ASTM A369 FP91 Alloy Steel Pipe (UNS K91560)
ASTM A369 FP91 (UNS K91560) is a high-strength 9% Chromium – 1% Molybdenum – Vanadium (9Cr-1Mo-V) ferritic alloy steel specifically designed for high-temperature and high-pressure service. Produced through a forged and bored manufacturing process, FP91 offers exceptional creep strength, thermal stability, and oxidation resistance.
It is one of the most preferred materials for supercritical boilers, power generation piping, superheaters, and high-pressure steam lines due to its excellent long-term performance at elevated temperatures.
Key Features
- High-performance 9Cr-1Mo-V alloy – UNS K91560
- Exceptional creep strength for long-term elevated temperature service
- Superior oxidation & corrosion resistance
- Forged & bored heavy-wall pipe for maximum durability
- Ideal for power plants, boilers, steam piping & petrochemical systems
- Excellent resistance to thermal fatigue and deformation
Available Sizes
| Parameter | Range |
|---|---|
| Outside Diameter (OD) | 50 mm – 1200 mm |
| Wall Thickness (WT) | 5 mm – 150 mm (Heavy-wall) |
| Inside Diameter (ID) | As per customer requirement |
| Length | Up to 12 meters (Custom lengths available) |
| Special Options | OD up to 1500 mm available |
Equivalent Grades
| Standard | Grade |
|---|---|
| ASTM | A369 FP91 |
| ASME | SA369 FP91 |
| UNS | K91560 |
| EN / DIN | — (Comparable to X10CrMoVNb9-1 in some standards) |
ASTM A369 FP91 Chemical Composition
| Element | Content (%) |
|---|---|
| Carbon (C) | 0.08 – 0.12 |
| Manganese (Mn) | 0.30 – 0.60 |
| Phosphorus (P) | 0.020 max |
| Sulfur (S) | 0.010 max |
| Silicon (Si) | 0.20 – 0.50 |
| Chromium (Cr) | 8.0 – 9.5 |
| Molybdenum (Mo) | 0.85 – 1.05 |
| Vanadium (V) | 0.18 – 0.25 |
| Niobium (Nb) | 0.06 – 0.10 |
| Nitrogen (N) | 0.03 – 0.07 |
Grade FP91 Mechanical Properties
| Property | Value |
|---|---|
| Tensile Strength | 585 MPa (min) |
| Yield Strength | 415 MPa (min) |
| Elongation | 20% (min) |
| Hardness | 250 HBW (max) |
Grade FP91 Physical Properties
| Property | Value |
|---|---|
| Density | 7.78 g/cm³ |
| Thermal Conductivity | ~27 W/m·K |
| Modulus of Elasticity | ~210 GPa |
| Melting Point | ~1425–1500°C |
Types Available
- Forged & Bored Alloy Steel Pipe
- Heavy-Wall Power Plant Pipe
- High-Temperature Seamless Pipes
- Precision Machined Bore Pipes
Applications
- Ultra-supercritical and supercritical boilers
- High-pressure steam lines
- Superheaters & reheaters
- Power generation piping
- Petrochemical units
- Heat recovery steam generators (HRSG)
- Refineries & high-temperature process lines
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