Zinc Alloy Die Casting (ZznAl) ingredients zinc, aluminum, copper, magnesium composition, wherein 95% to 96% zinc, aluminum 3.5% ~ 4.3%, the balance being copper and magnesium, models are more applications to ZznAl4-1 more easily than other models plating.
Plating (or plating) on aluminum exist many difficulties due to the aluminum chemically active, very negative electrochemical potential (E = -1.66V), a high affinity for oxygen, easily oxidized; linear expansion coefficient of aluminum is greater than the general metal (24 × 10-6 / ℃); it is an amphoteric metal, both in the acid labile, complex chemical reaction; coating internal stress, thus the aluminum plating (or plating) success, the key is to solve adhesion problems.
Chemical properties of zinc alloy die casting material and the surface morphology and structure, determine the plating process, the operating skills, even wash in the process, the residence time of the air, there are stringent requirements, otherwise it will affect the plating quality
Casting porosity analysis:
Casting defects, the most frequent is pores. Stomatal characteristics. Has a smooth surface, the casting surface forms can, pinholes or subcutaneously, may also be in the internal cast. (Inner wall casting porosity) were round or oval, have a smooth surface, usually shiny scales, sometimes yellow oil. (Surface pores) bubbles can be found by sandblasting, internal porosity bubble ray or machining may find that the pore bubbles on the X-ray film was black by X.
<1> gas source
(1) alloy was precipitated gas -a b and raw materials related to the smelting process related
(2) die-casting process involved in gas -a and b die casting process parameters related to the structure of the mold
(3) -a gas with release agent decomposition characteristics of the paint itself, b and spraying process related
<2> Raw materials and smelting process produces gas analysis
Liquid aluminum is mainly hydrogen gas, accounting for about 85% of the total amount of gas.
The melting temperature is higher, the higher solubility of hydrogen in liquid aluminum, but the solubility in solid aluminum is very low, so the solidification process, the hydrogen evolution to form pores. Hydrogen Source:
(1) atmospheric water vapor, liquid hydrogen-absorbing metal from the humid air.
Hydrogen content itself 
(2) raw materials, ingots surface moist, charge back dirty oil.
(3) tools, flux wet.
<3> casting process to produce gas analysis
Due to the pressure chamber, gating system, the cavity are vented to the atmosphere, and molten metal is high pressure, high speed filling, if not orderly, steady flow state, the molten metal vortex, will roll into gas.
Die-casting process developed to consider the following questions:
(1) liquid metal within the pouring system can clean, smooth flow, no separation and vortex.
(2) there are no sharp corners or dead zone area exist?
(3) whether there are changes in the gating system cross-sectional area?
(4) The exhaust slots overflow tank in the correct position? It is big enough?
You will be blocked? Gas ability to effectively and smoothly discharged?
A computer simulation of filling process, is to analyze the above phenomenon, in order to make judgments to choose reasonable parameters.
<4> Coatings produce gas analysis
Paint performance: such as sending large gas has a direct impact on the casting porosity.
Spraying: excessive use, resulting in a large amount of volatile gases, lubricants too much punch, or burning, is the source of the gas.
<5> The way to solve the casting porosity
First analyze what causes the stomata, again take the appropriate measures.
(1) dry, clean alloy material.
(2) control the melting temperature to avoid overheating, degassing process.
(3) a reasonable choice of die-casting process parameters, especially the injection speed. Adjust speed switching starting point.
(4) the order in favor of the cavity is filled with a gas discharge, sprue and runner are of sufficient length (> 50mm), in order to facilitate the smooth flow of alloy liquid and gas have the opportunity to discharge. Gate thickness can be varied, gate orientation, setting the overflow tank, exhaust groove is formed at the position of pores. Total relief goods can not be less than 60% cross-sectional area inside the gate cross-sectional area of the sum, or slag poor results.