Improved ejection test for evaluation of soldering tendency of cast alloy to die core materials

Abstract

© 2018 Elsevier B.V. Cast alloy soldering is a serious issue of a modern high pressure die casting (HPDC) industry. It endangers the die integrity, affects the casting quality and causes considerable production downtime, which altogether raise production costs. Development of new soldering resistant materials and coatings for HPDC dies is a promising approach in a struggle for the reduction of soldering effects. Performance of new materials for such application is most appropriately evaluated by laboratory tests. One of the tests is the ejection test in which a force required to eject a pin sample from a casting presents a measure of the cast alloy soldering tendency. In this paper, comparison between two currently used and one newly proposed method for the production of pin-casting assemblies is presented. For this purpose, pins made of X27CrMoV51 steel, and Al–Si–Cu cast alloy were used. The ejections of the pin samples were carried out on tensile testing machines, and force displacement diagrams were recorded. After the ejections, casting and pin surfaces were visually examined. The employed casting methods were numerically simulated. For the methods used so far, it was found that uniformity of a pin-casting contact is disrupted by the presence of shrinkage cavities, oxide films, and sinking-in of the casting surfaces. These imperfections formed due to inadequate casting filling and solidification conditions. On the other side, the newly designed method resulted in a uniform and a high-quality pin-casting contact, obtained through a casting process characterized with more severe soldering conditions. Consequently, for new method the recorded force and work of the ejection force are significantly higher and the cast alloy is evenly distributed on pin surfaces. New method more realistically replicates the conditions that exist between paired materials in real HPDC process. It is also simple for use and results are repeatable with a reasonable scatter.