Multistage strain aging phenomenon of low-carbon steels with rolling pre-strain

Abstract

In this study, a multistage strain aging method that used rolling pre-strain (compression) was developed to study the effects of temperature, and inter-pass time on static strain aging behavior of low carbon steel. An increase in hardness and strength caused by work hardening due to the forming process and aging at every stage of aging that is calculated separately. To comparing the effects of multistage aging against typical strain aging, the samples were rolled and subjected to the aging process both exist in typical one-stage aging that setting a 20% rolling pre-strain and in multiple stages pre-strain by setting a 5% rolling ratio in four stages. The mechanical properties of aged samples are compared with each other to study the effects of time and temperatures on strength and hardness. To evaluate the effects of pre-strain type (tensile or compression) on mechanical properties, one sample was subjected to tensile and compared with rolling pre-strain samples in similar conditions. The results show that in multistage static strain aged samples with rolling pre-strain, the peak of the strain stress curve occurs in 10–15 min rather than samples that aged after tensile pre-strain. Multistage strain aging increased samples’ strength by 10% and reduced their plasticity by 5%. To evaluate the effects of temperature on the time, we propose the maximum hardness and strength, the aging temperature of the samples was increased to 250 °C and it was observed that the maximum hardness and strength time is reduced by 10 min.