Aluminum Gravity Die Casting

Unlike aluminum pressure die casting, gravity die casting utilizes gravity to fill the mould with liquid aluminum alloy. In China, such gravity die casting can also be called as aluminum gravity casting.

Aluminum Gravity Die Casting Process

Like other casting processes, the aluminum gravity die casting process starts from the development of mold by CNC machines. Then, melt aluminum ingots into liquid status, and pour the aluminum liquid water into the permanent molds to fill the cavity by handwork or by gravity casting machines. Next, cool the poured aluminum alloy for a while for solidification. Finally, take the aluminum gravity die casting blanks from the mold, remove the flash and carry out necessary post operations like shot blasting, machining and others. Below is a video showing the aluminum gravity die casting process in our foundry:

Aluminum Gravity Die Casting Alloy: A356-T6

A356 is a type of aluminum alloy especially for gravity die casting. A356 cast aluminum alloy has good casting and machining performance, suitable for use in aircraft, pump housings, impellers, high-velocity blowers, and other structural castings that require high strength. This light alloy is often used to manufacture intricate and complex aluminum castings, which provide lightweight, pressure tightness and great mechanical properties. Sometimes, A356 is used as an alternative for 6061 aluminum.

Chemical Compositions

A356 Aluminum Alloy Elements
Cu Mg Mn Si Fe Zn Ti Others Al
≤0.2% 0.25%-0.45% ≤0.10% 6.5%-7.5% ≤0.2% ≤0.1% ≤0.2% ≤0.15% balance

Mechanical Properties

  • Elongation at Break: 3-6%
  • Fatigue Strength: 50-90 MPa
  • Shear Modulus: 26 GPa
  • Ultimate Tensile Strength: 160-270 MPa
  • Yield Tensile Strength: 83-200 MPa
  • Melting Onset: 570℃
  • Density: 2.6 g/cm³

After gravity die casting, T6 heat treatment is suggested to improve the mechanical properties of A356 aluminum castings. The hardness, tensile strength, and ductility of A356 castings could be improved by 106%, 106%, and 214% respectively.

Benefits of Aluminum Gravity Die Casting

  • The tolerances and surface finish are good.
  • The gravity die casting method is a competitive casting method when the production quantity is relatively small or when heat treatment is needed to improve the mechanical properties.
  • This casting method gives better tolerances and surface finish than sand casting. But the tooling costs are a bit higher than by sand casting.
  • Using sand cores in gravity die casting makes it possible to manufacture items with complicated inner shapes in a cost effective way in small and medium quantities.

Surface Finishing Options

Surface Finish  Images Process Advantages
Shot Blasted Finish Shot Blasted Finish High-speed steel shots are propelled at the surface to remove imperfections and improve surface quality.
  • High rate of material removal
  • Uniform surface finish
  • Prepares surface for further finishing or painting
Powder Coated Finish Powder Coated Finish A dry powder is applied electrostatically to the surface, which is then cured under heat to form a hard, durable coating.
  • Environmentally friendly
  • Durable and long-lasting finish
  • A wide range of colors and textures are available
Anodized Finish Anodized Finish An electrochemical process that converts the metal surface into a decorative, durable, and corrosion-resistant oxide layer.
  • Enhanced corrosion resistance
  • Improved aesthetic appearance
As Machined Finish As Machined Finish Computer numerical control (CNC) machines remove material from the die-cast part to achieve the desired shape and finish.
  • High precision and repeatability Suitable for complex geometries
  • Can achieve tight tolerances

When to Choose Aluminum Gravity Die Casting

Choosing the right casting process depends on various factors such as production volume, part complexity, material requirements, and surface finish requirements. Aluminum gravity die casting is particularly well-suited for specific components. Here are some situations where you might choose this method:

High Production Volume
Gravity die casting is a good option when you have a high production volume. The molds can be used multiple times, making the cost per unit more economical in the long run.

Complexity and Dimensional Accuracy
For complex geometries that require high dimensional accuracy, aluminum gravity die casting offers superior results compared to other casting methods like sand casting.

Material Requirements
If your project requires a lightweight material with a good strength-to-weight ratio, as well as good thermal and electrical conductivity, aluminum is an excellent choice.

Surface Finish Quality
This process typically provides a better surface finish than sand casting, reducing the need for additional surface treatments.

Rapid Production
Once the mold is prepared, the gravity die casting process is relatively quick, making it a good choice for projects with tight deadlines.

Mechanical Properties
Aluminum gravity die cast parts often have better mechanical properties compared to parts made from other casting methods due to the faster cooling rates, which result in a finer microstructure.

Aluminum Gravity Die Casting vs. Aluminum Sand Casting

Aspect Aluminum Gravity Die Casting Aluminum Sand Casting
Process Molten aluminum is poured into a metallic mold, relying on gravity for filling. Molten aluminum is poured into a sand mold, created using a pattern.
Precision High precision; good dimensional accuracy and repeatability. Moderate precision; can accommodate larger tolerances.
Surface Finish Smooth and fine surface finish. Rougher surface finish, often requires additional finishing processes.
Tooling Costs Higher due to metallic molds, which are more expensive to produce. Lower, as sand molds are generally less expensive to make.
Production Speed Faster, suitable for medium to high volume production. Slower, more suitable for low to medium volume production.
Complexity of Parts Suitable for complex geometries but may have limitations for very intricate parts. More flexible with complex shapes and internal geometries.
Material Waste Minimal waste, efficient use of material. Can result in more material waste and requires proper sand management.
Mechanical Properties Consistent mechanical properties due to controlled process. Can have varied mechanical properties depending on sand quality and process.
Economic Considerations More cost-effective for larger production runs due to mold reusability. Often more cost-effective for smaller batches and prototypes.
Environmental Impact Less waste and efficient energy consumption, but requires proper handling of molds. The use of sand can lead to waste management concerns and potential emissions.

Aluminum Gravity Die Casting in CFS Foundry

Aluminum Gravity Die Casting in CFS Foundry

CFS Foundry has been involved in aluminum gravity die casting since 1998. During these years, we have continuously introduced advanced gravity die casting machines to improve production efficiency. For large quantity orders, such machines greatly shorten the production cycle and offer our customers a much lower price. However, for some small orders, we also reserve our handwork gravity casting processin a cost effective manner.

Currently, our aluminum gravity die cast products are supplied to a wide range of industries, such as automobile industry, oil field industry, agriculture implements, furniture parts, housing appliances, etc. Typical products produced this way are, e.g. air intake components for diesel engines, valves for flow systems, tanks for air conditioning systems, etc. Those gravity die casting parts are mostly exported to American and European countries. We can provide custom aluminum gravity die casting with different aluminum alloys with value added services such as heat treatments, surface treatments (including electroplating, powder coating, painting), assembly, etc.

If you have RFQs for aluminum gravity die castings or other aluminum castings from China, please feel free to contact us. We are always waiting online for your services.