Influence of Cold Reduction on Hydrogen Behavior in High-Purity Iron

Abstract

Experiments to determine the effect of cold reduction on the behavior of hydrogen in high-purity sheet iron were conducted using two laboratory-melted heats. One heat was air-melted and poured and contained 0.00470 carbon and 0.17% oxygen; the other was vacuum-melted and poured and contained 0.003% carbon and 0.006% oxygen. An increase in hydrogen solubility (acid-charged) with increasing cold reduction was observed for both lots. The hydrogen solubility increase occurring from 0 to 80% cold reduction was much more pronounced, however, for the lot containing the higher amount of oxygen. Ground-coat reboiling tests were made on both lots of high-purity iron. The material containing high oxygen exhibited light reboiling for all levels of cold reduction, whereas the material containing low oxygen exhibited light reboiling for intermediate levels of cold reduction and heavier reboiling for low and for high levels of cold reduction. For the cold-reduced material containing high oxygen, the frequency of delayed defects decreased with increasing cold reduction. For the purer material, delayed defects were observed only for the specimens having the highest level of cold reduction.