Medium-Diameter Stainless Steel Coil Tube (Φ12mm – Φ25mm) — Product Technical Specification
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Product Category: Product Specifications → Geometric Parameters → Outer Diameter Series → Medium-Diameter Grade
Product Item No.: 33
1. Product Overview
The Medium-Diameter Stainless Steel Coil Tube (盘管 / Coil Tube) represents a critical segment within the full outer diameter spectrum offered by Wenzhou Jixing Metal Materials. This grade covers the nominal outer diameter range of Φ12 mm to Φ25 mm, bridging the gap between small-bore precision tubing and large-diameter process piping. The coil tube format — delivered as a continuous, helically wound bundle rather than straight-cut lengths — offers significant advantages in material utilization, storage density, and downstream processing efficiency.
This medium-diameter range is particularly well-suited for applications demanding a balance between flow capacity, mechanical flexibility, and formability. The coil configuration allows customers to cut custom-length segments on demand, minimizing offcuts and reducing inventory complexity. As a seamless, cold-drawn stainless steel product, the medium-diameter coil tube exhibits superior dimensional accuracy, surface finish, and metallurgical homogeneity compared to welded alternatives.
2. Material & Properties
Wenzhou Jixing's medium-diameter coil tubes are manufactured from high-purity austenitic and duplex stainless steel grades conforming to international standards. The following table summarizes the primary material specifications:
| Property | Specification |
|---|---|
| Primary Grades | 304 (UNS S30400), 304L (UNS S30403), 316 (UNS S31600), 316L (UNS S31603), 321 (UNS S32100), 310S (UNS S31008) |
| Equivalent Standards | ASTM A269 / A213 / A554; EN 10216-5; GB/T 12771; JIS G3459 |
| Chromium (Cr) Content | 18.0% – 27.0% (grade-dependent) |
| Nickel (Ni) Content | 8.0% – 25.0% (grade-dependent) |
| Molybdenum (Mo) Content | 0% – 3.0% (grade-dependent) |
| Tensile Strength (Annealed) | ≥ 515 MPa (75 ksi) for 304; ≥ 585 MPa (85 ksi) for 316L |
| Yield Strength (0.2% Offset) | ≥ 205 MPa (30 ksi) for 304; ≥ 170 MPa (25 ksi) for 316L |
| Elongation at Break | ≥ 40% (304); ≥ 35% (316L) |
| Hardness (Annealed) | ≤ 95 HRB (304); ≤ 95 HRB (316L) |
| Operating Temperature Range | −196 °C to +870 °C (304); −196 °C to +870 °C (316L) |
| Corrosion Resistance | Excellent resistance to atmospheric, chemical, and food-grade media; 316L offers superior pitting and crevice corrosion resistance |
| Surface Finish | Mill finish (2B), Bright Annealed (BA), Electropolished (EP), or custom Ra values (Ra 0.2 – 1.6 μm) |
3. Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) Range | Φ12 mm – Φ25 mm (0.472 in – 0.984 in) |
| OD Tolerance | ±0.05 mm (±0.002 in) for precision grade; ±0.10 mm for standard grade |
| Wall Thickness (WT) Range | 0.5 mm – 3.0 mm (0.020 in – 0.118 in) |
| WT Tolerance | ±10% of nominal (standard); ±0.03 mm (precision) |
| Coil Inner Diameter (ID) | Typically Φ150 mm – Φ400 mm (adjustable per customer requirement) |
| Coil Outer Diameter (OD) | Up to Φ1000 mm (customizable) |
| Coil Length per Bundle | 50 m – 500 m (typical); continuous coil available |
| Roundness | ≤ 1% of OD |
| Straightness (per 1000 mm) | ≤ 1.5 mm |
| End Condition | Open end, closed end, or custom-fitted (flanged, threaded, socket welded) |
| Applicable Standards | ASTM A269; ASTM A213; ASTM A554; EN 10216-5; GB/T 12771; JIS G3459 |
| Packaging | Coil wrapped in protective film, bundled with steel strapping, placed in wooden crate or export-grade pallet |
4. Manufacturing Process
The production of Wenzhou Jixing's medium-diameter stainless steel coil tubes follows a rigorous, multi-stage process designed to ensure dimensional precision, metallurgical integrity, and surface quality:
- Raw Material Selection: High-purity stainless steel billets or slabs are sourced from certified mills, with full chemical composition verification (Spectroscopic Analysis) and mill test report (MTR) traceability.
- Piercing & Hot Rolling: Billets are heated to forging temperature (1100 °C – 1250 °C) and pierced through a mandrel to form seamless hollow bars, which are subsequently hot-rolled to approximate final dimensions.
- Acid Pickling & Descaling: The hot-rolled tube is subjected to mixed acid pickling (HNO₃ / H₂SO₄) to remove oxide scale, revealing the underlying austenitic microstructure.
- Cold Drawing: The tube is cold-drawn through precision tungsten carbide (WC) dies to achieve the final medium-diameter dimensions (Φ12 mm – Φ25 mm) with tight tolerances. Multiple drawing passes are employed for high-precision grades.
- Intermediate Annealing: After each drawing pass, the tube is annealed at 1050 °C – 1150 °C in a protective atmosphere (hydrogen or nitrogen) to relieve cold-work stresses and restore ductility.
- Final Annealing & Pickling: The cold-drawn tube undergoes final solution annealing followed by acid pickling and passivation to achieve a corrosion-resistant surface finish.
- Coiling: The finished tube is wound into a continuous coil on a precision coiling machine, with tension control to prevent ovality or deformation.
- Quality Inspection: Each coil undergoes 100% ultrasonic testing (UT), eddy current testing (ECT), hydrostatic pressure testing (per ASTM A269), and dimensional verification (OD, WT, roundness, straightness).
