Stainless Steel Coil Tube (Coiltube) — Wenzhou Jixing Metal Materials Co., Ltd.
Product Overview
The Stainless Steel Coil Tube (also referred to as Coiltube or Coil Pipe) is a precision-engineered continuous-length tubular product supplied in a coiled configuration. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this product is designed for a wide range of industrial applications where corrosion resistance, mechanical integrity, and thermal conductivity are critical performance parameters. The coil form factor offers superior handling, storage, and deployment efficiency compared to cut-length straight pipe, making it particularly advantageous for automated manufacturing lines and large-scale installation projects.
This product line has been specifically evaluated and recommended for use in networked fan coil unit (FCU) temperature control systems within air conditioning energy-saving billing infrastructure, where precise thermal regulation and long-term reliability are paramount.
Material Composition & Properties
Available Grades
- 304 (UNS S30400) — General-purpose austenitic stainless steel with excellent corrosion resistance and formability
- 316 (UNS S31600) — Enhanced molybdenum-bearing grade offering superior resistance to pitting and crevice corrosion
- 316L (UNS S31603) — Low-carbon variant of 316, ideal for welding-intensive applications
- 321 (UNS S32100) — Titanium-stabilized grade resistant to intergranular corrosion at elevated temperatures
- 310S (UNS S31008) — High-temperature austenitic grade for extreme thermal environments
Mechanical Properties (Typical — Annealed Condition)
| Property | 304 Grade | 316 Grade | 321 Grade |
|---|---|---|---|
| Tensile Strength (MPa) | ≥ 520 | ≥ 520 | ≥ 520 |
| Yield Strength (MPa, 0.2% offset) | ≥ 205 | ≥ 205 | ≥ 205 |
| Elongation (%) | ≥ 40 | ≥ 40 | ≥ 40 |
| Hardness (HBW) | ≤ 201 | ≤ 201 | ≤ 201 |
| Density (g/cm³) | 7.93 | 8.00 | 7.99 |
| Thermal Conductivity (W/m·K, at 20°C) | 16.3 | 14.6 | 16.3 |
| Maximum Service Temperature (°C) | 870 | 870 | 900 |
Chemical Composition (ASTM Standard, wt%)
| Element | 304 | 316 | 321 |
|---|---|---|---|
| C (Carbon) | ≤ 0.08 | ≤ 0.08 | ≤ 0.08 |
| Cr (Chromium) | 18.0–20.0 | 16.0–18.0 | 17.0–19.0 |
| Ni (Nickel) | 8.0–10.5 | 10.0–14.0 | 9.0–12.0 |
| Mn (Manganese) | ≤ 2.0 | ≤ 2.0 | ≤ 2.0 |
| P (Phosphorus) | ≤ 0.045 | ≤ 0.045 | ≤ 0.045 |
| S (Sulfur) | ≤ 0.030 | ≤ 0.030 | ≤ 0.030 |
| Mo (Molybdenum) | — | 2.0–3.0 | — |
| Ti (Titanium) | — | — | 5×C to 0.70 |
Dimensions & Specifications
| Parameter | Specification Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 3.0 mm – 108.0 mm | ASTM A213 / A269, EN 10216-5 |
| Wall Thickness (WT) | 0.30 mm – 6.0 mm | ASTM A213 / A269 |
| OD Tolerance | ± 0.10 mm (≤ 25 mm); ± 0.5% (> 25 mm) | ISO 4200 |
| WT Tolerance | ± 10% (≤ 1.5 mm); ± 12.5% (> 1.5 mm) | ISO 4200 |
| Coil Inner Diameter (ID) | 200 mm – 600 mm | Manufacturer standard |
| Coil Weight (Typical) | 200 kg – 2,000 kg per coil | — |
| Surface Finish | Bright Annealed (BA), Pickled & Passivated, Hairline, Mirror Polish | ASTM A403 |
| End Treatment | Plain cut, Beveled, or Threaded | — |
| Heat Treatment Condition | Full Annealed (Solution Annealed at 1050–1100°C followed by rapid cooling) | ASTM A213 |
| Testing | Hydrostatic test, Eddy Current (EC) inspection, Visual inspection | ASTM A213, EN 10216-5 |
Manufacturing Process
- Raw Material Preparation: Stainless steel strip (coil) is sourced from certified mills and subjected to incoming chemical composition verification via Optical Emission Spectrometry (OES) and mechanical property confirmation through tensile testing.
