Stainless Steel Coil Tube (Coiltube) — Wenzhou Jixing Metal Materials Co., Ltd

1. Product Overview

The Stainless Steel Coil Tube (hereinafter referred to as "Coiltube") is a precision-engineered tubular product supplied in continuous coil form by Wenzhou Jixing Metal Materials Co., Ltd. Designed for high-demand industrial applications, this product combines the corrosion resistance and mechanical integrity of austenitic and duplex stainless steels with the processing advantages of coil-fed manufacturing. The Coiltube is manufactured under a fully integrated Manufacturing Execution System (MES) framework, ensuring traceability, process control, and quality consistency from raw material intake through final coil packaging.

The coil configuration enables high-throughput downstream processing — including mandrel drawing, cold reduction, and continuous heat treatment — making it particularly suited for mass production environments where efficiency and dimensional repeatability are paramount.

2. Material & Properties

2.1 Alloy Grades Offered

2.2 Mechanical Properties (Annealed Condition)

Property 304 / 304L 316 / 316L 321 316Ti
Tensile Strength (Rm), MPa ≥ 515 ≥ 515 ≥ 515 ≥ 515
Yield Strength (Rp0.2), MPa ≥ 205 ≥ 205 ≥ 205 ≥ 205
Elongation (A), % ≥ 40 ≥ 40 ≥ 40 ≥ 40
Density, g/cm³ 7.93 8.00 7.93 8.00
Thermal Conductivity at 20 °C, W/(m·K) 16.3 14.6 16.3 14.6

2.3 Chemical Composition (Typical, wt%)

Grade C Mn P S Si Cr Ni Mo Ti
304 ≤ 0.08 ≤ 2.00 ≤ 0.045 ≤ 0.030 ≤ 1.00 18.0–20.0 8.0–10.5 — —
304L ≤ 0.030 ≤ 2.00 ≤ 0.045 ≤ 0.030 ≤ 1.00 18.0–20.0 8.0–12.0 — —
316 ≤ 0.08 ≤ 2.00 ≤ 0.045 ≤ 0.030 ≤ 1.00 16.0–18.0 10.0–14.0 2.0–3.0 —
316L ≤ 0.030 ≤ 2.00 ≤ 0.045 ≤ 0.030 ≤ 1.00 16.0–18.0 10.0–14.0 2.0–3.0 —
321 ≤ 0.08 ≤ 2.00 ≤ 0.045 ≤ 0.030 ≤ 1.00 17.0–19.0 9.0–12.0 — 5×C to 0.70
316Ti ≤ 0.08 ≤ 2.00 ≤ 0.045 ≤ 0.030 ≤ 1.00 16.0–18.0 10.0–14.0 2.0–3.0 5×C to 0.90

3. Specifications

3.1 Geometric Dimensions

Parameter Range / Value Standard Reference
Outer Diameter (OD) 3.0 mm – 150.0 mm ASTM A554 / ASTM A553
Wall Thickness (WT) 0.25 mm – 6.00 mm ASTM A554 / ASTM A553
OD Tolerance ± 0.05 mm (OD ≤ 25 mm); ± 0.10 mm (OD > 25 mm) EN 10217-7
Wall Thickness Tolerance ± 10% of nominal ASTM A554
Coil Length (Continuous) Up to 5,000 m per coil —
Coil Core Diameter Φ 200 mm / Φ 300 mm / Φ 500 mm (configurable) —
Coil Outer Diameter Up to Φ 1,500 mm —
Surface Finish Bright Annealed (BA); Pickled & Passivated (P&P); Electropolished (EP) ASTM A478

3.2 Delivery Conditions

3.3 Governing Standards

4. Manufacturing Process

The production of the Coiltube at Wenzhou Jixing Metal Materials Co., Ltd follows a rigorously controlled, multi-stage process architecture governed by an enterprise-level Manufacturing Execution System (MES). The MES integrates real-time data acquisition, process parameter logging, and quality gate enforcement across all production stages.

  1. Raw Material Intake & Inspection

    Hot-rolled coil (HRC) of the specified alloy grade is received and subjected to spectral analysis (Optical Emission Spectrometry, OES) for chemical composition verification. Physical properties are validated through tensile testing and hardness measurement per ASTM A478.

  2. Slitting & Leveling

    The HRC is slit into strip of the required width using a precision slitting line. The resulting strip is leveled to ensure flatness within ± 0.5 mm/m, minimizing downstream forming defects.

  3. Tube Forming (Coil-to-Tube Conversion)

    The flat strip is fed into a progressive die roll-forming mill where it is progressively shaped into a tubular cross-section. Multiple forming stations (typically 12–18 rolls) incrementally reduce the forming angle, ensuring uniform plastic deformation without edge cracking or internal stress concentration.

  4. Seam Welding

    The formed tube undergoes continuous seam welding via one of the following methods:

    • Gas Tungsten Arc Welding (GTAW/TIG) — For seamless-equivalent quality in thin-wall applications
    • High-Frequency Induction Welding (HF) — For high-speed production of larger diameters
    • Laser Welding (LBW) — For precision micro-welds with minimal Heat-Affected Zone (HAZ)

  5. Online Dimensional Inspection

    Post-welding, the tube passes through laser-based inline measurement systems that monitor OD, wall thickness, roundness, and straightness in real time. Data is fed back to the MES for statistical process control (SPC) and deviation alerting.

  6. Heat Treatment (Annealing)

    The continuously welded coil tube is conveyed to a continuous annealing furnace operating under a controlled reducing atmosphere (typically endothermic gas or vacuum). Annealing temperatures range from 1010 °C to 1150 °C depending on alloy grade, followed by controlled cooling to relieve residual stresses, dissolve carbides, and restore the fully austenitic microstructure.

  7. Pickling & Passivation

    The annealed tube is pickled in a mixed acid bath (HNO₃ + H₂SO₄) to remove oxide scale, followed by passivation in a dilute nitric acid solution to restore the chromium oxide passive film and enhance corrosion resistance.

  8. Final Inspection & Testing

    Finished coils undergo:

    • Visual inspection for surface defects
    • Dimensional verification via ultrasonic thickness gauging
    • Hydrostatic pressure testing (per ASTM A554, Section 9)
    • Chemical re-verification via OES
    • Intergranular Corrosion Test (IGCT) per ASTM A262 Practice E, where applicable

  9. Coiling & Packaging

    The inspected tube is wound onto a precision-driven coiler to form the final coil product. Coils are wrapped with protective film, shrink-wrapped, and palletized for shipment. Each coil is labeled with a unique batch identifier traceable through the MES to raw material origin, process parameters, and test results.