304 Austenitic Stainless Steel Coil Tube — Technical Specification
1. Product Overview
The 304 Stainless Steel Coil Tube (SAE 304 / UNS S30400 / AISI 304) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a continuously wound, cold-drawn seamless coil tube designed for broad industrial and commercial applications. As the foundational grade within the austenitic stainless steel family, 304 coil tube represents the industry's most widely circulated and price-referenced product category. Its balanced composition of chromium and nickel provides reliable resistance to atmospheric corrosion, weak acidic media, and general environmental exposure, making it the default specification for applications where exceptional corrosion resistance is not required but dependable performance and cost-efficiency are paramount.
This product is supplied in continuous coil form, enabling high-speed feeding into downstream processing equipment including tube cutting, bending, welding, and forming lines. The coil configuration minimizes material waste through optimized cutting patterns and reduces handling labor compared to individual lengths.
2. Material Composition & Properties
2.1 Chemical Composition (Nominal)
| Element | Specification (%) | Functional Role |
|---|---|---|
| Carbon (C) | ≤ 0.08 | Controls grain boundary carbide precipitation; lower carbon improves weldability and intergranular corrosion resistance |
| Chromium (Cr) | 18.0 – 20.0 | Primary corrosion-resistant element; forms passive Cr₂O₃ oxide film on the surface |
| Nickel (Ni) | 8.0 – 10.5 | Stabilizes austenitic microstructure; enhances ductility, toughness, and corrosion resistance |
| Manganese (Mn) | ≤ 2.0 | Aids deoxidization during steelmaking; partially substitutes for nickel |
| Silicon (Si) | ≤ 1.0 | Deoxidizer; contributes to high-temperature oxidation resistance |
| Sulfur (S) | ≤ 0.03 | Controlled impurity; excessive levels cause hot shortness and inclusions |
| Phosphorus (P) | ≤ 0.045 | Controlled impurity; excessive levels reduce ductility and cold workability |
| Iron (Fe) | Balance | Matrix element |
2.2 Mechanical Properties (Annealed Condition, Reference)
| Property | Specification |
|---|---|
| Tensile Strength (Rm) | ≥ 515 MPa (74.7 ksi) |
| Yield Strength (Rp0.2) | ≥ 205 MPa (29.7 ksi) |
| Elongation at Break (A50mm) | ≥ 40 % |
| Hardness (HBW) | ≤ 201 |
| Density | 8.00 g/cm³ |
| Thermal Conductivity (20 °C) | 16.3 W/(m·K) |
| Thermal Expansion Coefficient (20–100 °C) | 17.3 × 10⁻⁶ /K |
| Maximum Service Temperature | 870 °C (1598 °F) — non-oxidizing atmosphere |
2.3 Corrosion Resistance Characteristics
- Atmospheric Corrosion: Excellent resistance to urban, rural, and industrial atmospheres under normal conditions.
- Weak Acid Media: Resistant to dilute sulfuric acid (< 20 %), dilute hydrochloric acid, and organic acids at ambient temperature.
- Oxidizing Environments: Good performance in neutral to mildly alkaline aqueous solutions.
- Limitations: Not recommended for concentrated chlorides (> 0.01 % Cl⁻) or highly reducing acids due to susceptibility to pitting and crevice corrosion.
3. Product Specifications
| Parameter | Specification / Range |
|---|---|
| Product Designation | 304 Stainless Steel Coil Tube (SAE 304 / UNS S30400) |
| Standard References | ASTM A554, ASTM A269, GB/T 12771, GB/T 14976, EN 10217-7 |
| Outer Diameter (OD) | 3.0 mm – 168.3 mm (configurable per order) |
| Wall Thickness (WT) | 0.25 mm – 6.00 mm (configurable per order) |
| Coil Inner Diameter (ID) | 508 mm (20 in) / 610 mm (24 in) — standard; custom available |
| Coil Length | 15 m – 150 m (continuous, cut-to-length available) |
| Coil Weight | 500 kg – 3,000 kg (typical) |
| Surface Finish | Bright Annealed (BA), No. 1 Annealed Pickled, No. 4 Brushed, No. 8 Mirror |
| Manufacturing Method | Seamless — Cold Drawing / Cold Roll Forming |
| Heat Treatment | Solution Annealing at 1050–1150 °C, followed by rapid air or water quench |
| Available Condition | Annealed (A), Half-Hard (H½), Three-Quarter Hard (H¾), Full Hard (H) |
| Dimensional Tolerance (OD) | ± 0.05 mm – ± 0.15 mm (per ASTM A554) |
| Dimensional Tolerance (WT) | ± 10 % of nominal (per ASTM A554) |
| Roundness Tolerance | ≤ 1 % of nominal OD |
| Straightness (after straightening) | ≤ 1.5 mm/m |
4. Manufacturing Process
The production of 304 stainless steel coil tube at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous multi-stage manufacturing workflow:
- Raw Material Selection: Virgin stainless steel billets or wire rod of certified 304 composition, verified through spectroscopic analysis (OES) for chemical compliance.
