304L Austenitic Stainless Steel Coil Tube — Technical Specification
1. Product Overview
The 304L Stainless Steel Coil Tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a high-performance austenitic stainless steel tubing product supplied in coiled form for maximum handling flexibility and on-site installation efficiency. Classified under the Austenitic – General Purpose category, this grade is engineered specifically for applications demanding superior weldability and resistance to intergranular corrosion (IGC) without the need for post-weld solution heat treatment. The ultra-low carbon content (C ≤ 0.03%) fundamentally differentiates 304L from its standard counterpart (304), making it the preferred material for critical welded assemblies and field-installed piping systems where thermal cycling or sensitization risks are present.
Unique Selling Proposition: With carbon content reduced to ≤ 0.03%, 304L coil tubes eliminate the formation of chromium carbides (Cr₂₃C₆) at weld heat-affected zones (HAZ), thereby preserving full resistance to intergranular corrosion in the as-welded condition — no post-weld annealing required.
2. Material & Properties
2.1 Chemical Composition (ASTM A270 / AMS 5528)
| Element | Specification | Function |
|---|---|---|
| Carbon (C) | ≤ 0.03% | Prevents chromium carbide precipitation; ensures weldability without sensitization |
| Chromium (Cr) | 18.0 – 20.0% | Primary passivation element; forms protective Cr₂O₃ film |
| Nickel (Ni) | 8.0 – 10.5% | Stabilizes austenitic microstructure; enhances ductility and toughness |
| Manganese (Mn) | ≤ 2.0% | Auxiliary austenite stabilizer |
| Silicon (Si) | ≤ 1.0% | Deoxidizer during melting |
| Nitrogen (N) | ≤ 0.10% | Controlled for strength contribution without embrittlement |
| Iron (Fe) | Balance | Matrix element |
2.2 Mechanical Properties (Annealed Condition)
| Property | Minimum / Typical Value | Test Standard |
|---|---|---|
| Tensile Strength (UTS) | ≥ 485 MPa (70 ksi) | ASTM A270 |
| 0.2% Yield Strength | ≥ 205 MPa (30 ksi) | ASTM A270 |
| Elongation (in 50 mm) | ≥ 40% | ASTM A270 |
| Hardness (Brinell) | ≤ 201 HB | ASTM A262 |
| Density | 8.00 g/cm³ | — |
| Thermal Conductivity (20 °C) | 16.3 W/(m·K) | — |
| Electrical Resistivity (20 °C) | 0.74 μΩ·m | — |
2.3 Corrosion Resistance Characteristics
- Intergranular Corrosion Resistance: 304L demonstrates no sensitization after exposure at 650–800 °C for extended durations, as confirmed by ASTM A262 Practice E (65% boiling HNO₃ test). The low carbon content ensures that chromium depletion at grain boundaries remains negligible even in the as-welded condition.
- Pitting & Crevice Corrosion: Adequate resistance in neutral and mildly acidic aqueous environments (chloride ≤ 500 ppm). For high-chloride service, 316L or duplex grades are recommended.
- Oxidation Resistance: Non-magnetic in the annealed state; forms a stable, self-healing chromium oxide passive layer in oxidizing atmospheres up to 870 °C.
3. Specifications
| Parameter | Specification / Range |
|---|---|
| Grade Designation | 304L (UNS S30403 / 1.4307) |
| Product Form | Coil Tube (盘管 / Coiltube) |
| Outer Diameter (OD) | 6.00 mm – 50.80 mm (¼" – 2") |
| Wall Thickness | 0.50 mm – 3.00 mm (0.020" – 0.118") |
| Coil Length | 15 m – 60 m (typical); custom lengths available |
| Surface Finish | Pickled & Passivated (2B), Bright Annealed (BA), or Custom |
| Manufacturing Process | Seamless (PWHT) or ERW (Electric Resistance Welded) |
| Dimensional Tolerance | ± 10% on OD and wall thickness (or per ASTM A269 / A270) |
| Applicable Standards | ASTM A269, ASTM A270, ASTM B730, EN 10217-7, GB/T 12771 |
| Heat Treatment Condition | Annealed (Solution Treated); no post-weld heat treatment required |
| Coil Packaging | Wooden pallet with moisture-proof wrapping; export-grade crating available |
4. Manufacturing Process
4.1 Production Workflow
- Raw Material Selection: Virgin stainless steel ingots or EAF (Electric Arc Furnace) + AOD (Argon Oxygen Decarburization) melt with certified low-carbon chemistry (C ≤ 0.03%).
