Stainless Steel Coil Tube — Product No. 1207
1. Product Overview
The Stainless Steel Coil Tube (Product No. 1207) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered coil tube designed for demanding thermal-fluid applications, particularly within fan coil unit (FCU) air conditioning systems and related HVAC (Heating, Ventilation, and Air Conditioning) infrastructure. The product is supplied in coiled configuration, enabling continuous-length processing, seamless coil winding, and reduced material waste during downstream fabrication. The coil tube is engineered to meet the stringent requirements of modern energy-efficient climate control systems, where thermal conductivity, corrosion resistance, and mechanical integrity are paramount.
Building upon advanced metallurgical practices, this coil tube integrates intelligent temperature control compatibility, making it an ideal conduit for chilled water, hot water, and refrigerant circulation in commercial and industrial HVAC installations. The product aligns with international standards governing stainless steel seamless and welded tubing, ensuring reliable performance across a wide operating temperature range of -40 °C to +450 °C.
2. Material & Properties
2.1 Base Alloy Composition
The coil tube is fabricated from high-grade austenitic stainless steel, primarily conforming to AISI 304 (UNS S30400) and AISI 316L (UNS S31603) grades, selected for their superior corrosion resistance, weldability, and cryogenic toughness.
| Element | 304 Grade (%) | 316L Grade (%) |
|---|---|---|
| Carbon (C) | ≤ 0.08 | ≤ 0.03 |
| Chromium (Cr) | 18.0 – 20.0 | 16.0 – 18.0 |
| Nickel (Ni) | 8.0 – 10.5 | 10.0 – 14.0 |
| Molybdenum (Mo) | — | 2.0 – 3.0 |
| Manganese (Mn) | ≤ 2.0 | ≤ 2.0 |
| Silicon (Si) | ≤ 1.0 | ≤ 1.0 |
| Phosphorus (P) | ≤ 0.045 | ≤ 0.045 |
| Sulfur (S) | ≤ 0.030 | ≤ 0.030 |
2.2 Mechanical Properties
| Property | Specification |
|---|---|
| Tensile Strength (Rm) | ≥ 520 MPa (75 ksi) |
| Yield Strength (Rp0.2) | ≥ 205 MPa (30 ksi) |
| Elongation (A50) | ≥ 40 % |
| Hardness (HV) | ≤ 200 |
| Thermal Conductivity (25 °C) | 16.3 W/(m·K) — 304; 14.3 W/(m·K) — 316L |
| Coefficient of Thermal Expansion (20–100 °C) | 17.3 × 10⁻⁶ /°C |
| Specific Heat Capacity | 500 J/(kg·K) |
| Density | 8.00 g/cm³ |
2.3 Surface Finish Options
- No. 1 Finish — Hot-rolled, annealed, and pickled; suitable for industrial applications.
- 2B Finish — Cold-rolled, annealed, and bright-pickled; standard commercial finish.
- Ba / No. 4 Brushed Finish — Directional grain appearance for aesthetic applications.
- Mirror / 8K Finish — High-polish reflective surface for food-grade and pharmaceutical uses.
- Pickled & Passivated (P&P) — Enhanced corrosion resistance through chromic acid passivation.
3. Specifications
| Parameter | Specification |
|---|---|
| Product Code | 1207 |
| Product Name | Coil Tube (盘管) |
| Outer Diameter (OD) | 6.0 mm – 50.8 mm (¼" – 2") |
| Wall Thickness | 0.5 mm – 3.0 mm |
| Coil Inner Diameter (ID) | 500 mm – 1,500 mm (adjustable) |
| Coil Weight | 500 kg – 2,500 kg per coil |
| Tube Length per Coil | Custom (up to 500 m continuous) |
| Manufacturing Method | Seamless (Pierced & Cold Drawn) / ERW Welded / TIG Welded |
| Applicable Standards | ASTM A269, ASTM A213, EN 10216-5, GB/T 12771, GB/T 21832 |
| Operating Pressure | Up to 2.5 MPa (373 psi) |
| Operating Temperature Range | −40 °C to +450 °C |
| Corrosion Resistance | Equivalent to ASTM G48 (pitting) / G53 (crevice) testing |
| End Form | Plain Cut / Beveled / Threaded (BSP, NPT, NPSM) |
| Packaging | Wooden pallet, stretch-wrapped, seaworthy export packaging |
| Customization | Available — custom OD, wall thickness, coil diameter, and surface finish |
4. Manufacturing Process
4.1 Seamless Tube Production Route
- Raw Material Inspection — Incoming stainless steel billets are verified via spectroscopic analysis (OES) to confirm alloy composition compliance with ASTM A269 / EN 10216-5 specifications.
- Hot Rolling & Piercing — Billets are heated to 1,150–1,250 °C and pierced on a Mannesmann-type piercing mill to produce hot-rolled seamless tube blanks.
