Permanent elimination of the yield-point phenomenon in AISI 430 stainless steel by skin-pass rolling

The different yielding behaviour of skin-pass and skin-pass plus annealed samples of AISI 430 stainless steel and its dependence on substructure has been studied. Skin-pass specimens show no yield elongation in tensile testing and do not strain age at room temperature. According to TEM observations, this seems to be due to submicroscopic precipitation of low-carbon carbonitrides — most probably Cr₂ (C,N) — preferably on grain boundaries. The locking of interstitials (N, C) by these precipitates could explain the absence of discontinuous yielding. On the other hand, annealing at 700C of skin-pass samples dissolves the carbonitride precipitates, interstitial solutes are able to segregate on dislocations, and the pinned dislocations give rise to yield-point phenomena.