The solution to 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 be continuously accelerated from the nozzle through the shunt cone and the runner into the cavity to form a smooth and consistent metal flow. The design of the runner, that is, the pouring flow should be gradually reduced from the nozzle to the inner gate at an accelerated rate, which can achieve this purpose. In the filling system, the mixed gas is due to the mixing of turbulent flow with the metal liquid phase to form pores. From the study of the simulated die-casting process in which the metal liquid enters the cavity from the casting system, it is obvious that the sharp transition in the runner and the incremental pouring The cross-sectional area of the runner will cause the molten metal to flow turbulently and entrain the gas. The stable molten metal is conducive to the gas entering the overflow groove and the exhaust groove from the runner and the cavity, and then being discharged out of the mold.
2. For the shrinkage cavity: in the process of die-casting solidification, all parts of the die-casting solidification process should be uniformly dissipated as much as possible at the same time, and solidified at the same time. Shrinkage cavities can be avoided through reasonable nozzle design, gate thickness and position, mold design, mold temperature control and cooling. For intergranular corrosion phenomenon: mainly control the content of harmful impurities in alloy raw materials, especially lead <0.003%. Pay attention to the impurity elements brought by the waste.
3. For water marks and cold separation lines: increase the temperature of the mold, increase the speed of the inner gate, or increase the overflow groove in the cold separation area to reduce the appearance of cold separation lines.
4. For hot cracks: the thickness of die castings should not be changed sharply to reduce stress; the relevant die casting process parameters should be adjusted; the mold temperature should be reduced.
