Stainless Steel Coil Tube (盘管) — Intelligent Production Line Series
1. Product Overview
The Stainless Steel Coil Tube (hereinafter referred to as "Coil Tube") is a precision-engineered tubular product manufactured in continuous coiled form, designed to meet the demanding requirements of industrial, HVAC, chemical processing, and heat exchange applications. Produced by Wenzhou Jixing Metal Materials Co., Ltd., this product line leverages advanced intelligent scheduling systems and anti-sway transfer mechanisms (移栽防摆技术) to ensure dimensional consistency, surface integrity, and mechanical reliability throughout the entire production cycle.
Unlike traditional straight-length seamless or welded tubes, coil tubes are supplied in helically wound coils, enabling continuous feed into downstream processing equipment such as bending machines, forming stations, and heat exchanger assembly lines. This configuration significantly reduces material waste, minimizes handling operations, and enhances production throughput in high-volume manufacturing environments.
2. Material & Properties
2.1 Base Alloy Composition
The Coil Tube is fabricated from austenitic and duplex stainless steel grades, selected to provide optimal combinations of corrosion resistance, mechanical strength, and formability. The primary alloying elements include:
- Chromium (Cr): 17–25 wt% — provides passive oxide layer formation and general corrosion resistance
- Nickel (Ni): 8–22 wt% — stabilizes the austenitic phase and enhances ductility
- Molybdenum (Mo): 1–6 wt% — improves pitting and crevice corrosion resistance (particularly in 316 and 317L grades)
- Nitrogen (N): 0.05–0.25 wt% — contributes to solid solution strengthening in duplex grades
- Carbon (C): ≤0.03 wt% (in "L" low-carbon variants) — prevents sensitization during welding
2.2 Mechanical Properties
- Tensile Strength (UTS): 515–750 MPa (depending on grade and heat treatment condition)
- Yield Strength (0.2% Proof Stress): ≥205–450 MPa
- Elongation at Break: ≥35–55% (gauge length 50 mm)
- Hardness (HV): 150–250 (annealed condition)
- Thermal Conductivity: 14–16 W/(m·K) at 25°C
- Thermal Expansion Coefficient: 16–18 × 10⁻⁶ /°C (25–300°C)
2.3 Corrosion Resistance Characteristics
The passive chromium oxide film (Cr₂O₃) formed on the tube surface provides inherent resistance to atmospheric corrosion, dilute mineral acids, and alkaline solutions. In chlorinated environments, the addition of molybdenum and nitrogen significantly elevates the Pitting Resistance Equivalent Number (PREN), defined as:
PREN = %Cr + 3.3 × %Mo + 16 × %N
Tubes with PREN ≥ 24 demonstrate excellent resistance to localized corrosion in marine and chemical processing environments.
3. Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 3.0 – 50.8 mm (1/8" – 2") | ASTM A778 / EN 10217 |
| Wall Thickness | 0.3 – 3.0 mm | ASTM A778 / EN 10217 |
| OD Tolerance | ±0.05 mm (≤10 mm OD); ±0.1 mm (>10 mm OD) | ISO 4413 |
| Wall Thickness Tolerance | ±10% of nominal | ASTM A778 |
| Coil Inner Diameter (CID) | 150 – 600 mm | Manufacturer Specification |
| Coil Length (per coil) | 100 – 2000 m (continuous) | — |
| Surface Finish | No. 1 Annealed / 2B / BA (Bright Annealed) / Pickled & Passivated | ASTM A480 |
| Available Grades | 304, 304L, 316, 316L, 310S, 321, 347, 904L, 2205, 2507 | ASTM A270 / EN 10217 |
| Manufacturing Method | ERW (Electric Resistance Welding) / Autoclaved Welded (AW) | ASTM A778 |
| Operating Temperature Range | −196°C to +870°C (grade-dependent) | ASME BPV Code |
| Maximum Working Pressure | Up to 32 MPa (pressure vessel applications) | ASME BPV Section VIII |
| Helix Pitch Tolerance | ±2 mm (controlled by intelligent scheduling system) | Internal Specification |
4. Manufacturing Process
4.1 Process Flow
- Steel Strip Uncoiling & Inspection: Cold-rolled stainless steel strip is fed from the mill coil onto the production line. Incoming material undergoes ultrasonic thickness measurement and surface defect scanning.
- Edge Trimming & Slitting: The strip is slit to precise width corresponding to the target tube OD, with laser-guided edge trimming to ±0.02 mm accuracy.
- Forming & Welding (ERW/AW): The flat strip is progressively formed through a series of roll stands into a tubular shape. The longitudinal seam is welded using high-frequency electric resistance welding (ERW) or autoclaved welding (AW) technology. Weld parameters are controlled by closed-loop feedback systems.
- Inline Heat Treatment: The welded tube passes through a continuous annealing furnace (typically 1000–1150°C in a protective atmosphere of endothermic gas or hydrogen) to homogenize the weld zone microstructure and restore full annealed ductility.
- Intelligent Scheduling & Anti-Sway Transfer (智能调度与移栽防摆): Following heat treatment, the tube enters the coiling station. An intelligent scheduling algorithm coordinates the transfer of the tube from the furnace exit to the coil winder. The anti-sway mechanism (移栽防摆系统) employs dynamic tension control, servo-driven guide rollers, and real-time positional feedback to eliminate lateral oscillation during transfer. This ensures:
- Coiling: The tube is wound onto a mandrel at controlled tension, with helix pitch monitored by laser sensors to maintain uniform coil geometry.
- Pickling & Passivation: Coiled tubes are treated with hydrochloric or citric acid solutions to remove oxide scale, followed by nitric acid passivation to regenerate the protective chromium oxide film.
