Stainless Steel Coiltube — Cold-Drawn Welded Tube (Re-Drawn Coil Tube)
1. Product Overview
The Stainless Steel Cold-Drawn Welded Coiltube (also referred to as re-drawn coil tube) is a precision-engineered stainless steel tube product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is produced through a specialized cold-drawing (cold pulling) process applied to previously welded stainless steel tube blanks. The re-drawing process effectively eliminates visible weld seam marks and significantly improves dimensional accuracy and surface finish, delivering a product that combines the length advantages of welded tubes with the performance characteristics of seamless tubes.
As a coiled (continuous-length) tube product, this coil tube is supplied in long, continuous lengths wound onto coils, making it ideal for high-volume fabrication environments where material utilization and processing efficiency are critical. The cold-drawing re-work refines the microstructure and geometry of the welded tube, resulting in a near-seamless performance profile at a more economical price point than fully seamless alternatives.
2. Material & Properties
The cold-drawn welded coiltube is available in a range of stainless steel grades commonly used in industrial and commercial applications:
- 304 / 304L (UNS S30400 / S30403) — General-purpose austenitic stainless steel with excellent corrosion resistance and formability.
- 316 / 316L (UNS S31600 / S31603) — Molybdenum-bearing austenitic stainless steel offering superior resistance to pitting and crevice corrosion.
- 321 / 321H (UNS S32100 / S32109) — Stabilized austenitic grade suitable for high-temperature service.
- 304H / 316H — High-carbon austenitic grades for elevated-temperature applications.
- 2205 (UNS S31803) — Duplex stainless steel with enhanced strength and corrosion resistance.
Key mechanical and physical properties after cold drawing include improved tensile strength (typically 5–15% increase over the as-welded condition), enhanced surface finish (achievable Ra ≤ 0.8 μm), and tighter dimensional tolerances. The cold-drawing process also refines the grain structure along the tube axis, improving fatigue resistance and mechanical homogeneity.
3. Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Cold-Drawn Welded Coiltube (Re-Drawn Coil Tube) |
| Outer Diameter (OD) | 6 mm – 168 mm (custom sizes available upon request) |
| Wall Thickness | 0.5 mm – 8.0 mm |
| OD Tolerance | ±0.05 mm – ±0.15 mm (per agreement) |
| Wall Thickness Tolerance | ±0.03 mm – ±0.10 mm (per agreement) |
| Coil Length | Typically 100 m – 500 m per coil (continuous length supply) |
| Surface Finish | BA (Bright Annealed), No. 1, 2B, or Custom |
| Weld Seam Treatment | Cold-drawn to eliminate visible weld seam marks |
| Applicable Standards | ASTM A269, ASTM A554, ASTM A312, EN 10217, GB/T 12771 |
| Supply Condition | Cold-drawn (re-drawn), annealed as required |
| End Treatment | Plain cut, beveled, or as specified |
4. Manufacturing Process
The production of cold-drawn welded coiltube involves a multi-stage manufacturing sequence that leverages the cost-efficiency of welded tube production while achieving near-seamless performance through subsequent cold drawing:
- Welded Tube Production: Stainless steel strip (coil) is cold-rolled into a hollow form and welded (typically via TIG or orbital welding) to produce a continuous welded tube. This stage provides the initial tube geometry and allows for long, continuous lengths that are difficult to achieve with seamless tube manufacturing.
- Weld Seam Preparation: The as-welded tube undergoes inspection to identify and assess the weld seam. Minor surface irregularities at the weld zone may be addressed through preliminary grinding or polishing.
- Cold Drawing (Re-Drawing): The welded tube is passed through a series of precision-diameter drawing dies under cold working conditions. This process:
- Uniformly reduces the outer diameter and wall thickness to precise target dimensions,
- Flattens and homogenizes the weld seam area, effectively eliminating visible weld marks,
- Improves dimensional accuracy and concentricity,
- Refines the internal grain structure, enhancing mechanical properties.
- Intermediate Annealing (if required): Depending on the degree of cold work applied, the tube may be annealed to relieve residual stresses and restore ductility, ensuring the material is suitable for subsequent forming operations.
- Surface Treatment & Finishing: The tube receives its final surface finish (BA, No. 1, 2B, etc.) through pickling, passivation, or mechanical polishing as specified.
- Coiling & Packaging: The finished tube is wound onto coils and packaged with appropriate protective wrapping for shipment.
The cold-drawing re-work is the critical differentiating step in this product line. By subjecting the welded tube to controlled plastic deformation through precision dies, the resulting product achieves dimensional tolerances and surface quality comparable to seamless tubes, while retaining the inherent length advantage of the welded tube base product.
5. Applications
The stainless steel cold-drawn welded coiltube is widely used across multiple industries where precision dimensions, surface quality, and continuous-length supply are essential:
- Automotive Industry: Fuel lines, brake lines, exhaust system components, and decorative trim tubes.
- Food & Beverage Processing: Sanitary piping systems, conveyor components, and equipment fabrication requiring high hygiene standards.
- Medical Devices: Instrument tubing, surgical tool components, and equipment housings.
- Chemical & Pharmaceutical Processing: Process piping, heat exchanger tubes, and reactor components.
- Architecture & Decoration: Structural handrails, balustrades, decorative profiles, and interior design elements.
- Energy Sector: Solar water heater tubes, fuel cell components, and energy system piping.
- General Engineering: Hydraulic systems, pneumatic components, and precision mechanical assemblies.
6. Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems to ensure product conformity and traceability:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001 — Environmental Management System certification
- ISO 45001 — Occupational Health and Safety Management System certification
- CE Marking — European Conformity for applicable products
- PED (Pressure Equipment Directive) — Compliance for pressure-containing applications
- Mill Test Reports (MTR) — Full chemical composition and mechanical property testing documentation provided per batch
- Third-Party Inspection — Available upon customer request (e.g., SGS, BV, TUV)
All products undergo comprehensive incoming material inspection, in-process quality control (including dimensional measurement, surface inspection, and hydrostatic testing), and final product verification before shipment. The cold-drawing process parameters are monitored and recorded to ensure consistent quality across production batches.
7. Unique Selling Points
- Weld Seam Elimination: The cold-drawing re-work effectively removes visible weld seam marks, delivering a uniform surface appearance comparable to seamless tube.
- Superior Dimensional Accuracy: Tighter tolerances on outer diameter, wall thickness, and roundness compared to standard welded tube, reducing downstream machining costs.
- Length Advantage: Continuous coil lengths (100–500 m+) minimize material waste and eliminate the need for weld joints in long-run applications — a significant advantage over seamless tube, which is typically limited to shorter straight lengths.
- Seamless-Grade Performance at Welded-Grade Economics: Achieves mechanical and surface performance approaching seamless tube while maintaining the cost-effectiveness of welded tube as the base material.
- Customization Flexibility: Available in a wide range of grades, dimensions, and surface finishes, with custom specifications supported through direct collaboration with the manufacturer.
- Enhanced Mechanical Properties: Cold work hardening from the drawing process increases tensile strength and fatigue resistance while maintaining good ductility after appropriate annealing.