Zinc alloy connector

Part name
Zinc alloy connector
Material
Zinc
weight
45g
Tolerance standard
ISO 2768-mk
Production equipment
60 Die Casting Machine
Surface finish
Sandblast
Production place
Guangdong, China
service
OEM
Process route
Die casting-deburring-CNC-Sandblast
Application field
EV car，car, automobile, auto

With the rapid development of new energy vehicles to intelligent driving, all new energy vehicles need countless sensing devices inside, and all sensing devices need countless connectors to connect. The structure of electronic connectors for automobiles is complex, and the accuracy and the The requirements for tightness, stability and service life are higher. Traditional hot-chamber zinc alloy die-casting cannot meet these high standards. Multi-slider high-speed zinc alloy connector die-casting products have been widely used in new energy vehicles such as Volkswagen, GAC and BYD.

What causes the blistering of zinc alloy die castings?
1, the hole causes:
is mainly the stomata and contraction mechanism. The stomata are often round, and the contraction is mostly irregular.
(1) Causes of stomata:
A. In the process of filling and solidification of molten metal, due to gas intrusion, holes are formed on the surface or inside of the casting.
B. The intrusion of gas from the paint.
C. The alloy liquid contains too much gas and precipitates during solidification.
When the gas in the cavity, the gas volatilized by the paint, and the gas precipitated by the solidification of the alloy, when the mold is poorly vented, the pores formed in the casting are finally left.
(2) Causes of shrinkage:
A. In the process of molten metal solidification, shrinkage cavities occur due to the reduction in volume or the failure of the final solidified part to be fed by the molten metal.
B. Castings with uneven thickness or local overheating of castings cause a certain part to solidify slowly, and the surface will form a recess when the volume shrinks. Due to the existence of pores and shrinkage holes, the holes may enter water during surface treatment of die castings. When painting and electroplating are carried out after baking, the gas in the holes will be heated and expanded; or the water in the holes will become steam and expand in volume. This results in blistering on the surface of the casting.
2. Intergranular corrosion: harmful impurities in zinc alloy components: lead, cadmium, and tin will gather at the grain boundary to cause intergranular corrosion. The metal matrix is broken due to intergranular corrosion, and electroplating accelerates this scourge. The intermittently corroded parts will expand and lift up the coating, causing blistering on the surface of the casting. Especially in a humid environment, intergranular corrosion can cause the casting to deform, crack, or even break.
3. Cracks cause: water lines, cold barrier lines, and hot cracks.
(1) Water pattern and cold barrier pattern: During the filling process of the molten metal, the molten metal that enters first contacts the mold wall to solidify prematurely, and then the molten metal cannot be fused with the solidified metal layer, forming at the butt of the casting surface Moiré, striped defects appear. The water mark is generally in the shallow layer on the surface of the casting; while the cold barrier may penetrate into the inside of the casting.
(2) Hot crack:
A. When the thickness of the casting is uneven, stress is generated during the solidification process;
B. Ejected prematurely, the metal strength is not enough;
C. Uneven force when ejected;
D. Excessive mold temperature makes the crystal grains coarse;
E. Harmful impurities are present.
The above factors may cause cracks. When there are water marks, cold barrier marks, and hot cracks in the die casting, the solution will penetrate into the cracks during electroplating, and it will be converted into steam during baking, and the pressure will lift the electroplated layer to form blisters.
How to solve the defects of zinc alloy die castings?
1. Control the generation of stomata:
The key is to reduce the amount of gas mixed into the casting. The ideal metal flow should continue to accelerate from the nozzle through the split cone and runner into the cavity to form a smooth and consistent metal flow. The tapered runner design is used, that is, pouring. The flow should be gradually reduced from the nozzle to the gate at an accelerating rate to achieve this goal. In the filling system, the mixed gas forms pores due to the mixing of turbulent flow and the liquid phase of the metal. From the study of the simulated die-casting process in which the molten metal enters the cavity from the casting system, it is obvious that the sharp transition position and the incremental casting in the runner The cross-sectional area of the channel will cause the molten metal flow to appear turbulent and entrain gas, and the stable molten metal is conducive to the gas entering the overflow groove and the exhaust groove from the runner and the cavity, and is discharged out of the mold.
2. For shrinkage holes:
During the solidification process of die-casting, all parts shall be as uniform as possible to dissipate heat at the same time and solidify at the same time. Reasonable nozzle design, inner gate thickness and position, mold design, mold temperature control and cooling can be used to avoid shrinkage. For the phenomenon of intergranular corrosion: mainly to control the content of harmful impurities in the alloy raw materials, especially lead <0.003%. Pay attention to the impurity elements brought by the waste.
3. For water pattern and cold partition pattern:
can increase the mold temperature, increase the speed of the inner gate, or increase the overflow groove in the cold partition area to reduce the appearance of cold partition lines.
4. For thermal cracking:
The thickness of the die-casting parts should not change sharply to reduce stress; adjust the relevant die-casting process parameters; reduce the mold temperature.