304 Stainless Steel Coil Tube — Technical Specification
Product Overview
The 304 Stainless Steel Coil Tube (Coiltube) is a precision-engineered austenitic stainless steel tubing product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is supplied in continuous coil form, offering exceptional flexibility for downstream forming, bending, and fabrication operations. The tube is designed in accordance with rigorous engineering standards and incorporates advanced metallurgical control measures to ensure resistance against cracking, stress corrosion, and other failure modes commonly encountered in austenitic stainless steel tubing.
Through extensive failure analysis research — particularly regarding 304 Stainless Steel Coil Tube Cracking Failure Analysis — the manufacturer has developed specialized process controls to mitigate susceptibility to intergranular corrosion, sensitization cracking, and stress-induced fracture. This expertise is directly translated into superior product integrity, reliability, and service life.
Material & Properties
The coil tube is fabricated from AISI 304 / ASTM A213 TP304 / EN 1.4301 austenitic stainless steel, a non-magnetic alloy renowned for its excellent corrosion resistance, formability, and weldability.
Chemical Composition (Typical, wt%)
| Element | Specification |
|---|---|
| Carbon (C) | ≤ 0.08% |
| Manganese (Mn) | ≤ 2.00% |
| Phosphorus (P) | ≤ 0.045% |
| Sulfur (S) | ≤ 0.030% |
| Silicon (Si) | ≤ 1.00% |
| Chromium (Cr) | 18.00 – 20.00% |
| Nickel (Ni) | 8.00 – 10.50% |
| Nitrogen (N) | ≤ 0.10% |
| Iron (Fe) | Balance |
Mechanical Properties (Annealed Condition)
| Property | Value |
|---|---|
| Tensile Strength (Rm) | ≥ 520 MPa (75,400 psi) |
| Yield Strength (Rp0.2) | ≥ 205 MPa (29,700 psi) |
| Elongation (A50mm) | ≥ 40% |
| Hardness | ≤ 201 HB / ≤ 92 HRB |
| Density | 8.0 g/cm³ |
| Thermal Conductivity (20°C) | 16.3 W/(m·K) |
| Modulus of Elasticity | 193 GPa |
Corrosion & Failure Resistance
- Intergranular Corrosion Resistance: Enhanced through strict carbon control (C ≤ 0.08%) and optimized heat treatment to prevent chromium carbide precipitation at grain boundaries.
- Stress Corrosion Cracking (SCC) Resistance: Improved via controlled residual stress elimination during the coiling and annealing process.
- Crevice Corrosion Resistance: Superior passive film formation due to high chromium content (≥ 18%).
- Oxidation Resistance: Stable up to 870°C in intermittent service; 815°C in continuous service.
Specifications
| Parameter | Specification |
|---|---|
| Product Name | 304 Stainless Steel Coil Tube (Coiltube) |
| Product Code | 754 |
| Material Grade | 304 / 304L (on request) |
| Standards | ASTM A213, ASTM A269, ASME SA-213, EN 10216-5, GB/T 12771 |
| Outer Diameter (OD) | 6.0 mm – 219.1 mm (1/4" – 8") |
| Wall Thickness | 0.5 mm – 6.0 mm |
| Coil Length | Custom (typically 2,000 – 6,000 mm) |
| Surface Finish | 2B (Cold Rolled Annealed), BA (Bright Annealed), No.4 Brushed |
| Surface Roughness | Ra ≤ 0.8 μm (BA finish); Ra ≤ 1.6 μm (2B finish) |
| Weld Seam | Continuous TIG welded or seamless (ERW) |
| Tolerance (OD) | ±0.1 mm to ±0.5 mm (per agreement) |
| Tolerance (Wall) | ±10% of nominal |
| Delivery Condition | Annealed (Solution Heat Treated) |
| Coil Packaging | Wooden case / export-standard packaging with moisture barrier |
Manufacturing Process
The production of 304 stainless steel coil tubes follows a rigorous multi-stage manufacturing sequence designed to ensure metallurgical integrity and dimensional precision:
- Raw Material Selection: Virgin 304 stainless steel strip sourced from certified mills with full chemical composition traceability.
- Coil Straightening & Forming: Precision roll-forming of flat strip into tubular geometry with controlled feed rates to minimize work hardening.
