Stainless Steel Coil Tube — Seamless Tube Cold Redrawing Process
Product Overview
The Stainless Steel Coil Tube (Product No. 57) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered product produced through the Seamless Tube Cold Redrawing (无缝管再冷拔) process. This advanced secondary forming technology is specifically designed to further enhance the dimensional accuracy, geometric tolerances, and surface finish of pre-manufactured seamless stainless steel tubes. The resulting coil tube product meets the stringent requirements of high-end instrumentation, electronic component manufacturing, and critical industrial applications where micron-level precision and superior surface integrity are paramount.
The cold redrawing process represents a critical value-adding step in the stainless steel tube production chain, transforming standard-grade seamless tubes into ultra-precision products capable of satisfying the most demanding engineering specifications.
Material & Properties
The base material for the Seamless Tube Cold Redrawing process is high-quality austenitic stainless steel seamless tube, typically supplied in the following grades:
- ASTM/UNS Grades: 304 (UNS S30400), 304L (UNS S30403), 316 (UNS S31600), 316L (UNS S31603), 321 (UNS S32100), 310S (UNS S31008)
- Equivalent Chinese Standards: 06Cr19Ni10, 022Cr19Ni10, 06Cr17Ni12Mo2, 022Cr17Ni12Mo2
- Mechanical Properties (Post-Redrawing):
- Tensile Strength (UTS): ≥ 520 MPa (minimum)
- Yield Strength (0.2%): ≥ 205 MPa
- Elongation: ≥ 40%
- Hardness: HV ≤ 200 (annealed condition)
- Surface Quality: Ra ≤ 0.4 μm (mirror finish available upon request, Ra ≤ 0.2 μm)
- Internal Surface: Free from scale, oxide inclusions, and drawing-induced defects
Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | Φ1.0 mm – Φ159.0 mm | ASTM A269 / GB/T 12771 |
| Wall Thickness (WT) | 0.1 mm – 8.0 mm | ASTM A269 / GB/T 12771 |
| OD Tolerance | ±0.02 mm (precision grade); ±0.05 mm (standard grade) | ASME B73.2 / DIN 2391 |
| Wall Thickness Tolerance | ±0.01 mm (precision grade); ±0.02 mm (standard grade) | ASME B73.2 / DIN 2391 |
| Roundness | ≤ 0.5% of OD | ISO 1128 |
| Coil Length | Customized; typically 5 m – 50 m per coil | Customer Specification |
| Coil Inner Diameter | Φ100 mm / Φ150 mm / Φ200 mm (standard options) | — |
| Surface Finish | Polished (Ra ≤ 0.4 μm) / Mirror (Ra ≤ 0.2 μm) / Electropolished (EP) | ASTM A269 |
| Heat Treatment Condition | Solution Annealed (SA) / Cold Worked (CW) | — |
| Ends | Plain / Beveled / Welded / Capped (as required) | — |
| Standards Compliance | ASTM A269, ASME B73.2, GB/T 12771, EN 10216-5, JIS G3459 | Multi-standard |
Manufacturing Process
3.1 Process Flow Summary
The Seamless Tube Cold Redrawing process at Wenzhou Jixing Metal Materials Co., Ltd follows a meticulously controlled multi-stage workflow:
- Incoming Seamless Tube Inspection: Raw seamless stainless steel tubes are received and subjected to comprehensive incoming quality control, including dimensional verification, chemical composition analysis (OES), and surface condition assessment.
- Pre-Treatment & Cleaning: Tubes undergo ultrasonic cleaning and chemical degreasing to remove oils, contaminants, and residual drawing lubricants from the prior manufacturing stage.
- Pilot & Die Preparation: Precision-ground tungsten carbide (WC-Co) dies and pilots are selected or custom-manufactured to achieve the target dimensional tolerances. Die surfaces are lapped to mirror finish (Ra ≤ 0.05 μm) to ensure optimal surface transfer.
- Cold Redrawing (Primary Draw): The seamless tube is pulled through the die-pilot assembly under controlled tensile force, reducing the cross-sectional area by a calculated reduction ratio (typically 5%–30% per pass). This step achieves significant improvement in dimensional accuracy and surface quality.
- Intermediate Inspection: In-line dimensional measurements and surface inspection are conducted between passes to verify conformance and prevent defect propagation.
- Secondary/Finish Redrawing (as required): For ultra-precision applications, an additional drawing pass is performed with a reduced reduction ratio (2%–8%) to achieve final tolerances of ±0.01–0.02 mm.
- Solution Annealing (if required): Tubes are heat-treated at 1050°C–1150°C followed by rapid quenching to relieve cold-work stresses and restore full austenitic microstructure.
