347 Stainless Steel: Niobium-Stabilized for High Heat

 

What defines 347's chemical composition?

It contains 17-19% chromium, 9-13% nickel, 0.75-1.5% niobium (plus tantalum), and 0.08% max carbon. Niobium forms stable carbides, preventing chromium depletion in weld zones, which enhances post-weld corrosion resistance.

 

How does 347 perform in high-temperature environments?

347 thrives in continuous use up to 1500°F (816°C), with good resistance to creep and oxidation. Its niobium stabilizer makes it more stable than 321 in prolonged high heat, suitable for furnace parts and turbine components.

 

What are its corrosion resistance properties?

It offers excellent resistance to intergranular corrosion, even after welding, outperforming 304 in welded structures. It resists general corrosion in mild chemicals and atmospheric conditions, though less resistant to chlorides than 316.

 

How does 347 compare to 321 in fabrication?

347 is weldable with standard techniques, producing more stable welds in high heat than 321. It has good formability for bending and rolling, with slightly lower ductility than 304 but better high-temperature strength.

 

Where is 347 commonly used?

Found in gas turbine components, nuclear reactor piping, and industrial furnace parts. It's also used in chemical processing equipment with welded joints operating at elevated temperatures.