Zinc alloys are mainly composed of zinc and aluminum. They are amphoteric metals, have poor chemical stability and are easy to handle in air, so they must be electroplated or plated. Zinc alloys are easy to die-cast, with low material cost and low processing cost. As long as the workpiece is not under too much pressure and the shape is complex, zinc alloys are often used to replace metal materials such as copper and iron.

Quality Control of Surface Condition of Zinc Alloy Die Castings

Workpiece geometry design

 When designing the geometry of zinc alloy castings, structures such as blind holes and deep grooves should be avoided as much as possible. Therefore, drainage process holes need to be left to facilitate the flow of solutions and gases without affecting the appearance and the site of use. In this way, not only can the plating be performed well, but also the degree of contamination of the plating solution can be reduced.

Die design and die casting process of die casting parts

The surface of the zinc alloy die casting is a dense layer with a thickness of about 0.1 mm, and the interior is a loose porous structure. During the mold design and die casting process, try to make the workpiece surface as smooth as possible to reduce casting defects such as cracks, pores, cold insulation gaps, flashes and burrs. Therefore, mechanical cleaning is necessary. At this time, damage to the surface dense layer should be avoided, so as not to expose the porous substrate, causing plating difficulties and affecting the plating quality. Release agents are commonly used in zinc alloy die casting. Attention should be paid to the use and removal of release agents, which are one of the factors that affect paint adhesion.

Material selection for workpiece

Commonly used zinc alloy materials for electroplating are 2znal43, 2ZnAl43, 2znal40.5 and 2ZnAl43. The most commonly used brands are znal25 znal903, but znal903 is better than znal925.

In addition, in the die casting process, the proportion of partially recycled materials should be controlled at 15%, preferably not more than 20%. Since other (such as silicon) components are easily doped into the recycled material, the adhesion of the coating can be affected. If castings from more recycled materials are used, activation is best used for electroplating.

Advantages of using a mold temperature machine in the die casting process

In the die casting process, the use of a mold temperature machine often brings many advantages:

• Extend the service life of the mold

• The heat distribution of the mold is more uniform, which can prolong the service life of the mold;

• Uniform and smooth preheating of the mold, eliminating stress cracks - flame preheating the mold, so local overheating or interstitial water cooling thermal shock is often caused, causing local internal stress, and thermal machine preheating is used to overcome this;

• The mold cost is in good condition, and the number of maintenance will be reduced;

• Reduce the amount of release agent;

• Stable casting quality can reduce inspection frequency and inspection cost;

• Shorten the warm-up time;

• The mold temperature is constant, under the process requirements, the liquid metal is not easy to adhere to the mold;

• The temperature is uniform, and the wear of the mold parts is small;

• With heat transfer oil, the cooling channel will not rust and scale, and water cooling will easily cause the channel to rust and block.

Conclusion

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