Steel A369 FP21
ASTM A369 FP21
A369 FP21 is a 3Cr-1Mo forged and bored alloy steel pipe to ASTM A369, the forged equivalent of A335 P21 seamless pipe.
Reference datasheet — A369 FP21 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the N+T condition
A369 FP21 tempers and conditions
A369 FP21 is supplied in 3 conditions, soft to hard. N+T is the default FabDigit quotes; the values on this page are for it.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Softest condition — pick when maximum machinability, bending or lowest residual stress is needed. | 260 | 480 | 32 | 150 HB | — |
N+TDefault Normalized and tempered | Standard supply condition for FP21 pressure piping: best combination of creep strength, toughness and machinability. | 330 | 530 | 27 | 175 HB | — |
Quenched and tempered | Occasional heavy-wall / high-strength option where a bainitic structure and higher yield are specified by the purchaser. | 450 | 620 | 22 | 19 HRC | — |
Supply forms, finishes and certifications
Ways A369 FP21 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
ISO-ANN | Isothermal annealed | Certification |
What is A369 FP21?
A369 FP21 is a 3Cr-1Mo forged and bored alloy steel pipe to ASTM A369, the forged equivalent of A335 P21 seamless pipe. It is used for high-temperature, high-pressure piping up to 595 °C, supplied normalized and tempered, annealed, ISO-annealed or quenched and tempered with 330 MPa yield, 530 MPa tensile, 27% elongation and 175 HB. Higher hardness and chromium reduce machinability to about 55 and demand strict preheat and PWHT control. Where 2.25Cr-1Mo material availability is better, FP22 is the usual alternative. A369 FP21 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,450°C (2,642 °F). A369 FP21 has a yield strength of 330 MPa (47.9 ksi) and a tensile strength of 530 MPa (76.9 ksi) — weaker than 78% of steel grades. Elongation at break is 27% and the elastic modulus is 207 GPa (30 Msi).
What is A369 FP21 used for?
- High-temperature steam headers
- Refinery process piping
- Hot reheat piping
- Forged header and nozzle fittings
- Hydrogen-service process lines
- Fired heater outlet piping
Advantages
- High service temperature — 595°C (1,103 °F), better than 97% of steel grades
- Tough — resists crack growth — 140 MPa·√m (127.4 ksi·√in), better than 94% of steel grades
- Ductile — tolerates forming and impact — 27%, better than 86% of steel grades
Limitations
- Low strength — 330 MPa (47.9 ksi), worse than 78% of steel grades
A369 FP21 properties
Typical room-temperature values for A369 FP21-N+T; bars are the position among steel grades.
Physical3
A369 FP21 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,450°C (2,642 °F).
Mechanical16
A369 FP21 has a yield strength of 330 MPa (47.9 ksi) and a tensile strength of 530 MPa (76.9 ksi) — weaker than 78% of steel grades. Elongation at break is 27% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
A369 FP21 is rated for continuous service to 595°C (1,103 °F). It conducts heat at 37 W/m·K (21.4 BTU/hr·ft·°F), worse than 71% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
A369 FP21 conducts electricity at 7.5 % IACS, worse than 67% of steel grades.
Chemical & Environmental2
Corrosion resistance is poor (20/100), better than 87% of steel grades.
Sustainability4
Producing a kilogram of A369 FP21 takes about 32 MJ of energy and emits 2.4 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 25%.
Manufacturability7
A369 FP21's machinability is good (55/100, better than 62% of steel grades); weldability good (55/100); formability fair (45/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. A369 FP21 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with A369 FP21
Is A369 FP21 easy to machine?
Machines like a medium-carbon low-alloy steel at ~55 % of AISI 1212; use rigid setups, carbide inserts at moderate speed and generous coolant, and finish-bore after final heat treatment to hold ID tolerance.
Can A369 FP21 be welded?
Weld with matching 3Cr-1Mo (E9015-B3 / ER90S-B3 type) consumables, 200–300 °C preheat/interpass, low hydrogen practice, and 700–760 °C PWHT to avoid HAZ hardening and hydrogen cracking.
Can A369 FP21 be formed, bent or molded?
Hot form/bend at 950–1050 °C followed by re-normalizing and tempering; cold bending is limited by high yield-to-tensile ratio and springback.
A369 FP21 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 | 0.1 |
| Mn | 0.3 – 0.6 | 0.45 |
| Si | ≤ 0.5 | 0.3 |
| P | ≤ 0.03 | 0.01 |
| S | ≤ 0.03 | 0.01 |
| Cr | 2.65 – 3.35 | 3 |
| Mo | 0.8 – 1.06 | 0.95 |
| Fe | balance |
What surface finishes work on A369 FP21?
No anodizing; protect with high-temperature aluminium/silicone paint, aluminizing or thermal-spray coatings, and shot blast or pickle mill scale before painting.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel A369 FP21 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- A335 P21
How much does A369 FP21 cost?
A369 FP21 is a premium-cost steel ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
A369 FP21 — frequently asked
What is A369 FP21 used for?
A369 FP21 is typically used for high-temperature steam headers, refinery process piping, hot reheat piping, forged header and nozzle fittings, hydrogen-service process lines and fired heater outlet piping. In short: 3Cr-1Mo high-pressure pipe; rated to 595 °C; stronger than FP22.
What is the yield strength of A369 FP21?
A369 FP21 has a typical yield strength of 330 MPa (47.9 ksi) and a tensile strength of 530 MPa (76.9 ksi) — weaker than 78% of steel grades. Strength varies by condition: see the 3 listed tempers.
Is A369 FP21 easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machines like a medium-carbon low-alloy steel at ~55 % of AISI 1212; use rigid setups, carbide inserts at moderate speed and generous coolant, and finish-bore after final heat treatment to hold ID tolerance.
Can A369 FP21 be welded?
Yes — weldability is rated good (55/100). Weld with matching 3Cr-1Mo (E9015-B3 / ER90S-B3 type) consumables, 200–300 °C preheat/interpass, low hydrogen practice, and 700–760 °C PWHT to avoid HAZ hardening and hydrogen cracking.
What surface finishes work on A369 FP21?
No anodizing; protect with high-temperature aluminium/silicone paint, aluminizing or thermal-spray coatings, and shot blast or pickle mill scale before painting.
Can A369 FP21 be formed, bent or molded?
Hot form/bend at 950–1050 °C followed by re-normalizing and tempering; cold bending is limited by high yield-to-tensile ratio and springback.
What is the maximum service temperature of A369 FP21?
A369 FP21 is rated for continuous use to about 595°C (1,103 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between A369 FP21 N+T and A369 FP21-ANN?
N+T is the default condition — standard supply condition for FP21 pressure piping: best combination of creep strength, toughness and machinability. ANN: softest condition — pick when maximum machinability, bending or lowest residual stress is needed. Yield strength is 330 MPa in N+T versus 260 MPa in ANN.
How much does A369 FP21 cost?
A369 FP21 is a premium-cost steel ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
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 P21) — ASTM International (2023)
- ASME BPVC Section II Part D — Properties (Metric) — ASME (2023)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol. 6 — Welding, Brazing, and Soldering (Cr-Mo steels) — ASM International (1993)
- 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; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.