- Piercing: Hot-rolled billets are pierced into seamless hollow blanks (tube blanks) via rotary or push-through piercing mills.
- Hot Rolling / Sizing: Preliminary sizing to approximate the target outer diameter and wall thickness.
- Pickling & Annealing: Hot-rolled scale is removed through acid pickling (mixed HNO₃/HF solution), followed by solution annealing to restore full austenitic microstructure.
- Cold Drawing / Cold Pilgering: The tube blank is drawn through precision dies to achieve final dimensions with tight tolerances. Multiple drawing passes may be employed for thin-wall products.
- Intermediate Annealing: Periodic annealing between cold work passes to relieve accumulated strain and maintain ductility.
- Cold Roll Forming (Alternative): For certain wall-thickness ranges, strip material is cold-formed into tube geometry via roll-forming stations.
- Final Annealing & Pickling: Final solution treatment ensures uniform properties and clean surface preparation.
- Coiling & Packaging: The finished tube is wound onto precision coilers, wrapped in protective film, and packaged in moisture-resistant cartons or steel containers.
5. Applications
The versatility of 304 coil tube renders it suitable for a wide spectrum of industries and end-use applications:
- Food Processing & Beverage Industry: Hygienic piping, conveyor components, brewing equipment, dairy processing lines (meeting FDA and EHEDG requirements).
- Chemical & Petrochemical: Transport lines for non-aggressive chemicals, heat exchanger tubes, reactor components in mild service conditions.
- Pharmaceutical: Process piping, equipment fabrication, CIP (Clean-in-Place) systems requiring sanitary-grade surfaces.
- Architecture & Construction: Structural elements, handrails, decorative trims, window frames, curtain wall supports.
- Automotive & Transportation: Exhaust system components, fuel lines, structural tubing, chassis parts.
- General Engineering: Fluid conveyance systems, hydraulic lines, instrumentation tubing, sensor housings.
- Household & Appliances: Washing machine drums, refrigerator components, water heater elements, kitchen fixtures.
- Energy Sector: Solar thermal collector tubes, boiler accessories, non-critical heat transfer applications.
6. Quality Certifications & Testing
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality assurance framework ensuring product conformity:
6.1 Certifications & Compliance
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System certification
- EN 10204 — Type 3.1 / Type 3.2 mill test certificates (MTC) available per shipment
- CE Marking — Conformity with European directives where applicable
- GB/T Standards Compliance — Full adherence to Chinese national standards for stainless steel tubing
6.2 In-Process & Final Inspection
- Chemical Analysis: Optical emission spectroscopy (OES) verification of elemental composition against ASTM/GB specifications.
- Mechanical Testing: Tensile testing, hardness testing, and elongation measurement on each production heat.
- Dimensional Inspection: Laser micrometer measurement of OD, WT, and roundness at defined intervals.
- Visual & Surface Inspection: Full-length visual examination for surface defects, seams, or mechanical damage.
- Hydrostatic / Pneumatic Testing: Pressure testing at specified multipliers of design pressure to verify tube integrity and absence of leaks.
- Non-Destructive Testing (NDT): Eddy current testing (per ASTM E709) or ultrasonic testing for detection of internal defects in critical applications.
- Corrosion Testing: Salt spray testing (ASTM B117) and intergranular corrosion testing (ASTM A262 Practice E) for qualification in specific service environments.
7. Unique Selling Points
- Market Benchmark Grade: As the most widely traded stainless steel grade globally, 304 coil tube offers the most transparent pricing, the broadest supplier base, and the highest liquidity in the metals market — ensuring procurement flexibility and cost predictability.
- Continuous Coil Supply: Delivered in optimized coil form for seamless integration with automated downstream processing lines, maximizing production throughput and minimizing material waste.
- Balanced Performance-to-Cost Ratio: Provides 90 %+ of the corrosion resistance of higher alloys (e.g., 316L) at significantly lower cost, making it the optimal choice for the majority of industrial applications.
- Full Range Configurability: Available across a wide spectrum of diameters, wall thicknesses, surface finishes, and temper conditions to match specific application requirements without tooling changes.
- Proven Track Record: Decades of global industrial usage provide extensive performance data, design codes, and engineering precedents, reducing qualification risk for new projects.
- Weldability: Excellent weldability in all standard welding processes (TIG, MIG, resistance, orbital) without preheating or post-weld heat treatment in most thickness ranges.
- Formability: Superior cold-work formability enables complex bending, stamping, and spinning operations without cracking or excessive work hardening.
Supplier Note: Wenzhou Jixing Metal Materials Co., Ltd. maintains the 304 coil tube grade as its core product offering, leveraging economies of scale in raw material procurement and continuous improvement in cold-drawing precision to deliver consistent quality at competitive market pricing. Technical support and custom specification development are available upon request.