What are ASTM A536 and ASTM A48 Cast Irons?
ASTM A536 ductile iron and ASTM A48 gray iron are cast iron specifications used for industrial components where castability, machinability, damping, and cost can matter more than copper alloy performance. They are sometimes reviewed as alternatives to bronze for housings, frames, pulleys, gears, valve components, and non-lubricated structural parts.
ASTM A536 is a ductile iron specification based on minimum tensile strength, yield strength, and elongation. ASTM A48 is a gray iron specification based mainly on minimum tensile strength class. Neither standard should be treated like a fixed copper alloy chemistry; foundry chemistry and microstructure are controlled to meet the required grade or class.
Common Names and Cross References
| Material | Common names |
|---|---|
| ASTM A536 | Ductile iron, nodular iron, spheroidal graphite iron |
| ASTM A48 | Gray iron, gray cast iron, flake graphite iron |
| A536 65-45-12 | Ductile iron with 65 ksi tensile, 45 ksi yield, 12% elongation minimum |
| A48 Class 40 | Gray iron with 40 ksi minimum tensile strength in a separately cast test bar |
Typical Chemistry Notes
ASTM A536 and ASTM A48 are property-driven cast iron specifications, not fixed-chemistry alloy pages. The ranges below are representative foundry datasheet examples, not universal limits for every casting.
| Material | Representative chemistry notes |
|---|---|
| ASTM A536 ductile iron | Carbon 3.4-3.8%, silicon 2.35-2.75%, manganese 0.40% max, magnesium 0.025-0.055% in common foundry examples |
| ASTM A48 gray iron | Carbon 2.60-3.75%, silicon 1.80-3.00%, manganese 0.60-0.95%, sulfur 0.07% max, phosphorus 0.12% max in one common Class 40 bar example |
ASTM A536 Ductile Iron Properties
| Grade | Minimum tensile strength | Minimum yield strength | Minimum elongation |
|---|---|---|---|
| 60-40-18 | 60 ksi | 40 ksi | 18% |
| 65-45-12 | 65 ksi | 45 ksi | 12% |
| 80-55-06 | 80 ksi | 55 ksi | 6% |
| 100-70-03 | 100 ksi | 70 ksi | 3% |
| 120-90-02 | 120 ksi | 90 ksi | 2% |
Typical physical values for ductile iron include density around 0.256 lb/in3 (7.1 g/cm3), thermal conductivity around 36 W/m-K for ferritic grades, specific heat around 461 J/kg-K, and melting temperature around 2100 F. Exact values vary by grade and microstructure.
ASTM A48 Gray Iron Properties
| Class | Minimum tensile strength |
|---|---|
| Class 20 | 20 ksi |
| Class 30 | 30 ksi |
| Class 40 | 40 ksi |
| Class 50 | 50 ksi |
| Class 60 | 60 ksi |
Gray iron is generally non-ductile, so yield strength and elongation are often not reported the way they are for ductile iron. For common Class 40 continuous cast gray iron bar, published hardness can vary by size, often around 183-301 HB.
Machining and Fabrication Notes
| Material | Notes |
|---|---|
| ASTM A536 ductile iron | Generally castable and machinable; machinability varies by grade, pearlite/ferrite balance, hardness, and heat treatment |
| ASTM A48 gray iron | Known for good machinability, vibration damping, and wear resistance; actual performance varies by class and section size |
| Welding | Weldability is not defined by these ASTM grades alone and should be reviewed by grade, casting design, and repair procedure |
Typical Applications
- Frames, housings, gearboxes, and structural cast components.
- Gears, pulleys, rams, slides, spindles, and ways.
- Pumps, valves, brake components, and power transmission parts.
- Automotive suspension, steering, and driveline components.
- Gray iron parts requiring vibration damping and machinability.
RFQ Details for Cast Iron Parts
Send the exact ASTM grade or class, drawing, casting method if specified, finished dimensions, quantity, machining tolerances, hardness requirements, coating or finish needs, and any inspection or certification requirements. Do not substitute cast iron for bronze bearing parts unless the engineering requirement allows it.
Available Forms
Available Forms and Shapes
Review common product forms for ASTM A536 Ductile Iron and ASTM A48 Gray Iron, then send drawings, dimensions, quantity, and finished-part requirements for material and production guidance.
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