- Welding (if applicable): High-frequency induction welding (ERW) or continuous TIG welding with inert gas (Ar) internal shielding to prevent oxidation at the weld seam.
- Solution Annealing: Continuous annealing at 1050–1100°C in a protective atmosphere (H₂/N₂ or vacuum) followed by controlled cooling to dissolve carbides and restore full austenitic microstructure — a critical step in preventing cracking failures.
- Pickling & Passivation: Removal of oxide scale via controlled acid pickling, followed by passivation treatment to enhance the protective chromium oxide film.
- Surface Finishing: Polishing, brushing, or bright annealing to achieve specified surface quality.
- Coiling & Packaging: Controlled coiling with protective paper wrapping, shrink-wrap, and export-grade wooden case packaging.
Applications
- Food & Beverage Industry: Processing equipment, piping systems, heat exchangers, and sanitary-grade fluid transfer lines.
- Pharmaceutical Industry: Clean-in-place (CIP) systems, reactor vessels, and process tubing requiring high purity.
- Automotive Industry: Exhaust systems, fuel lines, and structural components.
- Chemical Processing: Corrosive fluid handling, reactor coils, and heat transfer systems.
- Construction & Architecture: Structural tubing, decorative elements, and railing systems.
- Medical Equipment: Instrument tubing, surgical device components, and imaging equipment housings.
- Energy Sector: Solar water heating systems, heat exchanger coils, and cryogenic applications.
Quality Certifications & Assurance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring product conformity and traceability:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System
- ISO/IEC 17025 — Testing and Calibration Laboratory Competence
- CE Marking — European Conformity
- PED (Pressure Equipment Directive 2014/68/EU) — For pressure-containing applications
- EN 10204 3.1 — Third-party material test certificates
In-House Quality Control Measures
| Inspection Stage | Test Method | Standard |
|---|---|---|
| Incoming Material | Spectroscopic Analysis (OES) | ASTM E415 |
| In-Process | Dimensional Measurement (CMM) | ISO 1101 |
| Post-Annealing | Grain Boundary Attack Test (ASTM A262 Practice E) | ASTM A262 |
| Post-Annealing | Macro/Micro Etch Examination | ASTM E3 |
| Final | Hydrostatic Pressure Test | ASTM A213 |
| Final | Surface Defect Inspection (Dye Penetrant) | ASTM E709 |
| Final | Hardness Testing | ASTM E18 / E92 |
Unique Selling Points
Our 304 Stainless Steel Coil Tube products are distinguished by:
- Failure-Analysis-Driven Design: Extensive research into 304 coil tube cracking failure mechanisms informs our process parameters, ensuring superior resistance to intergranular cracking, sensitization, and stress corrosion.
- Precision Annealing Control: Optimized solution heat treatment eliminates carbide precipitation, preserving full ductility and corrosion resistance throughout the product's service life.
- Full Traceability: Each coil is accompanied by a complete material passport including heat number, chemical analysis, mechanical test data, and annealing cycle records.
- Customization Capability: Flexible specifications for OD, wall thickness, coil length, surface finish, and packaging to meet project-specific requirements.
- Global Compliance: Products conform to international standards (ASTM, EN, JIS, GB), enabling seamless integration into global supply chains.
- Cost-Effective Continuous Supply: Coil format minimizes cutting waste and facilitates automated downstream processing, reducing overall project costs.
Technical Note on Cracking Prevention
Based on comprehensive failure analysis studies, the following root causes of 304 coil tube cracking have been identified and addressed in our manufacturing protocol:
- Chromium Carbide Precipitation: Controlled carbon content and rapid quenching prevent sensitization in the 450–850°C range.
- Residual Stress Accumulation: Post-forming stress relief annealing eliminates work-hardening-induced residual stresses that can initiate crack propagation.
- Weld Seam Defects: Inert gas shielding and real-time weld monitoring prevent porosity, lack of fusion, and oxide inclusions at the weld zone.
- Chloride-Induced SCC: Material certification guarantees Ni/Cr ratios sufficient to maintain passive film stability in chloride-containing environments.
These engineering controls ensure that our 304 Stainless Steel Coil Tubes deliver exceptional reliability in demanding industrial applications where cracking failure is unacceptable.