Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is supplied in continuous coil form, enabling high-efficiency downstream processing through automated forming, cutting, and welding systems. Coil tubes are widely recognized in industrial applications for their superior thermal conductivity, corrosion resistance, and mechanical integrity. The product is designed to meet the rigorous requirements of HVAC (Heating, Ventilation, and Air Conditioning) systems, including Fan Coil Unit (FCU) heat exchangers, refrigeration circuits, and process piping systems.
Wenzhou Jixing Metal Materials Co., Ltd leverages advanced manufacturing infrastructure and a dedicated design calculation and performance analysis software system to ensure that each coil tube product meets exacting dimensional tolerances and performance benchmarks. The integration of computational fluid dynamics (CFD) modeling and thermal performance simulation during the design phase allows for optimized tube geometry, wall thickness, and coil configuration tailored to specific application requirements.
2. Material & Properties
2.1 Material Grades
The coil tube is manufactured from premium-grade austenitic stainless steel, with the following material options available:
- SUS304 / AISI 304 — General-purpose grade with excellent corrosion resistance and weldability
- SUS316 / AISI 316 — Enhanced resistance to chlorides and aggressive chemical environments
- SUS321 / AISI 321 — Stabilized grade with superior resistance to intergranular corrosion at elevated temperatures
2.2 Mechanical Properties
| Property | Specification | Test Method |
|---|---|---|
| Tensile Strength (Rm) | ≥ 520 MPa | ASTM E8 / ASTM E8M |
| Yield Strength (Rp0.2) | ≥ 205 MPa | ASTM E8 / ASTM E8M |
| Elongation (A) | ≥ 40% | ASTM E8 / ASTM E8M |
| Hardness (HBW) | ≤ 210 | ASTM E10 |
| Density | 7.93 g/cm³ | — |
| Thermal Conductivity (at 20°C) | 16.3 W/(m·K) | ASTM E153 |
| Thermal Expansion Coefficient (20–100°C) | 17.3 × 10⁻⁶ /K | ASTM E228 |
2.3 Chemical Composition (SUS304, Typical)
| Element | Content (wt%) |
|---|---|
| C (Carbon) | ≤ 0.08 |
| Si (Silicon) | ≤ 1.00 |
| Mn (Manganese) | ≤ 2.00 |
| P (Phosphorus) | ≤ 0.045 |
| S (Sulfur) | ≤ 0.030 |
| Cr (Chromium) | 18.00 – 20.00 |
| Ni (Nickel) | 8.00 – 10.50 |
3. Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.00 mm – 35.00 mm | ASTM A751 / EN 10217-7 |
| Wall Thickness (WT) | 0.30 mm – 2.00 mm | ASTM A751 / EN 10217-7 | OD Tolerance | ±0.10 mm | — |
| WT Tolerance | ±0.05 mm | — |
| Coil Inner Diameter (ID) | 300 mm – 600 mm | — |
| Coil Length per Spool | 500 m – 3,000 m | — |
| Surface Finish | 2B (Cold Rolled and Annealed) or BA (Bright Annealed) | ASTM A480 |
| Surface Roughness (Ra) | ≤ 0.4 μm (BA finish) | ASTM E1927 |
| End Condition | Plain cut, beveled, or pre-flanged | — |
| Operating Temperature Range | −196°C to +870°C (SUS304) | ASME BPV Code Section II |
| Maximum Working Pressure | Up to 6.0 MPa (design-dependent) | ASME B31.3 |
| Welding Compatibility | GTAW (TIG), OAW (MIG), SAW, Resistance Welding | ASME Section IX |
4. Manufacturing Process
The production of Wenzhou Jixing's stainless steel coil tubes follows a rigorous, multi-stage manufacturing process designed to ensure dimensional precision, metallurgical integrity, and surface quality:
- Raw Material Procurement: High-purity stainless steel strip is sourced from certified mills, with each batch accompanied by a mill test certificate (MTC) verifying chemical composition and mechanical properties.
- Strip Inspection & Preparation: Incoming strip undergoes visual inspection, thickness measurement via ultrasonic testing (UT), and surface defect screening using automated optical systems. Any material outside specification is rejected.
- Forming (Tube Milling): The flat strip is fed through a series of progressive roll sets in a rotary draw bending (RDB) or plug forming mill. This cold-forming process shapes the strip into a seamless circular tube with precise OD and WT control.
- Seam Welding: A high-frequency induction (HFI) welding process is employed to create a full-penetration, metallurgically sound longitudinal seam. The weld zone is heat-treated in-situ to restore the austenitic microstructure and prevent sensitization.
- Heat Treatment (Solution Annealing): Tubes are solution-annealed at 1,050°C – 1,100°C followed by rapid quenching to dissolve carbides and restore maximum corrosion resistance and ductility.
- Precision Sizing & Straightening: Post-annealing tubes pass through a sizing mill to achieve final dimensional tolerances. A straightening station eliminates any residual curvature from the coil winding process.
