Steel 9Cr18-CD vs 9Cr18 QT55-58
Steel · 9Cr18 temper comparison
9Cr18-CD and 9Cr18 QT55-58 are two conditions of the same steel grade, 9Cr18: CD (cold drawn) versus QT55-58 (Q&T 55–58 HRC). The chemistry is identical, so every difference below comes from the condition. 9Cr18 QT55-58 is the stronger of the two: yield strength 1,740 MPa (252 ksi) against 700 MPa (102 ksi) for 9Cr18-CD, about 149% more; tensile strength follows at 1,930 MPa (280 ksi) vs 900 MPa (131 ksi). In exchange, 9Cr18-CD is the more ductile: elongation 10% versus 3% for 9Cr18 QT55-58, and 9Cr18-CD is harder (275 HB vs 225 HB). 9Cr18-CD runs hotter in service (350°C vs 180°C continuous). On the shop floor, 9Cr18-CD machines more easily (fair vs not recommended).
9Cr18-CDChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
9Cr18 QT55-58Choose it when strength drives the design.
9Cr18-CD vs 9Cr18 QT55-58: 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, Brinell
Hardness, Rockwell B
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
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).
Corrosion Resistance
Same in both: Galvanic Potential (seawater, vs SCE) -0.25 V
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-CD vs 9Cr18 QT55-58 — frequently asked
Is 9Cr18 QT55-58 stronger than 9Cr18-CD?
Yes. 9Cr18 QT55-58 has a typical yield strength of 1,740 MPa (252 ksi) against 700 MPa (102 ksi) for 9Cr18-CD — about 149% more. Tensile strength is 1,930 MPa (280 ksi) vs 900 MPa (131 ksi).
Which condition does FabDigit quote by default, CD or QT55-58?
A is the default 9Cr18 condition in the FabDigit quote flow (neither CD nor QT55-58). 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, 9Cr18-CD or 9Cr18 QT55-58?
9Cr18-CD. Its machinability rates fair (48/100) against not recommended (10/100) for 9Cr18 QT55-58; for welding the order is 9Cr18-CD first (poor, 15/100) then 9Cr18 QT55-58 (not recommended, 8/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 9Cr18-CD and 9Cr18 QT55-58 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.