- Packaging & Dispatch: Coils are wrapped, strapped, and crated according to export or domestic delivery specifications.
5. Applications
The medium-diameter coil tube (Φ12 mm – Φ25 mm) serves as a versatile intermediate product across multiple high-demand industries. The following are the primary application domains:
5.1 Heat Exchanger U-Tubes (换热器U型管)
This is the flagship application for the medium-diameter coil tube. The coil format is ideally suited for the fabrication of U-tube heat exchangers, as the continuous coil eliminates the need for individual tube cutting and bending of each U-bend. Key advantages include:
- Significant reduction in bending-induced thinning and work hardening at the U-bend apex
- Improved thermal efficiency due to uniform wall thickness throughout the U-tube profile
- Enhanced resistance to flow-induced vibration (FIV) and tube-to-tubesheet fretting
- Compatibility with shell-and-tube heat exchanger designs per TEMA (Tubular Exchanger Manufacturers Association) standards
Typical U-tube dimensions for this grade: OD Φ19.05 mm (3/4 in), WT 1.65 mm (16 BWG); OD Φ21.34 mm (7/8 in), WT 1.65 mm (16 BWG).
5.2 Hydraulic Piping Systems (液压管路)
In hydraulic systems — including mobile hydraulics, industrial machinery, and aerospace actuators — the medium-diameter coil tube provides:
- High burst pressure resistance (typically ≥ 100 MPa for 316L grade)
- Superior fatigue resistance under cyclic pressure loading
- Excellent formability for crimping, flare fitting, and compression coupling installation
- Resistance to hydraulic fluid degradation and seal compatibility
- Corrosion resistance in marine and outdoor hydraulic environments
5.3 CIP Cleaning-in-Place Systems (CIP清洗管)
In the food and beverage, dairy, pharmaceutical, and biotechnology industries, CIP systems require tubing that withstands repeated cycles of hot alkaline cleaners, acidic sanitizers, and steam sterilization. The medium-diameter coil tube excels in this application due to:
- Electropolished (Ra ≤ 0.4 μm) or passivated surface finish that prevents microbial adhesion
- Resistance to caustic soda (NaOH) and nitric acid (HNO₃) cleaning solutions
- Compliance with FDA 21 CFR Part 178, EU 1935/2004, and 3-A Sanitary Standards
- Ability to be formed into complex manifold configurations for uniform cleaning flow distribution
- Long service life with minimal pitting or stress corrosion cracking (SCC)
5.4 Additional Applications
- Automotive exhaust systems: Catalyst carrier tubes and emissions control piping
- Medical device manufacturing: Endoscope guide tubes, surgical instrument shafts
- Chemical processing: Reactor internals, condenser tubes, and transfer lines
- Petrochemical industry: Heat exchanger bundles for sour service (H₂S-containing environments)
- Power generation: Boiler tubes, superheater tubes, and economizer components
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials maintains a comprehensive quality management framework ensuring that every medium-diameter coil tube meets or exceeds international standards. The following certifications and compliance documents are available upon request:
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification ensuring consistent product quality and process control |
| ISO 14001:2015 | Environmental Management System certification demonstrating sustainable manufacturing practices |
| ISO 45001:2018 | Occupational Health and Safety Management System certification |
| EN 10204 3.1 | Inspection Certificate stating that the product conforms to the specified order requirements |
| EN 10204 3.2 | Inspection Certificate stating that the product conforms to the specified order requirements, based on independent inspection |
| ASTM A269 / A213 / A554 | Full conformance to applicable ASTM specifications for seamless stainless steel tubing |
| Mill Test Report (MTR) | 100% chemical composition analysis, mechanical property verification, and dimensional inspection data provided per heat/coil |
| Third-Party Inspection (TPI) | Available upon request: SGS, Bureau Veritas, TÜV, or Intertek inspection services |
| PE Material Analysis | Particle evaluation (per ASTM E415) for critical applications requiring inclusion control |
| NDT Reports | Ultrasonic Testing (UT) and Eddy Current Testing (ECT) reports per EN 10229 / ASTM E309 |
7. Unique Selling Points
- Precision-Coil Synergy: The combination of cold-drawn precision manufacturing with coil delivery format provides customers with both tight dimensional tolerances (±0.05 mm) and the economic benefits of continuous-length processing — a rare offering in the medium-diameter segment.
- Grade Flexibility: Availability across the full spectrum of austenitic and duplex stainless steel grades (304, 304L, 316, 316L, 321, 310S) in the Φ12 mm – Φ25 mm range enables single-source procurement for multi-grade projects.
- Application-Optimized Surface Finishes: Electropolished and passivated finishes are available as standard options, reducing downstream processing requirements for CIP and food-grade applications.
- U-Tube Ready: The coil geometry and controlled cold-work properties are specifically optimized for U-bend fabrication, minimizing material waste and ensuring consistent U-bend geometry across large heat exchanger bundles.
- Full Traceability: Every coil is accompanied by a complete MTR, NDT reports, and heat-number traceability from raw material mill to final dispatch, supporting regulatory compliance in regulated industries.
- Custom Coiling: Coil inner diameter, outer diameter, and bundle length are customizable to accommodate specific downstream processing equipment, reducing handling and storage constraints.
Technical Note: The medium-diameter coil tube (Φ12 mm – Φ25 mm) occupies a strategically important position in the stainless steel tubing market. Its dimensional range aligns precisely with the most commonly specified sizes in heat exchanger design (ASME/TEMA), hydraulic system standards (ISO 6708/6709), and sanitary engineering codes (3-A, EHEDG). Wenzhou Jixing's commitment to precision manufacturing, material integrity, and application-specific optimization makes this product line a preferred choice for OEMs and EPC contractors worldwide.
Manufacturer: Wenzhou J