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Numerical analysis of influence of the mold material on the distribution of shrinkage cavities

Dyja R.

Archives of Foundry Engineering

2013

Vol. 13, iss. 1

15--18

Production of castings, like any other field of technology is aimed at providing high-quality product, free from defects. One of the main causes of defects in castings is the phenomenon of shrinkage of the casting. This phenomenon causes the formation of shrinkage cavities and porosity in the casting. The major preventive measure is supplementing a shortage of liquid metal. For supplement to be effective, it is necessary to use risers in proper shapes. Usually, the risers are selected on the basis of determination the place of formation of hot-spots in the castings. Although in these places the shrinkage defects are most likely to occur, shape and size of these defects are also affected by other factors. The article describes the original program setting out the shape and location of possible cavities in the casting. In the program is also taken into account the effect of temperature on the change in volume of liquid metal and the resultant differences in the shape and size of formed shrinkage cavities. The aim of the article is to describe the influence that have material properties of the mold on the simulation results.

Method for determining the formation of shrinkage defects in the castings

Dyja R., Sczygiol N.

Archives of Foundry Engineering

2011

Vol. 11, iss. 4

35-40

Simple simulations of solidification of metals and alloys generally provide results for determining the temperature distribution in a given time or solidification time for the specific locations of the casting. These data allow to unambiguously determine the position of thermal centers. However, knowledge about the location of thermal centers is not synonymous with the information about the location of any shrinkage defects in the casting, because the physical behaviour of molten metal should be still considered. This paper presents authors' own method of predicting the formation of shrinkage defects in the castings, basing on solidification simulation results, taking into account the basic rules of behaviour of the molten metal. The effectiveness of the method has been tested on the basis of example simulations performed for the flat shape of the casting inlet systems. The advantage of the method is that it requires little additional computational effort. The article is summarized by conclusions reached on the basis of simulations, as well as the program for further work containing possible improvements of the algorithm.