Steel 55Cr3 vs SUP9
Steel · grade comparison
Steel 55Cr3 and SUP9 are both steel grades, both spring steel. 55Cr3 is the stronger of the two: yield strength 480 MPa (69.6 ksi) against 440 MPa (63.8 ksi) for SUP9, about 9% more; tensile strength follows at 800 MPa (116 ksi) vs 760 MPa (110 ksi). In exchange, SUP9 is the more ductile: elongation 22% versus 16% for 55Cr3. 55Cr3 runs hotter in service (400°C vs 250°C continuous).
55Cr3Choose it when strength drives the design, or when the part sees heat.
SUP9Choose it when the part is bent, formed or impact-loaded.
55Cr3 vs SUP9: 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.
Shear 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)
Hardness, Brinell
Hardness, Rockwell B
Hardness, Rockwell C
Hardness, Vickers
Same in both: Elastic (Young's) Modulus 206 GPa29.9 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29 · Charpy V-Notch Impact (RT) 30 J22.1 ft·lbf
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.
Thermal Conductivity
Specific Heat Capacity
Thermal Expansion (CTE, 20–100 °C)
Max Service Temperature (continuous)
Same in both: Latent Heat of Fusion 250 J/g107 BTU/lb · 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).
Corrosion Resistance
Galvanic Potential (seawater, vs SCE)
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Weldability
Brazeability / Solderability
Same in both: Formability (cold) 45 / 100 · Polishability 60 / 100
Sustainability
Primary-production footprint per kilogram.
Embodied Water
Same in both: Embodied Energy (primary production) 26 MJ/kg11,178 BTU/lb · Embodied Carbon (primary production) 2 kg CO₂/kg · Typical Recycled Content 30%
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Modulus of Resilience
Thermal Diffusivity
Same in both: Specific Stiffness (E / density) 26.2 MN·m/kg · Thermal Shock Resistance Index 14
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.
Manufacturing and finishing
| Capability | 55Cr3 | SUP9 |
|---|---|---|
| Default condition | Annealed | Annealed |
| Relative cost | $$ Standard | $$ Standard |
| Min. machined wall | 0.8 mm | 0.8 mm |
| Best machined surface | Ra 1.6 µm | Ra 1.6 µm |
Both are offered for CNC machining and Sheet metal. Both take the same 38 finishes: AlCrN, AlTiN, Black Oxide, CVD Al2O3, CVD TiCN, CVD TiN, Cerakote, Chrome Plating, Copper Plating, CrN, DLC, E-Coating and 26 more.
55Cr3 vs SUP9 — frequently asked
Is 55Cr3 stronger than SUP9?
Yes. 55Cr3 has a typical yield strength of 480 MPa (69.6 ksi) against 440 MPa (63.8 ksi) for SUP9 — about 9% more. Tensile strength is 800 MPa (116 ksi) vs 760 MPa (110 ksi).
Which is cheaper, 55Cr3 or SUP9?
Both sit in the same relative cost tier ($$, standard); the part price will be decided by machining time, tolerance and quantity rather than by the material.
Which is easier to machine, 55Cr3 or SUP9?
SUP9. Its machinability rates good (55/100) against fair (50/100) for 55Cr3; for welding the order is SUP9 first (poor, 30/100) then 55Cr3 (poor, 25/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 55Cr3 and SUP9 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.