Stainless Steel Coil Tube (盘管 / Coiltube) — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (Coiltube), catalogued as Product No. 1312 by Wenzhou Jixing Metal Materials Co., Ltd., is a precision-engineered tubular product manufactured in continuous coil form for downstream processing into coils, loops, and helical configurations. Unlike standard straight-length stainless steel pipes, coil tubes are supplied in continuous lengths wound onto spools, enabling seamless fabrication of heat exchanger coils, evaporator coils, condenser coils, and other curved-tube assemblies without the need for post-welding butt joints.
The coil tube form factor is particularly advantageous for applications requiring U-bends, hairpin bends, and serpentine geometries, as the material is delivered in a pre-formed coiled state that minimizes material waste and fabrication labor. The associated manufacturing process — including the use of specialized Manual Pipe Bending Tools (手动煨管器) for on-site coil forming — represents a critical link in the value chain from raw coil stock to finished coil-tube assemblies.
2. Material & Properties
2.1 Common Grades
- Austenitic Grades: AISI 304 (UNS S30400), AISI 316 (UNS S31600), AISI 321 (UNS S32100), AISI 316L (UNS S31603)
- Super-Austenitic Grades: AISI 904L (UNS N08904), Alloy 220 (UNS N08220)
- Duplex Grades: 2205 (UNS S32205), 2507 (UNS S32750)
- High-Nickel Alloys: Inconel 625 (UNS N06625), Hastelloy C-276 (UNS N10276)
2.2 Mechanical Properties (Typical for Grade 316L)
| Property | Specification | Test Standard |
|---|---|---|
| Tensile Strength (抗拉强度) | ≥ 485 MPa (70 ksi) | ASTM A213 / ASTM A269 |
| Yield Strength (屈服强度) | ≥ 205 MPa (30 ksi) | ASTM A213 / ASTM A269 |
| Elongation (伸长率) | ≥ 40% | ASTM A213 / ASTM A269 |
| Hardness (硬度) | ≤ 210 HB (Brinell) | ASTM E10 |
| Corrosion Resistance (耐腐蚀性) | Excellent resistance to pitting, crevice, and intergranular corrosion (IGC) | ASTM G48 / ASTM A240 |
2.3 Chemical Composition (Grade 316L — Typical)
| Element | Percentage (%) |
|---|---|
| Carbon (C) | ≤ 0.030 |
| Chromium (Cr) | 16.0 – 18.0 |
| Nickel (Ni) | 10.0 – 14.0 |
| Molybdenum (Mo) | 2.0 – 3.0 |
| Manganese (Mn) | ≤ 2.0 |
| Silicon (Si) | ≤ 1.0 |
| Phosphorus (P) | ≤ 0.035 |
| Sulfur (S) | ≤ 0.030 |
| Nitrogen (N) | ≤ 0.10 |
3. Specifications
3.1 Geometric Dimensions
| Parameter | Specification Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD / 外径) | Ø 3.0 mm – Ø 108.0 mm | ASTM A213 / ASTM A269 |
| Wall Thickness (WT / 壁厚) | 0.3 mm – 6.0 mm | ASTM A213 / ASTM A269 |
| Coil Length (盘管长度) | Up to 200 m per coil (continuous) | Manufacturer Specification |
| Coil Diameter (盘管直径) | Ø 300 mm – Ø 1500 mm (spool ID) | Manufacturer Specification |
| Bend Radius (弯曲半径) | ≥ 3D (minimum, where D = tube OD) | ASME B31.3 |
| Tolerance — OD | ± 0.05 mm (precision) / ± 0.10 mm (standard) | ASTM A213 |
| Tolerance — Wall Thickness | ± 10% of nominal | ASTM A213 |
| Surface Finish (表面光洁度) | Mirror polish (Ra ≤ 0.1 μm), Electropolished (Ra ≤ 0.4 μm), Pickled & Passivated (Ra ≤ 0.8 μm), Cold-rolled finish | ASTM A269 |
3.2 Available Configurations
- Single-Coil Configuration: Continuous tube wound onto a single spool for downstream forming
- Pre-Bent Coil Assembly: Factory-formed helical or serpentine coil with fixed pitch and diameter
- U-Bend Coil (Hairpin Coil): Pre-formed U-bend segments connected in series for heat exchanger applications
- Spiral Coil (螺旋盘管): Continuous helical winding for evaporator and condenser coils
4. Manufacturing Process
4.1 Process Flow
- Raw Material Selection (原材料选择): High-purity stainless steel coil strip (SS coil) or seamless tube stock is procured from certified mills, with full chemical composition analysis (光谱分析) and mechanical property verification.
- Coil Unwinding & Straightening (盘管开卷与矫直): The stainless steel coil is unwound from the spool and passed through a multi-roller straightening machine to eliminate residual curvature and set-up stress from the coiling process.
- Forming & Sizing (成型与定径): For seamless coil tubes, the flat strip is formed into a tube via a roll-forming process, with precise control of the outer diameter and wall thickness through calibrated forming rolls. For welded coil tubes, a TIG (Tungsten Inert Gas) welding process is applied at the seam joint.
