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

Product Series: Coil Tube (盘管)  |  Catalog No.: 322  |  Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.

1. Product Overview

The Stainless Steel Coil Tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered, continuously wound tubular product designed for high-performance fluid conveyance, heat exchange, and structural applications across industrial, commercial, and residential sectors. Unlike traditional straight-length stainless steel tubes, coil tubes are delivered in continuous helical or spiral form, eliminating the need for field cutting, welding, or joint assembly — thereby reducing labor costs, minimizing leak risks, and ensuring seamless hydraulic integrity throughout the system life cycle.

Coil tubes are widely utilized in HVAC (Heating, Ventilation, and Air Conditioning) systems, hydronic piping networks, refrigeration circuits, solar thermal collectors, process instrumentation, and medical gas distribution. The product line encompasses a broad range of outer diameters (OD), wall thicknesses, and coil diameters tailored to specific engineering requirements.

2. Material Composition & Mechanical Properties

2.1 Available Grades

2.2 Mechanical Properties (Representative Values for Annealed Condition)

Property AISI 304 / 304L AISI 316 / 316L AISI 321 AISI 310S
Tensile Strength (Rm), MPa ≥ 520 ≥ 520 ≥ 515 ≥ 515
Yield Strength (Rp0.2), MPa ≥ 205 ≥ 205 ≥ 205 ≥ 205
Elongation (A50), % ≥ 40 ≥ 40 ≥ 40 ≥ 40
Hardness (HBW) ≤ 217 ≤ 217 ≤ 217 ≤ 217
Density, g/cm³ 7.93 8.00 7.93 8.00
Thermal Conductivity (20 °C), W/(m·K) 16.3 14.6 16.3 15.0
Maximum Service Temperature, °C 870 (oxidizing) 870 (oxidizing) 900 1150

2.3 Chemical Composition (Maximum Limits, wt%)

Element C Cr Ni Mn P S Mo Ti
AISI 304 0.08 18.0–20.0 8.0–10.5 2.0 0.045 0.030 — —
AISI 304L 0.03 18.0–20.0 8.0–10.5 2.0 0.045 0.030 — —
AISI 316 0.08 16.0–18.0 10.0–14.0 2.0 0.045 0.030 2.0–3.0 —
AISI 316L 0.03 16.0–18.0 10.0–14.0 2.0 0.045 0.030 2.0–3.0 —
AISI 321 0.08 17.0–19.0 9.0–12.0 2.0 0.045 0.030 — 5×(C−0.02)+0.40–1.00
AISI 310S 0.08 24.0–26.0 19.0–22.0 2.0 0.045 0.030 — —

3. Technical Specifications

Parameter Specification Range Standard / Reference
Outer Diameter (OD) 3.0 mm – 51.0 mm (1/8" – 2") ASTM A778 / EN 10217-7
Wall Thickness 0.30 mm – 3.00 mm ASTM A778 / EN 10217-7
Coil Diameter (Mean) 0.30 m – 3.00 m (customizable) Manufacturer's specification
Coil Length 50 m – 300 m per coil (continuous) Manufacturer's specification
Surface Finish 2B, BA (Bright Annealed), No. 4 Brushed, Mirror (8K) ASTM A480
Surface Roughness (Ra) 0.2 μm – 1.6 μm (BA finish); ≤ 0.4 μm (Mirror finish) ISO 1302
Tolerance on OD ± 0.05 mm (fine tolerance); ± 0.10 mm (standard) ASTM A778
Tolerance on Wall Thickness ± 0.03 mm (fine tolerance); ± 0.05 mm (standard) ASTM A778
Operating Pressure Up to 4.0 MPa (design dependent on OD × WT) ASME B31.3 / B31.9
Operating Temperature −196 °C (Cryogenic) to +870 °C (Oxidizing atmosphere) Grade-dependent
Heat Treatment Full Annealing (1010–1150 °C + Air/Water Quench) ASTM A778
Packaging Plastic film wrapped, wooden pallet, export-grade seaworthy packing ISO 4180

4. Manufacturing Process

The production of stainless steel coil tubes at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorously controlled, multi-stage process ensuring dimensional accuracy, metallurgical integrity, and surface quality:

