304 Austenitic Stainless Steel Coil Tube — 18Cr-8Ni General Purpose Grade
Product Overview
The 304 Stainless Steel Coil Tube (also designated as SUS304, X5CrNi18-10, or UNS S30400) is a general-purpose austenitic stainless steel coil tube supplied by Wenzhou Jixing Metal Materials Co., Ltd. As the most widely circulated stainless steel grade globally, 304 serves as the foundational benchmark for pricing, procurement, and specification across the metallurgical and pipe-making industries. Its designation "18Cr-8Ni" reflects its nominal composition of approximately 18% chromium and 8% nickel by mass, providing an excellent balance of corrosion resistance, formability, weldability, and mechanical strength.
Delivered in coil form, this product offers superior logistical efficiency, minimal material waste during downstream processing, and seamless continuity for automated forming and cutting operations. The coil configuration is particularly advantageous for high-volume production environments where straight-length tubes would impose handling and inventory constraints.
Material & Properties
The 304 grade belongs to the austenitic family of stainless steels (austenite structure at room temperature), characterized by a face-centered cubic (FCC) crystal lattice that confers non-magnetic properties in the annealed condition. The primary alloying elements and their metallurgical functions are as follows:
- Chromium (Cr, 18–20%): Forms a passive chromium oxide (Cr₂O₃) film on the surface, providing resistance to atmospheric corrosion, mild acids, and oxidizing environments.
- Nickel (Ni, 8–10.5%): Stabilizes the austenitic microstructure, enhances ductility, and improves resistance to reducing acids and alkali solutions.
- Carbon (C, ≤0.08%): Controlled at low levels to minimize intergranular sensitization during welding and heat treatment.
- Manganese (Mn, ≤2.0%): Partially substitutes for nickel in austenite stabilization while maintaining cost efficiency.
- Silicon (Si, ≤1.0%): Acts as a deoxidizer during steelmaking and contributes to high-temperature strength.
- Phosphorus (P) and Sulfur (S): Restricted to ≤0.045% each to prevent hot shortness and intergranular corrosion susceptibility.
The passive film thickness of 2–5 nm on the 304 surface provides self-healing corrosion protection in the presence of oxygen, making it suitable for atmospheric and weakly aggressive media environments including dilute sulfuric acid, acetic acid, and various organic acids.
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Material Grade | 304 / 1.4301 / SUS304 / S30400 | ASTM A269 / EN 10216-5 / JIS G3459 |
| Chemical Composition (Cr) | 18.0 – 20.0 wt% | ASTM A240 |
| Chemical Composition (Ni) | 8.0 – 10.5 wt% | ASTM A240 |
| Chemical Composition (C) | ≤ 0.08 wt% | ASTM A240 |
| Tube Outer Diameter (OD) | 6.0 – 219.1 mm (customizable) | ASTM A554 / EN 10217 |
| Wall Thickness | 0.5 – 6.0 mm (tolerance ±10%) | ASTM A554 |
| Coil Inner Diameter (ID) | 508 mm / 610 mm (standard) | Manufacturer specification |
| Coil Length | 6 – 20 m per loop (variable) | — |
| Surface Finish | 2B (Cold Rolled & Annealed) / No.4 Brushed / BA (Bright Annealed) | ASTM A480 |
| Hardness (Annealed) | ≤ 201 HB (Brinell) | ASTM A262 |
| Tensile Strength | ≥ 515 MPa (75 ksi) | ASTM A269 |
| Yield Strength (0.2% offset) | ≥ 205 MPa (30 ksi) | ASTM A269 |
| Elongation | ≥ 40% (in 50 mm / 2 in gauge length) | ASTM A269 |
| Operating Temperature Range | −196 °C to +870 °C | — |
| Magnetic Permeability | 1.00–1.05 (essentially non-magnetic) | — |
| Thermal Conductivity | 16.3 W/(m·K) at 100 °C | — |
| Linear Thermal Expansion | 17.3 × 10⁻⁶ /°C (20–100 °C) | — |
Manufacturing Process
The production of 304 stainless steel coil tubes follows a rigorous multi-stage metallurgical and mechanical processing sequence:
- Steelmaking: Vacuum Arc Remelting (VAR) or AOD (Argon Oxygen Decarburization) followed by VOD (Vacuum Oxygen Decarburization) to achieve ultra-low carbon and impurity levels.
