Page 18 - Module DMV20173

2.0 CASTING PROCESSES

2.5 PERMANENT-MOULD CASTING

1. In permanent-mould casting, (also called hard-mould casting), the moulds are made
from metals that maintain their strength at high temperatures.
2. This process has certain advantages over other casting processes such as it can be
run automated for large production runs.
3. This process is used mostly for aluminum, magnesium, copper alloys, and gray iron

because of their generally lower melting points, although steels also can be cast
using graphite or heat-resistant metal moulds.
4. Some of the examples of permanent-mould casting are vacuum casting, slush
casting, pressure casting, die casting and centrifugal casting.

Example 2.2:

What is the difference between expandable-mould casting and permanent-mould

casting?

Solution:

1. In expendable-mould casting, the mould that used in casting process is broken up
to remove the casting while permanent mould casting still maintiain the use of its
mould.
2. Compare to the expandable-mould casting, the mould that used permanent-mould
casting can be used several times to produce high volume casting productions.

2.2.1 VACUUM CASTING

1. Vacuum casting is a casting process with molten metal absorbed into a mould with
vacuum actions.
2. Fig 3.8. shows the schematic illustration of the vacuum-casting process.

3. Vacuum casting is an alternative to investment, shell-mould, and sand casting and is
suitable particularly for complex shapes with uniform properties.
4. The process can be automated, and production costs are similar to those for sand
casting.

BPLK 50 DMV 20173