Aluminium products are widely used in industries such as construction, transportation, and consumer goods. The lightweight and corrosion-resistant properties of aluminium make it an ideal material for manufacturing products such as car parts, aircraft components, packaging materials, and electronics. The versatile nature of aluminium allows it to be shaped and formed into various shapes and configurations, providing designers and engineers with flexibility in design and manufacturing.

Some knowledge about die-casting

 What, the aluminum die-casting hole processing, can not exceed 0.25mm?

 In order to fit for die casting, humans add a lot of silicon (si) to the aluminum alloy used for die casting. When the aluminum alloy condenses in the mold, these silicon, will float to the surface, forming a thin layer of silicon film. This layer of silicon film, the hardness is very hard, very wear-resistant. Some OEM designers, they take advantage of this feature. Count the inner surface of the die casting directly as bearing surface. This silicon surface layer is generally only 0.2 to 0.9mm thick. Too much processing, the life of the bearing surface will be shortened.

 Why is my aluminum die-casting piece, when polished, will have black spots? There are several reasons for this reason. It is possible that silicon oxide, or the formation of alumina. The solution is very simple, using fresh aluminum ingots. However, the biggest possibility is from the release agent. Maybe, we spray too much release agent. It is also possible that the organic matter content of the release agent is too high. At the temperature of hot molten aluminum, some are reduced to carbon and some become organic macropolymers. The mixture of these carbon molecules and polymers, when the aluminum cast forms, is included in the surface layer, becoming the black spots we see. We can reduce the concentration of spraying agent, switch to another spraying agent, or, lengthen the blowing time after spraying. To reduce the formation of carbon elements, and prevent the accumulation of macromolecular polymer. Another usual practice is this. De-wash with degaser. Zinc alloy die casting is currently widely used in a variety of decoration, such as furniture accessories, architectural decoration, bathroom accessories, lighting parts, toys, tie clip, belt buckle, all kinds of metal buckle, etc., so the surface quality of the casting is high, and requires good surface treatment performance. The most common defect of zinc alloy die castings is surface foaming.

Defect characterization: the surface of the die casting blister, found, polished or processed, oil injection or plating. Cause:

1.  Hole cause: mainly is the stoma and the contraction mechanism, the stoma is often round, and the contraction is mostly irregular shape.

1. Cause of pores: a in the process of filling and solidification of metal liquid, the gas intrusion produces holes in the surface or interior of the casting. b Gas gas out from the paint. The air content of c alloy liquid is too high and precipitated during solidification. When the gas in the type cavity, the gas emitted by the paint, the gas precipitated by the alloy solidification, the final air hole formed in the casting when the mold exhaust is bad.
2. The cause of shrinkage hole: in the process of a metal fluid solidification, the shrinkage hole occurs due to the volume reduction or the lack of metal fluid shrinkage in the final solidification part. b Uneven thickness of the casting or casting is locally overheated, resulting in slow solidification of a certain part and the formation of concave surface during volume shrinkage. Due to the existence of pores and shrinkage holes, the die casting may enter the water. When painting and electroplating and baking, the gas in the hole is heated and expanded, or the water in the hole will become vapor and the volume expands, resulting in the surface foaming of the casting.

2.  Intercrystalline corrosion caused by: Harmful impurities in zinc alloy composition: lead, cadmium and tin will gather at the grain junction, leading to intercrystalline corrosion, the metal matrix is broken due to intercrystalline corrosion, and electroplating accelerates this disaster, and the intercrystalline corrosion will expand and top the coating, resulting in surface foaming of the casting. Especially in the wet environment, the intercrystalline corrosion will make the casting deformation, cracking, and even broken.
3.  Crack causes: water grain, cold separation grain, heat crack.

Water pattern and cold separation pattern: in the process of filling the metal liquid, the contact wall of the metal liquid entered first solidifies prematurely, and then the metal liquid cannot be fused with the solidified metal layer, forming overlapping lines at the butt point on the surface of the casting, with strip defects,  The water pattern is generally shallow on the casting surface; and the cold partition pattern may penetrate into the interior of the casting.

heating crack:

A: When the thickness of the casting is uneven, the solidification process produces stress;

B: Early roof out, insufficient metal strength;

C: Uneven force during jacking out

D: Too much high mode temperature makes the grain coarse;

E: The presence of harmful impurities. The above factors may produce cracks.

When there are water lines, cold separation lines and thermal cracks in the die casting, the solution will penetrate into the cracks during electroplating, convert into steam during baking, and the air pressure tops the electroplating layer to form foaming. Defect solution: Control pores, the key is to reduce the amount of gas mixed in the casting, the ideal metal flow should be accelerated by the nozzle through the cone and pouring into the cavity, forming a smooth and the direction of the metal flow, using cone flow design, the flow should be accelerated by the nozzle to the inner gate gradually reduced, can achieve this goal. In the filling system, mixed gas is due to turbulence and metal liquid mixing and forming pores, from the metal liquid into the casting system into the simulation of die casting process, obviously in the sharp transition and increasing channel cross-sectional area, will make the metal flow turbulence and gas, smooth metal liquid is conducive to gas from the channel and cavity into the overflow tank and exhaust tank, discharge die. For the shrink hole: to make the die-casting solidification process of each part as far as possible, uniform heat dissipation, at the same time, solidification. Reasonable water design, inner gate thickness and position, mold design, mold temperature control and cooling can avoid the shrinkage hole. For intercrystalline corrosion phenomenon: mainly to control the content of harmful impurities in alloy raw materials, especially lead less than 0.003%. Pay attention to the impurities brought about by the waste material. For water lines and cold separation lines, it can improve the mold temperature, increase the speed of the inner pouring gate, or increase the overflow groove in the cold separation area to reduce the occurrence of cold separation lines. For hot cracks: do not change the thickness of the die casting sharply to reduce the stress generation; adjust the relevant die casting process parameters; reduce the die temperature.