Stainless Steel Coil Tube — Precision Engineered Coil Pipe Product
Product Overview
The Stainless Steel Coil Tube is a precision-manufactured continuous-length tubular product supplied in coiled form, engineered to deliver superior mechanical integrity, corrosion resistance, and dimensional accuracy across a broad spectrum of industrial, HVAC (Heating, Ventilation, and Air Conditioning), and process applications. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd, this coil tube product line represents the convergence of advanced metallurgical formulation, cold-drawing precision, and rigorous quality assurance protocols.
Unlike conventional cut-length seamless or welded pipes, coil tubes are delivered in continuous helical or spiral coils, enabling downstream processors to perform high-speed, low-waste forming, bending, and cutting operations without the interruption of joint seams at frequent intervals. This continuous supply format significantly reduces material waste, minimizes labor handling costs, and improves production throughput in automated manufacturing environments.
Material & Properties
The coil tube is fabricated from austenitic stainless steel grades conforming to international standards, with the following primary material options available:
- Grade 304 (UNS S30408 / EN 1.4301) — The most widely specified austenitic grade, offering excellent general-purpose corrosion resistance, weldability, and formability. Chromium (Cr) content of 18–20% and Nickel (Ni) content of 8–10.5% provide robust resistance to atmospheric, mild chemical, and food-grade environments.
- Grade 316 (UNS S31603 / EN 1.4401) — Enhanced corrosion resistance due to the addition of 2–3% Molybdenum (Mo), making it suitable for marine, chemical processing, and pharmaceutical environments where chloride-induced pitting and crevice corrosion are concerns.
- Grade 304L / 316L (Low-Carbon Variants) — Reduced carbon content (≤ 0.03%) to minimize intergranular corrosion risk during welding, making these grades ideal for applications involving extensive post-fabrication welding.
- Grade 321 (UNS S32100 / EN 1.4541) — Titanium-stabilized austenitic grade offering superior resistance to sensitization at elevated temperatures (up to 870 °C), suitable for high-temperature industrial service.
Key mechanical properties for cold-worked coil tube typically include:
- Tensile Strength (UTS): 515–720 MPa (depending on grade and cold-work condition)
- Yield Strength (0.2% offset): 205–450 MPa
- Elongation at Break: 35–60%
- Hardness (HB): 100–250 (depending on cold-drawing degree)
- Thermal Conductivity: 14–16 W/(m·K) at 20 °C
- Operating Temperature Range: −196 °C to 870 °C (Grade 304/316); up to 1000 °C (Grade 321)
Technical Specifications
| Parameter | Specification Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 3.0 mm – 50.8 mm (⅛" – 2") | ASTM A213 / EN 10216-5 / GB/T 14976 |
| Wall Thickness (WT) | 0.3 mm – 3.0 mm | ASTM A213 / EN 10216-5 / GB/T 14976 |
| Coil Inner Diameter (CID) | 150 mm – 600 mm (customizable) | Manufacturer standard |
| Coil Outer Diameter (COD) | 300 mm – 1200 mm (customizable) | Manufacturer standard |
| Coil Length (Continuous) | 50 m – 500 m per coil (typical) | Per customer requirement |
| Surface Finish | Bright Annealed (BA), Pickled & Passivated (2B), Polished (Mirror #4 / #8) | ASTM A478 / EN 10204 |
| Dimensional Tolerance (OD) | ±0.05 mm to ±0.15 mm (precision grade) | EN 10216-5 / ISO 4200 |
| Dimensional Tolerance (WT) | ±0.02 mm to ±0.08 mm (precision grade) | EN 10216-5 / ISO 4200 |
| Roundness Tolerance | ≤ 0.5% of nominal OD | ISO 4200 |
| Material Condition | Hot Rolled & Cold Drawn (HRC), Cold Worked Annealed (CWA), Full Hard (H) | ASTM A213 |
| End Condition | Plain, Beveled, or Custom (per application) | Per customer specification |
| Coating / Passivation | Chromic acid passivation, Citric acid passivation, or None | ASTM A967 |
Manufacturing Process
The production of high-quality stainless steel coil tube follows a rigorously controlled multi-stage manufacturing sequence:
- Raw Material Selection: Virgin stainless steel billets or slabs from certified suppliers are inspected for chemical composition (via Optical Emission Spectroscopy, OES) and mechanical properties prior to acceptance.
- Hot Rolling & Forming: The selected billets are reheated to 1100–1200 °C and hot-rolled into seamless tubes using a Mannesmann piercing mill or plug-rolling process. The continuous forming ensures uniform microstructure and eliminates weld seams.
- Pickling & Annealing: Hot-rolled tubes undergo continuous annealing in a protective atmosphere (H₂/N₂ mixture) at 1050–1150 °C, followed by pickling in a mixed acid bath (HNO₃/HF or H₂SO₄/HNO₃) to remove the mill scale oxide layer and restore the passive chromium oxide film.
- Cold Drawing / Cold Pilgering: Tubes are cold-drawn through precision tungsten carbide (WC) dies to achieve the target outer diameter and wall thickness with tight dimensional tolerances. This cold-working step induces work hardening, increasing tensile strength while maintaining ductility.
- Intermediate Annealing: For multi-pass cold drawing, intermediate annealing cycles are performed to relieve accumulated strain and prevent cracking, ensuring consistent mechanical properties throughout the coil.
- Final Annealing & Surface Treatment: The finished tube undergoes a final anneal in a bell jar furnace or continuous annealing line, followed by passivation treatment to ensure a protective chromium oxide surface layer. Surface finish is achieved through mechanical polishing or electropolishing as specified.