- Heat Treatment (热处理): Solution annealing (固溶退火) is performed at 1050–1150 °C for Grade 316L to dissolve carbides and ensure a uniform austenitic microstructure, followed by rapid water quenching to prevent chromium carbide precipitation at grain boundaries.
- Pickling & Passivation (酸洗与钝化): The tube surface is cleaned of oxide scale and contamination using a mixed acid bath (HNO₃ + H₂SO₄), followed by a passivation treatment to restore the protective chromium oxide layer (Cr₂O₃) to ≥ 100 Å thickness.
- Surface Finishing (表面处理): Depending on the application requirement, the tube may undergo electropolishing (电解抛光), mechanical polishing (机械抛光), or mirror polishing (镜面抛光) to achieve the specified surface roughness.
- Bending & Coiling (弯制与盘管成型): The straightened and finished tube is bent into the required coil geometry using a Manual Pipe Bending Tool (手动煨管器) or automated CNC bending machine. The bending process must maintain a minimum bend radius of 3D to prevent wall thinning, ovality exceeding 5%, and microstructural distortion at the bend apex.
- Quality Inspection (质量检验): Each coil tube lot undergoes dimensional inspection (dimensional gauging), hydrostatic pressure testing (水压试验, typically at 2× working pressure for 30 seconds), surface defect inspection (visual + magnetic particle inspection per ASTM E1444), and chemical composition verification (OES spectroscopy).
- Packaging & Shipping (包装与运输): Finished coil tubes are wound onto protective spools, wrapped in moisture-barrier film, and secured with steel strapping for shipment. Each package is accompanied by a Mill Test Certificate (MTC / 材质证明书) and Certificate of Compliance (CoC / 合格证书).
4.2 Manual Pipe Bending Tool (手动煨管器) — Application Note
The Manual Pipe Bending Tool (手动煨管器) is a specialized hand-operated device designed for forming stainless steel tubes into precise curved geometries, including coil shapes, U-bends, and custom radii. Key design features include:
- Adjustable bending mandrel (弯曲芯轴) to accommodate tube OD ranges from Ø 6 mm to Ø 38 mm
- Clamping mechanism with anti-slip jaws to prevent tube ovalization during bending
- Graduated angle scale (角度刻度尺) for repeatable bend angle accuracy within ± 1°
- Low-friction contact surfaces (PTFE-lined or polished steel) to minimize surface marking on the tube
This tool is particularly suited for small-batch fabrication, field repairs, and prototype coil assembly where automated bending equipment is impractical or uneconomical. The operator must ensure that the bend rate does not exceed the material's strain rate limit to avoid strain-induced martensitic transformation in austenitic stainless steel (γ → α' transformation), which would compromise corrosion resistance at the bend zone.
5. Applications
5.1 Primary Application Sectors
| Application Sector | Typical Use Case | Recommended Grade |
|---|---|---|
| Heat Exchangers (换热器) | Shell-and-tube heat exchanger coil tubes; plate-fin heat exchanger channels | 316L, 321, 904L |
| Refrigeration & HVAC (制冷与暖通空调) | Evaporator coils, condenser coils, refrigerant piping | 304, 316L |
| Chemical Processing (化工处理) | Reactor coil jackets, distillation column internals, corrosive fluid transfer | 316L, 904L, 2205, Hastelloy C-276 |
| Food & Pharmaceutical (食品与制药) | Sanitary heat exchangers, CIP/SIP coil loops, process piping | 304, 316L (EP finish) |
| Petroleum & Energy (石油与能源) | Subsea heat exchanger coils, oilfield instrumentation tubing | 316L, 2205, 2507 |
| Power Generation (发电) | Boiler economizer coils, superheater tubes, steam generator coils | 310, 321, Inconel 625 |
| Medical Equipment (医疗设备) | Endoscope sheaths, dialysis coil tubing, sterilization loops | 316L (mirror polish) |
5.2 Unique Selling Points
- Seamless Continuity: Coil tube delivery eliminates butt-weld joints inherent to straight-length pipe assemblies, reducing potential leak points by up to 80% in heat exchanger coil assemblies.
- Material Efficiency: Continuous coil form factor minimizes cutting waste (trim loss) to < 2% of total material, compared to 8–15% for straight-length pipe fabrication.
- Multi-Grade Availability: Full spectrum of austenitic, super-austenitic, duplex, and high-nickel alloy grades available from a single supplier, enabling material optimization for diverse corrosion and mechanical environments.
- Precision Dimensional Control: Tight tolerance manufacturing (± 0.05 mm OD) ensures interchangeability and reliable fit within heat exchanger tube sheets and coil supports.
- Surface Finish Versatility: Range from standard pickled finish to mirror polish (Ra ≤ 0.1 μm) accommodates both industrial and sanitary/hygiene-critical applications.
- On-Site Flexibility: Compatibility with manual pipe bending tools (手动煨管器) enables field-level coil formation and adaptation without specialized heavy equipment.
6. Quality Certifications & Standards Compliance
6.1 Applicable Standards
| Standard | Scope |
|---|---|
| ASTM A213 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for High-temperature Service |