Steel M-3 vs M4
Steel · grade comparison
Steel M-3 and M4 are both steel grades. M4 is the stronger of the two: yield strength 550 MPa (79.8 ksi) against 315 MPa (45.7 ksi) for M-3, about 75% more; tensile strength follows at 880 MPa (128 ksi) vs 360 MPa (52.2 ksi). M4 is the more ductile: elongation 12% versus 8% for M-3, and M4 is harder (265 HV vs 190 HV). M-3 is lighter (7.65 g/cm³ vs 7.97 g/cm³ for M4) and M4 is stiffer (217 GPa vs 120 GPa). On the shop floor, M-3 machines more easily (fair vs poor), M-3 welds better (fair vs poor), and M-3 sits in a lower cost tier (standard, $$) than M4 (specialty, $$$$$).
M-3Choose it when weight is the constraint, or when the part is machined in volume.
M4Choose it when strength drives the design, or when the part is bent, formed or impact-loaded.
M-3 vs M4: 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
Shear Strength
Fatigue Strength (Endurance Limit)
Charpy V-Notch Impact (RT)
Hardness, Rockwell B
Hardness, Vickers
Bulk Modulus
Reduction in Area
Compressive Strength
Fracture Toughness (K_IC)
Hardness, Brinell
Hardness, Rockwell C
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)
Latent Heat of Fusion
Max Service Temperature (continuous)
Same in both: Min Service Temperature -60°C-76 °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
Machinability Rating (AISI 1212 = 100 %)
Weldability
Formability (cold)
Brazeability / Solderability
Castability
Same in both: Polishability 50 / 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 | M-3 | M4 |
|---|---|---|
| CNC machining | — | Yes |
| Default condition | — | Annealed |
| Relative cost | $$ Standard | $$$$$ Specialty |
| Min. machined wall | — | 0.8 mm |
| Best machined surface | — | Ra 1.6 µm |
| AlCrN | — | Yes |
| AlTiN | — | Yes |
| Black Oxide | — | Yes |
| CVD Al2O3 | — | Yes |
| CVD TiCN | — | Yes |
| CVD TiN | — | Yes |
| Cerakote | — | Yes |
| Chrome Plating | — | Yes |
| CrN | — | Yes |
| DLC | — | Yes |
| E-Coating | — | Yes |
| HVOF Coating | — | Yes |
| Hot-Dip Galvanizing | — | Yes |
| MoS2 | — | Yes |
| Multilayer CVD | — | Yes |
| Nickel Plating | — | Yes |
| PTFE Coating | — | Yes |
| Painting | — | Yes |
They share 9 finishes: Copper Plating, Electroless Nickel (EN), Epoxy Coating, Gold Plating, Hard Chrome Plating, Manganese Phosphate, Plasma Spray, Silver Plating, Zinc Phosphate.
M-3 vs M4 — frequently asked
Is M4 stronger than M-3?
Yes. M4 has a typical yield strength of 550 MPa (79.8 ksi) against 315 MPa (45.7 ksi) for M-3 — about 75% more. Tensile strength is 880 MPa (128 ksi) vs 360 MPa (52.2 ksi).
Which is cheaper, M-3 or M4?
M-3 is the lower-cost material: it sits in the standard tier ($$) while M4 is specialty ($$$$$). 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, M-3 or M4?
M-3. Its machinability rates fair (35/100) against poor (25/100) for M4; for welding the order is M-3 first (fair, 40/100) then M4 (poor, 15/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in M-3 and M4 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.