Steel 38CrMoAlA vs SACM645
Steel · grade comparison
Steel 38CrMoAlA and SACM645 are both steel grades, both specialty steel. 38CrMoAlA is the stronger of the two: yield strength 880 MPa (128 ksi) against 780 MPa (113 ksi) for SACM645, about 13% more; tensile strength follows at 1,030 MPa (149 ksi) vs 950 MPa (138 ksi). 38CrMoAlA is harder — 310 HB against 270 HB for SACM645 — which matters for wear surfaces and threads. 38CrMoAlA runs hotter in service (500°C vs 450°C continuous).
38CrMoAlAChoose it when strength drives the design, or when surface hardness matters.
38CrMoAlA vs SACM645: 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
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell C
Hardness, Vickers
Same in both: Shear Modulus 80 GPa11.6 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29 · Reduction in Area 55% · Fracture Toughness (K_IC) 70 MPa·√m63.7 ksi·√in
Physical
Density and transition temperatures.
Melting Point (Solidus)
Same in both: Density 7.8 g/cm³0.28 lb/in³ · Liquidus Temperature 1,490°C2,714 °F
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Specific Heat Capacity
Thermal Expansion (CTE, 20–100 °C)
Latent Heat of Fusion
Max Service Temperature (continuous)
Same in both: Min Service Temperature -40°C-40 °F
Electrical
Conductivity and insulation.
Electrical Conductivity
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
Same in both: Galvanic Potential (seawater, vs SCE) -0.6 V
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Weldability
Formability (cold)
Castability
Brazeability / Solderability
Polishability
Sustainability
Primary-production footprint per kilogram.
Embodied Carbon (primary production)
Typical Recycled Content
Same in both: Embodied Energy (primary production) 34 MJ/kg14,617 BTU/lb · Embodied Water 55 L/kg6.6 gal/lb
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 14
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 | 38CrMoAlA | SACM645 |
|---|---|---|
| Default condition | Q&T | Q&T |
| Relative cost | $$ Standard | $$ Standard |
| Min. machined wall | 0.8 mm | 0.8 mm |
| Best machined surface | Ra 1.6 µm | Ra 1.6 µm |
Both are offered for CNC machining and Sheet metal. Both take the same 38 finishes: AlCrN, AlTiN, Black Oxide, CVD Al2O3, CVD TiCN, CVD TiN, Cerakote, Chrome Plating, Copper Plating, CrN, DLC, E-Coating and 26 more.
38CrMoAlA vs SACM645 — frequently asked
Is 38CrMoAlA stronger than SACM645?
Yes. 38CrMoAlA has a typical yield strength of 880 MPa (128 ksi) against 780 MPa (113 ksi) for SACM645 — about 13% more. Tensile strength is 1,030 MPa (149 ksi) vs 950 MPa (138 ksi).
Which is cheaper, 38CrMoAlA or SACM645?
Both sit in the same relative cost tier ($$, standard); the part price will be decided by machining time, tolerance and quantity rather than by the material.
When should I choose 38CrMoAlA over SACM645?
Pick 38CrMoAlA when strength drives the design, or when surface hardness matters.
Ready to make it?
Upload a CAD file and FabDigit prices the part in 38CrMoAlA and SACM645 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.