Stainless Steel Coil Tube (Coiltube) — Product No. 428
1. Product Overview
The Stainless Steel Coil Tube (Coiltube), Product No. 428, manufactured by Wenzhou Jixing Metal Materials Co., Ltd, is a precision-engineered continuous-length tubular product supplied in a wound coil configuration. Unlike traditional straight-length seamless or welded pipes, coil tubes are delivered in a continuous spiral form, offering significant advantages in downstream processing efficiency, material utilization, and inventory management. The product is designed to serve a broad spectrum of industrial, commercial, and consumer applications, with particular emphasis on thermal-fluid transfer systems including air-source heat pump fan coil heating systems, where adaptive variable-water-temperature control methodologies have demonstrated superior energy efficiency.
The coil tube form factor enables uninterrupted production runs in downstream forming, bending, and machining operations, thereby minimizing weld joints, reducing material waste, and enhancing structural integrity over extended lengths. This continuous supply capability positions the product as a preferred substrate in high-throughput manufacturing environments.
2. Material & Properties
2.1 Base Material
The coil tube is fabricated from austenitic stainless steel, predominantly conforming to the following standard grades:
- ASTM A213 TP304 / TP304L — General-purpose austenitic grade offering excellent corrosion resistance, formability, and weldability
- ASTM A213 TP316 / TP316L — Molybdenum-enhanced grade providing superior resistance to pitting and crevice corrosion in aggressive environments
- ASTM A213 TP321 / TP347 — Stabilized grades (Ti-stabilized / Nb-stabilized) suitable for elevated-temperature service conditions
2.2 Mechanical Properties
| Property | 304 / 304L Grade | 316 / 316L Grade | 321 Grade |
|---|---|---|---|
| Tensile Strength (ASTM) | ≥ 515 MPa (74,750 psi) | ≥ 515 MPa (74,750 psi) | ≥ 515 MPa (74,750 psi) |
| Yield Strength (0.2% Offset) | ≥ 205 MPa (29,750 psi) | ≥ 205 MPa (29,750 psi) | ≥ 205 MPa (29,750 psi) |
| Elongation (50 mm gauge) | ≥ 40% | ≥ 40% | ≥ 35% |
| Density | 8.0 g/cm³ | 8.0 g/cm³ | 8.0 g/cm³ |
| Thermal Conductivity (at 100°C) | 16.3 W/(m·K) | 16.3 W/(m·K) | 14.2 W/(m·K) |
| Maximum Service Temperature | 870°C (1,598°F) | 870°C (1,598°F) | 900°C (1,652°F) |
2.3 Chemical Composition (Typical)
| Element | 304 / 304L | 316 / 316L | 321 |
|---|---|---|---|
| Carbon (C) | ≤ 0.08% (L: ≤ 0.03%) | ≤ 0.08% (L: ≤ 0.03%) | ≤ 0.08% |
| Chromium (Cr) | 18.0 – 20.0% | 16.0 – 18.0% | 17.0 – 19.0% |
| Nickel (Ni) | 8.0 – 10.5% | 10.0 – 14.0% | 9.0 – 12.0% |
| Molybdenum (Mo) | — | 2.0 – 3.0% | — |
| Titanium (Ti) | — | — | 5×C to 0.70% |
| Iron (Fe) | Balance | Balance | Balance |
3. Specifications
| Parameter | Specification / Range |
|---|---|
| Product Designation | Stainless Steel Coil Tube (Coiltube), Product No. 428 |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd |
| Outer Diameter (OD) | 6.0 mm – 108.0 mm (customizable upon request) |
| Wall Thickness | 0.3 mm – 6.0 mm (customizable upon request) |
| Coil Width (Coil Body) | Up to 1,200 mm |
| Coil Weight | Up to 3,000 kg per coil |
| Surface Finish | Ba’red (Bright Annealed & Pickled), No. 1, No. 4, or Custom |
| Tolerance on OD | ± 0.10 mm (standard); ± 0.05 mm (precision grade) |
| Tolerance on Wall Thickness | ± 10% (standard); ± 5% (precision grade) |
| Manufacturing Method | Hot-Formed Extrusion (HFE), Cold-Drawn, or Welded (per ASTM A213 / ASME SA-213) |
| Heat Treatment | Solution Annealed (1050°C – 1150°C) followed by controlled cooling |
| Testing Standards | ASTM A213, ASME SA-213, EN 10216-5, GB/T 13296 |
| Packaging | Wooden pallet with steel banding, VCI (Volatile Corrosion Inhibitor) wrap, seaworthy export packaging available |
| Delivery Form | Continuous coil (spiral wound), ready for automated downstream processing |
4. Manufacturing Process
The production of stainless steel coil tubes at Wenzhou Jixing Metal Materials Co., Ltd follows a rigorously controlled multi-stage manufacturing workflow:
- Raw Material Selection & Inspection: High-purity austenitic stainless steel strip or rod stock is sourced from certified mills. Incoming materials undergo spectroscopic analysis (Optical Emission Spectrometry, OES) to verify chemical composition compliance with ASTM and equivalent standards.
