Stainless Steel 1.4378 +AT vs 1.4378 +C900
Stainless Steel · 1.4378 temper comparison
1.4378 +AT and 1.4378 +C900 are two conditions of the same stainless steel grade, 1.4378: +AT (solution annealed) versus +C900 (cold worked to Rm ≥ 900 MPa). The chemistry is identical, so every difference below comes from the condition. 1.4378 +C900 is the stronger of the two: yield strength 720 MPa (104 ksi) against 430 MPa (62.4 ksi) for 1.4378 +AT, about 67% more; tensile strength follows at 960 MPa (139 ksi) vs 780 MPa (113 ksi). In exchange, 1.4378 +AT is the more ductile: elongation 50% versus 14% for 1.4378 +C900, and 1.4378 +C900 is harder (285 HB vs 200 HB). 1.4378 +AT runs hotter in service (800°C vs 300°C continuous). On the shop floor, 1.4378 +AT welds better (very good vs good).
1.4378 +ATChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
1.4378 +C900Choose it when strength drives the design.
1.4378 +AT vs 1.4378 +C900: 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
Shear Strength
Fatigue Strength (Endurance Limit)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Vickers
Same in both: Elastic (Young's) Modulus 197 GPa28.6 Msi · Shear Modulus 76 GPa11 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29 · Fracture Toughness (K_IC) 180 MPa·√m164 ksi·√in · Hardness, Rockwell B 92 HRB
Physical
Density and transition temperatures.
Same in both: Density 7.8 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,380°C2,516 °F · Liquidus Temperature 1,420°C2,588 °F
Thermal
How each material carries heat and how hot it can run.
Max Service Temperature (continuous)
Same in both: Thermal Conductivity 14 W/m·K8.1 BTU/hr·ft·°F · Specific Heat Capacity 500 J/kg·K0.12 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 15.5 µm/m·K8.6 µin/in·°F · Latent Heat of Fusion 270 J/g116 BTU/lb · Min Service Temperature -196°C-321 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Conductivity 2.2 % IACS · Electrical Resistivity 8×10⁻⁷ Ω·m31.5 µΩ·in
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
Same in both: Galvanic Potential (seawater, vs SCE) -0.1 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: Brazeability / Solderability 55 / 100 · Polishability 70 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 46 MJ/kg19,776 BTU/lb · Embodied Carbon (primary production) 3.7 kg CO₂/kg · Embodied Water 150 L/kg18 gal/lb · Typical Recycled Content 55%
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.
1.4378 +AT vs 1.4378 +C900 — frequently asked
Is 1.4378 +C900 stronger than 1.4378 +AT?
Yes. 1.4378 +C900 has a typical yield strength of 720 MPa (104 ksi) against 430 MPa (62.4 ksi) for 1.4378 +AT — about 67% more. Tensile strength is 960 MPa (139 ksi) vs 780 MPa (113 ksi).
Which condition does FabDigit quote by default, +AT or +C900?
+AT is the default 1.4378 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 welds better, 1.4378 +AT or 1.4378 +C900?
1.4378 +AT. Its weldability rates very good (75/100) against good (60/100) for 1.4378 +C900.
Ready to make it?
Upload a CAD file and FabDigit prices the part in 1.4378 +AT and 1.4378 +C900 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.