Steel 27MnB4 vs 34MnB5
Steel · grade comparison
Steel 27MnB4 and 34MnB5 are both steel grades. 27MnB4 is the stronger of the two: yield strength 560 MPa (81.2 ksi) against 420 MPa (60.9 ksi) for 34MnB5, about 33% more; tensile strength follows at 660 MPa (95.7 ksi) vs 620 MPa (89.9 ksi). In exchange, 34MnB5 is the more ductile: elongation 14% versus 11% for 27MnB4, and 27MnB4 is harder (200 HB vs 185 HB). 34MnB5 runs hotter in service (400°C vs 350°C continuous). On the shop floor, 34MnB5 welds better (good vs fair) and 27MnB4 sits in a lower cost tier (budget, $) than 34MnB5 (standard, $$).
27MnB4Choose it when strength drives the design, or when cost is the deciding factor.
34MnB5Choose it when the part is bent, formed or impact-loaded, or when the part sees heat.
27MnB4 vs 34MnB5: 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.
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Reduction in Area
Compressive Strength
Fatigue Strength (Endurance Limit)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
Hardness, Vickers
Fracture Toughness (K_IC)
Same in both: Elastic (Young's) Modulus 210 GPa30.5 Msi · Shear Modulus 80 GPa11.6 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29 · Shear Strength 400 MPa58 ksi
Physical
Density and transition temperatures.
Melting Point (Solidus)
Liquidus Temperature
Same in both: Density 7.85 g/cm³0.28 lb/in³
Thermal
How each material carries heat and how hot it can run.
Thermal Expansion (CTE, 20–100 °C)
Max Service Temperature (continuous)
Min Service Temperature
Same in both: Thermal Conductivity 44 W/m·K25.4 BTU/hr·ft·°F · Specific Heat Capacity 470 J/kg·K0.11 BTU/lb·°F · Latent Heat of Fusion 250 J/g107 BTU/lb
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
Brazeability / Solderability
Same in both: Polishability 55 / 100
Sustainability
Primary-production footprint per kilogram.
Embodied Water
Typical Recycled Content
Same in both: Embodied Energy (primary production) 25 MJ/kg10,748 BTU/lb · Embodied Carbon (primary production) 2 kg CO₂/kg
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Modulus of Resilience
Thermal Shock Resistance Index
Same in both: Specific Stiffness (E / density) 26.8 MN·m/kg · Thermal Diffusivity 11.9 mm²/s
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 | 27MnB4 | 34MnB5 |
|---|---|---|
| Sheet metal | — | Yes |
| Default condition | — | CR |
| Relative cost | $ Budget | $$ Standard |
| Min. machined wall | — | — |
| Best machined surface | — | — |
| Black Oxide | — | Yes |
| Cerakote | — | Yes |
| Chrome Plating | — | Yes |
| E-Coating | — | Yes |
| Hot-Dip Galvanizing | — | Yes |
| Nickel Plating | — | Yes |
| PTFE Coating | — | Yes |
| Painting | — | Yes |
| Powder Coating | — | Yes |
| Tin Plating | — | Yes |
| Zinc Plating | — | Yes |
| Zinc-Flake (Dip-Spin) Coating | — | Yes |
| Zinc-Nickel Plating | — | 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.
27MnB4 vs 34MnB5 — frequently asked
Is 27MnB4 stronger than 34MnB5?
Yes. 27MnB4 has a typical yield strength of 560 MPa (81.2 ksi) against 420 MPa (60.9 ksi) for 34MnB5 — about 33% more. Tensile strength is 660 MPa (95.7 ksi) vs 620 MPa (89.9 ksi).
Which is cheaper, 27MnB4 or 34MnB5?
27MnB4 is the lower-cost material: it sits in the budget tier ($) while 34MnB5 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, 27MnB4 or 34MnB5?
34MnB5. Its machinability rates good (55/100) against fair (48/100) for 27MnB4; for welding the order is 34MnB5 first (good, 55/100) then 27MnB4 (fair, 40/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 27MnB4 and 34MnB5 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.