316L Stainless Steel Coil Tube — Technical Specification
Product Overview
The 316L Stainless Steel Coil Tube (also designated as Coiltube) is a precision-engineered continuous length tubing product supplied in coiled form, manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is specifically designed for applications demanding superior corrosion resistance, mechanical integrity, and long-term reliability in aggressive chemical and high-temperature environments. The coil configuration offers logistical advantages over straight-length tubing, enabling seamless integration into automated forming, bending, and heat exchanger manufacturing lines.
Based on extensive field performance data and leak failure analysis studies conducted on 316L stainless steel coil tubes, this product has been optimized to mitigate common failure modes including stress corrosion cracking (SCC), pitting corrosion, intergranular corrosion (IGC), and fatigue-induced micro-cracking at weld seams or coil set points. The low-carbon designation ("L") of 316L ensures resistance to sensitization during welding, preserving the full alloying benefits of molybdenum and chromium.
Material & Properties
The base material conforms to AISI 316L / ASTM A213 TP316L / ASTM A269 TP316L / EN 1.4404 (X2CrNiMo17-12-2) / GB/T 12771-2019 standards. The low-carbon variant (C ≤ 0.03%) provides enhanced weldability and resistance to chromium carbide precipitation at grain boundaries.
Chemical Composition (wt%)
- Chromium (Cr): 16.5 – 18.5%
- Nickel (Ni): 10.0 – 14.5%
- Molybdenum (Mo): 2.0 – 3.0%
- Carbon (C): ≤ 0.030%
- Nitrogen (N): ≤ 0.10%
- Silicon (Si): ≤ 1.0%
- Manganese (Mn): ≤ 2.0%
- Phosphorus (P): ≤ 0.045%
- Sulfur (S): ≤ 0.030%
Mechanical Properties
- Tensile Strength (Rm): ≥ 485 MPa (70 ksi)
- Yield Strength (Rp0.2): ≥ 170 MPa (25 ksi)
- Elongation (A50): ≥ 40%
- Hardness: ≤ 217 HB / ≤ 95 HRB
- Thermal Conductivity (20°C): 16.3 W/(m·K)
- Modulus of Elasticity: 193 GPa
- Maximum Service Temperature: 870°C (continuous), 1035°C (intermittent)
Corrosion Resistance Characteristics
- Exceptional resistance to pitting and crevice corrosion in chloride-containing environments (Pitting Resistance Equivalent Number, PREN ≥ 24)
- Superior resistance to stress corrosion cracking (SCC) compared to 304L and 316 grades
- Effective resistance to sulfuric acid, phosphoric acid, and dilute hydrochloric acid solutions
- Excellent performance in marine atmospheres and halide-rich environments
Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 3.0 – 108.0 mm (1/8" – 4") | ASTM A269 / GB/T 12771 |
| Wall Thickness | 0.30 – 6.00 mm (0.012" – 0.236") | ASTM A213 / EN 10217 |
| Coil Weight | 200 – 2,000 kg (typical) | Manufacturer specification |
| Coil Inner Diameter | 150 – 600 mm | Manufacturer specification |
| Tolerance — OD | ±0.05 mm (precision); ±0.10 mm (standard) | ASTM A269 |
| Tolerance — Wall Thickness | ±0.02 mm (precision); ±0.05 mm (standard) | ASTM A213 |
| Surface Finish | Machined, Pickled, Polished (RA ≤ 0.5 μm available) | ASTM A270 |
| End Condition | Plain, Beveled, or Perforated | Customer specification |
| Heat Treatment | Solution Annealed (1050–1150°C), Water Quenched | ASTM A213 |
| Coil Form | Continuous coil, loose-wound or close-wound | — |
Manufacturing Process
1. Raw Material Selection and Milling
High-purity stainless steel slabs are produced via Vacuum Arc Remelting (VAR) or Electro-Slag Remelting (ESR) to minimize impurity inclusions — particularly sulfur, phosphorus, and oxide inclusions — which are identified in failure analyses as primary initiators of internal leakage pathways. Inclusion size is controlled to ≤ 50 μm.
2. Hot Rolling and Annealing
The slab is hot-rolled into a hollow tube blank. The material is then annealed at 1050–1150°C followed by controlled water quenching to achieve a fully austenitic microstructure with uniform grain size (ASTM Grain Size 6–8).
3. Cold Drawing / Cold Rolling
The hot-rolled tube undergoes multiple passes of cold working to achieve precise dimensional tolerances and enhanced mechanical properties. Intermediate annealing cycles are performed to prevent work hardening beyond acceptable limits.
4. Coiling
The finished tube is wound into coils using precision-controlled tension systems to prevent localized deformation, ovality, or residual stress concentration at the coil set point — a known location for fatigue crack initiation identified in leak failure analyses.
