Stainless Steel E309 vs ER308Si
Stainless Steel · grade comparison
Stainless Steel E309 and ER308Si are both stainless steel grades. Both yield at about 420 MPa — strength does not separate them. E309 is harder — 185 HB against 175 HB for ER308Si — which matters for wear surfaces and threads. E309 runs hotter in service (850°C vs 760°C continuous). On the shop floor, ER308Si forms better (good vs fair) and ER308Si sits in a lower cost tier (premium, $$$) than E309 (high, $$$$).
E309Choose it when surface hardness matters, or when the part sees heat.
ER308SiChoose it when cost is the deciding factor.
E309 vs ER308Si: 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.
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Bulk Modulus
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, Rockwell C
Hardness, Vickers
Same in both: Shear Modulus 77 GPa11.2 Msi · Poisson's Ratio 0.29 · Tensile Strength (Ultimate) 600 MPa87 ksi
Physical
Density and transition temperatures.
Density
Same in both: Melting Point (Solidus) 1,400°C2,552 °F · Liquidus Temperature 1,450°C2,642 °F
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Thermal Expansion (CTE, 20–100 °C)
Max Service Temperature (continuous)
Min Service Temperature
Same in both: Specific Heat Capacity 500 J/kg·K0.12 BTU/lb·°F · Latent Heat of Fusion 270 J/g116 BTU/lb
Electrical
Conductivity and insulation.
Electrical Conductivity
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Galvanic Potential (seawater, vs SCE)
Corrosion Resistance
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Weldability
Formability (cold)
Polishability
Brazeability / Solderability
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Carbon (primary production)
Embodied Water
Same in both: Typical Recycled Content 55%
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
Modulus of Resilience
Thermal Diffusivity
Same in both: Thermal Shock Resistance Index 3
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.
Manufacturing and finishing
| Capability | E309 | ER308Si |
|---|---|---|
| Default condition | — | — |
| Relative cost | $$$$ High | $$$ Premium |
| Min. machined wall | — | — |
| Best machined surface | — | — |
Both take the same 7 finishes: Electroless Nickel (EN), Epoxy Coating, Gold Plating, Hard Chrome Plating, Pickling, Plasma Spray, Silver Plating.
E309 vs ER308Si — frequently asked
What is the difference between E309 and ER308Si?
Stainless Steel E309 and ER308Si are both stainless steel grades. Both yield at about 420 MPa — strength does not separate them. E309 is harder — 185 HB against 175 HB for ER308Si — which matters for wear surfaces and threads.
Which is cheaper, E309 or ER308Si?
ER308Si is the lower-cost material: it sits in the premium tier ($$$) while E309 is high ($$$$). Part price depends far more on geometry, tolerance and quantity than on raw stock — upload a CAD file for a live quote.
Which is easier to machine, E309 or ER308Si?
ER308Si, by a small margin. Both rate fair for machinability — 40/100 against 35/100 for E309; for welding the order is ER308Si first (excellent, 95/100) then E309 (excellent, 90/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in E309 and ER308Si 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.