Copper Alloy Sheathed Seamless Coil Tube (Coiltube) — Technical Product Specification
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Product Code: JX-CT-378
Category: Seamless Coil Tube with Copper Alloy Sheathing
1. Product Overview
The Copper Alloy Sheathed Seamless Coil Tube is a high-performance composite tubing product engineered for demanding industrial applications requiring superior thermal conductivity, corrosion resistance, and mechanical integrity. This product combines a seamless stainless steel inner tube with a precision-formed copper alloy outer sheath, delivering a synergistic material system that outperforms conventional monolithic tubing solutions.
Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this coil tube product is supplied in continuous coil form, enabling downstream fabricators to achieve maximum material utilization, minimize waste, and reduce processing time. The seamless construction of the inner tube eliminates weld seams, thereby eliminating potential leak paths and stress concentration points that could compromise long-term reliability.
Key Design Philosophy
- Bi-metallic synergy: The stainless steel core provides structural strength and mechanical durability, while the copper alloy sheath offers exceptional thermal and electrical conductivity.
- Seamless integrity: The absence of longitudinal welds ensures uniform metallurgical properties throughout the tube's cross-section.
- Coil-form economy: Continuous coil supply enables automated straightening, cutting, and forming operations with minimal material loss.
2. Material Composition and Properties
2.1 Inner Tube — Seamless Stainless Steel
The inner tube is fabricated from austenitic stainless steel conforming to recognized international standards. The primary grade utilized is SUS304 / AISI 304 (UNS S30400), with alternative grades including SUS316L / AISI 316L (UNS S31603) available upon request for enhanced chloride resistance.
| Element | C | Mn | P | S | Si | Cr | Ni | N |
|---|---|---|---|---|---|---|---|---|
| Specification | ≤0.08 | ≤2.00 | ≤0.045 | ≤0.030 | ≤1.00 | 18.0–20.0 | 8.0–10.5 | ≤0.10 |
2.2 Outer Sheath — Copper Alloy
The copper alloy sheath is typically fabricated from CuSn6 (Bronze, 6% Tin) or CuZn37 (Brass, 37% Zinc) depending on application requirements. The CuSn6 grade provides superior corrosion resistance in marine and chemical environments, while CuZn37 offers enhanced machinability and cost-effectiveness.
| Element | Cu | Sn | Pb | Zn | Fe | Ag |
|---|---|---|---|---|---|---|
| Specification | Balance (≥93.0) | 5.5–6.5 | ≤0.05 | ≤0.05 | ≤0.05 | ≤0.05 |
2.3 Mechanical Properties
| Property | Inner Tube (SS304) | Outer Sheath (CuSn6) |
|---|---|---|
| Tensile Strength (MPa) | ≥520 | ≥320 |
| Yield Strength (MPa) | ≥205 | ≥160 |
| Elongation (%) | ≥40 | ≥15 |
| Thermal Conductivity (W/m·K, 20°C) | 16.3 | 46.8 |
| Density (g/cm³) | 7.93 | 8.80 |
| Operating Temperature Range (°C) | −196 to +870 | −200 to +260 |
3. Product Specifications
| Parameter | Specification | Tolerance |
|---|---|---|
| Inner Tube Outer Diameter (OD) | 6.0 – 50.8 mm (1/4" – 2") | ±0.10 mm |
| Inner Tube Wall Thickness | 0.5 – 3.0 mm | ±0.05 mm |
| Outer Sheath Wall Thickness | 0.3 – 1.5 mm | ±0.03 mm |
| Overall Outer Diameter | 7.0 – 54.0 mm | ±0.15 mm |
| Coil Length (continuous) | 50 – 500 m per coil | — |
| Coil Inner Diameter | 200 – 600 mm | ±5 mm |
| Coil Outer Diameter | ≤1000 mm | — |
| Surface Finish (Inner Tube) | BA (Bright Annealed) or 2B | Ra ≤ 0.4 μm (BA) |
| Surface Finish (Outer Sheath) | Mirror polish or matte | Ra ≤ 0.2 μm (mirror) |
| End Condition | Plain, beveled, or threaded | Per customer drawing |
| Winding Tolerance | ±1.0 mm layer-to-layer | Uniform winding |
Available Standards
- ASTM A269 / A270 — Stainless Steel Seamless Tubing
- ASTM B751 — Copper Alloy Seamless Tubing
- GB/T 14976 — Chinese National Standard for Stainless Steel Seamless Tubes
- GB/T 2040 — Chinese National Standard for Copper Alloy Tubes
- EN 10216-5 — European Standard for Cold Drawn Tubes
- ISO 1127 — Seamless Tubes of Non-ferrous Metals
4. Manufacturing Process
4.1 Inner Tube — Seamless Production
- Hot Rolling: Stainless steel billets are heated to 1200–1250°C and hot-rolled to form hollow tubes (plugging mill or Mannesmann process).
