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Everything About TP347 Stainless Steel
ASTM A312 TP347 is a type of stainless steel seamless pipe that is highly corrosion-resistant. 1.4550 (AISI 347), S34700 is commonly used in applications that require high temperature resistance.
What makes ASTM A312 TP347 Unique?
The ASTM A312 specification covers seamless, straight-seam welded, and heavily cold-worked welded austenitic stainless steel pipes intended for high-temperature and general corrosive service.
Within this standard, TP347 is highly favored over standard grades like TP304 because of its columbium addition. The stabilization with columbium eliminates chromium carbide precipitation within the sensitization range of 800°F to 1500°F (427°C to 816°C). This crucial chemical advantage prevents intergranular corrosion (IGC), making it highly reliable for parts that require post-weld heat treatment or sustained thermal service.
Technical Note: For extreme stress-rupture and creep-strength requirements at temperatures exceeding 1000°F, we also manufacture and supply ASTM A312 TP347H (UNS S34709), which features a higher carbon content (0.04–0.10%) for enhanced high-temperature structural stability.
HT PIPE Sizing & Quality Assurance Framework
At Zhengzhou Huitong Pipeline Equipment Co., Ltd., our manufacturing yards implement strict product verification standards to ensure your pipelines operate without risk.
| Sizing Dimension Profile | Operational Manufacturing Scope |
| Outer Diameter (OD) | 1/8" NB to 24" NB (Seamless); up to 48" (Welded) |
| Wall Thickness Schedule | SCH 5S, 10S, 40S, 80S, 160, to XXS |
| Length Processing | Single Random, Double Random, or Cut-to-Length customized sizes |
| End Configurations | Plain End, Beveled End (for seamless welding alignment), or Threaded |
Chemical Composition & Mechanical Data
The precise metallurgical balance ensures outstanding performance under elevated high-pressure operations.
Chemical Composition limits (wt%) per ASTM A312 / ASME SA312
Chromium (Cr): 17.0% – 19.0% (Provides primary oxidation and corrosion barriers)
Nickel (Ni): 9.0% – 13.0% (Stabilizes the austenitic structure and increases toughness)
Columbium + Tantalum (Nb + Ta): 10 x Carbon min, 1.10% max (Acts as the stabilizing element)
Carbon (C): 0.08% max (0.04% – 0.10% for Grade 347H)
Manganese (Mn): 2.00% max
Silicon (Si): 0.75% max
Phosphorus (P): 0.045% max
Sulfur (S): 0.030% max
ASTM A312 UNS S34700 Pipe Mechanical Properties:
- Tensile Strength: ≥ 515 MPa
- Yield Strength: ≥ 205 MPa
- Elongation: ≥ 35%
1.4550 AISI 347 SS Seamless Pipe Resistance to Corrosion
One of the main properties of ASTM A312 TP347 stainless steel pipe is its resistance to corrosion. This is due to its high content of chromium, which creates a protective layer over the surface of the pipe, preventing rust and other forms of corrosion.
ASTM A312 Gr TP347 Temperature Resistance
Intergranular Corrosion Immunity: Because the columbium combines with carbon preferentially over chromium, the vital protective chromium barrier remains uniformly distributed across the metal grain boundaries.
Extended Thermal Performance: 1.4550 AISI 347 SS pipes maintain structural strength and scale resistance up to 1500°F (816°C), easily outperforming standard 304 or 316 grades in continuous-heat loops.
Aggressive Media Protection: Demonstrates superior resistance in strongly oxidizing environments, sour oil fields, and applications containing organic/polythionic acids.
Key B2B Engineering Applications
Thanks to its robust mechanical thresholds, UNS S34700 seamless pipes are critically utilized in:
Refineries & Petrochemical Plants: Fluid catalytic cracking units (FCCU), radiant tubes, and high-pressure piping manifolds.
Power Generation Facilities: Boiler tubes, superheater headers, and high-pressure steam distribution networks.
Chemical Processing: Equipment operating under high-temperature acid cycles and pharmaceutical clean-steam runs.
Aerospace & Exhaust Systems: Heavy-duty collector rings, engine exhaust manifolds, and high-temperature expansion joints.
ASTM A312 Grade 347 Seamless Pipe Physical Properties
In terms of its physical properties, ASTM A312 Type 347 stainless steel seamless pipe has a density of 7.96 g/cm³ and a melting point of 1398-1440°C (2550-2624°F).
