ASTM A312 347/347H stainless steel pipe is an austenitic, niobium-stabilized stainless steel renowned for its excellent high-temperature strength and resistance to intergranular corrosion, making it an ideal choice for industrial applications such as aerospace, petrochemical, power generation, and chemical processing. "347H" designates a high-carbon variant that offers exceptional strength and load-carrying capacity in high-stress environments. These pipes are available in both seamless and welded forms in a variety of sizes and shapes (round, square, and rectangular), and can be manufactured using standard welding processes.
What is 347 pipe made of?
347 grade stainless steel is an austenitic stainless steel. 347 stainless steel pipe features a high-quality chromium and nickel chemical composition. Additionally, these pipes are embedded with niobium and tantalum to help improve the pipe's stability within the system.
The ASTM A312 specification covers seamless, straight-seam welded, and high-strength cold-work welded austenitic stainless steel pipe suitable for use in high-temperature and generally corrosive environments. ASTM A312 TP347H (UNS S34709) is an austenitic stainless steel stabilized by the addition of niobium (Nb). It is commonly used in piping systems exposed to high-temperature and corrosive environments.
The basic composition of ASTM A312 TP347H seamless stainless steel pipe is primarily chromium (Cr) at approximately 17-19%, nickel (Ni) at approximately 9-13%, and carbon (C) at ≤0.08%. The key element is the addition of niobium (Nb) at ≥10 × C%, which combines with carbon to form niobium carbides, thereby reducing chromium carbide precipitation and preventing intergranular corrosion.
ASTM A312 Stainless Steel Seamless Pipe Chemical Composition
| SS GRADE |
UNS. |
ASTM A312/SA 312 CHEMICAL COMPOSITION % MAXIMUM | |||||||
|---|---|---|---|---|---|---|---|---|---|
| C | MN | P | S | SI | CR | NI | NB | ||
| TP347 | S34700 | 0.08 | 2.00 | 0.045 | 0.030 | 1.00 | 17.0-19.0 | 9.0-13.0 |
10 × C% |
| TP347H | S34709 | 0.04-0.10 | 2.00 | 0.045 | 0.030 | 1.00 | 17.0-19.0 | 9.0-13.0 |
10 × C% |
ASTM A312 TP347/TP347H Stainless Steel Seamless Pipe Mechanical Properties
| SS GRADE | HEAT TREATMENT | Tensile Strength, min ksi [MPa] | Yield Strength, min ksi [MPa] | |
|---|---|---|---|---|
| Cold Finished | Hot Finished | |||
| TP347 |
2000 °F [1100 °C] |
1925 °F [1050 °C] |
75 [515] | 30 [205] |
| TP347H | 2000 °F [1100 °C] | 1925 °F [1050 °C] | 75 [515] | 30 [205] |
Key Features of ASTM A312 347/347H Pipe
Stability: Both 347 and 347H grades are stabilized with niobium and/or tantalum to prevent the precipitation of chromium carbides at high temperatures. This maintains the material's mechanical integrity and offers long-term resistance to intergranular corrosion.
High-Temperature Performance: Compared to grades like 304 and 321, they offer superior heat resistance and are suitable for applications up to 850°C.
Corrosion Resistance: The addition of chromium and niobium/tantalum provides excellent resistance to a wide range of corrosion types, including intergranular corrosion and attack by aggressive chemicals.
High Carbon Content (347H): 347H grade has a higher carbon content, which increases its mechanical strength and load-bearing capacity in high-stress, high-temperature applications.
Mechanical Properties: These pipes offer high tensile strength and good weldability, making them durable and easy to fabricate.
ASTM A312 347/347H Piping Applications
ASTM A312 347/347H piping is suitable for a variety of demanding industries and applications, including:
Aerospace: Exhaust manifolds and branch lines for aircraft engines.
Petrochemical and Oil & Gas: High-temperature process piping, chemical equipment, and oil pipelines.
Power Generation: Boiler tubes, turbine tubing, and heat exchangers.
Chemical Processing: Piping for conveying corrosive fluids and chemicals.
Other Industries: Food processing, paper and pulp industry, and condensers.
Fabrication: Produced in seamless and welded construction.
Shapes: Available in round, square, and rectangular pipe.
Standards: Conforms to ASTM A312 and other global standards such as EN and DIN.
Gnee Steel specializes in the production and sale of a wide range of stainless steel products, including 304, 316, 321, 904, 904L, 2205 Duplex, 2205 Duplex, and 316L stainless steel. Gnee Steel's products are widely used in the kitchen, aerospace, chemical, power, automotive, and nuclear energy sectors. We also provide custom stainless steel solutions tailored to customer needs. For stainless steel pricing or custom alloy solutions, please email ru@gneesteelgroup.com for a quote.