- Continuous Casting: Slab or billet casting with controlled cooling rates to ensure uniform grain structure and minimize centerline segregation.
- Hot Rolling: Billets are reheated to 1100–1200 °C and hot-rolled into hollow round bars (HBR) or flat strips, depending on the tube forming route.
- Pickle & Descale: Removal of mill scale via mixed acid (HNO₃/HF or H₂SO₄/HNO₃) pickling to expose the clean passive surface.
- Cold Forming: Seamless tubes are cold-drawn through dies, or welded tubes are formed via ERW (Electrical Resistance Welding) or TIG (Tungsten Inert Gas) welding from cold-rolled strip.
- Cold Drawing & Sizing: Multi-pass cold drawing reduces wall thickness, tightens dimensional tolerances, and imparts beneficial strain hardening.
- Stress Relief Annealing: Solution heat treatment at 1010–1150 °C followed by water quenching to dissolve carbides, restore full austenitic structure, and achieve the annealed mechanical properties.
- Coiling: Finished tubes are wound onto standard coil spools with protective interlayer packaging to prevent mechanical damage during transport.
Applications
The 304 Stainless Steel Coil Tube finds extensive application across numerous industries due to its versatile performance characteristics:
- Food & Beverage Processing: Hygienic piping systems, dairy equipment, brewing lines, and food-grade transfer tubing (FDA compliant).
- Pharmaceutical & Biotechnology: Clean-in-Place (CIP) compatible piping, reactor internals, and sanitary process connections.
- Chemical Processing: Transport of dilute acids, alkali solutions, and organic compounds in non-oxidizing environments.
- Architecture & Construction: Decorative balustrades, structural supports, roofing systems, and facade cladding.
- Automotive & Transportation: Exhaust system components, heat exchangers, and structural tubing.
- Energy & Power Generation: Heat exchanger tubes, condensers, and low-pressure boiler components.
- General Engineering: Structural frameworks, furniture manufacturing, and appliance components.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring full traceability and compliance:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System
- EN 10204 3.1 / 3.2 — Material Test Certificates (Mill Certificates) with third-party inspection option
- CE Marking — Conformity with European directives (PED 2014/68/EU for pressure equipment)
- ASTM / ASME — Compliance with American national standards for materials and pressure vessels
- Mill Test Reports (MTR): Full chemical analysis (OES or wet chemistry) and mechanical test data provided per heat number
- Third-Party Inspection: Available through SGS, Bureau Veritas, or TÜV upon customer request
Unique Selling Points
Market Leadership & Price Benchmark: As the highest-volume stainless steel grade globally, 304 coil tube from Wenzhou Jixing Metal Materials Co., Ltd. represents the industry's price benchmark reference system, ensuring maximum supply chain liquidity, competitive pricing transparency, and guaranteed availability.
- Unmatched Availability: The largest market circulation volume ensures minimal lead times and consistent inventory depth for critical production schedules.
- Optimal Cost-to-Performance Ratio: Provides 90% of the corrosion resistance of premium grades at significantly lower alloying costs, making it the rational default selection for general-purpose applications.
- Superior Formability & Weldability: The high elongation (≥40%) and austenitic structure enable complex cold-forming operations without cracking and permit all standard welding processes without pre- or post-weld heat treatment.
- Cryogenic Capability: Retains full mechanical integrity down to liquid nitrogen temperatures (−196 °C), enabling use in cryogenic and LNG applications.
- Coil Configuration Advantage: Continuous coil delivery eliminates butt-weld joints inherent in straight lengths, reduces handling labor, and integrates seamlessly with automated tube-rolling and CNC cutting equipment.
- Full Traceability: Every coil is heat-number traceable with complete metallurgical documentation from steelmaking through final inspection.