Recrystallization and strain accumulation behaviors of high Nb-bearing line pipe steel in plate and strip rolling

The recovery and recrystallization behaviors of high Mn-high Nb line pipe steel were investigated by means of thermal-simulation and plane strain tests, and the morphology of prior-austenite grains in different conditions was revealed by special etching method. Proposed rolling windows of static recrystallization (SRX) and non-recrystallization were determined for industrial plate rolling. Moreover, partial dynamic recrystallization (DRX) behavior of high Mn-high Nb steel was proved by multi-pass plane strain tests. The results of SRX indicate the existence of a deformation temperature range for grain refinement by complete SRX, in which grains nucleate homogeneously and the coarsening rate is slow because of intense solute dragging. In non-recrystallization temperature range, partial DRX may be triggered by overmuch strain accumulation in the case of improper process design, and then, mixed grains and the loss of final Sv level take place.