- Honing / Piercing: Billet is pierced and drawn to produce seamless tube stock, or strip is fed for ERW production.
- Hot Rolling / Cold Drawing: Tubes are cold-drawn through precision dies to achieve dimensional accuracy and improved surface finish. The coiling process ensures uniform cold work and residual stress distribution.
- Solution Annealing: Tubes are heated to 1010–1150 °C in a controlled-atmosphere furnace and rapidly quenched to homogenize the austenitic structure and remove cold-work hardening.
- Pickling & Passivation: Acid pickling (HNO₃/HF blend) removes oxide scale; subsequent passivation restores the Cr₂O₃ protective layer.
- Coiling & Inspection: Finished tubes are coiled at controlled tension, inspected via Eddy Current (ECT) and ultrasonic testing, and packaged for shipment.
4.2 Key Process Advantages
- No Post-Weld Heat Treatment Required: Due to the ultra-low carbon content, the heat-affected zone (HAZ) adjacent to welds does not undergo sensitization. This eliminates the need for costly and time-consuming post-weld solution annealing, particularly critical for field-installed piping systems.
- Coil Form Efficiency: Continuous coil delivery reduces cutting waste, enables automated forming and bending operations, and minimizes handling time compared to straight-length tubes.
- Traceability: Each coil is heat-numbered and accompanied by a Mill Test Certificate (MTC) per EN 10204 3.1, ensuring full chemical and mechanical traceability.
5. Applications
5.1 Primary Applications
- Welded Structural Components: Frames, brackets, and load-bearing assemblies where welding is integral to the design and post-weld annealing is impractical.
- Field-Installed Piping Systems: Process piping, sanitary piping, and utility lines installed on-site where solution heat treatment cannot be performed after fabrication.
- Chemical & Petrochemical Equipment: Heat exchanger tubes, reactor internals, and process piping handling non-aggressive aqueous chemicals.
- Food & Pharmaceutical Industry: Sanitary tubing for CIP (Clean-In-Place) systems, milk processing, and pharmaceutical fluid transfer.
- Building & Construction: Architectural handrails, structural framing, and decorative elements requiring corrosion resistance and weldability.
- Automotive & Aerospace: Exhaust system components, fuel lines, and secondary structures where weight reduction and corrosion resistance are critical.
5.2 Service Environment Guidelines
| Environment | Suitability | Notes |
|---|---|---|
| Aqueous environments (low chloride) | Excellent | Chloride < 500 ppm; ambient to 80 °C |
| Welded assemblies (as-welded) | Excellent | No sensitization; no post-weld annealing needed |
| Atmospheric / Outdoor | Good | General industrial and coastal (non-marine) environments |
| High-temperature oxidizing | Good | Continuous service up to 870 °C; intermittent to 925 °C |
| High-chloride / Marine | Marginal | Consider 316L or duplex for chloride > 1000 ppm |
6. Quality Certifications & Compliance
- ISO 9001:2015 — Quality Management System certification for manufacturing and supply chain integrity.
- ISO 14001:2015 — Environmental Management System ensuring sustainable production practices.
- Mill Test Certificate (MTC) per EN 10204 3.1 — Chemical composition, mechanical properties, and heat treatment data certified by an authorized inspector.
- Compliance with ASTM / EN / GB Standards: Product conforms to ASTM A269/A270, EN 10217-7, and Chinese national standard GB/T 12771.
- Third-Party Inspection Available: On-site inspection by SGS, BV, or TÜV upon customer request.
- Non-Destructive Testing (NDT): Eddy Current Testing (ECT) and ultrasonic testing performed on all production coils to detect internal and surface defects.
- Intergranular Corrosion Testing: Available per ASTM A262 Practices E and F, or ASTM G28, to verify sensitization resistance.
7. Summary
The 304L Stainless Steel Coil Tube from Wenzhou Jixing Metal Materials Co., Ltd represents the optimal balance of corrosion resistance, weldability, and cost-effectiveness within the austenitic stainless steel family. Its defining characteristic — carbon content ≤ 0.03% — provides inherent immunity to sensitization-induced intergranular corrosion in welded configurations, making it indispensable for applications where post-weld heat treatment is impossible or impractical. Supplied in continuous coil form, the product delivers manufacturing efficiency, minimal material waste, and seamless integration into automated fabrication workflows. With full traceability, third-party inspection options, and compliance with international standards, this product meets the rigorous demands of industrial, process, and structural engineering applications worldwide.