Question

In the hydrogen removal process, carbon monoxide for ferrous alloys removes not only hydrogen but also nitrogen.

(a) True

(b) False

This question was addressed to me in quiz.

Question is taken from Gases in Metals in section Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I

Answer 1

Right answer is (a) True

For explanation I would say: Carbon monoxide for ferrous alloys removes not only hydrogen but also nitrogen. So, for ferrous metals, a marked decrease in the solubility of nitrogen during the phase change may give rise to porosity in the castings. And the re-entry of nitrogen from the air is also prevented by the impermeable slag at the top of the melt.