Question

Which of the following can be used for increasing feeding distance?

(a) Uniform temperature gradient

(b) Negative temperature gradient towards the riser

(c) No temperature gradient

(d) Positive temperature gradient towards the riser

I have been asked this question during a job interview.

My query is from Riser Design topic in section Pattern and Mould, Principles of Gating & Risering of Casting-Forming-Welding I

Answer 1

The correct choice is (d) Positive temperature gradient towards the riser

Explanation: If the temperature gradient is not there, the metal will not solidify. Same will happen in case of the uniform temperature gradient. In case of the negative thermal gradient, the metal will first solidify near riser which results in unsound casting. Hence positive thermal gradient is required so that metal will solidify near walls first hence feeding distance will be increased.