ASME SA335 P91 and P92 both belong to the ASME SA-335/SA-335M standard for high-temperature seamless ferritic alloy steel pipes, and are specialized pipe materials for high-temperature pressure equipment such as thermal power plants.
P91: High-temperature superheaters, reheaters, and main steam pipelines of subcritical/supercritical boilers, and high-temperature pyrolysis units in petrochemical plants.
P92: Main steam, high-temperature reheat steam pipelines, and high-pressure bypass systems of ultra-supercritical boilers.
Core Advantages: P92 vs P91 The development of P92 aims to surpass the performance ceiling of P91, with advantages including:
Stronger high-temperature creep strength: This is P92's most significant advantage. This means that under the same temperature and pressure, thinner wall thicknesses can be designed using P92.
Higher service temperature: P92's long-term safe service temperature can reach 625℃, while P91 is generally around 585℃.
Better resistance to thermal fatigue: P92's coefficient of linear expansion is similar to P91, both superior to austenitic stainless steel.
More weldable: Due to optimized alloy design, P92 is significantly less sensitive to preheating cracks, requiring a zero-crack preheating temperature of approximately 100°C, lower than P91's approximately 180°C. Core Advantages: P92 vs P91
P92 was developed to surpass the performance ceiling of P91, with advantages including:
Stronger high-temperature creep strength: This is P92's most significant advantage. This means that under the same temperature and pressure, P92 can be used to design thinner walls (approximately 30%-40% thinner).
Higher service temperature: P92's long-term safe service temperature can reach 625°C, while P91 is generally around 585°C.
Better resistance to thermal fatigue: P92's coefficient of linear expansion is similar to P91, both superior to austenitic stainless steels.
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| Chemical Composition |
| Element |
P91 |
P92 |
| Carbon (C) |
0.08 - 0.12 |
0.07 - 0.13 |
| Manganese (Mn) |
0.30 - 0.60 |
0.30 - 0.60 |
| Phosphorus (P) |
≤ 0.020 |
≤ 0.020 |
| Sulfur (S) |
≤ 0.010 |
≤ 0.010 |
| Silicon (Si) |
0.20 - 0.50 |
≤ 0.50 |
| Chromium (Cr) |
8.00 - 9.50 |
8.50 - 9.50 |
| Molybdenum (Mo) |
0.85 - 1.05 |
0.30 - 0.60 |
| Nickel (Ni) |
≤ 0.40 |
≤ 0.40 |
| Vanadium (V) |
0.18 - 0.25 |
0.15 - 0.25 |
| Niobium (Nb) |
0.06 - 0.10 |
0.04 - 0.09 |
| Nitrogen (N) |
0.03 - 0.07 |
0.03 - 0.07 |
| Tungsten (W) |
— |
1.50 - 2.00 |
| Boron (B) |
— |
0.001 - 0.006 |
| Aluminum (Al) |
≤ 0.02 |
≤ 0.04 |
| Mechanical Properties (Room Temperature) |
| Property |
P91 |
P92 |
| Tensile Strength (min.) |
≥ 585 MPa |
≥ 620 MPa |
| Yield Strength 0.2% offset (min.) |
≥ 415 MPa |
≥ 440 MPa |
| Elongation (min.) |
≥ 20% |
≥ 20% |
| Hardness (HBW) |
170 - 248 |
170 - 248 |
Application:
- Nuclear Power Plants: Used in the main steam system piping of some conventional islands, and high-temperature components such as steam generators.
- Chemical/Fertilizer Industry: Used in high-temperature and high-pressure reactors, heat exchangers, and process piping.
- Solar Thermal Power Generation: Used in molten salt or steam heat transfer piping systems for concentrated solar thermal power generation, meeting high-temperature durability requirements.
- Industrial High-Pressure Boilers: Water-cooled walls and superheater tubes.
