Small-Bore Stainless Steel Coil Tube (Φ3mm – Φ12mm)
Product Overview
The Small-Bore Stainless Steel Coil Tube, manufactured by Wenzhou Jixing Metal Materials Co., Ltd, represents a precision-engineered product category within the coil tube (Coiltube) product line. Designed specifically for applications requiring fine-bore tubing with superior corrosion resistance, mechanical integrity, and dimensional accuracy, this product line covers the outer diameter range of Φ3mm to Φ12mm. These small-bore coil tubes are supplied in continuous coil form, enabling efficient downstream processing through automated cutting, forming, and assembly operations while minimizing material waste and labor costs.
Positioned as a high-performance alternative to traditional copper tubing in refrigeration and HVAC applications, and as the preferred material for instrument pressure tubing and analytical sampling lines, this product line addresses the demanding requirements of modern industrial instrumentation, process control systems, and fluid handling applications where hygiene, durability, and chemical compatibility are paramount.
Material & Properties
Grade Designations
- Austenitic Stainless Steels: Primarily 304 (UNS S30408), 316 (UNS S31608), and 321 (UNS S32108)
- Super-Austenitic Grades: 316L (UNS S31603), 316Ti (UNS S31678) for enhanced pitting and crevice corrosion resistance
- Specialty Grades: 904L (UNS N08904), duplex 2205 (UNS S31803) for extreme chemical environments
Mechanical Properties (Typical for Grade 316L)
- Tensile Strength: ≥ 520 MPa (75 ksi)
- Yield Strength: ≥ 205 MPa (30 ksi)
- Elongation: ≥ 40% (minimum)
- Hardness: ≤ 230 HB (as-rolled condition)
- Operating Temperature Range: −196°C to +870°C (−320°F to +1,598°F)
Corrosion Resistance
- Excellent resistance to atmospheric, aqueous, and mild industrial environments
- Superior pitting and crevice corrosion resistance (316/316L grades) due to molybdenum (Mo) alloying
- Resistance to stress corrosion cracking (SCC) in chloride-containing environments
- Non-magnetic or weakly magnetic (austenitic microstructure)
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Product Name | Small-Bore Stainless Steel Coil Tube | — |
| Outer Diameter (OD) Range | Φ3.0 mm – Φ12.0 mm | ASTM A554 / EN 10217-7 |
| Wall Thickness Range | 0.3 mm – 1.5 mm | ASTM A554 |
| OD Tolerance | ±0.05 mm (fine bore) / ±0.10 mm (standard) | EN 10217-7 Class 1 |
| Wall Thickness Tolerance | ±10% of nominal | ASTM A554 |
| Surface Finish | Bright annealed / Electropolished (Ra ≤ 0.4 μm) / Mirror polished (Ra ≤ 0.2 μm) | ASTM A269 / EN 10217-7 |
| Coil Inner Diameter (ID) | 100 mm – 500 mm (customizable) | Manufacturer specification |
| Coil Weight | 5 kg – 200 kg per coil | Manufacturer specification |
| End Condition | Clean cut / Beveled / Flanged (optional) | ASTM A554 |
| Manufacturing Method | Seamless (cold-drawn) / Welded (TIG, orbital) | ASTM A554 / ASME B31.3 |
| Heat Treatment | Solution annealed and water quenched | ASTM A554 |
| Packaging | Wooden crate / Cardboard with moisture barrier | ISO 11607 (for medical) |
Manufacturing Process
Seamless Tube Production (Preferred for Φ3mm – Φ12mm)
- Billet Preparation: High-purity stainless steel billets are remelted via vacuum arc remelting (VAR) or electro-slag remelting (ESR) to ensure homogeneous composition and minimal inclusion content.
- Hollowing & Piercing: Billets are heated to 1,100–1,200°C and pierced using plug or Mandrelless Piercing (MPT) technology to form seamless hollow tubes (tube blanks).
- Hot Rolling / Hot Drawing: Tube blanks are hot worked to reduce wall thickness and achieve approximate final dimensions.
- Pickle & Descale: Hot-rolled scale is removed via acid pickling to reveal clean metal surface.
- Cold Drawing & Mandreling (CD&M): Tubes are cold-drawn over precision tungsten carbide dies with internal mandrels to achieve exact OD, wall thickness, and dimensional tolerances within ±0.05 mm.
- Solution Annealing: Tubes are annealed at 1,050–1,150°C in a controlled atmosphere (argon or vacuum) and rapidly water-quenched to restore full austenitic microstructure, relieve cold-work stresses, and maximize corrosion resistance.
- Surface Finishing: Optional electropolishing (EP) or mechanical polishing to achieve mirror-grade surface finish for hygienic and analytical applications.
- Coiling: Finished tubes are coiled onto precision mandrels using automated coiling equipment to prevent surface damage and maintain dimensional stability.
Welded Tube Production (Alternative for Larger Wall Thicknesses)
- Strip Rolling: Cold-rolled stainless steel strip is fed into a tube-forming mill.
