engleski

POSSIBILITIES FOR PROVIDING OF UNIDIRECTIONAL SOLIDIFICATION OF COMPLEX CASTINGS IN THE TECHNOLOGY OF HIGH-PRESSURE DIE-CASTING

In contemporary high pressure die casting (HPDC) foundries the mastery of each sequence in production cycle is the most important, where the strive to reliable master, as well as planning of composed molten metal, pouring and solidification process, ejection of castings, transport to the cooling place and cutting of gating system and overflows were done. For castings with a complex geometry and dimensional accuracy, the appropriate planning of pouring and feeding elements according to a heat economy of casting, rapid tooling and prototyping and then reliable manufacturing which includes the mastery of all the edge conditions in the process chain. In the paper the example of virtual analysis of casting from Al alloy will be presented with choosing of appropriate foundry technology HPDC, calculation of casting process which includes the filling process of cold chamber, model description of three phases at HPDC, flow of molten metal, solidification with considering the temporary air gap formation between the casting and tool, formation of stress and relaxation of it into deformations in each sequence, when the tool is opening, at ejection, cooling in water or on air and after cutting off the gating system. Since it is not always possible to produce the castings according to the principle of unidirectional solidification with a traditional approach, for the individual areas, which should be macroscopic dense (without porosity), the local squeezing process is performed in the sequence of the semi-solid state of the region. The location of the impression is marked by a local increase of pressure and a plastic deformation of the already solid part of the casting (solid shell). An example of a very detailed comprehensive treatment of these processes in the case of a real casting will be discussed. Further, the optimization of the processes of the local squeezing sequence and the overall solidification process will be presented. Comparisons will be made with calculations of volume defects, casting dimensions and deformations with experimentally obtained castings produced from LTH Castings' industrial technology practice. Proven complete master of high-pressure die-casting have the result of an important financial effect and decreasing of required time to start of serial production of castings.

high pressure die casting ; unidirectional solidification ; local squeezing ; pressure analyses ; shrinkage porosity

nije evidentirano