Steel M15 vs M4
Steel · grade comparison
Steel M15 and M4 are both steel grades. M4 is the stronger of the two: yield strength 550 MPa (79.8 ksi) against 340 MPa (49.3 ksi) for M15, about 62% more; tensile strength follows at 880 MPa (128 ksi) vs 470 MPa (68.2 ksi). In exchange, M15 is the more ductile: elongation 15% versus 12% for M4, and M4 is harder (250 HB vs 165 HB). M15 is lighter (7.65 g/cm³ vs 7.97 g/cm³ for M4) and M4 is stiffer (217 GPa vs 200 GPa). On the shop floor, M15 machines more easily (fair vs poor), M15 welds better (fair vs poor), and M15 sits in a lower cost tier (budget, $) than M4 (specialty, $$$$$).
M15Choose it when the part is bent, formed or impact-loaded, or when weight is the constraint.
M4Choose it when strength drives the design, or when the part sees heat.
M15 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
Bulk Modulus
Poisson's Ratio
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Shear Strength
Fatigue Strength (Endurance Limit)
Hardness, Brinell
Hardness, Rockwell B
Hardness, Vickers
Reduction in Area
Compressive Strength
Fracture Toughness (K_IC)
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.
Specific Heat Capacity
Thermal Expansion (CTE, 20–100 °C)
Max Service Temperature (continuous)
Same in both: Thermal Conductivity 22 W/m·K12.7 BTU/hr·ft·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · 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)
Castability
Same in both: Brazeability / Solderability 45 / 100 · 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 | M15 | M4 |
|---|---|---|
| CNC machining | — | Yes |
| Default condition | — | Annealed |
| Relative cost | $ Budget | $$$$$ Specialty |
| Min. machined wall | — | 0.8 mm |
| Best machined surface | — | Ra 1.6 µm |
| AlCrN | — | Yes |
| AlTiN | — | Yes |
| Black Oxide | — | Yes |
| CVD Al2O3 | — | Yes |
| CVD TiCN | — | Yes |
| CVD TiN | — | Yes |
| Cerakote | — | Yes |
| Chrome Plating | — | Yes |
| CrN | — | Yes |
| DLC | — | Yes |
| E-Coating | — | Yes |
| HVOF Coating | — | Yes |
| Hot-Dip Galvanizing | — | Yes |
| MoS2 | — | Yes |
| Multilayer CVD | — | Yes |
| Nickel Plating | — | Yes |
| PTFE Coating | — | Yes |
| Painting | — | Yes |
They share 9 finishes: Copper Plating, Electroless Nickel (EN), Epoxy Coating, Gold Plating, Hard Chrome Plating, Manganese Phosphate, Plasma Spray, Silver Plating, Zinc Phosphate.
M15 vs M4 — frequently asked
Is M4 stronger than M15?
Yes. M4 has a typical yield strength of 550 MPa (79.8 ksi) against 340 MPa (49.3 ksi) for M15 — about 62% more. Tensile strength is 880 MPa (128 ksi) vs 470 MPa (68.2 ksi).
Which is cheaper, M15 or M4?
M15 is the lower-cost material: it sits in the budget tier ($) while M4 is specialty ($$$$$). 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, M15 or M4?
M15. Its machinability rates fair (45/100) against poor (25/100) for M4; for welding the order is M15 first (fair, 50/100) then M4 (poor, 15/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in M15 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.