Stainless Steel Coil Tube (Coiltube) — Technical Product Specification
1. Product Overview
The Stainless Steel Coil Tube (Coiltube), manufactured by Wenzhou Jixing Metal Materials Co., Ltd., is a continuous-length tubular product wound into a helical coil configuration. Unlike straight-cut seamless or welded pipes, coil tubes are produced in uninterrupted lengths and delivered in a coiled form, enabling efficient transport, storage, and downstream processing without the need for butt-welding individual segments. This product is particularly valued for its dimensional consistency, superior surface finish, and excellent mechanical properties governed by standardized room-temperature tensile testing protocols.
Coil tubes find extensive application in heat exchangers, chemical processing equipment, food-grade piping systems, automotive exhaust components, and aerospace fluid conveyance systems. The continuous coil form factor minimizes material waste and reduces fabrication labor, making it an economically advantageous choice for high-volume manufacturing environments.
2. Material Composition & Mechanical Properties
2.1 Common Alloy Grades
- AISI 304 / ASTM A213 TP304 — General-purpose austenitic stainless steel with excellent corrosion resistance and formability.
- AISI 316 / ASTM A213 TP316 — Enhanced corrosion resistance due to molybdenum (Mo) addition; suitable for aggressive chemical environments.
- AISI 321 / ASTM A213 TP321 — Stabilized austenitic grade with titanium (Ti) addition to prevent intergranular corrosion at elevated temperatures.
- AISI 316L / ASTM A213 TP316L — Low-carbon variant of 316 with superior resistance to pitting and crevice corrosion.
- AISI 304L / ASTM A213 TP304L — Low-carbon variant of 304, ideal for welded structures requiring resistance to sensitization.
2.2 Typical Chemical Composition (ASTM A213 TP304, wt%)
| Element | Specification |
|---|---|
| Carbon (C) | ≤ 0.08 |
| Manganese (Mn) | ≤ 2.00 |
| Phosphorus (P) | ≤ 0.045 |
| Sulfur (S) | ≤ 0.030 |
| Chromium (Cr) | 18.00 – 20.00 |
| Nickel (Ni) | 8.00 – 10.50 |
| Nitrogen (N) | ≤ 0.10 |
2.3 Mechanical Properties at Room Temperature
The mechanical performance of stainless steel coil tubes is evaluated in accordance with ASTM A928 / GB/T 228.1 — "Standard Test Methods for Tensile Testing of Metallic Materials" and the industry-specific standard 《金属盘管的室温拉伸试验方法》 (Room Temperature Tensile Test Method for Metal Coil Tubes). Key parameters include:
| Property | Symbol | Typical Value (Annealed) |
|---|---|---|
| Tensile Strength (抗拉强度) | σb (Rm) | ≥ 515 MPa (74,700 psi) |
| Yield Strength (屈服强度) | σs (Rp0.2) | ≥ 205 MPa (29,700 psi) |
| Elongation (延伸率) | A (%EL) | ≥ 40% (in 50 mm gauge length) |
| Hardness (硬度) | HRB | ≤ 95 |
| Modulus of Elasticity (弹性模量) | E | 193 GPa (28,000 ksi) |
3. Dimensional Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 3.0 mm – 159.0 mm (0.118" – 6.26") | ASTM A213 / GB/T 12771 |
| Wall Thickness (WT) | 0.3 mm – 12.0 mm (0.012" – 0.472") | ASTM A213 / GB/T 12771 |
| OD Tolerance | ±0.05 mm to ±0.50 mm (depending on diameter) | ASTM A213 |
| Wall Thickness Tolerance | ±10% of nominal (minimum ±0.05 mm) | ASTM A213 |
| Coil Length (per coil) | 20 m – 200 m (65 ft – 656 ft) | Manufacturer specification |
| Coil Inner Diameter | 300 mm – 800 mm (12" – 32") | Manufacturer specification |
| Surface Finish | Pickled & Annealed (P&A) / Bright Annealed / Polished | ASTM A478 |
| End Condition | Plain, Beveled, or Threaded (upon request) | Per customer drawing |
4. Manufacturing Process
The production of stainless steel coil tubes at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous multi-stage process:
- Raw Material Selection (原材料选择): High-purity stainless steel billets or slabs are procured from certified suppliers with full material traceability documentation (Mill Test Certificate — MTC).
- Hole Piercing (穿孔): The heated billet is pierced on a rotary piercing mill to produce a hollow shell (tube blank).
- Elongation & Reduction (延拔与减径): The pierced shell undergoes multi-pass rolling on a seamless tube mill (e.g., Mannesmann type or plug mill) to achieve the target OD and wall thickness dimensions.
- Heat Treatment / Annealing (热处理/退火): The tube is annealed at 1050°C – 1150°C in a protective atmosphere (hydrogen or vacuum) followed by controlled cooling to restore full austenitic microstructure, relieve residual stresses, and achieve maximum ductility.
