Centrifugal casting — in true centrifugal casting of hollow cylindrical parts, do inclusions, slag, and gas porosity tend to segregate toward the geometric centre (bore) of the casting due to radial acceleration?

Introduction / Context:
Centrifugal casting is a foundry process used to produce hollow, axisymmetric parts such as pipes, sleeves, and rings. The mould rotates at high angular speed while molten metal is poured. The intense radial acceleration throws the denser liquid metal outward against the mould wall, shaping and solidifying the casting from the outside inward. This question probes whether impurities concentrate toward the centre (the bore) during this process.

Given Data / Assumptions:

• True centrifugal casting (no core is used; the bore forms naturally).
• Molten metal contains typical contaminants: non-metallic inclusions, dross/slag, and dissolved gases that can form porosity.
• Steady rotation at a prescribed speed during pouring and solidification.

Concept / Approach:

Under rotation, the apparent body force per unit mass is ω²r directed radially outward. Denser phases (metal) experience greater outward driving than lighter phases (slag, oxide skins, entrapped gases). Consequently, lighter constituents tend to migrate toward the axis where the effective radial acceleration is smaller, leading to segregation near the centre. Solidification also begins at the mould wall, pushing remaining liquid—and with it lighter inclusions—toward the inner surface (bore).

Step-by-Step Solution:

Verification / Alternative check:

Microstructural examinations and industry practice confirm denser, cleaner metal at the periphery and impurity concentration near the inner surface. Standards often specify machining allowance on the bore to remove this layer.

Why Other Options Are Wrong:

“No” is incorrect because both centrifugal segregation and directional solidification effects favour impurity concentration near the bore.

Common Pitfalls:

Confusing true centrifugal casting (hollow parts) with centrifuging/semi-centrifugal methods used for non-hollow geometries; assuming inclusions distribute uniformly.

Final Answer:

Yes