Texture and Microstructure Development during Intercritical Rolling of Low-Carbon Steels

摘要

Laboratory rolling trials have been performed to investigate the development of microstructure and crystallographic texture during and after intereritical rolling. The finishing temperature was varied over a wide range, and samples were taken just prior to the last pass, after quenching following the last pass, after air cooling and coiling, and after accelerated cooling and coiling. Cooling of the samples to the entry temperature for the last pass does not influence the texture of the sample, nor do higher cooling rates after austenitic finishing within the range of cooling rates in this study, although it may cause a refinement of the ferrite grains. Recrystallization after intereritical rolling leads to a decrease in texture intensity. In the case of recrystallization of low-carbon steels, the nucleation mechanism is strain-induced boundary migration (SIBM), which leads to unfavorable textures for deep drawing. In the case of recrystallization of interstitial-free (IF) steel after ferritic rolling, the nucleation mechanism shifts from the SIBM mechanism at high finishing temperatures to subgrain coalescence at (SGC) low finishing temperatures. The latter mechanism leads to more favorable textures for deep-drawing applications. Transformation-induced (TI) nucleation explains the occurrence of a sudden increase in ferrite grain size after high-temperature intereritical deformation of low-carbon (LC) steels.