- Pickling & Descaling (酸洗除鳞): The annealed tube is subjected to acid pickling (typically mixed HNO3/HF or citric acid solution) to remove oxide scale and restore the passive chromium oxide layer.
- Coiling (盘卷): The continuous tube is wound onto a coil reel at controlled tension to form the final coil configuration, ensuring uniform curvature without plastic deformation or surface marking.
- Non-Destructive Testing (无损检测): Each coil undergoes 100% electromagnetic (Eddy Current — EC) testing and/or ultrasonic testing (UT) to detect internal and surface defects. Hydrostatic testing (水压试验) is performed per ASTM A213 requirements.
- Room Temperature Tensile Testing (室温拉伸试验): Specimens are extracted from each production batch and tested per the standardized room temperature tensile test method for metal coil tubes (《金属盘管的室温拉伸试验方法》), evaluating tensile strength, yield strength, and elongation in accordance with ASTM A928 and GB/T 228.1.
- Packaging & Delivery (包装与交付): Coils are wrapped in protective film, secured with steel strapping, and placed on wooden pallets for shipping.
5. Applications
- Heat Exchangers & Boilers (热交换器与锅炉): Coil tubes are ideal for spiral-wound heat exchangers, shell-and-tube designs, and fired heaters due to their continuous length and superior thermal conductivity.
- Chemical Processing (化工行业): Grades 316 and 316L coil tubes resist aggressive media including sulfuric acid, chlorinated solutions, and alkali environments.
- Food & Pharmaceutical Industry (食品与制药行业): Hygienic-grade polished coil tubes (Ra ≤ 0.4 μm) comply with FDA and 3-A Sanitary Standards for dairy, beverage, and pharmaceutical processing lines.
- Automotive Industry (汽车工业): Used in exhaust system components, fuel lines, and turbocharger piping where high-temperature resistance and corrosion durability are critical.
- Petrochemical & Oil/Gas (石油化工与油气行业): Deployed in refinery piping, offshore platforms, and subsea umbilicals requiring resistance to chloride-induced stress corrosion cracking (SCC).
- Construction & Architecture (建筑与装饰): Decorative coil tubes are used in railings, handrails, and structural applications in coastal and high-humidity environments.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains the following quality certifications and standards compliance:
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System (质量管理体系) |
| ISO 14001:2015 | Environmental Management System (环境管理体系) |
| ISO 45001:2018 | Occupational Health & Safety Management System (职业健康安全管理体系) |
| EN 10204 3.1 | Material Test Certificate (材料试验证书) |
| ASTM A213 / A778 | Specification for Seamless Austenitic Stainless Steel Tube |
| GB/T 12771 | Chinese National Standard for Seamless Stainless Steel Tubes |
| GB/T 228.1 | Tensile Testing Method for Metallic Materials at Room Temperature |
| PED 2014/68/EU | European Pressure Equipment Directive compliance (upon request) |
| ASME SA-213 | American Society of Mechanical Engineers — Boilers & Heat Exchanger Tubes |
| EN 10217-7 | European Standard for Non-ferrous Tubes — Stainless Steel |
7. Unique Selling Points
- Continuous Length Advantage: The coil configuration eliminates butt-weld joints, reducing potential failure points and improving fatigue life in cyclic loading applications.
- Standardized Tensile Testing: Every production batch undergoes rigorous room-temperature tensile testing per the dedicated coil tube testing methodology, ensuring consistent mechanical performance and traceable quality data.
- Multi-Grade Flexibility: Availability across AISI 304, 304L, 316, 316L, 321, 347, and duplex grades (2205, 2507) allows customers to select optimal material for their specific service environment.
- Wide Dimensional Range: From capillary tubes (OD 3 mm) to large-diameter structural tubes (OD 159 mm), accommodating diverse engineering requirements from a single supplier.
- Full Traceability: Each coil is accompanied by a detailed Mill Test Certificate (MTC) including chemical analysis, mechanical test results, and heat number for complete supply chain traceability.
- Cost Efficiency: The coil form reduces material waste by up to 15% compared to straight-length pipes and minimizes downstream cutting and welding labor costs.
8. Testing & Inspection Summary
In accordance with the Room Temperature Tensile Test Method for Metal Coil Tubes (《金属盘管的室温拉伸试验方法》), specimens are prepared by cutting transverse and longitudinal samples from representative locations on each coil. Testing is conducted at a temperature of 23°C ± 5°C (73°F ± 9°F) with a crosshead speed of 0.5 mm/min (ASTM A928 Method A) or 1.0 mm/min (GB/T 228.1). The test evaluates ultimate tensile strength (UTS), 0.2% offset yield strength, and percent elongation at fracture, with results reported against the applicable product specification limits.
Additional quality assurance measures include:
- 100% Eddy Current (EC) inspection for wall thickness uniformity and surface defect detection
- Hydrostatic pressure testing at 2.5× design pressure per