- Surface Finishing: For BA (Bright Annealed) finish, tubes undergo pickling and passivation in a controlled atmosphere furnace (dew point ≤ −60°C). This produces a smooth, oxide-free surface with Ra ≤ 0.4 μm.
- Coiling & Packaging: Finished tubes are wound onto precision-machined coil drums, wrapped with protective film, and packed in moisture-proof containers with desiccants for shipment.
5. Applications
The stainless steel coil tube is engineered for demanding industrial and commercial applications where corrosion resistance, thermal efficiency, and long service life are paramount:
- Fan Coil Units (FCU) & Air Handling Units (AHU): Used as the primary heat exchanger tube in HVAC systems. The coil tube configuration enables compact, high-surface-area designs that maximize heat transfer coefficients while minimizing pressure drop.
- Refrigeration & Air Conditioning Systems: Employed in evaporator and condenser coils for commercial and industrial refrigeration plants, where resistance to ammonia, refrigerants, and condensate corrosion is critical.
- Food Processing & Beverage Industry: Compliant with FDA 21 CFR and EU 1935/2004 regulations for food-contact applications, including pasteurization systems, brewing equipment, and dairy processing lines.
- Pharmaceutical Manufacturing: Suitable for clean-in-place (CIP) systems, clean steam lines, and process piping where hygienic surface quality (Ra ≤ 0.4 μm) is mandatory.
- Chemical & Petrochemical Industry: SUS316 grade tubes are utilized in aggressive chemical environments, including chloride-containing solutions, acid processing, and desalination systems.
- Power Generation: Applied in condensers, feedwater systems, and waste heat recovery units in thermal and nuclear power plants.
- Marine & Offshore Engineering: Resistant to seawater corrosion in ballast systems, desalination plants, and offshore platform piping.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system and holds the following certifications and complies with the following standards:
6.1 Quality Management Certifications
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- ISO 45001:2018 — Occupational Health and Safety Management System
6.2 Product Standards & Compliance
| Standard | Scope |
|---|---|
| ASTM A751 | Standard Specification for Stainless Steel Shapes, Sheet, Plate, and Strip |
| ASTM A213 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for High-Temperature Service |
| EN 10217-7 | Non-alloy and Alloy Steel Tubes for Pressure Purposes — Heat-Resistant Tubes |
| ASME BPV Code Section II, Part D | Material Specifications for Boilers and Pressure Vessels |
| ASME B31.3 | Process Piping Design Code |
| GB/T 17895 | Chinese National Standard for Seamless Stainless Steel Tubes for Heat Exchangers |
| GB/T 4237 | Chinese National Standard for Cold-Rolled Stainless Steel Strip |
6.3 Testing & Inspection
- Dimensional Inspection: 100% automated measurement of OD, WT, and straightness using laser and ultrasonic gauging systems
- Hydrostatic Testing: Each coil is pressure-tested at 1.5× the maximum working pressure to verify seam integrity
- Eddy Current Testing (ECT): Non-destructive testing (NDT) of the weld seam to detect internal and surface defects
- Spectroscopic Analysis: XRF (X-Ray Fluorescence) verification of chemical composition for each production lot
- Hardness Testing: Rockwell B (HRB) or Vickers (HV) hardness verification per ASTM E92 / ASTM E18
- Pickling & Passivation Testing: Surface oxide removal and passive film integrity verification per ASTM A967
7. Unique Selling Points
- Design Optimization Software Integration: Wenzhou Jixing utilizes a proprietary Fan Coil Unit Design Calculation and Performance Analysis Software System to model heat transfer performance, pressure drop, and flow distribution prior to production. This computational approach ensures that coil tube geometry is optimized for the target thermal duty, resulting in energy-efficient heat exchanger assemblies with validated performance predictions.
- Seamless-Coil Hybrid Advantage: The combination of HFI welding technology with solution annealing produces a weld zone that achieves near-seamless metallurgical equivalence, eliminating the mechanical and corrosion weaknesses typically associated with welded tubing.
- Precision Dimensional Control: Automated in-line gauging and closed-loop roll adjustment maintain OD and WT tolerances within ±0.05 mm, enabling the use of tighter clearances in heat exchanger tube sheets and reducing leakage risks.
- Wide Range of Configurations: Availability in multiple material grades, diameters, wall thicknesses, and surface finishes provides flexibility for custom engineering solutions across diverse industries.
- Full Traceability: Each coil is assigned a unique heat number and batch code, with complete documentation of raw material origin, processing parameters, and test results, ensuring full supply chain traceability and compliance with industry audit requirements.
Note: All specifications listed in this document are representative values. Specific product dimensions, tolerances, and material grades should be confirmed through a formal technical inquiry with Wenzhou Jixing Metal Materials Co., Ltd. Custom specifications are available upon request, subject to engineering review and approval.