Steel 9Cr18 vs SUJ2
Steel · grade comparison
Steel 9Cr18 and SUJ2 are both steel grades. 9Cr18 is the stronger of the two: yield strength 450 MPa (65.3 ksi) against 420 MPa (60.9 ksi) for SUJ2, about 7% more; tensile strength follows at 760 MPa (110 ksi) vs 660 MPa (95.7 ksi). In exchange, SUJ2 is the more ductile: elongation 25% versus 18% for 9Cr18, and 9Cr18 is harder (225 HB vs 192 HB). 9Cr18 runs hotter in service (400°C vs 200°C continuous) and SUJ2 conducts heat better (46 W/m·K vs 24 W/m·K). On the shop floor, SUJ2 sits in a lower cost tier (standard, $$) than 9Cr18 (premium, $$$).
9Cr18Choose it when strength drives the design, or when the part sees heat.
SUJ2Choose it when the part is bent, formed or impact-loaded, or when cost is the deciding factor.
9Cr18 vs SUJ2: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all 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 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
Shear 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)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
Hardness, Vickers
Same in both: 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
Thermal Expansion (CTE, 20–100 °C)
Latent Heat of Fusion
Max Service Temperature (continuous)
Min Service Temperature
Same in both: Specific Heat Capacity 460 J/kg·K0.11 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 Rating (AISI 1212 = 100 %)
Weldability
Formability (cold)
Brazeability / Solderability
Polishability
Same in both: Machinability 45 / 100 · Castability 30 / 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 steel grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
Manufacturing and finishing
| Capability | 9Cr18 | SUJ2 |
|---|---|---|
| CNC machining | — | Yes |
| Sheet metal | — | Yes |
| Default condition | — | Annealed |
| Relative cost | $$$ Premium | $$ Standard |
| Min. machined wall | — | 0.8 mm |
| Best machined surface | — | Ra 1.6 µm |
| AlCrN | — | Yes |
| AlTiN | — | Yes |
| Black Oxide | — | Yes |
| CVD Al2O3 | — | Yes |
| CVD TiCN | — | Yes |
| CVD TiN | — | Yes |
| Cerakote | — | Yes |
| Chrome Plating | — | Yes |
| CrN | — | Yes |
| DLC | — | Yes |
| E-Coating | — | Yes |
| HVOF Coating | — | Yes |
| Hot-Dip Galvanizing | — | Yes |
| MoS2 | — | Yes |
| Multilayer CVD | — | Yes |
| Nickel Plating | — | Yes |
| PTFE Coating | — | Yes |
| Painting | — | Yes |
They share 9 finishes: Copper Plating, Electroless Nickel (EN), Epoxy Coating, Gold Plating, Hard Chrome Plating, Manganese Phosphate, Plasma Spray, Silver Plating, Zinc Phosphate.
9Cr18 vs SUJ2 — frequently asked
Is 9Cr18 stronger than SUJ2?
Yes. 9Cr18 has a typical yield strength of 450 MPa (65.3 ksi) against 420 MPa (60.9 ksi) for SUJ2 — about 7% more. Tensile strength is 760 MPa (110 ksi) vs 660 MPa (95.7 ksi).
Which is cheaper, 9Cr18 or SUJ2?
SUJ2 is the lower-cost material: it sits in the standard tier ($$) while 9Cr18 is premium ($$$). Part price depends far more on geometry, tolerance and quantity than on raw stock — upload a CAD file for a live quote.
Which welds better, 9Cr18 or SUJ2?
9Cr18. Its weldability rates poor (20/100) against not recommended (12/100) for SUJ2.
Ready to make it?
Upload a CAD file and FabDigit prices the part in 9Cr18 and SUJ2 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.