Effect of Heat Treatment on Microstructure and Mechanical

Abstract

In this paper, a Fe-based Mn-Ni–Cr–Mo high strength low alloy (HSLA) steel was prepared by using Vacuum melting, following by hot rolling with 78% deformation and various heat treatment processes. Microstructure were characterized by optical microscope (OM), scanning electron microscope (SEM) equipped with energy dispersive spectrometer. Tensile tests were performed. After direct quenching (Q) from 860℃, the samples were subjected to secondary quenching (L) at different intercritical temperatures within the two-phase region and various tempering temperatures (T). Results show that QLT treatment increases elongation and decreases yield ratio compared with conventional quenching and tempering process (QT). The optimum QLT heat treatment parameter in terms of temperature are determined as Q: 860℃, L: 700℃, and T: 600℃, resulting in the better combined properties with yield strength of 756MPa, tensile strength of 820MPa, tensile elongation of 16.76% and yield ratio of 0.923