The Characteristics Of Zinc-base Alloy And The Problems That Should Be Paid Attention To In Use
Ⅰ.Characteristics of zinc-based alloys
1. It's more important than that.
2. Good casting performance, it can die-cast the precision parts with complex shape and thin wall, and the casting surface is smooth.
3. Surface treatment: electroplating, spraying and painting.
4. No iron absorption, no corrosion, no mold adhesion during melting and die casting.
5. Good mechanical properties and wear resistance at room temperature.
6. Low melting point, melting at 385℃, easy die casting.
Ⅱ.Problems to be paid attention to during use:
1. Poor corrosion resistance. When the impurity elements of lead, cadmium and tin exceed the standard in the alloy composition, the casting aging and deformation will occur, which is manifested as volume expansion, mechanical properties, especially plasticity, significantly decreased, and the time is long and even broken.
The solubility of lead, tin and cadmium in zinc-based alloys is very small, so they concentrate on the grain boundary and become the cathode, and the aluminum-rich solid solution becomes the anode, which promotes the intercrystalline electrochemical corrosion in the presence of water vapor (electrolyte). Die casting is aged by intergranular corrosion.
The structure of zinc-based alloy is mainly composed of zinc-rich solid solution containing Al and Cu and zinc-rich solid solution containing Zn. However, due to the rapid solidification rate of die casting, the solubility of the solid solution is greatly saturated at room temperature.After a certain period of time, this phenomenon of oversaturation will be gradually removed, resulting in a slight change in casting shape and size.
3.Zinc-based alloy die castings are not suitable for high and low temperature (below 0℃) working environment.Zinc-based alloys have better mechanical properties at room temperature. However, the tensile strength and impact performance at high temperature and low temperature decrease significantly.