Steel 34CrMo4 +AC vs 34CrMo4 +QT
Steel · 34CrMo4 temper comparison
34CrMo4 +AC and 34CrMo4 +QT are two conditions of the same steel grade, 34CrMo4: +AC (spheroidize annealed) versus +QT (quenched and tempered). The chemistry is identical, so every difference below comes from the condition. 34CrMo4 +QT is the stronger of the two: yield strength 750 MPa (109 ksi) against 350 MPa (50.8 ksi) for 34CrMo4 +AC, about 114% more; tensile strength follows at 1,000 MPa (145 ksi) vs 560 MPa (81.2 ksi). In exchange, 34CrMo4 +AC is the more ductile: elongation 25% versus 12% for 34CrMo4 +QT, and 34CrMo4 +QT is harder (300 HB vs 178 HB). 34CrMo4 +QT runs hotter in service (500°C vs 450°C continuous). On the shop floor, 34CrMo4 +AC machines more easily (good vs fair) and 34CrMo4 +AC welds better (52 vs 40 out of 100).
34CrMo4 +ACChoose it when the part is bent, formed or impact-loaded, or when the part is machined in volume.
34CrMo4 +QTChoose it when strength drives the design, or when the part sees heat.
34CrMo4 +AC vs 34CrMo4 +QT: 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
Fatigue Strength (Endurance Limit)
Charpy V-Notch Impact (RT)
Hardness, Brinell
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 · Compressive Strength 780 MPa113 ksi · Shear Strength 620 MPa89.9 ksi · Fracture Toughness (K_IC) 90 MPa·√m81.9 ksi·√in · Hardness, Rockwell C 31 HRC
Physical
Density and transition temperatures.
Same in both: Density 7.85 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,420°C2,588 °F · Liquidus Temperature 1,500°C2,732 °F
Thermal
How each material carries heat and how hot it can run.
Max Service Temperature (continuous)
Same in both: Thermal Conductivity 42 W/m·K24.3 BTU/hr·ft·°F · Specific Heat Capacity 470 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 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) -0.6 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 50 / 100 · Polishability 70 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 29 MJ/kg12,468 BTU/lb · Embodied Carbon (primary production) 2.1 kg CO₂/kg · Embodied Water 60 L/kg7.2 gal/lb · Typical Recycled Content 35%
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.
34CrMo4 +AC vs 34CrMo4 +QT — frequently asked
Is 34CrMo4 +QT stronger than 34CrMo4 +AC?
Yes. 34CrMo4 +QT has a typical yield strength of 750 MPa (109 ksi) against 350 MPa (50.8 ksi) for 34CrMo4 +AC — about 114% more. Tensile strength is 1,000 MPa (145 ksi) vs 560 MPa (81.2 ksi).
Which condition does FabDigit quote by default, +AC or +QT?
+QT is the default 34CrMo4 condition in the FabDigit quote flow. 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, 34CrMo4 +AC or 34CrMo4 +QT?
34CrMo4 +AC. Its machinability rates good (68/100) against fair (52/100) for 34CrMo4 +QT; for welding the order is 34CrMo4 +AC first (fair, 52/100) then 34CrMo4 +QT (fair, 40/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 34CrMo4 +AC and 34CrMo4 +QT 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.