Which Metals Work Best for Die Casting?
As of 2018, the global aluminum die-casting market size was valued at USD 24.91 billion. It was then projected that the industry will experience a 10.1% Compound Annual Growth Rate from 2019 to 2025.
The reason for this growth rate is that die casting is becoming one of the most relied upon manufacturing methods. Die casting is used in the production of a wide range of products that can be found in just about any industry or vertical you can think of.
Of course, like with other metal fabrication processes, die cast products will only be as good as the metals being used in their production. The source metals will impact the overall quality, durability, and aesthetic appearance of the finished product. As such, this blog will explore the various metals involved in the die casting process.
Before getting into the most ideal metals for die casting, let’s first talk a bit about the die casting process.
What is Die Casting?
Die casting is a metal fabrication process that involves forcing molten metal under high pressure into reusable metal dies. Die casting allows for the creation of metal parts with accurate dimensions, sharp definition, and smooth or textured surfaces.
A General Breakdown of the Die Casting Process
Die casting is one of the most popular metal fabrication methods due to its simplicity, speed, and stability. Here’s a step-by-step look at the die casting process:
- A steel mold must be made into two (or more) sections to allow for the removal of castings.
- This mold can produce thousands of castings quickly in succession.
- After being securely mounted into the machine, the sections are arranged with one stationary section (fixed die half). At the same time, the other section can move (injector die half).
- These two halves are clamped together by the machine – thus, beginning the casting cycle.
- The die cavity is injected with a molten metal, which then rapidly solidifies.
- Once the die halves are pulled apart, the casting is ejected.
Dies can be designed to be simple or complex, can possess moveable slides, cores, or other sections, depending on the casting’s complexity.
The Two Main Die Casting Processes
Hot Chamber Die Casting
Hot-chamber die casting is just like other forms of casting in that molten metal is forced through the cavity of a pre-shaped mold using pressure. However, the difference with this method is that the metal is heated inside the casting machine rather than a separate machine or furnace.
- Hot chamber die casting is used for the following metals:
- Magnesium alloys
- Other metals with low melting points
- Hot chamber machines work for alloys that don’t erode metal pots, cylinders, and plungers.
Cold Chamber Die Casting
Contrary to what the name may lead you to believe, cold chamber die casting doesn’t actually involve cold metals. This process involves heating metal in a separate furnace and then transferring the newly molten metal into the casting machine.
- A cold chamber machine is beneficial for metals with high melting points (e.g., aluminum).
- This process liquifies metal, then ladles it into a cold chamber.
- In the cold chamber, a plunger – operated by hydraulics – pushes the metal into the die.
Die Casting Vs. Sand Casting
Similar to die casting, sand casting is another popular metal fabrication method that involves pouring molten metal into a mold. While these processes share a common goal, their individual machinations drastically differ.
Die casting is far and away the quickest way to produce precise non-ferrous metal parts, partially because it uses high pressure. When metal solidifies after cooling, it is removed from the mold, possibly sanded or polished, and then it’s done. The mold is then immediately reclosed and prepared for another pour.
Conversely, sand casting requires a new sand mold for each casting and doesn’t utilize any high pressure. Depending on the complexity of the mold, it can take hours, if not days to make a new mold. While it is lower cost and requires far less equipment to produce a sand mold, this process incurs far more downtime so it’s better suited for casting a lower quantity of parts.
What Metals Are the Most Popular Options for Die Casting?
When starting a die casting project, there are a number of metals and alloys that can be used. Each of the alloys has unique physical characteristics that have benefits for different applications.
It can be tricky to understand all of the mechanical properties, physical properties, and the compositions of different alloys, so it’s always a good idea to speak with an experienced metal fabrication company. The most commonly used die-cast metals are as follows:
Options such as brass, copper, lead, and tin are used as well, but more for custom die casting jobs due to their specialty status.
