High-pressure die casting is an accurate means of producing accurate and precise components. It is fast, and the cast parts are defect-free. The applications of high-pressure die casting are endless, from automotive engine blocks and gearbox lcasings to consumer electronics. However, the alloy used during this operation will determine how smooth it goes and the quality of the final products.
For the best high pressure die casting results, it is crucial to understand the properties of an alloy before using it. This article will be your guide on high-pressure die casting alloys. It will explain the eight common alloys used in high-pressure die casting and key factors to consider when selecting the right one for your project.
What Is High-Pressure Die Casting?
High-pressure die casting is a popular manufacturing technique used across various industries. It is an accurate means of producing high-quality parts with complex shapes and designs. The high-pressure die casting process begins with the preparation of the mold, which is usually made of steel. The mold preparation step involves cleaning and applying a release agent. After that, you melt the chosen metal above its melting point in a furnace for a predetermined time. You then transfer the molten metal into a shot chamber and inject it into the die cavity at a high pressure ranging from 1500 to 25,000 PSI. This high pressure ensures that the liquified material fills the die completely.
After cooling and solidification, eject the final castings from the mold. Inspect and trim off excess material. High-pressure die casting is fast and material efficient. The castings have good mechanical properties and excellent surface finish. However, it comes with a high initial cost, and there is a limit to the part size one can produce.
8 Common Alloys Used in High-Pressure Die Casting
High-pressure die casting is often reserved for non-ferrous alloys because of their compatible physical and mechanical properties. Most non-ferrous alloys have a low melting point and have excellent fluidity. They are easily castable, and the final parts are of a high quality. The following are the most common alloys in the high-pressure die casting process.
- Aluminum Alloys
Aluminum alloys are the most common high-pressure die casting material. They are known for their lightweight and high strength. Aluminum alloys have excellent dimensional stability, and you can use the casted products in demanding applications without fear of deformation over time. Examples of high-pressure die-casting aluminum alloys include A380, A360, and ADC12. They are castable and easy to handle.
Applications: Electronic enclosures, engine blocks, and car wheels.
- Magnesium Alloys
Magnesium alloys such as AZ91D and AM60B are suitable high-pressure die casting materials. Their selling point is their low density and extremely lightweight. They are rigid and impact-resistant. This material’s particular composition varies and depends on the alloy in question. The extra elements are added to reinforce the properties of magnesium. Note that magnesium alloy castings are hardly used as they are. It is essential to apply protective coatings because of their susceptibility to corrosion.
Applications: Automotive dashboards, seat frames, medical implants, and consumer electronics.
- Zinc Alloys
Zinc alloys are another material you can use for high-pressure die casting. Zinc alloys have a low melting point and excellent fluidity. When in the liquid state, zinc alloys move freely and fill up all corners of the mold cavity. Furthermore, zinc alloys stand out because of their high ductility and easy machinability. These alloys, including Zamak 3, Zamak 5, and ZA- 27, offer exceptional strength and hardness. They have low energy requirements and cut down manufacturing costs.
Applications: Bushings and bearings, household appliances, and building hardware.
- Copper Alloys
You can also use copper alloys in the form of bronze and brass for high-pressure die casting operations. Copper alloys come with a high mechanical strength and superior wear resistance. This property makes them useful in high-stress and heavy-load applications. Furthermore, high-pressure die-casted copper alloy products have good biofouling resistance. They prevent the attachment and growth of microorganisms on their surface.
Applications: Electrical connectors, industrial machine components, and jewellery making.
- Lead Alloys
Part manufacturers extensively use high-pressure die casting when processing lead alloys. Lead alloys have a low melting point and are easy to shape into complex structures. Additionally, they are highly corrosion resistant and casted parts are useful in acidic environments. Furthermore, the high thermal conductivity of lead alloys makes them stand out. They dissipate heat readily and prevent explosions in high-temperature applications.
Applications: Plumbing fixtures and building construction.
