Steel O7-ANN vs O7 HT-175
Steel · O7 temper comparison
O7-ANN and O7 HT-175 are two conditions of the same steel grade, O7: ANN (annealed) versus HT-175 (hardened & tempered 175 °C). The chemistry is identical, so every difference below comes from the condition. O7 HT-175 is the stronger of the two: yield strength 2,050 MPa (297 ksi) against 400 MPa (58 ksi) for O7-ANN, about 5.1 times as much; tensile strength follows at 2,400 MPa (348 ksi) vs 690 MPa (100 ksi). In exchange, O7-ANN is the more ductile: elongation 24% versus 1% for O7 HT-175, and O7 HT-175 is harder (800 HV vs 212 HV). O7-ANN runs hotter in service (200°C vs 170°C continuous). On the shop floor, O7-ANN machines more easily (good vs not recommended).
O7-ANNChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
O7 HT-175Choose it when strength drives the design.
O7-ANN vs O7 HT-175: 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.
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
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: Shear Modulus 80 GPa11.6 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29 · Reduction in Area 45% · Hardness, Brinell 202 HB · Hardness, Rockwell B 94 HRB
Physical
Density and transition temperatures.
Same in both: Density 7.8 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,400°C2,552 °F · Liquidus Temperature 1,450°C2,642 °F
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Max Service Temperature (continuous)
Same in both: Specific Heat Capacity 460 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 11.5 µm/m·K6.4 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 3 % IACS · Electrical Resistivity 5.5×10⁻⁷ Ω·m21.7 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)
Same in both: Castability 20 / 100 · Brazeability / Solderability 40 / 100 · Polishability 70 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 33 MJ/kg14,187 BTU/lb · Embodied Carbon (primary production) 2.4 kg CO₂/kg · Embodied Water 65 L/kg7.8 gal/lb · Typical Recycled Content 30%
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.
O7-ANN vs O7 HT-175 — frequently asked
Is O7 HT-175 stronger than O7-ANN?
Yes. O7 HT-175 has a typical yield strength of 2,050 MPa (297 ksi) against 400 MPa (58 ksi) for O7-ANN — about 5.1 times as much. Tensile strength is 2,400 MPa (348 ksi) vs 690 MPa (100 ksi).
Which condition does FabDigit quote by default, ANN or HT-175?
ANN is the default O7 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, O7-ANN or O7 HT-175?
O7-ANN. Its machinability rates good (55/100) against not recommended (8/100) for O7 HT-175; for welding the order is O7-ANN first (poor, 15/100) then O7 HT-175 (not recommended, 8/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in O7-ANN and O7 HT-175 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.