1. A376 TP347H Base Tube Chemical Composition (wt%):

Core Features:

Niobium Stabilization: Forms NbC carbides, preventing chromium depletion at grain boundaries and eliminating intergranular corrosion in weld zones.

Enhanced High-Temperature Performance: Retains oxidation resistance up to 750°C and creep strength ≤650°C (pressure applications).

Mechanical Properties: Tensile strength ≥530 MPa, yield strength ≥205 MPa, elongation ≥40%, hardness ≤289 HBW.

2. A376 TP347H Spiral Fin Tube Production Process

Key Manufacturing Stages:

Steelmaking:

Electric arc furnace + AOD/VOD refining to control impurities (e.g., P, S ≤0.030%) 5.

Strict control of trace elements (As, Sn, Pb ≤0.003%) to ensure purity 5.

Tube Formation:

Hot extrusion or cold drawing to achieve seamless tubes per ASTM A312/ASME SA213 standards 19.

Cold-rolling with >55% deformation per pass for thick-walled tubes (e.g., Φ163×13mm) 9.

Fin Attachment:

Spiral fins helically wound and TIG-welded to the base tube without filler metals 5.

Critical Heat Treatment:

Solution Annealing: 980–1150°C rapid water quenching to dissolve NbC and refine grains 28.

Stabilization Annealing: 850–930°C to precipitate NbC fully, preventing sensitization 110.

Table: Grain Size Control Challenges

Process Stage Temperature/Time Resultant Grain Size Issue
Initial Material - 5级 Acceptable
Standard Solution 1150°C, 3 minutes 9-10级 Over-coarsened (>7级)
Optimized Process Extended time/Re-treat 4-6级 Target achieved.

3. A376 TP347H Spiral Fin Tube ​Advantages 

Corrosion Resistance: Resists HCl, sulfuric acid, and chloride-induced stress corrosion.

Thermal Efficiency: Spiral fins increase surface area 3–8×, reducing energy loss by 15–30% vs. bare tubes.

Erosion Protection: Fins shield base tubes from abrasive flue gases in coal-fired plants.

4. A376 TP347H Spiral Fin Tube Primary Applications:

Power Generation: Superheaters/reheaters in 600MW+ ultra-supercritical boilers (steam: 600–650°C).

Petrochemicals: Heat exchangers for corrosive media (e.g., HCl-containing streams).

Waste-to-Energy: Economizers in incinerators (operating: 400–600°C).

5. A376 TP347H Spiral Fin Tube FAQ

Q1: How does TP347H differ from TP347HFG?

TP347HFG undergoes specialized thermomechanical processing to achieve finer grain size (ASTM 8–10级), enhancing steam oxidation resistance and reducing scaling in boilers.

Q2: Can TP347H be welded without post-weld annealing?

Yes, due to Nb stabilization, it resists sensitization. However, >300°C service with HCl >50 ppm requires post-weld heat treatment to prevent σ-phase embrittlement.

Q3: What causes grain coarsening during heat treatment?

Overly high solution annealing temperatures (>1150°C) or insufficient soaking time. Optimized protocols use 1120–1150°C with controlled cooling.

Q4: Procurement specifications for spiral finned tubes?

Specify: OD (10–762 mm), wall thickness (1–100 mm), fin height/pitch, stabilization annealing per ASME Sec. VIII, and EN 10204 3.1 certification.

6. A376 TP347H Spiral Fin Tube ​Operational Considerations

Oxidation Management: Monitor wall thickness in >600°C steam environments due to oxide layer growth.

HCl Sensitivity: Performance degrades above 300°C with >50 ppm HCl; protective coatings recommended.

Welding Constraints: Use low-heat-input methods (TIG) and avoid interpass temperatures >150°C.

7. Global Standards & Equivalents

Table: International Material Equivalents

Region Standard Equivalent Grade Key Specification
USA ASTM/ASME UNS S34709 SA213, SA312
Europe EN 1.4550/X6CrNiNb18-10 EN 10216-5
Japan JIS SUS347H High-temperature boilers

8. A376 TP347H Spiral Fin Tube ​Conclusion

TP347H spiral finned tubes excel in extreme environments through niobium stabilization, optimized thermal processing, and geometric efficiency. Critical applications span power generation, petrochemicals, and waste-to-energy systems, where corrosion resistance and heat transfer are paramount. For project-specific validation, refer to ASTM A999 supplementary testing and specify grain size control in procurement