Stainless Steel Coil Tube (Coiltube) — Pumping-Grade Product Specification
Product Overview
The Stainless Steel Coil Tube (hereinafter referred to as "Coiltube") manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a high-performance continuous-length tubular product engineered for demanding industrial and construction applications. This product category has achieved landmark engineering validation through the nation's first successful simulation of C130 concrete vertical pumping at 880 meters, demonstrating the exceptional structural integrity, pressure resistance, and fatigue performance of stainless steel coil tubes under extreme operational conditions.
Coiltubes are produced as continuous spirally wound tubes without butt welds, offering superior mechanical homogeneity compared to traditional welded pipe sections. The seamless nature of the coil tube eliminates weak points associated with longitudinal or circumferential welds, making it particularly suitable for high-pressure fluid transport, structural reinforcement, and extreme-height pumping operations.
Material Composition & Properties
Coiltubes are typically fabricated from austenitic and duplex stainless steel grades, selected based on the specific service environment. Common material grades include:
- 304 / 304L (UNS S30400 / S30403): General-purpose austenitic stainless steel with excellent corrosion resistance, formability, and weldability. Carbon content ≤ 0.08% (304L ≤ 0.03% for enhanced intergranular corrosion resistance).
- 316 / 316L (UNS S31600 / S31603): Molybdenum-bearing austenitic grade offering superior resistance to chlorides, acids, and pitting corrosion. Mo content 2.0–3.0%.
- 321 (UNS S32100): Titanium-stabilized austenitic grade for high-temperature service up to 900°C.
- Super Duplex 2205 (UNS S31803): High-strength duplex phase stainless steel with yield strength ≥ 450 MPa and excellent resistance to chloride stress corrosion cracking (Cl-SCC).
- 2507 Super Duplex (UNS S32750): Ultra-high-strength duplex with yield strength ≥ 550 MPa, suitable for the most aggressive marine and chemical environments.
Mechanical Properties (Typical — 304 Grade, Annealed Condition)
- Tensile Strength (UTS): ≥ 520 MPa
- Yield Strength (0.2% Offset): ≥ 205 MPa
- Elongation (A50mm): ≥ 40%
- Hardness (HBW): ≤ 217
- Density: 8.0 g/cm³
- Thermal Conductivity (20°C): 16.3 W/(m·K)
- Thermal Expansion Coefficient (20–100°C): 17.3 × 10⁻⁶ /°C
Corrosion Resistance
- Pitting Resistance Equivalent Number (PREN): 304: ~18–19; 316: ~24–26; 2205: ~24–28; 2507: ~38–40
- Intergranular Corrosion: Passes ASTM A262 Practice E (acid solution test) without sensitization
- Stress Corrosion Cracking (SCC): Duplex grades demonstrate immunity to Cl-SCC at temperatures up to 60°C in 5% NaCl solutions
Specifications
| Parameter | Specification | Applicable Standard |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 219.1 mm (¼" – 8½") | ASTM A554 / EN 10217-7 |
| Wall Thickness (WT) | 0.5 mm – 12.0 mm | ASTM A554 / EN 10217-7 |
| Coil Inner Diameter (CID) | 150 mm – 600 mm (adjustable) | Manufacturer specification |
| Coil Length (Continuous) | 500 m – 3,000 m per coil | — |
| Surface Finish | 2B (Cold Rolled + Annealed + Pickled), No. 4 Brushed, BA (Bright Annealed), or Custom | ASTM A480 / GB/T 4237 |
| Temperature Range (Continuous) | -196°C to +870°C (grade-dependent) | — |
| Pressure Rating (Typical, 304, OD 38 mm × WT 3 mm) | ≤ 25 MPa (3,625 PSI) | ASME B31.3 |
| Tolerance (OD) | ±0.1 mm to ±0.5 mm (per diameter range) | ASTM A554 |
| Tolerance (WT) | ±10% or ±0.05 mm (whichever is greater) | ASTM A554 |
| Roundness | ≤ 0.5% of OD | EN 10217-7 |
| Straightness (after uncoiling) | ≤ 2 mm/m | — |
| Packaging | Steel band strapping + export-grade wooden pallet or bulk coil | ISO 4180 |
Manufacturing Process
The production of stainless steel coil tubes follows a rigorous multi-stage manufacturing sequence to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection & Ingot Casting: High-purity stainless steel ingots are produced via Vacuum Arc Remelting (VAR) or Electro-Slag Remelting (ESR) to minimize inclusions and ensure compositional uniformity.
- Hot Rolling & Annealing: Billets are hot-rolled into seamless tube blanks (ferritic-austenitic or fully austenitic condition), followed by solution annealing at 1050–1150°C with rapid water quenching.
