- Water for Injection (WFI) systems in pharmaceutical facilities
- Deionized water (DI) systems
- Electropolished finish minimizes particle generation and microbial adhesion
Additional Applications
- Chemical processing equipment (acids, alkalis, organic solvents)
- Marine and offshore engineering
- Nuclear power plant components
- Medical device manufacturing
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality assurance system with the following certifications and compliance standards:
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification |
| ISO 14001:2015 | Environmental Management System certification |
| ISO 45001:2018 | Occupational Health and Safety Management System |
| EN 10204 3.1 | Third-party certified material test certificates |
| PED (EU 2014/68/EU) | Pressure Equipment Directive compliance (CE marking) |
| ASME / NB | National Board registration for pressure vessel components |
| 3-A Sanitary Standards | Approved for food and dairy industry equipment |
| NSF 61 / NSF 372 | Safe Drinking Water System Components certification |
| EU Reg. 1935/2004 | Food contact material compliance |
| API 5L / API 5CT | Oil and gas industry compliance (where applicable) |
Inspection and Testing Protocol:
- Chemical analysis: OES + ICP-AES (per heat lot)
- Mechanical testing: Tensile, hardness, and elongation per ASTM A270
- Corrosion testing: Intergranular corrosion (ASTM A262), pitting (ASTM G48), crevice corrosion
- Dimensional verification: Caliper, micrometer, and laser scanning
- Non-destructive testing: 100% ultrasonic (UT) and magnetic particle inspection (MPI) for welds
- Hydrostatic testing: Per ASTM A270 (typically 30–60 bar depending on size)
- Surface inspection: Visual + roughness profiling (Ra measurement)
Unique Selling Points
"The definitive choice for hygienic and high-corrosion applications — where material integrity is non-negotiable."
- Dual Superiority: Combines ultra-low carbon (intergranular corrosion immunity) with molybdenum alloying (pitting/crevice resistance) in a single alloy — no trade-offs required.
- Hygienic-Grade Surface: Available with electropolished finish (Ra ≤ 0.4 μm) suitable for pharmaceutical and bioprocessing without additional surface treatment.
- Coil Form Advantage: Continuous coil supply eliminates butt welds in process piping runs, reducing potential leak points and improving system reliability.
- Full Traceability: Every coil is heat-numbered with complete mill certificates (EN 10204 3.1) ensuring audit-ready documentation for regulated industries.
- Multi-Standard Compliance: Manufactured to meet simultaneous requirements of ASTM, EN, and GB standards, providing global project flexibility.
- Weldability: Fully austenitic microstructure ensures excellent weldability with no pre-heat or post-weld heat treatment requirements in standard thicknesses.
Technical Notes
Note 1: For temperatures exceeding 300°C (572°F) in load-bearing applications, 316L retains good strength but users should consider creep resistance limitations above 600°C.
Note 2: In environments containing concentrated sulfuric acid or hot concentrated hydrochloric acid, higher alloy grades (e.g., 904L, Alloy 20, or Hastelloy C-276) should be evaluated.
Note 3: The low carbon designation ("L" suffix) is critical for welded assemblies. Standard 316 (C ≤ 0.08%) may