Foundry processes — in the centrifugal casting method used for pipes, sleeves, and rings, what is used to create the internal cavity of the casting?

Introduction / Context:
In manufacturing technology, centrifugal casting is a moulding process in which molten metal is poured into a rotating mould. The high rotational speed generates a strong radial acceleration that forces the liquid metal outward against the mould wall. This question tests whether you know how the inner cavity is formed and whether a separate core is required, as is common in sand casting.

Given Data / Assumptions:

• Hollow cylindrical shapes such as pipes, bushings, and sleeves are typical products.
• The mould is rotated at high speed during pouring and solidification.
• No additional statements about special cores or inserts are provided.

Concept / Approach:

The basic principle is that centrifugal force distributes the molten metal outward, forming a dense outer wall while the central region remains void. Because the inner cavity results naturally from the absence of metal at the center, a discrete core is not required in standard true centrifugal casting. Any inclusions or lighter impurities migrate toward the bore and can be machined away after solidification.

Step-by-Step Solution:

Verification / Alternative check:

Process textbooks distinguish true centrifugal casting (no core for hollow axisymmetric parts) from semi-centrifugal and centrifuging methods. Only the latter may use cores for non-axisymmetric cavities.

Why Other Options Are Wrong:

Sand cores, ferrous cores, or non-ferrous cores are not normally used in true centrifugal casting because the rotation creates the bore automatically.

Common Pitfalls:

Confusing centrifugal casting with sand casting where cores are routine, or with semi-centrifugal methods that may include cores for hubs.

Final Answer:

no core is used