- Pilger Milling / Cross-Rolling: The tube blanks are cold-worked through pilger or cross-rolling mills to achieve precise outer diameter and wall thickness dimensions with tight tolerances.
- Pipe Welding (for welded coil tube): For welded variants, a continuous longitudinal weld is formed via Automatic Submerged Arc Welding (SAW) or Gas Metal Arc Welding (GMAW) with 100% radiographic inspection (RT) per ASTM E94.
- Solution Annealing & Pickling: Tubes are heat-treated in a protective atmosphere (95% N₂ + 5% H₂) at temperatures between 1010–1120°C, followed by acid pickling (HNO₃/HF blend) to remove scale and restore passivation.
- Precision Cold Drawing / Mandrel Drawing: Tubes are drawn through precision dies to achieve final dimensional tolerances, enhanced surface finish, and improved mechanical properties.
- Coiling & Stress Relief: The finished tube is coiled onto precision-mandrel reels with controlled tension to prevent deformation. Optional low-temperature stress relief (300–400°C) may be applied for dimensional stability.
- Non-Destructive Testing (NDT): Each coil undergoes 100% Electromagnetic Testing (ET) per ASTM E709/E309, and positive material identification (PMI) per ASTM E165 (XRF) or E1476 (OES).
- Final Inspection & Packaging: Dimensional verification (OD, WT, roundness), surface inspection, and chemical/physical testing per ASTM A327/A999 are completed before export-grade packaging.
Applications
The proven performance of stainless steel coil tubes in the landmark 880-meter vertical C130 concrete pumping experiment underscores their suitability for the following critical applications:
- Ultra-High-Pressure Concrete Pumping: Continuous-length coil tubes eliminate butt welds that could fail under extreme hydrostatic pressure in skyscraper construction (validated at 880 m vertical pumping height with C130 ultra-high-strength concrete).
- Oil & Gas Industry: Downhole tubing, casing, wellhead assemblies, and high-pressure flow lines in sour (H₂S-containing) environments.
- Chemical Processing: Reaction vessel heat exchanger tubing, acid transport lines, and corrosion-resistant piping systems.
- Food & Pharmaceutical Industry: Hygienic-grade tubing for CIP (Clean-in-Place) and SIP (Sterilization-in-Place) systems requiring 3-A sanitary compliance.
- Marine & Offshore Engineering: Seawater intake piping, ballast systems, and structural reinforcement in chloride-laden environments.
- Power Generation: Boiler tubes, superheater coils, and nuclear-grade instrumentation tubing.
- Automotive & Aerospace: Exhaust systems, fuel lines, hydraulic tubing, and structural components requiring weight optimization and corrosion resistance.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring traceability and compliance with international standards:
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- ISO 45001:2018 — Occupational Health & Safety Management System
- EN 10204 3.1 / 3.2 — Inspection and Test Certification (Mill Test Certificates)
- ASTM / ASME — Product compliance with ASTM A554, A778, A791, A795; ASME B31.3, B31.8
- EN / DIN — European compliance with EN 10217-7, EN 10216-5, DIN 18823, DIN 2393
- API — American Petroleum Institute standards where applicable
- NACE MR0175 / ISO 15156 — Compliance for sour service applications
- Third-Party Inspection: Available upon request (BV, DNV, Lloyd's, SGS, TUV)
- Full Heat Traceability: Each coil is traceable to the original heat number with complete chemical composition, mechanical test results, and NDT reports.
Unique Selling Points
1. Proven Extreme-Condition Performance: Validated through the world's first successful C130 concrete simulation vertical pumping experiment at 880 meters — an unprecedented demonstration of structural integrity under extreme hydrostatic and dynamic loading.
- 2. Zero Butt Welds: Continuous coil format eliminates longitudinal and circumferential welds, removing potential failure points and extending service life in cyclic pressure environments.
- 3. Material Versatility: Available in over 30 stainless steel grades ranging from standard austenitic (304, 316) to super duplex (2507), accommodating the most aggressive chemical and mechanical environments.
- 4. Precision Dimensional Control: Cold-drawn tolerance of ±0.05 mm on wall thickness ensures reliable fit-up, reduced waste in fabrication, and predictable pressure ratings.
- 5. Comprehensive NDT Coverage: 100% electromagnetic testing on every coil, with optional ultrasonic (UT), radiographic (RT), and eddy current (EC) inspection for critical applications.
- 6. Economical Material Utilization: Coil format reduces cutting losses by up to 80% compared to cut-length pipe, delivering significant cost savings on large-scale projects.
- 7. Full Documentation & Traceability: EN 10204 3.2 material certificates with full heat traceability, third-party verification, and digital quality records available upon request.