Steel 31CrMoV9 vs 42CrMo4
Steel · grade comparison
Steel 31CrMoV9 and 42CrMo4 are both steel grades. 31CrMoV9 is the stronger of the two: yield strength 880 MPa (128 ksi) against 550 MPa (79.8 ksi) for 42CrMo4, about 60% more; tensile strength follows at 1,100 MPa (160 ksi) vs 850 MPa (123 ksi). In exchange, 42CrMo4 is the more ductile: elongation 14% versus 12% for 31CrMoV9, and 31CrMoV9 is harder (330 HB vs 245 HB). 31CrMoV9 runs hotter in service (450°C vs 400°C continuous) and 42CrMo4 conducts heat better (42.6 W/m·K vs 36 W/m·K). On the shop floor, 42CrMo4 machines more easily (50 vs 40 out of 100) and 42CrMo4 welds better (fair vs poor).
31CrMoV9Choose it when strength drives the design, or when the part sees heat.
42CrMo4Choose it when the part is bent, formed or impact-loaded, or when the part is machined in volume.
31CrMoV9 vs 42CrMo4: 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)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell C
Hardness, Vickers
Same in both: Elastic (Young's) Modulus 210 GPa30.5 Msi · Shear Modulus 80 GPa11.6 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29 · Fracture Toughness (K_IC) 75 MPa·√m68.3 ksi·√in
Physical
Density and transition temperatures.
Liquidus Temperature
Same in both: Density 7.85 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,420°C2,588 °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.
Electrical Conductivity
Same in both: 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
Formability (cold)
Castability
Brazeability / Solderability
Same in both: Polishability 70 / 100
Sustainability
Primary-production footprint per kilogram.
Embodied Carbon (primary production)
Typical Recycled Content
Same in both: Embodied Energy (primary production) 30 MJ/kg12,898 BTU/lb · Embodied Water 60 L/kg7.2 gal/lb
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Modulus of Resilience
Thermal Diffusivity
Thermal Shock Resistance Index
Same in both: Specific Stiffness (E / density) 26.8 MN·m/kg
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 | 31CrMoV9 | 42CrMo4 |
|---|---|---|
| Default condition | Q&T | HR |
| 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.
31CrMoV9 vs 42CrMo4 — frequently asked
Is 31CrMoV9 stronger than 42CrMo4?
Yes. 31CrMoV9 has a typical yield strength of 880 MPa (128 ksi) against 550 MPa (79.8 ksi) for 42CrMo4 — about 60% more. Tensile strength is 1,100 MPa (160 ksi) vs 850 MPa (123 ksi).
Which is cheaper, 31CrMoV9 or 42CrMo4?
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, 31CrMoV9 or 42CrMo4?
42CrMo4, by a small margin. Both rate fair for machinability — 50/100 against 40/100 for 31CrMoV9; for welding the order is 42CrMo4 first (fair, 35/100) then 31CrMoV9 (poor, 20/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 31CrMoV9 and 42CrMo4 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.