- Coiling: Finished tubes are wound onto precision coils using a controlled-tension coiling machine to prevent deformation, kinking, or surface marking.
- Final Quality Assurance: Comprehensive final inspection including dimensional verification, surface finish measurement, hydrostatic testing, and visual examination.
3.2 Key Process Parameters
- Drawing Speed: 1 m/min – 15 m/min (dependent on tube size and reduction ratio)
- Reduction Ratio per Pass: 5% – 30% (cross-sectional area reduction)
- Drawing Temperature: Ambient (cold working); range 20°C – 35°C
- Lubricant System: Food-grade or process-specific drawing lubricant; applied via internal/external lubrication systems
- Die Material: Sintered Tungsten Carbide (WC-Co) with PVD/DLC coating for extended service life
3.3 EP (Electropolishing) Tube Mother Tube Preparation
A critical application pathway for the cold redrawing process is the production of Electropolished (EP) Tube Mother Tubes. The cold redrawing stage serves as the essential precursor to electropolishing, ensuring that the base tube geometry and surface condition are sufficiently refined to yield optimal EP results. Tubes produced through this process exhibit:
- Uniform wall thickness distribution enabling consistent EP material removal
- Smooth surface texture that promotes uniform electrical current distribution during EP
- Elimination of surface defects (scratches, dents, oxide inclusions) that would otherwise create EP non-conformances
- Post-EP achievable surface roughness of Ra ≤ 0.1 μm (0.04 μin)
Applications
4.1 High-End Instrumentation Tubes
Cold redrawing coil tubes are the preferred substrate for precision instrumentation applications including:
- Pressure transmitters and gauges (capillary tubes, Bourdon tubes)
- Thermocouple and RTD sheath tubes
- Flow meters and level sensors
- Medical diagnostic equipment tubing
- Scientific laboratory instrumentation
4.2 Electronic & Semiconductor Applications
- EP tube mother tubes for semiconductor wafer processing equipment
- Vacuum system tubing for particle beam transport
- Cryogenic applications in superconducting research
- High-purity chemical delivery systems
4.3 Additional Industrial Applications
- Pharmaceutical and bioprocessing equipment (GMP-compliant tubing)
- Food and beverage processing systems
- Hydraulic and pneumatic systems requiring tight bore tolerances
- Aerospace fuel and hydraulic lines
- Chemical processing and corrosion-resistant piping
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains rigorous quality management systems and holds the following certifications:
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- ISO/IEC 17025 — Testing and Calibration Laboratory Competence
- EN 10204 3.1 — Full material certification documentation
- ASME Stamp / PED (EU Pressure Equipment Directive) — where applicable
- Mill Test Reports (MTR) — Available for every heat lot
Every coil tube product batch is accompanied by comprehensive documentation including:
- Chemical analysis report (certified by accredited laboratory)
- Mechanical properties test data
- Dimensional inspection report (CMM and laser measurement)
- Surface finish measurement certificates
- Hydrostatic test records
- Traceability documentation linking product to heat number and production lot
Unique Selling Points
Ultra-Precision Dimensional Control: Achieving wall thickness tolerances of ±0.01 mm and OD tolerances of ±0.02 mm through multi-stage cold redrawing — exceeding standard industry capabilities.
Superior Surface Integrity: Mirror-polished die surfaces and controlled drawing parameters produce internal and external surface finishes of Ra ≤ 0.4 μm, eliminating the need for additional mechanical finishing in many applications.
EP-Ready Mother Tube Production: Optimized base tube quality specifically engineered as the ideal precursor for electropolishing, ensuring consistent, defect-free EP results for semiconductor and pharmaceutical applications.
Coil Format Advantage: Continuous coil delivery eliminates weld joints, reduces material waste, and enables seamless integration into automated downstream processing lines including bending, cutting, and welding operations.
Customization & Flexibility: Full customization of dimensions, tolerances, surface finishes, coil configurations, and end treatments to meet specific customer engineering requirements and application specifications.
Technical Notes
The Seamless Tube Cold Redrawing process described herein is classified under the manufacturing category of Forming Processes → Re-Drawing (Redrawing) within the comprehensive product taxonomy of Wenzhou Jixing Metal Materials Co., Ltd. This process is distinct from primary cold drawing in that it operates on already-formed seamless tubes to achieve incremental improvements in precision and surface quality, rather than establishing the initial tube geometry from a billet or hollow坯.
For detailed technical data sheets, sample evaluations, or custom specification development, please contact Wenzhou Jixing Metal Materials Co., Ltd engineering and technical services department.