Steel 8645 Annealed vs 8645-HR
Steel · 8645 temper comparison
8645 Annealed and 8645-HR are two conditions of the same steel grade, 8645: Annealed versus HR (hot rolled). The chemistry is identical, so every difference below comes from the condition. 8645-HR is the stronger of the two: yield strength 500 MPa (72.5 ksi) against 425 MPa (61.6 ksi) for 8645 Annealed, about 18% more; tensile strength follows at 830 MPa (120 ksi) vs 715 MPa (104 ksi). In exchange, 8645 Annealed is the more ductile: elongation 20% versus 17% for 8645-HR, and 8645-HR is harder (235 HB vs 197 HB).
8645 AnnealedChoose it when the part is bent, formed or impact-loaded.
8645-HRChoose it when strength drives the design.
8645 Annealed vs 8645-HR: 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
Reduction in Area
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
Hardness, Vickers
Same in both: Elastic (Young's) Modulus 205 GPa29.7 Msi · Shear Modulus 80 GPa11.6 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29
Physical
Density and transition temperatures.
Same in both: Density 7.85 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,420°C2,588 °F · Liquidus Temperature 1,490°C2,714 °F
Thermal
How each material carries heat and how hot it can run.
Same in both: Thermal Conductivity 45 W/m·K26 BTU/hr·ft·°F · Specific Heat Capacity 475 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 12.3 µm/m·K6.8 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Max Service Temperature (continuous) 400°C752 °F · Min Service Temperature -40°C-40 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 7.8 % IACS · Electrical Resistivity 2.2×10⁻⁷ Ω·m8.66 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: Brazeability / Solderability 55 / 100 · Polishability 60 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 34 MJ/kg14,617 BTU/lb · Embodied Carbon (primary production) 2.4 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.
8645 Annealed vs 8645-HR — frequently asked
Is 8645-HR stronger than 8645 Annealed?
Yes. 8645-HR has a typical yield strength of 500 MPa (72.5 ksi) against 425 MPa (61.6 ksi) for 8645 Annealed — about 18% more. Tensile strength is 830 MPa (120 ksi) vs 715 MPa (104 ksi).
Which condition does FabDigit quote by default, Annealed or HR?
Annealed is the default 8645 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, 8645 Annealed or 8645-HR?
8645 Annealed. Its machinability rates good (55/100) against fair (50/100) for 8645-HR; for welding the order is 8645 Annealed first (poor, 30/100) then 8645-HR (poor, 25/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 8645 Annealed and 8645-HR 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.