Steel A369 FP9-A (Solution annealed)
Temper
ASTM A369 FP9
Pick when maximum softness/machinability and lowest hardness for field bending or heavy machining are needed; slightly lower strength than N+T.
Values for the A condition
Other A369 FP9 tempers and conditions
A369 FP9 is listed in 2 conditions; see the grade overview at A369 FP9.
- A
- N+T
Compare all 2 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AThis page Solution annealed | Pick when maximum softness/machinability and lowest hardness for field bending or heavy machining are needed; slightly lower strength than N+T. | 250 | 450 | 36 | 150 HB | — |
N+TDefault Normalized and tempered | Standard supply condition for FP9 pressure piping: best creep strength and toughness combination for 500–600 °C service. | 300 | 490 | 33 | 170 HB | — |
What is A369 FP9-A?
A369 FP9-A is A369 FP9 in the A temper — pick when maximum softness/machinability and lowest hardness for field bending or heavy machining are needed; slightly lower strength than N+T. A369 FP9-A has a yield strength of 250 MPa (36.3 ksi) and a tensile strength of 450 MPa (65.3 ksi) — weaker than 94% of steel grades. Elongation at break is 36% and the elastic modulus is 213 GPa (30.9 Msi). A369 FP9-A has a density of 7.78 g/cm³ (0.281 lb/in³), lighter than 91% of steel grades. It melts at 1,450°C (2,642 °F). N+T is the default condition FabDigit quotes; A is available on request or by drawing note.
Advantages
- Ductile — tolerates forming and impact — 36%, better than 98% of steel grades
- High service temperature — 600°C (1,112 °F), better than 98% of steel grades
- Good corrosion resistance — 32/100, better than 96% of steel grades
- Tough — resists crack growth — 120 MPa·√m (109.2 ksi·√in), better than 81% of steel grades
Limitations
- Low strength — 250 MPa (36.3 ksi), worse than 94% of steel grades
- Poor heat conductor — 29 W/m·K (16.8 BTU/hr·ft·°F), worse than 84% of steel grades
A369 FP9-A properties
Typical room-temperature values for A369 FP9-A; 12 are specific to this condition. Other listed values are A369 FP9 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
A369 FP9-A has a density of 7.78 g/cm³ (0.281 lb/in³), lighter than 91% of steel grades. It melts at 1,450°C (2,642 °F).
Mechanical15
A369 FP9-A has a yield strength of 250 MPa (36.3 ksi) and a tensile strength of 450 MPa (65.3 ksi) — weaker than 94% of steel grades. Elongation at break is 36% and the elastic modulus is 213 GPa (30.9 Msi).
Thermal6
A369 FP9-A is rated for continuous service to 600°C (1,112 °F). It conducts heat at 29 W/m·K (16.8 BTU/hr·ft·°F), worse than 84% of steel grades. Thermal expansion is 11 µm/m·K (6.11 µin/in·°F).
Electrical2
A369 FP9-A has an electrical resistivity of 6×10⁻⁷ Ω·m.
Chemical & Environmental3
Corrosion resistance is poor (32/100), better than 96% of steel grades.
Sustainability4
Producing a kilogram of A369 FP9-A takes about 34 MJ of energy and emits 2.4 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 30%.
Manufacturability6
A369 FP9-A's machinability is fair (52/100, better than 52% of steel grades); weldability fair (50/100); formability fair (52/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with A369 FP9-A
Is A369 FP9 easy to machine?
Machines like a medium-hard Cr-Mo steel at roughly half the rate of 1212; use rigid setups, carbide inserts, moderate speeds and generous coolant — anneal first for heavy boring.
Can A369 FP9 be welded?
Weld with matching 9Cr-1Mo (E505/ER80S-B8) filler, preheat 200–300 °C, keep interpass hot, and PWHT 730–760 °C to avoid hard untempered martensite and hydrogen cracking.
Can A369 FP9 be formed, bent or molded?
Hot bend/form at 900–1050 °C followed by full re-normalizing and tempering; cold bending is limited and requires post-bend stress relief.
What surface finishes work on A369 FP9?
No passive film — shop-prime, paint or metallize for outdoor storage; in service the protective Cr-rich oxide forms above ~400 °C, and coatings must be chosen for the operating temperature.
A369 FP9 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| C | ≤ 0.15 | 0.1 |
| Mn | 0.3 – 0.6 | 0.45 |
| Si | 0.25 – 1 | 0.6 |
| Cr | 8 – 10 | 9 |
| Mo | 0.9 – 1.1 | 1 |
| Pimpurity limit | ≤ 0.03 | — |
| Simpurity limit | ≤ 0.03 | — |
| Fe | balance | — |
A369 FP9-A — frequently asked
What is A369 FP9-A used for?
A369 FP9-A is typically used for refinery high-temperature headers, hydrocracker piping, catalytic reformer transfer lines, fired heater outlet piping, sulfidic crude and vacuum unit piping and forged fittings for 9Cr-1Mo systems. In short: highest-chromium A369 pipe; best sulfidation resistance here; hardest to weld in family.
What is the yield strength of A369 FP9-A?
A369 FP9-A has a typical yield strength of 250 MPa (36.3 ksi) and a tensile strength of 450 MPa (65.3 ksi) — weaker than 94% of steel grades. Strength varies by condition: see the 2 listed tempers.
Is A369 FP9-A easy to machine?
Reasonably — machinability is rated fair (52/100, better than 52% of steel grades). Machines like a medium-hard Cr-Mo steel at roughly half the rate of 1212; use rigid setups, carbide inserts, moderate speeds and generous coolant — anneal first for heavy boring.
Can A369 FP9-A be welded?
With care — weldability is rated fair (50/100). Weld with matching 9Cr-1Mo (E505/ER80S-B8) filler, preheat 200–300 °C, keep interpass hot, and PWHT 730–760 °C to avoid hard untempered martensite and hydrogen cracking.
What surface finishes work on A369 FP9-A?
No passive film — shop-prime, paint or metallize for outdoor storage; in service the protective Cr-rich oxide forms above ~400 °C, and coatings must be chosen for the operating temperature.
Can A369 FP9-A be formed, bent or molded?
Hot bend/form at 900–1050 °C followed by full re-normalizing and tempering; cold bending is limited and requires post-bend stress relief.
What is the maximum service temperature of A369 FP9-A?
A369 FP9-A is rated for continuous use to about 600°C (1,112 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between A369 FP9 N+T and A369 FP9-A?
N+T is the default condition — standard supply condition for FP9 pressure piping: best creep strength and toughness combination for 500–600 °C service. A: pick when maximum softness/machinability and lowest hardness for field bending or heavy machining are needed; slightly lower strength than N+T. Yield strength is 300 MPa in N+T versus 250 MPa in A.
Sources
- ASTM A369/A369M — Carbon and Ferritic Alloy Steel Forged and Bored Pipe for High-Temperature Service — ASTM International (2018)
- ASTM A335/A335M — Seamless Ferritic Alloy-Steel Pipe for High-Temperature Service (Grade P9) — ASTM International (2022)
- ASME BPVC Section II Part D — Properties (Metric), 9Cr-1Mo — ASME (2023)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.