  1. Raw Material Selection: High-purity stainless steel strip (cold-rolled coil) is sourced from certified mills, with each batch accompanied by a Mill Test Certificate (MTC) verifying chemical composition and mechanical properties per ASTM/EN standards.
  2. Strip Inspection & Slitting: Incoming strip undergoes visual inspection, eddy current testing (ECT), and dimensional verification. The coil is slit to the required width with precision slitting machines to minimize edge defects and ensure uniform thickness across the strip.
  3. Tube Forming (Cold Roll Forming): The slitted strip is fed through a series of progressively shaped roll stations in a cold roll forming machine. Each station incrementally bends the strip into a tubular cross-section, achieving precise OD and wall thickness without plastic deformation or cracking.
  4. Seam Welding (TIG / Laser Welding): The formed tube seam is welded using either Gas Tungsten Arc (GTAW/TIG) welding or high-power fiber laser welding. Laser welding offers superior weld aesthetics, narrower heat-affected zones (HAZ), and faster production rates. Argon shielding gas is employed on both inside and outside of the seam to prevent oxidation.
  5. In-line Annealing: The welded tube passes through a controlled-temperature annealing furnace (typically 1010–1150 °C) to relieve residual welding stresses, restore full austenitic microstructure, and enhance corrosion resistance. The cooling rate is carefully controlled to prevent sensitization.
  6. Pickling & Passivation: Annealed tubes are immersed in a mixed acid solution (HNO₃ + HF or HNO₃ + HCl) to remove oxide scale (pickling), followed by nitric acid passivation to establish a uniform, protective chromium oxide layer (Cr₂O₃) on the surface.
  7. Surface Finishing: Depending on specification, tubes may undergo mechanical polishing (BA finish) or electrolytic polishing (EP) to achieve mirror-grade surface roughness (Ra ≤ 0.4 μm) for hygienic applications.
  8. Coiling & Winding: The finished tube is wound onto a precision coiling drum to form the final coil tube geometry. Coil diameter and winding tension are controlled to prevent kinking, flattening, or permanent deformation during storage and transportation.
  9. Final Quality Control: Each coil undergoes 100% inspection including: hydrostatic pressure testing (to verify weld integrity and absence of leaks), dimensional measurement (OD, WT, coil diameter), surface inspection (visual + magnetic particle inspection for weld defects), and optional spectral analysis (PMI) for material verification.

5. Applications

5.1 HVAC & Refrigeration Systems

Coil tubes serve as the primary heat exchange medium in fan coil units (FCUs), air handling units (AHUs), chiller systems, and refrigeration evaporators/condensers. The continuous coil form eliminates field joints, ensuring leak-free operation and optimal thermal transfer efficiency. In BIM (Building Information Modeling)-integrated HVAC design workflows, coil tube specifications are directly linked to digital building models, enabling automated pipe routing, clash detection, and material take-off calculations.

5.2 Hygienic & Pharmaceutical Piping

BA-finished and electrolytically polished coil tubes in AISI 316L grade are extensively used in pharmaceutical cleanroom piping, bioprocessing systems, and CIP (Clean-in-Place)/SIP (Sterilize-in-Place) circuits. The smooth surface finish minimizes microbial adhesion and facilitates complete drainage.

5.3 Food & Beverage Processing

Used in brewing equipment, dairy processing lines, juice pasteurization circuits, and bottling plant utility piping. AISI 304/304L coil tubes provide excellent resistance to organic acids and cleaning chemicals.

5.4 Solar Thermal & Geothermal Systems

Coil tubes are integral to evacuated tube solar collectors and ground-source heat exchanger loops. The flexible coil geometry facilitates compact installation in collector arrays and borehole heat exchangers.

5.5 Medical & Laboratory Gas Distribution

Low-pressure medical gas (oxygen, nitrogen, medical air) distribution systems utilize seamless coil tubes to ensure contamination-free gas delivery throughout hospital environments.

5.6 Process Instrumentation & Analytical Equipment

Capillary tubes and sample lines in chromatography systems, mass spectrometers, and process analyzers require ultra-clean, leak-tight stainless steel tubing delivered in coil form for flexible routing.

5.7 Automotive & Aerospace

Used in fuel lines, brake hydraulic circuits, turbo