Stainless Steel Welded Coil Tube with Verified Flattening Performance — Wenzhou Jixing Metal Materials Co., Ltd.
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. manufactures high-performance stainless steel welded coil tubes engineered for demanding industrial applications requiring reliable formability, structural integrity, and long-term corrosion resistance. These coil tubes are produced through advanced continuous welding and forming processes, delivering consistent wall thickness, precise dimensional tolerances, and superior mechanical properties across the full coil length.
A defining characteristic of this product line is its rigorous verification of weld integrity through standardized flattening testing. The coil tube is subjected to controlled compression between flat plates with the weld seam oriented along the direction of applied force — a critical quality assurance procedure that validates both the plastic deformation capacity of the base material and the metallurgical bond strength of the welded joint. Only tubes that exhibit zero cracking under prescribed compression are certified as conforming to specification.
Material & Properties
The stainless steel coil tubes are available in a range of austenitic and duplex grades, each selected to meet specific service conditions including temperature extremes, chemical exposure, and mechanical loading requirements.
- Base Material Grades: SUS304, SUS304L, SUS316, SUS316L, SUS321, SUS310S, SUS309S, SUS316Ti, and duplex grades (SUS2205, SUS2507) available upon request.
- Weld Process: High-frequency induction welding or laser welding with inert gas (argon) internal protection to minimize weld oxide formation and ensure clean, sound joints.
- Weld Integrity: Each coil lot is subjected to flattening tests per ASTM A213 / EN 10216-5 methodology. The test specimen is compressed between flat plates with the weld seam aligned parallel to the loading axis until the prescribed distance is achieved. Absence of any visible crack — particularly at the weld line — confirms adequate weld fusion and ductility.
- Corrosion Resistance: Chromium content of 18% or higher provides passive film stability; molybdenum addition in 316-series grades enhances pitting and crevice corrosion resistance.
- Mechanical Properties: Yield strength typically 205–310 MPa; tensile strength 515–730 MPa; elongation ≥ 40% (varies by grade and wall thickness).
Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 3.0 – 114.3 mm (0.118 – 4.500 in) |
| Wall Thickness | 0.3 – 6.0 mm (0.012 – 0.236 in) |
| Coil Length | Up to 1,000 m per coil (standard); custom lengths available |
| OD Tolerance | ±0.05 mm (±0.002 in) for OD ≤ 12.7 mm; ±0.1 mm (±0.004 in) for larger ODs |
| Wall Thickness Tolerance | ±10% of nominal (or ±0.05 mm, whichever is greater) |
| Surface Finish | 2B (mill finish), BA (bright annealed), No.4 brushed, No.8 mirror |
| Flattening Test Standard | ASTM A213 / EN 10216-5 / GB/T 14976 |
| Flattening Test Method | Compression between flat plates, weld seam in direction of force |
| Flattening Test Pass Criteria | No visible cracks at weld seam or base metal at prescribed compression distance |
| Available Grades | SUS304, 304L, 316, 316L, 321, 310S, 309S, 2205, 2507 |
| End Condition | Open ends, closed ends, or custom-formed ends |
Manufacturing Process
The production of these coil tubes follows a tightly controlled multi-stage process to ensure dimensional accuracy, surface quality, and mechanical reliability:
- Strip Selection & Inspection: Cold-rolled stainless steel strip is sourced from certified mills and inspected for surface defects, chemical composition, and mechanical properties prior to processing.
- Edge Trimming & Beveling: Strip edges are precision-trimmed and beveled to ensure uniform weld gap and consistent fusion during the welding stage.
- Forming: The strip is fed through a series of progressively shaped dies that gradually transform the flat strip into a seamless circular cross-section with precise OD and wall dimensions.
- Continuous Welding: High-frequency induction welding (or laser welding for thinner gauges) creates a longitudinal weld joint. Internal argon shielding prevents oxidation of the weld zone. Post-weld passivation treatment removes any residual mill scale or oxide from the interior surface.
