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Brass and Aluminum Die Casting - An Overview
Die casting is a metal casting process that is characterized by forcing molten metal under high pressure into a mold cavity. The mold cavity is created using two hardened tool steel dies which have been machined into shape and work similarly to an injection mold during the process. Die casting is popular for producing geometrically complex metal parts at high volumes. Brass and aluminum are two common alloys used for die casting.
Brass Die Casting
Brass is an alloy made from copper and zinc. The proportions of copper and zinc can be varied to create different types of brass alloys with varying mechanical and corrosion resistance properties. Some common types of brass alloys used for die casting include:
- Yellow Brass - An alloy with 15-37% zinc and the balance copper. It is strong, ductile, and relatively inexpensive so it is commonly used for basic castings.
- Red Brass - An alloy with 15-25% zinc that also includes tin, aluminum or lead in small quantities. It is used when good corrosion resistance is needed.
- High Strength Brass - Alloys with additions of manganese, aluminum, iron or nickel. These have high yield strength and tensile strength so are used when strength is critical.
Brass is a popular metal for die castings because it has relatively low melting temperatures between 900-940°C which makes it easy to work with. It produces smooth cast surfaces and offers excellent dimensional stability and rigidity. It also has good corrosion resistance and antimicrobial properties.
Common applications of brass die cast parts include:
- Plumbing fittings and fixtures
- Musical instruments
- Locks, latches, and furniture hardware
- Costume jewelry
- Automotive trim and radiator components
When compared to other casting processes like sand casting, brass die cast parts have tighter dimensional tolerances and smoother surfaces that require little to no secondary machining. Thin walls and complex geometries are possible with brass die casting.
Aluminum Die Casting
Aluminum is another very common alloy used for die casting. Some advantages of aluminum die casting include:
- Aluminum has a low melting point between 640-680°C so it is easy to use.
- It flows smoothly into the die cavities so it reproduces intricate details very well.
- Aluminum castings have excellent dimensional consistency and stability.
- Aluminum is lightweight with a density around one third of steel and brass. This makes aluminum castings ideal for applications where weight savings are critical.
- Aluminum castings offer high strength and hardness. They can be precipitation hardened after casting for additional strength.
- Aluminum is more corrosion resistant than many other alloys. Aluminum die castings can withstand exposure to water, many chemicals, and environmental corrosion.
Some of the most common aluminum die casting alloys:
- Aluminum 383 - Used when thin walls and good fluidity are needed. Also offers good corrosion resistance.
- Aluminum 360 - Offers optimal strength and hardness along with excellent corrosion resistance. One of the most widely used alloys.
- Aluminum 336 - Provides very high strength with good corrosion resistance. Used for parts that require strength.
Aluminum die castings are popular in the automotive industry due to their light weight, high dimensional accuracy, and excellent repeatability. Other common applications include consumer appliances, business machines, outdoor furniture, and machine components. Aluminum die castings can readily be plated or painted to achieve virtually any aesthetic appearance. Compared to plastic injection molded parts, aluminum die castings offer higher resilience and thermal resistance while still being cost-effective for complex, high volume products.
The Die Casting Process
While various types of metal can be die cast, including zinc, magnesium, and tin alloys, aluminum and brass are two of the most common. The die casting process for both brass and aluminum is essentially the same. It involves the following basic steps:
1. Molten metal is poured from a holding furnace into an unheated shot sleeve where it begins to cool and solidify.
2. A pistons pushes the metal from the shot sleeve into the die with intense force, typically around 15,000 psi. This forces the molten metal to flow into all the cavities and detail of the mold.
3. The metal in the die cools and solidifies into the desired shape, aided by water cooling channels in the die. Cooling takes between 15 to 90 seconds depending on the mass of the part.
4. The mold opens and the newly formed casting is ejected. The mold then closes and the cycle repeats.
5. Secondary finishing operations might be required to clean up the casting and apply coatings or surface treatments if needed.
Die casting is economical for complex, high volume production. It offers fast cycle times and minimal scrap losses. Initial die tooling costs are higher than other casting methods but are quickly offset by the low per-unit price once production is underway. Brass and aluminum die castings offer distinct advantages over other manufacturing techniques for metal components that require precision, complex shapes, and thin walls.
Brass and aluminum are two of the most commonly die cast alloys, thanks to their high fluidity, excellent mold filling characteristics, dimensional stability, and corrosion resistance. While the two alloys have slightly different properties, the die casting manufacturing process used for each is nearly identical. Die casting produces complex yet durable metal parts that are ideal for high production volumes across many industries including automotive, consumer products, industrial machinery, and more. Both brass and aluminum die castings deliver the benefits of tight dimensional tolerances, complex geometries, smooth surfaces, and high repeatability. CNC Milling CNC Machining