Steel 4140 Annealed vs 4140 Q&T
Steel · 4140 temper comparison
4140 Annealed and 4140 Q&T are two conditions of the same steel grade, 4140: Annealed versus Q&T (quenched and tempered). The chemistry is identical, so every difference below comes from the condition. 4140 Q&T is the stronger of the two: yield strength 860 MPa (125 ksi) against 415 MPa (60.2 ksi) for 4140 Annealed, about 107% more; tensile strength follows at 965 MPa (140 ksi) vs 655 MPa (95 ksi). In exchange, 4140 Annealed is the more ductile: elongation 25.7% versus 17% for 4140 Q&T, and 4140 Q&T is harder (285 HB vs 197 HB). 4140 Q&T runs hotter in service (480°C vs 425°C continuous). On the shop floor, 4140 Annealed welds better (fair vs poor).
4140 AnnealedChoose it when the part is bent, formed or impact-loaded, or when it will be welded.
4140 Q&TChoose it when strength drives the design, or when the part sees heat.
Buyer's decision notes
Choose annealed 4140 when machining or forming will be followed by a controlled final heat treatment. Choose quenched-and-tempered 4140 when delivered properties are part of the purchase and the remaining machining will not undo the certified condition.
Compare the same condition
The chemistry is the same, but “Q&T” is not one universal property set. Compare a named quenched-and-tempered class, section size and test location with an annealed product of the same form; hardness and through-section response depend on the heat-treatment route and section.
- Process sequence
- Annealed stock lowers cutting load before hardening, but the final quench and temper add movement, scale and decarburization risk. Delivered Q&T stock moves heat treatment upstream, yet heavy later machining can release stress or remove the certified test location.
- Section response
- Specify the controlling section, quench route, temper and property test location. ASTM A400 shows why section belongs in alloy selection, while ASTM A434 is the appropriate product specification when quenched-and-tempered bars are purchased to mechanical requirements.
- Machining and finish
- Set tool and grinding plans from the actual delivered hardness, not the 4140 name. Leave allowance for scale or decarburization after heat treatment and state whether final hardness is checked before or after grinding and straightening.
- Weld repair
- Do not permit an unplanned weld repair on either condition. Welding changes the local thermal history and may require preheat, controlled cooling, re-heat-treatment and renewed inspection to restore the specified properties.
Put this on the RFQ
- State ASTM A322 for alloy bar before final heat treatment or ASTM A434 for purchased Q&T bar, plus exact condition and certification.
- Define section size, required property or hardness range, test orientation and location, heat-treatment lot, decarburization limit and straightness.
- Assign responsibility for rough machining, heat treatment, straightening, finish grinding, nondestructive testing and final dimensional inspection.
Primary references
- ASTM — A322 — Active specification for standard-grade hot-wrought alloy steel bars used for machining, forging and heat treatment.
- ASTM — A434/A434M — Active specification for hot-wrought or cold-finished quenched-and-tempered alloy steel bars.
FabDigit resources: 4140 Annealed datasheet, 4140 Q&T datasheet, CNC design guide and sheet-metal design guide.
4140 Annealed vs 4140 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
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.
Same in both: Density 7.85 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,416°C2,581 °F · Liquidus Temperature 1,483°C2,701 °F
Thermal
How each material carries heat and how hot it can run.
Max Service Temperature (continuous)
Same in both: Thermal Conductivity 42.6 W/m·K24.6 BTU/hr·ft·°F · Specific Heat Capacity 473 J/kg·K0.11 BTU/lb·°F · 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.
Same in both: Electrical Conductivity 7.8 % IACS · Electrical Resistivity 2.2×10⁻⁷ Ω·m8.66 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.61 V · Corrosion Resistance 12 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Weldability
Formability (cold)
Same in both: Brazeability / Solderability 55 / 100 · Polishability 60 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 32 MJ/kg13,758 BTU/lb · Embodied Carbon (primary production) 2.2 kg CO₂/kg · Embodied Water 55 L/kg6.6 gal/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.
4140 Annealed vs 4140 Q&T — frequently asked
Is 4140 Q&T stronger than 4140 Annealed?
Yes. 4140 Q&T has a typical yield strength of 860 MPa (125 ksi) against 415 MPa (60.2 ksi) for 4140 Annealed — about 107% more. Tensile strength is 965 MPa (140 ksi) vs 655 MPa (95 ksi).
Which condition does FabDigit quote by default, Annealed or Q&T?
HR is the default 4140 condition in the FabDigit quote flow (neither Annealed nor Q&T). The other condition is available on request or by drawing note — specify it in the material field or the part notes and the quote is priced for it.
Which is easier to machine, 4140 Annealed or 4140 Q&T?
4140 Annealed, by a small margin. Both rate good for machinability — 63/100 against 55/100 for 4140 Q&T; for welding the order is 4140 Annealed first (fair, 45/100) then 4140 Q&T (poor, 30/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 4140 Annealed and 4140 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.