- Coiling: The formed and welded tube is wound onto a coil core under controlled tension to maintain dimensional stability and prevent distortion.
- Flattening Test (Quality Verification): Samples are drawn from each production coil. The test specimen is placed between two flat plates with the weld seam oriented in the direction of applied compressive force. The plates are brought together until the prescribed compression distance (calculated as a function of wall thickness per applicable standard) is achieved. The specimen is inspected under magnification for any crack initiation or propagation. A crack-free result confirms that the weld seam possesses adequate ductility and metallurgical bonding, and that the tube can withstand cold-forming operations without failure.
- Final Inspection & Packaging: Certified coils are labeled with heat number, grade, dimensions, and test certificate reference, then packaged for shipment.
Applications
The verified formability and weld integrity of these coil tubes make them suitable for a wide spectrum of industrial applications:
- Heat Exchangers & Condensers: Cold-bending and forming into tubesheets without cracking at the weld line.
- Automotive Industry: Exhaust systems, fuel lines, and structural tubing requiring repeated cold-forming operations.
- Food & Beverage Processing: Hygienic transfer lines, CIP systems, and processing equipment where both corrosion resistance and formability are critical.
- Medical Devices: Tubing for equipment housings, fluid delivery systems, and implant manufacturing substrates.
- Construction & Architecture: Decorative railings, structural elements, and facade systems requiring precise bending and welding.
- Petrochemical & Energy: Piping systems, instrument tubing, and process equipment in corrosive environments.
- Appliance Manufacturing: Refrigeration coils, water heater elements, and gas appliance components.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework to ensure product conformity and traceability:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing and testing operations.
- ISO 14001 — Environmental Management System certification for sustainable production practices.
- ASTM A213 — Conformity with standard specifications for austenitic stainless steel seamless, welded, and heavily cold-worked tubular products.
- EN 10216-5 — European standard for heat-resistant, hydraulic, and mechanical tubular products (welded).
- GB/T 14976 — Chinese national standard for cold-rolled stainless steel seamless and welded tubes.
- Third-Party Testing: Independent verification by SGS, BV, or TÜV available upon request, including chemical analysis, mechanical testing, and flattening test witness inspection.
Unique Selling Points
Weld-First Flattening Verification: Unlike conventional testing protocols that may orient the weld seam perpendicular to the load axis, Wenzhou Jixing Metal Materials specifically positions the weld seam along the direction of applied compressive force during the flattening test. This is the most stringent orientation for evaluating weld integrity, as it directly stresses the weld fusion zone and heat-affected zone in the critical loading direction. A pass result provides exceptional confidence that the tube will not crack during cold-forming, bending, or expansion operations in downstream fabrication.
- Comprehensive Formability Assurance: The flattening test result directly correlates to the tube's ability to withstand cold bending, U-bending, and mechanical expansion — critical requirements for heat exchanger and automotive applications.
- Full Traceability: Every coil is traceable to its heat number, production batch, and test certificate, enabling complete supply chain accountability.
- Customization Capability: Non-standard OD, wall thickness, surface finish, and coil length configurations available to meet specific project requirements.
- Weld Quality Excellence: Inert gas-protected welding with post-weld passivation ensures both interior and exterior weld surfaces are clean, smooth, and corrosion-resistant.
- Consistent Production Quality: Automated forming and welding lines with real-time monitoring ensure uniform properties across the entire coil length, eliminating batch-to-batch variability.
Conclusion
Wenzhou Jixing Metal Materials Co., Ltd. delivers stainless steel welded coil tubes that combine proven material performance with rigorously verified weld integrity. The flattening test protocol — with the weld seam oriented in the direction of force — represents a gold-standard approach to validating tube plasticity and weld bond strength. This commitment to exceeding standard quality requirements makes these coil tubes a reliable choice for manufacturers and engineers who demand confidence in cold-forming performance and long-term service durability.