Quick Answer
Material selection for casting alloys — choose based on application requirements: strength, corrosion resistance, wear resistance, machinability, cost, and casting process fit. Gray iron for damping and low cost; ductile iron for strength and toughness; aluminum for lightweight and corrosion; carbon steel for strength at low cost; stainless steel for corrosion and high temperature; bronze/brass for bearing surfaces and corrosion.
Key Selection Factors
| Factor | What to Consider | How to Evaluate |
|---|---|---|
| Mechanical strength | Yield strength, tensile strength, fatigue strength, impact resistance | Mechanical test data from material cert |
| Corrosion resistance | Environment: fresh water, salt water, chemicals, atmosphere, temperature | Alloy selection for environment; test data |
| Wear resistance | Abrasive wear, adhesive wear, impact wear | Hardness, microstructure |
| Machinability | How easy to machine after casting | Machinability rating, tool wear, chip formation |
| Cost | Material + processing + tooling + machining | Total cost per part vs. performance |
| Casting process fit | Can this alloy be cast by the required process? | Castability, fluidity, solidification range |
| Weight | Density; critical for automotive, aerospace, portable | Compare density (Al 2.7, Fe 7.2, Cu 8.9 g/cm³) |
| Thermal properties | Thermal conductivity, high temperature resistance | Heat sink, furnace, exhaust applications |
Gray Iron (Gray Cast Iron)
Properties: Excellent damping (vibration absorption), good wear resistance, excellent thermal stability, low cost.
Limitations: Brittle, low tensile strength, poor weldability, cannot be heat treated for strength.
| Grade | Tensile Strength | Best For |
|---|---|---|
| Class 20 | 140 MPa | General purpose, low stress |
| Class 30 | 210 MPa | Machine bases, housing |
| Class 40 | 280 MPa | Engine blocks, brake rotors |
Applications: Engine blocks, machine bases, brake rotors, gear housings, pump bodies.
Ductile Iron (Nodular Cast Iron)
Properties: High strength + ductility, excellent impact resistance, good fatigue strength, weldable.
Limitations: More expensive than gray iron, requires controlled casting process.
| Grade | Yield Strength | Elongation | Best For |
|---|---|---|---|
| 60-40-18 | 400 MPa | 18% | High ductility applications |
| 65-45-12 | 450 MPa | 12% | General purpose |
| 80-60-03 | 600 MPa | 3% | High strength applications |
Applications: Automotive suspension components, gears, crankshafts, structural parts, pressure fittings.
Aluminum Casting Alloys
Properties: Lightweight (2.7 g/cm³), excellent corrosion resistance, good thermal conductivity, castable by multiple processes.
Limitations: Lower strength than steel/iron, limited high temperature capability.
| Alloy | Process | Key Properties | Applications |
|---|---|---|---|
| A356 | Sand, investment, gravity die | Good strength, excellent castability | Automotive, aerospace, general |
| A380 | High pressure die casting | Excellent castability, moderate strength | Complex thin-wall parts, housings |
| 6061 (wrought equivalent) | Sand casting | Good strength, weldable | Structural parts |
Applications: Automotive parts, aerospace components, heat sinks, electronic housings, marine hardware.
Carbon Steel Castings
Properties: High strength, low cost, weldable, heat treatable for higher strength.
Limitations: Needs coating for corrosion, higher density than aluminum.
| Grade | Yield Strength | Best For |
|---|---|---|
| WCB | 240 MPa | General purpose, pressure fittings |
| WCC | 280 MPa | Higher strength applications |
| LCC | 350 MPa | Low temperature service |
Applications: Structural parts, machinery components, pressure fittings, railway components.
Stainless Steel Castings
Properties: Excellent corrosion resistance, good high temperature capability, good strength.
Limitations: Higher cost, harder to machine, some grades difficult to cast.
| Cast Grade | Wrought Equivalent | Best For |
|---|---|---|
| CF8 | 304 | General corrosion resistance, food processing |
| CG8M | 316 | Marine, chemical, medical applications |
| CK20 | 310S | High temperature furnace parts |
Applications: Marine hardware, chemical processing, medical devices, food processing, high temperature parts.
Bronze and Brass Castings
Properties: Excellent corrosion resistance (marine), good bearing properties, excellent machinability.
Limitations: Higher cost, lower strength than steel/iron, high density.
| Alloy | Key Properties | Applications |
|---|---|---|
| C93200 (bearing bronze) | Excellent bearing properties | Bearing sleeves, bushings |
| C95400 (aluminum bronze) | High strength, corrosion resistant | Marine hardware, pump parts |
| C83600 (red brass) | Good corrosion, excellent machinability | Valves, fittings, decorative |
Applications: Bearings, bushings, marine hardware, valve components, pump parts, decorative hardware.
Buyer Decision Checklist
- What is the primary application requirement (strength, corrosion, wear, weight)?
- What is the service environment (temperature, chemicals, atmosphere)?
- What casting process is required (sand, investment, die)?
- What is the realistic budget per part?
- Is machining required after casting? How does machinability affect cost?
- Is welding required? Which alloys are weldable?
- What is the expected service life?
- Has the foundry confirmed this alloy is castable by the required process?
Before finalizing the sourcing decision, many OEM buyers also compare Sand Casting, Aluminum Casting Buyer Guide, and Cast Iron vs Cast Steel to clarify process fit, cost trade-offs, tolerance expectations, and supplier risk.
If you need application-specific guidance, drawing review, or a quotation, you can Contact YCUMETAL.
FAQ
Which casting alloy is cheapest?
Gray iron for ferrous applications; aluminum A380 for lightweight applications. Gray iron is typically the lowest-cost casting alloy.
Which alloy for corrosion resistance?
Stainless steel (CF8/CG8M) for general corrosion; aluminum for atmospheric corrosion; bronze/brass for marine corrosion.
Which alloy for high strength?
High-grade ductile iron (80-60-03) or carbon steel castings (LCC) for cost-effective strength. For highest strength with corrosion, stainless steel castings.