- Piercing & Elongation: The hot-rolled tube is pierced and elongated to achieve the desired OD and wall thickness.
- Heat Treatment: Solution annealing at 1050–1100°C followed by rapid water quenching to achieve the desired austenitic microstructure and eliminate residual stresses.
- Pickle & Bright Anneal (BA): Acid pickling removes oxide scale; subsequent annealing in a controlled reducing atmosphere produces a clean, bright surface finish.
- Cold Drawing: The tube is cold-drawn through precision dies to achieve final dimensions with tight tolerances and improved mechanical properties.
- Final Annealing: A stress-relief anneal at 850–950°C ensures dimensional stability and optimal ductility.
- Coiling: The finished inner tube is wound onto a precision coil former with controlled tension to prevent deformation.
4.2 Outer Sheath — Forming and Application
- Sheet Preparation: Copper alloy strip is cold-rolled to the required thickness and cleaned to remove oils and contaminants.
- Sheath Forming: The copper strip is precision-formed into a helical or spiral sheath using CNC-controlled forming equipment.
- Bonding/Cladding: The copper sheath is applied to the stainless steel inner tube via one of the following methods:
- Mechanical bonding: Controlled interference fit with cold-expansion or roll-bonding for a metallurgical-free mechanical joint.
- Brazing: Silver-based or phosphorus-bronze brazing alloy is used to create a hermetic metallurgical bond between the two materials.
- Diffusion bonding: High-temperature diffusion bonding in a vacuum or inert atmosphere for maximum interface integrity.
- Dimensional Verification: Each coil undergoes 100% inspection via ultrasonic testing (UT) and optical measurement to verify bond integrity and dimensional accuracy.
- Final Coiling: The completed composite tube is coiled onto shipping coils with protective interlayers and edge protection.
4.3 Quality Control at Each Stage
- Incoming inspection: Spectroscopic analysis (OES) of raw materials; visual and dimensional inspection of billets and strips.
- In-process monitoring: Real-time dimensional feedback during cold drawing; ultrasonic flaw detection during sheath forming.
- Final inspection: Hydrostatic pressure testing, eddy current testing, dimensional gauging, and surface roughness measurement.
5. Applications
The Copper Alloy Sheathed Seamless Coil Tube finds extensive application across multiple high-value industries:
5.1 Heat Exchangers and Thermal Management
- Compact heat exchangers for HVAC (Heating, Ventilation, and Air Conditioning) systems
- Chilled water piping in commercial and industrial refrigeration
- Cryogenic heat exchangers for LNG (Liquefied Natural Gas) processing
- Plate-fin heat exchangers in aerospace thermal management systems
5.2 Chemical and Petrochemical Processing
- Corrosion-resistant heat transfer tubes in chemical reactors
- Condensers and evaporators in petrochemical distillation columns
- Process piping for aggressive chemical environments where both thermal conductivity and corrosion resistance are critical
5.3 Marine and Offshore Applications
- Sea water cooling systems on naval vessels and offshore platforms
- Heat exchangers in marine propulsion systems
- Underwater equipment thermal management
5.4 Food and Pharmaceutical Industry
- CIP (Clean-in-Place) compatible heat exchangers for dairy and beverage processing
- Pharmaceutical sterilization systems requiring hygienic-grade surfaces
- Waste heat recovery in food processing facilities
5.5 Electrical and Electronics
- High-current busbar assemblies requiring both structural support and electrical conductivity
- Thermal management in power electronics and semiconductor manufacturing
6. Quality Certifications and Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications:
| Certification / Standard | Scope | Status |
|---|---|---|
| ISO 9001:2015 | Quality Management System | Certified |
| ISO 14001:2015 | Environmental Management System | Certified |
| ISO 45001:2018 | Occupational Health & Safety Management | Certified |
| EN 10204 | 3.1 Material Test Certificate | Provided per order |
| ASTM A999 |