ASTM A312 TP347H Stainless Steel Seamless Tube for Boiler and Chemical Industry
ASTM A312 specification covers seamless, straight-seam welded, and heavily cold worked welded austenitic stainless steel pipe intended for high-temperature and general corrosive service. ASTM A312 TP347H (UNS S34709) is an austenitic stainless steel stabilized by adding niobium (Nb), commonly used in pipeline systems in high-temperature and corrosive environments.
The basic components of ASTM A312 TP347H stainless steel seamless pipes are mainly chromium (Cr) about 17-19%, nickel (Ni) about 9-13%, and carbon (C) ≤ 0.08%. The key lies in the addition of niobium (Nb) ≥ 10 × C%, which combines with carbon to form niobium carbide, reducing the precipitation of chromium carbide and avoiding 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%
|
Compared with other materials, the stabilization treatment of niobium in ASTM A312 TP347H stainless steel seamless pipe can prevent chromium carbide precipitation during welding or high temperature (450-850 ° C), protect grain boundaries, and enhance the resistance of pipes to intergranular corrosion; ASTM A312 TP347H stainless steel seamless pipes can maintain oxidation resistance and creep strength at high temperatures (≤ 800 ° C), which is superior to ordinary 304/316 stainless steel; TP347H stainless steel seamless pipes have good corrosion resistance to oxidizing media such as nitric acid and organic acids, but should be used with caution in reducing acids such as sulfuric acid and hydrochloric acid.
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] |
ASTM A312 TP347H Stainless Steel Seamless Pipe Application:
(1) High temperature industrial equipment
- Boiler and power station: Superheater and reheater pipelines, capable of withstanding high-pressure steam (≤ 800 ° C).
- Cracking furnace tube: a radiation section furnace tube in high-temperature cracking furnaces in the petrochemical industry.
- Heat exchanger: used for high-temperature gas or liquid heat exchange to avoid sensitization corrosion during long-term service.
(2) Chemical and Petrochemical Industry
- Nitric acid production equipment: nitric acid concentration device, storage tank, and transportation pipeline.
- Synthetic ammonia plant: synthesis tower and reactor pipelines under high temperature and high pressure environment.
(3) Other fields
- Food processing: High temperature sterilization equipment (must comply with hygiene standards).
- Nuclear industry: auxiliary pipelines for some nuclear fuel processing systems.
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ASTM A312 / ASME SA312 TP347H Stainless Steel Seamless Tube For Boiler Chemical Industry Images
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