Question

In relation to metal casting defects, match the following:

Defect	Description
P. Dross	I. Shallow blow found on a flat casting surface
Q. Scab	II. Lighter impurities appearing on the top surface of a casting
R. Scar	III. A rough, thin layer of metal, protruding above the casting surface, on top of a thin layer of sand

• A. P−II, Q−III, R−I
• B. P−II, Q−I, R−III
• C. P−III, Q−I, R−II
• D. P−III, Q−II, R−I

Hint:

Picture how each defect actually forms: floating impurities, a lifted sand flake, or a shallow surface blow.

Answer 1

The Correct Option is A

This is a definitions match: each casting defect name has to be paired with the description of how it actually looks on the casting.

1. Dross (P): dross is lighter, non-metallic impurities such as oxides that float up and collect on the top surface of the melt, which is description II.
2. Scab (Q): a scab forms when a layer of sand near the mold surface flakes off due to expansion and metal seeps under it, leaving a rough, thin layer of metal sitting on a thin sand layer above the casting surface, which is description III.
3. Scar (R): a scar is a shallow blow type defect that shows up on a flat part of the casting surface, which is description I.

So the correct pairing is P-II, Q-III, R-I, which is option (A).