ASTM A376 TP347H Stainless Steel Seamless Pipe Pickled Annealed Industry Pipe

ASTM A376 TP347H Stainless Steel Seamless Pipe High-performance Austenitic Stainless Steel Seamless Pipe

Comparison with Similar Grades

• vs. ASTM A312 TP347H: A376 and A312 both cover TP347H. The key difference is the intended service.

  • A376 is specifically for seamless pipe for high-temperature service (like power plant main steam lines). It has more stringent requirements on heat treatment (typically solution annealed above 1950°F / 1065°C) and mandatory hydrostatic or non-destructive electric tests.

  • A312 is a more general standard for both seamless and welded austenitic stainless steel pipe, used for a wider range of applications, including corrosive services at lower temperatures.

• vs. TP321/321H: Both 347 and 321 are stabilized grades. TP321 uses Titanium (Ti) instead of Niobium for stabilization. TP347H is generally preferred for its superior high-temperature strength and better fabrication characteristics in certain welding applications.

ASTM A376 TP347H Stainless Steel Seamless Pipe Specification

Key Features and Advantages

1. Excellent High-Temperature Strength: The primary advantage. The higher carbon content and niobium stabilization give TP347H superior creep and stress rupture strength at temperatures typically above 1000°F (540°C). This is essential for superheater and reheater tubes in boilers.

2. Resistance to Sensitization and Intergranular Corrosion:

   • When standard austenitic stainless steels (like 304) are heated in a critical temperature range (approx. 800°F - 1500°F / 427°C - 816°C), chromium carbides can form along the grain boundaries. This depletes chromium in adjacent areas, making them susceptible to corrosion, a phenomenon known as sensitization.

   • The addition of Niobium (Nb) in TP347H preferentially combines with carbon to form niobium carbides. This prevents the chromium from being tied up, thus maintaining the corrosion resistance of the alloy and preventing sensitization.

3. Good Oxidation Resistance: The high chromium content provides excellent resistance to scaling and oxidation in high-temperature environments, such as those found in fossil fuel power plants.

4. Good Fabricability: While harder to machine than carbon steels, it can be welded and formed using standard techniques for austenitic stainless steels, though care must be taken to preserve its corrosion and high-temperature properties.

Applications

• Food processing equipment, particularly in beer brewing, milk processing & wine making.
• Kitchen benches, sinks, troughs, equipment and appliances
• Architectural panelling, railings & trim
• Chemical containers, including for transport
• Heat Exchangers
• Woven or welded screens for mining, quarrying & water filtration
• Threaded fasteners
• Springs