I. Introduction to the pressure casting process
Pressure casting is the process of injecting molten metal into a mold and forming the desired shape under pressure. Zinc die casting and aluminum die casting are two common types of die casting.
Zinc die casting refers to the process of injecting molten zinc material into a mold and forming a product under pressure, while aluminum die casting refers to injecting molten aluminum material into a mold and forming formation of a product under pressure.
In industrial and civil applications, zinc and aluminum casting products are widely used, such as in automobile parts, building accessories, furniture accessories, etc.
In the following, we will delve into the differences and application scenarios of zinc die casting and aluminum die casting.
II. Zinc alloys and aluminum alloys
Zinc alloys and aluminum alloys are comparable in price, and if the structure and casting process permit, it is more economical to use aluminum alloys.
Given that the specific gravity of zinc alloys is about 2.5 times that of aluminum alloys and the price is similar, the material cost of zinc alloys is two to three times that of aluminum alloys.
Many companies look to replace zinc alloys with aluminum alloys to save costs, but this is not always possible because zinc alloys have much better strength, hardness and moldability.
If your product requires high-quality surface polishing and electroplating, you will have no choice but to use zinc alloys.
Achieving high surface quality with aluminum alloys is challenging due to their inferior casting performance, which often results in many surface pores and poor quality after electroplating.
The performance of zinc alloy die casting is superior, with many advantages.
Zinc alloys have a low melting point, a narrow solidification temperature range, are easy to fill and mold, and are less likely to produce shrinkage holes.
They can cast complex, thin-walled precision parts with smooth surfaces and high dimensional accuracy.
Lower casting temperature extends mold life, prevents sticking and does not corrode the mold.
Furthermore, zinc alloys exhibit higher mechanical properties at room temperature, particularly in terms of compression and wear resistance.
Zinc alloy castings can accept various surface treatments such as electroplating, spraying and painting.
The most serious disadvantage of zinc alloys is aging, which leads to volume expansion, reduced strength and, over time, can result in deformation or even fracture of castings. This is the main reason why the use of zinc alloys is limited.
Aluminum alloys significantly outperform zinc alloys in terms of properties, featuring excellent pressure casting performance, electrical conductivity and thermal conductivity, and decent machinability.
However, they have some notable disadvantages. Aluminum-silicon series alloys are prone to sticking and have a corrosive effect on metal crucibles. They also shrink significantly, which can cause shrinkage holes.
Because they affect molds differently, the prices of molds used for zinc alloy and aluminum alloy die casting also vary.
Zinc alloy die casting is less prone to sticking and does not corrode molds, so molds used for this process tend to be cheaper.
On the other hand, aluminum alloy die casting molds are generally more expensive due to their stickiness and corrosiveness compared to metal crucibles.
III. Zinc Pressure Casting
1. Process Flow
The process flow of zinc die casting mainly includes mold design, alloy melting and casting, injection, molding, cleaning and spraying. The specific process is as follows:
Mold Design: A suitable mold is designed according to the required shape and size.
Alloy melting and casting: The required casting alloy is added to the melting furnace, and after melting, it is poured into the injection machine.
Injection: The molten alloy is injected into the mold and enough pressure is applied to fill the entire mold.
Molding: After the alloy has cooled, the finished product is removed from the mold.
Cleaning: The cooled product is cleaned to remove any remaining substance from the mold.
Spraying: If necessary, a protective layer or color treatment is sprayed on the surface of the product.
2. Application features and scenarios
The advantages of zinc die casting are that it can manufacture products with precise dimensions and shapes, smooth surfaces, high density, high strength and good corrosion resistance. Therefore, zinc die casting is widely used in a variety of application scenarios, such as automobile parts, furniture accessories, mechanical components, clothing accessories, etc.
4. Aluminum Die Casting
1. Process Flow
The aluminum casting process is similar to zinc casting, which mainly includes mold design, alloy casting, injection, molding, cleaning and spraying. The specific process is as follows:
Mold design: Design a suitable mold according to the required shape and size.
Smelting molten alloys: Add the required smelting alloys to the furnace. After melting, pour them into the injection machine.
Injection: Inject the molten alloy into the mold and apply enough pressure to fill the entire mold.
Molding: After the alloy has cooled, remove the product from the mold.
Cleaning: Clean the cooled product to remove residual mold substance.
Spraying: Spray a protective layer or color treatment on the surface of the product as needed.
2. Features and application scenarios
The advantages of aluminum casting are fast molding, good heat transfer performance, light weight and high surface quality. It can produce complex and varied shapes. Aluminum die casting is mainly used in the fields of automobile parts, aviation parts, electronic equipment parts, communication parts, etc.
V. Zinc alloy vs aluminum alloy die casting
- Density is an important indicator of metallic material performance. Compared with common steel, zinc alloys have a lower density under the same strength. Therefore, under equal resistance, zinc alloys can be reduced.
- Hardness: Zinc alloys have lower hardness than common alloys. Therefore, when high hardness is required for pressure castings, zinc alloys must be used.
- Density and melting point: Under the same composition and processing conditions, the lower the density and melting point, the easier the metal will be processed and shaped. The higher the density and melting point, the more difficult the pressing will be. The lower the melting point, the faster it melts under pressure. Therefore, to achieve the same surface roughness requirements for die-cast parts, the melting point of the alloy must be lower.
- Density: Zinc alloys have a lower density and, under the same conditions, it is lower than that of aluminum.
- The composition of an alloy greatly affects its properties. Generally, the higher the aluminum content, the worse the fluidity; the higher the copper content, the better the fluidity; the higher the silicon content, the lower the fluidity.
- Melting point: At the same temperature, zinc alloys are more difficult to melt than aluminum alloys. Zinc alloys have a lower melting point, so castings do not overheat easily and can be molded better.
- Uses: Both aluminum and zinc can be used to produce automotive parts. However, as the price of aluminum is much higher than that of zinc, in general, aluminum is used to produce front bumpers, hoods and engine covers of cars. Zinc is most often used in the rear axle, alternator housing, and car wheels.
- Corrosion resistance: Aluminum alloys have greater corrosion resistance in corrosive media than zinc alloys. But if the aluminum foil is too thick, the aluminum will leak out of the mold and form gas holes. Therefore, before casting, the aluminum sheet must be pretreated.
- Strength: Both aluminum and zinc have high strength, but zinc has greater strength.
- Corrosion resistance: Due to the presence of zinc oxide in aluminum, aluminum alloys have good corrosion resistance in corrosive media and do not corrode.
- Surface quality: Due to the poor surface quality of aluminum, sand molds are generally used for pressure casting molding. However, due to the easy formation of gas holes and low surface roughness in aluminum castings, they are rarely used.
- Machinability: Due to aluminum's poor machinability, it is rarely used to produce machined products.
- Other aspects: The prices of aluminum and zinc alloys are relatively cheap.
SAW. Summary
Through the above analysis, we can conclude that the process flow of zinc smelting and aluminum smelting is similar, but their application scenarios are slightly different.
Zinc die casting is characterized by high density, high strength and good corrosion resistance and is mainly used for automobile parts, furniture accessories, mechanical components, clothing accessories, etc.
Aluminum die casting has the advantages of fast shaping, good heat transfer performance, light weight and high surface quality, and is suitable for automobile parts, aviation parts, electronic equipment parts, communication parts, etc. .