Metal die-cast parts incorporate several alloys – which are mixed elements – but choosing the ideal one necessitates plenty of consideration. It’s best to be strategic about alloys because each one has unique properties, advantages, and disadvantages.
Aluminum Die Casting
Aluminum is one of the most popular metals used in die casting. Aluminum is a very lightweight metal, so it’s great for creating lightweight parts without sacrificing strength. Aluminum parts can also withstand higher operating temperatures and have more finishing options.
Despite being pricier options, aluminum and aluminum-zinc alloys are definitely worth the cost in industrial applications. They are incredibly corrosion-resistant materials that contribute to an extended lifespan and improved safety. Furthermore, the strength, hardness, and weight ratios are unparalleled.
Another clear advantage of aluminum is that – plainly – it’s easy to cast. Its electrical and thermal conductivity properties are optimal. These characteristics make aluminum an excellent option in the production of components for computing, energy management, and other tech fields.
Because of these many benefits, aluminum is very popular in the production of things like industrial components, automobile parts, tech products, aerospace products, and much more.
Zinc Die Casting
In addition to aluminum, zinc is another very popular metal used in die casting. Zinc is typically used for casting products for the automotive and medical supply industries.
When items are being customized for aesthetic purposes, zinc castings tend to be the best choice. The material can be plated or painted depending on the need. It also offers a smooth surface to work on. Zinc allows fabricators to produce components capable of custom aesthetic quality as well as strict and narrow tolerances for shapes morphology
Zinc has a low melting point, which means it requires less energy for production. The low melting point also helps to extend the mold life which is another pivotal factor in die casting’s value to medical equipment.
Finally, zinc’s corrosion resistance levels are impressive, and it has heightened thermal conductivity. Thus, this material is durable, hard, and stable.
Magnesium Die Casting
Magnesium is another metal that is commonly used in die casting. Magnesium is the easiest metal to machine, it offers an excellent strength-to-weight ratio, and it is the lightest alloy commonly die cast.
Magnesium alloys have a variety of unique characteristics like excellent fluidity, less susceptibility to hydrogen porosity, and better castability over other cast metals such as aluminum and copper. Magnesium also offers EMI and RFI shielding properties which makes it perfect for connectors and electrical housings.
Magnesium is used in a wide range of applications. Since it’s Aside from connectors and electrical housings, magnesium is also often used to produce medical and laboratory equipment because it provides protection against interfering signals.
Magnesium is also 75% lighter than steel with no significant loss of strength. This makes it a much better material for thin-walled, complex net shape castings. It also offers greater dimensional stability.
Magnesium castings can meet tight tolerances that would be difficult or impossible to achieve with steel.
Does Die Cast Metal Rust?
Ferrous metals such as carbon steel, alloy steel, and stainless steel all can rust because they contain iron. It’s possible to die cast these metals, but due to their propensity to rust, it’s quite uncommon.
Non-ferrous metals, such as aluminum and copper, contain only trace amounts of iron, at most. Therefore, they don’t rust. But they can corrode, a factor that’s primarily dependent on the given working environment.
Additional Benefits of Die Casting
Many of the advantages already discussed are conducive to cost savings in both part prices and overall production expenses. The die casting process also minimizes secondary operations, because casting a part creates intricate net shapes. This often involves external threads and detailed internal features with negligible amounts of draft angles.
Combining multiple parts into one entity removes other assembly operations, thus, reducing labor costs. Lastly, this approach to metal casting offers streamlined stock control and improved component consistency compared to other processes.
Other benefits are as follows:
- Offers the option of thick walls or thin walls.
- Tolerances are tighter.
- Materials aren’t frequently wasted or left unused.
- With zinc and magnesium especially, there’s a long tool life.
Starting A Die Casting Project With TFG USA
Die casting is a thriving facet of the metal fabrication industry. It’s tried, tested, and proven method that is conducive to streamlined, high-quality production. Not only is it a cost-efficient way to produce custom metal parts and components, but also allows you to create complex net shapes and complex internal features.