- Tin Alloys
Tin alloys are food-grade materials used with high-pressure die casting. This alloy is non-toxic and safe for medical applications. Lead is the primary element alloyed with tin. The percentage of lead varies and is usually between 30-40%. This mixture allows you to maximise the benefits of tin and lead. Tin reduces the melting point and improves the flow rate of lead. Conversely, lead is corrosion-resistant and relatively more affordable.
Applications: Food processing machines, medical equipment, and jewellery.
- Silicon Alloys
Another crucial high-pressure die casting material available for everyday use is silicon alloys. Silicon is usually combined with other elements such as aluminum, copper, and magnesium. Of all grades of silicon alloys available, the most compatible with high-pressure die casting operations are AlSi9Cu3 and AlSi10Mg. They are thermally stable and can withstand the high temperature of high-pressure die casting. Additionally, silicon’s fluidity makes the alloys easy to cast.
Applications: Engine blocks, structural components, and architectural uses.
- Nickel Alloys
You can also use nickel alloys in high-pressure die casting. These alloys, including inconel and monel, have a high strength and will not deform under mechanical stress. Additionally, nickel alloys have good heat conductivity and low thermal expansion. Furthermore, nickel alloys are popular because of their excellent corrosion and oxidation resistance. They form a protective layer when exposed to corrosive environments.
Applications: Marine components, car parts, and heat exchangers.
Factors to Consider When Selecting High-Pressure Die Casting Alloy
Choosing the correct high-pressure die casting alloy is important as it will determine the success of the process. It would help if you considered some factors to simplify the selection process. Let’s look at some of these factors
- Mechanical Properties
A key factor to consider when selecting metal alloys for high-pressure die casting is the mechanical properties. These include tensile strength, yield strength, and hardness. The alloy must have the required strength and toughness to suit where the final part would be used. It would be best to consider ductility and fatigue resistance to ensure long-term durability.
- Surface Finish
The desired surface finish one wants to achieve is another factor to consider. Some alloys naturally produce castings with smooth surfaces and should be used in applications where physical appearance is essential. You should also check how amenable the alloys are to surface finishing techniques such as plating and anodizing. Regarding surface finish, it is crucial to assess susceptibility to porosity as it will impact quality.
- Thermal Properties
You should also consider the thermal properties and how the alloys behave in a high-temperature environment. Consider going for alloys with low melting point for easy castability. Thermal conductivity, thermal expansion, and heat resistance also come under thermal properties. The right alloy must have the needed thermal conductivity with a low coefficient of thermal expansion. It should be dimensionally stable after being exposed to extreme temperatures.
- Die Compatibility
It is essential to check the alloy’s and die’s compatibility to ensure a successful casting operation. Alloys not corrosion protective may react with the die and cause degradation. In this scenario, you must apply protective coatings on the die to serve as a barrier. Furthermore, you should also assess the flow behaviour of the alloy. It must work well with the pressure you want to use.
- Machinability
Most of the time, high-pressure die casted parts must be further processed using techniques like CNC machining before they can be used. In cases like this, you have to factor in the machinability properties of the alloy. The alloy should be easy to cut at a fast speed without wearing out the tools. Additionally, the chip’s production rate must be minimal and manageable.
- Cost
The cost of the alloy will determine the price of the casted products that will be sold. Always choose a cost-effective material in high-pressure die casting without sacrificing quality. The material cost includes the initial investment you would make. It also covers energy expenses and how easy it is to process the alloy. Additionally, go for highly recyclable materials as they reduce costs in the long run.
Conclusion
The alloy you use for metal casting will determine how smoothly the operation will go. It will also affect the quality of the final products. High-pressure die casting is usually reserved for non-ferrous metal alloys such as aluminum, zinc, and copper. They have a low melting point and will consume minimal energy. When selecting the right high-pressure die casting alloy for your project, you have to consider its mechanical and thermal properties. You should also factor in cost, die compatibility, and ease of machining.