Stainless Steel Coil Tube — Cold-Bent Coil Tube Product Specification
1. Product Overview
The Stainless Steel Coil Tube (Product No. 1637) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product produced through the Cold Bending Coil Tube (冷弯盘管) process. This product category represents a critical intermediate form in the stainless steel pipe and tube supply chain, where continuous coil stock is cold-formed and bent into predetermined geometric configurations to meet specific application requirements.
Unlike seamless or welded straight-length pipes, coil tubes are supplied in continuous coiled form, offering significant advantages in material utilization, logistics efficiency, and downstream processing flexibility. The cold-bending process ensures superior dimensional accuracy, controlled microstructure evolution, and consistent mechanical properties throughout the coil length.
Unique Selling Point: Wenzhou Jixing's cold-bent coil tube products leverage proprietary forming parameters and advanced process control to deliver coils with uniform wall thickness, minimal surface defects, and excellent formability — distinguishing them from conventionally produced alternatives in the market.
2. Material & Properties
2.1 Base Material Grades
The coil tube products are available in a range of austenitic and duplex stainless steel grades, conforming to international standards:
- Austenitic Grades: AISI 304 (UNS S30400), AISI 304L (UNS S30403), AISI 316L (UNS S31603), AISI 321 (UNS S32100), AISI 316Ti (UNS S31635)
- Duplex Grades: UNS S31803 (2205), UNS S32205 (2507)
- Specialty Grades: AISI 310S (UNS S31008), AISI 904L (UNS N08904)
2.2 Mechanical Properties (Typical Values for 304L Grade)
- Tensile Strength (UTS): ≥ 520 MPa (75,000 psi)
- Yield Strength (0.2% Offset): ≥ 205 MPa (29,700 psi)
- Elongation: ≥ 40% (in 50 mm gauge length)
- Hardness: ≤ 210 HB (Brinell)
- Density: 7.93 g/cm³
- Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /°C (20–100°C)
- Thermal Conductivity: 16.3 W/(m·K) at 100°C
2.3 Chemical Composition (AISI 304L — Maximum %)
- C ≤ 0.030
- Si ≤ 1.00
- Mn ≤ 2.00
- P ≤ 0.045
- S ≤ 0.030
- Cr: 18.00 – 20.00
- Ni: 8.00 – 10.50
- N ≤ 0.10
3. Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 168.3 mm (¼" – 6") | ASTM A554 / GB/T 12771 |
| Wall Thickness | 0.5 mm – 8.0 mm | ASTM A554 / EN 10217 |
| Coil Inner Diameter (CID) | 500 mm – 1,200 mm | Manufacturer Standard |
| Coil Length (Continuous) | Up to 5,000 m (customizable) | — |
| Coil Weight | Up to 5,000 kg per coil | — |
| Surface Finish | 2B, No. 4 (Brushed), BA (Bright Annealed), Mirror (8K) | ASTM A480 / GB/T 4237 |
| Dimensional Tolerance (OD) | ±0.15 mm (precision grade); ±0.30 mm (standard grade) | ASTM A554 |
| Dimensional Tolerance (Wall) | ±10% of nominal | ASTM A554 |
| Heat Treatment | Solution Annealed (1050–1150°C) + Water Quenched | ASTM A473 |
| Corrosion Resistance | Potential Difference (ECP) ≤ 120 mV in 3.5% NaCl (ASTM G5) | ASTM G5 / ASTM G48 |
4. Manufacturing Process
4.1 Process Flow Diagram (Textual)
- Raw Material Inspection: Incoming stainless steel coil strip (cold-rolled) undergoes spectrographic analysis (OES — Optical Emission Spectroscopy) and mechanical testing to verify grade compliance and property conformance.
- Strip Slitting & Edge Preparation: The coil strip is slit to the required width with precision slitter machines. Edge quality is inspected to prevent defect propagation during forming.
- Cold Bending / Forming: The slit strip is fed through a series of progressively shaped rolls in the Cold Bending Coil Tube Machine (冷弯盘管机). The forming rolls incrementally bend the flat strip into a tubular cross-section. Key parameters include:
- Roll gap adjustment (±0.05 mm precision)
- Feed speed control (variable, typically 5–30 m/min depending on section complexity)
- Roll material: H13 tool steel with hard chromium plating (HRC 58–62)
- Seam Welding (if applicable): For welded coil tubes, the formed tube passes through a high-frequency induction welding (HFW — High Frequency Welding) station. Weld parameters include:
- Welding frequency: 400–800 kHz
- Welding power: 300–1,500 kW (depending on wall thickness)
- Post-weld upset: 10–25% (controlled to ensure weld integrity)
- Heat Treatment / Annealing: The formed coil tube is solution-annealed in a continuous annealing furnace under protective atmosphere (argon or endothermic gas, dew point ≤ -60°C) at 1050–1150°C, followed by rapid water quenching. This eliminates cold-work hardening, restores full austenitic microstructure, and ensures optimal corrosion resistance.