- Coil Winding & Forming: The strip is fed through precision-calibrated forming rolls in a multi-station roll-forming line. Progressive deformation is applied to achieve the target inner diameter with controlled ovality and dimensional accuracy.
- Seam Welding: A high-frequency induction welding (HF-IW) or Transverse Pulse Plasma (TPP) welding process is employed to create the longitudinal seam. The welding parameters — including frequency, current, and roll pressure — are continuously monitored and logged for traceability.
- In-Line Heat Treatment: The welded tube passes through a controlled-atmosphere annealing furnace (typically using endothermic or dissociated ammonia gas) to restore full austenitic microstructure and relieve welding-induced residual stresses.
- Pickling & Passivation: The tube surface is treated in a mixed acid solution (HNO₃ + H₃PO₄) to remove oxide scale, followed by a passivation step to establish a protective chromium oxide layer (Cr₂O₃).
- Non-Destructive Testing (NDT): Eddy current (EC) scanning is performed at high speeds to detect internal and surface discontinuities. Hydrostatic pressure testing is conducted at 1.5× the maximum working pressure to verify wall integrity.
- Dimensional Inspection: Outer diameter, wall thickness, and coil geometry are verified using laser scanning and ultrasonic thickness gauging systems.
- Coiling & Packaging: Finished tube is wound onto steel cores or wooden spools, wrapped with protective film, and secured with steel strapping. Each coil is labeled with heat number, grade, dimensions, and test certificate reference.
Applications
Primary Application Domains
- Air Conditioning & HVAC Systems: Coiltube is extensively used in fan coil unit (FCU) air handlers, chiller evaporators/condensers, and heat exchanger cores. Its superior thermal conductivity and corrosion resistance make it ideal for refrigerant circuits and chilled water distribution loops within energy-efficient building management systems.
- Networked Temperature Control Systems: In advanced air conditioning energy-saving billing infrastructure — specifically systems utilizing networked FCU temperature controllers — stainless steel coil tubes serve as the primary heat transfer medium, enabling precise thermal regulation and accurate energy consumption metering across distributed zones.
- Food & Beverage Processing: Compliant with FDA and 3-A sanitary standards, the coil tube is used in pasteurization systems, beverage dispensing lines, and hygienic fluid transfer applications.
- Chemical & Pharmaceutical Processing: 316L grade coiltube is employed in reactor heat exchangers, distillation columns, and clean-in-place (CIP) systems where aggressive chemical exposure is present.
- Automotive & Aerospace: Used in exhaust system components, fuel lines, and hydraulic tubing where high-temperature resistance and fatigue performance are required.
- Oil & Gas: 316 and 316L grades are specified for sour service environments (H₂S-containing) in upstream and downstream processing facilities.
- Marine & Coastal Applications: Superior resistance to chloride-induced corrosion renders this product suitable for desalination plants, marine heat exchangers, and offshore platform piping systems.
Quality Certifications & Compliance
| Certification / Standard | Scope |
|---|---|
| ISO 9001:2015 | Quality Management System |
| ISO 14001:2015 | Environmental Management System |
| ISO 45001:2018 | Occupational Health & Safety Management |
| ASTM A213 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for High-Pressure Boilers and Heaters |
| ASTM A269 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for Chemical and Similar Severe Service |
| ASTM A403 | Standard Specification for Chromium and Chromium-Nickel Stainless Steel Tubing, Seamless and Welded, for High-Pressure Boiler and Heat Exchanger Applications |
| EN 10216-5 | Technical Delivery Conditions for Non-Alloy, Stainless and Heat Resistant Steel Tubes — Part 5: Austenitic Stainless Steel Tubes |
| GB/T 14976 | Chinese National Standard for Seamless Stainless Steel Tubes for Fluid Transport |
| GB/T 17899 | Chinese National Standard for Welded Stainless Steel Tubes for Fluid Transport |
| CE Marking (PED 2014/68/EU) | Pressure Equipment Directive compliance for pressure-vessel applications |
| NACE MR0175 / ISO 15156 | Sour Service resistance certification (316/316L grades) |
| FDA 21 CFR 178 | Food contact material compliance |
| 3-A Sanitary Standards | Dairy, food, and pharmaceutical processing compliance |
Unique Selling Points
- Continuous-Length Coil Configuration: Eliminates weld joints inherent in straight-pipe assemblies, reducing leak points and improving system reliability — a critical advantage in sealed refrigerant circuits and networked FCU temperature control systems.