- Coiling & Packaging: The continuous tube is wound into coils on precision coiling stands, with controlled tension to prevent ovalization or flattening. Coils are wrapped in protective film, wrapped in kraft paper, and strapped with steel bands for transport.
- Quality Inspection: Every coil undergoes 100% hydrostatic pressure testing (or electromagnetic testing), dimensional verification via ultrasonic thickness gauging, and visual inspection for surface defects. Chemical composition analysis and mechanical property testing are performed on representative samples per lot.
Applications
The stainless steel coil tube from Wenzhou Jixing Metal Materials Co., Ltd is engineered for diverse high-performance applications:
- HVAC & Fan Coil Units (FCU): The primary application domain for this coil tube product. Coil tubes are used as the heat exchange tubes in fan coil units, air handling units (AHU), and chiller systems. Their high thermal conductivity, corrosion resistance, and ability to be precisely coiled into compact heat exchanger geometries make them indispensable in commercial and residential HVAC systems. The continuous coil form allows for automated tube bending into serpentine, spiral, or zigzag heat exchanger configurations.
- Food & Beverage Processing: Grade 304 and 316 coil tubes are used in sanitary piping, brewing systems, dairy processing equipment, and food-grade heat exchangers where hygienic surface finish and resistance to organic acid corrosion are critical.
- Pharmaceutical & Medical Devices: Biocompatible stainless steel coil tubes are employed in pharmaceutical fluid transfer systems, medical instrument tubing, and clean-room process equipment requiring USP Class VI compliance.
- Automotive Industry: Precision coil tubes are used in fuel lines, brake lines, exhaust systems, and air conditioning refrigerant circuits within vehicles, where lightweight, corrosion-resistant, and high-pressure-rated tubing is essential.
- Chemical Processing & Petrochemicals: Grade 316 and 321 coil tubes serve in chemical plant piping, reactor internals, heat exchanger bundles, and distillation columns where exposure to aggressive chemicals and elevated temperatures is routine.
- Marine & Offshore: Resistant to chloride-induced corrosion, 316-grade coil tubes are used in marine cooling systems, ballast water piping, and offshore platform fluid handling systems.
- Medical & Laboratory Equipment: Used in autoclave tubing, dialysis machine components, and analytical instrument fluid paths requiring high purity and corrosion resistance.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management infrastructure ensuring that every coil tube product meets or exceeds international and national standards:
- ISO 9001:2015 — Quality Management Systems certification, demonstrating adherence to systematic quality control, process documentation, and continuous improvement protocols.
- ISO 14001:2015 — Environmental Management Systems certification, ensuring environmentally responsible manufacturing practices throughout the production lifecycle.
- CE Marking (European Conformity) — Compliance with applicable European Directives including the Pressure Equipment Directive (PED 2014/68/EU) and Machinery Directive, enabling unrestricted distribution within the European Economic Area (EEA).
- ASTM International Standards: Conformance to ASTM A213 (seamless austenitic stainless steel tubing), ASTM A269 (seamless and welded austenitic stainless steel tubing and pipe), ASTM A478 (tubes for general service), and ASTM A967 (chemical passivation of stainless steel).
- EN / DIN European Standards: Compliance with EN 10216-5 (metallic heat exchanger and heat transfer elements), EN 10217-7 (welded and seamless steel tubes for pressure purposes), and DIN 2395 (stainless steel tubes for food industry).
- GB/T Chinese National Standards: Conformance to GB/T 14976 (seamless steel tubes for fluid conveyance), GB/T 12771 (welded stainless steel tubes for fluid conveyance), and GB 4237 (hot-rolled and cold-rolled stainless steel plates and sheets).
- Mill Test Certificates (MTC / EN 10204 3.1): Every shipment is accompanied by a comprehensive Mill Test Certificate documenting chemical composition, mechanical test results, dimensional verification, and hydrostatic test data, traceable to the specific heat number and production lot.
Unique Selling Points
- Ultra-Precision Dimensional Control: Tolerances as tight as ±0.05 mm on outer diameter and ±0.02 mm on wall thickness, achieved through advanced cold-drawing technology with tungsten carbide tooling and real-time dimensional monitoring systems. This precision eliminates the need for secondary machining in downstream applications.
- Superior Surface Integrity: Multi-stage pickling and passivation processes ensure a defect-free, corrosion-resistant surface with chromium oxide film thickness of 2–5 nm, providing long-term protection against atmospheric and chemical corrosion.
- Continuous Coil Supply Advantage: The coil format enables automated, high-speed processing with material utilization rates exceeding 95%, significantly reducing waste compared to cut-length pipe alternatives. This translates to lower total cost of ownership for high-volume production environments.
- Full Traceability: Every coil is individually serialized with heat number, grade, dimensions, and production date, enabling complete supply chain traceability from raw material to end product — a critical requirement in pharmaceutical, aerospace, and nuclear applications.
- Custom Engineering Capability: Non-standard dimensions, surface finishes, mechanical properties, and coil configurations are available upon request, supported by a dedicated engineering team for application-specific consultation and product development.
- Comprehensive Testing Protocol: Beyond standard hydrostatic and dimensional testing, optional services include positive material identification (PMI) via X-ray fluorescence (XRF) spectrometry, ultrasonic flaw detection (UT), eddy current testing (ECT), and surface roughness verification (Ra ≤ 0.4 μm for sanitary applications).
Note: All specifications referenced in this document are subject to the applicable edition of the cited standards and may be updated periodically. Customers are advised to consult the latest product data sheet and Mill Test Certificate for specific lot information. Custom specifications and non-standard configurations are available upon written request to Wenzhou Jixing Metal Materials Co., Ltd technical sales department.