Abstract
Vacuum casting is widely used as an investment casting method for small parts of
complex geometry. Selection of casting conditions for acquiring sound castings is not a
trivial process. In modern casting machines, the application of pressure directly after
completion of melt pouring is used to ensure proper filling of the very fine details of the
casting tree. The present work concerns examination of casting conditions of brass on a
modern vacuum-pressure casting machine, in order to reveal their influence on part
quality. A parametric investigation was carried out with respect to pressure in the upper
chamber and vacuum in the lower chamber of the machine. The obtained cast samples
were examined with optical microscopy in order to identify possible defects, while image
analysis was used in order to quantify porosity in each sample. In addition, casting
simulation software was exploited to enhance process knowledge. The major issue in
obtaining realistic results from simulation was the determination of the interfacial heat
transfer coefficient (HTC). This was achieved using experimental cooling curves,
obtained with K-type thermocouples during casting under pre-defined conditions. The
heat transfer coefficient, once estimated in each case from the corresponding simulations,
was, then, used in further typical casting scenarios. These scenarios were analyzed with
commercially available casting simulation software. The purpose was to determine the
influence of casting parameters on mould filling time, porosity and solidification time.
complex geometry. Selection of casting conditions for acquiring sound castings is not a
trivial process. In modern casting machines, the application of pressure directly after
completion of melt pouring is used to ensure proper filling of the very fine details of the
casting tree. The present work concerns examination of casting conditions of brass on a
modern vacuum-pressure casting machine, in order to reveal their influence on part
quality. A parametric investigation was carried out with respect to pressure in the upper
chamber and vacuum in the lower chamber of the machine. The obtained cast samples
were examined with optical microscopy in order to identify possible defects, while image
analysis was used in order to quantify porosity in each sample. In addition, casting
simulation software was exploited to enhance process knowledge. The major issue in
obtaining realistic results from simulation was the determination of the interfacial heat
transfer coefficient (HTC). This was achieved using experimental cooling curves,
obtained with K-type thermocouples during casting under pre-defined conditions. The
heat transfer coefficient, once estimated in each case from the corresponding simulations,
was, then, used in further typical casting scenarios. These scenarios were analyzed with
commercially available casting simulation software. The purpose was to determine the
influence of casting parameters on mould filling time, porosity and solidification time.
| Original language | English |
|---|---|
| Title of host publication | Advances in Mechanical Engineering Research Volume 2 |
| Place of Publication | New York |
| Publisher | Nova Science Publishers |
| Chapter | 7 |
| Pages | 209-232 |
| Number of pages | 24 |
| Volume | 2 |
| ISBN (Electronic) | 978-1-61122-393-4 |
| Publication status | Published - 2010 |
Keywords
- vacuum-pressure casting
- Investment casting
- heat transfer coefficient
- porosity