Stainless Steel ER308Si vs ER409
Stainless Steel · grade comparison
Stainless Steel ER308Si and ER409 are both stainless steel grades. ER308Si is the stronger of the two: yield strength 400 MPa (58 ksi) against 320 MPa (46.4 ksi) for ER409, about 25% more; tensile strength follows at 600 MPa (87 ksi) vs 470 MPa (68.2 ksi). ER308Si is the more ductile: elongation 38% versus 22% for ER409, and ER308Si is harder (175 HB vs 165 HB). ER409 is lighter (7.7 g/cm³ vs 7.95 g/cm³ for ER308Si) and ER308Si runs hotter in service (760°C vs 675°C continuous). On the shop floor, ER409 machines more easily (good vs fair) and ER308Si welds better (excellent vs very good).
ER308SiChoose it when strength drives the design, or when the part is bent, formed or impact-loaded.
ER409Choose it when weight is the constraint, or when the part is machined in volume.
ER308Si vs ER409: 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
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
Hardness, Vickers
Same in both: Shear Modulus 77 GPa11.2 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29 · Reduction in Area 55%
Physical
Density and transition temperatures.
Density
Melting Point (Solidus)
Liquidus Temperature
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Specific Heat Capacity
Thermal Expansion (CTE, 20–100 °C)
Max Service Temperature (continuous)
Min Service Temperature
Same in both: 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
Same in both: Brazeability / Solderability 60 / 100
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Carbon (primary production)
Embodied Water
Typical Recycled Content
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
Modulus of Resilience
Thermal Diffusivity
Thermal Shock Resistance Index
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 | ER308Si | ER409 |
|---|---|---|
| Default condition | — | — |
| Relative cost | $$$ Premium | $$$ 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.
ER308Si vs ER409 — frequently asked
Is ER308Si stronger than ER409?
Yes. ER308Si has a typical yield strength of 400 MPa (58 ksi) against 320 MPa (46.4 ksi) for ER409 — about 25% more. Tensile strength is 600 MPa (87 ksi) vs 470 MPa (68.2 ksi).
Which is cheaper, ER308Si or ER409?
Both sit in the same relative cost tier ($$$, premium); the part price will be decided by machining time, tolerance and quantity rather than by the material.
Which is easier to machine, ER308Si or ER409?
ER409. Its machinability rates good (58/100) against fair (40/100) for ER308Si; for welding the order is ER308Si first (excellent, 95/100) then ER409 (very good, 75/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in ER308Si and ER409 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.