Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
Product Overview
The Stainless Steel Coil Tube (Coiltube) is a continuous, helically wound tubular product manufactured from austenitic or duplex stainless steel strip. Produced by Wenzhou Jixing Metal Materials Co., Ltd., this product is supplied in coil form, enabling high-volume, continuous feeding into downstream forming, welding, and processing operations. Unlike discrete lengths of seamless or welded pipe, coil tubes offer superior material utilization, reduced cutting waste, and seamless integration with automated production lines.
Coil tubes are extensively used in applications requiring high surface finish quality, corrosion resistance, and dimensional precision — including automotive exhaust systems, heat exchangers, hydraulic systems, food processing equipment, and architectural components. The coil format allows manufacturers to produce tubes of virtually any length without splicing, ensuring consistent metallurgical properties along the entire product length.
Material & Properties
Stainless steel coil tubes are fabricated from cold-rolled stainless steel strip conforming to international standards. The following grades are typically available:
- AISI 304 (UNS S30408) — General-purpose austenitic grade with excellent corrosion resistance and formability; contains 18% chromium and 8% nickel (Cr-Ni austenitic).
- AISI 316 (UNS S31608) — Enhanced corrosion resistance with 2–3% molybdenum addition; suitable for aggressive chemical and marine environments.
- AISI 316L (UNS S31603) — Low-carbon variant of 316; superior resistance to intergranular corrosion after welding.
- AISI 321 (UNS S32108) — Stabilized with titanium; excellent resistance to sensitization at elevated temperatures.
- AISI 430 (UNS S43000) — Ferritic grade with good corrosion resistance and lower cost; non-magnetic at room temperature.
- Duplex 2205 (UNS S32205) — High-strength duplex phase (austenite + ferrite); excellent resistance to chloride stress corrosion cracking (SCC).
Mechanical Properties (Typical for AISI 304)
- Tensile Strength: 515–725 MPa (75,000–105,000 psi)
- Yield Strength (0.2% Offset): 205–310 MPa (30,000–45,000 psi)
- Elongation: ≥ 35% (minimum)
- Hardness: ≤ 210 HB (annealed condition)
- Density: 8.0 g/cm³
Surface Finish Options
- 2B Finish — Standard cold-rolled and annealed finish; smooth, slightly reflective surface.
- No. 4 Brushed Finish — Directional grain pattern; widely used in architectural and appliance applications.
- Mirror Finish (8K) — Polished to high reflectivity; used in decorative and sanitary applications.
- BA (Bright Annealed) Finish — Annealed in a controlled atmosphere; clean, oxide-free surface with high reflectivity.
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Material Grades | AISI 304, 304L, 316, 316L, 321, 430, 2205 Duplex, 310S, 904L |
| Outer Diameter (OD) | 3.0 mm – 168.3 mm (1/8" – 6") |
| Wall Thickness (WT) | 0.3 mm – 6.0 mm (0.012" – 0.236") |
| Tolerance — OD | ±0.1 mm (thin wall); ±0.3 mm (heavy wall) |
| Tolerance — Wall Thickness | ±10% (standard); ±5% (precision) |
| Surface Finish | 2B, BA, No.4 Brushed, Mirror (8K), Custom |
| Coil Weight | 500 kg – 3,000 kg per coil (typical) |
| Coil Core Diameter | 508 mm (20") standard; customizable |
| Manufacturing Standard | ASTM A554, ASTM A213, ASTM A269, EN 10216-5, GB/T 12771 |
| Welding Type | Continuous Welded (TIG/Resistance), Seamless (Cold Drawn) |
| Heat Treatment | Annealed, Solution Annealed, Stress Relieved |
| Packaging | Wooden pallet with stretch film, export-grade seaworthy packing |
| Customization | OD, WT, grade, finish, coil weight, and packaging available upon request |
Manufacturing Process
The production of stainless steel coil tubes involves a series of precisely controlled metallurgical and mechanical processes:
- Strip Selection & Inspection: Cold-rolled stainless steel strip is sourced from certified mills and inspected for surface defects, dimensional accuracy, and chemical composition compliance via spectroscopic analysis (OES).
- Slitting: The master coil is slit to the required strip width using precision slitting lines, ensuring edge quality and dimensional consistency.
