In high-temperature boiler systems, many stainless steel tubes tend to suffer from intergranular corrosion, strength degradation, and even creep failure after long-term service. The key factors lie in whether the control of stabilizing elements, grain structure, and heat treatment processes truly meet the requirements for prolonged high-temperature operation.
The ASTM A213 TP347/347H stainless steel tubes we supply are specifically designed for high-temperature and high-pressure boiler applications. TP347/347H is a niobium (Nb)-stabilized austenitic stainless steel. By adding Nb (typically ≥10× the carbon content), the formation of chromium carbides is effectively suppressed, preventing chromium depletion at grain boundaries and thereby avoiding intergranular corrosion. This makes it particularly suitable for long-term high-temperature environments. The 347H grade further enhances high-temperature strength and creep resistance by increasing the carbon content to 0.04–0.10%.
In terms of grain size control, we optimize hot working and heat treatment processes to maintain a stable grain size within ASTM No. 5–8. Additionally, we can provide internal shot peening treatment, which introduces a compressive stress layer to improve fatigue resistance and reduce the risk of stress corrosion cracking. Meanwhile, tight dimensional tolerances on outer diameter and wall thickness ensure excellent fit-up during boiler installation and reliable operational safety.
All ASTM A213 TP347 stainless steel heat exchanger tubes undergo strict solution annealing, typically performed in the temperature range of 1050–1150°C followed by rapid cooling. This ensures complete dissolution of carbides and a uniform microstructure, significantly enhancing long-term stability and performance in high-temperature service environments.
ASTM A213 TP347H Stainless Steel Seamless Tube Chemical Composition
| Grade | 347 | 347H | 347HFG |
| UNS Designation | S34700 | S34709 | S34710 |
| Carbon (C) Max. | 0.08 | 0.04–0.10 | 0.06–0.10 |
| Manganese (Mn) Max. | 2 | 2 | 2 |
| Phosphorous (P) Max. | 0.04 | 0.04 | 0.04 |
| Sulphur (S) Max. | 0.03 | 0.03 | 0.03 |
| Silicon (Si) Max. | 0.75 | 0.75 | 0.75 |
| Chromium (Cr) | 17.0–20.0 | 17.0–20.0 | 17.0–20.0 |
| Nickel (Ni) | 9.0–13.0 | 9.0–13.0 | 9.0–13.0 |
| Molybdenum (Mo) | - | - | |
| Nitrogen (N) | - | - | - |
| Iron (Fe) | Bal. | Bal. | Bal. |
| Other Elements | Cb+Ta=10xC-1.0 | Cb+Ta=8xC-1.0 | Nb+Ta=8xC-1.0 |
ASTM A213 TP347H Stainless Steel Seamless Tube Physical Properties
| In the Annealed Condition at -20°F to +100°F | |||||
| Alloy | UNS Design | Density kg/dm³ | Modulus of Elasticity (x106 psi) | Mean Coefficient of Thermal Expansion (IN./IN./°F x 10-6) | Thermal Conductivity (BTU-in/ft2-h-°F) |
| 347 | S34700 | 7.98 | 29 | 9.2 | - |
| 347H | S34709 | 7.98 | 29 | 9.2 | - |
| 347HFG | S34710 | - | 29 | 9.2 | - |
ASTM A213 TP347H Stainless Steel Seamless Tube Mechanical Properties
| In the Annealed Condition at -20°F to +100°F | |||||||||
| Tensile Strength | Tensile Strength | Yield Strength | Yield Strength | ||||||
| Alloy | UNS | Spec | MPa | ksi | MPa | ksi | Elongation in 2 inches (min.) % | Grain Size Req. | Harndess HBW |
| 347 | S34700 | ASTM A213 | 515 | 75 | 205 | 30 | 35 | - | 192 |
| 347H | S34709 | ASME SA 213 | 515 | 75 | 205 | 30 | 35 | 7 or coarser | 192 |
| 347HFG | S34710 | - | 550 | 80 | 205 | 30 | 35 | 7 or coarser | 192 |
How does SA213 TP347H compare to other grades like TP304H or TP316H?
SA213 TP347H is a niobium-stabilized austenitic stainless steel optimized for high-temperature applications (up to 1650°F/900°C). Compared to TP304H, it exhibits superior creep strength and resistance to intergranular corrosion. Although TP316H possesses better chloride corrosion resistance due to its molybdenum content, TP347H is often the preferred material for boilers and high-pressure steam systems.
How should SA213 TP347H be welded?
SA213 TP347H can be welded using standard techniques like TIG, MIG, and SAW. It is important to use filler materials that match the grade to maintain the properties of the base material. Preheating and post-weld heat treatment are generally not required.
ASME SA213 TP347 TP347H Stainless tubes Applications Industry
Pharmaceutical Equipment
Chemical Equipment
Sea Water Equipment
Heat Exchangers
Condensers
Pulp and Paper Industry
Off-Shore Oil Drilling Companies
Power Generation
Petrochemicals
Gas Processing
Flattening Test
Flattening tests shall be made on specimens from each end of one finished tube, not the one used for the flaring test, from each lot.
Flaring Test
Flaring tests shall be made on specimens from each end of one finished tube, not the one used for the flattening test, from each lot.
Hydrostatic and Nondestructive Testing
Each TP347H Stainless Steel Seamless pipe shall be subjected to the nondestructive electric test or the hydrostatic test. The type of test to be used shall be at the manufacturer's option unless otherwise specified in the purchase order.
100% Ultrasonic Testing
100% Eddy Current Testing
100% Hydrostatic Testing
Note:
Mill test certificates will be issued according to EN10204-3.1 or 3.2
All tubes shall be supplied as per applicable ASME SA213/213M Specification.
Packing and Marking
Packed in bundles or ply wooden box wrapped in plastic, and suitably protected for sea-worthily delivery or as requested.
