High-Efficiency Thin-Wall Internal Thread Stainless Steel Coil Tube
Product Overview
The High-Efficiency Thin-Wall Internal Thread Stainless Steel Coil Tube (高效节能薄壁内螺纹不锈钢盘管) is an advanced heat transfer component manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product represents a significant advancement in thermal management technology, combining the inherent corrosion resistance and mechanical integrity of stainless steel with innovative internal threading geometry to maximize heat exchange efficiency. The coil tube is engineered for applications demanding superior thermal performance, energy conservation, and long-term operational reliability in aggressive chemical environments.
Unlike conventional smooth-bore coil tubes, the internal thread (Internal Threaded) design creates a turbulent flow regime within the tube bore, dramatically reducing the thermal boundary layer thickness and thereby enhancing the overall heat transfer coefficient (Heat Transfer Coefficient). This design philosophy aligns with the principles of high-efficiency energy-saving technology (High-Efficiency Energy-Saving Technology) that underpins modern industrial process engineering.
Material & Properties
Base Material
The coil tube is fabricated from high-purity austenitic stainless steel grades, primarily:
- AISI 304 / UNS S30408 — General-purpose grade with excellent corrosion resistance and formability; Cr: 18–20%, Ni: 8–10.5%
- AISI 316L / UNS S31603 — Enhanced corrosion resistance for aggressive environments; Cr: 17–18.5%, Ni: 10–14%, Mo: 2–3%
- AISI 321 / UNS S32100 — Stabilized grade for high-temperature service; Ti-stabilized to prevent intergranular corrosion
Mechanical Properties (Typical Values for 304 Grade)
| Property | Specification |
|---|---|
| Tensile Strength (抗拉强度) | ≥ 515 MPa (75 ksi) |
| Yield Strength (屈服强度, 0.2% offset) | ≥ 205 MPa (30 ksi) |
| Elongation (延伸率) | ≥ 40% (min. gauge length 50 mm) |
| Hardness (硬度) | ≤ 217 HB (annealed condition) |
| Density (密度) | 7.93 g/cm³ |
| Thermal Conductivity (热导率, 20°C) | 16.3 W/(m·K) |
| Specific Heat Capacity (比热容) | 500 J/(kg·K) |
| Thermal Expansion Coefficient (热膨胀系数, 20–100°C) | 17.3 × 10⁻⁶ /°C |
Surface Treatment
- Internal bore: Threaded with precision-cut helical ribs (Threaded Bore / 内螺纹)
- External surface: Bright annealed (Bright Annealed / 光亮退火) or passivated (Passivated / 钝化处理)
- Ra (Surface Roughness): ≤ 0.8 μm (internal), ≤ 0.4 μm (external)
Specifications
| Parameter | Specification Range | Unit |
|---|---|---|
| Outer Diameter (OD, 外径) | 9.52 – 50.80 | mm (⅜" – 2") |
| Wall Thickness (壁厚) | 0.50 – 2.00 | mm |
| Coil Inner Diameter (Coil ID, 盘管内径) | 200 – 2000 | mm |
| Coil Length per Roll (每盘长度) | 50 – 500 | m |
| Internal Thread Pitch (内螺纹螺距) | 1.0 – 3.0 | mm |
| Internal Thread Height (内螺纹高度) | 0.2 – 0.6 | mm |
| Maximum Working Pressure (最大工作压力) | 0.6 – 2.5 | MPa |
| Operating Temperature Range (工作温度范围) | -196 to +870 | °C |
| Heat Transfer Enhancement (换热增强系数) | 1.8 – 2.5× | vs. smooth tube |
| Pressure Drop Increase (压降增加) | 1.2 – 1.5× | vs. smooth tube |
Manufacturing Process
Step 1: Raw Material Preparation (原材料准备)
Stainless steel strip (Stainless Steel Strip) of the appropriate grade and thickness is sourced from certified mills. Incoming material undergoes spectroscopic analysis (Spectroscopic Analysis / 光谱分析) to verify chemical composition compliance with ASTM A240 / EN 10088-2 standards.
Step 2: Cold Rolling & Annealing (冷轧与退火)
The strip is cold-rolled to achieve precise wall thickness tolerances (±0.05 mm). Subsequent solution annealing (Solution Annealing / 固溶退火) at 1050–1100°C followed by controlled cooling restores full austenitic microstructure and eliminates residual stresses.
Step 3: Coil Forming (盘管成形)
The flat strip is wound into a helical coil (Helical Coil / 螺旋盘管) using precision CNC winding equipment. The winding process maintains uniform tension to ensure consistent coil geometry and dimensional accuracy throughout the length.
Step 4: Internal Threading (内螺纹加工)
The critical differentiating step involves precision internal threading (Internal Threading / 内螺纹加工). A multi-point cutting tool or rotary broaching mechanism (Rotary Broaching / 旋转拉削) creates uniform helical ribs inside the tube bore. This process:
- Increases effective heat transfer surface area by 30–45%
- Induces secondary flow patterns (Secondary Flow Patterns / 二次流) that disrupt laminar boundary layers
- Reduces fouling tendency (Fouling Resistance / 抗垢性能) through enhanced wall shear stress
Step 5: Heat Treatment & Passivation (热处理与钝化)
Post-threading stress relief annealing (Stress Relief Annealing / 去应力退火) at 600–700°C eliminates work-hardening effects. Chemical passivation (Chemical Passivation / 化学钝化) using nitric acid or citric acid solutions forms a protective chromium oxide film (Cr₂O₃) on the exposed internal surfaces.
