ANALYSIS OF INFLUENCING THE MACROSTRUCTURE AND HARDNESS OF CASTING SURFACE LAYER BY CHANGING CONDITIONS OF CRYSTALLIZATION

Abstract

In manufacturing technology, we often encounter the demand for increasing surface hardness of the machinery components. Although there are new varied coating and surface hardening technologies, those are processes implying increasing costs, economic burden and time required for the manufacturing process including increase in production capacities, increased need for machinery and equipment, or possible dependence on external suppliers. The capability of increasing hardness of components starts in casting itself. By understanding and mastering the processes involved in the process of solidification of the melt it is possible to adjust technical parameters so that the hardness characteristics of the casting is increased by the crystallization process and thereby also by the formation of the internal structure morphology. The article presented deals with assessing the changes in surface hardness of castings achieved by changing crystallization conditions. The issue of crystallization is addressed in terms of the processes accompanying the process of melt solidification in casting mould.   The parameters observed are macrostructure and hardness of castings fabricated using high pressure die casting technology and changes of these parameters compared to the surface hardness of the castings produced using conventional foundry technologies. At the same time, the influence of structural design of the gate on the selected parameters is observed.

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