310S Stainless Steel Coil Tube (25Cr-20Ni) — High-Temperature Austenitic Grade
Product Overview
The 310S Stainless Steel Coil Tube is a premium austenitic heat-resistant alloy manufactured by Wenzhou Jixing Metal Materials Co., Ltd. Designed for extreme thermal environments, this grade incorporates a high chromium (Cr) and nickel (Ni) composition—approximately 25% Cr and 20% Ni—delivering exceptional oxidation resistance, thermal stability, and mechanical integrity at temperatures up to 1,050°C (1,922°F) for continuous service. As a coiltube (spooled tube) product, it is supplied in continuous coils, enabling high-efficiency downstream processing, minimal waste, and seamless integration into automated forming and fabrication lines.
Material & Properties
The 310S grade is an improved variant of the original 310 austenitic stainless steel, with a slight reduction in carbon content to enhance weldability and minimize intergranular corrosion susceptibility. Its austenitic crystal structure (face-centered cubic, FCC) provides superior ductility, thermal fatigue resistance, and resistance to scaling and spalling at elevated temperatures.
- Chemical Composition: 24.0–26.0% Cr, 19.0–22.0% Ni, ≤0.08% C, ≤0.04% S, ≤0.03% P, ≤0.03% Si
- Microstructure: Fully austenitic (γ-phase) with retained δ-ferrite typically <5%
- Maximum Continuous Use Temperature: 1,050°C (1,922°F)
- Intermittent Service Temperature: Up to 1,150°C (2,094°F)
- Thermal Conductivity (at 1,000°C): ~30 W/m·K
- Thermal Expansion Coefficient (20–1,000°C): ~18.5 × 10⁻⁶/K
- Oxidation Resistance: Excellent in oxidizing atmospheres; forms a stable, self-healing Cr₂O₃ protective scale
- Magnetic Properties: Non-magnetic (austenitic)
Specifications
| Parameter | Specification |
|---|---|
| Grade / Standard | 310S (ASTM A213/A269, EN 10216-5, GB/T 12771) |
| Product Form | Coiltube (Continuous Spooled Tube) |
| Outer Diameter (OD) | 6.0 mm – 50.8 mm (custom sizes available upon request) |
| Wall Thickness | 0.5 mm – 3.0 mm |
| Coil Weight | Typically 300 kg – 800 kg per coil |
| Surface Finish | Pickled & Passivated (2B), or Polished upon request |
| Tolerance (OD) | ±0.05 mm – ±0.10 mm (per ASTM A213) |
| Tolerance (Wall) | ±10% of nominal wall thickness |
| Manufacturing Method | Seamless (hot-rolled or cold-drawn) or Welded (ERW/SAW) |
| Heat Treatment | Solution Annealed at 1,050–1,150°C, followed by rapid quenching |
| Yield Strength (at 20°C) | ≥205 MPa |
| Tensile Strength (at 20°C) | ≥515 MPa |
| Yield Strength (at 1,000°C) | ≥62 MPa |
| Application Category | Austenitic Heat-Resistant (奥氏体-耐热型) |
Manufacturing Process
The production of 310S stainless steel coiltube involves a multi-stage metallurgical and mechanical process chain, ensuring the final product meets rigorous dimensional and performance standards:
- Raw Material Preparation: High-purity chromium and nickel ingots are melted in vacuum arc or EAF (Electric Arc Furnace) + AOD (Argon Oxygen Decarburization) processes to achieve precise alloy composition and ultra-low sulfur/phosphorus content.
- Hot Rolling / Billet Extrusion: The refined billet is reheated to 1,200–1,300°C and hot-rolled or extruded into seamless tube blanks (hollow bars).
- Piercing & Elongation: Tube blanks are pierced and elongated through a series of mandrel-die reduction stands to achieve the target OD and wall thickness.
- Cold Drawing / Cold Pilgering (Optional): For tighter tolerances and superior surface finish, hot-rolled tubes are cold-drawn through tungsten carbide dies.
- Solution Annealing: Tubes are heated to 1,050–1,150°C in a protective atmosphere (H₂/N₂ or vacuum) and rapidly quenched in water to restore full austenitic structure and relieve residual stresses.
- Pickling & Passivation: The surface is cleaned via hydrofluoric/nitric acid pickling to remove scale, followed by passivation to form a protective chromium oxide film.
- Coiling & Inspection: Finished tubes are coiled onto spools, with each coil undergoing dimensional measurement, visual inspection, and optional NDT (Non-Destructive Testing) including eddy current and hydrostatic testing.
Applications
The 310S coiltube is engineered for the most demanding high-temperature industrial applications, including:
- Furnace Interior Components: Radiant tubes, burner tubes, muffles, and heating elements in industrial furnaces operating continuously above 900°C.
- Heat Treatment Equipment: Carburizing, nitriding, and annealing furnace fixtures requiring dimensional stability at extreme temperatures.
- High-Temperature Flue Gas Waste Heat Recovery: Heat exchanger tubes and ducting for recovering thermal energy from flue gases exceeding 800°C in power plants, cement kilns, and metallurgical processes.
- Petrochemical & Refinery Processes: High-temperature reforming coils, cracker tubes, and catalyst support structures in steam methane reforming (SMR) and ethylene production.
- Power Generation: Boiler tube components, superheater elements, and exhaust system parts in combined-cycle gas turbine (CCGT) facilities.
- Industrial Kilns & Drying Ovens: Conveyor chains, guides, and structural supports in ceramic, glass, and food-processing kilns.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system to ensure every batch of 310S coiltube meets or exceeds international standards:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System
- EN 10204 3.1 — Material Test Reports (MTR) provided with each shipment
- ASTM A213 / A269 — Compliance for seamless and welded austenitic stainless steel tubes
- EN 10216-5 — European standard for austenitic stainless steel tubes for pressure purposes
- GB/T 12771 — Chinese national standard for stainless steel seamless tubes
- Mill Test Certification: Full chemical analysis, mechanical testing (tensile, hardness, impact), and heat treatment verification
- Non-Destructive Testing: Eddy current inspection, hydrostatic pressure testing, and dye penetrant inspection (DPI) available
Unique Selling Points
1. Unmatched Thermal Endurance: Continuous service up to 1,050°C makes 310S the highest-temperature austenitic grade commonly available in coiltube form—eliminating the need for exotic superalloys in many applications.
2. Coil Supply Advantage: Delivered as continuous coils, reducing cutting waste by up to 30% compared to straight-length tubes, and enabling fully automated downstream processing.
3. Enhanced Weldability: The low-carbon (≤0.08% C) formulation of 310S provides superior weldability over the original 310 grade, minimizing sensitization and intergranular corrosion in welded assemblies.
4. Self-Healing Oxidation Protection: The high chromium content ensures rapid reformation of a protective Cr₂O₃ scale, maintaining component integrity through repeated thermal cycling.
5. Custom Fabrication Capability: Wenzhou Jixing offers tailored OD, wall thickness, and surface finish specifications to meet project-specific engineering requirements.