Stainless Steel S31730-1/4 Hard vs S31730-3/4 Hard
Stainless Steel · S31730 temper comparison
S31730-1/4 Hard and S31730-3/4 Hard are two conditions of the same stainless steel grade, S31730: 1/4 Hard (quarter hard) versus 3/4 Hard (three-quarter hard). The chemistry is identical, so every difference below comes from the condition. S31730-3/4 Hard is the stronger of the two: yield strength 960 MPa (139 ksi) against 560 MPa (81.2 ksi) for S31730-1/4 Hard, about 71% more; tensile strength follows at 1,240 MPa (180 ksi) vs 900 MPa (131 ksi). In exchange, S31730-1/4 Hard is the more ductile: elongation 20% versus 7% for S31730-3/4 Hard, and S31730-3/4 Hard is harder (350 HB vs 250 HB). S31730-1/4 Hard runs hotter in service (400°C vs 315°C continuous). On the shop floor, S31730-1/4 Hard machines more easily (fair vs poor) and S31730-1/4 Hard welds better (very good vs good).
S31730-1/4 HardChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
S31730-3/4 HardChoose it when strength drives the design.
S31730-1/4 Hard vs S31730-3/4 Hard: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all stainless 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 stainless 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.
S31730-1/4 HardS31730-3/4 Hard
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Reduction in Area
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Same in both: Shear Modulus 77 GPa11.2 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29 · Hardness, Rockwell B 100 HRB
Physical
Density and transition temperatures.
Same in both: Density 8 g/cm³0.29 lb/in³ · Melting Point (Solidus) 1,375°C2,507 °F · Liquidus Temperature 1,425°C2,597 °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 500 J/kg·K0.12 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 16.2 µm/m·K9 µin/in·°F · Latent Heat of Fusion 270 J/g116 BTU/lb · Min Service Temperature -196°C-321 °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) -0.08 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 60 / 100 · Polishability 65 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 82 MJ/kg35,254 BTU/lb · Embodied Carbon (primary production) 5.4 kg CO₂/kg · Embodied Water 150 L/kg18 gal/lb · Typical Recycled Content 55%
Strength versus weight
Yield strength against density for every stainless steel grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
S31730-1/4 Hard vs S31730-3/4 Hard — frequently asked
Is S31730-3/4 Hard stronger than S31730-1/4 Hard?
Yes. S31730-3/4 Hard has a typical yield strength of 960 MPa (139 ksi) against 560 MPa (81.2 ksi) for S31730-1/4 Hard — about 71% more. Tensile strength is 1,240 MPa (180 ksi) vs 900 MPa (131 ksi).
Which condition does FabDigit quote by default, 1/4 Hard or 3/4 Hard?
Annealed is the default S31730 condition in the FabDigit quote flow (neither 1/4 Hard nor 3/4 Hard). 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, S31730-1/4 Hard or S31730-3/4 Hard?
S31730-1/4 Hard. Its machinability rates fair (38/100) against poor (28/100) for S31730-3/4 Hard; for welding the order is S31730-1/4 Hard first (very good, 72/100) then S31730-3/4 Hard (good, 60/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in S31730-1/4 Hard and S31730-3/4 Hard 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.