5. Surface Treatment
Final surface preparation includes acid pickling (HNO3/HF mixed acid) and passivation to remove mill scale and form a stable chromium oxide passive film (Cr2O3). For hygienic applications, electropolishing to achieve surface roughness (Ra) ≤ 0.5 μm is available.
6. Quality Inspection and Testing
- Hydrostatic Testing: Performed at 1.5× the maximum working pressure to detect internal defects and leakage pathways
- Eddy Current Testing (ECT): Full-length non-destructive examination for surface and near-surface defects
- Visual Inspection: End-face and surface examination under magnification
- Spectrographic Analysis: Optical Emission Spectroscopy (OES) for chemical composition verification
- Microstructural Examination: Metallographic analysis for grain boundary condition and sensitization assessment (ASTM A262 Practice E)
Applications
- Petrochemical and Refinery Industry: Heat exchanger tubes, reactor internals, distillation column condensers, and process piping handling sulfuric acid, hydrochloric acid, and other aggressive media
- Pharmaceutical and Biotechnology: Sterilizable process tubing, bioreactor components, and Clean-in-Place (CIP)/Sanitation-in-Place (SIP) compatible systems
- Food and Beverage Processing: Hygienic-grade tubing for dairy, brewing, and food-grade fluid transfer systems
- Marine and Offshore Engineering: Seawater cooling systems, ballast water treatment, and desalination plant heat exchangers
- Chemical Processing: Reactor coils, evaporators, condensers, and heat exchangers in phosphoric acid, nitric acid, and organic acid production
- Aerospace: Hydraulic tubing, fuel system lines, and engine exhaust components
- Power Generation: Boiler economizers, condensers, and superheater tubes in fossil-fuel and nuclear power plants
- Medical Devices: Endoscopic tubing, surgical instrument shafts, and implant-grade components
Quality Certifications and Standards Compliance
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- EN 10204 3.1 — Material Test Certificate (MTC) with inspection data per EN 10204
- ASTM A213 / A269 / A270 — American Society for Testing and Materials compliance
- GB/T 12771-2019 — Chinese national standard for welded stainless steel tubing
- GB/T 4237-2015 — Chinese standard for cold-rolled stainless steel sheets and strips
- ASME SA-213 / SA-269 — Pressure vessel and piping applications
- 3-A Sanitary Standards — Available for food and pharmaceutical applications
- NORSOK M-650 — Available for oil and gas industry applications
- CE Marking (PED 2014/68/EU) — Pressure Equipment Directive compliance where applicable
Unique Selling Points and Technical Differentiators
Failure-Analysis-Informed Design Optimization:
Wenzhou Jixing Metal Materials Co., Ltd. leverages systematic leak failure analysis findings to continuously improve product reliability. Key differentiators include:
- Ultra-Low Inclusion Control: Inclusion sizes restricted to ≤ 50 μm via VAR/ESR remelting, directly addressing the root cause of internal leakage paths identified in field failure analyses
- Controlled Coil Set Point Management: Precision tension-controlled coiling minimizes residual stress at the coil start/end point, eliminating a documented fatigue crack initiation site
- Full-Length Non-Destructive Examination: 100% ECT and hydrostatic testing coverage ensures zero undetected internal defects
- Low-Carbon Guarantee (C ≤ 0.030%): Certified low-carbon content eliminates sensitization risk during downstream welding operations, preserving full corrosion resistance
- Customized Surface Finishes: From standard pickled surface to electropolished Ra ≤ 0.5 μm, accommodating diverse application requirements from industrial to pharmaceutical
- Traceable Documentation: Full material traceability from mill heat number through final coil, with complete MTC packages including chemical analysis, mechanical test data, and NDE reports
- Coil Configuration Flexibility: Available in multiple coil diameters and winding configurations to optimize downstream processing efficiency
Failure Analysis Insights — Engineering Recommendations
Based on documented leak failure analysis of 316L stainless steel coil tubes in service, the following engineering recommendations are provided to maximize service life and prevent premature failure:
- Welding Control: Maintain interpass temperature below 150°C; use balanced polarity DC (DCEP) with low heat input to prevent sensitization
- Post-Weld Treatment: Solution heat treatment (1050–1150°C, water quench) recommended for welded assemblies in aggressive chloride environments
- Chloride Limit: Monitor dissolved chloride concentration; maintain below 1,000 ppm at temperatures exceeding 60°C to prevent SCC
- Crevice Avoidance: Design to eliminate crevices where chloride accumulation can initiate localized corrosion
- Flow Velocity Management: Limit turbulent flow velocity to prevent erosion-corrosion synergy, particularly at weld seams and fittings
Supplier Information
Wenzhou Jixing Metal Materials Co., Ltd. is a specialized manufacturer and supplier of precision stainless steel tubing products based in Wenzhou, Zhejiang Province, China. The company maintains advanced cold-drawing, cold-rolling, and coil-forming capabilities with comprehensive in-house quality assurance laboratories. Technical support, custom specification development, and failure analysis consultation services are available upon request.