Question

In the solidification process, external angles have a lower cooling rate than re-entrant angles of the casting.

(a) True

(b) False

This question was posed to me during an interview.

Enquiry is from Product Design for Sand Castings in section Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I

Answer 1

Correct answer is (b) False

Easy explanation: Solidification progresses from thin to thick sections and external angles have a greater cooling rate than re-entrant angles; the reason being that sand around a re-entrant angle is surrounded on two sides by the heat sources. And re-entrant angle should be made proper to avoid cracks which often begin at the shrinkage cavities.