- Forming & Welding (for welded coil tubes): Pre-formed strip is fed through precision roll-forming stations to achieve the target outer diameter. A longitudinal seam is created using Automatic Submerged Arc Welding (ASAW) or Automatic Metal Inert Gas Welding (AMIG), followed by in-line weld inspection via Ultrasonic Testing (UT) or Eddy Current Testing (ECT).
- Hot-Formed Extrusion (for seamless coil tubes): Billet stock is heated to forging temperature and extruded through a calibrated die set to produce seamless tube blanks. This method eliminates weld seams entirely, yielding superior metallurgical homogeneity and pressure containment performance.
- Cold Drawing & Sizing: The formed tube blank is drawn through a series of progressively reducing dies to achieve the final outer diameter and wall thickness with tight dimensional tolerances. This process also introduces beneficial work-hardening and improved surface finish.
- Solution Annealing & Pickling: Tubes are heat-treated at temperatures between 1,050°C and 1,150°C in a controlled-atmosphere furnace to dissolve carbide precipitates and restore full austenitic microstructure. Subsequent acid pickling removes oxide scale, yielding a clean, corrosion-resistant surface. Bright Annealing & Pickling (B&P) is employed for applications requiring superior surface aesthetics.
- Coiling & Spooling: The finished tube is wound onto precision-engineered coil spools using a controlled tension system to prevent kinking, ovality, or surface damage. Coil geometry is optimized for compatibility with downstream automated forming equipment.
- Final Quality Assurance: Each coil undergoes non-destructive testing (NDT), dimensional verification, hydrostatic pressure testing (as applicable), and surface inspection before being approved for release.
5. Applications
The versatility of the stainless steel coil tube (Product No. 428) enables deployment across a wide range of engineering domains:
- Thermal-Fluid Transfer Systems: Primary application in air-source heat pump fan coil heating systems, where the coil tube serves as the heat exchange element. The continuous coil form supports efficient manufacturing of serpentine heat exchangers with optimized flow channel geometry, enabling adaptive variable-water-temperature control for enhanced thermal performance and energy efficiency.
- Automotive & Transportation: Fuel lines, brake lines, air conditioning tubing, and exhaust system components where corrosion resistance and high-temperature tolerance are critical.
- Petroleum & Chemical Processing: Process piping, heat exchanger tubes, and instrumentation lines in environments requiring resistance to chloride-induced stress corrosion cracking (SCC).
- Food & Beverage Industry: Sanitary process lines, brewing equipment, and dairy processing systems requiring compliance with FDA and 3-A sanitary standards.
- Building & Construction: Structural handrails, decorative elements, and plumbing fixtures where aesthetic finish and long-term durability are paramount.
- Medical & Pharmaceutical: Sterilizable process tubing, equipment frames, and instrument housings requiring biocompatibility and ease of cleaning.
- Household Appliances: Water heater coils, washing machine drainage tubing, and range hood components leveraging the coil tube's formability and corrosion resistance.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework ensuring product conformity to international standards:
- ISO 9001:2015 — Quality Management Systems certification, certifying consistent process control and continuous improvement protocols across all manufacturing operations.
- ISO 14001:2015 — Environmental Management Systems certification, demonstrating commitment to sustainable and environmentally responsible production practices.
- ISO 45001:2018 — Occupational Health and Safety Management Systems certification.
- CE Marking (EU) — Conformity with European Union directives for products intended for the European Economic Area.
- EN 10204 3.1 Certificates — Third-party inspection and material certification for each shipment, providing traceability from raw material to finished product.
- Mill Test Reports (MTR) — Comprehensive documentation of chemical composition, mechanical properties, and heat treatment parameters for every production lot.
- NDT Certification — Personnel and equipment certified to ASTM E164 (Ultrasonic Testing) and ASTM E309 (Eddy Current Testing) standards.
7. Unique Selling Points
The Stainless Steel Coil Tube (Product No. 428) distinguishes itself in the competitive landscape through the following value propositions:
- Continuous-Length Efficiency: The coil delivery format eliminates butt-weld joints inherent in straight-length pipe, reducing material waste by up to 15% and enhancing structural continuity for pressure-containing applications.
- Thermal System Optimization: Specifically engineered for integration into air-source heat pump fan coil heating systems, the coil tube geometry supports adaptive variable-water-temperature control methodologies, achieving coefficient of performance (COP) improvements of 8–12% over conventional fixed-temperature designs.
- Precision Dimensional Control: Tolerances as tight as ± 0.05 mm on outer diameter and ± 5% on wall thickness ensure drop-in compatibility with high-precision downstream assembly operations without secondary machining.
- Material Versatility: Availability in 304, 316, 321, and 347 grades provides engineering flexibility to match specific corrosion, temperature, and mechanical performance requirements.
- End-to-End Traceability: Every coil is accompanied by full material traceability documentation from mill heat number through to final inspection, satisfying the most stringent procurement and regulatory requirements.
- Customization Capability