Steel SACM645-A vs SACM645 Q&T
Steel · SACM645 temper comparison
SACM645-A and SACM645 Q&T are two conditions of the same steel grade, SACM645: A (solution annealed) versus Q&T (quenched and tempered). The chemistry is identical, so every difference below comes from the condition. SACM645 Q&T is the stronger of the two: yield strength 780 MPa (113 ksi) against 430 MPa (62.4 ksi) for SACM645-A, about 81% more; tensile strength follows at 950 MPa (138 ksi) vs 700 MPa (102 ksi). In exchange, SACM645-A is the more ductile: elongation 20% versus 17% for SACM645 Q&T, and SACM645 Q&T is harder (270 HB vs 205 HB). On the shop floor, SACM645-A machines more easily (52 vs 42 out of 100).
SACM645-AChoose it when the part is bent, formed or impact-loaded, or when the part is machined in volume.
SACM645 Q&TChoose it when strength drives the design.
SACM645-A vs SACM645 Q&T: 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
Fatigue Strength (Endurance Limit)
Charpy V-Notch Impact (RT)
Hardness, Brinell
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 · Reduction in Area 55% · Compressive Strength 790 MPa115 ksi · Shear Strength 570 MPa82.7 ksi · Fracture Toughness (K_IC) 70 MPa·√m63.7 ksi·√in · Hardness, Rockwell C 28 HRC · Hardness, Vickers 285 HV
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.
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 · Max Service Temperature (continuous) 450°C842 °F · 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).
Same in both: Galvanic Potential (seawater, vs SCE) -0.6 V · Corrosion Resistance 15 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Formability (cold)
Same in both: Weldability 18 / 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-A vs SACM645 Q&T — frequently asked
Is SACM645 Q&T stronger than SACM645-A?
Yes. SACM645 Q&T has a typical yield strength of 780 MPa (113 ksi) against 430 MPa (62.4 ksi) for SACM645-A — about 81% more. Tensile strength is 950 MPa (138 ksi) vs 700 MPa (102 ksi).
Which condition does FabDigit quote by default, A or Q&T?
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-A or SACM645 Q&T?
SACM645-A, by a small margin. Both rate fair for machinability — 52/100 against 42/100 for SACM645 Q&T.
Ready to make it?
Upload a CAD file and FabDigit prices the part in SACM645-A and SACM645 Q&T 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.