Annealing of cold-rolled rephosphorized steels containing Si and Cb

Abstract

The effects of continuous and batch annealing on the mechanical properties and strengthening mechanisms of rephosphorized steels containing Si and Cb were studied. Cold rolling in combination with continuous annealing provided a higher yield strength than was attained in the hot-rolled material because of the resultant finer ferrite grain size. On the other hand, batch annealing following cold reduction generally resulted in a lower yield strength because of grain growth and, for the Cb-alloyed steels, precipitate coarsening as well. For the steels alloyed with Si, in the case of batch annealing, increasing Si from 0 to 0.5 pct resulted in increasing yield stength due to both grain refinement and solid solution strengthening, whereas in the case of continuous annealing, the Si addition resulted solely in solid solution strengthening. For the Cb-steels, the increase in yield strength with increasing Cb content was due to increased precipitation strengthening in the case of continuous annealing and due to both increased precipitation strengthening and grain growth retardation in case of batch annealing.