- Hot Elongation — Tube blanks undergo hot elongation (hot cross rolling or continuous rolling) to reduce wall thickness and achieve target dimensions with ±0.1 mm tolerance.
- Acid Pickling & Descaling — The tube is immersed in a mixed acid bath (HNO₃ + HF) at 60–80 °C to remove oxide scale, followed by thorough water rinsing.
- Cold Drawing — Tubes are cold-drawn through tungsten carbide dies with a lubricant (calcium soap or graphite-based) to achieve precise dimensional tolerances (±0.05 mm) and improved surface finish.
- Intermediate Annealing — Periodic solution annealing at 1,050–1,100 °C in a controlled atmosphere (H₂/N₂ mixture) relieves cold-work stresses and restores ductility.
- Final Cold Drawing & Sizing — The final draw pass achieves the target OD, wall thickness, and roundness (eccentricity ≤ 1% of OD).
- Final Annealing & Pickling — Solution annealing followed by acid pickling and passivation to produce the required surface condition.
- Coiling — The finished tube is wound onto a precision coiling machine at controlled tension (typically 2–8 kN) to produce uniform coil geometry without kinking or deformation.
- Non-Destructive Testing (NDT) — Each coil undergoes 100% eddy current testing (ECT) and/or ultrasonic testing (UT) for wall defects, supplemented by hydrostatic pressure testing at 2× operating pressure for 10 seconds.
- Final Inspection & Packaging — Dimensional verification, surface inspection, and material certification (EN 10204 Type 3.1 mill certificate) prior to export-grade packaging.
4.2 Welded Tube Production Route (Alternative)
For larger diameters or specific application requirements, the coil tube may be manufactured via the ERW (Electric Resistance Welding) or TIG (Tungsten Inert Gas) orbital welding process:
- Stainless steel strip is fed through a roll-forming line to form the tube shape.
- The longitudinal seam is welded using ERW (high-frequency resistance) or TIG welding with a shielding gas (Ar/CO₂ mixture).
- The welded tube undergoes solution annealing at 1,050–1,100 °C to homogenize the weld microstructure and restore full corrosion resistance.
- Post-weld pickling and passivation treatment ensures the weld zone achieves equivalent corrosion performance to the base metal.
5. Applications
5.1 HVAC & Fan Coil Unit Systems
The primary application domain for this coil tube is in fan coil unit (FCU) air conditioning systems, where it serves as the heat exchange conduit for chilled or hot water circulation. The coil tube is wound into serpentine or spiral configurations within the FCU air handler, enabling efficient heat transfer between the fluid medium and the airstream. Its compatibility with intelligent temperature controllers (thermostatic valves, electronic expansion valves, and PID-based temperature regulation systems) facilitates precise thermal management, contributing to energy savings of 15–30% compared to conventional control methods.
5.2 Additional Application Domains
- Industrial Heat Exchangers — Shell-and-tube heat exchangers, plate-fin coils, and condenser/evaporator assemblies in chemical processing, power generation, and petrochemical industries.
- Refrigeration & Air Conditioning — Refrigerant tubing in commercial refrigeration systems, cold storage facilities, and automotive AC components.
- Food & Beverage Processing — Sanitary-grade tubing for pasteurization, brewing, dairy processing, and CIP (Clean-in-Place) systems, where 316L grade and mirror finish are specified.
- Pharmaceutical & Biotechnology — Sterilizable tubing for bioreactor cooling loops, pharmaceutical water systems (WFI/PW), and cleanroom HVAC installations.
- Marine & Offshore — Seawater-cooled heat exchanger tubes where 316L grade provides resistance to chloride-induced pitting and crevice corrosion.
- Automotive & Aerospace — Precision tubing for exhaust systems, hydraulic lines, fuel delivery systems, and thermal management circuits.
- Solar Thermal Systems — Heat collection tubes in evacuated tube solar collectors and concentrated solar power (CSP) systems.
6. Quality Certifications & Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification covering manufacturing, inspection, and documentation processes. |
| ISO 14001:2015 | Environmental Management System certification ensuring sustainable manufacturing practices. |
| EN 10204 Type 3.1 | Material Testing Certificate with inspection results specific to each batch/coil. |
| ASTM A269 / A213 | Compliance with American standards for austenitic stainless steel tubing. |
| EN 10216-5 | European standard for stainless steel tubes for heat exchangers and heat transfer equipment. |
| GB/T 12771 / GB/T 21832 | Chinese national standards for welded and seamless stainless steel tubes. |
| NACE MR0175 / ISO 15156 | Resistance to sulfide stress cracking for oil and gas applications (316L grade). |
| CE Marking (PED 2014/68/EU) | Conformity with European Pressure Equipment Directive for pressure-bearing applications. |
| 3-A Sanitary Standards | Food-grade certification for tubing used in dairy, beverage, and pharmaceutical processing. |
7. Unique Selling Points
- Intelligent System Compatibility — Designed for seamless integration with intelligent temperature control systems,