Effect of hot rolling process parameters on the microstructure and mechanical properties of continuously cooled low-carbon high-strength low-alloy (HSLA) steel

Abstract

In this work, high-strength low-alloy (HSLA) steel with 0.22 wt% carbon was produced in laboratory scale and hot rolled with a total deformation of 42% via 4, 5, or 6 passes. After multipass hot rolling process, samples were examined either in as-rolled (AR) or as-rolled and heat-treated (ARH) conditions. The results indicated that microstructural and mechanical properties of HSLA steels are influenced by hot rolling conditions for both cases. It was observed that strength values in AR samples have a tendency to increase with increment in rolling pass number. In contrast to AR samples, it was seen that the mechanical properties were slightly decreased in ARH samples that were austenitized at 1150 °C for 45 min and then cooled in still air. Microstructural investigations showed that finer precipitates in AR samples are obviously more than that of ARH samples, as an evidence for higher strength results by precipitation hardening. In addition to precipitation strengthening, refinement of lath bainite and amount of blocky martensite/austenite in AR samples favor the increase in strength.