Steel S4-AQ vs S4-HR
Steel · S4 temper comparison
S4-AQ and S4-HR are two conditions of the same steel grade, S4: AQ (as-quenched) versus HR (hot rolled). The chemistry is identical, so every difference below comes from the condition. S4-AQ is the stronger of the two: yield strength 1,900 MPa (276 ksi) against 620 MPa (89.9 ksi) for S4-HR, about 3.1 times as much; tensile strength follows at 2,200 MPa (319 ksi) vs 950 MPa (138 ksi). In exchange, S4-HR is the more ductile: elongation 15% versus 1% for S4-AQ, and S4-HR is harder (280 HB vs 210 HB). S4-HR runs hotter in service (400°C vs 150°C continuous) and S4-HR conducts heat better (25 W/m·K vs 21 W/m·K). On the shop floor, S4-HR machines more easily (poor vs not recommended) and S4-HR welds better (poor vs not recommended).
S4-AQChoose it when strength drives the design.
S4-HRChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
S4-AQ vs S4-HR: 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
Shear Strength
Fatigue Strength (Endurance Limit)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
Same in both: Elastic (Young's) Modulus 207 GPa30 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 7.79 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,420°C2,588 °F · Liquidus Temperature 1,480°C2,696 °F
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Max Service Temperature (continuous)
Same in both: Specific Heat Capacity 470 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 12.4 µm/m·K6.9 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).
Corrosion Resistance
Same in both: Galvanic Potential (seawater, vs SCE) -0.55 V
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 45 / 100 · Polishability 55 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 33 MJ/kg14,187 BTU/lb · Embodied Carbon (primary production) 2.4 kg CO₂/kg · Embodied Water 65 L/kg7.8 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.
S4-AQ vs S4-HR — frequently asked
Is S4-AQ stronger than S4-HR?
Yes. S4-AQ has a typical yield strength of 1,900 MPa (276 ksi) against 620 MPa (89.9 ksi) for S4-HR — about 3.1 times as much. Tensile strength is 2,200 MPa (319 ksi) vs 950 MPa (138 ksi).
Which condition does FabDigit quote by default, AQ or HR?
Annealed is the default S4 condition in the FabDigit quote flow (neither AQ nor HR). 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, S4-AQ or S4-HR?
S4-HR. Its machinability rates poor (32/100) against not recommended (5/100) for S4-AQ; for welding the order is S4-HR first (poor, 15/100) then S4-AQ (not recommended, 3/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in S4-AQ and S4-HR 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.