Cast Aluminum: The Ultimate Guide

Die Casting

Currently, aluminum castings hold an irreplaceable position in the industrial sector. Renowned for their lightweight, high strength, corrosion resistance, low cost, and high production efficiency, they play a significant role in many industries. This article will provide you with a detailed understanding of aluminum casting and guide you on selecting suitable castings for your project.

What is Cast Aluminum

Aluminum casting encompasses a broad meaning, referring to the process of heating solid aluminum or aluminum alloys to a molten state, then pouring the molten aluminum into pre-prepared product molds or heat-resistant cavities. After the molten aluminum cools and solidifies, you obtain an aluminum casting of the desired product.

Aluminum and many aluminum alloys have relatively low melting points and viscosity when melted, but they form solids with high strength upon cooling. The materials and structures of the cavities used for casting vary, and there are also many different processes involved.

Why Use Cast Aluminum

Aluminum components obtained through casting offer numerous advantages that other materials cannot match. Below, I’ll walk you through its advantages to help you understand why aluminum casting is utilized:

1. Lightweight with High Strength

Aluminum castings possess low density and excellent mechanical properties, making them lighter compared to materials like steel. However, their strength and stiffness are second only to expensive metals like magnesium and titanium. This makes aluminum castings an ideal choice for lightweight design. Particularly crucial for industries such as automotive and aerospace, where reducing product weight enhances fuel efficiency, reduces material costs, and improves safety to some extent.

2. Corrosion Resistance

Aluminum castings exhibit excellent corrosion resistance, resisting erosion from air, water, and chemicals. This ensures consistent performance and appearance in various harsh environments, suitable for long-term outdoor or marine applications.

3. Machinability

Aluminum alloys are less ductile than pure aluminum but offer excellent machinability, facilitating easier forming processes and enabling the manufacture of complex shapes and intricate parts. Aluminum casting has become the preferred choice for producing various complex parts and components.

4. Thermal and Electrical Conductivity

Aluminum boasts excellent thermal and electrical conductivity, making it widely used in manufacturing heat sinks, electronic devices, or products requiring good thermal and electrical conductivity.

5. Cost-Effectiveness

Aluminum casting is more cost-effective compared to other metal processing methods. Aluminum raw materials are relatively inexpensive and easy to process, and aluminum casting can be highly automated, saving time and labor costs.

6. Sustainability

Aluminum is a renewable material that can be recycled and reused multiple times. Additionally, waste generated during the aluminum casting process can be recycled, leading to lower environmental impact and better sustainability for aluminum casting products.

Cast Aluminum

Different Aluminum Casting Processes

1. Литье под давлением

Die casting is a common metal casting process, especially suitable for the production of low melting point alloys such as aluminum, zinc, and magnesium. During the die casting process, liquid metal is injected into molds, ultimately forming the desired castings. Die casting can produce high-precision and high-quality parts and features a sophisticated automation system, making it suitable for mass production.

The design and quality of molds directly influence the quality of die casting. Molds typically consist of two halves: the upper and lower halves. The gap between them defines the shape and size of the product.

2. Investment Casting

Investment casting, also known as precision casting, is a high-precision casting process used to manufacture parts with complex shapes, precise dimensions, and high surface quality requirements, such as aerospace engine components, automotive parts, and medical equipment parts. Products produced by investment casting have high accuracy, good surface quality, and require little or no post-processing. However, investment casting also entails higher costs and longer manufacturing cycles.

3. Sand Casting

Sand casting is suitable for manufacturing small metal components. Firstly, a set of molds is made based on the shape and size of the desired part. Then, a special sand material, usually silica sand, is used to fill the molds to create two-part cavities. These cavities can withstand the pressure and heat during casting. After merging the two-part cavities, casting is performed. Although automation is possible, sand casting is typically manual. Sand casting offers advantages such as low cost, short production cycles, and suitability for mass production. However, its molds are disposable and cannot be reused.

4. Permanent Mold Casting

Permanent mold casting is similar to die casting. Two permanent mold halves are clamped together to form a complete cavity, usually made of iron, steel, or aluminum. Unlike die casting, permanent mold casting fills the mold through gravity rather than pressure. This results in parts with better surface finish and higher strength.

5. Lost Foam Casting

Lost foam casting is similar to investment casting but uses polystyrene foam molds instead of wax. The molds are coated with a layer of ceramic shell after dipping, then dried and baked to create a ceramic shell. After the foam molds are vaporized, molten metal is poured in, yielding the desired castings.

6. Shell Molding

Shell molding uses molds typically composed of two parts: one forming the outer shape of the casting, and the other forming internal cavities and details. The mold surface is repeatedly coated and dried with special refractory materials such as silica sand to form a shell, ensuring sufficient strength and refractoriness. Shell molding is faster and cheaper than conventional sand casting and is suitable for medium to large castings requiring high precision.

7. Vacuum Casting

Vacuum casting is an advanced metal casting process that utilizes a vacuum environment during casting. Molten metal or alloy is injected into molds under negative pressure, effectively reducing the presence of bubbles and producing castings with high density, no porosity, and high surface finish.

8. Centrifugal Casting

Centrifugal casting involves injecting liquid metal into a high-speed rotating mold, allowing the metal to fill the mold through centrifugal force. The centrifugal force helps to eliminate gases and inclusions from the liquid metal and affects the metal’s crystallization process, thereby improving the mechanical and physical properties of the castings. Parts produced by centrifugal casting exhibit high hardness and strength, fewer defects such as pores and inclusions, and high process yield.

