What are zinc and aluminum?
The casting industry mainly involves aluminum and zinc alloy casting. In recent years, this technology has been widely applied. Understanding the differences between zinc and aluminum is crucial for selecting the appropriate materials for specific purposes and optimizing their usage.
What is zinc alloy?
Zinc alloy refers to a metal alloy mainly composed of zinc and other metal elements. Common elements used in zinc alloys include aluminum, magnesium, copper, cadmium, lead, titanium, and other low-temperature zinc alloys. Zinc alloys are obtained by melting the components and using casting or other pressure forming methods to achieve the desired material form.
The characteristics of zinc alloy
It has excellent casting properties, enabling the production of complex and thin-walled precision parts with a smooth surface.
It offers surface treatment options such as electroplating, spraying, painting, polishing and grinding.
During the melting and die-casting processes, it does not absorb iron, is resistant to pressure corrosion, and does not adhere to the mold.
It has good mechanical properties and provides wear resistance at ambient temperatures.
It has a low melting point of 385℃, making it convenient for die-casting.
What is aluminum alloy?
Aluminum alloy refers to a category of alloys based on aluminum. It contains various main alloying elements, such as copper, silicon, magnesium, zinc and manganese, as well as secondary alloying elements, such as nickel, iron, titanium, chromium and lithium.
The characteristics of aluminum alloy
Its lightweight nature makes it an ideal choice in industries that require weight reduction.
Excellent thermal conductivity.
Environmentally friendly composition.
Low-temperature resistance.
Good mechanical properties, physical characteristics and corrosion resistance can be achieved through heat treatment.
High strength characteristics.
Differences Between Zinc And Aluminum Alloy
Material
Zinc alloy material has a significant specific gravity and exhibits excellent casting performance. It boasts high density and strength, comparable to or even surpassing that of high-quality steel. As a result, zinc alloy die casting parts typically weigh more than aluminum alloy die casting parts.
Property
The zinc alloy material exhibits a low melting point, favorable mechanical properties, and wear resistance. It is also suitable for surface treatment applications. On the other hand, aluminum alloy demonstrates excellent electrical conductivity, thermal conductivity, and corrosion resistance.
Surface Finishing
Zinc castings exhibit a smoother and more patterned surface after casting, as they don't have pores. In contrast, aluminum castings can develop pores, pits, and blisters during casting, necessitating compensatory surface finishing.
Weight
In terms of weight, zinc alloy is generally denser and heavier than aluminum.Pure zinc has a specific density of 5g/cm3, while aluminum has a lower density of 2.7g/cm3. This higher density contributes to zinc alloys' superior impact resistance compared to aluminum parts, making them a preferred material for manufacturing castings intended for structural applications.
Die casting process
Zinc alloy die casting commonly employs a hot chamber die casting machine. The zinc alloy is melted within this machine, enabling faster cycle times.In contrast, aluminum alloy die casting utilizes a cold chamber die casting machine. The aluminum alloy is melted outside the machine and then poured into the injection machine. This process takes longer compared to hot chamber die casting.
Tooling Life
The molds employed in zinc die casting don't require high tensile strength due to the material's less abrasive nature and low melting point. These properties result in reduced mold damage and lower tooling costs. Consequently, molds used in zinc casting can withstand over 1,000,000 shots before requiring replacement, whereas molds used in aluminum casting typically last around 100,000 shots.
Costs
The cost of die casting production is affected by various factors, including material choice, production process, operator skill, cycle time, and surface finishing. Zinc die castings made from zinc alloys are less expensive but have lower strength and corrosion resistance compared to aluminum alloys. Aluminum die castings are stronger and more corrosion-resistant but come at a higher cost.Also, surface finishing, such as painting or plating, adds to the overall cost. Generally, zinc die castings are more cost-effective than aluminum die castings.
Cycle Time
Zinc die casting occurs at a high pressure and low melting point, distinguishing it from aluminum die casting. Consequently, zinc die casting exhibits a shorter cycle time, typically 150-200% faster than aluminum casting.
Additionally, the heating process for zinc die casting occurs internally, unlike aluminum die casting, which employs the cold chamber process. Furthermore, zinc casting's efficient heat dissipation enables faster solidification of the molten metal, contributing to a further reduction in cycle time.
Melting Point
Zinc has a lower melting point (around 420°C) than aluminum. The melting point is a crucial factor in die casting, influencing the choice of the casting process. Zinc's lower melting point makes it compatible with the hot chamber process.
This characteristic offers advantages such as reduced production costs, improved production efficiency, and a lower risk of mold degradation. Conversely, aluminum has a higher melting point (around 660°C), making it suitable for the cold chamber process.
When and Why You Should Choose Zinc Die Casting
When faced with the dilemma of choosing between zinc die casting and aluminum die casting, consider the following factors that make zinc die casting the preferred option
Parts with Thin Walls
Zinc die casting is well-suited for producing parts with thin walls due to its strength compared to other materials. The dense nature of zinc ensures structural integrity and stability, reducing material usage and die-casting costs.
01
Harsh Environmental Conditions
Zinc die casting excels in harsh environmental conditions, particularly those prone to corrosion. Its exceptional corrosion resistance forms a protective layer on the parts when exposed to such conditions.
02
Lesser Residual Stress
Die casting involves applying pressure to inject molten metal into the die. High-pressure die casting can lead to residual stress on parts, but zinc die casting, which utilizes low-pressure die casting, minimizes residual stress.
03
Die cast mold
Choosing zinc die casting is advantageous if you are working with delicate die casting molds. Zinc die casting molds can last approximately ten times longer than aluminum die-casting molds.
04
Faster Production
Zinc alloys have a low melting point, enabling a hot chamber die-casting process with high-pressure injection. Unlike in aluminum die casting where the operator melts the aluminum outside the machine before pouring it into the injection machine, in zinc die casting, the zinc is melted within the machine
05
Why and When Choose Aluminum Die Casting
When faced with the decision between aluminum vs zinc die casting parts, there are certain conditions where aluminum die casting should be given preference. Consider the following factors:
Strength-to-weight ratio
If you're seeking lightweight and high tensile strength properties, it's advisable to consider aluminum die casted parts. These parts are well-known for their ability to offer both characteristics. Notably, the aerospace industry widely utilizes die cast parts made from aluminum due to their lightweight nature.
High operating temperatures
Due to their high melting point and ability to withstand high temperatures, aluminum die castings are the favored option for applications that involve elevated operating temperatures, such as in metallurgical processes. This characteristic ensures that the structural and physical properties of the castings remain intact even when exposed to extreme heat.
Electrical conductivity
Due to their excellent electrical conductivity, aluminum die castings are the preferred choice for various electronic components in die casting. This is particularly important in applications such as EMI shielding, where parts must be protected from electromagnetic signals.
FAQs
Are zinc die casts stronger than aluminum die castings?
Zinc die casting parts exhibit greater strength compared to aluminum die casting. Experts assert that zinc die casting surpasses several common non-ferrous alloys in strength. Zinc alloys are reported to be 2.5 times stronger than aluminum die casting.
What are the parameters that differentiate aluminum and zinc castings?
The weight, corrosion resistance, melting point, and thermal conductivity distinguish the two castings. Zinc casting is characterized by its higher weight, lower melting point, superior corrosion resistance, and better thermal conductivity compared to the others.
Which is more corrosion-resistant: zinc or aluminum?
Aluminum die casting parts exhibit lower corrosion resistance than zinc casting, although this may vary depending on the pH level. For instance, in alkaline solutions with a pH of 11, the corrosion resistance of aluminum casting is equivalent to that of zinc.