Die-cast zinc alloy
Traditional die-cast zinc alloys are No. 2, 3, 4, 5, and No. 7 alloys, and No. 3 zinc alloy is the most widely used.
1. Relatively large.
2. Good casting performance, it can die-cast precision parts with complex shapes and thin walls, and the surface of the castings is smooth.
3. Surface treatment can be carried out: electroplating, spraying, painting, polishing, grinding, etc.
4. When melting and die-casting, it does not absorb iron, does not corrode the pressure, and does not stick to the mold.
5. It has good mechanical properties and abrasion resistance at room temperature.
6. Low melting point, melting at 385℃, easy to die-casting.
Zamak 3 aluminum 3.8 ~ 4.3%, copper <0.030%, magnesium 0.035 ~ 0.06%, iron <0.020%, lead <0.003%, cadmium <0.003%, tin <0.001%, zinc remaining
Zinc-aluminum alloy die-casting part with zinc as the main component. The surface of this part has a very dense surface layer, and the inside is an open porous structure,
which is also a lively amphoteric metal. Therefore, only by adopting appropriate pretreatment methods and electroplating processes can the electroplated layer on the zinc alloy have good adhesion and meet the requirements of qualified products.
The zinc alloy materials commonly used for electroplating are mainly composed of aluminum 3.5% to 4.5%, copper 0.75% to 1.25%, magnesium 0.03% to 0.08%,
the balance is zinc, and the sum of impurities is ≤0.2%.
The zinc alloy of 925 grade contains high copper content and is easy to be electroplated. Generally, the density of zinc alloy is 6.4～6.5g/cm3. If the density is less than 6.4g/cm3, blistering and pitting are likely to occur after electroplating. In short, we must strictly control the selection of materials. In addition, the mold must be designed reasonably during die-casting to avoid insurmountable defects (such as pitting) caused by electroplating.