The optimum conditions for manufacturing ultrafine-grained hot strips in super short interval multi-pass rolling (SSMR) process were discussed. As the first means of evaluation, the changes in austenite grain size and shape during multi-pass rolling were observed using experimental equipment. Deformed austenite grains could be observed with immediate quenching after each rolling pass. As the second means, a new numerical simulation method was used, which could predict the microstructure change of austenite, ferrite nucleation inside austenite grains, and ferrite grain growth. The effects of austenite grain size before finish rolling and also of temperature control between rolling passes on ferrite grain refinement were investigated. It was found that the temperature control between rolling passes is effective for grain refinement, whereas austenite grain refinement before finish rolling is not so effective. Therefore, deformation strain accumulation in austenite is important for ferrite grain refinement in SSMR process.
A new numerical simulation method that can be used to predict microstructure changes in ultrafine-grain generation in super short interval multi-pass rolling (SSMR) process is proposed. The SSMR process has been developed for manufacturing ultrafine-grained hot strips of about 1 μm grain size at ordinary rolling load. A new ferrite nucleation mechanism has been discussed in this process. Because multi-pass rolling and inter-pass and after-pass cooling are performed within a short time in a stable austenite temperature region, deformation strain is accumulated in the austenite. Then dislocation cells are formed inside a severely deformed and unrecrystallized austenite grain, and become the nucleation site of ferrite transformation. In this new simulation method, nucleation inside a deformed austenite grain was formulated in addition to nucleation at the austenite grain boundary.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.