Steel ZG35CrMnSi QT-320HB vs ZG35CrMnSi-SR
Steel · ZG35CrMnSi temper comparison
ZG35CrMnSi QT-320HB and ZG35CrMnSi-SR are two conditions of the same steel grade, ZG35CrMnSi: QT-320HB (Q&T 300–340 HB) versus SR (stress relieved). The chemistry is identical, so every difference below comes from the condition. ZG35CrMnSi QT-320HB is the stronger of the two: yield strength 850 MPa (123 ksi) against 400 MPa (58 ksi) for ZG35CrMnSi-SR, about 113% more; tensile strength follows at 1,050 MPa (152 ksi) vs 680 MPa (98.6 ksi). In exchange, ZG35CrMnSi-SR is the more ductile: elongation 12% versus 9% for ZG35CrMnSi QT-320HB, and ZG35CrMnSi QT-320HB is harder (320 HB vs 205 HB). ZG35CrMnSi-SR runs hotter in service (400°C vs 350°C continuous). On the shop floor, ZG35CrMnSi-SR machines more easily (fair vs poor).
ZG35CrMnSi QT-320HBChoose it when strength drives the design.
ZG35CrMnSi-SRChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
ZG35CrMnSi QT-320HB vs ZG35CrMnSi-SR: 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.
ZG35CrMnSi QT-320HBZG35CrMnSi-SR
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, Rockwell B
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
Physical
Density and transition temperatures.
Same in both: Density 7.82 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,420°C2,588 °F · Liquidus Temperature 1,490°C2,714 °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) 12.3 µm/m·K6.8 µin/in·°F · Latent Heat of Fusion 270 J/g116 BTU/lb · Min Service Temperature -20°C-4 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 7.5 % IACS · Electrical Resistivity 2.3×10⁻⁷ Ω·m9.06 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.62 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 %)
Weldability
Formability (cold)
Same in both: Castability 65 / 100 · Brazeability / Solderability 45 / 100 · Polishability 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 55 L/kg6.6 gal/lb · Typical Recycled Content 85%
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.
ZG35CrMnSi QT-320HB vs ZG35CrMnSi-SR — frequently asked
Is ZG35CrMnSi QT-320HB stronger than ZG35CrMnSi-SR?
Yes. ZG35CrMnSi QT-320HB has a typical yield strength of 850 MPa (123 ksi) against 400 MPa (58 ksi) for ZG35CrMnSi-SR — about 113% more. Tensile strength is 1,050 MPa (152 ksi) vs 680 MPa (98.6 ksi).
Which condition does FabDigit quote by default, QT-320HB or SR?
N+T is the default ZG35CrMnSi condition in the FabDigit quote flow (neither QT-320HB nor SR). 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, ZG35CrMnSi QT-320HB or ZG35CrMnSi-SR?
ZG35CrMnSi-SR. Its machinability rates fair (46/100) against poor (30/100) for ZG35CrMnSi QT-320HB.
Ready to make it?
Upload a CAD file and FabDigit prices the part in ZG35CrMnSi QT-320HB and ZG35CrMnSi-SR 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.