Stainless Steel Coil Tube (Coiltube) — Precision Round Coil Tube Manufacturing

1. Product Overview

Stainless Steel Coil Tubes (盘管, Coiltube) are precision-engineered tubular products manufactured in continuous coil form, primarily composed of austenitic and ferritic stainless steel grades. These products are distinguished from straight seamless or welded tubes by their continuous coiled geometry, which enables downstream processing operations—such as bending, forming, and coiling into heat exchanger tubes—without the need for additional cutting or joining operations. The coil tube configuration inherently reduces material waste, minimizes processing steps, and improves dimensional consistency along the entire tube length.

Wenzhou Jixing Metal Materials Co., Ltd. specializes in the production of high-quality stainless steel coil tubes, employing advanced manufacturing processes and dedicated tooling systems developed specifically for round coil tube fabrication. The company's approach integrates modern forming technology with rigorous quality control protocols to deliver products that meet or exceed international standards for dimensional accuracy, surface finish, and mechanical performance.

2. Material & Properties

2.1 Available Grades

2.2 Key Material Properties

3. Technical Specifications

Parameter Specification Range Standard Reference
Outer Diameter (OD) Φ3.0 mm – Φ114.3 mm ASTM A554 / GB/T 14976
Wall Thickness 0.2 mm – 6.0 mm ASTM A554 / GB/T 14976
Coil Diameter (Inner) Φ300 mm – Φ1500 mm Customer-specific / ISO 11612
Tube Length per Coil 50 m – 2000 m (continuous) Manufacturing capacity dependent
Diameter Tolerance ±0.05 mm – ±0.20 mm ASTM A554 Type A / Type B
Wall Thickness Tolerance ±10% of nominal (min. ±0.02 mm) ASTM A554
Roundness ≤ 0.1% of OD ISO 11612
Surface Finish 2B, BA (Bright Annealed), No. 4, Mirror (Ra ≤ 0.1 μm) ASTM A480 / GB/T 3280
End Condition Plain end, Beveled end (per customer spec) ASME B31.3
Delivery Condition Annealed, Cold Worked, Solution Treated ASTM A554

4. Manufacturing Process

The manufacturing of precision round coil tubes represents a specialized domain within stainless steel tube production, requiring dedicated tooling, process optimization, and deep understanding of material deformation mechanics. The following process flow outlines the comprehensive manufacturing methodology:

4.1 Process Flow Diagram

  1. Raw Material Preparation: Selection of high-purity stainless steel strip (cold-rolled) conforming to ASTM A240 / GB/T 3280 specifications. Incoming material undergoes spectroscopic verification (PMI — Positive Material Identification) to confirm grade composition.
  2. Strip Coiling & Straightening: The stainless steel strip is unwound from the master coil, passed through a high-precision straightener to eliminate coil set and ensure flatness within ±0.1 mm/m.
  3. Edge Trimming: Precision edge trimming removes mill scale, burrs, and irregularities from the strip edges to ensure uniform weld quality and dimensional accuracy.
  4. Forming (Roll Forming): The flat strip is passed through a series of progressive forming rolls (typically 8–14 stations) that gradually bend the strip into a semi-circular and then circular cross-section. The forming roll tooling is custom-designed for each tube diameter and wall thickness combination.
  5. Welding (TIG / Laser): The formed semi-circle is welded along the longitudinal seam using either Tungsten Inert Gas (TIG) welding with helium shielding or high-power laser welding. Internal gas shielding ensures a clean, oxide-free weld root. Weld parameters are precisely controlled to minimize distortion.
  6. Weld Annealing / Solution Treatment: The welded tube undergoes in-line annealing (typically at 1050°C–1150°C for austenitic grades) to restore the weld zone's corrosion resistance, relieve residual stresses, and achieve uniform microstructure. Annealing is performed under controlled atmosphere (N₂ or vacuum) to prevent re-oxidation.
  7. Precision Sizing (Cold Drawing / Mandrel Sizing): The annealed tube passes through a mandrel sizing station where precision-drawn rollers and a hardened mandrel reduce dimensional tolerances to ±0.05 mm. This step ensures consistent inner diameter (ID) and roundness.
  8. Surface Finishing: Depending on the specification, the tube may undergo electropolishing, passivation (nitric acid or citric acid treatment), or mechanical polishing to achieve the required surface finish grade.
  9. Coiling: The finished tube is wound onto a precision coiling mandrel at controlled tension to form the final coil configuration. Coiling tension is carefully calibrated to prevent ovalization or kinking.
  10. Quality Inspection & Packaging: Final inspection includes dimensional verification, visual examination, hydrostatic testing, and chemical composition analysis. Tubes are then wrapped in protective film, packed in wooden crates or cardboard cartons, and labeled with traceability documentation.

