Stainless Steel Coil Tube (Coiltube) — Technical Product Specification
Product Overview
The Stainless Steel Coil Tube (Coiltube), manufactured by Wenzhou Jixing Metal Materials Co., Ltd., is a precision-engineered seamless or welded tubular product delivered in continuous coil form. This product is designed to meet the demanding requirements of industrial applications where corrosion resistance, thermal conductivity, and mechanical integrity are critical. The coiled delivery format enables downstream customers to utilize automated cutting and forming equipment, significantly reducing material waste and labor costs associated with straight-length pipe handling.
Coil tubes are particularly valued in HVAC (Heating, Ventilation, and Air Conditioning), heat exchanger manufacturing, fluid transport systems, and food-grade processing equipment. The continuous coil configuration allows for efficient downstream processing through high-speed slitting, cutting, and bending operations without the need for butt-welding multiple short lengths together.
Material Composition & Properties
Stainless steel coil tubes are typically fabricated from austenitic stainless steel grades, selected for their superior combination of corrosion resistance, weldability, and formability. The primary grades offered include:
- SUS 304 (ASTM 304 / UNS S30400): The most widely used austenitic stainless steel, containing approximately 18% Chromium (Cr) and 8% Nickel (Ni). Offers excellent general corrosion resistance and good formability at ambient temperatures.
- SUS 316 (ASTM 316 / UNS S31600): Enhanced with 2–3% Molybdenum (Mo) for superior resistance to pitting and crevice corrosion, particularly in chloride-containing environments.
- SUS 321 (ASTM 321 / UNS S32100): Stabilized with Titanium (Ti) to prevent sensitization during welding and high-temperature service.
- SUS 304L / SUS 316L (Low-Carbon Grades): Reduced carbon content (≤0.03%) to minimize intergranular corrosion risk during welding operations.
Mechanical Properties (Typical Values for Cold-Worked Coil Tube)
| Property | Unit | SUS 304 | SUS 316 |
|---|---|---|---|
| Tensile Strength (Ultimate) | MPa | ≥ 520 | ≥ 515 |
| Yield Strength (0.2% Offset) | MPa | ≥ 205 | ≥ 170 |
| Elongation (at Break) | % | ≥ 40 | ≥ 40 |
| Hardness (Rockwell B) | HRB | ≤ 95 | ≤ 95 |
| Density | g/cm³ | 7.93 | 8.00 |
| Thermal Conductivity (at 100°C) | W/(m·K) | 16.3 | 14.6 |
| Maximum Service Temperature | °C | 870 | 870 |
Surface Finish Options
- No. 4 Finish (Brushed): Uniformly directional ground surface; suitable for general industrial and architectural applications.
- 2B Finish: Mill finish with a smooth, slightly reflective appearance; standard for mechanical and structural applications.
- Ba & Be Polished Finish: Mirror-like finish with Ra ≤ 0.05 μm; required for pharmaceutical, food processing, and optical applications.
- Pickled & Passivated: Chemical treatment to remove scale and restore passive chromium oxide layer for enhanced corrosion resistance.
Technical Specifications
| Parameter | Specification | Applicable Standard |
|---|---|---|
| Outside Diameter (OD) | 3.0 mm – 159.0 mm | ASTM A269 / ASTM A213 |
| Wall Thickness | 0.3 mm – 8.0 mm | ASTM A269 / EN 10216-5 |
| Coil Inner Diameter (ID) | 150 mm – 600 mm | Manufacturer Standard |
| Coil Length (Unwound) | 50 m – 500 m per coil | — |
| Tolerance on OD | ±0.10 mm (OD ≤ 25 mm); ±0.15% (OD > 25 mm) | ASTM A269 |
| Tolerance on Wall Thickness | ±10% of nominal | ASTM A269 |
| End Condition | Plain end / Beveled end (per customer specification) | — |
| Material Form | Seamless / Welded (ERW — Electric Resistance Welded) | ASTM A213 / EN 10217-7 |
| Heat Treatment | Solution Annealed (1050°C – 1150°C) + Water Quench | ASTM A269 |
| Packaging | Wooden pallet with moisture-proof wrapping and steel banding | ISO 4180 |
Manufacturing Process
The production of stainless steel coil tubes follows a rigorous multi-stage process to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection: High-purity stainless steel billets or strip are procured from certified mills with full chemical composition verification via Optical Emission Spectroscopy (OES) and Inductively Coupled Plasma (ICP) analysis.
- Hot Rolling / Piercing: Billets are heated to 1100°C–1200°C and hot-rolled or pierced to produce a seamless hollow section. For welded coil tubes, cold-rolled strip is prepared to precise width and thickness tolerances.
- Cold Drawing / Cold Rolling: The hot-rolled tube or strip undergoes cold working through sequential drawing dies to achieve the target OD and wall thickness with tight tolerances. This process enhances mechanical strength through strain hardening.
- Intermediate Annealing: When significant cold work accumulation occurs, intermediate annealing cycles at 1050°C–1100°C restore ductility and prevent cracking during further forming.
- Welding (for ERW tubes): High-frequency electric resistance welding (ERW) joins the strip edges with precise heat input control to minimize heat-affected zone (HAZ) and preserve metallurgical properties.
- Solution Annealing & Pickling: The coil tube is solution-annealed in a controlled-atmosphere furnace to dissolve carbides and restore full austenitic structure. Subsequent acid pickling (mixed HNO₃/HF) removes oxide scale.
- Passivation: A nitric acid or citric acid passivation treatment re-establishes the protective chromium oxide passive film on the surface.
