Metal die casting is a systematic process for producing various metal parts. This technology can produce strong, precise, and lightweight metal parts at a relatively low cost. The parts or components produced through the die casting process are suitable for both consumer products and industrial components.
Although metal die casting is a flexible production process, it is advisable to understand this technology before using it independently or hiring a company providing related services. So, what is die casting, how does it work, and what are its different types and advantages? Please keep reading to learn more.
Die casting involves forcing molten metal into a mold under high pressure. A hydraulic press ensures that the hardening tool steel sheets forming the cavity are pressed together, almost completely sealing the closed surfaces.
Metal die casting can produce precise metal parts with smooth surfaces and accurate dimensions. Due to its capability to manufacture complex parts, it is an ideal choice for mass production.
The choice of metal materials in die casting depends on the specific application's requirements. For example, due to its lightweight and corrosion resistance, aluminum is commonly used for manufacturing automotive parts. Let’s take a look at the different metal materials used in centrifugal die casting.
Aluminum is the primary metal in die casting, used in alloys for the cold chamber die casting process. These aluminum alloys typically contain elements such as magnesium, copper, and silicon.
Aluminum-based die casting alloys are lightweight and have good dimensional stability, making them an excellent choice for producing complex and fine artifacts. They have strong resistance to temperature fluctuations, corrosion, and good electrical and thermal conductivity. Here are some commonly used die casting aluminum alloys.
Aluminum Alloy 380: 380 is a versatile aluminum alloy known for balanced castability and mechanical properties. It is widely used in manufacturing engine brackets, furniture, electronic housings, frames, handles, gearboxes, power tools, etc.
Aluminum Alloy B390: This alloy has excellent vibration resistance and wear resistance. It is commonly used in pump bodies, valve bodies, and impellers.
Aluminum Alloy 413: It has excellent castability due to high pressure compressibility. AL413 is commonly used in manufacturing construction parts, food machinery, and hydraulic cylinders.
Aluminum Alloy 443: Out of all the aluminum alloys used for die casting, AL443 has the best ductility. This makes it very suitable for consumer goods, especially those needing plastic deformation after casting.
Magnesium is another commonly used material in die casting. Other elements in magnesium alloys include aluminum, zinc, manganese, and silicon. Magnesium alloys are not only lighter than aluminum but also easier to process, making them very suitable for objects that require additional processing or surface treatment after casting.
Compared to metals such as aluminum, die casting magnesium alloys are easier to cast, primarily because they are suitable for the hot chamber die casting process. Here are some typical magnesium alloys used in die casting.
AZ91D: The ideal combination of high strength-to-weight ratio, corrosion resistance, and castability make this alloy popular in powertrain components and mechanical parts.
AM60: Combining strength, ductility, shock absorption, and good castability, AM60 is the preferred choice for automotive parts such as panels and seat frames.
AS41B and AE42: These unique rare earth alloys have high-temperature resistance and good creep resistance, corrosion resistance, and ductility, but they are expensive.
Zinc alloys occupy a large proportion of die-casting metals. They are easy to manufacture, suitable for casting in hot chamber die casting machines, and offer additional advantages such as impact strength, ductility, and compatibility with electroplating. Here are some typical alloys used for zinc die casting.
Zamak 3: A general-purpose zinc alloy known for dimensional stability and ease of casting. Zamak 3 can be used to manufacture plumbing parts and ceiling fans.
Zamak 2: With additional copper, this alloy, although slightly more expensive, offers higher strength.
Zamak 5: Zamak 5 is a zinc-based alloy similar to Zamak 3 but with lower ductility and higher tensile strength. Therefore, it is the preferred alloy for products such as wheel balance weights.
In the die casting process, high pressure is critical for injecting molten metal into the mold. Here are the multiple steps involved in die casting.
First, the die casting mold is designed using computer-aided design (CAD) software. This software can create a three-dimensional (3D) model of the mold. Upon completion of the design, the actual mold can be made. This requires using a CNC machining to machine the mold from a block of metal. After cutting, the mold usually needs to be heat-treated to harden it.
Mold locking is the initial stage of die casting. To ensure the effective injection and removal of the solidified product, the mold must be lubricated and cleaned beforehand to eliminate any impurities. After cleaning and lubrication, apply strong pressure to clamp and close the mold.
When injecting the molten metal, it should be poured into the pouring chamber. This step varies depending on the process used, such as cold chamber die casting and hot chamber die casting. Note that this stage requires high pressure generated by the hydraulic system.
After the casting has formed, it must cool down and be removed from the mold. This step is crucial for maintaining the structural integrity of the casting. At this stage of die casting, manufacturers usually use forced cooling or natural cooling. However, the cooling method typically depends on the casting's size and complexity.
After cooling, manufacturers use ejector pins to expel the casting from the cavity and remove it from the mold. Ensure that the final product is solid before ejection.
The final stage is to remove any excess metal that may be present in the gates and runners of the finished product. Sawing, grinding, trimming dies, or other tools can be used for trimming. The advantage of this process is that the removed parts can be recycled and reused. In this process, it is essential to pay attention and be careful to prevent damage to the casting.