Cast Aluminum VS Forged Aluminum

Aluminum casting involves melting aluminum alloy and injecting it into molds, which, after cooling, form castings. Aluminum casting typically offers high degrees of formability, but the resulting grain structure tends to be relatively large, leading to lower strength and hardness compared to forged aluminum. It is commonly used for components with high complexity requirements, such as automotive engine casings and aerospace parts. The production cost of aluminum casting is relatively low, but additional machining processes may be required for specific engineering requirements.

Forged aluminum, on the other hand, is created by heating aluminum alloy to high temperatures and shaping it through mechanical forging processes such as hammering or pressing. During forging, aluminum undergoes deformation and processing, resulting in a finer grain structure and higher density. Forged aluminum typically exhibits higher strength, hardness, and wear resistance, making it suitable for applications requiring high strength and durability, such as automotive suspension systems and aircraft structural components. The production cost of forged aluminum is usually higher, but it often delivers superior mechanical performance.

How to Choose The Suitable Aluminum Casting Process

In fact, choosing the appropriate aluminum casting process involves considering many factors, including the complexity of the part’s shape, material performance requirements, production cost, and cycle time. Here are some recommendations for selecting an aluminum casting process:

1. Design Complexity

If your part has a complex design, die casting may be the preferred choice. It can produce aluminum parts with intricate shapes and precise dimensions by utilizing high pressure to inject aluminum liquid into molds, effectively filling small cavities. However, sand casting may be limited in handling complex parts due to difficulties in mold fabrication and inadequate filling of aluminum liquid.

2. Production Speed

If you need to produce parts quickly, die casting is the way to go. It can complete one molding cycle in a short time and can be performed continuously, making it suitable for high-volume rapid production. In contrast, sand casting and investment casting may have slower production speeds due to longer production cycles and are typically suitable for small batch production.

3. Production Cost

If cost reduction is a priority, sand casting offers lower costs. Its mold fabrication is relatively inexpensive, making it suitable for low-cost, high-volume production. While die casting entails higher equipment and mold fabrication costs, it can be offset by producing larger volumes.

4. Required Performance

Different casting processes exhibit variations in product performance. Die casting, vacuum casting, and centrifugal casting can provide higher product density and strength, suitable for applications requiring high hardness, strength, and wear resistance, such as automotive parts or industrial machinery. Sand casting and investment casting may lag slightly in performance but remain suitable choices for lightweight structures or non-critical components.

5. Surface Quality

If your part requires high surface quality, die casting or precision casting may be suitable options. They can provide a smoother, more uniform surface, particularly suitable for products requiring exquisite appearance or subsequent surface treatments such as painting or anodizing.

Optional Finishes For Casting Aluminum Parts

1. Spray Painting or Coating

Applying specific coatings or using spray painting techniques to form a protective film or enhance aesthetics on the surface of aluminum castings. This method can improve surface corrosion resistance, wear resistance, or aesthetics.

2. Anodizing

Placing aluminum castings in an acidic solution containing electrolytes and applying electric current to form an oxide layer. This oxide layer not only enhances the hardness and corrosion resistance of the aluminum surface but also provides a variety of color appearances.

3. Mechanical Polishing

Using mechanical grinding or polishing techniques to improve the surface roughness of aluminum castings, making it smoother and more uniform. This can enhance the surface appearance and glossiness.

4. Sandblasting

Using high-pressure air to blast sand particles onto the surface of aluminum castings to remove surface oxidation, dirt, etc., thereby improving surface quality.

5. Electroplating

Coating the surface of aluminum castings with a layer of metal or alloy, such as nickel, chromium, or copper, to enhance their corrosion resistance, hardness, and appearance.

Common Applications of Cast Aluminum

1. Automotive Industry

Engine components (such as cylinder heads, crankcases, pistons), gearbox housings, brake system parts, suspension system parts, etc.

2. Aerospace Industry

Structural components for aircraft and rockets, engine parts, turbine blades, aircraft casings, etc.

3. Electronic Products

Manufacturing of casings, radiators, connectors, and other components for electronic products, such as computer casings, phone casings, heat sinks, etc.

4. Industrial Machinery

Various machinery components, such as pump housings, valves, machine tool parts, pressure vessels, etc.

How Long is The Service Life of Cast Aluminum?

Aluminum castings have a long lifespan and can even be used indefinitely if the operating environment is ideal. However, this also requires regular maintenance and inspection on your part.

EVERGREEN’s Cast Aluminum Technology

At EVERGREEN, we possess advanced aluminum casting technology and extensive production experience. We can provide you with professional services and high-quality, high-performance aluminum castings. We aim to help you save costs and achieve a win-win situation for your projects. With various casting processes such as sand casting, die casting, precision casting, and more, we can meet all your needs.

Our technical team is highly experienced, capable of providing customized solutions for both small components and large structures. From design drawings to final product delivery, we’ve got you covered.

RFQ

Is aluminum casting heat-resistant?

Aluminum casting possesses good heat resistance, but the specific heat resistance depends on the alloy composition and the design of the casting. Some aluminum alloys exhibit high heat resistance but may experience deformation or failure under extreme temperatures.

What is the tensile strength of aluminum casting?

The tensile strength of aluminum casting also varies depending on the casting alloy. Generally, the tensile strength of aluminum casting ranges from 150 to 300 MPa, but specific alloys may exhibit different tensile strengths.

Can aluminum casting be used in 3D printing?

Aluminum casting can be manufactured through 3D printing. Current 3D printing technologies, such as selective laser melting or electron beam melting, are mature processes. They involve layer-by-layer melting of aluminum powder to sinter parts into the desired shapes. Moreover, EVERGREEN can provide this service for you.

Is aluminum casting pure aluminum?

Aluminum casting is typically not pure aluminum; it is an aluminum alloy. It is formed by alloying aluminum with other elements such as silicon, copper, magnesium, etc. These alloying elements can alter the characteristics of pure aluminum, such as strength, hardness, and corrosion resistance.

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