Stainless Steel ER308Si vs ER630
Stainless Steel · grade comparison
Stainless Steel ER308Si and ER630 are both stainless steel grades. ER630 is the stronger of the two: yield strength 760 MPa (110 ksi) against 400 MPa (58 ksi) for ER308Si, about 90% more; tensile strength follows at 965 MPa (140 ksi) vs 600 MPa (87 ksi). In exchange, ER308Si is the more ductile: elongation 38% versus 12% for ER630, and ER630 is harder (320 HB vs 175 HB). ER308Si runs hotter in service (760°C vs 300°C continuous) and ER630 conducts heat better (17.5 W/m·K vs 15 W/m·K). On the shop floor, ER308Si welds better (excellent vs very good) and ER308Si sits in a lower cost tier (premium, $$$) than ER630 (high, $$$$).
ER308SiChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
ER630Choose it when strength drives the design.
ER308Si vs ER630: 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)
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, Vickers
Hardness, Rockwell C
Same in both: Shear Modulus 77 GPa11.2 Msi · Bulk Modulus 160 GPa23.2 Msi
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)
Brazeability / Solderability
Same in both: Polishability 70 / 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 | ER630 |
|---|---|---|
| Default condition | — | — |
| Relative cost | $$$ Premium | $$$$ High |
| Min. machined wall | — | — |
| Best machined surface | — | — |
Both take the same 7 finishes: Electroless Nickel (EN), Epoxy Coating, Gold Plating, Hard Chrome Plating, Pickling, Plasma Spray, Silver Plating.
ER308Si vs ER630 — frequently asked
Is ER630 stronger than ER308Si?
Yes. ER630 has a typical yield strength of 760 MPa (110 ksi) against 400 MPa (58 ksi) for ER308Si — about 90% more. Tensile strength is 965 MPa (140 ksi) vs 600 MPa (87 ksi).
Which is cheaper, ER308Si or ER630?
ER308Si is the lower-cost material: it sits in the premium tier ($$$) while ER630 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 ER630?
ER308Si, by a small margin. Both rate fair for machinability — 40/100 against 35/100 for ER630; for welding the order is ER308Si first (excellent, 95/100) then ER630 (very good, 75/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in ER308Si and ER630 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.