Steel Böhler S390 Annealed vs Böhler S390 HT 66-68HRC
Steel · Böhler S390 temper comparison
Böhler S390 Annealed and Böhler S390 HT 66-68HRC are two conditions of the same steel grade, Böhler S390: Annealed versus HT 66-68HRC (hardened & triple tempered). The chemistry is identical, so every difference below comes from the condition. Both yield at about 700 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). Böhler S390 HT 66-68HRC is harder — 67 HRC against 31 HRC for Böhler S390 Annealed — which matters for wear surfaces and threads. Böhler S390 HT 66-68HRC is stiffer (245 GPa vs 230 GPa) and Böhler S390 HT 66-68HRC runs hotter in service (580°C vs 500°C continuous). On the shop floor, Böhler S390 Annealed machines more easily (poor vs not recommended).
Böhler S390 AnnealedChoose it when the part is machined in volume.
Böhler S390 HT 66-68HRCChoose it when surface hardness matters, or when the part sees heat.
Böhler S390 Annealed vs Böhler S390 HT 66-68HRC: 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.
Böhler S390 AnnealedBöhler S390 HT 66-68HRC
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Compressive Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Rockwell C
Hardness, Vickers
Same in both: Shear Modulus 94 GPa13.6 Msi · Bulk Modulus 200 GPa29 Msi · Poisson's Ratio 0.29 · Tensile Strength (Ultimate) 1,000 MPa145 ksi · Yield Strength (0.2% offset) 700 MPa102 ksi · Elongation at Break 10% · Reduction in Area 20% · Shear Strength 600 MPa87 ksi · Hardness, Brinell 300 HB · Hardness, Rockwell B 104 HRB
Physical
Density and transition temperatures.
Same in both: Density 8 g/cm³0.29 lb/in³ · Melting Point (Solidus) 1,260°C2,300 °F · Liquidus Temperature 1,420°C2,588 °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) 10.5 µm/m·K5.8 µin/in·°F · Min Service Temperature -60°C-76 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 3.4 % IACS · Electrical Resistivity 5×10⁻⁷ Ω·m19.7 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Corrosion Resistance 15 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Polishability
Same in both: Machinability Rating (AISI 1212 = 100 %) 25% · Weldability 20 / 100 · Formability (cold) 15 / 100 · Brazeability / Solderability 40 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 70 MJ/kg30,095 BTU/lb · Embodied Carbon (primary production) 5.5 kg CO₂/kg · Embodied Water 200 L/kg24 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.
Böhler S390 Annealed vs Böhler S390 HT 66-68HRC — frequently asked
What is the difference between Böhler S390 Annealed and Böhler S390 HT 66-68HRC?
Böhler S390 Annealed and Böhler S390 HT 66-68HRC are two conditions of the same steel grade, Böhler S390: Annealed versus HT 66-68HRC (hardened & triple tempered). The chemistry is identical, so every difference below comes from the condition. Both yield at about 700 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, Annealed or HT 66-68HRC?
Annealed is the default Böhler S390 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, Böhler S390 Annealed or Böhler S390 HT 66-68HRC?
Böhler S390 Annealed. Its machinability rates poor (25/100) against not recommended (4/100) for Böhler S390 HT 66-68HRC.
Ready to make it?
Upload a CAD file and FabDigit prices the part in Böhler S390 Annealed and Böhler S390 HT 66-68HRC 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.