- Pickling & Passivation: The annealed coil tube is pickled in mixed acid (HNO₃/HF) to remove oxide scale, followed by passivation treatment to establish a stable chromium oxide passive film on the surface.
- Coiling & Packaging: The processed coil tube is wound onto a mandrel, trimmed to specified lengths (if required), and packaged with moisture barrier wrapping, protective end caps, and steel banding for shipment.
4.2 Key Process Control Points
- Temperature Monitoring: Real-time thermocouple feedback at furnace exit ensures annealing temperature uniformity within ±10°C.
- Dimensional Monitoring: Laser-based OD and wall thickness gauges provide continuous in-line measurement with data logging for traceability.
- Surface Inspection: Automated surface inspection systems (machine vision) detect scratches, inclusions, and scale residue with minimum defect detection size of 0.1 mm².
- Weld Integrity: Ultrasonic testing (UT) or eddy current testing (ECT) is performed on weld seams to detect porosity, lack of fusion, or undercut defects.
5. Applications
The cold-bent stainless steel coil tube products from Wenzhou Jixing Metal Materials Co., Ltd. serve a broad spectrum of industrial applications:
- Heat Exchangers & Condensers: Boiler tubes, radiator coils, refrigeration tubing, and heat exchanger bundles where continuous coil form eliminates joint requirements.
- Automotive Industry: Exhaust system components, fuel lines, turbocharger manifolds, and structural tubing requiring high-temperature resistance and formability.
- Petroleum & Chemical Processing: Process piping, distillation columns, heat transfer coils, and reactor internals exposed to aggressive chemical environments.
- Food & Pharmaceutical: Sanitary tubing, CIP (Clean-In-Place) compatible piping systems, and pharmaceutical equipment requiring high surface finish and corrosion resistance.
- Construction & Architectural: Structural tubing, handrails, decorative elements, and building components requiring aesthetic finish and durability.
- Energy Sector: Solar thermal collectors, geothermal systems, and nuclear-grade tubing (special grades).
6. Quality Certifications & Standards Compliance
6.1 Management System Certifications
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- ISO 45001:2018 — Occupational Health & Safety Management System
- IATF 16949:2016 — Automotive Quality Management (for automotive-grade products)
6.2 Product Standards Compliance
- ASTM A554 — Standard Specification for Austenitic Stainless Steel Tube
- ASTM A473 — Standard Specification for Heat Treated Bars and Shapes of Austenitic and Ferritic Stainless Steels
- EN 10217-7 — Heat-resistant, creep-resistant and high-temperature mechanical properties austenitic and austenitic-ferritic (duplex) stainless steel tubes for pressure purposes
- GB/T 12771 — Stainless steel seamless tubes for fluid transport (Chinese National Standard)
- JIS G3459 — Stainless steel seamless tubes for pressure purposes (Japanese Industrial Standard)
6.3 Third-Party Testing & Inspection
- NDT (Non-Destructive Testing): Ultrasonic testing (UT) per ASTM E164/E213, Eddy Current Testing (ECT) per ASTM E309
- Hydrostatic Testing: Per ASTM A554 Section 9, with test pressure calculated per specified formula
- Corrosion Testing: Intergranular corrosion testing per ASTM A262 Practice E, Pitting resistance testing per ASTM G48 Practice A
- Third-Party Inspection: Available upon request — SGS, BV (Bureau Veritas), TUV, DNV
6.4 Traceability & Documentation
Each coil tube product is accompanied by a Mill Test Certificate (MTC) conforming to EN 10204 Type 3.1, providing full chemical composition analysis, mechanical test results, heat treatment records, and dimensional verification data. Full heat-to-heat traceability is maintained from raw material receipt through final shipment.
7. Packaging & Shipping
- Coil tubes are wound onto steel or wooden mandrels with inner diameter protection.
- Each coil is wrapped with PE (Polyethylene) moisture barrier film and glassine paper.
- Steel banding (minimum 3 bands) secures the coil for transport.
- Protective end caps prevent coil edge damage during handling.
- Export packaging available: seaworthy wooden crates or container-optimized configurations.
8. Technical Support & Customization
Wenzhou Jixing Metal Materials Co., Ltd. offers comprehensive technical support including:
- Custom coil tube dimensions and configurations tailored to specific application requirements
- Material selection guidance based on service environment (temperature, pressure, corrosion media)
- Process simulation and feasibility analysis for complex forming operations
- Sample provision and joint development programs for new product introductions
Note: All specifications listed herein are typical values and are subject to change based on production batch, material grade, and customer-specific requirements. For definitive specifications, please refer to the applicable Mill Test Certificate and purchase order documentation.