347 Stainless Steel Heat-Resistant Coil Tube — Nb/Ta Stabilized Austenitic Alloy
Product Overview
The 347 Stainless Steel Coil Tube is a premium-grade austenitic heat-resistant tubing product engineered for the most demanding high-temperature industrial environments. Supplied by Wenzhou Jixing Metal Materials Co., Ltd, this coil tube is specifically designed for applications where sustained exposure to extreme temperatures requires exceptional resistance to thermal creep, intergranular corrosion, and oxidation. As an austenitic heat-resistant alloy in the "Austenitic—Heat-Resistant" material classification, 347 coil tube represents a significant performance upgrade over its counterpart, Grade 321, delivering superior mechanical integrity and service life in high-temperature service conditions.
Material & Properties
Grade 347 stainless steel is a niobium (Nb) and/or tantalum (Ta) stabilized austenitic chromium-nickel alloy. The addition of these powerful stabilizing elements effectively prevents chromium carbide precipitation at grain boundaries during prolonged exposure to elevated temperatures, thereby eliminating the risk of sensitization and intergranular corrosion. This makes 347 coil tube the material of choice for continuous service in the 800–1150°C (1472–2102°F) temperature range.
Key Performance Characteristics
- Nb/Ta Stabilization: Niobium and tantalum form stable carbides (NbC, TaC) that are far more resistant to decomposition than titanium carbides found in Grade 321, ensuring long-term structural integrity at elevated temperatures.
- Superior High-Temperature Creep Resistance: 347 exhibits significantly higher creep strength than 321 at temperatures above 800°C, making it ideal for sustained-load applications under thermal stress.
- Enhanced Oxidation Resistance: The stabilized microstructure provides a robust protective oxide layer that resists scaling and spallation during prolonged high-temperature exposure.
- Non-Magnetic & Weldable: Maintains full austenitic non-magnetic properties and excellent weldability without requiring post-weld stabilization heat treatment.
- Corrosion Resistance: Provides good resistance to a wide range of oxidizing and mildly reducing acids, particularly where elevated temperatures are present.
Specifications
| Parameter | Specification |
|---|---|
| Material Grade | ASTM A313 / A313M Type 347 (UNS S34700) |
| Equivalent Grades | 1.4808 (EN), X10CrNiNb18-10 (DIN) |
| Classification | Austenitic — Heat-Resistant / Nb-Ta Stabilized |
| Chromium (Cr) | 17.0% – 19.0% |
| Nickel (Ni) | 9.0% – 13.0% |
| Niobium (Nb) | 8× (C max) – 10% |
| Carbon (C) | ≤ 0.08% |
| Manganese (Mn) | ≤ 2.0% |
| Silicon (Si) | ≤ 1.0% |
| Maximum Service Temperature | 1150°C (2102°F) |
| Creep Strength Advantage | Superior to Grade 321 at 800–1150°C |
| Available Forms | Coil Tube, Seamless Tubing, Cold-Drawn Coil |
| Typical Outer Diameters | 6.35 mm – 50.8 mm (1/4" – 2") |
| Wall Thicknesses | 0.5 mm – 6.35 mm (0.020" – 0.250") |
| Finish Options | Bright Annealed (BA), Pickled & Passivated (P&P), Polished |
| Supply Condition | Annealed, Cold-Drawn |
Manufacturing Process
Wenzhou Jixing Metal Materials Co., Ltd adheres to rigorous international manufacturing standards to produce 347 stainless steel coil tubes that meet the exacting requirements of high-temperature industrial applications. The manufacturing process encompasses the following critical stages:
- Raw Material Selection: Only certified 347-grade stainless steel billets and strip from approved mills are sourced, ensuring traceability and chemical composition compliance with ASTM A313 / ASME SA-313 specifications.
- Hot Rolling & Annealing: Billets are hot-rolled to the required outer diameter and wall thickness, followed by solution annealing to achieve a fully austenitic, stress-free microstructure.
- Pickling & Passivation: Tubes are chemically cleaned and passivated to remove oxide scales and form a protective chromium oxide film, ensuring maximum corrosion resistance.
- Cold Drawing / Cold Reduction: For tighter tolerances and enhanced mechanical properties, tubes undergo precision cold drawing through calibrated dies to achieve exact dimensional specifications.
- Coiling: Finished tubes are coiled to the required length and diameter using automated coiling equipment, maintaining uniform curvature and preventing mechanical damage.
- Quality Inspection: Every batch undergoes comprehensive inspection including chemical analysis, mechanical testing, dimensional verification, hydrostatic pressure testing, and surface quality assessment.
Applications
347 Stainless Steel Coil Tube is the preferred material for critical components operating under sustained high-temperature conditions where the limitations of Grade 321 are exceeded. Key application sectors include:
- Gas Turbine Components: Combustion chamber liners, turbine blade root housings, exhaust ducting, and hot gas path components where exceptional creep resistance and oxidation resistance are paramount.
- High-Temperature Catalytic Cracking Units: Reactor internals, heat exchanger tubes, and process piping in FCC (Fluid Catalytic Cracking) units operating at temperatures exceeding 800°C.
- Aerospace Engineering: Jet engine exhaust systems, thermal protection components, and high-temperature structural elements.
- Power Generation: Boiler tubes, superheater elements, and heat recovery steam generators (HRSG) in combined-cycle power plants.
- Petrochemical Processing: High-temperature reforming furnaces, catalytic converter substrates, and process equipment in refining and chemical plants.
- Industrial Furnace Components: Heat treat furnace fixtures, conveyor belts, and radiant tubes operating in oxidizing atmospheres at elevated temperatures.
- Waste-to-Energy Systems: Combustion chamber components and flue gas ducting in municipal solid waste incineration facilities.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd is committed to delivering products that meet the highest international quality standards. 347 Stainless Steel Coil Tube is manufactured and certified in accordance with:
- ISO 9001:2015 — Quality Management System Certification
- ASTM A313 / A313M — Standard Specification for Seamless Ferritic and Austenitic Cr-Fe and Cr-Ni-Fe-Al Alloy Tubing for High Temperature Service
- ASME SA-313 / SA-313M — Code specification for high-temperature tubing
- EN 10216-5 — European specification for austenitic stainless steel tubes
- EN 10088-1 — European designation for stainless steel grades
- Mill Test Certifications (MTC) — Full chemical composition and mechanical property documentation per batch
- Hydrostatic Pressure Testing — 100% inline testing of all tube lengths
- EDM (Electrical Discharge Machining) Inspection — Non-destructive testing for subsurface defects
- Surface Inspection — Visual and eddy current testing for surface integrity
Unique Selling Proposition: With its Nb/Ta dual-stabilization technology, 347 Stainless Steel Coil Tube delivers measurably superior high-temperature creep strength and oxidation resistance compared to conventional Grade 321 — extending service life, reducing maintenance intervals, and ensuring operational reliability in the most extreme thermal environments. Wenzhou Jixing Metal Materials Co., Ltd provides this premium material in precisely coiled configurations, ready for direct integration into fabrication workflows with minimal secondary processing.