Question

Which of the following formulas is used for the determination of solid friction (fs) between the mould and casting during solidification?

(a) fs = ηs-H

(b) fs = ηs/H

(c) fs = ηs+H

(d) fs = ηs*H

I had been asked this question at a job interview.

My query is from Solidification with Predominant Resistance in Mould in chapter Cooling and Solidification of Casting-Forming-Welding I

Answer 1

Correct choice is (d) fs = ηs*H

For explanation: When the relative movement occurs between the casting and the solidified mould slag, then the friction force is generated by the solid-solid contact. The resulting solid friction (fs) is expressed as fs = ηs*H, where ηs is the coefficient of solid friction, and H is the Ferro-static pressure of molten metal.