Steel A369 Grade FPB N+T
Heat-treated state
ASTM A369 Grade FPB
N+T = normalized and tempered
Choose when heavy sections need residual-stress relief and slightly improved toughness/uniformity for thick-wall bored pipe.
Values for the N+T condition
Other A369 Grade FPB tempers and conditions
A369 Grade FPB is listed in 4 conditions; see the grade overview at A369 Grade FPB.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest permitted condition — pick for maximum machinability and cold bending of the bored pipe, at the cost of lower strength margin. | 260 | 440 | 38 | 131 HB | — |
Isothermal annealed | Alternative anneal allowed by A369 giving very uniform ferrite-pearlite in heavy forged sections with minimal distortion. | 265 | 450 | 37 | 135 HB | 10 % IACS |
N+TThis page Normalized and tempered | Choose when heavy sections need residual-stress relief and slightly improved toughness/uniformity for thick-wall bored pipe. | 285 | 465 | 35 | 140 HB | 10 % IACS |
NDefault Normalized | Standard supply condition for FPB forged and bored pipe: uniform fine ferrite-pearlite, best combination of strength and toughness. | 295 | 480 | 34 | 147 HB | — |
What is A369 Grade FPB N+T?
A369 Grade FPB N+T is A369 Grade FPB heat treated to N+T — choose when heavy sections need residual-stress relief and slightly improved toughness/uniformity for thick-wall bored pipe. A369 Grade FPB N+T has a yield strength of 285 MPa (41.3 ksi) and a tensile strength of 465 MPa (67.4 ksi) — weaker than 89% of steel grades. Elongation at break is 35% and the elastic modulus is 200 GPa (29 Msi). A369 Grade FPB N+T has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,470°C (2,678 °F). N is the default condition FabDigit quotes; N+T is available on request or by drawing note.
Advantages
- Conducts heat well — 52 W/m·K (30 BTU/hr·ft·°F), better than 98% of steel grades
- Ductile — tolerates forming and impact — 35%, better than 97% of steel grades
- Easy to machine — 67/100, better than 95% of steel grades
- Readily welded — 90/100, better than 90% of steel grades
- Forms and bends easily — 72/100, better than 88% of steel grades
Limitations
- Low strength — 285 MPa (41.3 ksi), worse than 89% of steel grades
- Hard to polish — 45/100, worse than 84% of steel grades
A369 Grade FPB N+T properties
Typical room-temperature values for A369 Grade FPB N+T; 22 are specific to this condition. Other listed values are A369 Grade FPB reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
A369 Grade FPB N+T has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,470°C (2,678 °F).
Mechanical16
A369 Grade FPB N+T has a yield strength of 285 MPa (41.3 ksi) and a tensile strength of 465 MPa (67.4 ksi) — weaker than 89% of steel grades. Elongation at break is 35% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
A369 Grade FPB N+T is rated for continuous service to 425°C (797 °F). It conducts heat at 52 W/m·K (30 BTU/hr·ft·°F), better than 98% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
A369 Grade FPB N+T conducts electricity at 10 % IACS, better than 83% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of A369 Grade FPB N+T takes about 25 MJ of energy and emits 2 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 25%.
Manufacturability8
A369 Grade FPB N+T's machinability is good (67/100, better than 95% of steel grades); weldability excellent (90/100); formability very good (72/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with A369 Grade FPB N+T
Is A369 Grade FPB easy to machine?
Machines readily with carbide or HSS at ~60–65 % of AISI 1212; gummy in the annealed state so use positive rake and good chip control for the bore.
Can A369 Grade FPB be welded?
Excellent weldability by SMAW/GTAW/SAW with E7018 or ER70S-2 fillers; preheat 100–150 °C for heavy walls and PWHT per ASME B31.1/B31.3 for thick sections.
Can A369 Grade FPB be formed, bent or molded?
Hot forging and hot bending are routine; cold bending is possible in the annealed condition, and forged pipe must be re-heat-treated after hot forming.
What surface finishes work on A369 Grade FPB?
No anodizing; protect with shop primer, epoxy or zinc coatings, or aluminize/phosphate for high-temperature and outdoor service.
A369 Grade FPB 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 |
|---|---|---|
| Cmax per ASTM A369 Grade FPB | ≤ 0.3 | 0.25 |
| Mn | 0.29 – 1.06 | 0.8 |
| P | ≤ 0.04 | 0.02 |
| S | ≤ 0.04 | 0.02 |
| Siminimum only | ≥ 0.1 | 0.25 |
| Fe | balance | — |
A369 Grade FPB N+T — frequently asked
What is A369 Grade FPB N+T used for?
A369 Grade FPB N+T is typically used for high-pressure steam piping, boiler headers and power generation piping. In short: stronger than A369 FPA; weldable high-temperature pipe; common C-Mn header grade.
What is the yield strength of A369 Grade FPB N+T?
A369 Grade FPB N+T has a typical yield strength of 285 MPa (41.3 ksi) and a tensile strength of 465 MPa (67.4 ksi) — weaker than 89% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is A369 Grade FPB N+T easy to machine?
Reasonably — machinability is rated good (67/100, better than 95% of steel grades). Machines readily with carbide or HSS at ~60–65 % of AISI 1212; gummy in the annealed state so use positive rake and good chip control for the bore.
Can A369 Grade FPB N+T be welded?
Yes — weldability is rated excellent (90/100). Excellent weldability by SMAW/GTAW/SAW with E7018 or ER70S-2 fillers; preheat 100–150 °C for heavy walls and PWHT per ASME B31.1/B31.3 for thick sections.
What surface finishes work on A369 Grade FPB N+T?
No anodizing; protect with shop primer, epoxy or zinc coatings, or aluminize/phosphate for high-temperature and outdoor service.
Can A369 Grade FPB N+T be formed, bent or molded?
Hot forging and hot bending are routine; cold bending is possible in the annealed condition, and forged pipe must be re-heat-treated after hot forming.
What is the maximum service temperature of A369 Grade FPB N+T?
A369 Grade FPB N+T is rated for continuous use to about 425°C (797 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between A369 Grade FPB-N and A369 Grade FPB-A?
N is the default condition — standard supply condition for FPB forged and bored pipe: uniform fine ferrite-pearlite, best combination of strength and toughness. A: softest permitted condition — pick for maximum machinability and cold bending of the bored pipe, at the cost of lower strength margin. Yield strength is 295 MPa in N versus 260 MPa in A.
Sources
- ASTM A369/A369M — Carbon and Ferritic Alloy Steel Forged and Bored Pipe for High-Temperature Service — ASTM International (2018)
- ASME BPVC Section II Part D — Materials Properties — ASME (2023)
- ASME B31.3 Process Piping / B31.1 Power Piping — ASME (2022)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- Machinery's Handbook, 31st ed. — Industrial Press (2020)
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.