Seamless Stainless Steel TP347H Tube

ASTM A213 TP347H Seamless Stainless Steel Tube (UNS S34709) is a high-carbon, niobium-stabilized austenitic stainless steel tube designed for high-temperature and high-pressure service environments.

As the “H-grade” version of TP347, it features a controlled carbon content (0.04–0.10%) to enhance:

• Creep strength
• Stress rupture resistance
• Long-term thermal stability

TP347H seamless tubes are manufactured via cold drawing (CF)orhot finishing (HF) processes, ensuring:

• Uniform metallurgical microstructure
• High dimensional accuracy
• Superior pressure integrity (no weld seam risk)

These properties make TP347H the preferred material for boilers, superheaters, and heat exchangers operating above 538°C (1000°F).

Key Features & Technical Advantages

1. Niobium Stabilization (Anti-Sensitization)

• Niobium (Nb) binds carbon to prevent chromium carbide precipitation
• Eliminates risk of intergranular corrosion (IGC) in the heat-affected zone (HAZ)
• Suitable for long-term exposure at 427°C–816°C

2. Excellent High-Temperature Strength

• Optimizedcarbon-to-niobium ratio (Nb ≥ 8×C)
• Superior creep resistance compared to TP304H and TP321
• Ideal for load-bearing components under thermal stress

3. Outstanding Oxidation & Corrosion Resistance

• Performs well in:
  • High-temperature steam
  • Oxidizing atmospheres
  • Flue gas environments

4. Seamless Structural Integrity

• No longitudinal welds
• Enhanced pressure resistance
• Fully compliant with:
  • ASME Section I (Power Boilers)
  • ASME Section VIII (Pressure Vessels)

Technical Specifications

Applicable Standards

• ASTM A213 / ASME SA213
• EN 10216-5
• ASTM A312 (optional piping use)
• JIS G3463 / GB/T 14976

Chemical Composition (Weight %)

The key differentiator of TP347H is the Nb stabilization ratio:

Nb≥8×C

The stabilization ratio (Nb≥8xC) is the critical factor that distinguishes TP347H from standard 304 or 321 grades.