- Final Inspection & Packing: Each coil undergoes dimensional verification, hydrostatic testing (where applicable), and visual/surface inspection before packaging with coil protection bands and moisture-absorbing desiccants.
4.2 Intelligent Scheduling Technology (智能调度系统)
The production line employs a centralized Manufacturing Execution System (MES) that optimizes coil changeover sequences, minimizes material transitions between grades, and coordinates furnace loading schedules to maximize thermal efficiency. Real-time data acquisition from embedded sensors enables predictive maintenance scheduling and quality traceability for each coil lot.
4.3 Anti-Sway Transfer Mechanism (移栽防摆技术)
A critical innovation in this production system is the anti-sway transfer mechanism deployed at the interface between the straightening section and the coiling station. The system utilizes:
- Active Damping Rollers: Pneumatically or hydraulically actuated rollers that apply counter-force to lateral tube displacement
- Positional Tracking Sensors: Inductive or capacitive sensors measuring tube centerline deviation at multiple axial stations
- Adaptive Control Algorithm: PID-based controllers that adjust roller pressure and transfer speed in real time based on tube geometry and material properties
This technology reduces coil edge misalignment by up to 85% compared to conventional mechanical guides, resulting in superior coil stacking uniformity and reduced downstream processing defects.
5. Applications
5.1 Heat Exchanger Manufacturing
Coil tubes are the preferred feedstock for plate-and-tube heat exchangers, finned tube assemblies, and shell-and-tube heat exchanger tube bundles. The continuous coil form allows automated U-bend forming and tube sheet insertion without interruption.
5.2 HVAC & Refrigeration Systems
Used in air conditioning evaporators, condenser coils, chiller circuits, and industrial refrigeration systems. Grades 316L and 904L are specified for ammonia-based and halocarbon refrigerant circuits.
5.3 Chemical Processing & Petrochemical Industry
Employed in reactor cooling coils, distillation column internals, heat transfer loops, and process piping systems handling aggressive media such as sulfuric acid, hydrochloric acid, and chlorinated hydrocarbons.
5.4 Food & Pharmaceutical Industry
BA-finished 316L coil tubes are used in sanitary heat exchangers, CIP (Clean-In-Place) systems, and steam sterilization circuits where product contact purity is critical.
5.5 Marine & Offshore Engineering
2205 and 2507 duplex coil tubes serve in seawater cooling systems, ballast water treatment circuits, and offshore platform heat exchange systems requiring high PREN and resistance to chloride-induced stress corrosion cracking (Cl-SCC).
5.6 Power Generation
Utilized in superheater tubes, economizer coils, and waste heat recovery systems in combined-cycle power plants and biomass energy facilities.
6. Quality Certifications & Standards Compliance
6.1 International Standards
- ASTM A778 — Standard Specification for Stainless Steel Tube, Welded, Cold-Worked
- ASTM A270 — Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for Chemical and Similar Severe Service
- EN 10217-7 — Technical delivery conditions for seamless and welded tubes of stainless steels — Part 7: Cold-worked tubes
- ISO 4413 — Hydraulic fluid power — General rules and safety requirements for systems and components
- ASME BPV Code Section VIII, Division 1 — Rules for Construction of Pressure Vessels
6.2 Quality Management Certifications
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- ISO 45001:2018 — Occupational Health and Safety Management System
- NADCAP — National Aerospace and Defense Contractors Accreditation Program (for aerospace-grade products)
6.3 Third-Party Inspection & Testing
- Hydrostatic pressure testing at 1.5× maximum working pressure per ASTM A778
- Eddy current testing (ECT) for weld seam integrity verification
- X-ray radiographic testing (RT) for weld penetration confirmation (on request)
- Spectroscopic chemical analysis (OES) for each heat lot
- Third-party inspection by SGS, Bureau Veritas, or TÜV upon customer request
7. Unique Selling Points
- Intelligent Production Scheduling: The MES-integrated scheduling system enables optimal coil sequencing, minimizing grade transitions and reducing production downtime by up to 30%.
- Anti-Sway Precision Coiling: Proprietary anti-sway transfer technology ensures coil uniformity with helix pitch tolerance of ±2 mm, eliminating edge overlap defects common in conventional coiling.
- Full Traceability: Each coil is assigned a unique batch identifier linked to mill heat number, chemical analysis, mechanical test results, and dimensional inspection data.
- Custom Grade Availability: From standard austenitic grades (304/316) to high-alloy super-austenitics (904L, C-276) and duplex grades (2205, 2507), meeting the most demanding corrosion service requirements.
- Continuous Coil Supply: Eliminates butt welds and joint discontinuities inherent in straight-length tube supply, providing superior structural integrity for cyclic loading applications.
- Comprehensive Surface Treatment Options: Pickled & passivated, BA finish, or custom matte/polished finishes available to meet specific aesthetic and functional requirements.
8. Packaging & Delivery
Coil tubes are wound on steel mandrels, secured with steel banding, and wrapped with VCI (Vapor Corrosion Inhibitor) coated paper and moisture-absorbing desiccant packs. Outer protection consists of galvanized steel strapping and wooden or plastic coil saddles. Coils are suitable for both inland transport and ocean freight in 20-foot or 40-foot containers.
9. Conclusion
The Stainless Steel Coil Tube product line from Wenzhou Jixing Metal Materials Co., Ltd. represents a synthesis of advanced metallurgical engineering and intelligent manufacturing technology. The integration of automated scheduling systems and anti-sway transfer mechanisms distinguishes this product from conventional coil tube offerings, delivering superior dimensional accuracy, surface quality, and production consistency. With compliance to international standards and a comprehensive quality assurance framework, these coil tubes are suitable for the most demanding industrial applications across global markets.