Stainless Steel Coil Tube (Coiltube) — Specialized Butt-Joint Processing System
Product Overview
The Stainless Steel Coil Tube (Coiltube), designated as Product No. 1649 by Wenzhou Jixing Metal Materials Co., Ltd., is a continuous-length coiled tubing product engineered for precision applications requiring seamless or butt-welded joint integrity. Unlike conventional straight-length stainless steel tubes, coil tubes are supplied in continuous spiral-wound configurations, enabling high-efficiency downstream processing through automated forming, cutting, and assembly lines. This product category is particularly notable for its compatibility with specialized machine tools designed for the processing of butt-jointed coiled tubes (加工带接盘管子的专用机床), ensuring minimal material waste and superior joint quality throughout the manufacturing cycle.
The coil tube form factor offers significant logistical and manufacturing advantages, including reduced handling labor, optimized storage density, and the ability to feed directly into high-speed production machinery without manual repositioning between lengths.
Material & Properties
Stainless steel coil tubes from Wenzhou Jixing Metal Materials Co., Ltd. are manufactured from austenitic, ferritic, and duplex stainless steel grades conforming to international standards. The following key material grades are typically available:
- Austenitic Grades: AISI 304 (UNS S30400), AISI 304L (UNS S30403), AISI 316 (UNS S31600), AISI 316L (UNS S31603), AISI 321 (UNS S32100), AISI 321H (UNS S32109)
- Ferritic Grades: AISI 430 (UNS S43000), AISI 409L (UNS S40903)
- Duplex Grades: UNS S31803 (2205), UNS S32750 (2507)
- High-Nickel Alloys: Inconel 625 (UNS N06625), Hastelloy C-276 (UNS N10276)
Mechanical Properties (AISI 304 Reference Values):
- Tensile Strength: ≥ 515 MPa (74,700 psi)
- Yield Strength (0.2% offset): ≥ 205 MPa (29,700 psi)
- Elongation: ≥ 40% (minimum)
- Hardness: ≤ 210 HB (Brinell)
- Density: 7.93 g/cm³
- Thermal Conductivity: 16.3 W/(m·K) at 100°C
- Corrosion Resistance: Excellent resistance to atmospheric, aqueous, and chemical environments; pitting resistance (PREN) of 18–20 for 304 grade
Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 3.0 mm – 114.3 mm (1/8" – 4½") |
| Wall Thickness | 0.3 mm – 6.0 mm (0.012" – 0.236") |
| Coil Length | 20 m – 200 m per coil (configurable) |
| Coil Diameter | 300 mm – 1,200 mm (12" – 48") |
| Surface Finish | 2B, BA (Bright Annealed), No. 4 Brushed, Mirror (8K) |
| Manufacturing Process | Seamless (Pierced), Welded (ERW/AW), or Butt-Welded Coil |
| Joint Type | Butt-Welded (for continuous coil with splices) |
| Dimensional Tolerance | ±0.05 mm (OD), ±0.05 mm (wall thickness) |
| Standard References | ASTM A554, ASTM A269, ASTM A778, EN 10217, GB/T 14976 |
| Coil Weight | Up to 3,000 kg per coil (grade-dependent) |
| Delivery Condition | Annealed, Pickled & Passivated, Cold-Wrought |
Manufacturing Process
3.1 Coil Tube Production Flow
- Hot Rolling / Billet Preparation: Stainless steel billets are hot-rolled into seamless tube blanks via the Mannesmann piercing process or produced as flat strip for welded tube manufacturing.
- Cold Drawing / Cold Reduction: The tube blank undergoes multi-pass cold drawing through precision-die tooling to achieve the target OD and wall thickness with tight dimensional tolerances.
- Intermediate Annealing: Periodic solution annealing (1050°C – 1100°C) in a controlled atmosphere (argon or vacuum) relieves cold-work hardening and restores ductility for subsequent forming operations.
- Coil Winding: The finished straight tube is continuously wound onto a precision-controlled coil former, maintaining uniform curvature and avoiding surface scratches or deformation.
