The advantages of die casting include the excellent dimensional accuracy of the castings. This usually depends on the casting material, with a typical value of 0.1 mm for the initial 2.5 cm size and 0.002 mm for each additional 1 cm. Compared with other casting processes, its casting surface is smooth and the corner radius is about 1-2.5 microns. Compared to the sand box or permanent mold casting method, castings with a wall thickness of about 0.75 mm can be manufactured. It can directly cast internal structures such as wire sleeves, heating elements and high-strength bearing surfaces. Other advantages include the reduction or avoidance of secondary processing, fast production speed, casting tensile strength up to 415 MPa, and the ability to cast high-flow metals.

The disadvantage of die casting is the high cost. Casting equipment, molds, and mold-related parts are expensive compared to other casting methods. Therefore, when manufacturing die castings, it is more economical to produce a large number of products. Other disadvantages include: this process is only suitable for high-flow metals, and the casting quality must be between 30g and 10kg. In the usual die casting, the latter batch of castings will always have holes. Heat treatment or welding is not possible because the gases in the gap expand under the action of heat, causing internal microdefects and surface peeling.

What are the problems in the zinc alloy die casting process? When the impurity elements lead, cadmium and tin in the alloy composition exceed the standard, the casting will undergo aging deformation, manifested as volume expansion, mechanical properties, especially plasticity decreased significantly, long-term use or even cracking. Lead, tin and cadmium have little solubility in zinc alloy, concentrated in grain boundaries to become cathodes, aluminum-rich solid solutions to become anodes, and promote intergranular electrochemical corrosion in the presence of water vapor (electrolyte). Die castings age due to intergranular corrosion.

Comparison of different die-casting zinc alloy processes:

1. Gas stove production process

The use of high-purity zinc liquid as the raw material for alloy production, the use of gas stove to avoid the phenomenon of iron increase due to mixer melting. In order to control the weight of the alloy ingot within 0.3 kg, graphite cone flow control technology is adopted. The process flow is simple and the production cost is low. However, the disadvantage of gas stoves is that the direct output is low, and the mechanical stirring makes the alloy liquid composition uniform.

2. Electric furnace production process

The zinc is melted and slagged by a high-power power frequency core furnace, and then the zinc liquid flows out of the furnace mouth, and then flows into the coreless furnace to melt the alloying elements to form the alloy liquid. The alloy liquid is poured out by the tipping device, flows through the chute into the holding furnace, is scooped out with a mechanical spoon, and then injected into the zinc mold. The defect of the zinc die casting process is that a large amount of dross is generated during the tipping process from a coreless furnace to a resistive furnace. The crawling vibration of the linear ingot casting machine is not good for the surface quality of the alloy ingot. At the same time, the energy consumption is high.