Steel M3-2-ANN vs M3-2-HT66
Steel · M3-2 temper comparison
M3-2-ANN and M3-2-HT66 are two conditions of the same steel grade, M3-2: ANN (annealed) versus HT66 (hardened & triple tempered). The chemistry is identical, so every difference below comes from the condition. Both yield at about 550 MPa — the mechanical properties are the same, and the difference is in how the stock is processed and what it is certified to (annealed versus hardened & triple tempered). M3-2-HT66 is harder — 880 HV against 260 HV for M3-2-ANN — which matters for wear surfaces and threads. M3-2-HT66 is stiffer (228 GPa vs 213 GPa) and M3-2-HT66 runs hotter in service (580°C vs 400°C continuous). On the shop floor, M3-2-ANN machines more easily (poor vs not recommended) and M3-2-ANN forms better (12 vs 1 out of 100).
M3-2-ANNChoose it when the part is machined in volume.
M3-2-HT66Choose it when surface hardness matters, or when the part sees heat.
M3-2-ANN vs M3-2-HT66: 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
Compressive Strength
Charpy V-Notch Impact (RT)
Hardness, Vickers
Same in both: Shear Modulus 83 GPa12 Msi · Bulk Modulus 165 GPa23.9 Msi · Poisson's Ratio 0.29 · Tensile Strength (Ultimate) 880 MPa128 ksi · Yield Strength (0.2% offset) 550 MPa79.8 ksi · Elongation at Break 12% · Reduction in Area 20% · Shear Strength 560 MPa81.2 ksi · Hardness, Brinell 250 HB · Hardness, Rockwell B 102 HRB
Physical
Density and transition temperatures.
Same in both: Density 8.15 g/cm³0.29 lb/in³ · Melting Point (Solidus) 1,240°C2,264 °F · Liquidus Temperature 1,425°C2,597 °F
Thermal
How each material carries heat and how hot it can run.
Max Service Temperature (continuous)
Same in both: Thermal Conductivity 24 W/m·K13.9 BTU/hr·ft·°F · Specific Heat Capacity 420 J/kg·K0.1 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 10.6 µm/m·K5.9 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Min Service Temperature -50°C-58 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 3.2 % IACS · Electrical Resistivity 5.4×10⁻⁷ Ω·m21.3 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Corrosion Resistance 12 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Formability (cold)
Same in both: Machinability Rating (AISI 1212 = 100 %) 38% · Weldability 18 / 100 · Castability 25 / 100 · Brazeability / Solderability 55 / 100 · Polishability 70 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 42 MJ/kg18,057 BTU/lb · Embodied Carbon (primary production) 3.2 kg CO₂/kg · Embodied Water 70 L/kg8.4 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.
M3-2-ANN vs M3-2-HT66 — frequently asked
What is the difference between M3-2-ANN and M3-2-HT66?
M3-2-ANN and M3-2-HT66 are two conditions of the same steel grade, M3-2: ANN (annealed) versus HT66 (hardened & triple tempered). The chemistry is identical, so every difference below comes from the condition. Both yield at about 550 MPa — the mechanical properties are the same, and the difference is in how the stock is processed and what it is certified to (annealed versus hardened & triple tempered).
Which condition does FabDigit quote by default, ANN or HT66?
ANN is the default M3-2 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, M3-2-ANN or M3-2-HT66?
M3-2-ANN. Its machinability rates poor (30/100) against not recommended (3/100) for M3-2-HT66.
Ready to make it?
Upload a CAD file and FabDigit prices the part in M3-2-ANN and M3-2-HT66 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.