Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 1197) is a precision-engineered seamless or welded tubular product supplied in continuous coil form. Designed for a wide range of industrial, HVAC, and process applications, this product leverages the superior corrosion resistance, mechanical integrity, and formability inherent to austenitic and duplex stainless steel grades. The coil delivery format offers significant advantages in downstream processing efficiency, material utilization, and cost-effectiveness compared to straight-length pipe alternatives.
Material Composition & Properties
The Coiltube is available in multiple stainless steel grades conforming to international standards, including but not limited to:
- Austenitic Grades: 304 (UNS S30408), 304L (UNS S30403), 316 (UNS S31608), 316L (UNS S31603), 321 (UNS S32108), 310S (UNS S31008)
- Duplex Grades: 2205 (UNS S31803), 2507 (UNS S32750)
- Ferritic & Martensitic Grades: 430 (UNS S43000), 410 (UNS S41000)
Typical Chemical Composition (Grade 304 — Representative)
| Element | Carbon (C) | Chromium (Cr) | Nickel (Ni) | Manganese (Mn) | Silicon (Si) | Phosphorus (P) | Sulfur (S) |
|---|---|---|---|---|---|---|---|
| Specification Range | ≤ 0.08% | 18.0 – 20.0% | 8.0 – 10.5% | ≤ 2.0% | ≤ 1.0% | ≤ 0.045% | ≤ 0.030% |
Mechanical Properties (Cold Worked Condition)
| Property | Specification | Test Standard |
|---|---|---|
| Tensile Strength (UTS) | ≥ 515 MPa (74,700 psi) | ASTM A270 / ASTM A269 |
| Yield Strength (0.2% offset) | ≥ 205 MPa (29,700 psi) | ASTM A270 |
| Elongation (in 50 mm / 2 in) | ≥ 35% | ASTM A270 |
| Hardness (HBW) | ≤ 200 | ASTM A270 |
| Corrosion Resistance (Pitting — PREN) | ≥ 19 (Grade 304); ≥ 24 (Grade 316) | ISO 15658 |
Dimensional Specifications
| Parameter | Specification / Range | Applicable Standard |
|---|---|---|
| Outer Diameter (OD) | 3.0 mm – 168.3 mm (1/8" – 6") | ASTM A269 / ASTM A270 / EN 10217 |
| Wall Thickness (WT) | 0.3 mm – 6.0 mm (0.012" – 0.236") | ASTM A269 / ASTM A270 |
| OD Tolerance | ± 0.5% (for OD ≤ 12.7 mm); ± 0.75% (for OD > 12.7 mm) | ASTM A269 |
| Wall Thickness Tolerance | ± 10% | ASTM A269 |
| Coil Length | 5 m – 50 m per coil (customizable) | Manufacturer Specification |
| Coil ID (Inner Diameter) | 300 mm – 600 mm | Manufacturer Specification |
| Surface Finish | Bright Annealed (BA), Pickled & Passivated (2B), Mirror Polished (No. 7/8), Matte | ASTM A270 / Custom |
| Heat Treatment Condition | Solution Annealed, Cold Worked, Stress Relieved | ASTM A270 |
Manufacturing Process
1. Raw Material Preparation
High-purity stainless steel billets or strip are sourced from certified mills. Incoming materials undergo spectrographic analysis (OES/PMS) to verify chemical composition within specified ranges. Raw material traceability is maintained through heat number documentation throughout the entire manufacturing chain.
2. Hot Rolling or Extrusion
For larger diameter tubes, the manufacturing begins with hot rolling or extrusion of hollow bars. The material is heated to temperatures exceeding 1,150°C (2,094°F) and passed through calibrated dies to achieve the desired outer diameter and approximate wall thickness.
3. Cold Drawing (Pilotless or Conventional)
Cold drawing is the primary process for achieving precise dimensional tolerances. The tube blank is drawn through a hardened tool steel die with or without a pilot (plug) to reduce OD and wall thickness incrementally. This cold working process enhances mechanical properties through strain hardening and achieves surface finish requirements.
4. Intermediate Annealing
When multiple cold drawing passes are required, intermediate annealing is performed at temperatures between 1,050°C and 1,150°C (1,922°F – 2,094°F) followed by controlled cooling (air or water quench). This process relieves accumulated cold work stresses, restores ductility, and ensures uniform grain structure for subsequent forming operations.
5. Pickling & Passivation
Following final cold working, tubes undergo pickling to remove surface oxide scales and contaminants using mixed acid solutions (nitric/hydrofluoric acid blend). Subsequent passivation with nitric acid (20–30% concentration) establishes a stable chromium oxide passive film on the surface, enhancing corrosion resistance. The process conforms to ASTM A380.
6. Coiling & Packaging
Finished tubes are wound into coils of specified length on appropriate cores. Each coil is protected with anti-corrosion wrapping, moisture-absorbing desiccant packets, and outer packaging (wooden cases or steel crates) suitable for international shipping. Coil identification labels include product number, grade, heat number, dimensions, and certification reference.
