Stainless Steel Coil Tube (Coiltube) — Wenzhou Jixing Metal Materials Co., Ltd.

Product Code: 1608  |  Category: Literature Learning / Technical Reference  |  Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. (温州吉兴金属材料有限公司)

1. Product Overview

The Stainless Steel Coil Tube (Coiltube) is a precision-engineered continuous stainless steel tubing product wound into a controlled coil configuration, designed primarily for integration into Fan Coil Units (FCU), heat exchangers, refrigeration systems, and industrial thermal management applications. As a critical component in air-conditioning and ventilation (ACV) systems, the coil tube serves as the heat transfer medium, facilitating efficient thermal exchange between circulating refrigerant or water and ambient air.

Wenzhou Jixing Metal Materials Co., Ltd. specializes in the production and supply of high-grade stainless steel coil tubes that meet international standards for dimensional accuracy, corrosion resistance, and mechanical integrity. The company's coil tube products are engineered to address the evolving demands of the HVAC industry, particularly in enhancing the performance, durability, and energy efficiency of domestically manufactured fan coil unit systems.

2. Material & Properties

2.1 Base Materials

2.2 Key Physical Properties (Typical for Grade 304)

Property Value
Density 8.0 g/cm³
Melting Point 1400–1450 °C
Thermal Conductivity (at 100 °C) 16.3 W/(m·K)
Specific Heat Capacity 0.50 J/(g·K)
Thermal Expansion Coefficient (20–100 °C) 17.3 × 10⁻⁶ /°C
Young's Modulus 193 GPa
Poisson's Ratio 0.29

2.3 Mechanical Properties (Typical for Grade 304, Annealed Condition)

Property Value
Tensile Strength (Rm) ≥ 520 MPa
Yield Strength (Rp0.2) ≥ 205 MPa
Elongation (A50) ≥ 40 %
Hardness (HV) ≤ 210 HV
Impact Energy (Charpy V-notch, 20 °C) ≥ 47 J

3. Specifications

3.1 Dimensional Specifications

Parameter Specification Tolerance
Outer Diameter (OD) Φ 3.00 mm – Φ 12.70 mm ± 0.05 mm
Wall Thickness (WT) 0.30 mm – 1.00 mm ± 0.03 mm
Coil Length (per coil) 50 m – 500 m (configurable) ± 2 %
Coil Inner Diameter (Dcoil) Φ 200 mm – Φ 600 mm ± 5 mm
Surface Finish Bright Annealed (BA) / Pickled & Passivated Ra ≤ 0.4 μm
End Condition Deburred, cut square ± 1° —

3.2 Commonly Available Configurations

Designation OD (mm) WT (mm) Grade Typical Application
CT-3.0×0.5 3.00 0.50 304 Residential FCU, domestic refrigeration
CT-4.0×0.5 4.00 0.50 304 Commercial FCU, air-source heat pumps
CT-6.0×0.5 6.00 0.50 304 Industrial heat exchangers
CT-6.35×0.6 6.35 0.60 316 Marine HVAC, chemical processing
CT-8.0×0.8 8.00 0.80 304 Large-capacity FCU, industrial chiller
CT-10.0×0.8 10.00 0.80 321 High-temperature process heat exchangers
CT-12.7×1.0 12.70 1.00 316L Heavy-duty industrial applications

3.3 Applicable Standards

4. Manufacturing Process

The production of high-quality stainless steel coil tubes involves a multi-stage process requiring precise control over each step to ensure dimensional accuracy, metallurgical integrity, and surface quality.

4.1 Process Flow

  1. Raw Material Preparation: High-purity stainless steel wire rod (typically supplied in coils) is inspected for chemical composition compliance via Spectroscopic Analysis (Optical Emission Spectrometry — OES). Only certified grades meeting ASTM/EN/GB standards are accepted.
  2. Wire Drawing (Cold Drawing): The wire rod is cold-drawn through precision-die tooling (tungsten carbide or diamond dies) to achieve the target outer diameter and wall thickness. Multiple drawing passes may be required to achieve fine tolerances (± 0.03 mm). This process induces work hardening, improving the mechanical strength of the tube.
  3. Bright Annealing (BA): The cold-drawn tube is annealed in a controlled atmosphere (nitrogen or vacuum) at temperatures between 1050 °C and 1150 °C. This process relieves internal stresses, restores ductility, and produces a clean, bright, oxide-free surface finish without the need for subsequent pickling.
  4. Precision Sizing & Straightening: Post-annealing, the tube passes through a sizing block to refine dimensional tolerances and a straightening station to eliminate any residual curvature introduced during the annealing and cooling process.
  5. Coil Winding: The straightened tube is wound onto a precision-wound coil spool at controlled tension to prevent kinking, deformation, or surface damage. The winding process ensures uniform layer stacking and minimal inter-coil contact stress.
  6. End Processing: Tube ends are cut to square, deburred, and chamfered to facilitate downstream insertion into fittings, headers, or brazing/welding operations.
  7. Hydrostatic Testing: Each coil undergoes 100% hydrostatic pressure testing at a minimum of 2.0 × working pressure (typically 6.0–10.0 MPa) to verify integrity and freedom from porosity or defects.
  8. Surface Passivation: A final acid pickling and passivation treatment (using nitric/hydrofluoric acid blend) removes any residual iron contamination and establishes a protective chromium oxide layer, enhancing corrosion resistance.
  9. Final Inspection & Packaging: Each coil is subjected to dimensional verification (OD, WT via ultrasonic thickness gauge), visual surface inspection, and chemical composition spot-check. Approved coils are wrapped in protective film, packed in wooden or steel crates, and labeled with material certificates.

4.2 Quality Control Checkpoints

Stage Inspection Method Acceptance Criteria
Incoming Wire Rod OES Spectroscopy, Visual Chemical composition within ASTM/GB limits
Post-Drawing OD/WT Measurement, Roundness Check Dimensional tolerance ± 0.05 mm
Post-Annealing Metallographic Examination, Surface Finish Grain size ≥ ASTM E112 No. 6; Ra ≤ 0.4 μm
Hydrostatic Test 100% Pressure Test No leakage at 6.0–10.0 MPa for 10 seconds
Final Output UT Thickness, Chemical Verification Full compliance with purchase order specifications

5. Applications

The stainless steel coil tube from Wenzhou Jixing Metal Materials Co., Ltd. finds extensive application across multiple industries, with the following being the primary end-use sectors:

5.1 HVAC — Fan Coil Units (FCU)

This is the primary application domain. The coil tube serves as the core heat exchanger element in fan coil units used in commercial buildings, hotels, hospitals, and residential complexes. The tube is typically brazed or soldered into a serpentine configuration within the FCU's air handler, where chilled water or hot water circulates through the tube while a fan blows air across the fins, achieving space heating or cooling. Key performance advantages include:

5.2 Refrigeration & Air Conditioning