Steel M45 Annealed vs M45 Hardened & Tempered
Steel · M45 temper comparison
M45 Annealed and M45 Hardened & Tempered are two conditions of the same steel grade, M45: Annealed versus Hardened & Tempered (quenched and tempered). The chemistry is identical, so every difference below comes from the condition. Both yield at about 620 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 quenched and tempered). M45 Annealed is the more ductile: elongation 12% versus 0% for M45 Hardened & Tempered, and M45 Hardened & Tempered is harder (68 HRC vs 26 HRC). M45 Hardened & Tempered is stiffer (230 GPa vs 217 GPa) and M45 Hardened & Tempered runs hotter in service (620°C vs 200°C continuous). On the shop floor, M45 Annealed machines more easily (poor vs not recommended).
M45 AnnealedChoose it when the part is bent, formed or impact-loaded, or when the part is machined in volume.
M45 Hardened & TemperedChoose it when the part sees heat.
M45 Annealed vs M45 Hardened & Tempered: 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.
M45 AnnealedM45 Hardened & Tempered
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Elongation at Break
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Rockwell C
Hardness, Vickers
Same in both: Shear Modulus 84 GPa12.2 Msi · Bulk Modulus 165 GPa23.9 Msi · Poisson's Ratio 0.29 · Tensile Strength (Ultimate) 950 MPa138 ksi · Yield Strength (0.2% offset) 620 MPa89.9 ksi · Reduction in Area 25% · Hardness, Brinell 269 HB
Physical
Density and transition temperatures.
Same in both: Density 8.1 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 22 W/m·K12.7 BTU/hr·ft·°F · Specific Heat Capacity 420 J/kg·K0.1 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 10.8 µm/m·K6 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Min Service Temperature -60°C-76 °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: Galvanic Potential (seawater, vs SCE) -0.6 V · Corrosion Resistance 18 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Weldability
Formability (cold)
Polishability
Same in both: Castability 25 / 100 · Brazeability / Solderability 60 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 55 MJ/kg23,646 BTU/lb · Embodied Carbon (primary production) 4.2 kg CO₂/kg · Embodied Water 110 L/kg13.2 gal/lb · Typical Recycled Content 35%
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.
M45 Annealed vs M45 Hardened & Tempered — frequently asked
What is the difference between M45 Annealed and M45 Hardened & Tempered?
M45 Annealed and M45 Hardened & Tempered are two conditions of the same steel grade, M45: Annealed versus Hardened & Tempered (quenched and tempered). The chemistry is identical, so every difference below comes from the condition. Both yield at about 620 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 quenched and tempered).
Which condition does FabDigit quote by default, Annealed or Hardened & Tempered?
Annealed is the default M45 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, M45 Annealed or M45 Hardened & Tempered?
M45 Annealed. Its machinability rates poor (25/100) against not recommended (4/100) for M45 Hardened & Tempered; for welding the order is M45 Annealed first (poor, 15/100) then M45 Hardened & Tempered (not recommended, 8/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in M45 Annealed and M45 Hardened & Tempered 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.