ASME SA312 TP347H Stainless Steel Pipe
ASME SA312 TP347H Stainless Steel Pipe: High-Temperature Austenitic Grade for Elevated Temperature Service
Comprehensive technical data for ASME SA312 TP347H seamless and welded stainless steel pipe, including chemical composition, mechanical and physical properties, international equivalents, and application guidelines.
Hot rolling, cold drawing, welding, machining, bending, forming
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ASME SA312 TP347H Stainless Steel Pipe Introduction
ASME SA312 TP347H is an austenitic stainless steel pipe grade modified with niobium and tantalum to provide enhanced creep strength and resistance to intergranular corrosion at high temperatures. It is primarily intended for elevated-temperature service in boilers, heat exchangers, and pressure vessels. The higher carbon content (0.04–0.10%) compared to TP347 imparts improved high-temperature strength, making it suitable for applications up to approximately 800°C (1472°F). The alloy offers good weldability and can be supplied in seamless or welded condition. TP347H is widely used in power generation, chemical processing, and oil & gas industries where long-term thermal stability is critical.
ASME SA312 TP347H Stainless Steel Pipe Chemical Composition
Chemical composition limits as specified in ASME SA312 for TP347H. These values correspond to the heat analysis requirements and are consistent with ASTM A240 for 347H stainless steel. The alloy relies on niobium stabilization to prevent chromium carbide precipitation during welding or elevated temperature exposure.
- Niobium plus tantalum content is key to intergranular corrosion resistance.
- Carbon is intentionally higher than in TP347 to enhance creep strength.
| Element | Standard Value (max) | Remarks |
|---|---|---|
| Carbon (C) | 0.04 - 0.10 | |
| Manganese (Mn) | 2.00 | |
| Phosphorus (P) | 0.045 | |
| Sulfur (S) | 0.030 | |
| Silicon (Si) | 1.00 | |
| Chromium (Cr) | 17.0 - 19.0 | |
| Nickel (Ni) | 9.0 - 13.0 | |
| Niobium (Nb) + Tantalum (Ta) | 10 x C min, 1.10 max | For stabilization |
ASME SA312 TP347H Stainless Steel Pipe Thermal and Electrical Physical Properties
Typical physical properties of TP347H stainless steel at room temperature and elevated temperatures. These values are representative for material in the solution-annealed condition. Properties such as thermal expansion and thermal conductivity are crucial for design in high-temperature applications.
- Thermal expansion is higher than ferritic steels, requiring consideration in joint design.
- Electrical resistivity is relatively high, typical of austenitic alloys.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 8.0 | g/cm³ | At 20°C |
| Elastic Modulus (E) | 195 | GPa | At 20°C |
| Shear Modulus (G) | 78 | GPa | Calculated at 20°C |
| Poisson's Ratio (ν) | 0.3 | — | At 20°C |
| Thermal Expansion Coefficient (α) | 17.2 | 10⁻⁶/°C | 20°C to 100°C |
| Thermal Expansion Coefficient (α) | 17.7 | 10⁻⁶/°C | 20°C to 200°C |
| Thermal Expansion Coefficient (α) | 18.0 | 10⁻⁶/°C | 20°C to 300°C |
| Thermal Conductivity (λ) | 16.2 | W/m·K | At 100°C |
| Specific Heat Capacity | 500 | J/kg·K | At 20°C |
| Electrical Resistivity (ρ_e) | 0.72 | µΩ·m | At 20°C |
ASME SA312 TP347H Stainless Steel Pipe Mechanical Properties
Minimum mechanical property requirements from ASME SA312 for TP347H at room temperature. Tensile tests are performed on specimens in the solution-annealed condition. Higher properties can be achieved through cold working. Notched bar impact tests are generally not required for austenitic grades per this standard unless specified by supplementary requirements. The values are applicable to both seamless and welded pipe.
| Property | Standard Requirement | Unit | Test Condition |
|---|---|---|---|
| Yield Strength (ReH) | 205 min | MPa (ksi) | Room temperature; 0.2% offset |
| Tensile Strength (Rm) | 515 min | MPa (ksi) | Room temperature |
| Elongation (A) | 35 min | % | 50 mm (2 in) gauge length |
| Hardness (HBW) | ≤ 192 | HBW | Room temperature, converted from HRB |
| Hardness (HRB) | ≤ 90 | HRB | Room temperature |
ASME SA312 TP347H Stainless Steel Pipe Fully Equivalent Material Standards and Substitute Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| USA | ASTM A312/A312M | TP347H | Identical to ASME SA312 |
| EU | EN 10216-5 / EN 10217-7 | 1.4878 (X6CrNiNb18-10) | Matched composition; pressure purposes |
| Japan | JIS G3459 | SUS 347HTP | Stainless steel pipes for high temperature |
| China | GB/T 14976 | 12Cr18Ni11Nb | Similar composition, check carbon range for H-grade |
ASME SA312 TP347H Stainless Steel Pipe Application Introduction
TP347H is specifically designed for high-temperature service where long-term creep and stress-rupture properties are required. The niobium stabilization prevents intergranular corrosion in welded assemblies and in the temperature range of 427°C to 816°C (800°F to 1500°F). Common applications include:
- Boiler superheater and reheater tubes in thermal power plants
- High-pressure steam piping in petrochemical and refinery units
- High-temperature heat exchanger tubes in chemical processing
- Components for gas turbine exhaust systems
Product Applications: Seamless stainless steel pipes to ASME SA312, Welded stainless steel pipes (laser or TIG welded), Heat exchanger tubing, Boiler tubes, Process piping for high-temperature fluids
Processed into products: Superheater and reheater tube bundles, Header connections, High-temperature steam lines, Reformer tubes, Furnace coils, Expansion joints, Instrumentation nipples and fittings
Application industries: Power generation (fossil-fuel and nuclear), Petrochemical and oil refining, Chemical processing, Pulp and paper (digesters and recovery boilers), Aerospace (gas turbine exhaust)
ASME SA312 TP347H Stainless Steel Pipe Similar Alternative Materials with Comparable Properties
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| USA | ASTM A312/A312M | TP304H / TP316H | Non-stabilized H-grades for similar high-temp strength but lower resistance to sensitization |
| EU | EN 10216-5 | 1.4948 (X6CrNi18-10) / 1.4918 (X6CrNiMo17-12-2) | H-grade alternatives without Nb addition |
| USA | ASTM A213/A312 | TP321H | Titanium-stabilized equivalent with comparable creep properties |
Notes:
TP347H piping should be used in solution-annealed condition. Post-weld heat treatment is generally not required due to the stabilizing effect of niobium. For applications where the operating temperature exceeds 600°C (1112°F), the material's creep and oxidation resistance must be validated against specific service conditions. The higher carbon content provides greater hot strength compared to TP347, but it slightly reduces the resistance to intergranular corrosion in certain media. When ordering, specify ASME SA312 TP347H seamless or welded, with applicable supplementary requirements such as S1, S2, S3 etc. for product analysis, hydrostatic testing, or additional NDE.
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