Although die casting technology has many advantages, zinc alloy die casting is not perfect. There are often air holes on the surface of die castings. Gas expansion in the pore at high temperature will cause air bubbles in die castings, which seriously affects the appearance of die castings and reduces the overall quality of zinc alloy die castings.
Therefore, die castings usually cannot be heat treated and welded, nor can they work at high temperatures.
The specific gravity of zinc alloy is about 2.6 times that of aluminium alloy, but the quotation is suitable. Therefore, from the material cost point of view, zinc alloy die castings are two to three times more expensive than aluminium alloy die castings.
At present, in order to save cost, many companies want to replace zinc alloy die castings with aluminium alloy, but because the strength, hardness and formability of zinc alloy are better than aluminium alloy, some characteristics can not be replaced.
Quality standard is the life of the company, the center of improving the competitiveness of the company, and the important condition of improving the economic efficiency of the company.
Therefore, improving the quality of zinc alloy die castings is not only conducive to the economic benefits of die casting enterprises, but also conducive to reducing the social benefits of capital waste.
Zinc alloys are alloys based on zinc with other elements added. Aluminum, copper, magnesium, cadmium, lead, titanium and other low-temperature zinc alloys are commonly added.
Zinc alloy has low melting point, good fluidity, easy melting, brazing and plastic processing, corrosion resistance in the atmosphere, easy recovery and remelting of residual materials, but low creep strength, easy to change size due to natural aging.
Aluminum alloy is the general name of the alloy based on aluminium. The main alloying elements are copper, silicon, magnesium, zinc and manganese, while the minor alloying elements are nickel, iron, titanium, chromium and lithium.
Aluminum alloy is one of the most widely used non-ferrous metal structural materials in industry. It has been widely used in aviation, aerospace, automobile, machinery manufacturing, shipping and chemical industry.
The proportion of zinc alloy is about 2.5 times that of aluminium alloy, and the price is the same, so the cost of material is two or three times higher than that of aluminium alloy.
Nowadays, in order to save cost, many enterprises want to replace zinc alloy with aluminium alloy, but some can not be replaced, because the strength, hardness and formability of zinc alloy are much better than aluminium alloy.
The following considerations should be taken into account in the formulation of zinc alloy die casting process
1. Whether the liquid metal can flow cleanly and smoothly in the pouring system will not produce separation and eddy current.
2. Are there any sharp corners or dead zones?
3. Whether there is a change in the cross-sectional area of the gating system.
4. Is the location of exhaust and overflow grooves correct? Is it large enough? Will it be blocked? Can the gas be discharged effectively and smoothly? Computer simulation of filling process is to analyze the above phenomena and select reasonable process parameters for judgment.