Stainless Steel ER308Si vs ER309LSi
Stainless Steel · grade comparison
Stainless Steel ER308Si and ER309LSi are both stainless steel grades. Both yield at about 400 MPa — strength does not separate them. ER309LSi is harder — 185 HB against 175 HB for ER308Si — which matters for wear surfaces and threads. ER309LSi runs hotter in service (950°C vs 760°C continuous). On the shop floor, ER308Si sits in a lower cost tier (premium, $$$) than ER309LSi (high, $$$$).
ER308SiChoose it when cost is the deciding factor.
ER309LSiChoose it when surface hardness matters, or when the part sees heat.
ER308Si vs ER309LSi: 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
Poisson's Ratio
Tensile Strength (Ultimate)
Reduction in Area
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 · Yield Strength (0.2% offset) 400 MPa58 ksi · Elongation at Break 38% · Compressive Strength 400 MPa58 ksi · Shear Strength 400 MPa58 ksi · Fatigue Strength (Endurance Limit) 240 MPa34.8 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 Expansion (CTE, 20–100 °C)
Latent Heat of Fusion
Max Service Temperature (continuous)
Min Service Temperature
Same in both: Thermal Conductivity 15 W/m·K8.7 BTU/hr·ft·°F · Specific Heat Capacity 500 J/kg·K0.12 BTU/lb·°F
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
Weldability
Formability (cold)
Polishability
Castability
Same in both: Machinability Rating (AISI 1212 = 100 %) 45% · Brazeability / Solderability 60 / 100
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Same in both: Embodied Carbon (primary production) 5.5 kg CO₂/kg · Embodied Water 200 L/kg24 gal/lb · Typical Recycled Content 55%
Common Calculations
Ratios derived from the values above.
Specific Stiffness (E / density)
Modulus of Resilience
Same in both: Specific Strength (UTS / density) 75 kN·m/kg · Thermal Diffusivity 3.8 mm²/s · 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 | ER308Si | ER309LSi |
|---|---|---|
| Default condition | — | — |
| Relative cost | $$$ Premium | $$$$ High |
| Min. machined wall | — | — |
| Best machined surface | — | — |
Both take the same 7 finishes: Electroless Nickel (EN), Epoxy Coating, Gold Plating, Hard Chrome Plating, Pickling, Plasma Spray, Silver Plating.
ER308Si vs ER309LSi — frequently asked
What is the difference between ER308Si and ER309LSi?
Stainless Steel ER308Si and ER309LSi are both stainless steel grades. Both yield at about 400 MPa — strength does not separate them. ER309LSi is harder — 185 HB against 175 HB for ER308Si — which matters for wear surfaces and threads.
Which is cheaper, ER308Si or ER309LSi?
ER308Si is the lower-cost material: it sits in the premium tier ($$$) while ER309LSi 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, ER308Si or ER309LSi?
ER308Si, by a small margin. Both rate fair for machinability — 40/100 against 35/100 for ER309LSi.
Ready to make it?
Upload a CAD file and FabDigit prices the part in ER308Si and ER309LSi 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.