Abstract
The factors influencing absorption by Type 444 ferritic stainless steel of interstitial elements from gaseous environments deliberately contaminated with nitrogen and oxygen have been studied for induction melted weld simulations and actual tungsten inert gas welds. For weld simulations, nitrogen pick-up is limited by factors such as the formation of stable TiN surface films; induction melting is therefore considered unsatisfactory as a weld simulation for the purpose of studying gas absorption. It is found that titanium is consumed by both gaseous species, whereas niobium is not; dual stabilization is therefore recommended. Welds show greater nitrogen pick-up than simulations, the effect increasing with increasing heat input, while at the highest heat inputs the quantity absorbed exceeds predictions based on solubility equilibria. These effects are explained in terms of the enhanced gas transfer conditions that obtain and the dissociation of the gas that occurs in the welding arc.
MST/416
Get full access to this article
View all access options for this article.