Steel 38Si7 vs 42CrMo4
Steel · grade comparison
Steel 38Si7 and 42CrMo4 are both steel grades. 38Si7 is the stronger of the two: yield strength 1,150 MPa (167 ksi) against 550 MPa (79.8 ksi) for 42CrMo4, about 109% more; tensile strength follows at 1,300 MPa (189 ksi) vs 850 MPa (123 ksi). In exchange, 42CrMo4 is the more ductile: elongation 14% versus 9% for 38Si7, and 38Si7 is harder (390 HB vs 245 HB). 42CrMo4 runs hotter in service (400°C vs 250°C continuous) and 42CrMo4 conducts electricity better (7.8 % IACS vs 7 % IACS). On the shop floor, 42CrMo4 machines more easily (fair vs poor), 42CrMo4 welds better (fair vs poor), and 38Si7 sits in a lower cost tier (budget, $) than 42CrMo4 (standard, $$).
38Si7Choose it when strength drives the design, or when cost is the deciding factor.
42CrMo4Choose it when the part is bent, formed or impact-loaded, or when the part sees heat.
38Si7 vs 42CrMo4: 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
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 C
Hardness, Vickers
Same in both: Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29
Physical
Density and transition temperatures.
Density
Liquidus Temperature
Same in both: Melting Point (Solidus) 1,420°C2,588 °F
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)
Same in both: Latent Heat of Fusion 250 J/g107 BTU/lb · 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)
Brazeability / Solderability
Polishability
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Carbon (primary production)
Same in both: Embodied Water 60 L/kg7.2 gal/lb · Typical Recycled Content 30%
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 | 38Si7 | 42CrMo4 |
|---|---|---|
| CNC machining | — | Yes |
| Sheet metal | — | Yes |
| Default condition | — | HR |
| Relative cost | $ Budget | $$ 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.
38Si7 vs 42CrMo4 — frequently asked
Is 38Si7 stronger than 42CrMo4?
Yes. 38Si7 has a typical yield strength of 1,150 MPa (167 ksi) against 550 MPa (79.8 ksi) for 42CrMo4 — about 109% more. Tensile strength is 1,300 MPa (189 ksi) vs 850 MPa (123 ksi).
Which is cheaper, 38Si7 or 42CrMo4?
38Si7 is the lower-cost material: it sits in the budget tier ($) while 42CrMo4 is standard ($$). 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, 38Si7 or 42CrMo4?
42CrMo4. Its machinability rates fair (50/100) against poor (30/100) for 38Si7; for welding the order is 42CrMo4 first (fair, 35/100) then 38Si7 (poor, 15/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 38Si7 and 42CrMo4 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.