Testing of high pressure die castings produced with reduced squeeze pin velocity
Abstract
In the high pressure die casting process (HPDC), local squeezing is commonly used in castings, where shrinkage porosities can develop due to different wall thicknesses. Local squeezing is an integrated part of the casting process, but this can be considered an additional operation which occurs after the completion of the mold filling process. Usually, the squeeze pin starts postponed to a specific switching point, which term is called the delay time. Different delay times will cause different results in the microstructure, which is essential to understand reducing the potential rejects that may occur during production.
There are several ways to compare the properties of castings produced with different delay times. Comparisons must be made on a quantitative basis, excluding subjective factors. Such tests may include measurement of density, comparison of tensile strength, and computer tomography (CT) analysis. On the other hand, the examination of the fracture surfaces of the tensile test specimens can be done subjectively in most cases. By the analysis of the micrographs and CT scans in this manner, quantitative comparisons cannot be done, but important observations can be made.
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