Stainless Steel Coil Tube — Flattening Test Verified Welded Tube
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. manufactures high-performance stainless steel coil tubes engineered for demanding industrial applications. These welded coil tubes are produced to exacting standards and undergo rigorous mechanical testing, including the critical flattening test, to ensure superior plasticity, weld seam integrity, and long-term structural reliability. Each coil tube is supplied in continuous coil form, offering exceptional material utilization, reduced cutting waste, and streamlined downstream processing for fabricators and OEMs worldwide.
Material & Properties
The coil tubes are fabricated from high-grade austenitic stainless steel alloys, predominantly SUS304, SUS304L, SUS316, and SUS316L, selected for their outstanding corrosion resistance, formability, and weldability. Key material characteristics include:
- Corrosion Resistance: Excellent resistance to atmospheric, chemical, and marine environments; 316L grades offer superior pitting and crevice corrosion protection due to molybdenum content.
- Mechanical Properties: High yield strength and tensile strength with exceptional ductility, enabling cold bending, forming, and deep drawing without cracking.
- Temperature Performance: Maintains mechanical integrity across a wide temperature range from cryogenic to elevated temperatures (up to 870°C for 304/316 grades).
- Weld Seam Quality: The weld seam is fully verified through flattening tests, confirming uniform fusion, absence of porosity, and strong metallurgical bond between base metal and weld zone.
- Surface Finish: Available in bright annealed (BA), pickled, or polished surface finishes to meet aesthetic and functional requirements.
Specifications
| Parameter | Specification |
|---|---|
| Product Type | Welded Stainless Steel Coil Tube |
| Grade Options | SUS304 / 304L / 316 / 316L / 321 / 310S / Custom Alloys |
| Outer Diameter (OD) | Φ6.0 mm – Φ159.0 mm |
| Wall Thickness | 0.3 mm – 6.0 mm |
| Coil Length | 5 m – 50 m per coil (customizable) |
| Surface Finish | Bright Annealed (BA), Pickled, Polished (No.4 / Mirror) |
| Manufacturing Standard | ASTM A554 / ASTM A269 / GB/T 12771 / EN 10217 / JIS G3459 |
| Welding Method | Automatic Argon Arc (TIG) Welding |
| Flattening Test | Compressed to specified gap with weld seam in stress direction — no cracks = qualified |
| Heat Treatment | Solution Annealing (1050°C – 1150°C) followed by water quenching |
| Packaging | Export-grade wooden pallets or steel drums with moisture-proof wrapping |
Manufacturing Process
The production of Wenzhou Jixing's stainless steel coil tubes follows a tightly controlled, multi-stage manufacturing workflow designed to maximize dimensional accuracy and mechanical performance:
- Coil Slitting: High-quality stainless steel coil stock is precision-slitted to target width with tight edge tolerances, minimizing burr and edge defects.
- Forming & Rolling: The slit strip is cold-rolled through a series of precision-calibrated rolls to form the desired tube profile with consistent wall thickness and roundness.
- Welding: The formed strip is joined using automatic TIG (Tungsten Inert Gas) welding with high-purity argon shielding, producing a smooth, uniform weld seam free of oxidation and porosity.
- Heat Treatment: Welded tubes undergo solution annealing at 1050°C – 1150°C followed by rapid water quenching to eliminate residual welding stresses, restore full austenitic structure, and maximize corrosion resistance.
- Pickling & Passivation: Surface oxide scale is removed through controlled acid pickling, followed by passivation treatment to enhance the protective chromium oxide layer.
- Surface Finishing: Tubes are polished to the specified surface grade — from matte pickled to mirror finish — using automated polishing lines.
- Quality Inspection & Testing: Every batch undergoes comprehensive inspection including dimensional measurement, surface examination, chemical analysis, and mechanical property verification.
Flattening Test — Quality Assurance Detail
Test Objective: The flattening test is a critical mechanical property verification specifically designed to validate the plasticity of the welded tube body and the integrity of the weld seam bond.
The test procedure involves compressing a representative tube sample between two flat plates until the specified gap is reached, with the weld seam positioned in the direction of applied stress (perpendicular to the compression axis). This orientation ensures maximum stress concentration at the weld zone, providing the most rigorous assessment of weld quality.
Pass Criteria
- No cracks, splits, or separations observed at the weld seam or tube body.
- No excessive deformation or folding at the compression edges.
- Uniform wall thickness maintained throughout the test zone.
Only tubes that pass the flattening test with zero defects are certified as qualified, ensuring that every coil tube delivered by Wenzhou Jixing possesses verified structural integrity at the most critical junction — the weld seam.
Applications
Wenzhou Jixing's stainless steel coil tubes serve a broad spectrum of industrial applications where corrosion resistance, mechanical reliability, and formability are paramount:
- Heat Exchangers & Cooling Systems: Coil tubes for condenser coils, evaporator tubes, and heat exchanger assemblies in HVAC and industrial refrigeration.
- Petrochemical & Oil/Gas: Process piping, heat transfer tubes, and pressure vessels operating in aggressive chemical environments.
- Food & Beverage Processing: Hygienic-grade piping for dairy, brewing, and pharmaceutical production lines (316L preferred).
- Automotive & Transportation: Exhaust system components, fuel lines, and structural tubing.
- Medical Devices: Instrument tubing, dialysis equipment components, and surgical instrument shafts.
- Construction & Architecture: Decorative handrails, structural supports, and facade elements.
- Energy Sector: Solar thermal collector tubes, geothermal heat exchangers, and nuclear-grade components.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications and compliance standards:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001 — Environmental Management System Certification
- ISO 45001 — Occupational Health & Safety Management System
- CE / PED 2014/68/EU — European Pressure Equipment Directive Compliance
- EN 10204 3.1 — Third-Party Material Test Certificates available upon request
- ASTM & GB Standards Compliance — Full compliance with international and Chinese national standards
- Mill Test Reports (MTR) — Provided with every shipment, including chemical composition analysis, mechanical test results, and flattening test verification
Every production batch is traceable from raw material to finished product, with complete documentation supporting full quality assurance and regulatory compliance for international markets.
Why Choose Wenzhou Jixing Metal Materials Co., Ltd.
- Verified Weld Seam Integrity: Flattening test on every batch ensures zero-defect weld quality — the most critical factor in tube performance.
- Full Customization: Flexible OD, wall thickness, grade, surface finish, and coil length options to match exact project requirements.
- End-to-End Traceability: Complete mill documentation and lot traceability for regulatory and quality assurance compliance.
- Competitive Lead Times: Efficient production scheduling with reliable delivery timelines for both standard and custom orders.
- Global Export Experience: Established supply chain serving customers across Asia, Europe, the Americas, and the Middle East.