Stainless Steel Coil Tube — Reverse Alternating Bending Performance Verified
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. offers a premium-grade stainless steel coil tube engineered for applications demanding exceptional formability and fatigue resistance under repeated bending cycles. This coil tube product line is distinguished by its rigorous compliance with reverse alternating bending tests — a specialized quality assurance protocol that subjects the tubing to forward and reverse bending to a specified number of cycles, simulating real-world conditions where coil tubes are subjected to repeated flexing, kinking, and deformation.
Unlike conventional single-bend tests that validate only initial ductility, the reverse alternating bending test represents a significantly more stringent evaluation criterion. It verifies that the tube maintains structural integrity, dimensional stability, and surface quality through multiple cycles of opposing deformation — a critical requirement for coil tubes used in dynamic, high-cycle applications such as heat exchangers, refrigeration systems, and flexible conduit assemblies.
Material & Properties
- Base Grades Available: 304, 304L, 316, 316L, 321, 310S, and custom alloy compositions
- Formability: Exceptional cold-forming capability with proven performance under reverse alternating bending to prescribed cycle counts
- Corrosion Resistance: Superior resistance to intergranular corrosion, pitting, and general oxidation across a wide range of chemical environments
- Weldability: Low carbon variants (304L, 316L) ensure excellent weldability without sensitization concerns
- Temperature Range: Suitable for cryogenic to elevated-temperature service depending on grade selection
- Surface Finish: Available in annealed, pickled, polished, and custom finishes
Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 3.0 mm – 100 mm (custom sizes available upon request) |
| Wall Thickness | 0.3 mm – 5.0 mm |
| Coil Length | Standard 50 m / 100 m; custom lengths available |
| Coil Inner Diameter | Standard 150 mm / 300 mm; customizable |
| Manufacturing Method | Seamless (ETP/ATP) or Welded (TP/ERW) |
| Reverse Alternating Bending Test | Forward and reverse bending to specified cycle count — no cracking, splitting, or unacceptable deformation |
| Single Bending Test | Compliant with ASTM A213 / EN 10216 requirements |
| Tolerance (OD) | ±0.1 mm or per customer specification |
| Tolerance (Wall Thickness) | ±10% of nominal |
| Surface Quality | Free from cracks, seams, laps, and surface defects per visual inspection and eddy current testing |
| Applicable Standards | ASTM A269, ASTM A213, EN 10217, EN 10216, GB/T 12771, GB/T 14976 |
Manufacturing Process
- Raw Material Selection: Only certified stainless steel billets or strip from approved mills are sourced, ensuring traceability and consistent chemical composition.
- Piercing / Forming: For seamless tubes, the piercing and rotary piercing methods are employed to achieve precise wall thickness and dimensional accuracy.
- Hot Rolling & Cold Drawing: Tubes undergo hot rolling followed by precision cold drawing to achieve final dimensions and enhanced mechanical properties.
- Heat Treatment (Solution Annealing): Full solution annealing is performed to relieve residual stresses, restore full ductility, and ensure optimal corrosion resistance.
- Pickling & Passivation: Chemical pickling removes oxide scale, followed by passivation to form a protective chromium oxide layer.
- Coiling: Tubes are coiled to specified lengths and diameters using controlled tension and feed systems to prevent work-hardening or surface damage.
- Quality Inspection: Every coil undergoes ultrasonic testing (UT), eddy current testing (ECT), hydrostatic pressure testing, and dimensional verification.
- Reverse Alternating Bending Verification: Samples are subjected to forward and reverse bending to the prescribed number of cycles, confirming the tube's capacity to withstand repeated deformation without cracking or failure.
Applications
- Heat Exchangers & Condensers: Coil tubes in shell-and-tube and plate-fin heat exchangers where repeated thermal cycling induces bending stresses.
- Refrigeration & HVAC Systems: Evaporator and condenser coils requiring reliable performance under expansion and contraction cycles.
- Automotive & Aerospace: Fuel lines, brake lines, and hydraulic tubing subjected to vibration and flexural fatigue.
- Petrochemical & Process Industries: Flexible tubing in reactor coils, trace heating systems, and transfer lines.
- Medical & Pharmaceutical: Sterilizable tubing assemblies requiring repeated flexing without loss of integrity.
- Food & Beverage Processing: Sanitary tubing in pasteurization and CIP systems.
- Wire Drawing & Cable Manufacturing: Die tubes and guide coils in production lines with high-cycle bending demands.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications:
- ISO 9001:2015 — Quality Management System
- ISO 14001 — Environmental Management System
- ISO 45001 — Occupational Health and Safety Management System
- EN 10204 3.1 / 3.2 — Material Test Certificates
- NACE MR0175 / ISO 15156 — Compliance for sour service applications (where applicable)
- Mill Test Reports (MTR) provided with every shipment, including chemical analysis, mechanical properties, and test results
Key Differentiators
The reverse alternating bending test is a coil-tube-specific quality protocol that exceeds the requirements of standard single-bend formability tests. It validates the tube's performance under the most demanding real-world bending scenarios — ensuring zero cracking, splitting, or unacceptable thinning after multiple forward-and-reverse bending cycles. This commitment to superior formability assurance sets Wenzhou Jixing's coil tube products apart in the global stainless steel tubing market.
Ordering Information
Wenzhou Jixing Metal Materials Co., Ltd. supports standard and custom orders with flexible delivery terms. Customers are encouraged to provide detailed specifications including grade, dimensions, coil configuration, applicable standards, and any special test requirements. Technical consultation is available to assist in material selection and specification matching for specific end-use applications.