Applications
- HVAC & Refrigeration Systems: Heat exchanger tubes, condenser coils, evaporator coils, and fan coil unit components. The coil tube format enables efficient coil winding for heat transfer applications with optimal fluid flow geometry.
- Chemical & Petrochemical Processing: Reactor tubes, heat exchanger bundles, condensers, and process piping where resistance to aggressive chemical environments is critical.
- Food & Beverage Industry: Processing equipment tubing, sanitary piping, and heat exchangers requiring hygienic surface finishes and compliance with FDA/3-A standards.
- Pharmaceutical & Biotech: Piping systems, fermenter components, and CIP (Clean-In-Place) compatible tubing systems.
- Automotive & Aerospace: Exhaust system components, fuel lines, hydraulic tubing, and structural tubing requiring high strength-to-weight ratios.
- Construction & Architecture: Decorative elements, structural components, and plumbing systems.
- Medical Equipment: Instrument tubing, surgical instrument shafts, and medical device components requiring biocompatibility.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring product conformity with international standards:
| Certification / Standard | Scope of Applicability |
|---|---|
| ISO 9001:2015 | Quality Management System |
| ISO 14001:2015 | Environmental Management System |
| EN 10204 (3.1) | Material Test Certificate — Third-party verified chemical and mechanical test results |
| ASTM A269 / ASTM A270 | Standard specifications for austenitic stainless steel seamless and welded tubes |
| ASME SA-213 / SA-214 | Boiler, Heat Exchanger, and Condenser Tube specifications |
| EN 10217-7 | European standard for seamless cold-drawn austenitic stainless steel tubes |
| GB/T 14976 / GB/T 12771 | Chinese national standards for stainless steel tubes |
| CE Marking (PED 2014/68/EU) | Pressure Equipment Directive compliance for pressure-containing applications |
| NSF/ANSI 61 | Drinking water system component certification (select grades) |
Testing & Inspection Regime
Every production lot undergoes rigorous multi-stage testing:
- Chemical Analysis: Optical Emission Spectroscopy (OES) and/or Wet Chemical Analysis per ASTM E1922/E415
- Mechanical Testing: Tensile testing per ASTM E8/E8M; hardness testing per ASTM E10/E92
- Dimensional Verification: Optical measurement and laser scanning for OD, wall thickness, and straightness
- Non-Destructive Testing (NDT): Eddy Current Testing (ECT) per ASTM E709 for seamless tubes; Ultrasonic Testing (UT) per ASTM E213
- Hydrostatic Testing: Per ASTM A269, test pressure calculated per formula: P = 2 × S × t / D, where S is allowable stress, t is wall thickness, and D is outer diameter
- Corrosion Testing: Intergranular corrosion per ASTM A262 Practice E; Pitting resistance per ASTM G48
- Surface Quality Inspection: Visual and magnetic particle inspection (MPI) for surface defects
Unique Selling Points
1. Precision Engineering: Cold-drawn manufacturing process ensures dimensional accuracy within ±0.5% for outer diameter, enabling seamless integration into precision assemblies without secondary machining.
2. Coil Format Advantage: Continuous coil supply eliminates joint wastage, reduces downstream processing time by up to 40%, and enables automated coil-to-coil processing lines for high-volume production environments.
3. Multi-Grade Capability: Single-source availability of austenitic, duplex, ferritic, and martensitic grades from one supplier simplifies procurement and ensures consistent quality standards across product lines.
4. Surface Finish Versatility: Available in Bright Annealed (BA), 2B, Mirror Polished (No. 7/8 finish), and custom matte finishes to meet both functional and aesthetic requirements.
5. Full Traceability: Complete heat-to-heat traceability with EN 10204 3.1 material test certificates provides full documentation from raw material through final product delivery.
6. Compliance with Evolving Standards: Products are manufactured and tested in accordance with the latest revisions of applicable international standards, ensuring compliance with updated regulatory requirements including revised HVAC testing protocols and pressure vessel codes.
Storage & Handling Recommendations
- Store in a dry, well-ventilated warehouse environment; relative humidity should not exceed 65%.
- Coils must be stored on appropriate racks or stands to prevent deformation of the tube cross-section.
- Protect from direct contact with carbon steel and other reactive materials to prevent galvanic contamination.
- Do not remove protective wrapping until immediately prior to processing.
- Recommended maximum storage duration in original packaging: 24 months from date of manufacture.
Technical Advisory Note
Users are advised to verify dimensional tolerances, mechanical property requirements, and corrosion resistance specifications against the specific operating conditions of their application. For applications involving chloride-containing environments or elevated temperatures exceeding 450°C (842°F), Grade 316L or duplex stainless steel (2205/2507) is recommended over standard Grade 304 to mitigate risks of pitting corrosion and intergranular sensitization. Consultation with qualified metallurgical engineers is recommended for critical service applications.