Steel SUM31-A vs SUM31-HR
Steel · SUM31 temper comparison
SUM31-A and SUM31-HR are two conditions of the same steel grade, SUM31: A (solution annealed) versus HR (hot rolled). The chemistry is identical, so every difference below comes from the condition. SUM31-HR is the stronger of the two: yield strength 250 MPa (36.3 ksi) against 230 MPa (33.4 ksi) for SUM31-A, about 9% more; tensile strength follows at 430 MPa (62.4 ksi) vs 400 MPa (58 ksi). In exchange, SUM31-A is the more ductile: elongation 33% versus 28% for SUM31-HR, and SUM31-HR is harder (126 HB vs 116 HB).
SUM31-AChoose it when the part is bent, formed or impact-loaded.
SUM31-HRChoose it when strength drives the design.
SUM31-A vs SUM31-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
Fatigue Strength (Endurance Limit)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
Same in both: Elastic (Young's) Modulus 200 GPa29 Msi · Shear Modulus 80 GPa11.6 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29 · Compressive Strength 400 MPa58 ksi · Shear Strength 340 MPa49.3 ksi · Hardness, Vickers 158 HV
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.
Same in both: Thermal Conductivity 51 W/m·K29.5 BTU/hr·ft·°F · Specific Heat Capacity 480 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 11.9 µm/m·K6.6 µin/in·°F · Latent Heat of Fusion 247 J/g106 BTU/lb · Max Service Temperature (continuous) 350°C662 °F · Min Service Temperature -20°C-4 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 10.5 % IACS · Electrical Resistivity 1.6×10⁻⁷ Ω·m6.3 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.61 V · Corrosion Resistance 10 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Formability (cold)
Same in both: Weldability 30 / 100 · Brazeability / Solderability 60 / 100 · Polishability 35 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 25 MJ/kg10,748 BTU/lb · Embodied Carbon (primary production) 2 kg CO₂/kg · Embodied Water 45 L/kg5.4 gal/lb · Typical Recycled Content 25%
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.
SUM31-A vs SUM31-HR — frequently asked
Is SUM31-HR stronger than SUM31-A?
Yes. SUM31-HR has a typical yield strength of 250 MPa (36.3 ksi) against 230 MPa (33.4 ksi) for SUM31-A — about 9% more. Tensile strength is 430 MPa (62.4 ksi) vs 400 MPa (58 ksi).
Which condition does FabDigit quote by default, A or HR?
CD is the default SUM31 condition in the FabDigit quote flow (neither A 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.
When should I choose SUM31-A over SUM31-HR?
Pick SUM31-A when the part is bent, formed or impact-loaded. Pick SUM31-HR when strength drives the design.
Ready to make it?
Upload a CAD file and FabDigit prices the part in SUM31-A and SUM31-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.