- Forming & Welding: Strip is formed into a tube shape and welded using Transverse Inert Gas (TIG) welding or orbital automatic welding with argon shielding.
- Weld Heat-Affected Zone (HAZ) Treatment: Post-weld annealing eliminates weld sensitization and ensures homogenous properties.
- Dimensional Correction: Final sizing through cold drawing or rolling to achieve specified tolerances.
Applications
Instrument Pressure Tubing (Instrument Impulse Tubing)
- Pressure transmitters and gauges in process industries (petrochemical, oil & gas, power generation)
- Instrument impulse lines connecting process vessels to control instrumentation
- High-pressure and high-temperature process monitoring systems
- Compliant with ASME B31.3 (Process Piping) and ASME B31.1 (Power Piping) codes
Analytical Sampling Lines
- Process analyzers requiring clean, non-contaminating sample delivery
- Chromatography and spectroscopy sample lines
- Water quality monitoring and environmental analysis systems
- Pharmaceutical and bioprocess analytical instrumentation
- Electropolished surface finish eliminates dead legs and prevents sample contamination
Refrigeration & HVAC — Copper Tube Replacement
- Refrigerant piping in commercial and industrial refrigeration systems
- Heat exchanger coil tubing (condensers, evaporators, dry coolers)
- Applications where copper is prohibited due to environmental regulations or corrosion concerns
- Advantages over copper: superior corrosion resistance, longer service life, non-toxic, recyclable, compatible with ammonia and CO₂ refrigerants
Additional Applications
- Medical device tubing and endoscope channels
- Food and beverage processing hygienic piping
- Hydraulic and pneumatic control lines
- Automotive fuel and exhaust system components
- Semiconductor clean-room fluid delivery systems
Quality Certifications & Compliance
Standards Compliance
| Standard | Description | Scope |
|---|---|---|
| ASTM A554 | Standard Specification for Seamless and Wrought Stainless Steel Tube, Cold-Drawn | Material & dimensions |
| ASTM A269 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for Chemical and Similar Severe Service | Chemical service applications |
| EN 10217-7 | Non-ferrous metal tubes for pressure purposes — Technical delivery conditions — Stainless steel tubes | European pressure applications |
| ISO 1127 | Stainless steel seamless tubes for pressure purposes | International pressure applications |
| ASME B31.3 | Process Piping Code | Process instrumentation piping |
| 3-A Sanitary Standards | Dairy, Juice, and Food Industry Equipment | Hygienic surface finish |
Manufacturing Certifications
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- ISO 45001:2018 — Occupational Health & Safety Management
- EN 10204 3.1 — Inspection Certificate (material and dimensional verification)
- EN 10204 3.2 — Inspection Certificate (independent third-party verification available)
Inspection & Testing Protocols
- Chemical Analysis: Spark OES or wet chemistry for full compositional verification (Ni, Cr, Mo, C, N, S)
- Dimensional Inspection: Laser micrometry and optical measurement for OD, wall thickness, and roundness
- Mechanical Testing: Tensile testing per ASTM A370; hardness testing per ASTM E92
- Non-Destructive Testing (NDT): Eddy current testing (ECT) for internal/external defect detection; hydrostatic pressure testing at 1.5× design pressure
- Surface Inspection: Visual and dye penetrant testing (PT) per ASTM E709
- Intergranular Corrosion Testing: ASTM A262 Practice A or E (for sensitization assessment)
Unique Selling Points
1. Precision Dimensional Accuracy: Cold-drawn and mandrelled process achieves OD tolerances as tight as ±0.05 mm — critical for instrument fitting compatibility and leak-free assembly.
2. Superior Surface Integrity: Electropolished finish (Ra ≤ 0.4 μm) eliminates surface defects, reduces bacterial adhesion, and prevents sample contamination in analytical applications.
3. Full Traceability: Each coil is supplied with a mill test certificate (MTC) providing complete heat number traceability from raw material through final product.
4. Copper Replacement Advantage: Eliminates copper-related environmental and regulatory concerns while offering superior mechanical properties, corrosion resistance, and service life in refrigeration applications.
5. Flexible Customization: Custom coil diameters, surface finishes, end treatments, and cutting services available to meet specific project requirements.
Technical Notes
- For instrument impulse lines operating above 100 bar, specify wall thickness ≥ 0.8 mm and verify design per ASME B31.3 pressure rating calculations.
- For ammonia refrigeration systems, 304 grade is the minimum recommended; 316L is preferred for wet ammonia service.
- Electropolished tubes should be protected with anti-corrosion packaging (VCI film or desiccant) to prevent post-finishing contamination.
- Coil storage: maintain in original packaging in a dry environment (RH < 60%) to prevent surface staining or intergranular corrosion.
- Minimum order quantities and lead times vary by grade and specification — contact Wenzhou Jixing Metal Materials Co., Ltd for current availability.