- Surface Finishing: Mechanical polishing, electrolytic polishing, or brushing is applied per customer specification to achieve the required surface roughness (Ra value).
- Coiling & Packaging: The finished tube is wound onto a coil with controlled tension to prevent deformation, then packaged on wooden pallets with protective wrapping.
Applications
Stainless steel coil tubes from Wenzhou Jixing Metal Materials Co., Ltd. serve a broad spectrum of industrial applications:
- HVAC & Fan Coil Units: Coil tubes are integral components in fan coil units (FCUs), air handlers, and heat exchangers. Their high thermal conductivity and corrosion resistance ensure efficient heat transfer in air conditioning and refrigeration systems. The coil form factor allows automated tube-bending machines to produce precise fin-and-tube heat exchangers at high production rates.
- Food & Beverage Processing: Used in sanitary piping systems, heat exchangers, and product contact surfaces where compliance with FDA (U.S. Food and Drug Administration) and EHEDG (European Hygienic Engineering and Design Group) standards is required.
- Pharmaceutical & Biotechnology: Employed in cleanroom piping, reactor heat exchangers, and steam distribution systems requiring validated hygienic design (ASME BPE — Bioprocessing Equipment).
- Chemical & Petrochemical Industry: Resistant to aggressive chemical media, used in process piping, condensers, and heat recovery units. SUS 316 grade is preferred for chloride-containing environments.
- Automotive Industry: Used in exhaust systems, fuel lines, and turbocharger components requiring high-temperature resistance and durability.
- Construction & Architectural Applications: Structural tubing, handrails, decorative elements, and facade systems benefiting from the aesthetic appeal and long service life of stainless steel.
- Energy & Power Generation: Boiler tubes, superheater tubes, and condenser tubes in power plants where thermal cycling resistance and oxidation resistance are critical.
Quality Certifications & Testing Standards
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management systems and product certifications to ensure compliance with international standards:
- ISO 9001:2015: Quality Management System certification ensuring consistent product quality and continuous improvement processes.
- ISO 14001:2015: Environmental Management System certification demonstrating environmental responsibility in manufacturing operations.
- ISO 45001:2018: Occupational Health and Safety Management System certification.
- CE Marking (European Conformity): Compliance with EU directives for products sold within the European Economic Area.
- EN 10204 3.1: Third-party inspection and certification of material test reports for each production lot.
Incoming & In-Process Inspection
| Inspection Item | Method / Equipment | Frequency |
|---|---|---|
| Chemical Composition | OES Spectrometer / ICP-OES | Per heat number |
| Dimensional Accuracy | CMM (Coordinate Measuring Machine) / OD gauge / Ultrasonic wall thickness gauge | Per coil / 100% online |
| Mechanical Properties | Universal Testing Machine (UTM) per ASTM E8 | Per heat number |
| Surface Roughness | Surface Roughness Tester (Ra measurement) | Per batch |
| Corrosion Resistance | Salt Spray Test (ASTM B117) / Pitting Corrosion Test (ASTM G48) | Per grade / periodic |
| Internal Defects | Eddy Current Testing (ECT) / Ultrasonic Testing (UT) | 100% online |
| Hydrostatic Testing | Hydrostatic Pressure Test (1.5× working pressure, 10-second hold) | Per coil (for seamless) |
| Intergranular Corrosion | Astm A262 Practice E (65% Boiling HNO₃) | For stabilized grades / periodic |
Unique Selling Points
- Continuous Coil Delivery: Eliminates butt-weld joints in downstream fabrication, reducing leak points and improving structural integrity of the final assembly. Enables high-speed automated processing.
- Tight Dimensional Tolerances: Cold-drawn and cold-rolled processes achieve OD tolerances as tight as ±0.05 mm, critical for precision fitting and interference applications.
- Multi-Grade Availability: Full range of austenitic, duplex, and super-austenitic grades available from stock or made-to-order, providing flexibility for diverse application requirements.
- Custom Surface Finishes: Capability to deliver tubes with any required surface finish from matte to mirror polish, meeting stringent hygienic and aesthetic requirements.
- Full Traceability: Each coil is serialized with full material traceability from mill heat number through all processing stages, supported by EN 10204 3.1 certificates.
- Cost Efficiency: Coil format reduces material waste by up to 30% compared to straight-length pipe, and minimizes labor costs through automated downstream processing.
- Corrosion Resistance: Austenitic stainless steel grades provide service life exceeding 25 years in most industrial environments without coating or cathodic protection.
Compliance & Applicable Standards
| Standard | Title / Scope |
|---|---|
| ASTM A269 / A269M | Standard Specification for Seamless and Wrought Stainless Steel Tubing for Chemical and Allied Uses |
| ASTM A213 / A213M | Standard Specification for Seamless Ferritic and Austenitic Chromium-Chromium-Nickel Alloy Steel Tubing for High-Temperature Service |
| EN 10216-5 | Non-Alloy and Alloy Steel Tubes for Pressure Purposes — Technical Delivery Conditions for Austenitic Stainless Steel Tubes |
| EN 10217-7 | Welded Circular Hollow Sections for Mechanical Tubular Structures — Technical Delivery Conditions for Austenitic Stainless Steel |
| ASME BPE | Bioprocessing Equipment — Design and Construction of Process Equipment for Biotechnology (for pharmaceutical applications) |
| ISO 4180 | Steel and Steel Products — Packaging for Delivery |
Note: All specifications listed herein are representative values. Actual product dimensions, tolerances, and mechanical properties shall be confirmed through mutually agreed technical documentation between the manufacturer and the purchaser prior to order placement. Custom specifications are available upon request.