Steel SACM645 Q&T vs SACM645 Q&T+NIT
Steel · SACM645 temper comparison
SACM645 Q&T and SACM645 Q&T+NIT are two conditions of the same steel grade, SACM645: Q&T (quenched and tempered) versus Q&T+NIT (Q&T + Nitrided). The chemistry is identical, so every difference below comes from the condition. Both yield at about 780 MPa — the mechanical properties are the same, and the difference is in how the stock is processed and what it is certified to (quenched and tempered versus Q&T + Nitrided). SACM645 Q&T is the more ductile: elongation 17% versus 15% for SACM645 Q&T+NIT, and SACM645 Q&T+NIT is harder (67 HRC vs 28 HRC). SACM645 Q&T+NIT runs hotter in service (500°C vs 450°C continuous). On the shop floor, SACM645 Q&T machines more easily (fair vs not recommended).
SACM645 Q&TChoose it when the part is bent, formed or impact-loaded, or when the part is machined in volume.
SACM645 Q&T+NITChoose it when the part sees heat.
SACM645 Q&T vs SACM645 Q&T+NIT: 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, Rockwell C
Hardness, Vickers
Same in both: Elastic (Young's) Modulus 207 GPa30 Msi · Shear Modulus 80 GPa11.6 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29 · Compressive Strength 790 MPa115 ksi · Shear Strength 570 MPa82.7 ksi · Fracture Toughness (K_IC) 70 MPa·√m63.7 ksi·√in · Hardness, Brinell 270 HB
Physical
Density and transition temperatures.
Same in both: Density 7.8 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,425°C2,597 °F · Liquidus Temperature 1,490°C2,714 °F
Thermal
How each material carries heat and how hot it can run.
Max Service Temperature (continuous)
Same in both: Thermal Conductivity 36 W/m·K20.8 BTU/hr·ft·°F · Specific Heat Capacity 465 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 · Min Service Temperature -40°C-40 °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).
Corrosion Resistance
Same in both: Galvanic Potential (seawater, vs SCE) -0.6 V
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Same in both: Weldability 18 / 100 · Formability (cold) 25 / 100 · Brazeability / Solderability 40 / 100 · Polishability 60 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 34 MJ/kg14,617 BTU/lb · Embodied Carbon (primary production) 2.5 kg CO₂/kg · Embodied Water 55 L/kg6.6 gal/lb · Typical Recycled Content 28%
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.
SACM645 Q&T vs SACM645 Q&T+NIT — frequently asked
What is the difference between SACM645 Q&T and SACM645 Q&T+NIT?
SACM645 Q&T and SACM645 Q&T+NIT are two conditions of the same steel grade, SACM645: Q&T (quenched and tempered) versus Q&T+NIT (Q&T + Nitrided). The chemistry is identical, so every difference below comes from the condition. Both yield at about 780 MPa — the mechanical properties are the same, and the difference is in how the stock is processed and what it is certified to (quenched and tempered versus Q&T + Nitrided).
Which condition does FabDigit quote by default, Q&T or Q&T+NIT?
Q&T is the default SACM645 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, SACM645 Q&T or SACM645 Q&T+NIT?
SACM645 Q&T. Its machinability rates fair (42/100) against not recommended (8/100) for SACM645 Q&T+NIT.
Ready to make it?
Upload a CAD file and FabDigit prices the part in SACM645 Q&T and SACM645 Q&T+NIT 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.