Steel 4140 vs 4340M
Steel · grade comparison
Steel 4140 and 4340M are both steel grades. 4340M is the stronger of the two: yield strength 1,150 MPa (167 ksi) against 480 MPa (69.6 ksi) for 4140, about 140% more; tensile strength follows at 1,550 MPa (225 ksi) vs 690 MPa (100 ksi). In exchange, 4140 is the more ductile: elongation 22% versus 6% for 4340M, and 4340M is harder (444 HB vs 210 HB). 4140 runs hotter in service (425°C vs 290°C continuous) and 4140 conducts heat better (42.6 W/m·K vs 34 W/m·K). On the shop floor, 4140 machines more easily (good vs poor) and 4140 welds better (fair vs not recommended).
4140Choose it when the part is bent, formed or impact-loaded, or when the part sees heat.
4340MChoose it when strength drives the design.
4140 vs 4340M: 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)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
Hardness, Vickers
Hardness, Rockwell C
Same in both: Elastic (Young's) Modulus 205 GPa29.7 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29
Physical
Density and transition temperatures.
Density
Melting Point (Solidus)
Liquidus Temperature
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)
Min Service Temperature
Same in both: Latent Heat of Fusion 250 J/g107 BTU/lb
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
Formability (cold)
Brazeability / Solderability
Polishability
Castability
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Carbon (primary production)
Embodied Water
Typical Recycled Content
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 | 4140 | 4340M |
|---|---|---|
| Casting & forging | Yes | — |
| Default condition | HR | 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.
4140 vs 4340M — frequently asked
Is 4340M stronger than 4140?
Yes. 4340M has a typical yield strength of 1,150 MPa (167 ksi) against 480 MPa (69.6 ksi) for 4140 — about 140% more. Tensile strength is 1,550 MPa (225 ksi) vs 690 MPa (100 ksi).
Which is cheaper, 4140 or 4340M?
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, 4140 or 4340M?
4140. Its machinability rates good (60/100) against poor (15/100) for 4340M; for welding the order is 4140 first (fair, 40/100) then 4340M (not recommended, 12/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 4140 and 4340M 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.