Step 6: Quality Inspection & Packaging (质量检验与包装)
Each coil undergoes 100% dimensional verification, hydrostatic pressure testing (Hydrostatic Pressure Testing / 水压试验), and visual inspection. Final packaging includes protective end caps, moisture-absorbing desiccants, and rust-inhibitive wrapping.
Applications
- Heat Exchangers (换热器) — Shell-and-coil heat exchangers, air-cooled heat exchangers (Air-Cooled Heat Exchangers / 空冷器), and plate-fin heat exchangers
- Refrigeration & HVAC (制冷与暖通空调) — Evaporators (Evaporators / 蒸发器), condensers (Condensers / 冷凝器), and liquid subcoolers in ammonia and fluorocarbon refrigeration systems
- Chemical Processing (化工处理) — Reactor cooling coils, distillation column reboilers (Reboilers / 再沸器), and heat recovery systems in petrochemical and pharmaceutical plants
- Power Generation (发电) — Feedwater preheating (Feedwater Preheating / 给水预热), turbine exhaust condensers, and waste heat recovery systems
- Food & Beverage Industry (食品饮料工业) — Pasteurization (Pasteurization / 巴氏杀菌) systems, CIP (Clean-in-Place / 原位清洗) compatible heating coils, and dairy processing equipment
- Marine Applications (海洋应用) — Seawater heat exchangers, bilge heating systems, and shipboard refrigeration due to superior chloride resistance (Chloride Resistance / 抗氯离子腐蚀)
- Oil & Gas (石油天然气) — Subsea heat exchangers, wellhead equipment, and flare gas recovery systems
Quality Certifications & Standards
Product Standards Compliance
| Standard | Description |
|---|---|
| ASTM A269 / A270 | Standard Specification for Seamless and Wrought Stainless Steel Tubing and Pipes |
| ASTM A314 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Coil Heat Exchanger Tubing |
| EN 10217-7 | Heat Exchanger and Heat Transfer Component Tubing and Pipes — Technical Delivery Conditions |
| GB/T 17898 | Chinese National Standard for Stainless Steel Heat Exchanger Tubes |
| JIS G3459 | Japanese Industrial Standard for Stainless Steel Tubes for Heat Exchangers |
Quality Management Certifications
- ISO 9001:2015 — Quality Management Systems (质量管理体系)
- ISO 14001:2015 — Environmental Management Systems (环境管理体系)
- ISO 45001:2018 — Occupational Health and Safety Management (职业健康安全管理体系)
- NADCAP — National Aerospace and Defense Contractors Accreditation Program (for aerospace-grade products)
- API Q1 / Q2 — Quality Management System for Oil and Gas Industry (石油天然气行业质量管理体系)
Testing & Inspection Protocols
- Hydrostatic Testing (水压试验) — 100% of coils tested at 1.5× working pressure, held for minimum 30 seconds
- Chemical Analysis (化学分析) — PMI (Positive Material Identification / 材质光谱鉴定) verification per batch
- Dimensional Inspection (尺寸检验) — OD, wall thickness, coil ID, and pitch verified per ISO 286 tolerance classes
- Thread Geometry Inspection (螺纹几何检验) — Thread height, pitch, and profile verified using optical profilometry (Optical Profilometry / 光学轮廓测量)
- Pickling & Passivation Verification (酸洗钝化验证) — Blue dip test (Blue Dip Test / 蓝点试验) for passive film integrity
Unique Selling Points
The High-Efficiency Thin-Wall Internal Thread Stainless Steel Coil Tube from Wenzhou Jixing Metal Materials Co., Ltd. delivers a superior combination of thermal performance, energy efficiency, and service life that distinguishes it from conventional alternatives:
- Enhanced Heat Transfer Performance (换热性能增强) — The internal threading geometry provides 80–150% improvement in heat transfer coefficient compared to equivalent smooth-wall tubes, enabling significant reductions in heat exchanger surface area requirements and capital expenditure.
- Energy Efficiency (节能效率) — By achieving the same thermal duty with smaller heat exchanger footprints, downstream pumping power requirements are reduced, contributing to overall system energy savings of 15–25%.
- Anti-Fouling Characteristics (抗垢特性) — The enhanced wall shear stress generated by internal threads inhibits scale nucleation and deposition, extending cleaning intervals and reducing maintenance downtime by up to 60%.
- Corrosion Resistance (耐腐蚀性) — Full austenitic stainless steel construction provides exceptional resistance to pitting (Pitting Corrosion / 点蚀), crevice corrosion (Crevice Corrosion / 缝隙腐蚀), and stress corrosion cracking (Stress Corrosion Cracking / 应力腐蚀开裂) in aggressive process media.
- Wide Temperature Range (宽温适用范围) — Operational capability from cryogenic (-196°C) to elevated temperatures (up to 870°C for stabilized grades) without loss of mechanical integrity.
- Design Flexibility (设计灵活性) — Available in a broad range of ODs, wall thicknesses, coil diameters, and thread configurations to accommodate diverse engineering requirements.
- Long Service Life (长使用寿命) — Expected service life exceeding 20 years under normal operating conditions, significantly outperforming carbon steel and copper alternatives in corrosive service.