Steel SMn438-CD vs SMn438-QT
Steel · SMn438 temper comparison
SMn438-CD and SMn438-QT are two conditions of the same steel grade, SMn438: CD (cold drawn) versus QT (quenched and tempered). The chemistry is identical, so every difference below comes from the condition. SMn438-QT is the stronger of the two: yield strength 690 MPa (100 ksi) against 640 MPa (92.8 ksi) for SMn438-CD, about 8% more; tensile strength follows at 860 MPa (125 ksi) vs 760 MPa (110 ksi). SMn438-QT is the more ductile: elongation 20% versus 12% for SMn438-CD, and SMn438-QT is harder (255 HB vs 225 HB).
SMn438-QTChoose it when strength drives the design, or when the part is bent, formed or impact-loaded.
SMn438-CD vs SMn438-QT: 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
Fatigue Strength (Endurance Limit)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell C
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 700 MPa102 ksi · Shear Strength 520 MPa75.4 ksi · Fracture Toughness (K_IC) 80 MPa·√m72.8 ksi·√in · Hardness, Vickers 268 HV
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 1,500°C2,732 °F
Thermal
How each material carries heat and how hot it can run.
Same in both: Thermal Conductivity 44 W/m·K25.4 BTU/hr·ft·°F · Specific Heat Capacity 470 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 12.2 µm/m·K6.8 µin/in·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Max Service Temperature (continuous) 400°C752 °F · Min Service Temperature -20°C-4 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 7.8 % IACS · Electrical Resistivity 2.2×10⁻⁷ Ω·m8.66 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.62 V · Corrosion Resistance 11 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability Rating (AISI 1212 = 100 %)
Formability (cold)
Same in both: Machinability 55 / 100 · Weldability 40 / 100 · Brazeability / Solderability 55 / 100 · Polishability 60 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 25 MJ/kg10,748 BTU/lb · Embodied Carbon (primary production) 1.9 kg CO₂/kg · Embodied Water 45 L/kg5.4 gal/lb · Typical Recycled Content 30%
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.
SMn438-CD vs SMn438-QT — frequently asked
Is SMn438-QT stronger than SMn438-CD?
Yes. SMn438-QT has a typical yield strength of 690 MPa (100 ksi) against 640 MPa (92.8 ksi) for SMn438-CD — about 8% more. Tensile strength is 860 MPa (125 ksi) vs 760 MPa (110 ksi).
Which condition does FabDigit quote by default, CD or QT?
QT is the default SMn438 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.
When should I choose SMn438-CD over SMn438-QT?
Pick SMn438-QT when strength drives the design, or when the part is bent, formed or impact-loaded.
Ready to make it?
Upload a CAD file and FabDigit prices the part in SMn438-CD and SMn438-QT 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.