4.2 Advanced Process Innovations

Wenzhou Jixing Metal Materials Co., Ltd. has developed proprietary process improvements and specialized tooling for round coil tube manufacturing that distinguish their products in the market:

5. Applications

5.1 Heat Exchange Systems

5.2 Piping Systems

5.3 Specialized Applications

6. Quality Certifications & Standards Compliance

6.1 Applicable Standards

6.2 Quality Assurance System

6.3 Inspection & Testing Protocol

  1. Chemical Composition Analysis: Spectrographic verification (OES — Optical Emission Spectroscopy) of each heat batch
  2. Dimensional Inspection: 100% online measurement of OD, wall thickness, roundness, and straightness
  3. Hydrostatic Testing: Performed at 1.5× maximum allowable working pressure (MAWP) with minimum dwell time of 3 seconds
  4. Non-Destructive Testing (NDT): Magnetic Particle Testing (MPT) or Eddy Current Testing (ECT) for weld seam integrity
  5. Surface Quality Inspection: Visual examination under controlled illumination; roughness measurement via contact profilometer
  6. Mechanical Testing: Tensile testing, hardness testing (HV), and impact testing (Charpy V-Notch) per ASTM A370
  7. Intergranular Corrosion Testing: ASTM A262 Practice A (65°C) or Practice E for sensitization resistance verification
  8. Traceability Documentation: Each coil is accompanied by a Material Test Certificate (MTC) per EN 10204 Type 3.1, including heat number, chemical analysis, mechanical test results, and dimensional data

7. Unique Selling Points

Wenzhou Jixing Metal Materials Co., Ltd. distinguishes itself in the stainless steel coil tube market through the following competitive advantages:

  1. Proprietary Forming Tooling: Custom-designed progressive roll forming tooling optimized for each tube specification, achieving roundness and dimensional accuracy unmatched by standard production methods.
  2. Continuous In-Line Annealing: Integrated solution treatment furnace eliminates batch processing delays, ensures uniform microstructure, and preserves surface finish integrity throughout the weld zone.
  3. Wide Range Capability: Single production line capable of handling tube diameters from Φ3.0 mm to Φ114.3 mm with wall thicknesses from 0.2 mm to 6.0 mm, offering customers a one-stop sourcing solution.
  4. Superior Weld Quality: Advanced internal gas shielding TIG welding combined with controlled-atmosphere annealing produces welds with corrosion resistance equivalent to the base metal, verified by ASTM A262 testing.
  5. Customization Flexibility: Ability to produce custom coil diameters, special surface finishes, and non-standard grades to meet unique customer specifications and application requirements.
  6. Full Traceability: Complete material traceability from raw steel mill certification through final product delivery, supported by digital documentation systems and bar-code tracking.
  7. Cost Efficiency: Continuous coil production eliminates end-loss waste associated with straight tube cutting, delivering 3–5% material savings compared to conventional straight tube solutions for downstream applications.

8. Ordering Information

Customers are advised to specify the following information when placing orders for stainless steel coil tubes:

Wenz