Steel Gray Iron Annealed vs Gray Iron-SR
Steel · Gray Iron temper comparison
Gray Iron Annealed and Gray Iron-SR are two conditions of the same steel grade, Gray Iron: Annealed versus SR (stress relieved). The chemistry is identical, so every difference below comes from the condition. Gray Iron-SR is the stronger of the two: tensile strength 215 MPa (31.2 ksi) against 180 MPa (26.1 ksi) for Gray Iron Annealed, about 19% more. In exchange, Gray Iron Annealed is the more ductile: elongation 0.8% versus 0.5% for Gray Iron-SR, and Gray Iron-SR is harder (180 HB vs 150 HB). Gray Iron-SR is stiffer (103 GPa vs 95 GPa).
Gray Iron AnnealedChoose it when the part is bent, formed or impact-loaded.
Gray Iron-SRChoose it when strength drives the design.
Gray Iron Annealed vs Gray Iron-SR: 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-SR
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)
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% · Fracture Toughness (K_IC) 15 MPa·√m13.7 ksi·√in
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.
Same in both: Electrical Conductivity 1.7 % IACS · Electrical Resistivity 1×10⁻⁶ Ω·m39.4 µΩ·in
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
Same in both: Formability (cold) 3 / 100 · 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-SR — frequently asked
Is Gray Iron-SR stronger than Gray Iron Annealed?
Yes. Gray Iron-SR has a typical tensile strength of 215 MPa (31.2 ksi) against 180 MPa (26.1 ksi) for Gray Iron Annealed — about 19% more.
Which condition does FabDigit quote by default, Annealed or SR?
As Cast is the default Gray Iron condition in the FabDigit quote flow (neither Annealed nor SR). 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-SR?
Gray Iron Annealed, by a small margin. Both rate excellent for machinability — 92/100 against 87/100 for Gray Iron-SR; for welding the order is Gray Iron-SR first (poor, 30/100) then Gray Iron Annealed (poor, 25/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in Gray Iron Annealed and Gray Iron-SR 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.