- Coiling & Forming: The strip is fed through a forming mill where progressive rolls shape the flat strip into a tubular cross-section. The coil tube is wound continuously onto a coil core.
- Welding (for welded coil tubes): A continuous longitudinal weld is formed using TIG (Tungsten Inert Gas) welding or high-frequency resistance welding. The weld zone is ground and polished to achieve surface continuity.
- Cold Drawing / Sizing (for seamless coil tubes): Tubes are cold-drawn through a die and mandrel to achieve precise OD and wall thickness tolerances, improving mechanical properties and surface finish.
- Heat Treatment: Tubes undergo solution annealing (typically at 1010–1150°C followed by rapid quenching) to restore full austenitic microstructure, relieve residual stresses, and achieve maximum corrosion resistance.
- Pickling & Passivation: Post-welding oxide scale is removed through acid pickling (nitric/hydrofluoric acid blend), followed by passivation to restore the chromium oxide protective layer.
- Surface Finishing: Depending on the required finish, tubes undergo polishing, brushing, or bright annealing in a controlled atmosphere furnace.
- Quality Inspection: Final products are subjected to hydrostatic testing, eddy current inspection, dimensional verification, and visual examination.
- Coiling & Packaging: Finished tubes are re-coiled to specified weight and packaged for shipping.
Applications
- Automotive Industry: Exhaust systems, fuel lines, brake lines, and turbocharger components.
- Heat Exchangers & HVAC: Refrigeration tubing, condenser and evaporator coils, radiators.
- Food & Beverage Processing: Hygienic piping, milk processing lines, brewing equipment, sanitary fittings.
- Chemical & Petrochemical: Process piping, reactor internals, corrosion-resistant transfer lines.
- Medical Devices: Surgical instrument tubing, catheters, implant components (biocompatible grades).
- Hydraulic & Pneumatic Systems: High-pressure fluid transfer lines, hydraulic hose inner tubes.
- Architectural & Decorative: Handrails, balustrades, structural components, facade cladding.
- Electronics & Appliances: Condenser tubes, heat sink components, appliance structural parts.
Quality Certifications & Testing Standards
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality assurance programs aligned with international standards:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control.
- ISO 14001 — Environmental Management System certification for sustainable manufacturing practices.
- EN 10204 3.1 — Mill Test Certificates (MTC) issued for each batch, including chemical composition, mechanical properties, and dimensional data.
- ASTM A999 — Standard Practice for Chemical Analysis of Stainless Steel Products.
- EN 10216-5 — European standard for welded stainless steel tubes for pressure purposes.
- GB/T 12771 — Chinese national standard for welded austenitic stainless steel tubes for general service.
- Hydrostatic Testing — All tubes tested at 1.5× working pressure per ASTM A530.
- Eddy Current Testing (ECT) — Non-destructive inspection per ASTM A999 for weld quality and wall thickness verification.
- Spectroscopic Analysis (OES) — 100% chemical composition verification per ASTM E415.
- Intergranular Corrosion Testing — ASTM A240 Annex A (ASTM A923 Method E) for sensitization resistance verification.
Unique Selling Points
- Continuous Length Supply: Coil format eliminates splicing and butt-welding requirements, reducing material waste by up to 15% compared to discrete-length pipe.
- High Dimensional Precision: Tight tolerances on OD and wall thickness ensure interchangeability and compatibility with automated processing equipment.
- Wide Grade Selection: Availability of multiple stainless steel grades including duplex and super-austenitic options provides versatility across diverse application requirements.
- Custom Surface Finishes: From industrial 2B to mirror-polished 8K, surface treatments are tailored to functional and aesthetic requirements.
- Traceability: Each coil is accompanied by a full traceability document package including heat number, chemical analysis, and mechanical test results.
- Cost Efficiency: The coil format reduces handling, storage, and processing costs compared to individual pipe lengths, making it ideal for high-volume manufacturing operations.
Note: All specifications listed above represent standard capabilities. Custom specifications — including non-standard diameters, wall thicknesses, grades, and finishes — are available upon request. Wenzhou Jixing Metal Materials Co., Ltd. encourages technical consultation to match product specifications precisely to application requirements.