複雑な砂型鋳造部品に最適な合金は何ですか？

Alloy Selection Criteria for Complex Sand Castings

Choosing the optimal alloy for complex sand-cast components requires balancing castability, mechanical performance, and post-processing requirements. Sand casting excels at producing large, intricate parts with complex internal passages using sand cores. The ideal alloys demonstrate excellent fluidity to fill detailed molds, controlled shrinkage to prevent hot tearing, and machinability for final precision. The part's intended service environment—including exposure to corrosion, high temperatures, or structural loads—directly informs the choice between aluminum, copper, or zinc-based alloys.

Aluminum Alloys: Excellent Castability and Strength-to-Weight

Aluminum alloys are the premier choice for complex sand castings due to their superior fluidity and relatively low melting point. A356 is exceptionally suited for intricate designs, offering excellent castability, resistance to hot tearing, and compatibility with T6 heat treatment to enhance tensile strength and ductility. This makes it ideal for complex structural components in aerospace and automotive applications. For parts demanding high pressure tightness and corrosion resistance, A413 is an excellent alternative due to its high silicon content, which improves fluidity and minimizes shrinkage.

Copper Alloys for Corrosion Resistance and Strength

Copper-based alloys are ideal for components exposed to corrosive environments, wear, or requiring self-lubricating properties. Leaded Bronze C83600 (Ounce Metal) offers excellent machinability due to its lead content, enabling the creation of complex internal features during post-machining. It provides pressure tightness and corrosion resistance, making it standard for valves, pumps, and plumbing fittings. For higher strength and corrosion resistance, Aluminum Bronze C95400 is commonly used in marine and industrial applications for gears, liners, and heavy-duty bearings.

Zinc Alloys for Dimensional Stability and Thin Walls

Zinc alloys, while more typical in die casting, are also suitable for sand-cast components requiring high dimensional accuracy and stability. ZA-8 combines strength, bearing properties, and castability, supporting thin-walled complex parts. It maintains tensile strength and hardness at elevated temperatures better than many aluminum alloys, offering a cost-effective solution for intricate industrial hardware and low-speed, high-load bearing applications.

Design and Process Integration

Successful complex sand-cast parts require integrating alloy selection with expert design and engineering. Section thickness uniformity, proper gating and riser placement, and accurate core positioning are critical to ensure defect-free solidification. For low-volume manufacturing or rapid prototyping, sand casting with these versatile alloys provides a flexible and cost-effective route to producing highly intricate components.