Stainless Steel Coil Tube (Coiltube) — Technical Specification

Product Overview

The Stainless Steel Coil Tube, also referred to as Coiltube, is a continuously formed tubular product manufactured through cold-drawn or cold-rolled processes and wound into coil form for storage, transportation, and downstream processing. Produced by Wenzhou Jixing Metal Materials Co., Ltd., this product line adheres to the technical conditions outlined in the authoritative document "Coil Tube — Technical Conditions" (盘管技术条件), which governs dimensional tolerances, mechanical properties, chemical composition requirements, and testing protocols for coiled stainless steel tubing.

Coiltube differs fundamentally from straight-length tubing in that it is delivered in continuous coil form, enabling uninterrupted downstream forming, bending, and welding operations without the need for butt-welding individual straight sections. This characteristic makes it an indispensable material in high-volume manufacturing environments where material utilization efficiency and production continuity are paramount.

Material & Properties

Applicable Grades

Coiltube products are manufactured from a wide range of austenitic, ferritic, and duplex stainless steel grades, including but not limited to:

Mechanical Properties (Typical, Annealed Condition)

Property 304 / 304L 316 / 316L 321 / 321H 2205 Duplex
Tensile Strength (Rm, MPa) ≥ 520 ≥ 520 ≥ 520 ≥ 550
Yield Strength (Rp0.2, MPa) ≥ 205 ≥ 205 ≥ 205 ≥ 450
Elongation (A, %) ≥ 40 ≥ 40 ≥ 40 ≥ 25
Hardness (HBW) ≤ 217 ≤ 217 ≤ 217 ≤ 250
Maximum Operating Temperature (°C) 870 870 900 350

Chemical Composition Requirements

All grades conform to the chemical composition limits specified in ASTM A269, ASTM A270, EN 10217-7, GB/T 14976, and equivalent international standards. Key alloying elements include Chromium (Cr), Nickel (Ni), Molybdenum (Mo), Titanium (Ti), and Stabilized Carbon (C) levels controlled to prevent intergranular corrosion and ensure long-term service reliability.

Specifications

Parameter Specification / Range Standard Reference
Outer Diameter (OD) 3.00 mm – 120.00 mm EN 10217-7 / GB/T 14976
Wall Thickness (WT) 0.25 mm – 8.00 mm EN 10217-7 / ASTM A269
Coil Inner Diameter (ID) 150 mm / 200 mm / 250 mm / 300 mm (customizable) Manufacturer Specification
OD Tolerance ± 0.10 mm (fine tolerance: ± 0.05 mm) EN 10217-7
WT Tolerance ± 10% (fine tolerance: ± 5%) EN 10217-7
Surface Finish Bright Annealed (BA), Pickled & Passivated (2B), Polished (No.4 / Mirror) ASTM A480 / EN 10088
Heat Treatment Condition Annealed (Solution Annealed), Cold Worked ASME SA-213 / SA-219
End Condition Plain, Beveled, Flanged (upon request) Per Customer Drawing
Coil Length (Continuous) 50 m – 500 m (typical) Manufacturer Specification
Maximum Coil Weight Up to 2,500 kg per coil Logistics Specification

Manufacturing Process

The production of Stainless Steel Coil Tube follows a rigorous multi-stage manufacturing sequence designed to ensure dimensional accuracy, metallurgical integrity, and surface quality:

  1. Raw Material Inspection: Incoming stainless steel strip or bar stock is subjected to spectrographic analysis (OES — Optical Emission Spectroscopy) to verify chemical composition compliance. Each heat lot is traced to mill certificates (MTC — Material Test Certificate) per EN 10204 3.1.
  2. Slitting and Leveling: Stainless steel strip is slit to precise widths and passed through a leveling mill to eliminate coil set and ensure flatness uniformity, critical for downstream forming accuracy.
  3. Forming (Cold-Drawing or Cold-Rolling): The leveled strip is fed through a series of progressive dies or roll stations, progressively reducing the cross-section from a square or round billet to the final tubular geometry. Multi-stand cold-drawing permits tight dimensional control with minimal material waste.
  4. Intermediate Annealing (if required): For products requiring multiple forming passes, intermediate annealing at 1,050°C – 1,150°C followed by controlled cooling relieves accumulated cold work strain, restores ductility, and prevents cracking.
  5. Solution Annealing: The final heat treatment involves austenitization at temperatures between 1,010°C and 1,150°C (grade-dependent), followed by rapid water quenching. This process dissolves carbides, restores full solution-strengthened microstructure, and eliminates residual stresses.
  6. Pickling and Passivation: Tubes are immersed in a mixed acid solution (typically HNO₃/HF or H₂SO₄/HNO₃) to remove oxide scale and surface contaminants, followed by passivation treatment to form a stable, protective chromium oxide film (Cr₂O₃) on the surface.
  7. Dimensional Inspection: Each coil undergoes ultrasonic thickness testing (UT), optical diameter measurement, and visual inspection for surface defects, including cracks, pits, seams, and laps.
  8. Coiling and Packaging: Finished tubes are wound onto precision-machined coil cores, wrapped in protective film or paper, and secured with steel strapping to prevent deformation during transit.

Applications

The continuous coil form of this product offers distinct advantages in high-volume manufacturing and specialized engineering applications:

Quality Certifications and Compliance

Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management and product certification systems ensuring full traceability and compliance with international standards:

Unique Selling Points

1. Continuous Coil Advantage: Unlike straight-length tubing, coil form eliminates butt-weld joints in downstream assembly, significantly reducing leak risk and material waste. A single coil can supply production lines for extended durations without interruption.

2. Technical Conditions Compliance: All products are manufactured and inspected in strict accordance with the "Coil Tube — Technical Conditions" (盘管技术条件) specification, ensuring that every parameter — from chemical composition to dimensional tolerance to surface finish — meets defined acceptance criteria.

3. Broad Grade Availability: Stock maintained across austenitic, ferritic, duplex, and precipitation-hardening grades, enabling single-source procurement for multi-material engineering projects.

4. Customization Capability: Non-standard dimensions, special surface finishes, custom coil configurations, and application-specific heat treatment schedules are available upon request.

5. Full Traceability: Every coil is assigned a unique identification number traceable to the original mill heat, manufacturing batch, and inspection records, ensuring complete supply chain transparency.

Standards Reference Summary

Standard Description Scope
EN 10217-7 Seamless stainless steel tubes for technical purposes — Technical delivery conditions — Part 7: Austenitic tubes Primary European standard for austenitic coil tubes
ASTM A269 Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubes for General Use Primary American standard for general-purpose tubing
GB/T 14976 Seamless stainless steel tubes for fluid conveyance Chinese national standard for fluid service tubing
ASME SA-213 Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubes for Heat Exchangers Boiler and Pressure Vessel Code, Section VIII
EN 10204 Delivery documentation for metallic products — Types of inspection documents Governs MTC (3.1) documentation requirements

This technical specification is intended for engineering reference and procurement evaluation purposes. All values are typical and subject to verification against specific product certificates. For detailed dimensional drawings, grade-specific data sheets, and certification documentation, contact Wenzhou Jixing Metal Materials Co., Ltd. directly.