Steel O1 Annealed vs O1 Hardened & Tempered
Steel · O1 temper comparison
O1 Annealed and O1 Hardened & Tempered are two conditions of the same steel grade, O1: Annealed versus Hardened & Tempered (quenched and tempered). The chemistry is identical, so every difference below comes from the condition. O1 Hardened & Tempered is the stronger of the two: yield strength 1,900 MPa (276 ksi) against 400 MPa (58 ksi) for O1 Annealed, about 4.8 times as much; tensile strength follows at 2,200 MPa (319 ksi) vs 690 MPa (100 ksi). In exchange, O1 Annealed is the more ductile: elongation 25% versus 1% for O1 Hardened & Tempered, and O1 Hardened & Tempered is harder (730 HV vs 210 HV). O1 Annealed runs hotter in service (400°C vs 180°C continuous). On the shop floor, O1 Annealed machines more easily (fair vs not recommended) and O1 Annealed welds better (poor vs not recommended).
O1 AnnealedChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
O1 Hardened & TemperedChoose it when strength drives the design.
O1 Annealed vs O1 Hardened & Tempered: 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.
O1 AnnealedO1 Hardened & Tempered
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Charpy V-Notch Impact (RT)
Hardness, Vickers
Same in both: Elastic (Young's) Modulus 205 GPa29.7 Msi · Shear Modulus 79 GPa11.5 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29 · Reduction in Area 45% · Hardness, Brinell 200 HB · Hardness, Rockwell B 94 HRB
Physical
Density and transition temperatures.
Same in both: Density 7.85 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,400°C2,552 °F · Liquidus Temperature 1,460°C2,660 °F
Thermal
How each material carries heat and how hot it can run.
Max Service Temperature (continuous)
Same in both: Thermal Conductivity 35 W/m·K20.2 BTU/hr·ft·°F · Specific Heat Capacity 460 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 11.9 µm/m·K6.6 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Min Service Temperature -30°C-22 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 7 % IACS · Electrical Resistivity 2.5×10⁻⁷ Ω·m9.84 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.6 V · Corrosion Resistance 12 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Weldability
Formability (cold)
Polishability
Same in both: Brazeability / Solderability 45 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 32 MJ/kg13,758 BTU/lb · Embodied Carbon (primary production) 2.4 kg CO₂/kg · Embodied Water 55 L/kg6.6 gal/lb · Typical Recycled Content 40%
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.
O1 Annealed vs O1 Hardened & Tempered — frequently asked
Is O1 Hardened & Tempered stronger than O1 Annealed?
Yes. O1 Hardened & Tempered has a typical yield strength of 1,900 MPa (276 ksi) against 400 MPa (58 ksi) for O1 Annealed — about 4.8 times as much. Tensile strength is 2,200 MPa (319 ksi) vs 690 MPa (100 ksi).
Which condition does FabDigit quote by default, Annealed or Hardened & Tempered?
Annealed is the default O1 condition in the FabDigit quote flow. 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, O1 Annealed or O1 Hardened & Tempered?
O1 Annealed. Its machinability rates fair (45/100) against not recommended (8/100) for O1 Hardened & Tempered; for welding the order is O1 Annealed first (poor, 20/100) then O1 Hardened & Tempered (not recommended, 10/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in O1 Annealed and O1 Hardened & Tempered 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.