Steel ZG55SiMnMo QT45-50HRC vs ZG55SiMnMo QT50-55HRC
Steel · ZG55SiMnMo temper comparison
ZG55SiMnMo QT45-50HRC and ZG55SiMnMo QT50-55HRC are two conditions of the same steel grade, ZG55SiMnMo: QT45-50HRC versus QT50-55HRC. The chemistry is identical, so every difference below comes from the condition. ZG55SiMnMo QT50-55HRC is the stronger of the two: yield strength 1,450 MPa (210 ksi) against 1,300 MPa (189 ksi) for ZG55SiMnMo QT45-50HRC, about 12% more; tensile strength follows at 1,800 MPa (261 ksi) vs 1,600 MPa (232 ksi). In exchange, ZG55SiMnMo QT45-50HRC is the more ductile: elongation 5% versus 3% for ZG55SiMnMo QT50-55HRC, and ZG55SiMnMo QT50-55HRC is harder (530 HB vs 460 HB). ZG55SiMnMo QT45-50HRC runs hotter in service (350°C vs 200°C continuous).
ZG55SiMnMo QT45-50HRCChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
ZG55SiMnMo QT50-55HRCChoose it when strength drives the design.
ZG55SiMnMo QT45-50HRC vs ZG55SiMnMo QT50-55HRC: 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.
ZG55SiMnMo QT45-50HRCZG55SiMnMo QT50-55HRC
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Reduction in Area
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell C
Hardness, Vickers
Same in both: Elastic (Young's) Modulus 205 GPa29.7 Msi · Shear Modulus 80 GPa11.6 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29 · Compressive Strength 1,700 MPa247 ksi · Shear Strength 960 MPa139 ksi · Fatigue Strength (Endurance Limit) 620 MPa89.9 ksi
Physical
Density and transition temperatures.
Same in both: Density 7.8 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.
Max Service Temperature (continuous)
Same in both: Thermal Conductivity 38 W/m·K22 BTU/hr·ft·°F · Specific Heat Capacity 470 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 12 µm/m·K6.7 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Min Service Temperature -30°C-22 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 6.2 % IACS · Electrical Resistivity 2.8×10⁻⁷ Ω·m11 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.6 V · Corrosion Resistance 12 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Same in both: Weldability 25 / 100 · Formability (cold) 5 / 100 · Castability 60 / 100 · Brazeability / Solderability 30 / 100 · Polishability 55 / 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 kg CO₂/kg · Embodied Water 40 L/kg4.8 gal/lb · Typical Recycled Content 80%
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.
ZG55SiMnMo QT45-50HRC vs ZG55SiMnMo QT50-55HRC — frequently asked
Is ZG55SiMnMo QT50-55HRC stronger than ZG55SiMnMo QT45-50HRC?
Yes. ZG55SiMnMo QT50-55HRC has a typical yield strength of 1,450 MPa (210 ksi) against 1,300 MPa (189 ksi) for ZG55SiMnMo QT45-50HRC — about 12% more. Tensile strength is 1,800 MPa (261 ksi) vs 1,600 MPa (232 ksi).
Which condition does FabDigit quote by default, QT45-50HRC or QT50-55HRC?
QT45-50HRC is the default ZG55SiMnMo condition in the FabDigit quote flow. 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, ZG55SiMnMo QT45-50HRC or ZG55SiMnMo QT50-55HRC?
ZG55SiMnMo QT45-50HRC. Its machinability rates poor (15/100) against not recommended (8/100) for ZG55SiMnMo QT50-55HRC.
Ready to make it?
Upload a CAD file and FabDigit prices the part in ZG55SiMnMo QT45-50HRC and ZG55SiMnMo QT50-55HRC 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.