Steel 70Mn4 +H58 vs 70Mn4 +U
Steel · 70Mn4 temper comparison
70Mn4 +H58 and 70Mn4 +U are two conditions of the same steel grade, 70Mn4: +H58 (hardened) versus +U (hot rolled). The chemistry is identical, so every difference below comes from the condition. 70Mn4 +H58 is the stronger of the two: yield strength 1,800 MPa (261 ksi) against 550 MPa (79.8 ksi) for 70Mn4 +U, about 3.3 times as much; tensile strength follows at 2,100 MPa (305 ksi) vs 950 MPa (138 ksi). In exchange, 70Mn4 +U is the more ductile: elongation 8% versus 1% for 70Mn4 +H58, and 70Mn4 +U is harder (280 HB vs 205 HB). 70Mn4 +U runs hotter in service (300°C vs 180°C continuous). On the shop floor, 70Mn4 +U machines more easily (fair vs not recommended).
70Mn4 +H58Choose it when strength drives the design.
70Mn4 +UChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
70Mn4 +H58 vs 70Mn4 +U: 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
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Vickers
Same in both: Elastic (Young's) Modulus 207 GPa30 Msi · Shear Modulus 80 GPa11.6 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29 · Hardness, Rockwell B 94 HRB
Physical
Density and transition temperatures.
Same in both: Density 7.85 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,420°C2,588 °F · Liquidus Temperature 1,480°C2,696 °F
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Max Service Temperature (continuous)
Same in both: Specific Heat Capacity 470 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 11.7 µm/m·K6.5 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Min Service Temperature -20°C-4 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 9 % IACS · Electrical Resistivity 1.9×10⁻⁷ Ω·m7.48 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.62 V · Corrosion Resistance 10 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Weldability
Formability (cold)
Polishability
Same in both: Brazeability / Solderability 50 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 26 MJ/kg11,178 BTU/lb · Embodied Carbon (primary production) 2.1 kg CO₂/kg · Embodied Water 50 L/kg6 gal/lb · Typical Recycled Content 25%
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.
70Mn4 +H58 vs 70Mn4 +U — frequently asked
Is 70Mn4 +H58 stronger than 70Mn4 +U?
Yes. 70Mn4 +H58 has a typical yield strength of 1,800 MPa (261 ksi) against 550 MPa (79.8 ksi) for 70Mn4 +U — about 3.3 times as much. Tensile strength is 2,100 MPa (305 ksi) vs 950 MPa (138 ksi).
Which condition does FabDigit quote by default, +H58 or +U?
+A is the default 70Mn4 condition in the FabDigit quote flow (neither +H58 nor +U). The other condition is available on request or by drawing note — specify it in the material field or the part notes and the quote is priced for it.
Which is easier to machine, 70Mn4 +H58 or 70Mn4 +U?
70Mn4 +U. Its machinability rates fair (38/100) against not recommended (8/100) for 70Mn4 +H58; for welding the order is 70Mn4 +U first (not recommended, 12/100) then 70Mn4 +H58 (not recommended, 3/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 70Mn4 +H58 and 70Mn4 +U 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.