Steel 4340 vs D2
Steel · grade comparison
Steel 4340 and D2 are both steel grades. 4340 is the stronger of the two: yield strength 620 MPa (89.9 ksi) against 450 MPa (65.3 ksi) for D2, about 38% more; tensile strength follows at 950 MPa (138 ksi) vs 750 MPa (109 ksi). 4340 is the more ductile: elongation 18% versus 15% for D2, and 4340 is harder (285 HB vs 220 HB). 4340 conducts heat better (44.5 W/m·K vs 20 W/m·K). On the shop floor, 4340 machines more easily (fair vs poor), 4340 welds better (33 vs 15 out of 100), and 4340 sits in a lower cost tier (premium, $$$) than D2 (specialty, $$$$$).
4340Choose it when strength drives the design, or when the part is bent, formed or impact-loaded.
4340 vs D2: 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, Brinell
Hardness, Rockwell B
Hardness, Rockwell C
Hardness, Vickers
Same in both: Shear Modulus 80 GPa11.6 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)
Min Service Temperature
Same in both: Latent Heat of Fusion 250 J/g107 BTU/lb · Max Service Temperature (continuous) 400°C752 °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
Formability (cold)
Castability
Brazeability / Solderability
Polishability
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 | 4340 | D2 |
|---|---|---|
| Sheet metal | Yes | — |
| Default condition | HR | Annealed |
| Relative cost | $$$ Premium | $$$$$ Specialty |
| Min. machined wall | 0.8 mm | 0.8 mm |
| Best machined surface | Ra 1.6 µm | Ra 1.6 µm |
Both are offered for CNC machining. Both take the same 38 finishes: AlCrN, AlTiN, Black Oxide, CVD Al2O3, CVD TiCN, CVD TiN, Cerakote, Chrome Plating, Copper Plating, CrN, DLC, E-Coating and 26 more.
4340 vs D2 — frequently asked
Is 4340 stronger than D2?
Yes. 4340 has a typical yield strength of 620 MPa (89.9 ksi) against 450 MPa (65.3 ksi) for D2 — about 38% more. Tensile strength is 950 MPa (138 ksi) vs 750 MPa (109 ksi).
Which is cheaper, 4340 or D2?
4340 is the lower-cost material: it sits in the premium tier ($$$) while D2 is specialty ($$$$$). 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, 4340 or D2?
4340. Its machinability rates fair (48/100) against poor (30/100) for D2; for welding the order is 4340 first (poor, 33/100) then D2 (poor, 15/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 4340 and D2 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.