Effect of Prior Cold Work on Grain Refinement in ST 44-2 Mild Steel by Cyclic Re-Austenitizing

Abstract

The effect of prior cold work on grain refinement in mild steel by cyclic re-austenization has been studied. Cyclic re-austenization consists of repeated heating to the austenite range, soaking for a short time at the peak temperature and then quenching in water. A steel grade, ST 44-2 (0.14-0.20%C, 0.18-0.28%Si, 0.40-0.60%Mn), was cold worked to various degrees of deformation and subjected to various isothermal heat treatments, keeping the holding time constant while the peak temperature was varied and vice-versa for a number of cycles. The higher the degree of cold work the finer the average grain size for a given number of cycles. Average grain size decreases with increasing number of cycles up to an optimum number and the optimum number of cycles decreases with increasing degree of cold work. The effect of cold work is more pronounced at lower temperature, shorter time and smaller number of austenitizing cycles. For a given condition of temperature and time, the higher the degree of cold work, the smaller the number of cycles required for optimum grain refinement.

Keywords: Mild Steel, Grain Refinement, Cyclic Re-Austenitization, Cold-Work

Journal of Applied Science, Engineering and Technology Vol. 6 (1) 2006 pp. 48-55