Stainless Steel 418-H vs 418 Q&T-650
Stainless Steel · 418 temper comparison
418-H and 418 Q&T-650 are two conditions of the same stainless steel grade, 418: H (hardened) versus Q&T-650 (hardened and tempered ~650 °C). The chemistry is identical, so every difference below comes from the condition. 418-H is the stronger of the two: yield strength 1,200 MPa (174 ksi) against 860 MPa (125 ksi) for 418 Q&T-650, about 40% more; tensile strength follows at 1,550 MPa (225 ksi) vs 1,070 MPa (155 ksi). In exchange, 418 Q&T-650 is the more ductile: elongation 18% versus 8% for 418-H, and 418-H is harder (430 HB vs 320 HB). 418 Q&T-650 runs hotter in service (590°C vs 250°C continuous). On the shop floor, 418 Q&T-650 machines more easily (fair vs not recommended) and 418 Q&T-650 welds better (poor vs not recommended).
418-HChoose it when strength drives the design.
418 Q&T-650Choose it when the part is bent, formed or impact-loaded, or when the part sees heat.
418-H vs 418 Q&T-650: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all stainless 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 stainless 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)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell C
Hardness, Vickers
Same in both: Elastic (Young's) Modulus 215 GPa31.2 Msi · Shear Modulus 83 GPa12 Msi · Bulk Modulus 165 GPa23.9 Msi · Poisson's Ratio 0.29
Physical
Density and transition temperatures.
Same in both: Density 7.75 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,425°C2,597 °F · Liquidus Temperature 1,510°C2,750 °F
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Max Service Temperature (continuous)
Same in both: Specific Heat Capacity 460 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 10.6 µm/m·K5.9 µin/in·°F · Latent Heat of Fusion 270 J/g116 BTU/lb · Min Service Temperature -40°C-40 °F
Electrical
Conductivity and insulation.
Electrical Conductivity
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
Same in both: Galvanic Potential (seawater, vs SCE) -0.3 V
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Weldability
Formability (cold)
Same in both: Castability 40 / 100 · Brazeability / Solderability 45 / 100 · Polishability 75 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 57 MJ/kg24,506 BTU/lb · Embodied Carbon (primary production) 5.2 kg CO₂/kg · Embodied Water 200 L/kg24 gal/lb · Typical Recycled Content 35%
Strength versus weight
Yield strength against density for every stainless steel grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
418-H vs 418 Q&T-650 — frequently asked
Is 418-H stronger than 418 Q&T-650?
Yes. 418-H has a typical yield strength of 1,200 MPa (174 ksi) against 860 MPa (125 ksi) for 418 Q&T-650 — about 40% more. Tensile strength is 1,550 MPa (225 ksi) vs 1,070 MPa (155 ksi).
Which condition does FabDigit quote by default, H or Q&T-650?
Q&T-650 is the default 418 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, 418-H or 418 Q&T-650?
418 Q&T-650. Its machinability rates fair (35/100) against not recommended (12/100) for 418-H; for welding the order is 418 Q&T-650 first (poor, 30/100) then 418-H (not recommended, 10/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in 418-H and 418 Q&T-650 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.