Stainless Steel Coil Tube — Product Technical Specification

1. Product Overview

The Stainless Steel Coil Tube (Coil Tube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered continuous-length tubular product supplied in coiled form. This product serves as a critical raw material and intermediate component across multiple industrial sectors, including HVAC&R (Heating, Ventilation, Air Conditioning, and Refrigeration), heat exchanger fabrication, fan coil unit assembly, and process piping systems. The coil tube is available in seamless and welded configurations, rolled into tight coils to facilitate downstream processing, storage efficiency, and continuous feeding into automated manufacturing lines.

This product is specifically engineered to meet the demanding thermal, mechanical, and corrosion-resistance requirements of modern heat exchange applications, including card-type exposed fan coil units with dual-blow and four-blow configurations, where compactness, thermal conductivity, and long-term durability are paramount.

2. Material & Properties

2.1 Available Grades

2.2 Key Mechanical Properties (Annealed Condition)

3. Specifications

Parameter Specification Range
Outer Diameter (OD) 3.0 mm – 50.8 mm (custom sizes available)
Wall Thickness (WT) 0.3 mm – 3.0 mm
Inner Diameter (ID) 2.4 mm – 47.8 mm (derived from OD and WT)
Coil Length 50 m – 500 m per coil (standard); custom lengths available
Coil Weight 50 kg – 500 kg per coil
Coil Inner Diameter 150 mm – 300 mm (standard)
Dimensional Tolerance — OD ±0.1 mm to ±0.3 mm (per ISO 6508 / ASTM A554)
Dimensional Tolerance — WT ±10% of nominal wall thickness
Surface Finish Bright Annealed (BA), No. 4 Brushed, No. 8 Mirror, Pickled & Passivated
Surface Roughness (Ra) 0.2 μm – 1.6 μm (depending on finish grade)
Manufacturing Method Seamless (Piercing & Pilger) or Welded (ERW — Electric Resistance Welding)
Heat Treatment Solution Annealing at 1050°C – 1150°C followed by rapid quench
Delivery Condition Coiled, annealed, pickled, passivated, and protected with VCI (Vapor Corrosion Inhibitor) film
Applicable Standards ASTM A554 / A269, EN 10216-5, ISO 6508, GB/T 14976, JIS G3446
Minimum Order Quantity 500 kg (subject to stock availability)

4. Manufacturing Process

4.1 Seamless Coil Tube Production

  1. Raw Material Selection: High-purity stainless steel ingots or continuous-cast billets are selected with strict chemical composition control (C ≤ 0.08% for standard grades; C ≤ 0.03% for L-grades).
  2. Hot Rolling: Billets are heated to 1200°C–1300°C and hot-rolled into hollow tubes with controlled wall thickness and outer diameter.
  3. Pilger Milling / Cross Rolling: Tubes are further reduced in diameter and wall thickness using pilger or cross-rolling mills to achieve precise dimensional tolerances.
  4. Piercing: For seamless production, solid billets are pierced to form hollow tubes, followed by multiple reduction passes.
  5. Solution Annealing: Tubes are reheated to 1050°C–1150°C in a controlled atmosphere furnace to dissolve carbides and restore full austenitic microstructure, then rapidly quenched.
  6. Pickling & Passivation: Surface scale and oxide layers are removed via acid pickling (nitric/hydrofluoric acid blend), followed by passivation to restore the chromium oxide protective layer.
  7. Coiling: Finished tubes are coiled onto mandrels at controlled tension to prevent kinking or deformation. Coils are wound to specified inner diameters with consistent pitch.
  8. Quality Inspection: Each coil undergoes ultrasonic testing (UT), hydrostatic testing (pressure testing), chemical composition analysis, and dimensional verification.

4.2 Welded Coil Tube Production (ERW)

  1. Strip Coiling: Cold-rolled stainless steel strip of specified width and thickness is uncoiled and fed into the welding mill.
  2. Forming: The flat strip is progressively formed into a tubular shape using a series of roll stands.
  3. Edge Trimming: Strip edges are trimmed to remove scale and irregularities for a clean weld zone.
  4. Electric Resistance Welding (ERW): High-frequency current is applied to the forming edges, heating them to welding temperature (approximately 1250°C–1350°C). The edges are pressed together to form a full-penetration weld seam.
  5. Weld Heat-Affected Zone Treatment: The weld zone is annealed or heat-treated to restore mechanical properties and corrosion resistance.
  6. Final Annealing, Pickling & Passivation: Identical to seamless process steps.
  7. Coiling & Inspection: As per seamless process.

5. Applications

5.1 HVAC&R — Fan Coil Unit Manufacturing

Stainless steel coil tubes are extensively used in the fabrication of card-type exposed fan coil units, including dual-blow and four-blow configurations. These units utilize the coil tube as the primary heat exchange element, where chilled or heated water circulates through the tube while air is blown across the tube surfaces. The high thermal conductivity and corrosion resistance of stainless steel ensure efficient heat transfer and long service life, even in environments with high humidity or chemical exposure. The coil form allows for continuous tube-rolling machines to form precise U-bends and serpentine coil patterns at high production rates.

5.2 Additional Application Domains

6. Quality Certifications & Compliance

Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems to ensure product conformity with international standards:

7. Unique Selling Points

Technical Note: All specifications listed in this document represent standard offerings. Custom specifications, including non-standard alloy compositions, special surface treatments, and bespoke coil configurations, are available upon submission of detailed engineering requirements to the Wenzhou Jixing Metal Materials Co., Ltd. technical sales team.