Steel A369 FP91-N vs A369 FP91 SUBCRIT-ANN
Steel · A369 FP91 temper comparison
A369 FP91-N and A369 FP91 SUBCRIT-ANN are two conditions of the same steel grade, A369 FP91: N (normalized) versus SUBCRIT-ANN (sub-critical annealed). The chemistry is identical, so every difference below comes from the condition. A369 FP91-N is the stronger of the two: yield strength 900 MPa (131 ksi) against 400 MPa (58 ksi) for A369 FP91 SUBCRIT-ANN, about 125% more; tensile strength follows at 1,250 MPa (181 ksi) vs 570 MPa (82.7 ksi). In exchange, A369 FP91 SUBCRIT-ANN is the more ductile: elongation 28% versus 10% for A369 FP91-N, and A369 FP91-N is harder (400 HB vs 180 HB). On the shop floor, A369 FP91 SUBCRIT-ANN machines more easily (good vs poor) and A369 FP91 SUBCRIT-ANN welds better (fair vs poor).
A369 FP91-NChoose it when strength drives the design.
A369 FP91 SUBCRIT-ANNChoose it when the part is bent, formed or impact-loaded, or when the part is machined in volume.
A369 FP91-N vs A369 FP91 SUBCRIT-ANN: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all steel grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
How to read these bars
- One bar per material. A full bar is the highest value among all steel grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
A369 FP91-NA369 FP91 SUBCRIT-ANN
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Reduction in Area
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell C
Hardness, Vickers
Same in both: Elastic (Young's) Modulus 218 GPa31.6 Msi · Shear Modulus 84 GPa12.2 Msi · Bulk Modulus 180 GPa26.1 Msi · Poisson's Ratio 0.3
Physical
Density and transition temperatures.
Same in both: Density 7.77 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,450°C2,642 °F · Liquidus Temperature 1,500°C2,732 °F
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Same in both: Specific Heat Capacity 480 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 10.8 µm/m·K6 µin/in·°F · Latent Heat of Fusion 270 J/g116 BTU/lb · Max Service Temperature (continuous) 600°C1,112 °F · Min Service Temperature -30°C-22 °F
Electrical
Conductivity and insulation.
Electrical Conductivity
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.58 V · Corrosion Resistance 30 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Weldability
Formability (cold)
Same in both: Castability 45 / 100 · Brazeability / Solderability 35 / 100 · Polishability 60 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 34 MJ/kg14,617 BTU/lb · Embodied Carbon (primary production) 2.5 kg CO₂/kg · Embodied Water 60 L/kg7.2 gal/lb · Typical Recycled Content 25%
Strength versus weight
Yield strength against density for every steel grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
A369 FP91-N vs A369 FP91 SUBCRIT-ANN — frequently asked
Is A369 FP91-N stronger than A369 FP91 SUBCRIT-ANN?
Yes. A369 FP91-N has a typical yield strength of 900 MPa (131 ksi) against 400 MPa (58 ksi) for A369 FP91 SUBCRIT-ANN — about 125% more. Tensile strength is 1,250 MPa (181 ksi) vs 570 MPa (82.7 ksi).
Which condition does FabDigit quote by default, N or SUBCRIT-ANN?
N+T is the default A369 FP91 condition in the FabDigit quote flow (neither N nor SUBCRIT-ANN). The other condition is available on request or by drawing note — specify it in the material field or the part notes and the quote is priced for it.
Which is easier to machine, A369 FP91-N or A369 FP91 SUBCRIT-ANN?
A369 FP91 SUBCRIT-ANN. Its machinability rates good (55/100) against poor (15/100) for A369 FP91-N; for welding the order is A369 FP91 SUBCRIT-ANN first (fair, 45/100) then A369 FP91-N (poor, 15/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in A369 FP91-N and A369 FP91 SUBCRIT-ANN side by side — material, machining time, tolerance and finish in one quote. Certified material data ships with the order on request.
Typical handbook values for the conditions named above, normalised for comparison. Hardness on non-Brinell scales is converted approximately for charting only. Request certified data with your order for design-critical properties.