Steel 9Cr18 QT55-58 vs 9Cr18 QT58-60
Steel · 9Cr18 temper comparison
9Cr18 QT55-58 and 9Cr18 QT58-60 are two conditions of the same steel grade, 9Cr18: QT55-58 (Q&T 55–58 HRC) versus QT58-60 (Q&T + sub-zero 58–60 HRC). The chemistry is identical, so every difference below comes from the condition. Both yield at about 1,740 MPa — the mechanical properties are the same, and the difference is in how the stock is processed and what it is certified to (Q&T 55–58 HRC versus Q&T + sub-zero 58–60 HRC). 9Cr18 QT55-58 is the more ductile: elongation 3% versus 2% for 9Cr18 QT58-60, and 9Cr18 QT58-60 is harder (700 HV vs 650 HV). On the shop floor, 9Cr18 QT58-60 welds better (poor vs not recommended).
9Cr18 QT55-58Choose it when the part is bent, formed or impact-loaded.
9Cr18 QT58-60Choose it when it will be welded.
9Cr18 QT55-58 vs 9Cr18 QT58-60: 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)
Charpy V-Notch Impact (RT)
Hardness, Vickers
Same in both: Elastic (Young's) Modulus 200 GPa29 Msi · Shear Modulus 78 GPa11.3 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.28 · Hardness, Brinell 225 HB · Hardness, Rockwell B 97 HRB
Physical
Density and transition temperatures.
Same in both: Density 7.7 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,370°C2,498 °F · Liquidus Temperature 1,450°C2,642 °F
Thermal
How each material carries heat and how hot it can run.
Max Service Temperature (continuous)
Same in both: Thermal Conductivity 24 W/m·K13.9 BTU/hr·ft·°F · Specific Heat Capacity 460 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 10.4 µm/m·K5.8 µin/in·°F · Latent Heat of Fusion 270 J/g116 BTU/lb · Min Service Temperature -50°C-58 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 2.9 % IACS · Electrical Resistivity 6×10⁻⁷ Ω·m23.6 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.25 V · Corrosion Resistance 48 / 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: Castability 30 / 100 · Brazeability / Solderability 45 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 50 MJ/kg21,496 BTU/lb · Embodied Carbon (primary production) 3.4 kg CO₂/kg · Embodied Water 100 L/kg12 gal/lb · Typical Recycled Content 40%
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.
9Cr18 QT55-58 vs 9Cr18 QT58-60 — frequently asked
What is the difference between 9Cr18 QT55-58 and 9Cr18 QT58-60?
9Cr18 QT55-58 and 9Cr18 QT58-60 are two conditions of the same steel grade, 9Cr18: QT55-58 (Q&T 55–58 HRC) versus QT58-60 (Q&T + sub-zero 58–60 HRC). The chemistry is identical, so every difference below comes from the condition. Both yield at about 1,740 MPa — the mechanical properties are the same, and the difference is in how the stock is processed and what it is certified to (Q&T 55–58 HRC versus Q&T + sub-zero 58–60 HRC).
Which condition does FabDigit quote by default, QT55-58 or QT58-60?
A is the default 9Cr18 condition in the FabDigit quote flow (neither QT55-58 nor QT58-60). 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 welds better, 9Cr18 QT55-58 or 9Cr18 QT58-60?
9Cr18 QT58-60. Its weldability rates poor (20/100) against not recommended (8/100) for 9Cr18 QT55-58.
Ready to make it?
Upload a CAD file and FabDigit prices the part in 9Cr18 QT55-58 and 9Cr18 QT58-60 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.