Steel A369 FP11 N+T
Heat-treated state · default condition
ASTM A369 FP11
N+T = normalized and tempered
Standard supply condition for FP11 forged/bored pipe used in creep-range steam and hydrogen service; best balance of strength, toughness and code allowables.
Values for the N+T condition
Other A369 FP11 tempers and conditions
A369 FP11 is listed in 3 conditions; see the grade overview at A369 FP11.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest permitted condition; choose when maximum machinability, cold bending or lowest residual stress is wanted and only minimum spec strength is required. | 285 | 470 | 32 | 140 HB | 8 % IACS |
N+TDefaultThis page Normalized and tempered | Standard supply condition for FP11 forged/bored pipe used in creep-range steam and hydrogen service; best balance of strength, toughness and code allowables. | 330 | 510 | 28 | 155 HB | — |
Quenched and tempered | Occasionally supplied for thick forged sections or valve/fitting bodies where higher yield and uniform bainitic structure are specified; still tempered high to stay code-compliant. | 400 | 560 | 24 | 12 HRC | 7.6 % IACS |
What is A369 FP11 N+T?
A369 FP11 N+T is A369 FP11 heat treated to N+T — standard supply condition for FP11 forged/bored pipe used in creep-range steam and hydrogen service; best balance of strength, toughness and code allowables. A369 FP11 N+T has a yield strength of 330 MPa (47.9 ksi) and a tensile strength of 510 MPa (74 ksi) — weaker than 78% of steel grades. Elongation at break is 28% and the elastic modulus is 207 GPa (30 Msi). A369 FP11 N+T has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,490°C (2,714 °F).
Advantages
- High service temperature — 565°C (1,049 °F), better than 96% of steel grades
- Ductile — tolerates forming and impact — 28%, better than 89% of steel grades
- Tough — resists crack growth — 130 MPa·√m (118.3 ksi·√in), better than 89% of steel grades
Limitations
- Low strength — 330 MPa (47.9 ksi), worse than 78% of steel grades
A369 FP11 N+T properties
Typical room-temperature values for A369 FP11 N+T; 10 are specific to this condition. Other listed values are A369 FP11 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
A369 FP11 N+T has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,490°C (2,714 °F).
Mechanical15
A369 FP11 N+T has a yield strength of 330 MPa (47.9 ksi) and a tensile strength of 510 MPa (74 ksi) — weaker than 78% of steel grades. Elongation at break is 28% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
A369 FP11 N+T is rated for continuous service to 565°C (1,049 °F). It conducts heat at 39 W/m·K (22.5 BTU/hr·ft·°F), worse than 67% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical2
A369 FP11 N+T has an electrical resistivity of 2.2×10⁻⁷ Ω·m.
Chemical & Environmental2
Corrosion resistance is poor (18/100), better than 83% of steel grades.
Sustainability4
Producing a kilogram of A369 FP11 N+T takes about 32 MJ of energy and emits 2.4 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 25%.
Manufacturability6
A369 FP11 N+T's machinability is good (58/100, better than 75% of steel grades); weldability good (60/100); formability good (60/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with A369 FP11 N+T
Is A369 FP11 easy to machine?
Machines like a medium-carbon low-alloy steel at ~60 % of 1212 — use rigid setups, carbide inserts and moderate speeds; the high Si content makes it slightly gummy and abrasive on tool edges.
Can A369 FP11 be welded?
Weldable by GTAW root / SMAW-FCAW fill with matching B2/1.25Cr-0.5Mo filler; preheat 150–200 °C, interpass ≤ 300 °C and PWHT 700–760 °C are normally mandatory to avoid hydrogen cracking and to restore toughness.
Can A369 FP11 be formed, bent or molded?
Hot bend or hot form at 900–1000 °C followed by full re-heat treatment; cold bending is possible on thin walls but should be followed by stress relief.
What surface finishes work on A369 FP11?
Not corrosion-resistant on its own — shot blast then apply high-temperature aluminium/silicone paint or leave under insulation with a coating; polishes to a clean matte finish for NDE and dye-penetrant inspection.
A369 FP11 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 | 0.05 – 0.15 | 0.11 |
| Mn | 0.3 – 0.6 | 0.45 |
| Sideliberately high Si distinguishes P11/FP11 from 13CrMo4-5 min Si | 0.5 – 1 | 0.7 |
| Cr | 1 – 1.5 | 1.25 |
| Mo | 0.44 – 0.65 | 0.55 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Fe | balance | — |
A369 FP11 N+T — frequently asked
What is A369 FP11 N+T used for?
A369 FP11 N+T is typically used for power plant steam piping, refinery high-temperature piping, superheater outlet headers, hydrogen-service transfer lines, catalytic reformer piping and forged pipe spools and thick-wall elbows. In short: 565 °C creep piping grade; forged equivalent of P11; mandatory preheat and PWHT.
What is the yield strength of A369 FP11 N+T?
A369 FP11 N+T has a typical yield strength of 330 MPa (47.9 ksi) and a tensile strength of 510 MPa (74 ksi) — weaker than 78% of steel grades. Strength varies by condition: see the 3 listed tempers.
Is A369 FP11 N+T easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% of steel grades). Machines like a medium-carbon low-alloy steel at ~60 % of 1212 — use rigid setups, carbide inserts and moderate speeds; the high Si content makes it slightly gummy and abrasive on tool edges.
Can A369 FP11 N+T be welded?
Yes — weldability is rated good (60/100). Weldable by GTAW root / SMAW-FCAW fill with matching B2/1.25Cr-0.5Mo filler; preheat 150–200 °C, interpass ≤ 300 °C and PWHT 700–760 °C are normally mandatory to avoid hydrogen cracking and to restore toughness.
What surface finishes work on A369 FP11 N+T?
Not corrosion-resistant on its own — shot blast then apply high-temperature aluminium/silicone paint or leave under insulation with a coating; polishes to a clean matte finish for NDE and dye-penetrant inspection.
Can A369 FP11 N+T be formed, bent or molded?
Hot bend or hot form at 900–1000 °C followed by full re-heat treatment; cold bending is possible on thin walls but should be followed by stress relief.
What is the maximum service temperature of A369 FP11 N+T?
A369 FP11 N+T is rated for continuous use to about 565°C (1,049 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between A369 FP11 N+T and A369 FP11-A?
N+T is the default condition — standard supply condition for FP11 forged/bored pipe used in creep-range steam and hydrogen service; best balance of strength, toughness and code allowables. A: softest permitted condition; choose when maximum machinability, cold bending or lowest residual stress is wanted and only minimum spec strength is required. Yield strength is 330 MPa in N+T versus 285 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 (P11) — ASTM International (2023)
- EN 10216-2 — Seamless steel tubes for pressure purposes, 13CrMo4-5 (1.7335) — CEN (2020)
- ASME BPVC Section II Part D — allowable stresses and physical properties, SA-369 FP11 — ASME (2023)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys (Cr-Mo steels) — ASM International (1990)
- API RP 941 — Steels for Hydrogen Service at Elevated Temperatures — API (2016)
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.