Which metals are most suitable for sand casting?

The Foundation of Sand Casting Versatility

Sand casting's greatest strength is its remarkable compatibility with a wide range of ferrous and non-ferrous metals, from common alloys to exotic superalloys. The process can accommodate the high melting temperatures of steel and iron, which are unsuitable for many other casting methods, while also being highly effective for lower-temperature non-ferrous metals. The selection of the most suitable metal depends on the component's functional requirements, including needed strength, weight, corrosion resistance, machinability, and cost-effectiveness.

Aluminum Alloys: Lightweight and Corrosion-Resistant

Aluminum alloys are among the most popular choices for sand casting due to their excellent castability, good strength-to-weight ratio, and inherent resistance to corrosion. Key alloys include A356, which is renowned for its exceptional ductility and responsiveness to heat treatment, making it ideal for high-strength, structural components in aerospace and automotive applications. For parts requiring superior pressure tightness and fluidity, such as complex pump housings, A413 is an excellent choice due to its high silicon content.

Cast Iron and Steel for Strength and Durability

For applications demanding high strength, wear resistance, and the ability to withstand significant loads, ferrous metals are unmatched. Gray Iron is widely used for its excellent damping capacity and compressive strength, commonly seen in engine blocks and machine bases. Ductile Iron offers greater tensile strength and impact resistance. Carbon and Low-Alloy Steels are selected for the most demanding structural applications, such as large gears and heavy-duty machinery components, where toughness is critical. The sand casting process is one of the few capable of producing large and complex shapes from these high-melting-point metals.

Copper-Based Alloys for Specialized Properties

Copper alloys (brasses and bronzes) are chosen for their outstanding corrosion resistance, wear properties, and antimicrobial characteristics. Leaded Bronze C83600 is a classic sand casting alloy, offering excellent machinability and pressure tightness for valves, pumps, and plumbing fittings. For higher strength and superior corrosion resistance in marine environments, Aluminum Bronze C95400 is a robust choice for gears, bearings, and ship propellers.

Other Suitable Metals and Selection Criteria

Other metals well-suited to sand casting include Zinc Alloys like ZA-8, which provide high strength and hardness with excellent bearing properties, and Magnesium alloys, which are even lighter than aluminum. The final selection is a balance of the part's functional needs and the alloy's casting characteristics, such as fluidity and shrinkage, which are critical considerations during the design service phase to ensure a high-quality, cost-effective casting.