Steel Gray Iron Annealed vs Gray Iron Class 40
Steel · Gray Iron temper comparison
Gray Iron Annealed and Gray Iron Class 40 are two conditions of the same steel grade, Gray Iron: Annealed versus Class 40 (ASTM A48 Class 40). The chemistry is identical, so every difference below comes from the condition. Gray Iron Class 40 is the stronger of the two: yield strength 215 MPa (31.2 ksi) against 165 MPa (23.9 ksi) for Gray Iron Annealed, about 30% more; tensile strength follows at 293 MPa (42.5 ksi) vs 180 MPa (26.1 ksi). In exchange, Gray Iron Annealed is the more ductile: elongation 0.8% versus 0.4% for Gray Iron Class 40, and Gray Iron Class 40 is harder (217 HB vs 150 HB). Gray Iron Class 40 is stiffer (124 GPa vs 95 GPa) and Gray Iron Annealed conducts heat better (50 W/m·K vs 42 W/m·K). On the shop floor, Gray Iron Annealed machines more easily (excellent vs very good).
Gray Iron AnnealedChoose it when the part is bent, formed or impact-loaded, or when the part is machined in volume.
Gray Iron Class 40Choose it when strength drives the design.
Gray Iron Annealed vs Gray Iron Class 40: 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.
Gray Iron AnnealedGray Iron Class 40
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
Hardness, Vickers
Same in both: Shear Modulus 41 GPa5.9 Msi · Bulk Modulus 72 GPa10.4 Msi · Poisson's Ratio 0.26 · Reduction in Area 0%
Physical
Density and transition temperatures.
Same in both: Density 7.15 g/cm³0.26 lb/in³ · Melting Point (Solidus) 1,150°C2,102 °F · Liquidus Temperature 1,200°C2,192 °F
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Same in both: Specific Heat Capacity 460 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 11.5 µm/m·K6.4 µin/in·°F · Latent Heat of Fusion 220 J/g94.6 BTU/lb · Max Service Temperature (continuous) 400°C752 °F · Min Service Temperature -30°C-22 °F
Electrical
Conductivity and insulation.
Electrical Conductivity
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.61 V · Corrosion Resistance 18 / 100
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 95 / 100 · Brazeability / Solderability 50 / 100 · Polishability 35 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 18 MJ/kg7,739 BTU/lb · Embodied Carbon (primary production) 1.5 kg CO₂/kg · Embodied Water 40 L/kg4.8 gal/lb · Typical Recycled Content 90%
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.
Gray Iron Annealed vs Gray Iron Class 40 — frequently asked
Is Gray Iron Class 40 stronger than Gray Iron Annealed?
Yes. Gray Iron Class 40 has a typical yield strength of 215 MPa (31.2 ksi) against 165 MPa (23.9 ksi) for Gray Iron Annealed — about 30% more. Tensile strength is 293 MPa (42.5 ksi) vs 180 MPa (26.1 ksi).
Which condition does FabDigit quote by default, Annealed or Class 40?
As Cast is the default Gray Iron condition in the FabDigit quote flow (neither Annealed nor Class 40). 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, Gray Iron Annealed or Gray Iron Class 40?
Gray Iron Annealed. Its machinability rates excellent (92/100) against very good (72/100) for Gray Iron Class 40; for welding the order is Gray Iron Annealed first (poor, 25/100) then Gray Iron Class 40 (poor, 20/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in Gray Iron Annealed and Gray Iron Class 40 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.