Steel 3Cr2Mo vs P21
Steel · grade comparison
Steel 3Cr2Mo and P21 are both steel grades. P21 is the stronger of the two: yield strength 1,150 MPa (167 ksi) against 830 MPa (120 ksi) for 3Cr2Mo, about 39% more; tensile strength follows at 1,300 MPa (189 ksi) vs 1,000 MPa (145 ksi). P21 is harder — 375 HB against 300 HB for 3Cr2Mo — which matters for wear surfaces and threads. P21 runs hotter in service (450°C vs 400°C continuous) and 3Cr2Mo conducts electricity better (8 % IACS vs 4.9 % IACS). On the shop floor, 3Cr2Mo machines more easily (good vs fair), P21 welds better (good vs fair), and 3Cr2Mo sits in a lower cost tier (standard, $$) than P21 (premium, $$$).
3Cr2MoChoose it when the part is machined in volume, or when cost is the deciding factor.
P21Choose it when strength drives the design, or when surface hardness matters.
3Cr2Mo vs P21: 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
Bulk Modulus
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Hardness, Brinell
Hardness, Rockwell C
Hardness, Vickers
Same in both: Shear Modulus 80 GPa11.6 Msi · Poisson's Ratio 0.29 · Reduction in Area 50% · Charpy V-Notch Impact (RT) 25 J18.4 ft·lbf
Physical
Density and transition temperatures.
Density
Same in both: 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
Thermal Expansion (CTE, 20–100 °C)
Latent Heat of Fusion
Max Service Temperature (continuous)
Same in both: Specific Heat Capacity 460 J/kg·K0.11 BTU/lb·°F · Min Service Temperature -30°C-22 °F
Electrical
Conductivity and insulation.
Electrical Conductivity
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Galvanic Potential (seawater, vs SCE)
Corrosion Resistance
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Weldability
Polishability
Castability
Same in both: Formability (cold) 15 / 100 · Brazeability / Solderability 40 / 100
Sustainability
Primary-production footprint per kilogram.
Typical Recycled Content
Same in both: Embodied Energy (primary production) 34 MJ/kg14,617 BTU/lb · Embodied Carbon (primary production) 2.4 kg CO₂/kg · Embodied Water 60 L/kg7.2 gal/lb
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
Modulus of Resilience
Thermal Diffusivity
Thermal Shock Resistance Index
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 | 3Cr2Mo | P21 |
|---|---|---|
| Default condition | — | — |
| Relative cost | $$ Standard | $$$ Premium |
| Min. machined wall | — | — |
| Best machined surface | — | — |
Both take the same 9 finishes: Copper Plating, Electroless Nickel (EN), Epoxy Coating, Gold Plating, Hard Chrome Plating, Manganese Phosphate, Plasma Spray, Silver Plating, Zinc Phosphate.
3Cr2Mo vs P21 — frequently asked
Is P21 stronger than 3Cr2Mo?
Yes. P21 has a typical yield strength of 1,150 MPa (167 ksi) against 830 MPa (120 ksi) for 3Cr2Mo — about 39% more. Tensile strength is 1,300 MPa (189 ksi) vs 1,000 MPa (145 ksi).
Which is cheaper, 3Cr2Mo or P21?
3Cr2Mo is the lower-cost material: it sits in the standard tier ($$) while P21 is premium ($$$). Part price depends far more on geometry, tolerance and quantity than on raw stock — upload a CAD file for a live quote.
Which is easier to machine, 3Cr2Mo or P21?
3Cr2Mo. Its machinability rates good (55/100) against fair (45/100) for P21; for welding the order is P21 first (good, 55/100) then 3Cr2Mo (fair, 40/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 3Cr2Mo and P21 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.