Steel 4140 Q&T vs 4340 Q&T
Steel · grade comparison
Steel 4140 Q&T and 4340 Q&T are both steel grades, both high strength steel, compared here in the Q&T condition. 4340 Q&T is the stronger of the two: tensile strength 1,030 MPa (149 ksi) against 965 MPa (140 ksi) for 4140 Q&T, about 7% more. 4340 Q&T is harder — 302 HB against 285 HB for 4140 Q&T — which matters for wear surfaces and threads. 4140 Q&T runs hotter in service (480°C vs 400°C continuous) and 4140 Q&T conducts electricity better (7.8 % IACS vs 7 % IACS). On the shop floor, 4140 Q&T machines more easily (good vs fair) and 4140 Q&T sits in a lower cost tier (standard, $$) than 4340 Q&T (premium, $$$).
4140 Q&TChoose it when the part sees heat, or when the part is machined in volume.
4340 Q&TChoose it when strength drives the design, or when surface hardness matters.
4140 Q&T vs 4340 Q&T: 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)
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 · Shear Modulus 80 GPa11.6 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29
Physical
Density and transition temperatures.
Liquidus Temperature
Same in both: Density 7.85 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,416°C2,581 °F
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Specific Heat Capacity
Max Service Temperature (continuous)
Same in both: Thermal Expansion (CTE, 20–100 °C) 12.3 µm/m·K6.8 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Min Service Temperature -40°C-40 °F
Electrical
Conductivity and insulation.
Electrical Conductivity
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Galvanic Potential (seawater, vs SCE)
Same in both: Corrosion Resistance 12 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Formability (cold)
Polishability
Castability
Same in both: Weldability 30 / 100 · Brazeability / Solderability 55 / 100
Sustainability
Primary-production footprint per kilogram.
Embodied Carbon (primary production)
Embodied Water
Same in both: Embodied Energy (primary production) 32 MJ/kg13,758 BTU/lb · Typical Recycled Content 30%
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 Q&T | 4340 Q&T |
|---|---|---|
| Casting & forging | Yes | — |
| Default condition | HR | HR |
| Relative cost | $$ Standard | $$$ Premium |
| 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 Q&T vs 4340 Q&T — frequently asked
Is 4340 Q&T stronger than 4140 Q&T?
Yes. 4340 Q&T has a typical tensile strength of 1,030 MPa (149 ksi) against 965 MPa (140 ksi) for 4140 Q&T — about 7% more.
Which is cheaper, 4140 Q&T or 4340 Q&T?
4140 Q&T is the lower-cost material: it sits in the standard tier ($$) while 4340 Q&T is premium ($$$). 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, 4140 Q&T or 4340 Q&T?
4140 Q&T. Its machinability rates good (55/100) against fair (43/100) for 4340 Q&T.
Ready to make it?
Upload a CAD file and FabDigit prices the part in 4140 Q&T and 4340 Q&T 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.