Stainless Steel Coil Tube (Coiltube) — Technical Specification

Product Overview

The Stainless Steel Coil Tube (Coiltube), manufactured by Wenzhou Jixing Metal Materials Co., Ltd., is a continuous-length tubular product formed through cold-drawn or cold-rolled processes and wound onto a coil form. Unlike straight-cut seamless or welded pipes, coil tubes are supplied in continuous helical wound configurations, enabling high-efficiency downstream processing including cutting, bending, forming, and welding with minimal material waste. This product category encompasses both seamless stainless steel coil tubes and longitudinally welded coil tubes, designed for demanding thermal, mechanical, and corrosion-resistant service conditions.

A defining characteristic of stainless steel coil tubes is their inherent thermal mass and heat transfer behavior. As documented in advanced control literature (e.g., "Research on the Application of Smith-Fuzzy Controller in the Outlet Temperature Lag Control of Coil Tubes"), the coiled geometry introduces significant thermal lag at the outlet, necessitating sophisticated process control strategies. This thermal lag property, while presenting control challenges, also confers advantages in heat exchanger and thermal storage applications where uniform temperature distribution is paramount.

Material & Properties

Base Materials

Key Physical and Mechanical Properties

Corrosion Resistance Characteristics

Specifications

Parameter Specification Range Standard Reference
Outer Diameter (OD) 3.0 mm – 219.0 mm ASTM A213 / ASTM A269
Wall Thickness 0.25 mm – 12.0 mm ASTM A213 / ASTM A269
Coil Diameter 1,000 mm – 3,000 mm Manufacturer standard
Coil Length (Continuous) 50 m – 2,000 m (typical) Manufacturer standard
OD Tolerance ±0.10 mm to ±0.50 mm (OD-dependent) ASTM A213 / ASTM A269
Wall Thickness Tolerance ±10% (OD < 15 mm); ±7.5% (OD ≥ 15 mm) ASTM A213 / ASTM A269
Surface Finish 2B (Cold Rolled & Annealed), No. 4 (Brushed), Mirror (8K), BA (Bright Annealed) ASTM A480 / ASTM A240
Heat Treatment Solution Annealed (1050°C – 1150°C), Pickled & Passivated ASTM A213 / ASTM A269
End Condition Plain end, Beveled end (per customer specification) Customer specification
Coil Weight 500 kg – 5,000 kg (typical) Manufacturer standard
Applicable Standards ASTM A213, ASTM A269, ASME SA-213, EN 10217-7, EN 10216-5, GB/T 12771 Multi-standard compliance
Test Standards ASTM A262 (Intergranular Corrosion), ASTM A923 (Pitting), ASTM E1099 (Eddy Current) ASTM / ASME

Manufacturing Process

Seamless Coil Tube Production

  1. Ingot Production: Primary steelmaking via Basic Oxygen Furnace (BOF) or Electric Arc Furnace (EAF) with ladle refinement and Vacuum Arc Remelting (VAR) or Vacuum Induction Melting (VIM) for high-purity grades.
  2. Billet Casting: Continuous casting of round billets (typically 100–200 mm diameter) with controlled cooling rates to achieve uniform grain structure.
  3. Piercing: Hot piercing of reheated billets through rotary piercing mills (RPM) or plug-type piercing mills to produce seamless hollow tubes.
  4. Hot Rolling: Multi-stand reduction of the pierced tube through laminar reduction mills or plug mills to intermediate dimensions.
  5. Cold Drawing / Cold Rolling: Multi-pass cold working through draw benches or rotary cold mills to achieve final dimensions, enhanced mechanical properties, and surface finish. Drawing dies are precision-machined tungsten carbide tooling.
  6. Solution Annealing: High-temperature furnace annealing (1050°C – 1150°C) followed by rapid quenching to dissolve carbide precipitates and restore full austenitic microstructure with maximum corrosion resistance.
  7. Pickling and Passivation: Immersion in mixed acid bath (HNO₃ + H₂SO₄ or citric acid) to remove oxide scale, followed by passivation treatment to establish a stable chromium oxide passive layer.
  8. Coiling: Continuous winding onto precision steel or aluminum coil cores with controlled tension to prevent deformation, kinking, or ovality. Coiling tension is typically maintained at 15–30% of yield strength.

Welded Coil Tube Production

  1. Strip Supply: Cold-rolled stainless steel strip with precise thickness and width tolerances.
  2. Forming: Progressive roller forming to convert flat strip into circular tube cross-section.
  3. Welding: High-frequency induction welding (HF) or orbital TIG welding to create a continuous longitudinal weld seam.
  4. Post-Weld Heat Treatment: Solution annealing to homogenize the weld microstructure and eliminate weld-affected zone sensitization.
  5. Surface Treatment: Pickling, passivation, and optional electropolishing.
  6. Coiling: Winding onto coil cores under controlled tension.

Thermal Lag Control Considerations

As highlighted in advanced process control research, the continuous coiled geometry of stainless steel coil tubes introduces significant thermal lag between the inlet and outlet during heating or cooling operations. The Smith-Fuzzy controller methodology — combining Smith predictive control (which compensates for transport delay) with Fuzzy Logic Control (which handles nonlinearities and uncertainty) — has been demonstrated to effectively manage outlet temperature lag in coil tube processing lines. This has direct implications for:

Applications

Industrial Applications

Quality Certifications and Testing

Applicable Quality Standards

Incoming Material Inspection

Process Control and Testing

Final Product Certification

Unique Selling Points