- Butt-Joint Processing (Specialized Machine Tool): When coil length exceeds single-length production capacity, butt-welded splices are created using a dedicated machine tool (专用机床) designed for coiled tube processing. This equipment features:
- Automatic tube alignment and end-preparation (beveling/chamfering)
- Pulsed TIG (Gas Tungsten Arc) welding with argon shielding
- Real-time weld quality monitoring via inline optical inspection
- Automated coil feed and tension control to prevent distortion at the joint
- Post-weld heat treatment station for weld zone homogenization
- Pickling & Passivation: The coil is subjected to acid pickling (nitric/hydrofluoric acid mixture) to remove oxide scale, followed by passivation treatment to establish a stable chromium oxide surface film.
- Quality Inspection: 100% visual inspection, hydrostatic pressure testing (per ASTM A269), and optional eddy-current or ultrasonic testing for subsurface defect detection.
- Coil Packaging: Final coils are wrapped in protective film, crated, or shrink-wrapped for shipment.
3.2 Butt-Joint Quality Assurance
The specialized butt-joint processing machine tool ensures that spliced coil tubes meet or exceed the mechanical and metallurgical properties of the base material. Key quality parameters include:
- Weld Penetration: Full penetration with minimum 95% fusion ratio
- Weld Zone Hardness: Within 10% of base material hardness
- Tensile Strength at Joint: ≥ 90% of parent material tensile strength
- Corrosion Resistance at Joint: Equivalent to base material (verified by salt spray test per ASTM B117)
Applications
- Automotive Industry: Fuel lines, brake lines, exhaust system components, and structural tubing for lightweight vehicle assemblies
- Food & Beverage Processing: Hygienic piping systems, CIP (Clean-In-Place) compatible tubing for dairy, brewing, and pharmaceutical applications
- Petrochemical & Oil/Gas: High-pressure process piping, heat exchanger tubes, and subsea umbilical components
- Medical Devices: Hypodermic needles, surgical instrument tubing, and implant-grade components (316L)
- Architecture & Decoration: Handrails, structural framing, decorative trim, and elevator components
- Heat Exchangers & HVAC: Condenser tubes, evaporator coils, and refrigeration system tubing
- Aerospace: Hydraulic lines, fuel system tubing, and structural components (Inconel/Hastelloy grades)
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems and holds the following certifications:
- ISO 9001:2015 — Quality Management System
- ISO 14001 — Environmental Management System
- ISO 45001 — Occupational Health & Safety Management
- EN 10204 — Type 3.1 Mill Test Certificates (MTC) for all shipments
- AD 2000-W0 — German pressure vessel certification (for pressure applications)
- ASME PE Stamp — Pressure equipment compliance
- PED 2014/68/EU — European Pressure Equipment Directive conformity
- NSF/ANSI 61 — Drinking water system certification (for food-grade applications)
- 3-A Sanitary Standards — Dairy and food processing compliance
Unique Selling Points
- Specialized Butt-Joint Processing: Proprietary machine tool technology ensures butt-welded coil splices are indistinguishable from seamless tube in terms of mechanical and corrosion performance — a critical advantage for continuous-feed automated production lines.
- Continuous-Length Supply: Eliminates the need for on-site welding, reducing labor costs by up to 35% and improving production throughput.
- Precision Dimensional Control: Tight tolerances (±0.05 mm) enable direct integration into CNC machining, bending, and forming operations without secondary finishing.
- Multi-Grade Flexibility: Availability of 15+ stainless steel and alloy grades from a single supplier simplifies procurement and ensures material consistency.
- Custom Coil Configuration: Tailored coil diameters, lengths, and surface finishes to match specific customer machinery and application requirements.
- Full Traceability: Each coil is traceable to the heat number, enabling complete supply chain accountability and rapid recall if necessary.
Technical Learning Notes
Key Insight from Specialized Machine Tool Study (加工带接盘管子的专用机床): The development and application of dedicated machine tools for butt-jointed coil tube processing represents a significant advancement in stainless steel coil manufacturing. Traditional methods required cutting coils into straight lengths for welding and re-coiling, introducing inefficiencies, potential defects, and material loss. The specialized machine tool integrates tube feeding, alignment, welding, inspection, and re-coiling into a single automated process, achieving cycle times of 2–5 seconds per joint while maintaining weld quality equivalent to manual TIG welding. This technology is particularly valuable for high-volume production environments where continuous coil supply is essential for maintaining line speed and minimizing downtime.