Steel SKH51 Annealed vs SKH51 Nitrided
Steel · SKH51 temper comparison
SKH51 Annealed and SKH51 Nitrided are two conditions of the same steel grade, SKH51: Annealed versus Nitrided. The chemistry is identical, so every difference below comes from the condition. SKH51 Nitrided is the stronger of the two: yield strength 1,950 MPa (283 ksi) against 550 MPa (79.8 ksi) for SKH51 Annealed, about 3.5 times as much; tensile strength follows at 2,100 MPa (305 ksi) vs 850 MPa (123 ksi). In exchange, SKH51 Annealed is the more ductile: elongation 20% versus 0.5% for SKH51 Nitrided, and SKH51 Nitrided is harder (63 HRC vs 22 HRC). SKH51 Nitrided is stiffer (230 GPa vs 217 GPa) and SKH51 Nitrided runs hotter in service (560°C vs 400°C continuous). On the shop floor, SKH51 Annealed machines more easily (poor vs not recommended) and SKH51 Annealed welds better (poor vs not recommended).
SKH51 AnnealedChoose it when the part is bent, formed or impact-loaded, or when the part is machined in volume.
SKH51 NitridedChoose it when strength drives the design, or when the part sees heat.
SKH51 Annealed vs SKH51 Nitrided: 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
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, Rockwell C
Hardness, Vickers
Same in both: Shear Modulus 84 GPa12.2 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.28 · Hardness, Brinell 240 HB · Hardness, Rockwell B 99 HRB
Physical
Density and transition temperatures.
Same in both: Density 8.16 g/cm³0.29 lb/in³ · Melting Point (Solidus) 1,370°C2,498 °F · Liquidus Temperature 1,450°C2,642 °F
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Max Service Temperature (continuous)
Same in both: Specific Heat Capacity 420 J/kg·K0.1 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 11 µm/m·K6.1 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Min Service Temperature -60°C-76 °F
Electrical
Conductivity and insulation.
Electrical Conductivity
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
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: Castability 25 / 100 · Brazeability / Solderability 55 / 100 · Polishability 70 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 45 MJ/kg19,347 BTU/lb · Embodied Carbon (primary production) 3.2 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.
SKH51 Annealed vs SKH51 Nitrided — frequently asked
Is SKH51 Nitrided stronger than SKH51 Annealed?
Yes. SKH51 Nitrided has a typical yield strength of 1,950 MPa (283 ksi) against 550 MPa (79.8 ksi) for SKH51 Annealed — about 3.5 times as much. Tensile strength is 2,100 MPa (305 ksi) vs 850 MPa (123 ksi).
Which condition does FabDigit quote by default, Annealed or Nitrided?
Annealed is the default SKH51 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, SKH51 Annealed or SKH51 Nitrided?
SKH51 Annealed. Its machinability rates poor (30/100) against not recommended (3/100) for SKH51 Nitrided; for welding the order is SKH51 Annealed first (poor, 20/100) then SKH51 Nitrided (not recommended, 5/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in SKH51 Annealed and SKH51 Nitrided 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.