Steel D7-ANN vs D7 HT-SEC
Steel · D7 temper comparison
D7-ANN and D7 HT-SEC are two conditions of the same steel grade, D7: ANN (annealed) versus HT-SEC (hardened & double tempered 510–540 °C). The chemistry is identical, so every difference below comes from the condition. D7 HT-SEC is the stronger of the two: yield strength 1,750 MPa (254 ksi) against 500 MPa (72.5 ksi) for D7-ANN, about 3.5 times as much; tensile strength follows at 1,950 MPa (283 ksi) vs 860 MPa (125 ksi). In exchange, D7-ANN is the more ductile: elongation 10% versus 1% for D7 HT-SEC, and D7 HT-SEC is harder (59 HRC vs 24 HRC). D7 HT-SEC runs hotter in service (480°C vs 400°C continuous). On the shop floor, D7-ANN machines more easily (poor vs not recommended).
D7-ANNChoose it when the part is bent, formed or impact-loaded, or when the part is machined in volume.
D7 HT-SECChoose it when strength drives the design, or when the part sees heat.
D7-ANN vs D7 HT-SEC: 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.
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Compressive Strength
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Rockwell C
Hardness, Vickers
Same in both: Elastic (Young's) Modulus 207 GPa30 Msi · Shear Modulus 80 GPa11.6 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.28 · Reduction in Area 15% · Shear Strength 560 MPa81.2 ksi · Fatigue Strength (Endurance Limit) 380 MPa55.1 ksi · Hardness, Brinell 248 HB
Physical
Density and transition temperatures.
Same in both: Density 7.67 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,250°C2,282 °F · Liquidus Temperature 1,380°C2,516 °F
Thermal
How each material carries heat and how hot it can run.
Max Service Temperature (continuous)
Same in both: Thermal Conductivity 20 W/m·K11.6 BTU/hr·ft·°F · Specific Heat Capacity 460 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 10.5 µm/m·K5.8 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Min Service Temperature -40°C-40 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 2.7 % IACS · Electrical Resistivity 6.5×10⁻⁷ Ω·m25.6 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.4 V · Corrosion Resistance 22 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Same in both: Machinability Rating (AISI 1212 = 100 %) 25% · Weldability 12 / 100 · Formability (cold) 10 / 100 · Brazeability / Solderability 30 / 100 · Polishability 50 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 34 MJ/kg14,617 BTU/lb · Embodied Carbon (primary production) 2.6 kg CO₂/kg · Embodied Water 70 L/kg8.4 gal/lb · Typical Recycled Content 45%
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.
D7-ANN vs D7 HT-SEC — frequently asked
Is D7 HT-SEC stronger than D7-ANN?
Yes. D7 HT-SEC has a typical yield strength of 1,750 MPa (254 ksi) against 500 MPa (72.5 ksi) for D7-ANN — about 3.5 times as much. Tensile strength is 1,950 MPa (283 ksi) vs 860 MPa (125 ksi).
Which condition does FabDigit quote by default, ANN or HT-SEC?
ANN is the default D7 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, D7-ANN or D7 HT-SEC?
D7-ANN. Its machinability rates poor (22/100) against not recommended (4/100) for D7 HT-SEC.
Ready to make it?
Upload a CAD file and FabDigit prices the part in D7-ANN and D7 HT-SEC 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.